On 9/5/17 9:09 AM, 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.
fsaverage is appropriate
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?
Not sure what you mean here
(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?
Yes, for surface area and volume analysis. Such an adjustment is not
needed for thickness analysis
To me, it appears that scans registered to fsaverage have been warped
to Talairach space, so the whole brain adjustment has been implicitly
made.
All FS analysis is done in native space, so no adjustments are done.
Surface-based warping to fsaverage does not account for changes in volume.
Thank you in advance for your great insights!
Best,
Chintan
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