WO2012114709A1

WO2012114709A1 - Photoacoustic imaging device, probe unit used therein, and photoacoustic imaging device operation method

Info

Publication number: WO2012114709A1
Application number: PCT/JP2012/001100
Authority: WO
Inventors: 覚入澤
Original assignee: 富士フイルム株式会社
Priority date: 2011-02-22
Filing date: 2012-02-20
Publication date: 2012-08-30
Also published as: JP2012173136A

Abstract

[Problem] To facilitate alignment of multiple branched beams and multiple optical fibers in photoacoustic imaging in which multiple optical fibers are used to guide a laser. [Solution] A photoacoustic imaging device (10) provided with: an optical branching unit (12) having both a homogenizer (41) which equalizes the intensity distribution of a laser (Lo), and a microlens array (40) which branches the laser (Lo) having the equalized intensity distribution into multiple branched beams (Ld) in accordance with a prescribed branching pattern; and a fiber bundle (14) which encompasses multiple optical fibers (13) and in which the surfaces (13e) at one end of the optical fibers (13) at the surface (14e) at one end of the fiber bundle (14) are arranged corresponding to the branching pattern. The fiber bundle (14) is arranged such that each of the plurality of branched beams (Ld) is incident to the core (13a) of a corresponding optical fiber (13).

Description

Photoacoustic imaging apparatus, probe unit used therefor, and method of operating photoacoustic imaging apparatus

The present invention relates to a photoacoustic imaging device that generates a photoacoustic image by detecting a photoacoustic wave generated in a subject by irradiating the subject with light, and a probe unit used therefor and an operation of the photoacoustic imaging device It is about the method.

Conventionally, as a method for acquiring a tomographic image inside a subject, an ultrasonic image is generated by detecting ultrasonic waves reflected in the subject by irradiating the subject with ultrasonic waves. Ultrasonic imaging for obtaining a morphological tomographic image is known. On the other hand, in the examination of a subject, development of an apparatus that displays not only a morphological tomographic image but also a functional tomographic image has been advanced in recent years. One of such devices is a device using a photoacoustic analysis method. This photoacoustic analysis method irradiates a subject with light having a predetermined wavelength (for example, visible light, near infrared light, or mid infrared light), and a specific substance in the subject absorbs the energy of this light. A photoacoustic wave, which is the resulting elastic wave, is detected and the concentration of the specific substance is quantitatively measured. The specific substance in the subject is, for example, glucose or hemoglobin contained in blood. Such a technique for detecting a photoacoustic wave and generating a photoacoustic image based on the detection signal is called photoacoustic imaging (PAI) or photoacoustic tomography (PAT).

Conventionally, there are the following problems in photoacoustic imaging using the photoacoustic effect as described above. The intensity of light applied to the subject is significantly attenuated by absorption and scattering in the process of propagating through the subject. Further, the intensity of the photoacoustic wave generated in the subject based on the irradiated light is also attenuated by absorption and scattering in the process of propagating in the subject. Therefore, in photoacoustic imaging, it is difficult to obtain information on the deep part of the subject. In order to solve this problem, for example, it is conceivable to increase the generated photoacoustic wave by increasing the amount of energy of light irradiated into the subject.

However, it is difficult to guide high-energy (1 mJ or more) pulsed laser light required in photoacoustic imaging using a single optical fiber. This is because there is a high possibility that the end face of the optical fiber will be broken, resulting in a problem of durability of the optical fiber. Therefore, it is preferable that the pulsed laser beam can be branched and guided by a plurality of optical fibers.

Further, in a photoacoustic imaging apparatus using photoacoustic imaging, a probe unit in which an optical system and an ultrasonic detection probe are combined together is used. Accordingly, the cord portion of the probe unit is required to be flexible from the viewpoint of user handling performance.

Thus, for example, Patent Document 1 discloses a method of guiding pulsed laser light to the tip of a probe unit using a bundle fiber in which a large number of thin silica optical fibers having a core and cladding structure (core / cladding structure) are bundled. Has been. However, a specific method for making the pulse laser beam incident on each of the optical fibers in the bundle fiber is not disclosed.

On the other hand, as a method of generating a plurality of branched light beams that are incident on a plurality of optical fibers, for example, a method of splitting one laser beam n times using n−1 beam splitters, and a method using a microlens array 1 A method of splitting a laser beam of a book (Patent Document 2) is mentioned.

JP 2010-12295 A JP-A-6-230240

However, in the former method, in order to obtain a large number (for example, 16 or more) of laser beams, a large number (for example, 15 or more) of beam splitters are required, and the arrangement of the optical system becomes complicated. However, there is a problem that each of the plurality of branched lights and each of the plurality of optical fibers must be separately aligned. On the other hand, in the latter method, the energy distribution of the laser light remains strong at the center of the beam, and the durability problem of the optical fiber cannot be improved.

The present invention has been made in view of the above problems, and in photoacoustic imaging performed by guiding laser light using a plurality of optical fibers, each of the plurality of branched lights and each of the plurality of optical fibers are provided. An object of the present invention is to provide a photoacoustic imaging apparatus that facilitates alignment and solves the problem of durability of optical fibers, a probe unit used therefor, and a method of operating the photoacoustic imaging apparatus. .

