JPH1119074A - Measuring apparatus for degree of oxygenation of tissue blood of living body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring apparatus for the degree of oxygenation of tissue blood of a living body which enables directly measuring of the degree of oxygenation of blood in a tissue of a living body easily. SOLUTION: This apparatus is provided with measuring light output parts 11-15, 2, 4 and 6 to directly irradiate more than three kinds of measuring lights (a), (b), (c) and (d) as near infrared rays with the wavelength thereof close to each other to a tissue 8 of a living body at a specified intensity and detection parts 5, 7 and 16 to detect the intensity of transmission light or scattered light when the outputted measuring lights (a), (b), (c) and (d) pass through the living body tissue 8. Also provided is a degree of oxygenation computing part 17 which computes the degree of oxygenation as ratio of the number of red corpuscles oxygenated to the total number of red corpuscles in the tissue 8 or the amount of hemoglobin oxygenated to the total amount of hemoglobin based on the amount of light absorbed to all red corpuscles in the tissue 8 of the living being obtained from the intensities of the outputted measuring lights (a), (b), (c) and (d) and the transmission light or the scattered light detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the degree of oxygenation of blood in a living tissue using an optical measurement technique.

[0002]

2. Description of the Related Art When red blood cells (or hemoglobin) in a living tissue before and after exercise are transmitted with light having a specific wavelength in the near-infrared region, infrared light absorption spectra differ between before and after exercise. Is known. This is because the amount of oxygenated erythrocytes and the amount of deoxygenated erythrocytes fluctuate before and after exercise, and this appears as a change in light absorption.

[0003] Accordingly, light of a specific wavelength in the near-infrared region is transmitted to red blood cells in a living tissue, and the change in the amount of red blood cells in the living tissue is determined using the relationship between the change in the amount of red blood cells and the change in the amount of light absorbed. Methods and devices for measuring have been proposed.

For example, in the quantification method disclosed in Japanese Patent Application Laid-Open No. 63-33642, a change in absorbance of a subject before and after a change in the state of the subject is measured for light of a plurality of wavelengths, and the amount of change in the subject is measured. Is disclosed.

Further, the measuring apparatus disclosed in Japanese Patent Application Laid-Open No. HEI 3-11835 directly irradiates near-infrared light (measuring light) of three wavelengths to a muscle before applying a certain exercise and a muscle after applying the exercise. Further, there is disclosed an apparatus which measures transmitted light transmitted through a muscle before and after exercise load and checks a change in the amount (increase / decrease) of red blood cells in muscle blood from a change in absorbance of the transmitted light at each wavelength.

As described above, the conventional measuring method and measuring device examine the change in the number of red blood cells before and after the state change.

[0007]

By the way, one step forward from measuring only the change from the start of measurement, is to count the number of oxygenated red blood cells (or the amount of oxygenated hemoglobin) in the living tissue.
And deoxygenated red blood cell count (or deoxygenated hemoglobin amount)
There is a demand for the development of a technique for directly measuring the degree of blood oxygenation, which indicates the percentage of the oxygen.

However, the intensity of the transmitted light transmitted through the living tissue is attenuated not only by the absorption by the red blood cells in the living tissue but also by the scattering and absorption by the living tissue itself. The degree of scattering and the degree of absorption by the living tissue itself differ for each tissue and are unknown.

Therefore, according to the prior art, the variation (increase / decrease) of oxygenated erythrocytes and deoxygenated erythrocytes can be measured from the temporal change of the degree of absorption for each measurement light, but the degree of blood oxygenation can be measured. It was very difficult to measure directly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an apparatus for measuring the degree of oxygenation of blood in a living tissue which can easily and directly measure the degree of oxygenation of blood in the living tissue. And

[0011]

