JP2011092631A - Biological information processor and biological information processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biological information processor which can obtain a correct light attenuation coefficient in a subject. <P>SOLUTION: The biological information processor includes: a light source which irradiates the subject with light; a first light absorbing member which is located separating between an irradiation site of a light from the light source to the subject and the subject and in which optical characteristics for the irradiated light is previously recognized; an elastic wave detector which detects an elastic wave generated from the first light absorbing member when the irradiated light reaches the first light absorbing member through the subject and is absorbed; and an arithmetic section which calculates the light attenuation coefficient in the subject based on the intensity of the irradiated light, the optical characteristics of the first light absorbing member and the intensity of the detected elastic wave generated from the first light absorbing member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a biological information processing apparatus that measures optical characteristics inside a subject.

Biological information processing devices that measure the optical properties inside living tissues are used for diagnosis by determining the formation of new blood vessels associated with tumor growth and oxygen metabolism of hemoglobin from the light absorption characteristics of specific substances such as hemoglobin in the blood. It is what you use. In such an apparatus, near infrared light having a wavelength (about 600 to 1500 nm) having good transmission characteristics for living tissue is used.
However, the light transmitted through the living tissue propagates while repeating strong scattering by cells of several tens of μm size constituting the living body, and thus becomes multiple scattered light (diffused light). With this diffused light, it is difficult to obtain local light absorption characteristics in the living tissue because all the paths through which the light propagates cannot be specified.
Therefore, conventionally, an apparatus using a photoacoustic effect has been developed in order to measure a local light absorption characteristic in a living tissue. As an example of such an apparatus, Patent Document 1 describes a biological information processing apparatus that irradiates a living tissue with pulsed light. Then, this apparatus measures _a light absorption coefficient μ _a (Optical absorption coefficient) in a region where the elastic wave is generated from the elastic wave generated by the photoacoustic effect based on the irradiated light energy.

US Pat. No. 5,843,0023

ここで、Ｐは、光音響効果によって発生した弾性波の圧力であり、超音波トランスデューサなどで構成される弾性波検出手段で得ることができる。また、Γは、光吸収体のグリュナイゼンパラメーター（Gruneisen coefficient）である。生体組織内の部位により若
干値が異なるが一定値として扱うことができる。また、μ_ａは、吸収体の光吸収係数である。また、Φは、光吸収体に照射された光強度である。また、αは、光吸収体から弾性波検出手段へ弾性波が伝搬した時の効率である。生体組織内の部位により若干値が異なるが一定値として扱うことができる。 However, a conventional biological information processing apparatus that measures optical characteristics in a biological tissue has the following problems. In a spherical light absorber in a living tissue, an elastic wave generated by the photoacoustic effect can be expressed by Expression (1).

Here, P is the pressure of the elastic wave generated by the photoacoustic effect, and can be obtained by an elastic wave detecting means constituted by an ultrasonic transducer or the like. Further, Γ is a Gruneisen coefficient of the light absorber. Although the value differs slightly depending on the site in the living tissue, it can be treated as a constant value. Μ _a is the light absorption coefficient of the absorber. Moreover, (PHI) is the light intensity irradiated to the light absorber. Α is the efficiency when the elastic wave propagates from the light absorber to the elastic wave detecting means. Although the value differs slightly depending on the site in the living tissue, it can be treated as a constant value.

Thus, in order to quantitatively obtain the light absorption coefficient mu _a is, P, gamma, [Phi, alpha is required. Here, as described above, light attenuates in the living tissue. Since the light attenuation coefficient indicating the degree of attenuation varies depending on the type (or individual) of the subject, the apparatus disclosed in Patent Document 1 can accurately measure the light intensity Φ at the measurement depth. There was a problem that it was impossible. As a result, the light absorption coefficient could not be obtained quantitatively, preventing accurate identification of the light absorber.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a biological information processing apparatus that can accurately acquire a light attenuation coefficient inside a subject.

  In order to achieve the above object, the biological information processing apparatus of the present invention employs the following configuration. That is, a light source that irradiates the subject with light, and a first light absorbing member that is disposed with the subject separated from the light irradiation portion from the light source to the subject and has optical characteristics with respect to the irradiation light that are known in advance. An elastic wave detector that detects an elastic wave generated from the first light absorbing member when the irradiated light reaches the first light absorbing member through the subject and is absorbed, and the intensity of the irradiated light, Biological information processing comprising: an arithmetic unit that calculates a light attenuation coefficient inside the subject based on the optical characteristics of the first light absorbing member and the detected intensity of the elastic wave generated from the first light absorbing member Device.

  The biological information processing method of the present invention adopts the following configuration. That is, a step of disposing a first light-absorbing member whose optical characteristics with respect to irradiation light are known in advance at a position that separates the subject from the irradiation site of light irradiated on the subject, and the irradiation light passes through the subject. Detecting an elastic wave generated from the first light-absorbing member when it reaches and is absorbed by the first light-absorbing member, intensity of irradiation light, and optical characteristics of the first light-absorbing member; And calculating a light attenuation coefficient inside the subject based on the detected intensity of the elastic wave generated from the first light absorbing member.

