Opto-acoustic thrombolysis

• US 20020045890A1
• Filed: 09/10/2001
• Published: 04/18/2002
• Est. Priority Date: 04/24/1996
• Status: Abandoned Application

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: London, Richard, Matthews, Dennis, Celliers, Peter, Mailland, Ducan, Fitch, Joseph P., Glinsky, Michael, Silva, Luiz Da
• Application Number:
  US09/952,512
• Publication Number:
  US 20020045890A1
• Time in Patent Office: Days
• US Class Current: 606/7
• CPC Class Codes: A61B 17/2202 the ultrasound transducer being inside patient's body at the distal end of the catheter
• CPC Class Codes: A61B 18/26 for producing a shock wave, e.g. laser lithotripsy
• CPC Class Codes: A61B 2017/00022 Sensing or detecting at the treatment site
• CPC Class Codes: A61B 2017/22084 stone- or thrombus-dissolving
• CPC Class Codes: A61B 2090/378 using ultrasound

Abstract

This invention is a catheter-based device for generating an ultrasound excitation in biological tissue. Pulsed laser light is guided through an optical fiber to provide the energy for producing the acoustic vibrations. The optical energy is deposited in a water-based absorbing fluid, e.g. saline, thrombolytic agent, blood or thrombus, and generates an acoustic impulse in the fluid through thermoelastic and/or thermodynamic mechanisms. By pulsing the laser at a repetition rate (which may vary from 10 Hz to 100 kHz) an ultrasonic radiation field can be established locally in the medium. This method of producing ultrasonic vibrations can be used in vivo for the treatment of stroke-related conditions in humans, particularly for dissolving thrombus or treating vasospasm. The catheter can also incorporate thrombolytic drug treatments as an adjunct therapy and it can be operated in conjunction with ultrasonic detection equipment for imaging and feedback control and with optical sensors for characterization of thrombus type and consistency.

Claims

1. A method for delivering acoustic energy into the cerebrovasculature during percutaneous transluminal access procedures, comprising:

inserting a fiber optic into the vasculature to a point near an occlusion, wherein said fiber optic comprises a proximal end and a distal end; and

coupling laser light into said proximal end, wherein said laser light has (i) a pulse frequency within the range of 5 kHz to 25 kHz, (ii) a wavelength within the range of 200 nm to 5000 nm and (iii) an energy density within the range of 0.01 J/cm² to 4 J/cm², wherein said laser light emerges from said distal end to generate an acoustic radiation field in a liquid ambient medium, wherein said acoustic radiation field is generated through a mechanism selected from a group consisting of thermoelastic expansion within said liquid ambient medium and superheated vapor expansion within said liquid ambient medium.

2. A method, comprising:

inserting a fiber optic into the vasculature to a point near an occlusion, wherein said fiber optic comprises a proximal end and a distal end; and

coupling laser light into said proximal end, wherein said laser light has (i) a pulse frequency within the range of 10 Hz to 100 kHz, (ii) a wavelength within the range of 200 nm to 5000 nm and (iii) an energy density within the range of 0.01 J/cm² to 4 J/cm², wherein said laser light emerges from said distal end to generate an acoustic radiation field in a liquid ambient medium.

3. The method of claim 2, wherein said laser light has a pulse frequency within the range of >

1 kHz to 25 kHz.

4. The method of claim 3, wherein said laser light has a pulse duration of less than 200 ns, wherein said laser light that emerges from said distal end generates said acoustic radiation field through thermoelastic expansion of said liquid ambient medium.

5. The method of claim 3, wherein said laser light that emerges from said distal end generates an acoustic radiation field through superheated vapor expansion.

6. The method of claim 3, wherein said laser light emerges from said distal end to generate an acoustic radiation field in a liquid ambient medium for the removal of an intravascular occlusion in said vasculature.

7. The method of claim 6, wherein said intravascular occlusion is selected from a group consisting of atherosclerotic plaque and thrombus.

8. The method of claim 3, wherein said liquid ambient medium is selected from a group consisting of blood, a biological saline solution, a biological saline solution containing an absorbing dye, a thrombolytic pharmaceutical and thrombus.

9. The method of claim 3, wherein said fiber optic is located within a catheter, said method further comprising injecting through said catheter into said liquid ambient medium a thrombolytic drug to emulsify said occlusion.

10. The method of claim 9, wherein a working channel runs parallel to said fiber optic within said catheter, wherein the step of injecting through said catheter into said liquid ambient medium a thrombolytic drug to emulsify said occlusion includes injecting through said working channel within said catheter said thrombolytic drug to emulsify said occlusion.

