WO2015015893A1 - Sonde de détection d'onde acoustique et dispositif de mesure photo-acoustique - Google Patents

Sonde de détection d'onde acoustique et dispositif de mesure photo-acoustique Download PDF

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Publication number
WO2015015893A1
WO2015015893A1 PCT/JP2014/064615 JP2014064615W WO2015015893A1 WO 2015015893 A1 WO2015015893 A1 WO 2015015893A1 JP 2014064615 W JP2014064615 W JP 2014064615W WO 2015015893 A1 WO2015015893 A1 WO 2015015893A1
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Prior art keywords
light
acoustic wave
wave detection
bundle fiber
homogenizer
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PCT/JP2014/064615
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English (en)
Japanese (ja)
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覚 入澤
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富士フイルム株式会社
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Publication of WO2015015893A1 publication Critical patent/WO2015015893A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0093—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy
    • A61B5/0095—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy by applying light and detecting acoustic waves, i.e. photoacoustic measurements
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/14532—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring glucose, e.g. by tissue impedance measurement
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/14535—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring haematocrit
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/04—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4292—Coupling light guides with opto-electronic elements the light guide being disconnectable from the opto-electronic element, e.g. mutually self aligning arrangements

Definitions

  • the present invention relates to a probe and a photoacoustic measurement apparatus that detect acoustic waves by applying measurement light to a measurement object.
  • a subject In photoacoustic spectroscopy, a subject is irradiated with pulsed light having a predetermined wavelength (for example, a wavelength band of visible light, near-infrared light, or mid-infrared light), and a specific substance in the subject is irradiated with the pulsed light.
  • a photoacoustic wave which is an elastic wave generated as a result of absorbing energy, is detected, and the concentration of the specific substance is quantitatively measured (for example, Patent Document 1).
  • 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).
  • PAI photoacoustic imaging
  • PAT photoacoustic tomography
  • the end face of the optical fiber is disposed at a position near the focal point of the condenser lens so that the beam diameter of the light is within the core diameter of the optical fiber. This is because when the light is condensed by the condensing lens, the light is too narrowed and the energy is locally concentrated, and damage to the end face of the optical fiber proceeds from the portion where the energy is concentrated.
  • Patent Document 2 for example, a bundle fiber (fused bundle fiber) in which an incident end portion is fusion-processed is used to efficiently reduce the energy of light incident per unit area. Implementing transmission is disclosed.
  • Patent Document 3 discloses an energy density distribution at an optical fiber incident end surface using an optical system that spatially divides a laser beam with a lens array and focuses the divided beam bundle on the optical fiber end surface. Is disclosed.
  • Patent Document 2 Even if the method of Patent Document 2 is applied to photoacoustic measurement, there is a problem that the uniformity of the energy profile of the light emitted from the fused bundle fiber cannot be ensured. This is because the method of Patent Document 2 does not ensure the uniformity of the energy profile when light enters the fused bundle fiber.
  • paragraph 0017 of Patent Document 2 there is a description that light is irradiated with a spot having a diameter substantially the same as the diameter of the fused bundle fiber.
  • light is applied to the incident end of the fused bundle fiber. Is simply condensed with a lens. In this case, it is considered that the energy profile when light enters the fused bundle fiber has a Gaussian distribution, similar to the energy profile of normal light. Then, it is estimated that there is a bias in the amount of energy of light traveling through each optical fiber in the bundle fiber.
  • Patent Document 2 it is only necessary to be able to transmit light, so it is not necessary to ensure the uniformity of the energy profile of the emitted light.
  • high energy is used from the viewpoint of reconstructing a high-quality photoacoustic signal.
  • the uniformity of the energy profile of the light actually irradiated on the subject is also required. For that purpose, it is important to eliminate the bias of the amount of energy of light traveling through each of the optical fibers in the bundle fiber.
  • Patent Document 3 even when a beam bundle is divided using a microlens array, the energy of each beam bundle may be locally concentrated inside the optical fiber. The possibility of internal damage cannot be excluded.
  • the present invention has been made in response to the above-described demand, and enables transmission of high-energy light in photoacoustic measurement and elimination of a bias in the amount of light energy traveling through each of a plurality of optical fibers.
  • An object of the present invention is to provide an acoustic wave detection probe and a photoacoustic measurement apparatus.
  • an acoustic wave detection probe includes: In an acoustic wave detection probe comprising a light guide that guides measurement light to be emitted toward a subject, and an acoustic wave detection element that detects a photoacoustic wave generated in the subject by emission of the measurement light,
  • the light guide is A condensing member that condenses the measurement light incident on the light guide, A homogenizer that flattenes the energy profile of the measurement light transmitted through the light collecting member;
  • a bundle fiber that includes a plurality of optical fibers and guides measurement light that has passed through the homogenizer.
  • the measurement light is once narrowed by passing the measurement light through the condensing member, and the beam diameter when entering the bundle fiber is controlled by the homogenizer.
  • the homogenizer preferably diffuses measurement light.
  • the focal length of the light collecting member is f and the distance between the light collecting member and the homogenizer is x
  • the minimum beam diameter D of the measurement light defined by the following formula 1 is the bundle fiber diameter d.
  • the incident end of the bundle fiber is preferably disposed at a position where the measurement light is incident in a state where the beam diameter of the measurement light is 0.8 d or more and 1.2 d or less.
  • ⁇ represents the divergence angle of the measurement light when entering the homogenizer
  • ⁇ represents the diffusion angle of the homogenizer.
  • the “diameter of the bundle fiber” means the maximum distance between the outer circumferences of the cores of the most distant optical fibers among the plurality of optical fibers in the bundle fiber.
  • the “expansion angle” means an angle at which the beam diameter of the laser light expands with propagation.
  • the “diffusion angle” of the homogenizer means a designed diffusion angle, that is, an angle at which the beam diameter of the laser beam incident on and transmitted through the homogenizer as parallel light spreads as it propagates. It should be noted that the “expansion angle” and the “diffusion angle” are expressed as full-plane angles. When measuring these angles, the beam diameter is measured at about 10 points within a range of propagation distance from a certain beam diameter to a beam diameter that is 2.0 times the beam diameter. It is preferable to obtain from the slope of change.
  • the “beam diameter” is a diameter of a circle centering on the center of the beam (usually the maximum position of the beam intensity) including approximately 86.5% of the energy profile of the laser beam, so-called 1 / e 2 diameter. It can be. In this case, when it is difficult to obtain the center of the beam due to irregular distribution of the beam intensity, a circle having an energy of 86.5% in the vicinity of the position estimated to be the center of the beam is comprehensively created. The diameter of the circle with the smallest value may be used as the beam diameter.
  • the light guide unit includes a beam expander optical system that expands the beam diameter of the measurement light immediately before the incident side of the light collecting member, and the beam expander optical system includes: It is preferable that the beam diameter of the measurement light is changed to a beam diameter adapted to the opening angle of the optical fiber in the bundle fiber.
  • the incident end portion of the bundle fiber is subjected to fusion processing.
  • the plurality of optical fibers at the incident end of the bundle fiber are covered with quartz.
  • the arrangement of each optical fiber at the exit end of the bundle fiber is an optical fiber in a relatively low energy profile region and an optical fiber in a relatively high energy profile region. It is preferable that these are mixed.
  • the optical fiber in the region with a relatively high energy profile is an optical fiber in the center of the bundle fiber, and the optical fiber in the region with a relatively low energy profile is on the outer peripheral side of the center. A fiber is preferred.
