[Virtual colonography]

Abstract

Recent technical developments in computed tomography (CT) and magnetic resonance imaging (MRI) have made a virtual presentation of the colon possible. The results of clinical investigations comparing virtual colonography and conventional colonoscopy up to now are promising. Virtual colonography is a potential tool for colorectal carcinoma screening in the future, but it still has an unsatisfactory sensitivity for the detection of small and flat lesions and exposes the patient to substantial doses of ionizing radiation. Recent investigations using ultra-low-dose (< 2 mSv) multislice CT colonography show promising results. Magnetic resonance (MR) colonography as a radiation-free modality is the technique of the future. Although encouraging results using virtual MR colonography for the detection of colorectal polyps have been reported, the sensitivity of detecting small polyps (</= 10 mm) and flat lesions is poor. Main reason is the limited spatial resolution in MRI of the colon. The potential role of virtual colonography in the prevention of colorectal cancer is not yet clear. Larger studies with asymptomatic persons at average risk are needed, and further improvements in the detection of flat and very small (< 5 mm) lesions need to be achieved before advocating the use of virtual colonography for routine colorectal cancer screening.