JP4077475B2 - Method and apparatus for measuring absorption information of scatterers - Google Patents

Description

  The present invention relates to a method and an apparatus for measuring absorption information of a scatterer, and more specifically, a method and apparatus for measuring a temporal change and a spatial distribution of the concentration of an absorption component in a scatterer having a non-re-incident surface, and a plurality of wavelengths. The present invention relates to a method and an apparatus for measuring the concentration of an absorption component inside a scatterer using light.

  There is a strong demand for non-invasive and precise measurement of the concentration of specific absorption components inside a scatterer such as a living body, as well as absorption information such as temporal changes and spatial distribution, and so far continuous light (cw light). Various methods have been attempted, such as a method using modulated light (for example, pulsed light, square wave light, sine wave modulated light, etc.), and a method using light having different wavelengths (multi-wavelength spectroscopy).

  However, with these conventional technologies, the concentration of specific internal absorption components is accurately determined for tissues and organs that have various shapes, such as living organisms, or for objects that have the same individual tissue or organ shape. No method or apparatus has been developed yet that can be measured. This is a big problem of non-invasive measurement of a living body using light, and the improvement is strongly desired.

  Light incident on a scatterer such as a living body propagates inside while being scattered and absorbed, and a part of the light emerges on the surface. And since the outside of the scatterer is usually air, the light emitted to the surface dissipates in free space. In the internal information measurement of the scatterer, the light that emerges from the surface is detected as described above. At this time, the propagation light spreads over the entire area of the scatterer and dissipates from the entire surface to the outside. Therefore, when the output light is detected at a specific position on the surface, if the shape of the medium changes, the amount of detection light and the time waveform vary greatly depending on whether the medium is a sphere or a rectangular parallelepiped, for example.

  In order to improve the measurement accuracy in the above cases, it is necessary to fully understand the behavior of light inside the scatterer. Recently, the behavior of light inside scatterers has been analyzed, experimented, and studied by computer Monte Carlo simulation. It is also known that it can be described and analyzed to some extent by the Photon Diffusion Theory. However, Monte Carlo simulation requires an extremely long calculation time, and the concentration of the specific absorption component inside the scatterer cannot be calculated from the result. Furthermore, when the light diffusion theory is used, it is necessary to set boundary conditions when solving the light diffusion equation. However, since this boundary condition greatly depends on the shape of the scatterer, it is necessary to solve the light diffusion equation by setting a new boundary condition every time the shape of the scatterer changes in order to perform accurate measurement. become. In addition, the scatterers that can set the boundary conditions to a certain degree of accuracy are limited to extremely simple shapes such as an infinite space, a semi-infinite space, an infinite cylinder, and an infinitely wide finite slab. As a result, it is indispensable to use approximate boundary conditions in measurement of a living tissue or the like whose shape is not simple, which causes a large measurement error.

  The above problems are also discussed in Non-Patent Document 1 below, for example.

As described above, there is still no sufficient method for measuring absorption information that can be applied uniformly to scatterers with different shapes. It has been extremely difficult to accurately and efficiently measure the concentration of the specific absorption component.
AlbertCerussi et al. "The Frequency Domain Multi-Distance Method in the Presence of Curved Boundaries", in Biomedical Optical Spectroscopy and Diagnostics, 1996, Technical Digest (Optical Society of America, Washington DC, 1996) pp.24-26

  The present invention has been made in view of the above-described problems of the prior art, and newly discloses a method (basic relational expression) for describing the behavior of light inside a scatterer having a different shape, and uses this relationship. It is possible to measure the concentration change and absolute value of specific absorption components inside scatterers of various shapes, greatly improve the measurement accuracy, and also to measure the time change and spatial distribution efficiently. An object of the present invention is to provide a measuring method and measuring apparatus for absorption information inside a scatterer.

In the first method for measuring absorption information of a scatterer of the present invention, (a) a modulated light having a predetermined modulation frequency component is incident in a spot shape on the surface of a scatterer that is a measurement object excluding a human , (b) The modulated light propagated inside the measurement object is received at a plurality of timings and / or a plurality of positions on the surface of the scatterer to obtain measurement signals, respectively, and (c) the modulation frequency from the measurement signals Detecting component signals, and (d) obtaining slopes of the sine component and cosine component of the modulation frequency component signal obtained by measurement at the plurality of timings and / or a plurality of positions with respect to the modulation angular frequency. , (e) the sine components, and the inclination against modulation angular frequency of the cosine component, between the difference in absorption coefficient at a plurality of timings and / or position of the, is scattered That on the basis of a predetermined relationship derived on the basis of the bare-Lambert law holds for the accumulation of the flight distance of the light, calculates a difference between the absorption coefficient is the primary information, characterized in that it is mETHODS.

  In the second scatterer absorption information measurement method of the present invention, (a) modulated light having a predetermined modulation frequency component is incident in a spot shape on the surface of a scatterer that is a measurement object, and (b) measurement is performed. Receiving the modulated light propagating inside the object at a plurality of timings and / or a plurality of positions on the surface of the scatterer to obtain measurement signals, respectively, and (c) modulating the frequency component from the measurement signal And (d) obtaining the cosine component of the signal of the modulation frequency component obtained by the measurement at the plurality of timings and / or the plurality of positions, and the slope of the sine component with respect to the modulation angular frequency, (E) A predetermined relationship between the cosine component, the slope of the sine component with respect to the modulation angular frequency, and the difference in absorption coefficient at the plurality of timings and / or the plurality of positions. Zui and calculates the difference of the absorption coefficient is the primary information, characterized in that, a method of removing a medical practice.

  Furthermore, in the third method for measuring absorption information of a scatterer according to the present invention, (a) modulated light having a predetermined modulation frequency component is incident in the form of a spot on the surface of a scatterer that is a measurement object, and (b) measurement is performed. Receiving the modulated light propagating inside the object at a plurality of timings and / or a plurality of positions on the surface of the scatterer to obtain measurement signals, respectively, and (c) modulating the frequency component from the measurement signal (D) obtain the amplitude of the signal of the modulation frequency component obtained by the measurement at the plurality of timings and / or the plurality of positions, and the slope of the phase with respect to the modulation angular frequency, respectively (e ) Based on a predetermined relationship between the amplitude, the slope of the phase with respect to the modulation angular frequency, and the difference in absorption coefficient at the plurality of timings and / or the plurality of positions; Calculating a difference between absorption coefficients is the information, characterized in that, a method of removing a medical practice.

  Furthermore, in the fourth method for measuring absorption information of a scatterer according to the present invention, (a) modulated light having a predetermined modulation frequency component is incident in the form of a spot on the surface of the scatterer that is the measurement object; The modulated light propagated inside the measurement object is received at a plurality of timings and / or a plurality of positions on the surface of the scatterer to obtain measurement signals, respectively, and (c) the modulation frequency from the measurement signals (D) the phase of the modulation frequency component signal obtained by the measurement at the plurality of timings and / or the plurality of positions, and the slope of the natural logarithm of the natural logarithm with respect to the modulation angular frequency. (E) between the phase, the slope of the natural logarithm of the amplitude with respect to the modulation angular frequency, and the difference in absorption coefficient at the plurality of timings and / or at a plurality of positions. Based on the constant relationship, and calculates the difference of the absorption coefficient is the primary information, characterized in that, a method of removing a medical practice.

  In the method of the present invention, using the difference in absorption coefficient obtained as described above, the difference in absorption coefficient, the absorption coefficient per unit concentration of the absorption component, and the difference in concentration of the absorption component. It is possible to quantify the difference in the concentration of the absorption component based on a predetermined relationship between the two.

