WO2012111336A1

WO2012111336A1 - Photoacoustic imaging device, probe unit used in same, and method for operating photoacoustic imaging device

Info

Publication number: WO2012111336A1
Application number: PCT/JP2012/001025
Authority: WO
Inventors: 覚入澤
Original assignee: 富士フイルム株式会社
Priority date: 2011-02-16
Filing date: 2012-02-16
Publication date: 2012-08-23
Also published as: JP2012168091A; JP5559080B2

Abstract

In order to enable the facilitation of the alignment of a plurality of branched lights and a plurality of optical fibers in photoacoustic imaging performed by guiding laser light using the plurality of optical fibers, this photoacoustic imaging device is provided with: a light branching unit that has a branching diffraction optical element that branches a single beam of laser light, which has entered from the upstream side of an optical system, into a plurality of branched lights in accordance with a predetermined branching pattern; and a bundled fiber that contains the plurality of optical fibers having a core/cladding structure and that arrays, in correspondence with the branching pattern, one end surface of the plurality of optical fibers that are at one end surface of the bundled fiber. The bundled fiber is disposed in a manner so that the plurality of branched lights are caused to enter the respective cores of the plurality of optical fibers.

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 the end face of the optical fiber is likely to be destroyed. 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 for generating a plurality of branched light beams to be incident on a plurality of optical fibers, for example, Patent Document 2 discloses a method in which n-1 beam splitters are used to split one laser beam into n branches, and diffraction. A method of splitting one laser beam into a plurality of beams using an optical element (DOE: Diffractive / Optical / Elements) is disclosed.

JP 2010-12295 A JP 2005-308967 A

However, in the former method in Patent Document 2, 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 necessary, and the arrangement of the optical system is complicated. However, there is a problem that the apparatus becomes large, and 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 in Patent Document 2, although it is possible to branch the laser beam at once using a diffractive optical element, each of the plurality of branched lights and each of the plurality of optical fibers are positioned separately. There is no change in the points that must be matched. The operation of individually aligning each of the plurality of branched lights and each of the plurality of optical fibers is very complicated.

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. It is an object of the present invention to provide a photoacoustic imaging apparatus that can facilitate alignment, a probe unit used therefor, and a method for 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 irradiating unit for irradiating measurement light into the subject, an electroacoustic conversion unit for detecting a photoacoustic wave generated in the subject by irradiation of the measuring light and converting the photoacoustic wave into an electrical signal, and an electrical signal In a photoacoustic imaging device comprising an image generation unit that generates a photoacoustic image based on
An optical branching unit having a branching diffractive optical element that splits one laser beam incident from the upstream side of the optical system as a plurality of branching lights according to a predetermined branching pattern;
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;
This bundle fiber allows each of a plurality of branched lights to enter each of a plurality of optical fiber cores from the one end face of the bundle fiber, and the plurality of branched lights incident on the core are connected to the other end face of the bundle fiber. It is arranged to guide the light irradiated part,
The light irradiating unit irradiates a plurality of branched lights as measurement light.

In this specification, the “branch pattern” means a pattern of bright spots on a virtual plane perpendicular to the traveling direction of the laser beam before branching about the laser beam (branching light) branched by the branching diffractive optical element. To do. In such a branch pattern, since the branched laser beam has a divergence angle, the scale of the pattern varies depending on the position of the virtual plane. Therefore, in general, a pattern obtained by removing the scale information from a pattern including such scale information (including an array pattern described later) and standardizing the pattern (for example, the length between the two most distant points is 1) is used. This is called the “standard pattern” of the pattern.

One end face of the plurality of optical fibers is “arranged corresponding to the branch pattern” means that the standard pattern of the end face array pattern substantially matches the standard pattern of the branch pattern. It means that the end faces are arranged in the same plane. 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 it is handled as a match.

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.

And in the photoacoustic imaging device according to the present invention, the optical branching unit has a condenser lens system on the downstream side of the optical system of the branching diffractive optical element,
The condensing lens system is preferably arranged so that the focal point of the condensing lens system corresponds to the incident position of the laser beam in the branching diffractive optical element.

In the photoacoustic imaging apparatus according to the present invention, the light branching section preferably has a lens position adjusting section that adjusts the position of the condensing lens system in the optical axis direction.

In the photoacoustic imaging apparatus according to the present invention, it is preferable that the condenser lens system is capable of adjusting the scales of the branch patterns of the plurality of branch lights.

In the photoacoustic imaging apparatus according to the present invention, the light branching section preferably has a homogenizer optical element on the upstream side of the optical system of the branching diffractive optical element.

In the photoacoustic imaging apparatus according to the present invention, the light branching section preferably has a holographic diffusion plate on the downstream side of the optical system of the branching diffractive optical element.

In the photoacoustic imaging apparatus according to the present invention, the light branching section preferably has a variable beam expander on the upstream side of the optical system of the branching diffractive optical element.

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.

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 irradiation part is the other end face of the plurality of optical fibers,
The other end face is preferably 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,
The other end surface of the bundle fiber is preferably 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;
An optical branching unit having a branching diffractive optical element that splits one laser beam incident from the upstream side of the optical system as a plurality of branching lights according to a predetermined branching pattern;
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;
This bundle fiber allows each of a plurality of branched lights to enter each of a plurality of optical fiber cores from the one end face of the bundle fiber, and the plurality of branched lights incident on the core are connected to the other end face of the bundle fiber. It is arranged to guide the light irradiated part,
The light irradiating 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.

And in the probe unit according to the present invention, the optical branching unit has a condensing lens system on the downstream side of the optical system of the branching diffractive optical element,
The condensing lens system is preferably arranged so that the focal point of the condensing lens system corresponds to the incident position of the laser beam in the branching diffractive optical element.

In the probe unit according to the present invention, the light branching section preferably has a lens position adjusting section that adjusts the position of the condensing lens system in the optical axis direction.

In the probe unit according to the present invention, it is preferable that the condensing lens system is capable of adjusting the scales of the branch patterns of a plurality of branch lights.

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,
One laser beam incident on the branch diffractive optical element from the upstream side of the optical system is branched as a plurality of branch lights according to a predetermined branch pattern defined by the branch diffractive optical element;
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 light incident on the core is guided to the light irradiation unit,
A plurality of branched lights guided to the light irradiation unit are irradiated as measurement light.

The photoacoustic imaging device and the probe unit according to the present invention particularly include an optical branching unit having a branching diffractive optical element that splits one laser beam incident from the upstream side of the optical system as a plurality of branching lights according to a predetermined branching pattern. And 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 a branching pattern. The bundle fiber is configured to cause 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 to input the plurality of branch lights incident on the core to the other end face of the bundle fiber. It is arranged so as to be guided to the light irradiation unit connected inTherefore, 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. As a result, in photoacoustic imaging performed by guiding laser light using a plurality of optical fibers, it is easy to align each of the plurality of branched lights and each of the plurality of optical fibers.

In addition, the photoacoustic imaging device according to the present invention has a method of operating, in particular, a plurality of laser beams incident on the branch diffractive optical element from the upstream side of the optical system according to a predetermined branch pattern defined by the branch diffractive optical element. A bundle fiber including a plurality of optical fibers having a core / cladding structure, and one end face of the plurality of optical fibers arranged in one end face of the bundle fiber corresponding to the branch pattern The bundle fiber is used, and 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. 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. As a result, in photoacoustic imaging performed by guiding laser light using a plurality of optical fibers, it is possible to easily align each of the plurality of branched lights and each of the plurality of optical fibers. .

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 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 a schematic sectional drawing which shows the example of a structure of the optical system which can adjust the scale of the branch pattern of several branch light. 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 comprises the other position adjustment part which adjusts the positional relationship of an optical branching part and bundle fiber in FIG. It is a schematic sectional drawing which shows a structure when the light branching part further provided with the homogenizer optical element 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 a schematic sectional drawing which shows a structure when the optical branching part is further equipped with the variable beam expander 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. Yes.

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, one laser light Lo incident on the branch diffractive optical element 40 from the upstream side of the optical system is A bundle fiber 14 that includes a plurality of optical fibers 13 having a core 13a / cladding 13b structure that is branched as a plurality of branched lights Ld in accordance with a predetermined branch pattern defined by the branch DOE 40. The bundle fiber 14 in which one end face 13e of the plurality of optical fibers 13 on the end face 14e is arranged corresponding to the branch pattern is used to Each is made to enter each of the cores 13a of the plurality of optical fibers 13 from the one end face 14e of the bundle fiber 14, and the plurality of branched lights Ld incident on the cores 13a are guided to the light irradiation unit 15, and the light irradiation unit The photoacoustic imaging device 10 that irradiates a plurality of branched lights Ld guided to 15 as 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 beam 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 beam may be a pulse train in which a plurality of the above pulsed beams 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 branching diffractive optical element 40 (branching DOE). In this specification, the branched DOE means an optical element that generates a plurality of branched lights having different traveling directions by utilizing a light diffraction phenomenon. 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 branching DOE 40 and a condenser lens system 44. A condensing lens system means a group of one or more lenses arranged along one optical axis for the purpose of condensing. The surface of the branch DOE 40 is subjected to predetermined processing, and a predetermined branch pattern is defined by the content of the processing. The branch pattern is not particularly limited, but is preferably a square structure or a hexagonal structure, and more preferably a hexagonal structure, from the viewpoint of reducing aberrations in the condenser lens system. The condensing lens system 44 makes it easy for a plurality of branched lights Ld generated by the branched DOE to be incident on the bundle fiber 14 and makes it easy to align each of the plurality of branched lights Ld with the bundle fiber 14. A plurality of branched lights Ld are collimated. The condensing lens system 44 is arranged so that its focal point corresponds to the incident position of the laser light Lo on the branch DOE 40. “The focus of the condensing lens system corresponds to the incident position” of the laser light in the branch DOE means that the focus of the condensing lens system is a predetermined part of the branch DOE and the laser light is incident as the branched light. It means that the light is included in a portion through which it can pass before it is emitted. In general, the focusing lens system is generally focused on the beam center of the exit surface. Further, when the light branching portion 12 has the condensing lens system 44, the light branching portion 12 is a lens that moves the condensing lens system 44 in the optical axis direction in order to enable fine adjustment of the condensing lens system 44. It is preferable to have a position adjustment unit. The condensing lens system 44x may be composed of one condensing lens, or may be a combined lens composed of two or more condensing lenses. The condensing lens system 44 is preferably disposed so that the front focal point of the condensing lens system 44 is aligned with the branched light emission position of the branch DOE 40 and the rear focal plane is aligned with the end surface 14 e of the bundle fiber 14.

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 branch DOE 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 is a square structure from the viewpoint of ease of arrangement in the bundle fiber 14 and reduction of aberrations in the condenser lens system 44. Alternatively, 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. 4A and 4B are conceptual diagrams illustrating an example of an 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. FIG. 4A shows a case where the arrangement of the end faces 13e of the 64 optical fibers 13 has a square structure, and FIG. 4B 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. 4A and W2 in FIG. 4B) are compared with each other, the distance W2 of the close-packed structure is more square. It turns out that it becomes shorter than the said distance W1. As the distance increases, the divergence angle of the plurality of branched lights is set to increase accordingly, so that the aberration of the condenser lens system increases. As a result, the accuracy of alignment between each of the plurality of branched lights Ld and each of the plurality of optical fibers 13 decreases. 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 branch DOE 40 is designed according to the line arrangement of the plurality of optical fibers 13.

When each of the plurality of branched lights Ld is actually incident on each of the cores 13a of the plurality of optical fibers 13, the branch pattern of the plurality of branched lights Ld substantially matches the arrangement pattern of the end face 13e of the optical fiber 13. It is necessary to make it. That is, it is necessary to substantially match not only the standard patterns of the branch pattern and the array pattern but also these patterns including the scale. Therefore, it is preferable that the optical system is set so that adjustment for substantially matching these patterns can be performed by configuring the condensing lens system as follows.

FIG. 5 is a schematic cross-sectional view showing an example of the configuration of an optical system that can adjust the scales of the branch patterns of a plurality of branch lights. A pattern interval y (interval between adjacent bright spots on a virtual plane passing through the focus and perpendicular to the optical axis) on the focal plane of the plurality of branched lights Ld generated from the branched DOE 90 is between the branched DOE 90 and the bundle fiber 94. There is a property proportional to the focal length of the condensing lens system. For example, as shown in FIG. 5, consider a case where the condensing lens system between the branching DOE 90 and the bundle fiber 94 is a coupled lens composed of a condensing lens 91 and a condensing lens 92. Focal length of the condenser lens 91 is f _2, the focal length of the condenser lens 92 is f _1, the distance of the condenser lens 91 and the condenser lens 92 is d, the synthesis of the binding system lens The focal length f is given by f = f ₁ · f ₂ / (f ₁ + f ₂ −d). Further, the distance s ″ from the reference plane P to the second main surface H ₂ ″ of the condenser lens 91 is given by s ″ = f ₂ (f ₁ −d) / (f ₁ + f ₂ −d). Specifically, the distance d means the distance from the first main surface H ₂ of the condensing lens 91 to the second main surface H ₁ ″ of the condensing lens 92, and the reference surface P is the surface of the branch DOE 90 on the lens side. That is, it means the exit surface of a plurality of branched lights. The combined focal length f of the coupling system lens means a distance from the reference plane P to the first main surface H of the coupling system lens.

