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DICOMImaging Pipeline Model

Cor loef

Philips Medical Systems

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Presentation OverviewPresentation Overview• ScopeScope

• Image Processing and Viewing Image Processing and Viewing

• DICOM Pixel Processing model DICOM Pixel Processing model

• Processing FunctionsProcessing Functions– Single Pixel– Pixel Set– Geometric transformations

• Color representationColor representation

• Annotations and view areaAnnotations and view area

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ScopeScope

• Pixel processing operations supported Pixel processing operations supported by DICOM conceptsby 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

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Image ObjectViewing device

Columns

Pixel Size

Image Processing and ViewingImage Processing and Viewing

Processing

Row

s

Pixel Value Gray Level

Annotations

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Image Processing and Image Processing and ViewingViewing

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

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OriginalAcquiredImage

Modality LUT or LinearTransformation

VOI LUT orLinearTransformation

NormalizePhysical Value

Meaningful for Modality,manufacturer independent

Application dependentsubrange selection

Stored Pixel Value

DICOM Pixel Processing modelDICOM Pixel Processing model

(Non-DICOM)Acquisitionprocessing

Presentation LUTor LinearTransformation

Gray Levels

Normalize Perception

P-ValuesPhotometric Intepretation:Monochrome 1: min value -> WhiteMonochrome 2: min value -> Black

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

Acquisition specificImage improvements

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Processing Functions(1)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

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Max Stored Pixel Value Range

Y=a.X+b

Processing Functions(1)Processing Functions(1)

Single Pixel, Single Image

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

Input XRange

Output YRange

a

b

Output=RSxPixel + RI

Max Rescale TypeRange

Rescale Slope

Rescale Intercept

DICOM

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Processing Functions(1)Processing Functions(1)

Non-Linear operation: Output=F(Input)

Y=F(X)

Input XRange

Output YRange

Y[n]=F[Start Value + n-1]

N Number of Entries

Output YRange[0..2B-1]

DICOM:Modality LUT,VOI LUT

Start Value

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Processing Functions(1)Processing Functions(1)

Histogram operations: Contrast Stretching, Contrast Compression

Histogram is pixel intensity distribution

Frequency

Pixel value ( intensity )

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Processing Functions(1)Processing Functions(1)

Histogram, Contrast StretchingApplied 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 RangeDisplay Device)

Max Input range

No values

No valuesWC

WW

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Processing Functions(1)Processing Functions(1)

Histogram, Contrast CompressionApplied to an Image to suppress a part of the dynamic rangeof the display device.

DICOM:VOI Window Width/Window Center

Max Output Range(Dynamic RangeDisplay Device)

Max Input rangeNo values

WC

WW

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Processing Functions(2)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

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Processing Functions(2)Processing Functions(2)

ConvolutionP1 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 InImage Out

Kernel

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Processing Functions(2)Processing Functions(2)

Add,Subtract and Average operations on multiple Images, Frames

Operations on 1 pixel in multiple frames, and generationof output pixel based on two (processed) input pixel values.

Images/Frames

Sum N

_

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Processing Functions(2)Processing Functions(2)

Sum N

Sum N

_

Mask Frames

Applicable Contrast Frames

Pixel Intensity Relationship is LOG

DICOM XA Multi-framesupports subtraction

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Processing Functions(3)Processing Functions(3)

Geometry operations: Scaling, Rotate/Flip/Displayed AreaSingle 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

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Processing Functions(3)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.

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Processing Functions(3)Processing Functions(3)

Replicate:

Bilinear:

Cubic:

P[i] P[i+1]X

P[i] P[i+1]X

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

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Processing Functions(3)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

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Processing Functions(3)Processing Functions(3)

Pixel sizeDifferent 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 Widthand 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

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Color representationColor 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

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Annotations and view areaAnnotations 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.

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X

(Anchor)

Bounding Box

Text

Polyline (Filled)

Vector Graphics

AnnotationsAnnotations

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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

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Annotations and view areaAnnotations and view area

Shutter, geometric mask applied on the image during displayto neutralize the display of any pixels located outside theshutter shape.DICOM has the following shutter shapes:Rectangular,Circular,Polygonal