Virtual endoscopy - Comparison with colonoscopy in the detection of space-occupying lesions of the colon

Background and Study Aims: A new technique has been described which combines abdominal helical computed tomography (CT) scanning and virtual reality computer technology, known as virtual colonoscopy (VC); the reconstructed images provide a simulation of the interior of the colon as viewed by endoscopy, We compared VC with conventional colonoscopy in patients with suspected or known colonic neoplasia. Patients and Methods: A total of 38 patients, in whom there was a high likelihood of colonic polyps or cancer, underwent a noncontrast helical CT scan of the abdomen and pelvis after regular colonoscopy bowel preparation,The images were reconstructed into a VC presentation and compared with the subsequent conventional colonoscopy in a blinded manner. Results: Conventional colonoscopy identified a total of 24 polyps 5 mm or greater. VC correctly identified five of 13 polyps 5-9 mm in size, and ten of II lesions greater than or equal to 10 mm in diameter. The reasons for four missed lesions were identified as being secondary to a collapsed rectum in two patients and stool in the right colon in two patients, The sensitivity and specificity per patient of VC for lesions greater than or equal to 5 mm were 66.7% and 75.0% respectively, and for lesions greater than 1 cm were 90.0% and 82.1%, respectively. Conclusions: Virtual colonoscopy is feasible, well tolerated, and capable of detecting most lesions seater than 10 mm in diameter, This technique is continuing to be developed and warrants further evaluation as a diagnostic and screening tool in colorectal neoplasia.