title: Multiple-electrode radiofrequency ablation creates confluent areas of necrosis: in vivo porcine liver results.
abstract: OBJECTIVE
  To prospectively evaluate, in vivo in pigs, an impedance-based multiple-electrode radiofrequency (RF) ablation system for creation of confluent areas of hepatic coagulation.
  
  
  METHODS
  The study was preapproved by the institutional research animal care and use committee. A prototype multiple-electrode RF system that enables switching between three electrically independent electrodes at impedance spikes was created. Forty-two coagulation zones (18 with single, 12 with cluster, and 12 with multiple [three single electrodes spaced 2 cm apart] electrodes) were created at laparotomy in 15 female pigs. Half the ablations were performed for 12 minutes, and half were performed for 16 minutes. The coagulation zones were excised and sliced into approximately 3-mm sections for measurement. Analysis of variance and two-sample t tests (with Bonferroni correction, alpha = .0033) were used to assess for differences between groups.
  
  
  RESULTS
  At 12 minutes, the mean multiple-electrode coagulation was significantly larger than the mean single-electrode coagulation (minimum diameter, 2.8 vs 1.6 cm; maximum diameter, 4.2 vs 2.0 cm; volume, 22.1 vs 6.7 cm(3); P < .0033 for all comparisons). The mean maximum diameter achieved at 12 minutes with multiple electrodes was significantly larger than that achieved with the cluster electrode (4.2 vs 2.9 cm, P = .02). At 16 minutes, the mean multiple-electrode coagulation (minimum diameter, 3.2 cm; maximum diameter, 4.2 cm; volume, 29.1 cm(3)) was significantly larger than the mean single-electrode (minimum diameter, 1.7 cm; maximum diameter, 2.2 cm; volume, 7.1 cm(3); P < .0033 for all comparisons) and cluster-electrode (minimum diameter: 2.3 cm, P = .007; maximum diameter: 3.2 cm, P = .005; volume: 13.1 cm(3), P = .001) coagulations.
  
  
  CONCLUSIONS
  Compared with the single and cluster systems used as controls, the multiple-electrode RF ablation system enabled the creation of significantly larger coagulation zones.
authors.affiliation: Department of Radiology, University of Wisconsin, Box 3252, Clinical Science Center-E3, 600 Highland Ave, Madison, WI 53792, USA. plaeseke@wisc.edu
authors.forename: Paul F
authors.initials: PF
authors.lastname: Laeseke
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Sampson
authors.forename: Dieter
authors.initials: D
authors.lastname: Haemmerich
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Brace
authors.forename: Jason P
authors.initials: JP
authors.lastname: Fine
authors.forename: Tina M
authors.initials: TM
authors.lastname: Frey
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Winter
authors.forename: Fred T
authors.initials: FT
authors.lastname: Lee
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D005260:Female; D008099:Liver / Q000473:pathology / Q000601:surgery*; D009336:Necrosis; D013552:Swine