[Freesurfer] mri_segstats

Dear FS experts, I have PET image "pet.anat.mgz" in subject space. I want to calculate the mean PET signal for every parcellate and segment in the atlas "wmparc.mgz". Which one of the following commands is more accurate?

1. mri_segstats --seg $SUBJECTS_DIR/${subj}/mri/wmparc.mgz --ctab $FREESURFER_HOME/FREESURFERColorLUT.txt --i PET.anat.mgz --sum PET.wmparc.stats

2. mri_segstats --seg mri/wmparc.mgz --sum stats/wmparc.stats --pv mri/norm.mgz --excludeid 0 --brainmask mri/brainmask.mgz --in mri/ PET.anat.mgz--in-intensity-name norm --in-intensity-units MR --subject ${subj} --surf-wm-vol --ctab /usr/local/freesurfer/stable5_3_0/WMParcStatsLUT.txt --etiv

Best, Mohamad