title: RF tumor ablation with internally cooled electrodes and saline infusion: what is the optimal location of the saline infusion?
abstract: BACKGROUND
  Radiofrequency ablation (RFA) of tumors by means of internally cooled electrodes (ICE) combined with interstitial infusion of saline may improve clinical results. To date, infusion has been conducted through outlets placed on the surface of the cooled electrode. However, the effect of infusion at a distance from the electrode surface is unknown. Our aim was to assess the effect of perfusion distance (PD) on the coagulation geometry and deposited power during RFA using ICE.
  
  
  METHODS
  Experiments were performed on excised bovine livers. Perfusion distance (PD) was defined as the shortest distance between the infusion outlet and the surface of the ICE. We considered three values of PD: 0, 2 and 4 mm. Two sets of experiments were considered: 1) 15 ablations of 10 minutes (n > or = 4 for each PD), in order to evaluate the effect of PD on volume and diameters of coagulation; and 2) 20 additional ablations of 20 minutes. The effect of PD on deposited power and relative frequency of uncontrolled impedance rises (roll-off) was evaluated using the results from the two sets of experiments (n > or = 7 for each PD). Comparisons between PD were performed by analysis of variance or Kruskal-Wallis test. Additionally, non-linear regression models were performed to elucidate the best PD in terms of coagulation volume and diameter, and the occurrence of uncontrolled impedance rises.
  
  
  RESULTS
  The best-fit least square functions were always obtained with quadratic curves where volume and diameters of coagulation were maximum for a PD of 2 mm. A thirty per cent increase in volume coagulation was observed for this PD value compared to other values (P < 0.05). Likewise, the short coagulation diameter was nearly twenty five per cent larger for a 2 mm PD than for 0 mm. Regarding deposited power, the best-fit least square function was obtained by a quadratic curve with a 2 mm PD peak. This matched well with the higher relative frequency of uncontrolled impedance rises for PD of 0 and 4 mm.
  
  
  CONCLUSIONS
  Saline perfusion at around 2 mm from the electrode surface while using an ICE in RFA improves deposition of energy and enlarges coagulation volume.
authors.affiliation: Department of Surgery, Hospital del Mar, Barcelona, Spain. fburdio@hotmail.com
authors.forename: Fernando
authors.initials: F
authors.lastname: Burdío
authors.forename: Enrique J
authors.initials: EJ
authors.lastname: Berjano
authors.forename: Ana
authors.initials: A
authors.lastname: Navarro
authors.forename: José M
authors.initials: JM
authors.lastname: Burdío
authors.forename: Antonio
authors.initials: A
authors.lastname: Güemes
authors.forename: Luis
authors.initials: L
authors.lastname: Grande
authors.forename: Ramón
authors.initials: R
authors.lastname: Sousa
authors.forename: Jorge
authors.initials: J
authors.lastname: Subiró
authors.forename: Ana
authors.initials: A
authors.lastname: Gonzalez
authors.forename: Ignacio
authors.initials: I
authors.lastname: Cruz
authors.forename: Tomás
authors.initials: T
authors.lastname: Castiella
authors.forename: Eloy
authors.initials: E
authors.lastname: Tejero
authors.forename: Ricardo
authors.initials: R
authors.lastname: Lozano
authors.forename: Miguel A
authors.initials: MA
authors.lastname: de Gregorio
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D003080:Cold Temperature; D004566:Electrodes; D006498:Hepatectomy / Q000379:methods*; D066298:In Vitro Techniques; D036502:Infusions, Intralesional; D008113:Liver Neoplasms / Q000503:physiopathology* / Q000601:surgery*; D012965:Sodium Chloride / Q000008:administration & dosage*; D013552:Swine
chemical_list: D012965:Sodium Chloride