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What is Virtual Colonoscopy?

Virtual colonoscopy is an evolving non-invasive imaging technique that allows doctors to detect colorectal polyps (growths) and cancers.

Conventional (left) and virtual (right) colonoscopy images of the same pedunculated polyp in the sigmoid colon.

Currently, most centers that perform virtual colonoscopy use computed tomography (CT) to obtain images (1). With CT, a three-dimensional picture of part of the body is put together from a number of cross-sectional x-ray images. In Europe and several centers in the United States, some investigators are using magnetic resonance imaging (MRI) for virtual colonoscopy (2). MRI uses radio waves to induce nuclear magnetic resonance in the atoms of the body and produces computerized images of the inside of the body. A potential advantage of MR imaging is that it doesn't expose the patient to ionizing radiation, as CT does. However, the amount of radiation used in CT for virtual colonoscopy can be substantially lower than the amount used for routine abdominal and pelvic CT (3). In either case, whether CT or MR is used, certain common characteristics of virtual colonoscopy exams have emerged since the procedure was first performed in 1994 (4).