Multiple-Antenna Microwave Ablation: Spatially Distributing Power Improves Thermal Profiles and Reduces Invasiveness

BACKGROUND: Microwave ablation is an emerging tumor ablation modality. To date, microwave systems have generally utilized single large-diameter antennas to deliver high input powers. OBJECTIVE: To determine whether spatially distributing power through an array of multiple smaller antennas creates a more uniform thermal profile and increases peripheral tissue temperatures when compared with microwave ablation using a single larger antenna. METHODS: Microwave ablations were performed in ex vivo bovine liver using a single 2.45-GHz magnetron generator and a constant total input power (90 W) delivered through either a single 13-gauge antenna, two 17-gauge antennas, or three 18-gauge antennas. Multiple antennas were driven coherently. Temperatures were recorded at 5-mm radial distances and the resulting thermal profiles and ablation zones were compared using analysis of variance. RESULTS: Multiple-antenna configurations were less invasive (ie, the area of tissue punctured was smaller) than the single-antenna configuration; despite this, ablation zones created using multiple smaller antennas were larger and as circular when compared with those created using a single larger antenna. Multiple-antenna configurations resulted in more uniform thermal profiles and higher peripheral tissue temperatures. CONCLUSION: Distributing power evenly among multiple smaller antennas resulted in larger ablation zones with more uniform thermal profiles than more invasive ablations with a larger single antenna.