Design of Microwave Ablation Antenna for Flexible Omnidirectional/Directional Ablation Zone Control

In this letter, a structure that can flexibly regulate omnidirectional/directional ablation zones is proposed. By fine-tuning the electrical length of tri-reflector, both ablation zones can be regulated in a similar antenna structure. Two prototypes were fabricated and tested: one for generating an omnidirectional ablation zone and the other for generating a directional ablation zone. Ablation experiments were performed in ex vivo porcine liver to observe the effects of different ablation times and reflector geometries on the antenna heating pattern. When the ablation lasted for 3 minutes at an input power of 20 W, the omnidirectional MWA antenna created a symmetric ablation zone of 22 mm x 19 mm with an aspect ratio of 91%; the directional MWA antenna generated an asymmetric ablation zone of 23 mm x 13 mm, with minimal heating occurring behind the reflector (< 2 mm) and a directivity ratio of 83.3%, which is significantly improved compared with the traditional method. This experiment validated the feasibility and effectiveness of the algorithm to control the ablation zone, providing a promising approach for designing other MWA antennas.