Development and experimental verification of the wide-aperture catheter-based microwave cardiac ablation antenna

A new type of catheter-based microwave antenna cardiac ablation applicator has been developed, Unlike previously developed ablation catheters, this de vice forms a wide aperture that produces a large heating pattern, The anten na consists of the center conductor of a coaxial line, shaped into a spiral and insulated from blood and tissue by a nonconductive fluid-filled balloo n, The antenna will be stretched straight inside a catheter for translumina l guiding, Once in place at the cardiac target, the balloon will be inflate d, and the coiled spiral antenna will be ejected into the inflated balloon. The wide aperture antenna generates a ring-shaped power pattern. The heat generated from this deposited power is conducted through a volume larger th an the spiral diameter, ablating diseased tissue. The resultant lesion prof ile is both wider and deeper than that of either conventionally used RF cat heter-based ablation electrodes or that of other recently reported microwav e applicators, and may offer greater heating accuracy and controllability, The new antenna design is tested by measuring S-11- and S-21-parameters, an d by comparing power deposition patterns to conventional monopole antenna i n a tissue-equivalent phantom, Heating experiments on in vitro organ tissue and on live pigs using 50, 100, and 150 W of 915-MHz microwave power have been performed to test the efficacy of the wide-aperture antenna design, Th ese studies confirm the hypotheses that the wide-aperture microwave antenna can create lesions of significant depth that may be applicable for the abl ative therapy of ventricular tachycardia.