Methylation of cfDNA in Diagnosing and Monitoring Pulmonary Nodule

plasma cfDNA will be performed in patients with pulmonary nodules (0.5-3 cm) found by CT scanning. Evaluation of benign and malignant diagnostic efficacy of cfDNA methylation in pulmonary nodules with clear pathological findings. Pulmonary nodules that could not or temporarily not require invasive examination will be performed CT follow-up and dynamically monitored methylation changes of cfDNA.