Microwave ablation with multiple simultaneously powered small-gauge triaxial antennas: Results from an in vivo swine liver model

Purpose: To prospectively investigate the ability of a single generator to power multiple small-diameter antennas and create large zones of ablation in an in vivo swine liver model. Materials and Methods: Thirteen female domestic swine (mean weight, 70 kg) were used for the study as approved by the animal care and use committee. A single generator was used to simultaneously power three triaxial antennas at 55 W per antenna for 10 minutes in three groups: a control group where antennas were spaced to eliminate ablation zone overlap ( n = 6; 18 individual zones of ablation) and experimental groups where antennas were spaced 2.5 cm ( n = 7) or 3.0 cm ( n = 5) apart. Animals were euthanized after ablation, and ablation zones were sectioned and measured. A mixed linear model was used to test for differences in size and circularity among groups. Results: Mean ( +/- standard deviation) cross- sectional areas of multiple-antenna zones of ablation at 2.5- and 3.0-cm spacing ( 26.6 cm(2) +/- 9.7 and 32.2 cm(2) +/- 8.1, respectively) were significantly larger than individual ablation zones created with single antennas ( 6.76 cm(2) +/- 2.8, P < .001) and were 31% ( 2.5- cm spacing group: multiple antenna mean area, 26.6 cm(2); 3X single antenna mean area, 20.28 cm(2)) to 59% ( 3.0-cm spacing group: multiple antenna mean area, 32.2 cm(2); 3X single antenna mean area, 20.28 cm(2)) larger than 3 times the mean area of the single- antenna zones. Zones of ablation were found to be very circular, and vessels as large as 1.1 cm were completely coagulated with multiple antennas. Conclusion: A single generator may effectively deliver microwave power to multiple antennas. Large volumes of tissue may be ablated and large vessels coagulated with multiple-antenna ablation in the same time as single- antenna ablation. (c) RSNA, 2007.