title: Comparison of four microwave ablation devices: an experimental study in ex vivo bovine liver.
abstract: OBJECTIVE
  To compare volume, sphericity, and short-axis diameter of the coagulation zone of four commercially available microwave ablation systems with three technical concepts in an ex vivo setting and to formulate mathematical models to predict these quantities.
  
  
  METHODS
  Two high-power systems (systems A and B), a system that enables simultaneous use of three antennas (system C), and a non-perfusion-cooled system that automatically adapts power and frequency (system D) were tested in ex vivo bovine livers (108 ablations). Coagulation volume, sphericity, and mean short-axis diameter were assessed, and mathematical functions were fitted for each system and assessed with the coefficient of determination (R(2)). Analysis of variance and Tukey post hoc tests were used for interdevice comparison after 5 and 10 minutes and after maximum recommended ablation time.
  
  
  RESULTS
  Volume and short-axis diameter were determined by using a mathematical model for every system, with coefficients of determination of 0.75-0.98 and 0.70-0.97, respectively. Correlation for determination of sphericity was lower (R(2) = 0.01-0.68). Mean results with ablation performed according to manufacturer recommendations were as follows: Volume, sphericity, and short-axis diameter were 57.5 cm(3), 0.75, and 43.4 mm, respectively, for system A; 72.3 cm(3), 0.68, and 45.5 mm, respectively, for system B; 17.1 cm(3), 0.58, and 26.8 mm, respectively, for system C (one antenna); 76.5 cm(3), 0.89, and 50.6 mm, respectively, for system C (three antennas); and 56.0 cm(3), 0.64, and 40.9 mm, respectively, for system D. Systems A (mean volume, 52.4 cm(3) ± 4.5 [standard deviation]) and B (39.4 cm(3) ± 1.7) reach large ablation zones with 5-minute ablation.
  
  
  CONCLUSIONS
  The largest ablation zone is obtained with systems B and C (three antennas) under maximum recommended ablation duration and with system A under short ablation time. The most spherical zone is obtained with system C (three antennas).
authors: Department of Diagnostic and Interventional Radiology and Department of Medical Biometry, Eberhard-Karls-University, Hoppe-Seyler-Strasse 3, 72076 Tübingen, Germany. Ruediger.Hoffmann@med.uni-tuebingen.de
authors: Rüdiger
authors: R
authors: Hoffmann
authors: Hansjörg
authors: H
authors: Rempp
authors: Ludwig
authors: L
authors: Erhard
authors: Gunnar
authors: G
authors: Blumenstock
authors: Philippe L
authors: PL
authors: Pereira
authors: Claus D
authors: CD
authors: Claussen
authors: Stephan
authors: S
authors: Clasen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation*; D002417:Cattle; D004867:Equipment Design; D066298:In Vitro Techniques; D008099:Liver / Q000601:surgery*; D008872:Microwaves; D015233:Models, Statistical