JP2002365209A - Living-body light measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a living-body light measuring apparatus whose detection sensitivity is high in the deep part of a living body. SOLUTION: A subject 7 is irradiated, via irradiation optical fibers 5-1, 5-2, with beams of light from light sources 1-1, 1-3 (at a wavelength of λ1) and light sources 1-2, 1-4 (at a wavelength of λ2), the beams of light are condensed by condensation optical fibers 8-1, 8-2 so as to be photoelectrically converted and amplified by detectors 9-1, 9-2. Output signals from the detectors 9-1, 9-2 are distributed into two, they are input to phase detectors 10-1, 10-2, 10-3, 10-4, intensities of beams of transmitted light at each wavelength from the fibers 8-1, 8-2 in positions facing the fibers 5-1, 5-2 are separated, a mutual time correlation is computed at each wavelength so as to be processed, and a computed result is displayed on a display device 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological optical measurement device, and more particularly to a biological optical measurement device for non-invasively measuring and imaging a change in concentration of a light absorbing substance in a living body using light.

[0002]

2. Description of the Related Art An apparatus for simply and non-invasively measuring the inside of a living body is desired in clinical medicine, and living body optical measurement is very effective for this demand. The first reason is that the oxygen metabolism function in the living body corresponds to the concentration of a specific dye (hemoglobin, cytochrome aa3, myoglobin, etc.) in the living body, that is, the concentration of a light absorbing substance. This is because it is determined from the amount of absorption in the outer region). Also,
The second and third reasons why optical measurement is effective are that light is easy to handle with an optical fiber and that it does not harm the living body when used within the safety standards.

[0003] Taking advantage of the above-mentioned optical measurement, the living body is irradiated with light having a wavelength from visible to near-infrared, and 10 to 5 light is applied from the irradiation position.
A biological light measuring device for measuring the inside of a living body from reflected light at a position separated by about 0 mm is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-2770.
38 and JP-A-5-300887. Further, an invention for solving the same problem as the problem to be solved by the present invention to be described later is described in JP-A-9-135825.

[0004]

In living body measurement using light, strong light scattering characteristics of a living body (scattering coefficient = about 1.0 [1 /
mm]), the irradiated light is greatly spread in the living body, so that the measured amount includes a wide range of the concentration of the absorbing substance in the living body. In particular, the spatial characteristic of the detection sensitivity has a problem in that the sensitivity of a shallow portion of the living body near the light irradiation and detection position is larger than the sensitivity of a deep portion of the living body. For this reason, it is difficult to accurately measure a change in the concentration of an absorbent substance in a deep part of a living body. For example, when measuring the hemodynamic change of the living brain from above the scalp, there is a problem that the hemodynamic change of the skin or the skull greatly reflects on the measured value for the above-described reason. For this reason, it is difficult to measure the concentration change of the absorbent substance in the deep part of the living body with high accuracy.

As a prior art for solving the above problem, there is an invention described in Japanese Patent Application Laid-Open No. Hei 9-135825.
This conventional technique employs a method of multiplying signals from a plurality of detectors.However, when hemodynamic changes at different positions in a shallow part of a living body have a certain degree of correlation, simple multiplication and integration alone can reduce the effect. It cannot be completely removed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a living body optical measurement device for measuring the change in the concentration of an absorbing substance in a deep part of a living body with higher accuracy by further eliminating the influence of a change in hemodynamics in a shallow part of the living body. is there.

[0007]

In order to achieve the above object, an apparatus according to the present invention uses irradiation light radiated from a plurality of irradiation units as transmitted light transmitted through the object to detect a plurality of detection positions of the object. And a means for calculating a mutual time correlation of signals from the detectors so that the respective optical paths of irradiation light emitted from the respective irradiation units overlap.

Further, the apparatus of the present invention converts transmitted light having an intensity modulation frequency or transmitted light having a predetermined wavelength having a predetermined intensity modulation frequency into a transmitted light intensity signal having the predetermined intensity modulation frequency by photoelectric conversion. A photoelectric conversion unit and a phase detection unit to which a transmitted light intensity signal is input; a signal corresponding to an intensity modulation frequency given to light having a predetermined wavelength at a light irradiation position is input to the phase detection unit; For detecting the output signal from the controller as the intensity of transmitted light having a predetermined intensity modulation frequency.

