Bipolar radiofrequency ablation with four electrodes : Ex vivo liver experiments and finite element method analysis. Influence of inter-electrode distance on coagulation size and geometry

Thu, 15/11/2012 - 16:03 — Luc Michel
Bipolar radiofrequency ablation with four electrodes : Ex vivo liver experiments and finite element method analysis. Influence of inter-electrode distance on coagulation size and geometry
International Journal of Hyperthermia 2012; 28:1-12.
RESEARCH
 ARTICLE
Abstract
Purpose: The aim of this study was to develop an electrode system with simple needle electrodes which would allow a reliable
and predictable ablation zone with radiofrequency ablation (RFA).
Materials and methods: In the first step, four parallel electrodes (active length 3 cm, diameter 1.8mm) were inserted in ex vivo
bovine liver. A power of 50W was applied between two pairs of electrodes for 10 min or until current shut-off due to
impedance rise. In the second step, the influence of changing inter-electrode distance on coagulation size and geometry was
measured. In the third step, a finite element method (FEM) analysis of the experiment was performed to better understand
the experimental findings.
Results: A bipolar four-electrode system with templates adjusting the inter-electrode distance was successfully developed for
ex vivo experiments. A complete and reliable coagulation zone of a 322-cm block was obtained most efficiently with an
inter-electrode distance of 2 cm in 5.120.71 min. Above 2 cm, coagulation was incomplete due to a too low electric field,
as demonstrated by the FEM analysis.
Conclusions: The optimal inter-electrode distance of the present bipolar four-electrode system was 2 cm, allowing a reliable
and predictable ablation zone in ex vivo liver. The FEM analysis correctly simulated and explained the findings in ex vivo
liver. The experimental set-up may serve as a platform to gain more insight and to optimise the application of RFA by means
of four or more simple needle electrodes.
Keywords: bipolar, experimental, finite element method, liver, radiofrequency ablation
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