A piecewise function of resistivity of liver: determining parameters with finite element analysis of radiofrequency ablation

Abstract

Radiofrequency ablation (RFA) is a widely used thermal treatment for liver tumors. Knowledge about the resistivity of liver is a prerequisite for the predictability of producible thermo-necrosis with RFA. Most research to date has focused on performing specific experiments to determine the resistivity of a given liver. This work aims to determine the resistivity from the time course of impedance obtained in RFA. We assume that the liver resistivity obeys a piecewise function of temperature. We determine in this work the means and standard derivations of parameters in the resistivity function with finite element analysis of ex vivo bipolar RFA. We experimentally found the temperature at the electrode equal to 125.2 °C. This finding validates a parameter in the function relating to the temperature at which the resistivity starts to rise exponentially. We conclude that it is feasible and reliable to characterize the resistivity function of liver in using the time course of impedance from RFA. This work opens a pathway for the automatic determination of the patient specific resistivity of in vivo liver.

Radiofrequency ablation with four electrodes as a building block for matrix radiofrequency ablation: Ex vivo liver experiments and finite element method modelling. Influence of electric and activation mode on coagulation size and geometry

“…RAFEM-2 was an updated version taking into account the temperature dependence of electric and thermal conductivity [139][140][141] and has been described in detail before [51,142,152].…”

“…The initial Pennes' bioheat equation for FEM modelling of RFA is constantly being refined, taking into account more and more electrophysical phenomena such as the heat-sink effect [137], evaporation, water shift and pressure increase [138] and the temperature dependency of electrophysical features [51,[139][140][141][142]. More accurate simulation has been proposed as a way to improve reliability and safety of clinical ablation in patients [143].…”