  According to the biological information processing apparatus of the present invention, the light attenuation coefficient inside the subject can be accurately acquired.

The figure explaining the structure of the apparatus of Example 1, and an acoustic signal. It shows the absorption spectra of HbO ₂ and Hb. The figure explaining another structure in Examples 1-3. The figure explaining the structure and acoustic signal of the apparatus of Example 2. FIG. FIG. 6 is a diagram for explaining a measurement example of a subject according to the second embodiment. The light absorption coefficient distribution figure _{calculated |} required from the pressure distribution _{calculated |} required from the acoustic signal, and _μeff . FIG. 6 is a diagram illustrating a configuration of a device according to a third embodiment. FIG. 9 is a diagram illustrating another configuration of the third embodiment. The figure explaining the structure and acoustic signal of the apparatus of Example 4. FIG. FIG. 6 is a diagram illustrating a configuration of a device according to a fifth embodiment. The figure which shows the acoustic signal in the position A and the position B of Example 5. FIG. FIG. 10 is a diagram illustrating a configuration of a device according to a sixth embodiment. The figure at the time of irradiating light from the 1st and 2nd compression board side of Example 6. FIG.

  The biological information processing apparatus of the present invention will be described below with reference to the drawings.

<Example 1>
In the first embodiment, a configuration example of a biological information processing apparatus to which the present invention is applied will be described.
FIG. 1A is a schematic diagram illustrating the configuration of the biological information processing apparatus according to the present embodiment. In FIG. 1A, 1 is a light source, 2 is a first compression plate, 3 is a second compression plate, 4 is a light absorbing member, 5 is an elastic wave detector, and E is a subject. The subject E is a living tissue such as a breast, for example, and is held between the first compression plate 2 and the second compression plate 3 arranged at a predetermined distance L.
The biological information processing apparatus of the present embodiment includes a light source 1 that irradiates light on a subject E, a light absorbing member 4 that is disposed at a predetermined distance L from the light irradiation portion of the subject, and an elastic wave generated by the light absorbing member 4. The elastic wave detector 5 to detect, the calculating part 14, and the display apparatus 15 are provided.

Details of each component will be described below.
The light source 1 is a light source that emits pulsed light in a nanosecond order with a specific wavelength that irradiates the subject E. The wavelength of the light emitted from the light source 1 is selected according to the absorption spectrum of water, fat, protein, oxyhemoglobin, deoxyhemoglobin and the like that constitute the living tissue. As an example, the range of 600 to 1500 nm is suitable because it absorbs water, which is the main component of the internal tissue of the living body, and transmits light well, and is characterized by the spectra of fat, oxyhemoglobin, and reduced hemoglobin.
Further, it is known that when a tumor such as cancer grows in a living tissue, the formation of new blood vessels and the consumption of oxygen increase. As a method for evaluating the formation of new blood vessels and the increase in oxygen consumption, the characteristics of absorption spectra of oxygenated hemoglobin (HbO ₂ ) and reduced hemoglobin (Hb) can be used. FIG. 2 is an absorption spectrum of HbO ₂ and Hb in the wavelength range of 600 to 1000 nm.
The biological information processing apparatus measures the concentrations of HbO ₂ and Hb contained in the blood in the biological tissue from the absorption spectra of multiple wavelengths of HbO ₂ and Hb. Then, measure the HbO ₂ and Hb and the concentration at a plurality of locations, it is possible to determine the area where new blood vessels are formed in the living tissue by creating an image of the density distribution. Further, it is possible to calculate the oxygen saturation from the concentrations of HbO ₂ and Hb, and to determine the region where the oxygen consumption is increasing from the oxygen saturation. Thus, the spectral information of HbO ₂ and Hb measured by the biological information processing apparatus can be used for diagnosis.
As a specific light source 1, for example, a semiconductor laser that generates different wavelengths, a wavelength tunable laser, or the like can be used.

Further, an optical system 6 for guiding the light emitted from the light source 1 to the subject E is provided. The optical system 6 includes an optical fiber and a lens. The light emitted from the light source 1 is enlarged by the optical system 6 so that the entire area of the contact surface between the first compression plate 2 and the subject E is illuminated, and the surface of the subject E through the first compression plate 2. Led to.
The first compression plate 2 is a flat plate having high transmission characteristics and low attenuation characteristics with respect to light emitted from the light source 1. Examples of the material constituting the first compression plate 2 include glass, polymethylpentene polymer, polycarbonate, and acrylic. The light transmittance of the first compression plate 2 is β.
The second compression plate 3 is a flat plate having high transmission characteristics and low attenuation characteristics with respect to elastic waves generated by the subject E and the light absorbing member 4 due to the photoacoustic effect. Examples of the material constituting the second compression include polymethylpentene polymer, polycarbonate, and acrylic.