  • the light guide section includes a connection surface connected to at least a part of the emission end portions of the plurality of optical fibers, and an emission surface from which the measurement light incident from the connection surface is emitted. It is preferable to provide the light-guide plate which has these. In this case, it is preferable that a plurality of light guide plates are provided so as to face each other with the acoustic wave detection element interposed therebetween.
  • the homogenizer is preferably a lens diffusion plate in which a minute lens is arranged on one side of a substrate.
  • the acoustic wave detection probe according to the present invention preferably has a position adjusting unit that allows the light collecting member or the homogenizer to move in the optical axis direction.
  • the acoustic wave detection probe according to the present invention preferably includes a holding portion that integrally holds the homogenizer and the bundle fiber.
  • the holding portion integrally holds the light collecting member including the light collecting member.
  • the acoustic wave detection probe according to the present invention further includes a holding portion that covers the incident surface of the bundle fiber and holds the incident end portion of the bundle fiber, and has a window portion at a portion where the measurement light is incident. It is preferable.
  • the window part can be constituted by an ND filter (Neutral Density filter).
  • the holding portion includes a cap member that protects the incident end portion of the bundle fiber, and a tip that is formed of a material that is resistant to light energy and is a ring-shaped tip that is fitted to the cap member. It is preferable to include an optical member, or it is preferable to include a light guide member including a diaphragm and a relay lens system.
  • the photoacoustic measuring device is: The acoustic wave detection probe described above; Signal processing means for processing the photoacoustic signal detected by the acoustic wave detecting element.
  • a light source that outputs measurement light
  • a device housing that has a mounting portion that is optically connected to the light source and holds a light collecting member and a homogenizer
  • a holding structure that holds an incident end so as to cover the incident surface of the bundle fiber, and has a holding part having a window part at a part where measurement light is incident, and a connector structure in which the mounting part and the holding part are detachable from each other It is preferable to have it.
  • the signal processing means includes an acoustic image generation means for generating a photoacoustic image based on the photoacoustic signal.
  • the acoustic wave detecting element detects a reflected acoustic wave with respect to the acoustic wave transmitted to the subject, and the acoustic image generating means generates a reflected acoustic wave image based on the reflected acoustic wave signal. It is preferable to produce it.
  • the light guide unit collects the measurement light incident on the light guide unit and the energy profile of the measurement light transmitted through the light collection member.
  • a flat top homogenizer and a bundle fiber that includes a plurality of optical fibers and guides measurement light transmitted through the homogenizer are included.
  • FIG. 3A and FIG. 3B are schematic cross-sectional views showing other configuration examples of the light guide portion of the acoustic wave detection probe. It is the schematic which shows the end surface arrangement
  • FIG. 5A is a diagram showing an energy profile of laser light collected by a lens after the energy profile is flattened by a homogenizer.
  • FIG. 5B is a diagram showing an energy profile of laser light that is simply focused by a lens without using a homogenizer. It is a graph which shows the relationship between the optical characteristic of a lens diffusing plate and a condensing member, and the minimum beam diameter. It is a graph which shows the relationship between the distance from a condensing member to a lens diffusing plate, and the minimum beam diameter. It is the schematic which shows the structure of the light guide part in the case of including a beam expander.
  • FIG. 9A to FIG. 9C are schematic views showing a configuration example of the light guide plate.
  • FIG. 12A is a schematic diagram showing a design change of the optical fiber arrangement method in the probe of the first embodiment.
  • FIG. 12B is a schematic diagram showing a design change for the optical fiber arrangement method in the acoustic wave detection probe of the second exemplary embodiment.
  • FIG. 13A is a schematic diagram showing the configuration of a mounting portion and a holding portion of an apparatus housing including a light source.
  • FIG. 13B is a schematic diagram illustrating a state in which the holding unit is mounted on the mounting unit of FIG. 13A. It is the schematic which shows the other structure of the mounting part and holding
  • FIG. 1 is a schematic cross-sectional view showing a configuration example of a light guide portion of an acoustic wave detection probe in the present embodiment.
  • FIG. 2 is a schematic cross-sectional view showing the arrangement of transducer arrays and optical fibers in the acoustic wave detection probe of the present embodiment.
  • the acoustic wave detection probe 11 includes a light guide unit 44 including a light collecting member 41, a homogenizer 40, and a fused bundle fiber 42, and vibration.
  • a child array 20 and an output end E2 of the bundle fiber 42 and a housing 11a that holds the transducer array 20 are provided.
  • the acoustic wave detection probe 11 is used by being optically connected to the laser unit 13 so that the laser light L output from the laser unit 13 enters the light collecting member 41.
  • the laser light L incident on the light condensing member 41 enters the incident end E1 of the bundle fiber 42 via the homogenizer 40. Thereafter, the laser light L guided by the bundle fiber 42 is emitted from the emission end E2 of each optical fiber 42a in the bundle fiber 42, and is irradiated to the subject M as measurement light.
  • Measurement light is not limited to laser light.
  • the housing 11 a also functions as a holding member for the operator of the acoustic wave detection probe 11 to hold the acoustic wave detection probe 11.
  • the housing 11a has a handheld shape, but the housing 11a of the present invention is not limited to this.
  • the condensing member 41 is for guiding the laser light L incident from the upstream side of the optical system to the homogenizer 40 while condensing the light, and using a condensing lens, a mirror, or a combination thereof.
  • the condensing member 41 is a condensing lens system composed of one condensing lens.
  • the focal length of the condensing member 41 (the distance between the principal point on the bundle fiber 42 side and the focal point) is preferably 10 to 100 mm, and more preferably 15 to 50 mm.
  • the condensing member 41 can also be a coupled lens composed of a plurality of lenses.
  • the focal length of the condensing member 41 refers to the combined focal length of the coupled lens.
  • the light collecting member 41 may be configured to be held integrally with the homogenizer 40 and the bundle fiber 42 by the holding portion 60a.
  • the homogenizer 40 is an optical element that flattens the energy profile (energy distribution) of the laser light L that has passed through the condensing member 41.
  • the flat-topped laser beam L is guided to the bundle fiber 42 and enters the incident end E1 in a state having a flat-top energy profile.
  • “To make the energy profile flat” means, in other words, shaping the laser light incident on the homogenizer into a laser beam having a flat-top energy profile near the center.
  • the term “flat top” refers to a case where a concentric circle whose diameter is 80% of the beam diameter in the energy profile of the laser beam emitted from the homogenizer is taken, and a standard deviation is obtained for the energy at each point in the concentric circle. , which means that the standard deviation is within 25% of the average energy within the concentric circles.
  • a homogenizer is structurally designed so that light is completely flat top at infinity (that is, the standard deviation is substantially equal to 0).
  • the energy profile when the measurement light is incident on the incident end of the bundle fiber is not necessarily in a completely flat top state, and may be in a flat top state within the above range.
  • the homogenizer 40 of the present embodiment has a function of diffusing the laser light L transmitted through the condensing member 41 to increase the beam diameter of the laser light L, that is, a function of expanding the distribution of the propagation angle of the light beam included in the laser light L. It is preferable to have. As shown in FIG. 1, the laser light diffused at a certain position becomes diffused light Ld and enters the bundle fiber 42 while diffusing in various directions. Thereby, since the light emitting surface of the homogenizer 40 becomes a secondary light source of the laser light L, it is possible to prevent the laser light L from being excessively narrowed even when the laser light L is condensed.
