On the influence of tissue anisotropy in numerical modelling of radiofrequency ablation

The numerical modeling of radiofrequency ablation (RFA) has improved considerably in recent years. Successful modeling requires a detailed understanding of the properties of biological tissue. Due to their anatomical structure, skeletal and cardiac muscles exhibit anisotropic properties that can lead to different conduction of electrical current and heat transfer depending on fiber orientation. We therefore investigated whether tissue anisotropy also has an influence at the relatively high frequencies used in RFA (∼500 kHz). In a time-dependent study, we used the finite element method to model the electrical currents and heat transfer to calculate the temperature distribution in vivo. We investigated the effects of the anisotropic electrical and thermal properties of the muscles on the accuracy of the model. The model was compared with the experimental results and the accuracy of the model was quantitatively evaluated using the Sørensen-Dice coefficient. Despite the relatively high frequency of the alternating electric current used in RFA, the anisotropy of the electrical conductivity of the muscles has a significant effect on the accuracy of the model. The numerical model with an anisotropy ratio of 1.5 achieved the highest average Sørensen-Dice coefficient. However, the anisotropy of the thermal conductivity does not seem to affect the model accuracy (no significant change compared to the model without anisotropy).