JP6250132B2 - Subject information acquisition device - Google Patents

Description

  The present invention relates to a subject information acquisition apparatus.

  As one method for obtaining optical property values in a living body, there is photoacoustic tomography (PAT) using the properties of ultrasonic waves that are less scattered in the living body than light (Non-Patent Document 1). When the living body is irradiated with pulsed light generated from the light source, the light propagates while diffusing in the living body. When the absorber contained in the living body absorbs the propagated light, an acoustic wave such as an ultrasonic wave is generated by the photoacoustic effect. By receiving this ultrasonic wave with the probe and analyzing the received signal, it is possible to obtain an optical characteristic value distribution in the living body, particularly a light absorption density distribution.

According to Non-Patent Document 1, the sound pressure P of ultrasonic waves obtained from an in-vivo absorber by light absorption in PAT can be expressed by the following equation (1).
P = Г ・ μ _a・ Φ (1)
Here, Γ is a Gruneisen coefficient that is an elastic characteristic value, and is obtained by dividing the product of the square of the volume expansion coefficient β and the speed of sound c by the specific heat C _p . μ _a is an absorption coefficient of the absorber, and Φ is a light beam absorbed by the absorber.

  As can be seen from equation (1), the sound pressure of the ultrasonic wave in the PAT is proportional to the amount of light reaching the absorber. Therefore, in order to obtain a strong signal, it is necessary to increase the amount of light applied to the living body.

  On the other hand, the maximum exposure allowance (MPE: Maximum Permissible Exposure) is defined as the maximum value of the irradiation density irradiated on the living body in the standards related to laser safety (JISC6802). In order to increase the amount of light applied to the living body while considering MPE, uniform illumination is required.

  In the PAT, it is desirable to scan the illumination unit and the reception unit in order to perform measurement over a wide range of the living body. When the light source is large like a solid laser, it is difficult to scan the light source body. For this reason, it is preferable to transmit the light emitted from the light source through an optical fiber and scan the exit portion of the optical fiber. When the amount of light is large and transmission is not possible with one optical fiber, a bundle fiber in which optical fibers are bundled is preferable.

  As a characteristic of the bundle fiber, since the light is spread after being emitted, the amount of light in the peripheral portion is smaller than that in the central portion. Although it is conceivable to make the beam uniform by using a lens or the like between the bundle fiber and the living body, in that case, there is a disadvantage that the apparatus becomes large. In particular, in a PAT in which the illumination unit is a handheld type, it is desirable to configure the operation unit with a minimum number of parts for weight reduction.

  In the field of image display devices, an example is disclosed in which the emission part of a bundle fiber is branched into a plurality of equal sub-bundles (Patent Document 1). This is because the light emitted from the light source is transmitted through an optical fiber whose emission part is branched into a plurality of sub-bundles, and each display element is illuminated by placing the sub-bundle at a position corresponding to each display element. Variation in the amount of light is obtained to obtain a high-quality image.

JP 2002-214707 A

M.M. Xu, L .; Wang "Photoacoustic imaging in biomedicine, Review of scientific instruments, 77, 041101 (2006)

  The technique of Patent Document 1 has a problem that when the fiber emitting part is close to the illumination area, a dark part that is not illuminated is formed between the illumination areas of the sub-bundles, and uniform illumination is not achieved. Further, when the fiber emitting portion and the illumination area are far from each other, there is a problem that uniform illumination is not achieved because the light overlap in the central portion is stronger than the peripheral portion of the illumination region.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve the uniformity of light emitted from a bundle fiber to a subject.

The present invention employs the following configuration. That is,
A light source;
A bundle fiber including a plurality of optical fibers;
A processing unit that acquires information in the subject using an acoustic wave generated when light from the light source is irradiated on the irradiation surface of the subject from the emission unit of the bundle fiber;
Have
The exit portion of the bundle fiber is branched into a plurality of sub-bundles each including a plurality of optical fibers, and the exit ends of the plurality of sub-bundles are arranged in an array ,
The number of optical fibers constituting the sub-bundle is different between the sub-bundle at the center of the emitting portion and the sub-bundle at the peripheral portion, so that per unit area on the irradiation surface when light is irradiated. An object information acquiring apparatus characterized in that the amount of light is substantially uniform .

