DICOM Singapore Seminar:DICOM Singapore Seminar:

Author:Author:

Rob HornRob Horn

Agfa HealthcareAgfa Healthcare

Chair, DICOM WG-06Chair, DICOM WG-06

Consistent Presentation of Images:Consistent Presentation of Images:

Presenter:Presenter:

Kevin O’DonnellKevin O’Donnell

Toshiba Medical Systems CompanyToshiba Medical Systems Company

Member, DICOM WG-06Member, DICOM WG-06

The Grayscale Image Presentation The Grayscale Image Presentation Problem: 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.

Optimal image viewing parameters (e.g. window/ level) Optimal image viewing parameters (e.g. window/ level) selected on one device appear different when displayed selected on one device appear different when displayed on a different deviceon a different device

Device capabilities/ characteristics vary - the same Device capabilities/ characteristics vary - the same number of gray levels cannot be rendered or perceived number of gray levels cannot be rendered or perceived on different deviceson different devices

Displayed images look different from printed imagesDisplayed images look different from printed images ……otherother

The Grayscale Consistency Problem: The Grayscale Consistency Problem:

Problems of InconsistencyProblems of Inconsistency

mass visible mass invisible

•VOI chosen on one display device

•Rendered on another with different display

•Mass expected to be seen is no longer seen

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Problems of InconsistencyProblems of Inconsistency

0.5

1.5

1.0

3.0

•Not all display levelsare perceivable on alldevices

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Problems of InconsistencyProblems of Inconsistency0.5

1.5

1.0

3.0

•Not all display levelsare perceivable on alldevices

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Problems of InconsistencyProblems of Inconsistency

Digital Modality Laser Printer

•Printed images don’t looklike displayed images

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Causes of InconsistencyCauses of Inconsistency

Gamut of deviceGamut of device– Minimum/maximum luminance/densityMinimum/maximum luminance/density

Characteristic curveCharacteristic curve– Mapping digital input to luminance/densityMapping digital input to luminance/density– ShapeShape– LinearityLinearity

Ambient light or illuminationAmbient light or illumination

Causes of InconsistencyCauses of Inconsistency

1.0 .66

•Display devicesvary in the maximumluminance they canproduce

•Display CRT vs. film on a light box is an extreme example

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Towards a Standard DisplayTowards a Standard Display

Can’t use absolute luminance since display Can’t use absolute luminance since display capabilities differentcapabilities different

Can’t use relative luminance since shape of Can’t use relative luminance since shape of characteristic curves varycharacteristic curves vary

Solution: exploit known characteristics of Solution: exploit known characteristics of the contrast sensitivity of human visual the contrast sensitivity of human visual system - contrast perception is different at system - contrast perception is different at different levels of luminancedifferent levels of luminance

Human Visual SystemHuman Visual System

Model contrast sensitivityModel contrast sensitivity– assume a target similar to image featuresassume a target similar to image features– confirm model with measurementsconfirm model with measurements– Barten’s modelBarten’s model

Grayscale Standard Display Function:Grayscale Standard Display Function:– Input: Just Noticeable Differences (JNDs)Input: Just Noticeable Differences (JNDs)– Output: absolute luminanceOutput: absolute luminance

Printer Calibration Tools Printer Calibration Tools (Densitometer)(Densitometer)

Display Calibration Tools Display Calibration Tools (Photometer)(Photometer)

Slide Provided by Jerry Gaskill, Image Smiths Inc.

Perceptual LinearizationPerceptual Linearization

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Grayscale Standard Display Function

JND Index

Same number of Just Noticeable Difference == Same perceived contrast

Despite different changein absolute luminance

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Monitor Characteristic CurveMonitor Characteristic Curve

Monitor Characteristic Curve

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0 50 100 150 200 250 300Digital Driving Level

Ambient Light

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Standard Display FunctionStandard Display Function

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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+ Ambient Light

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Standardizing a DisplayStandardizing a Display

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DDL or P-Values

Standard

Characteristic Curve

Slide Provided by David Clunie, Quintiles Intelligent Imaging

Standardizing a DisplayStandardizing a Display

Mapping P-Values to Input of Characteristic Curve (DDL’s)

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P-Values

DD

L

Slide Provided by David Clunie, Quintiles Intelligent Imaging

To Achieve Consistent Presentation of To Achieve Consistent Presentation of Images, the DICOM Standard Defines:Images, the DICOM Standard Defines:

Basic Print Management with Presentation Look Basic Print Management with Presentation Look Up Table, for controlling the consistent Up Table, for controlling the consistent appearance of preformatted images on printed appearance of preformatted images on printed outputoutput

Grayscale Softcopy Presentation State, for Grayscale Softcopy Presentation State, for controlling the consistent appearance of images controlling the consistent appearance of images on softcopy displayon softcopy display

Basic Print Management Meta SOP ClassBasic Print Management Meta SOP Class

Print (SCU)Print (SCU) Print (SCP)

Association Negotiation - “Contract Agreement”Association Negotiation - “Contract Agreement”

Agreed set of SOP Classes and Transfer SyntaxesAgreed set of SOP Classes and Transfer Syntaxes( Basic Print Meta SOP Class)( Basic Print Meta SOP Class)

Film SheetFilm Sheet

Basic Print Meta SOP Class consist of four SOP ClassesBasic Print Meta SOP Class consist of four SOP Classes(Film Session, Film Box, Image Box, and Printer)(Film Session, Film Box, Image Box, and Printer)

N-Create (create film sheet, format printer)N-Create (create film sheet, format printer)

N-Set (place images on film sheet)N-Set (place images on film sheet)

N-Action (request to print the film sheet)N-Action (request to print the film sheet)

N-Event-Report (status of the printer)N-Event-Report (status of the printer)

Slide Provided by Don Van Syckle, Merge Technologies Inc.

