Segmentation of the skull in MRI volumes using and taking the partial volume effect into account deformable model

Segmentation of the skull in medical imagery is an important stage in appli cations that require the construction of realistic models of the head. Such models are used, for example, to simulate the behavior of electro-magnetic fields in the head and to model the electrical activity of the cortex in E EG and MEG data. in this paper, we present a new approach for segmenting re gions of bone in MRI volumes using deformable models. Our method takes into account the partial volume effects that occur with MRI data, thus permitti ng a precise segmentation of these bone regions. At each iteration of the p ropagation of the model, partial volume is estimated in a narrow band aroun d the deformable model, Our segmentation method begins with a pre-segmentat ion stage, in which a preliminary segmentation of the skull is constructed using a region-growing method. The surface that bounds the pre-segmented sk ull region offers an automatic 3D initialization of the deformable model. T his surface is then propagated (in 3D) in the direction of its normal. This propagation is achieved using level set method, thus permitting changes to occur in the topology of the surface as it evolves, an essential capabilit y for our problem. The speed at which the surface evolves is a function of the estimated partial volume. This provides a sub-voxel accuracy in the res ulting segmentation. (C) 2000 Elsevier Science B.V. All rights reserved.