• From the Department of Radiology, Nuclear Medicine and Anatomy, Radboud University Nijmegen Medical Center, Nijmegen, Geert Grooteplein 10, 6525 GA, Nijmegen, the Netherlands (C.J., A.S., S.J.v.R., E.T.S., B.G., M.P., C.S.P., B.v.G.); Department of Radiology, Netherlands Cancer Institute, Amsterdam, the Netherlands (R.W.); Department of Diagnostic Imaging, Section of Radiology, Nordsjællands Hospital, Hillerød, Denmark (M.M.W.W.); Department of Radiology, Streekziekenhuis Koningin Beatrix, Winterswijk, the Netherlands (B.d.H.); Department of Radiology, Meander Medical Center, Amersfoort, the Netherlands (C.S.P.); Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands (O.M.M.); Department of Radiology, Amsterdam University Medical Centers, Amsterdam, the Netherlands (O.M.M., R.S.); and Fraunhofer MEVIS, Bremen, Germany (B.v.G.).

Purpose To compare the inter- and intraobserver agreement and reading times achieved when assigning Lung Imaging Reporting and Data System (Lung-RADS) categories to baseline and follow-up lung cancer screening studies by using a dedicated CT lung screening viewer with integrated nodule detection and volumetric support with those achieved by using a standard picture archiving and communication system (PACS)-like viewer. Materials and Methods Data were obtained from the National Lung Screening Trial (NLST). By using data recorded by NLST radiologists, scans were assigned to Lung-RADS categories. For each Lung-RADS category (1 or 2, 3, 4A, and 4B), 40 CT scans (20 baseline scans and 20 follow-up scans) were randomly selected for 160 participants (median age, 61 years; interquartile range, 58-66 years; 61 women) in total. Seven blinded observers independently read all CT scans twice in a randomized order with a 2-week washout period: once by using the standard PACS-like viewer and once by using the dedicated viewer. Observers were asked to assign a Lung-RADS category to each scan and indicate the risk-dominant nodule. Inter- and intraobserver agreement was analyzed by using Fleiss κ values and Cohen weighted κ values, respectively. Reading times were compared by using a Wilcoxon signed rank test. Results The interobserver agreement was moderate for the standard viewer and substantial for the dedicated viewer, with Fleiss κ values of 0.58 (95% CI: 0.55, 0.60) and 0.66 (95% CI: 0.64, 0.68), respectively. The intraobserver agreement was substantial, with a mean Cohen weighted κ value of 0.67. The median reading time was significantly reduced from 160 seconds with the standard viewer to 86 seconds with the dedicated viewer (P < .001). Conclusion Lung-RADS interobserver agreement increased from moderate to substantial when using the dedicated CT lung screening viewer. The median reading time was substantially reduced when scans were read by using the dedicated CT lung screening viewer. Keywords: CT, Thorax, Lung, Computer Applications-Detection/Diagnosis, Observer Performance, Technology Assessment Supplemental material is available for this article. © RSNA, 2021.