Dear Bruce, Thank you for the response. So, I more thing if I want to get the mean cortical thickness for whole brain I could simply take the mean between both hemisphere ? If I understood right from the FAQ.
Q. I am trying to measure the global mean cortical thickness (i.e combined across hemispheres), how would I do this? A: One suggestion is to use the surface area of each hemisphere as the weighting factor. In which case the global mean thickness including both hemispheres would be given by: bh.thickness = ( (lh.thickness * lh.surfarea) + (rh.thickness * rh.surfarea) ) / (lh.surfarea + rh.surfarea) If you use the values in the ?h.aparc.stats, it already factors out the 'unknown' region, so you don't have to do it yourself. Regards, Nabin On Sat, Jun 25, 2016 at 3:29 PM, Bruce Fischl <fis...@nmr.mgh.harvard.edu> wrote: > Hi Nabin > > unless the areas are the same size, the mean of the areal means won't > equal the overall mean. > > cheers > Bruce > > On Sat, 25 Jun 2016, Nabin Koirala wrote: > > Hi freesurfer team, >> I extracted the cortical thickness values using aparcstats2table command >> and >> I got the cortical thickness values for 34 regions and mean cortical >> thickness for each hemisphere. But when I averaged the cortical thickness >> from those 34 regions regions it was different than the mean cortical >> thickness obtained by aparcstats2table. I would expect it to be the same >> or >> very close but I checked it for more than 100 subjects and they are >> significantly different. Am I missing something silly here ? >> >> Thank you. >> >> Regards, >> Nabin >> >> > _______________________________________________ > 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. > >
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