Deformable Registration Grid DICOM import

Hi there,

I am trying to get my head around how Slicer reads TPS exported Displacement fields and calculates its Grid Orientation values.

For example, I have exported an arbitrary displacement field from my TPS and have the following values for Grid orientation,


However, when I look at the DICOM metadata regarding the same displacement field I get the following,

I assume the FrameOfReferenceTransformationMatrix DICOM tag has something to do with the previously mentioned Grid orientation but they seem to be inverted compared to one another.

All of this is important because I want to accumulate dose by applying the inverse displacement field to a dose distribution. I am wondering if I need to rotate/tilt my dose distribution before applying the inverse displacement field.

Any help would be greatly appreciated!

DICOM uses LPS coordinate system, while Slicer internally uses RAS. When the displacement field is imported from DICOM, the position and orientation is converted accordingly. See details here.

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