Microwave Ablation versus Radiofrequency Ablation in the Kidney: High-power Triaxial Antennas Create Larger Ablation Zones than Similarly Sized Internally Cooled Electrodes
Received 1 October 2008; received in revised form 12 May 2009; accepted 15 May 2009. published online 21 July 2009.
Purpose
To determine whether microwave ablation with high-power triaxial antennas creates significantly larger ablation zones than radiofrequency (RF) ablation with similarly sized internally cooled electrodes.
Materials and Methods
Twenty-eight 12-minute ablations were performed in an in vivo porcine kidney model. RF ablations were performed with a 200-W pulsed generator and either a single 17-gauge cooled electrode (n = 9) or three switched electrodes spaced 1.5 cm apart (n = 7). Microwave ablations were performed with one (n = 7), two (n = 3), or three (n = 2) 17-gauge triaxial antennas to deliver 90 W continuous power per antenna. Multiple antennas were powered simultaneously. Temperatures 1 cm from the applicator were measured during two RF and microwave ablations each. Animals were euthanized after ablation and ablation zone diameter, cross-sectional area, and circularity were measured. Comparisons between groups were performed with use of a mixed-effects model with P values less than .05 indicating statistical significance.
Results
No adverse events occurred during the procedures. Three-electrode RF (mean area, 14.7 cm2) and single-antenna microwave (mean area, 10.9 cm2) ablation zones were significantly larger than single-electrode RF zones (mean area, 5.6 cm2; P = .001 and P = .0355, respectively). No significant differences were detected between single-antenna microwave and multiple-electrode RF. Ablation zone circularity was similar across groups (P > .05). Tissue temperatures were higher during microwave ablation (maximum temperature of 123°C vs 100°C for RF).
Conclusions
Microwave ablation with high-power triaxial antennas created larger ablation zones in normal porcine kidneys than RF ablation with similarly sized applicators.
aDepartment of Radiology, University of Wisconsin, 600 Highland Avenue, Madison, WI 53792
bDepartment of Electrical and Computer Engineering, University of Wisconsin, 600 Highland Avenue, Madison, WI 53792
Address correspondence to P.F.L.
P.F.L. and C.L.B. have ownership interest in and receive consulting fees from NeuWave Medical (Madison, Wisconsin), which owns the license to the triaxial microwave antenna design described in this study. F.T.L. and D.W.v.d.W. have ownership interest in NeuWave Medical. L.A.S. receives consulting fees from NeuWave Medical.
This study was funded in part by the National Institutes of Health (Bethesda, Maryland).
ABSTRACT