Alternatively, the apparatus of the present invention has an analog-to-digital converter to which a transmitted light intensity signal is input, and inputs the transmitted light intensity signal to an analog-to-digital converter to perform Fourier transform to transmit the transmitted light intensity signal to a living body in a frequency space. A light intensity signal is obtained, and a signal corresponding to an intensity modulation frequency given for each predetermined wavelength of the light irradiation position or for each predetermined light irradiation position is analog-converted.
A predetermined reference frequency is obtained by performing a Fourier transform by inputting to the digital conversion unit, and a living body transmitted light intensity signal of the frequency space at a frequency equal to the predetermined reference frequency,
Means are provided for calculating the intensity of transmitted light having a predetermined intensity modulation frequency.

[0010] In the apparatus of the present invention, the irradiating section and the condensing section are on at least one circle centered on a point where a straight line passing substantially through the center of the predetermined area and the surface of the subject intersect. The irradiation unit and the light condensing unit are arranged at equal intervals on a circle having a diameter of, and the center of the circle is a point symmetric center, and a plurality of wavelengths from each of the light irradiation positions are arranged. Detects the transmitted light intensity of
From the transmitted light intensity for each of the plurality of wavelengths from each of the light irradiation positions, the transmitted light intensity for each of the wavelengths from the irradiation position that is symmetrical with the light condensing position is selected.
A second time correlation is calculated between the second light-collecting position and the transmitted light intensity of the same wavelength from the second irradiation position at the point-symmetric position in the second light-collecting unit arranged at the position of the degree. .

FIG. 4 shows the first irradiating section 101 and the first condensing section 111, and the second irradiating section 102 and the second condensing section 1.
12 is a conceptual diagram of an optical path when 12 is arranged on a circle 100. FIG. The two sets of transmitted light signals commonly include information of a predetermined area where the optical paths overlap, and additionally include information of an area where the optical paths do not overlap. Hereinafter, the region 140 where the optical paths overlap is referred to as a region A, and the regions 131 and 132 where the optical paths do not overlap are referred to as regions B1 and B2, respectively.

If the activities of areas B1 and B2 are uncorrelated with each other and have no correlation with the activities of area A,
The information resulting from the activity in the area A can be extracted by multiplying or integrating the two sets of transmitted light signals. However, when there is a correlation between the activity in the region A and the activity in the regions B1 and B2, the effects of the regions B1 and B2 cannot be eliminated by simple multiplication or integration.

The cross-correlation time T between the area B1 and the area B2
If the autocorrelation time TA of the region A is different from B1B2 and the cross-correlation time between the region A and the region B1 or B2 (referred to as TAB1 and TAB2, respectively), these are separated using the difference in the correlation time. be able to.

For example, when observing information in the deep brain caused by an external stimulus, since the external stimulus time substantially corresponds to TA, the TA is controlled by controlling the time during which the external stimulus is continued to be applied to TB1B2, TAB1 or TAB1. It can be larger than TAB2. Assuming that the two sets of transmitted light signals are f1 (t) and f2 (t), a time correlation G (τ) shown in Expression 2 is calculated for a time τ satisfying Expression 1.

[0015]

(Equation 1)

(Equation 2) Here, the integration times ti and tf are observation times at which a good S / N ratio can be realized. However, in order to eliminate the influence of the regions B1 and B2, it is desirable that the integration times be sufficiently longer than τ.
In order to observe the time change of the activity, it is necessary to make it shorter than TA. Note that the normal correlation coefficient is normalized to express the degree of correlation, but is not normalized here to obtain the magnitude of G (τ) depending on the change in the absorption coefficient of the region.

The cross-correlation coefficient TB1B2 between the areas B1 and B2
Are smaller by separating the regions, so that two positions of the irradiating part and the condensing part are arranged at the position where the mutual distance is the largest on the same circle, that is, at the position where the angle between each other is 90 degrees on the circle. A correlation operation is performed on the transmitted signals from the set. The two irradiation unit-condenser units at the position of 90 degrees are regarded as one operation group, and a plurality of operation groups are arranged on the same circle for one area A, and the correlation operation result from each group is obtained. Is calculated, the influence of the regions B1 and B2 can be further reduced.

Further, the transmitted light condensed by the condensing portion provided on the circle having a small diameter is used as information on the shallow portion of the subject, and condensed by the condensing portion provided on a circle having a large diameter. The transmitted light is subjected to arithmetic processing using the transmitted light as information on the deep part of the subject.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described. In the present embodiment, two wavelengths are used as irradiation wavelengths for the purpose of measuring changes in the concentrations of oxidized and reduced hemoglobin in a living body, and two light irradiation positions and two light detection positions are described. It is easy to increase the irradiation position and the light detection position. In addition, by increasing the number of wavelengths, it is possible to measure a change in the concentration of other light absorbing substances such as cytochrome and myoglobin in addition to a change in the concentration of oxidized and reduced hemoglobin.

