External Email - Use Caution Hi Anastasia,
Thank you for your reply. So for segmentation.stats, should I divide the regional areas by eTIV or treat it as a covariate for a group comparison? Is it the same with Total cerebral white matter volume for wmparc.stats. For Diffusion measurement, for example, FA, if a subject has lower FA in general in the brain, should I adjust the whole brain FA or average FA for that matter? Best, Qi On Mon, Aug 31, 2020 at 6:53 PM Yendiki, Anastasia <ayend...@mgh.harvard.edu> wrote: > Hi Qi - Correcting for overall brain size is important when you are > comparing measures of length/area/volume. As in, you want to know if a > region specifically is bigger in population A vs. B, and not just because > the whole brain is bigger. In that case, use eTIV (estimated total > intracranial volume) from the freesurfer segmentation stats. > > FA is not measuring size of a region, so correcting for brain size is less > of an issue there. It's a possibility perhaps that for someone with a > substantially smaller brain there may be more partial voluming affecting > FA, so it can't hurt to check for an effect before including it in your > analysis. > > Anastasia. > ------------------------------ > *From:* freesurfer-boun...@nmr.mgh.harvard.edu < > freesurfer-boun...@nmr.mgh.harvard.edu> on behalf of Zeng, Qi < > qi.z...@icahn.mssm.edu> > *Sent:* Monday, August 31, 2020 11:44 AM > *To:* Freesurfer support list <freesurfer@nmr.mgh.harvard.edu> > *Subject:* [Freesurfer] group level analysis > > > External Email - Use Caution > > Hi, > > When conducting group-level analysis, for example comparing volumetric > differences or tractography FA across subjects between groups. How we > correct for the size of the brain when comparing volumetric differences or > correct for the whole brain FA? > Thank you so much! > > Best, > Qi > > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer -- Ph.D. candidate Icahn School of Medicine at Mount Sinai
_______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