In the method of the present invention, modulated light having a plurality of wavelengths may be used. That is, the fifth method for measuring absorption information of a scatterer according to the present invention includes: (a) a surface of a scatterer that is a measurement object excluding a human having a predetermined modulation frequency component and a scattering coefficient with respect to the measurement object. A plurality of types of modulated light having different wavelengths that can be regarded as being equal or equal to each other are incident in a spot shape, and (b) the modulated light propagating through the measurement object is received at a predetermined position on the surface of the scatterer. A measurement signal for each of the wavelengths, (c) detecting a signal of the modulation frequency component from the measurement signal, and (d) a signal of the modulation frequency component obtained for each of the wavelengths. Determination of inclination with respect to the sinusoidal component, and modulation angular frequency of the cosine component, (e) and the sine component, and the inclination against modulation angular frequency of the cosine component, between the difference in absorption coefficients for each of said wavelengths Based on a predetermined relationship derived on the basis of the bare-Lambert law holds for the accumulation of flight distance of the scattered light being, calculates the difference between the absorption coefficient is the primary information, and characterized in that it is be that way.

  In the sixth method for measuring absorption information of a scatterer according to the present invention, (a) whether the surface of the scatterer that is the measurement object has a predetermined modulation frequency component and the scattering coefficient is equal to the measurement object. Or a plurality of types of modulated light having different wavelengths that can be regarded as being equal, and (b) receiving the modulated light propagating through the measurement object at a predetermined position on the surface of the scatterer, Obtaining a measurement signal for each wavelength; (c) detecting a signal of the modulation frequency component from the measurement signal; and (d) a cosine component of the signal of the modulation frequency component obtained for each of the wavelengths. And (e) based on a predetermined relationship between the cosine component, the slope of the sine component with respect to the modulation angular frequency, and the difference in absorption coefficient for each of the wavelengths. There are, for calculating a difference between the absorption coefficient is the primary information, characterized in that, a method of removing a medical practice.

  Further, according to the seventh scatterer absorption information measuring method of the present invention, (a) whether the surface of the scatterer that is the measurement object has a predetermined modulation frequency component and the scattering coefficient is equal to the measurement object. Or a plurality of types of modulated light having different wavelengths that can be regarded as being equal, and (b) receiving the modulated light propagating through the measurement object at a predetermined position on the surface of the scatterer, Obtaining a measurement signal for each wavelength; (c) detecting a signal of the modulation frequency component from the measurement signal; and (d) an amplitude of the signal of the modulation frequency component obtained for each of the wavelengths, And (e) based on a predetermined relationship between the amplitude, the slope of the phase with respect to the modulation angular frequency, and the difference in absorption coefficient for each of the wavelengths. Next Calculating a difference between the absorption coefficient is broadcast, characterized in that a method of removing a medical practice.

  Furthermore, according to the eighth method for measuring absorption information of a scatterer of the present invention, (a) the surface of the scatterer that is the measurement object has a predetermined modulation frequency component and the scattering coefficient is equal to that of the measurement object. Or a plurality of types of modulated light having different wavelengths that can be regarded as being equal, or (b) receiving the modulated light propagating through the measurement object at a predetermined position on the surface of the scatterer, Obtaining a measurement signal for each of the wavelengths; (c) detecting a signal of the modulation frequency component from the measurement signal; and (d) a phase of the signal of the modulation frequency component obtained for each of the wavelengths. And (e) a predetermined value between the phase, the slope of the natural logarithm of the amplitude with respect to the modulation angular frequency, and the difference between the absorption coefficients for each of the wavelengths. Based on the relationship, and calculates the difference of the absorption coefficient is the primary information, characterized in that, a method of removing a medical practice.

  In the method of the present invention using modulated light having a plurality of wavelengths, the difference between the absorption coefficients obtained as described above and the absorption component for each of the wavelengths are used. Based on a predetermined relationship between the absorption coefficient per unit concentration and the concentration of the absorbing component, the concentration of the absorbing component can be quantified. The measurement signal may be a plurality of measurement signals received at a plurality of positions on the surface of the measurement object.

The first scatterer absorption information measuring device of the present invention comprises: (i) a light incident part that injects modulated light having a predetermined modulation frequency component in a spot shape on the surface of a scatterer that is a measurement object; ) A light detection unit that receives the modulated light propagated inside the measurement object at a plurality of timings and / or a plurality of positions on the surface of the scatterer, and (iii) the measurement A signal detector for detecting the signal of the modulation frequency component from the signal, and (iv) a sine component and a cosine of the signal of the modulation frequency component obtained by the measurement at the plurality of timings and / or the plurality of positions, respectively. A first computing unit that computes the slope of the component with respect to the modulation angular frequency; (v) the slope of the sine component and the cosine component with respect to the modulation angular frequency; and the plurality of timings and / or the plurality of positions. Based on a predetermined relationship derived based on the Bare-Lambert law established for the accumulated flight distance of scattered light with respect to the difference in absorption coefficient, the absorption coefficient of the primary information is And a second computing unit that computes the difference.

  Further, the second scatterer absorption information measuring device of the present invention comprises: (i) a light incident portion that injects a modulated light having a predetermined modulation frequency component in a spot shape on the surface of the scatterer that is a measurement object; (ii) a light detection unit that receives the modulated light propagated inside the measurement object at a plurality of timings and / or a plurality of positions on the surface of the scatterer, and obtains measurement signals, respectively (iii) A signal detector for detecting the signal of the modulation frequency component from the measurement signal, and (iv) a cosine component of the signal of the modulation frequency component respectively obtained by measurement at the plurality of timings and / or a plurality of positions, And (v) the cosine component, the slope of the sine component with respect to the modulation angular frequency, and the plurality of timings and / or the plurality of positions. And a second computing unit that computes the difference in absorption coefficient, which is primary information, based on a predetermined relationship between the difference in absorption coefficient in the apparatus.

  Furthermore, the third scatterer absorption information measuring device of the present invention comprises: (i) a light incident portion that makes a modulated light having a predetermined modulation frequency component incident on the surface of a scatterer that is a measurement object; (ii) a light detection unit that receives the modulated light propagated inside the measurement object at a plurality of timings and / or a plurality of positions on the surface of the scatterer, and obtains measurement signals, respectively (iii) A signal detector for respectively detecting the signal of the modulation frequency component from the measurement signal, and (iv) the amplitude of the signal of the modulation frequency component respectively obtained by the measurement at the plurality of timings and / or the plurality of positions, and A first calculator that calculates a slope of the phase with respect to the modulation angular frequency; (v) the amplitude, the slope of the phase with respect to the modulation angular frequency, and the absorption coefficient at the plurality of timings and / or the plurality of positions. And a second calculation unit that calculates a difference in absorption coefficient, which is primary information, based on a predetermined relationship with the difference.

  Furthermore, the fourth scatterer absorption information measuring apparatus of the present invention comprises: (i) a light incident portion that injects modulated light having a predetermined modulation frequency component in a spot shape onto the surface of the scatterer that is the measurement object; (Ii) a light detector that receives the modulated light propagated inside the measurement object at a plurality of timings and / or a plurality of positions on the surface of the scatterer, and obtains measurement signals, respectively (iii) ) A signal detector for detecting the modulation frequency component signal from the measurement signal, and (iv) the phase of the modulation frequency component signal respectively obtained by the measurement at the plurality of timings and / or the plurality of positions, And (v) the phase, the slope of the natural logarithm of the natural logarithm with respect to the modulation angular frequency, and / or the plurality of timings, and / or A second computing unit that computes the difference between the absorption coefficients, which is the primary information, based on a predetermined relationship between the absorption coefficient differences at a plurality of positions. is there.

  And in the said 2nd calculating part of the apparatus of the said invention, using the difference of the said absorption coefficient calculated | required as mentioned above, this absorption coefficient difference and the absorption coefficient per unit concentration of an absorption component are obtained. It is possible to calculate the difference in the concentration of the absorption component based on a predetermined relationship with the difference in the concentration of the absorption component.