11. The method of claim 3, wherein said fiber optic is located within a catheter, said method further comprising injecting through said catheter into said liquid ambient medium a radiographic contrast agent to facilitate visualization.

12. The method of claim 3, further comprising monitoring and controlling the magnitude of the acoustic vibrations induced in the tissue through a feedback mechanism.

13. The method of claim 3, wherein said step of inserting a fiber optic into the vasculature includes inserting a fiber optic having a tip selected from a group consisting of a concave tip, a convex tip and a planar tip.

14. The method of claim 3, wherein said step of inserting a fiber optic into the vasculature includes inserting a fiber optic having variable diameter fiber optic into said vasculature.

15. The method of claim 3, wherein said step of inserting a fiber optic into the vasculature includes inserting a fiber optic comprising a composite of glass and plastic into said vasculature.

16. The method of claim 3, wherein said laser light emerges from said distal end to generate, through a mechanism selected from a group consisting of thermoelastic, thermodynamic and a combination of thermoelastic and thermodynamic mechanisms, an acoustic radiation field in a liquid ambient medium for the removal of an intravascular occlusion in said blood vessel.

17. The method of claim 3, wherein said laser light emerges from said distal end to generate an acoustic radiation field in a liquid ambient medium for the removal of an intravascular occlusion in said blood vessel, wherein said laser light has a pulse duration of less than 200 ns, wherein said laser light that emerges from said distal end generates an acoustic radiation field through thermoelastic expansion of said liquid ambient medium, wherein said laser light provides a controlled level of energy in said liquid ambient medium which creates a large thermoelastic stress in a small volume of said liquid ambient medium, wherein said volume of said liquid ambient medium that is heated by said laser light is determined by the absorption depth of said laser light in said liquid ambient medium, and wherein said absorption depth is controlled to produce a desired thermoelastic stress in said volume.

18. The method of claim 3, wherein said laser light emerges from said distal end to generate an acoustic radiation field in a liquid ambient medium for the removal of an intravascular occlusion in said blood vessel, wherein said laser light has a pulse duration that is short enough to deposit all of the laser energy into the absorbing fluid in a time scale shorter than the acoustic transit time across the smallest dimension of absorbing region, wherein said laser light that emerges from said distal end generates an acoustic radiation field through thermoelastic expansion of said liquid ambient medium.

19. The method of claim 3, wherein said fiber optic comprises a bundle of fiber strands, wherein said laser light is coupled into said proximal end at varying times, wherein said laser light within individual strands of said bundle arrives at said distal end at different times, wherein said different times are adjusted to control the directionality and shape of said acoustic radiation field, wherein said different times are adjusted in combination with the different spatial positions of said individual strands.

20. The method of claim 3, wherein said laser light is used as a signal source for producing acoustic images of structures in body tissues.

22. The method of claim 20, further comprising synchronizing the laser pulse repetition rate of said laser energy with the cavity lifetime to achieve resonant operation.

24. The method of claim 23, further comprising the step of matching the pulse period of said laser energy to the cavitation lifetime of said cavitation bubble to achieve resonant operation.

26. The apparatus of claim 25, wherein said laser light has a pulse frequency within the range of >

1 kHz to 25 kHz.

27. The apparatus of claim 26, wherein said laser light has a pulse duration of less than 200 ns, wherein said laser light that emerges from said distal end generates said acoustic radiation field through thermoelastic expansion of said liquid ambient medium.

28. The apparatus of claim 26, wherein said laser light that emerges from said distal end generates said acoustic radiation field through superheated vapor expansion.

29. The apparatus of claim 26, wherein said laser light emerges from said distal end to generate an acoustic radiation field in a liquid ambient medium for the removal of an intravascular occlusion in said vasculatur.

30. The apparatus of claim 29, wherein said intravascular occlusion is selected from a group consisting of atherosclerotic plaque and thrombus.

31. The apparatus of claim 25, wherein said liquid ambient medium is selected from a group consisting of blood, a biological saline solution, a biological saline solution containing an absorbing dye, a thrombolytic pharmaceutical and thrombus.

32. The apparatus of claim 25, further comprising a catheter, wherein said fiber optic is located within said catheter, wherein a thrombolytic drug may be injected through said catheter into said liquid ambient medium to emulsify said occlusion.

33. The apparatus of claim 32, further comprising a working channel that runs parallel to said fiber optic within said catheter, wherein said thrombolytic drug may be injected through said working channel to emulsify said occlusion.

34. The apparatus of claim 25, further comprising a catheter, wherein said fiber optic is located within a catheter, wherein a radiographic contrast agent may be injected through said catheter into said liquid ambient medium to facilitate visualization.

35. The apparatus of claim 25, further comprising means for monitoring and controlling the magnitude of said acoustic radiation field induced in said liquid ambient medium.

