JP3035791B2 - Method and apparatus for measuring light-absorbing substance concentration in living tissue and thickness of intervening tissue in living body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for non-invasively measuring the concentration of a light-absorbing substance such as hemoglobin in a living tissue using near-infrared light, and a living body surface and a light-absorbing substance to be measured. The present invention relates to a method for measuring the thickness of a tissue interposed between a living tissue and a living tissue mainly present, and a measuring device therefor.

BACKGROUND ART For example, a tissue oxygen measurement device using near-infrared light emits near-infrared light from the surface of a living body, receives reflected light from living tissue, and measures tissue oxygen based on the amount of received light. is there. For example, Japanese Patent Publication No. 4-502563 discloses a hemoglobin meter that can be worn by a user, which measures the metabolic state of a test subject during exercise by near-infrared light. Such a device is extremely useful for knowing the temporal change in tissue metabolism of the brain and muscle, and is expected in patient monitoring, emergency medicine, rehabilitation medicine, sports medicine, and the like.

By the way, when a light-absorbing substance such as oxyhemoglobin in a muscle tissue is measured from the surface of a living body by near-infrared light, the subcutaneous fat layer as an intervening tissue has less light absorption than a muscle tissue because almost no blood is present. It is about an order of magnitude smaller and transmits near infrared light well. However, in the conventional apparatus, for example, oxygen in muscle tissue is not measured by distinguishing between muscle tissue and subcutaneous fat layer, and measurement without considering the influence of intervening tissue such as fat layer uses near infrared light. With the widespread use of tissue oxygen measurement, it becomes a major problem.

That is, for example, when measuring muscle tissue, if a subcutaneous fat layer is interposed between the surface of the living body and the muscle tissue, the measurement includes the fat layer, and the measurement sensitivity is greatly affected by the thickness of the fat layer. Will change. This is also the case when measuring brain tissue.The skull exists between the head surface and the brain tissue, and the cerebrospinal fluid exists between the skull and the brain tissue. And the measurement sensitivity greatly changes. For this reason, measurement values cannot be compared between individuals, and the measurement values are only used as relative values for measuring the change speed and the change pattern, but cannot be evaluated as absolute values, and thus are not used for diagnosis.

Unlike the continuous light method, a method of measuring the absolute value of oxygen saturation by a method such as a time-resolved method has also been developed. The presence of such an intervening tissue greatly affects the measured values. Such a problem is a major problem common to both systems, such as a continuous light system and a time-resolved system.

The present invention has been made in view of such a conventional problem, and it is intended to measure the concentration of a light absorbing substance without being affected by the thickness of an intervening tissue between a living body surface and a tissue to be measured. It is an object of the present invention to provide a method and a device for measuring the concentration of a light-absorbing substance in a living tissue, which can be performed.

Another object of the present invention is to provide a method and a device for measuring the thickness of an intervening tissue in a living body, which can measure the thickness of the intervening tissue between the surface of the living body and the living tissue mainly containing the light-absorbing substance to be measured. That is.

DISCLOSURE OF THE INVENTION In order to achieve the above object, according to an aspect of the present invention, a measurement method measures an absorbance change on a material surface by a plurality of sensors having different distances between transmission and reception, and based on a ratio of the obtained absorbance change. And calculating the thickness of the light absorbing substance layer.

According to another aspect of the present invention, a measurement method measures a change in absorbance in a biological tissue with a plurality of sensors or a single sensor having different distances between transmission and reception, and based on a ratio of the obtained change in absorbance, a light-absorbing substance. It is characterized in that the thickness of the layer is calculated.

According to another aspect of the present invention, a measurement method measures a change in absorbance on the surface of a living body with a plurality of sensors or a single sensor having different distances between sending and receiving light, and based on a ratio of the obtained absorbance change, a method for measuring fat in vivo. It is characterized in that the thickness of the layer is calculated.

According to another aspect of the present invention, the measurement method includes a plurality of sensors or a single sensor having different transmission / reception distances.
A linear change in the amount of received light when the amount of emitted light was changed linearly with respect to the living body was measured, and a proportional coefficient related to the obtained linear change was obtained from the known transmission / reception distance of the sensor. The thickness of the light-absorbing substance layer is calculated based on the proportional coefficient.

