A 2 1/4-turn spiral antenna for catheter cardiac ablation

To investigate the delivery of microwave energy by a catheter positioned in side the heart for ablating small abnormal regions producing cardiac arrhyt hmias, a 2 1/4-turn spiral catheter-based microwave antenna applicator has been developed. The antenna consists of the center conductor with continuou s insulating material extending from the coaxial feed cable formed into a s piral antenna. The insulator completely isolates the center conductor from tissue. Phantom experiments were performed on homogeneous tissue equivalent medium. The reflection coefficient of the antenna at different frequencies and for different spiral lengths, the time course and temperature profile of an ablation, and the dosimetry of power versus temperature, ail indicate that the high-power heating patterns from this antenna are both wider and deeper than with the other microwave antenna systems and radio-frequency el ectrodes.