[Freesurfer] creating a cortical label using a 3D image ROI and calculating its volume and average thickness

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Dear Freesurfer users,

I would like to do the following:

- there is an ROI mask image file in the same space as the T1-weighted image

- I would like to use that mask to define the borders of a cortical area

- and then calculate volume and average thickness of the above defined cortical area

I know that I can get a rough estimate of the volume by applying the ROI mask to the the aparc* file and calculating the number of voxels, but what I would really like to do is use the ROI mask to constrain the WM and pial surfaces to the volume inside the ROI and then calculate statistics using the surfaces approach.

I also know that I can combine existing labels, but unfortunately this custom ROI contains parts of various cortical regions, not whole regions.

Any advice would be appreciated!

Best wishes,

Renat.