Hifu applications with feedback control

• US 6,508,774 B1
• Filed: 03/09/2000
• Issued: 01/21/2003
• Est. Priority Date: 03/09/1999
• Status: Expired due to Term

• Current Assignee: Profound Medical Inc. (Profound Medical Corp.)
• Original Assignee: Transurgical, Inc.
• Inventors: Lopath, Patrick David, Acker, David E.
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Shah, Devaang
• Application Number:
  US09/523,915
• Time in Patent Office: 1,048 Days
• Field of Search: 601/1, 601/2, 600/439
• US Class Current: 601/2
• CPC Class Codes: A61B 8/0833 involving detecting or locating foreign bodies or organic structures
• CPC Class Codes: A61N 7/02 Localised ultrasound hyperthermia hyperthermia in general A61F7/00

Abstract

High intensity focused ultrasound heating is provided by applying therapeutic ultrasonic waves using an array of transducers. Cavitation is detected by using some or all of the transducers in the array to detect ultrasonic waves emanating from or reflected from the patient'"'"'s body or the interface. A feedback signal is generated based on such detection. If the feedback signal indicates the presence of cavitation, the therapeutic ultrasonic waves are terminated or altered. Obstacles to ultrasound transmission, such as bony structures or bubbles at the interface between the transducer array and the patient can be detected using the same transducers.

Claims

1. Ultrasonic therapy apparatus comprising:

(a) an ultrasonic emitter including an array of ultrasonic transducers;

(b) a drive and sensing circuit connected to said transducers for applying drive signals to a first set of one or more transducers in said array to thereby cause said first set of transducers to emit therapeutic ultrasonic waves so that said emitted waves are focused at a focal location and heat tissue at such focal location and for acquiring received signals generated by a second set of one or more transducers in said array responsive to ultrasonic waves impinging on said transducers of second set to thereby provide a detected signal representing ultrasonic waves reflected or emanating from said focal location, at least some of the same ones of said transducers being included in said first and second sets during operation of said drive and sensing circuits; and

(c) a feedback control circuit responsive to said detected signal for producing a feedback signal indicating whether cavitation has occurred or is likely to occur at said focal location and adjusting said drive circuit so as to alter or terminate said emitted therapeutic ultrasonic waves in response to said feedback signal.

2. Apparatus as claimed in claim 1 wherein said drive and sensing circuit is operative to select particular ones of said transducers included in said first and second sets.

3. Apparatus as claimed in claim 2 wherein said drive and sensing circuit is operative to vary said selection of transducers during successive intervals of operation, the transducers constituting said second set during each interval of operation being excluded from said first set during the same interval of operation.

4. Apparatus as claimed in claim 3 wherein said drive and sensing circuit is operative to apply said drive signals in a drive frequency band and to provide said detected signal responsive to components of said receive signals in a detection band of frequencies outside of said drive frequency band, said drive and sensing circuit also being operative to apply monitoring signals in said detection band to at least some of said transducers and thereby produce emitted monitoring ultrasonic waves so that said detected signal represents an echo from said focal location of said emitted monitoring ultrasonic waves.

5. Apparatus as claimed in claim 3 wherein said drive and sensing circuit is operative to apply said drive signals in a drive frequency band and to provide said detected signal responsive to components of said receive signals in a detection band of frequencies outside of said drive frequency band so that said detected signal represents ultrasonic sound in said detection band emanating from said focal location.

6. Apparatus as claimed in claim 3 or claim 4 or claim 5 wherein said drive and sensing circuit is operative to apply said drive signals and to acquire said receive signals simultaneously.

7. Apparatus as claimed in claim 1 wherein said drive and sensing circuit is operative to apply said drive signals during drive irntervals, to suspend application of said drive signals during one or more receive intervals interspersed with said drive intervals, and to acquire said receive signals during said receive intervals.

8. Apparatus as claimed in claim 7 wherein said drive and sensing circuit is operative to include at least one of said transducers both in the first set during one of said drive intervals and in the second set during one of said receive intervals immediately succeeding that one of said drive intervals.

9. Apparatus as claimed in claim 8 wherein said drive and sensing circuit is operative to include all of said transducers in said first set during each one of said drive intervals and to include all of said transducers in the second set during each one of said receive intervals.

