Screening CT colonography

CT colonography (Virtual Colonoscopy) was first introduced in 1994 as a novel imaging technique for the detection of colorectal polyps and cancer. It is currently proposed as a new screening tool for colorectal carcinoma that may be more acceptable to patients than current methods. There are a growing number of published studies evaluating all aspects of CT colonography, including technique, imaging displays, interpretation methods, patient acceptance, and lesion detection accuracy. While there are multiple studies that have found excellent CT colonography results for the detection of larger polyps in high risk or symptomatic patient cohorts, there are very few published studies evaluating the performance of CT colonography in asymptomatic screening patients. Although we do not have the results of large, randomized, controlled trials documenting the performance of CT colonography in screening-type patients, this technique is currently employed at some sites as a screening tool for colorectal carcinoma. Thus, CT colonography has become a part of the controversy surrounding total body CT screening. In this article, the current techniques for colonic preparation and distention will be discussed, as well as the optimum CT protocol, and the recommended use of image displays for time-efficient interpretation. The results of the larger and newer studies will be presented, as well as some of the current clinical uses of CT colonography. Issues specific to the use of CT colonography as a screening test will also be discussed.