  • the diffusion angle of the homogenizer 40 is preferably 0.2 to 5.0 °, and more preferably 0.4 to 3.0 °. This is because the transmission efficiency is high.
  • the distance between the condensing member 41 and the homogenizer 40 is appropriately adjusted so that the laser light L transmitted through the condensing member 41 is efficiently coupled to the homogenizer 40.
  • the homogenizer 40 is disposed on the downstream side of the optical system with respect to the light collecting member 41 and within the range from the light collecting member 41 to its focal length.
  • the minimum beam diameter of the measurement light L can be changed by changing the distance. Therefore, in order to enable the adjustment of the distance, it is preferable to have a position adjusting unit (not shown) that allows the condenser lens 41 or the homogenizer 40 to move in the optical axis direction, for example. Details of the relationship between the distance and the minimum beam diameter will be described later.
  • the homogenizer 40 may be composed of a single optical element or a combination of a plurality of optical elements.
  • a single optical element for example, a ⁇ shaper manufactured by AdlOptica can be used as the homogenizer 40.
  • the homogenizer 40 having a diffusion function for example, it is preferable to use a lens diffusion plate 53 in which minute concave lenses or the like are randomly arranged on one side 53S of the substrate (FIGS. 3A and 3B).
  • a lens diffusion plate 53 for example, Engineereder Diffusers (model number: EDC-2.0-A, diffusion angle: 2.0 °) manufactured by RPC Photonics can be used.
  • EDC-2.0-A diffusion angle: 2.0 °
  • the homogenizer 40 (for example, the lens diffusion plate 53) may be configured to be held integrally with the light collecting member 41 and the bundle fiber 42 by the holding portion 60a, as shown in FIG. 3B.
  • the holding unit 60b may be configured to be held integrally with only the bundle fiber 42. In this case, it is not necessary to adjust the positional relationship between the homogenizer 40 and the light collecting member 41, and the optical system can be downsized.
  • the bundle fiber 42 guides the laser light L flattened by the homogenizer 40 (that is, transmitted through the homogenizer 40) to the vicinity of the transducer array 20.
  • another light guide member may be provided between the homogenizer 40 and the bundle fiber 42.
  • the bundle fiber 42 includes a plurality of optical fibers 42a composed of a core and a clad, a covering member 42c such as a ferrule and a sheath, an outer periphery of the plurality of optical fibers 42a, and a covering member 42c. It is comprised from the filling member 42b which fills between.
  • the core diameter of the optical fiber 42a in the bundle fiber 42 is preferably 20 to 300 ⁇ m, and more preferably 50 to 200 ⁇ m.
  • the optical fiber 42a in the bundle fiber 42 is not particularly limited, but is preferably a quartz fiber.
  • the fusing process is a bundle processing technique in which, when bundling optical fiber strands, processing is performed with heat and pressure instead of an adhesive.
  • the clads are fused together, and the optical fibers are bundled in a hexagonal honeycomb shape, and an extra gap between the optical fibers is eliminated as compared with the bundle processing using an adhesive. Therefore, there is an advantage that the area occupied by the core per unit area is improved. Further, since a material weak to light energy (for example, a resin constituting an adhesive) does not appear at the incident end of the bundle fiber, there is an advantage that durability against light energy is also improved.
  • the filling member 42b is preferably made of a material having durability against light energy.
  • a material having durability against light energy is a glass material such as quartz.
  • a bundle fiber for example, a plurality of optical fibers are inserted into a cylindrical member made of quartz, and the optical fiber and the cylindrical member are fused together, and then the surroundings are covered with a covering member. Can be manufactured.
  • the position of the bundle fiber 42 is adjusted so that, for example, the incident end E1 is positioned at the focal point of the light collecting member 41.
  • a bundle fiber position adjusting unit (not shown) that moves the bundle fiber 42 in the optical axis direction may be provided. By doing so, it is possible to adjust the position in the vicinity of the focal position within a range that does not impair the flat top property, and it is also possible to finely adjust the beam diameter when entering the incident end E1. It becomes.
  • the homogenizer 40 and the bundle fiber 42 are integrally held by the holding portion 60a, or as shown in FIG. 3B, the homogenizer 40 and the bundle are held by the holding portion 60b.
  • the bundle fiber 42 has a structure that enables attachment and detachment such as a screw structure so that the position of the incident end E1 of the bundle fiber 42 can be easily adjusted. It is preferable to be fixed to 60a and 60b.
  • each of the joints 100a on the homogenizer 40 side of the holding parts 60a and 60b and the connection part 100b on the bundle fiber 42 side have complementary screw structures, whereby the bundle fiber 42 is held.
  • the bundle fiber position adjusting portion is not necessary, and the optical system can be downsized. Further, since the bundle fiber 42 can be easily replaced simply by removing the screw from the holding portion 60a or 60b, it is not necessary to align the homogenizer 40 and the bundle fiber 42 again when replacing the damaged bundle fiber 42. The maintainability is improved.
  • the emission end portions E2 of the plurality of optical fibers 42a are substantially around the transducer array 20 in order to improve the uniformity of the energy profile of the light irradiated to the subject. Evenly arranged.
  • the transducer array 20 is a one-dimensional or two-dimensional array of a plurality of acoustic wave detection elements (or acoustic wave detection elements), and converts acoustic wave signals into electrical signals.
  • the acoustic wave detection element is, for example, a piezoelectric element made of a polymer film such as piezoelectric ceramics, piezoelectric single crystal, or polyvinylidene fluoride (PVDF).
  • PVDF polyvinylidene fluoride
  • acoustic wave means an ultrasonic wave and a photoacoustic wave.
  • ultrasonic wave means an elastic wave generated in the subject due to vibration of the transducer array and its reflected wave
  • photoacoustic wave means the inside of the subject due to the photoacoustic effect caused by the measurement light irradiation. It means the elastic wave generated in
  • the transducer array 20 preferably includes acoustic elements such as an acoustic matching layer, an acoustic lens, and a backing material in order to detect an accurate acoustic wave signal.
  • the minimum beam diameter D of the measurement light (that is, the beam diameter at the focal plane). ) Is defined by Equation 3 below.
  • Each characteristic of the condensing member 41 and the homogenizer 40 and their positional relationship are designed so that the minimum beam diameter D satisfies the following formula 4 in relation to the diameter d of the bundle fiber 42, and the incident end of the bundle fiber 42 Is preferably arranged at a position where the laser beam is incident in a state where the beam diameter D of the laser beam L is 0.8d to 1.2d.
  • the reference of the condensing member 41 is the main surface as the lens on the homogenizer side
  • the reference of the homogenizer 40 is the diffusion surface in the case of the diffusion plate in which the diffusion surface is formed only on one side.
  • a diffusing plate in which diffusing surfaces are formed on both sides it is a plane parallel to both diffusing surfaces and passing through the center of the diffusing plate.
  • the reason why the minimum beam diameter D is set to 0.8 d or more is to suppress damage of the incident end E1 of the bundle fiber 42 (core damage mode) by constricting the beam diameter. Specifically, it is as follows.
  • FIG. 5A is a diagram showing an energy profile in the focal plane of the laser light L condensed by the lens after the energy profile is flattened by the homogenizer 40.
  • FIG. 5B is a diagram showing an energy profile in the focal plane of the laser light that is merely condensed by the lens without using the homogenizer 40.
