I would like to extract the outer surface from those volumes to be able to use in Freesurfer. 

I tried 'mri_vol2surf' but I didn't have the registration file. So I try make_register to create a registration file and the system give me an error as it couldn't open the header file to configure the fctstem...

Does anyone know another way for extract the surface ( even with Matlab) ? 

Thanks, 

VP