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Influence of Computer-Aided Detection False-Positives on Reader Performance and Diagnostic Confidence for CT Colonography

¹ Department of Specialist Imaging, University College Hospital, 235 Euston Rd., 2F Podium, London NW1 2BU, United Kingdom.
² Department of Clinical Radiology, Pinderfields General Hospital, Wakefield, West Yorkshire, United Kingdom.
³ Department of Clinical Radiology, Leeds General Infirmary, Leeds Teaching Hospitals NHS Trust, Leeds, United Kingdom.
⁴ Department of Intestinal Imaging, St. Marks Hospital, Harrow, United Kingdom.
⁵ Medicsight PLC, London, United Kingdom.
⁶ Statistical Consultancy, Ruislip Middlesex, United Kingdom.

OBJECTIVE. The objective of our study was to investigate whether an increasing number of computer-aided detection (CAD) false-positives decreases reader sensitivity, specificity, and confidence for nonexpert readers of CT colonography (CTC).

MATERIALS AND METHODS. Fifty CTC data sets (29 men; mean age, 65 years), 25 of which contained 35 polyps 5 mm, were selected in which CAD had 100% polyp sensitivity at two sphericity settings (0 and 75) but differed in the number of false-positives. The data sets were read by five readers twice: once at each sphericity setting. Sensitivity, specificity, report time, and confidence before and after second-read CAD were compared using the paired exact and Student's t test, respectively. Receiver operating characteristic (ROC) curves were generated using reader confidence (1–100) in correct case classification (normal or abnormal).

RESULTS. CAD generated a mean of 42 (range, 3–118) and 15 (range, 1–36) false-positives at a sphericity of 0 and 75, respectively. CAD at both settings increased per-patient sensitivity from 82% to 87% (p = 0.03) and per-polyp sensitivity by 8% and 10% for a sphericity of 0 and 75, respectively (p < 0.001). Specificity decreased from 84% to 79% (sphericity 0 and 75, p = 0.03 and 0.07). There was no difference in sensitivity, specificity, or reader confidence between sphericity settings (p = 1.0, 1.0, 0.11, respectively). The area under the ROC curve was 0.78 (95% CI, 0.70–0.86) and 0.77 (0.68–0.85) for a sphericity of 0 and 75, respectively. CAD added a median of 4.4 minutes (interquartile range [IQR], 2.7–6.5 minutes) and 2.2 minutes (IQR, 1.2–4.0 minutes) for a sphericity of 0 and 75, respectively (p < 0.001). CONCLUSION. CAD has the potential to increase the sensitivity of readers inexperienced with CTC, although specificity may be reduced. An increased number of CAD-generated false-positives does not negate any beneficial effect but does reduce efficiency.

Keywords: colorectal cancer • computer-aided detection • CT colonography • screening

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				S. A. Taylor, C. Robinson, D. Boone, L. Honeyfield, and S. Halligan Polyp Characteristics Correctly Annotated by Computer-aided Detection Software but Ignored by Reporting Radiologists during CT Colonography Radiology, September 29, 2009; (2009) radiol.2533090356v1. [Abstract] [Full Text]