Computed tomographic colonography for colorectal screening

Computed tomographic colonography (CTC) is a specialized computed tomographic examination that has been optimized for the detection of colorectal polyps. The technology has undergone major advances in recent years and there is emerging consensus that state-of-the-art CTC results in performance characteristics comparable to those of optical colonoscopy for polyps > or = 8 mm in size. Effective polyp detection rests on the quality of several components of the examination, which must all be optimized in order to maintain appropriate sensitivity and specificity, including adequate bowel preparation, good colonic distension, sufficient scanning parameters, and appropriate interpretation. The emergence of CTC provides another method of colonic evaluation for colorectal cancer screening and prevention. In contrast to a mutually exclusive approach to screening, the availability of both optical colonoscopy and CTC should hopefully improve overall compliance rates for colorectal screening. The ultimate role of this technique in the screening program continues to evolve. There is currently considerable variability in the materials and methods used in CTC. This article describes the approach used at the University of Wisconsin, which has been validated in a large multicenter screening trial and which is currently used for an active CTC-based colorectal cancer screening program.