RT 255

Digital Imaging Review

Display Workstationsbull Conventional filmscreen

radiography uses large multiviewer lightboxes

bull With early PACS radiologists thought that they needed 4-6 monitors

bull Now the number of monitors has dropped to an average of 2

bull Development of viewing software and better hardware

CRTbull The CRT is the most popular monitor on the market

bull It consists of a cathode and anode within a vacuum tube

bull Cathode boils off a cloud of electrons and then a potential difference is placed on the tube

bull A stream of electrons is sent across to the anode which in the case of the monitor is a sheet of glass coated with a phosphor layer

MONITORSDisplay Workstationsbull Early PACS reading rooms required

supplemental air-conditioning to offset the heat from multiple CRTs

bull Resolution and orientation of the monitor is also a factor in determining which type of monitor is to be used

bull Most cross-sectional imaging is read on a 1K square monitor

bull Most computed radiography (CR) and digital radiography (DR) images are read on at least a

2K portrait monitor

LCD

bull 13 megapixels bull to 5 megapixels bull mammography imaging =bull at least 5 megapixel resolution is

required

bull Rads VIEWERbull 4K or higher

Physician Review Stations Monitorsbull Step-down model of the radiologistrsquos reading

station (lower res)bull Some functions reducedbull One of the most important features bull is ability to view current and previous reports

with imagesbull Many vendors are integrating bull the RIS functions bull with PACS software

Technologist QC Stationsbull review images after acquisition

but before sending them to the radiologist

bull May be used to improve or adjust image-quality characteristics

bull May be used to verify patient demographic information

bull Placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Display Workstationsbull Conventional filmscreen

radiography uses large multiviewer lightboxes

bull With early PACS radiologists thought that they needed 4-6 monitors

bull Now the number of monitors has dropped to an average of 2

bull Development of viewing software and better hardware

CRTbull The CRT is the most popular monitor on the market

bull It consists of a cathode and anode within a vacuum tube

bull Cathode boils off a cloud of electrons and then a potential difference is placed on the tube

bull A stream of electrons is sent across to the anode which in the case of the monitor is a sheet of glass coated with a phosphor layer

MONITORSDisplay Workstationsbull Early PACS reading rooms required

supplemental air-conditioning to offset the heat from multiple CRTs

bull Resolution and orientation of the monitor is also a factor in determining which type of monitor is to be used

bull Most cross-sectional imaging is read on a 1K square monitor

bull Most computed radiography (CR) and digital radiography (DR) images are read on at least a

2K portrait monitor

LCD

bull 13 megapixels bull to 5 megapixels bull mammography imaging =bull at least 5 megapixel resolution is

required

bull Rads VIEWERbull 4K or higher

Physician Review Stations Monitorsbull Step-down model of the radiologistrsquos reading

station (lower res)bull Some functions reducedbull One of the most important features bull is ability to view current and previous reports

with imagesbull Many vendors are integrating bull the RIS functions bull with PACS software

Technologist QC Stationsbull review images after acquisition

but before sending them to the radiologist

bull May be used to improve or adjust image-quality characteristics

bull May be used to verify patient demographic information

bull Placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

CRTbull The CRT is the most popular monitor on the market

bull It consists of a cathode and anode within a vacuum tube

bull Cathode boils off a cloud of electrons and then a potential difference is placed on the tube

bull A stream of electrons is sent across to the anode which in the case of the monitor is a sheet of glass coated with a phosphor layer

MONITORSDisplay Workstationsbull Early PACS reading rooms required

supplemental air-conditioning to offset the heat from multiple CRTs

bull Resolution and orientation of the monitor is also a factor in determining which type of monitor is to be used

bull Most cross-sectional imaging is read on a 1K square monitor

bull Most computed radiography (CR) and digital radiography (DR) images are read on at least a

2K portrait monitor

LCD

bull 13 megapixels bull to 5 megapixels bull mammography imaging =bull at least 5 megapixel resolution is

required

bull Rads VIEWERbull 4K or higher

Physician Review Stations Monitorsbull Step-down model of the radiologistrsquos reading

station (lower res)bull Some functions reducedbull One of the most important features bull is ability to view current and previous reports

with imagesbull Many vendors are integrating bull the RIS functions bull with PACS software

Technologist QC Stationsbull review images after acquisition

but before sending them to the radiologist

bull May be used to improve or adjust image-quality characteristics

bull May be used to verify patient demographic information

bull Placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

MONITORSDisplay Workstationsbull Early PACS reading rooms required

supplemental air-conditioning to offset the heat from multiple CRTs

bull Resolution and orientation of the monitor is also a factor in determining which type of monitor is to be used

bull Most cross-sectional imaging is read on a 1K square monitor

bull Most computed radiography (CR) and digital radiography (DR) images are read on at least a