The present invention also employs the following configuration. That is,
A light source;
A bundle fiber including a plurality of optical fibers;
A processing unit that acquires information in the subject using an acoustic wave generated when light from the light source is irradiated on the irradiation surface of the subject from the emission unit of the bundle fiber;
Have
The exit portion of the bundle fiber is branched into a plurality of sub-bundles each including a plurality of optical fibers, and the exit ends of the plurality of sub-bundles are arranged in an array ,
The light quantity per unit area on the irradiation surface when light is irradiated is substantially uniform because the area of the emission end is different between the sub-bundle in the central part and the peripheral sub-bundle of the emission part. An object information acquiring apparatus characterized by the above.

The present invention also employs the following configuration. That is,
A light source;
A bundle fiber including a plurality of optical fibers;
A processing unit that acquires information in the subject using an acoustic wave generated when light from the light source is irradiated on the irradiation surface of the subject from the emission unit of the bundle fiber;
Have
The exit portion of the bundle fiber is branched into a plurality of sub-bundles each including a plurality of optical fibers, and the exit ends of the plurality of sub-bundles are arranged in an array ,
The light density per unit area on the irradiation surface when light is irradiated is different because the density of the sub-bundles arranged between the sub-bundle in the central part and the sub-bundle in the peripheral part is different. An object information acquiring apparatus characterized by being substantially uniform .

  ADVANTAGE OF THE INVENTION According to this invention, the uniformity of the light irradiated to a test object from bundle fiber can be improved.

1 illustrates an exemplary embodiment of the present invention. The figure which shows the light radiate | emitted from the sub-bundle. FIG. 3 is a diagram showing an irradiation density distribution of Example 1. The figure explaining a prior art method. FIG. 6 is a diagram illustrating a second embodiment. FIG. 6 is a diagram illustrating Example 3; FIG. 6 is a diagram illustrating Example 4; The figure which shows the irradiation density distribution by a conventional method. FIG. 6 is a diagram illustrating Example 5; FIG. 6 is a diagram illustrating Example 6;

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the following description.

  The present invention can be preferably applied to an illumination device that emits light using a bundle fiber. In particular, if the present invention is applied to a subject information acquisition apparatus including such an illumination device, it is possible to improve the uniformity of light irradiated to the subject. The subject information acquisition device includes a device using a photoacoustic effect that receives acoustic waves generated in the subject by irradiating the subject with light (electromagnetic waves) and acquires subject information as image data. .

  The object information acquired by the device using the photoacoustic effect is the distribution of the acoustic wave generated by the light irradiation, the initial sound pressure distribution in the object, or the light energy absorption density distribution derived from the initial sound pressure distribution. And absorption coefficient distribution, and concentration distribution of substances constituting the tissue. The concentration distribution of the substance is, for example, an oxygen saturation distribution or an oxidized / reduced hemoglobin concentration distribution.

  The acoustic wave referred to in the present invention is typically an ultrasonic wave, and includes an elastic wave called a sound wave, an ultrasonic wave, or an acoustic wave. An acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave. An acoustic detector (for example, a probe) receives an acoustic wave generated or reflected in a subject.

  Hereinafter, the configuration of the object information acquiring apparatus according to the embodiment of the present invention, particularly the illumination apparatus that is a feature of the present invention will be described.

FIG. 1 is a diagram showing a schematic configuration of a lighting device according to an exemplary embodiment of the present invention. The illumination device includes a light source 101, a bundle fiber 102, and a sub-bundle 103. The sub-bundle 103 includes a sub-bundle 103a with a large number of included fibers and a sub-bundle 103b with a small number of included fibers. The light irradiation surface 105 is irradiated with the outgoing light 104 from the sub-bundle. Furthermore, the subject information acquisition apparatus includes various configurations in addition to the illumination device. Hereinafter, each component will be described.

(light source)
When the subject is a living body, the light source emits light having a wavelength that is absorbed by a specific component among the components constituting the living body. The light source may be provided integrally with the biological image acquisition apparatus of the present embodiment, or may be provided separately from the light source. In order to generate photoacoustic waves efficiently, the pulse width is preferably about 10 to 50 nanoseconds.

