JP2012090862A - Probe for photoacoustic inspection and photoacoustic inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a photoacoustic wave of a higher S/N in a photoacoustic inspection using a photoacoustic effect.SOLUTION: A probe 70 used in the photoacoustic inspection includes a light applying part 15 for applying light L to a body 7 to be inspected, an electro-acoustic transducer 3 for converting the photoacoustic wave into an electric signal and a light diffusing liquid part 8 having an acoustic matching function for matching an acoustic impedance of the body 7 to be inspected with an acoustic impedance of the electro-acoustic transducer 3 and a diffusing function for diffusing the light L so as to apply to the body 7 to be inspected the light L having a substantially uniform intensity distribution on the body 7 to be inspected. The light diffusing liquid part 8 includes acoustic matching liquid 83 having the acoustic matching function and diffused particles 84 having the diffusing function which are dispersed in the acoustic matching liquid 83. The electro-acoustic transducer 3 is provided so that at least a part of the electro-acoustic transducer 3 comes into contact with the acoustic matching liquid 83.

Description

  The present invention relates to a probe used in a photoacoustic inspection for generating a photoacoustic image by detecting a photoacoustic wave generated in a subject by irradiating the subject with light, and a photoacoustic inspection including the probe. It relates to the device.

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

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

  However, when the subject is a living body, the maximum allowable exposure amount (MPE: Maximum Permissible Exposure) per unit area that can irradiate the living body is avoided because the living tissue is not damaged by the energy of the irradiated light. It has been established. Therefore, even if the amount of light is increased, MPE becomes the upper limit.

  Therefore, in Patent Document 1, the light intensity distribution is uniform by dispersing diffusing particles in an acoustic matching layer such as an epoxy resin so that a photoacoustic wave having a high S / N can be detected even when the amount of light is less than or equal to MPE. An apparatus for irradiating light is disclosed.

JP 2010-125260 A

  However, the method as disclosed in Patent Document 1 has a problem in that a photoacoustic wave having a sufficiently high S / N may not be detected because the acoustic matching function and the diffusion function are in a trade-off relationship. This is because the acoustic impedance of the acoustic matching layer such as epoxy resin changes when the concentration of the diffusing particles responsible for the diffusion function is increased in order to achieve a uniform intensity distribution, and appropriate acoustic impedance cannot be maintained in acoustic matching. is there.

  The present invention has been made in view of the above problems, and in a photoacoustic inspection utilizing a photoacoustic effect, a photoacoustic inspection probe capable of detecting a photoacoustic wave having a higher S / N, and An object of the present invention is to provide a photoacoustic inspection apparatus.

In order to solve the above problem, a probe for photoacoustic inspection according to the present invention is:
Irradiating the subject with light, guiding the light to the subject, detecting the photoacoustic wave generated in the subject by irradiating the subject with the light, and converting the photoacoustic wave into an electrical signal; In a probe used for photoacoustic inspection that performs inspection based on this electrical signal,
A light irradiation unit for irradiating the subject with light;
An electroacoustic transducer that converts photoacoustic waves into electrical signals;
An acoustic matching function that matches the acoustic impedance of the subject and the acoustic impedance of the electroacoustic transducer, and a diffusion function that diffuses light so that the subject is irradiated with light having a substantially uniform intensity distribution on the subject A light diffusing liquid part,
The light diffusing liquid part comprises an acoustic matching liquid responsible for the acoustic matching function, and diffusing particles responsible for the diffusion function dispersed in the acoustic matching liquid,
The electroacoustic transducer is provided so that at least a part of the electroacoustic transducer is in contact with the acoustic matching liquid.

In the photoacoustic test probe according to the present invention, the acoustic impedance of the diffusing particles is preferably 1.2 to 1.9 × 10 ⁶ kg / m ² / s, and in particular, the diffusing particles are lipid particles. Preferably there is.

The light diffusing liquid part includes a diffusion tank for holding the acoustic matching liquid,
It is preferable that the diffusion tank has an acoustic transmission film in a portion in contact with the subject.

  And it is preferable that a diffusion tank equips the inner wall with a light reflection member.

  And it is preferable that the spreading | diffusion tank is comprised so that attachment or detachment is possible.

