Paul Laeseke, Abstract Co-Author: Nothing to Disclose

Lisa Ann Sampson, Abstract Co-Author: Nothing to Disclose

Tina M Tatum, Abstract Co-Author: Nothing to Disclose

Christopher L Brace, Presenter: Nothing to Disclose

Thomas Charles Winter MD, Abstract Co-Author: Nothing to Disclose

Fred T. Lee MD, Abstract Co-Author: Nothing to Disclose

The ability of radiofrequency (RF) ablation to create large zones of ablation is limited primarily by vascular-mediated cooling. High power and multiple electrodes have been independently shown to increase the size of resulting zones of coagulation. The purpose of this study was to evaluate the feasibility of combining multiple, switched electrodes with a high-power RF generator to create even larger zones of ablation in the liver.

An experimental high power RF generator (2.3 A output current, ~250 W) and switching system (Valleylab, Boulder, CO) were used to perform 12 min hepatic RF ablations in 12 pigs (mean wt=55 kg). There were four experimental groups: 1.) cluster electrodes and standard generator (2.0 A, ~200 W, n=4), 2.) single electrodes at high power (2.3 A, n=9), 3.) cluster electrodes at high power (2.3 A, n=8), and 4.) three single, switched electrodes spaced at 2.0 cm at high power (2.3 A, n=8). Active electrode lengths were 2.5 cm for the cluster electrodes and 4 cm for single and switched electrodes. Zones of ablation were sliced in ~4 mm transverse sections for evaluation of size. Specimens were stained with triphenyltetrazolium chloride (TTC, a marker of mitochondrial enzyme activity) to determine cell viability. ANOVA was used to test for increases in ablation zone size.

Mean minimum diameter, maximum diameter, and volume were greatest for the 2.3 A switched group (3.4 ± 0.9 cm / 5.2 ± 0.8 cm / 41.7 ± 14 cm3). Maximum diameter and volume were significantly larger for the high-power, switched group compared to conventional 2.0 A cluster and 2.3 A single (P<.05). Maximum diameter was also significantly greater for high-powered cluster versus high-powered single (P<.05).

Multiple, switched electrodes combined with a higher power RF generator resulted in significant increases in ablation zone size relative to lower-powered cluster electrodes and higher-powered single electrodes. Combining the switching system and high power generator resulted in ablation zones 33% greater in volume than a similar switching system with a conventional generator. Further optimization and characterization of this system appears warranted.

F.T.L.: Valleylab board of advisors, patent holder

Laeseke, P, Sampson, L, Tatum, T, Brace, C, Winter, T, Lee, F, Multiple-electrode Radiofrequency Ablation using an Experimental, High-power Generator: In Vivo Results.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4418878.html