JP2017202313A - Acoustic wave reception device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for performing excellent imaging in an acoustic wave reception device which performs photoacoustic imaging and ultrasonic echo imaging.SOLUTION: An acoustic wave reception device comprises: a light irradiation unit which irradiates a target region with light; a reception array made by arranging a plurality of reception elements which receive a photoacoustic wave caused by the light irradiation to output a photoacoustic signal; a transmission/reception array including a plurality of transceiver elements which transmit a supersonic wave to the target region and receive an echo wave of the supersonic wave reflected by the target region to output an ultrasonic signal; an array support part including a first part which supports the reception array to form an effective reception area where oriented axes of the reception array are gathered and a second part which supports the transmission/reception array; and a scan unit which integrally scans the reception array and the transmission/reception array with respect to the target area by moving the array support part. The array support part is constituted so that the effective reception area formed by the reception array is not overlapped with a convergence area of the transmission/reception array.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an acoustic wave receiving apparatus.

  Research on optical imaging devices that irradiate a subject such as a living body with light from a light source such as a laser and image information in the subject obtained based on incident light is being actively promoted in the medical field. . As one of the optical imaging techniques, there is Photoacoustic Imaging (PAI: photoacoustic imaging). In photoacoustic imaging, an acoustic wave (typically an ultrasonic wave) generated from a tissue of a subject that irradiates the subject with pulsed light generated from a light source and absorbs the energy of the pulsed light that has propagated and diffused within the subject. ) And image information on the portion to be examined based on the received signal.

  When the test part is irradiated with light, due to the difference in the absorption rate of the light energy between the target site such as a tumor and other tissues, the test site that absorbed the light energy instantaneously expands, An acoustic wave (called a photoacoustic wave) is generated. In photoacoustic imaging, a photoacoustic wave generated by this photoacoustic effect is received using a probe (receiving element).

  By mathematically analyzing the received signal, information in the test portion, particularly, an initial sound pressure distribution, a light energy absorption density distribution, an absorption coefficient distribution, or the like can be acquired. Such information can also be used for quantitative measurement of a specific substance in the test portion, for example, oxygen saturation in blood. In recent years, preclinical research for imaging blood vessels of small animals using this photoacoustic imaging and clinical research for applying this principle to diagnosis of breast cancer and the like have been actively promoted.

  Non-Patent Document 1 describes an acoustic wave receiving apparatus that acquires information on a test portion using a sensor in which receiving surfaces of a plurality of receiving elements are arranged on the inner surface of a hemispherical shell-shaped array support portion. According to this sensor, photoacoustic waves generated in a specific area can be received with high sensitivity, so that the resolution of the test part information in the specific area is increased.

  Further, in the acoustic wave receiving device of Non-Patent Document 1, an acoustic matching fluid made of a liquid or gel is filled inside the hemispherical array support portion to propagate the acoustic wave to the ultrasonic probe. And it is described that the information of the test part having high resolution in a wide range is acquired by moving the position of the sensor in the horizontal direction with respect to the test part immersed in the acoustic matching fluid.

  A container-like sensor in which a liquid acoustic matching fluid is held can be used not only for photoacoustic imaging but also for ultrasonic echo diagnosis. When using such a sensor, it is preferable that an acoustic matching fluid is filled between the test part and the sensor, and the sensor and the test part are acoustically coupled.

  Further, Patent Document 1 discloses an apparatus that captures both a photoacoustic image and an ultrasonic echo image.

JP 2005-021380 A

“Dedicated 3D Photoacoustic Breast Imaging”, Robert, Cherie M. Kuzmiak, Richard B. Lam, Daniel R. Reinecke, Stephen P. Del Te, Del Te, Del Te and Del P

  Patent Document 1 can perform both photoacoustic imaging and ultrasonic echo imaging, but has a problem in that the image quality is not good because the field of view in photoacoustic imaging cannot be sufficiently expanded. In order to improve the image quality of both photoacoustic imaging and ultrasonic echo imaging, a sensor array in which a plurality of receiving elements for photoacoustic imaging are arranged on the inner surface of a hemispherical array support, and an ultrasonic echo imaging sensor It is preferable to provide each array independently. However, sufficient studies have not been made so far regarding the arrangement method of these two types of sensor arrays. Further, when two types of sensor arrays are used in combination, the array support section that supports these sensor arrays is likely to be larger than when only a photoacoustic imaging receiving element array is used. And like the apparatus described in the nonpatent literature 1, when an array support part is accommodated in the bed where a subject lies, the whole apparatus containing a bed will enlarge. In this case, the posture of the subject under examination may be limited by the shape and size of the apparatus, which may impair the comfort of the subject. In addition, since an unnecessarily large distance is generated between the assistant and the subject, the workability of the assistant's assistance work may be impaired.

  The present invention has been made in view of the above problems. An object of the present invention is to provide a technique for performing good imaging in an acoustic wave receiving apparatus that performs photoacoustic imaging and ultrasonic echo imaging.

The present invention employs the following configuration. That is,
A light irradiator optically connected to the light source and irradiating the subject's subject with light; and
A receiving array comprising a plurality of receiving elements for receiving a photoacoustic wave generated by irradiating the test portion with light irradiated from the light irradiation unit and outputting a photoacoustic signal;
A transmission / reception array including a plurality of transmission / reception elements that transmit ultrasonic waves to the test part, receive ultrasonic waves reflected by the test part and output ultrasonic signals;
An array support unit comprising: a first part that supports the reception array so that an effective reception area where at least a part of the directivity axes of the reception array gathers is formed; and a second part that supports the transmission / reception array When,
A scanning unit that integrally scans the reception array and the transmission / reception array with respect to the test unit by moving the array support unit;
Have
The array support unit is an acoustic wave receiving device configured so that an effective reception area formed by the reception array and a focusing area of the transmission / reception array do not overlap.