The light absorbing member 4 is a spherical light absorber, and is embedded in a surface in contact with the subject E inside the second compression plate 3. The size of the light absorbing member 4 is set to several mm or less in accordance with a frequency band that can be detected by the elastic wave detector 5 described later. As a material constituting the light absorbing member 4, colored silicon rubber, a polymer resin material, or the like can be used. The light absorbing member 4 corresponds to the first light absorbing member of the present invention.
Optical characteristics such _{as the} light absorption coefficient μ _as for the light of the specific wavelength emitted from the light source 1 of the light absorbing member 4 and the Gruneisen parameter Γs are determined by the material constituting the light absorbing member 4 and are known in advance. It is.

The elastic wave detector 5 detects elastic waves generated from the subject E and the light absorbing member 4 by the photoacoustic effect. This elastic wave (typically an ultrasonic wave) is also called an acoustic wave.
The elastic wave detector 5 is composed of a piezoelectric element having a piezoelectric effect for converting a pressure change caused by the received elastic wave into an electric signal. In the present specification, an acoustic signal is obtained by converting an elastic wave generated by the photoacoustic effect into an electric signal by a piezoelectric element. It is known that the formation of new blood vessels associated with the growth of a tumor such as cancer increases when the size of the tumor becomes about 2 mm or more. For this reason, as a piezoelectric element, 0 generated from a light absorber of several mm or less due to the photoacoustic effect.
. A material suitable for detecting an elastic wave of 5 MHz to several tens of MHz may be used. As an example of the material for this purpose, a piezoelectric ceramic material typified by PZT (lead zirconate titanate) or a polymer piezoelectric film material typified by PVDF (polyvinylidene fluoride) can be used.
As described above, the frequency of the elastic wave generated by the light absorbing member 4 is set to the same band as the frequency band of the elastic wave generated by the subject E. Therefore, the elastic wave generated from each of the light absorbing member 4 and the subject E can be detected with high sensitivity by the common elastic wave detector 5.

The acoustic wave detector 5 is provided with an acoustic lens 7. The material constituting the acoustic lens is preferably a material having acoustic characteristics similar to those of the subject E and the second compression plate 3, and examples thereof include silicon rubber and a polymer resin material.
When the acoustic lens 7 is made of a material having a sound velocity slower than that of the subject E and the second compression plate 3, the shape becomes a convex lens. In that case, the focal length is determined by the curvature of the convex surface, and the focusing size and the focal depth are determined by the focal length and the diameter of the lens. The acoustic lens 7 is set so that the depth of focus becomes longer than L, and an elastic wave generated from the subject E and the absorbing member 4 on the central axis of the acoustic lens 7 can be selectively detected.
In this embodiment, an acoustic lens is used, but a concave piezoelectric element may be used. An array probe in which a plurality of piezoelectric elements used in an ultrasonic echo device or nondestructive inspection are arranged in an array may be used. In this case, a signal at a desired position is acquired from a plurality of acoustic signals acquired from a plurality of piezoelectric elements using the Sum And Delay Beamforming method.
The computing unit 14 is configured by an information processing device that performs computation using a CPU or the like, acquires a set value in the light source 1, a detection value by the elastic wave detector 5, and the like, and performs various computations using mathematical formulas described later. . Furthermore, image reconstruction is performed using the calculation result as necessary. The display device 15 is a display capable of displaying the calculation result of the calculation unit 14 and the reconstructed image. For example, a liquid crystal display can be used.

Next, a specific method for quantitatively obtaining the light absorption coefficient of the subject E with the biological information processing apparatus having the configuration of FIG.
The irradiation light to the subject E propagates while repeating strong scattering by cells constituting the tissue. Further, since the light is absorbed by blood in the tissue in the course of propagation, the light intensity is significantly attenuated. An average optical attenuation coefficient indicating such an average attenuation characteristic of the subject E is defined as μ _eff . Further, if the light intensity of the light beam emitted from the optical system 6 is Φ1, and the light intensity of the light beam that has propagated through the subject E having a thickness L and reaches the light absorbing member 4 is Φ2, Φ2 is expressed by Equation (2). Can be represented.

ここで、光透過率βは圧迫板の材料により、Γｓとμ_ａｓとαｓは光吸収部材の材料により定まる。Φ１は光を照射する際の強度と光学系６の効率により定まる。Ｌは実測により求められる。したがって、弾性波の圧力Ｐｓが検出できれば、式（２）と式（３）からμ_ｅｆｆを求めることができる。 In FIG. 1B, the elastic wave detector 5 detects the elastic wave generated by the photoacoustic effect from the subject E and the light absorbing member 4 that has received the irradiation light, and the calculation unit 14 creates and displays the display device 15. It is the profile of the acoustic signal displayed on the screen. The acoustic signal is acquired as a spike-like waveform generated from the contact surface between the first compression plate 2 and the subject E and the light absorbing member 4.
The vertical axis in the figure indicates the pressure of the elastic wave obtained by converting the acoustic signal from the characteristics of the piezoelectric element used in the elastic wave detector 5. The horizontal axis indicates the distance converted from the time and the sound velocity of the subject E. At this time, if the propagation efficiency of the elastic wave from the light absorbing member 4 to the elastic wave detector 5 is αs, the pressure Ps of the elastic wave generated from the light absorbing member 4 can be expressed by Expression (3).

