Optical shield for a laser catheter

• US 5,034,010 A
• Filed: 09/22/1989
• Issued: 07/23/1991
• Est. Priority Date: 03/22/1985
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Feld, Michael S., Kittrell, Carter, Cothren, Robert M. Jr.
• Primary Examiner(s): HINDENBURG, MAX F
• Application Number:
  US07/411,326
• Time in Patent Office: 669 Days
• Field of Search: 128/395-398, 128/664, 128/665, 128/633, 128/634, 606/13-16
• US Class Current: 606/15
• CPC Class Codes: A61B 1/00096 Optical elements
• CPC Class Codes: A61B 18/245 for removing obstructions in blood vessels or calculi
• CPC Class Codes: A61B 2018/2238 with means for selectively laterally deflecting the tip of the fibre
• CPC Class Codes: A61B 5/0071 by measuring fluorescence emission
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: G02B 6/04 formed by bundles of fibres G02B6/24 takes precedence
• CPC Class Codes: G02B 6/14 Mode converters
• CPC Class Codes: G02B 6/241 Light guide terminations
• CPC Class Codes: G02B 6/3504 Rotating, tilting or pivoting the waveguides, or with the waveguides describing a curved path rotary joint G02B6/3628
• CPC Class Codes: G02B 6/3508 Lateral or transverse displacement of the whole waveguides, e.g. by varying the distance between opposed waveguide ends, or by mutual lateral displacement of opposed waveguide ends
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3516 the reflective optical element moving along the beam path, e.g. controllable diffractive effects using multiple micromirrors within the beam
• CPC Class Codes: G02B 6/3548 1xN switch, i.e. one input and a selectable single output of N possible outputs
• CPC Class Codes: G02B 6/3598 Switching means directly located between an optoelectronic element and waveguides, including direct displacement of either the element or the waveguide, e.g. optical pulse generation based on changing the optical properties of the medium G02F1/00; optical pulse generation in optical transmitters H04B10/508; optical pulse generation by controlling laser operation H01S3/00
• CPC Class Codes: G02B 6/4296 coupling with sources of high radiant energy, e.g. high power lasers, high temperature light sources

Abstract

A laser catheter is disclosed wherein optical fibers carrying laser light are mounted in a catheter for insertion into an artery to provide controlled delivery of a laser beam for percutaneous intravascular laser treatment of atherosclerotic disease. A transparent protective shield is provided at the distal end of the catheter for mechanically diplacing intravascular blood and protecting the fibers from the intravascular contents, as well as protecting the patient in the event of failure of the fiber optics. Multiple optical fibers allow the selection of tissue that is to be removed. A computer controlled system automatically aligns fibers with the laser and controls exposure time. Spectroscopic diagnostics determine what tissue is to be removed.

Claims

1. A method for treatment of lesions or obstructions in tissue of a body vessel or cavity comprising the steps of:

providing a plurality of optical fibers in which the distal end of the catheter is enclosed by an optical shield transparent to optical light radiation and wherein the proximal end of the catheter and optical fibers may be coupled to a laser or other light source;

inserting said catheter into said body vessel or cavity until the optical shield is brought into contact with a suspected lesion or obstruction;

selecting an optical fiber such that radiation will fall on tissue or an obstruction to be treated;

coupling laser radiation of appropriate power and energy into the proximal end of said selected fiber such that radiation is transmitted through said fiber to a region on the distal surface of the shield to irradiate with a predetermined dose and thereby remove at least a portion of the selected amount of tissue or obstruction;

repeating the selecting and coupling steps with other optical fibers that direct radiation onto additional regions of the shield until a desired amount of tissue or obstruction adjacent to the optical shield has been removed;

repositioning the catheter and optical shield so as to bring it in contact with additional tissue or obstruction to be removed, and repeating the above steps as needed until all the desired tissue or obstruction has been removed.

2. The method of treatment of claim 1 wherein the selecting step further comprises coupling low power light from a light source to the proximal end of said optical fiber whereby the light enters the proximal end of the laser fiber and the light is transmitted to the distal end of said fiber through the optical shield to impinge on the lesion such that light emitted by the tissue is returned to the proximal end of the selected optical fiber and is coupled to a spectral analyzer wherein it is determined if the material contacted by or adjacent to the optical shield and, in particular, the portion irradiated by the incident light from the selected optical fiber, is healthy material or other material;

and, in the event that the material is to be treated proceeding with the step of coupling laser radiation.

3. The method of claim 1 wherein the laser catheter is inserted into an artery.

4. The method of claim 3 wherein the light source is one or any combination of the ultraviolet wavelengths of an argon ion or krypton ion laser.

5. The method of claim 3 wherein the light source is a laser device.

6. The method of claim 3 wherein the light is pulsed laser radiation taken from the class comprising nitrogen lasers, excimer lasers, harmonics of Nd:

YAG lasers, or a copper vapor laser, or a pulsed dye laser.

7. The method of claim 3 wherein the appropriate spectral or temporal analysis is stored in computer memory for any fiber, forming a "map" of tissue types adjacent to the catheter;

and when ao appropriate fiber is selected, laser radiation is coupled into the proximal end of said fiber, thereby treating or removing corresponding tissue at the distal end of said fiber.

