The objective is to screen and monitor the efficacy of cfDNA methylation in patients with stage I lung cancer after ablation, to compare the similarities and differences of cfDNA methylation between surgical treatment and ablation in patients with stage I lung cancer, and to look for new indicators to assess the efficacy of ablation therapy and to monitor lung cancer recurrence.

The objective is to screen and monitor the efficacy of cfDNA methylation in patients with stage I lung cancer after ablation, to compare the similarities and differences of cfDNA methylation between surgical treatment and ablation in patients with stage I lung cancer, and to look for new indicators to assess the efficacy of ablation therapy and to monitor lung cancer recurrence.

The main research content is to screen the cfDNA methylation index that can monitor the efficacy of stage I lung cancer ablation and compare the similarities and differences of cfDNA methylation in patients with stage I lung cancer after surgery and ablation.

Inclusion Criteria:

1. Age: 18-85 years old;
2. The peripheral pulmonary nodules found in patients with chest CT, preoperative examination showed that the clinical stage of patients was T1N0M0, IA;
3. patients are not suitable for surgical treatment through multidisciplinary assessment, agree to accept ablation
4. Patients have good compliance with the tests and follow-ups, understand the situation of the study and sign informed consent.

Exclusion Criteria:

1. The patient is generally in poor condition and cannot tolerate the examination;
2. patients with a cardiac pacemaker or stent in the heart; peripheral tumors of the lungs are adjacent to large blood vessels or important structures;
3. patients with poor compliance;
4. Researchers believe that it is not appropriate to participate in this trial.