FIG. 1 shows an apparatus configuration according to the present invention. Light of a specific wavelength is emitted from the light sources 1-1, 1-2, 1-3, 1-4, and the optical fibers 2-1, 2-2, 2-, respectively.
3, 2-4. Here, the light sources 1-1, 1-3
Is λ1, and the wavelength from the light sources 1-2 and 1-4 is λ2, which is selected from the range of 400 nm to 2400 nm. In particular, when measuring hemodynamics in a living body,
From the range of 700 nm to 1100 nm, the wavelength difference is 50
It is desirable to select so as to be within nm.

The light sources 1-1, 1-2, 1-3, 1-
4 is a light source drive circuit 4-1, 4-2, 4-3, 4
-4, the intensity is modulated at different frequencies f1, f2, f3, f4 between 100 Hz and 10 MHz. The frequency signals from the respective light source driving circuits 4-1, 4-2, 4-3, and 4-4 are used as reference frequency signals, respectively, for the phase detectors 10-1, 10-2, 10-3, and 10-4. Has been entered.

The optical fibers 2-1 and 2-2 are connected to the optical directional coupler 3-1, and the optical fibers 2-3 and 2-4 are connected to the optical directional coupler 3-2. Light from the light sources 1-1 and 1-2 is mixed and incident on the irradiation optical fiber 5-1. Light from the light sources 1-3 and 1-4 is mixed and incident on the irradiation optical fiber 5-2. You. Irradiation optical fiber 5-
1, 5-2 and the condensing optical fibers 8-1 and 8-2 are fixed by an optical fiber holder 6.

The subject 7 is irradiated with light from the irradiation optical fibers 5-1 and 5-2, and the light transmitted through the living body is collected by the collection optical fibers 8-1 and 8-2. Here, the irradiation optical fiber 5-
The optical fibers 1 and 5-2 and the condensing optical fibers 8-1 and 8-2 are arranged at equal intervals on the circle of the optical fiber holder 6, and are located at positions opposed to the irradiation optical fibers 5-1 and 5-2. The light collecting optical fibers 8-1 and 8-2 are arranged. The optical fiber holder 6 is desirably coated with a black material or a black material to enhance the light blocking effect, and has a hollow structure. It is also desirable that the irradiation optical fibers 5-1 and 5-2 and the condensing optical fibers 8-1 and 8-2 be covered with a black material on the surface other than the subject contact surface. Further, the irradiation optical fiber 5-1,
For the purpose of reducing the pain due to the contact, the 5-2 and the light-condensing optical fibers 8-1 and 8-2 have good transparency to the irradiation wavelength such as vinyl resin for the purpose of reducing the pain caused by the contact. Cover with material.

The light transmitted through the living body condensed by the condensing optical fibers 8-1 and 8-2 is incident on the photodetectors 9-1 and 9-2, respectively. Converted and amplified. A photomultiplier or an avalanche photodiode is used for the photodetectors 9-1 and 9-2. After the output signal from the photodetector 9-1 is divided into two, it is input to the phase detectors 10-1 and 10-2, and the output signal from the photodetector 9-2 is divided into two. Later, the phase detector 10-
Input to 3, 10-4.

The signals input to the respective phase detectors are mixed with the irradiated light transmitted through the living body of all wavelengths.
-1, 10-2, 10-3, and 10-4 are input with reference frequencies from the light source driving circuits 4-1, 4-2, 4-3, and 4-4, respectively. -1, the intensity of light transmitted through the living body from the light source 1-1 is compared with the phase detector 10-2.
Then, the intensity of light transmitted through the living body from the light source 1-2 is measured by the phase detector 1
At 0-3, the transmitted light intensity of the living body from the light source 1-3 is detected separately, and at the phase detector 10-4, the transmitted light intensity of the living body from the light source 1-4 is separately detected.

