the mean across both lh.cortex.label and rh.cortex.label should be pretty
close. If you want it to be exact you should weight by area then
normalize
On Sat, 25 Jun 2016, Nabin Koirala wrote:
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.
_______________________________________________
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.
