An ultrasound system has a catheter including an elongate flexible catheter body having at least one lumen extending longitudinally therethrough. An ultrasound transmission wire extends longitudinally through the lumen of the catheter body, and has a proximal region, a distal region, and an intermediate region between the proximal region and the distal region. A sonic connector is connected to the proximal region of the ultrasound transmission wire, and a distal head is positioned at the distal end of the catheter body and coupled to the distal region of the ultrasound transmission wire. The proximal region of the ultrasound transmission wire has a larger diameter than the intermediate region, the intermediate region is continuously tapered with a progressively decreasing diameter from its proximal end to its distal end, and the distal region has a greater diameter than the distal end of the intermediate region.