In order to solve the above-mentioned problems, a living tissue blood oxygenation degree measuring apparatus according to the present invention comprises four or more kinds of near-infrared measuring lights having wavelengths close to each other at a predetermined intensity. A measurement light output unit that directly irradiates the measurement light, a detection unit that detects the intensity of transmitted light or scattered light in which the output measurement light has passed through the living tissue, and the output measurement light and the detected transmission. The degree of oxygenation, which is the ratio of the number of oxygenated red blood cells to the total number of red blood cells in the living tissue based on the amount of light absorbed in the living tissue obtained from the difference in intensity of light or scattered light, or the amount of oxygenated hemoglobin relative to the total amount of hemoglobin And an oxygenation degree calculation unit for calculating the oxygenation degree which is the ratio of

[0012] With the above arrangement, the light absorption amount in the living tissue obtained from the intensity difference between the four or more types of measurement light and the transmitted light or the scattered light, the light absorption amount caused by the scattering and absorption by the living tissue itself. Is removed, and the degree of oxygenation of red blood cells in the living tissue is calculated.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A biological tissue blood oxygenation measuring apparatus according to an embodiment of the present invention will now be described with reference to the drawings. This apparatus directly measures the degree of blood oxygenation indicating the ratio between the number of oxygenated red blood cells (or the amount of oxygenated hemoglobin) and the number of deoxygenated red blood cells (or the amount of deoxygenated hemoglobin) in living tissue. .

First, the configuration of the living tissue blood oxygenation degree measuring apparatus of the present invention will be described. As shown in FIG. 1, a biological tissue blood oxygenation degree measuring apparatus 1 of the present invention comprises four or more types of near-infrared measurement lights a, b, and c having a wavelength close to each other for a biological tissue (hereinafter, referred to as tissue) 8. , D at a predetermined intensity, and the intensity of the transmitted light or scattered light passing through the tissue 8 when the output measurement light a, b, c, d passes through the tissue 8. Detectors 5, 7, 16 for detecting
Oxygenated erythrocytes relative to the total number of red blood cells in the tissue 8 based on the amount of light absorption for the total number of red blood cells in the tissue 8 obtained from the output measurement light a, b, c, d and the intensity of the detected transmitted light or scattered light. An oxygenation degree calculator 17 is provided for calculating the oxygenation degree which is a ratio of numbers or the oxygenation degree which is the ratio of the oxygenated hemoglobin amount to the total hemoglobin amount.

The measuring light output units 11 to 15,
Each of 2, 4, and 6 includes a light source 11, 12, 13, and 14, an optical multiplexer 15, an optical connector 2, an optical fiber 4, and a probe 6.

Among them, the light sources 11, 12, 13, 14
Is composed of a light emitting element that emits four single light colors that are close to each other but have four different wavelengths, and a light collector that efficiently guides light to an optical fiber or the like. This light emitting element is, for example, a laser diode (Laser Diode) that oscillates laser light (measuring light a, b, c, d) that is four types of near-infrared light in a narrow wavelength range. Further, the light sources 11, 1
2, 13 and 14 are connected to an optical multiplexer 15, and the output measurement lights a, b, c and d are condensed by a condenser and sent to the optical multiplexer 15. Further, a driving current is supplied from the driving circuit 19 to the light sources 11, 12, 13, and 14.

The reason that near-infrared light is used for the light sources 11, 12, 13, and 14 is that light transmittance in the tissue 8 is good,
This is because detection of transmitted light or scattered light that has passed through the tissue 8 is easy. Further, the absorbance (absorption coefficient) and scattering degree (scattering coefficient), which were unknown numbers differently for each tissue, change linearly with the wavelength of near-infrared light in a narrow wavelength range, as described later. Because.

The optical multiplexer 15 includes a light source 11,
12, 13, and 14, and connected to the optical connector 2, and the collected measurement lights a, b, c, and d are guided to one or a plurality of optical fibers 4 via the optical connector 2. Light.

Each light source is supplied to a driving circuit 19 which is supplied at a time-divisional time-division designated by a timing circuit 18.
, And is guided to the optical fiber 4 via the optical connector 2.