In order to solve the above-described problems, a photoacoustic imaging device according to the present invention includes:
A light irradiator for irradiating measurement light into the subject, an electroacoustic converter for detecting a photoacoustic wave generated in the subject by irradiation of the measurement light and converting the photoacoustic wave into an electric signal, and an electric signal In a photoacoustic imaging device provided with an image generation part which generates a photoacoustic image based on,
A homogenizer that uniformizes the intensity distribution of a single laser beam incident from the upstream side of the optical system, and a microlens array that branches the laser beam having a uniform intensity distribution into a plurality of branched light beams according to a predetermined branching pattern. An optical branch having
A bundle fiber including a plurality of optical fibers having a core / clad structure, wherein one end face of the plurality of optical fibers on one end face of the bundle fiber includes a bundle fiber arranged corresponding to a branching pattern;
The bundle fiber causes each of the plurality of branched lights to enter each of the cores of the plurality of optical fibers from the one end face of the bundle fiber, and the plurality of branch lights incident on the core are incident on the other end face of the bundle fiber. It is arranged to guide light to the connected light irradiation part,
The light irradiating unit irradiates a plurality of branched lights as measurement light.

In this specification, the “branch pattern” means a bright spot pattern formed on a focal plane perpendicular to the optical axis of the microlens array by the laser beam (branched light) branched by the microlens array.

One end face of a plurality of optical fibers is “arranged corresponding to the branch pattern” means that the end faces are arranged in the same plane so that the arrangement pattern of the end faces substantially matches the branch pattern. It means to arrange. The “array pattern” of the end faces means an array pattern of representative points (for example, the centers of the end faces) related to one end face of a plurality of optical fibers. The two patterns “substantially match” means that even if these patterns are different, each of the plurality of branched lights can enter each of the cores of the plurality of optical fibers. This means that they are treated as matching.

And it is preferable that the photoacoustic imaging apparatus according to the present invention further includes a position adjusting unit that adjusts the positional relationship between the one end face of the bundle fiber and the light branching unit.

In the photoacoustic imaging apparatus according to the present invention, the light branching section preferably has a holographic diffusion plate between the homogenizer and the microlens array.

And in the photoacoustic imaging device according to the present invention, the branch pattern has a hexagonal structure,
The one end face of the plurality of optical fibers is preferably arranged in a close-packed structure.

In the photoacoustic imaging apparatus according to the present invention, it is preferable that the one end face of the bundle fiber has a reflection mask on the end face so that the core on the end face is exposed.

And in the photoacoustic imaging device according to the present invention, the light branching part is for branching the laser light into 16 or more,
The bundle fiber preferably includes at least 16 optical fibers.

In the photoacoustic imaging apparatus according to the present invention, the homogenizer is preferably composed of a holographic diffusion plate, a condensing plano-convex lens, and a light pipe.

In the photoacoustic imaging apparatus according to the present invention, the homogenizer is preferably composed of a flat top laser beam shaver.

And in the photoacoustic imaging device according to the present invention, the light irradiation part is the other end face of the plurality of optical fibers,
It is preferable that the other end surfaces of the plurality of optical fibers are arranged in a line at intervals.

And in the photoacoustic imaging device according to the present invention, the light irradiation part is a light guide plate having a tapered shape,
It is preferable that the other end surface of the bundle fiber is connected to the end surface on the short side of the light guide plate in a detachable state.

Furthermore, the probe unit according to the present invention is:
Light that irradiates the subject with measurement light, detects photoacoustic waves generated in the subject due to measurement light irradiation, converts the photoacoustic waves into electrical signals, and generates a photoacoustic image based on the electrical signals In a probe unit used in an acoustic imaging device,
A light irradiator for irradiating measurement light into the subject;
An electroacoustic conversion unit that detects a photoacoustic wave generated in the subject by irradiation of measurement light and converts the photoacoustic wave into an electrical signal;
A homogenizer that uniformizes the intensity distribution of a single laser beam incident from the upstream side of the optical system, and a microlens array that branches the laser beam having a uniform intensity distribution into a plurality of branched light beams according to a predetermined branching pattern. An optical branch having
A bundle fiber including a plurality of optical fibers having a core / clad structure, wherein one end face of the plurality of optical fibers on one end face of the bundle fiber includes a bundle fiber arranged corresponding to a branching pattern;
In this bundle fiber, each of the plurality of branched lights is incident on each of the cores of the plurality of optical fibers from the one end face of the bundle fiber, and the plurality of branched lights incident on the core are incident on the other end face of the bundle fiber. It is arranged to guide light to the connected light irradiation part,
The light irradiation unit irradiates a plurality of branched lights as measurement light.

In the probe unit according to the present invention, it is preferable that the probe unit further includes a position adjusting unit that adjusts the positional relationship between the one end face of the bundle fiber and the light branching unit.

In the probe unit according to the present invention, the light branching section preferably has a holographic diffusion plate between the homogenizer and the microlens array.

And in the probe unit according to the present invention, the branch pattern has a hexagonal structure,
The one end face of the plurality of optical fibers is preferably arranged in a close-packed structure.

In the probe unit according to the present invention, it is preferable that the one end face of the bundle fiber has a reflection mask on the end face so that the core on the end face is exposed.

And in the probe unit according to the present invention, the light branching part is for branching the laser light into 16 or more,
The bundle fiber preferably includes at least 16 optical fibers.

In the probe unit according to the present invention, the homogenizer is preferably composed of a holographic diffuser plate, a condensing plano-convex lens, and a light pipe.

In the probe unit according to the present invention, the homogenizer is preferably composed of a flat top laser beam shaver.

