Hello Doug and Freesurfers,
I am trying to compute a structural measure called 'BrainSegVolNotVent' as an approximate value of total brain volume. 'BrainSegVolNotVent' is now present in aseg.stats files but the dataset I'm working on was preprocessed using FS 5.0, which did not produce this variable. Per your advice I found in a previous email, I reran mri_segstats adding the flags --brainmask mri/brainmask.mgz --brain-vol-from-seg.
The new aseg.stats file contains the following lines that were added after running this command:
# Measure BrainMask, BrainMaskNVox, Number of Brain Mask Voxels, 1667093, unitless # Measure BrainMask, BrainMaskVol, Brain Mask Volume, 1667093.000000, mm^3 # Measure BrainSegNotVent, BrainSegVolNotVent, Brain Segmentation Volume Without Ventricles, 232145.000000, mm^3 # Measure BrainSeg, BrainSegNVox, Number of Brain Segmentation Voxels, 1410666, unitless # Measure BrainSeg, BrainSegVol, Brain Segmentation Volume, 1410666.000000, mm^3
The numbers look a bit odd. BrainSegVol and BrainSegVolNotVent should normally be close to each other, right? Also unitless values such as BrainSegNVox and BrainMaskNVox seem to be equal to their corresponding volumetric values.
Do you have any idea what might have gone wrong? Here's the command I ran:
mri_segstats --seg mri/aseg.mgz --sum stats/aseg.stats --pv mri/norm.mgz --empty --excludeid 0 --excl-ctxgmwm --supratent --subcortgray --in mri/norm.mgz --in-intensity-name norm --in-intensity-units MR --etiv --surf-wm-vol --surf-ctx-vol --totalgray --ctab /usr/local/freesurfer/stable5_0_0/ASegStatsLUT.txt --subject SUBJECT_ID --brainmask mri/brainmask.mgz --brain-vol-from-seg
Thanks very much for your help!
Best, Hamdi