Design of a Microwave Global Endometrial Ablation Device

Abstract

Endometrial ablation is a minimally invasive treatment employed for thermal coagulation of the endometrial lining of the uterus for treatment of menstrual heavy bleeding. Here, we present an applicator employing a microwave loop antenna for global endometrial ablation enabling conformal ablation of uterine cavities of varying size in the range 4–6.5 cm in length and 2.5–4.5 cm in width, with a single positioning of the device. For treating large cavities, conformal microwave radiation is achieved by coupling the loop antenna with a passive element. A 3-D-coupled finite element method electromagnetic and heat transfer simulator was employed to optimize the antenna geometry with the goal of maximizing return loss at the 915 MHz operating frequency, and achieving adequate ablation depths for a range of uterine cavity sizes. Proof-of-concept devices were fabricated and experimentally evaluated in ex vivo tissue. The simulated and measured return loss of the optimized design was 20 dB at 915 MHz. Experiments in ex vivo tissue demonstrated the ability of the presented device to achieve mean ablation depths of 7.3 mm. We demonstrated a technique for creating planar ablation patterns suitable for global endometrial ablation of different uterine cavity sizes by employing a loop antenna with a passive element. Our design provides a planar ablation pattern by using a loop antenna with a passive element that will allow for ablation applications not realizable with conventional coaxial monopole, dipole, and slot antennas.