[Freesurfer] estimated total intracranial volume

Hi All,

I'm interested in the relationship between estimated total intracranial volume (eTIV), and the volume measures generated in aseg.stats and lh/rh.aparc.stats. I have used freesurfer v3.0.3 for this data set.

Here I am using the output of aseg.stats for all volumes except the cerebral cortex while using the output of aparc.stats exclusively for estimates of cortical gray matter volume. As I'm looking at this data for multiple subjects I've used asegstats2table and aparcstats2table to extract the volume data for each subject (using the "--meas volume" flag).

Question: When I add these volumes generated in aseg.stats (excluding cortex), and rh,lh aparc.stats (cerebral cortex only), should the total be very close to the eTIV value found in aseg.stats?

Thanks, Paul