According to another aspect of the present invention, a light-absorbing material layer thickness measuring device includes a plurality of sensors or one sensor having different distances between transmission and reception, and an absorbance change measuring device that measures an absorbance change with respect to the thickness of the light-absorbing material layer using the sensor. Means, and a light-absorbing material layer thickness calculating means for calculating the thickness of the light-absorbing material layer based on the obtained ratio of the change in absorbance.

According to another aspect of the present invention, an apparatus for measuring a fat layer thickness of a living body includes a plurality of sensors or one sensor having different distances between transmission and reception, and an absorbance change measuring unit configured to measure an absorbance change on the surface of the living body with the sensor. And a fat layer thickness calculating means for calculating the thickness of the fat layer based on the obtained ratio of the change in absorbance.

According to another aspect of the present invention, an apparatus for measuring the thickness of an intervening tissue of a living body includes a plurality of sensors or ones having different distances between transmission and reception.
Sensor, light-receiving-amount measuring means for measuring a linear change in the received light amount when the light-emitting amount is linearly changed with respect to the living body by the sensor, and a sensor for calculating a proportional coefficient relating to the obtained linear change. The intervening tissue thickness calculating means for calculating the thickness of the intervening tissue between the living tissue where the light-absorbing substance to be measured mainly exists and the living body surface, based on the known transmission-reception distance, and based on the obtained proportionality coefficient. It is characterized by having.

More preferably, the sensor has a plurality of light emitting elements having different wavelengths.

More preferably, the measuring device has a plurality of mounting portions for detachably holding the light emitting element or the light receiving element of the sensor, and has a probe for changing the distance between transmission and reception by the plurality of mounting portions.

According to another aspect of the present invention, a method of measuring the concentration of a light-absorbing substance in a living tissue is performed by using a plurality of sensors or a single sensor having different distances between transmission and reception by using a biological tissue and a living body surface where the light-absorbing substance to be measured mainly exists. Measure the thickness of the intervening tissue between, determine the change in measurement sensitivity at each transmission and reception distance to the thickness of the intervening tissue, and based on the change in the measurement sensitivity, the thickness of the intervening tissue and a correction coefficient for the measurement sensitivity and And a correction coefficient is calculated from the relationship between the known inter-transmission / reception distance of the sensor and the thickness of the intervening tissue at the measurement target site, and measurement is performed based on the obtained correction coefficient so as not to be affected by the intervening tissue. The value is corrected.

More preferably, the thickness of the intervening tissue is determined in advance based on the amount of received light with respect to the thickness of the intervening tissue and the amount of transmitted light at that time is set, and the amount of transmitted light is measured based on the amount of received light when the living body is irradiated. It is characterized by.

According to another aspect of the present invention, a light-absorbing substance concentration measuring device includes a plurality of sensors or one sensor having different distances between transmission and reception, and a living tissue and a living body surface where the light-absorbing substance to be measured is mainly present by the sensor. Intervening tissue thickness measuring means for measuring the thickness of the intervening tissue, measuring sensitivity calculating means for determining a change in the measuring sensitivity at each distance between the transmitting and receiving light with respect to the intervening tissue thickness, and interposing based on the change in the measuring sensitivity. Correction coefficient calculating means for determining the relationship between the thickness of the tissue and the correction coefficient for the measurement sensitivity, and determining the correction coefficient from the relationship between the known inter-transmission / reception distance of the sensor and the thickness of the intervening tissue at the measurement target site from the relationship; Measurement value correction means for correcting the measurement value based on the corrected coefficient so as not to be affected by the intervening tissue.

More preferably, the intervening tissue thickness measuring means obtains the amount of received light with respect to the thickness of the intervening tissue in advance, sets the amount of transmitted light at that time, and calculates the amount of transmitted light based on the amount of received light when the living body is irradiated with the amount of transmitted light during measurement. It is characterized by being.

More preferably, the sensor has near-infrared multi-wavelength light emitting elements having different wavelengths.

More preferably, the distance between the sending and receiving of the sensor is 20 mm, 30
mm, 40 mm.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a measuring device according to a first embodiment of the present invention.