2K portrait monitor

LCD

bull 13 megapixels bull to 5 megapixels bull mammography imaging =bull at least 5 megapixel resolution is

required

bull Rads VIEWERbull 4K or higher

Physician Review Stations Monitorsbull Step-down model of the radiologistrsquos reading

station (lower res)bull Some functions reducedbull One of the most important features bull is ability to view current and previous reports

with imagesbull Many vendors are integrating bull the RIS functions bull with PACS software

Technologist QC Stationsbull review images after acquisition

but before sending them to the radiologist

bull May be used to improve or adjust image-quality characteristics

bull May be used to verify patient demographic information

bull Placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

LCD

bull 13 megapixels bull to 5 megapixels bull mammography imaging =bull at least 5 megapixel resolution is

required

bull Rads VIEWERbull 4K or higher

Physician Review Stations Monitorsbull Step-down model of the radiologistrsquos reading

station (lower res)bull Some functions reducedbull One of the most important features bull is ability to view current and previous reports

with imagesbull Many vendors are integrating bull the RIS functions bull with PACS software

Technologist QC Stationsbull review images after acquisition

but before sending them to the radiologist

bull May be used to improve or adjust image-quality characteristics

bull May be used to verify patient demographic information

bull Placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull Rads VIEWERbull 4K or higher

Physician Review Stations Monitorsbull Step-down model of the radiologistrsquos reading

station (lower res)bull Some functions reducedbull One of the most important features bull is ability to view current and previous reports

with imagesbull Many vendors are integrating bull the RIS functions bull with PACS software

Technologist QC Stationsbull review images after acquisition

but before sending them to the radiologist

bull May be used to improve or adjust image-quality characteristics

bull May be used to verify patient demographic information

bull Placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Physician Review Stations Monitorsbull Step-down model of the radiologistrsquos reading

station (lower res)bull Some functions reducedbull One of the most important features bull is ability to view current and previous reports

with imagesbull Many vendors are integrating bull the RIS functions bull with PACS software

Technologist QC Stationsbull review images after acquisition

but before sending them to the radiologist

bull May be used to improve or adjust image-quality characteristics

bull May be used to verify patient demographic information

bull Placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Technologist QC Stationsbull review images after acquisition

but before sending them to the radiologist

bull May be used to improve or adjust image-quality characteristics

bull May be used to verify patient demographic information

bull Placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Technologist QC Stationbull Generally has a 1K monitorbull Does not have the resolution capabilities of the

radiologistrsquos reading stationbull Care required of technologist when manipulating

images not to change the appearance too much from original acquired image

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Technologist workstation monitors are used in brightly lighted areas So monitor luminance the brightness of a monitor display is an important consideration Also the monitor must allow a technologist to visualize enough detail to discern motion and that the recorded lines are sharp and visible

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

The File Room Workstationbull Workstation may be used to bull look up exams for a physician bull or to print copies of images bull for the patient to take to an bull outside physicianbull Many hospitals are moving away from

printing films because of the costbull Hospitals are moving toward burning

compact disks (CDs) with the patientrsquos images

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Name the 3 types of monitors

bull Two major types of monitors with a third type gaining acceptance

bull CRTbull LCDbull Plasma screen

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Image Display= MONITORSbull viewing conditions

ndash (ieluminanceambient lighting)bull spatial resolution bull contrast resolutiondynamic range bull DICOM gray scale function bull window level and width function

ARRT DEFINITIONS

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

viewing conditions luminanceambient lighting

bull How does this affect viewing imagesbull Surrounding light impacted what was seen on

image ndash now With different monitors

bull LCD gives more lightbull LCD can be used in areas with a high amount of ambient light

ldquodark roomsrdquo not necessary

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

WINDOW LEVEL WIDTHWhich one controls

Denisty (brightness) Contrast

What else control these in DIGITAL IMAGING

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull The ability to window is a valuable feature of all digital images

bull Windowing is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptors) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black

bull Important pointContrast will be visible only for the pixel values that are within the selected window All pixel values that are either below or above the window will be all white or all black and display no contrast

bull The person controlling the display can adjust both the center and the width of the window The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Enhanced Visualization Image Processing

bull Takes image diagnostic quality to a new levelbull Increases latitude while preserving contrastbull Process decreases windowing and levelingbull Virtually eliminates detail loss in dense tissues

