title: Comparison of a single perfusion device and an internally cooled cluster device: laboratory experience in ex vivo liver tissue with longer duration of energy application.
abstract: OBJECTIVE
  To determine with comparison of two different monopolar radiofrequency (RF) devices whether a longer duration of energy application has an effect on coagulation necrosis in ex vivo bovine liver tissue.
  
  
  METHODS
  The volume and short- and long-axis diameters of the coagulation were assessed in ex vivo bovine livers after RF application for 5-60 minutes. A power of 60 W was used for the single perfusion applicator (n = 48), and a power of 200 W was used for the internally cooled cluster applicator (n = 48). Reproducibility and coagulation shape were assessed and compared. For statistical evaluation, the mean values of the dimensions were compared by using analysis of variance with the following factors: applicator, RF duration, and their interaction.
  
  
  RESULTS
  RF application up to 60 minutes produced a mean maximum volume of coagulation of 116.8 cm(3)(95% confidence interval [CI]: 98.4 cm(3), 138.8 cm(3)) for the single perfusion device and 89.5 cm(3)(95% CI: 75.4 cm(3), 106.3 cm(3)) for the internally cooled cluster applicator. For both devices, duration of energy application up to 60 minutes showed a significant interaction for the volume and the short- and long-axis diameters of coagulation (P < .0001). The volumes of coagulation necrosis induced with the internally cooled cluster applicator were more reproducible than those induced with the single perfusion applicator (P < .0001). The shape of the lesion was closer to a sphere (mean shape ratio, 0.98) for the internally cooled cluster than for the single perfusion applicator (mean shape ratio, 1.21) (P < .0001).
  
  
  CONCLUSIONS
  There is a significant interaction between RF duration and both RF devices influencing the dimensions of coagulation. Longer durations of energy application expand the volume of coagulation with a better reproducibility and more spherical shape of coagulation for the internally cooled cluster device.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University, Tübingen, Germany. diethard.schmidt@med.uni-tuebingen.de
authors.forename: Diethard
authors.initials: D
authors.lastname: Schmidt
authors.forename: Stephan
authors.initials: S
authors.lastname: Clasen
authors.forename: Andreas
authors.initials: A
authors.lastname: Boss
authors.forename: Tina
authors.initials: T
authors.lastname: Herberts
authors.forename: Christoph
authors.initials: C
authors.lastname: Aubé
authors.forename: Jochen
authors.initials: J
authors.lastname: Truebenbach
authors.forename: Claus D
authors.initials: CD
authors.lastname: Claussen
authors.forename: Phillipe L
authors.initials: PL
authors.lastname: Pereira