Ex-vivo and simulation comparison of multi-angular ablation patterns using catheter-based ultrasound transducers

Catheter based ultrasound ablation devices have been suggested as the least minimally invasive procedure for thermal therapy. The success of such procedures depends on accurately delivering the thermal dose to the tissue. One of the main challenges of such therapy is to deliver thermal therapy at the target location without damaging the surrounding tissue or major vessels and veins. To achieve such multi-directional capability, a multi-angular beam pattern is required. The purpose of this study was to build a multi-sectored tubular ultrasonic transducer and control the directionality of the acoustic power delivered to the tissue by each sector simultaneously. Multi-zoned tubular ultrasonic transducer arrays with three active sectors were constructed. Using these transducer configurations, a multi-angular ablation pattern was created in ex vivo chicken breast tissue. Experiments were conducted by activating two and three zones separately to investigate the ablation pattern of each case. Simulations results were presented by solving the Penne bio-heat equation using finite element method. The simulation results were compared with ex vivo results with respect to temperature and dose distribution in the tissue. Thermocouples located at 15 mm radially from the applicator indicated a peak temperature of greater than 52-55 degrees C and thermal dose of 10(3)-10(4) EQ mins at 43 degrees C. It was observed through visual inspection that the proposed technology could ablate a specific tissue region or multiple regions selectively while not damaging the desired surrounding tissue. Good agreement between experimental and simulation results was obtained.