Christopher L. Brace PhD, Presenter: Shareholder, NeuWave Medical Inc, Madison, WI Consultant, NeuWave Medical Inc, Madison, WI

Paul F. Laeseke PhD, Abstract Co-Author: Stockholder, NeuWave Medical Inc, Madison, WI Consultant, NeuWave Medical Inc, Madison, WI

Teresa Diaz, Abstract Co-Author: Nothing to Disclose

J. Louis Hinshaw MD, Abstract Co-Author: Research grant, Endocare, Inc

Lisa Ann Sampson, Abstract Co-Author: Research Consultant, NeuWave Medical Inc

Fred T. Lee MD, Abstract Co-Author: Stockholder, NeuWave Medical Inc, Madison, WI Patent holder, Covidien AG, Boulder, CO

Early results with pulmonary RF ablation are encouraging, but RF may be substantially limited in its ability to heat lung tumors due to the high electrical impedance of surrounding lung parenchyma. Microwaves do not require electrical conduction so are not inherently limited by aerated lung. Microwaves also heat tissue more effectively than RF and, as a result, have been shown to create larger and more reproducible ablations than RF in other organ systems. The purpose of this study was to compare the performance of 17-gauge RF and high-power microwave ablation devices in a normal porcine lung model.

A total of 18 ablations were performed in vivo in normal porcine lungs. Using CT-fluoroscopic guidance, a 17-gauge cooled triaxial microwave antenna (n=9) and 17-gauge cooled RF electrode (n=9) were place percutaneously. Ablations were performed for 10 min using a microwave continuous generator output of 135 W, and 200 W of RF power delivered with an impedance feedback and power pulsing algorithm. Animals were sacrificed following the ablations. Ablation zones were sectioned transverse to the applicator in 5 mm increments and measured for minimum and maximum diameter, cross-sectional area, length and circularity. Comparisons of each measurement were performed using Student's t-test with P < .05 indicating statistical significance.  

Microwave ablations were 25% larger in mean diameter (33 ± 2 mm versus 27 ± 2 mm, P < .0001) and 50% larger in cross-sectional area (825 ± 92 mm2 versus 545 ± 110 mm2, P < .0001) compared to RF ablations. Microwave ablations were also significantly more circular in cross section (circularity: 0.90 ± 0.06 versus 0.82 ± 0.09, P < .05). Two small pneumothoraces were noted during RF ablations but both stabilized without intervention. No other complications were observed.

Microwave ablation with a 17-gauge high-power triaxial antenna creates larger and more circular zones of ablation than a similarly sized RF applicator at clinical settings.

Microwaves appear to be a more effective means of pulmonary ablation than RF energy and should see increased clinical utility.

Brace, C, Laeseke, P, Diaz, T, Hinshaw, J, Sampson, L, Lee, F, Percutaneous Pulmonary Thermal Ablation: High-power Microwaves Create Larger and More Consistent Zones of Ablation than Radiofrequency in an in Vivo Porcine Lung Model.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/7110456.html