mrconvert dwi.mif tmp-[].mif && testing_diff_image tmp-[].mif dwi.mif
mrcat tmp-??.mif - | testing_diff_image - dwi.mif
mrcat tmp-[0:4].mif tmp-[5:20].mif tmp-[21:67] - | testing_diff_image - dwi.mif
mrcat tmp-[0:4].mif tmp-[5:20].mif tmp-21.mif tmp-[22:67] - | testing_diff_image - dwi.mif
mrcat tmp-[0:16].mif tmp-[17:33].mif tmp-[34:50].mif tmp-[51:67].mif -axis 4 - | testing_diff_image - mrcat/out.mif
