Ultrasonic lithotresis apparatus

Abstract

A large number of piezoelectric elements are arranged in a mosaic pattern on a spherical surface so that ultrasonic waves generated by the elements converge on a single point. The arrangement of the elements constitutes a transducer. With the transducer applied to a subject through a liquid bag filled with water, ultrasonic shock waves from each piezoelectric element are concentrated on a lithotresis object, or a calculus so as to break it. The ultrasonic shock waves are generated by applying driving impulses (voltage) to each piezoelectric element. In order to locate the calculus, the transducer is coupled to an ultrasonic diagnosis apparatus having a mechanical scanning type ultrasonic probe. The piezoelectric elements have resonance frequencies set such that the piezoelectric element positioned at the center of the transducer has the lowest resonance frequency and the resonance frequency of each piezoelectric element is increased in accordance with its distance from the center. Thus, the frequency range of vibration of the transducer is broadened so that the ultrasonic shock waves become low in negative sound pressure and narrow in pulse width at the point of convergence.

Dependencies are inferred from the claim text.