  As the light source, a laser capable of obtaining a large output is preferable, but a light emitting diode, a flash lamp, or the like can be used instead of the laser. As the laser, various lasers such as a solid laser, a gas laser, a dye laser, and a semiconductor laser can be used. The timing, waveform, intensity, etc. of irradiation are controlled by the light source controller.

  In addition, this light source control part may be integrated with the light source. The wavelength of the light source used in the present invention is desirably a wavelength at which light propagates to the inside of the subject. Specifically, when the subject is a living body, the thickness is 500 nm or more and 1200 nm or less.

(Bundle fiber)
The bundle fiber is configured by bundling a plurality of optical fibers. The optical fiber has a core made of quartz glass or the like. Specifically, for example, a core having a diameter of 190 μm can be mentioned. Light from the light source is incident from the incident portion of the bundle fiber and transmitted by each fiber.

  The exit side of the bundle fiber is branched into a plurality of sub-bundles, and each sub-bundle is provided with an exit end for emitting transmitted light. The exit end of each sub-bundle is fixed to the exit portion so that the end faces of the exit end are arranged. The surface on which the sub-bundle end faces of the emission part are arranged forms an emission face, and the light emitted from the plurality of sub-bundle end faces on the emission face is superimposed to illuminate the target. The central sub-bundle corresponds to the first sub-bundle, and the peripheral sub-bundle corresponds to the second sub-bundle.

  If the same sub-bundles are arranged at equal intervals, the light overlap of the sub-bundles in the peripheral part is weaker than the light overlap of the sub-bundles in the central part. Therefore, in order to increase the amount of light at the peripheral portion and increase the uniformity, the bundle fiber of the present invention is such that the density of the optical fiber at the peripheral portion (sub-bundle 103a) is the optical fiber at the central portion (sub-bundle 103b). It has the feature that it is larger than the density. However, if the exit end of the sub-bundle and the light irradiation surface are too close, the light does not overlap and the effect cannot be obtained.

  Therefore, a range in which the effect of the present invention can be obtained will be described with reference to FIG. FIG. 2A shows a state in which light 202 a and 202 b emitted from two sub-bundles 201 a and 201 b overlap on the light irradiation surface 203. Point A is a point on the light irradiation surface 203 that is in front of the middle of the sub-bundles 201a and 201b. Here, the distance from the emission end face of the sub-bundle to the irradiation surface is L, the shortest pitch between two adjacent sub-bundles is p, and the width of the sub-bundle is W.

FIG. 2B shows the distribution of light emitted from a single fiber as a comparison of angle and intensity (angle distribution of light intensity). Here, the spread angle of the light emitted from the fiber is defined as an angle θ until the intensity decreases from the maximum intensity to 1 / e ² . The degree of overlap of light emitted from the sub-bundles 201a and 201b is represented by a ratio a between the maximum intensity of light on the irradiated surface and the light intensity at point A. FIG. 2C is a diagram showing the overlap of light emitted from two sub-bundles. FIG. 2D shows a and L · tan θ / p when W / p is changed from 0.2 to 0.8.
FIG.

FIG. 2E shows the relationship between L · tan θ / p and W / p when a = 0.5. From FIG. 2 (e), the relationship between L · tan θ / p and W / p can be approximated almost linearly, and if the range in which the present invention is significant is a ≧ 0.5, the following equation (2) Can be expressed as:
L · tan θ ≧ 0.76p−0.63W (2)
Therefore, all of the following examples satisfy this condition.

(Subject information acquisition device)
The subject information acquisition apparatus according to the present embodiment is a biological image acquisition apparatus that calculates a living body as a subject and information inside the living body as image data. However, the subject information acquisition apparatus may be a subject other than a living body. The object information acquisition apparatus includes a light source, a bundle fiber, a probe that receives an acoustic wave, and a processing unit that performs image reconstruction as a basic hardware configuration.

