DICOM PS3.17 2020b - Explanatory Information

KKKK Encoding Quantitative Image Family Parameters (Informative) (Current)
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# KKKK Encoding Quantitative Image Family Parameters (Informative)

## KKKK.1 Encoding of Quantitative Image Family Parameters With RWVM

In this example, the real-world value mapped pixel value represents attenuation of water. The pixel values range from 0 to 4095 like a conventional CT Image and are mapped starting from -1024.

Table KKKK.1-1. Example Material Specific Images for the Real World Value Mapping Macro

Attribute | Tag | Value | Comment
--- | --- | --- | ---
Real World Value Mapping Sequence | (0040,9096) |  |
ITEM 1
>Real World Value First Value Mapped | (0040,9216) | 0 |
>Real World Value Last Value Mapped | (0040,9211) | 4095 |
>Real World Value Intercept | (0040,9224) | -1024 |
>Real World Value Slope | (0040,9225) | 1 |
>LUT Explanation | (0028,3003) | "Water component of image with water and iodine as base materials" |
>LUT Label | (0040,9210) | MAT_SPECIFIC | Per guidance in Section C.11.1.1.2.1 “Recommended Rescale Type Assignments For Multi-energy CT Image” in PS3.3 this corresponds to Image Type Value 4
>Measurement Units Code Sequence | (0040,08EA) |  |
>>Include Table 8.8-1 “Code Sequence Macro Attributes” in PS3.3 | ([hnsf'U], UCUM, "Hounsfield unit") |
>Quantity Definition Sequence | (0040,9220) |  |
>>CODE (105590001, SCT, "Substance") | (11713004, SCT, "Water") |
>>CODE (370129005, SCT, "Measurement Method") | (129323, DCM, "Material Specific image") |

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 the encoding of Quantitative Image Family parameters, by adding coded concepts to the RWVM that describe the material, the method and the value range in case of Value-based images.

In this example, a Value-based material map image has been created where pixel values between 0 and 20 correspond to voxels that are associated with Uric Acid and pixel values between 20 and 40 correspond to voxels that are associated with Calcium:

- In the Quantity Definition Sequence (105590001, SCT, "Substance") is used to indicate that the pixel value in the specified range is deemed to represent the presence of that substance, regardless of the actual pixel value within that range. It would be inappropriate to use (246205007, SCT, "Quantity") since the transformed pixel values do not represent a quantitative value.

- The measurement method of (113250, DCM, "Value-based material image") might be replaced by a more specific code that actually described the method of computation such as "Gaussian distribution".

- For the sake of illustration, in this image a pixel value of 20 maps to both "Uric Acid" and "Calcium".

Table KKKK.1-2. Example Value Based Images for the Real World Value Mapping Macro

Attribute | Tag | Value | Comment
--- | --- | --- | ---
Real World Value Mapping Sequence | (0040,9096) |  |
ITEM 1
>Real World Value First Value Mapped | (0040,9216) | 0 |
>Real World Value Last Value Mapped | (0040,9211) | 20 |
>Real World Value Intercept | (0040,9224) | 0 |
>Real World Value Slope | (0040,9225) | 1 |
>LUT Explanation | (0028,3003) | "Value-based substance map for kidney stone" |
>LUT Label | (0040,9210) | MAT_ VALUE_BASED |
>Measurement Units Code Sequence | (0040,08EA) |  |
>>Include Table 8.8-1 “Code Sequence Macro Attributes” in PS3.3 | (1, UCUM, "no units") |
>Quantity Definition Sequence | (0040,9220) |  |
>>CODE (105590001, SCT, "Substance") | (1710001, SCT, "Uric Acid") |
>>CODE (370129005, SCT, "Measurement Method") | (129322, DCM, "Value-based image") |
ITEM 2
>Real World Value First Value Mapped | (0040,9216) | 20 |
>Real World Value Last Value Mapped | (0040,9211) | 40 |
>Real World Value Intercept | (0040,9224) | 0 |
>Real World Value Slope | (0040,9225) | 1 |
>LUT Explanation | (0028,3003) | "Value-based substance map for kidney stone" |
>LUT Label | (0040,9210) | MAT_ VALUE_BASED |
>Measurement Units Code Sequence | (0040,08EA) | (1, UCUM, "no units") |
>>Include Table 8.8-1 “Code Sequence Macro Attributes” in PS3.3 |  |  |
>Quantity Definition Sequence | (0040,9220) |  |
>>CODE (105590001, SCT, "Substance") | (5540006, SCT, "Calcium") |
>>CODE (370129005, SCT, "Measurement Method") | (129322, DCM, "Value-based image") |

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DICOM PS3.17 2020b - Explanatory Information