  • FIG. 5 shows that the ratio of the full width at half maximum W1 to the minimum beam diameter D1 of the laser beam in FIG. 5A is larger than the ratio of the full width at half maximum W2 to the minimum beam diameter D2 of the laser beam in FIG. .
  • the divergence angle ⁇ of the laser light L when output from the laser unit is small (about 0.15 ° at most)
  • the condensed laser light L is narrowed down at the incident end E1 of the bundle fiber 42. It will be.
  • the energy of the laser beam L is concentrated at the incident end of the bundle fiber 42, and the incident end E1 of the bundle fiber 42 is damaged.
  • FIG. 6 is a graph showing the relationship between the optical characteristics and the minimum beam diameter of the lens diffuser (Engineered Diffusers) and the condensing member.
  • the horizontal axis represents the diffusion angle (deg.) Of the lens diffusion plate, and the vertical axis represents the minimum beam diameter ( ⁇ m).
  • the round plot in the graph shows data when the focal length of the light collecting member is 100 mm
  • the square plot shows data when the focal length of the light collecting member is 50 mm
  • the triangular plot shows the data when the focal length of the light collecting member is 50 mm.
  • Data when the focal length of the optical member is 25 mm is shown.
  • FIG. 6 shows that the minimum beam diameter can be adjusted by adjusting the optical characteristics of the homogenizer and the condensing member.
  • the laser light beam is condensed at a position corresponding to each angle.
  • the condensing range (including the skirt) of the entire laser beam obtained by superimposing the condensing points corresponding to the angle becomes larger.
  • the angular distribution of the laser beam that was within about ⁇ / 2 before the homogenizer was incident is approximately ⁇ (half angle after transmission through the homogenizer). Since it extends within ( ⁇ / 2) 2 + ( ⁇ / 2) 2 ), the condensing range of the entire laser light subsequently collected by the condensing member is further increased correspondingly.
  • the diameter of the condensing range is 2f ⁇ tan ( ⁇ (( ⁇ / 2) 2 + ( ⁇ / 2) 2 ) )
  • the minimum beam diameter D 0 that is, the minimum beam diameter when arranged in the order of the homogenizer, the condensing member, and the bundle fiber
  • FIG. 7 is a graph showing the relationship between the distance x from the light collecting member to the lens diffusion plate and the minimum beam diameter D in the present embodiment. More specifically, this graph shows that a laser beam having a wavelength of 1064 nm, a pulse width of 3.5 ns, a beam diameter of 3.5 mm, and a divergence angle ⁇ of 0.13 ° is condensed by a condenser lens, and a diffusion angle is obtained. 1.0 deg. The measured value of the minimum beam diameter when diffusing with the lens diffusing plate is shown.
  • the minimum beam diameter D can be easily controlled only by changing the distance x from the light collecting member to the lens diffusion plate. The energy density can be lowered as the beam diameter is increased.
  • the minimum beam diameter is determined by the parameters of each optical component used, and it is difficult to change the minimum beam diameter after configuring the probe.
  • the focal length f can be changed by combining a plurality of lenses.
  • the distance or size of the optical system increases, or such an optical system cannot be used in practice. There's a problem.
  • the minimum beam diameter can be increased or decreased simply by adjusting the distance x.
  • the minimum beam diameter can be controlled in real time even after the probe is configured. This is effective when the minimum beam diameter is changed in accordance with the diameter of the bundle fiber to be used, for example, when a plurality of bundle fibers having different diameters are exchanged and used depending on the application. Note that the minimum beam diameter cannot be changed by changing the distance between the lens array and the condenser lens.
  • the bundle fiber 42 is controlled by controlling the minimum beam diameter D of the laser light L using the relationship between the focal length of the light collecting member, the diffusion angle of the homogenizer, and the distance from the light collecting member to the homogenizer. It is possible to guide the high-energy laser beam L through the bundle fiber 42 so as not to exceed the damage threshold energy density at the incident end.
  • the reason why the minimum beam diameter D is set to 1.2 d or less in relation to the diameter d of the bundle fiber 42 is that the member around the incident end E1 of the bundle fiber 42 is moved to the laser beam L because the minimum beam diameter D increases. This is to prevent the discharge of dust and gases from the damaged part. Such emissions may cause a problem (ambient damage mode) that adheres to the end face of the bundle fiber 42 and induces destruction of the core in the vicinity of the end face and inhibits energy transmission. That is, the minimum beam diameter D is set to 1.2 d or less in order to suppress the occurrence of the surrounding damage mode as described above.
  • the members around the bundle fiber mean, for example, the filling member 42b made of resin and the covering member 42c such as a metal ferrule covering the outer periphery thereof.
  • the minimum beam diameter D is 0.8 d or more and 1.0 d or less.
  • the bundle fiber 42 is arranged so that the laser light L is incident in a state where the beam diameter D of the laser light L is not less than 0.8d and not more than 1.2d. This is because the laser beam L is efficiently incident on the incident end E1 of the bundle fiber 42.
  • the laser beam (measurement light) condensed by the condensing member is passed through the homogenizer so that the energy profile is flattened and incident on the bundle fiber.
  • the beam diameter is controlled by the focal length of the light collecting member, the diffusion angle of the homogenizer, and the distance from the light collecting member to the homogenizer.
  • the acoustic wave detection probe of this embodiment is different from that of the first embodiment in that the light guide has a beam expander optical system on the upstream side of the bundle fiber 42. Therefore, detailed description of the same components as those in the first embodiment is omitted unless particularly necessary.
  • FIG. 8 is a schematic diagram showing a configuration of the light guide unit including a beam expander.
  • the acoustic wave detection probe 11 includes a light guide unit 44 including a beam expander 55, a condensing member 41, a homogenizer 40, and a fused bundle fiber 42, a transducer array, and a bundle fiber. 42 and a housing for holding the transducer array.
  • the probe 11 is used by being optically connected to the laser unit 13 so that the laser light L output from the laser unit 13 enters the beam expander 55.
  • the laser light L incident on the beam expander 55 enters the incident end E1 of the bundle fiber 42 via the condensing member 41 and the homogenizer 40. Thereafter, the laser light L guided by the bundle fiber 42 is emitted from the emission end portions of the plurality of optical fibers 42a in the bundle fiber 42, and is irradiated on the subject as measurement light.
  • the housing, the light collecting member 41, the homogenizer 40, and the transducer array are the same as those in the first embodiment.
  • the beam expander optical system 55 has a beam diameter adapted to the aperture angles of the plurality of optical fibers 42a in the bundle fiber 42, and further to an optimum beam diameter for the aperture angles. It expands the measurement light.
  • Changing the beam diameter to “a beam diameter adapted to the aperture angle of the optical fiber” means that when the light is condensed at the incident end of the bundle fiber via the light collecting member and the homogenizer, the light collecting angle is changed. It means close to the aperture angle of the optical fiber, and “optimizing the beam diameter with respect to the aperture angle of the optical fiber” means that the light collection angle is almost the same as the aperture angle of the optical fiber.
  • the beam expander optical system 55 is disposed on the upstream side (that is, the light source side) of the light collecting member 41.
  • the expansion ratio of the beam expander optical system 55 is such that the laser light L can enter the incident end E1 of the bundle fiber 42 with a wider divergence angle within a range not exceeding the numerical aperture of the optical fiber 42a. It is adapted to the opening angle of the fiber 42a.