  And it is preferable that a light irradiation part is provided with the several light guide part which branches the light arranged at a fixed space | interval. Or it is preferable that a light irradiation part is provided with the combination of the some light guide part which branches light, and a some circular lens. Or it is preferable that a light irradiation part is provided with the combination of the some light guide part and square lens which branch the light arranged at a fixed space | interval.

Furthermore, the photoacoustic inspection apparatus according to the present invention is:
A light source that generates light to irradiate the subject, a light irradiation unit that irradiates the subject with light, and a photoacoustic wave that detects photoacoustic waves generated in the subject by irradiating the subject with light. In a photoacoustic inspection apparatus including an electroacoustic conversion unit that converts an electrical signal into an electrical signal and an image generation unit that generates a photoacoustic image based on the electrical signal.
An acoustic matching function that matches the acoustic impedance of the subject and the acoustic impedance of the electroacoustic transducer, and a diffusion function that diffuses light so that the subject is irradiated with light having a substantially uniform intensity distribution on the subject With a light diffusing liquid part,
The light diffusing liquid part comprises an acoustic matching liquid responsible for the acoustic matching function, and diffusing particles responsible for the diffusion function dispersed in the acoustic matching liquid,
The electroacoustic transducer is provided so that at least a part of the electroacoustic transducer is in contact with the acoustic matching liquid.

In the photoacoustic inspection apparatus according to the present invention, the acoustic impedance of the diffusing particles is preferably 1.2 to 1.9 × 10 ⁶ kg / m ² / s, and in particular, the diffusing particles are lipid particles. preferable.

The light diffusing liquid part includes a diffusion tank for holding the acoustic matching liquid,
It is preferable that the diffusion tank has an acoustic transmission film in a portion in contact with the subject.

  According to the photoacoustic test probe and the photoacoustic test apparatus according to the present invention, in the photoacoustic test using the photoacoustic effect, the light irradiation unit that irradiates the subject with light, and the photoacoustic wave as an electrical signal. The electroacoustic transducer to be converted, the acoustic matching function for matching the acoustic impedance of the subject and the acoustic impedance of the electroacoustic transducer, and the subject is irradiated with light having a substantially uniform intensity distribution A light diffusing liquid part having a diffusing function for diffusing light, and the light diffusing liquid part includes an acoustic matching liquid having an acoustic matching function and diffusing particles having a diffusing function dispersed in the acoustic matching liquid. The electroacoustic transducer is provided so that at least a part of the electroacoustic transducer is in contact with the acoustic matching liquid. Therefore, in order to separate the acoustic matching function and the diffusion function, a trade-off between these functions is required. Off The engagement of can be low threat. This is because the diffusion particles are dispersed in a liquid in which ultrasonic attenuation hardly occurs, so that the distance for light diffusion can be increased, and there is little difference in density with water and there is little scattering of ultrasonic waves. This is because diffusing particles of such a material are used. Therefore, it is possible to irradiate light so as to make the light intensity distribution uniform by dispersing the diffusing particles without impairing the acoustic matching function. As a result, a photoacoustic wave having a higher S / N can be detected in the photoacoustic inspection using the photoacoustic effect.

It is the schematic which shows the structure of one Embodiment of the photoacoustic imaging device of this invention. It is the schematic which shows the structure of the image generation part in FIG. In embodiment, it is the schematic which shows the example of the light irradiation part comprised so that it could irradiate from the upper direction of an electroacoustic conversion part.

  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.

  An embodiment of a photoacoustic inspection apparatus 10 including a photoacoustic inspection probe according to the present invention will be described. FIG. 1 is a schematic diagram showing a configuration of the entire photoacoustic inspection apparatus 10 in the present embodiment. FIG. 2 is a block diagram illustrating a configuration of the image generation unit 2 of FIG.

  The photoacoustic inspection apparatus 10 according to the present embodiment generates a light L including a specific wavelength component and irradiates the subject 7 with the light L, and the subject 7 is irradiated with the light L. An image generation unit 2 that detects photoacoustic waves U generated in the specimen and generates photoacoustic image data of an arbitrary cross section, an electroacoustic conversion unit 3 that converts an acoustic signal and an electrical signal, an object 7 and an electrical A light diffusing liquid portion 8 for interposing between the acoustic conversion portions 3 to achieve acoustic matching between them and diffusing the light L irradiated to the subject 7, and a display portion for displaying this photoacoustic image data 6, an operation unit 5 for an operator to input patient information and imaging conditions of the apparatus, and a system control unit 4 for comprehensively controlling these units.