  ADVANTAGE OF THE INVENTION According to this invention, in the acoustic wave receiver which performs photoacoustic imaging and ultrasonic echo imaging, the technique for performing favorable imaging can be provided.

The figure showing the 1st acoustic wave receiver The figure showing the 2nd acoustic wave receiver The figure showing a 3rd acoustic wave receiver Diagram showing sensitivity characteristics of photoacoustic element Diagram showing the structure of an ultrasonic echo linear array Diagram explaining electronic focus Diagram showing connection between computer and peripheral devices

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions. Therefore, the scope of the present invention is not intended to be limited to the following description.

  The present invention relates to a technique for detecting an acoustic wave propagating from a test part, and generating and acquiring characteristic information inside the test part. Therefore, the present invention can be understood as a test part information acquisition apparatus or a control method thereof, or a test part information acquisition method or a signal processing method. The present invention can also be understood as a program that causes an information processing apparatus including hardware resources such as a CPU to execute these methods, and a storage medium that stores the program. The present invention can also be understood as an acoustic wave measuring device and a control method thereof.

  The present invention is a photoacoustic tomography technique for irradiating a test part with light (electromagnetic waves) and receiving (detecting) an acoustic wave generated and propagated at a specific position in the test part or the surface of the test part according to a photoacoustic effect. It can be applied to a test part information acquisition apparatus using the above. Such an apparatus obtains characteristic information inside the test portion in the form of image data, characteristic distribution information, or the like based on photoacoustic measurement, so that it is a photoacoustic imaging apparatus, a photoacoustic image forming apparatus, or simply a photoacoustic apparatus. I can call you. Or since the apparatus of this invention test | inspects the to-be-tested part inside, you may call an acoustic wave receiver.

  Characteristic information in the photoacoustic device is composed of the source distribution of acoustic waves generated by light irradiation, the initial sound pressure distribution in the test area, or the optical energy absorption density distribution and absorption coefficient distribution derived from the initial sound pressure distribution. Such as the concentration distribution of substances to be treated. The substance concentration includes oxygen saturation, oxyhemoglobin concentration, deoxyhemoglobin concentration, total hemoglobin concentration, and the like. The total hemoglobin concentration is the sum of the oxyhemoglobin concentration and the deoxyhemoglobin concentration. In addition, fat, collagen, moisture distribution, and the like are also targeted. Further, the characteristic information may be obtained not as numerical data but as distribution information of each position in the test portion. That is, distribution information such as an absorption coefficient distribution and an oxygen saturation distribution may be used as test part information.

  The present invention is an apparatus using ultrasonic echo technology that transmits ultrasonic waves to a test part, receives reflected waves (echo waves) reflected inside the test part, and acquires test part information as image data It can also be applied to. In the case of an apparatus using the ultrasonic echo technique, the acquired test part information is information reflecting the difference in acoustic impedance of the tissue inside the test part.

  The acoustic wave referred to in the present invention is typically an ultrasonic wave and includes an elastic wave called a sound wave or an acoustic wave. An acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave, and the reflected wave (echo wave) in the ultrasonic echo technique described above is also included in the acoustic wave. An electrical signal converted from an acoustic wave by a probe is also called an acoustic signal, an acoustic signal derived from a photoacoustic wave is called a photoacoustic signal, and an acoustic signal that can be made into a reflected wave in ultrasonic echo technology is particularly ultrasonic. Called a signal. Note that the description of ultrasonic waves or acoustic waves in this specification is not intended to limit the wavelength of those elastic waves.

A living body breast can be assumed as the test part in the present invention. However, the test part is not limited to this, and other parts of the living body and non-biological materials can be inspected. Therefore, the present invention can also be understood as a test subject information acquisition device or a control method thereof, or an acoustic wave reception device or a control method thereof.

  In an acoustic wave receiving apparatus, a sensor array (receiving array) in which a plurality of receiving elements are arranged on the inner surface of a photospherical hemispherical array support, and a linear sensor array (transmitting / receiving array) used for ultrasonic echo diagnosis ) Can be used in both modalities. However, if both sensor arrays are arranged so that their receiving areas do not overlap, the members of the array support section become large. Further, when imaging a wide range, the relative positional relationship between the array support section on which the sensor array is mounted and the test section is changed using a scanning section. However, if both sensor arrays are arranged separately and scanning parts are provided on both of them, the members of the scanning part become large and the structure becomes complicated. Furthermore, the moving distance of the array support part increases. As a result, the cost increases and the imaging time becomes longer.

  Furthermore, a support member that supports the subject may be provided in the acoustic wave receiving apparatus. However, as the array support member becomes larger, the support member also becomes larger. As a result, the workability of the assistant who assists the subject is reduced. In addition, it becomes difficult for the subject to take a comfortable posture. Therefore, in an acoustic wave receiving apparatus including both a photoacoustic imaging sensor array and an ultrasonic echo imaging sensor array, it is necessary to suppress the member size and increase the workability of the assistant and the comfort of the subject. is there.

[Embodiment]
1, 2, and 3 are schematic diagrams illustrating the configuration and operation of the acoustic wave receiving apparatus according to the present embodiment. The acoustic wave receiving apparatus acquires the characteristic information of the test part E by the photoacoustic effect and the ultrasonic echo technique. 1A is a top view of the first acoustic wave receiving device, FIG. 1B is a side sectional view, and FIG. 1C is a detailed view of a portion surrounded by a broken line in FIG. 1B. . 2A is a top view of the second acoustic wave receiving apparatus, and FIG. 2B is a side sectional view. FIG. 3A is a top view of the third acoustic wave receiving device, and FIG. 3B is a side sectional view.

