Modeling of RF thermal ablation taking into account the temperature dependence of the tissue properties

Resumen

The outcome of radio frequency thermal ablation (RFTA) is significantly affected by the tissue electrical conductivity; thus, understanding the changes of this property during heating is fundamental to suitably model the medical procedure. In this work a reasonable procedure is proposed for selecting the appropriate experimental data of the temperature dependence of electrical conductivity for the simulation taking into account the heating rate at which the data was acquired and the power that will be delivered to the electrodes in the RFTA situation of interest, based on the computing of the time average of the heating rate in a representative point of the ablation zone. The numerical results confirmed that the use of lower frequencies (20 kHz) than currently used during RFTA (450 kHz) may result in preferential heating of the tumor and consequently in less damage on healthy tissue. Also, the effect on the computed thermal lesion size of three different models of the temperature dependence of electrical conductivity used for the simulation of a RFTA situation at 20 and 450 kHz, entailing the presence of three materials with different dielectric properties (normal liver tissue, tumor gel phantom and muscle saline phantom) was investigated. The results demonstrated that not only the initial (baseline) electrical conductivity is important in predicting the lesion size, but also it is the model of the temperature dependence of electrical conductivity.