Multiphase active contour segmentation constrained by evolving medial axes

This paper describes a novel multiphase level set active contour segmentation method enabling simultaneous segmentation of multiple complex objects. The proposed technique supports preservation of prior topological configuration between different objects as well as to provide soft shape constraints. Whereas each contour evolves using its own evolution equation the contours are constrained and interrelated to each other by specially designed normal velocity component in the contours evolution equations. This velocity component is calculated using adaptively estimated set of medial axes between the corresponding contour and all other contours. In the proposed implementation the medial axes are represented by level set functions calculated from the level set functions representing active contours. By design, the proposed constraint can be used with edge, area or hybrid based methods and can easily incorporate additional constraints. The paper shows performance of the method on simulated as well as real images.