Combined 3D intracardiac echo and ultrasound ablation

We have integrated real time volumetric ultrasound imaging and ultrasound ablation in the same intracardiac catheter. This single device could be used to visualize ablation sites in three dimensions immediately prior to inducing necrosis to eliminate cardiac arrythmias. After the course of therapy, the ablated tissue could be examined ultrasonically. The 12 Fr catheter includes a 2D transducer array for imaging and a single element piston for ablation. The imaging transducer consists of 38 active elements built on a multilayer flex circuit operating at 5.2 Mhz. The ablation piston is a 4 mm by 2 mm piece of air backed PZT-4. Our real time 3D scanner (Volumetrics Medical Imaging) and the 2D array were used to image phantom targets. The spatial peak, temporal average intensity (I_SPTA) and acoustic power of the ablation beam were measured using a hydrophone. A 7 mm thick slab of beef was imaged and then ablated for 1 minute. The ultrasound ablation piston produced an ISFTA of nearly 30 W/cm² and a corresponding acoustic power of 2.6 W. The electrical to acoustic power efficiency of the transducer was 39%. The minute long ablation produced a transmural lesion in the beef 2mm by 4 mm by 7 mm deep.