Apparatus and method for producing high intensity focused ultrasonic energy for medical applications

• US 20010014780A1
• Filed: 12/01/2000
• Published: 08/16/2001
• Est. Priority Date: 05/14/1999
• Status: Active Grant

• Current Assignee: Andrew H. Proctor, Mark D. Brentnall, Roy W. Martin
• Original Assignee: Andrew H. Proctor, Mark D. Brentnall, Roy W. Martin
• Inventors: Proctor, Andrew H., Brentnall, Mark D., Martin, Roy W.
• Granted Patent: US 6,500,133 B2
• Time in Patent Office: Days
• US Class Current: 601/2
• CPC Class Codes: A61B 17/22004 using mechanical vibrations, e.g. ultrasonic shock waves A61B17/225 takes precedence
• 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: A61B 17/3203 Fluid jet cutting instruments
• CPC Class Codes: A61B 18/14 Probes or electrodes therefor
• CPC Class Codes: A61B 2017/320069 for ablating tissue
• CPC Class Codes: A61B 2090/0813 Accessories designed for easy sterilising, i.e. re-usable
• CPC Class Codes: A61B 8/4272 involving the acoustic interface between the transducer and the tissue
• CPC Class Codes: A61B 8/4444 related to the probe
• CPC Class Codes: A61N 7/00 Ultrasound therapy lithotripsy A61B17/22, A61B17/225; massage using supersonic vibration A61H23/00 ; using ultrasound for introducing media into the body A61M37/0092
• CPC Class Codes: B06B 3/00 Methods or apparatus specially adapted for transmitting mechanical vibrations of infrasonic, sonic, or ultrasonic frequency

Abstract

A medical instrument uses solid tapered cones mounted to a preferably concave, spherically curved, piezoelectric ultrasound transducer which focuses and concentrates the ultrasound energy to a narrow tip so very high levels of ultrasound can be delivered to the tissue adjacent to the tip. Ultrasound matching layers or variable curvature geometries are employed at the tip aid in transferring the energy from the tip to the tissue.

Claims

1. A method for producing a therapeutic, high intensity, focused, ultrasonic energy pattern in living tissue, comprising the steps of:

focusing a beam of ultrasound through a solid material such that it converges towards a focal point in the solid material;

truncating the solid material behind the focal point;

refocusing the beam with a lens at the focal point to provide a predetermined focal region externally of the solid material; and

coupling the lens to the living tissue such that the focal region is directed to a target point within the living tissue.

2. The method as set forth in

claim 1

, comprising the steps of:

generating a sonic wave with a concave transducer;

coupling the transducer to a solid coupler, the coupler having a predetermined geometric apex, wherein the sonic wave is transmitted through the coupler within a predetermined external boundary layer of the coupler;

prior to the wave reaching the apex, subjecting the wave to a lens means for redirecting the sonic wave; and

coupling the lens means directly to the living tissue such that the focal region is directed to a target within the living tissue.

3. The method as set forth in

claim 2

, comprising the steps of:

tailoring transducer geometry and coupler geometry and transducer generating frequency to specific therapeutic tasks.

13. The device as set forth in

claim 1

, comprising:

the transducing means has a backside open to air such that sonic energy generated by the transducing means is directed only into the coupling means and the backside provides a cooling surface at the backside of the transducing means.

4. A high intensity focused ultrasonic device for performing medical procedures, comprising:

transducing means for generating a focused ultrasound beam;

mounted to the transducing means, coupling means for transmitting the beam toward a focal point within the coupling means, wherein the coupling means is formed of a solid material; and

a lens means for redirecting the beam, wherein the lens means is located between the transducing means and the focal point such that the focal point is external to the coupling means solid material.

5. The device as set forth in

claim 4

, comprising:

the transducing means is a concave piezoelectric element having a thickness approximately equal to one-half wavelength of a predetermined ultrasound beam frequency generated thereby.

6. The device as set forth in

claim 5

, comprising:

the coupling means is a semi-cone of a solid material having low acoustic attenuation.

7. The device as set forth in

claim 6

, comprising:

the semi-cone having a rear geometry for mounting the piezoelectric element directly to the semi-cone such that the semi-cone provides mechanical support for the piezoelectric element.

8. The device as set forth in

claim 6

, comprising:

the semi-cone is formed of a solid material selected from a group of materials including ceramic, glass, fused quartz, and metal.

