Perspective Isosurface and Direct Volume Rendering for Virtual Endoscopy Applications

Abstract

Virtual endoscopy has proven to be a very powerful tool in endoscopic surgery. However, most virtual endoscopy systems are restricted to rendering isosurfaces or require segmentation in order to visualize additional objects behind occluding tissue. This paper presents a system for real-time perspective direct volume and isosurface rendering, which allows to simultaneously visualize both the interesting tissue and everything that is behind. Large volume data can be viewed seamlessly from inside or outside the volume without any pre-computation or segmentation. Our system uses a novel ray-casting pipeline for GPUs that has been optimized for the requirements of virtual endoscopy and also allows easy incorporation of auxiliary geometry, e.g., for displaying parts of the endoscopic device, pointers, or grid lines for orientation purposes. We present three main applications of this system and the underlying ray-casting algorithm. Although our ray-casting approach is of general applicability, we have specifically applied it to virtual colonoscopy, virtual angioscopy, and virtual pituitary surgery.