Dear TORTOISE experts,
When I using ImportDICOM to import diffusion data, it reported in the terminal, "Warning: DTI gradient directions only tested for axial (transverse) acquistions, please validate bvec files".
I have no idea with this warning. And I check the generated bvec files, it is no same as the b vector table I import in MRI scanner. But when I check diffsuion tensor with "ComputeGlyphMaps", the orientation in axial, coronal, sagittal are all right.
What else things shoud I do to ensure the step of data importing is right?
Thanks very much.
The warning "Warning: DTI gradient directions only tested for axial (transverse) acquistions, please validate bvec files" comes from dcm2niix that the ImportDICOM routine internally uses.
Even for some axial acquisitions, dcm2niix can not figure out the orientation of the images (due to missing or unconventional information) and print out that warning message.
TORTOISE uses different coordinate systems for the images and the gradients. For images, it is the scanner coordinate system as provided by the DICOMs (or NIFTIs). Additionally all scanners use different coordinate systems too. So it is VERY rare to have the b-vectors imported in the scanner to be identical to the TORTOISE's bvecs.
All you have to do is to check the ComputeGlyphMaps and ComputeNSDECMap. If as you mentioned, they are correct, then your gradients are correct.
Hope this helps.