Hubert Schwark

Extracorporeal shock wave source with a piezoelectric generator

An extracorporeal lithotripter with a piezoceramic pressure source which emits focused pressure waves focussed at a point within a patient at which a calculus to be disintegrated is located. A number of discrete piezoceramic elements are arranged along a curve forming an ultrasound resonator having a diameter of at least about 10 cm and a radius of curvature up to about 20 cm, and operated at an ultrasound frequency below about 500 kHz. The volume between the ultrasound resonator and a terminating membrane through which the pressure waves pass is filled with a A having an acoustic impedance higher than water, preferably greater than or equal to the acoustic impedance of ethylene glycol, so that the piezoceramic elements, forming the pressure source, can be disposed closer to the focus, thereby reducing losses due to non-linear attenuation. The overall efficiency of the lithotripter is thereby increased, and the load of acoustical energy on the patient is diminished. A coupling member may be disposed between the terminating membrane and the patient.

Apparatus for generating acoustic rarefaction pulses

An apparatus for generating acoustic rarefaction pulses, i.e., a negative pressure pulse, has a pressure pulse source and reflector having a negative reflection factor, and an acoustic propagation medium filling the space between the pressure pulse source and the reflector. The reflector has a boundary surface facing toward the pressure pulse source, consisting of a medium which is acoustically soft in comparison to the acoustic propagation medium. The boundary surface medium is separated from the acoustic propagation medium by a wall which is impenetrable by the acoustic propagation medium.

Shock wave source with increased degree of effectiveness

A shock wave source, especially useful for a lithotriptor, has a pressure source for the generation of a pressure wave impulse, a focusing device for focusing the pressure wave pulse, and a seal diaphragm for coupling the pressure wave pulse into the body of a patient, perhaps via a coupling body placed between the seal diaphragm and the patient. The seal diaphragm and the focusing device of the pressure source form a space which serves as a prepassage. The prepassage space is filled with a liquid substance which has a high B/A ratio and an acoustic impedance less than or equal to that of water. The advantage of this configuration is that the pressure wave pulse can be built up very rapidly in its course through the space. At a given point in the space, with the selection of the above-mentioned substances, as compared to water, a given minimum value of the quotient amplitude/build-up time of the pressure wave pulse can be achieved inspite of a reduced output amplitude at the pressure source. Consequently, the life expectancy of the pressure source is higher and less stress is placed on the patient by the acoustic energy. Thus, the degree of effectiveness of the lithotriptor is increased.