The arithmetic unit 14 has an analog-digital conversion function and a memory for storing time-series data.
Is calculated. That is, for the wavelength λ1, the time series signal of the phase detector 10-1 is f1 (t), the time series signal of the phase detector 10-3 is f2 (t), and these accumulated time series data are used. G (τ) is calculated using the value of τ specified in advance by software. Similarly, the calculation of λ2 is performed using the signal data of the phase detectors 10-2 and 10-4. Here, ti = −0.5 seconds, tf = 0 seconds, τ =
0.2 seconds. That is, every time data is acquired, G (τ) is calculated using data from 0.5 seconds before to the time of data acquisition, a time change of G (τ) is sequentially obtained, and the value of the square root is displayed on the display device. 15. If all the fetched time-series data is stored, it is also possible to change τ later and recalculate.

Further, in the arithmetic unit 14, the change in oxyhemoglobin concentration, the change in reduced hemoglobin concentration, the change in oxyhemoglobin concentration representing blood volume and the change in oxyhemoglobin concentration, Is calculated and displayed on the display device 15 as a time series graph.

The case where two irradiation optical fibers and two light collecting optical fibers are arranged on one circle has been described above. Hereinafter, an embodiment in which a large number of irradiation optical fibers and a large number of light collecting optical fibers are arranged will be described.

FIG. 2 shows a first example of the arrangement of the irradiation optical fiber and the condensing optical fiber. In this arrangement example, four irradiation optical fibers and four condensing optical fibers are arranged on a double concentric circle.
Although an example of arranging the optical fibers and the converging optical fibers on the concentric circles is shown in each of the above examples in which the optical fibers for irradiation and the optical fibers for condensing are arranged on the concentric circles, it is possible to increase the measurement sensitivity at predetermined positions of various depths. it can.

Irradiation optical fibers 5-1, 5-2, 5-
3, 5-4 are arranged on the concentric circle 17-1, and the condensing optical fibers 8-1,
8-2, 8-3, and 8-4 are arranged. A plurality of irradiation optical fibers 5-11, 5-12, 5-13, and 5-14 are arranged on a concentric circle 17-2 provided inside the concentric circle 17-1, and the opposing optical fibers (180 Degree) position, the condensing optical fibers 8-11, 8-12, 8-13, 8-1
4 is arranged. The fixing of such an arrangement position is performed using an optical fiber holder described in, for example, Japanese Patent Application Laid-Open No. 9-135825.

A change in hemoglobin concentration inside the living body is calculated by assigning the result calculated using the intensity of the transmitted light from the living body detected on the concentric circle 17-1 as information on the deep part, and is detected on the concentric circle 17-2. A change in hemoglobin concentration inside the living body can be calculated by assigning a result calculated using the intensity of light transmitted through the living body as information of a shallow portion. Further, the change in hemoglobin concentration calculated from the intensity of the transmitted light of the living body detected on the concentric circle 17-2 is multiplied by a predetermined weighting factor estimated from the sensitivity distribution, and the intensity of the transmitted light of the living body detected on the concentric circle 17-1 is multiplied. By subtracting from the change in hemoglobin concentration calculated from the above, it is possible to further improve the relative sensitivity of a deep portion at a predetermined depth.

FIG. 3 shows a second example of the arrangement of the irradiation optical fiber and the condensing optical fiber. In this arrangement example, an efficient arrangement example in a case where measurement is performed at various positions of a living body based on the present invention is shown. In this example, an example is shown in which two sets of irradiation optical fibers and light collecting optical fibers are arranged on a single circle. To extend the measurement area, as shown in FIG. 3, an irradiation optical fiber and a converging optical fiber are arranged on the square lattice apex, and the irradiation optical fiber and the converging optical fiber are mutually diagonal to each lattice. It is arranged so that the optical fiber for light is located.

Here, nine measurement positions, that is, a circle 18
In the case where nine pieces from -1 to 18-18 are set, as shown in FIG.
-12 and the optical fibers 8-1 to 8-12 for focusing are arranged on the vertices of the square lattice. With this arrangement, the irradiation optical fiber and the condensing optical fiber arranged at the intersections of different circles function with respect to the same number of measurement positions as the number of circular intersections. Measurement becomes possible. Since a wider area is measured, it is easy to increase the measurement position. An image of hemodynamics in a deep part of a living body can be obtained from the result obtained by widening the measurement area.

In this embodiment, irradiation light having a wavelength of 805 nm is used.
The change in total hemoglobin concentration calculated from the sum of the change in reduced hemoglobin concentration and the change in oxyhemoglobin concentration and the change in reduced hemoglobin concentration was determined, and the time change of the total hemoglobin concentration change was displayed. And the irradiation light is 700 nm
Irradiation light of at least two wavelengths from the range of 1 to 1100 nm may be used.

