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Comparison of Supine and Prone Scanning Separately and in Combination at CT Colonography¹

¹ From the Department of Radiology (114), Veterans Affairs Medical Center, 4150 Clement St, San Francisco, CA 94121 (J.Y., N.N.K., R.K.H., P.R.G.K., S.D.W.); and Departments of Radiology (J.Y., N.N.K., R.K.H., P.R.G.K., S.D.W.) and Gastroenterology (G.A.A.), University of California School of Medicine, San Francisco. Received March 28, 2001; revision requested May 21; final revision received June 25, 2002; accepted July 16. Address correspondence to J.Y. (e-mail: judy.yee@radiology.ucsf.edu).

View larger version (29K): [in a new window]   Figure 1. Graph shows number of segments with grade 1 distention according to location of polyps. A combination of prone and supine scanning yielded a significantly larger number of segments with grade 1 distention for all colonic segments, with the exception of supine scanning in the cecum, ascending colon, and hepatic flexure. C = cecum, AC = ascending colon, HF = hepatic flexure, TC = transverse colon, SF = splenic flexure, DC = descending colon, S = sigmoid colon, R = rectum. -- = supine scanning, -- = prone scanning, -- = combined scanning. P values: * = combined versus supine scanning, P < .05; = combined versus prone scanning, P < .05; = supine versus prone scanning, P < .05.

View larger version (30K): [in a new window]   Figure 2. Graph shows number of segments with grade 1 preparation according to location of polyps. A combination of prone and supine scanning yielded a significantly larger number of segments with grade 1 preparation compared with that for either position alone for all colonic segments. C = cecum, AC = ascending colon, HF = hepatic flexure, TC = transverse colon, SF = splenic flexure, DC = descending colon, S = sigmoid colon, R = rectum. -- = supine scanning, -- = prone scanning, -- = combined scanning. P values: * = combined versus supine scanning, P < .005; = combined versus prone scanning, P < .05; = supine versus prone scanning, P < .05.

View larger version (25K): [in a new window]   Figure 3. Graph shows sensitivity for polyp detection according to size. Superior polyp detection sensitivity was found by using a combination of prone and supine scanning, compared with use of either position alone for polyps of all sizes. -- = supine scanning, -- = prone scanning, -- = combined scanning. P values: * = combined versus supine scanning, P < .001; = combined versus prone scanning, P < .001.

View larger version (31K): [in a new window]   Figure 4. Graph shows sensitivity for polyp detection according to location of polyps. Increased polyp detection sensitivity was found by using a combination of prone and supine scanning, compared with use of either position alone. Statistically significant improvement was seen for all segments, except for the cecum with supine scanning and the splenic flexure with both supine and prone scanning. C = cecum, AC = ascending colon, HF = hepatic flexure, TC = transverse colon, SF = splenic flexure, DC = descending colon, S = sigmoid colon, R = rectum. -- = supine scanning, -- = prone scanning, -- = combined scanning. P values: * = combined versus supine scanning, P < .05; = combined versus prone scanning, P < .05; = supine versus prone scanning, P < .05.

View larger version (115K): [in a new window]   Figure 5a. Images obtained with the patient in the supine position show inadequate preparation leading to a false-positive finding of a polyp. (a) Transverse two-dimensional CT image demonstrates a polypoid lesion (arrowhead) with heterogeneous attenuation in the ascending colon. (b) Three-dimensional endoluminal CT image in the same area shows how stool in an adequately prepared segment can be mistaken for a polyp (arrowhead).

View larger version (152K): [in a new window]   Figure 5b. Images obtained with the patient in the supine position show inadequate preparation leading to a false-positive finding of a polyp. (a) Transverse two-dimensional CT image demonstrates a polypoid lesion (arrowhead) with heterogeneous attenuation in the ascending colon. (b) Three-dimensional endoluminal CT image in the same area shows how stool in an adequately prepared segment can be mistaken for a polyp (arrowhead).

View larger version (129K): [in a new window]   Figure 6a. Images obtained with the patient in the supine position show a bulbous fold as the cause of a false-positive finding of a polyp. (a) Three-dimensional endoluminal CT image demonstrates a polypoid-appearing lesion (arrow) in the descending colon. (b) Coronal two-dimensional reformatted CT image from the same location shows a thick fold (arrowhead).

View larger version (109K): [in a new window]   Figure 6b. Images obtained with the patient in the supine position show a bulbous fold as the cause of a false-positive finding of a polyp. (a) Three-dimensional endoluminal CT image demonstrates a polypoid-appearing lesion (arrow) in the descending colon. (b) Coronal two-dimensional reformatted CT image from the same location shows a thick fold (arrowhead).

View larger version (135K): [in a new window]   Figure 7a. Images obtained with the patient in the supine position show motion artifact as the cause of false-negative findings of a polyp. (a) Two-dimensional reformatted sagittal CT image demonstrates the "saw-tooth" appearance (arrowhead) of motion artifact. (b) Three-dimensional endoluminal CT image of the same area shows how motion artifacts (arrow) distort the colonic mucosa and create false projections, which make polyp detection difficult.

View larger version (149K): [in a new window]   Figure 7b. Images obtained with the patient in the supine position show motion artifact as the cause of false-negative findings of a polyp. (a) Two-dimensional reformatted sagittal CT image demonstrates the "saw-tooth" appearance (arrowhead) of motion artifact. (b) Three-dimensional endoluminal CT image of the same area shows how motion artifacts (arrow) distort the colonic mucosa and create false projections, which make polyp detection difficult.