CT Colonography: The Essentials
Pieter Vandaele, MD ; M. Raquel Oliva, MD ; Matthew A. Barish, MD ; Koenraad J. Mortelé, MD
1 Dr. Vandaele is a Resident in Radiology, University Hospital Gasthuisberg, Leuven, Belgium and a Visiting Fellow, Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women’s Hospital, Boston, MA. Dr. Oliva is a Clinical Fellow, Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women’s Hospital, Boston, MA. Dr. Barish is the Director of International Symposium on Virtual Colonoscopy, Boston, MA. He is also the Director of the 3D Imaging and Processing Center, and a Staff Radiologist, Division of Abdominal Imaging and Intervention, Brigham and Women’s Hospital, and an Assistant Professor of Radiology, Harvard Medical School, Boston, MA. Dr. Mortelé is the Associate Director, Division of Abdominal Imaging and Intervention, and the Director, Abdominal and Pelvic MRI, Brigham and Women’s Hospital, and an Associate Professor of Radiology, Harvard.
Computed tomography (CT) colonography (virtual colonoscopy) is a promising new method for detecting colorectal polyps and cancers. Although multiple articles on this issue have been published since the mid-1990s, it remains an important discussion topic in current radiology and gastroenterology societies. Regarding its clinical role, there is no doubt that this imaging technique is best suited and highly recommended for those patients who are unable or unwilling to undergo conventional colonoscopy. Its role as a general screening tool for colon cancer is obvious for many, equivocal for some, and doubtful for others. This article is de-signed to highlight issues of importance for radiologists who are considering or who have recently started offering CT colonography to their patients and referring physicians. Colorectal cancer is the second leading cause of cancer-related deaths in the United States. 1 The majority of colorectal cancers are believed to arise within benign adenomatous polyps and follow the adenoma-carcinoma sequence. The duration of this sequence is very long (±10 years), 2 and the removal of these precursor adenomatous polyps decreases the risk for lethal colorectal cancer significantly. 3 CT colonography uses multidetector-row CT to generate data, which is then converted by computer software into 2-dimensional (2D) and 3-dimensional (3D) displays of the colon. CT colonography has several advantages over conventional colonoscopy: No sedation is needed, it is only minimally invasive, and the examination is less time-consuming than conventional colonoscopy. However, there is still a need for bowel cleansing and insufflation of gas to expand the colon. Moreover, exposure to radiation is inherent to CT, and there is no possibility of biopsy, polypectomy, or treatment during the examination.