Volumetric layer segmentation using coupled surfaces propagation

The problem of segmenting a volumetric layer of finite thickness is encountered in several important areas within medical image analysis. Key examples include the extraction of the cortical gray matter of the brain and the left ventricle myocardium of the heart. The coupling between the two bounding surfaces of such a layer provides important information that helps to solve the segmentation problem. Here we propose a new approach of coupled surfaces propagation via level set methods, which takes into account coupling as an important constraint. By evolving two embedded surfaces simultaneously, each driven by its own image-derived information while maintaining the coupling, we capture a representation of the two bounding surfaces and achieve automatic segmentation on the layer. Characteristic gray level values, instead of image gradient information alone, are incorporated in deriving the useful image information to drive the surface propagation, which enables our approach to capture the homogeneity inside the layer. The level set implementation offers the advantage of easy initialization, computational efficiency and the ability to capture deep folds of the sulci. As a test example, we apply our approach to unedited 3D Magnetic Resonance (MR) brain images. Our algorithm automatically isolates the brain from non-brain structures and recovers the cortical gray matter.