Optimization of CT colonography technique: Prospective trial in 180 patients

PURPOSE: To assess the added benefits of prone positioning in addition to s upine positioning and oral iodinated contrast medium for help in the detect ion of colonic polyps at computed tomographic (CT) colonography. MATERIALS AND METHODS: CT colonography was performed in prone and supine po sitions in 180 patients with polyps or risk factors for colonic neoplasia. Patients were randomly assigned to receive a standard bower preparation or a standard preparation plus oral iodinated contrast medium. One radiologist interpreted supine images alone, and another analyzed supine and prone ima ges. All patients subsequently underwent colonoscopy. RESULTS: At colonoscopy, 121 large (greater than or equal to 1-cm-diameter) polyps and 142 smaller (0.5-0.9-cm) polyps were identified. Prone position ing resulted in increased sensitivity for identification of patients with l arge (greater than or equal to 1-cm) polyps (increase from 70% to 85%, P = .004) and of patients with polyps 0.5 cm or larger (increase from 75% to 88 %, P < .005), with no change in specificity. Use of oral contrast medium di d not significantly improve polyp detection even in the subset of patients in whom colonic fluid attenuation was markedly increased. CONCLUSION: Acquisition and review of supine and prone CT colonographic ima ges significantly improves the ability to identify patients with polyps 0.5 cm in diameter or larger. Administration of oral iodinated contrast medium does not significantly improve polyp detection.