Hi Chintan
(a) yes, I would think fsaverage would be fine in this age range
(b) we do *not* resample into talairach coords, so volumes and surface
areas should include eIV or something equivalent as a covariate. Thickness
shouldn't require it.
cheers
Bruce
On Tue, 5
Sep 2017, Mehta, Chintan wrote:
Dear FreeSurfer users,
I am new to surface based analysis in FreeSurfer (version 6.0). My data
consists of T1-weighted scan
from normally developing youth of 8 to 21 years of age. I have two questions on
assumptions of this
analysis for pediatric data:
(a) Is "fsaverage" an appropriate common template for all subjects of ages 8 to
21? Online tutorials
suggest that fsaverage is the most commonly used template in FreeSurfer
analyses and, furthermore,
imply that FreeSurfer can be used on scans of normally developing children as
young as five years
old.
I am running analyses separately over different age groups (like ages 8 to 12,
13 to 16, 17 to 21)
to ensure robustness. However, would combining results be inaccurate?
(b) Previous posts in this forum and FreeSurfer documentation strongly
recommend somehow normalizing
for head size or total brain volume in models of ROI area/volume. Would the
eTIV covariate also be
appropriate for surface-based analysis of scans registered to fsaverage when
using mri_glmfit?
To me, it appears that scans registered to fsaverage have been warped to
Talairach space, so the
whole brain adjustment has been implicitly made.
Thank you in advance for your great insights!
Best,
Chintan
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