In vivo evaluation of lung microwave ablation in a porcine tumor mimic model

Purpose: To evaluate the microwave ablation of created tumor mimics in the lung of a large animal model (pigs), with examination of the ablative synergy of multiple antennas. Methods: Fifty-six tumor-mimic models of various sizes were created in 15 pigs by using barium-enriched minced collected thigh muscle injected into the lung of the same animal. Tumors were ablated under fluoroscopic guidance by single-antenna and multiple-antenna microwaves. Results: Thirty-five tumor models were treated in 11 pigs with a single antenna at 75 W for 15 min, with 15 measuring 20 mm in diameter, 10 measuring 30 mm, and 10 measuring 40 mm. Mean circularity of the single-antenna ablation zones measured 0.64 ± 0.12, with a diameter of 35.7 ± 8.7 mm along the axis of the antenna and 32.7 ± 12.8 mm perpendicular to the feeding point. Multiple-antenna delivery of 75 W for 15 min caused intraprocedural death of 2 animals; modified protocol to 60 W for 10 min resulted in an ablation zone with a diameter of 43.0 ± 7.7 along the axis of the antenna and 54.8 ± 8.5 mm perpendicular to the feeding point; circularity was 0.70 ± 0.10 Conclusions: A single microwave antenna can create ablation zones large enough to cover lung tumor mimic models of ≤4 cm with no heat sink effect from vessels of ≤6 mm. Synergic use of 3 antennas allows ablation of larger volumes than single-antenna or radiofrequency ablation, but great caution must be taken when 3 antennas are used simultaneously in the lung in clinical practice.