The apparatus of the present invention may use modulated light having a plurality of wavelengths. That is, the fifth scatterer absorption information measuring apparatus of the present invention is (i) whether the surface of the scatterer that is the measurement object has a predetermined modulation frequency component and the scattering coefficient is equal to the measurement object. Or a light incident part for incidenting a plurality of types of modulated light having different wavelengths that can be regarded as equal, and (ii) receiving the modulated light propagating through the measurement object at a predetermined position on the surface of the scatterer A light detection unit for acquiring a measurement signal for each of the wavelengths; (iii) a signal detection unit for detecting a signal of the modulation frequency component from the measurement signal; and (iv) for each of the wavelengths. A first computing unit that computes a sine component of the obtained modulation frequency component signal and a slope of the cosine component with respect to the modulation angular frequency; (v) a slope of the sine component and a slope of the cosine component with respect to the modulation angular frequency; Each of the wavelengths Based on a predetermined relationship derived based on the Bare-Lambert law established for the accumulated flight distance of scattered light between the difference in absorption coefficient with respect to the absorption coefficient as the primary information And a second computing unit that computes the difference between them.

  In the sixth scatterer absorption information measuring device of the present invention, (i) whether the surface of the scatterer that is the measurement object has a predetermined modulation frequency component and the scattering coefficient is equal to the measurement object. Or a light incident part for incidenting a plurality of types of modulated light having different wavelengths that can be regarded as equal, and (ii) receiving the modulated light propagating through the measurement object at a predetermined position on the surface of the scatterer A light detection unit for acquiring a measurement signal for each of the wavelengths; (iii) a signal detection unit for detecting a signal of the modulation frequency component from the measurement signal; and (iv) for each of the wavelengths. A first computing unit that computes a slope of the cosine component and sine component of the obtained modulation frequency component signal with respect to the modulation angular frequency; (v) a slope of the cosine component and a slope of the sine component with respect to the modulation angular frequency; , For each of the wavelengths And a second computing unit that computes the difference in absorption coefficient, which is primary information, based on a predetermined relationship between the difference in absorption coefficient.

  Further, the seventh scatterer absorption information measuring apparatus of the present invention is (i) whether the surface of the scatterer that is the measurement object has a predetermined modulation frequency component and the scattering coefficient is equal to the measurement object. Or a light incident part for incidenting a plurality of types of modulated light having different wavelengths that can be regarded as equal, and (ii) receiving the modulated light propagating through the measurement object at a predetermined position on the surface of the scatterer A light detection unit for acquiring a measurement signal for each of the wavelengths; (iii) a signal detection unit for detecting a signal of the modulation frequency component from the measurement signal; and (iv) for each of the wavelengths. A first computing unit that computes the amplitude of the signal of the modulation frequency component obtained and the slope of the phase with respect to the modulation angular frequency; (v) the amplitude, the slope of the phase with respect to the modulation angular frequency, and the wavelength Of the absorption coefficient for each And a second calculation unit that calculates a difference between the absorption coefficients, which is primary information, based on a predetermined relationship between the difference and the difference.

  Furthermore, according to the eighth scatterer absorption information measuring apparatus of the present invention, (i) the surface of the scatterer being the measurement object has a predetermined modulation frequency component and the scattering coefficient is equal to that of the measurement object. Or (ii) the modulated light propagating through the inside of the measurement object at a predetermined position on the surface of the scatterer. A light detector that receives the light and obtains a measurement signal for each of the wavelengths; (iii) a signal detector that respectively detects a signal of the modulation frequency component from the measurement signal; and (iv) for the wavelength. A first computing unit that computes the phase of the signal of the modulation frequency component obtained and the slope of the natural logarithm of the amplitude with respect to the modulation angular frequency, and (v) the phase and the modulation angular frequency of the natural logarithm of the amplitude. And the wavelength A second computing unit that computes the difference between the absorption coefficients, which is the primary information, based on a predetermined relationship between the absorption coefficient differences with respect to each other. is there.

  Then, in the second calculation unit of the apparatus of the present invention using modulated light having a plurality of wavelengths, the difference in absorption coefficient and the wavelength are calculated using the difference in absorption coefficient obtained as described above. It is possible to quantify the concentration of the absorption component based on a predetermined relationship between the absorption coefficient per unit concentration of the absorption component and the concentration of the absorption component. The light detection unit may include a light receiving unit capable of receiving light at a plurality of positions on the surface of the measurement object. In this case, a plurality of light detection units on the surface of the measurement object may be used as the measurement signal. It is possible to use a plurality of measurement signals respectively received at the positions.

  As described above, according to the method and apparatus for measuring absorption information of a scatterer according to the present invention, the concentration change or absolute concentration of an absorption component inside a scatterer having an arbitrary shape composed of surfaces that cannot be reincident is efficiently measured. It becomes possible to do. Further, according to the present invention, it is possible to measure the spatial distribution of the density change, the temporal change in density, and the spatial distribution. Furthermore, since the modulated light is used in the method and apparatus of the present invention, the light utilization rate is high, the signal-to-noise ratio is increased, and high measurement accuracy is obtained. Therefore, according to the method and apparatus of the present invention, real-time measurement of the amount of oxygen in the brain, the amount of oxygen in the muscles of the person's leg during exercise, the concentration of absorbed components such as standing trees, etc. is performed with high accuracy and efficiency. It becomes possible.

(Principle of the present invention)
First, the principle of the present invention will be described. The findings described below are disclosed for the first time by the present inventors.

  Various components in the living tissue are heterogeneously mixed, that is, localized when viewed microscopically. However, when considering the spectroscopic analysis of biological tissues from a medical and biological standpoint, the optical properties of a complex biological tissue viewed macroscopically, that is, the measured value measured as an average value, It is often sufficient to quantify the specific components contained. This idea can be seen in the impulse response and system function of the black box in linear system theory. In the following, a uniform scatterer is considered, light is incident on the surface, the light propagated inside the scatterer is received at other positions on the surface, a measurement signal is obtained, and the absorption contained in the measurement signal from the measurement signal is obtained. Consider quantifying the concentration of ingredients. In this case, the outer shape of the scatterer has a surface that cannot be incident again, that is, a medium having an arbitrary shape in which diffused light emitted from the medium does not enter the medium again. Further, the incident light is assumed to have an arbitrary time waveform. In this case, incident light having an arbitrary time waveform is represented by superposition of light modulated at various frequencies, as is clear from the Fourier transform principle. Consider incident light at a modulation frequency.

FIG. 1 shows an example of a track in which a detected photon propagates inside a scatterer or scattering medium. Light is strongly scattered by the scattering component, and the optical path of the photon is bent zigzag. At this time, the Lambert-Beer's low is established for the zigzag flight distance, and the intensity of the propagating light attenuates exponentially with respect to the zigzag flight distance (cumulative distance). That is, if the velocity of light in the medium c, and flight time and t, flight distance (optical path length) l = ct, and the survival rate of the photon when the absorption coefficient was mu _a is exp (-cμ _a t) It becomes. Light detects at (light beam) and is incident from the position P position Q, but the photons that have passed through the various optical paths are detected, the detection light quantity is their sum, i.e. survival exp (-cμ _a t) Is proportional to

  Therefore, the light output h (t) when the impulse light is incident on the scatterer, that is, the impulse response is as follows.

Here, J is an impulse response that is output light, _s (μ s, t) is response when the absorption coefficient μ _a = 0 (i.e., the response when there is scattering only), the exponential term exp (-cμ _a t ) Is a term representing attenuation due to the absorption coefficient μ _a . Both functions are time-causal functions that are zero when t <0. Μ _s is a scattering coefficient.

  The Fourier transform of the impulse response h (t) represents a system function. Considering that the impulse response h (t) is a time-causal function and considering the Fourier transform of equation (1.1), the following system function H (ω) is derived.

Here, R (cμ _a , ω) and X (cμ _a , ω) represent the real part and imaginary part, respectively, and A (cμ _a , ω) and φ (cμ _a , ω) represent the amplitude and phase, respectively. The phase delay is obtained by changing the sign of the phase.

  Next, substituting equation (1.1) into equation (2) and rearranging it reveals that the following relational expression called Cauchy-Riemann relational expression holds in complex function theory.

  Further, when the expressions (3.1) and (3.2) are established, it is proved that the following relation is established.

Any of the equations (3.1) to (4.2) may be used to calculate the absorption coefficient μ _a which is the first object of the present invention. Specifically, these equations the integral in mu _a, i.e. it is preferable to use the following formula obtained from the above equation.