Here, the light transmittance β is the material of the compression plate, gamma] s and mu _{the as} and αs is determined by the material of the light absorbing member. Φ1 is determined by the intensity of light irradiation and the efficiency of the optical system 6. L is obtained by actual measurement. Therefore, if the pressure Ps of the elastic wave can be detected, μ _eff can be obtained from the equations (2) and (3).

As described above, in the biological information processing apparatus according to the present embodiment, the average light attenuation coefficient μ _eff of the subject E can be obtained by arranging the light absorbing member and performing the measurement.

  In this embodiment, the first compression plate 2 and the second compression plate 3 are used to hold the subject E such as a breast at a predetermined distance L. However, as shown in FIG. A non-configuration is also possible. In this case, the light absorbing member 4 made of the same material as that of the acoustic lens 7 can be embedded in the surface in contact with the subject E inside the acoustic lens 7.

<Example 2>
In the second embodiment, a biological information processing apparatus having a configuration different from that of the first embodiment will be described. FIG. 4A is a schematic diagram illustrating the configuration of the biological information processing apparatus according to this embodiment. The configuration of the basic biological information processing apparatus is the same as that shown in the first embodiment, and the constituent members having the same numbers have the same functions as those described in the first embodiment. In this embodiment, since the present light absorber 8 in the inside of the subject E, describe a procedure for quantitatively obtaining an optical absorption coefficient mu _a is its optical characteristic value. When the subject is a human body, examples of the light absorber include HbO _{2 in} new blood vessels accompanying a tumor and a contrast agent.

FIG. 4B shows a profile of an acoustic signal obtained by detecting an elastic wave generated by the subject E, the light absorbing member 4 and the light absorber 8 by the photoacoustic effect by the elastic wave detector 5. The acoustic signal is acquired as a spike-like waveform generated from the contact surface between the first compression plate 2 and the subject E, the light absorbing member 4, and the light absorber 8. In the figure, the vertical axis represents the pressure of the elastic wave, and the horizontal axis represents the distance. Therefore, by analyzing the profile, it is possible to acquire the distance x from the irradiation site to the light absorber inside the subject and having different optical characteristics from the surroundings. Specifically, since the average light attenuation coefficient mu _eff is been determined, it is possible to obtain the distance x from the pressure P _X is the intensity of the acoustic wave generated from the light absorber 8. Alternatively, the distance x can be obtained simply from the detection time of the acoustic signal shown in FIG.
At this time, the light intensity Φx of the light beam that has propagated through the subject E by the distance x and has reached the light absorber 8 can be expressed by Expression (4).

ここで、光透過率βは圧迫板の材料により定まる。Φ１は光を照射する際の強度と光学系６の効率により定まる。μ_ｅｆｆは実施例１の方法により求められ、距離ｘは上記のように音響信号のプロファイルから求められる。αは光吸収部材の特性により定まる。従って、弾性波の圧力Ｐｘが求められれば、式（４）と式（５）から光吸収係数μ_ａを定量的に求めることができる。 If the Gruneisen parameter of the light absorber 8 is Γ and the propagation efficiency of the elastic wave from the light absorber 8 to the elastic wave detector 5 is α, the pressure Px of the elastic wave generated by the light absorber 8 is It can be expressed by equation (5).

Here, the light transmittance β is determined by the material of the compression plate. Φ1 is determined by the intensity of light irradiation and the efficiency of the optical system 6. μ _eff is obtained by the method of Example 1, and the distance x is obtained from the profile of the acoustic signal as described above. α is determined by the characteristics of the light absorbing member. Therefore, as long demanded pressure Px of the elastic wave can be determined from equation (4) and (5) the light absorption coefficient mu _a quantitatively.

A measurement example of the subject in the present embodiment will be described with reference to FIGS. The arrows in FIGS. 5 to 6 indicate the light irradiation direction.
FIG. 5 shows a schematic configuration of the apparatus in the measurement example of the subject E, which is the same configuration as described in FIGS. 1 (a) and 4 (a). Light absorber 8a inside the specimen E with the same light absorption coefficient mu _a, 8b are present. FIG. 6A is a pressure distribution image in which the pressure obtained from the acoustic signal of the measurement example of FIG. 5 is plotted, and the higher the pressure, the higher the density is displayed. 6 (b) is an example of measurement of an acoustic signal and quantitative light absorption coefficient mu optical absorption coefficient mu _a distribution image obtained by plotting _a determined from mu _eff of 5, the larger the optical absorption coefficient mu _a Displayed at a high concentration.
Here, in the pressure distribution image of FIG. 6A, a high contrast is obtained in the image 8a ′ close to the light irradiation site, but the contrast of the image 8b ′ far from the light irradiation site is low in the surroundings. It is difficult to distinguish the boundary. On the other hand, the light absorption coefficient mu _a distribution image of FIG. 6 (b), the image of 8a closer to the irradiation site of the light '' and far 8b from the irradiation site of the light '' has a higher contrast both at the same concentration to obtain The boundary with the surroundings can be distinguished well.

