CTC has progressed rapidly over the past 6 years. There have been many technical advances including new methods of display and multi-slice helical CT scanners. Clinical experience with CTC has grown rapidly: CTC is being done at more and more institutions throughout the world. MRC may also play a role in colon cancer screening, especially in Europe, where there are greater concerns about radiation exposure. Barium enema and conventional colonoscopy are both good tests for colon cancer screening, with reported sensitivities for colorectal cancer detection of 83% and 95%, respectively. The sensitivity of CTC for larger, more clinically significant polyps is approximately 90%. Advantages of CTC include reduced invasiveness relative to barium enema and conventional colonoscopy and possibly improved patient preference. Disadvantages include possible interobserver variability, the continued necessity for unpleasant bowel preparation, and (albeit small) radiation exposure. The usefulness of CTC in a number of clinical settings has been described, including the situation of incomplete colonoscopy, the setting of obstructive or occlusive colon cancers, inflammatory bowel disease, and high-risk individuals. The number of indications is likely to expand in the future. The sizes of patient populations have also steadily increased, with the largest reported series (in a meeting abstract) in the range of 300 patients, although some institutions have enrolled many more subjects than this. The American College of Radiology Imaging Network (ACRIN; www.acrin.org) is now performing a small clinical trial to determine appropriate scanning protocols for CTC and advantages and disadvantages of different interpretation software. Results should be available in the near future. Computer-aided diagnosis may play an important role in CTC interpretations, since the interpretation times are still 15 to 20 minutes, increasing the cost of the examination. Investigation of computer-aided diagnosis is just beginning, and very little is known about what approaches will be successful. However, advances in computer science and image processing are likely to have a positive impact on computer-aided diagnosis for polyp and cancer detection. In conclusion, colonography, whether performed with CT or MRI, remains a vibrant area of clinical and basic science research in radiology. With continued progress, it is hoped that colonography will assume an important role in colon cancer screening and prevention.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging