COMPUTED RADIOGRAPHY (CR)COMPUTED RADIOGRAPHY (CR)Moving with the timeMoving with the time

Avi Avner BVSc BSc CVR DVDI MRCVSAvi Avner BVSc BSc CVR DVDI MRCVS

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CRCR--BasicsBasicsA five step process:

1. X-ray image received on phosphor plate

2. Image extracted from phosphor plate by

Laser (Raw image)

3. Raw image processed for quality

improvement

4. Final image in DICOM format

5. DICOM image can be either printed,

burned on CD, or sent to PACS

Image Plate Plate reader Quality control monitor

Workstation

Computed radiography

CR 30CR 30--X X -- WorkflowWorkflow

1NX Receives DMW (*)

from RIS

5CR 30-X Scans

image

4Identify image (Direct ID)

3Insert cassette in digitizer

6Control image quality

8Cassette ready for next

image

2Take Image

(*) DMW = DICOM Modality worklist

7DICOM Print or Archive

PACS system

Hardcopy printer

CR 30-X Digitizer and NX Modality Workstation

RIS system

Firewire connection

IMAGE PLATEIMAGE PLATE

�� Photosensitive phosphor Photosensitive phosphor

layer (e.g. europium layer (e.g. europium

activated barium activated barium

fluorohalidefluorohalide

�� Thin and flexibleThin and flexible

�� Placed in a conventional Placed in a conventional

cassettecassette

�� Stores the latent image Stores the latent image

after xafter x--ray exposureray exposure

LabelClip

Format

Opening ock

Shutter Opening Mechanism

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CONDUCTANCE BAND (LOW ENERGY LEVEL)

VALENCE BAND (HIGH ENERGY LEVEL)

X-Ray

Photon

PHOSPHOR PLATE

PhotoElectron

Trap

UV Photon

Laser

light

PM

Image: Capture, Reading, DetectionExposure,

Exposure

stage

Reading

stage

CR - Physics

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1. Plate is scanned by the laser

Scanning Procedure

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Scanning Procedure

3. Plate is erased with

light (not laser) and

returned to the cassette

2. Blue light (diffused)

is emitted from the

plate and detected by

the photomultiplier

QUALITY CONTROL QUALITY CONTROL WORKSTATIONWORKSTATION

��Digital data transferred Digital data transferred

��Raw data adjusted by Raw data adjusted by

softwaresoftware

��Processing Processing

algorithmalgorithm

��Define contrast, Define contrast,

latitude and edge latitude and edge

enhancementenhancement

PACS AND WORKSTATIONPACS AND WORKSTATION

Picture Archiving and Communication System

Limitations of Limitations of Conventional radiographyConventional radiography

Limitations of Limitations of conventional radiologyconventional radiology

�� Films cannot tolerate a wide range in Films cannot tolerate a wide range in

radiation exposure (D logE curve)radiation exposure (D logE curve)

�� One has to chose between good One has to chose between good

contrast and good latitudecontrast and good latitude

�� Image cannot be adjusted once takenImage cannot be adjusted once taken

�� Require space for dark room and film/ Require space for dark room and film/

chemicals storage.chemicals storage.

Limitations of screenLimitations of screen--film film systemssystems

�� Price of films and chemicals is Price of films and chemicals is

constantly going up (4constantly going up (4--10% per year)10% per year)

�� Need several exposures to show Need several exposures to show

different tissues (bone vs soft tissue)different tissues (bone vs soft tissue)

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Advantages of CRAdvantages of CR

�� Image quality comparable with to Image quality comparable with to

conventional screenconventional screen--film systemsfilm systems

�� Wide dynamic rangeWide dynamic range-- ability to image ability to image

structures of different attenuation structures of different attenuation

values (thorax and abd)values (thorax and abd)

�� Reduction of repeat exposuresReduction of repeat exposures

Advantages of CRAdvantages of CR

�� CR is compatible with most CR is compatible with most

conventional xconventional x--ray systemsray systems

�� Increased savings: no film, chemicals, Increased savings: no film, chemicals,

dark room and storage room requireddark room and storage room required

�� Computer processing of raw image: Computer processing of raw image:

brightness, contrast, sharpness brightness, contrast, sharpness

enhancement, zooming, enhancement, zooming,

measurementsmeasurements……

Advantages of CRAdvantages of CR

� CR is more tolerant of under / over exposure (wide latitude)

