JP5855994B2 - Probe for acoustic wave detection and photoacoustic measurement apparatus having the probe - Google Patents

Description

  The present invention relates to a probe for detecting an acoustic wave applied to a subject such as a living body or an inorganic structure, and a photoacoustic measurement apparatus including the probe.

  Conventionally, a probe (or probe) for acoustic wave detection is used in, for example, an ultrasonic image generation device and a photoacoustic image generation device used for diagnosis, a fish detector used in fisheries, and the like. . Such a probe incorporates an acoustic lens in order to focus the acoustic wave beam and improve resolution.

  For example, Patent Document 1 discloses that in order to improve the adhesion with a living body, it is desired that the acoustic lens mainly satisfy six characteristics. Six specific requirements are: (1) Minimizing the reflection of ultrasonic waves at the contact portion with the subject, (2) Transmitting and receiving ultrasonic waves with high sensitivity, and (3) To make a convex shape The sound velocity in the acoustic lens is made of a material having a sound velocity (about 1500 m / s) or less in the subject, (4) it is made of a material having excellent moldability and particularly high tear strength, and (5) an additive. The constituent material of the included acoustic lens is safe for the living body, and (6) it is made of a material having a hardness that does not easily deform during use.

  Therefore, Patent Document 1 discloses a composition in which a zinc oxide powder or a platinum powder is mixed with silicone rubber at a predetermined weight concentration in order to provide an acoustic lens that satisfies all of the above six requirements.

  In relation to this, Patent Document 2 discloses an acoustic lens in which titanium oxide particles having a particle size of 0.08 to 0.20 μm are mixed with silicone rubber.

JP 2005-125071 A JP 58-216294 A

  By the way, when this inventor performs photoacoustic measurement, it discovered that there existed the subject about the acoustic lens resulting from irradiation of measurement light. Specifically, when the light reflected by the subject passes through the acoustic lens and is absorbed by the acoustic wave vibrator, artifacts (virtual images or false images) due to the vibration of the acoustic wave vibrator are projected, When the reflected light is absorbed by the acoustic lens, artifacts due to the photoacoustic wave generated there are projected. It is difficult to solve the problem only by satisfying the above six requirements in photoacoustic measurement.

  The present invention has been made in view of the above problems, and in an acoustic measurement using a probe, an acoustic wave detection probe capable of reducing the occurrence of artifacts due to irradiation of measurement light and the probe are provided. It is an object of the present invention to provide a photoacoustic measuring device provided.

In order to solve the above-described problem, an acoustic wave detection probe according to the present invention includes:
A light guide for guiding measurement light for irradiating a subject, an acoustic wave transducer capable of detecting an acoustic wave, and an acoustic lens having an acoustic wave focusing function provided on the subject side of the acoustic wave transducer In an acoustic wave detection probe comprising an electroacoustic transducer including
A light diffusing acoustic part having acoustic wave transparency provided on the subject side of the electroacoustic conversion part, wherein at least a part of the layer is composed of a light diffusing acoustic member having light diffusibility. Prepared,
The measurement light emission end face of the light guide section is arranged in the vicinity of the light diffusion acoustic section so that the optical path of the measurement light from the emission end face to the subject is not obstructed by the light diffusion acoustic section. It is characterized by.

  In the acoustic wave detection probe according to the present invention, the light diffusing acoustic member is preferably composed of an elastic material containing the first inorganic pigment. In this case, the first inorganic pigment is preferably at least one oxide particle of titanium oxide, zirconium oxide, iron oxide and cerium oxide. Furthermore, the particle size of the first inorganic pigment is preferably 0.05 to 0.35 μm, and the addition amount of the first inorganic pigment is preferably 2 to 65 wt%.

  In the acoustic wave detection probe according to the present invention, the light diffusing acoustic part constitutes a part that contacts the subject, and the surface part of the light diffusing acoustic part on the subject side is covered by the light diffusing acoustic part. It is preferably made of an elastic material that is soft enough to adapt to the surface shape of the contact portion when it comes into contact with the specimen. In this case, the surface shape on the subject side of the light diffusing acoustic part preferably has a flat shape.

  Alternatively, in the acoustic wave detection probe according to the present invention, an acoustic coupler that constitutes a portion in contact with the subject and transmits the measurement light and the acoustic wave, the subject-side surface and the emission end surface of the light diffusion acoustic part, It is preferable to provide a connected acoustic coupler. In this case, the light diffusing acoustic unit has a function of canceling the acoustic wave focusing function, and the light diffusing acoustic unit and the acoustic coupler have a configuration that can be detached from the electroacoustic conversion unit or the light guide unit. Preferably there is.

  In the acoustic wave detection probe according to the present invention, the light guide section includes at least one optical fiber that guides measurement light, an incident surface to which one end of the at least one optical fiber is connected, and an incident surface from the incident surface. It is preferable to have at least one light guide plate having an exit surface as the exit end surface from which the measured light exits. In this case, it is preferable that a plurality of light guide plates are arranged so that the light guide plates face each other with the electroacoustic conversion unit interposed therebetween.

