The methods are somewhat different. For the value in the aseg.stats table, the method is to compute the total volume inside the pial surface and subtract the total volume inside the white surface. For mris_anatomical_stats, the method is to compute the thickness times area of each vertex. This method will probably underestimate the total volume because it uses the area of the white surface when it should use the area of the surface in the middle between the white and pial surfaces. I've added this to the list of known issues on our release page.

doug

Alexopoulos, Dimitrios wrote:

I have generated surfaces using the the centos4 build (version 5.0) and want to confirm that my surface-based GM and WM volumes are correct. For the surface-based GM calculation I originally used 'mris_anatomical_stats -l lh.cortex.label subjectID hemi' (run from within the 'label' subdirectory) and for WM i used 'mris_wm_volume subjectID hemi' (run from within the 'surf' subdirectory). When I add the calculated left/right cortical volumes, I get a total that is different from what is output in the 'aseg.stats' file, which in version 5.0 is noted to contain total surface-based GM volume (Cortex, CortexVol: Total cortical gray matter volume (based on surface-stream).

What are the correct GM and WM surface-based volumes? Thanks. Jim

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