Hi Rashmi
of course they are different - there is noise in the scans and motion and other sources of corruption! The amount of difference will depend on the structure and the quality of the data.
cheers Bruce On Thu, 14 Mar 2013, Rashmi Singh wrote:
Hello experts, I am doing volumetric studies where I am comparing the subcortical structures volumes among different experimental groups. I usually do two mprages on one subject in a single scan at two time-points. I run recon all on both mprages for a single subjects. To my surprise the volumes of same structure of a single subject calculated by freesurfer using two mprages are different.
I did longitudinal run using the two mprages from same subject, however then also the volumes show differences.
May you please advise me what to do. Thanks, Rashmi