Location and geometric description of carpal bones in CT images

CT images were obtained of the wrist region of 15 cadavers and several living patients. Boundaries of bones were located using a technique based on dynamic programming. The resulting set of surface points on each bone was used to compute principal and antipodal axes and distances between surfaces of the bones, and an interpolation technique was developed to increase the apparent resolution of the 3-D reconstruction. A spatial coordinate system was established based on internal landmarks in the carpal anatomy. The angular orientations of all carpal bones were determined with respect to this system. The principal axes for the same bone among the multiple wrist specimens proved to be more widely dispersed than the antipodal axes for the same bones. The antipodal axes also correspond more closely to an intuitive notion of the "longest axis" of the bones. A method was developed to interpolate surface points between the coarsely-distributed points located by our boundary tracker, and to interpolate data between CT slices, producing a uniformly spaced 3-D data set. The surface of this representation of the bone was used to determine the spacing between the bones in the wrist. The enhanced resolution of the interpolated data improves the resolution of the spacing determination, compared to determinations based only on the points actually located by the boundary tracker.