AC measurements and simulations of hepatic radiofrequency ablation

Abstract

Introduction

The radiofrequency ablation (RFA) of liver cancer is a desirable treatment option, as it is minimally invasive. An accurate numerical simulation can greatly help physicians better plan their surgical protocols. Previously, the displacement current in the RFA process was considered negligible, and therefore RFA simulation was modeled as a direct current (DC) system instead of an alternating current (AC) system. Our study investigated the hypothesis that the displacement current in the RFA process should not always be considered negligible.

Methods

AC measurements of ex vivo bovine liver ablation were performed, and numerical simulations were also conducted to test the hypothesis that the relative permittivity would significantly decrease after the liver tissue reached a high temperature.

Results

The displacement current was observed to be a sizable fraction of the conduction current, especially before the onset of the first pause. The simulation results indicated that the relative permittivity is likely to decrease to several hundred or lower at elevated temperatures.

Conclusions

Our study results suggest that the DC model may be inadequate, especially before the first roll-off and that additional information could be available during RFA treatment by considering the AC nature of RFA, which could lead to improved numerical simulation. Additional measurements of tissue parameters are needed to reach the full potential of the AC model for further development of ablation control.

Keywords:

• Radiofrequency ablation (RFA)
• alternating current (AC)
• relative permittivity
• dielectric constant
• phase
• finite element method (FEM) simulation
• bovine liver

Disclosure statement

The Biomedical Technology and Device Research Laboratories at the Industrial Technology Research Institute are developing their own RFA system.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This study was supported by the Ministry of Economic Affairs, Taiwan, via the Technology Development Project on RFA devices under grant number 109-EC-17-A-22-1125.