36. The apparatus of claim 25, wherein said fiber optic comprises a tip having a shape that is selected from a group consisting of concave, convex and planar.

37. The apparatus of claim 25, wherein said fiber optic comprises a variable diameter.

38. The apparatus of claim 37, wherein said fiber optic comprises a variable diameter that is tapered at the tip of said fiber optic.

39. The apparatus of claim 25, wherein said fiber optic comprises a composite of glass and plastic.

40. The apparatus of claim 39, wherein said fiber optic comprises a composite of glass and a short section of plastic at the tip of said fiber optic, wherein said short section has a length within the range of 3 mm to 3 cm.

41. The apparatus of claim 25, wherein the volume of said liquid ambient medium that is heated by said laser light is determined by the absorption depth of said laser light in said liquid ambient medium, and wherein said absorption depth is controlled to produce a desired thermoelastic stress in said volume.

42. The apparatus of claim 25, wherein said laser light has a pulse duration that is short enough to deposit all of the laser energy into the absorbing fluid in a time scale shorter than the acoustic transit time across the smallest dimension of the absorbing region, wherein said laser light that emerges from said distal end generates an acoustic radiation field through thermoelastic expansion of said liquid ambient medium.

43. The apparatus of claim 25, wherein said fiber optic comprises a tip configured for use as an optical element to focus the light energy in said liquid ambient medium, wherein said tip is further configured to optimize the beam profile of said laser energy for generation of a desired acoustic energy.

44. The apparatus of claim 25, wherein said fiber optic comprises a tip having a surface that is prepared by a process selected from a group consisting of grinding, polishing and chemically etching.

45. The apparatus of claim 25, wherein said laser comprises a tunable wavelength.

47. The apparatus of claim 46, further comprising means for synchronizing the laser pulse repetition rate of said laser energy with the cavity lifetime.

21. A method for producing an ultrasonic radiation field through thermoelastic expansion of a liquid ambient medium located within vasculature, comprising:

inserting a fiber optic into said vasculature;

depositing laser energy in a volume of said liquid ambient medium comparable to the diameter of said fiber optic, in a time scale of duration less than the acoustic transit time across the length of said volume;

controlling said laser energy such that the maximum size of a cavitation bubble is approximately the same as the fiber diameter; and

pulsing said laser energy at a repetition rate such that multiple cycles of this process generates an acoustic radiation field in the surrounding fluid.

23. A method for producing an ultrasonic radiation field through vapor expansion of a liquid ambient medium located within vasculature, comprising:

inserting a fiber optic into said vasculature;

depositing laser energy in a small volume of said liquid ambient medium to produce a cavitation bubble;

controlling said laser energy such that the maximum size of said cavitation bubble is approximately the same as the diameter of said fiber diameter; and

pulsing said laser energy at a repetition rate such that multiple cycles of the generation of said cavitation bubble and the collapse thereof generates an acoustic radiation field in said liquid ambient medium.

25. An apparatus, comprising:

a fiber optic for insertion into the vasculature to a point near an occlusion, wherein said fiber optic comprises a proximal end and a distal end; and

a laser to provide laser light for coupling into said proximal end, wherein said laser light has (i) a pulse frequency within the range of 10 Hz and 100 kHz, (ii) a wavelength within the range of 200 nm and 5000 nm and (iii) an energy density within the range of 0.01 J/cm² to J/cm², wherein said laser light emerges from said distal end to generate an acoustic radiation field in a liquid ambient medium.

46. A apparatus for producing an ultrasonic radiation field through thermoelastic expansion of a liquid ambient medium located within vasculature, comprising:

a fiber optic for insertion into said vasculature;

means for depositing laser energy in a volume of said liquid ambient medium, wherein said volume is comparable to the diameter of said fiber optic, wherein said laser energy is deposited in a time scale of duration less than the acoustic transit time across the length of said volume;

means for controlling said laser energy such that the maximum size of a cavitation bubble is approximately the same as the diameter of said fiber optic; and

means for pulsing said laser energy at a repetition rate such that multiple cycles of this process generates an acoustic radiation field in the surrounding fluid.

48. A apparatus for producing an ultrasonic radiation field through vapor expansion of a liquid ambient medium located within vasculature, comprising:

a fiber optic for insertion into said vasculature;

means for depositing laser energy in a small volume of said liquid ambient medium to produce a cavitation bubble;

means for controlling said laser energy such that the maximum size of said cavitation bubble is approximately the same as the diameter of said fiber optic; and

means for pulsing said laser energy at a repetition rate such that multiple cycles of the generation of said cavitation bubble and the collapse thereof generates an acoustic radiation field in said liquid ambient medium.