However, the second term on the right side of the equations (5.1) to (5.4) is an integral constant, and represents the value when μ _a = 0. Hereinafter, a method for calculating information relating to absorption from a measured value using equations (5.1) to (5.4) will be described.

(Measurement of concentration change of absorption components)
Consider a case in which one type of absorption component is included in the medium, and its concentration changes to change the absorption coefficient μ _a from μ _a1 to μ _a2 . If the equations (5.1) to (5.4) are established before and after the change, and s (μ _s , t) does not change before and after the change, the following equation is obtained using μ _a1 and μ _a2 before and after the change. Is derived.

  It should be noted that in the case of a normal scatterer, the scattering characteristics do not change even if the concentration of the absorbing component changes. This is just like putting ink in milk.

  Next, when the average value theorem is used, the following equations are obtained from the equations (6.1) to (6.4).

However, μ _xi (i = 1, 2, 3, 4) is an appropriate value that satisfies the condition of μ _a1 ≦ μ _xi ≦ μ _a2 or μ _a1 ≧ μ _xi ≧ μ _a2 .

From the above, the modulation angular frequency ω of the modulated light used for the measurement and the inclinations of the four parameters at μ _a = μ _xi ∂X / ∂ω, ∂R / ∂ω, ∂φ / ∂ω, ∂lnA / ∂ω Can be obtained from the values of X, R, A, and φ before and after the change (all of which can be obtained from the observed values) and the value of c determined by the refractive index of the medium and the speed of light. A difference μ _a2 −μ _a1 between the absorption coefficients before and after can be calculated.

In the above case, the slope ∂B _i / ∂ω | μ _xi at μ _a = μ _xi of the above four parameters B _i (i = 1,2,3,4) is the slope at μ _a1 and μ _a2 . And can be expressed as follows.

However, p _i is an appropriate value that satisfies the condition of 0 ≦ p _i ≦ 1. In this case, B _i is a monotonic function, and normally the slopes at μ _a1 and μ _a2 are almost equal, so p _i = 1/2 may be set.

Furthermore, the gradients ∂B _i / ∂ω | ω ₁ of the four parameters at the modulation angular frequency ω ₁ are modulated light having two modulation angular frequency components of ω = ω ₁ ± Δω / 2 (> 0). Can be measured. This relationship can be expressed as follows.

Therefore, the slopes ∂B _i / ∂ω of the equations (7.1) to (7.4) are as follows when the equation (9) is substituted into the equation (8) and p _i = 1/2.

以上、∂Ｂ_i/∂ωを精密に求める方法を説明した。

This completes the description of the method for accurately obtaining ∂B _i / ∂ω.

On the other hand, it is empirically known that when the modulation frequency is low (for example, when f = ω / 2π = 100 MHz or less in measurement of a living body or the like), the approximation ∂φ / ∂ω≈φ / ω holds. ing. This can be derived by analyzing the response of a scatterer with a simple shape using the light diffusion equation. In other words, for a semi-infinite medium or a cuboid medium of a certain size or larger, the boundary condition is determined and the light diffusion equation is solved to obtain the slope ∂B _i / ∂ω on the right side of equations (7.1) to (7.4). Thus, an approximate expression of the inclination ∂B _i / ∂ω can be derived. For example, the relationship of 式 φ / ∂ω≈φ / ω holds in the relationship of equation (7.3). Therefore, when the modulation frequency is low, ∂φ / ∂ω≈φ / ω may be set in the equation (7.3). In this case, the above equation (7.3) is as follows.

  However, p is a coefficient similar to that used in the equation (8), and here, it is also possible to normally set p = 1/2. It is apparent that approximate expressions corresponding to the respective expressions can be derived in the same manner as described above with respect to the above expressions (7.1), (7.2) and (7.4).

  Further, in order to calculate the concentration change ΔV of the absorption component, the following equation derived from the Bare-Lambert law is used.

εΔV = μ _a2 −μ _a1 (12)

However, ε is an absorption coefficient (or extinction coefficient) per unit concentration of the absorption component, and can be measured with a spectrophotometer. In addition, the change of the density | concentration of two or more types of absorption components can also be measured using the light which has two or more types of wavelengths with said method.

  As described above, the method of measuring the concentration change ΔV of the absorption component inside the scatterer has been clarified from the equations (7.1) to (7.4) and (12). The above measurement can also be performed using modulated light having different wavelengths. Therefore, the measurement position can be fixed, and the temporal change in the concentration of the absorption component inside the scatterer can be measured. Such measurement can be applied to measurement of the temporal change in hemoglobin concentration at a predetermined site.

  (Measurement of concentration change of absorption component or spatial distribution of concentration difference with respect to reference value) Measures the distribution of temporal change in concentration of absorption component inside the scatterer by performing the above measurement while moving or scanning the measurement position. You can also In addition, while the positions of light incidence and light reception are relatively fixed, the measurement position is measured by moving or scanning along the measurement target, and the measurement value at an arbitrary position is used as a reference value. It is also possible to measure a difference distribution with respect to a reference value of the concentration of the internal absorption component. Such measurement can be applied to optical mammography for diagnosing breast cancer. These measurements according to the present invention can be applied to various shapes of scatterers having a non-re-incident outer shape. In addition to optical mammography, they can be used for fluoroscopic devices, optical CT, surgery, and treatment. There are clinical monitors. In these examples, methods such as light reception at multiple locations, light incident position and light reception position scanning, and time-division measurement are appropriately used.

(Measurement of concentration of specific absorption components)
Next, a case where measurement is performed using modulated light (modulation angular frequency is ω) of light having _two wavelengths λ ₁ and λ ₂ , that is, a two-wavelength spectroscopic measurement method will be described.

First, it is assumed that the absorption coefficient of a scatterer including one type of absorption component is μ _a1 for light of wavelength λ ₁ and μ _a2 for light of wavelength λ ₂ . The scattering coefficients of the medium for the light of wavelengths λ ₁ and λ ₂ are the same or approximately the same. Such a condition is easily realized by selecting a wavelength used for measurement. If it does in this way, the same form formula as (6.1)-(6.4) will be derived from the above-mentioned formulas (5.1)-(5.4). However, the definitions of the absorption coefficients μ _a1 and μ _a2 are different from those in the equations (6.1) to (6.4). Here, μ _a1 and μ _a2 are the absorption coefficients of the measured medium for light of wavelengths λ ₁ and λ _2. To express. Furthermore, equations similar to the above-mentioned equations (7.1) to (7.4) are obtained, and the difference μ _a2 −μ _a1 of the absorption coefficient with respect to light of two wavelengths of the measured medium can be obtained using these equations. .

The concentration V of the specific absorption component is calculated from the following equation using the absorption coefficients (or extinction coefficients) ε ₁ and ε ₂ per unit concentration of the specific absorption component with respect to light of wavelengths λ ₁ and λ ₂ .

V (ε ₂ −ε ₁ ) = μ _a2 −μ _a1 (13)

However, the values of ε ₁ and ε ₂ can be measured in advance with a spectrophotometer. Therefore, the absolute concentration V of the absorption component can be measured in exactly the same manner as the measurement of the concentration change of the absorption component.

In consideration of the wavelength dependency of the scattering coefficient, for example, the expression corresponding to the above-described expression (6.3) is _expressed as follows using the scattering coefficients μ _s1 and μ _s2 of the measured medium with respect to the light of the wavelengths λ ₁ and λ ₂ . It becomes like this.

However, the wavelength dependence of ∂φ / ∂ω is ignored here. B ₂ / b ₁ is the ratio of the intensity of incident light at wavelengths λ ₁ and λ ₂ , and A (μ _s1,0 , ω) and A (μ _s2,0 , ω) are when μ _s = 0. Is the value of In this way, the following equation is obtained from equation (14) in the same manner as equation (7.3).

Here, as in the equation (7.3), μ _x is an appropriate value that satisfies the condition of μ _a1 ≦ μ _x ≦ μ _a2 or μ _a1 ≧ μ _x ≧ μ _a2 . This equation (15) is equivalent to the above equation (7.3) if b ₂ / b ₁ = 1 and k = 1. The coefficient b ₂ / b ₁ can be set to b ₂ / b ₁ = 1 by adjusting the intensity of incident light. It is also possible to estimate the b ₂ / b ₁ value from the measured value of the intensity of the light source. Furthermore, k = μ ′ _s1 / μ ′ _s2 is derived by solving the light diffusion equation for a medium having a simple shape. Where μ ′ _s1 and μ ′ _s2 are transport scattering coefficients at wavelengths λ ₁ and λ ₂ , respectively. Therefore, the difference μ _a2 −μ _a1 of the absorption coefficient for the light of two wavelengths of the medium including the specific absorption component is calculated from the equation (15). Further, the concentration V of the specific absorption component can be calculated from the equation (13).

Further, in the above-described two-wavelength spectroscopic measurement, when two-point measurement is performed in which output light is received at two positions, a relationship in which the above-described coefficient b ₂ / b ₁ is deleted is obtained. That is, it is possible to factor b ₂ / b ₁ is by utilizing the fact that does not depend on the detection position, to erase the coefficient b ₂ / b _1. Furthermore, it will be appreciated that the method described above can be extended to multi-wavelength spectroscopy using light having more than two wavelengths.

(Measurement of the spatial distribution of absorption component concentration)
The measurement of the spatial distribution of the concentration of the absorption component is achieved by performing the above-described measurement at multiple locations. According to such measurement according to the present invention, it is possible to measure various types of scatterers having an outer shape that cannot be reincident. Specific application examples include optical mammography, fluoroscopy, and optical CT. In these examples, methods such as light reception at multiple locations, scanning of light incident positions and light reception positions, and time division measurement are appropriately used. As described above, the features of these measurements are the spatial distribution of the concentration of the specific absorption component, the spatial distribution of the difference in the absorption coefficient with respect to the light of the two wavelengths of the measured medium, and the space over time of the concentration of the specific absorption component. The distribution can be measured. In addition, this information is used for clinical monitoring, diagnosis and analysis, surgery and treatment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. However, in the following description, the same elements are denoted by the same reference numerals, and redundant description is omitted.

Example 1
FIG. 2 shows a first embodiment of the apparatus of the present invention for carrying out the method of the present invention, and shows the configuration of the apparatus 1 for measuring the change over time of the concentration of the absorption component inside the scatterer 2. In the configuration of the apparatus 1, modulated light having a predetermined wavelength λ and modulation frequency f (modulation angular frequency ω = 2πf) is incident on a position P (light incident position) on the surface of the scatterer 2, and another position Q on the surface. Light propagated through the scatterer 2 at (light detection position) is received. Then, repeated measurement is performed to quantify the change in the concentration of the absorbing component inside the scatterer. In this case, if the concentration of the absorption component at the first measurement is taken as a reference value, the change in the concentration of the absorption component can be quantified. The measuring device 1 is integrated and accommodated in one housing.

  A laser diode or the like is used as the light source 10 to generate modulated light having a wavelength λ and a predetermined modulation angular frequency ω. In this case, the wavelength is selected according to the scatterer to be measured and the absorption component. In the measurement of a living body, oxidation / reduction hemoglobin and oxidation / reduction myoglobin are often measured, and an absorption spectrum of these absorption components is shown in FIG. Therefore, light of 600 nm to 1.3 μm is usually used for living body measurement. The modulation frequency f is appropriately selected in the range of 1 MHz to 1 GHz. When measuring the spatial distribution, the modulation frequency should be high. In the following, it is assumed that f = 100 MHz. As the light source 10, in addition to the laser diode, a light emitting diode, a HeNe laser, or the like can be used.

  The sinusoidal modulated light having a predetermined angular frequency is generated by current modulation of a laser diode as shown in FIG. 4R> 4 (a). Further, as shown in FIG. 4B and FIG. 4C, the sine wave modulated light can be generated using the beats of two cw lasers or an optical modulator.

  The modulated light emitted from the light source 10 is incident on the surface of the scatterer 2 to be measured through the light guide 12. The space between the light guide 12 and the scatterer 2 is very small in the embodiment of FIG. However, in practice, this gap may be widened to fill a liquid or jelly-like object (hereinafter referred to as an interface material) having a refractive index and a scattering coefficient substantially equal to those of the scatterer 2. That is, since the modulated light propagates through the interface material and enters the measurement object, no problem occurs. Further, when the surface reflection of the scatterer becomes a problem, the influence of the surface reflection or the like can be reduced by appropriately selecting the interface material.

  The modulated light propagated inside the scatterer is received by the light guide 13 placed at the position Q at a distance r from the light incident position P. Again, an interface material may be used for the same reason as described above. The photodetector 14 converts the optical signal of the received light into an electrical signal, amplifies it as necessary, and outputs a measurement signal. As the photodetector 14, in addition to the photomultiplier tube, a phototube, a photodiode, an avalanche photodiode, a PIN photodiode, or the like can be used. In selecting a photodetector, it is only necessary to have a spectral sensitivity characteristic for detecting light of a predetermined wavelength and a required time response speed. When the optical signal is weak, a high gain photodetector is used. Further, a time correlation photon coefficient method for counting photons may be used. It is desirable that a place other than the light receiving surface of the photodetector has a structure that absorbs or blocks light.

  The signal detection unit 15 detects a signal having a predetermined modulation frequency component from the measurement signal. Specifically, a well-known monodyne detection, heterodyne detection, lock-in detection method, or the like is used. In this case, the signal detection unit 15 uses a signal synchronized with the modulated light emitted from the light source 10 as necessary. The first computing unit 16 computes the slope (differential coefficient) ∂φ / ∂ω of the amplitude A and the phase φ with respect to the modulation angular frequency from the signal of the predetermined modulation frequency component. Then, the above measurement is repeated. Here, m-th measurement and (m + 1) -th measurement are considered.

Second arithmetic unit 17, m-th and (m + 1) th two obtained in the measurement of the amplitude A _m and A _{m + 1,} and two of the phase slope ∂φ obtained from the phase slope Substituting / ∂ω | μ _x3 into equation (7.3) above to calculate the amount of change μ _{a (m + 1)} −μ _am (primary information) of the scatterer 2 The amount of change in the absorption component is calculated using the above equation (12).

At this time, for the calculation of the phase gradient ∂φ / ∂ω | μ _x3 , sufficient accuracy can be obtained with p = 1/2 using the above equation (8). Since f = 100 MHz, it may be approximated as ∂φ / ∂ω≈φ / ω as described above. When f> 100 MHz, the modulated light is measured as two kinds of modulation angular frequencies ω = ω ₁ ± Δω / 2 (> 0), and the above equation (10) is used to calculate ∂φ / ∂ω | μ _x3 is calculated. These arithmetic processes are executed at high speed by a microcomputer or the like incorporated in the first and second arithmetic units.

  The second calculation unit 17 has a function of storing the concentration information of the absorption component thus obtained, and the display recording unit 18 displays or records these.

  In the above description, modulated light having one wavelength is used, but actually, modulated light having two or more wavelengths can also be used. Furthermore, light can be incident from one position, and propagating light can be detected at two or more positions. These may be detected in parallel or in time division.

  Means for making light incident on the scatterer 2 are a method using a condensing lens (FIG. 5A), a method using an optical fiber (FIG. 5B), a pinhole instead of the light guide 12 shown in FIG. And the like (FIG. 5C), and the method of entering light from the body like a stomach camera (FIG. 5D). Further, a thick beam of light may be incident on the scatterer 2. In this case, it can be considered that a plurality of spot-like light sources are arranged.

  As means for detecting the light diffused and propagated inside the scatterer 2, in addition to the method using the light guide 13 shown in FIG. 2, a direct detection method (FIG. 6A) and a method using an optical fiber (FIG. 6). (B)) and a method using a lens (FIG. 6C).