  Furthermore, in the case where a plurality of light guide plates are arranged so as to face each other with the electroacoustic conversion unit interposed therebetween, light diffusion that diffuses measurement light leaked from the side surface of the light guide plate between the light guide plate and the electroacoustic conversion unit It is preferable to provide a member. In this case, the light diffusing member is preferably a metal plate coated with a paint containing a second inorganic pigment, and the second inorganic pigment is selected from titanium oxide, zirconium oxide, iron oxide and cerium oxide. It is preferable that it is at least one oxide particle. Alternatively, it is preferable that the light diffusing member is formed by pressing and baking a polytetrafluoroethylene powder.

  The photoacoustic measuring device which concerns on this invention is equipped with the probe as described above, It is characterized by the above-mentioned.

  And the photoacoustic measuring device which concerns on this invention WHEREIN: It is preferable to provide the light source which outputs the measurement light of a near-infrared wavelength range.

  Moreover, the photoacoustic measurement apparatus according to the present invention preferably includes an acoustic image generation unit that generates a photoacoustic image of the photoacoustic signal based on the photoacoustic signal of the photoacoustic wave detected by the probe. In this case, the probe detects a reflected ultrasonic wave with respect to the ultrasonic wave transmitted to the subject, and the acoustic image generation unit generates an ultrasonic image based on the ultrasonic signal of the reflected ultrasonic wave. It is preferable.

  The acoustic wave detection probe and the photoacoustic measurement device according to the present invention are in particular a light diffusing acoustic part having acoustic wave permeability provided on the subject side of the electroacoustic conversion part, and at least a part of the layers is light. It comprises a light diffusing acoustic part composed of a light diffusing acoustic member having diffusibility. Thereby, it can suppress that the light reflected by the subject passes through the acoustic lens and is absorbed by the acoustic wave vibrator or absorbed by the acoustic lens. As a result, in photoacoustic measurement using a probe, it is possible to reduce the occurrence of artifacts due to irradiation of measurement light.

It is the schematic which shows the structure of the probe of 1st Embodiment. It is the schematic which shows the structure of an electroacoustic conversion part, a light-diffusion acoustic part, and a light-guide plate. It is the schematic which shows the relationship between the particle size regarding an oxide particle, and scattering efficiency. It is the schematic which shows the structure of the probe of 2nd Embodiment. It is the schematic which shows the structure of the probe of 3rd Embodiment. It is the schematic which shows the structure of the photoacoustic measuring device of 1st Embodiment. It is the schematic which shows the structure of the photoacoustic measuring device of 2nd Embodiment.

  Hereinafter, although an embodiment of the present invention is described using a drawing, the present invention is not limited to this. In addition, for easy visual recognition, the scale of each component in the drawings is appropriately changed from the actual one.

“First Embodiment of Probe for Acoustic Wave Detection”
First, a first embodiment of an acoustic wave detection probe will be described. FIG. 1 is a schematic diagram showing the configuration of the probe of this embodiment, and FIG. 2 is a schematic diagram showing the configuration of an electroacoustic conversion unit, a light diffusion acoustic unit, and a light guide plate.

  As shown in FIG. 1, the probe 11 of this embodiment mainly includes an electroacoustic conversion unit 20, a light diffusion acoustic unit 43, an optical fiber 40, a light guide plate 42, a housing 44, and a cable 45. For example, the probe 11 irradiates the subject M with the laser light L from the light source, and detects photoacoustic waves generated in the subject M due to the photoacoustic effect. The wavelength of the laser light L is appropriately determined according to the light absorption characteristics of the substance in the subject M to be measured. For example, when the measurement target is a living body, light in the near infrared wavelength region is generally used as the laser light L in consideration of the absorption characteristics of hemoglobin. The near-infrared wavelength region means a wavelength region of about 700 to 850 nm. However, the wavelength of the laser beam L is naturally not limited to this.

<Electroacoustic transducer>
As shown in FIG. 2, the electroacoustic transducer 20 includes a backing material 50, an acoustic wave transducer array 51, and an acoustic lens 52, for example.

  The backing material 50 functions to absorb the acoustic wave that has passed through the acoustic wave transducer array 51 and to prevent the reflected wave of the acoustic wave from returning to the subject M side. The backing material 50 has a configuration in which a high-density powder material such as tungsten (W), lead (Pb), and zinc oxide (ZnO) is mixed with, for example, an epoxy resin that is a base resin.

  The acoustic wave transducer array 51 is a one-dimensional or two-dimensional arrangement of a plurality of acoustic wave transducers, and actually converts an acoustic wave signal into an electrical signal. The acoustic wave vibrator is a piezoelectric element made of a polymer film such as piezoelectric ceramics or polyvinylidene fluoride (PVDF). In this specification, “acoustic wave” means an ultrasonic wave and a photoacoustic wave. Here, “ultrasonic wave” means an elastic wave and its reflected wave generated in the subject due to vibration of the acoustic wave transducer array, and “photoacoustic wave” means a wave due to a photoacoustic effect caused by irradiation of measurement light. It means the elastic wave generated in the specimen.

  The acoustic lens 52 focuses the ultrasonic wave irradiated from the acoustic wave transducer array 51 as an acoustic wave beam. For example, the acoustic lens 52 has a flat plate shape in the present embodiment. As a material of the acoustic lens 52, for example, a rubber material such as silicone rubber and polyurethane can be used.

