Microwave ablation is to release microwave magnetic field to make tumor tissue reach a high temperature above 60 ℃, resulting in protein degeneration and necrosis, so as to achieve the purpose of treatment. However, unlike other substantial organs, lung is full of air with a natural high impedance. It will affect the size and shape of microwave coagulation zone, making accurate prediction and control of the coagulation zone very challenging. In this paper, in ex-vivo experiments combined with simulations are used to study the microwave coagulation zone of the lungs in an inflated state.The in ex-vivo experiment is divided into inflatable lung ablation group and deflated lung ablation group, combined with different ablation power (40W, 50W, 60W) and ablation time (100s, 200s, 300s) for experiment, each power and time combination are repeated five times. A total of 90 ablation experiments were performed. The simulation experiment uses the finite element method with the electromagnetic field model and the biological heat transfer model. And the changes of several key physical parameters of the lung in the inflated state were considered, including the relative permittivity, electrical conductivity and density of the lung tissue.Under the same ablation power and ablation time, the average long diameter (LD) and short diameter (SD) of the coagulation zone of the deflated group are larger than those of the inflated group. The average LD of the deflated group is 7.6%-30.9% larger than that of the inflated group, and the average SD of the deflated group is 27.3%-45.7% larger than that of the inflated group. The results show that the size of coagulation zone is smaller in the inflated lung than in the collapsed lung, which is mainly due to the smaller ablation SD. In ex-vivo and simulation experiment were designed to verify the influence of lung inflation on the microwave coagulation zone, It shows that the ablation size becomes smaller when the lung is inflated. Therefore, if the deflated ex-vivo lung ablation parameters are still used, the actual coagulation zone will become smaller, which will affect the clinical effect. So, it is necessary to fully consider different inflation states for lung ablation in order to truly guide clinical practice.
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