  The pulsed light emitted from the light source is transmitted through the bundle fiber and irradiated on the living body. When a part of the energy of light propagating through the living body is absorbed by a light absorber such as blood (resulting in a sound source), an acoustic wave is generated due to thermal expansion of the light absorber. The acoustic wave is received by the probe, becomes an electric signal, and is transferred to the processing unit. The processing unit generates in-vivo optical characteristic value distribution information based on the electrical signal (image reconstruction). The format of the optical characteristic value distribution information is not particularly limited, and can be arbitrarily determined depending on the purpose of measurement, the configuration of the apparatus, or the like, such as two-dimensional or three-dimensional.

(Probe)
The probe receives acoustic waves generated by the pulsed light on the surface of the living body and inside the living body. Therefore, the probe has a capability of converting an acoustic wave into an electric signal (reception signal) that is an analog signal. Any probe that can receive an acoustic wave signal, such as a probe that uses a piezoelectric phenomenon, a probe that uses resonance of light, or a probe that uses a change in capacitance, can be used. It may be used. The probe of this embodiment typically has a plurality of receiving elements arranged one-dimensionally or two-dimensionally. By using such a multidimensional array element, acoustic waves can be received simultaneously at a plurality of locations, and the measurement time can be shortened. When there is one receiving element, the probe may be scanned and received at a plurality of positions.

  The subject information acquisition apparatus desirably includes a conversion unit that converts an electrical signal obtained by the probe from an analog signal to a digital signal, and a circuit that amplifies the electrical signal. When there are a plurality of reception signals obtained from the probe, it is desirable that a plurality of signals can be processed simultaneously. Thereby, the time until the image is formed can be shortened. The converted signal is stored in the memory.

(Processing part)
The processing unit uses the signal stored in the memory to form data related to optical characteristic value distribution information such as an initial sound pressure distribution of the acoustic wave. For the formation of this optical characteristic value distribution, back projection in the time domain can be used, for example. As the processing unit, for example, an information processing device or a circuit that operates according to a program can be used.

<Example 1>
In the present embodiment, an example will be described in which the density of the fibers contained in the sub-bundle in the central part is smaller than the density of the fibers contained in the sub-bundle in the peripheral part.

FIG. 3A is an overall view of an illumination device including a light source and a bundle fiber according to the present embodiment. FIG. 3B is a diagram illustrating the shape of the fiber emitting portion of the present embodiment. This illumination device transmits light from a light source 301 that is a solid-state laser having an oscillation wavelength of 800 nm through a bundle fiber 302. A titanium sapphire laser was used as the light source 301.

  The diameter of the core of the fiber strand is 190 μm. The fiber strands are filled in a hexagonal close-packed state at the entrance. The exit portion of the bundle fiber 302 is branched into nine sub-bundles 303 having a size of 1 mm □. The nine sub-bundles are arranged in a 3 × 3 array, and the pitch p between two adjacent sub-bundles is 6 mm and is equally spaced.

As a feature of the present embodiment, the number of optical fibers included in each sub-bundle is different between the central portion and the peripheral portion. That is, when the number of fibers per unit area included in the peripheral sub-bundle 303a is 1, the number of fibers per unit area included in the central sub-bundle 303b is 0.3. The light emitted from each fiber can approximate a Gaussian distribution. In this example, when the divergence angle θ of light from one optical fiber was measured, tan θ = 0.1. In this case, the angle until the intensity decreases from the maximum intensity to 1 / e ² is defined as θ.

  FIG. 3C shows an irradiation density distribution on the light irradiation surface when the distance L from the central sub-bundle to the light irradiation surface is 100 mm. Further, FIG. 3D shows the irradiation density distribution of the cross section when the center of the irradiation density distribution of FIG.

  On the other hand, the example in the conventional illuminating device is shown in FIG. 4 as a comparison object. FIG. 4A shows a state in which the number of optical fibers per unit area included in the nine sub-bundles 401 is the same. In addition, FIG. 4B shows the irradiation density distribution on the light irradiation surface in this case. FIG. 4C shows the irradiation density distribution of the cross section when the center of FIG. 4B is cut in the horizontal direction.

