We are obtaining MRS data and functional MRI data on two separate days for each subject. We use structural scan obtained during both these sessions for the freesurfer segmentation. MRS scan gives us a binary mask (nii format) in the same space as the structural image obtained during that particular scan. We want to use this binary mask during the surface based functional MRI analysis. I am not sure how to transform this binary mask to the surface space. Is there a way to do this?