<Basic configuration>
With reference to FIG. 1C, the basic configuration of the test subject information acquisition apparatus that is the acoustic wave reception apparatus of the present embodiment will be described. The acoustic wave receiving apparatus includes a light source 100, an optical system 200, a receiving array 300 including a plurality of receiving elements 310, a transmitting / receiving array 1300 including a plurality of transmitting / receiving elements 1310, an array support unit 400, a scanner 500, and a subject appearance information acquisition unit. 600, a computer 700, a display 900, an input unit 1000, a shape holding unit 1100, and a support member 1200.

(Examination part)
The test part E is a measurement target. Specific examples include a living body such as a breast, and a phantom that simulates the acoustic and optical characteristics of a living body, which are used in the scene of device adjustment and calibration. The acoustic characteristics are specifically the propagation speed and attenuation rate of acoustic waves. Specifically, the optical characteristics are light absorption coefficient and scattering coefficient. A light absorber having a large light absorption coefficient exists inside and on the surface of the test portion. In the living body, hemoglobin, water, melanin, collagen, lipid, and the like are light absorbers. In the phantom, a substance simulating optical characteristics is enclosed inside as a light absorber. For convenience, the test portion E is indicated by a broken line in FIG.

(light source)
The light source 100 generates pulsed light. As a light source, a laser is desirable to obtain a large output, but a light emitting diode or the like may be used. In order to effectively generate the photoacoustic wave, it is necessary to irradiate light in a sufficiently short time according to the thermal characteristics of the test portion. When the test portion is a living body, the pulse width of the pulsed light generated from the light source 100 is preferably set to several tens of nanoseconds or less. The wavelength of the pulsed light is in the near infrared region called a biological window, and is preferably about 700 nm to 1200 nm. Since light in this region reaches a relatively deep part of the living body, information on the deep part can be acquired. If it is limited to the measurement of the surface of the living body, the visible light to near infrared region of about 500 to 700 nm may be used. Further, it is desirable that the wavelength of the pulsed light has a high absorption coefficient with respect to the observation target.

(Optical system)
The optical system 200 guides the pulsed light generated by the optically connected light source 100 to the test part E. Specifically, it is an optical device such as a lens, a mirror, a prism, an optical fiber, a diffusion plate, or a combination thereof. Moreover, when guiding light, it is also preferable to change the shape and density of light using these optical devices so that the irradiation light has a desired light distribution. In this embodiment, the optical system 200 is configured to illuminate a region of the center of curvature of the hemisphere. The optical system 200 corresponds to the light irradiation unit of the present invention.

  In addition, the maximum permissible exposure (MPE) is determined by safety standards for the intensity of light allowed to irradiate living tissue. As the safety standard, for example, there is “IEC 60825-1: Safety of laser products”. There are also safety standards such as “JIS C 6802: Laser Product Safety Standards”, “FDA: 21 CFR Part 1040.10”, “ANSI Z136.1: Laser Safety Standards”. The maximum allowable exposure defines the intensity of light that can be irradiated per unit area. Therefore, a large amount of light can be guided to the test portion E by irradiating the surface of the test portion E with a large area all together. As a result, photoacoustic waves can be received with a high SN ratio. For this reason, it is preferable to spread the light over a certain area as shown by a two-dot chain line in FIG.

(Receiving element)
The receiving element 310 is an element that receives a photoacoustic wave and converts it into an electrical signal. The receiving array 300 includes a plurality of receiving elements 310. It is desirable that the photoacoustic wave from the test part E has high reception sensitivity and a wide frequency band. The name “receiving element” does not limit the material of the element. As the receiving element 310, various elements generally used for receiving acoustic waves (ultrasound) can be used. The acoustic wave receiving apparatus includes a signal processing circuit that performs amplification processing and digital conversion processing on the electrical signal converted by the receiving element 310.

As a material of the receiving element 310, a piezoelectric ceramic material typified by PZT (lead zirconate titanate) or a polymer piezoelectric film material typified by PVDF (polyvinylidene fluoride) can be used. In addition, cMUT (Capacitive Micro-machined
A member other than the piezoelectric material, such as a capacitive element such as Ultrasonic Transducers) or a receiving element using a Fabry-Perot interferometer, may be used. In addition, the cMUT has a wider frequency band than a piezoelectric element whose frequency band is determined by the thickness of the piezoelectric material, and thus is suitable for receiving a photoacoustic wave whose frequency band generated from the test part is unknown.

  FIG. 4 shows an example of the reception sensitivity characteristic of the receiving element 310. The “angle” shown on the horizontal axis in FIG. 4 is an incident angle formed by the normal direction of the receiving surface of the receiving element 310 and the incident direction of the photoacoustic wave. The vertical axis represents the relative value of the reception sensitivity at each incident angle. In FIG. 4, the reception sensitivity is highest when the acoustic wave is incident from the normal direction of the reception surface. That is, when the incident angle = 0, sensitivity = S (maximum value). As the incident angle increases, the reception sensitivity decreases. It is assumed that the receiving element 310 according to the present embodiment has a circular planar receiving surface.

  Also, the incident angle when the reception sensitivity is 50% (S / 2) of the maximum value is α. In the present invention and the present specification, the area where the photoacoustic wave is incident on the receiving surface of the receiving element 310 at an incident angle α or less is defined as the receiving area of the element, and the absolute value of the angle formed with the normal direction of the receiving surface is A direction equal to or less than α (a direction in which the reception sensitivity is at least half of the maximum value) is referred to as a reception direction. However, the reception area is not limited to such a half-value width, and may be determined according to element characteristics, accuracy required for measurement, and the like. In FIG. 1C, the direction with the highest receiving sensitivity of the receiving element 310 is indicated by a one-dot chain line.

(Transceiver element)
The transmission / reception element 1310 is an element that transmits an ultrasonic wave and receives a reflected wave to convert it into an electric signal. The transmission / reception array 1300 includes a plurality of transmission / reception elements 1310. The name “transmission / reception element” is not intended to limit the wavelength of a transmission wave or an echo wave. FIG. 5 shows a structure of a linear sensor array as an example of a transmission / reception array including a plurality of transmission / reception elements constituting the acoustic wave receiving apparatus in the present embodiment. Reference numeral 1301 denotes a piezoelectric element array, reference numeral 1302 denotes an acoustic matching layer, reference numeral 1303 denotes an acoustic lens, reference numeral 1304 denotes a backing material, and reference numeral 1305 denotes a lead wire. The acoustic wave receiving apparatus includes a signal processing circuit that performs amplification processing and digital conversion processing on the electrical signal converted by the transmission / reception element 1310. These signal processing circuits may be shared with the receiving element 310. The configuration in which the receiving element group is arranged on the hemispherical array support unit and the transmitting / receiving element group is arranged in a linear array as in the present apparatus is an acoustic wave that uses ultrasonic echo imaging as an auxiliary purpose mainly for photoacoustic imaging, for example. Suitable for a receiving device.

  The piezoelectric element array 1301 is a linear array of a plurality of strip-shaped piezoelectric elements 1301a to 1301g. With this structure, the transmitting / receiving element 1310 of the present invention is configured in a linear array. Lead wires 1305a to 1305g are connected to each piezoelectric element. In addition, an acoustic matching layer 1302 is provided on the surface of the piezoelectric element array 1301 in the direction in which ultrasonic waves are transmitted. On the other hand, a backing material 1304 is provided on the opposite side in the direction in which ultrasonic waves are transmitted. Further, an acoustic lens 1303 (acoustic wave focusing means) is provided on the surface of the acoustic matching layer 1302 facing the piezoelectric element array 1301.

  As the piezoelectric elements 1301a to 1301g constituting the piezoelectric element array 1301, the same type of piezoelectric elements as the receiving element 310 described above can be used. Note that a piezoelectric element made of a piezoelectric ceramic material or a polymer piezoelectric film material is particularly preferable for the transmission / reception element 1310 because it is suitable for transmitting ultrasonic waves.

  As the acoustic lens 1303, a cylindrical lens that focuses ultrasonic waves in a direction perpendicular to the arrangement direction of the piezoelectric element array 1301 is used. By setting the region where the cylindrical lens focuses the ultrasonic wave as the region of interest of the test part, the ultrasonic wave is selectively transmitted to the region of interest of the test part and generated from the region of interest of the test part E. The reflected wave can be selectively received. The material constituting the acoustic lens is preferably a material having acoustic characteristics similar to that of a living tissue, and examples thereof include silicone rubber. If it is made of a material having a sound velocity slower than the sound velocity inside the living tissue, the shape becomes a convex lens, the focal position is determined by the curvature of the convex surface, and the focal size is determined by the focal length and the width of the cylindrical lens. On the other hand, as a method of focusing in the arrangement direction of the piezoelectric elements 1301, electronic focusing is used. The electronic focus (acoustic wave focusing means) will be described later.

The acoustic matching layer 1302 is provided to efficiently transmit an acoustic signal. In general, the acoustic impedance differs greatly between a piezoelectric element material and a living body or an acoustic matching fluid. Therefore, when the piezoelectric element material and the acoustic matching fluid are in direct contact with each other, reflection at the interface becomes large and an acoustic signal cannot be efficiently transmitted. Therefore, an acoustic signal is efficiently transmitted by inserting an acoustic matching layer 1302 composed of a substance having an intermediate acoustic impedance between the piezoelectric element material and the living body or acoustic matching fluid. Examples of the material constituting the acoustic matching layer 1302 include epoxy resin and quartz glass.

  Next, electronic focusing using a linear array probe will be described with reference to FIG. Reference numeral 1306 denotes a variable delay element, and reference numeral 1307 denotes a pulsar receiver. Variable delay elements 1306a to 1306g are connected to the plurality of arranged piezoelectric elements 1301a to 1301g via lead wires 1305, respectively. Each of the variable delay elements 1306a to 1306g is connected to a pulsar receiver 1307.

  The variable delay element 1306 is composed of a long and thin electric wire wound in a coil shape, etc., and delays conduction of an electric signal transmitted through the electric wire. Moreover, the delay time of an electric signal can be adjusted by switching a plurality of taps provided in the middle of the coil. The pulsar receiver 1307 is a device that receives an acoustic signal converted into a voltage by the piezoelectric element array 1301. The acoustic waves generated from the position X of the acoustic wave generation source reach the piezoelectric element array 1301 with time differences τa, τb, τc, τd, τe, τf, and τg, respectively. The time difference may be a time difference from the moment when the acoustic wave is generated or may be a time difference from the moment when the acoustic wave is generated in any one of the piezoelectric elements included in the piezoelectric element array 1301 or may be set separately. It may be a time difference from the reference timing.

