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CT Colonography: False-Negative Interpretations¹

¹ From the Department of Radiology, University of Chicago, Department of Radiology, MC 2026, 5841 S Maryland Ave, Chicago, IL 60637 (T.D., D.R., K.S., A.H.D.), Department of Radiology, Medical College of Virginia–Virginia Commonwealth University, Richmond, Va (R.A.H.); and Division of Digestive and Liver Disease, University of Texas Southwestern Medical Center, Dallas, Tex (D.C.R.). From the 2006 RSNA Annual Meeting. Received June 28, 2006; revision requested August 30; revision received October 6; accepted November 2; final version accepted December 15. Supported by the University of Chicago Department of Radiology Research Fund. Address correspondence to A.H.D. (e-mail: ahdachma{at}uchicago.edu).

View larger version (84K): [in this window] [in a new window] [Download PPT slide]   Figure 1a: Error classification. (a) Observer error: 7-mm adenoma missed at CT colonography in original study. Left: Prone transverse soft-tissue image shows polyp (arrow). Right: 3D endoluminal view of polyp. (b) Observer measurement error: In original study, polyp (arrow) was measured as 7 mm at CT colonography and 15 mm at colonoscopy. Consensus retrospective CT colonographic measurement was 9.5 mm. Left: Supine transverse soft-tissue image. Right: Endoluminal view. (c) Artifact error: Severe respiratory motion caused by breathing during both supine sagittal (left) and prone transverse (right) acquisitions prevents polyp identification. Error classification. (d) Distention error: Arrows highlight limited distention that prevents polyp identification in supine (right) and prone (left) transverse views. (e) Excessive fluid error: 15-mm polyp found at colonoscopy was not visible in cecum at CT colonography owing to excess fluid (arrows) in colon. Left: Supine transverse view. Right: Prone transverse view. (f) Excessive stool error: 100-mm polyp in cecum is indistinguishable from large clumps of stool which appear throughout the colon. Arrow pointing up = stomach, arrow pointing right = small bowel; all other arrows = clumps of stool. Left: Supine coronal view (very small arrow in upper left corner is computer cursor). Right: Supine transverse view.

View larger version (84K): [in this window] [in a new window] [Download PPT slide]   Figure 1b: Error classification. (a) Observer error: 7-mm adenoma missed at CT colonography in original study. Left: Prone transverse soft-tissue image shows polyp (arrow). Right: 3D endoluminal view of polyp. (b) Observer measurement error: In original study, polyp (arrow) was measured as 7 mm at CT colonography and 15 mm at colonoscopy. Consensus retrospective CT colonographic measurement was 9.5 mm. Left: Supine transverse soft-tissue image. Right: Endoluminal view. (c) Artifact error: Severe respiratory motion caused by breathing during both supine sagittal (left) and prone transverse (right) acquisitions prevents polyp identification. Error classification. (d) Distention error: Arrows highlight limited distention that prevents polyp identification in supine (right) and prone (left) transverse views. (e) Excessive fluid error: 15-mm polyp found at colonoscopy was not visible in cecum at CT colonography owing to excess fluid (arrows) in colon. Left: Supine transverse view. Right: Prone transverse view. (f) Excessive stool error: 100-mm polyp in cecum is indistinguishable from large clumps of stool which appear throughout the colon. Arrow pointing up = stomach, arrow pointing right = small bowel; all other arrows = clumps of stool. Left: Supine coronal view (very small arrow in upper left corner is computer cursor). Right: Supine transverse view.

View larger version (67K): [in this window] [in a new window] [Download PPT slide]   Figure 1c: Error classification. (a) Observer error: 7-mm adenoma missed at CT colonography in original study. Left: Prone transverse soft-tissue image shows polyp (arrow). Right: 3D endoluminal view of polyp. (b) Observer measurement error: In original study, polyp (arrow) was measured as 7 mm at CT colonography and 15 mm at colonoscopy. Consensus retrospective CT colonographic measurement was 9.5 mm. Left: Supine transverse soft-tissue image. Right: Endoluminal view. (c) Artifact error: Severe respiratory motion caused by breathing during both supine sagittal (left) and prone transverse (right) acquisitions prevents polyp identification. Error classification. (d) Distention error: Arrows highlight limited distention that prevents polyp identification in supine (right) and prone (left) transverse views. (e) Excessive fluid error: 15-mm polyp found at colonoscopy was not visible in cecum at CT colonography owing to excess fluid (arrows) in colon. Left: Supine transverse view. Right: Prone transverse view. (f) Excessive stool error: 100-mm polyp in cecum is indistinguishable from large clumps of stool which appear throughout the colon. Arrow pointing up = stomach, arrow pointing right = small bowel; all other arrows = clumps of stool. Left: Supine coronal view (very small arrow in upper left corner is computer cursor). Right: Supine transverse view.

