Design of a closed dual-slot antenna for spherical hepatic microwave ablation

Microwave ablation has been considered as a promising therapy for the treatment of liver tumors. However, many antennas proposed in previous literature generated ellipsoidal ablation and also were not suitable for percutaneous intervention due to the lack of mechanical properties. To address these problems, a closed dual-slot antenna was investigated to generate spherical ablation and designed with zirconia tip, which facilitated its ability to puncture into tissues, and metal tube, which provided mechanical strength for percutaneous puncture. A numerical model was constructed to optimize antenna geometry and analyze antenna performance. The reflection coefficient, specific absorption rate, and temperature distribution of the closed and conventional dual-slot antennas were all simulated by using finite element method. The two antennas were also validated with ex vivo porcine livers, finding a great agreement between simulated and experimental results. The closed dual-slot antenna generated a more spherical ablation zone (34.0 mm x 37.2 mm vs. 29.1 mm x 48.5 mm at 50 W for 10 min) with a lower reflection coefficient (-30.3 vs. -9.5 dB) than did conventional dual-slot antenna, and showed qualified mechanical properties for clinical application, which may be further applied to clinical percutaneous intervention to treat liver tumors effectively.