METHODS FOR NONINVASIVELY MEASURING ANALYTE LEVELS IN A SUBJECT

• US 20110319731A1
• Filed: 09/09/2011
• Published: 12/29/2011
• Est. Priority Date: 08/11/2004
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: GLT Acquisition Corporation
• Inventors: Schurman, Matthew J., Shakespeare, Walter J., Bennett, William Henry
• Granted Patent: US 8,548,549 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters

Abstract

A method for noninvasively measuring analytes such as blood glucose levels includes using a non-imaging OCT-based system to scan a two-dimensional area of biological tissue and gather data continuously during the scanning. Structures within the tissue where measured-analyte-induced changes to the OCT data dominate over changes induced by other analytes are identified by focusing on highly localized regions of the data curve produced from the OCT scan which correspond to discontinuities in the OCT data curve. The data from these localized regions then can be related to measured analyte levels.

Claims

1. A physiological monitoring system for determining a hemoglobin level using an optical coherence tomography (OCT) sensor, the system comprising:

a non-invasive OCT sensor configured to irradiate biological tissue using a beam of light; and

a physiological monitor comprising at least one processor, the physiological monitor configured to;

obtain measurements of light from the beam, the light attenuated by the biological tissue;

identify portions of the measurements of the attenuated light corresponding to measurements taken within one or more blood vessels within the biological tissue; and

estimate a hemoglobin level based at least partly on the measurements taken within the one or more blood vessels.

2. The system of claim 1, wherein the beam comprises at least two different wavelengths having measurably different scattering properties for hemoglobin-containing tissue.

3. The system of claim 2, wherein the physiological monitor is configured to estimate the hemoglobin level by identifying hemoglobin-containing tissue based at least partly on the different scattering properties of the at least two different wavelengths of the beam.

4. The system of claim 1, wherein the physiological monitor is configured to identify the portions of the measurements by:

generating a first OCT scattering profile;

identifying a localized region in the first scattering profile where measurement changes due to blood hemoglobin predominate; and

selecting portions of the measurements of the attenuated light corresponding to the identified localized region.

5. The system of claim 4, wherein the physiological monitor is further configured to:

generate a second OCT scattering profile; and

compare the second OCT scattering profile with the first OCT scattering profile to identify a region where measurement changes due to blood hemoglobin predominate.

6. The system of claim 1, wherein the beam comprises at least one of infrared and near infrared light.

7. The system of claim 1, wherein the non-invasive OCT sensor is configured to generate a reference beam that is adjusted to constructively interfere with the attenuated light.

8. The system of claim 1, wherein the attenuated light includes light reflected from the biological tissue.

9. A physiological monitoring system for determining a hemoglobin level using an optical coherence tomography (OCT) sensor, the system comprising:

a physiological monitor comprising at least one processor, the physiological monitor configured to;

obtain measurements of attenuated light detected by a non-invasive OCT sensor for scanning biological tissue, the OCT sensor configured to

     1) generate a beam of light comprising two or more wavelengths selected to differentiate hemoglobin cells from another biological constituent based on scattering properties of the beam and

     2) illuminate biological tissue with the beam;

generate OCT measurements based at least partly on the measurements of attenuated light;

process the OCT measurements to determine a hemoglobin level of the biological tissue based at least partly on identifying the hemoglobin cells.

10. The system of claim 9, wherein the physiological monitor is configured to process the OCT measurements by identifying the hemoglobin cells based at least partly on the scattering properties of the beam.

11. The system of claim 9, wherein the non-invasive OCT sensor is configured to generate a reference beam that is adjusted to constructively interfere with the attenuated light from the illuminated biological tissue.

12. The system of claim 9, wherein the attenuated light includes light reflected from the illuminated biological tissue.

13. The system of claim 9, wherein the beam comprises at least two wavelengths, each having different absorption or scattering properties for hemoglobin-containing tissues from the other.

14. The system of claim 13, wherein the at least two wavelengths comprise wavelengths at about 1310 nm, and either about 1450 nm or about 820-960 nm.

15. The system of claim 13, wherein at least one of the two wavelengths of light is infrared or near infrared light.

16. The system of claim 13, wherein differences in the scattering properties produced by the at least two wavelengths indicates the presence of hemoglobin cells.

17. The system of claim 13, wherein differences in the absorption properties produced by the at least two wavelengths indicates the presence of hemoglobin cells.

18. A method of measuring hemoglobin concentration within biological tissue, the method comprising:

generating a beam of light, the beam comprising two or more wavelengths selected to differentiate hemoglobin cells from another biological constituent based on scattering properties of the beam; and

illuminating biological tissue with the beam;

generating optical coherence tomography (OCT) measurements based at least partly on light from the beam attenuated by the illuminated biological tissue; and

processing the OCT measurements to determine a hemoglobin level of the biological tissue based at least partly on identifying the hemoglobin cells based on the scattering properties of the beam.

19. The method of claim 18, further comprising generating a reference beam and interfering said reference beam with the light from the beam to generate OCT measurements.

20. The method of claim 18, wherein the beam comprises at least two wavelengths, each having different absorption or scattering properties for hemoglobin-containing tissues from the other.

21. The method of claim 20, wherein the at least two wavelengths comprise wavelengths at about 1310 nm, and either about 1450 nm or about 820-960 nm.

22. The method of claim 20, wherein at least one of the two wavelengths of light is infrared or near infrared light.

23. The method of claim 20, wherein differences in the scattering properties produced by the at least two wavelengths indicates the presence of hemoglobin cells.

24. The method of claim 20, wherein differences in the absorption properties produced by the at least two wavelengths indicates the presence of hemoglobin cells.

25. The method of claim 20, wherein the at least two wavelengths are selected to accentuate contrast between hemoglobin cells and one or more other biological constituents.

26. The method of claim 18, wherein the beam comprises at least three wavelengths, each having different absorption or scattering properties for hemoglobin-containing tissues from the other.

27. The method of claim 18, wherein the hemoglobin level is estimated based at least partly on identifying hemoglobin cells using OCT measurements corresponding to one or more blood vessels.

28. The method of claim 25, wherein the one or more other biological constituents are located around the hemoglobin cells.

29. The method of claim 18, wherein the light from the beam attenuated by the illuminated biological tissue includes light reflected from the illuminated biological tissue.