METHODS AND SYSTEMS FOR NON-INVASIVE TREATMENT OF TISSUE USING HIGH INTENSITY FOCUSED ULTRASOUND THERAPY

• US 20110251528A1
• Filed: 04/12/2011
• Published: 10/13/2011
• Est. Priority Date: 04/12/2010
• Status: Active Grant

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Canney, Michael S., Khokhlova, Vera A., Kreider, Wayne, Sapozhnikov, Oleg A., Bailey, Michael R., Khokhlova, Tatiana D., Crum, Lawrence A., Hwang, Joo Ha
• Granted Patent: US 8,876,740 B2
• Time in Patent Office: Days
• US Class Current: 601/3
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2018/00005 Cooling or heating of the probe or tissue immediately surrounding the probe
• CPC Class Codes: A61B 2090/374 NMR or MRI
• CPC Class Codes: A61B 2090/378 using ultrasound
• CPC Class Codes: A61N 7/02 Localised ultrasound hyperthermia hyperthermia in general A61F7/00

Abstract

Methods and systems for non-invasive treatment of tissue using high intensity focused ultrasound (“HIFU”) therapy. A method of non-invasively treating tissue in accordance with an embodiment of the present technology, for example, can include positioning a focal plane of an ultrasound source at a target site in tissue. The ultrasound source can be configured to emit HIFU waves. The method can further include pulsing ultrasound energy from the ultrasound source toward the target site, and generating shock waves in the tissue to induce boiling of the tissue at the target site within milliseconds. The boiling of the tissue at least substantially emulsifies the tissue.

Claims

1. A method of non-invasively treating tissue, the method comprising:

positioning a focus of an ultrasound source at a target site in tissue, the ultrasound source being configured to emit high intensity focused ultrasound (HIFU) waves;

pulsing ultrasound energy from the ultrasound source toward the target site; and

generating shock waves in the tissue to induce boiling of the tissue at the target site, wherein boiling the tissue at least substantially emulsifies the tissue.

2. The method of claim 1 wherein:

pulsing the ultrasound energy further comprises pulsing the ultrasound energy at a pulse repetition frequency between approximately 1 Hz and approximately 1 kHz, wherein individual pulses have a pulse length between approximately 100 μ

s and approximately 100 ms; and

generating shock waves further comprises generating shock waves at the focus having a peak positive pressure between approximately 30 MPa and approximately 80 MPa.

3. The method of claim 1 wherein pulsing the ultrasound energy comprises raising tissue temperature at the target site to at least 100°

C. during individual pulses of ultrasound energy.

4. The method of claim 1 wherein pulsing the ultrasound energy further comprises pulsing the ultrasound energy at a pulse length between approximately 1 ms and approximately 40 ms.

5. The method of claim 1 wherein:

pulsing the ultrasound energy further comprises pulsing the ultrasound energy at an ultrasound frequency between approximately 0.5 MHz and approximately 20 MHz and a focal intensity between approximately 1 kW/cm² and approximately 25 kW/cm²; and

generating shock waves further comprises generating shock waves having a shock amplitude between approximately 10 MPa and approximately 100 MPa.

6. The method of claim 1 wherein pulsing the ultrasound energy comprises delivering pulses of ultrasound energy having a peak positive pressure at a focus between approximately 30 MPa and approximately 80 MPa, wherein the ultrasound source has a frequency is approximately 2 MHz.

7. The method of claim 1 wherein pulsing the ultrasound energy further comprises pulsing the ultrasound energy at a duty cycle of less than 10%.

8. The method of claim 1, further comprising cooling the tissue at the target site under 100°

C. between individual pulses.

9. The method of claim 1, further comprising monitoring the boiling of the tissue at the target site in real-time with a monitoring system configured to distinguish boiling bubbles from cavitation bubbles, wherein the monitoring system comprises at least one of an imaging system, a voltage probe, a high-speed camera, and a passive cavitation detection device.

10. The method of claim 1, further comprising mechanically damaging the tissue at the target site with substantially no thermal damage to tissue at the target site and surrounding the target site.

11. The method of claim 1 wherein generating shock waves comprises producing boiling bubbles in the tissue having a cross-sectional dimension on the order of the ultrasound source beam-width at the focus between approximately 10 μ

m and approximately 4 mm.

12. The method of claim 1, further comprising focusing energy deposition of an ultrasound beam from the ultrasound source within approximately 100 microns of the target site.

