Soft Copy Presentation State Herman Oosterwijk, OTech Inc. PACS and DICOM training and consulting herman@otechimg.com

Scenario: Radiologist:

Radiologist: Suspect Suspected area

Radiologist: Physician: Suspect Suspected area

Grayscale Softcopy Presentation State Storage: 1. Accommodate conversion of Pixels to Presentation values (P-values) Note: P-values are device independent values (defined by Grayscale Standard Display Function). 2. Preserve additional transformations, annotations, shutter, spatial xforms 7

Softcopy Presentation State: - Separation of Stored Image Instances from Display characteristics and changes Presn param: WW, Ctr, rescl, intc. Pres State Composite Image Object n : m Presn param: WW, Ctr, rescl, intc. Presn param: WW, Ctr, rescl, intc. Image Object 8

Softcopy Presentation State: - Separation of Images and Pres states (ctd) Examples: Zoom applied to multiple CT slices (e.g. Spine) Double Window Width/Ctr for CT chest Separate Overlays that generated by CAD Reduction of data transfer and storage because only one instance needed of image data 8

Softcopy Presentation State: Important: Softcopy Presentation State contains parameters that are present in the image as well (e.g. WW/level): Presentation State values/operations overrides the values in the image If no values in Presentation State for particular operation than identity transformation Photometric Interpretation (0028,0004) shall be ignored in Image 12

Softcopy Presentation State: Image Pres State Modality LUT Mask VOI LUT Presentation LUT Overlays, Curves Modality LUT Mask VOI LUT Presentation LUT Overlays, Curves Shutters Img Annotation Spatial Xform Displ Area Annotn Ptr. 13

Softcopy Presentation State: Composite object containing the presentation state parameters Link this Composite object to one or more images (Series, filters); stored using same Study Instance UID (same Storage SOP Class!) Communicate with regular Storage service (C_Store); Retrieve with Query/Retrieve service Pres State SOP Instances are immutable: changes require a new SOP Inst UID Note: generation and applying (selection) of pres states (SCU and SCP) outside scope of DICOM 9

Softcopy Pres. State: Image pipeline / I n t r M d i y L U T Presentation LUT W i n d o w / L e v l r V O I U T M o d a l i t y L U T r n s f m ( S u b t r a c i o n ) M s k T r a n s f o m t i V O I L U Presentation LUT Transformation O r i g n a l I m e e T r a n s f o m t i S h u e A n o t a i I m g e S p a t i l T r n s f o m A n o t a i D s p . r e P - V a l u e s D i s p l a y 10

Softcopy Pres. State: Image pipeline / I n t r M d i y L U T Presentation LUT W i n d o w / L e v l r V O I U T M o d a l i t y L U T r n s f m ( S u b t r a c i o n ) M s k T r a n s f o m t i V O I L U Presentation LUT Transformation O r i g n a l I m e e 10

Softcopy Presentation State: Shutter Image Spatial Disp. Area P-Values Display Transformation Transformation Annotation Annotation look Flip, Rotate, Zoom, Pan Text, independent from spatial transformation 11

Softcopy Presentation State Module Table:

Patient, Study, Series module as well as SOP Common makes this a composite object Presentation Series specializes Modality (0008,0060) of Gnl. Series Module: “PR”

Modules vs Pipeline: MASK VOI LUT PRES LUT SHUTR IMG ANN MOD LUT SPATL XFORM DISPL ANN IMAGE

Presentation State Module: To identify the Pres. State object: Instance (aka Image) number Label, description, creation date/time, and creator’s name Applies to which images: Ref series/image sequence Misc: Shutter presentation value (P-values) Mask subtraction (average-time delay) 14

Modality LUT Module: Manufacturer values to modality pixel values MASK VOI LUT PRES LUT MOD LUT Manufacturer values to modality pixel values (Hounsfield, OD); LUT OR Rescale Slope/Interc. - Modality LUT: LUT Descriptor: Number of entries in table First stored pixel value mapped Number of bits for each entry in LUT data Modality LUT Type: output units (OD, US) LUT data Shttr Img Anntn Spatl Xform Displ Anntn 14

Modality LUT Module: Mod LUT: Output LUT: Unsigned MASK VOI LUT PRES LUT MOD LUT Mod LUT: Shttr Img Anntn Spatl Xform Displ Anntn Output LUT: Unsigned Number of entries in LUT; Number of bits for each entry: (8 or 16)---> range is 256 or 65536 Data range First Stored Pixel (FSP) value mapped (VR is defined by Pix.Repres.) 14

Modality LUT Module: Rescale Slope Intercept: Linear: Slope/ Intercept MASK MOD LUT VOI LUT PRES LUT Rescale Slope Intercept: Shttr Img Anntn Spatl Xform Displ Anntn Linear: Slope/ Intercept Example: shift linear 2048 output values Input values 14

Modality LUT Module: Issues/notes: Provides Mod LUT for MASK MOD LUT VOI LUT PRES LUT Issues/notes: Provides Mod LUT for CT (is normally not part of CT Image IOD) Output range depends on whether Mod Lut is used or rescale/Intercept: Unsigned for Mod LUT Defined by value of rescale slope/Intercept and Pixel representation; could be signed even if Pixel representation is unsigned Shttr Img Anntn Spatl Xform Displ Anntn 14

