BROAD-AREA IRRADIATION OF SMALL NEAR-FIELD TARGETS USING ULTRASOUND

• US 20100160837A1
• Filed: 12/18/2009
• Published: 06/24/2010
• Est. Priority Date: 12/22/2008
• Status: Active Grant

• Current Assignee: Cutera Incorporated
• Original Assignee: Cutera Incorporated
• Inventors: HUNZIKER, Lukas, May, Justin, Smith, Tonee
• Granted Patent: US 8,585,618 B2
• Time in Patent Office: Days
• US Class Current: 601/2
• CPC Class Codes: A61B 2017/00752 Hair removal or transplantation
• CPC Class Codes: A61B 2018/00005 Cooling or heating of the probe or tissue immediately surrounding the probe
• CPC Class Codes: A61N 2007/0056 Beam shaping elements
• 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

Abstract

An ultrasonic transducer system for treating a portion of tissue. The ultrasonic transducer system includes a frequency generator, an ultrasonic transducer, and a transmitter element. The transducer receives an AC voltage from the frequency generator and produces an ultrasonic energy pulse at an ultrasonic frequency for a pulse width. The transmitter element is coupled to the transducer and is for irradiating a portion of skin tissue. The transmitter element has a chilled surface in contact with the skin tissue and an acoustic aperture for producing a substantially collimated energy beam. The beam has a width greater than 4 mm.

Claims

1. An ultrasonic transducer system for treating tissue comprising:

a frequency generator for generating an AC voltage;

a transducer receiving the AC voltage from the frequency generator for producing an ultrasonic energy pulse at an ultrasonic frequency for a pulse width; and

a transmitter element coupled to the transducer for irradiating a portion of skin tissue;

the transmitter element having;

an acoustic aperture for producing a substantially collimated energy beam, the beam having a width greater than 4 mm; and

a chilled surface in contact with the skin tissue.

2. The ultrasonic transducer system of claim 1, wherein the transmitter element is comprised of at least one layer with a thickness and an acoustic impedance, the thickness and acoustic impedance selected so that at least 50% of the ultrasonic energy pulse is transmitted into the skin tissue.

3. The ultrasonic transducer system of claim 1, wherein the cross-sectional area of the substantially collimated energy beam does not vary by more than 20% over a distance of at least 5 mm from the surface of the skin tissue to a treatment plane.

4. The ultrasonic transducer system of claim 1, wherein the intensity of the ultrasonic energy pulse at the transducer is greater than 150 W/cm².

5. The ultrasonic transducer system of claim 1, wherein the pulse width is less than 100 milliseconds.

6. The ultrasonic transducer system of claim 1, wherein the ultrasonic frequency is between 5 and 20 MHz.

7. The ultrasonic transducer system of claim 1, wherein the ultrasonic energy pulse has an acoustic wavelength, and the square of half the acoustic aperture, divided by the product of the acoustic wavelength and the distance from the acoustic aperture to 5 mm below the skin surface, is greater than 3.

8. The ultrasonic transducer system of claim 1, wherein the ultrasonic energy pulse has an acoustic wavelength, and the square of half the acoustic aperture, divided by the product of the acoustic wavelength and the distance from the acoustic aperture to 5 mm below the skin surface, is greater than 10.

9. The ultrasonic transducer system of claim 1, wherein the Fresnel number of the beam is greater than 3.

10. The ultrasonic transducer system of claim 1, wherein the Fresnel number of the beam is greater than 10.

11. The ultrasonic transducer system of claim 1, wherein the transmitter element has an effective thermal conductivity equal to or greater than 1.0 W/m K.

12. The ultrasonic transducer system of claim 1, wherein the chilled surface is between 5 and 30 degrees Celsius.

13. The ultrasonic transducer system of claim 1, wherein the substantially collimated energy beam has a cross sectional area at least 16 mm² from the surface of the skin tissue to 5 mm below the surface of the of skin tissue.

14. The ultrasonic transducer system of claim 1, wherein the intensity of the ultrasonic energy pulse is greater than or equal to 150 W/cm, the ultrasonic frequency is between 5 and 20 MHz, and the pulse width is less than 100 milliseconds.

