I am planning an analysis using freesurfer to compare 2 groups. The SPGRs
that will be used vary in regard to slice thickness (from 0.86 to 1.5 in
each axis), number of slices acquired (100-256), and orientation (axial;
coronal) due to the fact that these were collected over a number of years on
the same scanner. In another posting I read that this might be a problem
but wanted to revisit this to see if any specific heterogeneity in the
parameters should be particularly avoided. Also, if the groups differ such
that one group has largely similar scan parameters and the second group is
more heterogeneous, will this introduce any systematic bias in cortical
thickness estimates, parcellation, or segmentation values? Thanks for any
advice on this issue.