Component concentration measurement method and device

• US 7,239,904 B2
• Filed: 05/07/2003
• Issued: 07/03/2007
• Est. Priority Date: 05/08/2002
• Status: Expired due to Fees

• Current Assignee: ARKRAY, Inc
• Original Assignee: ARKRAY, Inc
• Inventors: Hirao, Konomu
• Primary Examiner(s): Winakur; Eric F
• Application Number:
  US10/514,785
• Publication Number:
  US 20050171415A1
• Time in Patent Office: 1,518 Days
• Field of Search: 600/310, 600/316, 600/322
• US Class Current: 600/316
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/14558 by polarisation
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence

Abstract

The invention relates to measuring the concentration of a target component in an object. The invention provides a component concentration measurement method including a first step in which light is irradiated onto a measurement object held in a first magnetic field state for detecting the light from the object, a second step in which light is irradiated onto the object held in a second magnetic field state different from the first state for detecting the light from the object, and a third step in which the concentration of the target component is calculated based on the detection results in the first and the second steps. The first magnetic field state may be a magnetic-field-modulated state, while the second state may be a non-magnetic-field-modulated state.

Claims

1. A component concentration measurement method, comprising:

a first step of irradiating light onto an object of measurement with the object of measurement in a first magnetic field state, and detecting a state of light from the object of measurement at this time;

a second step of irradiating light onto the object of measurement with the object of measurement in a second magnetic field state different from the first magnetic field state, and detecting a state of light from the object of measurement at this time; and

a third step of calculating the concentration of a target component based on a detection result in the first step and a detection result in the second step;

wherein in the first and second steps, the state of light from the object of measurement is detected as the absorbance or the amount of light; and

wherein in the third step, the concentration of the target component is calculated based on the difference Δ

between the absorbance or the amount of light measured in the first step and the absorbance or the amount of light measured in the second step.

2. The component concentration measurement method according to claim 1, wherein the first magnetic field state is a magnetic-field-modulated state obtained by applying a magnetic field to the object of measurement from outside, the second magnetic field state being a non-magnetic-field-modulated state.

3. The component concentration measurement method according to claim 2, wherein the first magnetic field state is attained by applying a magnetic field to the object of measurement such that the magnetic flux density at the center of the luminous flux of the light irradiated onto the object of measurement is 100 to 1000 gauss.

4. The component concentration measurement method according to claim 1, wherein the light irradiated onto the object of measurement is linearly polarized light.

5. The component concentration measurement method according to claim 4, wherein in the first and second steps, the state of light from the object of measurement is detected after making the light into linearly polarized light using an analyzer.

6. The component concentration measurement method according to claim 5, wherein the analyzer is disposed so as to selectively transmit light having a different oscillation plane to the oscillation plane of the light irradiated onto the object of measurement.

7. The component concentration measurement method according to claim 6, wherein the analyzer is disposed in a state with the polarization axis thereof shifted by 1.0 to 10.0°

in terms of the absolute value from a position of the polarization axis of the analyzer at which the amount of light transmitted by the analyzer is lowest when light is irradiated onto the object of measurement in the second magnetic field state.

8. The component concentration measurement method according to claim 1, wherein the absorbance or the amount of light is measured based on light transmitted through the object of measurement.

9. The component concentration measurement method according to claim 1, wherein in the third step, the coefficient α

₁ and the coefficient β

₁ in following equation (1) are determined, and the concentration of the target component is calculated based on the coefficients α

₁ and β

₁,

Difference Δ

=α

₁×

X₁+β

₁Δ

Y₁ 

 

(1)

X₁;

Change in absorbance due to change in state of optical rotation for target component between first and second magnetic field states,

Y₁;

Change in absorbance due to state of optical rotation for at least one component other than target component between first and second magnetic field states.

10. The component concentration measurement method according to claim 9, wherein X₁ is determined by subtracting the change in the absorbance for a reference between the first and second magnetic field states from the change in the absorbance for the object of measurement between the first and second magnetic field states, and

wherein Y₁ is determined as the change in the absorbance for the reference between the first and second magnetic field states.

11. The component concentration measurement method according to claim 10, wherein the reference is pure water.

12. The component concentration measurement method according to claim 10, wherein the reference is one in which a state containing noise components is constructed in pseudo fashion.

13. The component concentration measurement method according to claim 9, wherein the target component is blood sugar and in measuring a blood sugar value, X₁ in equation (1) is determined as the change in the absorbance due to a change in the state of optical rotation for glucose between the first and second magnetic field states,

wherein the calculation is carried out with the term β

₁×

Y₁ in equation (1) represented by following equation (2),

β

₁×

Y₁=β

₁₁×

Y₁₁+β

₁₂×

Y₁₂+β

₁₃×

Y₁₃ 

 

(2),

wherein in equation (2), β

₁₁, β

₁₂ and β

₁₃ are respectively a coefficient for plasma, a coefficient for oxyhemoglobin and a coefficient for reduced hemoglobin,

wherein Y₁₁, Y₁₂ and Y₁₃ are respectively the change in the absorbance due to a change in the state of optical rotation for plasma, oxyhemoglobin and reduced hemoglobin between the first and second magnetic field states.

