Cite this article as: Kobayashi H, Ohkubo M, Narita A, Marasinghe JC, Murao K, Matsumoto T, et al. A method for evaluating the performance of computer-aided detection of pulmonary nodules in lung cancer CT screening: detection limit for nodule size and density. Br J Radiol 2017; 90: 20160313.
FULL PAPERA method for evaluating the performance of computeraided detection of pulmonary nodules in lung cancer CT screening: detection limit for nodule size and density 1,2 HAJIME KOBAYASHI, MS Objective: We propose the application of virtual nodules to evaluate the performance of computer-aided detection (CAD) of lung nodules in cancer screening using lowdose CT. Methods: The virtual nodules were generated based on the spatial resolution measured for a CT system used in an institution providing cancer screening and were fused into clinical lung images obtained at that institution, allowing site specificity. First, we validated virtual nodules as an alternative to artificial nodules inserted into a phantom. In addition, we compared the results of CAD analysis between the real nodules (n 5 6) and the corresponding virtual nodules. Subsequently, virtual nodules of various sizes and contrasts between nodule density and background density (DCT) were inserted into clinical images (n 5 10) and submitted for CAD analysis.Results: In the validation study, 46 of 48 virtual nodules had the same CAD results as artificial nodules (kappa coefficient 5 0.913). Real nodules and the corresponding virtual nodules showed the same CAD results. The detection limits of the tested CAD system were determined in terms of size and density of peripheral lung nodules; we demonstrated that a nodule with a 5-mm diameter was detected when the nodule had a DCT . 220 HU. Conclusion: Virtual nodules are effective in evaluating CAD performance using site-specific scan/reconstruction conditions. Advances in knowledge: Virtual nodules can be an effective means of evaluating site-specific CAD performance. The methodology for guiding the detection limit for nodule size/density might be a useful evaluation strategy.
INTRODUCTIONScreening by low-dose CT has been shown to reduce mortality from lung cancer in high-risk individuals.