title: Wet radio-frequency ablation using multiple electrodes: comparative study of bipolar versus monopolar modes in the bovine liver.
abstract: OBJECTIVE
  To determine whether hypertonic saline (HS)-mediated bipolar radio-frequency (rf) application as advantages over monopolar simultaneous and alternating rf applications for creating larger areas of coagulation necrosis.
  
  
  METHODS
  A total of 60 rf ablations using double perfused-cooled electrodes and a 200 W generator (CC-3 model, Radionics) were performed in three different modes in explanted bovine livers: simultaneous monopolar mode (groups A and A'); alternating monopolar mode (groups B and B'); or bipolar mode (groups C and C'). Electrodes were placed at inter-electrode distances of 3 and 5 cm, and HS (6% NaCl solution) was instilled into tissue at a rate of 1 mL/min through the electrodes. rf was applied for 10 (3 cm distance) or 15 min (5 cm distance). During rf application, we measured the tissue temperature at the mid-point between the two electrodes. Dimensions of the thermal ablation zones, and temperatures were compared between the 3 groups using analysis of variance or the Kruskal-Wallis test. To compare configurations of the ablation zones in each group, the ratio of longitudinal diameter (Dl) to vertical diameter (D(v)) was calculated.
  
  
  RESULTS
  With a 3-cm inter-electrode spacing, the D(v) between the electrodes of ablated lesions was 2.4 +/- 1.2 cm in group A, 4.5 +/- 1.0 cm in group B, and 6.1 +/- 0.9 cm in group C (P < 0.05), and at a 5-cm spacing, groups B' and C' produced a single ablation area, but group A' produced two separated ablation spheres: the D(v)s were 1.4 +/- 0.2 in group A, 2.9 +/- 1.0 mm in group B, and 6.6 +/- 0.4 cm in group C (P < 0.05). For both 5- and 3-cm spacings, the temperatures at the mid-point were higher in bipolar mode than in either monopolar simultaneous or alternating modes. The ratios of Dl/D(v) of groups A, B, and C were 2.5 +/- 0.2, 1.4 +/- 0.1, and 1.1 +/- 0.1, respectively, and the corresponding figures of groups A', B' and C' were 4.5 +/- 0.2, 2.7 +/- 0.1, and 1.1 +/- 0.1, respectively (P < 0.05).
  
  
  CONCLUSIONS
  HS-enhanced bipolar rf ablation creates larger, more regular coagulation necrosis than either monopolar simultaneous or alternating rf ablation.
authors.affiliation: Department of Radiology, Seoul National University Hospital, 28 Yongon-Dong, Chongno-Gu, Seoul 110744, Republic of Korea. leejm@radcom.snu.ac.kr
authors.forename: Jeong Min
authors.initials: JM
authors.lastname: Lee
authors.forename: Joon Koo
authors.initials: JK
authors.lastname: Han
authors.forename: Se Hyung
authors.initials: SH
authors.lastname: Kim
authors.forename: Chang Jin
authors.initials: CJ
authors.lastname: Han
authors.forename: Su Kyung
authors.initials: SK
authors.lastname: An
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Byung In
authors.initials: BI
authors.lastname: Choi
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation*; D002417:Cattle; D004566:Electrodes; D008099:Liver / Q000601:surgery*; D009336:Necrosis; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage*; D018709:Statistics, Nonparametric
chemical_list: D012462:Saline Solution, Hypertonic