Dual-Frequency Microwave Ablation Antenna With Tunable Directional Ratio for Tumor Treatment

This paper presents a dual-frequency microwave ablation antenna (DMWAA) with tunable directional-ratio heating for precise tumor ablation near sensitive organs. The dual-frequency antenna (2.45/5.8 GHz) comprises a notched-edge monopole and a reflector based on the substrate-integrated coaxial line (SICL), eliminating the need for a balun structure. Two pairs of symmetrical rectangles are etched at the monopole edge for dual-frequency operation, and the bottom conductor of the SICL is extended as a reflector for directional ablation. Full-wave electromagnetic and transient thermal simulations are used to analyze the antenna’s performance. The antenna prototype is fabricated and utilized in ex vivo porcine liver ablation experiments across different frequencies. The results demonstrate distinct advantages at both operating frequencies: at 2.45 GHz, it achieves uniform ablation with a time-stable directional ratio between 1.3 and 1.4 with input power levels of 20 W. At 5.8 GHz, the antenna offers a tunable directional ratio ranging from 1.1 to 2.5, enabling customized ablation patterns through adjustments of operating duration (5 or 10 minutes) and input power (15 W or 20 W), with higher values (e.g., 2.8) associated with early-stage thermal damage under a 2-minute operation time. At a reduced input power of 15 W, the ablation area decreases with improved uniformity, while the directionality exhibits 1.4 times compared to that at 20 W. These findings validate that the proposed DMWAA achieves precise, adaptable ablation for complex clinical needs.