  The optical transmission unit 1 includes a light source unit 11 including a plurality of light sources having different wavelengths, an optical multiplexing unit 12 that synthesizes light of a plurality of wavelengths on the same optical axis, and a multipath that guides the light to the body surface of the subject 7. A waveguide unit 14 of a channel, an optical scanning unit 13 that performs scanning by switching channels used in the waveguide unit 14, a light irradiation unit 15 that emits light supplied by the waveguide unit 14, and a light diffusion liquid A cylindrical lens 16 and a mirror 17 which are optical systems for guiding the light L emitted from the light irradiation unit 15 through the unit 8 to the subject 7 are provided.

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

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

  The optical multiplexing unit 12 is for superimposing light having different wavelengths generated from the light source unit 11 on the same optical axis. Each light is first converted into parallel rays by a collimating lens, and then optical axes are aligned by a right-angle prism or a dichroic prism. With such a configuration, a relatively small multiplexing optical system can be obtained, but a multiple wavelength multiplexer / demultiplexer developed for optical communication may be used. Further, when a light source such as an OPO laser whose wavelength can be continuously changed is used for the light source unit 11, the optical multiplexing unit 12 is not necessarily required.

  The waveguide unit 14 is for guiding the light output from the optical multiplexing unit 12 to the light irradiation unit 15. An optical fiber or a thin film optical waveguide is used for efficient light propagation, but direct light propagation is also possible. Here, the waveguide unit 14 includes a plurality of optical fibers 71. A predetermined optical fiber 71 is selected from the plurality of optical fibers 71, and the subject 7 is irradiated with light by the selected optical fiber 71. In addition, although not shown clearly in FIG. 1, it can also be used in combination with an optical system such as an optical filter or a lens.

  The optical scanning unit 13 scans the subject 7 with light by supplying light while sequentially selecting a plurality of optical fibers 71 arranged in the waveguide unit 14.

  In the present embodiment, the light irradiation unit 15 includes a plurality of emission end portions of the plurality of optical fibers 71. And the light irradiation part 15 comprises the ultrasonic probe 70 which is the probe for photoacoustic inspections of this invention with the electroacoustic conversion part 3. FIG. A plurality of emission end portions of the plurality of optical fibers 71 constituting the light irradiation unit 15 are arranged along the periphery of the electroacoustic conversion unit 3. Moreover, when the some conversion element 54 which comprises the electroacoustic conversion part 3 is a transparent material, you may arrange | position the light irradiation part 15 so that the whole conversion element can be irradiated from the upper direction of the conversion element 54. FIG. The plurality of light emitting ends of the plurality of optical fibers 71 form a plane, a convex surface or a concave surface together with the plurality of conversion elements 54 constituting the electroacoustic conversion unit 3. Here, it is a plane. Moreover, in FIG. 1, although the light irradiation part 15 is arrange | positioned so that the acoustic matching liquid 83 may be contacted, an arrangement place is not limited to such a position.

  The cylindrical lens 16 and the mirror 17 function as an optical system that guides the light L emitted from the light irradiation unit 15 to the subject 7. The light L reflected by the mirror 17 passes through an acoustic transmission film 82 described later and is irradiated on the subject 7. In addition, such an optical system is not limited to said two, You may use the optical system which combined the other collimating lens etc. In FIG. 1, these optical systems are arranged in the acoustic matching liquid 83, but the arrangement location is not limited to such a position.

  The electroacoustic conversion unit 3 includes a plurality of minute conversion elements 54 arranged in a one-dimensional or two-dimensional manner, for example. The conversion element 54 is a piezoelectric element made of a polymer film such as piezoelectric ceramics or polyvinylidene fluoride (PVDF). The surface of the piezoelectric element is covered with a layer of epoxy resin and silicone rubber for acoustic matching with the piezoelectric element and the acoustic matching liquid 83. In the present invention, the electroacoustic conversion unit 3 is disposed so that at least a part of the electroacoustic conversion unit 3 is in contact with an acoustic matching liquid 83 described later. The electroacoustic conversion unit 3 receives the photoacoustic wave U generated in the subject by the light irradiation from the light irradiation unit 15 via the acoustic matching liquid 83. The conversion element 54 has a function of converting the photoacoustic wave U into an electric signal at the time of reception. The electroacoustic conversion unit 3 is configured to be small and light, and is connected to a receiving unit 22 described later by a multi-channel cable. The electroacoustic conversion unit 3 is selected according to the diagnostic region from among sector scanning, linear scanning, convex scanning, and the like. The electroacoustic conversion unit 3 may include an acoustic matching layer in order to efficiently transmit the photoacoustic wave U. This acoustic matching layer is separate from the light diffusion liquid portion 8 described later. When such an acoustic matching layer is provided, the acoustic matching layer functions to achieve acoustic matching between the electroacoustic conversion unit 3 and an acoustic matching liquid 83 described later.

  The light diffusion liquid part 8 includes a diffusion tank 81, an acoustic matching liquid 83 accommodated in the diffusion tank 81, and diffusion particles 84 dispersed in the acoustic matching liquid 83. In the present invention, the light diffusing liquid unit 8 is configured to match the acoustic impedance of the subject 7 and the acoustic impedance of the electroacoustic conversion unit 3 and the light L having a substantially uniform intensity distribution on the subject 7. It has a diffusion function of diffusing the light L so as to irradiate the subject 7. The acoustic matching function is a function for achieving acoustic matching between the subject 7 and the electroacoustic transducer 3. Thereby, a photoacoustic wave can be detected efficiently. In general, the acoustic impedance of the piezoelectric element material and the living body are greatly different. Therefore, when the piezoelectric element material and the living body are in direct contact with each other, reflection at the interface becomes large and the photoacoustic wave cannot be efficiently transmitted. For this reason, the photoacoustic wave U can be efficiently transmitted by arrange | positioning the acoustic matching liquid 83 comprised with the liquid substance which has an intermediate acoustic impedance between piezoelectric element material and a biological body. The diffusion function is a function for diffusing the light L propagating through the acoustic matching liquid 83 and making the intensity distribution of the light L on the subject 7 substantially uniform. This avoids a situation where the intensity of the light L is less than the MPE in one region but exceeds the MPE in another region, and generates a photoacoustic wave U having a strong intensity from a wide region. be able to.

  The diffusion tank 81 holds the acoustic matching liquid 83. As a material of the diffusion tank 81, for example, ABS resin can be used. In the present embodiment, the bottom of the diffusion tank 81 is in direct contact with the subject 7. The portion of the diffusion tank 81 that contacts the subject 7 preferably includes an acoustic transmission film 82 having a photoacoustic wave transmittance of 70% or more so that the photoacoustic wave can be efficiently transmitted. When the transmittance of the photoacoustic wave is less than 70%, the absolute amount of the photoacoustic wave U reaching the electroacoustic conversion unit 3 is excessively decreased, and it becomes difficult to obtain a photoacoustic wave U having sufficient intensity. As a material of the sound transmission film 82, for example, low density polyethylene can be used. Moreover, it is preferable that the diffusion tank 81 is provided with a light reflecting member on its inner wall. Thereby, the loss of the light energy by absorption or permeation | transmission of the light L by the diffusion tank 81 can be reduced.

  As the light reflecting member, for example, a metal plate or a metal film can be used. In order to maintain the positional relationship between the tissue in the subject 7 where the photoacoustic wave U is generated and the electroacoustic transducer 3, the diffusion tank 81 is fixed to the ultrasonic probe 70 at the time of examination, for example. Is preferred. On the other hand, it is preferable that the diffusion tank 81 can be replaced for each examination, for each subject, or for each examination site. Therefore, the diffusion tank 81 is preferably configured to be detachable from the photoacoustic inspection apparatus 10.

  The acoustic matching liquid 83 is a part responsible for the acoustic matching function of the light diffusion liquid part 8. An example of the material of the acoustic matching liquid 83 is water. The photoacoustic wave U generated in the subject 7 is detected by the electroacoustic conversion unit 3 through the acoustic matching liquid 83.

