CONTINUOUS OPTOACOUSTIC MONITORING OF HEMOGLOBIN CONCENTRATION AND HEMATOCRIT

• US 20040054268A1
• Filed: 03/01/2001
• Published: 03/18/2004
• Est. Priority Date: 03/01/2000
• Status: Active Grant

• Current Assignee: Donald Prough, Massoud Motamedi, Rinat Esenaliev
• Original Assignee: Donald Prough, Massoud Motamedi, Rinat Esenaliev
• Inventors: Esenaliev, Rinat, Motamedi, Massoud, Prough, Donald
• Granted Patent: US 6,751,490 B2
• Time in Patent Office: Days
• US Class Current: 600/322
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters

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 contact with a tissue site of an animal body. The probe further includes an optical fiber 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 piezoelectric transducer for detecting an acoustic response to the radiation pulses connected to a processing unit which converts the transducer signal into a measure of hemoglobin concentration and/or hematocrit of blood.

Claims

1. An optoacoustic apparatus for monitoring hemoglobin concentration in a blood vessel of an animal comprising:

a pulsed radiation source;

an optical system including an optical fiber, an optical screen and an acoustic screen, where the system is connected to an output of the radiation source at its proximal end;

a probe including a housing, a tip, a ring-shaped piezoelectric element, a backing element and an isolating layer, where the optical system enters the housing at its proximal end passes through a center of the piezoelectric element and terminates flush with the housing at the probe'"'"'s tip;

a cable connected to the transducer at its proximal end and exiting the probe out of the back portion of the probe; and

a processing unit connected to the distal end of the cable for converting the transducer output into a measure of blood hemoglobin concentration and/or hematocrit.

2. The apparatus of claim 1, wherein the radiation source is a laser and the pulses are of a nanosecond duration.

3. The apparatus of claim 1, wherein the hemoglobin is associated with blood in a blood vessel or tissue site.

4. A probe comprising:

an optical system including an optical fiber, an optical screen and an acoustic screen, where the system is connected to an output of the radiation source at its proximal end;

a probe including a housing, a tip, a ring-shaped piezoelectric element, a backing element and an isolating layer, where the optical system enters the housing at its proximal end passes through a center of the piezoelectric element and terminates flush with the housing at the probe'"'"'s tip;

a cable connected to the transducer at its proximal end and exiting the probe out of the back portion of the probe.

5. A method of hemoglobin concentration monitoring that comprises the steps of:

irradiating a blood vessel with an optical pulse resulting in a thermoelastic optoacoustic pressure wave in said vessel or tissue site;

time-resolved detecting of the optoacoustic wave with an acoustic detector;

analyzing a temporal profile and/or amplitude of the optoacoustic wave with a data processing unit including software adapted to convert the acoustic detector data into data representing a hemoglobin concentration in blood.

6. A system for measuring hemoglobin concentrations and hematocrit comprising:

a pulsed optical source adapted to generate short optical pulses to provide irradiation of a vessel or tissue site;

an optical delivery system adapted to deliver the optical pulses to the vessel or tissue site having a proximal end in light communication with the source and a distal end out of which the light pulses will exit;

an adjustable holder or probe including a housing, an acoustic transducer adapted to detect pressure waves resulting from the pulsed irradiation of the vessel or tissue site and mounted near a distal end of the probe, where the transducer has sufficient sensitivity, temporal resolution, and bandwidth to collect data from which a hemoglobin concentration can be derived and a cable connected to the transducer, where the probe is adapted to receive the distal end of the light delivery system at its proximal end and situate the distal end of the light delivery system flush with the housing at the distal end of the probe to provide appropriate irradiation conditions and acoustic contact between the vessel or tissue site and the acoustic transducer; and

an electronic signal recording and processing system connected to the cable, where the signal recording and processing system includes a digital processing unit or computer calculating a hemoglobin concentration from the recorded optoacoustic pressure profiles and amplitudes.

7. The system of claim 6, wherein the source produces light pulses in the spectral range from about 400 to about 2500 nm.

8. The system of claim 6, wherein the source comprises two sources having producing light pulses of different wavelengths.

9. The system of claim 6, wherein the source comprises a laser.

10. The system of claim 6, wherein the vessel comprises an aorta and wherein the probe inserted into an esophagus and the irradiation occurs through the esophagus wall adjacent the arota.

11. The system of claim 6, wherein the vessel comprises a radial artery.

12. The system of claim 6, wherein the vessel comprises a carotid artery.

13. The system of claim 6, wherein the vessel comprises a brachial artery.

14. The system of claim 6, wherein the vessel comprises a femoral artery.

15. The system of claim 6, wherein the vessel comprises an artery.

16. The system of claim 6, wherein the vessel comprises a vein.

17. The system of claim 6, wherein the vessel comprises a vein under the skin or in a hollow organ.

18. The system of claim 17, wherein the light pulses have a wavelength of about 548, 568, 587, 805 nm or mixture or combinations thereof or the wavelength is in spectral ranges from about 400 to about 640 or above about 1120 nm where an absorption coefficient of oxy- and deoxygenated blood are similar so that the hemoglobin concentration can be derived from both oxygenated and deoxygenated blood.

19. The system of claim 6, wherein the source comprises a Nd:

YAG laser or a tunable laser or an optical parametric generator or mixtures or combinations thereof.

20. The system of claim 19, wherein the tunable lasers comprises a Ti:

Sapphire laser or a dye laser or mixtures or combinations thereof.

21. The system of claim 6, wherein the system is used for hematocrit measurements in the spectral range from 400 to 2500 nm and preferably in the spectral range above 1350 nm where optoacoustic signal characteristics are more sensitive to the changes in blood scattering and, therefore, to changes in hematocrit.

22. The system of claim 6, wherein the system is used for blood volume measurements.

23. The system of claim 6, wherein the system is used for ultrasound-guided optoacoustic monitoring of fetal anemia during pregnancy.

24. The system of claim 6, wherein the system is used for measuring hematocrit and a hemoglobin concentration in cord blood.

25. The system of claim 6, wherein the system is used for hemoglobin concentration monitoring in patients with kidney failure or patients on dialysis.