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

Suspected

area

Example Continued: Radiologist Magnifies Example Continued: Radiologist Magnifies Chest XRAY Image, Pans to Upper Right Chest XRAY Image, Pans to Upper Right Hand Quadrant and Adds an AnnotationHand Quadrant and Adds an Annotation

Referring Physician:Radiologist:

Suspected

area

Example Continued: Referring Physician Example Continued: Referring Physician Views the Original Image…Views the Original Image…

Radiologist Should Store the Viewing Parameters Using GSPS!Radiologist Should Store the Viewing Parameters Using GSPS!

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)

Grayscale Softcopy Presentation State:Grayscale Softcopy Presentation State:

IEIE ModuleModule UsageUsage

PatientPatient PatientPatient MM

StudyStudy General StudyGeneral Study MM

Patient StudyPatient Study UU

SeriesSeries General SeriesGeneral Series MM

Presentation SeriesPresentation Series MM

EquipmentEquipment General EquipmentGeneral Equipment MM

PresentationPresentation Presentation StatePresentation State MM

Modality LUTModality LUT C - Required if to be appliedC - Required if to be applied

MaskMask C - Required if multi-frame and to be appliedC - Required if multi-frame and to be applied

VOI LUTVOI LUT C - Required if to be appliedC - Required if to be applied

Softcopy Presentation LUTSoftcopy Presentation LUT MM

Graphic AnnotationGraphic Annotation C - Required if to be appliedC - Required if to be applied

Spatial TransformationSpatial Transformation C - Required if rotation, flipping or magnification are to be appliedC - Required if rotation, flipping or magnification are to be applied

Displayed AreaDisplayed Area MM

Display ShutterDisplay Shutter C - Required if to be applied and the Bitmap Display Shutter Module is notC - Required if to be applied and the Bitmap Display Shutter Module is notpresentpresent

Bitmap Display ShutterBitmap Display Shutter C - Required if to be applied and the Display Shutter Module is not presentC - Required if to be applied and the Display Shutter Module is not present

Overlay PlaneOverlay Plane C - Required if to be applied or the BM C - Required if to be applied or the BM Displ. Shutter Module is presentDispl. Shutter Module is present

Overlay/Curve ActivationOverlay/Curve Activation C- Required if image contains curve or overlay which is to be displayedC- Required if image contains curve or overlay which is to be displayed

Graphic LayerGraphic Layer C - Required if Graphic Annotation or Overlays or Curves are to be appliedC - Required if Graphic Annotation or Overlays or Curves are to be applied

SOP CommonSOP Common MM

GSPS Module Table:GSPS Module Table:

DICOM Grayscale Image DICOM Grayscale Image Transformation ModelTransformation Model

Trans formation

VOI LUT(Subtrac t ion)

Mas kModality

LUT

Trans formation

Annotat ion

Image

Trans format ion

Shutter Spat ia lTrans format ion

Annotat ion

Disp. Area

Presentation LUT

Presentation LUT

Transformation

Window/Levelor VOI LUT

Rescale Slope/Interceptor Modality LUT

OriginalImage

DisplayP-Values

Grayscale Transformations

Shutter, Annotation and Spatial Transformations

What about color ?What about color ?

Consistency is harder to achieveConsistency is harder to achieve– Not just colorimetry (i.e. not just CIELAB)Not just colorimetry (i.e. not just CIELAB)– Gamut of devices much more variableGamut of devices much more variable– Greater influence of psychovisual effectsGreater influence of psychovisual effects

Extensive standards efforts e.g. ICCExtensive standards efforts e.g. ICC DICOM is defining color presentation in a manner DICOM is defining color presentation in a manner

very similar to grayscale, but utilizing the ICC very similar to grayscale, but utilizing the ICC profiles instead of the GSDF, see Supplement 100.profiles instead of the GSDF, see Supplement 100.– Many display and print devices already have ICC Many display and print devices already have ICC

profiles, but few medical imaging devices support color profiles, but few medical imaging devices support color presentation state.presentation state.

Consistent Presentation is Consistent Presentation is Provided byProvided by

Use of DICOM GSDF for calibration of monitorsUse of DICOM GSDF for calibration of monitors Use of Presentation LUT for Grayscale PrintUse of Presentation LUT for Grayscale Print Creation of GSPS SOP Instances to capture the Creation of GSPS SOP Instances to capture the

presentation of softcopy images.presentation of softcopy images. Use of GSPS SOP Instances when displaying Use of GSPS SOP Instances when displaying

images from archivesimages from archives

( Devices that claim conformance to ( Devices that claim conformance to IHE Consistent Presentation of ImagesIHE Consistent Presentation of Imagesprovide these functions. )provide these functions. )