Furthermore, the operation method of the photoacoustic imaging device according to the present invention is as follows.
Light that irradiates the subject with measurement light, detects photoacoustic waves generated in the subject due to measurement light irradiation, converts the photoacoustic waves into electrical signals, and generates a photoacoustic image based on the electrical signals In the operation method of the acoustic imaging apparatus,
The intensity distribution of one laser beam incident on the homogenizer from the upstream side of the optical system is homogenized by the homogenizer,
The laser light having a uniform intensity distribution is branched as a plurality of branched lights according to a predetermined branching pattern defined by the microlens array,
A bundle fiber including a plurality of optical fibers having a core / clad structure, wherein one end face of the plurality of optical fibers on one end face of the bundle fiber is used in a bundle pattern,
Each of the plurality of branched lights is incident on each of a plurality of optical fiber cores from the one end face of the bundle fiber,
A plurality of branched lights incident on the core are guided to the light irradiation unit,
It is operated to irradiate a plurality of branched lights guided to the light irradiator as measurement light.

A photoacoustic imaging apparatus and a probe unit according to the present invention include a homogenizer that uniformizes the intensity distribution of a single laser beam incident from the upstream side of the optical system, and a laser beam having a uniform intensity distribution with a predetermined branch pattern. And a bundle fiber including a plurality of optical fibers having a core / cladding structure, and a plurality of optical fibers on one end face of the bundle fiber. A bundle fiber having one end face of the bundle fiber arranged corresponding to the branching pattern, and the bundle fiber allows each of the plurality of branch lights to enter each of the cores of the plurality of optical fibers from the one end face of the bundle fiber. And a plurality of branched lights incident on the core are placed on the other end face of the bundle fiber. Characterized in that the connected light irradiation unit in which are arranged to guide. Therefore, by using the bundle fiber in which one end face of the plurality of optical fibers is arranged corresponding to the branching pattern, the alignment of each of the plurality of branched lights and each of the plurality of optical fibers can be performed collectively. it can. On the other hand, by homogenizing the intensity distribution of the laser beam, it is possible to prevent the energy distribution of the laser beam from branching while being strong at the center of the beam. As a result, in photoacoustic imaging in which laser light is guided using a plurality of optical fibers, the alignment of each of the plurality of branched lights and each of the plurality of optical fibers is facilitated. It becomes possible to solve the durability problem.

In addition, the operation method of the photoacoustic imaging apparatus according to the present invention is a laser beam in which the intensity distribution of one laser beam incident on the homogenizer from the upstream side of the optical system is made uniform by the homogenizer, and the intensity distribution is made uniform. Is a bundle fiber that includes a plurality of optical fibers having a core / cladding structure according to a predetermined branch pattern defined by the microlens array, and includes a plurality of optical fibers having a core / cladding structure. Using a bundle fiber in which one end face of the optical fiber is arranged corresponding to the branching pattern, each of the plurality of branched lights is operated to enter each of the cores of the plurality of optical fibers from the one end face of the bundle fiber. Yes. Therefore, by using the bundle fiber in which one end face of the plurality of optical fibers is arranged corresponding to the branching pattern, the alignment of each of the plurality of branched lights and each of the plurality of optical fibers can be performed collectively. it can. On the other hand, by making the intensity distribution of the laser light uniform with a homogenizer, it is possible to prevent the energy density of the laser light from branching while being strong at the center of the beam. As a result, in photoacoustic imaging in which laser light is guided using a plurality of optical fibers, the alignment of each of the plurality of branched lights and each of the plurality of optical fibers is facilitated. It becomes possible to solve the durability problem.

It is the schematic which shows the structure of one Embodiment of the photoacoustic imaging device of this invention. It is a block diagram which shows the structure of the image generation part in FIG. It is a schematic sectional drawing which shows the structure of one Embodiment of the optical branching part and bundle fiber of this invention. It is a schematic sectional drawing which shows the structural example of a homogenizer. It is a schematic sectional drawing which shows the structural example of a homogenizer. It is a schematic sectional drawing which shows the structural example of a homogenizer. It is the schematic which shows the example of the arrangement | sequence of the end surface of the some optical fiber in the incident end surface of a bundle fiber. It is the schematic which shows the example of the arrangement | sequence of the end surface of the some optical fiber in the incident end surface of a bundle fiber. It is the schematic which shows the reflective mask provided in the incident end surface of bundle fiber. It is a schematic sectional drawing which shows a structure when the optical branching part further has the position adjustment part which adjusts the positional relationship of a light branching part and bundle fiber in FIG. It is a schematic sectional drawing which shows a structure when the optical branching part further provided with the holographic diffusion plate in FIG. It is the schematic which shows the structure of the front-end | tip part of the probe unit of this invention. It is the schematic which shows the other structure of the front-end | tip part of the probe unit of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. In addition, for easy visual recognition, the scale of each component in the drawings is appropriately changed from the actual one.

“Embodiments of Photoacoustic Imaging Device, Probe Unit, and Photoacoustic Imaging Device Operation Method”
An embodiment of the photoacoustic imaging apparatus 10 of the present invention will be described. FIG. 1 is a schematic diagram illustrating the overall configuration of the photoacoustic imaging apparatus 10 according to the present embodiment. FIG. 2 is a block diagram illustrating a configuration of the image generation unit 2 of FIG. FIG. 3 is a schematic sectional view showing the configuration of an embodiment of the optical branching section 12 and the bundle fiber 14 of the present invention.

The photoacoustic imaging apparatus 10 according to the present embodiment generates a measurement light L including a specific wavelength component and irradiates the subject 7 with the measurement light L, and the measurement light L is irradiated to the subject 7. An image generation unit 2 that detects photoacoustic waves U generated in the subject 7 to generate photoacoustic image data of an arbitrary cross section, an electroacoustic conversion unit 3 that converts an acoustic signal and an electrical signal, A display unit 6 for displaying the photoacoustic image data, an operation unit 5 for an operator to input patient information and imaging conditions of the apparatus, and a system control unit 4 for comprehensively controlling these units. .

