## 1 Introduction  
Lung cancer is one of the greatest threats to human health and life. About 2.1 million of the total diagnosed lung cancer patients worldwide are diagnosed annually, and the highest incidence rate of malignancies in the world [1]. Surgical resection is the main treatment for primary lung cancer, but only one-third of patients are suitable for surgery. For non-surgical lung cancer patients, thermal ablation has become an important and effective treatment option [2; 3; 4; 5].  
In recent years, thermal ablation has become one of the treatment methods for unresectable primary and secondary tumors [6]. According to different ablation principles, thermal ablation is mainly divided into microwave ablation (MWA), radio frequency ablation (RFA), high intensity focused ultrasound (HIFU) and laser ablation (LA) [7]. As a local treatment, thermal ablation has a highly effective killing effect on primary and metastatic lung cancer, and has the advantages of less damage to surrounding normal tissues and rapid postoperative recovery [8; 9].  
At present, RFA is the most commonly used thermal ablation therapy for cancer. The advantage of RFA is its rich experience in clinical application. Since [PERSON] et al. [10] reported three cases of lung cancer in 2000, this technique has been applied to lung cancer for about 20 years. However, this treatment method is easily affected by the heat sink effect of peripheral blood vessels and tissue carbonization, resulting in incomplete ablation. Therefore, it cannot achieve ideal therapeutic effect in the treatment of lung cancer [11; 12].  
MWA is one of the local minimally invasive treatment techniques for lung tumors, which has been developed in recent years. At present, microwave ablation has been widely used in parts of Western countries, mainly for the ablation of solid tumors of liver, spleen, lung, adrenal and other organs [13]. Due to its effectiveness in the treatment of solid organ tumors, the use of MWA in patients with primary or metastatic lung tumors is gradually increasing [14]. Compared with RFA, microwave ablation is not easy to be affected by heat sink effect, and can produce higher temperature and larger ablation area in a shorter time. Therefore, MWA is more suitable for the treatment of lung tumors, and has received more and more attention in clinical applications [15; 16; 17].  
However, the current clinical microwave ablation lacks the best imaging guidance mode, and cannot monitor the size of the ablation area in real time. Therefore, microwave ablation may not be effective for some large or irregularly shaped tumors. [PERSON] et al. [5] have carried out some in vitro experiments and simulation studies on microwave ablation of porcine lungs and established prediction models, but did not consider the effect of air in the lungs on the microwave ablation. In contrast with other solid organs, the lungs are filled with hot and humid air, which makes the lung tissue have a natural high impedance [18; 19; 20], which will affect the temperature distribution of the microwave ablation area and cause great difficulties in accurately predicting and controlling the microwave ablation area.  
In this paper, in vitro experiments and simulations of microwave ablation of porcine lung were designed, and the two were verified by each other to determine the effect of microwave ablation in the inflated lung, and compared with the deflated lung.