  Comparing FIG. 3D, which is a cross section in the present embodiment, with FIG. 4C, which is a conventional cross section, the light uniformity is improved and a more uniform illumination distribution can be obtained in this embodiment. I understand that. This is because the number of fibers is changed for each sub-bundle position. In other words, the low irradiation density in the central part can be compensated by the fact that light from the peripheral part having a high irradiation density is incident on the irradiation surface opposite to the central part in an oblique direction. Irradiation can be realized.

  In the above description, an example in which square sub-bundles are arranged in a 3 × 3 array at equal intervals is shown, but the present invention is not limited to this. As an example, FIG. 3E shows a state in which square sub-bundles are arranged in 4 × 4. The number of optical fibers included in the four sub-bundles 304b in the central portion is smaller than the number of optical fibers included in the twelve sub-bundles 304a on the outside (peripheral portion). Even in this case, the low irradiation density in the central part is supplemented by the incident light in the oblique direction from the peripheral part, and the uniformity of the light on the irradiation surface is improved.

  The present invention is applicable not only to the same number of sub-bundle arrangements as shown in FIG. 3 but also to sub-bundle arrangements such as 4 × 5 and 5 × 7. Even in that case, the light can be uniformly irradiated by making the density of the optical fiber near the center of the emitting part smaller than the density of the optical fiber in the core around the emitting part. Further, although all the fibers have the same shape, the core area per unit area may be changed by using optical fibers having different core diameters in the central and peripheral sub-bundles. In addition, even if the sub-bundles are arranged in a circle, the present invention can be applied by relatively suppressing the light amount in the central portion assuming the central portion and the peripheral portion.

<Example 2>
In the present embodiment, an example in which a more uniform illumination distribution is obtained by changing the density of the optical fiber included in the sub-bundle depending on the location in the peripheral portion will be described. Specifically, when the array of sub-bundles is a quadrangle, the density of the optical fibers contained in the sub-bundle corresponding to the sides of the quadrangle is set higher than the density of the optical fibers contained in the sub-bundle at the corners (vertices) of the square. Make it smaller.

  FIG. 5A is an overall view of an illumination device including a light source and a bundle fiber according to the present embodiment. FIG. 5B is a diagram illustrating the shape of the fiber emitting portion of the present embodiment. The illumination device includes a light source 501 and a bundle fiber 502.

  The output part of the bundle fiber 502 is branched into nine sub-bundles having a size of 1 mm □, as in the first embodiment. The nine sub-bundles are arranged in a 3 × 3 array, and the pitch p between two adjacent sub-bundles is 6 mm and is equally spaced.

As a feature of the present embodiment, the number of optical fibers included in each sub-bundle varies depending on the position of the sub-bundle. That is, assuming that the number of optical fibers per unit area included in the sub-bundle 503a at the periphery and the vertex of the quadrangle is 5, per unit area included in the sub-bundle 503b and the center portion 503c in the side part of the periphery. The number of optical fibers is 3 and 1, respectively. The light emitted from each optical fiber can approximate a Gaussian distribution. In this example, the spread angle θ of light from one optical fiber was tan θ = 0.1. Here, the angle until the intensity decreases from the maximum intensity to 1 / e ² is defined as θ.

  FIG. 5C shows the irradiation density distribution on the light irradiation surface when the distance L from the central sub-bundle to the light irradiation surface is 100 mm. Further, the irradiation density distribution of the cross section when the center of the irradiation density distribution in FIG. 5C is cut in the horizontal direction, and a point 1 pitch (6 mm) away from the center of the irradiation density distribution are cut in the horizontal direction. The irradiation density distribution of the cross section at the time is shown in FIG. 5D and FIG. 5E, respectively.

  As a comparison object, FIG. 4D shows a cross-sectional irradiation density distribution when a point separated by 1 pitch (6 mm) from the center of the irradiation density distribution in FIG. Comparing FIG. 5D and FIG. 4C, it can be seen that the irradiation density distribution of the cross section at the center of the irradiation density distribution is equivalent. Further, comparing FIG. 5E and FIG. 4D, the irradiation density distribution of the cross section at a point 1 pitch (6 mm) away from the center of the irradiation density distribution is improved in the present embodiment. I understand that. This lowers the irradiation density of the side that receives obliquely incident light from both sides in the peripheral part, and reduces the irradiation density of the vertex that receives only obliquely incident light from the adjacent side part in the peripheral part. This is because the amount of light on the irradiated surface can be made uniform by increasing it.

