title: Comparison of bipolar radiofrequency ablation zones in an in vivo porcine model: Correlation of histology and gross pathological findings.
abstract: BACKGROUND
  Continuing research ex vivo and in vivo with animal models is performed to advance the oncological safety of radiofrequency ablation (RFA) of liver tumors. In these experiments, frequently imaging modalities (e.g. MRI or CT) or macro-morphological measurements are used to determine the full extent of the different ablation zones inside of RFA lesions. However, no systematic study has been performed so far, which verified the accuracy of the macro-morphological findings. Therefore, the present study aimed to correlate histological and gross pathological findings of bipolar radiofrequency ablation zones of porcine livers with regard to cell viability in vivo.
  
  
  METHODS
  Bipolar RFA was performed in the liver of anaesthetized female domestic pigs under CT-guidance using an internally cooled 20 mm RFA applicator. Afterwards RFA cross sections of the liver were made in a perpendicular orientation to the applicator. Ablation zones were initially documented by photography and thereafter prepared for histological analysis. Latter was based on HE-staining and NADH-diaphorase cell viability staining. Micro- and macro-morphological sections were digitally analyzed along the cross-section area for statistical correlation.
  
  
  RESULTS
  Three different RF ablation zones could be differentiated. A central zone showing no cell viability (white zone) was surrounded by a red zone. The red zone could be divided into an inner zone of viable and non-viable cells (red zone 1), followed by a zone of edema with mostly viable cells (red zone 2).Micro- and macro-morphological data showed a strong correlation for the white zone (r = 0.95, p < 0.01), the red zone 1 (r = 0.85, p < 0.01), and the red zone 2 (r = 0.89, p < 0.01).
  
  
  CONCLUSIONS
  White zone and red zone could clearly be distinguished in gross pathology and histology after bipolar RFA of porcine liver tissue in vivo. The red zone could be differentiated into an inner zone of viable and non-viable cells and an outer zone with high cell viability and intercellular edema. A strong correlation of micro- and macro-morphology could be shown for all three ablation zones. With this knowledge, gross pathological examination can be used as a reliable indicator of lethally damaged tissue in bipolar RFA of in vivo porcine liver.
authors.affiliation: Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Ole
authors.initials: O
authors.lastname: Gemeinhardt
authors.affiliation: Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Franz G M
authors.initials: FG
authors.lastname: Poch
authors.affiliation: Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Hannover, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hiebl
authors.affiliation: Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Urte
authors.initials: U
authors.lastname: Kunz-Zurbuchen
authors.affiliation: Institute of Veterinary Anatomy, Freie Universität Berlin, Berlin, Germany.
authors.forename: Giuliano M
authors.initials: GM
authors.lastname: Corte
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Stefan F
authors.initials: SF
authors.lastname: Thieme
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Janis L
authors.initials: JL
authors.lastname: Vahldiek
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Niehues
authors.affiliation: Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Martin E
authors.initials: ME
authors.lastname: Kreis
authors.affiliation: Institute of Veterinary Pathology, Freie Universität Berlin, Berlin, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Klopfleisch
authors.affiliation: Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Kai S
authors.initials: KS
authors.lastname: Lehmann
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D004195:Disease Models, Animal; D005260:Female; D008099:Liver / Q000473:pathology*; D008113:Liver Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D013552:Swine
keywords: Liver; NADH-diaphorase; animal model; bipolar; radiofrequency ablation (RFA); viability staining