title: Temperature-dependent electrode repositioning for multiple overlapping radiofrequency ablation in ex vivo porcine livers.
abstract: OBJECTIVE
  Overlapping ablations can be used to increase radiofrequency ablation volume. Our goal was to determine, in a porcine model, the relationship of ablation size and temperature for single ablation, and to compare the extent of necrosis resulting from temperature-dependent electrode positioning versus fixed-distance dual ablation.
  
  
  METHODS
  The experiments were performed in two parts (single and dual ablations). During single ablation in ex vivo porcine livers, maximum necrotic diameter was compared with the diameters at the level at which temperatures reached 60°C, 55°C, and 50°C. Dual ablations were performed using 60°C (group 60C), 55°C (group 55C), and 50°C (group 50C), and distances of 3 cm (group 3cm) and 4.1cm (group 4.1cm) as the starting point (RFA2-start) for the second ablation.
  
  
  RESULTS
  The maximum necrotic diameter (3.3 ± 0.6 cm) and the necrotic diameters reached at 60°C (2.8 ± 0.8 cm) and 55°C (2.2 ± 0.7 cm) were significantly greater than that at 50°C (0.9 ± 0.5cm; P < .05). In dual ablations, there was no difference between RFA2-start and the maximum diameter of the preceding and subsequent ablations in all temperature-dependent dual ablations (groups 60C, 55C, and 50C) and in group 3cm. (P > .05) However, there was a significant difference between RFA2-start and maximum diameter of the preceding and subsequent ablations in Group 4.1cm (P = .038), resulting in dumbbell-shaped necrosis.
  
  
  CONCLUSIONS
  The necrotic diameter proportionally decreases with the temperature in single ablation. Withdrawing the electrode up to 50° or by 3 cm before reablating results in fusion of the two ablation zones versus withdrawal of 4.1 cm, which results in incomplete necrosis in between two ablation zones.
authors.affiliation: Section of Gastroenterology, Endoscopy Unit, University of Santo Tomas Hospital, Espaňa Street, Manila. Philippines. swongliver@yahoo.com
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Wong
authors.forename: Grace Esperanza
authors.initials: GE
authors.lastname: Santi
authors.forename: Hendra
authors.initials: H
authors.lastname: Nurjadin
authors.forename: Redigo
authors.initials: R
authors.lastname: Aguilar
authors.forename: Susana
authors.initials: S
authors.lastname: Gosalvez-Pe
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D004867:Equipment Design; D066298:In Vitro Techniques; D008099:Liver / Q000473:pathology / Q000601:surgery*; D009336:Necrosis; D013552:Swine; D013696:Temperature