## 4 Conclusions  
The lung tissue contains a lot of hot and humid air, and the microwave energy is not easily transmitted in the tissue, which makes the prediction and control of the ablation area very difficult for MWA in clinical application [35]. This paper designed an ex-vivo experiment and a simulation experiment to explore the influence of lung inflation on the effect of MWA. The results of the in vitro experiments show that the inflated lung weakens the microwave ablation effect, which is due to the inflatable reduces the relative permittivity, electrical conductivity, thermal conductivity and other physics parameters of the lung tissue, which affects the transmission and accumulation of microwave energy in the tissue [36]. Under the same ablation power and time, DI and Ds of the inflated lung were 7.6-30.9% and 24.5-45.7% smaller than those of the deflated lung, respectively, and the isoperimetric ratio was 0.011-0.097 smaller than deflated group. The maximum temperature and heating rate at different positions of the ablation antenna were also lower than deflated group. In addition, we used the COMSOL Multiphysics software to simulate the microwave ablation of the inflated lung, and obtained similar results to the in vitro experiments, which verified the correctness of the in vitro experiments. Specifically, DI, Ds and the isoperimetric ratio of the inflated lung are, respectively, 0-7.3%, 15.5-28.0% and 0.059-0.072 smaller than deflated group. This is consistent with the simulation experiment conclusion that inflated lung weakens the microwave ablation effect reported in the literature, which further verifies the correctness of the experiment in this paper [37; 38; 39]. Compared with RFA, MWA has the advantage of activating multiple microwave antennas, and the synergistic effect of multiple antennas in ablation can effectively expand the volume of the ablation area, solve the ablation deficiency in the treatment of large tumors, and reduce the recurrence rate after ablation [40]. [PERSON] et al. [41] used multi-antenna to ablate pig lungs in vivo experiments. When the ablation power was 60 W, the ablation time was 10 min, and three antennas were used for ablation, the average longitudinal diameter was 43.0 mm \(\pm\) 7.7 mm, and the transverse diameter was 54.8 mm \(\pm\) 8.5 mm, and the isoperimetric ratio was 0.70 \(\pm\) 0.10. Compared with single-antenna ablation under the same conditions, the average longitudinal diameter is increased by about 20%, the average transverse diameter is increased by about 67.5%, and the isoperimetric ratio is increased by about 9%. It can be seen that multi-antenna ablation can produce a larger volume of ablation and a higher isoperimetric ratio. However, when three-antenna ablation was used, and the power and ablation time were increased to 75 W and 15 min, two animals died of heart failure due to carbonization of lung tissue and myocardial burn, so the use of multi-antenna ablation in clinical treatment must comprehensively consider ablation power and time. [PERSON] et al. [42] studied the shape and volume of the ablation area obtained by multi-antenna microwave ablation of liver tumors. For tumors larger than 3 cm in diameter, three-antenna ablation was used, and tumors with a diameter of 2-3 cm were \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Time/s**} & \multicolumn{2}{c}{**40 W**} & \multicolumn{2}{c}{**50 W**} & \multicolumn{2}{c}{**60 W**} \\ \cline{2-7}  & **Deflated** & **Inflated** & **Deflated** & **Inflated** & **Deflated** & **Inflated** \\ \hline
100 & 0.836 & 0.765 & 0.827 & 0.757 & 0.819 & 0.760 \\ \hline
200 & 0.855 & 0.788 & 0.849 & 0.783 & 0.847 & 0.785 \\ \hline
300 & 0.863 & 0.792 & 0.859 & 0.787 & 0.851 & 0.792 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Isoperimetric ratio of ablation area. ablated with dual antennas. 65 W, ablation time 10 min, antenna spacing 2 cm.