Extracorporeal shock wave source with a piezoelectric generator

• US 4,823,773 A
• Filed: 04/01/1987
• Issued: 04/25/1989
• Est. Priority Date: 04/01/1986
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Schwark, Hubert, Reichenberger, Helmut, Naser, Georg
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US07/032,603
• Time in Patent Office: 755 Days
• Field of Search: 128/24 A, 128/328, 128/660, 128/804, 367/147
• US Class Current: 601/4
• CPC Class Codes: A61B 17/2251 characterised by coupling elements between the apparatus, e.g. shock wave apparatus or locating means, and the patient, e.g. details of bags, pressure control of bag on patient
• CPC Class Codes: G10K 11/02 Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
• CPC Class Codes: G10K 11/32 characterised by the shape of the source

Abstract

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.

Claims

1. An extracorporeal shock wave source positionable against a patient for directing shock waves at a selected focus locating within said patient, comprising:

a piezo-electric ultrasound generator means for generating pressure pulses, said generator means having a diameter of at least about 10 cm and an effective radius of curvature for focussing of less than or equal to about 20 cm;

means for operating said generator at an ultrasound frequency less than or equal to about 500 kHz; and

transmission means connected between said ultrasound generator means and said patient for propagating said pressure pulses toward said focus location, said transmission means including a propagation medium selected form the group consisting of glycerine, and ethylene glycol.

2. A shock wave source as claimed in claim 1, wherein said ultrasound generator means comprises a plurality of piezoceramic ultrasound transducer elements.

3. A shock wave source as claimed in claim 1, wherein said transmission means has a convex-concave shape.

4. A shock wave source as claimed in claim 1, further comprising a coupling member abutting said transmission means and disposed between said transmission means and said patient.

5. A shock wave source as claimed in claim 1, wherein said ultrasound generator means has a pressure pulse emission surface, and wherein said emission surface is concave.