Methods for laser induced fluorescence intensity feedback control during laser angioplasty

• US 5,350,375 A
• Filed: 03/15/1993
• Issued: 09/27/1994
• Est. Priority Date: 03/15/1993
• Status: Expired due to Fees

• Current Assignee: Yale University
• Original Assignee: Yale University
• Inventors: Scott, John J., Deckelbaum, Lawrence I.
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): PEFFLEY, MICHAEL F
• Application Number:
  US08/031,540
• Time in Patent Office: 561 Days
• Field of Search: 606/7, 606/10-12, 606/3, 606/15, 128/633, 128/634, 128/898, 607/89
• US Class Current: 606/7
• CPC Class Codes: A61B 18/245 for removing obstructions in blood vessels or calculi
• CPC Class Codes: A61B 2017/00057 Light
• CPC Class Codes: A61B 2017/00061 spectrum

Abstract

Methods are provided for laser induced fluorescence intensity feedback and control during laser angioplasty. In a first aspect of the invention, a catheter including an eccentric guidewire lumen and at least one optical fiber is positioned relative to an obstruction in a blood vessel by rotating the catheter and monitoring the fluorescence intensity. When the fluorescence intensity has a maximum value, the optical fiber is aligned with the obstruction. In another aspect of the invention, fluorescence intensity feedback is used to determine when a laser ablation device has crossed an occlusion. An abrupt drop in fluorescence intensity indicates that the ablation device has crossed the occlusion. In a further aspect of the invention, fluorescence intensity feedback is used to determine the effectiveness of fluid flushing in a blood vessel. In yet another aspect of the invention, fluorescence spectroscopy and fluorescence intensity monitoring are performed sequentially for different subsets of optical fibers in a laser catheter to provide precise control over fiber positioning, tissue diagnosis and ablation. Preferably, the fluorescence intensity feedback is used in conjunction with fluorescence spectroscopy.

Claims

1. A method for controlling the effectiveness of fluid flushing in a blood vessel, comprising the steps of:

advancing a catheter through a blood vessel to a region of interest, said catheter including an optical fiber extending therethrough;

introducing a flushing fluid into the region of interest in the blood vessel;

stimulating fluorescence from material in the region of interest adjacent to the distal end of said optical fiber by transmitting through said optical fiber laser radiation having a wavelength and intensity to stimulate such fluorescence;

monitoring the intensity of the fluorescence from material in the region of interest; and

increasing the amount of flushing fluid in the region of interest if the intensity of said fluorescence is representative of less than a desired amount of flushing fluid in the region of interest.

2. A method as defined in claim 1 wherein the step of increasing the amount of flushing fluid is performed until the fluorescence intensity exceeds a predetermined value representative of the desired amount of flushing fluid in the region of interest.

3. A method as defined in claim 2 wherein the step of monitoring the fluorescence intensity includes monitoring the sum of fluorescence intensities at two or more wavelengths.

4. A method as defined in claim 3 wherein the step of monitoring the sum of fluorescence intensities includes monitoring the sum of fluorescence intensities at 380 nanometers and 440 nanometers.

5. A method as defined in claim 2 wherein the step of monitoring the fluorescence intensity includes monitoring the fluorescence intensity near a single wavelength.

6. A method as defined in claim 5 wherein the step of monitoring the fluorescence intensity near a single wavelength is performed near 380 nanometers.

7. A method as defined in claim 1 wherein the step of increasing the amount of flushing fluid includes increasing a rate of fluid flow to the region of interest.

8. A method as defined in claim 1 wherein the step of increasing the amount of flushing fluid includes introducing additional fluid into the region of interest.

9. A method as defined in claim 1 wherein said flushing fluid is substantially transparent to the fluorescence wavelengths of interest.

10. A method as defined in claim 1 wherein said flushing fluid comprises saline.

11. A method as defined in claim 1 wherein the step of stimulating fluorescence includes transmitting laser radiation in a wavelength range of 280 to 400 nanometers.