<Light diffusion acoustic part>
The light diffusing acoustic unit 43 is an element having acoustic wave permeability and light diffusibility provided on the subject side of the electroacoustic conversion unit 20. That is, according to the present invention, by providing the light diffusing acoustic part 43, an acoustic wave such as a photoacoustic wave U propagating through the subject M can be detected by the electroacoustic conversion unit 20 as usual, and on the surface of the subject M. A part of the measurement light (noise light Ld) reflected or diffused inside thereof is prevented from reaching the electroacoustic conversion unit 20. Further, since the light diffusing acoustic unit 43 has light diffusibility, the noise light Ld can be returned to the subject M again, and light energy can be efficiently used. In the light diffusing acoustic part 43, it is necessary to have sound transmission over the whole, but it is sufficient that the light diffusing property is at least partially included. That is, the light diffusing acoustic part 43 is composed of a light diffusing acoustic member in which at least a part of the layer has light diffusibility. This is because it is sufficient if the noise light Ld can be blocked at any location of the light diffusion acoustic unit 43. In this case, however, the acoustic matching layer 53 needs to be a transparent member that does not absorb light. This is because noise acoustic waves are generated when light is absorbed by the acoustic matching layer 53. For example, in the present embodiment, the light diffusing acoustic unit 43 includes an acoustic matching layer 53 and a light diffusing acoustic member 54 provided closer to the subject M than the acoustic matching layer 53. The acoustic matching layer 53 functions to match acoustic impedance. Examples of the material constituting the acoustic matching layer 53 include epoxy resin and quartz glass. The acoustic matching layer 53 is not necessarily essential, and the light diffusing acoustic part 43 may be composed of only the light diffusing acoustic member 54.

  In this specification, “having acoustic transparency” means that it is difficult to attenuate acoustic waves, and specifically, it is not more than a biological attenuation rate (0.5 to 1.0 dB / cm · MHz). Means. Thereby, attenuation of the acoustic wave which passes the light-diffusion acoustic part 43 can be reduced.

  On the other hand, “having light diffusibility” means that the diffuse reflectance with respect to light is high, and specifically means that the average diffuse reflectance in the wavelength region of the measurement light is 85% or more. The “wavelength range of the measurement light” means a wavelength range corresponding to the full width at half maximum in the wavelength distribution of the measurement light. For example, in this embodiment, the wavelength range of the measurement light is included in the near infrared wavelength range. Furthermore, the “average diffuse reflectance” is the diffuse reflectance at the average thickness of the light diffusing acoustic member 54 and means the average value of the diffuse reflectance of light belonging to a predetermined wavelength region. The average value of the diffuse reflectance of light belonging to a predetermined wavelength range can be obtained, for example, by obtaining the diffuse reflectance for several lights belonging to the wavelength range and taking the average. The diffuse reflectance is measured by a spectrophotometer or the like.

  Such a light diffusing acoustic member 54 can be formed, for example, by mixing and molding an inorganic pigment into an acoustic material having acoustic transparency. In this case, the inorganic pigment is preferably at least one oxide particle of titanium oxide, zirconium oxide, iron oxide and cerium oxide. On the other hand, rubber materials such as silicone rubber and polyurethane can be used as the acoustic material. In addition, the size of the inorganic pigment particles is appropriately adjusted in such a range that generation of artifacts described later becomes an electric noise level and does not cause a problem on an image. Furthermore, the size of the inorganic pigment particles is preferably 0.05 to 0.35 μm. This considers the relationship between the particle size and the scattering efficiency (which is proportional to the reduction scattering constant at a constant particle concentration) for the oxide particles, as shown in FIG.

  The graph of FIG. 3 is a plot of scattering efficiency values calculated assuming Mie scattering in 756 nm light. The plot of A is data for a sample in which titanium rubber (refractive index: 2.6) is mixed with silicone rubber (refractive index: 1.41), and the plot of B is zirconium oxide (refractive index: 2.4) is the data for the sample mixed, and the plot of C is the data for the sample in which silicone rubber is mixed with polystyrene (refractive index: 1.6). As can be seen from FIG. 3, in the range where the size of the particles is 0.05 to 0.35 μm, a high diffuse reflectance can be obtained even if the oxide particle concentration (particle concentration) relative to the acoustic material is low. Furthermore, the size of the inorganic pigment particles is preferably 0.08 to 0.2 μm in consideration of not increasing the acoustic attenuation rate. In the present specification, “particle size” means an average value of the diameters of particles of the material type. For example, dynamic light scattering method, laser diffraction method, and image imaging method using a scanning electron microscope (SEM). Measured by etc.

  The thickness of the light diffusing acoustic member 54 (referring to the thickness of the thickest portion) is preferably 0.5 to 2 mm. This is because if the thickness is too thin, it is difficult to obtain a diffuse reflectance in the wavelength region of the measurement light at a predetermined concentration, and if it is thick, absorption in the wavelength region of the measurement light L by the material of the member increases. .

  The amount of the inorganic pigment added is appropriately adjusted in such a range that generation of artifacts described later becomes an electric noise level and does not cause a problem on an image. Furthermore, it is preferable that the addition amount of an inorganic pigment is 2-65 wt%. This is because when the addition amount is lower than this range, the average diffuse reflectance in the wavelength region of the measurement light does not reach 85%, and when it is large, the average diffuse reflectance in the wavelength region of the measurement light is increased. This is because it is saturated.

