Background. The character of ablation processes with high-frequency electrical current is similar in most biological tissues; however, quantitative characteristics are very different. Consequently, mathematical models of the process have a lot of specific aspects. In this study, we developed mathematical model of radiofrequency ablation in liver tissues with experimental validation of model in ex vivo porcine liver. Methods. The finite element nonlinear computational model for the simulation of the radiofrequency ablation processes and taking into account coupled electrical and thermal phenomena has been developed. The radiofrequency electric current processes are dominated by the active electric conductivity. The heat generation in biological tissues is determined by the electric current density. Simultaneously, the conductivity of the tissue is nonlinearly dependent upon the temperature of the tissue. The model has been implemented in COMSOL Multiphysics computational environment. Tests on physical characteristics of the thermal effect in ex vivo liver tissue have been performed and results compared. Results. Two oval-shaped zones of total and relative tissue destruction were highlighted. The principal distribution of the thermal effect is congruous with the theoretical model; however, the discrepancy of temperatures in experimental and theoretical models increases distally from active perfusion electrode. Conclusions. Distribution of the thermal effect is congruous in the theoretical and experimental model; however, discrepancies of temperatures imply certain inadequacies of the mathematical models. Differences of computed and actual temperatures should be regarded predicting tissue ablation in clinical setting.
Broadband Dielectric Properties of Ex Vivo Bovine Liver Tissue Characterized at Ablative Temperatures