Hello all,

I want to calculate a Ventricle-to-Brain ratio (VBR) as a measure of parenchymal atrophy using Freesurfer version 5.3.0. I have tried to go about this using the aseg.stats output (using asegstats2table), but am running into inconsistencies.

The basic calculation for VBR is:

(Total Ventricular Volume/Total Brain Volume) * 100

i.e. Bigler, E. D. (2013). Traumatic brain injury, neuroimaging, and neurodegeneration. Frontiers in human neuroscience, 7, 395.

What is the best way to get Total Ventricular Volume (TVV) and Total Brain Volume (TBV) for this calculation? I have tried several ways, which lead to different values:

TVV = left lateral ventricle + left inf lateral ventricle + right lateral ventricle + right inf lateral ventricle + 3rd ventricle + 4th ventricle + 5th ventricle + choroid plexus

which gives me a different result than

TVV = BrainSegVol - BrainSegVolNotVent

and for TBV

TBV = TotalGrayVol + CorticalWhiteMatterVol

which differs from

TBV = BrainSegVolNotVent

Thank you for your help,

James Gullickson