  In general, when the particle concentration increases to such an extent that the particles are close to a distance of half or less of the particle diameter, the scattering ability is saturated. For example, assuming that 0.2 μm particles enter a cubic space with a side of 0.3 μm, the scattering ability (diffuse reflectance) is, for example, that the volume fraction of an inorganic pigment in a mixture of silicone rubber and inorganic pigment is 0.155. When it is saturated. Therefore, in the present invention, the addition amount of the inorganic pigment is appropriately set in the range where the volume fraction of the inorganic pigment in the material constituting the light diffusing acoustic member 54 is 0.155. The same applies to iron oxide and cerium oxide not shown in the graph of FIG.

  Further, as in the present embodiment, when the light diffusing acoustic unit 43 constitutes a part in contact with the subject M, the surface part of the light diffusing acoustic unit 43 on the subject M side is the light diffusing acoustic unit 43. It is preferable that the elastic member is made of an elastic material that is soft enough to adapt to the surface shape of the contact portion when it comes into contact with the subject M. In such a case, the probe 11 can be brought into contact with the subject M so that no gap is generated between the light diffusing acoustic unit 43 and the subject M, so that light can be efficiently transmitted to the subject M side. It becomes possible to return. In this case, the surface shape on the subject side of the light diffusing acoustic part 43 preferably has a flat shape. This is because the versatility that can be adapted to various shapes is high. Rubber materials such as silicone rubber and polyurethane can also be used as the elastic material.

  On the other hand, portions other than the light diffusing acoustic member 54 in the light diffusing acoustic portion 43 can be formed using a known acoustic material.

  In addition, about the material of the light-diffusion acoustic part 43, it is preferable that the acoustic impedance is the same as that of the subject M, or close. Artifacts due to multiple reflections of acoustic waves inside the light diffusion acoustic unit 43 can be reduced.

<Optical fiber>
The optical fiber 40 is optically connected to a light source that outputs the laser light L, and guides the laser light L to the light guide plate 42 in the present embodiment. The optical fiber 40 is connected to the incident surface S1 of the light guide plate. The optical fiber 40 is not particularly limited, and a known fiber such as a quartz fiber can be used. One optical fiber may be used, but it is preferable to use a plurality of optical fibers in order to increase the transmission amount of light energy. For example, a bundle fiber can be used as the optical fiber.

<Light guide plate>
The light guide plate 42 is a plate that performs special processing on the surface of an acrylic plate or a quartz plate, for example, and uniformly emits light from one end surface (incident surface S1) from the other end surface (exit surface S2). is there. The optical fiber 40 and the light guide plate 42 as a whole correspond to the light guide section in the present invention. As shown in FIG. 1b, in this embodiment, two light guide plates 42 are arranged so as to face each other with the electroacoustic conversion unit 20 interposed therebetween, and two optical fibers 40 are provided on each light guide plate 42, for example. It is connected. For example, as shown in FIG. 1a, the light guide plate 42 is formed in a tapered shape whose width increases from the incident surface S1 connected to the optical fiber 40 toward the output surface S2. Further, the portion of the light guide plate 42 connected to the optical fiber 40 is preferably formed of a glass material in order to avoid damage due to light energy. On the other hand, other portions are formed of a resin material such as acrylic.

  The laser light L guided by the optical fiber 40 is incident on the light guide plate 42 from the incident surface S1, and then irradiated on the subject M from the opposite exit surface S2. That is, in the present embodiment, the emission surface S2 of the light guide plate 42 corresponds to the emission end surface of the light guide unit in the present invention. The light guide plate 42 has a mechanism (such as a resin containing scattering particles) for diffusing light at the tip thereof or a traveling direction of the light so that the subject M can be irradiated with a wider range of the subject M with the laser light L. You may have the mechanism (a notch etc. for refracting light) which turns to the side. As shown in FIG. 2, the exit surface S <b> 2 of the light guide plate 42 has a light diffusing acoustic unit so that the optical path of the laser light L from the exit surface S <b> 2 to the subject M is not obstructed by the light diffusing acoustic unit 43. 43 is arranged in the vicinity. Further, the presence of the light diffusing acoustic part 43 on the optical path causes an increase in the noise light Ld. In other words, the laser light L is emitted while avoiding the light diffusion acoustic unit 43 in order to efficiently transmit light energy to the subject M.

<Housing and cable>
The housing 44 is made of, for example, acrylonitrile, butadiene, and styrene copolymer resin (ABS resin). In this embodiment, it has a handheld shape, but the housing 44 of the present invention is not limited to this. The cable 45 includes the electrical wiring 41 and the optical fiber 40, the other end of the electrical wiring 41 is connected to a measuring device, and the other end of the optical fiber 40 is connected to a light source that outputs laser light L.

  As will be described below, the acoustic wave detection probe according to the present embodiment, in particular, the measurement light (laser light) until it enters the subject M from the exit surface S2 at a position closer to the subject than the electroacoustic transducer 20. L) is provided with a light diffusing acoustic part 43 having light diffusibility and sound transmission at a position that does not interfere with the optical path of L), so that the noise light Ld passes through the acoustic lens 52 and is absorbed by the acoustic wave vibrator. Absorption can be suppressed. As a result, in photoacoustic measurement using a probe, it is possible to reduce the occurrence of artifacts due to irradiation of measurement light.

