I'm wondering if there is any way of figuring out the surface size within a mask image (mask.mgh)

which is generated after running a group-level GLM analysis (2nd RFX) using mri_glmfit. 

As I'm thinking, this may be: 

  number of vertex by dimension of one vertex (1mm).

But I could be wrong and let me know if anyone knows the solution. 

-Glen 

fyi) the group analysis was performed in freesurfer sym space.