FFF.2.4.2.3 Encoding Details
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##### FFF.2.4.2.3 Encoding Details

This section provides detailed recommendations of the key attributes to address this particular scenario.

Table FFF.2.4-6. Enhanced X-Ray Angiographic Image IOD Modules

IE | Module | PS3.3 Reference | Usage
--- | --- | --- | ---
Image | Enhanced XA/XRF Image | C.8.19.2 | Specifies the image type: ORIGINAL or DERIVED.

Table FFF.2.4-7. Enhanced XA Image Functional Group Macros

Functional Group Macro | PS3.3 Reference | Usage
--- | --- | ---
Derivation Image | C.7.6.16.2.6 | Specifies the different derivation steps (including the latest step) that led to this instance.
Pixel Intensity Relationship LUT | C.7.6.16.2.13 | Specifies the relationship between the stored pixel data values and the X-Ray intensity of the resulting derived instance.
XA/XRF Frame Characteristics | C.8.19.6.1 | Specifies the latest derivation step that led to this instance.
XA/XRF Frame Pixel Data Properties | C.8.19.6.4 | Specifies the characteristics of the derived pixel data, both geometric and densitometric.

###### FFF.2.4.2.3.1 Enhanced XA/XRF Image Module Recommendations

The usage of this module is recommended to specify the image type.

Table FFF.2.4-8. Enhanced XA/XRF Image Module Recommendations

Attribute Name | Tag | Comment
--- | --- | ---
Image Type | (0008,0008) | The first value is DERIVED in this scenario.

###### FFF.2.4.2.3.2 Derivation Image Macro Recommendations

The usage of this macro is recommended to encode the information of the different derivation processes and steps, as well as the source SOP instance(s) when the image or frame are derived from other SOP Instance(s).

Table FFF.2.4-9. Derivation Image Macro Recommendations

Attribute Name | Tag | Comment
--- | --- | ---
Derivation Image Sequence | (0008,9124) | Contains one item per derivation process that led to this SOP Instance.
>Derivation Description | (0008,2111) | Free text description of this derivation process, typically for display purposes.
>Derivation Code Sequence | (0008,9215) | Contains as many items as derivation steps in this derivation process.
>Source Image Sequence | (0008,2112) | Contains one item per source SOP Instance used in this derivation process.

If this image is not derived from source SOP Instances, the Derivation Image macro is not present, and the XA/XRF Frame Characteristics macro is used instead.

###### FFF.2.4.2.3.3 Pixel Intensity Relationship LUT Macro Recommendations

The usage of this macro is recommended to enable the applications to get the pixel values back to a linear relationship with the X-Ray intensity.

If readers of the image do not recognize the Pixel Intensity Relationship value, readers can use the value "OTHER" as default.

The number of bits in the LUT Data attribute (0028,3006) may be different from the value of Bits Stored attribute (0028,0101).

###### FFF.2.4.2.3.4 XA/XRF Frame Characteristics Macro Recommendations

The usage of this macro is recommended to specify the derivation characteristics

Table FFF.2.4-10. XA/XRF Frame Characteristics Macro Recommendations

Attribute Name | Tag | Comment
--- | --- | ---
XA/XRF Frame Characteristics Sequence | (0018,9412) |
>Derivation Description | (0008,2111) | Contains the description of the latest derivation process.
>Derivation Code Sequence | (0008,9215) | Contains as many items as derivation steps in this derivation process.
>Acquisition Device Processing Description | (0018,1400) | Specifies the derivation made at the acquisition system.
>Acquisition Device Processing Code | (0018,1401) | Specifies the derivation made at the acquisition system.

If the image is derived from one or more SOP Instances, the XA/XRF Frame Characteristics Sequence always contains the same values as the last item of the Derivation Image Sequence.

If the image is derived but not from other SOP Instances, it means that the derivation was performed on the Acquisition system, and the Acquisition Device Processing Description (0018,1400) and the Acquisition Device Processing Code (0018,1401) contain the information of that derivation.

An image derived from a derived image will change the Derivation Description but not the Acquisition Device Processing Description.

###### FFF.2.4.2.3.5 XA/XRF Frame Pixel Data Properties Macro Recommendations

The usage of this macro is recommended to specify the type of processing applied to the stored pixel data of the derived frames.

Table FFF.2.4-11. XA/XRF Frame Pixel Data Properties Macro Recommendations

Attribute Name | Tag | Comment
--- | --- | ---
Frame Pixel Data Properties Sequence | (0028,9443) | Recommended in this scenario.
>Frame Type | (0008,9007) | The first value is DERIVED in this scenario
>Image Processing Applied | (0028,9446) | In case of derivation from a derived image, this attribute contains a concatenation of the previous values plus the new value(s) of the latest derivation process.

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