15. The ultrasonic transducer system of claim 1, wherein the acoustic aperture has a non-circular shape.

16. The ultrasonic transducer system of claim 1, wherein the acoustic aperture has a quadrilateral shape.

17. The ultrasonic transducer system of claim 1, wherein the acoustic aperture has an elliptical shape.

18. The ultrasonic transducer system of claim 1, wherein the acoustic aperture has a rounded shape with one of a serrated, rippled, notched, or jagged edge profile.

19. The ultrasonic transducer system of claim 1, wherein the transducer produces a plurality of ultrasonic energy pulses, each energy pulse at a different frequency and pulse width.

20. The ultrasonic transducer system of claim 1, wherein the transducer produces a plurality of ultrasonic energy pulses and the difference between a highest pulse frequency and a lowest pulse frequency is greater than 0.25% of an average frequency of the plurality of ultrasonic energy pulses.

21. The ultrasonic transducer system of claim 1, wherein the transducer produces a pulse that is continuously swept over a range of frequencies.

22. The ultrasonic transducer system of claim 1, wherein the transducer produces an ultrasonic frequency that is swept at a rate greater than or equal to 0.25% of the average frequency per 100 milliseconds.

23. The ultrasonic transducer system of claim 1, wherein the transducer is comprised of two or more active elements.

24. The ultrasonic transducer system of claim 23, wherein each active element is for producing an ultrasonic energy pulse at a different ultrasonic frequency.

25. The ultrasonic transducer system of claim 1, wherein the edge of the acoustic aperture is apodized to attenuate the transmitted power near a perimeter of the energy beam.

26. The ultrasonic transducer system of claim 25, wherein the transmitter element includes an apodizing annulus for attenuating the transmitted power near the perimeter of the energy beam.

27. The ultrasonic transducer system of claim 25, wherein the intensity of the transmitted power near the perimeter of the energy beam is within 20% of the intensity of the transmitted power near the center of the energy beam.

28. The ultrasonic transducer system of claim 1, wherein the energy beam within the near-field of the acoustic aperture is imaged onto the surface of the tissue using one or more mirrors or lenses.

29. A method of inhibiting hair growth in a skin tissue, the method comprising:

placing an ultrasonic transducer in contact with the skin tissue,

the transducer having an acoustic aperture for producing a substantially collimated energy beam over a treatment area greater than 16 mm², and a chilled surface in contact with the skin tissue,

the tissue having a plurality of hair follicles within the treatment area,

generating one or more ultrasonic energy pulses, each energy pulse at a corresponding frequency and pulse width.

30. The method of claim 29, wherein the cross-sectional area of the substantially collimated energy beam does not vary by more than 20% over a distance of at least 5 mm from the surface of the skin tissue to a treatment plane.

31. The method of claim 29, wherein the one or more ultrasonic energy pulses is a single pulse having a continuous frequency sweep.

32. The method of claim 29, wherein the combined pulse widths of all of the energy pulses total less than 100 ms.

33. The method if claim 29, wherein the intensity of the ultrasonic energy pulse at the transducer is greater than 150 W/cm².

34. The method of claim 29, wherein the frequency of the ultrasonic energy pulse is between 5 and 20 MHz.

35. The method of claim 29, wherein the one or more ultrasonic energy pulses results in a substantially homogenous ultrasonic energy absorption in the plurality of hair follicles.

36. An ultrasonic transducer system for treating a tissue comprising:

a controller for setting a treatment protocol, the protocol comprised of a sequence of ultrasonic frequencies and a corresponding sequence of exposure times;

a frequency modulator controlled by the controller for producing the sequence of ultrasonic frequencies for the corresponding sequence of exposure times; and

a transducer driven by the frequency modulator for producing a sequence of ultrasonic energy pulses at the sequence of frequencies for the sequence of exposure times,

the transducer having a treatment area larger than 16 mm² and adapted for direct contact with the tissue.

37. A method of inhibiting hair growth in a skin tissue, the method comprising:

placing an ultrasonic transducer in contact with the skin tissue,

the skin tissue including a plurality of hair follicles,

the transducer having a surface area greater than 1 cm² in contact with the skin tissue;

generating one or more ultrasonic energy pulses, by driving the transducer with a drive frequency; and

varying the drive frequency to create a substantially uniform energy distribution in the skin tissue underlying the transducer.