Evaluation of methods for shaded surface display of CT volumes.

There are several ways to compute a shaded surface display of radiological 3D density volumes. In this paper we evaluate 12 methods which are different combinations of principles for detection of the surface to be displayed (gray-value threshold, gradient threshold, zero-crossing of 2nd derivative), localizing this surface in space (grid-point accuracy, subvoxel accuracy) and finally estimating the direction of the surface normal (from the gradient in the 2D depth image, from the gradient in the 3D-volume). The best quality is obtained by zero-crossing detection, subvoxel localization, and 3D-gradient orientation.