We are working on calculating the volume of thalamic nuclei in our participants and noticed that there is often a discrepancy in measured volume in the ThalamicNuclei.v12.T1.volumes.txt and the volume calculated for the same thalamic nucleus using fslstats -V. (Note that the nuclei are all created in FreeSurfer, just extracted to individual .nii files afterwards). 

For example: in one control subject, the volume of the right VPL was measured in FreeSurfer as 264.650938 mm^3, but the same extracted label in fslstats shows a volume of 242 mm^3. What could be causing this discrepancy?

Thanks

Corinna