Post on 27-Dec-2015
RT 244 -12 Wk 14Digital Artifacts amp Imaging ERRORS
The advantages of CR are its large dynamic range digital format portability and post-processing capability
But not PERFECT ndashImaging Errors can still occur
See NOTES at bottom of slides for additional information
Some information obtained from AR Online raquo Current Issue raquo Artifacts and misadventures in digital radiography
By Charles E Willis PhD DABR Stephen K Thompson MS DABR S Jeff Shepard MS DABRVolume 33 Number 1 January 2004 1
Artifacts
bull Any irregularity on an image that is not caused by proper shadowing of tissue by the primary x-ray beam
bull Are undesirable optical densities or blemishes on a radiograph
bull Can be very interesting at times You become the detective what caused that
2
bull CR artifacts require special attention bull This is due to the fact that CR artifacts may be
produced from various components of the CR system itself
bull Artifacts may also be generated by the users who are not aware of the proper imaging techniques or selection of appropriate image processing protocols
bull Since CR is also very sensitive to scattered radiation it is vital that anti-scattered grids be used as in conventional radiography
bull Radiographers should be concerned since these may generate unwanted artifacts that could not be corrected by any image processing algorithm
3
Artifact Classification Review of FilmScreen
4
Artifact Classification Digital ndash CR amp DR
5
OPTIMIZATION OF CR IMAGES
Quality of CR imagesbullTechnologists are the key personsbull delivering good quality radiographsbulldose given to the patients bullCR images can NOT always be adjusted after exposing bullCRITICAL to CRDR Imaging isTechnique Positioning Collimation
6
Optimization of a CR image quality may be achieved by optimizing the following
factors
bull OBJECT ARTIFACTSndashPositioning and collimation
bull Exposure techniquesbull Image processing selectionbull Lifetime of the PSP
7
CR Artifactsbull Positioning errorsbull Collimation errorsbull Backscatter radiationbull LUT selectionhistogram
8
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Artifacts
bull Any irregularity on an image that is not caused by proper shadowing of tissue by the primary x-ray beam
bull Are undesirable optical densities or blemishes on a radiograph
bull Can be very interesting at times You become the detective what caused that
2
bull CR artifacts require special attention bull This is due to the fact that CR artifacts may be
produced from various components of the CR system itself
bull Artifacts may also be generated by the users who are not aware of the proper imaging techniques or selection of appropriate image processing protocols
bull Since CR is also very sensitive to scattered radiation it is vital that anti-scattered grids be used as in conventional radiography
bull Radiographers should be concerned since these may generate unwanted artifacts that could not be corrected by any image processing algorithm
3
Artifact Classification Review of FilmScreen
4
Artifact Classification Digital ndash CR amp DR
5
OPTIMIZATION OF CR IMAGES
Quality of CR imagesbullTechnologists are the key personsbull delivering good quality radiographsbulldose given to the patients bullCR images can NOT always be adjusted after exposing bullCRITICAL to CRDR Imaging isTechnique Positioning Collimation
6
Optimization of a CR image quality may be achieved by optimizing the following
factors
bull OBJECT ARTIFACTSndashPositioning and collimation
bull Exposure techniquesbull Image processing selectionbull Lifetime of the PSP
7
CR Artifactsbull Positioning errorsbull Collimation errorsbull Backscatter radiationbull LUT selectionhistogram
8
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
bull CR artifacts require special attention bull This is due to the fact that CR artifacts may be
produced from various components of the CR system itself
bull Artifacts may also be generated by the users who are not aware of the proper imaging techniques or selection of appropriate image processing protocols
bull Since CR is also very sensitive to scattered radiation it is vital that anti-scattered grids be used as in conventional radiography
bull Radiographers should be concerned since these may generate unwanted artifacts that could not be corrected by any image processing algorithm
3
Artifact Classification Review of FilmScreen
4
Artifact Classification Digital ndash CR amp DR
5
OPTIMIZATION OF CR IMAGES
Quality of CR imagesbullTechnologists are the key personsbull delivering good quality radiographsbulldose given to the patients bullCR images can NOT always be adjusted after exposing bullCRITICAL to CRDR Imaging isTechnique Positioning Collimation
6
Optimization of a CR image quality may be achieved by optimizing the following
factors
bull OBJECT ARTIFACTSndashPositioning and collimation
bull Exposure techniquesbull Image processing selectionbull Lifetime of the PSP
7
CR Artifactsbull Positioning errorsbull Collimation errorsbull Backscatter radiationbull LUT selectionhistogram
8
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Artifact Classification Review of FilmScreen
4
Artifact Classification Digital ndash CR amp DR
5
OPTIMIZATION OF CR IMAGES
Quality of CR imagesbullTechnologists are the key personsbull delivering good quality radiographsbulldose given to the patients bullCR images can NOT always be adjusted after exposing bullCRITICAL to CRDR Imaging isTechnique Positioning Collimation
6
Optimization of a CR image quality may be achieved by optimizing the following
factors
bull OBJECT ARTIFACTSndashPositioning and collimation
bull Exposure techniquesbull Image processing selectionbull Lifetime of the PSP
7
CR Artifactsbull Positioning errorsbull Collimation errorsbull Backscatter radiationbull LUT selectionhistogram
8
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Artifact Classification Digital ndash CR amp DR
5
OPTIMIZATION OF CR IMAGES
Quality of CR imagesbullTechnologists are the key personsbull delivering good quality radiographsbulldose given to the patients bullCR images can NOT always be adjusted after exposing bullCRITICAL to CRDR Imaging isTechnique Positioning Collimation
6
Optimization of a CR image quality may be achieved by optimizing the following
factors
bull OBJECT ARTIFACTSndashPositioning and collimation
bull Exposure techniquesbull Image processing selectionbull Lifetime of the PSP
7
CR Artifactsbull Positioning errorsbull Collimation errorsbull Backscatter radiationbull LUT selectionhistogram
8
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
OPTIMIZATION OF CR IMAGES