The probe unit 70 of the present embodiment includes the electroacoustic conversion unit 3, the light branching unit 12, the bundle fiber 14, and the light irradiation unit 15.

The method of operating the photoacoustic imaging apparatus of the present invention irradiates the subject 7 with the measurement light L, detects the photoacoustic wave U generated in the subject 7 by the irradiation of the measurement light L, and detects the photoacoustic wave. In the operation method of the photoacoustic imaging apparatus 10 that converts U into an electrical signal and generates a photoacoustic image based on the electrical signal, the intensity distribution of one laser light Lo incident on the homogenizer 41 from the upstream side of the optical system is calculated. A plurality of optical fibers 13 having a core / cladding structure are obtained by branching the laser light Lo, which is made uniform by the homogenizer 41 and has a uniform intensity distribution, into a plurality of branched lights Ld according to a predetermined branching pattern defined by the microlens array 40. And one end face 13e of the plurality of optical fibers 13 on one end face 14e of the bundle fiber 14 is branched. The bundle fibers 14 are arranged corresponding to the loops, and each of the plurality of branched lights Ld is made incident on each of the cores 13a of the plurality of optical fibers 13 from the one end face 14e of the bundle fiber 14, and enters the core 13a. The photoacoustic imaging device 10 that guides the plurality of incident branched lights Ld to the light irradiation unit 15 and irradiates the plurality of branched lights Ld guided to the light irradiation unit 15 as the measurement light L is operated. .

The optical transmission unit 1 includes a light source unit 11 including a plurality of light sources having different wavelengths, a light branching unit 12 that branches the laser light Lo output from the light source unit 11 as a plurality of branched lights Ld, and a plurality of branched lights Ld. A bundle fiber 14 that guides light to the light irradiation unit 15 and a light irradiation unit 15 that irradiates the body surface of the subject 7 with the measurement light L are provided.

The light source unit 11 includes, for example, one or more light sources that generate light having a predetermined wavelength. As the light source, a light emitting element such as a semiconductor laser (LD), a solid-state laser, or a gas laser that generates a specific wavelength component or monochromatic light including the component can be used. The light source unit 11 preferably outputs pulsed light having a pulse width of 1 to 100 nsec as laser light. The wavelength of the laser light is appropriately determined according to the light absorption characteristics of the substance in the subject to be measured. Although hemoglobin in a living body has different optical absorption characteristics depending on its state (oxygenated hemoglobin, reduced hemoglobin, methemoglobin, carbon dioxide hemoglobin, etc.), it generally absorbs light of 600 nm to 1000 nm. Therefore, for example, when the measurement target is hemoglobin in a living body (that is, when imaging a blood vessel), it is generally preferable to set the thickness to about 600 to 1000 nm. Further, from the viewpoint of reaching the deep part of the subject 7, the wavelength of the laser light is preferably 700 to 1000 nm. The output of the laser beam is 10 μJ / cm ² to several tens of mJ / cm ² from the viewpoints of propagation loss of laser beam and photoacoustic wave, efficiency of photoacoustic conversion, detection sensitivity of the current detector, and the like. Is preferred. Further, the repetition of the pulsed light output is preferably 10 Hz or more from the viewpoint of image construction speed. Further, the laser light may be a pulse train in which a plurality of the above-mentioned pulse lights are arranged.

More specifically, for example, when the hemoglobin concentration of the subject 7 is measured, an Nd: YAG laser (emission wavelength: about 1000 nm) which is a kind of solid-state laser, or a He—Ne gas laser (emission light) which is a kind of gas laser. A laser beam having a pulse width of about 10 nsec is formed using a wavelength of 633 nm. When a small light emitting element such as an LD is used, a material such as InGaAlP (emission wavelength: 550 to 650 nm), GaAlAs (emission wavelength: 650 to 900 nm), InGaAs or InGaAsP (emission wavelength: 900 to 2300 nm) is used. Can be used. Recently, a light-emitting element using InGaN that emits light with a wavelength of 550 nm or less is becoming available. Furthermore, an OPO (Optical Parametrical Oscillators) laser using a nonlinear optical crystal capable of changing the wavelength can be used.

The light branching unit 12 branches the laser light Lo output from the light source unit 11 using the homogenizer 41 and the microlens array 40. The number of branches is not particularly limited, but it is preferable to branch to 16 or more from the viewpoint of effectively dispersing the energy of the laser light Lo. In the present embodiment, the light branching unit 12 includes a homogenizer 41 and a microlens array 40.

The microlens array 40 includes a plurality of microlenses arranged in a lattice pattern, and a predetermined branch pattern is defined by the number and arrangement of the microlenses. The branch pattern is not particularly limited, but is preferably a square structure or a hexagonal structure, and more preferably a hexagonal structure.

The homogenizer 41 is an optical element for making the intensity distribution of the laser light Lo incident from the upstream side of the optical system uniform and guiding the laser light with the uniform intensity distribution to the microlens array 40. Further, the homogenizer 41 may be configured to expand the beam diameter of the laser light Lo having a uniform intensity distribution. In the present embodiment, the homogenizer 41 expands the laser light Lo output from the light source unit 11 in accordance with the width of the microlens array 40 (FIG. 3). The homogenizer 41 may be composed of a single optical element or a combination of a plurality of optical elements.

