Hi Mark, Sorry about the confusion again. I am multiplying my ROI (which is grey matter) by sienax pve_1 mask. The aim was to make the ROI fit within the grey matter region as much as possible. So, I thresholded and binarized pve_1 and multipled by my grey matter ROI then transferred it to DTI space. I hope this is clearer. Would you recommend this approach? Thanks. Best,