Dear Freesurfer experts,

I would like to run surface based paired  t test of PET data on surface. For every subject I have visit pre treatment and post treatment. I tried to follow the instructions here https://surfer.nmr.mgh.harvard.edu/fswiki/PairedAnalysis but the toturial seems to be for cortical thickness data.

How can i modify the command mris_preproc to do paired test of PEt data on brain surface

 mris_preproc --target fsaverage --hemi lh \
   --meas thickness --out lh.paired-diff.thickness.mgh \
   --fsgd pairs.fsgd --paired-diff

thanks for any suggestion

John