title: Multiple-electrode radiofrequency ablation of in vivo porcine liver: comparative studies of consecutive monopolar, switching monopolar versus multipolar modes.
abstract: OBJECTIVE
  To evaluate the in vivo efficiency of 2 multiple-electrode radiofrequency (RF) systems to create confluent areas of coagulation in porcine liver, compared with consecutive overlapping ablation.
  
  
  METHODS
  A total of 18 coagulations were created with 3 RF devices and 3 internally cooled electrodes at laparotomy in 6 female pigs. RF was applied to the porcine livers in a consecutive, monopolar mode (group A), in a switching monopolar mode (group B), or in a multipolar mode (group C). Energy efficiency values for the RF systems, shape and dimensions, and the coefficients of variation of the coagulation zones were compared in the 3 groups.
  
  
  RESULTS
  The duration of the RF ablation procedures in groups A, B, and C were 36 minutes, 18 minutes, and 21.2 +/- 1.9 minutes. The average energy delivered to produce 1 cm(3) coagulation was greater in group A (5.6 +/- 2.3 kJ/cm(3)) than in group B (1.8 +/- 0.5 kJ/cm(3)) or in group C (2.0 +/- 0.8 kJ/cm(3)) (P < 0.05). The mean volumes of the coagulations in groups A, B, and C were 28.8 +/- 13.2 cm(3) in group A, 49.1 +/- 12.3 cm(3) in group B, and 40.6 +/- 16.3 cm(3) in group C, respectively (P = 0.07). Regarding the shape of the coagulations, the coagulations of groups B (isoperimetric ratio; 0.88) and C (0.84) were more spherical than those of group A (0.69) (P < 0.05). In addition, the coefficients of variation of the volumes of the ablation zones in groups A, B, and C were 0.46, 0.25, and 0.40, respectively.
  
  
  CONCLUSIONS
  Multiple-electrode RF systems in switching monopolar and multipolar modes more efficiently created a larger, confluent, spherical-shaped coagulation than conventional consecutive RF ablation.
authors.affiliation: Department of Radiology, Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jeong Min
authors.initials: JM
authors.lastname: Lee
authors.forename: Joon Koo
authors.initials: JK
authors.lastname: Han
authors.forename: Hyo Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Se Hyung
authors.initials: SH
authors.lastname: Kim
authors.forename: Kyung Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Seung Moon
authors.initials: SM
authors.lastname: Joo
authors.forename: Byung Ihn
authors.initials: BI
authors.lastname: Choi
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D005260:Female; D008099:Liver / Q000473:pathology*; D008107:Liver Diseases / Q000628:therapy*; D008113:Liver Neoplasms / Q000628:therapy*; D013552:Swine