title: The vascular cooling effect in hepatic multipolar radiofrequency ablation leads to incomplete ablation ex vivo.
abstract: Major limitations of conventional RFA are vascular cooling effects. However, vascular cooling effects are supposed to be less pronounced in multipolar RFA. The objective of this ex vivo study was a systematic evaluation of the vascular cooling effects in multipolar RFA.
  
  
  
  Multipolar RFA with three bipolar RFA applicators was performed ex vivo in porcine liver (applicator distance 20 mm, energy input 40 kJ). A saline-perfused glass tube ('vessel') was placed parallel to the applicators in order to simulate a natural liver vessel. Five applicator-to-vessel geometries were tested. A liquid-filled glass tube without perfusion was used as a dry run. Ablations were orthogonally cut to the applicators at a defined height. Cooling effects were analysed qualitatively and quantitatively along these cross sectional areas.
  
  
  
  Thirty-six ablations were performed. A cooling effect could be seen in all ablations with perfused vessels compared to the dry run. While this cooling effect did not have any influence on the ablation areas (859-1072 mm(2) versus 958 mm(2) in the dry run, p > 0.05), it had a distinctive impact on ablation shape. A vascular cooling effect could be observed in all ablations with perfusion directly around the vessel independent of the applicator position compared to the dry run (p < 0.01).
  
  
  
  A vascular cooling effect occurred in all multipolar RFA with simulated liver vessels ex vivo independent of the applicator-to-vessel geometry. While the cooling effect did not influence the total ablation area, it had a distinctive impact on the ablation shape.
authors.affiliation: a Department of General, Visceral and Vascular Surgery , Charité - Campus Benjamin Franklin , Berlin ;
authors.forename: Franz G M
authors.initials: FG
authors.lastname: Poch
authors.affiliation: b Fraunhofer MEVIS, Institute for Medical Image Computing , Bremen ;
authors.forename: Christian
authors.initials: C
authors.lastname: Rieder
authors.affiliation: b Fraunhofer MEVIS, Institute for Medical Image Computing , Bremen ;
authors.forename: Hanne
authors.initials: H
authors.lastname: Ballhausen
authors.affiliation: c Laser- und Medizin-Technologie GmbH , Berlin ;
authors.forename: Verena
authors.initials: V
authors.lastname: Knappe
authors.affiliation: d Klinik für Allgemein- und Viszeralchirurgie, HELIOS Kliniken Schwerin , Schwerin , Germany.
authors.forename: Jörg-Peter
authors.initials: JP
authors.lastname: Ritz
authors.affiliation: a Department of General, Visceral and Vascular Surgery , Charité - Campus Benjamin Franklin , Berlin ;
authors.forename: Ole
authors.initials: O
authors.lastname: Gemeinhardt
authors.affiliation: a Department of General, Visceral and Vascular Surgery , Charité - Campus Benjamin Franklin , Berlin ;
authors.forename: Martin E
authors.initials: ME
authors.lastname: Kreis
authors.affiliation: a Department of General, Visceral and Vascular Surgery , Charité - Campus Benjamin Franklin , Berlin ;
authors.forename: Kai S
authors.initials: KS
authors.lastname: Lehmann
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D006801:Humans; D008099:Liver / Q000528:radiation effects*; D010477:Perfusion; D013552:Swine
keywords: Cooling effect; heat sink effect; hepatic; liver; multipolar; radiofrequency ablation