� Ability to extract information not possible on conventional radiographs (e.g edge enhancement, masking, cropping)

�� Faster image acquisitionFaster image acquisition

Advantages of CRAdvantages of CR

�� DICOMDICOM--Digital imaging Digital imaging

communications in medicinecommunications in medicine

�� PACSPACS-- Images retrieved from Images retrieved from

computer archivecomputer archive

�� TeleradiologyTeleradiology

ADVANTAGE: ADVANTAGE: LATITUDE AND CONTRASTLATITUDE AND CONTRAST

ADVANTAGE: ADVANTAGE: LATITUDE AND CONTRASLATITUDE AND CONTRAS

ADVANTAGES: ADVANTAGES: BONE AND SOFT TISSUEBONE AND SOFT TISSUE

Disadvantages of CRDisadvantages of CR

�� Initial cost Initial cost

�� Additional costAdditional cost

�� Transition to a new systemTransition to a new system

�� Wider latitude Wider latitude –– Tend to overexposeTend to overexpose--

degrade contrast.degrade contrast.

Disadvantages of CRDisadvantages of CR

�� IP sensitive to fogging: use grid, need IP sensitive to fogging: use grid, need

to be erased dailyto be erased daily

UNDEREXPOSURE UNDEREXPOSURE ‘‘QUANTUM MOTTLEQUANTUM MOTTLE’’

UNDEREXPOSURE UNDEREXPOSURE ‘‘QUANTUM MOTTLEQUANTUM MOTTLE’’

OVEREXPOSURE OVEREXPOSURE ‘‘CLIPPINGCLIPPING’’

EDGE ENHANCEMENTEDGE ENHANCEMENT→→→→→→→→`̀ÜÜBERSCHWINGERBERSCHWINGER’’

EDGE ENHANCEMENT EDGE ENHANCEMENT

Optimization of imagesOptimization of images

�� Erase plate not used for 24hrsErase plate not used for 24hrs

�� Scatter controlScatter control-- GridGrid

�� Scatter controlScatter control-- avoid overexposureavoid overexposure

�� Centering / collimationCentering / collimation-- histogram histogram

should represent anatomyshould represent anatomy

�� CollimationCollimation-- reduce scatter and reduce scatter and

improves contrastimproves contrast

Optimization of imagesOptimization of images

�� Multiple fields per IPMultiple fields per IP-- not not

recommended.recommended.

�� If multiple fields: uniform distributionIf multiple fields: uniform distribution--

symmetry, strict collimationsymmetry, strict collimation-- no no

overlap.overlap.

Practical tipsPractical tips

�� Systems breakSystems break-- reliable servicereliable service

�� Computer will eventually crash (3Computer will eventually crash (3--

5yrs)5yrs)

�� Vendor reliability (going out of Vendor reliability (going out of

business)business)-- Safety net.Safety net.

�� BackBack--up your system outside the main up your system outside the main

serverserver

Practical tipsPractical tips

�� Purchase price may only be just the Purchase price may only be just the

beginningbeginning-- make sure you know what make sure you know what

you are getting (you may not be you are getting (you may not be

getting the system that was shown to getting the system that was shown to

you)you)

�� Know who is providing your serviceKnow who is providing your service

�� Service: contract, software upgrade, Service: contract, software upgrade,

computer crashes, replacing computercomputer crashes, replacing computer

Practical tips: focus onPractical tips: focus on

�� Image quality Image quality –– Image processing has Image processing has

greatest effect greatest effect

�� MultiMulti--scale Image Contrast scale Image Contrast

Amplification (MUSICAAmplification (MUSICA--Agfa)Agfa)

��MUSICA (Agfa)MUSICA (Agfa) תוכנת עיבוד התמונה תוכנת עיבוד התמונה

מאפשרת קבלת תמונה דיאגנוסטית באיכות מאפשרת קבלת תמונה דיאגנוסטית באיכות

CRCRהגבוהה ביותר הקיימת כיום במערכות הגבוהה ביותר הקיימת כיום במערכות

The tip of the dayThe tip of the day

��Where you buy from is as Where you buy from is as

important as what you buyimportant as what you buy

�� Image quality Image quality –– Image Image

processing has greatest effect processing has greatest effect

(e.g. MUSICA(e.g. MUSICA--Agfa)Agfa)