Segmentation and representation of human brain cortex from Magnetic Resonance (MR) images is an important
step for visualization and analysis in many neuro imaging applications. In this paper, we propose an automatic
and fast algorithm to segment the brain cortex and to represent it as a geometric surface on which analysis
can be carried out. The algorithm works on T1 weighted MR brain images with extracranial tissue removed.
A fuzzy clustering algorithm with a parametric bias field model is applied to assign membership values of
gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) to each voxel. The cortical boundaries,
namely the WM-GM and GM-CSF boundary surfaces, are extracted as iso-surfaces of functions derived from
these membership functions. The central surface (CS), which traces the peak values (or ridges) of the GM
membership function, is then extracted using gradient vector diffusion. Our main contribution is to provide a
generic, accurate, fast, yet fully-automatic approach to (i) produce a soft segmentation of the MR brain image
with intensity field correction, (ii) extract both the boundary and the center of the cortex in a surface form,
where the topology and geometry can be explicitly examined, and (iii) use the extracted surfaces to model the
curvy, folding cortical volume, which allows an intuitive measurement of the thickness. As a demonstration,
we compute cortical thickness from the surfaces and compare the results with what has been reported in the
literature. The entire process from raw MR image to cortical surface reconstruction takes on average between five to ten minutes.