3D geometrical features of anatomic structures: the example of the ulna and radius bones

This paper addresses two important issues of three-dimensional (3D) natural shape analysis. The first concerns the segmentation of these shapes into 3D primitives and the second deals with their geometric characterisation by means of intrinsic features. Restricting ourselves to 3D objects formed from two-dimensional (2D) cross-sectional adjacent slices (i.e., long bones), we present a method of contextual classification and results concerning the ulnar bone. With respect to the second issue, a curvature-torsion analysis of the medullar axis is introduced and the results are represented by means of torsion images. A first application to ulnar structures is given. It is shown that radius bones have zero torsion and that their curvatures can be studied in 2D. A preliminary statistical study of the 2D curvature of the radius is also presented.