Dear FreeSurfer experts

I'm trying to study WM-lesions of my data. As I saw in previous messages to the forum and papers, it is contained in the aseg.mgz as the WM-hypointensities volume (label-ID 77), but it has only one value from the whole brain in the aseg.mgz, the left/right fields appear empty in the aseg.stats, and I would be interested in subtract this volume value, or volume label image for each hemisphere. Is it possible on FS?

May thanks in advanced,
Gabriel.