Bipolar radiofrequency ablation with 2 × 2 electrodes as a building block for matrix radiofrequency ablation: Ex vivo liver experiments and finite element method modelling

Abstract

Purpose: Size and geometry of the ablation zone obtained by currently available radiofrequency (RF) electrodes is highly variable. Reliability might be improved by matrix radiofrequency ablation (MRFA), in which the whole tumour volume is contained within a cage of x × y parallel electrodes. The aim of this study was to optimise the smallest building block for matrix radiofrequency ablation: a recently developed bipolar 2 × 2 electrode system. Materials and methods: In ex vivo bovine liver, the parameters of the experimental set-up were changed one by one. In a second step, a finite element method (FEM) modelling of the experiment was performed to better understand the experimental findings. Results:The optimal power to obtain complete ablation in the shortest time was 50–60 W. Performing an ablation until impedance rise was superior to ablation for a fixed duration. Increasing electrode diameter improved completeness of ablation due to lower temperature along the electrodes. A chessboard pattern of electrode polarity was inferior to a row pattern due to an electric field void in between the electrodes. Variability of ablation size was limited. The FEM correctly simulated and explained the findings in ex vivo liver. Conclusions: These experiments and FEM modelling allowed a better insight in the factors influencing the ablation zone in a bipolar 2 × 2 electrode RF system. With optimal parameters, complete ablation was obtained quickly and with limited variability. This knowledge will be useful to build a larger system with x × y electrodes for MRFA.

• Bipolar
• finite element method
• liver
• matrix
• radiofrequency ablation

Acknowledgements

The authors wish to thank Marie-Bernadette Jacqmain, Mr. Axel Bailey and Christian Deneffe for the illustrations. The work is dedicated to the loving memory of Maurits Van Buggenhout, mathematician.

Declaration of interest

This work was partially supported by the grants awarded by the KU Leuven Molecular Small Animal Imaging Centre MoSAIC (KUL EF/05/08); the centre of excellence In vivo Molecular Imaging Research (IMIR) of KU Leuven; and a European Union project Asia-Link CfP 2006- EuropeAid/123738/C/ACT/Multi-Proposal No. 128- 498/111. Yicheng Ni is currently a Bayer Lecture Chair holder.

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.