The homogenizer 41 includes, for example, a microlens array A45 (lens pitch p = 0.5 mm, focal length f = 46.7 mm), a microlens array B46 (p = 0.5 mm, f = 15.3 mm), a plano-convex lens 47 (f = 100 mm), and a variable beam expander 48 (5 × magnification) can be arranged and configured as shown in FIG. 4A. At this time, the lens pitch and the focal length for the microlens array 40 are, for example, p = 0.5 mm and f = 13.8 mm, respectively. The homogenizer 41 is appropriately combined with a holographic diffusion plate 49, a condensing plano-convex lens 50 (f = 50 mm), and a light pipe 51 (for example, the length is 150 mm and the cross-sectional size is 2 mm square) as shown in FIG. 4B. It can also be configured as shown in FIG. The holographic diffusion plate 49 is preferably a low-angle diffusion plate of about 0.2 degrees to about 2.0 degrees. At this time, the lens pitch and the focal length for the microlens array 40 are, for example, p = 0.3 mm and f = 4.8 mm, respectively. Further, as shown in FIG. 4C, the homogenizer 41 can also be constituted by a flat top laser beam shaver 52 in which an aspheric lens for correcting the beam intensity distribution, for example, is incorporated. The specific configuration of the homogenizer 41 is an example in which the beam diameter of the laser light Lo is 3.0 mm.

The bundle fiber 14 guides the laser beam Lo branched by the light branching unit 12 to the light irradiation unit 15. The bundle fiber 14 includes a plurality of optical fibers 13 having a core 13a and a clad 13b. The optical fiber 13 is not particularly limited, but is preferably a quartz fiber. The plurality of optical fibers 13 are arranged corresponding to a predetermined branch pattern defined by the microlens array 40 from the viewpoint of efficiently guiding the plurality of branch lights Ld. The arrangement pattern of the end faces 13e of the plurality of optical fibers 13 on the incident end face 14e of the bundle fiber 14 can be appropriately selected according to the shape of the microlens array 40, and the arrangement of the plurality of optical fibers 13 in the bundle fiber 14 is easy. From the viewpoint of the above, a square structure or a hexagonal structure is preferable, and a hexagonal structure is more preferable. The end faces 13e of the plurality of optical fibers 13 are particularly preferably arranged in a close-packed structure. This is for the following reason. 5A and 5B are conceptual diagrams illustrating an example of the arrangement of the end faces 13e of the plurality of optical fibers 13 on the incident end face 14e of the bundle fiber 14. FIG. 5A shows a case where the arrangement of the end faces 13e of the 64 optical fibers 13 has a square structure, and FIG. 5B shows a case where the arrangement of the end faces 13e of the 61 optical fibers 13 has a close-packed structure. Thus, consider the case where the same number of optical fibers 13 are arranged in a square structure and the case where they are arranged in a close-packed structure. At this time, when the distances from the center of the array pattern to the end face of the optical fiber farthest (W1 in FIG. 5A and W2 in FIG. 5B) are compared with each other, the above-mentioned distance W2 of the close-packed structure is a square structure. It turns out that it becomes shorter than the said distance W1. That is, the optical system can be made more compact when the arrangement pattern has the closest packing structure. Therefore, the arrangement of the end faces 13e of the plurality of optical fibers 13 on the incident end face 14e of the bundle fiber 14 is particularly preferably a close-packed structure.

Further, apart from the above viewpoint, when it is particularly important to increase the alignment accuracy of the plurality of optical fibers 13 in the bundle fiber 14, they may be divided and arranged for each line using a V-groove substrate. By arranging each line with reference to a glass or metal surface processed with a V-groove with high accuracy, the arrangement accuracy of the plurality of optical fibers 13 can be further increased. In such a case, the V-groove substrate is selected so that the plurality of optical fibers 13 are arranged corresponding to the branch pattern of the microlens array 40, or the micro-groove is matched to the arrangement of the plurality of optical fibers 13 by the V-groove substrate. A lens array 40 is designed.

When each of the plurality of branched lights Ld is incident on each of the cores 13a of the plurality of optical fibers 13, the branch pattern of the branched lights Ld and the arrangement pattern of the end faces 13e of the plurality of optical fibers 13 are substantially matched. is important.

In the bundle fiber 14, the one end face 14e of the bundle fiber 14 preferably has a reflective mask M on the end face 14e so that the core 13a on the end face 14e is exposed as shown in FIG. The bundle fiber 14 is usually manufactured by fixing a gap between the plurality of optical fibers 13 with an adhesive. However, the adhesive has lower durability against laser light than optical fiber materials such as quartz. Therefore, the reflection mask M as described above can prevent the laser light from being irradiated to the region excluding the region of the core 13a where the plurality of branched lights Ld are incident. Such a reflective mask M is formed by, for example, depositing a dielectric multilayer film on a thin glass plate that has been drilled in accordance with the arrangement pattern of the cores 13a, and then the glass 13 so that the cores 13a and the holes are matched with each other. It is possible to form the plate by sticking it to the one end face 14e of the bundle fiber 14.

In this embodiment, the light irradiation unit 15 includes a plurality of emission end faces 13e of the plurality of optical fibers 13. The plurality of emission end faces 13e of the plurality of optical fibers 13 constituting the light irradiation unit 15 are arranged along the periphery of the electroacoustic conversion unit 3, for example. In this case, the plurality of emission end faces 13 e of the plurality of optical fibers 13 form a plane, a convex surface, or a concave surface together with the plurality of conversion elements 54 constituting the electroacoustic conversion unit 3. In this embodiment, it is a plane. Moreover, when the some conversion element 54 which comprises the electroacoustic conversion part 3 is a transparent material, you may arrange | position the light irradiation part 15 so that the whole conversion element can be irradiated from the upper direction of the conversion element 54. FIG.

