[Freesurfer] Sampling vertex-wise data across various distances from the core of a mask to a somewhere else on fsaverage

Hi Doug and Freesurfer Experts,

I am trying to see whether cortical thinning gets progressively less severe as we move further away from a seed/voxel (e.g. precuneus). Is it possible to perform correlations between the (a) distance between a given vertex to specific point on fsaverage, and the (b) measurement (i.e. thickness) of the vertex?

Say I have a binary mask of the precuneus seed, as well as a second binary mask that surrounds it. How may I go about getting the thickness values at various distances, starting from the central core of the precuneus seed to the outer boundary of the second mask?

I was thinking of something analogous to the proj-frac function in mri_vol2surf where we could sample PET/fMRI data at different values along the cortical ribbon.

Apologies if that was rather confusing. If you like, I could make a drawing of what I am trying to do.

Thanks for your time.

Best Wishes, Elijah