Radiology: Volume 256: Number 3—September 2010
Edward M. Lawrence, BS Perry J. Pickhardt, MD David H. Kim, MD Jessica B. Robbins, MD
Purpose: To evaluate stand-alone performance of computer-aided detection (CAD) for colorectal polyps of 6 mm or larger at computed tomographic (CT) colonography in a large asymptomatic screening cohort.
Materials and Methods: In this retrospective, institutional review board-approved, HIPAA-compliant study, a CAD software system was ap¬plied to screening CT colonography in 1638 women and 1408 men (mean age, 56.9 years) evaluated at a single medical center between March 2006 and December 2008. All participants underwent cathartic preparation with stool tagging; electronic cleansing was not used. The reference standard consisted of interpretation by experienced radi-ologists in all cases. This interpretation was further re¬fined for the subset of cases with positive findings by using subsequent colonoscopic or CT colonographic confirma¬tion, as well as retrospective expert localization of polyps with CT colonography. This test set was not involved in training the CAD system. The Fisher exact test was used to evaluate significance; 95% confidence intervals (CIs) were obtained by using the exact method.
Results: Per-patient CAD sensitivities were 93.8% (350 of 373; 95% CI: 90.9%, 96.1%) and 96.5% (137 of 142; 95% CI: 92.0%, 98.8%) at 6- and 10-mm threshold sizes, re¬spectively. Per-polyp CAD sensitivities for all polyps, re¬gardless of histologic features, were 90.1% (547 of 607; 95% CI: 88.0%, 92.8%) and 96.0% (168 of 175; 95% CI: 91.9%, 98.4%) at 6- and 10-mm threshold sizes, respec¬tively; CAD sensitivities for advanced neoplasia and can¬cer were 97.0% (128 of 132; 95% CI: 92.4%, 99.2%) and 100% (13 of 13; 95% CI: 79.4%, 100%), respectively. The mean and median false-positive rates were 4.7 and 3 per series, respectively (9.4 and 6 per patient). Among 373 patients with a positive finding at CT colonography, CAD marked an additional 15 polyps of 6 mm or larger, includ¬ing four large polyps, that were missed at the prospective three-dimensional reading by an expert but were found at subsequent colonoscopy.
Conclusion: Stand-alone CAD demonstrated excellent performance for polyp detection in a large screening population, with high sensitivity and an acceptable number of false-positive results.