8. The method of claim 1 the laser catheter is used for ablating or tunnelling into any tissue.

9. The method of claim 1 wherein the proximal ends of the optical fibers are aligned in a linear array which may be translated past the source of laser radiation.

10. The method of claim 1 in which the proximal ends of the optical fibers are aligned in a circular array and the source of laser radiation may be directed onto them by a rotating mirror.

11. The method of claim 1 wherein the proximal ends of the optical fibers are held in an array and the source of laser radiation is directed onto them using one or more mirrors and one or more translational devices.

12. The method of claim 1 wherein the source of laser radiation is directed onto the proximal ends of the optical fibers by galvo scanners or an acousto-optic or electro-optic beam deflector.

13. The method of claim 1 wherein correct alignment of the laser radiation coupling into the selected optical fiber is monitored by detecting scattered light from the proximal end with a photodiode or similar photodetector.

14. The method of claim 13 wherein an automatic control connected to said photodetector maintains optimal alignment.

15. The method of claim 1 wherein light returning in the same or adjacent fibers is monitored for sudden increases in return light indicative of fiber failure, and laser radiation is terminated when such a failure is detected.

16. The method of claim 1 wherein the power of the laser radiation is regulated by an attenuator.

17. The method of claim 16 wherein the attenuator is a rotating half wave plate in combination with a polarizer.

18. The method of claim 16 wherein the attenuator comprises an array of tilting Fresnel reflection plates.

19. The method of claim 1 wherein the exposure time of the laser catheter is regulated by a shutter.

20. The method of treatment of claim 1 wherein tissue is removed asymetrically or primarily on one side of the optical shield.

21. The method of claim 20 wherein the optical shield is advanced in an approximately helical path as tissue is removed.

22. The method of claim 21 wherein the catheter is provided with a guide wire and the radius of the lumen being formed as the shield is advanced is determined by the spacing between guide wire and the optical shield.

23. A method for treatment of arterial tissue of obstructions comprising the steps of:

a) providing a catheter with a plurality of optical fibers in which the distal end of the catheter is enclosed by an optical shield transparent to light radiation and wherein the proximal end of the catheter and optical fibers may be coupled to light sources of optical radiation of relatively high or lower power wherein the high power radiation is capable of removing tissue and the lower power radiation is capable of exciting but not of removing tissue;

b) inserting said catheter into an artery until the optical shield is brought into contact with the suspected arterial lesion;

c) selecting an optical fiber and coupling the low power optical radiation from the light source to the proximal end of said optical fiber whereby the light enters the proximal end of the optical fiber and is transmitted by the selected optical fiber to the distal end of said fiber out the optical shield and impinges on the suspected lesion, and light emitted by the tissue is returned to the proximal end of the selected optical fiber, and is coupled to a spectral analyzer wherein the light excited by said light is analyzed to determine if the material contacted by the optical shield and, irradiated by the incident light from the selected optical fiber is healthy arterial tissue or plaque or other material;

d) in the event it is determined that the material is to be removed, coupling the proximal end of said selected optical fiber to the source of relatively high power radiation and coupling said radiation to the proximal end of said selected optical fiber whereby such radiation is transmitted through said fiber to the distal end to irradiate a portion of the tissue;

e) repeating the above steps until the shield is in contact only with healthy tissue.

24. The method of claim 23 wherein determination of the nature of the tissue being removed is based on fluorescence or scattered light returning from the tissue irradiated by the high power radiation, instead of the second lower power source of radiation.

25. A method for tunneling into and/or treatment of lesions or bodily tissue comprising the steps of:

a) providing a laser cannula with a plurality of optical fibers in which the distal end of the cannula is enclosed by an optical shield transparent to optical light radiation and wherein the proximal end of the cannula and optical fibers may be coupled to a laser or other light source of relatively high or low power;

b) inserting said cannula into or against said body tissue until the optical shield is brought into contact with a suspected lesion or tissue to be removed;

c) selecting an optical fiber such that radiation will fall on tissue or lesion to be treated; and

coupling laser radiation of appropriate power and energy into the proximal end of said selected fiber whereby such radiation is transmitted through said fiber to the distal end to irradiate and thereby remove the selected tissue or lesion;

d) repeating the above steps with other optical fibers until all tissue or lesion adjacent to the optical shield has been treated and/or removed as needed;

e) repositioning the catheter and optical shield forward or laterally so as to bring it in contact with or adjacent to additional tissue or lesion to be treated, and repeating the above steps as needed until all the desired tissue or obstruction has been treated or removed.

26. The method of treatment of claim 25 wherein selecting an optical fiber and coupling low power light from a light source to the proximal end of said optical fiber whereby the light enters the proximal end of the laser fiber and the light is transmitted to the distal end of said fiber out the optical shield to impinge on the lesion and the scattered and fluorescent light is returned to the proximal end of the selected optical fiber and is coupled to a spectral analyzer wherein it is determined if the material contacted by or adjacent to the optical shield and, in particular, the portion irradiated by the incident light from the selected optical fiber, is healthy material or other material;

and, in the event that the material is to be treated or proceeding with step (c) of claim 25.