2A to 2C are diagrams showing changes in oxygen (oxyhemoglobin) when a load and a no-load exercise by an automobile ergometer are alternately repeated.

FIG. 3 is a diagram showing a change in oxygen (oxygenated hemoglobin) with respect to the thickness of the fat layer at each transmission / reception distance (20, 30, 40 mm).

FIG. 4 is a diagram showing a change in absorbance with respect to the thickness of the fat layer at each inter-transmission / reception distance (20, 30, 40 mm). FIG. 5 is a diagram illustrating the fat layer at each inter-transmission / reception distance (20, 30, 40 mm). FIG. 6 is a diagram showing a relationship between the thickness of the image and the correction coefficient.

FIG. 6 is a diagram showing a change in the received light current value with respect to the thickness of the fat layer at each of the inter-transmission / reception distances (20, 30, 40 mm).

FIG. 7 is a diagram showing a change in received light intensity with respect to the thickness of the fat layer at each distance between transmission and reception (20, 30, 40 mm).

FIG. 8 is a diagram for explaining the principle of the measurement method according to the second embodiment of the present invention, showing the relationship between the thickness of the fat layer and the change in absorbance.

9A and 9B are diagrams illustrating the relationship between the amount of emitted light and the amount of received light for explaining the principle of the measurement method according to the second embodiment of the present invention.

FIG. 10 is a diagram illustrating the relationship between the thickness of the fat layer and the log of the slope at each distance between light transmission and reception for describing a modification of the measurement method according to the second embodiment of the present invention.

11A to 11C are external views showing the configuration of a probe according to the third embodiment of the present invention.

12A to 12C show that the distance between the light emitting unit 110 and the light receiving unit 112 is different.
It is an external view of the probe which is 10 mm.

13A to 13C show that the distance between the light emitting unit 110 and the light receiving unit 112 is different.
It is an external view of the probe which is 20 mm.

14A to 14C show that the distance between the light emitting unit 110 and the light receiving unit 112 is different.
It is an external view of the probe which is 30 mm.

15A to 15C show that the distance between the light emitting unit 110 and the light receiving unit 112 is different.
It is an external view of the probe which is 40 mm.

FIG. 16 is a block diagram illustrating a configuration of a measuring device according to the fourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the accompanying drawings.

First Embodiment FIG. 1 is a block diagram illustrating a configuration of a measurement device according to a first embodiment of the present invention.

This measuring device includes a probe 10 mounted on the surface of a living body (tissue) 1 and a main body 20 connected to the probe 10 by a cable or the like.

The probe 10 includes a light emitting element 11 as a light source for irradiating the living body 1 with light, three photodiodes (PD) 12, 13, and 14 as light receiving elements for receiving reflected light from the living body 1, and each PD.
It has amplifiers 15, 16, and 17 that amplify the light receiving signals of 12, 13, and 14 to low impedance signals in the first stage in order to improve the S / N.

The light-emitting element 11 is composed of near-infrared two-wavelength light-emitting diodes (LEDs, wavelengths: 760 nm and 840 nm) having different wavelengths.
The PDs 12, 13, and 14 are arranged at a distance of 20 mm, 30 mm, and 40 mm from the LED 11, respectively. Thereby, the reflected light from the living body 1 can be simultaneously received at three different positions. In this embodiment, a sensor is constituted by the LED 11 and the PDs 12 to 14.

The main body 20 includes an LED driver 21 for driving the LED 11 and each PD 1
It has a multiplexer 22 for switching signals from 2, 13, and 14, an amplifier 23 for amplifying the switched signals, and a CPU 24. Further, the body 20 is not shown in FIG.
D, memory card interface, power supply, etc.
The amplifier 23 converts the signal amplified at the first stage into a 20-
Amplify up to 2000 times.

