Method and apparatus for determination of analyte concentration

• US 20080137066A1
• Filed: 12/12/2006
• Published: 06/12/2008
• Est. Priority Date: 12/12/2006
• Status: Active Grant

• Current Assignee: OrSense Ltd.
• Original Assignee: OrSense Ltd.
• Inventors: Primack, Harel, Weinstein, Aharon
• Granted Patent: US 7,952,692 B2
• Time in Patent Office: Days
• US Class Current: 356/39
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427

Abstract

A method and system are presented for use in determination of the concentration of an analyte in a subject'"'"'s medium. The medium is irradiated with at least two radiation components to produce detectable radiation responses of the medium thereto. These at least two radiation components are selected to have different mean wavelengths and such that the spectral bandwidth of at least one of said at least two radiation components is characterized by relatively high variability of the extinction coefficient of the analyte of interest across said spectral bandwidth. This enables analysis of data indicative of detected radiation responses of the medium to said at least two radiation components and determination of the concentration of said analyte.

Claims

1. A method for use in measurements of the concentration of an analyte in a medium, said method comprising:

irradiating the medium with at least two radiation components during a certain measurement time to produce detectable radiation responses of the medium thereto, said at least two radiation components being selected to have different mean wavelengths and such that the spectral bandwidth of at least one of said at least two radiation components is characterized by relatively high variability of the extinction coefficient of the analyte of interest across said spectral bandwidth, thereby enabling analysis of data indicative of detected radiation responses of the medium to said at least two radiation components in order to determine the concentration of said analyte.

2. The method of claim 1, wherein said at least one radiation component is selected to contain a plurality of wavelengths with radiation intensities that can be in a fixed relation to each other during the measurement time.

3. The method of claim 1, comprising applying at least two different sources of radiation to the medium to irradiate it by said at least two radiation components, respectively.

4. The method of claim 1, wherein said selecting of the mean wavelength of the spectral bandwidth for said at least one radiation component to be used in the measurements comprises analyzing data indicative of the extinction coefficient spectrum of the analyte of interest.

5. The method of claim 1, wherein said at least one radiation component is emitted by a broadband light source configured for emitting the plurality of wavelengths with radiation intensities that can be in a fixed relation to each other during the measurement time.

6. The method of claim 5, wherein said at least one radiation component is emitted by at least one Light Emitting Diode (LED).

7. The method of claim 1, wherein said at least one other radiation component is selected with a spectral bandwidth corresponding to the variability of the extinction coefficient of the analyte across this spectral bandwidth different to that of said at least one radiation component.

8. The method of claim 7, wherein said at least one other radiation component is emitted by at least one Light Emitting Diode (LED).

9. The method of claim 8, wherein said at least one other radiation component is emitted by at least one monochromatic source.

10. The method of claim 1, wherein said at least one radiation component is emitted by at least one Light Emitting Diode (LED), and said at least one other radiation component is emitted by at least one laser source.

11. The method of claim 6, wherein said at least one LED has the spectral bandwidth of about 20-50 nm.

12. The method of claim 10, wherein said at least one LED has the spectral bandwidth of about 20-50 nm.

13. The method claim 1, wherein the mean wavelength and the spectral bandwidth of said at least one radiation component are selected such that the variability of the extinction coefficient of said analyte across this spectral bandwidth is one of global and local maxima in absolute value.

14. The method claim 1, wherein the mean wavelength and the spectral bandwidth of said at least one other radiation component are selected such that the variability of the extinction coefficient of said analyte across this spectral bandwidth is one of global and local minima in absolute value.

15. The method of claim 14, wherein the mean wavelength and the spectral bandwidth of said at least one other radiation component are selected such that the variability of the extinction coefficient of said analyte across this spectral bandwidth is one of global and local minima in absolute value.

16. The method of claim 1, wherein the mean wavelength of said at least two radiation components contains red-near infrared optical spectral regions.

17. The method of claim 1, wherein the mean wavelength of said at least two radiation components is within about 400 nm-2300 nm.

18. The method claim 1, wherein the radiation response comprises intensities of at least one of transmitted and reflected radiation through and from an irradiated part of the medium, respectively, for said at least two radiation components.

19. The method claim 1, comprising detecting said radiation responses as functions of time and wavelength, analyzing data indicative thereof for said at least two radiation components to determine a relation between the detected radiation responses, and analyzing said relation to determine the analyte concentration.

20. The method of claim 19, wherein said relation is in the form of a quotient of time derivatives of the logarithms of said at least two radiation responses.

21. The method of claim 19, wherein said relation is determined as a parametric slope PS:

22. The method of claim 19, wherein said analyzing of the relation between the detected radiation responses comprises comparing said relation to pre-determined calibration data, and extracting the value of said analyte concentration.

23. The method of claim 20, wherein said analyzing of the relation between the detected radiation responses comprises comparing said quotient to pre-determined calibration data, and extracting the value of said analyte concentration.

24. The method of claim 20, wherein said analyzing of the relation between the detected radiation responses comprises applying to said relation a linear-regression algorithm and extracting the desired value of said analyte concentration.

25. The method of claim 22, wherein said calibration data is obtained by measuring and analyzing the radiation responses for a plurality of subjects together with their respective analyte concentrations and generating the calibration data.

26. The method of claim 23, wherein said calibration data is obtained by measuring and analyzing the radiation responses for a plurality of subjects together with their respective analyte concentrations and generating the calibration data.

27. The method of claim 1, wherein said analyte is one of the following:

hemoglobin, hematocrit, glucose, oxygen saturation, cholesterol, albumin and bilirubin.

28. The method of claim 1, wherein said analyte is a blood analyte.

29. The method of claim 1, wherein said analyte is a tissue analyte.

30. The method of claim 1, wherein said medium is a finger.

31. The method of claim 1, wherein said medium is a fleshy body part.

32. A method for use in determination of a hematocrit concentration, the method comprising:

providing at least two sources of electromagnetic radiation operable in different spectral regions;

selecting an operating spectral bandwidth of at least one of said sources of radiation such that variability of an absorption coefficient of said hematocrit is substantial across the operating spectral bandwidth of said source;

measuring the intensity of the radiation transmitted through and/or reflected from the medium radiation; and

deriving from said transmitted and/or reflected radiation intensity the value of said hematocrit.

33. A method for use in determination of the concentration of an analyte in a subject'"'"'s medium utilizing illumination of the medium with at least two different radiation components during a certain measurement time and detecting radiation responses of the medium to said at least two radiation components, the method comprising:

selecting said at least two radiation components to have different mean wavelengths such that the spectral bandwidth of at least one of said at least two radiation components is characterized by relatively high variability of an extinction coefficient of the analyte of interest across said spectral bandwidth and said at least one radiation component contains a plurality of wavelengths with radiation intensity being in a fixed relation to each other during the measurement time.

34. A system for use in measuring the concentration of an analyte in a subject'"'"'s medium, the system comprising a light source unit configured and operable to produce at least two radiation components having different mean wavelengths, with the spectral bandwidth of at least one of said at least two radiation components being characterized by relatively high variability of an extinction coefficient of the analyte of interest across said spectral bandwidth.

35. The system of claim 34, wherein said at least one radiation component contains a plurality of wavelengths with radiation intensity that can be in a fixed relation to each other.

36. The system of claim 34, wherein said light source unit comprises at least one light source producing said at least one radiation component having the relatively broad spectral bandwidth, and at least one other light source producing light of the relatively narrow spectral bandwidth.

37. The system of claim 35, wherein said at least one light source is a Light Emitting Diode (LED), and said at least one other light source is a laser.

38. The system of claim 35, wherein said at least one light source and said at least one other light source are Light Emitting Diodes (LEDs).

39. The system of claim 36, wherein said at least one LED has the spectral bandwidth of about 20-50 nm.

40. The system of claim 37, wherein said LEDs have the spectral bandwidth of about 20-50 nm.

41. The system of claim 34, wherein the spectral bandwidth of said at least one radiation component is selected such that the variability of the extinction coefficient of said analyte across this spectral bandwidth is maximal in absolute value.

42. The system of claim 34, wherein the spectral bandwidth of said at least one other radiation component is selected such that the variability of the extinction coefficient of said analyte across this spectral bandwidth is minimum in absolute value.

43. The system of claim 41, wherein the spectral bandwidth of said at least one other radiation component is selected such that the variability of the extinction coefficient of said analyte across this spectral bandwidth is minimum in absolute value.

44. The system of claim 34, wherein the mean wavelength of said at least two radiation components is within red-near infrared optical spectral regions.

45. The system of claim 34, wherein the mean wavelength of said at least two radiation components is within about 400 nm-2300 nm.

46. The system of claim 34, comprising a detector unit comprising one or more light detectors for collecting light from the medium and generating data indicative thereof.

47. The system of claim 46, wherein said one or more detectors are adapted to collect light of said at least radiation components transmitted through and/or reflected from the illuminated medium.

48. The system of claim 46, comprising a control unit connectable to the light source unit and to the detector unit, and being configured for processing and analyzing said data indicative of the detected light to determine a relation between the detected radiation components, and analyze said relation to derive therefrom the analyte concentration.

49. The system of claim 48, wherein the control unit is preprogrammed to determine said relation as a quotient of time derivatives of logarithms of said at least two detected radiation components.

50. The system of claim 48, wherein the control unit is preprogrammed to determine said relation as a parametric slope PS:

51. The system of claim 48, wherein said control unit is preprogrammed to analyze the relation between the detected radiation components by comparing said relation to pre-determined calibration data and extracting the value of said analyte concentration.

52. The system of claim 49, wherein said control unit is preprogrammed to analyze the relation between the detected radiation components by comparing said quotient to pre-determined calibration data, and extracting the value of said analyte concentration.

53. The system of claim 48, wherein said control unit is preprogrammed to analyze the relation between the detected radiation components by applying to said relation a linear-regression algorithm and extracting the desired value of said analyte concentration.

54. The system of claim 51, wherein said calibration data is indicative of detected radiation components recorded for a plurality of subjects together with their respective analyte concentrations.

55. The system of claim 52, wherein said calibration data is indicative of detected radiation components recorded for a plurality of subjects together with their respective analyte concentrations.

56. A system for use in determination of the concentration of an analyte in a subject'"'"'s medium, the system comprising a measurement unit and a control unit connectable to the measurement unit, the measurement unit comprising a light source unit and a light detector unit, the light source unit being configured and operable to produce at least two radiation components having different mean wavelengths, with the spectral wavelength of at least one of said at least two radiation components being characterized by relatively high variability of an extinction coefficient of the analyte of interest across said spectral bandwidth and said at least one radiation component containing a plurality of wavelengths with radiation intensity being in a fixed relation to each other during the measurement time, the detector unit comprising one or more light detectors adapted for collecting the radiation components after being transmitted through and/or reflected from the illuminated medium and generating data indicative of the detected light components, the control unit being configured for analyzing said data to determine a relation between the detected light components and analyze said relation to derive therefrom the analyte concentration.