End-fire catheter antenna for microwave ablation of the endocardium

A novel catheter antenna for microwave medical applications has been developed. The antenna provides an end-fire heating pattern and dielectric bifurcated choke to minimize current leakage. The concept employed for end-fire performance involves impedance loading on the antenna structure to achieve a traveling wave distribution of current. The antenna need not be in contact with the endocardium for successful launching of the microwave energy in the end-fire direction. Simply pointing it at the target tissue is sufficient to create deep lesions. The capacitive loading effect on the antenna by myocardium and catheter construction are considered in the design of the system for optimum radiation and energy coupling efficiency. Numerical modeling provides a way to optimize the design of antennas such as the catheterized end-fire antenna discussed previously. The numerical electromagnetics code (NEC-4) a method-of-moments code and XFDTD which employs a finite-difference time domain technique are examples. Data are presented using NEC-4 showing how the heating pattern at microwave frequency can become end-fire by moving an impedance load to the correct position on the antenna. The value of the impedance load on the antenna and position were determined using Romberg integration to solve for the antenna's expansion parameter.