title: 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: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: a Department of Surgery , Leopold Park Clinic, CHIREC Cancer Institute , Brussels , Belgium .|b Department of Radiology , Gasthuisberg University Hospital , Leuven , Belgium .
authors.forename: Stefaan
authors.initials: S
authors.lastname: Mulier
authors.affiliation: b Department of Radiology , Gasthuisberg University Hospital , Leuven , Belgium .
authors.forename: Yansheng
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: c Department of Biostatistics , Mont-Godinne University Hospital , Yvoir , Belgium .
authors.forename: Jacques
authors.initials: J
authors.lastname: Jamart
authors.affiliation: d Alegrete Technology Centre, Federal University of Pampa , Alegrete , Rio Grande do Sul , Brazil , and.
authors.forename: Chong
authors.initials: C
authors.lastname: Wang
authors.affiliation: b Department of Radiology , Gasthuisberg University Hospital , Leuven , Belgium .
authors.forename: Yuanbo
authors.initials: Y
authors.lastname: Feng
authors.affiliation: b Department of Radiology , Gasthuisberg University Hospital , Leuven , Belgium .
authors.forename: Guy
authors.initials: G
authors.lastname: Marchal
authors.affiliation: e Department of Surgery , Mont-Godinne University Hospital , Yvoir , Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: Michel
authors.affiliation: b Department of Radiology , Gasthuisberg University Hospital , Leuven , Belgium .
authors.forename: Yicheng
authors.initials: Y
authors.lastname: Ni
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation; D002417:Cattle; D004566:Electrodes; D020342:Finite Element Analysis; D008099:Liver / Q000601:surgery*; D008954:Models, Biological
keywords: Bipolar; finite element method; liver; matrix; radiofrequency ablation