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Nyquist frequency Reviewbull The highest spatial frequency that can be

recorded by a digital detector bull is determined by the ________________ bull The Nyquist frequency is half the number

of pixelsmm

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

10 PIXEL DENSITYWHAT IS THE NYQUIST FREQUENCY=

A digital system with a pixel density of 10 pixelsmm would have a Nyquist frequency of 5 line pairmm

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Sampling Frequency Define helliphellip

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Sampling Frequency

bull The sampling frequency is the rate atbull which the laser extracts the image databull from the plate

bull What other term does this relate to

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Nyquist Frequency

bull The Nyquist Frequency will be frac12 of the sampling frequencybull A plate that is scanned using a sampling

frequency of 10 pixels per millimeter would not be able to demonstrate more than 5 line pairs per millimeter based upon the Nyquist Frequency

bull The Nyquist Frequency allows thebull determination of the spatial resolution forbull a given sampling frequency

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull In the typical digital radiographic system a variety of LUTs are installed

bull The appropriate LUT is then automatically selected to give the desired contrast characteristics to match the type of procedure (chest extremity etc) that is designated by the operator

LUT

a histogram of the luminance values derived during image acquisition used as a reference to evaluate the raw information and correct the luminance values a mapping function in which all pixels are changed to a new gray value

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

LOOK UP TABLE (LUT)

Linear LUT

Black Shirt

Facial Tones

Black Saturation

White Saturation

No Detail in Black Areas High Contrast Only Detail in White Areas can be seen

No Detail in White Areas Low Contrast Only Detail in Black Areas can be seen

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

image signal (exposure related) Exposure Indicators

bull The amount of light given off by the imaging plate is a result of the radiation exposure that the plate has received

bull The light is converted into a signal that is used to calculate the exposure indicator number which is a different number from one vendor to another

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Digital artifacts

bull Grid Lines Appear as grid cutoff bull Moire (Aliasing)

ndash wavy artifact occurs because the grid lines and the scanning laser are parallel

ndash When the spatial frequency is greater than the Nyquist frequency

bull Maintenance (eg detector fog) When errors occur in equipment performance corrective action must occur These corrections will generally be done by service personnel employed by the vendor

bull non-uniformity erasure - blub problems

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

How else can Morie OCCUR

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

quantum mottleARRT definitions

failure of an imaging system to record densities usually caused by a lack of x-ray photons

ldquoPHOTON STARVEDrdquo

KVP amp MAS HOW IS THIS AFFECTED IN DR CR

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

PREPROCESSING ARTIFACTS

- dead detector elements- dead columns or rows- nonuniform response- heel effect (fixed systems)- light guide variations- ghosting

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Image Receptors

digital image characteristicsndash spatial resolutionndash sampling frequencyndash DEL (detector element size)ndash receptor size and matrix sizendash image signal (exposure related)ndash quantum mottlendash SNR (signal to noise ratio) orndash CNR (contrast to noise ratio)

ARRT definitions

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Image Acquisition and Readout

bull PSP (photo-stimulable phosphor)bull flat panel detectors

ndash (direct and indirect)

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

CR Imaging Platebull Constructionbull Image recorded on a thin sheet of plastic known

as the imaging plate - PSPbull Consists of several layersbull Phosphor

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Imaging Platebull Phosphor

bull BARIUM FLUORO bull HALIDE WITH bull A EUROPIUM BASE

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull Two types of digital radiographybull Indirect capture DR

bull Machine absorbs x-rays and converts them to light

bull CCD or thin-film transistor (TFT) converts light to electric signals

bull Computer processes electric signalsbull Images are viewed on computer

monitor

Digital Radiography

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull Direct capture DRbull Photoconductor

absorbs x-raysbull TFT collects signalbull Electrical signal is

sent to computer for processing

bull Image is viewed on computer screen

Digital Radiography

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Image Acquisition and Readout

flat panel detectorsPhosphors

ndash direct = Am SELENIUM

ndash indirect = Am SILICON

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull CR PSL light guide PMTPDbull Indirect CsIGOS contact layer PDTFT

arraybull Direct a-Se none TFT

arraybull CCDCMOS CsGOS lensfiber

CCDCMOS

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

CMOS

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

CMOS

bull Complimentary metal-oxide semi-conductor (CMOS) ndash A photographic detector

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull CCD and CMOS systems ndash both use a scintillator These systems are camera-like

bull they both use lenses to focus the light onto a detector

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull Digital Systemsbull electronic collimationbull grayscale rendition or look-up table (LUT)bull edge enhancement

ndash noise suppressionbull contrast enhancementbull system malfunctions (eg ghost image

banding erasure dead pixels readout problems printer distortion)