The timing circuit 18 is provided in
As shown in the pulse diagram of FIG.
1, P2, P3, P4, ... are engraved. Further, the timing circuit 18 notifies the drive circuit 19 to emit the measurement light a at the time of the pulse P1 (see FIG. 2B). Similarly, the timing circuit 18 supplies the drive circuit 19 with the measurement light b at the time of the pulse P2 (see FIG. 2C), the measurement light c at the time of the pulse P3 (see FIG. 2D), and the pulse P4. At this time, the measurement light d is notified (see FIG. 2E) to emit light.

The measurement light beams a, b, c, and d which have been guided and transmitted and scattered by the tissue 8 are shifted in time by time division specified by the timing circuit 18 and detected by the photodetector 7 described later. .

The optical connector 2 is detachably connected to the optical fiber 4, and is a connector for outputting the measuring lights a, b, c, and d from the apparatus main body 1 to the outside (the tissue 8) via the optical fiber 4. It is.

The optical fiber 4 is, for example, a silica-based optical fiber. One end is detachably connected to the optical connector 2 and the other end is connected to the probe 6. Also,
The optical fiber 4 has four types of measurement light a,
The tissue 8 is irradiated with b, c, and d through the probe 6.

Further, the probe 6 is arranged in close contact with a certain point on the tissue 8, and outputs the measuring lights a, b, c, and d emitted from the optical fiber 4 to the tissue 8. Then, the outputted measurement lights a, b, c, and d pass through the oxygenated red blood cells (or oxygenated hemoglobin), deoxygenated red blood cells (or deoxygenated hemoglobin), and other body fluids in the tissue 8 and are detected. Detected by the units 3, 5, 7, and 16.

The detection units 3, 5, 7, and 16
An electrical connector 3, an electric wire 5, a photodetector 7, and an optical amplifier (amplifier) 16 are provided. Among them, the photodetector 7 is, for example, a photodiode, a device that receives measurement light (that is, transmitted light) from the tissue 8 and detects the intensity of the received transmitted light. It is arranged at a point about several cm away from the position of the probe 6. Further, this photodetector 7 is connected to the electric wire 5,
The intensity information of the detected transmitted light is transmitted to the apparatus main body 1 via the electric wire 5.
Notify.

This electric wire 5 is, for example, a shielded wire,
One end is detachably connected to the electrical connector 3 on the apparatus body 1 side, and the other end is connected to the photodetector 7. The electric connector 3 is detachably connected to the electric wire 5, and the electric connector 3 is connected to an amplifier 16.

The amplifier 16 is a device that is connected to the electrical connector 3 and amplifies the intensity information of the four types of transmitted light introduced from the electrical connector 3. In addition, this amplifier 1
6 is connected to an oxygenation degree calculation unit (calculation processing circuit) 17.

The oxygenation degree calculating section 17 is connected to the timing circuit 18 to identify the intensity information of the detected transmitted light based on the time division designated by the timing circuit 18 and to determine the intensity information of the detected tissue 8. Calculate the degree of oxygenation of all red blood cells.

Next, the operation procedure of the operation processing circuit 17 will be described. The intensity (intensity information) of the transmitted light received by the photodetector 7 is attenuated (changed) by not only absorption by blood in the tissue 8 but also scattering and absorption by the tissue 8 itself including body fluid. That is, according to the Bouguer-Lambert-Beer law, the intensity of the measurement light transmitted through the tissue 8 is exponentially related to the passing distance due to scattering and absorption by the tissue 8 itself. To decrease.

Therefore, the intensity I of transmitted light of a single wavelength can be generally expressed by the following equation (1). I = ηI ₀ exp (−α ₁ V ₁ L−α ₂ V ₂ L−μL) Expression (1) In Expression (1), I represents the transmitted light intensity detected by the photodetector 7, η indicates a coefficient relating to the optical system, I ₀ indicates an irradiated measurement light intensity, and exp () indicates an exponential function.

Α ₁ indicates the absorption coefficient of oxygenated erythrocytes per unit volume and unit optical path length, V ₁ indicates the volume of oxygenated erythrocytes, α ₂ indicates deoxygenation per unit volume and unit optical path length shows the absorption coefficient of the red blood cells, V ₂ represents the volume of deoxygenated red blood cells, mu is the tissue per unit length, the sum of all scattering coefficient and absorption coefficient, L is shown an optical path length.

The arithmetic processing circuit 17 determines the degree of oxygenation of blood in the tissue 8 (the ratio of the volume V ₁ of oxygenated red blood cells to the volume V ₂ of deoxygenated red blood cells). Then, in Equation (1), the absorption coefficient alpha ₂ of the absorption coefficient alpha ₁ and deoxygenated red blood oxygenation red blood cells, as shown in wavelength characteristic diagram of FIG. 3, is a measurable numerical by spectrophotometer However, the sum μ of the scattering coefficient and the absorption coefficient is an unknown number. However, it is known that the wavelength characteristics of the scattering coefficient and the absorption coefficient have linearity in a narrow wavelength region (particularly, in a near infrared region). For example, the wavelength characteristic diagram of FIG.
Fig.8 (IEEE TRANSACTIONS ON BIOMEDICAL
ENGINEERING. VOL.36. NO.12.DECEMBER 1989, P1152)
Is referred to. In FIG. 4, the scattering coefficient and the absorption coefficient are shown in experimental data (a), (b), (c), and (d).
The linearity is shown in the narrow wavelength region indicated by the broken line.

Therefore, the arithmetic processing circuit 17 expresses mathematical expressions indicating the transmission intensities of the measuring lights a, b, c, d based on the mathematical expression (1), and deletes the unknown μ from the mathematical expressions. At this time, since the random coefficient and the absorption coefficient (unknown number) show linear characteristics, the measurement is performed with the wavelength difference λ _ab between the measurement light b and the measurement light a based on the sum μ of the scattering coefficient and the absorption coefficient of the measurement light b. The sum of the scattering coefficient and the absorption coefficient of the light a is shown, and the wavelength difference λ _cb between the measurement light b and the measurement light c shows the sum of the scattering coefficient and the absorption coefficient of the measurement light c, and the wavelength difference between the measurement light b and the measurement light d. it is possible to indicate the sum of the scattering and absorption coefficients of the measured light d in lambda _d-b. Then, between the mathematical expressions, first, the sum μ of the scattering coefficient and the absorption coefficient of the measurement light b is deleted, and then the respective expressions are multiplied by the wavelength difference between them to obtain the scattering coefficient and the absorption coefficient of the measurement light a, c, and d. Is performed to eliminate the sum of.

That is, based on the equation (1), the photodetector 7
In the intensity of transmitted light detected four wavelengths I _a, I _b,
I _c and I _d are represented by the following equations (2), (3), (4), and
It can be expressed as (5).

I_a= ΗI_a0exp [｛(− ρ_Oσ_a−ρ_Dσ_b− (Μ−λ_ab(S + U))｝ L] Equation (2) I_b= ΗI_b0exp [｛(− ρ_Oσ_c−ρ_Dσ_d−μ｝ L] Equation (3) I_c= ΗI_c0exp [｛(− ρ_Oσ_e−ρ_Dσ_f− (Μ−λ_cb(S + U))｝ L] Equation (4) I_d= ΗI_d0exp [｛(− ρ_Oσ_g−ρ_Dσ_h− (Μ−λ_db(S + U))｝ L] Equation (5) where I_a0, I_b0, I_c0, I_d0Are a, b, c, d respectively
Indicates the measurement light (irradiation light) intensity of the light of
Indicates the coefficient involved, ρ₀ Is the unit tissue volume of oxygenated red blood cells
Per number density, ρ_D Is a unit set of deoxygenated red blood cells
Indicates the number density per woven volume, and ρ (= ρ_O+ Ρ_D) Is red blood
Indicates the number density per unit tissue volume of the sphere, σ_a Is I_a0light
Indicates the absorption cross section of oxygenated red blood cells at the wavelength, σ_b Is I_a0
Indicates the absorption cross section of deoxygenated red blood cells at the light wavelength, σ_c Is
I_b0Indicates the absorption cross section of oxygenated red blood cells at the light wavelength, σ_d 
Is I_b0Shows the absorption cross section of deoxygenated red blood cells at the light wavelength,
σ _e Is I_c0Shows the absorption cross section of oxygenated red blood cells at the optical wavelength
Then σ_f Is I_c0Absorption cross section of deoxygenated red blood cells at optical wavelengths
And σ_g Is I_d0Absorption cross section of oxygenated red blood cells at optical wavelengths
The product, σ_h Is I_d0Absorption of deoxygenated red blood cells at light wavelengths
L indicates the optical path length. Μ is I_b0Light wave
Shows the sum of the scattering coefficient and the absorption coefficient of the tissue 8 at the length, λ_ab 
Is I_a0Light and I_b0Indicates the wavelength difference of light, λ_cb Is I_c0Light and I
_b0Indicates the wavelength difference of light, λ_db Is I_d0Light and I_b0Light wavelength difference
And S indicates the slope of the tissue scattering coefficient with respect to wavelength.
U represents the slope of the absorption coefficient of the tissue with respect to the wavelength.

Therefore, in the equations (2) to (5),
The transmitted light intensities I _a , I _b , I _c , and I _d are numerical values detected by the light detector 7 for each transmitted light, and the measured light intensities I _a0 , I _b0 ,
I _c0 and I _d0 are numerical values preset by the light sources 11 to 14, and the absorption cross sections σ _{a to} σ _h are numerical values that can be measured by a spectrophotometer or the like, as shown in FIG. Is also a numerical value determined from the positions of the probe 6 and the photodetector 7.

Next, the arithmetic processing circuit 17 uses the equations (2) to (5) to determine the unknown “μ”, “S”, “U”
Perform an operation to delete. That is, from equation (2) to equation (5)
Is converted to logarithm, the following equation is obtained.

[0038] _{Δa / L = -ρ O σ a} -ρ D σ b - (μ-λ ab T) ... Equation (6) Δb / L = -ρ O σ c -ρ D σ d -μ ... Equation (7 ) Δc / L = −ρ _O σ _e −ρ _D σ _f − (μ−λ _cb T) Equation (8) Δd / L = −ρ _O σ _g −ρ _D σ _h − (μ−λ _db T) ... Equation (9) In order to simplify the equation, LN (I _a / ηI _a0 )
= Δa, LN (I _b / ηI _b0 ) = Δb, LN (I _c / ηI
_c0 ) = Δc, LN (I _d / ηI _d0 ) = Δd,
S + U = T (ie, “T” is unknown).

Then, when “μ” is eliminated by the equations (8) and (6), (Δc−Δa) / L = ρ _O (σ _a −σ _e ) + ρ _D (σ _b −σ _f ) + λ _ca T ... Equation (10) is obtained. Here, λ _cb -λ _ab = λ _ca was replaced.

Further, when “μ” is deleted from Expressions (7) and (9), (Δd−Δb) / L = ρ _O (σ _c −σ _g ) + ρ _D (σ _d −σ _h ) + λ _db T ... Equation (11) is obtained.

Next, the arithmetic processing circuit 17 deletes the unknown "T" using the equations (10) and (11). That is,
Equation (10) is _multiplied by λ _db and equation (11) is _multiplied by λ _ca to perform subtraction. (Δc−Δa) λ _db / L− (Δd−Δb) λ _ca / L = ρ _O ｛(σ _a −σ _e ) λ _db − (σ _c −σ _g ) λ _ca ｝ + ρ _D ｛(σ _b −σ _f ) λ _db − (σ _d −σ _h ) λ _ca ＝ = ρ [R ｛(σ _a − σ _e ) λ _db − (σ _c −σ _g ) λ _ca ｝ + (1−R) ｛(σ _b −σ _f ) λ _db − (σ _d −σ _h ) λ _ca ｝] can get. Here, R indicates the ratio (oxygenation degree) of the number of oxygenated red blood cells to the total number of red blood cells, and ρ _O = Rρ, ρ _D =
(1-R) ρ.

Similarly, when “μ” is eliminated by the equations (6) and (7), (Δa−Δb) / L = ρ _O (σ _c −σ _a ) + ρ _D (σ _d −σ _b ) + λ _ab T ... Equation (13) is obtained. Here, λ _cb −λ _ca = λ _ab was replaced.

Similarly, when “μ” is eliminated by the equations (7) and (8), (Δb−Δc) / L = ρ _O (σ _e −σ _c ) + ρ _D (σ _f −σ _d ) + λ _cb T ... Equation (14) is obtained.

Next, the arithmetic processing circuit 17 deletes the unknown "T" using the equations (13) and (14). That is,
When Expression (13) is _multiplied by λ _cb and Expression (14) is _multiplied by λ _ab to perform subtraction, (Δa−Δb) λ _cb / L− (Δb−Δc) λ _ab / L = ρ _O ｛(σ _c −σ _a ) λ _cb − (σ _e −σ _c ) λ _ab ｝ + ρ _D ｛(σ _d −σ _b ) λ _cb + (σ _f −σ _a ) λ _ab ｝ = ρ [R ｛(σ _c − σ _a ) λ _cb − (σ _e −σ _c ) λ _ab ｝ + (1−R) ｛(σ _d −σ _b ) λ _cb + (σ _f −σ _a ) λ _ab ｝] can get.

By the above calculations, the unknowns “μ”, “S”,
“U” can be deleted. Next, from this equation (15), the number density ρ per unit tissue volume of red blood cells is

[0046]

(Equation 1)

Is obtained. Further, the following equation is obtained from Equation (12). _{{(Δc-Δa) λ db} / L- (Δd-Δb) λ ca / L} / ρ = R {(σ a -σ e -σ b + σ f) λ db + (σ g -σ c + σ d - σ _h ) λ _ca ｝ + (σ _b −σ _f ) λ _db + (σ _h −σ _d ) λ _ca Equation (17) Here, to simplify the expression, (Δa−Δb) λ _cb =
A, (Δb−Δc) λ _ab = B, (Δc−Δc)
a) λ _db = C, (Δb−Δd) λ _ca = D,
(Σ _c −σ _a −σ _d + σ _b ) λ _cb = E, and (σ _e −σ _c −
σ _f + σ _a ) λ _ab = F, and (σ _a −σ _e −σ _b + σ _f ) λ
and _db = G, and _{(σ g -σ c + σ d} -σ h) λ ca = H,
(Σ _d −σ _b ) λ _cb = J, (σ _f −σ _a ) λ _ab = K, (σ _b −σ _f ) λ _db = M, (σ _h −σ _d ) λ _ca =
If N, the arithmetic processing circuit 17 calculates Equation (16) and Equation (17).
Thus, the oxygenation degree R of tissue blood is calculated as follows: R = {(A + B) (M + N)-(C + D) (J + K)} / {(C + D) (E + F)-(G + H) (A + B)} Equation (18) Can be obtained by

The arithmetic processing circuit 17 can calculate the number density ρ of red blood cells per unit tissue volume by the following equation: ρ = {(A + B) / L} / {R (E + F) + J + K} (19) .

Next, the operation of the living tissue blood oxygenation degree measuring apparatus of the present invention will be described. It is assumed that predetermined numerical values required for the arithmetic processing circuit 17 to perform the arithmetic operation, such as the intensity of the measurement light, the absorption cross sections σ _{a to} σ _h, and the optical path length L are set in advance. Further, it is assumed that the optical fiber 4 is connected to the apparatus main body via the optical connector 2, and the electric wire 5 is connected to the apparatus main body via the electric connector 3.

A user (hereinafter, referred to as a user) of the living tissue blood oxygenation degree measuring apparatus of the present invention arranges the probe 6 provided at the end of the optical fiber 4 in close contact with the upper surface of the tissue 8 to be measured. Further, the user closely arranges the photodetector 7 at a position separated by a predetermined distance (for example, 5 cm) from the close contact position of the probe 6.

Next, when the user starts the apparatus main body 1, the drive circuit 19 drives the light sources 11, 12, 13, and 13 based on the timing of the pulse wave of the timing circuit 17.
14 is supplied in a time sharing manner. Then, the measuring lights a, b,
c and d are output to the optical multiplexer 15 in a time division manner, and are sequentially guided to the optical fiber 4.

The guided measurement light beams a, b, c, and d are output from the probe 6 into the tissue 8 and are attenuated by scattering and absorption when passing through a body fluid containing blood in the tissue 8. Next, the photodetector 7 sequentially receives the attenuated transmitted lights, which are the measurement lights a, b, c, and d, and detects the intensity of the transmitted light. Then, the photodetector 7 notifies the amplifier 16 of the detected value as intensity information for each measurement light via the electric wire 5 and the electrical connector 3.

Then, the amplifier 16 amplifies the notified intensity information for each measurement light and notifies the arithmetic processing circuit 17 of the amplified intensity information.
Then, based on the timing of the pulse wave of the timing circuit 17, the arithmetic processing circuit 17 sends the notified measurement light a,
In addition to identifying the intensity information of b, c, and d, the oxygenation degree R and the number density ρ of all the red blood cells in the tissue 8 are calculated according to a predetermined calculation procedure. That is, the arithmetic processing circuit 17
Is based on the intensity information for each transmitted light and the measured light intensity at the time of irradiation, removes the amount of light absorption caused by scattering and absorption by the tissue 8 itself, and provides the oxygenation degree R and number density for all red blood cells in the tissue 8 Calculate ρ. Then, the calculated degree of oxygenation R and number density ρ are output from the arithmetic processing circuit 17 to external display means (not shown) and displayed.

In the above embodiment, the laser diode is used as the light source. However, the light source is not limited to the laser diode. Or a light emitting diode.

In the above-described embodiment, the description has been made using the electrical connector 3, the electric wire 5, and the photodiode 7 as the detection unit. However, the detection unit has the same configuration as the optical connector 2, the optical fiber 4, and the probe 6 of the measurement light output unit. Alternatively, the detection unit may be configured as the optical connector 3, the optical fiber 5, and the light receiving probe 7 in which the tip of the optical fiber 5 is processed. However, the detection unit is an optical connector 3, an optical fiber 5, and a light receiving probe 7.
, The amplifier 16 includes a photoelectric conversion circuit.

[0056]

As described above, according to the present invention, the amount of light absorbed in the living tissue obtained from the intensity difference between the four or more types of measuring light and the transmitted light or the scattered light is determined by the scattering and absorption by the living tissue itself. The generated light absorption amount is removed, and the degree of oxygenation with respect to all red blood cells in the living tissue can be calculated.

Therefore, it is possible to provide a living tissue blood oxygenation degree measuring apparatus capable of easily and directly measuring the oxygenation degree of blood in the living tissue.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a living tissue blood oxygenation degree measuring device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a pulse of a timing circuit.

FIG. 3 is a wavelength characteristic diagram of light absorption coefficient of oxygenated hemoglobin and deoxygenated hemoglobin.

FIG. 4 is a wavelength characteristic diagram of a scattering coefficient and an absorption coefficient.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Device main body 2, 3 Optical connector 4, 5 Optical fiber 6 Probe 7 Photodetector 8 Living tissue (tissue) 11, 12, 13, 14 Light source (laser diode) 15 Optical multiplexer 16 Amplifier (amplifier) 17 Operation processing circuit 18 Timing circuit

Claims (1)

[Claims] 1. A measuring light output section for directly irradiating living tissue with four or more types of near-infrared measuring lights having wavelengths close to each other at a predetermined intensity, and transmitting the output measuring light through the living tissue. A detection unit that detects the intensity of light or scattered light, and the amount of light absorbed in the living tissue obtained from the output measurement light and the detected difference in transmitted light or scattered light intensity. A living body comprising: an oxygenation degree calculation unit that calculates an oxygenation degree that is a ratio of the number of oxygenated red blood cells to the total number of red blood cells, or an oxygenation degree that is a ratio of the amount of oxygenated hemoglobin to the total amount of hemoglobin. Tissue blood oxygenation degree measurement device.