From 3dSkullStrip's help description, see step #2:
The fully automated process consists of three steps:
1- Preprocessing of volume to remove gross spatial image
non-uniformity artifacts and reposition the brain in
a reasonable manner for convenience.
** Note that in many cases, using 3dUnifize before **
** using 3dSkullStrip will give better results. **
2- Expand a spherical surface iteratively until it envelopes
the brain. This is a modified version of the BET algorithm:
Fast robust automated brain extraction,
by Stephen M. Smith, HBM 2002 v 17:3 pp 143-155
Modifications include the use of:
. outer brain surface
. expansion driven by data inside and outside the surface
. avoidance of eyes and ventricles
. a set of operations to avoid the clipping of certain brain
areas and reduce leakage into the skull in heavily shaded
data
. two additional processing stages to ensure convergence and
reduction of clipped areas.
. use of 3d edge detection, see Deriche and Monga references
in 3dedge3 -help.
3- The creation of various masks and surfaces modeling brain
and portions of the skull
--pt
