As you noted, the surfaces bisect the hippocampus and amygdala, so the small amount of tissue outside the pial surface is not included in the surface based measures of total GM volume. Compared to the overall variation in brain size, this should be inconsequential.
cheers, -MH On Mon, 2011-12-19 at 15:39 +0000, _andre...@sapo.pt wrote: > Hello, > > Recalling these emails: > > "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" > > > I question came up to me: > > The surfaces in the hippocampus/amygdala are inaccurate and should be > ignored. However, in version 5.0 the cortical volume is surface-based, > thus it takes into account the surfaces in the hippocampus/amygdala, > is this correct? > > If so, it is expected that an error is introduced in the surface-based > calculation of cortical volume. Has anyone checked the influence of > this error? Or FS compensates for the inaccuracy of the surface > estimation of these regions somehow? > > Thanks! > > Andreia > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > The information in this e-mail is intended only for the person to whom it is > addressed. If you believe this e-mail was sent to you in error and the e-mail > contains patient information, please contact the Partners Compliance HelpLine > at > http://www.partners.org/complianceline . If the e-mail was sent to you in > error > but does not contain patient information, please contact the sender and > properly > dispose of the e-mail. _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
