Comparison of supine and prone scanning separately and in combination at CT colonography

PURPOSE: To compare colonic distention, adequacy of colonic preparation, and colorectal polyp detection as assessed with supine and prone scanning separately and in combination at computed tomographic (CT) colonography. MATERIALS AND METHODS: CT colonography and colonoscopy were performed in 182 patients. Distention and preparation of eight colonic segments were rated separately on a scale of 1-4 (1, segment completely distended or no residual material; 4, segment collapsed or large amounts of residual material). The distention, preparation, and polyp detection data were compared with regard to each position alone and then in combination. CT findings were correlated with colonoscopic findings. RESULTS: The percentage of colonic segments with grade 1 distention and preparation was 93.7% (1,364 of 1,456) and 66.6% (969 of 1,456), respectively, with combined scanning; 86.4% (1,258 of 1,456) and 52.1% (759 of 1,456), respectively, with supine scanning alone; and 85.6% (1,246 of 1,456) and 57.1% (831 of 1,456), respectively, with prone scanning alone. The sensitivity for detection of colorectal polyps 10 mm or larger, 5.0-9.9 mm, and smaller than 5 mm and polyps of all sizes was 92.7%, 79.8%, 60.3%, and 69.9%, respectively, with combined scanning. Sensitivity was 58.5%, 47.2%, 36.3%, and 42.1%, respectively, with supine scanning and 51.2%, 41.6%, 30.2%, and 36.3%, respectively, with prone scanning. The improved sensitivities for use of combined versus individual scanning positions were highly significant (P < .001) for polyps in all size categories. CONCLUSION: Colonic distention and preparation at CT colonography were significantly improved by using supine and prone scanning in combination, and results correlated directly with improved sensitivity of polyp detection.