[0034]

According to the present invention, a change in the concentration of an absorbent at a predetermined depth in a living body can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical measurement device according to the present invention.

FIG. 2 is an explanatory view showing an arrangement example of an irradiation optical fiber and a condensing optical fiber in the optical measurement device according to the present invention.

FIG. 3 is an explanatory view showing another arrangement example of the irradiation optical fiber and the condensing optical fiber in the optical measurement device according to the present invention.

FIG. 4 is a conceptual diagram showing an observation area of the optical measurement device according to the present invention.

[Explanation of symbols]

1-1, 1-2, 1-3, 1-4 ... light source, 2-1 and 2-
2, 2-3, 2-4: optical fiber, 3-1, 3-2: optical directional coupler, 4-1, 4-2, 4-3, 4-4: light source drive circuit, 5-1 , 5-2,5-3,5-4,5-5
5-6, 5-7, 5-8, 5-11, 5-12, 5-1
3, 5-14: irradiation optical fiber, 6: optical fiber holder, 7: subject, 8-1, 8-2, 8-3, 8-4,
8-5,8-6,8-7,8-8,8-11,8-1
2,8-13,8-14 ... concentrating optical fiber, 9-1,
9-2 Photodetector, 10-1, 10-2, 10-3, 1
0-4: phase detector, 14: arithmetic device, 15: display device, 17-1, 17-2: concentric circles, 18-1, 18-
2,18-3,18-4,18-5,18-6,18-
7, 18-8, 18-9: circle, 100: circle, 101, 1
02: irradiating section, 111, 112: condensing section, 131: area B1, 132 ... area B2, 140 ... area A.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Atsushi Maki 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Pref.Hitachi, Ltd. F-term in Hitachi Basic Research Laboratory (reference) 2G059 AA06 BB12 BB13 EE01 GG03 HH01 HH02 JJ17 KK02 KK03 MM09

Claims (3)

[Claims] A light irradiating means having a plurality of irradiating units for irradiating irradiation light of a plurality of wavelengths to a plurality of irradiation positions of a subject; and transmitting light transmitted through the subject to a plurality of detection positions of the subject. A plurality of condensing portions for condensing the light, and a condensing means having a plurality of condensing portions for condensing the transmitted light so that respective optical paths of the irradiation light emitted from the respective irradiation portions overlap each other. Detecting means for detecting the light intensity of the transmitted light from the transmitted light for each of the plurality of light irradiation positions and for each of the wavelengths; and arithmetic processing means for calculating the intensity of the transmitted light; The irradiating means has a modulating unit for applying intensity modulation of a different frequency for each wavelength to the irradiating light irradiated for each of the irradiating positions, and the arithmetic processing means has a predetermined intensity modulating frequency of the transmitted light from the transmitting light. Detect light or select from the above transmitted light Has a detection means for calculating the intensity of light intensity modulation frequencies, the biological light measuring device, in particular characterized by calculating the cross-time correlation detection calculation signal for each of the detection positions. 2. The method according to claim 1, wherein the arithmetic processing means sets a correlation time parameter used for performing the cross-time correlation calculation shorter than an auto-correlation time of a predetermined area of the subject, and of the subject through which the transmitted light passes. The living body light measurement device according to claim 1, wherein the biological light measurement device is set to be longer than a cross-correlation time between an area other than the predetermined area and the predetermined area. 3. The irradiating section and the condensing section are on at least one circle centered on a point at which a straight line passing substantially through the center of the predetermined region of the subject and the surface of the subject intersect. Are arranged at equal intervals on a circle having a predetermined diameter, the irradiating unit and the condensing unit are arranged at point-symmetric positions such that the center of the circle becomes the center of point symmetry, and the detecting means The transmitted light intensity for each of the plurality of wavelengths from each of the light irradiation positions is detected for each of the plurality of condensing positions, and the arithmetic processing unit performs the processing for each of the plurality of wavelengths from each of the light irradiation positions. From the transmitted light intensity, the transmitted light intensity for each wavelength from the irradiation position which is point-symmetrical to the light-collecting position is selected, and the second light-collecting position located at 90 ° on the same circle as the selected light-collecting position is selected. It is located at a point symmetrical position with respect to the second focusing position detected at the light position. The biological light according to claim 1 or 2, wherein a transmitted light intensity having a predetermined wavelength from the second irradiation position is selected, and a mutual time correlation between the selected two transmitted light intensities is calculated. Measuring device.