  The diffusing particle 84 is a part that bears the diffusing function of the light diffusing liquid part 8. Such diffusing particles 84 are preferably lipid particles. This is because lipid particles are softer than particles of inorganic materials such as metal particles, and even if dispersed in the acoustic matching liquid 83, the influence on the acoustic matching function is small. In the present invention, the diffusing particles are not limited to lipid particles as long as they are particles made of a material such as lipid. More specifically, in the present invention, the diffusing particles may be a liquid phase or droplet having a hydrophobic part covered with a hydrophilic film. Thereby, the diffusion particles are stabilized in the acoustic matching liquid 83. The hydrophobic portion may have a spherical structure (that is, a structure in which an organic solvent is surrounded by an amphiphilic molecule) or a spherical shell structure (that is, a vesicle structure in which the amphiphilic molecule has a double membrane structure). Examples of the spherical structure include, for example, a structure in which a phospholipid as an emulsifier is regularly arranged on the surface layer of a neutral fat (for example, triacylglycerol) with a hydrophilic group on the outside and a hydrophobic group on the inside. . Moreover, as an example of a spherical shell structure, the liposome by a phospholipid bilayer membrane etc. are mentioned, for example.

The diffusion particle 84 has a predetermined light transmittance, which is a ratio of the amount of light L that has passed through the acoustic matching liquid 83 and the diffusion tank 81 (acoustic transmission film 82) to the amount of light L emitted from the light irradiation unit 15. It is dispersed in the acoustic matching liquid 83 so as to be in a range. By diffusing such diffusing particles 84 in the acoustic matching liquid 83, a diffusing function can be imparted without harming the acoustic matching function. The range of the light transmittance is preferably 10 to 90%. If the light transmittance is less than 10%, the absolute amount of the light L reaching the subject 7 is excessively reduced, and it becomes difficult to obtain a photoacoustic wave U having sufficient intensity. On the other hand, if the light transmittance exceeds 90%, it is difficult to make the intensity distribution of the light L uniform on the subject 7. From the viewpoint of realizing the light transmittance, the refractive index of the material constituting the diffusing particles is preferably 1.40 to 1.60. Moreover, it is preferable that the particle size of a diffusion particle is 0.1-5.0 micrometers, and the density | concentration of the diffusion particle in the acoustic matching liquid 83 is 0.01-0.30 wt%. In addition, since the influence of the light absorption by a diffusion particle can be disregarded because the density | concentration of a diffusion particle is set low as mentioned above, the light absorption coefficient of the material which comprises a diffusion particle is not specifically limited. On the other hand, from the viewpoint of realizing the above-described transmittance of the photoacoustic wave, the acoustic impedance of the material constituting the diffusing particles is preferably close to the acoustic impedance of the acoustic matching liquid 83 (particularly water), and the value is 1.2. It is preferable that it is -1.9 * 10 < ⁶ > kg / m < ² > / s. Alternatively, the density of the diffusing particles is preferably 0.90 to 1.10 g / cc, and the sound velocity in the material constituting the diffusing particles is preferably 1300 to 1700 m / s. In addition, since the influence of absorption of the photoacoustic wave by a diffusion particle is negligible because the density | concentration of a diffusion particle is set low as mentioned above, the viscosity of the material which comprises a diffusion particle is not specifically limited.

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

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

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

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

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

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

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

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

  The image data memory 62 is a storage circuit that stores the photoacoustic image data generated as described above. Under the control of the system control unit 4, cross-sectional data is read from the image data memory 62, and photoacoustic image data of the cross-section is generated by spatially interpolating at the time of reading.

  The display unit 6 includes a display image memory 63, a photoacoustic image data converter 64, and a CRT monitor 65. The display image memory 63 is a buffer memory that temporarily stores photoacoustic image data to be displayed on the CRT monitor 65, and one line of photoacoustic image data from the image data memory 62 is stored in the display image memory 63. Are combined into one frame. The photoacoustic image data converter 64 performs D / A conversion and television format conversion on the composite image data read from the display image memory 63, and the output is displayed on the CRT monitor 65.

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

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

  Next, an ultrasonic probe 70 in which the light irradiation unit 15 and the electroacoustic conversion unit 3 are integrated will be described.

  The ultrasonic probe 70 has a plurality of conversion elements 54. The conversion elements 54 are arranged one-dimensionally along a predetermined direction, for example. The optical fiber 71 guides the light from the light source unit 11 to the light irradiation unit 15 provided in the ultrasonic probe 70. As shown in FIG. 1, the light irradiation part 15 is arrange | positioned along the circumference | surroundings of the conversion element 54 arranged in one dimension, for example. In FIG. 1, the light irradiation unit 15 is disposed only on one of the conversion elements 54 (electroacoustic conversion unit 3) arranged one-dimensionally, but the light irradiation unit 15 may be disposed on both. .