  As described above, a more uniform illumination distribution can be obtained by changing the density of the optical fiber included in the sub-bundle depending on the location in the peripheral portion as in the present embodiment. In the present embodiment, an example in which an array of square sub-bundles is arranged in a quadrangle has been described, but the present invention is not limited to this. It is also possible to arrange the sub-bundles in a hexagonal close-packed structure.

  An example of the arrangement of sub-bundles other than a quadrangle is a case where the sub-bundles are arranged in a polygonal shape such as a triangle or a hexagon. In that case, if the number of optical fibers per unit area included in the polygonal central part and the side and vertex sub-bundles is (central part) <(side part) <(vertical part) Good.

<Example 3>
In the present embodiment, an example will be described in which the number of optical fibers per unit area included in each sub-bundle is the same, and a uniform illumination distribution is obtained by changing the area of each sub-bundle according to the position.

FIG. 6A is an overall view of an illumination device including a light source and a bundle fiber according to the present embodiment.
FIG. 6B is a diagram illustrating the shape of the fiber emitting portion of the present embodiment. This illumination device includes a light source 601 and a bundle fiber 602.

  The emission part of the bundle fiber 602 is branched into nine sub-bundles. Although the number of optical fibers per unit area included in each sub-bundle is the same, the size of the sub-bundle varies depending on the arrangement of the sub-bundles, and the smaller the closer to the center, the smaller. The size of each sub-bundle is 1.2 mm □ near the apex of the peripheral portion, 1 mm □ at the side portion 603 b of the peripheral portion, and 0.7 mm □ at the central portion 603 c.

  FIG. 6C shows the irradiation density distribution on the light irradiation surface when the distance from the central sub-bundle to the light irradiation surface is 100 mm. Further, FIG. 6D shows the irradiation density distribution of the cross section when the center of the irradiation density distribution of FIG. 6C is cut in the horizontal direction. As can be seen by comparing FIG. 6D and FIG. 4C, even if the number of optical fibers per unit area included in each sub-bundle is the same, the size of each sub-bundle is changed. Thus, a more uniform illumination distribution can be obtained.

The illumination device of the present embodiment has an advantage that it is easy to manufacture as compared to the method of changing the number of optical fibers per unit area as in the first and second embodiments.
<Example 4>
In Examples 1 to 3, an example in which the irradiation density or area of the emission end is different for each sub-bundle has been described. In the present embodiment, an example will be described in which, when sub-bundles having the same irradiation density and area are arranged, the density in the central portion is smaller than the density in the peripheral portion.

  FIG. 7A is an overall view of an illumination device including a light source and a bundle fiber according to the present embodiment. FIG. 7B is a diagram illustrating the shape of the fiber emitting portion of the present embodiment. The illumination device includes a light source 701 and a bundle fiber 702.

  The emission part of the bundle fiber 702 is branched into 21 sub-bundles 703 having a size of 1 mm □. The 21 sub-bundles 703 are arranged as shown in FIG. 7B, and the dotted mesh pitch is 4 mm. The number of optical fibers included in each sub-bundle is the same. As shown in the figure, the emission ends are sparse at the central portion and dense at the peripheral portion. Further, in the peripheral part, the apex part is denser than the side part.

  FIG. 7C shows the irradiation density distribution on the light irradiation surface when the distance from the central sub-bundle to the light irradiation surface is 100 mm. Further, FIG. 7D shows the irradiation density distribution of the cross section when the center of the irradiation density distribution of FIG. 7C is cut in the horizontal direction.

  As a comparison target, FIG. 8 shows an example in which the sub-bundles are arranged at equal intervals. As shown in FIG. 8B, the emission ends in the illumination device of FIG. 8A are arranged so that the density of the sub-bundle is the same at the center and the peripheral part. Further, FIG. 8C shows the irradiation density distribution on the light irradiation surface, and FIG. 8D shows the irradiation density distribution of the cross section when the center of FIG. 8C is cut in the horizontal direction. The pitch of the dotted mesh in FIG. 8B is 4 mm.