  Further, by providing a light diffusing property to the light diffusing acoustic part which is a member different from the acoustic lens, for example, a sheet-like light diffusing acoustic member is used as the light diffusing acoustic part by using an existing photoacoustic probe. It is possible to carry out the present invention by a simple method such as attaching the film to an acoustic lens. Furthermore, since the light diffusing acoustic part, which is a member different from the acoustic lens, has light diffusibility, the degree of freedom in designing the acoustic lens can be ensured.

  As a prior art document that raises the problem of light reflected from the surface of the subject as in the present invention, there is, for example, Japanese Patent Application Laid-Open No. 2012-40361. Specifically, in this document, in the back detection type photoacoustic probe, when backscattered light on the surface of the subject is incident on the acoustic wave transducer, the acoustic wave generated on the acoustic wave transducer surface by the light is noise. In order to suppress these problems, it is disclosed that a light reflecting member for reflecting scattered light on the subject surface is provided between the acoustic wave vibrator and the subject surface.

  However, the present invention is different from the above-described literature in that the light reflected from the surface of the subject is not only specularly reflected but also diffusely reflected. In the present invention, by diffusely reflecting the light reflected on the surface of the subject, there is an advantage that the light can be irradiated more uniformly when the surface of the subject is irradiated again. In other words, in the present invention, even when there is a local reflection component on the surface of the subject, it is possible to uniformly irradiate and reuse such a component, thereby preventing image unevenness. .

“Second Embodiment of Probe for Acoustic Wave Detection”
Next, a second embodiment of the acoustic wave detection probe will be described. FIG. 4 is a schematic view showing the configuration of the probe of this embodiment. In particular, the present embodiment differs from the first embodiment in that the structure of the light diffusing acoustic unit 43, the structure of the light guide plate 42, and the shape of the acoustic lens 52 are different, and the acoustic coupler 46 is provided. Therefore, a detailed description of the same configuration as that of the first embodiment is omitted unless particularly required.

  As shown in FIG. 4, the probe 11 of this embodiment mainly includes an electroacoustic conversion unit 20, a light diffusion acoustic unit 43, an optical fiber 40, a light guide plate 42, a housing 44, a cable 45, and an acoustic coupler 46. .

<Electroacoustic transducer>
The electroacoustic conversion unit 20 in the present embodiment differs from the first embodiment in that the acoustic lens 52 has a plano-convex shape (a shape in which the center is thick and the end is thin). This is the same as the embodiment.

<Light diffusion acoustic part>
The light diffusing acoustic part 43 of the present embodiment is composed of only a light diffusing acoustic member and has a concave shape complementary to the convex shape of the acoustic lens 52 so that the acoustic wave focusing function of the acoustic lens 52 is canceled (the center is thin). A shape having a thick end). Therefore, in the present embodiment, when the convex shape of the acoustic lens 52 and the concave shape of the light diffusing acoustic unit 43 are combined, the acoustic wave focusing function of the acoustic lens 52 is canceled and the acoustic wave transducer array 51 is irradiated. Ultrasonic waves will not be focused. The acoustic lens 52 and the light diffusion acoustic unit 43 are configured to be detachable.

<Light guide plate>
The light guide plate 42 of the present embodiment is broadly divided into a first light guide region 42a on the incident surface S1 side and a second light guide region 42b on the output surface S2 side. The first light guide region 42a is formed on the basis of a material having high resistance to light energy (for example, quartz glass), and the second light guide region 42b is a material flexible enough to be deformable according to external force ( For example, a rubber material) is formed. With this configuration, it is possible to suppress damage on the incident surface S1 side having a high energy density and facilitate connection to an acoustic coupler 46 described later.

<Acoustic coupler>
The acoustic coupler 46 constitutes a portion in contact with the subject M and transmits the laser light L and the acoustic wave. For example, the acoustic coupler 46 is used to increase the distance between the subject M and the electroacoustic conversion unit 20. The acoustic coupler 46 is preferably transparent at least in the wavelength region of the laser light L. In the present invention, the acoustic coupler 46 is connected to the surface of the light diffusing acoustic unit 43 on the subject M side and the emission surface S <b> 2 of the light guide plate 42. Here, the acoustic coupler 46 and the emission surface S2 of the light guide plate 42 are configured to be detachable. The light diffusing acoustic unit 43 and the acoustic coupler 46 may be configured to be detachable or may not be configured as such. As the material of the acoustic coupler 46, rubber materials such as silicone rubber and polyurethane can be used as in the case of the acoustic lens.

  For example, as shown in FIG. 4, the side surface of the acoustic coupler 46 is inclined at a predetermined angle with respect to the detection surface of the acoustic wave transducer array 51. When such an acoustic coupler 46 is attached to the probe 11, the second light guide region 42 b of the light guide plate 42 is deformed according to an external force when attached. Specifically, as shown in FIG. 4 a, the second light guide region 42 b is deformed so that the emission surface S <b> 2 is parallel to the side surface of the acoustic coupler 46. Thereby, the laser beam L can be irradiated to the subject M at a desired angle corresponding to the inclination angle of the side surface of the acoustic coupler 46. That is, the irradiation angle of the laser light L can be adjusted by adjusting the inclination angle of the side surface of the acoustic coupler 46 or by preparing a plurality of acoustic couplers 46 having different inclination angles.

