Subsolid and part-solid nodules in lung cancer screening: comparison between visual and computer-aided detection

Purpose: To compare visual detection and computer aided diagnosis (CAD) for detection of non-solid nodules (NSN) and part-solid nodules (PSN), in a lung cancer screening trial. Methods and Materials: Baseline low-dose computed tomography (LDCT) of 2303 subjects were assessed by 2 independent operators: a) visual detection (VD); b) CAD software (CIRRUS Lung Screening). CAD was run also on first and second incidence round. Rate of agreement was calculated by weighted k test. Sensitivity and negative predictive value (NPV) were calculated according to cumulative number of subjects with detected nodules (VD and CAD). LDCT features were compared between CAD-only and VD-only detected nodules. Results: Nodules were detected in 215/2303 subjects (dominant nodule: 171/215 NSN and 44/215 PSN), notably 149 were CAD-only detected (113 NSN and 36 PSN), 27 were VD-only detected (25 NSN and 2 PSN), and 39 were CAD and VD detected (33 NSN and 6 PSN). The agreement was fair (weighted k=0.276). Sensitivity and NPV for CAD 87.4\% and 98.7\%, and for VD 30.7\% and 93.3\%. Automatic and manual caliper were similar for the assessment of maximum diameter (p=0.111). CAD-only and VD-only detected nodules showed similar nodule diameter (p=0.727) and proportion of PSN (p=0.073). Volume of CAD-only detected nodules was significantly smaller (p=0.019). Among the 27 VD-only detected nodules, 11 NSN were subsequently detected by CAD at the incidence rounds. Conclusion: Detection of NSN and PSN showed only fair agreement between VD and CAD. Combined assessment of LDCT by both VD and CAD is needed to achieve optimal sensitivity.