Virtual Colon Dissection for Colorectal Cancer Screening

Virtual colonoscopy is a minimally invasive alternative for conventional optical colonoscopy to detect diseases of the colon, including polyps, diverticulosis, and cancer. In virtual colonoscopy computer tomography is combined with specialized visualization techniques in order to provide the physician with a comprehensive view of the colon wall. Due to the tortuous nature of the colon, the traditionally used fly-through visualization is time consuming and error prone. The recently emerging virtual colon dissection or flattening visualization, on the other hand, can result in a full coverage of the colon and this with a reduced inspection time. The unfolding, however, is a complicated process that introduces distortions and also care must be taken not to repeat or miss parts.

In this research, new techniques are proposed for virtual colon unfolding. Where previous techniques either preserve angles or areas, these new techniques strive to balance the angle and area distortions. In this way, down-scaling of important features, e.g. polyps, in the flattened representation can be avoided while preserving the shape as much as possible. This leads to significantly improved visibility of certain classes of polyps. The unfolding is realized in two steps. First, a cylindrical parameterization is calculated for the colon, together with the optimal length of the cylindrical domain. And then the cylindrical surface is cut open and rolled open to a rectangular area in the plane. In this way, a complete and one-to-one unfolding of the colon wall can be obtained. Finally, the details of the colon wall can be visualized on the obtained planar representation by the use of surface shading or volume rendering. A comparison, in terms of metric distortion and visual quality, of this new technique with state-of-the-art techniques demonstrates the advantages of the new approach.