hi everyone             i run fnirt on structural volume, the result is "MN_str2diff.mat.nii.gz" which is a non linear transformation between the structural space and the MNI space. i want to use its inverse (using convert_xfm) in running probtrackx using a seed volume in the MNI space. can i make the inversion in this format (.nii.gz), or there is another way ? thanks