We conducted an observer study to evaluate the effect of computer-aided detection (CAD) on human readers' performance in the detection of polyps in CT colonography (CTC). Twenty data sets including 11 polyps were retrospectively selected from our CTC database. A sequential test was used, in which four observers interpreted CTC examinations by use of our colon CAD workstation in two sequential sessions: one without CAD and the other with CAD. At each session, the observers rated the confidence level regarding whether the case was abnormal, i.e., at least one polyp>5 mm was present in the colon. Receiver operating characteristic (ROC) analysis was performed based on the confidence levels for the abnormality of the CTC data sets, and the area under the ROC curve (Az) was calculated as a measure of the observers' detection performance. The results showed that, for all of the observers, the detection performance increased with use of CAD. The average Az values without and with CAD were 0.70 and 0.85, respectively. A two-tailed t-test showed that the difference between these Az values was statistically significant (p=0.025). The result indicates that CAD can be a useful tool for improving human readers' performance in the detection of polyps in CTC.