From the above equation, it can be seen that when the distance d changes, the combined focal length f and the distance s ″ also change. That is, the distance d is adjusted by moving the lens position adjusting unit 91a and / or 92a in the optical axis direction. Thus, the combined focal length f of the coupled lens can be adjusted, and as a result, the pattern interval y on the focal plane of the plurality of branched lights Ld, that is, the scale of the branched pattern can be adjusted. For other coupling lenses, the scale of the branching pattern can be adjusted by adjusting the synthetic focal length, which differs depending on the elements constituting the coupling lens. It is easy for a person skilled in the art to determine by a known method. It is preferred that the branched light exit position of Toki DOE90 (reference plane P), placing the rear composite focal in accordance with the end face of the bundle fiber 94.

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. 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. In addition, the several output end surface 13e of the some optical fiber 13 forms a plane, a convex surface, or a concave surface with the several conversion element 54 which comprises the electroacoustic conversion part 3. FIG. Here, it is a plane.

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 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. In addition, when a plurality of optical fibers are arranged so that each area can be individually irradiated with light, the light output per time does not need to be increased, so an expensive light source with a large output is used. There is also an advantage that it is not necessary. 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 stores the photoacoustic image data generated as described above. Under the control of the system control unit 4, cross-sectional data is read from the image data memory 62, and photoacoustic image data of the cross-section is generated by spatially interpolating at the time of reading.

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 temporarily stores photoacoustic image data to be displayed on the monitor 65, and the photoacoustic image data for one line from the image data memory 62 is stored in the display image memory 63. It is synthesized into one frame. The photoacoustic image data converter 64 performs D / A conversion and television format conversion on the composite image data read from 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 branch a single laser beam Lo incident from the upstream side of the optical system as a plurality of branched beams Ld according to a predetermined branch pattern. A bundle fiber 14 including an optical branching section 12 having a branching DOE 40 and a plurality of optical fibers 13 having a core 13a / cladding 13b structure, and a plurality of optical fibers 13 on one end face 14e of the bundle fiber 14 One end face 13e is provided with a bundle fiber 14 arranged in correspondence with the branch pattern, and this bundle fiber 14 is configured so that each of the plurality of branch lights Ld is respectively connected to the core 13a of the plurality of optical fibers 13 of the bundle fiber 14. A plurality of components incident from one end face 14e and incident on the core 13a. Characterized in that the light irradiation unit 15 connected to the light Ld on the other end surface 14e of the bundle fiber 14 are those which are disposed to guide. That is, according to the present invention, the branch patterns of the branch DOE 40 and the arrangement patterns of the end faces 13e of the plurality of optical fibers 13 on the incident end face 14e of the bundle fiber 14 are made to correspond to each other. It became possible to perform alignment with each of them at once. Accordingly, it is not necessary to separately align each of the plurality of branched lights Ld and each of the plurality of optical fibers 13, and easy alignment of each of the plurality of branched lights Ld and each of the plurality of optical fibers 13 is facilitated. It becomes.

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, as shown in FIG. 8, a position adjusting unit 40a for controlling the branch DOE 40 may be provided. The

position adjusting units

14a and 40a 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 homogenizer optical element 41 on the upstream side of the optical system of the branching DOE 40, as shown in FIG. Can do. The homogenizer optical element 41 arranged in this way makes the intensity profiles of the beams of the plurality of branched lights Ld uniform. Therefore, it is possible to prevent the branched light Ld having a high energy density from locally entering the optical fiber 13 and damaging the optical fiber 13. That is, the plurality of branched lights Ld can be guided so as not to exceed the damage threshold energy density of the optical fiber 13 throughout the plurality of branched lights Ld.

