gsps.md

from: http://dicom.nema.org/dicom/Conf-2005/Day-2_Selected_Papers/B304_Harvey&DC_UserInterfaceIssuesForPresentationStates.pdf

User Interface Issues for DICOM Presentation StatesDICOM Presentation States

Overview of Softcopy Presentation State (GSPS)Presentation State (GSPS)

• Added in 1999 as supplement 33
• Major departure for DICOM moving from data content and transmission into display
• Closely related to (but independent of) Supplement 28/Part 14 (Grayscale Standard Display Function)

GSPS Design

• 3GSPS DesignGSPS Design
• GSPS objects may be created at any time after imaging by any equipment
• GSPS are independent of the original image(s) and do NOT require modifications to the original image(s)
• Handled exactly like other instance objects
  • C-STORE, G-FIND, C-MOVE etc.
  • Easy for existing SCPs to handle
• No specific GSPS support in the Q/R model

Items controlled by GSPS

• All LUTs/transformations
  • Modality
  • VOI
  • Presentation
• Displayed Area & Shuttering
• Rotation & Flipping
• Mask Subtraction
• Independent Annotations
  • Text & graphics
  • Both image & display relative
• Activation of overlays in the image, or in the GSPS object

Place of GSPS objects in the DICOM Model

• Strictly part of one study
• Only refer to image(s) in that study
• In their own series
• May be stored on off-line media etc.
• Generally, they may be treated just like any other composite object

Relationship to Images

• One "manifest" (Referenced Series Sequence) sequence defines a list of images to which this PS object relates
• Huge choice of granularity
  • All series in a study
  • One or more specific series
  • One or more specific images
  • One of more specific frames within an image
  • Any combination of the above!

"Top level" Items: No reference to series / images

• Masking
• Shuttering (geometric & overlay)
• Spatial Transformation (Rotate & Flip)
• Modality LUT/rescale
• Presentation LUT
• Overlay Activation

"Image specific" Items: With Reference Image Sequence

• Displayed Area
• Annotations - graphic & Text
• VOI LUT/Windowing

How PS objects may be created

• Automatically by the modality
  • As default or reflection of radiographer choices
  • As part of PGP
• Explicitly by users
  • As part of reporting
  • For conferences etc.
  • For teaching
  • etc.

Key Object Note Support

• KON (and SR) objects can specify the relationship between images and GSPS objects
• Achieved using the “Referenced SOP Sequence” element (0008,1199) in the Image Reference Macro
  • This is specialised to allow only a single entry, and to specify a GSPS object only.

Clinical Scenarios (in a GSPS capable viewer):

• User has queried for and retrieved image instances directly
  • The PACS has PS objects for that study
  • Possibly many for the same image with different scope
• User selects and retrieves GSPS object
• User selects and retrieves KON object

GSPS Deficiencies, Ambiguities & Problems:

• No C-FIND method to find GSPS objects for a given instance
• So need to retrieve every PS object in the study to inspect them internally
• What should the viewer do if > 1 possible GSPS for an image?
• There is no predefined coding (like there is in KON) to indicate “intent” of the GSPS object
• How to handle overlapping GSPS

Better Clinical Scenarios

• User retrieves a KON (or SR) with GSPS references
  • All is well-defined and unambiguous
• User retrieves a PS and associated images
  • e.g. IHE presentation of grouped procedures (PGP)
  • semantically suspect but technically OK

Summary of GSPS Issues

• There is no clearly defined mechanism to indicate which GSPS object should be used as the default for which image
• There is even a lack of supporting data (such as the document title used in KON – CID 7010) to assist choice algorithms

SOP Class Support

• Greyscale Softcopy Presentation State
• Colour Softcopy Presentation State
• Pseudo-Colour Softcopy Presentation State
• Record application of false colour LUT to greyscale images
• Private Attributes
• Convolution Filters (edge enhancement etc.)
• ROI stats

Creation Granularity

• Presentation state created for series
• Multiple states used to record “conceptual” state of one series
• “Streamlined” method to create presentation states for study

Application Granularity

• Automatic application of “best” presentation state
• Apply to series
• Coalescence of “similar” states to form single conceptual state
• Apply to image

Metadata

• Prompt for metadata on creation
• Content Label (pick list)
• Description
• Creator name and date/time
• Used to choose “best” initial state

AutoAuto

• Load presentation state + referenced images
• Load study/series/images + relevant presentation states
• Applies to Query/Retrieve and DICOMDIR sources

Loose Ends

• Font selection
• Curve algorithms (for INTERPOLATED graphic annotation)
• Representation of existing graphic annotations
• Angle measurements