Optoacoustic monitoring of blood oxygenation

• US 6,498,942 B1
• Filed: 08/07/2000
• Issued: 12/24/2002
• Est. Priority Date: 08/06/1999
• Status: Expired due to Term

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: University of Texas System
• Inventors: Esenaliev, Rinat O., Prough, Donald S., Motamedi, Massoud, Oraevsky, Alexander A.
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): KREMER, MATTHEW J
• Application Number:
  US09/633,597
• Time in Patent Office: 869 Days
• Field of Search: 600/309-310, 600/322-325, 600/327, 600/332, 600/339, 600/341-343
• US Class Current: 600/310
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/4076 Diagnosing or monitoring particular conditions of the nervous system A61B5/4821, A61B5/4824 take precedence
• CPC Class Codes: A61B 8/0808 for diagnosis of the brain
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids

Abstract

An optoacoustic apparatus is disclosed which includes a radiation source of pulsed radiation and a probe having a front face to be placed in close proximity to or in contact with a tissue site of an animal body. The probe further includes a plurality of optical fibers terminating at the surface of the front face of the probe and connected at their other end to a pulsed laser. The front face of the probe also has mounted therein or thereon a transducer for detecting an acoustic response from blood in the tissue site to the radiation pulses connected to a processing unit which converts the transducer signal into a measure of venous blood oxygenation.

Claims

1. An optoacoustic apparatus comprising:

a pulsed laser;

an optical delivery system connected to an output of the pulsed laser and adapted to deliver pulsed radiation to a target site of an animal including a human; and

an acoustic sensing system adapted to be placed in close proximity to or in contact with the target site and to receive an acoustic signal induced in the target site by the pulsed radiation, where the acoustic signal is time resolved and a slope of the time resolved acoustic signal represents a quantitative measure of blood oxygenation in the target site and changes in an amplitude of the time-resolved acoustic signal represents a measure of changes in blood oxygenation in the target site.

2. The apparatus of claim 1, further comprising a digital processing unit in electrical communication with the acoustic sensing system and adapted to convert an acoustic sensing system output signal into the measure of blood oxygenation in the target site and a probe comprising the optical delivery system and the acoustic sensing system, where the probe is adapted to provide irradiation conditions between the target site and the optical delivery system and acoustic contact between the target site and the acoustic sensing system sufficient to permit detection of induced pressure waves in the target site due to the pulsed optical from the optical delivery system.

3. The apparatus of claim 1, wherein the pulsed laser generates pulses of relatively short duration at a wavelength between about 600 nm and about 1400 nm.

4. The apparatus of claim 1, wherein the optical delivery system terminates in an irradiation probe having a distal face adapted to be placed in close proximity to or in contact with the target site and the acoustic sensing system comprises a transducer having sufficient sensitivity, temporal resolution, and bandwidth to detect a pressure profile induced in the the target site due to the pulsed radiation and mounted in a distal face of an acoustic probe and an acoustic cable connected to the transducer, where the cable is adapted to supply power to the transducer and to carry the acoustic signal from the transducer.

5. The apparatus of claim 1, where the optical delivery system terminates in a distal face of a probe and the acoustic sensing system comprises a transducer having sufficient sensitivity, temporal resolution, and bandwidth to detect a pressure profile induced in a tissue or vessel by the pulsed radiation and mounted in the distal face of the probe and an acoustic cable connected to the transducer, where the cable is adapted to supply power to the transducer and to carry the acoustic signal from the transducer.

6. The apparatus of claim 5, wherein the optical delivery system comprises a plurality of optical fibers having ends that terminate in or on the distal face of the probe.

7. The apparatus of claim 6, wherein the ends of the optical fibers are arranged adjacent the transducer.

8. The apparatus of claim 6, wherein the ends of the optical fibers partially or completely surround the transducer.

9. The apparatus of claim 6, wherein the transducer partially or completely surrounds the ends of the optical fibers.

10. The apparatus of claim 1, wherein the target site comprise a heart tissue, a pulmonary artery, an aorta, an artery or vein in a neck or an artery or vein in a brain, and the quantitative measure of blood oxygenation is used to detect or monitor a stroke or to detect or monitor changes in blood oxygenation in a brain tissue, a superior sagittal sinus, an intracerebral vessel, a jugular bulb, a liver tissue, a portal vein, a kidney tissue, or a kidney vein or artery.

11. The apparatus of claim 1, wherein irradiation of the target site by the pulsed radiation and detection of the induced acoustic signal in the target site are performed on a same or different surface of the target site.