The electroacoustic conversion unit 3 is composed of, for example, a plurality of minute conversion elements 54 arranged in a one-dimensional or two-dimensional manner. The conversion element 54 is a piezoelectric element made of a polymer film such as piezoelectric ceramics or polyvinylidene fluoride (PVDF). The electroacoustic conversion unit 3 receives the photoacoustic wave U generated in the subject 7 by the light irradiation from the light irradiation unit 15. The conversion element 54 has a function of converting the photoacoustic wave U into an electric signal at the time of reception. The electroacoustic conversion unit 3 is configured to be small and light, and is connected to a receiving unit 22 described later by a multi-channel cable. The electroacoustic conversion unit 3 is selected according to the diagnostic region from among sector scanning, linear scanning, convex scanning, and the like. The electroacoustic conversion unit 3 may include an acoustic matching layer in order to efficiently transmit the photoacoustic wave U. In general, the acoustic impedance of the piezoelectric element material and the living body are greatly different. Therefore, when the piezoelectric element material and the living body are in direct contact with each other, reflection at the interface becomes large and the photoacoustic wave cannot be efficiently transmitted. For this reason, a photoacoustic wave can be efficiently transmitted by inserting the acoustic matching layer comprised with the substance which has an intermediate acoustic impedance between piezoelectric element material and a biological body. Examples of the material constituting the acoustic matching layer include epoxy resin and quartz glass.

The image generation unit 2 of the photoacoustic imaging apparatus 10 selectively drives the plurality of conversion elements 54 constituting the electroacoustic conversion unit 3 and gives a predetermined delay time to the electric signal from the electroacoustic conversion unit 3 to adjust the electric signal. A receiving unit 22 that generates a received signal by performing phase addition, a scanning control unit 24 that controls the selection drive of the conversion element 54 and the delay time of the receiving unit 22, and various types of received signals obtained from the receiving unit 22 And a signal processing unit 25 for performing the above processing.

As shown in FIG. 2, the receiving unit 22 includes an electronic switch 53, a preamplifier 55, a reception delay circuit 56, and an adder 57.

The electronic switch 53 selects a predetermined number of adjacent conversion elements 54 when receiving photoacoustic waves in photoacoustic scanning. For example, when the electroacoustic conversion unit 3 includes 192 conversion elements CH1 to CH192 of an array type, such an array conversion element is converted into an area 0 (area of conversion elements from CH1 to CH64 by an electronic switch 53). ), Area 1 (region of the conversion element from CH65 to CH128) and area 2 (region of the conversion element from CH129 to CH192) are handled by being divided. When an array type conversion element composed of N conversion elements in this way is handled as a group (area) of n (n <N) adjacent transducers, and an imaging operation is performed for each area, It is not necessary to connect preamplifiers or A / D conversion boards to the conversion elements of all channels, the structure of the probe unit 70 can be simplified, and an increase in cost can be prevented. Further, when the emission ends of the plurality of optical fibers 13 are arranged so that each area can be individually irradiated with light, the light output per one time does not need to be increased, so that the high output is expensive. There is also an advantage that it is not necessary to use a simple light source. Each electric signal obtained by the conversion element 54 is supplied to the preamplifier 55.

The preamplifier 55 amplifies a minute electric signal received by the conversion element 54 selected as described above, and ensures sufficient S / N.

The reception delay circuit 56 forms a converged reception beam by matching the phase of the photoacoustic wave U from a predetermined direction with the electrical signal of the photoacoustic wave U obtained from the conversion element 54 selected by the electronic switch 53. Give a delay time to do.

The adder 57 adds together the electric signals of a plurality of channels delayed by the reception delay circuit 56, and combines them into one reception signal. By this addition, phasing addition of acoustic signals from a predetermined depth is performed, and a reception convergence point is set.

The scanning control unit 24 includes a beam focusing control circuit 67 and a conversion element selection control circuit 68. The conversion element selection control circuit 68 supplies position information of a predetermined number of conversion elements 54 at the time of reception selected by the electronic switch 53 to the electronic switch 53. On the other hand, the beam focusing control circuit 67 supplies delay time information for forming reception convergence points formed by a predetermined number of conversion elements 54 to the reception delay circuit 56.

The signal processing unit 25 includes a filter 66, a signal processor 59, an A / D converter 60, and an image data memory 62. The electrical signal output from the adder 57 of the receiving unit 22 removes unnecessary noise in the filter 66 of the signal processing unit 25, and thereafter, the signal processor 59 performs logarithmic conversion of the amplitude of the received signal to make the weak signal relative. Stress. In general, the received signal from the subject 7 has an amplitude with a wide dynamic range of 80 dB or more, and a weak signal is emphasized in order to display it on a normal monitor having a dynamic range of about 23 dB. Amplitude compression is required. The filter 66 has a band pass characteristic, and has a mode for extracting a fundamental wave in a received signal and a mode for extracting a harmonic component. The signal processor 59 performs envelope detection on the logarithmically converted received signal. The A / D converter 60 A / D converts the output signal of the signal processor 59 to form photoacoustic image data for one line. The photoacoustic image data for one line is stored in the image data memory 62.

The image data memory 62 is a storage circuit that sequentially stores the photoacoustic image data for one line generated as described above. The system control unit 4 reads out data for one line of a certain section stored in the image data memory 62 and necessary for generating a one-frame photoacoustic image. The system control unit 4 combines the data for one line while spatially interpolating to generate photoacoustic image data for one frame of the cross section. Then, the system control unit 4 stores the photoacoustic image data for one frame in the image data memory 62.