Quality of CR imagesbullTechnologists are the key personsbull delivering good quality radiographsbulldose given to the patients bullCR images can NOT always be adjusted after exposing bullCRITICAL to CRDR Imaging isTechnique Positioning Collimation
6
Optimization of a CR image quality may be achieved by optimizing the following
factors
bull OBJECT ARTIFACTSndashPositioning and collimation
bull Exposure techniquesbull Image processing selectionbull Lifetime of the PSP
7
CR Artifactsbull Positioning errorsbull Collimation errorsbull Backscatter radiationbull LUT selectionhistogram
8
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Optimization of a CR image quality may be achieved by optimizing the following
factors
bull OBJECT ARTIFACTSndashPositioning and collimation
bull Exposure techniquesbull Image processing selectionbull Lifetime of the PSP
7
CR Artifactsbull Positioning errorsbull Collimation errorsbull Backscatter radiationbull LUT selectionhistogram
8
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
CR Artifactsbull Positioning errorsbull Collimation errorsbull Backscatter radiationbull LUT selectionhistogram
8
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Positioning of Part Collimationbull 2 or more two projections on one IR bull Is not a good practice with CR technique bull since double or multiple exposures on a single
PSP) can lead to a failure of the image processing software to detect the image boundary
bull Matching the positioning and collimation with the image processing parameters is also crucial
bull Image processing will eventually fail to process since the input information is totally different
9
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
10
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Errors in collimation can cause mistakes in detection of the boundary with a dramatic loss of image
contrast
11
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
12
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Positioning Errors
13
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Collimation Errors 14
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
15
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Loss of contrast due to partitioning errors
16
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
17
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Alignment Error Same technique different centering and collimation
S 592S 664
18
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
19
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
2 on 24 X 301048697Same technique1048697Rescaling error
10486972 on 24 X 301048697Technique adjusted
20
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Single field per plate - better
21
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
What is the problem
22
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Placement of gonadal shields is no longer trivial
but may adversely affect image quality
23
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Software to compensate for metal in patient
24
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Same pt ndash what improved this image
25
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Acquiring good quality images
bull Regardless of the acquisition technology good radiographic images can be produced only when certain fundamental requirements are met
bull Appropriate radiographic technique must be used bull proper tube potential (kVp) bull beam current (mAs) bull source-to-image distance (SID) bull collimation bull alignment of the X-ray central ray bull and positioning of detector and subject for the specific
anatomic projection
26
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Exposure techniquesbull CR may be operated at a different film speed
and then optimizing the exposure technique accordingly
bull Existing CR has a speed similar to medium speed film-screen system (200 -400) while spatial resolution is still generally inferior
bull Proper selection of an image processing algorithm specific to each type of x-ray examination is thus important
bull The technical skills of radiographers definitely play a crucial role in determining the quality of the radiographic image
27
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Exposure factor ldquocreepbull related to the wide exposure latitude of DR bull noise in DR images exposed at one-fourth to one-
half of the appropriate level bull artifacts are generally not apparent until the
exposure exceeds 10 times the appropriate level bull Technologists avoid repeating an underexposed
study by routinely increasing the radiographic technique
bull Thus the potential for gross overexposure exists in DR Image optical density (OD) the usual indicator of proper exposure is arbitrary in DR
bull Managment of exposure factor in DR must rely on the value of a derived exposure indicator
28
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Errors in the selection of the anatomic projection can cause inappropriate processing
29
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Wrong Algorithm
30
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
OverUnder Exposedbull Even though a CR image may be adjusted to improve
the image visibility in the cases of over- or under-exposures it would still be impossible for an image processing to improve the visibility of clinical features that were not available in the raw image
31
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
32
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
33
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
34
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
the same image now shows acceptable image quality as a result of proper selection of image processing
35
bull Example of artifacts in CR an image with loss of contrast as a result of improper selection of image processing
bull
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
36
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
37
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Too many X-rays are a disservice to the patient and may also produce poor images (Figure 3)
38
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Whether from underexposure or misalignment of a scatter reduction grid too few X-rays produce noisy images
39
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Different exam parametersin different rooms
40
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Double exposure is a classic operator error
bull that constitutes approximately 2 of all rejected images
