title: Experimental Evaluation of the Heat Sink Effect in Hepatic Microwave Ablation.
abstract: OBJECTIVE
  To demonstrate and quantify the heat sink effect in hepatic microwave ablation (MWA) in a standardized ex vivo model, and to analyze the influence of vessel distance and blood flow on lesion volume and shape.
  
  
  METHODS
  108 ex vivo MWA procedures were performed in freshly harvested pig livers. Antennas were inserted parallel to non-perfused and perfused (700,1400 ml/min) glass tubes (diameter 5mm) at different distances (10, 15, 20mm). Ablation zones (radius, area) were analyzed and compared (Kruskal-Wallis Test, Dunn's multiple comparison Test). Temperature changes adjacent to the tubes were measured throughout the ablation cycle.
  
  
  RESULTS
  Maximum temperature decreased significantly with increasing flow and distance (p<0.05). Compared to non-perfused tubes, ablation zones were significantly deformed by perfused tubes within 15 mm distance to the antenna (p<0.05). At a flow rate of 700 ml/min ablation zone radius was reduced to 37.2% and 80.1% at 10 and 15 mm tube distance, respectively; ablation zone area was reduced to 50.5% and 89.7%, respectively.
  
  
  CONCLUSIONS
  Significant changes of ablation zones were demonstrated in a pig liver model. Considerable heat sink effect was observed within a diameter of 15 mm around simulated vessels, dependent on flow rate. This has to be taken into account when ablating liver lesions close to vessels.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
authors.forename: Kristina I
authors.initials: KI
authors.lastname: Ringe
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Lutat
authors.affiliation: Institute for Medical Image Computing, Fraunhofer MEVIS, Bremen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Rieder
authors.affiliation: Institute for Medical Image Computing, Fraunhofer MEVIS, Bremen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Schenk
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Wacker
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Raatschen
mesh_terms: D055011:Ablation Techniques / Q000379:methods*; D000818:Animals; D006358:Hot Temperature; D066298:In Vitro Techniques; D008099:Liver / Q000098:blood supply / Q000502:physiology / Q000601:surgery*; D008872:Microwaves / Q000627:therapeutic use*; D023421:Models, Animal; D034421:Sus scrofa