Hi all,
I used MRIConvert (revised 190) to extract bvecs from Siemens Syngo data. The problem is that Siemens stores the gradient directions in physical coordinates in the dicom. FSL need this vectors in the image coordinate system to perform appropriate tractography. But if I think well this version of MRIConvert doesn't perform the conversation of the bvecs to image coordinate system, so I did a TBSS analysis using the unrotated bvecs (bvecs in physical coordinate system). Because FA and MD are not sensible to rotation (rotationally invariant), I think the calculated FA and MD values won't be affacted whether they are calculated using bvecs in the physical coordinate system or bvecs in the image coordinate system. Am I right, or do I need to recalculate the whole TBSS analysis?
I'd be appreciate an early reply, thanks a lot.
|