Microwave Ablation with Permittivity Feedback Control in the Lung of a Porcine Model: A Safety Test

Objectives: Ablation treatment has been used in primary and metastatic lung tumors for tumor therapy. There have been reports about complications due to the ablation of tumors abutting vital organs. Although microwave ablation is getting more widely accepted as a treatment choice for lung tumors, no study addressing its safety issues has been reported to date. This pilot study is designed to determine the effect and the safety of microwave energy on important thoracic structures in the vicinity of target lung tumors. Materials and Methods: Microwave ablation was performed in the thoracic organs of a pig using a bilateral thoracosternotomy (clam-shell approach) under general anesthesia. Microwave energy was delivered via a microwave antenna with intelligent tissue permittivity feedback and real-time temperature control to the lung tissues and pressed to the surface of respective vital organs under investigation. Tissues were harvested after ablation and studied by gross and histopathological examinations. Results: Superficial thermal injury was noted in the aorta, inferior vena cava, pulmonary artery, trachea and main bronchus after microwave ablation. The pericardium and the diaphragm had moderate thermal damage. The pulmonary vein, pulmonary arteriole, and the phrenic nerve were also partially injured. There was severe thermal injury to the vagus nerve and the esophagus. Conclusions: During microwave lung tumor ablation, caution should be taken to avoid unwanted injury to the neighboring vital organs, especially thinner vessels with less blood flow such as the pulmonary vein and arteriole, the vagus nerve and the esophagus.