Hi Fernanda, The choice between ICV vs a measure of total "brain volume" or total cortical gray matter volume depends on whether you want to control for potential overall brain atrophy. Using ICV will control for overall "head size", but not for potential overall brain atrophy (e.g., with age, or related to dementia). Using total cortical gray matter will control for overall brain atrophy and thus would allow you to say that changes in a given structure were "above and beyond" any existing global atrophy.
Personally, I find it more informative to control for potential global atrophy, and thus use total cortical gray matter rather than ICV. After all, if a structure is decreased in size, but the overall brain is decreased as well, you have not established anything regarding the specificity of that change to the structure of interest if you use ICV as the covariate. cheers, -MH On Tue, 2011-05-17 at 09:19 -0300, Fernanda Palhano wrote: > Hello, > > I have two questions about volumetric analysis: > First: Are the volume measures in the files aseg.stats or ? > h.aparc.stats (Gray Matter Volume) already normalized by ICV? Or > should I divide > all the structure volumes which I want to compare between subjects by > the ICV of each subject? > Second: When comparing gray matter volumes the correct is use the ICV > or the total cortical gray matter volume to normalize? And if I have > to use the total cortical gray matter volume, how can I obtain it? I > know that this information is in the aseg.stats file, but I was > wondering if I can use asegstats2table to extract it. > > > Thank you very much, > > Fernanda > > _______________________________________________ > 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
