Shape analysis based on medial models incorporating object variability

Knowledge about the biological variability of anatomical objects is essential for statistical shape analysis and discrimination between healthy and pathological structures. This paper describes a novel approach that incorporates variability of an object population into the generation of a characteristic 3D shape model. The proposed shape representation is a coarse-scale sampled medial description derived from a fine-scale spherical harmonics (SPHARM) boundary description. This medial description is composed of a net of medial samples (m-rep) with fixed graph properties. The medial model is computed automatically from a predefined shape space using pruned 3D Voronoi skeletons to determine the stable medial branching topology. An intrinsic coordinate system and an implicit correspondence between shapes is defined on the medial manifold. Our novel representation describes shape and shape changes in a natural and intuitive fashion. Several studies of biological structures are presented. A new medial shape similarity study of group differences between Monozygotic and Dizygotic twins in lateral ventricle shape demonstrates the meaningful and powerful representation of local and global form. 6/09/2001; 11:27; p.1 Shape analysis based on medial models 2