Robert J. Siegel

Ultrasonic angioplasty device having surface disruptions

An ultrasonic angioplasty device comprising an elongate ultrasound transmission member having a proximal end attachable to an ultrasound generating device and a bulbous distal head or probe formed on the distal end thereof for effecting ablative treatment of an occluding lesion. The ultrasound transmission member may be formed of one or more superelastic metal alloys such as NiTi (50 at. % Ni). A guidewire lumen may be formed in the distal head or probe to permit passage of a guidewire therethrough. Portions of the ultrasound transmission member may be curved or bent. Portions of the ultrasound transmission member may be tapered or narrowed. One or more surface disruptions may be formed on the distal head or probe to improve treatment efficacy. An increased hardness coating or outer skin may be formed on the ultrasound transmission member. The device of the present invention may be incorporated into an angioscopic device.

Technical Aspects of a Therapeutic Intravascular Ultrasound Angioplasty System

The concept of using acoustic energy for vascular intervention has been known for over 30 years. Ultrasound refers to mechanical vibrations at frequencies above the human limit of audibility, or above approximately 17,000 cycles per second. Ultrasound frequencies generally are considered in the range of 20 kilohertz (kHz) to 100megaHertz (mHz) or 20,000–100 million cycles per second. Ultrasound differs from other higher forms of radiation, such as x-rays and microwaves, in that it is a mechanical form of energy and is non-ionizing. Therapeutic ultrasound differs significantly from diagnostic ultrasound. Lower frequencies and higher power intensities are used in therapeutic applications. Therapeutic frequencies of 20–100 kHz are used, as opposed to 2–40 mHz for diagnostic imaging. Higher power intensities are translated to the form of higher amplitudes, which give low-frequency ultrasound mechanical vibration characteristics not seen with the higher frequency counterparts. (See Chapters 1 and 2 for details on the mechanisms as well as application of high-intensity, low-frequency ultrasound.)