1. DICOM Singapore Seminar:
Consistent Presentation of Images:
Author:
Rob Horn
Agfa Healthcare
Chair, DICOM WG-06
Presenter:
Kevin O’Donnell
Toshiba Medical Systems Company
Member, DICOM WG-06

2. The Grayscale Image Presentation Problem:
The appearance of grayscale images displayed on different types of softcopy display devices or printed on different types of hardcopy output devices has often been inconsistent.

3. The Grayscale Consistency Problem:
Optimal image viewing parameters (e.g. window/ level) selected on one device appear different when displayed on a different device
Device capabilities/ characteristics vary - the same number of gray levels cannot be rendered or perceived on different devices
Displayed images look different from printed images
…other

4. Problems of Inconsistency
VOI chosen on one display device
Rendered on another with different display
Mass expected to be seen is no longer seen
mass visible
mass invisible
Slide Provided by David Clunie, Quintiles Intelligent Imaging

5. Problems of Inconsistency
0.5
1.5
1.0
3.0
Not all display levels are perceivable on all devices
Slide Provided by David Clunie, Quintiles Intelligent Imaging

6. Problems of Inconsistency
0.5
1.5
1.0
3.0
Not all display levels are perceivable on all devices
Slide Provided by David Clunie, Quintiles Intelligent Imaging

7. Problems of Inconsistency
Laser Printer
Digital Modality
Printed images don’t look like displayed images
Slide Provided by David Clunie, Quintiles Intelligent Imaging

8. Causes of Inconsistency
Gamut of device
Minimum/maximum luminance/density
Characteristic curve
Mapping digital input to luminance/density
Shape
Linearity
Ambient light or illumination

9. Causes of Inconsistency
1.0
.66
Display devices vary in the maximum luminance they can produce
Display CRT vs. film on a light box is an extreme example
Slide Provided by David Clunie, Quintiles Intelligent Imaging

10. Towards a Standard Display
Can’t use absolute luminance since display capabilities different
Can’t use relative luminance since shape of characteristic curves vary
Solution: exploit known characteristics of the contrast sensitivity of human visual system - contrast perception is different at different levels of luminance

11. Human Visual System Model contrast sensitivity
assume a target similar to image features
confirm model with measurements
Barten’s model
Grayscale Standard Display Function:
Input: Just Noticeable Differences (JNDs)
Output: absolute luminance

12. Printer Calibration Tools (Densitometer)

13. Display Calibration Tools (Photometer)
Slide Provided by Jerry Gaskill, Image Smiths Inc.

14. Perceptual Linearization
.01 .1 1 10
100
1000
200
400
600
800
Grayscale Standard Display Function
JND Index
Same number of Just Noticeable Difference == Same perceived contrast
Despite different change
in absolute luminance
Slide Provided by David Clunie, Quintiles Intelligent Imaging

15. Monitor Characteristic Curve
100 10
0.1
Ambient Light
0.01 50
100
150
200
250
300
Digital Driving Level
Slide Provided by David Clunie, Quintiles Intelligent Imaging

16. Standard Display Function
.01 .1 1 10
100
1000
200
400
600
800
Grayscale Standard Display Function
JND Index
Monitor’s Capability
Jmax == P-Value of 2n-1
Jmin == P-Value of 0
Minimum Luminance
+ Ambient Light
Maximum Luminance
Slide Provided by David Clunie, Quintiles Intelligent Imaging

17. Standardizing a Display
0.1 1 10
100 50
150
200
250
DDL or P-Values
Standard
Characteristic Curve
Slide Provided by David Clunie, Quintiles Intelligent Imaging

18. Standardizing a Display
Mapping P-Values to Input of Characteristic Curve (DDL’s) 50
100
150
200
250
300
P-Values
DDL
Slide Provided by David Clunie, Quintiles Intelligent Imaging

19. To Achieve Consistent Presentation of Images, the DICOM Standard Defines:
Basic Print Management with Presentation Look Up Table, for controlling the consistent appearance of preformatted images on printed output
Grayscale Softcopy Presentation State, for controlling the consistent appearance of images on softcopy display

20. Basic Print Management Meta SOP Class
Print (SCU)
Print (SCP)
Association Negotiation - “Contract Agreement”
Agreed set of SOP Classes and Transfer Syntaxes
( Basic Print Meta SOP Class)
Film Sheet
Basic Print Meta SOP Class consist of four SOP Classes
(Film Session, Film Box, Image Box, and Printer)
N-Create (create film sheet, format printer)
N-Set (place images on film sheet)
N-Action (request to print the film sheet)
N-Event-Report (status of the printer)
Slide Provided by Don Van Syckle, Merge Technologies Inc.

21. Example: A Radiologist “Flips” Chest XRAY Image on Softcopy Display

22. Example Continued: Radiologist Magnifies
Chest XRAY Image, Pans to Upper Right Hand Quadrant and Adds an Annotation
Suspected
area

23. Example Continued: Referring Physician Views the Original Image…
Radiologist:
Suspected
area
Referring Physician:
Radiologist Should Store the Viewing Parameters Using GSPS!

24. Grayscale Softcopy Presentation State:
Composite object containing the image display settings parameters
Composite object links to one or more images (Series, filters); stored using same Study Instance UID (same Storage SOP Class!)
Uses regular Storage services (C-STORE); uses Query/Retrieve services
GSPS SOP Instances are immutable: changes require a new SOP Instance UID
Note: generation and specific application of GSPS is outside the scope of DICOM, but not outside the scope of IHE (e.g. Virtual Image Set Split) 9

25. GSPS Module Table: IE Module Usage Patient M Study General Study
Patient Study U
Series
General Series
Presentation Series
Equipment
General Equipment
Presentation
Presentation State M
Modality LUT
C - Required if to be applied
Mask
C - Required if multi-frame and to be applied
VOI LUT
Softcopy Presentation LUT
Graphic Annotation
Spatial Transformation
C - Required if rotation, flipping or magnification are to be applied
Displayed Area M
Display Shutter
C - Required if to be applied and the Bitmap Display Shutter Module is not
present
Bitmap Display Shutter
C - Required if to be applied and the Display Shutter Module is not present
Overlay Plane
C - Required if to be applied or the BM
Displ. Shutter Module is present
Overlay/Curve Activation
C- Required if image contains curve or overlay which is to be displayed
Graphic Layer
C - Required if Graphic Annotation or Overlays or Curves are to be applied
SOP Common

26. DICOM Grayscale Image Transformation ModelV O I L U ( S u b c ) M k d l y A g e h p D .
Presentation
LUT
Transformation
Window/Level
or VOI LUT
Rescale Slope/Intercept
or Modality LUT
Original
Image
Display
P-Values
Grayscale Transformations
Shutter, Annotation and Spatial Transformations e 10

27. What about color ? Consistency is harder to achieve
Not just colorimetry (i.e. not just CIELAB)
Gamut of devices much more variable
Greater influence of psychovisual effects
Extensive standards efforts e.g. ICC
DICOM is defining color presentation in a manner very similar to grayscale, but utilizing the ICC profiles instead of the GSDF, see Supplement 100.
Many display and print devices already have ICC profiles, but few medical imaging devices support color presentation state.

28. Consistent Presentation is Provided by
Use of DICOM GSDF for calibration of monitors
Use of Presentation LUT for Grayscale Print
Creation of GSPS SOP Instances to capture the presentation of softcopy images.
Use of GSPS SOP Instances when displaying images from archives
( Devices that claim conformance to IHE Consistent Presentation of Images provide these functions. )