Detecting thermal discrepancies in vessel walls

• US 5,935,075 A
• Filed: 09/20/1996
• Issued: 08/10/1999
• Est. Priority Date: 09/20/1995
• Status: Expired due to Term

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Texas Heart Institute
• Inventors: Willerson, James T., Casscells, S. Ward, Eastwood, Michael L., Krabach, Timothy N., Bearman, Gregory H.
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US08/717,449
• Time in Patent Office: 1,054 Days
• Field of Search: 128/653.1, 128/664, 128/736, 128/666, 600/473, 600/474, 600/475, 600/549, 600/479, 600/407
• US Class Current: 600/474
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2017/22001 Angioplasty, e.g. PCTA
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/0071 by measuring fluorescence emission
• CPC Class Codes: A61B 5/0073 by tomography, i.e. reconstruction of 3D images from 2D projections A61B5/0066 takes precedence
• 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 5/0086 using infrared radiation
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/015 By temperature mapping of body part
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/413 Monitoring transplanted tissue or organ, e.g. for possible rejection reactions after a transplant
• CPC Class Codes: A61B 5/6853 with a balloon

Abstract

An infrared, heat-sensing catheter particularly useful for identifying potentially fatal arterial plaques in patients with disease of the coronary or other arteries and its use are detailed. In one embodiment, an infrared fiberoptic system (with or without ultrasound) is employed at the tip of the catheter to locate inflamed, heat-producing, atherosclerotic plaque, which is at greater risk for rupture, fissure, or ulceration, and consequent thrombosis and occlusion of the artery. In another embodiment, a catheter with an infrared detector (with or without ultrasound) employed at its tip will likewise locate inflamed heat-producing atherosclerotic plaque. The devices and methods of the invention may be used to detect abscesses, infection, and cancerous regions by the heat such regions differentially display over the ambient temperature of immediately adjacent tissues. The methods and devices of the invention may also be used to detect regions of cooler than ambient tissue in a vessel or organ which indicate cell death, thrombosis, cell death, hemorrhage, calcium or cholesterol accumulations, or foreign materials.

Claims

1. An apparatus for analyzing optical radiation of a vessel, comprising:

at least one fiber having a proximal and a distal end, said fiber being capable of transmitting optical radiation and capable of placement of said distal end proximate to a locus on a wall of said vessel;

a balloon encasing said distal end of at least one said fiber and capable of transmitting optical radiation from said locus or a vessel wall portion into said fiber distal end, when inflated and in contact with said locus or vessel wall portion during use of said apparatus;

a detector optically connected to said at least one fiber proximal end and comprising means for digitizing an optical signal received from said fiber proximal end; and

a computer capable of receiving said digitized signal and mathematically fitting said digitized signal to a curve selected from a spectrum of curves for black body radiations held at preselected temperatures, to ascertain the temperature of said locus or wall portion.

2. The apparatus of claim 1, wherein said balloon, upon inflation, substantially excludes fluids between said at least one fiber and said wall of said vessel most proximate to said locus.

3. The apparatus of claim 1, wherein said balloon is opaque to said radiation and has a black inner surface capable of emitting a black body spectrum corresponding to the radiation emitted bv said locus or vessel wall portion when said balloon is inflated and in contact with said locus or vessel wall portion during use of said apparatus.

4. The apparatus of claim 1 wherein said at least one fiber is at least two fibers.

5. The apparatus of claim 4 wherein at least one of said fibers is a reference fiber and at least one other of said fibers is a signal fiber.

6. The apparatus of claim 5, further comprising an optically reflective surface attached to said signal fiber distal end, said optically reflective surface being capable of directing optical radiation arising radially to said distal end, into said fiber.

7. The apparatus of claim 5, wherein said reference fiber is coated on its distal end with a material that substantially prevents said optical radiation from entering said reference fiber.

8. The apparatus of claim 5, wherein said detector further comprises a multi-wavelength radiometer optically connected between said at least one fiber proximal end and said means for digitizing.

9. The apparatus of claim 8, wherein said radiometer comprises a spinning circular variable filter whose transmission wavelength is a function of its angle of rotation.

10. The apparatus of claim 8 wherein said filter is transparent to radiation with a wavelength of approximately between 2 to 14 micrometers.

11. The apparatus of claim 9, wherein said filter is transparent to radiation with a wavelength of approximately between 3 to 7 micrometers.

12. The apparatus of claim 9, wherein said distal ends of said signal fiber and said reference fiber are offset from one another a distance sufficient to allow sampling of radiation emitted from either fiber to pass said filter at a substantially identical location on said filter.

13. The apparatus of claim 8, wherein said means for digitizing an optical signal includes at least one photoelectric device capable of converting said optical signal into an electrical signal.

14. The apparatus of claim 13, wherein said means for digitizing an optical signal further comprises a device capable of converting said electrical signal into a digital signal.