  As can be seen by comparing FIG. 7D and FIG. 8D, a more uniform illumination distribution can be obtained by arranging the sub-bundles at different densities at the center and the peripheral portion of the emitting portion. This is because, in the central portion, the amount of obliquely incident light from the bundle fiber corresponding to the adjacent region is large, and therefore the total amount of light is equal to that of the peripheral portion even if the emission ends are sparsely arranged. . On the contrary, in the peripheral portion, even if the emission ends are densely arranged, the total amount of light becomes the same as that in the central portion because of a small amount of incident light.

However, in this embodiment, an example in which the sub-bundle is a square array is shown, but the present invention is not limited to this. Specifically, the sub-bundles are arranged in a polygonal shape such as a triangle or a hexagon, and the number of sub-bundles at the central part, side part, and vertex part of the polygonal part is arranged as (central part) <( (Side part) <(Vertex part).

<Example 5>
In the first to fourth embodiments, the illumination device has been described. In this embodiment, an example in which the illumination distribution is made uniform without using a lens system between the bundle fiber and the living body in the subject information acquisition device will be described.

  FIG. 9 shows an object information acquiring apparatus according to this embodiment. Light from the light source 901 is transmitted through the bundle fiber 902 and emitted from the sub-bundles 903a and 903b. Here, the arrangement of the sub-bundles was the same as in Example 1. 903a is a sub-bundle having a small number of optical fibers per unit area, and 903b is a sub-bundle having a large number of optical fibers per unit area.

  The light 904 emitted from the sub-bundle illuminates the living body 906 held by the holding plate 905a on the bundle fiber 902 side and the holding plate 905b on the opposite side of the bundle fiber 902. The holding plate 905a is preferably easy to transmit light, and the holding plate 905b is preferably easy to transmit acoustic waves and has an acoustic impedance close to that of a living body. As an example, the holding plate 905a may be acrylic, and the holding plate 905b may be polymethylpentene. In this embodiment, the thickness of both acrylic and polymethylpentene is 10 mm. Here, the refractive index of acrylic is 1.49. In order to set the optical path length from the fiber exit end to the living body to 100 mm as in Example 1, the distance from the fiber exit end to the acrylic plate was set to 85.1 mm.

  The illuminated light diffuses inside the living body 906, and an acoustic wave 908 is generated when the diffused light is absorbed by the absorber 907. The acoustic wave 908 propagates in the living body 906 that is the subject, and a part of the acoustic wave 908 is received by the probe 909. The received signal 910 is sent to the processing unit 911, and in-vivo optical characteristic value distribution information is formed. The sub-bundles 903a and 903b and the probe 909 can be moved in a two-dimensional direction parallel to the holding plate 905.

  With the above configuration, the variation in the light intensity distribution for each light irradiation position is reduced as in the first embodiment. As a result, a photoacoustic signal can be obtained more efficiently.

<Example 6>
In the fifth embodiment, the method of scanning the sub-bundle and the probe on the holding plate has been described. However, in this embodiment, a handheld object information acquisition apparatus that manually moves the sub-bundle and the probe on the living body. explain.

  FIG. 10A shows the subject information acquisition apparatus of the present embodiment. The light from the light source 1001 is transmitted through the bundle fiber 1002 and emitted from the sub-bundles 1003a and 1003b. Here, 1003a is a sub-bundle having a small number of optical fibers per unit area, and 1003b is a sub-bundle having a large number of optical fibers per unit area. The sub-bundles 1003a and 1003b are integrated with each other at the emitting portion 1004.

At the time of measurement, the emitting unit 1004 is applied to the living body 1006 that is the subject, and the light 1005 illuminates the living body 1006. The illuminated light diffuses in the living body 1006, and when the diffused light is absorbed by the absorber 1007, an acoustic wave 1008 is generated. The acoustic wave 1008 propagates through the living body 1006 and a part thereof is received by the probe 1009. Here, the probe 1009 is integrated with the emitting unit 1004 and can manually scan the living body 1006.

  FIG. 10B is a view of the emission unit 1004 and the probe 1009 integrated from the living body 1006 side. A reception signal 1010 received by the probe 1009 is sent to the processing unit 1011 to form an optical characteristic value distribution in the living body.

