Convert FS volume into MNI space using mri_vol2vol

I want to convert fs volume into MNI space so I can get some ROIs in MNI space

I tried using the mri_vol2vol function in free surfer

mri_vol2vol --mov Subject_FS1mm.nii.gz --targ MNI152_T1_1mm_brain.nii.gz --o Subject_MNI_FS1mm.nii.gz

Subject_FS1mm.nii.gz - volume I want to convert

MNI152_T1_1mm_brain.nii.gz - reference template

Subject_MNI_FS1mm.nii.gz - name of output file

However, I am getting and error " error: File exists

error: ERROR: no registration (R) is specified"

Is there any work around it

Hi @Reubebe,

Try adding the --regheader flag, and if that doesn’t work, additionally try converting the niftis to .mgz with mri_convert.