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TH‐AB‐207A‐12: CT Lung Cancer Screening and the Effects of Further Dose Reduction On CAD Performance
Author(s) -
Young S,
Lo P,
Hoffman J,
Kim H,
Hsu W,
Flores C,
Lee G,
Brown M,
McNittGray M
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4958088
Subject(s) - medicine , nuclear medicine , nodule (geology) , lung cancer , lung cancer screening , national lung screening trial , cad , radiology , hounsfield scale , computed tomography , paleontology , engineering drawing , engineering , biology
Purpose: CT lung screening is already performed at low doses. In this study, we investigated the effects of further dose reduction on a lung‐nodule CAD detection algorithm. Methods: The original raw CT data and images from 348 patients were obtained from our local database of National Lung Screening Trial (NLST) cases. 61 patients (17.5%) had at least one nodule reported on the NLST reader forms. All scans were acquired with fixed mAs (25 for standard‐sized patients, 40 for large patients) on a 64‐slice scanner (Sensation 64, Siemens Healthcare). All images were reconstructed with 1‐mm slice thickness, B50 kernel. Based on a previously‐published technique, we added noise to the raw data to simulate reduced‐dose versions of each case at 50% and 25% of the original NLST dose (i.e. approximately 1.0 and 0.5 mGy CTDIvol). For each case at each dose level, a CAD detection algorithm was run and nodules greater than 4 mm in diameter were reported. These CAD results were compared to “truth”, defined as the approximate nodule centroids from the NLST forms. Sensitivities and false‐positive rates (FPR) were calculated for each dose level, with a sub‐analysis by nodule LungRADS category. Results: For larger category 4 nodules, median sensitivities were 100% at all three dose levels, and mean sensitivity decreased with dose. For the more challenging category 2 and 3 nodules, the dose dependence was less obvious. Overall, mean subject‐level sensitivity varied from 38.5% at 100% dose to 40.4% at 50% dose, a difference of only 1.9%. However, median FPR quadrupled from 1 per case at 100% dose to 4 per case at 25% dose. Conclusions: Dose reduction affected nodule detectability differently depending on the LungRADS category, and FPR was very sensitive at sub‐screening levels. Care should be taken to adapt CAD for the very challenging noise characteristics of screening. Funding support: NIH U01 CA181156; Disclosures (McNitt‐Gray): Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics.