JP2004267613A - Glucose concentration measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy in measurement by increasing the S/N ratio in the non-invasive measurement of the concentration of glucose. <P>SOLUTION: The concentration measuring apparatus 1 for measuring the concentration of glucose comprises a light emitting part 6 disposed on the surface of an organism A for applying near-infrared rays into the organism A, a detector 7 for detecting the light diffused or penetrating inside the organism A from the outside of the organism A, and an operating means 18 for calculating the concentration of glucose inside the organism A based on a light receiving signal detected by the detector 7. In the concentration measuring apparatus 1, a plurality of detectors 7 are disposed around the light irradiating part 6 in contact with the outer peripheral surface of the light irradiating part 6. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a glucose concentration measuring device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, blood glucose concentration has been measured to determine diabetes, and in particular, glucose concentration has been measured to test a blood sugar level that determines the insulin dose of a diabetic patient. The measurement of glucose concentration is generally performed by directly analyzing blood collected from a finger or an arm. Since the glucose concentration in blood in the body of a patient changes depending on measurement conditions such as before and after a meal and after exercise, frequent glucose concentration measurement is required to obtain an accurate blood glucose level.
However, in the above method of directly analyzing the collected blood, blood must be collected by puncturing an injection needle or the like every time the glucose concentration is measured, and there is a problem that the burden on the patient is large.
[0003]
To solve this problem, fingers, arms, and earlobes are irradiated with near-infrared light from the outside and diffused in the living body to detect non-invasive light emitted outside the living body. A glucose concentration measuring method has been proposed (for example, see Patent Document 1). In the method disclosed in Patent Document 1, an optical fiber bundle formed by bundling a plurality of light emitting fibers and a plurality of light receiving fibers is prepared, and the distal end surface of each optical fiber constituting the optical fiber bundle is brought into contact with the surface of a living body. Place in state. Then, by irradiating near-infrared light from the tip surfaces of the plurality of light-emitting fibers, the light enters the living body, and the light that is diffused in the living body and returns from the living body surface to outside the living body is received by the plurality of light-receiving fibers, The glucose concentration is calculated by analyzing the spectrum of the received light.
[0004]
[Patent Document 1]
JP 2000-131322 A (FIG. 3 etc.)
[0005]
[Problems to be solved by the invention]
However, there is a problem that the S / N ratio is low because light returned from the living body and received by the light receiving fiber includes diffused light in epithelial tissue or the like that does not contribute to the glucose concentration.
The method disclosed in Patent Literature 1 uses a large number of light-emitting fibers and light-receiving fibers to increase the amount of irradiation light and the amount of detected light, thereby increasing the information amount of the detected glucose concentration. However, in such a method, since the optical fiber is used in the first place, there is a problem that the light guide detection efficiency is low due to the attenuation of the light in the optical fiber and the limitation of NA (numerical aperture). In addition, since the light receiving area of the light receiving fiber is limited, a part of the diffused light emitted outside the living body may not be detected and may be lost.
[0006]
The present invention has been made in view of the above-described circumstances, and has as its object to provide a glucose concentration measuring device capable of improving the measurement accuracy by increasing the S / N ratio.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides the following means.
The invention according to claim 1 includes a light irradiating unit arranged on the surface of a living body and irradiating the living body with near-infrared light, a detector for detecting light diffused or transmitted in the living body outside the living body, Calculating means for determining the glucose concentration in the living body based on the light receiving signal detected by the detector, a plurality of detectors are arranged around the light irradiator, in contact with the outer peripheral surface of the light irradiator. A glucose concentration measuring device.
[0008]
According to the present invention, the near-infrared light emitted from the light irradiating unit enters the living body, is diffused or transmitted in the living body, and is detected by the detector disposed outside the living body. Since the light reception signal detected by the detector includes information corresponding to the tissue that has passed, the glucose concentration is obtained based on the light reception signal by the operation of the arithmetic unit.
In this case, since the plurality of detectors are arranged around the light irradiation unit, light emitted from the light irradiation unit and diffused in the living body and returned to the outside of the living body is detected by the plurality of detectors without leakage. Is done. Therefore, the information lost without being detected by the detector can be reduced, and the S / N ratio can be improved.
[0009]
Further, among the living tissues, the dermis tissues which contribute to the measurement of the glucose concentration are present in a range of 200 μm to 1300 μm below the surface of the living body. In order to obtain glucose concentration information, it is necessary to detect a large amount of diffused light in this region, but if the optical path length in a living body exceeds 3 mm, the light is almost absorbed and the signal deteriorates. There's a problem. According to the present invention, the opening of the detector is provided in a contact state on the outer peripheral surface of the light irradiation unit, and a plurality of light detectors capable of efficiently detecting the light of the opening are arranged. It is possible to detect light that is diffused light and has an optical path length of 3 mm or less in a living body.
[0010]
The invention according to claim 2 is the glucose concentration measuring device according to claim 1, wherein the detector comprises a sensor having a circular cross section having a larger diameter than the light irradiation unit, and the detector includes the light irradiation unit. And providing two to five glucose concentration measuring devices adjacent to the outer peripheral surface of the part.
[0011]
According to the present invention, since the detector including the sensor having a larger diameter than the light irradiation unit is arranged adjacent to the periphery of the light irradiation unit, the light enters the living body from the light irradiation unit and is diffused in the living body. The returned light can be detected by the sensor without deteriorating. In this case, by setting the number of large-diameter sensors arranged around the light irradiation unit to be two to five, the light irradiation unit and the detector can be arranged without any space in the radial direction. That is, when an off-the-shelf product is to be used as a sensor, particularly, a sensor provided with an electronic cooling element has to have a large outer diameter, and there is an off-the-shelf product having a diameter of 14 mm. According to the present invention, it is possible to efficiently detect diffused light using such a large-sized sensor that is already manufactured.
[0012]
The invention according to claim 3 is the glucose concentration measurement device according to claim 2, wherein the detector is housed in a cylindrical light detection unit formed around the light irradiation unit, and the light irradiation unit is And a glucose concentration measuring device provided with an opening having a diameter of about 2 mm, the light detection section provided with an opening having a diameter of about 6 mm, and a light shielding member disposed between the light irradiation section and the light detection section.
According to the present invention, the light incident into the living body from the opening of the light irradiation unit is emitted outside the living body after being scattered in the living body, and housed in the light detection unit through the opening of the light detection unit around the light irradiation unit. Will be detected by the detector. In this case, since the opening of the light irradiation unit has a diameter of about 2 mm and the opening of the light detection unit has a diameter of about 6 mm, the light is 200 μm to 1300 μm below the surface of the living body and the light path length in the living body is 200 μm to 1300 μm. Light of 3 mm or less can be efficiently collected.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a glucose concentration measuring device according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the glucose concentration measurement device 1 according to the present embodiment includes a measurement head 2, a control unit 3 connected to the measurement head 2, and a display unit 4 connected to the control unit 3. Have.
[0014]
The measuring head 2 has a light irradiating section 6 disposed in the center of a hollow section (light detecting section) 5 having an opening 2b opening to the measuring end face 2a and a light irradiating section 6 disposed around the light irradiating section 6. A PbS sensor (detector) 7. The light irradiation section 6 is a hollow cylindrical member having a circular cross section with a diameter of about 2 mm, an inner surface of which is subjected to aluminum vapor deposition, and a tip opening (opening) 6a is disposed near the measurement end face 2a. ing. Accordingly, the light that has entered the light irradiation unit 6 is emitted from the distal end opening 6a while being reflected on the inner surface of the light irradiation unit 6.
[0015]
The cavity 5 has a ring-shaped opening 2b around a distal end opening 6a of the light irradiating section 6, and is formed so as to have a diameter of about 6 mm. Thereby, the distance from the outer periphery of the measuring head 2 to the opening 2b is ensured, and the influence of extraneous light incident on the opening 2b is reduced. Further, the cylindrical member constituting the light irradiation unit 6 constitutes a light blocking member, and prevents light incident on the living body from the light irradiation unit 6 from directly entering the hollow portion 5.
[0016]
The PbS sensor 7 is formed in a cylindrical shape having a circular cross section with a diameter of about 14 mm. As the PbS sensor 7, for example, P2532-1 (manufactured by Hamamatsu Photonics) is used. As shown in FIG. 2, three PbS sensors 7 are arranged around the light irradiation unit 6. Thus, all the PbS sensors 7 are arranged so as to surround the light irradiation unit 6 and substantially contact each other, and are arranged so as to circumscribe the outer peripheral surface of the light irradiation unit 6.
Reference numeral 8 denotes a heat sink provided on a side surface of the measuring head 2 for cooling an electronic cooling element (Peltier element) used in the PbS sensor 7, and reference numeral 9 denotes incidence of external light to the PbS sensor 7. 4 shows a visible light cut filter to be prevented.