15. The apparatus of claim 5 wherein said balloon is transparent to said optical radiation.

16. The apparatus of claim 1, further comprising a guidewire slidably connected to said at least one fiber.

17. The apparatus of claim 1 wherein said detector includes means for filtering an optical signal received from said at least one fiber proximal end into a filtered optical signal of 2-14 micrometers wavelength, means for converting said filtered optical signal into an electrical signal, and means for converting said electrical signal into a digital signal.

18. The apparatus of claim 1 wherein said computer is further capable of comparing a temperature value of a particular locus to an average of temperature values along said vessel wall.

19. An apparatus for analyzing infra-red radiation of a blood vessel, comprising:

a catheter containing at least two optical fibers each having a proximal and distal end and being capable of transmitting said infra-red radiation and capable of placement of said distal end along an axis of said vessel proximate to a plaque-containing locus of an interior wall of said vessel, at least one of said fibers being a reference fiber coated on its distal end with a material that substantially prevents said optical radiation from entering said reference fiber; and

at least one of the other of said fibers being a signal fiber whose distal end is optically connected to an optically reflective surface capable of directing infra-red radiation arising radially to said distal end of said signal fiber, into said signal fiber, said catheter including a balloon encasing said distal end of each of said fibers, said balloon being adapted for substantially limiting the flow of fluids within said vessel, and said balloon being adapted for substantially excluding said fluids between said fibers and said wall of said vessel most proximate to said locus, upon placement of said catheter inside said vessel and upon inflation of said balloon, said balloon also being capable of transmitting infra-red radiation arising from a locus or portion of said vessel wall into said fiber distal end, when said balloon is inflated and in contact with said locus during use of said apparatus;

a guidewire slidably connected to said catheter in such a manner as to allow insertion and retraction of said catheter into and out of said vessel, upon using said apparatus; and

a detector optically connected to each said proximal end of each of said fibers, and capable of receiving infra-red radiation from said proximal end arising from infra-red radiation emitted by said locus or said vessel wall, said detector comprising a multi-wavelength radiometer with a spinning circular variable filter, said filter being such that its transmission wavelength is a function of its angle of rotation and is transparent to infra-red radiation with a wavelength of approximately 3-7 micrometers, said distal ends of said reference and signal fiber being offset from one another a distance sufficient to allow sampling of infra-red radiation emitted from either fiber to pass said filter at a substantially identical position on said filter;

said detector further comprising at least one photoelectric device capable of receiving infra-red radiation from said radiometer and converting said received infra-red radiation into an electrical signal and said detector further comprising a digitizer capable of receiving and converting said electrical signal into a digital signal; and

a computer capable of receiving and mathematically fitting said digitized signal to a curve selected from a spectrum of curves for black body radiations held at preselected temperatures, said curves plotted as numbers of photons for each of said wavelengths at a preselected temperature.

20. A method of detecting an elevated temperature locus within a vessel, comprising:

providing the apparatus of claim 19;

inserting said catheter into a vessel;

positioning said at least one fiber distal end proximate to a locus or vessel wall portion;

inflating said balloon whereby said balloon contacts said locus or vessel wall portion;

flow of fluids within said vessel is limited, and radiation emitted from said locus or vessel wall portion is transmitted through said balloon into said at least one fiber distal end;

transmitting said radiation along said fiber to said detector optically connected to said fiber proximal end, whereby said detector converts received radiation into a digitized signal; and

performing a computer analysis of said digitized signal whereby digitized signals from said at least one fiber are mathematically fitted to a black body spectrum to determine the temperature of a locus or vessel wall portion;

optionally determining an average temperature along said vessel wall;

comparing the temperature of a locus to that of a vessel wall portion, or to an average temperature along said vessel wall, whereby an elevated temperature is detected.

21. A method of detecting a locus of inflammation in a vessel comprising:

providing the apparatus of claim 19;

inserting said catheter into a vessel;

positioning said at least one fiber distal end proximate to a locus potentially containing a population of inflammatory cells or proximate to a vessel wall portion;

inflating said balloon whereby said balloon contacts said locus or wall portion;

flow of fluids between said at least one fiber distal end and said wall portion is limited, and radiation emitted from said locus or wall portion is transmitted through said balloon into said at least one fiber distal end;

transmitting said radiation along said fiber to said detector optically connected to said fiber proximal end, whereby said detector converts received radiation into a digitized signal; and

performing a computer analysis of said digitized signal whereby digitized signals from said at least one fiber are mathematically fitted to a black body spectrum to determine the temperature of a locus or wall portion;

optionally determining an average wall temperature along said vessel wall;

comparing the temperature of a locus to that of a wall portion, or to an average temperature along said vessel wall, whereby an elevated locus temperature is detected.

22. A method of detecting the absence of actively metabolizing cells in a vessel comprising:

providing the apparatus of claim 19;

inserting said catheter into a vessel;

positioning said at least one fiber distal end proximate to a locus or a wall portion of said vessel;

inflating said balloon whereby said balloon contacts said locus or wall portion;

flow of fluids between said at least one fiber distal end and said wall portion is limited, and radiation emitted from said locus or wall portion is transmitted through by said balloon into said at least one fiber distal end;

transmitting said radiation along said fiber to said detector optically connected to said fiber proximal end, whereby said detector converts received radiation into a digitized signal; and

performing a computer analysis of said digitized signal whereby digitized signals from said at least one fiber are mathematically fitted to a black body spectrum to determine the temperature of a locus or wall portion;

determining an average temperature of said wall portions;

comparing the temperature of a locus to that of a wall portion, or to an average temperature of said wall, whereby a lower locus temperature is detected.