  In the above description, the first calculating unit 16 calculates the slope ∂φ / ∂ω with respect to the modulation angular frequency of the amplitude A and the phase φ from the signal of the predetermined modulation frequency component. However, here, as described above, from the signal of the predetermined modulation frequency component, (i) the sine component and the slope (differential coefficient) of the cosine component with respect to the modulation angular frequency, and (ii) the modulation angle of the cosine component and sine component Any combination of the slope with respect to frequency (derivative coefficient) or (iii) the slope with respect to the modulation angular frequency of the natural logarithm of amplitude (differential coefficient) may be calculated. In this case, in the first embodiment, “amplitude A, inclination ∂φ / ∂ω with respect to modulation angular frequency of phase φ, and equation (7.3)” is expressed as (i) “modulation angular frequency of sine component and cosine component. Slope (derivative coefficient) and (7.2) ", (ii)" slope (derivative coefficient) and (7.1) expression for modulation angular frequency of cosine and sine components ", or (iii)" phase and amplitude The slope (derivative coefficient) of the natural logarithm with respect to the modulation angular frequency and the equation (7.4) may be read. Therefore, in the first embodiment described here, the change in the concentration of the absorbing component can be quantified by the equations (7.1) to (7.4).

Example 2
Measurement is performed in the same manner as in Example 1 except that the light incident position P and the light detection position Q of the modulated light with respect to the scatterer 2 are scanned synchronously, and the concentration of the absorption component at an arbitrary position is used as a reference value. The spatial distribution of the concentration difference with respect to the reference value can be measured. Also in this case, the spatial distribution of the difference with respect to the reference value of the concentration of the absorption component can be measured using the equations (7.1) to (7.4) in the same manner as in the first embodiment.

  FIG. 7 shows a second embodiment of the apparatus of the present invention for carrying out the method of the present invention. The apparatus 1 (mammography) measures the spatial distribution of the concentration of the absorption component inside the scatterer 2 such as the breast. ). In FIG. 7, the same symbols are used for those having the same functions as those shown in FIG. 2 according to the first embodiment. Modulated light having a predetermined wavelength λ and modulation frequency f (modulation angular frequency ω = 2πf) is incident on the surface of the scatterer 2 and receives the light propagated through the scatterer at the position of the surface on the opposite side. At this time, measurement is performed by scanning the incident position of the modulated light and the light detection position in synchronization. For example, if the concentration of the absorption component when the measurement is performed at the first position (the first light incident position and the first light detection position) is taken as a reference value, the spatial distribution of the concentration difference of the absorption component is obtained. It can be measured.

  The apparatus 1 shown in FIG. 7 according to the second embodiment includes a first mechanism unit 30 that lightly sandwiches the scatterer 2 in parallel. That is, the first mechanism 30 can measure the scatterer 2 such as a breast by extending it slightly flat. The first mechanism unit 30 is provided with a second mechanism unit 31 for scanning the incident position of the modulated light and the light detection position in synchronization. Then, a position signal indicating a scanning position is emitted from the second mechanism section 31 and this position signal is supplied to the display recording section 18 and used for display recording of the spatial distribution. Further, a wavelength selector 11 is provided at the subsequent stage of the light source 10 that generates the modulated light so that the modulated light having a desired wavelength can be selected as appropriate. Other parts are the same as those of the apparatus of the first embodiment.

  In the above description, modulated light having one wavelength is used, but actually, modulated light having two or more wavelengths can also be used. Furthermore, light can be incident from one light incident position, and propagation light can be detected simultaneously or in time division at two or more light detection positions.

Example 3
FIG. 8 shows a third embodiment of the apparatus of the present invention for carrying out the method of the present invention, and shows the configuration of the apparatus for measuring the concentration of the absorption component inside the scatterer 2. In FIG. 8, the same symbols are used for those having the same functions as those shown in FIG. 2 according to the first embodiment and FIG. 7 according to the second embodiment. In this configuration, two types of modulated light having wavelengths λ ₁ and λ ₂ and two types of light detection distances r ₁ and r ₂ are used. In this case, the above-described equation (15) is established for each of the two types of light detection distances r ₁ and r ₂ . Accordingly, the coefficient b ₂ / b ₁ in the equation (15) is eliminated from the simultaneous equations consisting of two equations for the equation (15), and the difference μ in the absorption coefficient for the light of the two wavelengths of the scatterer 2 to be measured μ _a2 −μ _a1 can be obtained. In this case, modulated light having two different wavelengths that can be regarded as having the same or equal scattering coefficient is incident on the scatterer, so that k in the equation (15) becomes k = 1 and lnk is erased. Further, in the case of a simple-shaped medium, as described above, k = μ ′ _s1 / μ ′ _s2 may be set. As described above, the difference μ _a2 −μ _a1 of the absorption coefficient for the light of two wavelengths of the medium including the specific absorption component is calculated from the equation (15), and the absorption component inside the scatterer is calculated based on the relationship shown in the equation (13). The concentration of can be quantified.

A laser diode or the like is used as the light source 10 to generate modulated light having two different wavelengths λ ₁ and λ ₂ , for example, modulation frequency f = 100 MHz. The modulated light from the light source 10 is wavelength-selected by the wavelength selector 11 and is incident on the surface of the scatterer 2 to be measured through the light guide 12. In this case, a method in which modulated light of two types of wavelengths is incident simultaneously may be used, and in this case, the wavelength selector 11 is omitted.

  The space between the light guide 12 and the scatterer 2 is very small in the embodiment of FIG. In practice, however, this may be widened in the same manner as in the first embodiment, and a liquid or jelly-like object (interface material) having a refractive index and a scattering coefficient almost equal to those of the scatterer 2 may be filled in this space. Good. That is, since the modulated light propagates through the interface material and enters the measurement object, no problem occurs. Further, when the surface reflection of the scatterer becomes a problem, the influence of the surface reflection or the like can be reduced by appropriately selecting the interface material.

The light propagating through the scatterer ₂ is received by the first and second light guides 13 ₁ and 13 ₂ placed at positions r ₁ and r ₂ (light detection positions) from the light incident position. Again, an interface material may be used for the same reason as described above.

The first photodetector 14 ₁ and the second photodetector 14 ₂ convert the optical signal of the received light into an electrical signal, amplify it if necessary, and two types of light detection distances r ₁ and A measurement signal for the measurement at r ₂ is output. As the photodetectors 14 ₁ and 14 ₂ , a phototube, a photodiode, an avalanche photodiode, a PIN photodiode, or the like can be used in addition to the photomultiplier tube. In selecting a photodetector, it is only necessary to have a spectral sensitivity characteristic for detecting light of a predetermined wavelength and a required time response speed. When the optical signal is weak, a high gain photodetector is used. Further, a time correlation photon coefficient method for counting photons may be used. It is desirable that a place other than the light receiving surface of the photodetector has a structure that absorbs or blocks light. Further, as described above, when two kinds of modulated light having different wavelengths are simultaneously incident on the scatterer, a wavelength selection filter (not shown) is disposed at an appropriate position between the photodetectors 14 ₁ and 14 ₂ and the scatterer 2. Z).

The signal detection unit 15 and the first calculation unit 16 perform the following calculation based on the respective measurement signals obtained for the measurement at the two types of light detection distances r ₁ and r ₂ . First, the signal detector 15 detects a signal having a predetermined modulation frequency component from each of the measurement signals obtained for modulated light of two types of wavelengths. In this case, the signal detection unit 15 uses a signal synchronized with the modulated light emitted from the light source 10 as necessary. Next, the first arithmetic unit 16 calculates the gradient (differentiation) of each amplitude A and phase with respect to the modulation angular frequency from the signals of the predetermined modulation frequency components obtained for the modulated light of two types of wavelengths. Coefficient) ∂φ / ∂ω is calculated.

The second arithmetic unit 17 obtains the phase inclinations ∂φ / ∂ obtained from the amplitudes A and the phase inclinations obtained from the two types of light detection distances with respect to the modulated light of two types of wavelengths. By substituting ω | μ _x into the above equation (15), a simultaneous equation consisting of two equations obtained for measurement at two types of light detection distances r ₁ and r ₂ is solved, and scatterer 2 The difference between the absorption coefficients μ _a2 −μ _a1 (primary information) for light having the two wavelengths is calculated, and the concentration of the absorption component is calculated using the above equation (13). For the calculation of the phase gradient ∂φ / ∂ω | μ _x3 , sufficient accuracy can be obtained with p = 1/2 using the above equation (8). Since f = 100 MHz, it may be approximated as ∂φ / ∂ω≈φ / ω as described above. When f> 100 MHz, the modulated light is measured as two kinds of modulation angular frequencies ω = ω ₁ ± Δω / 2 (> 0), and the above equation (10) is used to measure ∂φ / ∂ ω | μ _x3 is calculated. These arithmetic processes are executed at high speed by a microcomputer or the like incorporated in the first and second arithmetic units.

  The second calculation unit 17 has a function of storing the concentration information of the absorption component thus obtained, and the display recording unit 18 displays or records these.

Note that the second photodetector 14 ₂ is omitted when the intensity of incident light to the scatterer ₂ of the two types of wavelengths λ ₁ and λ ₂ is equal to or equal to each other. can do. In this case, the coefficient b ₂ / b ₁ in the above equation (15) becomes b ₂ / b ₁ = 1, and ln (b ₂ / b ₁ ) is eliminated, so that the scatterer directly from the equation (15) 2 two types of difference mu _a2 - [mu] of the absorption coefficient for light having a wavelength _a1 (primary information) calculated, it is possible to calculate the concentration of the absorbing component using further supra equation (13).

  In the above description, the method of entering light from one place and detecting light at the other two places has been described. However, in practice, light having different wavelengths may be incident from two locations, and the light may be detected in parallel or in time division at other positions.

  In the third embodiment, there are a method of entering light including light of different wavelengths and a method of using light of different wavelengths incident in a time division manner. In the former case, the light of different wavelengths is made into a coaxial beam, and the wavelength is selected by a wavelength selection filter provided immediately before the light incident position, or is directly incident on the scatterer and immediately before the photodetector. There are a method of selecting a wavelength with a provided wavelength selection filter, a method of branching each detection light into two, selecting a wavelength, and detecting in parallel with a total of four photodetectors. In the latter case, a light beam switch using a mirror on the light source side, a wavelength switch using a filter, an optical switch using an optical switch, or the like can be used. The means for injecting light into the scatterer and the means for detecting light diffused and propagated inside the scatterer include those shown in the first embodiment.

In the above description, the first calculation unit 16 calculates the slope ∂φ / ∂ω with respect to the amplitude A and the modulation angular frequency of the phase φ from the signal of the predetermined modulation frequency component. However, here, as described above, from the signal of the predetermined modulation frequency component, (i) the slope (differential coefficient) with respect to the modulation angular frequency of the sine component and cosine component, (ii) the modulation angle of the cosine component and sine component Any combination of the slope with respect to frequency (differential coefficient) or (iii) the slope with respect to the modulation angular frequency of the natural logarithm of phase and amplitude (differential coefficient) may be calculated. In this case, in the third embodiment, “amplitude A, inclination ∂φ / ∂ω with respect to modulation angular frequency of phase φ, and equation (15)” is expressed as (i) “modulation angular frequency of sine component and cosine component. (Ii) "Slope (derivative coefficient) of cosine component and sine component with respect to modulation angular frequency (derivative coefficient), and (5.1) Eq. (15) derived from Eq. (15) derived from Eq. (15) derived from Eq. (15), or (iii) “Slope (derivative coefficient) of natural logarithm of phase and amplitude with respect to modulation angular frequency” Can be read as “similar expression”. Specifically, in the case of b ₁ = b ₂ and μ _s1 = μ _s2 , the equations equivalent to the above equation (15) are the equations (7.1) and (ii) in the case of (i), respectively. When this is the case, equation (7.2) is obtained, and when (iii) is obtained, equation (7.4) is obtained. Therefore, in the third embodiment described here, the concentration of the absorbing component can be quantified by four types of methods.

  In the third embodiment described above, if light of three types of wavelengths is used, the concentration of each of the scatterers containing two types of absorption components or the scatterer containing various types of absorption components The concentration of one type of absorption component and the total concentration of other absorption components can be measured. For example, oxyhemoglobin and reduced hemoglobin have different absorption coefficients depending on the wavelength, as shown in FIG. Therefore, by using light of three types of wavelengths that are appropriately selected, these concentrations, oxygen saturation, and the like can be measured. In general, the concentration of each of the (n-1) types of absorption components can be measured using light of n (n is an integer of 2 or more) types of wavelengths. Moreover, the precision of the density measurement of (n-1) types of absorption components can also be improved by using light having a wavelength larger than n types.

  Further, if the above measurement is performed at different times (timing), it is possible to measure a change in the concentration of the specific absorption component with time. Furthermore, if the concentration of the absorption component of each part of the scatterer is measured by synchronously scanning the incident position of the light with respect to the scatterer and the light detection position, the spatial distribution of the concentration can be measured. The second calculation unit 17 can have a function of storing the concentration information of the absorption component thus obtained.

Example 4
FIG. 9 shows a fourth embodiment of the apparatus of the present invention for carrying out the method of the present invention. The concentration of oxyhemoglobin inside the scatterer 2 such as the human head or the oxygen saturation (oxidation) of hemoglobin. A configuration of an apparatus for measuring or monitoring (a ratio between the concentration of hemoglobin and the concentration of whole hemoglobin) is shown. In the fourth embodiment, three types of modulated light having wavelengths λ ₁ , λ ₂ , and λ ₃ and two types of light detection distances r ₁ and r ₂ are used. In this case, in the same manner as in the above-described embodiment, four types of three simultaneous equations can be obtained based on each of the expressions (7.1) to (7.4) described above. Therefore, by solving these simultaneous equations, calculating the difference (primary information) of the absorption coefficient at each wavelength, and using the above equation (13), the oxidized / reduced hemoglobin concentration and the oxygen saturation of hemoglobin, etc. Can be quantified.

The apparatus shown in FIG. 9 includes a container 40 having an attachment band attached to the head 2 like a headband, and includes a signal detection unit, a first calculation unit, a second calculation unit, and a display recording unit. The external device 41 is connected to the container 40 via the cable 42. In the apparatus shown in this embodiment, three types of light having predetermined wavelengths λ ₁ , λ ₂ , and λ ₃ are used, and their operations and components are almost the same as those of the apparatus of the third embodiment. FIG. 10 shows details of a part of the apparatus shown in FIG.

As shown in FIG. 10, a light source 10, a wavelength selector 11, a first photodetector 14 ₁ , a second photodetector 14 _2, and light guides 12, 13 ₁ , 13 ₂ are built in the container 40. The modulated light of the predetermined wavelengths λ ₁ , λ ₂ , λ ₃ emitted from the light source 10 is wavelength-selected by the wavelength selector 11 and is incident on the head 2 through the light guide 12. At this time, the three types of wavelengths are appropriately selected with reference to the absorption spectrum of hemoglobin shown in FIG.

The light diffusely propagated in the head 2 is received by the light guides 13 ₁ and 13 ₂ placed at distances r ₁ and r ₂ (light detection positions) from the light incident position, and the first photodetector 14 is received. _It is converted into an electric signal by the _first and second photodetectors 14 ₂ and amplified as necessary. Electric power (power supply), various signals, and the like are sent from the external device 41 and sent to the external device 41 via the connector 43 and the signal cable 42 attached to the container 40. In the signal detection unit, the first calculation unit, the second calculation unit, and the display recording unit (all not shown) arranged in the external device 41, three types of wavelengths and two types of light detection distances are used. Thus, signal detection and calculation similar to those in the third embodiment are performed.

In this embodiment, signals obtained at wavelengths λ ₁ and λ ₂ and wavelengths λ ₁ and λ ₃ , signals obtained at wavelengths λ ₁ and λ ₂ and wavelengths λ ₂ and λ ₃ , or wavelengths λ ₁ and λ ₃ For the signals obtained at the wavelengths λ ₂ and λ ₃ , four types of simultaneous equations similar to the above equation (15) are established. The above arithmetic processing is executed at high speed by a microcomputer or the like built in the first and second arithmetic units. Furthermore, a signal can be converted into a radio wave or an optical signal in the container 40 and transmitted to the external device 41 without using a signal cable.

