The image rendering techniques that have used to study renal
artery stenosis fall into two categories: surface rendering and volume
rendering. In surface rendering, Shaded Surface Display (SSD) begins by
choosing a threshold value, and then geometric primitives are automatically
fit to the high contrast contours in the volume that match the threshold.
The technique of Maximum Intensity Projection(MIP), which is one of the
volume rendering techniques, projects the brightest voxels along each ray
passing through the volume [5]. Direct Volume Rendering(DVR)
methods, which are another class of volume rendering techniques, are
characterized by mapping elements directly into screen space without using
geometric primitives as intermediate representation.