[Freesurfer] Subcutaneous fat and intensity normalisation

Dear FreeSurfers,

I have a question concerning pctsurfcon and subcutaneous fat. The first step in the Freesurfer processing pipeline is intensity normalisation, which assumes that high intensity signal is due to white matter and uses this as a reference point. However this happens prior to skull stripping and therefore slices contain subcutaneous fat, which also has a high signal intensity. When processing images from obese subjects might the large amount of subcutaneous fat affect intensity normalisation thereby affecting measures like pctsurfcon further down the line? Or does freesurfer distinguish between subcutaneous fat and white matter?

Thanks Nenad