  • a quartz fiber having a general core / cladding structure has a numerical aperture of 0.20 to 22 and an opening angle of 11.4 to 12.7 °.
  • the divergence angle of the light emitted from the optical fiber 42a can be increased as much as possible, and the illumination can be made uniform at a shorter distance from the emission end face of the optical fiber 42a.
  • the beam expander optical system 55 is disposed at a position (immediately before) on the upstream side of the light collecting member 41 as shown in FIG. 8 from the viewpoint of controllability.
  • the above-described beam expander optical system 55 can be made by appropriately combining, for example, a concave lens and a convex lens according to the numerical aperture of the optical fiber 42a.
  • the energy profile is flattened and incident on the bundle fiber. Is controlled by the focal length of the light collecting member, the diffusion angle of the homogenizer, and the distance from the light collecting member to the homogenizer.
  • the beam expander optical system 55 is used to expand the measurement light to an optimum beam diameter with respect to the aperture angles of the plurality of optical fibers 42a in the bundle fiber 42, so that the uniformity of illumination is improved. This can be further improved.
  • the acoustic wave detection probe according to the present embodiment is different from the first embodiment in that the measurement light guided by the bundle fiber 42 via the light guide plate is irradiated. Therefore, detailed description of the same components as those in the first embodiment is omitted unless particularly necessary.
  • FIG. 9A to FIG. 9C are schematic diagrams showing a configuration example of the light guide plate.
  • FIG. 10 is a schematic cross-sectional view showing the arrangement of the acoustic wave detection element, the optical fiber, and the light guide plate in the acoustic wave detection probe of the present embodiment.
  • the acoustic wave detection probe 11 includes a light condensing member, a homogenizer, a light guide unit composed of a fused bundle fiber 42 and a light guide plate 43, the transducer array 20, and the emission of the bundle fiber 42. And a housing 11a for holding the end E2 and the transducer array 20. Also in the present embodiment, the acoustic wave detection probe 11 is used by being optically connected to the laser unit so that the laser light L output from the laser unit is incident on the condensing member. The laser light L incident on the light condensing member is incident on the incident end of the bundle fiber 42 via the homogenizer.
  • the laser light L guided by the bundle fiber 42 is directly incident on the connection surface S1 of the light guide plate 43 from the emission ends E2 of the plurality of optical fibers 42a in the bundle fiber 42, and is guided by the light guide plate 43.
  • the laser beam L thus emitted is emitted from the emission surface S2 of the light guide plate 43 and is irradiated on the subject M as measurement light.
  • the housing, the light collecting member, the homogenizer, and the transducer array 20 are the same as those in the first embodiment.
  • the light guide plate 43 is a plate that performs special processing on the surface of, for example, an acrylic plate or a quartz plate, and uniformly emits light from one end surface (connection surface S1) from the other end surface (output surface S2). is there.
  • the light guide plate 43 can be manufactured by forming a resin film 43b having a low refractive index on a pair of opposing side surfaces of the quartz plate 43a. In this case, the laser light incident from the connection surface S1 propagates while being subjected to multiple reflection at the interface S3 between the quartz plate 43a and the resin thin film 43b, and is emitted from the emission surface S2.
  • the emission end E2 of the optical fiber 42a is arranged substantially evenly on the connection surface S1 of the light guide plate 43 and is optically connected.
  • the light guide plate 43 may have a rectangular parallelepiped shape as shown in FIG. 9C.
  • two light guide plates 43 are arranged so as to face each other with the transducer array 20 interposed therebetween, and an optical fiber 42 a is connected to the connection surface S ⁇ b> 1 of each light guide plate 43. Yes.
  • the light guide plate 43 has a mechanism for diffusing light at the tip thereof (diffusion plate, resin containing scattering particles, etc.) or a traveling direction of the light so that a wider range of the subject M can be irradiated with the laser light L. It may have a mechanism (notch or the like for refracting light) directed to the array 20 side.
  • the energy profile is flattened and incident on the bundle fiber. Is controlled by the focal length of the light collecting member, the diffusion angle of the homogenizer, and the distance from the light collecting member to the homogenizer.
  • the measurement light is irradiated through the light guide plate, it is possible to further improve the uniformity of the energy profile of the light irradiated to the subject.
  • the energy profile is flattened by passing the measurement light once through a homogenizer.
  • a homogenizer it may be difficult to make the energy profile completely uniform, and it is preferable to eliminate such an uneven energy profile. Therefore, in the present invention, it is preferable to consider the position of each optical fiber in the bundle fiber when arranging the emission end of the optical fiber.
  • the energy profile of a normal laser beam has a Gaussian distribution centered on the optical axis.
  • a homogenizer is used, even when a homogenizer is used, a local intensity bias depending on the distance from the optical axis may occur.
  • the arrangement of each optical fiber at the exit end of the bundle fiber is an arrangement in which an optical fiber in a relatively low energy profile region and an optical fiber in a relatively high energy profile region are mixed. .
  • a plurality of optical fibers are divided into a divided region near the center of the bundle fiber 42 (center side region 62) and a divided region near the outer periphery (outer side region 64). . Then, the optical fiber 62a belonging to the central region 62 (the optical fiber in the central portion) and the optical fiber 64a belonging to the outer peripheral region 64 (the optical fiber located on the outer peripheral side from the central portion) are mixed to be uniform. Deploy.
  • “arrange” means that the emission ends of the optical fibers 62a and 64a are arranged at equal intervals around the transducer array 20 as shown in FIG.
  • the emission ends of the fibers 62a and 64a are arranged on the connection surface of the light guide plate 43 at equal intervals.
  • the ratio of the number of optical fibers belonging to each divided region is not necessarily 1: 1, and the mixing ratio may be adjusted according to the ratio of the number of optical fibers belonging to each divided region. By doing so, it is possible to reduce the influence of the local intensity deviation and further improve the uniformity of the energy profile of the measurement light actually irradiated on the subject.
  • the region dividing method is not limited to the above method.
  • the region can be divided into three regions according to the distance from the center of the bundle fiber, or the angle around the center can be divided into six equal parts.
  • FIG. 13A is a schematic diagram illustrating the configuration of the mounting portion 69 and the holding portion 65a of the apparatus housing 68 including the laser unit 13 (light source).
  • the apparatus housing 68 incorporates the laser unit 13, and the laser unit 13 and the condensing member 41 are optically connected by mounting the holding unit 65 a on the mounting unit 69.
  • the connector structure of the holding portion 65a is basically the same as that of the holding portion 60a of FIG. 3A, but differs in that it has a protrusion 66 that can be moved in the vertical direction on the paper surface by an elastic member 67 such as a spring.
  • the protrusion 66 is pushed down into the groove of the holding portion 65a when an external force is applied from above, and then returns to the original state by the restoring force of the elastic member 67 when the external force stops working.
  • the surface of the protruding portion of the protruding portion 66 forms a curved surface so that the protruding portion 66 is pushed down into the groove of the holding portion 65a even when an external force in the horizontal direction of the paper surface acts.
  • the mounting portion 69 is provided with an engaging portion 69a formed of a groove having a shape complementary to the protruding portion 66, for example.
  • the projecting portion 66 is pushed down by the inner wall of the mounting portion 69, and when the projecting portion 66 reaches the engaging portion 69a, the projecting portion 66 returns to its original position.
  • the protrusion 66 and the engaging portion 69a are engaged (FIG. 13B).
  • the output laser light L is guided to the light collecting member 41 by the optical system 70 and then propagates through the probe of the present invention.