13. The method of claim 1, further comprising:

delivering at least one test pulse of ultrasound energy to the tissue;

monitoring the target site during the test pulse in real-time for tissue boiling; and

adjusting at least one of peak positive pressure, shock amplitude, pulse length, pulse repetition frequency, and duty cycle to induce tissue boiling at the target site during individual pulses.

14. The method of claim 1, further comprising:

applying at least one test pulse to water to obtain the shock amplitude of the pulse at the focus for boiling water within a selected pulse length;

derating pressure amplitude at the ultrasound source to account for absorption of ultrasound energy propagating through the tissue to the focus;

determining a pulse protocol for the ultrasound source, wherein the pulse protocol includes ultrasound source frequency, peak positive pressure, shock amplitude, pulse length, pulse repetition frequency, and duty cycle to induce tissue boiling at the target site during individual pulses; and

delivering the ultrasound energy using the pulse protocol.

15. A method treating tissue at a target site, the method comprising:

treating the target site with high intensity focused ultrasound (HIFU), wherein the HIFU is delivered from an ultrasound source, and wherein the HIFU is delivered using a pulsing protocol with individual pulse lengths between approximately 1 ms and approximately 100 ms; and

forming a lesion at the target site in the tissue, wherein the lesion is formed by shock waves generated proximate to the target site that induce boiling of the tissue at the target site, and wherein the target site is proximate to a focal plane of the ultrasound source.

16. The method of claim 15 wherein forming a lesion further comprises generating shock waves having amplitudes between approximately 10 MPa and approximately 100 MPa.

17. The method of claim 15 wherein treating the target site further comprises treating the target site with an ultrasound source having a frequency range between approximately 0.5 MHz and approximately 20 MHz.

18. The method of claim 15 wherein treating the target site further comprises pulsing ultrasound waves with a duty cycle of less than 10%.

19. The method of claim 15 wherein forming a lesion comprises raising tissue temperature at the target site to at least 100°

C. during individual pulses of shock waves, the tissue forming boiling bubbles having a cross-sectional dimension between approximately 100 μ

m and 4 mm.

20. The method of claim 15, further comprising distinguishing boiling of the tissue at the target site from cavitation with at least one of an imaging system, a voltage probe, a high-speed camera, and a passive cavitation detection device.

21. The method of claim 15, further comprising:

delivering at least one test pulse of ultrasound energy to the tissue;

monitoring the target site during the test pulse in real-time for tissue boiling; and

adjusting the pulsing protocol to induce tissue boiling at the target site during individual pulses, wherein the pulsing protocol comprises at least one of ultrasound source frequency, peak positive pressure, pulse length, shock wave amplitude, pulse repetition frequency, and duty cycle.

22. A high intensity focused ultrasound (HIFU) system for treating tissue, the HIFU system comprising:

an ultrasound source having a frequency range between approximately 0.5 MHz and approximately 20 MHz, the ultrasound source being configured to deliver a peak positive pressure of between approximately 10 MPa and 100 MPa; and

a function generator operably coupled to the ultrasound source, the function generator being configured to generate a pulsing protocol delivered by the ultrasound source to a target site of tissue, wherein the pulsing protocol comprises at least one of ultrasound source frequency, peak positive pressure, pulse length, shock wave amplitude, pulse repetition frequency, and duty cycle.

23. The HIFU system of claim 22 wherein the ultrasound source is configured to generate shock waves proximate to the target site in the tissue.

24. The HIFU system of claim 22, further comprising a monitoring system configured to distinguish boiling from cavitation in the tissue.

25. The HIFU system of claim 24, further comprising a controller operably coupled to the ultrasound source and the function generator, wherein the controller is configured to adjust the pulsing protocol during treatment in response to feedback from the monitoring system to induce boiling during each pulse with substantially no thermal damage to the tissue at the target site and surrounding the target site.

26. The HIFU system of claim 25 wherein the monitoring system comprises an imaging device configured to detect hyperechoic images in the tissue.

27. The HIFU system of claim 25 wherein the monitoring system comprises a voltage probe configured to detect fluctuations in drive voltage of the ultrasound source.

28. The HIFU system of claim 25 wherein the monitoring device system comprises a passive cavitation detector (PCD) having a focus aligned with a focus of the ultrasound source, the focus being configured to detect changes in acoustic signals related to boiling.

29. The HIFU system of claim 25 wherein the monitoring system comprises a magnetic resonance imaging system configured to detect temperature and boiling activity at the target site.