Numerical simulations of microwave liver tumor ablation

Branislav Radjenović and Marija Radmilović-Radjenović
Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia

Abstract: Hepatocellular carcinoma accounts for around 75% of all liver cancers, and represents the fourthmost common cause of cancer-related deaths. Microwave ablation is a well esatblished treatmentof hepatocellular carcinoma. The success rate for completely eliminating small liver tumors inpatients treated with microwave ablation isgreater than 85%. Microwave ablation is also highlyrecommended for COVID-19 patients with liver tumors as a fast treatment with a short recoverytime. The involvement of the temperature dependence of the heat capacity, the thermalconductivity, and blood perfusion, is pivotal for establishing the correct ablation process andpreserving the healthy tissue.Every mathematical model for the simulation of microwave ablation consists of threefundamental components. The first component is the model of the antenna probe (or applicator)that generates a microwave field in the tissue. The antennas are usually mechanically andgeometrically complex, and the simulation relies on having accurate electromagnetic materialand tissue properties. In this study, we use a compact 10-slot microwave antenna with animpedance pi-matching network that creates near-spherical ablation zones. The secondcomponent describes the heat distribution in the tissue including sources and sinks and the phasechanges. Heat transfer during the MWA process can be accurately described by the Pennesbioheat equation. In our case, the microwave field is the source of heat, and the heat sinks arerepresented by the blood perfusion term in the heat transfer equation. The third part deals withthe effect of heat on tumor cells and their destruction. All these components of the ablationmodel depend on a variety of material parameters, which themselves depend on the variousstates of the tissue. Finally, to define realistic simulation model, we were using the data from the3D-IRCADb-01 database of hepatocellular carcinoma.The 3D finite elements method (FEM) is used to solve coupled electromagnetic-field and heat-transfer equations, including all details of antenna design and properties of healthy and tumoraltissue. Our 3D model is created within the COMSOL Multiphysics FEM-based simulationplatform.