Simulation of combined heating for tumor ablation

In the field of oncology therapy in the last few decades, methods of local thermal destruction have been intensively developed, which is heating a malignant neoplasm to a coagulation temperature and above. Among them, radiofrequency ablation (RFA) and microwave ablation (MWA) are the most common. The main problem of the existing MWA and RFA units is the insufficient degree of tissue coagulation. Depending on the type of tissue, various methods of exposure to an electromagnetic field can be used. In the radio frequency (RF) range, ohmic heating can be used, suitable for highly conductive tissues, and dielectric heating for low conductivity tissues. To increase the heating volume, it is proposed to combine ohmic and dielectric heating. The purpose of this work was to study the possibility of combining the processes of ohmic and dielectric heating based on methods of microwave and radiofrequency thermal destruction. A computer simulation of the combined heating electrode was carried out. The COMSOL Multiphysics software package was used to create the model. The algorithm for constructing the model consisted in creating the geometry, choosing the sizes of the working zones of the electrodes, setting the power parameters and imposing a finite element mesh. The model was two-dimensional. Various configurations of the combined heating electrode were considered. As a result, it was found that it is possible to create a heating area of a larger volume than with separate exposure. The overall shape of the resulting heating in all cases had an elliptical shape. At the same time, the heating pattern for RF working zones with a size of 5 mm had a shape more suitable for the treatment of spherical tumors than for working zones with a size of 10–20 mm. The results obtained demonstrate the possibility of increasing the heating volume by more than 40% compared to single operating modes. The most suitable sizes of RF heating zones are calculated, at which the heating volume will be maximum. The use of combined heating in clinical practice will partially solve the problems of insufficient heating volume inherent in the single-electrode heating mode in both RFA and MWA.