  For example, the ultrasonic probe 70 has the conversion elements 54 for 192 channels. The width corresponding to the conversion element 54 is divided into, for example, three partial areas (areas A to C) in relation to the photoacoustic image generation, and the width of each partial area is a width corresponding to the conversion element 54 for 64 channels. Suppose that In such a case, if the width of the living tissue corresponding to the 192ch conversion element 54 is 57.6 mm, the width of each partial region is 19.2 mm. That is, when generating the photoacoustic image, the photoacoustic inspection apparatus 10 repeatedly performs light irradiation and data collection on, for example, a partial region having a width of 19.2 mm, and acquires data for all 192 channels.

  Further, the present invention is not limited to the electroacoustic conversion unit 3 in which the conversion elements 54 are arranged one-dimensionally. That is, the present invention can also be applied to the electroacoustic conversion unit 3 in which the conversion elements 54 are two-dimensionally arranged.

  In the case where the light irradiation unit 15 is configured so that the entire transducer can be irradiated from above the transducer 54 in the ultrasonic probe 70, for example, as shown in FIG. 3 from the viewpoint of obtaining a uniform light intensity distribution. Such a configuration is preferable.

  Here, FIG. 3A shows an optical transmission unit 1 including a combination of a plurality of optical fibers 73 for branching light from an optical fiber 71 as a waveguide unit 14 via an optical fiber coupler 72 and a plurality of circular lenses 74. It is the schematic which shows the structure. In this configuration, a plurality of circular lenses 74 are arranged in an array along the length direction of the electroacoustic transducer 3. An irradiation range including the corresponding region of the electroacoustic conversion unit 3 is realized by the entire light L emitted from each circular lens 74. In FIG. 3 a, a plurality of circular lenses 74 serve as the light irradiation unit 15.

  FIG. 3 b shows the configuration of the optical transmission unit 1 including a combination of a plurality of optical fibers 73 that branch light from an optical fiber 71 serving as a waveguide unit 14 via an optical fiber coupler 72 and one rectangular lens 75. FIG. In this configuration, the rectangular lenses 75 having a length equal to or longer than the length of the electroacoustic transducer 3 are arranged along the length direction of the electroacoustic transducer 3. An irradiation range including the corresponding region of the electroacoustic transducer 3 is realized by the light L emitted from the square lens 75. An example of the square lens is a cylindrical lens. In FIG. 3 b, the square lens 75 becomes the light irradiation unit 15.

  As described above, according to the photoacoustic inspection probe and the photoacoustic inspection apparatus according to the present invention, in the photoacoustic inspection using the photoacoustic effect, the light irradiation unit that irradiates the subject with light, and the photoacoustic An electroacoustic transducer that converts a wave into an electrical signal, an acoustic matching function that matches the acoustic impedance of the subject and the acoustic impedance of the electroacoustic transducer, and light having a substantially uniform intensity distribution on the subject A light diffusing liquid part having a diffusing function for diffusing light so as to irradiate the light, and the light diffusing liquid part is responsible for the acoustic matching liquid responsible for the acoustic matching function and the diffusion function dispersed in the acoustic matching liquid. Since the electroacoustic transducer is provided so that at least a part of the electroacoustic transducer is in contact with the acoustic matching liquid, in order to achieve functional separation of the acoustic matching function and the diffusion function, Of these features The relationship of trade-off can be a low threat. This is because the diffusion particles are dispersed in a liquid in which ultrasonic attenuation hardly occurs, so that the distance for light diffusion can be increased, and there is little difference in density with water and there is little scattering of ultrasonic waves. This is because diffusing particles of such a material are used. Therefore, it is possible to irradiate light so as to make the light intensity distribution uniform by dispersing the diffusing particles without impairing the acoustic matching function. As a result, a photoacoustic wave having a higher S / N can be detected in the photoacoustic inspection using the photoacoustic effect.

