It's because "Brain Segmentation Volume Without Ventricles" stat is computed with partial volume correction but "Number of Brain Segmentation Voxels" stat is not. Please refer to this wiki for more info.
https://surfer.nmr.mgh.harvard.edu/fswiki/BrainVolume
Sita
On Wed, 1 Jul 2009, Jared Price wrote:
Gurus, Looking over some stats recently I noticed that if you add up all of the freesurfer stats for ventricles, namely the left and right lateral ventricles plus 3rd, 4th, and 5th ventricles and subtract that from the "Number of Brain Segmentation Voxels" stat, you do not get the value of the "Brain Segmentation Volume Without Ventricles" stat. Anyone know why?
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