The CT system consisted of a full-ring time-of-flight 64-slice positron emission tomography (PET)/CT scanner (Discovery PET/CT 690 VCT; GE Healthcare, Chicago, IL, USA). The CT diagnosis system was used to analyze NSCLC tumor size using the preprogrammed setting. The preprogrammed setting was optimized, as described previously (17 (link)) to achieve the best image formation. The lungs in all patients underwent contrast-enhanced CT according to the manufacturer's protocols (Discovery PET/CT 690 VCT). The Tumor-Node-Metastasis (TNM) stage (seventh edition) (18 (link)) was assigned based on intraboard consensus decision.