The usage in this scenario is on a “per frame” context to allow individual pixel shift factors for each Subtraction Item ID.
The Subtraction Item ID specified in the Mask Subtraction Sequence (0028,6100) as well as in the Frame Pixel Shift Sequence (0028,9415) allows creating a relationship between the subtraction (mask and contrast frames) and a corresponding set of pixel shift values.
The Pixel Shift specified for a given frame in the Frame Pixel Shift Macro is the shift to be applied when this frame is subtracted to its associated mask for the given Subtraction Item ID.
Not all frames may have the same number of items in the Frame Pixel Shift Macro, but all frames that are in the scope of a Subtraction Item ID and identified as “contrast” frames in the Mask module are recommended to have a Frame Pixel Shift Sequence item with the related Subtraction Item ID.
Table FFF.2.3-9 FRAME PIXEL SHIFT MACRO Recommendations
|Frame Pixel Shift Sequence||(0008,9415)||Recommended in this scenario. The number of items may differ for each frame.|