10. Apparatus as claimed in claim 7 wherein said drive and sensing circuit is operative to provide said detected signal for each said receive interval so that the detected signal for each said receive interval represents an echo of the therapeutic ultrasonic waves applied during the immediately preceding one of said drive intervals reflected from said focal location.

11. Apparatus as claimed in claim 1 wherein said drive and sensing circuit is operative to apply said drive signals in a drive frequency band and to provide said detected signal responsive to components of said received signals in a detection band of frequencies outside of said drive frequency band.

12. Apparatus as claimed in claim 11 wherein said drive and sensing circuit is operative to apply said drive signals and to acquire said received signals simultaneously.

13. Apparatus as claimed in claim 1 wherein said array of transducers is adapted for insertion into the body of a mammalian subject.

14. Apparatus as claimed in claim 1 wherein said array of transducers is deformable.

15. Apparatus as claimed in claim 1 wherein said transducers are polymeric piezoelectric transducers.

16. Ultrasonic therapy apparatus comprising:

(a) an ultrasonic emitter;

(b) a drive circuit connected to said transducers for applying one or more drive signals to said emitter to thereby cause said emitter to emit therapeutic ultrasonic waves so that said emitted waves are focused at a focal location;

(c) means for moving said focal location relative to a body of a patient;

(d) means for providing a detected signal representing ultrasonic waves reflected or emanating from said focal location; and

(e) a feedback control circuit responsive to said detected signal for producing a feedback signal indicating whether cavitation has occurred or is likely to occur at said focal location and adjusting said moving means so as to move said focal location relative to the body of the patient in response to said feedback signal.

17. Apparatus as claimed in claim 16 wherein said emitter includes a plurality of transducers, said drive circuit is operative to apply a plurality of drive signals to said transducers so that different ones of said drive signals are applied to different ones of said transducers, and said moving means is operative to adjust said drive circuit so as to vary the phases of said drive signals relative to one another.

18. Apparatus as claimed in claim 16 wherein said moving means is operative to sweep said focal location through a pseudofocal region of the patients body according to a preselected pattern and to alter said pattern responsive to said feedback signal.

19. A method of applying and controlling high intensity focused ultrasound heating comprising:

(a) applying drive signals to a first set of one or more transducers in an array of transducers to thereby cause said first set of transducers to emit therapeutic ultrasonic waves focused at a focal location and thereby heat tissue at such focal location;

(b) acquiring receive signals generated by a second set of one or more transducers in said array responsive to ultrasonic waves impinging on said transducers of second set to thereby provide a detected signal representing ultrasonic waves reflected or emanating from said focal location, one or more of said transducers being included in said first set at at least some part of said drive signal applying set and included in said second set during at least some part of said acquiring step; and

(c) producing a feedback signal based on said detected signal indicating whether cavitation has occurred or is likely to occur at said focal location and adjusting said drive circuit so as to alter or terminate said emitted therapeutic ultrasonic waves in response to said feedback signal.

20. A method as claimed in claim 19 further comprising the step of selecting particular ones of said transducers included in said first and second sets and varying such selection of transducers during successive intervals of operation.

21. A method as claimed in claim 19 wherein said drive signals are in a drive frequency band and said detected signal is provided responsive to components of said received signals in a detection band of frequencies outside of said drive frequency band.

22. A method as claimed in claim 21 further comprising the step of applying monitoring signals in said detection band to at least some of said transducers to produce emitted monitoring ultrasonic waves so that said detected signal represents an echo from said focal location of said emitted monitoring ultrasonic waves.

23. A method as claimed in claim 19 wherein said detected signal represents noise produced by the patient'"'"'s body.

24. A method as claimed in claim 19 wherein said drive signals are applied during drive intervals, application of said drive signals is suspended during one or more receive intervals interspersed with said drive intervals, and said receive signals are acquired during said receive intervals.

25. A method as claimed in claim 24 wherein said detected signal is acquired during each said receive interval and the detected signal acquired during each said receive interval represents an echo of the therapeutic ultrasonic waves applied during the immediately preceding one of said drive intervals reflected from said focal location.