23. A method for analyzing optical radiation of a locus in a vessel wall, comprising:

inserting into a vessel a catheter comprising at least one fiber having a proximal and a distal end, each said fiber being capable of transmitting optical radiation, a balloon encasing a distal end of at least one said fiber and capable of transmitting optical radiation from a locus or vessel wall portion into said fiber distal end, upon contacting said locus or vessel wall portion with said balloon;

placing at least one said fiber distal end proximate to said locus or vessel wall portion;

inflating said balloon within said vessel to cause said balloon to limit flow of fluids within said vessel;

receiving said transmitted radiation arising from a locus or vessel wall portion into said at least one fiber distal end;

transmitting said radiation along said at least one fiber to a detector optically connected to said at least one fiber proximal end;

converting transmitted radiation emerging from said proximal end, by means of said detector, into a digitized signal; and

performing a computer analysis of said detector output signal whereby digitized signals from each said at least one fiber is mathematically fitted to a curve selected from a spectrum of curves for black body radiations held at preselected temperatures to detect a difference in temperature between said locus and an average temperature along said vessel wall.

24. The method of claim 23, wherein said inserting step includes first inserting a guidewire into the vessel, the catheter being slidingly attached to said guidewire, and said inserting and placing steps further include slidingly advancing or retracting said catheter along said guidewire to place said at least one fiber distal end proximate to said locus or vessel wall portion.

25. The method of claim 24, wherein said step of converting said transmitted radiation emerging from said fiber proximal end comprises passing said radiation through a multi-wavelength radiometer to obtain an optical signal.

26. The method of claim 25 wherein said converting step further comprises optically connecting said radiometer to at least one photoelectric device to convert said optical signal into an electrical signal.

27. The method of claim 26, wherein said converting step further comprises digitizing said electrical signal.

28. The method of claim 27, wherein said perfoming a computer analysis further comprises mathematically fitting said digitized signal to a curve selected from a spectrum of curves for black body radiations held at preselected temperatures said curves plotted as numbers of photons emitted for each of said wavelengths at a preselected temperature.

29. The method of claim 28 wherein the step of performing a computer analysis includes correcting a digitized signal from said signal fiber for a background signal obtained from said reference fiber, and using the resulting adjusted digital signal for said mathematical curve fitting whereby a temperature difference between said locus and an average temperature of said vessel wall is detected, said curve fitting step including using a signal corresponding to a 3 micrometer wavelength radiation sample as a reference for each said curve.

30. A method of detecting an atherosclerotic plaque at risk of rupturing or at risk of thrombosis, comprising:

inserting a guidewire into said vessel;

slidingly introducing along said guidewire to a position proximate to a plaque locus of an interior wall of said vessel, a catheter comprising at least two fibers each having a proximal and distal end and being capable of transmitting infra-red radiation, a balloon encasing said distal ends, at least one of said fibers being a reference fiber coated on its distal end with a material that substantially prevents said optical radiation from entering said reference fiber, and at least one of the other of said fibers being a signal fiber whose distal end is optically connected to an optically reflective surface capable of directing optical radiation arising radially from said locus or vessel wall to said distal end of said signal fiber, into said signal fiber;

inflating said balloon, which balloon upon inflation substantially limits the flow of fluids within said vessel, and which balloon substantially excludes said fluids between said fibers and said wall of said vessel most proximate to said locus, said balloon being capable of transmitting infra-red radiation arising from said locus or vessel wall to said fiber distal end;

transmitting said infra-red radiation to a detector optically connected to a proximal end of each of said fibers, said detector comprising a multi-wavelength radiometer with a spinning circular variable filter, said filter being such that its transmission wavelength is a function of its angle of rotation and is transparent to radiation with a wavelength of approximately 3 to 7 micrometers, whereupon a filtered optical signal is produced, said distal ends of said reference and signal fibers being offset from one another a distance sufficient to allow sampling of radiation emitted from either fiber to pass said filter at a substantially identical position on said filter;

converting said filtered optical signal by means of at least one photoelectric device into an electrical signal, and

converting said electrical signal into a digitized signal by means of a digitizer;

subtracting a digitized background signal created by said at least one reference fiber from a digitized signal transmitted by said at least one signal fiber, by means of a computer, to produce an adjusted digitized signal;

by means of said computer, mathematically fitting said adjusted signal to a curve selected from a spectrum of curves for black body radiations held at preselected temperatures, said curves plotted as numbers of photons emitted for each of said wavelengths at a preselected temperature; and

,

determining if a specific plaque locus has a temperature elevated above that of vessel wall portions outside the specific locus.