12. The apparatus of claim 1, wherein the target site comprises an internal organ and wherein the pulsed radiation is delivered endoscopically and the acoustic sensing system is in close proximity to or in contact with an exterior surface of the target site.

13. The apparatus of claim 1, wherein the target site comprises an internal organ and wherein the pulsed irradiation is delivered at an exterior surface of the animal body including a human body and wherein the acoustic sensing system is positioned endoscopically in close proximity to or in contact with an interior surface of the target site.

14. The apparatus of claim 1, wherein the target site comprises an internal organ and wherein a distal end of the optical delivery system and a distal end of the acoustic sensing system are incorporated in an optoacoustic probe and wherein the probe is positioned inside the organ, so that irradiation and detection are performed from a same internal surface of the organ.

15. The apparatus of claim 1, wherein the target site comprises a tumor and wherein quantitative measure of blood oxygenation is sufficient to differentiate between a malignant tumor and a benign tumor.

16. The apparatus of claim 1, wherein the target site is a cardiac chamber.

17. A probe including a front face having mounted thereon a transducer connected to an output cable and a plurality of optical fibers terminating at or in the front face, where light from a radiation source sent down the fibers exits the probe at the face and enters a tissue site of an animal including a human causing an acoustic response which is detected by the transducer causing the transducer to generate a time resolved output signal, where a slope of the time resolved data output signal represents a quantitative measure of blood oxygenation and changes in an amplitude of the time-resolved output signal represents a measure of changes in blood oxygenation in the target site.

18. An optoacoustic apparatus comprising:

a first pulsed radiation source;

a first fiber-optics delivery system including a first plurality of optical fibers, where the system is connected to an output of the first radiation source at its proximal end;

a probe including a face having a transducer mounted therein and adapted to receive the first fiber-optics delivery system, where distal ends of the first plurality of optical fibers terminate at or near the face of the probe;

a transducer cable connected, at its proximal end, to the transducer and adapted to supply power to the transducer and carry a transducer output signal from the transducer; and

a digital processing unit connected to a distal end of the transducer cable adapted to time resolve the transducer output signal and to convert a slope of the time resolved transducer output signal into a quantitative measure of blood oxygenation and to convert changes in an amplitude of the time-resolved transducer output signal into a measure of changes in blood oxygenation in the target site.

19. The apparatus of claim 18, further comprising:

a second pulsed radiation source and a second fiber-optics delivery system including a second plurality of optical fibers,

where the second fiber-optics delivery system is connected to an output of the second pulsed radiation source at its proximal end and the second plurality of optical fibers terminate at or near the face of the probe and wherein the first pulsed radiation source comprises a Nd;

YAG laser, the second pulsed radiation source comprises an Alexandrite laser and the pulses from both lasers have a relatively short pulse duration.

20. The apparatus of claim 19, wherein the distal ends of the first and second plurality of optical fibers partially or completely surround the transducer, the transducer partially or completely surrounds the distal ends of the first and second plurality of optical fibers or the ends of the optical fibers are adjacent to the transducer.

21. A probe including a front face having mounted thereon a transducer connected to an output cable that exits a back portion of the probe, a first and second plurality of optical fibers terminating at or in the front face of the probe, where light from a first radiation source sent down the first plurality fibers and light from a second radiation source sent down the second plurality of fibers and exit the probe at the face and enters a tissue of an animal including a human causing a time resolved acoustic response which causes the transducer to generate an output signal, where a slope of the time resolved data output signal represents a quantitative measure of blood oxygenation and changes in an amplitude of the time-resolved output signal represents a measure of changes in blood oxygenation in the target site.

22. A method for measuring blood oxygenation comprising the steps of:

directing radiation pulses from a pulsed radiation source into a target site of an animal including a human;

receiving acoustic or pressure waves induced in the target site by the pulsed radiation;

generating an output signal corresponding to the received acoustic waves, where a slope of the output signal is linearly related to blood oxygenation and changes in the amplitude of the output signal is linearly related to changes in blood oxygenation; and

converting the output signal into a measure of blood oxygenation and changes in blood oxygenation in the target site.

23. The method of claim 22, further comprising the step of:

displaying the measure of blood oxygenation or changes in blood oxygenation on a display device.

24. The method of claim 22, wherein the measure of blood oxygenation is performed intra-operatively on open brain tissue, superior sagittal sinus, myocardium, or other exposed tissue or blood vessel.

25. The method of claim 22, wherein absorbing dyes sensitive to blood oxygenation are used to provide higher accuracy of the measure of blood oxygenation.