The CPU 24 controls the timing of light emission so that the LED 11 alternately repeats lighting at each wavelength, and also adjusts the amount of light via a D / A converter. Also, the CPU 24 has an intervening tissue thickness measurement function of measuring the thickness of the intervening tissue between the living tissue and the living body surface where the light-absorbing substance to be measured mainly exists by the sensor,
A measurement sensitivity calculation function that calculates the change in measurement sensitivity at each inter-transmit / receive distance with respect to the thickness of the intervening tissue, and a correction coefficient calculation function that calculates the relationship between the thickness of the intervening tissue and the correction coefficient for the measurement sensitivity based on the change in the measurement sensitivity From the relationship, a correction coefficient is calculated based on the known distance between the transmitting and receiving light of the sensor and the thickness of the intervening tissue at the measurement target site, and the measurement is performed based on the obtained correction coefficient so that the measured value is corrected so as not to be affected by the intervening tissue. It has a value correction function and the like. The LCD displays information necessary for measurement so that the measurement state and conditions can be checked.

The measuring device composed of the probe 10 and the main body 20 may be used alone (this kind of use is called off-line use). However, as shown in FIG. A connection may be made via a serial input / output line such as −232C, and a CRT 31 may be further connected to the personal computer 30 (this use is called online use).

In this case, the measurement data of the main body 20 is taken into the personal computer 30 via the RS-232C at the time of online use, and the real-time data such as a change in the concentration of the light-absorbing substance (oxyhemoglobin, etc.), a change in the blood volume, the thickness of the intervening tissue, etc. Are stored in the memory card inserted into the main unit 20 when the device is used offline.

Next, a method of correcting a measured value using the measuring device configured as described above will be described.

First, using a measuring device shown in Fig. 1, a 120W load and no load (empty row) exercise by a car ergometer is repeated every 30 seconds, and the amount of oxygen change of the thigh outside wide muscle during the exercise is measured. The results obtained are shown in FIGS.

Here, the oxyhemoglobin (HbO ₂ ) concentration in the living tissue is measured, and FIG. 2A shows the case where the distance between sending and receiving is 20 mm.
FIG. 2B shows a case of 30 mm, and FIG. 2C shows a case of 40 mm. Figures 2A-2C
From this, it can be seen that the longer the distance between transmission and reception, the greater the measurement sensitivity of oxygen change. This is because the average optical path length increases with an increase in the distance between light transmission and reception, so that a deeper tissue can be measured.

The average value of the oxygen concentration change width at each transmission / reception distance is
The result of plotting based on the measured values by 13 subjects is shown in FIG. 3 (relationship between fat layer thickness and oxygen concentration). FIG. 4 (relationship between thickness of fat layer and change in absorbance) shows the result of theoretical calculation by Monte Carlo simulation.
Both results agree very well, and it can be seen that the measurement sensitivity changes depending on the thickness of the fat layer, that is, the measurement sensitivity greatly decreases irrespective of the distance between transmission and reception when the fat layer becomes thicker.

The following processing is performed to correct the measurement sensitivity.
For example, as shown in FIG. 4, using a theoretical curve of a change in absorbance (measurement sensitivity) with respect to the thickness of the fat layer at each distance between transmission and reception, a polynomial approximation formula of this curve is obtained. From the obtained polynomial approximation formula, the ratio to the oxygen change when the thickness of the fat layer is 0 at each transmission / reception distance is obtained, and the reciprocal of the obtained ratio is used as a correction coefficient.

Fig. 5 shows the thickness range of practical fat layer (about 0 to 12mm)
FIG. 5 is a diagram showing a relationship between a correction coefficient and a thickness of a fat layer at each inter-transmission / reception distance in FIG.

If the distance between transmission and reception is known from the relationship between the thickness of the fat layer and the correction coefficient and the thickness of the fat layer at the measurement target site is known, the correction coefficient at that time can be obtained. Further, by multiplying the measured value by the obtained correction coefficient, it is possible to correct the measurement sensitivity (that is, the measured value) when the thickness of the fat layer is 0. For example, if the distance between the sending and receiving light is 20 mm and the thickness of the fat layer is 8 mm, the correction coefficient is about 4.2 from FIG. 5, and if this 4.2 is multiplied by the measured value,
It is possible to calculate a measurement value that is not affected by the thickness of the fat layer.

On the other hand, from FIG. 3 showing the relationship between the thickness of the fat layer and the measurement sensitivity, the measurement sensitivity can be corrected if the thickness of the fat layer is known and the distance between transmission and reception is known.

In the above embodiment, the known fat layer thickness is used to obtain the correction coefficient. However, in order to calculate the fat layer thickness using the measurement device, for example, the following processing is performed.

FIG. 6 is a graph showing the relationship between the thickness of the fat layer and the distance between light transmission and reception, with the initial value of the measured light amount in the measurement state in which the probe 11 is attached to the measurement site as the light reception current value in each of the light receiving elements 12, 13, and 14. Shown in

FIG. 7 shows theoretical calculation results of the same relationship (the relationship between the thickness of the fat layer and the intensity of received light at each inter-transmission / reception distance) by Monte Carlo simulation. According to these, it can be seen that both have almost the same results.

Therefore, the amount of received light when the thickness of the fat layer is all is determined in advance, the amount of transmitted light at that time is set, and calibration is performed using a phantom or the like so that the amount of transmitted light is measured at the time of measurement. The thickness of the fat layer at the measurement site can be calculated from the amount of light received when the living body is irradiated with the amount of transmitted light, using the following calculation formula obtained from FIG. 7 based on theoretical calculation.

That is, the thickness H of the fat layer is calculated as follows: H = {log (I / 2200) +1.241} /0.113 (I: about 0 to 3600 when inputting an A / D with an emission wavelength of 840 nm at a distance between transmission and reception of 40 mm) Can be

In the above embodiment, the thickness of the fat layer is measured by the measuring device as an example, but may be obtained by another measuring method such as an ultrasonic method. In the above embodiment, the thickness of the fat layer is measured. However, other intervening tissues (skull, skin, cerebrospinal fluid, etc.) can be measured in the same manner, and the light absorbing material is not affected by the thickness. The concentration can be measured.

Further, in the above embodiment, one LE is used as a sensor.
Although D and three PDs are used, conversely, three LEDs and one PD may be used, or one LED and one PD may be used. However, by using a plurality of sensors having different transmission / reception distances, the measurement area is expanded.

Further, in the above-described embodiment, the thickness of the fat layer of the living body is measured, but the thickness of, for example, meat other than the living body can also be measured.

As described above, according to the method and the apparatus for measuring the concentration of the light-absorbing substance in the living tissue in the present embodiment,
In any case, the thickness of the intervening tissue (skin, skull, subcutaneous fat layer, cerebrospinal fluid, etc.) between the living tissue to be measured and the surface of the living body can be removed and the concentration of the light-absorbing substance can be measured. .

(1) Individual differences in measurement can be eliminated, and measured values can be quantitatively compared between individuals.

(2) The measured value can be used as an absolute value index.

(3) At the same time as the measurement, information on the thickness of the intervening tissue can be measured and displayed.

(4) Due to the effects of the above (1) to (3), the physiological significance at the time of measurement is large, and it is extremely useful for clinical diagnosis.

[Second Embodiment] The hardware configuration of a measuring apparatus according to a second embodiment of the present invention is the same as that of the first embodiment, and thus description thereof will not be repeated.

Hereinafter, the principle of measuring the thickness of the intervening tissue (fat layer) in the living body by the measuring device according to the present embodiment will be described.

(First Measurement Method) First, the first measurement method will be described. Figure 8 shows LE
9 is a graph showing the relationship between the thickness of a fat layer obtained in each of PDs 12, 13, and 14 having different distances from D11 and the change in absorbance measured on the surface of a living body when the absorbance of muscle tissue changes.

From this graph, it can be seen that the measurement sensitivity greatly changes depending on the thickness of the fat layer, that the degree of decrease in the measurement sensitivity differs depending on the distance between transmission and reception, and that the ratio of the change in absorbance at each distance differs. Here, for example, when the thickness of the fat layer is about 4 mm, 7 mm, and 10 mm, the ratio of the change in absorbance at each distance is shown in a bar graph shown in FIG. According to the ratio of the change in absorbance, when the thickness of the fat layer is small, the change in absorbance at the distance between transmission and reception of 20 mm is relatively large, and when the thickness of the fat layer is large, the distance between transmission and reception is 30 mm and 40 mm. Has a relatively large absorbance change.

Therefore, within the range of the actual measurement (the thickness of the fat layer is about 4 to 12 mm), the thickness of the fat layer can be calculated by calculating the ratio of the change in absorbance at each distance between transmission and reception.

However, while measuring the thickness of the fat layer, the thickness of the fat layer can be calculated by using the fluctuation itself during the measurement. When calculating the thickness, it is necessary to change the oxygen concentration. To do this, for example:-Press the probe strongly against the measuring part of the living body.

・ Cuff cuffs the measuring unit.

-Heat the measuring section.

-Raise or lower the height of the measurement unit with respect to the height of the heart.

And so on.

(Second Measurement Method) Next, a second measurement method will be described. The amount of received light with respect to the thickness of the fat layer when the amount of light emitted from the LED 11 is changed linearly changes linearly as shown in FIG. 9A. According to this, the larger the thickness of the fat layer, the larger the change in the amount of received light. Further, when the amount of light emitted from the LED 11 is changed linearly, the amount of received light with respect to the distance between transmission and reception changes linearly as shown in FIG. 9B. According to this, the change in the amount of received light is smaller when the distance between transmission and reception is longer. In other words, the proportional coefficient relating to the linear change when the thickness of the fat layer is large is large,
When the distance between transmission and reception is long, the proportional coefficient relating to the linear change becomes small.

Therefore, the proportional coefficient of this linear change can be obtained from the known distance between transmission and reception (here, 20 mm, 30 mm, and 40 mm), and the thickness of the fat layer can be calculated based on the obtained proportional coefficient.

As a modification of this measuring method, the thickness of the fat layer can also be calculated by calculating the coefficients in the same manner for the different distances between the transmitting and receiving light and calculating the ratio of the coefficients.

For example, here, the distance between sending and receiving light is 20mm, 30mm, 40mm
Therefore, as shown in FIG. 10, taking the length log at each distance, the thickness ratios of the fat layers a and b at the distances of 20 mm and 40 mm are a1 / a2 and b1 / b2, respectively. And the ratio of the coefficients differs depending on the thickness of the fat layer. Therefore, the thickness of the fat layer can be calculated by calculating the ratio of the coefficients at different distances between the transmission and reception.

According to the second measurement method, there is an advantage that it is not necessary to calibrate the light emission amount of the LED 11 first. In addition, since the thickness of the fat layer is calculated from several different data, the thickness of the fat layer can be calculated stably and accurately, the amount of light is less likely to be saturated, and the range of the thickness of the fat layer that can be calculated. In addition, there is an advantage that the distance between light transmission and reception and the light amount optimal for measurement can be selected.

In the above embodiment, the case where the thickness of the fat layer is measured as an intervening tissue has been described, but the case of a skull, cerebrospinal fluid, etc. interposed between the head surface and the brain tissue when measuring the brain tissue Can be similarly measured.

Further, in the above embodiment, one LED and three PDs are used as sensors, but three LEDs and one PD may be used on the contrary, or one LED and one PD may be used. It does not matter. However, by using a plurality of sensors having different transmission / reception distances, the measurement area is expanded.

Furthermore, in the present embodiment, measurement of a living body is performed, but measurement of meat other than a living body, such as meat, may be performed.

As described above, according to the method and the apparatus for measuring the thickness of an intervening tissue in a living body according to the present embodiment, any of the tissues (skin, skull, subcutaneous, Fat layer, cerebrospinal fluid, etc.), so that not only the thickness of the intervening tissue itself can be measured, but also by using it, oxygen measurement of the living tissue to be measured without being affected by the thickness of the intervening tissue Can be performed with high accuracy.

Third Embodiment FIGS. 11A to 11C are diagrams showing a configuration of a probe used in a measuring apparatus according to a third embodiment of the present invention.
11A is a side view, FIG. 11B is a plan view, and FIG. 11C is a front view.

Referring to the drawing, the probe includes a connector 101 for connecting to the main body, a probe base 100 made of silicon rubber for detachably attaching a light receiving section, a cable 102 for connecting the probe base and the connector, and a probe base. The light-emitting unit 110 includes a light-emitting unit 110 fixed to 100 and light-receiving unit mounting units 111a to 111d for detachably mounting the light-receiving unit 10 mm to 40 mm from the light-emitting unit at intervals of 10 mm.

In this embodiment, the light emitting unit 110 has two identical LEDs mounted thereon to increase the amount of light. However, if one LED can secure a sufficient amount of light, one LED may be attached to the probe base.

In the present embodiment, the light receiving unit is set at 10 to 40
The distance is set to 10 mm for each 10 mm and is detachable. Therefore, even if a plurality of light receiving units are not used, the measurement is performed with the arrangement of the light receiving units having different intervals of 2 to 4 times, and the results are combined. -The same effects as those of the second embodiment can be obtained.

FIGS. 12A to 15C show that the distance between the light emitting unit and the light receiving unit is
It is a figure showing the state which is 10 mm, 20 mm, 30 mm, and 40 mm.

Fourth Embodiment FIG. 16 is a block diagram illustrating a configuration of a measuring device according to a fourth embodiment of the present invention.

Referring to the figure, the measuring device is roughly a measuring device main body 200.
And a probe 200.

The probe is a light emitting diode (LED) 211-213, a photodiode (light receiving element) 210, and an amplifier 21 that amplifies the signal from the photodiode to a low impedance signal in the first stage.
And 4 inclusive. At the time of measurement, the probe 200 is attached to the living tissue 1.

The main body 220 includes an amplifier 221 for further amplifying a signal from the amplifier 214, LED drivers 222 to 224 for driving light emitting diodes, and a CPU 225.

The main body 220 is connected to the personal computer 30 and the CRT 31.

In the present embodiment, one photodiode 210 and three light emitting diodes 211 to 213 are used as sensors. As a result, the distance between the photodiode and the light emitting diode can be changed in the same manner as in the first and second embodiments, and the concentration of the light absorbing substance in the living tissue and the thickness of the intervening tissue in the living body can be measured. it can.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the concentration of a light-absorbing substance in a living tissue and the thickness of an intervening tissue in a living body can be accurately measured. Can be applied.

Continuation of the front page (72) Inventor Kazuhisa Tabe 10 Okado Dodocho, Ukyo-ku, Kyoto-shi, Kyoto Omron Corporation (56) References JP-A-9-168531 (JP, A) JP-A-8-182654 (JP) (A) JP-A-4-132540 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 A61B 5/06-5/22

Claims (17)

(57) [Claims] 1. A method of measuring a change in absorbance on a material surface with a plurality of sensors having different distances between transmission and reception, and calculating a thickness of a light-absorbing material layer based on a ratio of the obtained change in absorbance. Measurement method of material layer thickness. 2. A method of measuring a change in absorbance in a living tissue with a plurality of sensors or a single sensor having different distances between transmission and reception.
A method for measuring the thickness of a light-absorbing substance layer of a living body, comprising calculating the thickness of a light-absorbing substance layer based on the obtained ratio of absorbance change. 3. A method of measuring a change in absorbance on the surface of a living body using a plurality of sensors or a single sensor having different distances between transmission and reception, and calculating a thickness of a fat layer in the living body based on a ratio of the obtained change in absorbance. Characteristic method for measuring fat layer thickness of a living body. 4. A linear change in the amount of received light when the amount of emitted light is linearly changed with respect to a living body is measured by a plurality of sensors or one sensor having different distances between transmission and reception. A method for measuring the thickness of a light-absorbing substance layer of a living body, wherein a proportional coefficient relating to a change is obtained from a known distance between the sensor and the sensor, and a thickness of the light-absorbing substance layer is calculated based on the obtained proportional coefficient. 5. A plurality of sensors or one sensor having different distances between sending and receiving light, an absorbance change measuring means for measuring an absorbance change with respect to the thickness of the light absorbing material layer using the sensor, and a ratio of the obtained absorbance change. A light-absorbing substance layer thickness calculating means for calculating the thickness of the light-absorbing substance layer. 6. A plurality of sensors or one sensor having different distances between transmitting and receiving light, an absorbance change measuring means for measuring an absorbance change on the surface of a living body with the sensor, and a sensor for detecting a change in the fat layer based on a ratio of the obtained absorbance change. Characterized by comprising a fat layer thickness calculating means for calculating the thickness,
Measuring device for fat thickness of living body. 7. A plurality of sensors or one sensor having different distances between transmission and reception, and a sensor for detecting a linear change in the amount of received light when the amount of emitted light is linearly changed with respect to a living body using the sensor. Measuring means, the proportional coefficient according to the obtained linear change is determined by the known inter-transmission / reception distance of the sensor, and based on the determined proportional coefficient, the biological tissue and the biological surface mainly containing the light-absorbing substance to be measured are determined. And an intervening tissue thickness calculating means for calculating the thickness of the intervening tissue between the two. 8. The thickness measuring device according to claim 5, wherein said sensor has a plurality of light emitting elements having different wavelengths. 9. A sensor having a plurality of mounting portions for detachably holding a light emitting element or a light receiving element of the sensor, and a probe for varying the distance between the light transmitting and receiving light by the plurality of mounting portions. To claim 5
Item 8. The thickness measuring device according to any one of items 7 to 7. 10. A method for measuring the thickness of an intervening tissue between a living tissue mainly containing a light-absorbing substance to be measured and a living body surface using a plurality of sensors or a single sensor having different distances between transmission and reception. The change in the measurement sensitivity at each inter-transmission / reception distance with respect to is determined, and the relationship between the thickness of the intervening tissue and the correction coefficient of the measurement sensitivity is determined based on the change in the measurement sensitivity. A light-absorbing substance in living tissue, wherein a correction coefficient is obtained based on the distance and the thickness of the intervening tissue at the measurement target site, and the measured value is corrected based on the obtained correction coefficient so as not to be affected by the intervening tissue. How to measure the concentration. 11. The thickness of the intervening tissue is calculated in advance based on the amount of light received with respect to the thickness of the intervening tissue, the amount of light transmitted at that time is set, and the amount of light transmitted is applied to the living body at the time of measurement. 11. The method for measuring the concentration of a light-absorbing substance in a biological tissue according to claim 10, wherein: 12. A plurality of sensors or one sensor having different distances between transmitting and receiving light, and an intervening tissue for measuring the thickness of the intervening tissue between the living tissue and the living body surface mainly containing the light-absorbing substance to be measured by the sensor. Thickness measuring means; measuring sensitivity calculating means for determining a change in measurement sensitivity at each inter-transmit / receive distance with respect to the thickness of the intervening tissue; and a relationship between the thickness of the intervening tissue and a correction coefficient of the measuring sensitivity based on the change in the measuring sensitivity. And a correction coefficient calculating means for obtaining a correction coefficient from the relationship between the known transmission / reception distance of the sensor and the thickness of the intervening tissue at the measurement target site based on the relationship, and there is no influence of the intervening tissue based on the obtained correction coefficient. And a measurement value correcting means for correcting the measurement value as described above. 13. The intervening tissue thickness measuring means obtains the amount of received light with respect to the thickness of the intervening tissue in advance, sets the amount of transmitted light at that time, and based on the amount of received light when irradiating the living body with the amount of transmitted light during measurement. 13. The apparatus for measuring the concentration of a light-absorbing substance in a biological tissue according to claim 12, wherein the measurement is performed by calculation. 14. A sensor according to claim 1, wherein said sensor has near-infrared multi-wavelength light emitting elements having different wavelengths.
14. The measuring device for measuring the concentration of a light-absorbing substance in a biological tissue according to item 12 or 13. 15. The distance between transmission and reception of the sensor is 20 mm, 30
13. The measuring apparatus for measuring the concentration of a light-absorbing substance in a biological tissue according to claim 12, wherein the measuring distance is mm and 40 mm. 16. The distance between transmission and reception of the sensor is 20 mm, 30
14. The apparatus for measuring the concentration of a light-absorbing substance in a living tissue according to claim 13, wherein the measuring apparatus has a diameter of 40 mm. 17. The distance between transmission and reception of the sensor is 20 mm, 30
15. The light-absorbing substance concentration measuring device according to claim 14, wherein the measuring device has a diameter of 40 mm.