DICOM Singapore Seminar:

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DICOM Singapore Seminar
Consistent Presentation of Images

• Author
• Rob Horn
• Agfa Healthcare
• Chair, DICOM WG-06

Presenter Kevin ODonnell Toshiba Medical
Systems Company Member, DICOM WG-06
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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.
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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

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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
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Problems of Inconsistency
Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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Problems of Inconsistency
Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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Problems of Inconsistency

• Printed images dont looklike displayed images

Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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Causes of Inconsistency

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

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Causes of Inconsistency
Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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Towards a Standard Display

• Cant use absolute luminance since display
  capabilities different
• Cant 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

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Human Visual System

• Model contrast sensitivity
• assume a target similar to image features
• confirm model with measurements
• Bartens model
• Grayscale Standard Display Function
• Input Just Noticeable Differences (JNDs)
• Output absolute luminance

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Printer Calibration Tools (Densitometer)
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Display Calibration Tools (Photometer)
Slide Provided by Jerry Gaskill, Image Smiths Inc.
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Perceptual Linearization
Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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Monitor Characteristic Curve
Monitor Characteristic Curve
100
10
0.1
Ambient Light
0.01
0
50
100
150
200
250
300
Digital Driving Level
Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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Standard Display Function
Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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Standardizing a Display
Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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Standardizing a Display
Slide Provided by David Clunie, Quintiles
Intelligent Imaging
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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

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Basic Print Management Meta SOP Class
Slide Provided by Don Van Syckle, Merge
Technologies Inc.
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Example A Radiologist Flips Chest XRAY Image
on Softcopy Display
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Example Continued Radiologist Magnifies Chest
XRAY Image, Pans to Upper Right Hand Quadrant and
Adds an Annotation
Suspected area
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Example Continued Referring Physician Views the
Original Image
Referring Physician
Radiologist Should Store the Viewing Parameters
Using GSPS!
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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)

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GSPS Module Table
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DICOM Grayscale Image Transformation Model
e
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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.

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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 Imagesprovide these
  functions. )