  As will be described below, the acoustic wave detection probe according to the present embodiment, in particular, the measurement light (laser light) from the electroacoustic conversion unit 20 to the subject side and from the emission surface S2 to the subject M. Since the light diffusing acoustic part 43 having light diffusibility and sound transmittance is provided at a position that does not obstruct the optical path of L), the same effects as those of the first embodiment are obtained.

  In the present embodiment, in particular, since the light diffusing acoustic unit 43 that cancels the acoustic wave focusing function is configured to be detachable with respect to the electroacoustic conversion unit 20, flexible measurement can be performed according to the purpose of the photoacoustic measurement. Is possible. For example, when generating a cross-sectional photoacoustic image, the light diffusion acoustic unit 43 and the acoustic coupler 46 are removed, photoacoustic measurement is performed, and volume data of the photoacoustic image is generated by two-dimensional scanning. Measurements such as photoacoustic measurement with the acoustic unit 43 and the acoustic coupler 46 attached may be considered.

  In the present embodiment, the emission surface S2 that is the emission end surface is connected to the side surface of the acoustic coupler 46 that is inclined at a predetermined angle with respect to the detection surface of the acoustic wave transducer array 51. The irradiation angle of the laser light L can be adjusted with respect to the detection surface of the transducer array 51 and the surface of the measurement site of the subject M.

“Third embodiment of probe for acoustic wave detection”
Next, a third embodiment of the acoustic wave detection probe will be described. FIG. 5 is a schematic view showing the configuration of the probe of this embodiment. In particular, the present embodiment differs from the second embodiment in that the shapes of the light diffusing acoustic part 43 and the acoustic lens 52 are different and the light diffusing member 47 is provided. Therefore, a detailed description of the same configuration as that of the second embodiment is omitted unless particularly necessary.

  As shown in FIG. 5, the probe 11 of this embodiment mainly includes an electroacoustic conversion unit 20, a light diffusion acoustic unit 43, an optical fiber 40, a light guide plate 42, a housing 44, a cable 45, an acoustic coupler 46, and a light diffusion member. 47.

<Acoustic lens and light diffusion acoustic part>
In the present embodiment, the acoustic lens 52 and the light diffusing acoustic unit 43 each have a flat plate shape.

<Light diffusion member>
The light diffusing member 47 functions to return such leaked light to the subject M side by diffusing the laser light L leaked from the side surface of the light guide plate 42. As illustrated in FIG. 5, the light diffusing member 47 is disposed in a space between the light guide plate 42 and the electroacoustic conversion unit 20. The light diffusion member 47 is preferably white in order to efficiently diffuse the laser light L. Therefore, the light diffusing member 47 is preferably a metal plate (for example, a steel plate, an aluminum plate, etc.) coated with a paint containing an inorganic pigment, for example. Thereby, not only the reflection effect due to the metal plate but also the diffusion effect due to the inorganic pigment can be obtained. The inorganic pigment is preferably at least one oxide particle of titanium oxide, zirconium oxide, iron oxide, and cerium oxide, similar to the one added to the light diffusion acoustic member 54 described above. In addition, as a main component of a coating material, it does not restrict | limit in particular, The material generally used as a coating material can be used. The thickness of the coating film is set to 0.03 mm or more, for example. In addition, the size and addition amount of the inorganic pigment particles are appropriately adjusted within a range in which the generation of artifacts, which will be described later, becomes an electric noise level and does not cause a problem on an image. Furthermore, the particle size of the inorganic pigment is preferably 0.05 to 0.35 μm, and the addition amount of the inorganic pigment is preferably 2 to 65 wt%. This is for the same reason as in the case of the light diffusing acoustic member 54. Alternatively, the light diffusing member 47 may be obtained by pressing and baking polytetrafluoroethylene (PTFE) powder.

  As will be described below, the acoustic wave detection probe according to the present embodiment, in particular, the measurement light (laser light) from the electroacoustic conversion unit 20 to the subject side and from the emission surface S2 to the subject M. Since the light diffusing acoustic part 43 having light diffusibility and sound transmittance is provided at a position that does not obstruct the optical path of L), the same effects as those of the first embodiment are obtained.

  In the present embodiment, in particular, since the light diffusing member 47 is provided between the light guide plate 42 and the electroacoustic conversion unit 20, the leakage of the laser light L leaked from the side surface of the light guide plate 42 causes such leakage. The light can be returned to the subject M side, and the measurement light can be used efficiently.

“First Embodiment of Photoacoustic Measuring Device”
Next, a first embodiment of the photoacoustic measurement device will be described. In the present embodiment, the case where the photoacoustic measurement device is a photoacoustic image generation device that generates a photoacoustic image based on a photoacoustic signal will be specifically described. FIG. 6 is a block diagram illustrating a configuration of the photoacoustic image generation apparatus 10 of the present embodiment.

  The photoacoustic image generation apparatus 10 of the present embodiment includes a 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.

<Laser unit>
The laser unit 13 outputs, for example, laser light L as measurement light for irradiating 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 probe 11 using 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.

