[Freesurfer] brain parenchymal fraction

Dear Freesurfers, I need to extract the brain parenchymal fraction to check brain atrophy in my patients. The BPF is defined as "the ratio of brain parenchymal tissue volume to the total volume contained within the brain surface contour". In the text file aseg.stats, I found this info: # Measure BrainSeg, BrainSegVol, Brain Segmentation Volume, 1052408.000000, mm^3 # Measure BrainSegNotVent, BrainSegVolNotVent, Brain Segmentation Volume Without Ventricles, 1032104.000000, mm^3 # Measure BrainSegNotVentSurf, BrainSegVolNotVentSurf, Brain Segmentation Volume Without Ventricles from Surf, 1030608.836503, mm^3

Can I extract the BPF from those, or is any of them the BPF?

Thank you, Valeria