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Image Data Recognitionand Preprocessing shutter

bull Agfa uses the term collimation Kodak uses the term segmentation and Fuji uses the phrase ldquoexposure data recognitionrdquo

bull All systems use a region of interest to define the area where the part to be examined is recognized and the exposure outside the region of interest is subtracted

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull Excessive exposure to receptor without rescaling

bull Excessive exposure to receptor with rescaling

bull So in essence rescaling provided an acceptable image despite an excess level of exposure to the receptor

What about the dose to the patient

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Rescalingbull image pixel values to appear appropriate

display properly can lead to overexposing a patient

bull The visual cue to the technologist that overexposure has occurred isnrsquot present

bull With an analog system a technologist would have seen the image on the left as it came out of the processor and used the excessive density of the image as a visual cue to repeat the image

bull Rescaling forces a technologist to look elsewhere for signs that a proper exposure was used to produce an image

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Dose creep

bull refers to the potential to gradually increase patient exposure over time

bull However a technologist lacks visual feedback that additional radiation is being used to produce the images

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

DAPbull The dose area product (DAP) meter is a device that may

be interlinked with the x-ray unit to determine the actual patient entrance skin exposure dose with accurately calibrated equipment Currently no standards are established for using a dose area product meter

These two radiographs show the difference in entrance skin exposure measured by the DAP meter The area with a smaller exposure field size carries a lower exposure without reducing image quality

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Exposure Latitude

bull The analog receptor exposure latitude ranges from approximately

bull 30 underexposedbull to 50 overexposed relative tobull the ldquoidealrdquo exposure level

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Exposure Latitude

The digital image receptorbull exposure latitude ranges frombull approximately bull 50 underexposedbull to 100 over exposurebull relative to the ldquoidealrdquo exposure level

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

NoteIt is important to note that just because abull digital imaging system has the capacity tobull produce an image from gross underexposurebull or gross overexposure it does not equate tobull greater exposure latitude bull The reason the system is capable of producing

an image when significant exposure errors occur is through a process called automatic rescaling

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull In a digital system underexposure ofbull 50 or greater will result in a mottledbull image

bull 1048737 In a digital system overexposurebull greater than 200 of the ideal will resultbull in loss of image contrast

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Image EvaluationBrightness and Contrast in Images

bull Exposure Field Recognition Errorbull Gross Overexposurebull Excessive Scatter Striking the Receptorbull Excessive Fog on the Receptorbull Grid Cutoff bull Intra-Field or Off-Focus Radiationbull Wrong Menu Selection

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

EDR

bull Exposure Data Recognitionbull When laser scans it is looking for area of

plate that has exposurebull Some read from center out and look for

two sides of collimationbull Works best when image centered

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

S 12361 lat CXR

S 8357

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Exposure Numbers

bull The exposure numbers can only be used if all other parameters are correctndash Centering to platendash Collimation

bull Position over AEC look at mAs readout to determine if poor positioning caused light or dark image

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Same technique different centering and collimation

S 592 S 664

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

ARRT SPECS - DIGITAL

bull PACSbull HIS (hospital information system) - work

listbull RIS (radiology information system)bull DICOMbull Workflow (inappropriate documentation

lost images mismatched images corrupt data)

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

PACSbull Image is stored on a computer retrieval and

viewing system for digital imaging examinationsbull The PACS software provides ldquotoolsrdquo that enable

a PACS operator to manipulate images bull The basic image manipulations possible are

magnification and minification of an image altering image brightness and contrast and annotating the image using text symbols lines and arrows

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Picture Archival andCommunication Systems

bull Networked group of computers servers and archives to store digital images

bull Can accept any image that is in DICOM format

bull Serves as the file room reading room duplicator and courier

bull Provides image access to multiple users at the same time on-demand images electronic annotations of images and specialty image processing

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

HIS ndash RIS INTERFACE

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

RIS Data Storage

bull Less ERRORS

bull A radiology information system or RIS is a data system for patient-related functions in the radiology department Examples of functionality a RIS provides within a radiology department include (but are not limited to)

bull scheduling bull appointments bull collecting and displaying orders for radiologic

examinationsbull storing and displaying patient data bull tracking patients bull providing patient and order data to a PACS storing and

distributing radiology reports providing billing services and providing a database to track and project trends

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

HIS

bull A hospital information system or HIS is a paper andor data system that manages the administrative financial and clinical information necessary to operate a hospital or health care system

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Health Level 7 (HL7)

bull HL7 are the software standards established for exchanging electronic information in health care PACS is mainly concerned with images and data associated with images whereas HL7 sets standards for transmitting text-based information throughout a medical center

