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
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
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