title: Optimization of direct current-enhanced radiofrequency ablation: an ex vivo study.
abstract: The purpose of this study was to investigate the optimal setting for radiofrequency (RF) ablation combined with direct electrical current (DC) ablation in ex vivo bovine liver. An electrical circuit combining a commercially available RF ablation system with DC was developed. The negative electrode of a rectifier that provides DC was connected to a 3-cm multitined expandable RF probe. A 100-mH inductor was used to prevent electrical leakage from the RF generator. DC was applied for 15 min and followed by RF ablation in freshly excised bovine livers. Electric current was measured by an ammeter. Coagulation volume, ablation duration, and mean amperage were assessed for various DC voltages (no DC, 2.2, 4.5, and 9.0 V) and different RF ablation protocols (stepwise increase from 40 to 80 W, 40 W fixed, and 80 W fixed). Results were compared using Kruskal-Wallis and Mann-Whitney U test. Applying DC with 4.5 or 9.0 V, in combination with 40 W fixed or a stepwise increase of RF energy, resulted in significantly increased zone of ablation size compared with 2.2 V or no DC (P = 0.009). At 4.5 V DC, the stepwise increase of RF energy resulted in the same necrosis size as a 40 W fixed protocol (26.6 +/- 3.9 vs. 26.5 +/- 4.0 ml), but ablation duration was significantly decreased (296 +/- 85 s vs. 423 +/- 104 s; P = 0.028). Mean amperage was significantly lower at 4.5 V compared with 9.0 V (P = 0.028). Combining a stepwise increase of RF energy with a DC voltage of 4.5 V is most appropriate to increase coagulation volume and to minimize procedure time.
authors.affiliation: Applied Medical Engineering, Helmholtz-Institute Aachen, RWTH Aachen University, 52074, Aachen, Germany. toshihir@bf6.so-net.ne.jp
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Tanaka
authors.forename: Peter
authors.initials: P
authors.lastname: Isfort
authors.forename: Philipp
authors.initials: P
authors.lastname: Bruners
authors.forename: Tobias
authors.initials: T
authors.lastname: Penzkofer
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Kichikawa
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmitz-Rode
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Mahnken
mesh_terms: D000818:Animals; D001674:Bioelectric Energy Sources; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D002417:Cattle; D004566:Electrodes; D004867:Equipment Design; D066298:In Vitro Techniques; D008099:Liver / Q000601:surgery*; D023421:Models, Animal; D018709:Statistics, Nonparametric