MASK Module: Mask operation: Subtract frames with fixed LUT VOI LUT PRES LUT MASK Mask operation: Subtract frames with fixed position or time interval: AVG_SUB; Average subtraction: Average frames identified by MASK Frame Numbers, shift by MASK Sub-Pixel Shift and subtract from frames Applicable Frame Range TID; Time Interval differencing: Subtract TID Offset from frame number to select the mask to be subtracted Shttr Img Anntn Spatl Xform Displ Anntn 14

MASK Module: Issues/Notes: LUT VOI LUT PRES LUT MASK Shttr Img Anntn Spatl Xform Displ Anntn Issues/Notes: For X-ray images, subtraction needs to be in log space relative to X-ray intensity; could be done by applying Mod LUT (if so needed) Output is signed value, one bit longer than source frames 14

VOI LUT Module: Map modality pixel values (Hounsfield) to application PRES LUT MASK VOI LUT Map modality pixel values (Hounsfield) to application significant values: VOI LUT or WW/Center - VOI LUT: LUT Descriptor: Number of entries in table First input value mapped Number of bits for each entry in LUT data LUT data Shttr Img Anntn Spatl Xform Displ Anntn 14

VOI LUT Module: Window Width/Center: (is better defined!) width PRES LUT MASK VOI LUT Window Width/Center: (is better defined!) Shttr Img Anntn Spatl Xform Displ Anntn width output values center Input values 14

VOI LUT Module: WW/Ctr Issues/Notes: Assume floating point PRES LUT MASK VOI LUT WW/Ctr Issues/Notes: Assume floating point calculation: WW 1, Ctr 0: -0.5 <= value <= 0.5 WW 100, Ctr 0: -50 <= value <= +50 WW 4095, Ctr 2047: -0.5 <= value <= 4095.5 Selected input range may exceed actual input range: image will be “flattened” Output is scaled to display device OR to range of Pres LUT Shttr Img Anntn Spatl Xform Displ Anntn 14

VOI LUT Module: Issues/Notes: Photometric Interpret. Is ignored PRES LUT MASK VOI LUT Issues/Notes: Photometric Interpret. Is ignored VOI LUT can have sections with negative slope Image VOI LUT shall not be used Only a single VOI LUT shall be present (multiple requires different Pres States); this is not the case for the VOI Lut’s as present in the images (can be multiple) Shttr Img Anntn Spatl Xform Displ Anntn 14

SC Pres. LUT Module: Pixels to P-values: (assumes Grayscale MASK VOI LUT PRES LUT Pixels to P-values: (assumes Grayscale Display Function standard) LUT Descriptor: Number of entries in table First input value mapped (always scaled to 0) Number of bits for each entry in LUT data LUT data Pres LUT shape; reqd if no LUT Shttr Img Anntn Spatl Xform Displ Anntn 14

SC Pres LUT Module: LUT maps full range Output LUT: Unsigned MASK VOI LUT PRES LUT MOD LUT LUT maps full range Shttr Img Anntn Spatl Xform Displ Anntn Output LUT: Unsigned Number of entries in LUT; Number of bits for each entry: (8<=n<=16) Data range First Stored Pixel (FSP) value mapped; scaled to 0 (VR is US) 14

SC Pres. LUT Module: Issues/Notes: MASK VOI LUT PRES LUT Issues/Notes: If no Pres LUT and VOI LUT, Mod LUT has to make sure that output is in P-values LUT Shape might reflect Monochrome 1/2 in case not reflected in the pipeline before (IDENTITY-INVERSE) No separate polarity inversion is defined Pres LUT is Required (M); xform could be “Identity” Shttr Img Anntn Spatl Xform Displ Anntn 14

VR at different stages: MOD LUT MASK VOI LUT PRES LUT Pix data [Pix Repres] P-values Ident US MOD LUT VOI LUT US US SC Pr LUT US MASK RSC/ INT WW/ Ctr SS/US SS/US 14

Shutter XForm: Two modules: Display shutter module: LUT MASK VOI LUT PRES LUT Two modules: Display shutter module: Shape: Rectangular, Circular, Polygonal Coordinates (edge, ctr, radius, vertices) optional Presentation (padding) Value Bitmap Display Shutter Module: Shape (bitmap) Overlay group [60xx] (in Pres State Object!) reqd Presentation (padding) Value Shttr Img Anntn Spatl Xform Displ Anntn 14

Image Annotation: Pre-spatial xform annotation (e.g. ROI shapes) MOD LUT MASK VOI LUT PRES LUT Pre-spatial xform annotation (e.g. ROI shapes) Use Overlay/Curve Activation Module: If Curve activated, only curve contained in images are activated (curves are replaced by Graphic Annotation Module in SC Pres State) If Overlay activated, could be in Image or SC Pres State object Shttr Img Anntn Spatl Xform Displ Anntn 14