Further, an InGaAs PIN photodiode (for example, G5853-103 (manufactured by Hamamatsu Photonics)) may be used instead of the PbS sensor.
[0017]
The control unit 3 includes a light source 10, a collimating lens 11 for collimating the light emitted from the light source 10, a polarizer 12 for polarizing the collimated light in a certain polarization direction, and An acousto-optic tunable filter (AOTF) 13 that disperses the light polarized by the polarizer 12 and further polarizes and emits only light of a specific wavelength (near-infrared light); A filter control unit 14 for supplying and controlling a high frequency to the acousto-optic tunable wavelength filter 13; an analyzer 15 for passing only light of a specific wavelength polarized in the acousto-optic tunable wavelength filter 13; A condensing lens 16 for condensing the collected light and making it incident on the light irradiation unit 6; An amplifier 17 for amplifying the force signal, and an arithmetic unit 18 for calculating a glucose concentration based on an output signal amplified by the amplifier 17. In the figure, reference numeral 19 denotes a wiring connected from the PbS sensor 7 to the amplifier.
[0018]
The filter control unit 14 synchronizes with supplying a high frequency of a specific frequency to the acousto-optic tunable wavelength filter 13 and, in synchronization with the frequency, outputs a wavelength signal of light emitted from the acousto-optic tunable wavelength filter 13. Is supplied to the arithmetic unit 18. In addition, the filter control unit 14 sequentially changes the frequency of the high frequency supplied to the acousto-optic tunable wavelength filter 13.
[0019]
The arithmetic unit 18 determines a specific wavelength region based on the spectral distribution of the output signal obtained from the plurality of output signals obtained from the amplifier 17 and the wavelength signal corresponding to each output signal obtained from the filter control unit 14. For example, the glucose concentration is calculated from the output signal value in the region near the wavelength of 1.5 μm. The light source 10 is, for example, a halogen lamp. The display unit 4 is a display connected to the arithmetic device 18 and displays the glucose concentration value output from the arithmetic device 18.
[0020]
The operation of the thus configured glucose concentration measuring device 1 according to the present embodiment will be described below.
In order to measure the glucose concentration of the body fluid in the living body A using the glucose concentration measuring device 1 according to the present embodiment, the measurement end face 2a of the measuring head 2 is brought into close contact with the living body A, for example, the surface of a fingertip. Thereby, the visible light cut filter 9 provided on the measurement end face 2a is brought into close contact with the surface of the living body A. Note that the measurement site may be a palm, a forearm, or the like in addition to the fingertip.
[0021]
In this state, the light source 10 and the acousto-optic tunable wavelength filter 13 are operated to split the near-infrared light from the light emitted from the light source 10 and make it incident on the light irradiation unit 6. The near-infrared light that has entered the light irradiation unit 6 is emitted from the distal end opening 6a of the light irradiation unit 6, passes through the visible light cut filter 9, and adheres to the visible light cut filter 9. The light is made to enter the living body A from the surface of the living body A.
[0022]
The near-infrared light incident on the living body A collides with the living tissue and is diffused while traveling in the living body A along the incident direction. The light absorbs light in a specific wavelength range according to the components of the living tissue or body fluid passing therethrough. Therefore, the amount of light that is diffused in the living body A, returns to the surface of the living body A, and exits outside the living body A has a reduced light amount in a specific wavelength region according to the passing biological tissue or body fluid. Then, the light emitted outside the living body A in this manner is detected by the PbS sensor 7, and the output signal from the PbS sensor 7 is amplified by the amplifier 17 and then input to the arithmetic unit 18. The arithmetic device 18 calculates the glucose concentration in the living body A based on the input output signal from the PbS sensor 7. Then, the calculated glucose concentration is displayed on the display unit 4.
[0023]
In this case, the amount of light emitted to the outside of the living body A is the largest in the vicinity over the entire circumference of the light irradiation unit 6, and rapidly decreases as the distance from the light irradiation unit 6 in the radial direction increases.
According to the glucose concentration measuring device 1 according to the present embodiment, since the PbS sensor 7 is arranged so as to substantially contact the outer peripheral surface of the light irradiating section 6 and to surround the entire circumference of the light irradiating section 6, Light emitted outside A can be detected almost without leakage.
[0024]
In other words, light emitted from the single light irradiation unit 6 and diffused in all directions in a specific region in the living body A can be collected almost without leakage. As a result, the amount of information on the glucose concentration in the body fluid in the living body A included in the detected light is large, and the S / N ratio can be improved. Further, as compared with the conventional method of receiving light by the light receiving fiber, the light emitted from the surface of the living body A to the outside of the living body A is directly detected by the PbS sensor 7, so that the deterioration of the light is prevented and the S / N ratio is reduced. There is an effect that can be increased.
