[Freesurfer] Freesurfer longitudinal analysis accuracy

Dear all,

We've run longitudinal Freesurfer on 30 healthy subjects. We have two subgroups (n=15) and we found a significant longitudinal change in the left and right cerebellar cortex in one of our subgroups. However, this change is very small: mean=0.67% range: -1.61-2.3% for the right cerebellar cortex; mean=0.86% range: -1.64-3.7% for the left cerebellar cortex. Although statistics indicate significant cerebellar cortex increase, we are sceptical that Freesurfer's accuracy allows reliable detection of such small differences. Is there any article on how accurate the longitudinal Freesurfer for cerebellum segmentation or any suggestion on how to decide whether our results are reliable?

Best, Gabor