Dear Freesurfer experts,

I have two groups of subjects (healthy and patients). The patients have different degrees of atrophy. Looking into the individual scans, the subjects are largely different in the space between the sulcuses and the size of ventricles. My questions are:

1. Is there any way to correct for these differences in the surface based analysis?

2. Including eTIV covariate does it help in this case?

3. Does the resampling to "fsaverage" overcome the challenge of these differences between the subjects? 

I appreciate any advice,

John