The display unit 6 includes a display image memory 63, a photoacoustic image data converter 64, and a monitor 65. The display image memory 63 is a buffer memory that reads photoacoustic image data for one frame to be displayed on the monitor 65 from the image data memory 62 and temporarily stores it. The photoacoustic image data converter 64 performs D / A conversion and television format conversion on the photoacoustic image data for one frame stored in the display image memory 63, and the output is displayed on the monitor 65.

The operation unit 5 includes a keyboard, a trackball, a mouse, and the like on the operation panel, and is used by an apparatus operator to input necessary information such as patient information, apparatus imaging conditions, and a display section.

The system control unit 4 includes a CPU (not shown) and a storage circuit (not shown), and controls each unit such as the optical transmission unit 1, the image generation unit 2, and the display unit 6 according to a command signal from the operation unit 5 and the entire system. Supervised. In particular, the input command signal of the operator sent via the operation unit 5 is stored in the internal CPU.

Next, the operation of the present invention will be described.

As shown in FIG. 3, the photoacoustic imaging device 10 and the probe unit 70 of the present invention particularly include a homogenizer 41 that uniformizes the intensity distribution of one laser beam Lo incident from the upstream side of the optical system, and an intensity distribution. Includes a light branching section 12 having a microlens array 40 for branching the laser light Lo, which has been made uniform, into a plurality of branching lights Ld according to a predetermined branching pattern, and a plurality of optical fibers 13 having a core 13a / cladding 13b structure. A bundle fiber 14 in which one end face 13e of the plurality of optical fibers 13 on one end face 14e of the bundle fiber 14 is arranged corresponding to a branching pattern. Each of the plurality of branched lights Ld is connected to each of the cores 13a of the plurality of optical fibers 13. The plurality of branched lights Ld incident on the one end surface 14e of the dollar fiber 14 and incident on the core 13a are guided to the light irradiation unit 15 connected on the other end surface 14e of the bundle fiber 14. It is characterized by that. That is, according to the present invention, the branch pattern of the microlens array 40 and the arrangement pattern of the end faces 13e of the plurality of optical fibers 13 on the incident end face 14e of the bundle fiber 14 correspond to each of the plurality of branch lights Ld and the plurality of lights. It is possible to perform alignment with each of the fibers 13 at once. Further, the intensity distribution of the laser light Lo is made uniform by the homogenizer 41, thereby preventing the energy distribution of the laser light Lo from branching while being strong at the beam center. This eliminates the need to separately align each of the plurality of branched lights Ld and each of the plurality of optical fibers 13, and further solves the problem of durability of the optical fiber.

As a result, high-energy pulsed laser light can be transmitted, and a high-quality photoacoustic image can be captured. Furthermore, the flexibility and durability of the cord portion of the probe unit can be easily achieved.

"Design change of operation method of photoacoustic imaging device, probe unit and photoacoustic imaging device"
The photoacoustic imaging device 10 and the probe unit 70 of the present invention are not limited to the embodiment described above.

For example, as shown in FIG. 7, the photoacoustic imaging apparatus 10 and the probe unit 70 of the present invention include a position adjusting unit 14 a that adjusts the positional relationship between the one end surface 14 e of the bundle fiber 14 and the light branching unit 12. Can be configured. Alternatively, a position adjustment unit may be provided to control the microlens array 40. The position adjusting unit 14a can be configured to measure the measurement light L emitted from the probe unit 70 and automatically adjust the positional relationship so that the measured light quantity becomes the maximum value. This makes it easier to align each of the plurality of branched lights Ld and each of the plurality of optical fibers 13.

Further, for example, the photoacoustic imaging device 10 and the probe unit 70 of the present invention are configured such that the optical branching unit 12 has a holographic diffusion plate 42 between the homogenizer 41 and the microlens array 40 as shown in FIG. can do. The holographic diffusion plate 42 arranged in this manner changes the direction in which the condensing spot diameter of the plurality of branched lights Ld increases, and the plurality of branched lights when entering the core 13a on the incident end face 14e of the bundle fiber 14. The beam diameter of Ld is optimized. Therefore, the plurality of branched lights Ld can be guided so as not to exceed the damage threshold energy density of the optical fiber 13.

Further, for example, in the photoacoustic imaging device 10 and the probe unit 70 of the present invention, as shown in FIG. 9, the light irradiation unit 15 is the other end surface 13e of the plurality of optical fibers 13, and the other end surface 13e is spaced. It can be configured to be arranged in a line with the With this configuration, it is not necessary to provide an optical system with a complicated structure at the probe unit tip 71, and a uniform line-shaped light source can be obtained. In addition, a more uniform line light source can be obtained by adjusting the distance in consideration of the intensity of the branched light Ld emitted from each of the plurality of optical fibers 13. For example, it is preferable that the interval is adjusted to be wide when the intensity of the branched light Ld is strong, and to be narrowed when the intensity is weak.

Further, for example, as shown in FIG. 10, the photoacoustic imaging device 10 and the probe unit 70 of the present invention are a light guide plate 72 in which the light irradiation unit 15 has a tapered shape, and the other end face 14 e of the bundle fiber 14. However, it can be configured to be connected to the end face on the short side of the light guide plate 72 in a detachable state. For example, in FIG. 13, the other end surface 14 e of the bundle fiber 14 and the end surface on the short side of the light guide plate 72 are connected to each other in the connector portion 73. With this configuration, when the bundle fiber 14 is damaged, it is possible to replace only the bundle fiber, and the maintenance performance is improved.

