Volume 131, Issue 6, Pages 1690-1699 (December 2006) Computed Tomographic Colonography: Assessment of Radiologist Performance With and Without Computer-Aided Detection  Steve Halligan, Douglas G. Altman, Susan Mallett, Stuart A. Taylor, David Burling, Mary Roddie, Lesley Honeyfield, Justine McQuillan, Hamdan Amin, Jamshid Dehmeshki  Gastroenterology  Volume 131, Issue 6, Pages 1690-1699 (December 2006) DOI: 10.1053/j.gastro.2006.09.051 Copyright © 2006 AGA Institute Terms and Conditions

Figure 1 Change in the number of correct per-patient classifications with and without CAD assistance in 60 patients with polyps. Patients are ordered by the size of their largest polyp. The dark gray bars indicate increased correct classification with CAD (41 patients), and the light gray bars indicate decreased correct classification with CAD (8 patients). There was no change in 11 patients. Gastroenterology 2006 131, 1690-1699DOI: (10.1053/j.gastro.2006.09.051) Copyright © 2006 AGA Institute Terms and Conditions

Figure 2 Per-reader change in sensitivity for detection of 60 patients with polyps (for all polyp sizes) when assisted by CAD (bars span 95% CI). Sensitivity increased significantly in 7 of 10 readers. Gastroenterology 2006 131, 1690-1699DOI: (10.1053/j.gastro.2006.09.051) Copyright © 2006 AGA Institute Terms and Conditions

Figure 3 Per-reader change in specificity for detection of 47 patients without polyps when assisted by CAD (bars span 95% CI). Specificity decreased significantly in one reader. Gastroenterology 2006 131, 1690-1699DOI: (10.1053/j.gastro.2006.09.051) Copyright © 2006 AGA Institute Terms and Conditions

Figure 4 Change in per-patient sensitivity and specificity for each of 10 readers when assisted by CAD, for all polyp sizes. The arrows point in the direction of each reader’s change. Gastroenterology 2006 131, 1690-1699DOI: (10.1053/j.gastro.2006.09.051) Copyright © 2006 AGA Institute Terms and Conditions

Figure 5 The number of true-positive observations made by readers both (A) without and (B) with CAD assistance, plotted against the ease of polyp visualization determined by experienced readers. Individual polyp visualization was graded as “easy,” “neither easy nor difficult,” and “difficult.” (A) Without CAD assistance, there is a clear trend for polyps that were graded as “difficult” to be less well detected than those that were “easy,” with “neither easy nor difficult” intermediate. (B) This observation is diminished by CAD assistance. Gastroenterology 2006 131, 1690-1699DOI: (10.1053/j.gastro.2006.09.051) Copyright © 2006 AGA Institute Terms and Conditions

Figure 6 Graphs showing the overall median (+++) increased per-polyp detection by 10 readers when using CAD, grouped by polyp size (large, medium, and small). (A) Increase for polyps correctly identified to the reader by CAD. The number of medium- and small-sized polyps detected increased significantly compared with the CAD-unassisted read (median of 5 [interquartile range, 4–8] and 7 [interquartile range, 4–9], respectively). (B) Increase for polyps not identified to the reader by CAD. There was no significant increase in detection compared with the CAD-unassisted read. Gastroenterology 2006 131, 1690-1699DOI: (10.1053/j.gastro.2006.09.051) Copyright © 2006 AGA Institute Terms and Conditions

Figure 7 Mean change in reading time per-patient, averaged across all 10 readers. When using CAD assistance, the per-patient interpretation time was shorter in 87% (93/107) of patients, with the average reading time significantly shorter by 1.9 minutes (95% CI, 1.4–2.4 minutes) for patients with polyps and 2.9 minutes (95% CI, 2.5–3.3 minutes) for patients without polyps. Gastroenterology 2006 131, 1690-1699DOI: (10.1053/j.gastro.2006.09.051) Copyright © 2006 AGA Institute Terms and Conditions

Figure 8 CT colonography, supine study with CAD assistance. A proven sigmoid polyp of 9-mm maximal diameter has been correctly identified by the CAD software and prompted to the reader by concentric circles. However, all readers misinterpreted this prompt as false positive, and no reader correctly identified the polyp. Gastroenterology 2006 131, 1690-1699DOI: (10.1053/j.gastro.2006.09.051) Copyright © 2006 AGA Institute Terms and Conditions