  For example, in this embodiment, the laser unit 13 is a Q switch (Qsw) alexandrite laser. In this case, 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. For example, when the measurement target is hemoglobin in a living body (that is, when a blood vessel is imaged), generally, the wavelength is preferably a wavelength belonging to the near-infrared wavelength region. The laser beam L may be a single wavelength or may include a plurality of wavelengths (for example, 750 nm and 800 nm). Furthermore, when 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.

<Probe>
The probe 11 is a probe according to the present invention for detecting the photoacoustic wave U generated in the subject M, and for example, the probe shown in FIGS. 1 and 2 is used.

<Ultrasonic unit>
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 reception circuit 21, AD conversion means 22, reception memory 23, photoacoustic image reconstruction means 24, detection / logarithmic conversion means 27, and photoacoustic image construction means 28 together correspond to the acoustic image generation means in the present invention.

  The control unit 29 controls each unit of the photoacoustic image generation apparatus 10 and includes a trigger control circuit 30 in the present 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. As a result, 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 unit 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. In the present embodiment, 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 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. For example, 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). Then, the reception memory 23 outputs the photoacoustic signal detected by the probe 11 to the photoacoustic image reconstruction unit 24.

  The photoacoustic image reconstruction unit 24 reads out the photoacoustic signal from the reception memory 23 and generates data of each line of the photoacoustic image based on the photoacoustic signal detected by the electroacoustic conversion unit 20 of the probe 11. The photoacoustic image reconstruction unit 24 adds data from, for example, 64 acoustic wave transducers of the probe 11 with a delay time corresponding to the position of the acoustic wave transducer, and generates data for one line (delay). Addition method). The photoacoustic image reconstruction means 24 may perform reconstruction by the 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 an envelope of the data of each line, and logarithmically converts 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 a 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 synthesizing unit 38 generates volume data using sequentially acquired photoacoustic signals. 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. When 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. Further, if there is no signal value to be assigned, it is preferable to interpolate using the peripheral signal values as necessary. Interpolation is performed, for example, by assigning weighted average values of four adjacent points in order from the closest point to the interpolation location. As a result, more natural volume data can be generated. Further, the image composition unit 38 performs necessary processing (for example, scale correction and coloring according to the voxel value) on the generated volume data.

  In addition, the image composition unit 38 generates a photoacoustic image according to the observation method selected by the observation method selection unit 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. In the above-described photoacoustic image generation method, after the photoacoustic image is once generated, the user can naturally rotate or move the image as necessary. In other words, when a three-dimensional image is displayed, 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.

  As described above, since the photoacoustic measurement apparatus according to the present embodiment uses the probe of the present invention, in the photoacoustic measurement using the probe, the occurrence of artifacts due to irradiation of measurement light is reduced. It becomes possible.

“Second Embodiment of Photoacoustic Measuring Device”
Next, a second embodiment of the photoacoustic measurement apparatus will be described. Also in this embodiment, the case where a photoacoustic measuring device is a photoacoustic image generation apparatus is demonstrated concretely. FIG. 7 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.

  Similar to the first embodiment, the photoacoustic image generation apparatus 10 of the present embodiment includes a 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.

<Ultrasonic unit>
In addition to the configuration of the photoacoustic image generation apparatus shown in FIG. 6, 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. In the present embodiment, the reception circuit 21, AD conversion means 22, reception memory 23, data separation means 34, photoacoustic image reconstruction means 24, detection / logarithmic conversion means 27, photoacoustic image construction means 28, ultrasonic image reconstruction. The means 35, the detection / logarithm conversion means 36, and the ultrasonic image construction means 37 are integrated and correspond to the acoustic image generation means in the present invention.

  In the present embodiment, in addition to detecting a photoacoustic signal, the probe 11 performs output (transmission) of ultrasonic waves to the subject and detection (reception) of reflected ultrasonic waves from the subject with respect to the transmitted ultrasonic waves. As the acoustic wave transducer for transmitting and receiving ultrasonic waves, the acoustic wave transducer array 51 described above may be used, or a new acoustic wave transducer array separately provided in the probe 11 for transmitting and receiving ultrasonic waves. May be used. In addition, transmission and reception of ultrasonic waves may be separated. For example, ultrasonic waves may be transmitted from a position different from the probe 11, and reflected ultrasonic waves with respect to the transmitted ultrasonic waves may be received by the probe 11.

  When generating an ultrasonic image, the trigger control circuit 30 sends an ultrasonic transmission trigger signal to the transmission control circuit 33 to instruct ultrasonic transmission. Upon receiving this trigger signal, the transmission control circuit 33 transmits an ultrasonic wave from the probe 11. The probe 11 detects the reflected ultrasonic wave from the subject after transmitting the ultrasonic wave.

  The reflected ultrasonic wave detected by the 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. Here, the reflected ultrasonic waves reciprocate between the probe 11 and the ultrasonic reflection position, whereas the photoacoustic signal is one way from the generation position to the probe 11. Since the detection of the reflected ultrasonic wave takes twice as long as the detection of the photoacoustic signal generated at the same depth position, 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 separator 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. On the other hand, the data separation unit 34 inputs the separated reflected ultrasound sampling signal to the ultrasound image reconstruction unit 35.