View larger version (77K): [in this window] [in a new window] [Download PPT slide]   Figure 1d: Error classification. (a) Observer error: 7-mm adenoma missed at CT colonography in original study. Left: Prone transverse soft-tissue image shows polyp (arrow). Right: 3D endoluminal view of polyp. (b) Observer measurement error: In original study, polyp (arrow) was measured as 7 mm at CT colonography and 15 mm at colonoscopy. Consensus retrospective CT colonographic measurement was 9.5 mm. Left: Supine transverse soft-tissue image. Right: Endoluminal view. (c) Artifact error: Severe respiratory motion caused by breathing during both supine sagittal (left) and prone transverse (right) acquisitions prevents polyp identification. Error classification. (d) Distention error: Arrows highlight limited distention that prevents polyp identification in supine (right) and prone (left) transverse views. (e) Excessive fluid error: 15-mm polyp found at colonoscopy was not visible in cecum at CT colonography owing to excess fluid (arrows) in colon. Left: Supine transverse view. Right: Prone transverse view. (f) Excessive stool error: 100-mm polyp in cecum is indistinguishable from large clumps of stool which appear throughout the colon. Arrow pointing up = stomach, arrow pointing right = small bowel; all other arrows = clumps of stool. Left: Supine coronal view (very small arrow in upper left corner is computer cursor). Right: Supine transverse view.

View larger version (77K): [in this window] [in a new window] [Download PPT slide]   Figure 1e: Error classification. (a) Observer error: 7-mm adenoma missed at CT colonography in original study. Left: Prone transverse soft-tissue image shows polyp (arrow). Right: 3D endoluminal view of polyp. (b) Observer measurement error: In original study, polyp (arrow) was measured as 7 mm at CT colonography and 15 mm at colonoscopy. Consensus retrospective CT colonographic measurement was 9.5 mm. Left: Supine transverse soft-tissue image. Right: Endoluminal view. (c) Artifact error: Severe respiratory motion caused by breathing during both supine sagittal (left) and prone transverse (right) acquisitions prevents polyp identification. Error classification. (d) Distention error: Arrows highlight limited distention that prevents polyp identification in supine (right) and prone (left) transverse views. (e) Excessive fluid error: 15-mm polyp found at colonoscopy was not visible in cecum at CT colonography owing to excess fluid (arrows) in colon. Left: Supine transverse view. Right: Prone transverse view. (f) Excessive stool error: 100-mm polyp in cecum is indistinguishable from large clumps of stool which appear throughout the colon. Arrow pointing up = stomach, arrow pointing right = small bowel; all other arrows = clumps of stool. Left: Supine coronal view (very small arrow in upper left corner is computer cursor). Right: Supine transverse view.

View larger version (86K): [in this window] [in a new window] [Download PPT slide]   Figure 1f: Error classification. (a) Observer error: 7-mm adenoma missed at CT colonography in original study. Left: Prone transverse soft-tissue image shows polyp (arrow). Right: 3D endoluminal view of polyp. (b) Observer measurement error: In original study, polyp (arrow) was measured as 7 mm at CT colonography and 15 mm at colonoscopy. Consensus retrospective CT colonographic measurement was 9.5 mm. Left: Supine transverse soft-tissue image. Right: Endoluminal view. (c) Artifact error: Severe respiratory motion caused by breathing during both supine sagittal (left) and prone transverse (right) acquisitions prevents polyp identification. Error classification. (d) Distention error: Arrows highlight limited distention that prevents polyp identification in supine (right) and prone (left) transverse views. (e) Excessive fluid error: 15-mm polyp found at colonoscopy was not visible in cecum at CT colonography owing to excess fluid (arrows) in colon. Left: Supine transverse view. Right: Prone transverse view. (f) Excessive stool error: 100-mm polyp in cecum is indistinguishable from large clumps of stool which appear throughout the colon. Arrow pointing up = stomach, arrow pointing right = small bowel; all other arrows = clumps of stool. Left: Supine coronal view (very small arrow in upper left corner is computer cursor). Right: Supine transverse view.

View larger version (11K): [in this window] [in a new window] [Download PPT slide]   Figure 2: Flowchart of patient analysis. CTC = CT colonography, FN = false-negative findings, TP = true-positive findings.