Quintiles intelligent imaging clear vision for the healthcare industry
This presentation is the property of its rightful owner.
Sponsored Links
1 / 18

Quintiles Intelligent Imaging Clear Vision for the Healthcare Industry PowerPoint PPT Presentation


  • 47 Views
  • Uploaded on
  • Presentation posted in: General

I 2. Quintiles Intelligent Imaging Clear Vision for the Healthcare Industry. DICOM Lookup Table Encoding Issues David Clunie. LUT Encoding Issues. Review LUT encoding LUT cascading and linear operations Signed values Bit width of values Window center/width operation Implicit scaling

Download Presentation

Quintiles Intelligent Imaging Clear Vision for the Healthcare Industry

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Quintiles intelligent imaging clear vision for the healthcare industry

I2

Quintiles Intelligent ImagingClear Vision for the Healthcare Industry

DICOM Lookup Table Encoding Issues

David Clunie


Lut encoding issues

LUT Encoding Issues

  • Review LUT encoding

  • LUT cascading and linear operations

  • Signed values

  • Bit width of values

  • Window center/width operation

    • Implicit scaling

    • Precise definition


Lut descriptor

First value mapped

First value mapped

Number of entries

Number of entries

Number of bits

Number of bits

LUT Descriptor


Cascaded luts

Cascaded LUTs

Pixel

Data

Modality

LUT

VOI

LUT

Presentation

LUT


Luts with linear transforms

LUTs with Linear Transforms

Pixel

Data

Modality

LUT

Window

Center/Width

Presentation

LUT


First value mapped

First value mapped

  • First value mapped may be negative

    • Value is specified in LUT Descriptor

    • Index increments sequentially

    • May wrap around across zero

    • Constrained by bit width of input values

  • But …

    • Are input values signed or unsigned ?

    • What is bit width of input values ?


Lut input values sign

LUT Input Values - Sign ?

  • Are input values signed or unsigned ?

    • Modality LUT == Pixel Representation

    • Same for VOI LUT with no Modality LUT

    • What about VOI LUT after Modality LUT ?

  • Therefore new questions:

    • are output values of LUT signed ?

    • are output values of linear ops signed ?


Lut descriptor vr and sign

LUT Descriptor VR and Sign

  • Number of entries - always unsigned

  • Number of bits - always unsigned

  • First value mapped - signed or unsigned

  • Implicit VR - only matters internally

  • Explicit VR - can only be one: US or SS

  • Dictionary no help “US/US or US/SS”

  • Proposed: always unsigned (and US)


Lut input values width

LUT Input Values - Width ?

  • What is bit width of input values ?

    • Bits Allocated if input is Pixel Data

    • Bit width of previous LUT (3rd descriptor)

    • What if follows linear transformation ?

    • Does it matter ?

      • Wraparound vs. continue count

      • e.g. 255,256,257 or 255 (== -1),0,1

      • Problem is signed values beyond pixel data


Lut output values width

LUT Output Values - Width ?

  • Bit width (== output value range)

    • 3rd value of LUT descriptor

    • Normally 8 or 16 bits allocated, i.e. range is from 0 to 28-1 or 216-1

    • N.B. For most existing objects including CR one cannot have a 12 bit LUT !@#$

    • DX and Sup 33 more flexible


Lut output values sign

LUT Output Values - Sign ?

  • Not specified in existing DICOM

  • Always same as Pixel Representation ?

    • What about unsigned CT pixel data -> HU

  • Recommendation is to be always unsigned


What does window mean

What Does “Window” Mean ?

  • Not actually defined

  • Common understanding ...

    “map values of input selected to full width of display grayscale”

  • Linearly or with default gamma or characteristic curve ?


Usual meaning of window

Usual Meaning of “Window”

Window Center/Width

Selects range of values to map

Display

System

Scaling of selected input values to full grayscale range that

display is capable of using monitor chracteristic curve


Window and presentation lut

Window and Presentation LUT

  • There is no “output value range” for window operation

  • Selects range of input values to “use”

  • Therefore either

    • Presentation LUT different for each window

    • Implicit Scalingi.e. linearly map selected to defined LUT input range


Implicit scaling

First value mapped

Number of entries

Number of bits

Implicit Scaling

Window Center/Width

Selects range of values to map

Presentation

LUT

Linear scaling of selected input values to range from

first value mapped to first value+number of entries


Precise meaning of window

Precise Meaning of “Window”

  • What does “center” mean ?

  • What does “width” mean ?

  • Integer or decimal ? (VR is DS)

  • Is with odd or even ?

  • What do width of 0 or 1 “mean” ?

  • Can input range “exceed” data range ?If so, flatten contrast or clip window ?


Proposed meaning of window

Proposed Meaning of Window

  • Specify as equation

    (C-W/2) <= value <= (C+W/2)

  • Calculation equivalent to floating point

  • Meaning of width of 0 and 1 equal

  • Odd width specifies fractional bounds

  • Exercise:

    • How does one specify identity transform ?


Conclusion

Conclusion

  • LUT encoding is an issue for

    • Existing objects

    • Softcopy Presentation State

  • Sup. 33 proposes extensive fixes

    • Precise definitions & extensive examples

    • Restrictions to unsigned LUT output

    • Open issue is LUT Descriptor VR

    • Affect existing image object definitions


  • Login