PULSED CAVITATIONAL ULTRASOUND THERAPY

• US 20080319356A1
• Filed: 05/15/2008
• Published: 12/25/2008
• Est. Priority Date: 09/22/2005
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Hall, Timothy L., Roberts, William W., CAIN, CHARLES A., Fowlkes, J. Brian, Xu, Zhen
• Granted Patent: US 8,057,408 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 17/225 for extracorporeal shock wave lithotripsy [ESWL], e.g. by using ultrasonic waves
• CPC Class Codes: A61B 2017/00154 pulsed
• CPC Class Codes: A61B 2017/00172 Pulse trains, bursts, intermittent continuous operation
• CPC Class Codes: A61B 2017/22008 used or promoted
• CPC Class Codes: A61B 2017/22088 ultrasound absorbing, drug activated by ultrasound
• CPC Class Codes: A61B 2017/22089 Gas-bubbles
• CPC Class Codes: A61B 2090/378 using ultrasound
• CPC Class Codes: A61B 5/0536 Impedance imaging, e.g. by tomography
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 8/00 Diagnosis using ultrasonic, sonic or infrasonic waves imaging of objects using sonar G01S15/00
• CPC Class Codes: A61B 8/08 Detecting organic movements or changes, e.g. tumours, cysts, swellings A61B8/02 - A61B8/06 take precedence
• CPC Class Codes: A61B 8/4272 involving the acoustic interface between the transducer and the tissue
• CPC Class Codes: A61B 8/485 involving measuring strain or elastic properties
• CPC Class Codes: A61M 37/0092 using ultrasonic, sonic or infrasonic vibrations, e.g. phonophoresis

Abstract

Therapy methods using pulsed cavitational ultrasound therapy can include the subprocesses of initiation, maintenance, therapy, and feedback of the histotripsy process, which involves the creation and maintenance of ensembles of microbubbles and the use of feedback in order to optimize the process based on observed spatial-temporal bubble cloud dynamics. The methods provide for the subdivision or erosion of tissue, liquification of tissue, and/or the enhanced delivery of therapeutic agents. Various feedback mechanisms allow variation of ultrasound parameters and provide control over the pulsed cavitational process, permitting the process to be tuned for a number of applications. Such applications can include specific tissue erosion, bulk tissue homogenization, and delivery of therapeutic agents across barriers.

Claims

1. A method for controlled mechanical sub-division of soft tissue comprising:

actuating a transducer to output an initiation pulse sequence;

detecting initiation of a bubble cloud in the soft tissue in response to said initiation pulse sequence;

actuating said transducer to output a bubble cloud maintenance and sustaining pulse sequence; and

actuating said transducer to output a therapy pulse sequence which generates and interacts with said bubble cloud to at least partially fractionate the soft tissue.

2. The method according to claim 1 wherein said detecting initiation of said bubble cloud in the soft tissue in response to said initiation pulse sequence comprising detecting initiation of said bubble cloud in the soft tissue in response to said initiation pulse sequence using feedback techniques.

3. The method according to claim 2, further comprising:

detecting cessation of said bubble cloud.

4. The method according to claim 3 wherein said detecting cessation of said bubble cloud comprises detecting cessation of said bubble cloud using said feedback techniques.

5. The method according to claim 4 wherein said feedback techniques are chosen from the group consisting of acoustic backscatter detection, optical attenuation detection, electrical impedance tomography, low frequency hydrophone detection, ultrasound imaging, magnetic resonant imaging, and combinations thereof.

6. The method according to claim 3 wherein said detecting cessation of said bubble cloud is performed simultaneously with said actuating said transducer to output said bubble cloud maintenance and sustaining pulse sequence.

7. The method according to claim 3, further comprising:

re-actuating said transducer to output said initiation pulse sequence in response to said detecting cessation of said bubble cloud.

8. The method according to claim 3, further comprising:

re-actuating said transducer to output said therapy pulse prior to said cessation of said bubble cloud.

9. The method according to claim 1 wherein said actuating a transducer to output said initiation pulse sequence comprises actuating a transducer to output high intensity ultrasound pulses which generate said bubble cloud and produce cavitation nuclei in a treatment volume, said cavitation nuclei reducing a cavitation threshold.

10. The method according to claim 1 wherein said maintenance and sustaining pulse sequence comprises a pulse intensity lower than or equal to a pulse intensity of said initiation pulse sequence.

11. The method according to claim 1 wherein said actuating said transducer to output a bubble cloud sustaining sequence comprises actuating said transducer to output a bubble cloud sustaining sequence without thermally degrading said soft tissue.

12. The method according to claim 1 wherein said detecting initiation of said bubble cloud is completed simultaneously with said actuating said transducer to output an initiation pulse sequence.

13. The method according to claim 1 wherein said initiation pulse sequence, said bubble cloud maintenance and sustaining pulse sequence, and said therapy pulse sequence comprise ultrasound pulses having at least one identical acoustic parameter chosen from the group consisting of acoustic frequency, pulse duration, pulse intensity, pulse repetition frequency and pulse pressure.

14. The method according to claim 1 wherein said initiation pulse sequence, said bubble cloud maintenance and sustaining pulse sequence, and said therapy pulse sequence comprise identical output from said transducer.

15. A method for controlled mechanical sub-division of soft tissue comprising:

actuating a first transducer to output an initiation pulse sequence;

detecting initiation of a bubble cloud in the soft tissue in response to said initiation pulse sequence;

actuating a second transducer to output a bubble cloud maintenance and sustaining pulse sequence; and

actuating a third transducer to output a therapy pulse sequence which generates and interacts with said bubble cloud to at least partially fractionate the soft tissue.

16. The method according to claim 16 wherein at least one of said first transducer, said second transducer, and said third transducer is different than the remaining transducers.

17. A method for controlled mechanical sub-division of soft tissue comprising:

de-initiating a non-treatment portion of the soft tissue to increase a cavitation threshold from a first threshold to a second threshold in said non-treatment portion of the soft tissue;

outputting an initiation pulse sequence at a treatment portion of the soft tissue;

detecting initiation of a bubble cloud in said treatment portion of the soft tissue in response to said initiation pulse sequence;

outputting a bubble cloud maintenance and sustaining pulse sequence at said treatment portion; and

outputting a therapy pulse sequence which generates and interacts with said bubble cloud to at least partially fractionate the soft tissue in said treatment portion.

18. The method according to claim 18 wherein said de-initiating said non-treatment portion of the soft tissue comprises de-initiating said non-treatment portion of the soft tissue using a deleting pulse sequence at a pulse intensity less than said first threshold.

19. The method according to claim 18 wherein said de-initiating a non-treatment portion of the soft tissue and said outputting an initiation pulse sequence are performed simultaneously.