  • the holding portion has a connector structure that can be attached to and detached from the mounting portion, a mode as shown in FIG.
  • the holding portion 65c is a holding portion that holds the incident end so as to cover the incident surface of the bundle fiber 42, and includes a projection 66 similar to the above and a window portion 74 at a portion where the laser light L is incident. It is a holding part which has.
  • the window portion 74 is made of a light transmissive material (for example, quartz), and is provided on the optical path of the laser light L so as to close the groove where the incident surface of the bundle fiber 42 is exposed. Thereby, for example, the incident surface of the bundle fiber 42 exists in the space sealed by the holding portion 65c.
  • the surface of the window 74 on the light source side preferably has an antireflection coating (AR coating) such as an MgF 2 film, a Ta 2 O 5 film, or a SiO 2 multilayer film.
  • AR coating antireflection coating
  • the mounting portion 69 is provided with a beam expander 73, a light condensing member 41, and a homogenizer 40, in addition to an engaging portion 69a formed of a groove complementary to the protruding portion 66, for example.
  • the beam expander 73 includes a plano-concave lens 71 and a convex lens 72. The mounting procedure between the holding portion 65c and the mounting portion 69 is the same as described above.
  • the laser light L that has passed through the beam expander 73, the condensing member 41, and the homogenizer 40 passes through the window portion 74 and enters the incident surface of the bundle fiber 42.
  • dust or the like is attached to the light source side surface of the window portion 74 having a lower energy density than the incident surface of the bundle fiber 42, there is an advantage that end face damage is less likely to occur. Also in the holding part of FIG. 13, the same effect can be obtained if a window part is provided.
  • the condensing member 41 is installed on the light source system side, when attaching and detaching the holding portion 65c and the mounting portion 69, the requirement of the angle accuracy of the holding portion 65c is alleviated, and the positional accuracy is emphasized. There is also an advantage that it should be considered.
  • an ND filter can also be used as the window unit 74.
  • the ND filter is, for example, a quartz substrate coated with an oxide multilayer film. In such a case, the intensity of the laser beam L can be reduced on the probe side, and a laser beam intensity adjusting mechanism is not required on the light source system side.
  • the holding unit has a through hole through which measurement light incident on the bundle fiber passes and has an opening member having a tapered structure at the incident end of the bundle fiber 42.
  • the diameter of the through hole is formed so as to decrease to a size corresponding to the diameter of the bundle fiber toward the incident end.
  • the diameter of the opening on the bundle fiber side of the opening member 75 matches the diameter of the bundle fiber.
  • the taper angle of the taper structure is preferably larger than the light collection angle when entering the bundle fiber 42 and smaller than the NA of the optical fiber.
  • the inner surface of the through hole of the opening member 75 is configured to reflect, scatter, or absorb light.
  • the inner surface of the through-hole reflects or scatters light
  • light having an angle component deviating from the incident angle that can be received by the optical fiber can enter the optical fiber via reflection or scattering.
  • the light transmission efficiency is further improved.
  • the inner surface of the through-hole absorbs light
  • light with an angle component deviating from the incident angle that can be received by the optical fiber is absorbed in a wide range away from the optical fiber. Damage to the optical fiber is suppressed compared to when it is done.
  • the inner surface of the through-hole may be subjected to a smoothing process such as mirror finish, or a film having a high reflectance such as a gold thin film may be formed.
  • the opening member is formed of a ceramic thick powder or sintered body such as Al 2 O 3 , TiO 2 or ZrO 2 , (Registered trademark) or unpolished glass.
  • the opening member may be formed of a metal such as aluminum, brass or copper.
  • the light guide member of FIGS. 16A and 16B includes a cap member that protects the incident end of the bundle fiber 42 and a material that is resistant to light energy (for example, light absorption in the wavelength band of measurement light to be used).
  • a quartz rod 76a (FIG. 16A) or an air gap optical fiber 76b (FIG. 16B) can be used as the cap member.
  • the tip 77 is fitted to the incident end of the cap member.
  • the air gap optical fiber 76b is used as a cap member, it is preferable that the chip 77 is embedded in the connector of the air gap optical fiber 76b.
  • the air gap optical fiber 76b of FIG. 16B is provided with a connector 65d on the bundle fiber 42 side, an detachable output side connector 65e and an incident side connector 65f, and a chip 77 is embedded in at least the incident side connector 65f. .
  • the light at the base is absorbed or reflected by, for example, the chip 77 and blocked (FIG. 17). Accordingly, the light at the base portion is prevented from reaching the peripheral member of the bundle fiber, and the occurrence of the peripheral damage mode is prevented.
  • the light guide member of FIG. 18 includes a first diaphragm 78 (for blocking the bottom portion), a second diaphragm 79 (for adjusting the light amount), a relay lens system 80, and a third diaphragm 81 (for blocking the bottom portion).
  • the first diaphragm 78 is disposed in the vicinity of the focal point of the condensing member 41
  • the second diaphragm 79 is disposed in the vicinity of the relay lens system 80
  • the third diaphragm 81 is disposed in the vicinity of the incident end of the bundle fiber.
  • the beam diameter can be enlarged or reduced before and after the relay lens system 80, and the relay lens system 80 is adjusted when the bundle fiber diameter differs depending on the probe used.
  • the beam diameter can be set to a desired size.
  • the light skirt portion is blocked by the first diaphragm 78 and the third diaphragm 81, and the second diaphragm 79 provided immediately before the relay lens system 80 is used for adjusting the amount of light.
  • the light guide member (FIG. 16A) composed of the quartz rod 76 a and the chip 77, or the light guide member (FIG. 18) composed of the diaphragms 78, 79, 81 and the relay lens system 80 is shown in FIG. It can also be provided inside the holding part as shown in FIG.
  • the convenience of the probe is improved by providing the holding portion with a connector structure that is detachable from the mounting portion.
  • the connector structure is not limited to the above structure, and the holding part is preferably compact.
  • FIG. 19 is a block diagram showing a configuration of the photoacoustic image generation apparatus 10 of the present embodiment.
  • the photoacoustic image generation apparatus 10 of this embodiment includes an acoustic wave detection probe 11, an ultrasonic unit 12, a laser unit 13, an image display unit 14, and an input unit 16 according to the present invention.
  • the laser unit 13 corresponds to a light source in the present invention, and outputs, for example, laser light L as measurement light that irradiates the subject M.
  • the laser unit 13 is configured to output a laser beam L in response to a trigger signal from the control unit 29, for example.
  • the laser light L output from the laser unit 13 is guided to the acoustic wave detection probe 11 using a light guide means such as an optical fiber, and is irradiated from the probe 11 to the subject M.
  • the laser unit 13 preferably outputs pulsed light having a pulse width of 1 to 100 nsec as laser light.
  • the pulse width t P (ns) of the laser light L preferably satisfies the following formula 6.
  • A is the pulse energy (J) when the laser light used is incident on the bundle fiber
  • ⁇ is the wavelength (nm) of the laser light used
  • G is the damage threshold energy density (J / Mm 2 )
  • ⁇ G and tG are the wavelength and pulse width of the laser light for which the damage threshold energy density was obtained, respectively
  • d is the diameter (mm) of the bundle fiber.
  • the laser unit 13 is a Q switch (Qsw) alexandrite laser.
  • the pulse width of the laser light L is controlled by, for example, Qsw.
  • the wavelength of the laser light is appropriately determined according to the light absorption characteristics of the substance in the subject to be measured.
