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impipemod.ppt - DICOM Image Pixel Presentation Workshop January 28

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impipemod.ppt - DICOM Image Pixel Presentation Workshop January 28 Powered By Docstoc
					       DICOM
Imaging Pipeline Model
          Cor loef
  Philips Medical Systems


                            1
        Presentation Overview
•   Scope
•   Image Processing and Viewing
•   DICOM Pixel Processing model
•   Processing Functions
    – Single Pixel
    – Pixel Set
    – Geometric transformations
• Color representation
• Annotations and view area        2
                  Scope
• Pixel processing operations supported
  by DICOM concepts
• Contrast and Spatial Resolution
• Single image view, with annotations
• Monitor display and Film printing



                                          3
Image Processing and Viewing

               Image Object      Annotations             Viewing device
               Columns

                              Pixel Value   Gray Level
Rows




                                    Processing



  Pixel Size




                                                                          4
Image Processing and
      Viewing

Image Object              Viewing Device

• Spatial Resolution      • Spatial resolution
    • Rows, Columns           • Rows, Columns
    • Pixel Size              • Pixel Size
• Contrast Resolution     • Contrast Resolution
    • Pixel Value Range       • Pixel Luminance/Density Range
• Number of Images        • Number of Images
• Annotations             • Annotations



                                                     5
DICOM Pixel Processing model
  Acquisition specific      Normalize
  Image improvements        Physical Value          Application dependent       Normalize Perception
                                                    subrange selection


           (Non-DICOM)       Modality LUT
           Acquisition                               VOI LUT or                 Presentation LUT
                             or Linear               Linear                     or Linear
           processing        Transformation          Transformation             Transformation


Original
                                   Meaningful for Modality,       Gray Levels
Acquired      Stored Pixel Value   manufacturer independent                                    P-Values
Image
                                                              Photometric Intepretation:
                                                              Monochrome 1: min value -> White
                                                              Monochrome 2: min value -> Black

                                                              Polarity: Opposite of what’s specified
                                                              with Photometric Interpretation (Print)


                                                                                           6
Processing Functions(1)
  Single Pixel, Single Image

  Image Object                         Viewing Device

  • Spatial Resolution              = • Spatial resolution
      • Rows, Columns               =     • Rows, Columns
      • Pixel Size                  =     • Pixel Size
  •Contrast Resolution              ->• Contrast Resolution
      • Pixel Value Range           -> • Pixel Luminance/Density Range
  • 1 Image                         = • 1 Image

                               Processing




                                                              7
Processing Functions(1)

Single Pixel, Single Image
Linear operation: Add, Subtract, Divide and Multiply by Constant Value

                                            DICOM
                                                        Output=RSxPixel + RI


                Y=a.X+b             Max Rescale Type
     Output Y                       Range
     Range


                    a                                    Rescale Slope


                                                       Rescale     Max Stored Pixel
                b       Input X
                                                                   Value Range
                        Range                          Intercept



                                                                      8
Processing Functions(1)


 Non-Linear operation: Output=F(Input)            DICOM:
                                                  Modality LUT,
                                                  VOI LUT
                                                  Y[n]=F[Start Value + n-1]

   Output Y                       Output Y
   Range                          Range
              Y=F(X)              [0..2B-1]




                Input X                               N Number of Entries
                Range
                                    Start Value



                                                                       9
Processing Functions(1)

Histogram operations: Contrast Stretching, Contrast Compression

Histogram is pixel intensity distribution



    Frequency




                       Pixel value ( intensity )



                                                            10
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
             No values



                         Max Output Range
                         (Dynamic Range
                         Display Device)                 No values
                                                 WC


                                                Max Input range

                                                WW

                                                                      11
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)
                                                     WC
              No values
                                                 Max Input range

                                                      WW


                                                                       12
Processing Functions(2)
 Set Pixels, Single Image or Multiple Frames
 Image Object                    Viewing Device

 • Spatial Resolution         = • Spatial resolution
     • Rows, Columns          =      • Rows, Columns
     • Pixel Size             =      • Pixel Size
 •Contrast Resolution         -> • Contrast Resolution
     • Pixel Value Range      ->     • Pixel Luminance/Density Range
 • >=1 Images                 -> • 1 Image




                                                            13
Processing Functions(2)
Convolution
                                                              Image Out
    Image In                   P1 P2 P3

                               P4 P5 P6            X
                               P7 P8 P9


                              C1 C2 C3    Kernel
                              C4 C5 C6

                              C7 C8 C9
 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)


                                                                      14
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




                                _




                                                                 15
Processing Functions(2)
                   Mask Frames
                                            DICOM XA Multi-frame
                                            supports subtraction

                                 Sum
                                  N



                  Applicable Contrast Frames
                                                 _


                                 Sum
                                  N




      Pixel Intensity Relationship is LOG
                                                                   16
Processing Functions(3)

 Geometry operations: Scaling, Rotate/Flip/Displayed Area
 Single Image
    Image Object                  Viewing Device

    • Spatial Resolution          •
                                 ->Spatial resolution
        • Rows, Columns          -> • Rows, Columns
        • Pixel Size             -> • Pixel Size
    •Contrast Resolution          •
                                 ->Contrast Resolution
        • Pixel Value Range      -> • Pixel Luminance/Density Range
    • 1 Image                     •
                                 = 1 Image




                                                            17
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.



                                                             18
Processing Functions(3)

Replicate:


                          P[i] X   P[i+1]

Bilinear:

                          P[i] X   P[i+1]

Cubic:


               P[i-1]     P[i] X   P[i+1]   P[i+2]

                                                     19
Processing Functions(3)

Rotate/Flip

 Rotate may result in rescaling operation
                                            Horizontal Flip
              Rotate




DICOM: Presentation State has Rotate ( 90,180, 270)
and Horizontal Flip
                                                              20
Processing Functions(3)
 Pixel size                                           Processing
 Different pixel size may result in the need
 to interpolate                                   Pixel Aspect Ratio 2/1


 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
                                                                   21
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
  Sample pixel value

                                     Green-Palette Color LUT


                                     Blue-Palette Color LUT


                                                               22
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.




                                                              23
Annotations
                             Vector Graphics
              Bounding Box

              Text

        Polyline (Filled)

                                         (Anchor)
                                         X




                                                24
             DICOM: Overlays and Curves ( in Image space )

         Image                Overlay: ROI or Graphic

                              - 1 bit, on-off
                 Overlay      - Origin, Rows, Columns
Origin                        - Type: Graphics or ROI
                              - Max 16 planes
                              - May be multi-frame

                              Curve Type: ROI or POLY
                              - List of (x,y) coordinates




                                                             25
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




                                                             26

				
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