If you subtract them, eg, fscalc vol1.mgz sub vol2.mgz abs gte 0.5 -o diff.mgz This command will subtract the two, take the absolute values, then threshold (binarize) the differences. I'm not sure what you are looking for in terms of aparc+aseg, but you can do something like mri_segstats --ctab-default --seg aparc+aseg.mgz --excludeid 0 --i diff.mgz --sum sum.dat and sum.dat will tell you the percent of each ROI that had edits

On 10/1/2021 4:01 PM, Kang, Jee Won wrote:

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Hello all,

I'm very new to Freesurfer and have started with quality-checking recons. I wanted to know if there is a way to compare volumes before and after edits were made before recon-all has been re-run.

For example, if we have brainmask.mgz that has been edited and brainmask_ORIG.mgz before any edits were made, is there a way to create a volume overlay and extract the areas where edits were made (perhaps parsed from aparc+aseg)?

Thank you for your assistance on this!

-Jee Won

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