title: Determination of the temperature-dependent electric conductivity of liver tissue ex vivo and in vivo: Importance for therapy planning for the radiofrequency ablation of liver tumours.
abstract: BACKGROUND
  Knowledge about the changes in the electric conductivity during the coagulation process of radiofrequency ablation of the liver is a prerequisite for the predictability of produceable thermonecrosis in the liver.
  
  
  METHODS
  Continuous measurements of the electric conductivity sigma in ex vivo porcine liver (n = 25) were done during the coagulation and cooling process at the temperature range of the radiofrequency ablation at a frequency of 470 kHz relevant for the radiofrequency ablation. Measurements of the electric conductivity were performed in both perfused porcine liver (n = 3) and a human surgical specimen from a colorectal liver metastasis.
  
  
  RESULTS
  At a body temperature of 37 degrees C, conductance sigma was 0.41 siemens per metre (0.32 S/m; 0.52 S/m). Conductance sigma increased continuously and uniformly at a temperature of 77 degrees C. Maximum conductance sigma with 0.79 S/m (0.7 S/m; 0.87 S/m) was reached at 80 degrees C. A continuous reduction of conductance was observed during the cooling phase. At 37 degrees C, the specific conductance sigma in the healthy perfused porcine liver was 0.52 S/m, 0.55 S/m and 0.57 S/m (mean 0.55 S/m). The electric conductivity of the human colorectal liver metastasis was clearly higher.
  
  
  CONCLUSIONS
  Changes in the specific conductivity during the coagulation and the cooling phase play an important role for the produceable size of a coagulation necrosis and necessitates an adaptation of the therapy parameters during radiofrequency ablation.
authors.affiliation: Department of General, Vascular and Thoracic Surgery, Charité Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin 12200, Germany. urte.zurbuchen@charite.de
authors.forename: Urte
authors.initials: U
authors.lastname: Zurbuchen
authors.forename: Christoph
authors.initials: C
authors.lastname: Holmer
authors.forename: Kai S
authors.initials: KS
authors.lastname: Lehmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Stein
authors.forename: André
authors.initials: A
authors.lastname: Roggan
authors.forename: Claudia
authors.initials: C
authors.lastname: Seifarth
authors.forename: Heinz-J
authors.initials: HJ
authors.lastname: Buhr
authors.forename: Jörg-Peter
authors.initials: JP
authors.lastname: Ritz
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D015179:Colorectal Neoplasms / Q000473:pathology; D004553:Electric Conductivity; D006801:Humans; D008099:Liver / Q000473:pathology / Q000503:physiopathology*; D008113:Liver Neoplasms / Q000473:pathology / Q000503:physiopathology* / Q000556:secondary / Q000601:surgery; D013552:Swine; D013696:Temperature