title: Bimodal electric tissue ablation (BETA): a study on ablation size when the anode is placed on the peritoneum and the liver.
abstract: BACKGROUND
  In bimodal electric tissue ablation (BETA), the cathode of the DC circuit is attached to the radiofrequency (RF) electrode to increase the surrounding tissue hydration. This will delay tissue desiccation and allowing the ablation process to continue for a longer period of time before "roll-off" occurs, resulting in larger ablations compared with standard radiofrequency ablation (RFA). Previous research showed that attaching the anode to the skin using electrosurgical grounding pads would reduce the efficacy of BETA because of the high electrical resistivity of the skin. This study investigated the ablation size produced when the anode was attached to the peritoneum (BETA-peritoneum) and the liver (BETA-liver) respectively.
  
  
  METHODS
  The anode of the DC circuit in BETA was attached to the peritoneum and the liver in a pig model using ECG dots. In BETA, 9 V of DC was provided for 10 min, after which the radiofrequency generator were switched on and both electrical circuits allowed to run concurrently until "roll-off." The size of ablations produced was compared to when the anode attached to the skin (BETA-skin) and standard RFA, respectively. The sites of anode placement were examined for local tissue injury.
  
  
  RESULTS
  The transverse diameters in BETA-peritoneum and BETA-liver were significantly larger compared with BETA-skin and standard RFA, respectively (P < 0.001). The axial diameter in the BETA-peritoneum and BETA-liver groups were also larger compared with the BETA-skin and RFA groups, although the differences did not reach statistical significance (P = 0.09). Hematoxylin and eosin (H and E) examination of the peritoneum and the liver where the anode was attached showed coagulation necrosis involving the superficial epithelium and the liver capsule, respectively.
  
  
  CONCLUSIONS
  BETA can be used to treat larger liver tumors more effectively and may reduce the tumor recurrence rates compared with standard RFA. The efficacy of BETA depends on ensuring good electrical conductivity between the cathode and the anode of the DC circuit. Research so far has shown that BETA works best when the anode is placed deep to the skin as the stratum corneum consisted of a layer of a-nucleated cells, which have high electrical resistivity. The liver could be the ideal location to place the anode as it has excellent electrical conductivity, therefore ensuring maximum tissue hydration around the cathode to produce the largest ablations possible.
authors.affiliation: Department of Surgery, The Queen Elizabeth Hospital, Adelaide, Australia.
authors.forename: Leong U
authors.initials: LU
authors.lastname: Tiong
authors.forename: John W
authors.initials: JW
authors.lastname: Finnie
authors.forename: John B
authors.initials: JB
authors.lastname: Field
authors.forename: Guy J
authors.initials: GJ
authors.lastname: Maddern
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods*; D003681:Dehydration; D062109:Dermatologic Surgical Procedures; D004553:Electric Conductivity; D004562:Electrocardiography; D004566:Electrodes; D005260:Female; D008099:Liver / Q000473:pathology* / Q000601:surgery*; D023421:Models, Animal; D009336:Necrosis; D010537:Peritoneum / Q000473:pathology* / Q000601:surgery*; D012867:Skin / Q000473:pathology; D013552:Swine