Authors
Daniel Wagner, daniel@wagner.tzo.net, Institute of Computer Graphics and Algorithms
Rainer Wegenkittl, rainer.wegenkittl@tiani.com, Tiani Medgraph
Eduard Gröller, groeller@cg.tuwien.ac.at, Institute of Computer Graphics and Algorithms

Abstract
Virtual endoscopy can be used for preoperative planning, for training and intraoperatively. Surface rendering displays the inner lumen very well. Volume rendering has to be used if the external structures are of interest. For certain applications, e.g. endoluminal biopsy, it is of great advantage to be able to use both techniques at once. In this work we describe an approach that allows using these two methods in combination on a low-end standard personal computer. Since image generation is done in a preprocessing step, any high quality volume or polygonal rendering technique can be used and mixed together without any loss in performance at run-time. This work extends a previous image based rendering system for virtual bronchoscopy to include tracking of a rigid or flexible endoscope and finding one's way in the tracheal tree by displaying the endoscope's position in a top-view map of the trachea. Natural landmarks, i.e. bifurcations in the bronchial tree, are used for registration. Properties of the technique are explored on a phantom data set.

Keywords
medical visualization, virtual endoscopy, registration, image based rendering