As described above, in the biological information processing apparatus according to the present embodiment, the average light attenuation coefficient μ _eff of the subject E can be acquired, and the light absorption of the light absorber 8 inside the subject E can be obtained. it can be quantitatively obtain the coefficient mu _a. For example, when the subject is a human body, if the light absorption coefficient of HbO ₂ can be detected by such an apparatus, the generation of new blood vessels can be noticed.

  In this embodiment, the first compression plate 2 and the second compression plate 3 are used to hold the subject E such as a breast at a predetermined distance L. However, as shown in FIG. A non-configuration is also possible.

<Example 3>
In the third embodiment, a biological information processing apparatus having a configuration different from that of the above-described embodiment will be described. FIG. 7 is a schematic diagram illustrating the configuration of the biological information processing apparatus according to the present embodiment. The basic configuration of the biological information processing apparatus is the same as that shown in the second embodiment, and the constituent members having the same numbers have the same functions as those described in the first embodiment.

この時、光吸収部材４が発生した弾性波の圧力Ｐｓは、実施例１と同様に式（３）で表すことができる。また、光吸収体８が発生した弾性波の圧力Ｐｘは、実施例２と同様に式（５）で表すことができる。よって、式（３）と式（６）からμ_ｅｆｆを求めることができる。さらに、求めたμ_ｅｆｆと式（５）と式（７）から光吸収係数μ_ａを定量的に求めることができる。 In this embodiment, an optical system 9 is provided as an optical system for guiding the irradiation light from the light source 1 to the subject E instead of the optical system 6 described in the first embodiment.
The optical system 9 is composed of an optical fiber and a lens, like the optical system 6. The optical system 6 has expanded the light emitted from the light source 1 so as to illuminate the entire area of the contact surface between the first compression plate 2 and the subject E. On the other hand, the optical system 9 has a light beam diameter irradiated onto the subject E smaller than that of the optical system 6 and illuminates from a partial region of the contact surface, so that the optical energy density per unit area is increased. Is set. In this case, when considered as propagation of a point light source starting from the light irradiation site of the subject E, Φ2 can be expressed by Equation (6). Moreover, (PHI) x can be represented by Formula (7).

At this time, the pressure Ps of the elastic wave generated by the light absorbing member 4 can be expressed by Expression (3) as in the first embodiment. Further, the pressure Px of the elastic wave generated by the light absorber 8 can be expressed by Expression (5) as in the second embodiment. Therefore, μ _eff can be obtained from the equations (3) and (6). Further, the light absorption coefficient μ _a can be quantitatively determined from the determined μ _eff and the equations (5) and (7).

As described above, the biological information processing apparatus according to the present embodiment obtains the average light attenuation coefficient μ _eff of the subject E even when the point light source starting from the light irradiation site of the subject E is used. can do. Further, it is possible to quantitatively obtain the light absorption coefficient mu _a light absorbing body 8 at the inside of the subject E.

  In this embodiment, the first compression plate 2 and the second compression plate 3 are used to hold the subject E such as a breast at a predetermined distance L. However, as shown in FIG. A non-configuration is also possible. Further, in the present embodiment, the light source 1 and the elastic wave detector 5 are arranged on the same axis, but a structure not arranged on the same axis as shown in FIG. 8 is also possible.

<Example 4>
In the fourth embodiment, a biological information processing apparatus having a configuration different from that of the above-described embodiment will be described. FIG. 9A is a schematic diagram illustrating the configuration of the biological information processing apparatus according to the present embodiment. The configuration of the basic biological information processing apparatus is the same as that shown in the second embodiment, and the constituent members having the same numbers have the same functions as those described in the second embodiment.
In the present embodiment, a second light absorbing member 10 is newly provided. The second light absorbing member 10 is a spherical light absorber and is embedded in a surface in contact with the subject E inside the first compression plate 2. The size of the second light absorbing member 10 is set to several mm or less in accordance with the frequency band that can be detected by the elastic wave detector 5 as in the case of the light absorbing member 4 described above. Moreover, the material which comprises the 2nd light absorption member 10 can utilize the silicon rubber, the polymeric resin material, etc. which were colored similarly to the light absorption member 4. The second light absorbing member 10 corresponds to the second light absorbing member of the present invention.
The optical characteristics such as the light absorption coefficient μ _as2 and the _Gruneisen parameter Γs2 for the irradiation light of a specific wavelength emitted from the light source 1 of the second light absorbing member 10 are determined by the material constituting the second light absorbing member 10. .

