Slicer DICOM Scalar volume plugin relies on (old) GDCM: why do we not use DCMTK?

Yes, I think it is a idea to have the DICOM image type code available in ITK without duplication, but it should not be a blocker to move forward. Could an issue please be created here:

GitHub - KitwareMedical/ITKDICOM: Better support for DICOM in ITK.

that points to the appropriate code as a reference?

The overall plan sounds good :thumbsup:

Worth noting, @pieper did some digging the other week and found these DICOM datasets from GDCM:

Grassroots DICOM / Gdcmdata / [a0bba5]

These are a good resource for regression testing.