[Freesurfer] Regarding cortical thickness

I am Bharti, a M.Tech./Ph.D student at School of Computer & Systems Sciences, Jawaharlal Nehru University, New Delhi, India. My area of interest is pattern recognition and image processing. In one of my research work, i used freely available freesurfer software to find cortical thickness using recon-all -all command.

But, while retrieving cortcal thickness maps using read_curv() function, i am getting different number of vertices for different brains. Are different number of cortical vertices possible for two different brains? I have gone through FAQ provided by Freesurfer but i did not find any related answer.

Kindly clarify.

Thanks in advance.