前記の実施例では、Φ１は光源１が発する光強度値と光学系６或いは光学系９の効率によって定まる値としていたが、本実施例では式（８）によってΦ１を求めるようにしている。光源１を構成する半導体レーザーや波長可変レーザーなどは、周囲の温度変化などにより出力する光強度値が変化することがある。そこで本実施例のように第二光吸収部材１０を設けてＰｓ２を取得すれば、Γｓ２，μａｓ２，αｓ２は第二光吸収部材の材質により定まるので、式（８）からΦ１を求めることが可能になる。その結果、光源１が発する光強度値が変化する場合にも正確な測定を行うことができる。 FIG. 9B shows a profile of an acoustic signal obtained by detecting an elastic wave generated by the light absorbing member 4, the light absorber 8, and the second light absorbing member 10 by the photoacoustic effect by the elastic wave detector 5. The acoustic signal is acquired as a spike-like waveform generated from the light absorbing member 4, the light absorber 8, and the second light absorbing member 10. In the figure, the vertical axis represents pressure, and the horizontal axis represents distance.
At this time, if the propagation efficiency of the elastic wave from the second light absorbing member 10 to the elastic wave detector 5 is αs2, the pressure Ps2 of the elastic wave generated by the second light absorbing member 10 is expressed by Expression (8). Can do.

In the above embodiment, Φ1 is a value determined by the light intensity value emitted from the light source 1 and the efficiency of the optical system 6 or 9, but in the present embodiment, Φ1 is obtained by the equation (8). A semiconductor laser, a wavelength tunable laser, or the like constituting the light source 1 may change its output light intensity value due to a change in ambient temperature. Therefore, if Ps2 is obtained by providing the second light absorbing member 10 as in the present embodiment, Γs2, μas2, and αs2 are determined by the material of the second light absorbing member, so that Φ1 can be obtained from Equation (8). become. As a result, accurate measurement can be performed even when the light intensity value emitted from the light source 1 changes.

Μ _eff can be obtained from the equations (2), (3), and (8) described in the first embodiment. Further, the light absorption coefficient μ _a can be quantitatively determined from the determined μ _eff and the equations (4) and (5) described in the second embodiment.

As described above, in the biological information processing apparatus according to the present embodiment, the average light attenuation coefficient of the subject E is provided even when the second light absorbing member 10 is provided and the light intensity value emitted from the light source 1 is changed. μ _eff can be obtained. Further, it is possible to quantitatively obtain the light absorption coefficient mu _a light absorbing body 8 at the inside of the subject E.

<Example 5>
In the fifth embodiment, a biological information processing apparatus having a configuration different from that of the above-described embodiment will be described. FIG. 10 is a schematic diagram illustrating the configuration of the biological information processing apparatus according to the present embodiment. The configuration of the basic biological information processing apparatus is the same as that shown in the third embodiment, and the constituent members having the same numbers have the same functions as those described in the third embodiment.

In this embodiment, the light source 1, the optical system 9, the light absorbing member 4, the elastic wave detector 5, and the acoustic lens 7 are configured to be movable from the position A to the position B in the y-axis direction. As the drive mechanism, a mechanism such as a rack and pinion or a lead screw that converts the rotational motion of the motor into a linear motion can be used. Similarly to the structure described with reference to FIG. 3, the light absorbing member 4 made of the same material as the acoustic lens 7 is embedded in the surface in contact with the subject E inside the acoustic lens 7.
When the light absorber 8 exists on the axis connecting the light source 1 and the elastic wave detector 5, the light intensity Φ 2 of the irradiation light to the light absorbing member 4 is affected by the light absorber 8. In particular, this effect becomes significant when considered as propagation of a point light source starting from the light irradiation portion of the subject E described in the third embodiment.
In order to obtain the light absorption coefficient μ _a of the subject E with high accuracy, it is preferable to obtain an average light attenuation coefficient μ _eff excluding the influence of the light absorber 8. For this reason, it is considered that the profile of the acoustic signal is acquired at a plurality of positions, a profile in which no light absorber exists between the light irradiation part and the light absorbing member 4 is selected, and the average light attenuation coefficient μ _eff is obtained. It is done.

実施例３で説明した式（６）と本実施例の式（９）からμ_ｅｆｆが求められる。
また、位置Ｂで測定した光吸収体８が発生した弾性波の圧力ＰｘＢは、式（１０）で表すことができる。

上で求めたμ_ｅｆｆと実施例３で説明した式（７）と本実施例の式（１０）から光吸収係数μ_ａを定量的に求めることができる。 FIG. 11A shows a profile of an acoustic signal detected by the elastic wave detector 5 at the position A. FIG. The acoustic signal is acquired as a spike-like waveform generated from the contact surface between the first compression plate 2 and the subject E and the light absorbing member 4. FIG. 11B is a profile of the acoustic signal detected by the elastic wave detector 5 at the position B. The acoustic signal is acquired as a spike-like waveform generated from the contact surface of the first compression plate 2 and the subject E, the light absorber 8, and the light absorbing member 4. 11A and 11B, the vertical axis represents pressure, and the horizontal axis represents distance.
FIG. 11A in which it is considered that no light absorber exists between the light irradiation part and the light absorbing member 4.
) To obtain an average optical attenuation coefficient μ _eff .
When the attenuation when the elastic wave propagates inside the acoustic lens 7 can be ignored, the pressure PsA of the elastic wave generated by the light absorbing member 4 measured at the position A can be expressed by Expression (9).

