title: Minimal vascular flows cause strong heat sink effects in hepatic radiofrequency ablation ex vivo.
abstract: BACKGROUND
  The present paper aims to assess the lower threshold of vascular flow rate on the heat sink effect in bipolar radiofrequency ablation (RFA) ex vivo.
  
  
  METHODS
  Glass tubes (vessels) of 3.4 mm inner diameter were introduced in parallel to bipolar RFA applicators into porcine liver ex vivo. Vessels were perfused with flow rates of 0 to 1,500 ml/min. RFA (30 W power, 15 kJ energy input) was carried out at room temperature and 37°C. Heat sink effects were assessed in RFA cross sections by the decrease in ablation radius, area and by a high-resolution sector planimetry.
  
  
  RESULTS
  Flow rates of 1 ml/min already caused a significant cooling effect (P ≤ 0.001). The heat sink effect reached a maximum at 10 ml/min (18.4 mm/s) and remained stable for flow rates up to 1,500 ml/min.
  
  
  CONCLUSIONS
  Minimal vascular flows of ≥1 ml/min cause a significant heat sink effect in hepatic RFA ex vivo. A lower limit for volumetric flow rate was not found. The maximum of the heat sink effect was reached at a flow rate of 10 ml/min and remained stable for flow rates up to 1,500 ml/min. Hepatic inflow occlusion should be considered in RFA close to hepatic vessels.
authors.affiliation: Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Kai S
authors.initials: KS
authors.lastname: Lehmann
authors.affiliation: Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Franz G M
authors.initials: FG
authors.lastname: Poch
authors.affiliation: Fraunhofer Institute for Medical Image Computing MEVIS, Bremen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Rieder
authors.affiliation: Fraunhofer Institute for Medical Image Computing MEVIS, Bremen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Schenk
authors.affiliation: Institute for Biometry and Clinical Epidemiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Stroux
authors.affiliation: Department of Diagnostic and Interventional Radiology, DRK Kliniken Berlin Westend, Berlin, Germany.
authors.forename: Bernd B
authors.initials: BB
authors.lastname: Frericks
authors.affiliation: Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Ole
authors.initials: O
authors.lastname: Gemeinhardt
authors.affiliation: Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Holmer
authors.affiliation: Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Martin E
authors.initials: ME
authors.lastname: Kreis
authors.affiliation: Department of General and Visceral Surgery, HELIOS Kliniken Schwerin, Schwerin, Germany.
authors.forename: Jörg P
authors.initials: JP
authors.lastname: Ritz
authors.affiliation: Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Urte
authors.initials: U
authors.lastname: Zurbuchen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001783:Blood Flow Velocity; D017115:Catheter Ablation / Q000009:adverse effects / Q000379:methods*; D006358:Hot Temperature; D066298:In Vitro Techniques; D008099:Liver / Q000601:surgery*; D008113:Liver Neoplasms / Q000601:surgery; D023421:Models, Animal; D015999:Multivariate Analysis; D063177:Pulse Wave Analysis / Q000009:adverse effects*; D018570:Risk Assessment; D018709:Statistics, Nonparametric; D013552:Swine
keywords: Bipolar; Cooling effect; Heat sink; Liver metastases; Radiofrequency ablation