In the present embodiment, the light source, the light incident portion, the light detection means, and the like described in the first embodiment can be used. Further, in a human head or the like, surface reflection or a gap between the light guide and the head may become a problem. In this case, the interface material described above may be used. In this case, the light guide shown in FIG. 10 is omitted, and the measurement target is between the head 2 and the wavelength selector 11 and between the head 2 and the photodetectors 14 ₁ and 14 _2. An interface material having substantially the same scattering coefficient and absorption coefficient can be arranged.

  In addition to the measurement of information in the brain, such a device can be used for measuring or monitoring the concentration of oxyhemoglobin in the leg muscle of a person during a marathon, for example.

Example 5
In the fifth embodiment, the three types of modulated light having the wavelengths λ ₁ , λ ₂ , and λ ₃ generated by the light source in the fourth embodiment are used as modulated light having an arbitrary waveform and a predetermined repetition frequency. . That is, in the fourth embodiment, sinusoidal modulated light having a predetermined angular frequency is used, but the modulated light includes any waveform as long as it includes a predetermined frequency component. The method of the fourth embodiment can be applied as it is to a specific frequency component. For example, in the repetitive pulsed light, there are frequency components that are the same as the repetitive frequency and an integral multiple of the repetitive frequency. Therefore, the method of the fourth embodiment can be applied to any frequency component as it is. The performance required for modulated light having a predetermined repetition frequency is a stable repetition frequency and a stable light intensity.

It is a schematic diagram which shows the track of the photon which propagated the inside of the scatterer. 1 is a schematic configuration diagram of an apparatus according to a first embodiment of the present invention. It is a graph which shows the absorption spectrum of hemoglobin and myoglobin. (A)-(c) is the schematic which shows the generation method of modulated light, respectively. (A)-(d) is the schematic which shows the light-injection method to a scatterer, respectively. (A)-(c) is the schematic which shows the light-receiving method, respectively. It is a structure schematic of the apparatus of 2nd Example concerning this invention. It is a block schematic diagram of the apparatus of 3rd Example concerning this invention. It is a block schematic diagram of the apparatus of 4th Example concerning this invention. It is the structure schematic of the light-incidence / detection part of the apparatus of 4th Example.

Explanation of symbols

1 ... absorbing information measuring device, 2 ... scatterer, 10 ... light source, 11 ... wavelength selector, 12,13,13 _1, 13 ₂ ... light guide, 14, 14 _1, 14 ₂ ... photodetector, 15 ... signal Detection unit, 16 ... first calculation unit, 17 ... second calculation unit, 18 ... display recording unit, 30 ... first mechanism unit, 31 ... second mechanism unit, 40 ... container, 41 ... external device, 42 ... Cable, 43 ... connector, P ... light incident position, Q ... light detection position.

Claims (10)

A modulated light having a predetermined modulation frequency component is incident in a spot shape on the surface of a scatterer that is a measurement object excluding humans .
The modulated light propagated inside the measurement object is received at a plurality of timings and / or a plurality of positions on the surface of the scatterer to obtain measurement signals, respectively.
Detecting the modulation frequency component signal from the measurement signal,
Obtaining a sine component of the signal of the modulation frequency component obtained by measurement at the plurality of timings and / or a plurality of positions, and a slope of the cosine component with respect to the modulation angular frequency,
Applicable to accumulation of flight distance of scattered light between the sine component, the slope of the cosine component with respect to the modulation angular frequency, and the difference in absorption coefficient at the plurality of timings and / or the plurality of positions. Calculating a difference between the absorption coefficients as the primary information based on a predetermined relationship derived based on the Bare-Lambert law .
Absorption information measuring method that scattering bodies be characterized by.
The difference in the concentration of the absorption component is quantified based on a predetermined relationship among the difference in the absorption coefficient, the absorption coefficient per unit concentration of the absorption component, and the difference in the concentration of the absorption component. Item 4. A method for measuring absorption information of a scatterer according to Item 1. A plurality of types of modulated light having a predetermined modulation frequency component and having different wavelengths that can be regarded as equal to or equal to the measurement object in the form of spots on the surface of the scatterer that is the measurement object excluding humans. Incident,
Receiving the modulated light propagating through the inside of the measurement object at a predetermined position on the surface of the scatterer, and obtaining a measurement signal for each of the wavelengths;
The modulation frequency component signal is detected from the measurement signal, respectively, the sine component of the modulation frequency component signal obtained with respect to the wavelength, and the inclination of the cosine component with respect to the modulation angular frequency,
Based on the Bare-Lambert law that holds for the accumulated flight distance of scattered light between the sine component, the slope of the cosine component with respect to the modulation angular frequency, and the difference in absorption coefficient for each of the wavelengths Calculating the difference between the absorption coefficients as the primary information based on the predetermined relationship
Absorption information measuring method that scattering bodies be characterized by.
The concentration of the absorption component is quantified based on a predetermined relationship among the difference in the absorption coefficient, the absorption coefficient per unit concentration of the absorption component for each of the wavelengths, and the concentration of the absorption component. The method for measuring absorption information of a scatterer according to claim 3. The scatterer absorption information measurement method according to claim 3 or 4, wherein the measurement signals are a plurality of measurement signals received at a plurality of positions on the surface of the measurement object. A light incident portion for incident modulated light having a predetermined modulation frequency component in a spot shape on the surface of a scatterer that is a measurement object;
A light detector that receives the modulated light propagating through the measurement object at a plurality of timings and / or a plurality of positions on the surface of the scatterer, and obtains measurement signals, respectively;
A signal detector for detecting each of the modulation frequency component signals from the measurement signal;
A first computing unit that computes a slope of the signal of the modulation frequency component obtained by measurement at the plurality of timings and / or a plurality of positions, and a slope of the cosine component with respect to the modulation angular frequency;
Applicable for the accumulated flight distance of scattered light between the sine component, the slope of the cosine component with respect to the modulation angular frequency, and the difference in absorption coefficient at the plurality of timings and / or positions. A second calculation unit that calculates a difference between the absorption coefficients, which is primary information, based on a predetermined relationship derived based on the Bare-Lambert rule .
An apparatus for measuring absorption information of scatterers, characterized in that.
The second calculation unit further determines the concentration of the absorption component based on a predetermined relationship among the difference in absorption coefficient, the absorption coefficient per unit concentration of the absorption component, and the difference in concentration of the absorption component. The scatterer absorption information measuring apparatus according to claim 6, wherein the difference is calculated. Light that has a predetermined modulation frequency component on the surface of the scatterer that is the object to be measured, and a plurality of types of modulated light having different wavelengths that can be regarded as being equal to or equal to the object to be measured in the form of spots An incident part;
A light detector that receives the modulated light propagated inside the measurement object at a predetermined position on the surface of the scatterer, and obtains a measurement signal for each of the wavelengths;
A signal detector for detecting each of the modulation frequency component signals from the measurement signal;
A first calculation unit that calculates a sine component of the signal of the modulation frequency component obtained with respect to the wavelength and a slope of the cosine component with respect to the modulation angular frequency;
Based on the Bare-Lambert law that holds for the accumulated flight distance of scattered light between the sine component, the slope of the cosine component with respect to the modulation angular frequency, and the difference in absorption coefficient for each of the wavelengths A second computing unit that computes the difference between the absorption coefficients as the primary information based on the predetermined relationship derived in
An apparatus for measuring absorption information of scatterers, characterized in that.
The second calculation unit is further configured based on a predetermined relationship among the difference in the absorption coefficient, the absorption coefficient per unit concentration of the absorption component for each of the wavelengths, and the concentration of the absorption component. The apparatus for measuring absorption information of a scatterer according to claim 8, wherein the concentration is quantified. The light detection unit includes a light receiving unit capable of receiving light at a plurality of positions on the surface of the measurement object, and the measurement signal is received at a plurality of positions on the surface of the measurement object. The scatterer absorption information measuring apparatus according to claim 8, wherein the apparatus is a plurality of measurement signals.

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