  • the wavelength is preferably a wavelength belonging to the near-infrared wavelength region.
  • the near-infrared wavelength region means a wavelength region of about 700 to 850 nm.
  • the laser beam L may be a single wavelength or may include a plurality of wavelengths (for example, 750 nm and 800 nm).
  • the laser light L includes a plurality of wavelengths, the light of these wavelengths may be irradiated to the subject M at the same time, or may be irradiated while being switched alternately.
  • the acoustic wave detection probe 11 is a probe according to the present invention that detects a photoacoustic wave U generated in the subject M, and in this embodiment, is an acoustic wave detection probe according to the third embodiment.
  • the ultrasonic unit 12 includes a reception circuit 21, an AD conversion unit 22, a reception memory 23, a photoacoustic image reconstruction unit 24, a detection / logarithm conversion unit 27, a photoacoustic image construction unit 28, a control unit 29, an image synthesis unit 38, and Observation method selection means 39 is provided.
  • the receiving circuit 21, the AD converting means 22, the receiving memory 23, the photoacoustic image reconstruction means 24, the detection / logarithmic conversion means 27, and the photoacoustic image construction means 28 are integrated into a photoacoustic as a signal processing means in the present invention. It corresponds to image generation means.
  • the control means 29 controls each part of the photoacoustic image generation apparatus 10, and includes a trigger control circuit 30 in this embodiment.
  • the trigger control circuit 30 sends a light trigger signal to the laser unit 13 when the photoacoustic image generation apparatus is activated, for example.
  • the flash lamp is turned on in the laser unit 13 and the excitation of the laser rod is started. And the excitation state of a laser rod is maintained and the laser unit 13 will be in the state which can output a pulse laser beam.
  • the control means 29 then transmits a Qsw trigger signal from the trigger control circuit 30 to the laser unit 13. That is, the control means 29 controls the output timing of the pulsed laser light from the laser unit 13 by this Qsw trigger signal.
  • the control unit 29 transmits the sampling trigger signal to the AD conversion unit 22 simultaneously with the transmission of the Qsw trigger signal.
  • the sampling trigger signal serves as a cue for the start timing of the photoacoustic signal sampling in the AD conversion means 22. As described above, by using the sampling trigger signal, it is possible to sample the photoacoustic signal in synchronization with the output of the laser beam.
  • the receiving circuit 21 receives the photoacoustic signal detected by the acoustic wave detection probe 11.
  • the photoacoustic signal received by the receiving circuit 21 is transmitted to the AD conversion means 22.
  • the AD conversion means 22 is a sampling means, which samples the photoacoustic signal received by the receiving circuit 21 and converts it into a digital signal.
  • the AD conversion unit 22 includes a sampling control unit and an AD converter.
  • the reception signal received by the reception circuit 21 is converted into a sampling signal digitized by an AD converter.
  • the AD converter is controlled by the sampling control unit, and is configured to start sampling when the sampling control unit receives a sampling trigger signal.
  • the AD converter 22 samples the received signal at a predetermined sampling period based on, for example, an AD clock signal having a predetermined frequency input from the outside.
  • the reception memory 23 stores the photoacoustic signal sampled by the AD conversion means 22 (that is, the sampling signal).
  • the reception memory 23 outputs the photoacoustic signal detected by the acoustic wave detection probe 11 to the photoacoustic image reconstruction means 24.
  • the photoacoustic image reconstruction means 24 reads the photoacoustic signal from the reception memory 23, and based on the photoacoustic signal detected by the transducer array 20 of the acoustic wave detection probe 11, the data of each line of the photoacoustic image is obtained. Generate.
  • the photoacoustic image reconstruction unit 24 adds, for example, data from 64 acoustic wave detection elements of the acoustic wave detection probe 11 with a delay time corresponding to the position of the acoustic wave detection element, and outputs data for one line. Generate (delayed addition method).
  • the photoacoustic image reconstruction unit 24 may perform reconstruction by a CBP method (Circular Back Projection) instead of the delay addition method. Alternatively, the photoacoustic image reconstruction unit 24 may perform reconstruction using the Hough transform method or the Fourier transform method.
  • the detection / logarithm conversion means 27 obtains the envelope of the data of each line, and logarithmically transforms the obtained envelope.
  • the photoacoustic image construction means 28 constructs a photoacoustic image for one frame based on the data of each line subjected to logarithmic transformation.
  • the photoacoustic image construction means 28 constructs a photoacoustic image by converting, for example, a position in the time axis direction of the photoacoustic signal (peak portion) into a position in the depth direction in the photoacoustic image.
  • the observation method selection means 39 is for selecting the display mode of the photoacoustic image.
  • Examples of the volume data display mode for the photoacoustic signal include a mode as a three-dimensional image, a mode as a cross-sectional image, and a mode as a graph on a predetermined axis.
  • the display mode is selected according to the initial setting or the input from the input unit 16 by the user.
  • the image synthesis means 38 generates volume data using the photoacoustic signals acquired sequentially.
  • the volume data is generated by assigning the signal value of each photoacoustic signal to the virtual space according to the coordinates associated with each frame of the photoacoustic image and the pixel coordinates in the photoacoustic image. For example, the coordinates when the Qsw trigger signal is transmitted, the coordinates when light is actually output, the coordinates when sampling of the photoacoustic signal is started, and the like are associated for each frame of the photoacoustic image.
  • assigning signal values if the locations to be assigned overlap, for example, the average value of the signal values or the maximum value among them is adopted as the signal value of the overlapping location.
  • the image composition unit 38 performs necessary processing (for example, scale correction and coloring according to the voxel value) on the generated volume data.
  • the image composition means 38 generates a photoacoustic image according to the observation method selected by the observation method selection means 39.
  • the photoacoustic image generated according to the selected observation method becomes the final image (display image) to be displayed on the image display means 14.
  • the user can naturally rotate or move the image as necessary.
  • the user sequentially designates or moves the viewpoint direction using the input means 16 to recalculate the photoacoustic image and rotate the three-dimensional image. Will do. It is also possible for the user to change the observation method as appropriate using the input means 16.
  • the image display means 14 displays the display image generated by the image composition means 38.
  • the energy profile is flattened by passing laser light (measurement light) once through a homogenizer, and the beam diameter when entering the bundle fiber is set as the condensing member. Is controlled by.
  • laser light measurement light
  • the beam diameter when entering the bundle fiber is set as the condensing member.
  • the bias in the amount of energy of light traveling through each optical fiber is a major factor causing uneven brightness in the photoacoustic image. Therefore, it is possible to reduce luminance unevenness of the photoacoustic image by eliminating the uneven energy amount of light.
  • an anesthetic is injected into a target organ with a puncture needle
  • the ultrasonic image and the photoacoustic image are superimposed, and the position of the puncture needle is confirmed with the photoacoustic image while checking the position of the target organ with the ultrasonic image. Confirmation is done.
  • luminance unevenness in the photoacoustic image it is difficult to visually check whether the puncture needle has reached the target organ. In such a case, by eliminating the unevenness in the amount of light energy, the luminance unevenness of the photoacoustic image is reduced, and accurate puncture can be performed.
  • the laser light transmission cable can be reduced in size and weight, and the operability of the photoacoustic measurement apparatus is improved.
