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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ex vivo</i> 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 × 19 mm with an aspect ratio of 91%; the directional MWA antenna generated an asymmetric ablation zone of 23 mm × 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.