[0025]
In addition, in the glucose concentration measuring device 1 according to the present embodiment, a hollow cylindrical member is used as the light irradiating unit 6, but an optical rod made of anhydrous quartz may be used instead. Further, as shown in FIG. 3, a funnel-shaped cylindrical body 20 tapered toward the measurement end face 6a and having an inner surface and an outer surface subjected to a mirror surface treatment or a light diffusion surface treatment may be employed. In this case, a cavity 5 for accommodating the funnel-shaped cylinder 20 is provided in the measuring head 2, and the inner surface of the cavity 5 is subjected to mirror surface treatment or light diffusion surface treatment. The PbS sensor 7 may be arranged without any gap in the circumferential direction in the ring-shaped space between. By doing so, it is possible to increase the number of PbS sensors 7 arranged in a substantially contact state with the outer peripheral surface of the cylindrical body 20. As for the light irradiating section 6, an optical fiber may be adopted if the light amount of the light source 10 is increased.
[0026]
Further, as shown in FIG. 4, a lens 22 is disposed in a cylindrical light irradiation unit 21 to converge near-infrared light in a range of 200 μm to 1.3 mm forward from the measurement end surface 6a in the light traveling direction. You may be comprised so that it may make it. By doing so, there is an advantage that near-infrared light can be collected in the dermis region where capillaries are present, and diffused light containing much information on glucose concentration can be obtained.
[0027]
Although the number of the PbS sensors 7 is three in order to arrange the PbS sensors 7 in a substantially contact state around the optical fiber 6, the number of the PbS sensors 7 may be two instead. If the outer diameter of the PbS sensor 7 can be reduced, the number may be increased.
[0028]
The output signal from the amplifier 17 detected by the PbS sensor 7 is irradiated by turning on / off the amount of light input from the light source 10 in a rectangular wave shape or by intermittently applying a high frequency to the acousto-optic tunable wavelength filter 13. The signal component at the time and the signal component at the time of non-irradiation are alternately generated, and by subtracting these signal components from each other, a noise component and a zero-dimensional leakage due to a dark current are removed, and the S / N ratio is further increased. It may be improved.
[0029]
【The invention's effect】
As described above, according to the glucose concentration measuring device of the present invention, a plurality of detectors arranged in a substantially contact state around the light irradiating section are incident on the living body from the light irradiating section, and the living body in the specific area is detected. Light diffused in each direction in the tissue can be collected almost without leakage. As a result, the amount of information on the glucose concentration can be increased, and there is an effect that the S / N ratio can be improved and the glucose concentration can be measured with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a glucose concentration measuring device according to an embodiment of the present invention.
FIG. 2 is a front view schematically showing an arrangement of a light irradiation unit and a detector in a measurement head of the glucose concentration measuring device of FIG.
FIG. 3 is a longitudinal sectional view showing a modification of the measuring head of the glucose concentration measuring device of FIG.
FIG. 4 is a longitudinal sectional view showing another modified example of the measuring head of the glucose concentration measuring device of FIG.
[Explanation of symbols]
A Living body 1 Glucose concentration measuring device 2b Opening 5 Cavity (light detector)
6,21 Light irradiating section 6a Tip opening (opening)
7 PbS sensor (detector)
18 arithmetic means 20 cylinder (light irradiation part)

Claims (3)

A light irradiator that is arranged on the surface of the living body and irradiates the living body with near-infrared light, a detector that detects light diffused or transmitted in the living body outside the living body, and a light receiving signal detected by the detector. Computing means for determining the glucose concentration in the living body based on the
A glucose concentration measuring device, wherein a plurality of detectors are arranged around the light irradiating section and in contact with an outer peripheral surface of the light irradiating section. The detector comprises a sensor having a circular cross section having a larger diameter than the light irradiation unit,
The glucose concentration measuring device according to claim 1, wherein two to five detectors are arranged adjacent to an outer peripheral surface of the light irradiation unit. The detector is housed in a cylindrical light detection unit formed around the light irradiation unit,
The light irradiation unit includes an opening having a diameter of about 2 mm,
The light detection unit includes an opening having a diameter of about 6 mm,
The glucose concentration measuring device according to claim 2, wherein a light-blocking member is disposed between the light irradiation unit and the light detection unit.

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