TTT.2.3.3 Encoding Details
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#### TTT.2.3.3 Encoding Details

##### TTT.2.3.3.1 X-Ray 3D Angiographic Image IOD

###### TTT.2.3.3.1.1 Frame of Reference Module Recommendations

Since the two volumes are reconstructed from the same projections, the reconstruction application will use the same patient coordinate system on both volumes so that the spatial location of the object of interest in both volumes will be the same. Therefore the two X-Ray 3D Instances will have the same Frame of Reference (FoR) UID. If the originating 2D Instances do not deliver a value of FoR UID, a new FoR UID has to be created for the reconstructed volumes.

Table TTT.2.3-1. Frame of Reference Module Recommendations

Attribute Name | Tag | Recommendation
--- | --- | ---
Frame of Reference UID | (0020,0052) | Use the same value for the full field of view volume and the sub-region volume.

###### TTT.2.3.3.1.2 Pixel Measures Macro Recommendations

The detailed size of the volume element (Pixel Spacing for x/y dimension and Slice Thickness for z dimension) may be different between the full field of view reconstruction and the sub-region reconstruction.

Table TTT.2.3-2. Pixel Measures Macro Recommendations

Attribute Name | Tag | Recommendation
--- | --- | ---
Pixel Measures Sequence | (0028,9110) | The pixel sizes and/or slice thickness are not necessarily equal in the two reconstructed volumes. Within each individual volume this sequence is encoded as "shared".

###### TTT.2.3.3.1.3 Plane Position (Patient) Macro Recommendations

The plane position of the first slice in the first volume may have a different value than in the second volume, as the sub-region volume can be smaller and shifted with respect to the full field of view volume.

###### TTT.2.3.3.1.4 Plane Orientation (Patient) Macro Recommendations

The plane orientation could be different in the second volume depending on the application needs, e.g., to align the slices with the object of interest.

###### TTT.2.3.3.1.5 Frame Content Macro Recommendations

This module encodes the timing information of the frames, as well as dimension and stack index values.

Table TTT.2.3-3. Frame Content Macro Recommendations

Attribute Name | Tag | Recommendation
--- | --- | ---
Frame Content Sequence | (0020,9111) | Provides details for each frame.
>Frame Acquisition Duration | (0018,9220) | Use the duration of the rotational acquisition in the two reconstructed volumes.

###### TTT.2.3.3.1.6 Frame Anatomy Macro Recommendations

The volume directly reconstructed from a sub-region of each of the original projection X-Ray frames does not necessarily reflect the same anatomy or laterality as the full field of view volume. Therefore the Frame Anatomy macro may point to a different anatomic context than the one documented for the originating frames.

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