  • FIG. 20 is a block diagram illustrating a configuration of the photoacoustic image generation apparatus 10 of the present embodiment. This embodiment is different from the first embodiment in that an ultrasonic image is generated in addition to the photoacoustic image. Therefore, a detailed description of the same components as those in the first embodiment will be omitted unless particularly necessary.
  • the photoacoustic image generation apparatus 10 includes the acoustic wave detection probe 11, the ultrasonic unit 12, the laser unit 13, the image display unit 14, and the input unit 16 according to the present invention. Prepare.
  • the ultrasonic unit 12 of the present embodiment includes a transmission control circuit 33, a data separation unit 34, an ultrasonic image reconstruction unit 35, a detection / logarithmic conversion unit 36, And an ultrasonic image constructing means 37.
  • the unit 35, the detection / logarithm conversion unit 36, and the ultrasonic image construction unit 37 are integrated to correspond to an acoustic image generation unit as a signal processing unit in the present invention.
  • the acoustic wave detection probe 11 outputs (transmits) ultrasonic waves to the subject, and detects (receives) reflected ultrasonic waves from the subject with respect to the transmitted ultrasonic waves, in addition to detecting the photoacoustic signal. )I do.
  • the acoustic wave detecting element for transmitting and receiving ultrasonic waves the above-described transducer array 20 may be used, or a new transducer array provided in the acoustic wave detecting probe 11 separately for transmitting and receiving ultrasonic waves. May be used.
  • transmission and reception of ultrasonic waves may be separated. For example, ultrasonic waves may be transmitted from a position different from the acoustic wave detection probe 11, and reflected ultrasonic waves with respect to the transmitted ultrasonic waves may be received by the acoustic wave detection probe 11.
  • the trigger control circuit 30 sends an ultrasonic transmission trigger signal for instructing ultrasonic transmission to the transmission control circuit 33 when generating an ultrasonic image.
  • the transmission control circuit 33 Upon receiving this trigger signal, the transmission control circuit 33 transmits an ultrasonic wave from the probe 11.
  • the acoustic wave detection probe 11 detects reflected ultrasonic waves from the subject after transmitting the ultrasonic waves.
  • the reflected ultrasonic wave detected by the acoustic wave detection probe 11 is input to the AD conversion means 22 via the receiving circuit 21.
  • the trigger control circuit 30 sends a sampling trigger signal to the AD conversion means 22 in synchronization with the timing of ultrasonic transmission, and starts sampling of reflected ultrasonic waves.
  • the reflected ultrasonic wave reciprocates between the acoustic wave detection probe 11 and the ultrasonic wave reflection position, whereas the photoacoustic signal is one way from the generation position to the acoustic wave detection probe 11.
  • the sampling clock of the AD conversion means 22 is half the time when the photoacoustic signal is sampled, for example, It may be 20 MHz.
  • the AD conversion means 22 stores the reflected ultrasonic sampling signal in the reception memory 23. Either sampling of the photoacoustic signal or sampling of the reflected ultrasonic wave may be performed first.
  • the data separating means 34 separates the photoacoustic signal sampling signal and the reflected ultrasonic sampling signal stored in the reception memory 23.
  • the data separation unit 34 inputs a sampling signal of the separated photoacoustic signal to the photoacoustic image reconstruction unit 24.
  • the generation of the photoacoustic image is the same as that in the first embodiment.
  • the data separation unit 34 inputs the separated reflected ultrasound sampling signal to the ultrasound image reconstruction unit 35.
  • the ultrasonic image reconstruction means 35 generates data of each line of the ultrasonic image based on the reflected ultrasonic waves (its sampling signals) detected by the plurality of acoustic wave detection elements of the acoustic wave detection probe 11. For the generation of the data of each line, a delay addition method or the like can be used as in the generation of the data of each line in the photoacoustic image reconstruction means 24.
  • the detection / logarithm conversion means 36 obtains the envelope of the data of each line output from the ultrasonic image reconstruction means 35 and logarithmically transforms the obtained envelope.
  • the ultrasonic image construction means 37 generates an ultrasonic image based on the data of each line subjected to logarithmic transformation.
  • the image composition unit 38 synthesizes the photoacoustic image and the ultrasonic image.
  • the image composition unit 38 performs image composition by superimposing a photoacoustic image and an ultrasonic image, for example.
  • the synthesized image is displayed on the image display means 14. It is also possible to display the photoacoustic image and the ultrasonic image side by side on the image display means 14 without performing image synthesis, or to switch between the photoacoustic image and the ultrasonic image.
  • the energy profile is flattened by passing laser light (measurement light) once through a homogenizer, and the beam diameter when entering the bundle fiber is set as the condensing member. Is controlled by. Thereby, there exists an effect similar to 1st Embodiment.
  • the photoacoustic measurement device of the present embodiment generates an ultrasonic image in addition to the photoacoustic image. Therefore, by referring to the ultrasonic image, a portion that cannot be imaged in the photoacoustic image can be observed.
  • the photoacoustic measuring device demonstrated the case where a photoacoustic image and an ultrasonic image were produced
  • the photoacoustic measurement device can be configured to measure the presence / absence of a measurement target and a physical quantity based on the magnitude of the photoacoustic signal.
  • Photoacoustic image generation apparatus 11 Acoustic wave detection probe 12 Ultrasonic unit 13 Laser unit 14 Image display means 16 Input means 20 Transducer array 21 Reception circuit 24 Photoacoustic image reconstruction means 28 Photoacoustic image construction means 30 Trigger control circuit 33 Transmission control circuit 34 Data separation means 35 Ultrasound image reconstruction means 37 Ultrasound image construction means 38 Image composition means 39 Observation method selection means 40 Homogenizer 41 Condensing member 42 Bundle fiber 42a Optical fiber 43 Light guide plate 44 Light guide part 53 Lens diffuser plate 55 Beam expander optical system 60a, 60b Holding part 62 Center side area 64 Outer side area 65a, 65b, 65c Holding part D having connector structure Minimum laser beam diameter E1 Incident end E2 Emission end L Laser Light M Subject U Light sound Wave

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Abstract

La présente invention concerne une sonde de détection d'onde acoustique, qui transmet une lumière haute énergie et rend possible d'éliminer les écarts dans les niveaux d'énergie de la lumière traversant chacune des multiples fibres optiques durant la mesure photo-acoustique, et un dispositif de mesure photo-acoustique. Une sonde de détection d'onde acoustique (11) est dotée d'une section guide de lumière (44) pour guider la lumière de mesure (L) de manière à ce que la lumière de mesure (L) soit irradiée sur un objet à examiner (M) et un élément de détection d'onde acoustique (20) pour détecter les ondes photo-acoustiques (U) générées dans l'objet à examiner (M) par l'irradiation de la lumière de mesure (L), la section guide de lumière (44) comprenant : un élément de collecte de lumière (41) pour collecter la lumière de mesure (L) entrant dans la section guide de lumière (44) ; un homogénéisateur (40) pour générer un profil d'énergie à sommet plat de la lumière de mesure (L) qui a traversé l'élément de collecte de lumière (41) ; et un faisceau de fibres (42) qui comprend de multiples fibres optiques (42a) et guide la lumière de mesure (L) qui a traversé l'homogénéisateur (40).
PCT/JP2014/064615 2013-08-02 2014-06-02 Sonde de détection d'onde acoustique et dispositif de mesure photo-acoustique WO2015015893A1 (fr)

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JP2019191338A (ja) * 2018-04-24 2019-10-31 株式会社島津製作所 バンドルファイバ光結合装置

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