Monopole antennas for microwave catheter ablation of the myocardium.

Abstract

We investigate monopole antennas at 2.45 GHz for microwave ablation of the myocardium. Three geometries are considered: open-tip, dielectric-tip, and metal-tip. Their performance is compared using a theoretical model of the antenna radiation in lossy media. The model is implemented using the Galerkin Finite Element Method in the frequency domain. Calculations are made for the magnetic field, the reflection coefficient, and the power deposition pattern of the antennas immersed in normal saline. The theoretical results are confirmed using experimental measurements of the reflection coefficient and temperature profiles of several prototypes. The temperature profile measurements are made using a phantom tissue with properties similar to those of normal saline. There is good agreement between the experimental and numerical results. The antenna characteristics suggest that the metal-tip monopole best fulfills the requirements of catheter ablation. It has the advantage of having uniform heating along the length of the antenna and an exposed metallic part useful to record electrocardiograms. The computer model is then used to compare metal-tip monopoles of different dimensions and to determine design trade-offs.