Μ _eff is obtained from the equation (6) described in the third embodiment and the equation (9) of the present embodiment.
Further, the pressure PxB of the elastic wave generated by the light absorber 8 measured at the position B can be expressed by Expression (10).

The light absorption coefficient μ _a can be quantitatively obtained from μ _eff obtained above, equation (7) described in Example 3, and equation (10) of the present example.

As described above, in the biological information processing apparatus according to the present embodiment, an average light attenuation coefficient μ of the subject E is selected by selecting a profile in which no light absorber exists between the light irradiation portion and the light absorbing member 4. _eff can be obtained. Further, it is possible to quantitatively obtain the light absorption coefficient mu _a light absorbing body 8 at the inside of the subject E.

<Example 6>
In the sixth embodiment, a biological information processing apparatus having a configuration different from that of the above-described embodiment will be described.
FIG. 12 is a schematic diagram illustrating the configuration of the biological information processing apparatus according to the present embodiment. The basic configuration of the biological information processing apparatus is the same as that shown in the fourth embodiment, and the constituent members having the same numbers have the same functions as those described in the fourth embodiment.
In the present embodiment, a second compression plate 11 is provided instead of the second compression plate 3 with respect to the configuration of the fourth embodiment described with reference to FIG. 9A, and a second light source is provided on the second compression plate 11 side. 1 'and 2nd optical system 6' and the acousto-optic beam splitter 12 are additionally provided. The second compression plate 11 is a flat plate having high transmission characteristics and low attenuation characteristics with respect to elastic waves generated by the subject E, the light absorbing member 4 and the second light absorbing member 10 by the light emitted from the light source 1 and the photoacoustic effect. It is. Examples of materials having high transmission characteristics and low attenuation characteristics with respect to both light and sound include resin materials such as polymethylpentene polymer, polycarbonate, and acrylic.
The acousto-optic beam splitter 12 reflects the light emitted from the second light source 1 ′ and transmits the elastic wave generated by the photoacoustic effect. Similar to the second compression plate 11 described above, a resin material having high transmission characteristics and low attenuation characteristics for light and sound, aluminum, silver, etc. having high reflection characteristics for light emitted from the second light source 1 ′, etc. The thin film layer 13 is provided. Although the difference in acoustic impedance between the resin material and the metal material used for the thin film layer 13 is large, the thin film layer 13 has a thickness of about several μm and is sufficiently small with respect to the acoustic wavelength, so that it hardly affects. Further, the light use efficiency when both the second compression plate 11 and the acousto-optic beam splitter 12 are combined is represented by βn.
By simultaneously irradiating the subject E with light from the light source 1 and the second light source 1 ′ arranged so as to face each other, the light energy of the irradiation light from both light sources is superimposed inside the subject E. The light intensity reaching the deep part can be increased. In this embodiment, it will be described quantitatively procedure for obtaining an optical absorption coefficient mu _a light absorbing body 8 in case of using two light sources.

FIG. 13A is a schematic diagram for explaining a case where light is irradiated only from the first compression plate 2 side.
In this case, in the same manner as described in the first embodiment, the light absorbing member 4 propagates through the subject E having a light intensity of Φ1 m and a thickness L emitted from the optical system 6 on the first compression plate 2 side. If the light intensity of the light flux that has reached Φ2m is Φ2m, it can be expressed by Equation (11). Further, the light intensity of the light beam that has propagated through the subject E by the distance x and arrived at the light absorber 8 can be expressed by Expression (12).

On the other hand, FIG.13 (b) is a figure explaining the case where light is irradiated only from the 2nd compression board 11 side. This case can also be considered in the same manner as in FIG. The light intensity of the light beam emitted from the second optical system 6 ′ on the second compression plate 11 side is Φ2n, and the light intensity of the light beam that has propagated through the subject E having a thickness L and reached the second light absorbing member 10 is Φ1n. Then, Φ1n can be expressed by Equation (13). Further, the light intensity of the light beam that has propagated through the subject E by the distance (Lx) and reached the light absorber 8 can be expressed by Expression (14).

