1 DICOM Imaging Pipeline Model Cor loef Philips Medical Systems

2 Presentation Overview ScopeScope Image Processing and ViewingImage Processing and Viewing DICOM Pixel Processing modelDICOM Pixel Processing model Processing FunctionsProcessing Functions –Single Pixel –Pixel Set –Geometric transformations Color representationColor representation Annotations and view areaAnnotations and view area

3 Scope Pixel processing operations supported by DICOM conceptsPixel processing operations supported by DICOM concepts Contrast and Spatial ResolutionContrast and Spatial Resolution Single image view, with annotationsSingle image view, with annotations Monitor display and Film printingMonitor display and Film printing

4 Image Object Viewing device Columns Pixel Size Image Processing and Viewing Processing Rows Pixel ValueGray Level Annotations

5 Image Processing and Viewing Image Object Spatial Resolution Rows, Columns Pixel Size Contrast Resolution Pixel Value Range Number of Images Annotations Viewing Device Spatial resolution Rows, Columns Pixel Size Contrast Resolution Pixel Luminance/Density Range Number of Images Annotations

6 Original Acquired Image Modality LUT or Linear Transformation VOI LUT or Linear Transformation Normalize Physical Value Meaningful for Modality, manufacturer independent Application dependent subrange selection Stored Pixel Value DICOM Pixel Processing model (Non-DICOM) Acquisition processing Presentation LUT or Linear Transformation Gray Levels Normalize Perception P-Values Photometric Intepretation: Monochrome 1: min value -> White Monochrome 2: min value -> Black Polarity: Opposite of what’s specified with Photometric Interpretation (Print) Acquisition specific Image improvements

7 Processing Functions(1) Single Pixel, Single Image Image Object Spatial Resolution = Rows, Columns = Pixel Size = Contrast Resolution -> Pixel Value Range-> 1 Image= Viewing Device Spatial resolution Rows, Columns Pixel Size Contrast Resolution Pixel Luminance/Density Range 1 Image Processing

8 Max Stored Pixel Value Range Y=a.X+b Processing Functions(1) Single Pixel, Single Image Linear operation: Add, Subtract, Divide and Multiply by Constant Value Input X Range Output Y Range a b Output=RSxPixel + RI Max Rescale Type Range Rescale Slope Rescale Intercept DICOM

9 Processing Functions(1) Non-Linear operation: Output=F(Input) Y=F(X) Input X Range Output Y Range Y[n]=F[Start Value + n-1] N Number of Entries Output Y Range [0..2 B -1] DICOM: Modality LUT, VOI LUT Start Value

10 Processing Functions(1) Histogram operations: Contrast Stretching, Contrast Compression Histogram is pixel intensity distribution Frequency Pixel value ( intensity )

11 Processing Functions(1) Histogram, Contrast Stretching Applied to an Image to stretch (part of) a histogram to fill the full dynamic range of the display device. DICOM: VOI Window Width/Window Center Max Output Range (Dynamic Range Display Device) Max Input range No values WC WW

12 Processing Functions(1) Histogram, Contrast Compression Applied to an Image to suppress a part of the dynamic range of the display device. DICOM: VOI Window Width/Window Center Max Output Range (Dynamic Range Display Device) Max Input range No values WC WW

13 Processing Functions(2) Set Pixels, Single Image or Multiple Frames Image Object Spatial Resolution = Rows, Columns = Pixel Size = Contrast Resolution -> Pixel Value Range-> >=1 Images-> Viewing Device Spatial resolution Rows, Columns Pixel Size Contrast Resolution Pixel Luminance/Density Range 1 Image

14 Processing Functions(2) Convolution P1 P2 P3 P4 P5 P6 P7 P8 P9 C1 C2 C3 C4 C5 C6 C7 C8 C9 X DICOM: Convolution operations not supported. Could become part of the Advanced Presentation State SOP Class. Example of Industry use: Edge Enhancement: Output=Input + Gain*(Input-Convoluted_Region) Image In Image Out Kernel

15 Processing Functions(2) Add,Subtract and Average operations on multiple Images, Frames Operations on 1 pixel in multiple frames, and generation of output pixel based on two (processed) input pixel values. Images/Frames Sum N _

16 Processing Functions(2) Sum N Sum N _ Mask Frames Applicable Contrast Frames Pixel Intensity Relationship is LOG DICOM XA Multi-frame supports subtraction

17 Processing Functions(3) Geometry operations: Scaling, Rotate/Flip/Displayed Area Single Image Image Object Spatial Resolution -> Rows, Columns -> Pixel Size -> Contrast Resolution -> Pixel Value Range-> 1 Image= Viewing Device Spatial resolution Rows, Columns Pixel Size Contrast Resolution Pixel Luminance/Density Range 1 Image

18 Processing Functions(3) Scaling, Zoom-in, Zoom-out No more 1-to-1 mapping of pixels => “holes” and “overlaps” in pixel view area Need for interpolation. Interpolation types: Replicate, Bilinear, Cubic DICOM: Print has Magnification Type with the mentioned interpolation options. Requested Image Size, Rows/Columns and Pixel Aspect Ratio.

19 Processing Functions(3) Replicate: Bilinear: Cubic: P[i]P[i+1] X P[i]P[i+1] X P[i]P[i+1] X P[i-1]P[i+2]

20 Processing Functions(3) Rotate/Flip Rotate may result in rescaling operation DICOM: Presentation State has Rotate ( 90,180, 270) and Horizontal Flip Rotate Horizontal Flip

21 Processing Functions(3) Pixel size Different pixel size may result in the need to interpolate DICOM: CT/MR has Pixel Spacing, absolute Row Height/Column Width X-Ray has Pixel Aspect Ratio, relative Row Height/Column Width and Imager Pixel Spacing ( absolute, on detector plate ) Print has Requested Image Size, x-dimension in mm of image in Image Box, and Image Display Format. Printer Pixel Spacing retrieved with new SOP Class: Printer Configuration Processing Pixel Aspect Ratio 2/1

22 Color representation DICOM: Photometric Interpretation: - Palette Color, 1 sample value with 3 Palette Color LUTs that define R,G,B - RGB, 3 sample values for R,G,B Red-Palette Color LUT Green-Palette Color LUT Blue-Palette Color LUT Sample pixel value

23 Annotations and view area Text and Vector graphics, added to the Image pixels Currently in DICOM only Overlay and Curve. In Presentation State directly text and vector graphics, both in Image space and Display Device coordinate space.

24 X (Anchor) Bounding Box Text Polyline (Filled) Vector Graphics Annotations

25 DICOM: Overlays and Curves ( in Image space ) Overlay: ROI or Graphic - 1 bit, on-off - Origin, Rows, Columns - Type: Graphics or ROI - Max 16 planes - May be multi-frame Curve Type: ROI or POLY - List of (x,y) coordinates Image Overlay Origin

26 Annotations and view area Shutter, geometric mask applied on the image during display to neutralize the display of any pixels located outside the shutter shape. DICOM has the following shutter shapes: Rectangular, Circular, Polygonal