  As described above, it is desirable that the light applied to the living body is uniform. However, in the case of the handheld type, it is desirable to reduce the number of parts of the illumination system in order to reduce the weight of the operation unit. Since the illumination system shown in the present embodiment does not use an optical system for uniform illumination between the bundle fiber and the living body, the illumination system can be configured with a minimum number of parts. In the present embodiment, a configuration in which no lens is used between the emitting portion and the living body is shown, but a more uniform optical system can be obtained by using an optical component such as a diffusion plate. It is also possible to provide a cover glass or the like at the exit end of the bundle fiber.

  101: light source, 102: bundle fiber, 103a: second sub-bundle, 103b: first sub-bundle, 909: probe, 911: processing unit

Claims (11)

A light source;
A bundle fiber including a plurality of optical fibers;
A processing unit that acquires information in the subject using an acoustic wave generated when light from the light source is irradiated on the irradiation surface of the subject from the emission unit of the bundle fiber;
Have
The exit portion of the bundle fiber is branched into a plurality of sub-bundles each including a plurality of optical fibers, and the exit ends of the plurality of sub-bundles are arranged in an array ,
The number of optical fibers constituting the sub-bundle is different between the sub-bundle at the center of the emitting portion and the sub-bundle at the peripheral portion, so that per unit area on the irradiation surface when light is irradiated. A subject information acquiring apparatus characterized in that the amount of light is substantially uniform .   The density of the optical fiber constituting the central sub-bundle is smaller than the density of the optical fiber constituting the peripheral sub-bundle.
The object information acquiring apparatus according to claim 1, wherein:   The light source is composed of a laser or a light emitting diode
The object information acquiring apparatus according to claim 1, wherein the object information acquiring apparatus is an object information acquiring apparatus.   Further comprising a probe connected to the sub-bundle;
  The subject information acquisition device is a handheld subject information acquisition device that manually moves the probe.
The object information acquiring apparatus according to claim 1, wherein the object information acquiring apparatus is an object information acquiring apparatus. A light source;
A bundle fiber including a plurality of optical fibers;
A processing unit that acquires information in the subject using an acoustic wave generated when light from the light source is irradiated on the irradiation surface of the subject from the emission unit of the bundle fiber;
Have
The exit portion of the bundle fiber is branched into a plurality of sub-bundles each including a plurality of optical fibers, and the exit ends of the plurality of sub-bundles are arranged in an array ,
The light quantity per unit area on the irradiation surface when light is irradiated is substantially uniform because the area of the emission end is different between the sub-bundle in the central part and the peripheral sub-bundle of the emission part. consisting <br/> object information acquiring apparatus, characterized in that.   The number of optical fibers per unit area in the sub-bundle is the same between the central sub-bundle and the peripheral sub-bundle.
The subject information acquiring apparatus according to claim 5.   The light source is composed of a laser or a light emitting diode
The object information acquiring apparatus according to claim 5 or 6, characterized in that   Further comprising a probe connected to the sub-bundle;
  The subject information acquisition device is a handheld subject information acquisition device that manually moves the probe.
The object information acquiring apparatus according to claim 5, wherein the object information acquiring apparatus is an object information acquiring apparatus. A light source;
A bundle fiber including a plurality of optical fibers;
A processing unit that acquires information in the subject using an acoustic wave generated when light from the light source is irradiated on the irradiation surface of the subject from the emission unit of the bundle fiber;
Have
The exit portion of the bundle fiber is branched into a plurality of sub-bundles each including a plurality of optical fibers, and the exit ends of the plurality of sub-bundles are arranged in an array ,
The light density per unit area on the irradiation surface when light is irradiated is different because the density of the sub-bundles arranged between the sub-bundle in the central part and the sub-bundle in the peripheral part is different. A subject information acquiring apparatus characterized by being substantially uniform .   The light source is composed of a laser or a light emitting diode
The object information acquiring apparatus according to claim 9.   Further comprising a probe connected to the sub-bundle;
  The subject information acquisition device is a handheld subject information acquisition device that manually moves the probe.
The object information acquiring apparatus according to claim 9 or 10, wherein:

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