Hi,

My understanding of etiv  is that it is derived from the registration of a brain to atlas space and not actually derived from the freesurfer segmentation.  I have a set of patients imaged at 2 time points that all have different etiv values between the first and second scan that are statistically significant.  As there was no change in their skulls between scans,  I am having difficulty understanding how this is possible.  Can anyone suggest what I may be doing wrong?

Best wishes,

Salil