Notes on Brain Volume

Note: The descriptions below refer to version 4.5 and earlier. For version 5.0 and on, please refer to MorphometryStats.

Measures of brain volume

from mri_segstats --help

There will be four measures of brain volume in the output summary file produced by mri_segstats (aka <subj>/stats/aseg.stats):

  1. BrainSegNotVent - sum of the volume of the structures identified in the aseg.mgz volume. This will include cerebellum but not ventricles, CSF and dura. Includes partial volume compensation with --pv. This is probably the number you want to report.

  2. BrainMask/BrainMaskNVox - total volume of non-zero voxels in brainmask.mgz. This will include cerebellum, ventricles, and possibly dura. This is probably not what you want to report.

  3. BrainSeg/BrainSegVol - sum of the volume of the structures identified in the aseg.mgz volume. This will include cerebellum and ventricles but should exclude dura. This does not include partial volume compensation, so this number might be different than the sum of the segmentation volumes.

  4. IntraCranialVol (ICV) - estimate of the intracranial volume based on the talairach transform. See eTIV for more details. This is the same measure as Estimated Total Intracranial Volume (eTIV).