Since estimated intracranial volume (eTIV) from FreeSurfer is calculated from the alignment of the input MR images to the MNI305 brain atlas, and is not segmentation-based, a concern was raised that this might lead to a bias by total brain volume. This study managed to prove the existence of bias by total brain volume in eTIV.

Article: Estimated intracranial volume from FreeSurfer is biased by total brain volume

Authors: Niklas Klasson, Erik Olsson, Carl Eckerström, Helge Malmgren and Anders Wallin