9. The device as set forth in

claim 6

, comprising:

the semi-cone has an outer boundary wider than a taper of the sonic beam pattern imposed by the concave piezoelectric element wherein beam reflections and mode conversions at the boundary are minimized.

10. The device as set forth in

claim 6

, comprising:

the lens means is a selectively truncated tip of the semicone.

11. The device as set forth in

claim 4

, comprising:

mounted to the lens means, an acoustic impedance matching means for coupling the lens to the living tissue.

12. The device as set forth in

claim 11

, comprising:

the matching means is a quarter-wavelength matching-layer of a material selected from a group including DER-322 epoxy, silver-epoxy, Plexiglas, crown glass, aluminum and known manner composites.

14. The device as set forth in

claim 4

, comprising:

the lens means is a truncated tip of a predetermined geometric shape coupling means, the tip having a predetermined geometry for either refocusing the ultrasound beam to a predetermined focal length or for spreading the ultrasound beam immediately adjacent the tip.

15. A high intensity focused ultrasound medical instrument comprising:

a handle;

mounted to the handle, a housing including a cavity;

a transducer having a substantially concave geometry for providing a focused ultrasonic beam from a transducer concave frontside thereof, wherein the transducer is mounted in the housing such that a transducer backside thereof is open to the cavity; and

an ultrasound applicator, having an applicator backside having a convex geometry substantially identical to the concave geometry of the transducer, the applicator is nested with the transducer with the transducer concave frontside substantially adjacent the applicator backside, the applicator being a solid material having a truncated tip such that the tip forms a lens for refocusing the beam, wherein the handle is adapted for providing a conduit for coupling power and a cooling medium to the cavity.

16. The instrument as set forth in

claim 15

, comprising:

the instrument is autoclavable.

17. The instrument as set forth in

claim 15

, comprising:

the handle has a geometric construct adapted for facilitating reaching selective target regions within living tissue during medical procedures.

18. The instrument as set forth in

claim 15

, comprising:

the transducer generates sonic waves having frequencies in a range of approximately 0.5 MHZ to 50 MHZ.

19. The instrument as set forth in

claim 15

, comprising:

the applicator is of a conical geometric configuration, and

the truncated tip is a concave surface subjacent the apex of a cone wherein the concave surface has a radius of curvature substantially equal to the radius of curvature of the concave geometry of the transducer.

20. The instrument as set forth in

claim 15

, comprising:

the truncated tip is a concave surface within the solid material of the cone wherein the concave surface has a radius of curvature substantially equal to the radius of curvature of the concave geometry of the transducer, the concave surface being recessed into the cone a predetermined distance such that the distance is approximately equal to a focal length of the beam.

21. The instrument as set forth in

claim 15

, comprising:

the truncated tip is a concave surface subjacent the apex of the cone wherein the concave surface has a predetermined radius of curvature selected to generate a focal region of the beam a predetermined distance from the tip based upon the focal length of the transducer.

22. The instrument as set forth in

claim 15

, comprising:

the truncated tip is a convex surface subjacent the apex of the cone whereby beam spreading is initiated immediately adjacent the tip.

23. The instrument as set forth in

claim 15

, comprising:

the applicator having a central passageway, extending from the applicator backside through to the truncated tip, for conducting secondary energy means for providing medical therapy therethrough.

24. The instrument as set forth in

claim 15

, further comprising:

means for providing a secondary energy to the tip.

25. The instrument as set forth in

claim 15

, further comprising:

means for controlling operational characteristics of the instrument.

26. The instrument as set forth in

claim 15

, further comprising:

coupled to the truncated tip, waveguide means for refocusing the beam from the tip to a distal end of the waveguide means.

27. The instrument as set forth in

claim 15

, comprising:

the transducer is a piezoelectric element mounted directly to the applicator.

28. The instrument as set forth in

claim 15

, comprising:

the applicator has outer boundary wider than the taper of a sonic beam pattern imposed by the transducer in order to minimizes reflections and mode conversions at the boundary.

29. The instrument as set forth in

claim 24

, comprising:

the secondary energy is bi-directional.

30. The instrument as set forth in

claim 15

, comprising:

the instrument is battery-powered.

31. The instrument as set forth in

claim 15

, comprising:

the applicator is removable from the instrument.