14. The component concentration measurement method according to claim 1, wherein in the first and second steps, a spectrum is obtained by measuring the absorbance or the amount of light at a plurality of wavelengths for the object of measurement and a reference, and in the third step, the difference Δ

is obtained as a spectrum, and the coefficient α

₂ and the coefficient β

₂ in following equation (3) are determined, and the concentration of the target component is calculated based on the coefficients α

₂ and β

₂,

Difference Δ

=α

₂×

X₂+β

₂×

Y₂ 

 

(3)

X₂;

Spectrum of change in absorbance due to change in state of optical rotation for target component between first and second magnetic field states,

Y₂;

Spectrum of change in absorbance due to state of optical rotation for at least one component other than target component between first and second magnetic field states.

15. The component concentration measurement method according to claim 14, wherein X₂ is determined by subtracting the spectrum of the change in the absorbance for the reference from the spectrum of the change in the absorbance for the object of measurement, and

wherein Y₂ is determined as the spectrum of the change in the absorbance for the reference.

16. The component concentration measurement method according to claim 14, wherein the target component is blood sugar and in measuring a blood sugar value, X₂ in equation (3) is determined as the spectrum of the change in the absorbance due to a change in the state of optical rotation for glucose between the first and second magnetic field states, and the calculation is carried out with the term β

₂×

Y₂ in equation (3) represented by following equation (4),

β

₂×

Y₂=β

₂₁×

Y₂₁+β

₂₂×

Y₂₂+β

₂₃×

Y₂₃ 

 

(4),

wherein in equation (4), β

₂₁, β

₂₂ and β

₂₃ are respectively a coefficient for plasma, a coefficient for oxyhemoglobin and a coefficient for reduced hemoglobin, and

wherein Y₂₁, Y₂₂ and Y₂₃ are respectively the spectrum of the change in the absorbance due to a change in the state of optical rotation for plasma, oxyhemoglobin and reduced hemoglobin between the first and second magnetic field states.

17. The component concentration measurement method according to claim 14, wherein the reference is pure water.

18. The component concentration measurement method according to claim 14, wherein the reference is one in which a state containing noise components is constructed in pseudo fashion.

19. The component concentration measurement method according to claim 14, wherein the coefficients α

₂ and β

₂ are determined based on a singular value decomposition procedure.

20. The component concentration measurement method according to claim 1, wherein the target component of which the concentration is measured is glucose.

21. The component concentration measurement method according to claim 20, wherein the wavelength of the light irradiated onto the object of measurement is selected from a range of 780 to 1320 nm.

22. The component concentration measurement method according to claim 1, wherein the first and second steps are carried out by irradiating light directly onto a target component in a human body.

23. A component concentration measurement device, comprising:

a magnetic field applier for applying a magnetic field to an object of measurement from outside;

a controller for controlling the magnetic field applier to produce a first state in which the magnetic field applier does not apply a magnetic field to the object of measurement and a second state in which the magnetic field applier applies a magnetic field to the object of measurement;

a light irradiator for irradiating light onto the object of measurement in the first and second states, respectively;

a light receiver for receiving light from the object of measurement in the first and second states, respectively; and

a calculator for calculating concentration of a target component contained in the object of measurement based on results of light reception by the light receiver in the first and second states.

24. The component concentration measurement device according to claim 23, wherein the light irradiator emits linearly polarized light.

25. The component concentration measurement device according to claim 24, wherein the light irradiator comprises a laser light source.

26. The component concentration measurement device according to claim 24, further comprising an analyzer for making light to be received by the light receiver into linearly polarized light.

27. The component concentration measurement device according to claim 26, wherein the analyzer has a polarization axis thereof disposed so as to selectively transmit linearly polarized light having a different oscillation plane from an oscillation plane of the linearly polarized light emitted from the light irradiator.

28. The component concentration measurement device according to claim 23, wherein the light irradiator comprises a titanium sapphire laser.

29. The component concentration measurement device according to claim 23, wherein the magnetic field applier comprises a rotating magnetic plate or an electromagnet.

30. The component concentration measurement device according to claim 23, further comprising a fixer for fixing the light irradiator, the magnetic field applier and the light receiver with a desired positional relationship relative to a predetermined site on a human body.

31. The concentration measurement device according to claim 30, wherein the fixer is constituted such as to be suitable for fixing onto a fingertip or an earlobe.