Claims

A light irradiating unit that irradiates measurement light into the subject, an electroacoustic conversion unit that detects a photoacoustic wave generated in the subject by the irradiation of the measuring light, and converts the photoacoustic wave into an electrical signal; In a photoacoustic imaging device comprising an image generation unit that generates a photoacoustic image based on the electrical signal,
A homogenizer for homogenizing the intensity distribution of one laser beam incident from the upstream side of the optical system, and a microlens array for diverging the laser beam having the uniform intensity distribution into a plurality of branched light beams according to a predetermined branching pattern; An optical branch having
A bundle fiber including a plurality of optical fibers having a core / cladding structure, wherein one end face of the plurality of optical fibers on one end face of the bundle fiber is arranged corresponding to the branch pattern; With
The bundle fiber causes each of the plurality of branched lights to enter each of the cores of the plurality of optical fibers from the one end face of the bundle fiber, and the plurality of branched lights incident on the core are incident on the bundle fiber. Is arranged so as to be guided to the light irradiation part connected at the other end face of
The photoacoustic imaging apparatus, wherein the light irradiation unit irradiates the plurality of branched lights as the measurement light.
The photoacoustic imaging apparatus according to claim 1, further comprising a position adjusting unit that adjusts a positional relationship between the one end face of the bundle fiber and the light branching unit.
3. The photoacoustic imaging apparatus according to claim 1, wherein the optical branching unit includes a holographic diffusion plate between the homogenizer and the microlens array.
The branch pattern has a hexagonal structure;
4. The photoacoustic imaging apparatus according to claim 1, wherein the one end face of the plurality of optical fibers is arranged in a close-packed structure. 5.
5. The photoacoustic imaging apparatus according to claim 1, wherein the one end face of the bundle fiber has a reflection mask on the end face so that the core on the end face is exposed.
The light branching part branches the laser light into 16 or more;
6. The photoacoustic imaging apparatus according to claim 1, wherein the bundle fiber includes at least 16 optical fibers.
The photoacoustic imaging device according to any one of claims 1 to 6, wherein the homogenizer includes a holographic diffuser plate, a condensing plano-convex lens, and a light pipe.
7. The photoacoustic imaging apparatus according to claim 1, wherein the homogenizer includes a flat top laser beam shaver.
The light irradiation part is the other end face of the plurality of optical fibers;
9. The photoacoustic imaging apparatus according to claim 1, wherein the other end faces of the plurality of optical fibers are arranged in a line at intervals.
The light irradiation part is a light guide plate having a tapered shape,
9. The photoacoustic imaging apparatus according to claim 1, wherein the other end face of the bundle fiber is connected to an end face on a short side of the light guide plate in a detachable state. .
Irradiating measurement light into a subject, detecting a photoacoustic wave generated in the subject by the irradiation of the measurement light, converting the photoacoustic wave into an electric signal, and photoacoustic image based on the electric signal In the probe unit used in the photoacoustic imaging device that generates
A light irradiator for irradiating measurement light into the subject;
An electroacoustic conversion unit that detects a photoacoustic wave generated in the subject by irradiation of the measurement light and converts the photoacoustic wave into an electric signal;
A homogenizer for homogenizing the intensity distribution of one laser beam incident from the upstream side of the optical system, and a microlens array for diverging the laser beam having the uniform intensity distribution into a plurality of branched light beams according to a predetermined branching pattern; An optical branch having
A bundle fiber including a plurality of optical fibers having a core / cladding structure, wherein one end face of the plurality of optical fibers on one end face of the bundle fiber is arranged corresponding to the branch pattern; With
The bundle fiber causes each of the plurality of branched lights to enter each of the cores of the plurality of optical fibers from the one end face of the bundle fiber, and the plurality of branched lights incident on the core are incident on the bundle fiber. Is arranged so as to be guided to the light irradiation part connected at the other end face of
The probe unit, wherein the light irradiation unit irradiates the plurality of branched lights as the measurement light.
The probe unit according to claim 11, further comprising a position adjusting unit that adjusts a positional relationship between the one end face of the bundle fiber and the optical branching unit.
The probe unit according to claim 11 or 12, wherein the optical branching unit includes a holographic diffusion plate between the homogenizer and the microlens array.
The branch pattern has a hexagonal structure;
The probe unit according to claim 11, wherein the one end face of the plurality of optical fibers is arranged in a close-packed structure.
The probe unit according to any one of claims 11 to 14, wherein the one end face of the bundle fiber has a reflection mask on the end face so that the core on the end face is exposed.
The light branching part branches the laser light into 16 or more;
The probe unit according to claim 11, wherein the bundle fiber includes at least 16 optical fibers.
The probe unit according to any one of claims 11 to 16, wherein the homogenizer includes a holographic diffuser plate, a condensing plano-convex lens, and a light pipe.
The probe unit according to any one of claims 11 to 16, wherein the homogenizer includes a flat top laser beam shaver.
Irradiating measurement light into a subject, detecting a photoacoustic wave generated in the subject by the irradiation of the measurement light, converting the photoacoustic wave into an electrical signal, and photoacoustic image based on the electrical signal In a method of operating a photoacoustic imaging device that generates
The intensity distribution of one laser beam incident on the homogenizer from the upstream side of the optical system is homogenized by the homogenizer,
Branching the laser light having a uniform intensity distribution as a plurality of branch lights according to a predetermined branch pattern defined by the microlens array;
A bundle fiber including a plurality of optical fibers having a core / cladding structure, wherein one end face of the plurality of optical fibers on one end face of the bundle fiber is arranged corresponding to the branch pattern. Use
Allowing each of the plurality of branched lights to enter each of the cores of the plurality of optical fibers from the one end face of the bundle fiber;
Guiding the plurality of branched lights incident on the core to the light irradiation unit;
An operation method of a photoacoustic imaging apparatus, wherein the plurality of branched lights guided to the light irradiation unit are irradiated as the measurement light.