Fig. 1

Pulmonary nodules (PNs) recruitment process at four centers. CQ Center, The First Affiliated Hospital of Chongqing Medical University; HB Center, Hubei Cancer Hospital; SC Center, Sichuan Provincial People’s Hospital; SX Center, The Second Hospital of Shanxi Medical University. SN, solid nodule; PSN, partial solid nodule; GGN, ground-glass nodule