以上、式（１１）〜式（１７）までの７個の式が独立に成り立つ。Φ１ｍは光源１が発する光の強度と、光学系６の効率によって定まる。Φ２ｎは第二光源１’が発する光の強度と、第二光学系６’の効率によって定まる。また、ＰｓとＰｓ２とＰｘとｘは、音響信号のプロファイルから取得できる。上述の式における未知数は、Φ２ｍ、Φｘｍ、Φ１ｎ、Φｘｎ、μ_ｅｆｆ、μ_ａの６個であるので、式（１１）〜式（１７）を用いてμ_ｅｆｆと光吸収係数μ_ａを定量的に求めることができる。 Next, consider a case where the light source 1 and the second light source 1 ′ are simultaneously irradiated with light. At this time, the pressure Ps of the elastic wave generated by the light absorbing member 4 can be expressed by Expression (15). Moreover, the pressure Ps2 of the elastic wave generated by the second light absorbing member 10 can be expressed by Expression (16). Further, the pressure Px of the elastic wave generated by the light absorber 8 can be expressed by Expression (17).

As described above, the seven expressions from Expression (11) to Expression (17) are independently established. Φ1m is determined by the intensity of light emitted from the light source 1 and the efficiency of the optical system 6. Φ2n is determined by the intensity of light emitted from the second light source 1 ′ and the efficiency of the second optical system 6 ′. Ps, Ps2, Px, and x can be acquired from the profile of the acoustic signal. Since there are six unknowns in the above equation, Φ2m, Φxm, Φ1n, Φxn, μ _eff , and μ _a , μ _eff and the light absorption coefficient μ _a are quantitatively calculated using Equations (11) to (17). Can be requested.

As described above, the biological information processing apparatus according to the present embodiment can acquire the average light attenuation coefficient μ _eff of the subject E even when the subject E is irradiated with a plurality of light sources. As a result, it is possible to quantitatively obtain the light absorption coefficient mu _a light absorbing body 8 at the inside of the subject E.

Moreover, in Examples 1-6, although the elastic wave which generate | occur | produces from a known absorber is detected with the probe which measures the light absorption coefficient distribution of a subject, the elastic wave from a known absorber is detected. Therefore, the same effect can be obtained even if another detection means is arranged.
Moreover, in Examples 1-6, although the case where the light absorption member was provided in the predetermined position was shown, it is sufficient to arrange the light absorption member only when detecting the elastic wave generated by the light absorption member, The same effect can be obtained by retracting the light absorbing member during measurement.
Moreover, in Examples 1-6, although the case where the light absorption member was embed | buried under the 1st or 2nd compression board was shown, the 1st or 2nd compression board which has the light absorption coefficient and Gruneisen parameter peculiar to material Can also be used as a light absorbing member.

1: Light source 4: Light absorbing member 5: Elastic wave detector 14: Calculation unit

Claims (7)

A light source for irradiating the subject with light;
A first light-absorbing member that is disposed in a manner that separates the subject from the light-irradiated portion of the subject from the light source, the optical characteristics of the irradiation light being known in advance,
An elastic wave detector for detecting an elastic wave generated from the first light absorbing member when irradiated light reaches the first light absorbing member through the subject and is absorbed;
An operation for calculating a light attenuation coefficient inside the subject based on the intensity of irradiation light, the optical characteristics of the first light absorbing member, and the detected intensity of the elastic wave generated from the first light absorbing member. And a biological information processing apparatus. The elastic wave detector further detects an elastic wave generated from the light absorber when the irradiated light reaches the light absorber inside the subject and is absorbed,
The computing unit is
Calculate the position of the light absorber based on the acoustic signal of the elastic wave generated from the detected light absorber,
The biological information processing apparatus according to claim 1, wherein the intensity of light reaching the light absorber is calculated from the calculated light attenuation coefficient of the subject and the calculated position of the light absorber. The calculation unit calculates an optical characteristic of the light absorber from the detected intensity of the elastic wave generated from the light absorber and the calculated intensity of light reaching the light absorber. Item 3. The biological information processing apparatus according to Item 2. A second light-absorbing member that is disposed in a region irradiated with light on the subject and has predetermined optical characteristics with respect to the irradiated light;
The elastic wave detector further detects an elastic wave generated from the second light absorbing member when irradiation light is absorbed by the second light absorbing member,
The said calculating part calculates the intensity | strength of irradiated light based on the optical characteristic of a said 2nd light absorption member, and the intensity | strength of the elastic wave generate | occur | produced from the detected said 2nd light absorption member. Item 4. The biological information processing apparatus according to any one of Items 1 to 3. Further comprising a compression plate for compressing the subject between the light source and the subject;
The biological information processing apparatus according to claim 1, wherein the irradiation light is applied to the entire region of the contact surface between the subject and the compression plate. Further comprising a compression plate for compressing the subject between the light source and the subject;
The biological information processing apparatus according to claim 1, wherein the irradiation light is applied as a point light source to a part of a contact surface between the subject and the compression plate. Placing a first light-absorbing member whose optical characteristics with respect to the irradiation light are known in advance at a position separating the object from the irradiation site of the light irradiated to the object;
Detecting an elastic wave generated from the first light absorbing member when the irradiated light reaches the first light absorbing member through the subject and is absorbed;
A step of calculating a light attenuation coefficient inside the subject based on the intensity of irradiation light, the optical characteristics of the first light absorbing member, and the detected intensity of the elastic wave generated from the first light absorbing member. And a biological information processing method.

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