bull The consequence of double exposure can be either a single repeated examination when an inanimate object is involved (Figure 11) or two repeated examinations when two patients are involved (Figure 12)
bull In DR double exposures can also be caused by power interruptions and communications errors as well as by inadequate erasure secondary to overexposure or erasure mechanism failure
41
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Double exposure (Figure 11)
42
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Double exposure 12
43
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
44
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
8
45
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Edge Enhancementbull The secondary function of image processing is to
customize contrast in the region of interest bull This type of image processing includes modifying the
image to enhance the contrast and sharpness of some features while compromising the contrast and sharpness of others
bull as well as modifying the image to make it appear more like a conventional film
bull This secondary image processing is applied in a manner that is usually specific to the anatomic projection
46
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
standard image edge sharpening
47
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
bull Halo effect with Edge enhancement48
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
49
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Post Processing
bull An auxiliary purpose of image processing is to improve the usability of the digital image
bull This includes imprinting demographic overlays adding annotations applying borders and shadow masks flipping and rotating increasing magnification conjoining images for special examinations like scoliosis and modifying the sequence of views
bull This processing may require a separate QC workstation
50
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
51
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
IR Artifact - Digital
bull Pixel Failure = CR amp DR plates should last for thousands of exposures Interpolation can be used to fix defects in a small area
bull Ghosting artifacts = exposure to environmental radiation or incomplete erasure
52
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
background radiation
53
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Image Receptor Artifacts
bull Debris on image receptor in DR can be confused with foreign bodies
54
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Image Receptor Artifacts
Line caused from dirt collected in a CR Reader
55
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
imaging plate was not fully erased before the chest examination was performed
56
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Dirt on screens
57
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
9
58
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
59
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
60
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
61
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
62
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Lifetime of the PSPbull One of the major advantages of CR is that the
phosphor plate is reusable bull However there are a number of factors that may
affect the lifetime of an imaging plate bull The plates are subjected to normal wear and tear
from scratches scuffs cracks and contamination with dust and dirt which may interfere with the production of a good image
bull The establishment of a well-organized quality control program will play an important role in assessing the clinical quality of the imaging plate This may easily be carried out by artifact assessment and uniformity evaluation across the plate
63
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Software Artifacts
64
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Processing Errors
65
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Digital Radiography Image Sampling
bull Image sampling the plate is scanned and the imagersquos location and its orientation are determined The size of the signal is then determined and a value is placed on each pixel A histogram is generated from the image data
bull The raw data used to form the histogram are compared with a ldquonormalrdquo histogram of the same body part by the computer
66
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
The Nyquist Theorem
bull States that when sampling a signal (such as the conversion from an analog to a digital image) the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
bull At least twice the number of pixels needed to form the image must be sampled If too few pixels are sampled the result will be a lack of resolution
67
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Aliasing amp Grid errors = Moireacute
bull Spatial frequency is greater than the Nyquist frequency a wraparound image is produced moireacute effect
bull Stationary Grids grid lines and the scanning laser are parallel moireacute effect
68
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Moireacute effect
69
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Software Artifacts
bull Image Compression ndash Used with teleradiology
Compression techniques ldquolosslessrdquo or ldquolossyrdquo
70
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Image Compression
bull Lossless compression image can be reconstructed to be exactly the same as the original image Compressed 10 or 50
bull Lossy compression image is compressed 1001 Used only when fine detail is not required Not useful for medical imaging
71
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Image Compression
72
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
bull Wider dynamic range means that technologists have to pay attention to exposure indicator values instead of brightness and contrast Without this attention patient dose will escalate If exposure indicator logs are available they need to be evaluated If they arent this will need to be done manually
73
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74
Misuses of image processing include
bull compensating for inappropriate radiographic technique bull compensating for poor calibration of acquisition and display
devices bull and surreptitious deletion of nondiagnostic imagesbull Image processing to recover nondiagnostic images to prevent
re-exposure should be a last resort not a routine activity bull Routine reprocessing indicates a problem with automatic
image processing or technical practice Access to image-processing software is essential to develop and maintain appropriate processing parameters
74