Microwave ablation with a triaxial antenna: results in ex vivo bovine liver

TLDR

The study applies a novel triaxial microwave antenna to ex vivo bovine liver to evaluate its ablation performance. The antenna is a coaxial monopole inserted through a biopsy needle positioned a quarter‑wavelength from the base, forming a triaxial structure that improves return loss by >10 dB, and its design was optimized via numerical electromagnetic and thermal simulations, with pulsing algorithms also investigated. Lesion size increased with ablation time and average input power but not peak power, and a 3.8‑cm lesion was achieved at 50 W for 7 min, the largest reported with a 17‑gauge needle.

Abstract

We apply a new triaxial antenna for microwave ablation procedures to an ex vivo bovine liver. The antenna consists of a coaxial monopole inserted through a biopsy needle positioned one quarter-wavelength from the antenna base. The insertion needle creates a triaxial structure, which enhances return loss more than 10 dB, maximizing energy transfer to the tissue while minimizing feed cable heating and invasiveness. Numerical electromagnetic and thermal simulations are used to optimize the antenna design and predict heating patterns. Numerical and ex vivo experimental results show that the lesion size depends strongly on ablation time and average input power, but not on peak power. Pulsing algorithms are also explored. We were able to measure a 3.8-cm lesion using 50 W for 7 min, which we believe to be the largest lesion reported thus far using a 17-gauge insertion needle.