[Freesurfer] drawing circle around vertex on surface

Hi all,

I'm trying to create a label by making a circle with a fixed radius around a defined vertex. I'm trying to use the method described here:

https://www.mail-archive.com/freesurfer@nmr.mgh.harvard.edu/msg44098.html

I made the initial surface overlay with my vertex of interest having a value of 1 and 0 everywhere else with:

mri_volsynth --pdf delta --delta-crsf 108555 0 0 0 --o pBECTS007_spike.mgh --template rh.thickness

Then I smoothed with fwhm:

mri_surf2surf --s pBECTS007 --hemi rh --sval pBECTS007_spike.mgh --fwhm 10 --tval ./pBECTS007_spike_fwhm.mgh

My question is, is there an easy way to divide all vertices by the value of my vertex of interest after smoothing in tksurfer? If not, is there a command that will allow me to extract the vertex values and indices to do so?

Thank you!

Dan Song Clinical Research Coordinator Massachusetts General Hospital Neurology Department