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 on the downstream side of the optical system of the branching DOE 40 as shown in FIG. be able to. FIG. 10 shows a configuration in which the holographic diffusion plate 42 is provided between the condenser lens system 44 and the incident end face 14e of the bundle fiber 14, but the holographic diffusion plate 42 is connected to the branch DOE 40 and the collecting DOE 40. A configuration provided between the optical lens system 44 and the optical lens system 44 is also possible. However, the holographic diffusion plate 42 is provided between the condensing lens system 44 and the incident end face 14e of the bundle fiber 14 from the viewpoint of easy adjustment when changing the distance to control the condensing spot diameter. Is preferred. 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, 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 variable beam expander 43 on the upstream side of the optical system of the branching DOE 40 as shown in FIG. be able to. Since the variable beam expander 43 arranged in this way can change the beam diameter appropriately for each wavelength of the laser light Lo used in photoacoustic imaging, the converging diameters of the plurality of branched lights Ld (bundle fiber 14 The diameter of the incident end face 14e when entering the core 13a can be controlled. Further, the measurement light L emitted from the probe unit 70 is measured, and the beam diameter can be automatically controlled for each wavelength of the laser light Lo so that the measured light amount becomes the maximum value.

Further, for example, in the photoacoustic imaging device 10 and the probe unit 70 of the present invention, as shown in FIG. 12, the light irradiation unit 15 is the other end face 13e of the plurality of optical fibers 13, and the other end face 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. 13, the photoacoustic imaging device 10 and the probe unit 70 of the present invention are light guide plates 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,
An optical branching unit having a branching diffractive optical element that splits one laser beam incident from the upstream side of the optical system as a plurality of branching lights according to a predetermined branching pattern;
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.
The light branching unit has a condenser lens system on the downstream side of the optical system of the branching diffractive optical element;
3. The condenser lens system according to claim 1, wherein the condenser lens system is disposed so that a focal point of the condenser lens system corresponds to an incident position of the laser beam in the branch diffractive optical element. Photoacoustic imaging apparatus.
The photoacoustic imaging apparatus according to claim 3, wherein the light branching unit includes a lens position adjusting unit that adjusts a position of the condensing lens system in an optical axis direction of the condensing lens system.
5. The photoacoustic imaging apparatus according to claim 3, wherein the condenser lens system is capable of adjusting a scale of a branch pattern of the plurality of branch lights.
6. The photoacoustic imaging apparatus according to claim 1, wherein the light branching unit has a homogenizer optical element upstream of the optical system of the branching diffractive optical element.
The photoacoustic imaging apparatus according to any one of claims 1 to 6, wherein the light branching unit includes a holographic diffusion plate on the downstream side of the optical system of the branching diffractive optical element.
The photoacoustic imaging apparatus according to any one of claims 1 to 7, wherein the light branching unit includes a variable beam expander on an upstream side of the optical system of the branching diffractive optical element.
The light branching part branches the laser light into 16 or more;
The photoacoustic imaging apparatus according to claim 1, wherein the bundle fiber includes at least 16 optical fibers.
The branch pattern has a hexagonal structure;
10. The photoacoustic imaging apparatus according to claim 1, wherein the one end faces of the plurality of optical fibers are arranged in a close-packed structure.
The photoacoustic imaging device according to any one of claims 1 to 10, 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 irradiation part is the other end face of the plurality of optical fibers;
The photoacoustic imaging apparatus according to claim 1, wherein the other end face is arranged in a line at intervals.
The light irradiation part is a light guide plate having a tapered shape,
The photoacoustic imaging device according to any one of claims 1 to 11, wherein the other end surface of the bundle fiber is connected to an end surface 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 electrical signal, and photoacoustic image based on the electrical 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;
An optical branching unit having a branching diffractive optical element that splits one laser beam incident from the upstream side of the optical system as a plurality of branching lights according to a predetermined branching pattern;
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.
15. The probe unit according to claim 14, 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 light branching unit has a condenser lens system on the downstream side of the optical system of the branching diffractive optical element;
16. The condenser lens system according to claim 14, wherein the condenser lens system is disposed so that a focal point of the condenser lens system corresponds to an incident position of the laser beam in the branch diffractive optical element. Probe unit.
The probe unit according to claim 16, wherein the light branching unit includes a lens position adjusting unit that adjusts a position of the condensing lens system in an optical axis direction of the condensing lens system.
The probe unit according to claim 16 or 17, wherein the condenser lens system is capable of adjusting a scale of a branch pattern of the plurality of branched lights.
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
One laser beam incident on the branch diffractive optical element from the upstream side of the optical system is branched as a plurality of branch lights according to a predetermined branch pattern defined by the branch diffractive optical element;
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.