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Cassette-based systems

PSP plates

bull Turbid phosphors

bull Structured phosphors

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull Turbid Phosphor ndash A phosphor layer with a random distribution of phosphor crystals within the active layer

bull Structured (needle) phosphor ndash A phosphor layer with columnar phosphor crystals within the active layer Resembles needles lined up on end and packed together

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Exposure indexbull Cassette basedndash represents exposure level to platebull a Vendor specific valuesbull 1) Sensitivity ldquoSrdquo (Fuji Philips Konica) inversely related

to exposure- 200 S =1mR to the plate ndash optimal range 250-300 for trunk 75-125 for extremities

bull 2) Exposure Index (EI)- (Kodak) ndash directly related to exposure has a logarithmic component (change of 300 in EI = factor of 2 ie 1800 is exposed twice as much as 1500) optimal range 1800-1900

bull 3) Log Mean (LgM) - (Agfa) ndash directly related to exposure has a logarithmic component (change of 03 in LgM = factor of 2 ie 23 is exposed twice as much as 20) optimal range 19-21

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

bull MTF

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

MODULATION TRANSFER FUNCTION - MTF

bull A measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution

bull Every image can be described in terms of the amount of energy for each of its spatial frequency components

bull MTF often is regarded as the ideal expression of the image quality provided by a detector

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Exposure myths associated with digital systems

1 mAs ndash myth digital is mAs driven Truth digital is exposure driven The digitaldetector is unable to discriminate whether theexposure change was mAs or kVp Theonly thing that matters is exposure to pixels2 kVp ndash myth digital is kVp driven Truth see above3 Collimation ndash myth you cannot collimate Truth you can and should collimateInappropriate collimation will cause a histogram

analysis error

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Exposure myths associated with digital systems

4 Grid ndash myth cannot use grids and donrsquot need them

Truth digital systems are sensitive to scatter just like film in fact they are more sensitive Appropriate grid useis even more important A grid should be used when the remnant beam is more than 50 scatter chest larger than 24cm and anything else larger than 12cm

5 SID ndash myth magnification doesnrsquot occur with digital so SID is unimportant

TruthGeometric rules of recorded detail and distortion are unchanged from film to digital

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Exposure myths associated with digital systems

7 Fog ndash myth digital systems canrsquot be fogged by scatter or background radiation Truthdigital systems are more sensitive to both

8 Myth fluorescent lights fog PSP plates Truth that is not true

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next

Next

bull ODIA - Summer Reviewbull Prep for Registry Exam

• Digital Imaging Review
• Display Workstations
• CRT
• MONITORSDisplay Workstations
• LCD
• Slide 6
• Physician Review Stations Monitors
• Technologist QC Stations
• Technologist QC Station
• Slide 10
• The File Room Workstation
• Name the 3 types of monitors
• Image Display= MONITORS
• viewing conditions luminanceambient lighting
• WINDOW LEVEL WIDTH Which one controls Denisty (brightness)
• Slide 16
• Enhanced Visualization Image Processing
• Nyquist frequency Review
• Slide 19
• Slide 20
• Sampling Frequency Define helliphellip
• Sampling Frequency
• Nyquist Frequency
• Slide 24
• LOOK UP TABLE (LUT)
• Slide 26
• Image Receptors
• image signal (exposure related) Exposure Indicators
• Digital artifacts
• How else can Morie OCCUR
• quantum mottle
• PREPROCESSING ARTIFACTS
• Slide 33
• Slide 34
• Image Receptors (2)
• Image Acquisition and Readout
• CR Imaging Plate
• Imaging Plate
• Digital Radiography
• Digital Radiography (2)
• Image Acquisition and Readout (2)
• Slide 42
• CMOS
• CMOS (2)
• Slide 45
• Slide 46
• Image Data Recognition and Preprocessing shutter
• Rescaling
• Dose creep
• DAP
• Exposure Latitude
• Exposure Latitude (2)
• Note
• Slide 55
• Image Evaluation Brightness and Contrast in Images
• EDR
• Slide 58
• Slide 59
• Slide 60
• Exposure Numbers
• Same technique different centering and collimation
• ARRT SPECS - DIGITAL
• PACS
• Picture Archival and Communication Systems
• HIS ndash RIS INTERFACE
• RIS Data Storage
• HIS
• Health Level 7 (HL7)
• Slide 70
• Slide 71
• Slide 72
• Exposure index
• Slide 74
• MODULATION TRANSFER FUNCTION - MTF
• Exposure myths associated with digital systems
• Exposure myths associated with digital systems (2)
• Exposure myths associated with digital systems (3)
• Next