  The acoustic wave that has reached the piezoelectric element array 1301 is converted into a voltage (electric signal). The electrical signal is received by the pulsar receiver 1307 through the variable delay element 1306. At this time, the variable delay element 1306 corrects the difference in distance between the position X of the acoustic wave generation source and each piezoelectric element 1301, thereby aligning the phases of the electrical signals. In the illustrated example, the delay time provided by the variable delay element 1306 is increased as the piezoelectric element has a shorter distance from the position X. In addition, when the piezoelectric elements that are equidistant from the position X have the same delay time given by the variable delay element 1306 (τa = τg <τb = τf <τc = τe <τd), the phase when the pulsar receiver 1307 receives the signal. Match. In this way, by controlling the delay time provided by the variable delay element 1306, electronic focusing of the linear array probe is performed. As a result, the focal length and the focal position in the arrangement direction of the piezoelectric elements 1301 can be controlled.

  When a command pulse for transmitting an ultrasonic wave to the region of interest of the test part E is transmitted from the pulsar receiver 1307, the pulse reaches the piezoelectric elements 1301a to 1301g. At that time, the arrival time to each element is delayed by the variable delay elements 1306a to 1306g. Specifically, the piezoelectric elements 1301a to 1301g are reached with time differences τPa, τPb, τPc, τPd, τPe, τPf, and τPg, respectively. In this way, by adjusting the generation timing of the ultrasonic wave by each element according to the distance between the region of interest of the test part E and each of the piezoelectric elements 1301a to 1301g, the transmitted ultrasonic wave is the region of interest of the test part E. Focus on.

  Similarly, when receiving the reflected wave generated from the region of interest of the part E to be examined, signal delay processing corresponding to the distance between the region of interest and each element is performed. The reflected waves generated from the region of interest of the test part E reach the piezoelectric elements 1301a to 1301g with time differences τRa, τRb, τRc, τRd, τRe, τRf, and τRg, respectively, and are converted into electric signals. Each electric signal is received by the pulser receiver 1307 after being delayed by time τRa to τRg by the corresponding variable delay elements 1306a to 1306g.

  At this time, each variable delay element 1306 corrects the time according to the distance between the region of interest of the test part E and each piezoelectric element, so that the phase at which the pulsar receiver 1307 receives the electrical signal is aligned. As a result, a focused region is formed in the region of interest of the test part E, and a reflected wave generated from this focused region is selectively received. In the illustrated example, the shorter the distance between the region of interest and the piezoelectric element, the longer the delay time.

  In this way, what forms a focusing region for ultrasonic waves to be transmitted and received electrically is called electronic focus. In the acoustic wave receiving apparatus of the present invention, the depth of the converging region formed in the region of interest of the test part E by the electronic focus and the depth of the converging region formed by the acoustic lens 1303 are the same. Here, the “depth” refers to the distance from the surface where the relative position of the linear array-shaped transmitting / receiving element group or the hemispherical receiving element group changes with respect to the portion to be examined, and the support member support. The distance from the surface is said to be the same when the position in the z-axis direction in the figure is the same.

(Array support)
The array support unit 400 is a container having a combination of a hemispherical portion (first portion) and a substantially bottomed cylindrical portion (second portion). The hemispherical portion is arranged so as to protrude from the bottom surface of the cylinder forming the second portion. The first and second parts are combined to form a container that can accommodate the acoustic matching fluid 800 as a whole. A plurality of receiving elements 310 are installed on the inner surface of the hemisphere. That is, array support section 400 that supports a plurality of receiving elements 310 constitutes receiving array 300. A plurality of transmitting / receiving elements 1310 are installed in a part of a region corresponding to the bottom surface of the second portion outside the hemisphere. The optical system 200 is installed at the bottom (pole) of the hemisphere. The inside of the array support part 400 is filled with an acoustic matching fluid 800. The array support unit 400 is preferably configured using a metal material having high mechanical strength in order to support these members.

  In addition, since the attenuation occurs when the ultrasonic wave propagates through the acoustic matching fluid, it is preferable to shorten the distance between the test portion and the transmission / reception element 1310. For this reason, in the acoustic wave receiving apparatus of the present embodiment, the transmitting / receiving element 1310 is installed on the bottom surface of the substantially cylindrical portion of the array support unit 400.

  The reception direction center (the direction with the highest sensitivity) of the plurality of reception elements 310 provided on the array support unit 400 is directed to the center of curvature of the hemisphere. The center in the reception direction is indicated by a one-dot chain line converging on a partial region in the test part E. FIG. 1C is a cross-sectional view taken along the central axis of the hemispherical array support 400. Thus, each element of the plurality of receiving elements 310 is arranged on the array support part 400 so as to receive photoacoustic waves generated in a specific region with high sensitivity. In the present embodiment, this specific area is referred to as an effective reception area. Here, the above-described effective reception area can be said to be an isocenter (ISOCENTER) in which a plurality of reception directing axes of each of a plurality of reception elements intersect each other.

  In the case of the arrangement of the plurality of receiving elements 310 as described above, the test portion information obtained using the received signal by the method described later has a high resolution at the center of curvature of the hemisphere, and the resolution decreases as the distance from the center increases. In this embodiment, the effective reception area refers to an area from the point with the highest resolution (the center of curvature of the hemisphere) to the half resolution of the highest resolution, and the area surrounded by the dotted line in FIG. G corresponds to this.

  In the acoustic wave receiving apparatus of the present invention, the depth of the focusing region formed in the region of interest of the test part by the transmitting / receiving element that acquires the ultrasonic echo image is the depth direction of the region G where the photoacoustic image is acquired with high sensitivity. (In the z-axis direction, it is located below the upper end and above the lower end of the region indicated by the symbol G). Thereby, the photoacoustic image and ultrasonic echo image of the same depth of a to-be-tested part can be imaged with high image quality. In the acoustic wave receiving apparatus of the present invention, a plurality of transmission / reception elements 1310 are arranged outside the reception areas of the plurality of reception elements 310, and a plurality of reception elements 310 are arranged outside the transmission / reception areas of the plurality of transmission / reception elements 1310. Yes.

