Virtual endoscopic colonography based on 3D MRI

To evaluate the potential of magnetic resonance colonography (MRC) in detecting colorectal mass lesions.

Twenty patients underwent MR imaging (MRI) before colonoscopy. The colon was filled with a gadolinium (0.5 mol):water mixture (1:100) under MRI control, and patients were imaged while breath-holding imaged with a three-dimensional spoiled gradient echo sequence in the prone and supine positions. Images were interactively analyzed based on the combination of multiplanar reconstruction and virtual colonoscopy by a radiologist blinded to colonoscopic findings and the patient's history. MRC interpretations were correlated with colonoscopic results.

Polyps smaller than 5 mm could not be identified with MRC. The sensitivity for detecting polyps of 5-10 mm was 70%, whereas mass lesions larger than 10 mm were all detected (sensitivity = 100). The sensitivity, specificity, and accuracy for identifying polyp-positive patients including the three patients with small (<5 mm) polyps were 64%, 89%, and 75%, respectively.

Virtual colonoscopy based on MRI data is feasible and should be evaluated in a larger sample of patients.