title: Finding Optimal Ablation Parameters for Multipolar Radiofrequency Ablation.
abstract: OBJECTIVE
  Radiofrequency ablation (RFA) for primary liver tumors and liver metastases is restricted by a limited ablation size. Multipolar RFA is a technical advancement of RFA, which is able to achieve larger ablations. The aim of this ex vivo study was to determine optimal ablation parameters for multipolar RFA depending on applicator distance and energy input.
  
  
  METHODS
  RFA was carried out ex vivo in porcine livers with three internally cooled, bipolar applicators in multipolar ablation mode. Three different applicator distances were used and five different energy inputs were examined. Ablation zones were sliced along the cross-sectional area at the largest ablation diameter, orthogonally to the applicators. These slices were digitally measured and analyzed.
  
  
  RESULTS
  Sixty RFA were carried out. A limited growth of ablation area was seen in all test series. This increase was dependent on ablation time, but not on applicator distance. A steady state between energy input and energy loss was not observed. A saturation of the minimum radius of the ablation zone was reached. Differences in ablation radius between the three test series were seen for lowest and highest energy input ( P < .05). No differences were seen for medium amounts of energy ( P > .05).
  
  
  CONCLUSIONS
  The ablation parameters applicator distance and energy input can be chosen in such a way, that minor deviations of the preplanned ablation parameters have no influence on the size of the ablation area.
authors.affiliation: 1 Charité-Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Franz G M
authors.initials: FGM
authors.lastname: Poch
authors.affiliation: 2 Fraunhofer MEVIS, Institute for Medical Image Computing, Bremen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Rieder
authors.affiliation: 2 Fraunhofer MEVIS, Institute for Medical Image Computing, Bremen, Germany.
authors.forename: Hanne
authors.initials: H
authors.lastname: Ballhausen
authors.affiliation: 3 Laser- und Medizin-Technologie GmbH, Berlin, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Knappe
authors.affiliation: 4 Klinik für Allgemein- und Viszeralchirurgie, HELIOS Kliniken Schwerin, Schwerin, Germany.
authors.forename: Jörg Peter
authors.initials: JP
authors.lastname: Ritz
authors.affiliation: 1 Charité-Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Ole
authors.initials: O
authors.lastname: Gemeinhardt
authors.affiliation: 1 Charité-Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Martin E
authors.initials: ME
authors.lastname: Kreis
authors.affiliation: 1 Charité-Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Kai S
authors.initials: KS
authors.lastname: Lehmann
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D008099:Liver / Q000601:surgery*; D008113:Liver Neoplasms; D013552:Swine; D013696:Temperature
keywords: colorectal surgery; simulation; surgical oncology