26. A method as claimed in claim 19 wherein said received signals are acquired during application of said drive signals.

27. A method as claimed in claim 26 wherein said drive signals are in a drive frequency band and said detected signal is provided responsive to components of said received signals in a detection band of frequencies outside of said drive frequency band.

28. A method as claimed in claim 19 wherein said array of transducers is disposed within the body of a living subject.

29. A method as claimed in claim 19 wherein said array of transducers is deformable.

30. A method as claimed in claim 19 further comprising the step of discarding and replacing said array of transducers.

31. A method of applying and controlling high intensity focused ultrasound heating comprising:

(a) emitting therapeutic ultrasonic waves so that said emitted waves are focused at a focal location within the body of a mammalian subject;

(b) providing a detected signal representing ultrasonic waves reflected or emanating from said focal location; and

(c) producing a feedback signal based on said detected signal indicating whether cavitation has occurred or is likely to occur at said focal location and moving said focal location relative to the body of the subject in response to said feedback signal.

32. A method as claimed in claim 31 further comprising the step of sweeping said focal location through a pseudofocal region of the patient'"'"'s body according to a preselected pattern, said step of moving the focal location including altering said pattern responsive to said feedback signal.

33. A method of applying and controlling ultrasound to a subject comprising the steps of:

(a) positioning an array of transducers adjacent the body of a subject and coupling said transducers to the body of the subject at an interface;

(b) actuating a set of less than all of said transducers to emit monitoring ultrasonic waves;

(c) detecting echoes of said ultrasonic waves and generating a feedback signal if said detected echoes include echoes having more than a preselected magnitude and a return time less than a preselected minimum return time less than the return time for echoes of said monitoring ultrasonic waves reflected from a desired focal location, whereby said feedback signal indicates sound-reflective obstacles adjacent said set of said transducers;

(d) repeating said actuating and detecting steps using different sets of said transducers in said array in different repetitions;

(e) disabling transducers in those sets for which a feedback signal is generated in said detecting step; and

(f) operating at least some of said transducers in said array other than transducers in disabled sets to emit therapeutic ultrasonic waves focused at said desired focal location to thereby heat tissue of the subject at such focal location.

34. A method as claimed in claim 33 wherein said step of detecting echoes is performed using at least some of said transducers.

35. A method of applying and controlling ultrasound to a subject comprising the steps of:

(a) positioning an array of transducers adjacent the body of a subject and coupling said transducers to the body of the subject at an interface;

(b) actuating one or more of said transducers to emit monitoring ultrasonic waves;

(c) detecting echoes of said ultrasonic waves and generating a feedback signal if said detected echoes include echoes having more than a preselected magnitude and a return time less than a preselected minimum return time less than the return time for echoes of said monitoring ultrasonic waves reflected from a desired focal location, whereby said detected echoes indicate sound-reflective obstacles adjacent said one or more of said transducers,

wherein said actuating step includes applying monitoring drive signals to a set of said transducers including less than all of said transducers so that said set of said transducers emits said monitoring ultrasonic waves, said step of detecting echoes including terminating application of said monitoring drive signals and then acquiring received signals from said set of said transducers representing ultrasonic waves impinging on the transducers in said set.

36. A method as claimed in claim 35 wherein said steps of applying drive monitoring drive signals and acquiring received signals are repeated cyclically, using different sets of said transducers in different cycles, until such steps have been performed using sets including allow said transducers.

37. A method as claimed in claim 36 wherein the set of transducers used in each said cycle includes only one of said transducers.

38. A method of applying and controlling ultrasound to a subject comprising the steps of:

(a) positioning an array of transducers adjacent the body of a subject and coupling said transducers to the body of the subject at an interface;

(b) actuating one or more of said transducers to emit monitoring ultrasonic waves

(c) detecting echoes of said ultrasonic waves and generating a feedback signal if said detected echoes include echoes having more than a preselected magnitude and a return time less than a preselected minimum return time less than the return to me for echoes of said monitoring ultrasonic waves reflected from a desired focal location, whereby said detected echoes indicate sound-reflective obstacles adjacent said one or more of said transducers, wherein said obstacles include air bubbles at said interface.

39. A method as claimed in claim 38 further comprising the step of generating a human-perceptible alarm signal in response to said feedback signal.