  The ultrasonic image reconstruction unit 35 generates data of each line of the ultrasonic image based on the reflected ultrasonic wave (its sampling signal) detected by the plurality of acoustic wave transducers of the 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 unit 37 generates an ultrasonic image based on the data of each line subjected to logarithmic transformation.

  The image synthesizing 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.

  As described above, since the photoacoustic measurement apparatus according to the present embodiment also uses the probe of the present invention, in the photoacoustic measurement using the probe, the generation of artifacts due to irradiation of measurement light is reduced. It becomes possible.

  Furthermore, the photoacoustic measuring device of this 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.

  In addition, although the case where a photoacoustic measuring device produced | generated a photoacoustic image and an ultrasonographic image was demonstrated above, such image generation is not necessarily required. For example, 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.

DESCRIPTION OF SYMBOLS 10 Photoacoustic image generation apparatus 11 Probe 12 Ultrasonic unit 13 Laser unit 14 Image display means 16 Input means 20 Electroacoustic conversion part 40 Optical fiber 42 Light guide plate 43 Light diffusion acoustic part 46 Acoustic coupler 47 Light diffusion member 50 Backing material 51 Acoustic Wave transducer array (acoustic wave transducer)
52 Acoustic Lens 54 Light Diffusing Acoustic Member L Laser Light (Measurement Light)
Ld noise light M subject S1 entrance surface S2 exit surface (exit end surface)
U photoacoustic wave

Claims (19)

A light guide that guides measurement light for irradiating the subject, an acoustic wave transducer capable of detecting acoustic waves, and an acoustic wave having an acoustic wave focusing function provided on the subject side of the acoustic wave transducer In an acoustic wave detection probe comprising an electroacoustic transducer including a lens,
A light diffusing acoustic part having acoustic wave transparency provided on the subject side of the electroacoustic conversion unit, wherein at least a part of the layer has a light diffusibility with respect to the measurement light reflected by the subject. Comprising a light diffusing acoustic part comprising a light diffusing acoustic member having
The measurement light emission end face of the light guide part is arranged in the vicinity of the light diffusion acoustic part so that the optical path of the measurement light from the emission end face to the subject is not obstructed by the light diffusion acoustic part. The probe characterized by being made.   The probe according to claim 1, wherein the light diffusing acoustic member is made of an elastic material containing a first inorganic pigment.   The probe according to claim 2, wherein the first inorganic pigment is at least one oxide particle of titanium oxide, zirconium oxide, iron oxide, and cerium oxide.   4. The probe according to claim 2, wherein the first inorganic pigment has a particle size of 0.05 to 0.35 [mu] m.   The probe according to any one of claims 2 to 4, wherein the added amount of the first inorganic pigment is 2 to 65 wt%. The light diffusing acoustic part constitutes a part that contacts the subject,
The surface portion on the subject side of the light diffusing acoustic portion is made of an elastic material that is soft enough to adapt to the surface shape of the contact portion when the light diffusing acoustic portion contacts the subject. The probe according to any one of claims 1 to 5, wherein:   The probe according to claim 6, wherein a surface shape on the subject side of the light diffusing acoustic part has a flat shape.   An acoustic coupler that constitutes a portion in contact with the subject and transmits the measurement light and acoustic waves, the acoustic coupler including an acoustic coupler connected to the subject-side surface and the emission end face of the light diffusing acoustic part. The probe according to claim 1, wherein: The light diffusion acoustic unit has a function of canceling the acoustic wave focusing function,
9. The probe according to claim 8, wherein the light diffusing acoustic part and the acoustic coupler have a configuration that is detachable from the electroacoustic conversion part or the light guide part.   The light guide section includes at least one optical fiber for guiding the measurement light, an incident surface to which one end of the at least one optical fiber is connected, and the emission end surface from which the measurement light incident from the incident surface is emitted. The probe according to claim 1, further comprising: at least one light guide plate having an emission surface.   The probe according to claim 10, wherein a plurality of the light guide plates are arranged such that the light guide plates face each other with the electroacoustic conversion unit interposed therebetween.   The probe according to claim 11, further comprising a light diffusion member that diffuses the measurement light leaked from a side surface of the light guide plate between the light guide plate and the electroacoustic conversion unit.   The probe according to claim 12, wherein the light diffusing member is a metal plate coated with a paint containing a second inorganic pigment.   The probe according to claim 13, wherein the second inorganic pigment is at least one oxide particle of titanium oxide, zirconium oxide, iron oxide, and cerium oxide.   The probe according to claim 12, wherein the light diffusing member is obtained by pressing and baking a polytetrafluoroethylene powder.   A photoacoustic measuring device comprising the probe according to claim 1.   The photoacoustic measurement apparatus according to claim 16, further comprising a light source that outputs the measurement light in a near-infrared wavelength region.   18. The photoacoustic according to claim 16, further comprising an acoustic image generation unit configured to generate a photoacoustic image of the photoacoustic signal based on a photoacoustic signal of a photoacoustic wave detected by the probe. Measuring device. The probe detects reflected ultrasonic waves with respect to ultrasonic waves transmitted to the subject;
The photoacoustic measurement apparatus according to claim 18, wherein the acoustic image generation unit generates an ultrasonic image based on an ultrasonic signal of the reflected ultrasonic wave.

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