DESCRIPTION OF SYMBOLS 1 Light transmission part 2 Image generation part 3 Electroacoustic conversion part 4 System control part 5 Operation part 6 Display part 7 Subject 8 Light diffusion liquid part 10 Photoacoustic inspection apparatus 11 Light source part 12 Optical multiplexing part 13 Optical scanning part 14 Waveguide Unit 15 Light irradiation unit 16 Cylindrical lens 17 Mirror 22 Reception unit 24 Scan control unit 25 Signal processing unit 70 Ultrasonic probe 71 Optical fiber 74 Circular lens 75 Square lens 81 Diffusion tank 82 Acoustic transmission film 83 Acoustic matching liquid 84 Diffusion particle L light U photoacoustic wave

Claims (13)

Irradiating the subject with light, guiding the light to the subject, detecting the photoacoustic wave generated in the subject by irradiating the subject with the light and detecting the photoacoustic wave In a probe used for photoacoustic inspection, which is converted into an electrical signal and inspected based on the electrical signal,
A light irradiation unit for irradiating the subject with the light;
An electroacoustic transducer that converts the photoacoustic wave into an electrical signal;
An acoustic matching function for matching the acoustic impedance of the subject and the acoustic impedance of the electroacoustic transducer, and the light to irradiate the subject with the light having a substantially uniform intensity distribution on the subject. A light diffusion liquid part having a diffusion function to diffuse,
The light diffusing liquid part includes an acoustic matching liquid responsible for the acoustic matching function, and diffusing particles responsible for the diffusing function dispersed in the acoustic matching liquid,
A probe for photoacoustic inspection, wherein the electroacoustic transducer is provided so that at least a part of the electroacoustic transducer is in contact with the acoustic matching liquid. ^{2. The} probe for photoacoustic inspection according to claim 1, wherein an acoustic impedance of the diffusing particles is 1.2 to 1.9 × 10 ⁶ kg / m ² / s.   The probe for photoacoustic inspection according to claim 1 or 2, wherein the diffusion particles are lipid particles. The light diffusing liquid part includes a diffusion tank that holds the acoustic matching liquid,
The probe for photoacoustic inspection according to any one of claims 1 to 3, wherein the diffusion tank has an acoustic transmission film in a portion in contact with the subject.   The probe for photoacoustic inspection according to claim 4, wherein the diffusion tank includes a light reflecting member on an inner wall of the diffusion tank.   The probe for photoacoustic inspection according to claim 4 or 5, wherein the diffusion tank is configured to be detachable.   The probe for photoacoustic inspection according to any one of claims 1 to 6, wherein the light irradiating unit includes a plurality of light guiding units for branching the light arranged at regular intervals. Child.   7. The photoacoustic inspection probe according to claim 1, wherein the light irradiation unit includes a combination of a plurality of light guide units for branching the light and a plurality of circular lenses. Tentacles.   The said light irradiation part is provided with the combination of the some light guide part and the square lens which branch the said light arranged at a fixed space | interval, The one in any one of Claim 1 to 6 characterized by the above-mentioned. Probe for photoacoustic inspection. A light source that generates light to irradiate the subject, a light irradiation unit that irradiates the subject with the light, and a photoacoustic wave generated in the subject by irradiating the subject with the light Then, in a photoacoustic inspection apparatus including an electroacoustic conversion unit that converts the photoacoustic wave into an electric signal, and an image generation unit that generates a photoacoustic image based on the electric signal.
An acoustic matching function for matching the acoustic impedance of the subject and the acoustic impedance of the electroacoustic transducer, and the light to irradiate the subject with the light having a substantially uniform intensity distribution on the subject. A light diffusing liquid part having a diffusing function to diffuse,
The light diffusing liquid part includes an acoustic matching liquid responsible for the acoustic matching function, and diffusing particles responsible for the diffusing function dispersed in the acoustic matching liquid,
The photoacoustic inspection apparatus, wherein the electroacoustic transducer is provided so that at least a part of the electroacoustic transducer is in contact with the acoustic matching liquid. The probe for photoacoustic inspection according to claim 10, wherein an acoustic impedance of the diffusion particles is 1.2 to 1.9 × 10 ⁶ kg / m ² / s.   The photoacoustic inspection apparatus according to claim 10 or 11, wherein the diffusion particles are lipid particles. The light diffusing liquid part includes a diffusion tank that holds the acoustic matching liquid,
The photoacoustic inspection apparatus according to claim 10, wherein the diffusion tank has an acoustic transmission film in a portion in contact with the subject.

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