DICOM PS3.17 2020b - Explanatory Information

OOOO Encoding Perfusion Parameters for Parametric Maps and ROI Measurements (Informative) (Current)
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# OOOO Encoding Perfusion Parameters for Parametric Maps and ROI Measurements (Informative)

This Annex contains examples of how to encode perfusion models and acquisition parameters within the Quantity Definition Sequence of Parametric Maps and in ROIs in Measurement Report SR Documents.

Some measurements described as "relative" or "normalized" are calculated by dividing the measurement in a region of interest by a corresponding measurement from a reference region chosen for comparison purposes.

The approach suggested is to describe that a perfusion value is being measured by using absolute or relative regional blood flow or volume (generic) as the concept name of the numeric measurement, and to add post-coordinated concept modifiers to describe:

- the general anatomic location and type of finding that mirror common usage of terminology specific to the application

- the size of any reference region used

- a coded description of the location of any reference region in terms of:

  - anatomic site (drawn from CID 7192 "Anatomical Structure Segmentation Property Types")

  - laterality (drawn from CID 244 “Laterality” or CID 246 “Relative Laterality” )

Also illustrated is how the (121050, DCM, "Equivalent Meaning of Concept Name") can be used to communicate a single human readable textual description for the entire concept.

The example used is from the oncology domain, but similar patterns can be used for other applications, e.g., for stroke.

## OOOO.1 Encoding Relative Cerebral Tumor Blood Flow for Parametric Maps

This example shows how to use the Table C.7.6.16-12b “Real World Value Mapping Item Macro Attributes” in PS3.3 to describe pixel values of blood flow maps. It elaborates on the simple example provided in Section C.7.6.16.2.11.1.2 “Real World Values Mapping Sequence Attributes” by adding coded concepts that describe the location of the measurement and the location and size of the reference region.

- Real World Value Mapping Sequence (0040,9096)

  - ...

  - Real World Value Intercept (0040,9224) = "0"

  - Real World Value Slope (0040,9225) = "1E-03"

  - LUT Explanation (0028,3003) = "Relative Cerebral Tumor Blood Flow, relative to 150mm2 contralateral normal cerebellar gray matter"

  - LUT Label (0040,9210) = "rCBF"

  - Measurement Units Code Sequence (0040,08EA) = ({ratio}, UCUM, "ratio")

  - Quantity Definition Sequence (0040,9220):

    - CODE (246205007, SCT, "Quantity") = (126397, DCM, "Relative Regional Blood Flow)

    - CODE (363698007, SCT, "Finding Site") = (12738006, SCT, "Brain")

    - CODE (121071, DCM, "Finding") = (108369006, SCT, "Neoplasm")

    - CODE (C94970, NCIt, "Reference Region") = (25991003, SCT, "Cerebellar Cortex")

      - CODE (272741003, SCT, "Laterality") = (255209002, SCT, "Contralateral")

      - NUMERIC (42798000, SCT, "Area") = 150 (mm2, UCUM, "mm2")

    - TEXT (121050, DCM, "Equivalent Meaning of Concept Name") = "Relative cerebral tumor blood flow relative to 150mm2 contralateral normal cerebellar gray matter"

In this usage, the text of the (121050, DCM, "Equivalent Meaning of Concept Name") is redundant with the value of LUT Explanation (0028,3003); either or both could be omitted.

The qualifiers of the quantity in this example, specifically the finding and finding site, are intentionally more generic (i.e., brain and neoplasm, respectively) than the more specific locations used in the SR examples that follow (i.e., left temporal lobe and primary neoplasm), since the purpose is to specify the type of the quantity, not encode an entire report in the quantity definition.

The nesting of the indented modifiers in the example illustrates that laterality and area are modifiers of the reference region (i.e., encoded in the Content Item Modifier Sequence (0040,0441) of the Quantity Definition Sequence (0040,9220)).

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DICOM PS3.17 2020b - Explanatory Information