As for the first portion, as long as a desired effective reception area can be formed, the direction in which each receiving element has the highest sensitivity may not necessarily intersect. Also, the direction (directing axis) with the highest reception sensitivity of at least some of the plurality of reception elements 310 supported by the array support unit 400 so that photoacoustic waves generated in a specific region can be received with high sensitivity. Should be suitable for a specific area. If this condition is satisfied, the shape of the first portion is not limited to a hemisphere. For example, a spherical crown shape, a shape obtained by cutting out a part of an ellipsoid, or a shape obtained by combining a plurality of planes or curved surfaces may be used.

  Further, the shape of the second portion is not limited to the substantially bottomed cylinder. A member having a bottom surface portion and a side surface portion, wherein the bottom surface is connected to the first portion and a transmitting / receiving element can be installed, and the side surface portion is used for acoustic matching between the test portion and the piezoelectric element array. Any member that can accommodate the amount of acoustic matching fluid required for maintenance can be used as the second portion. Further, the side surface portion of the second portion is not shaped to stand from the bottom surface portion, and may be connected by drawing a rounded shape on the bottom surface portion. For example, as the second portion, in FIG. 1, a shape in which a cylinder and a rectangular parallelepiped with rounded corners are fused is adopted, and in FIG. 3, a substantially elliptical column shape is adopted.

(scanner)
The scanner 500 is a device that changes the relative position of the array support part 400 with respect to the test part E by moving the position of the array support part 400 in the X and Y directions in FIG. Therefore, the scanner 500 includes a guide mechanism (not shown) in the X and Y directions, a drive mechanism in the X and Y directions, and a position sensor that detects the position of the array support unit 400 in the X and Y directions. Since the array support unit 400 is stacked on the scanner 500, it is preferable to use a linear guide or the like that can withstand a large load as the guide mechanism. Moreover, a lead screw mechanism, a link mechanism, a gear mechanism, a hydraulic mechanism, etc. can be utilized as a drive mechanism. The driving force can be a motor. As the position sensor, a potentiometer using an encoder, a variable resistor, or the like can be used. Any member can be used as the scanner 500 as long as it can move the array support section 400 with respect to the test section E. The scanner 500 corresponds to the scanning unit of the present invention. The scanning unit integrally scans the transmission / reception array and the reception array.

  The acoustic wave receiving apparatus of the present invention is configured such that the effective reception area by the plurality of reception elements 310 and the focusing area by the transmission / reception element 1310 do not overlap each other. It is preferable that the path of the photoacoustic signal received by the plurality of receiving elements 310 and the transmitting / receiving element 1310 do not overlap. In order for the path of the photoacoustic signal and the transmission / reception element 1310 not to overlap, the transmission / reception element 1310 is placed outside the reception area of the reception element 310 (area where the angle with the reception surface of the photoacoustic wave signal is −α or less or α or more). Just place it. Therefore, the hemispherical portion for forming the above-described effective reception region G and the installation position of the transmission / reception element 1310 are arranged offset in the horizontal direction (XY direction). Therefore, the shape of the bottom part of the second part of the array support part 400 is also a shape suitable for the arrangement of the transmitting / receiving element 1310. In this way, the effective reception area by the plurality of reception elements 310 and the focusing area by the transmission / reception element 1310 are configured so as not to overlap each other, so that the transmission / reception element receives a photoacoustic signal from the subject at the time of photoacoustic signal acquisition. Can be reduced. Similarly, the influence of the receiving element 310 on the ultrasonic signal from the subject when acquiring the ultrasonic signal can be reduced. As shown in FIGS. 5 and 6, the plurality of transmission / reception probes 1310 (transmission / reception arrays) have a common reception surface. The focusing area of the plurality of transmitter / receiver probes 1310 can typically be replaced by the center normal NL of such a common receiving surface. Therefore, in the acoustic wave receiving apparatus according to the present invention, “the effective reception area formed by the plurality of receiving elements 310 and the center normal NL of the common receiving surface of the plurality of transmitting / receiving elements 1310 do not overlap each other (do not overlap). ) ”In other words.

Further, in order to obtain a good image of the region of interest of the test part E by both ultrasonic echo imaging and photoacoustic imaging, the positional relationship in which the effective reception region G and the converging region of the transmitting / receiving element 1310 overlap with the region of interest. It must be possible. The scanner 500 is configured to realize a moving distance and a moving position that satisfy this condition.

(Examination part appearance information acquisition part)
The test part appearance information acquisition unit 600 is an apparatus that acquires the appearance information of the test part E. For example, an imaging device that images the test part E such as a camera can be used as the test part appearance information acquisition unit 600. You may display the image of the to-be-tested part E to the display 900 mentioned later. In addition, the operator of the acoustic wave receiving apparatus may specify the region of interest of the part E to be examined by using the input unit 1000 described later by looking at the captured image displayed on the display 900. Further, at the time of image reconstruction, the obtained appearance information may be used for acquiring a light amount distribution in the test portion E and acquiring an acoustic wave attenuation degree.

(Computer)
The computer 700 includes a calculation unit 710 and a storage unit 720. The arithmetic unit 710 is typically composed of elements such as a CPU, GPU, A / D converter, and amplifier, and circuits such as an FPGA and an ASIC. Note that the arithmetic unit is not limited to a single element or circuit, but may be composed of a plurality of elements or circuits. In addition, any element or circuit may execute each process performed by the computer 700. The storage unit 720 typically includes a storage medium such as a ROM, a RAM, and a hard disk. Note that the storage unit is not limited to one storage medium, and may be configured from a plurality of storage media.

  The arithmetic unit 710 performs signal processing on the electrical signals output from the plurality of receiving elements 310 and the transmitting / receiving element 1310. Further, the calculation unit 710 as a control unit controls the operation of each component constituting the test subject information acquiring apparatus via the bus 2000 as shown in FIG. The operations controlled by the calculation unit 710 include switching of photoacoustic and ultrasonic echo imaging modes, designation and change of the imaging area, and the like. In addition, the computer 700 is preferably configured to be able to pipeline process a plurality of signals simultaneously. Thereby, the time until acquiring the test part information can be shortened. Each process performed by the computer 700 can be stored in the storage unit 720 as a program to be executed by the arithmetic unit 710.

  The switching of the imaging mode described above may be performed by imaging an ultrasonic echo after photoacoustic imaging, or vice versa. Moreover, you may image a photoacoustic and an ultrasonic echo alternately. When the same part of the test part E is imaged with photoacoustics and ultrasonic echoes, and the images are superimposed and displayed, if the photoacoustics and ultrasonic echoes are imaged alternately, there is little positional deviation in both imagings. Is preferred. In addition, after the entire test portion E is imaged with photoacoustic (or ultrasonic echo), a photoacoustic image is displayed on the display 900, a region of interest is designated on the display image by the input unit 1000, and an ultrasonic wave of the region of interest is displayed. Echo (or photoacoustic) may be imaged. Screening the entire test part E with photoacoustics (or ultrasonic echoes), determining the region of interest and imaging the ultrasonic echoes (or photoacoustics), so both images are not taken by the entire test part E Therefore, inspection time can be shortened.

  The arithmetic unit 710 can generate photoacoustic image data derived from the electrical signal (photoacoustic signal) output from the receiving element 310 and ultrasonic image data derived from the electrical signal (ultrasound signal) output from the transmitting / receiving element 1310. It is. For the generation of image data, any known image reconstruction method (eg, phasing addition method, filtered back projection method, universal back projection method, Fourier transform method, inverse problem analysis, etc.) can be used. At this time, the computer 700 functions as an information processing unit of the present invention. Different methods may be used for photoacoustic image data and ultrasonic image data. The generated photoacoustic image data and ultrasonic image data may be displayed on the display 900 or stored in a memory.

(Acoustic matching fluid)
The acoustic matching fluid 800 fills a space between the test part E and the receiving element 310 and acoustically couples the test part E and the receiving element 310. Therefore, it is preferable to arrange the acoustic matching fluid 800 between the receiving element 310 and the shape holding unit 1100 and between the shape holding unit 1100 and the test part E. Further, different acoustic matching fluids 800 may be arranged between the receiving element 310 and the shape holding unit 1100 and between the shape holding unit 1100 and the test part E, respectively.

  The acoustic matching fluid 800 is preferably a material having an acoustic impedance close to that of the test part E and the receiving element 310. Furthermore, the acoustic matching fluid 800 is more preferably a material having an acoustic impedance intermediate between the test part E and the receiving element 310. The acoustic matching fluid 800 is preferably a material that transmits the pulsed light generated by the light source 100. The acoustic matching fluid 800 is preferably a liquid. Specifically, the acoustic matching fluid 800 may be a liquid such as water or castor oil, or a gel.

(display)
The display 900 (display unit) displays test portion information output from the computer 700 as a distribution image, numerical data of a specific region of interest, or the like. The display may be any type of display such as a liquid crystal display or an organic EL display. The display 900 may be provided separately from the acoustic wave receiving apparatus of the present invention.

(Input section)
The input unit 1000 is a user interface for the user to input / designate desired information to the computer 700. As the input unit 1000, a keyboard, a mouse, a touch panel, a dial, a button, and the like can be used. When a touch panel is employed as the input unit 1000, the display 900 may be a touch panel that also serves as the input unit 1000.

(Shape holding part)
The shape holding part 1100 is a member for keeping the shape of the test part E constant. The shape holding part 1100 is attached to the attachment part 1200. In order to change the holding shape of the test part E or to cope with individual differences in the size of the test part E, a configuration in which a plurality of shape holding parts having different shapes and sizes can be exchanged is preferable.

  When the test part E is a breast, it is preferable that the shape holding part 1100 has a spherical crown shape or a bowl shape in order to reduce the deformation of the breast shape. In addition, the shape of the shape holding part 1100 can be designed according to the volume of the test part and the desired shape after holding. When irradiating the test part E with light through the shape holding unit 1100, the shape holding unit 1100 preferably transmits the irradiation light. Therefore, polymethylpentene, polyethylene terephthalate, or the like is suitable as a material for the shape holding unit 1100.

  Further, as another material of the shape holding unit 1100, a material having flexibility such as rubber that can be deformed according to the shape of the test portion E can be used. The material having flexibility has the advantage that it is difficult to wrinkle when the test part E is held. In addition, it is preferable to use a member having a high light transmittance of the light source 100 (preferably 90% or more). Specifically, silicone rubber, urethane rubber, styrene elastomer, olefin elastomer, acrylic elastomer and the like are suitable.

(Support member)
The support member 1200 supports the subject and inserts the subject's subject portion into the insertion portion (
Insertion slot). Further, as shown in FIG. 1C, an array support section 400, a scanner 500, and the like are housed below the support member 1200. The illustrated support member 1200 is suitable for supporting a prone subject. A breast is assumed as the test part. The array support 400 that is moved by the scanner 500 of the acoustic wave receiving apparatus of the present invention is a relatively large member having a hemispherical portion and a bottom portion on which the transmitting / receiving element array can be arranged. Therefore, the size of the support member 1200 is also relatively large. As a result, the workability of the assistant and the comfort of the subject may be affected.