Image Annotation: Graphic Layer: Groups related graphics, MOD LUT MASK VOI LUT PRES LUT Graphic Layer: Groups related graphics, identifies with text string, provides order number and display value (incl color) as well as free text description Referenced from the Graphic annotation module Shttr Img Anntn Spatl Xform Displ Anntn 14

Image Annotation: Graphic Ann. Module: - Graphics, text or both LUT MASK VOI LUT PRES LUT Graphic Ann. Module: - Graphics, text or both Bounding box OR Anchor points units: “Pixel” Types are Polyline, Interpolated, Circle or Elipse Graphic could be filled Addressing: Pixel 1\1 is in between Point (0.0\0.0) and Point (1.0\1.0) Shttr Spatl Xform Img Anntn Displ Anntn 14

Image Annotation: Graphic Ann. Module: - Issues/Notes: LUT MASK VOI LUT PRES LUT Graphic Ann. Module: - Issues/Notes: Text could be outside bounding box Text could be in scrolling box or link to other window Transparency, opacity or “exclusive or” of bounding box is implementation specific “Anchor Point visibility” determines line or arrow from point to text; text might be repositioned as appropriate for zoom Shttr Spatl Xform Img Anntn Displ Anntn 14

Spatial Xform: Rotate, Flip, Minify/Zoom and region selection: MOD LUT MASK VOI LUT PRES LUT Rotate, Flip, Minify/Zoom and region selection: Spatial Xform module: Rotate (0, 90, 180, 270) CW Horizontal flip Displayed area module: Top Left hand Corner and Bottom Right Hand Corner of data to be displayed relative to pixel data (1\1) Shttr Img Anntn Spatl Xform Displ Anntn 14

Spatial Xform: Displayed area module: (1\1) TLHC BRHC (Rows\columns) LUT MASK VOI LUT PRES LUT Displayed area module: Shttr Img Anntn Spatl Xform Displ Anntn (1\1) TLHC BRHC (Rows\columns) 14

Spatial Xform: Notes/Issues: Area can be greater than MOD LUT MASK VOI LUT PRES LUT Notes/Issues: Area can be greater than result from spatial transformation (e.g. a 1200 by 1000 display displaying a 1k by 1k image) Result shall be displayed as large as possible within display area (magnified if applicable) Minification is achieved by a negative TLHC and/or BRHC greater than Rows or Columns Rotate/Flip applied BEFORE zoom/minify Shttr Img Anntn Spatl Xform Displ Anntn 14

Displ. Area Annotation: MOD LUT MASK VOI LUT PRES LUT Display dependent graphics Graphic Ann. Module: Graphics, text or both Bounding box OR Anchor points units: “DISPLAY” Types are Polyline, Interpolated, Circle or Elipse Graphic could be filled Addressing: Pixel 1\1 is in between Point (0.0\0.0) and Point (1.0\1.0) Shttr Spatl Xform Img Anntn Displ Anntn 14

Softcopy Presentation State Conformance Statement requirements: SCU: How are presentation attributes derived from Image, operator intervention, defaults How is info included in IOD Which Image Storage SOP classes are supported and can be referenced by the SC Presentation State 14

Softcopy Presentation State Conformance Statement requirements (ctd): SCP: How are attributes used to influence image display Which Image Storage SOP classes are supported and may be referenced by the Sofcopy presentation State 14

Softcopy Presentation State media extensions: Directory Type added “Presentation” Included below Series Directory record entry Can be stored on a general purpose CD-R 14

Status Softcopy Presentation State supplement: Draft for trial implementation Demonstration/implementation funded by DICOM committee at ECR, March ‘99 Main contractor OTech, proj. Mgt. lake Grifin, implementation by OFFIS (U Oldenburgh) and Microtherapy (U Witten/herdecke) Main sponsors are Imation, Philips, Siemens, GE and ISG; Image Smiths provides calibration Software will be in available in public domain 14

Goals Softcopy Presentation State demo: Education of user community and sollicitation of feedback Demonstration of this specific supplement Promotion of early implementation and adoption Modality simulator Diagn workstation Physician workstation 14

Softcopy Presentation State does NOT (yet) address: - Color (no Color Display function) - No screen layout issues are addressed, including size of images on screen - No query of display characteristics (like Print configuration) - No 3D display and/or image fusion (CT/MR/NM) 14

Softcopy Presentation State provides: Image Presentation consistency (vs grayscale consistency defined by Grayscale function) Tighter definition of presentation parameters (WW/Ctr, etc) Uncoupling of presentation and images; eliminates multiple instances of images with same pixel data Address exchange of overlays and text (currently often solved with proprietary means) 14

(Print) Presentation LUT: Relates to Image Box, Film Box or Film Session Normalized IOD: Presentation LUT Module: LUT descriptor Explanation LUT data LUT Shape: IDENTITY or LIN OD (range is Min density to max density) 14

DICOM Presentation LUT GOAL: Consistent image quality. Transformation of pixel values into P-values For hardcopy, P-values are transformed into optical density Image display can be tailored for specific modalities, applications and user preferences