  According to the study by the inventors, a suitable width of the support member 1200 in order for the subject to be able to be placed on the support member 1200 without anxiety and for the assister to perform the assisting operation of the subject satisfactorily. It was found that there was a range of (distance in the Y direction). Further, as shown in FIGS. 2 (b) and 3 (b), it has been found that the posture in which the legs are gently lowered from the hip joint of the subject to support the whole body is comfortable for the subject. Furthermore, since there are individual differences in the physique of the subject, it has been found that a member should be provided on the support member 1200 in order to adjust the position to lower the hip joint.

(First arrangement)
Hereinafter, the arrangement and configuration of the transmission / reception element 1310 that allows the assistant to work well and allows the subject to take a comfortable posture will be described. In the first acoustic wave receiving apparatus according to FIG. 1, the positional relationship in the X-axis direction is defined as follows. That is, the direction in which the subject's head side is arranged is called the head side, and the direction in which the subject's leg side is arranged is called the tail. At this time, for example, in the case of FIG. 1, it can be said that the transmission / reception element 1310 is arranged on the head side with respect to the reception element 310. In addition, it can be said that the transmitting / receiving element 1310 is disposed relatively closer to the head side in the array support unit 400.

  In this way, the configuration in which the transmitting / receiving element 1310 is arranged on the head side of the array support unit 400 is such that the support member 1200 is enlarged on the head-tail side compared to the configuration having a simple hemispherical array support unit. Does not expand. For this reason, the assistant can satisfactorily carry out the work of assisting the subject from the left and right sides of the support member 1200. With this configuration, even when compared with an acoustic wave receiving apparatus including a simple hemispherical array support unit 400, the workability of assistance does not deteriorate.

  Even in the configuration in which the transmitting / receiving element 1310 is arranged on the tail side of the array support unit 400, the assistant can favorably perform the work of assisting the subject from the left and right sides of the support member 1200. However, as will be described later, from the viewpoint of comfort of the posture of the subject, the arrangement on the head side is preferable.

(Second arrangement)
In the second acoustic wave receiving apparatus according to FIG. 2, the transmitting / receiving element 1310 is arranged on one of the left and right sides of the array support 400 as viewed from the subject. In FIG. 2, the transmitting / receiving element 1310 is arranged on the left side of the prone subject (the side with the left hand extended as viewed from the prone subject, the lower side on the paper). However, it may be on the right side of the prone subject (the side with the right hand extended as viewed from the prone subject, the upper side on the paper). In the second acoustic wave receiving apparatus according to FIG. 2, the transmitting / receiving element 1310 is thus arranged on either the left side or the right side of the array support unit 400. According to this configuration, the support member 1200 does not expand to the tail side as compared with a configuration having a simple hemispherical array support. Therefore, the height of the support member 1200 on the caudal side than the waist of the subject can be reduced. As a result, the subject can take a comfortable posture because the leg is gently lowered from the hip joint and the whole body is supported by the support member 1200.

(Third arrangement)
In the third acoustic wave receiving apparatus according to FIG. 3, the transmitting / receiving elements 1310 are arranged on both the left and right sides of the array support unit 400. According to such a configuration, imaging can be performed by the transmitting / receiving element 1310 in which the left half region of the test part E is arranged on the left side and the transmitting / receiving element 1310 in which the right half region of the test part E is arranged on the right side. As a result, the moving distance of the scanner 500 in the left-right direction is significantly shorter than the configuration in which one transmitting / receiving element 1310 is arranged on one of the left and right sides as shown in FIG. Also, the moving distance of the scanner 500 in the left-right direction is only slightly increased compared to a simple hemispherical array support acoustic wave receiver.

  According to the configuration of the third acoustic wave receiving device, the degree of expansion of the support member 1200 to the left and right sides does not deteriorate the workability of the caregiver. Therefore, workability by the assistant is not impaired. 3 does not enlarge the support member 1200 to the caudal side, the height of the support member 1200 on the caudal side can be made lower than the waist of the subject. Therefore, the subject can maintain a comfortable posture.

(Fourth arrangement)
A configuration in which the transmitting / receiving element 1310 is arranged on the head side and the tail side of the array support unit 400 is also conceivable. In this case, the upper half of the breast is measured by the head-side transmitting / receiving element, and the lower half is measured by the tail-side transmitting / receiving element. In this case, since the amount of expansion of the support member 1200 to the tail side is suppressed, the influence on the comfort of the subject can be reduced. Further, similarly to the case of FIG. 3, the movement amount of the scanner 500 can be suppressed. Furthermore, since this structure does not expand the support member 1200 to the left and right sides, the workability of the assistant is kept good. In the third arrangement or the fourth arrangement, the transmission / reception element 1310 on one side images half of the test part E. Therefore, it is suitable for imaging the whole test portion E alternately with the receiving element and the transmitting / receiving element. Further, by combining the third and fourth arrangements, transmission / reception elements may be provided at four positions on the left and right and top and bottom (head and tail) of the test part E, or transmission / reception elements may be provided at angles other than left and right and top and bottom. .

  In addition, in FIG. 1C, the case where the orientation of the array support unit 400 itself with respect to the support member 1200 is static has been described. However, the scanner 500 may have a function of changing the relative position of the array support unit 400 in the rotation direction. With such a rotationally moving configuration, the expansion of the moving region of the array support unit 400 can be limited.

  As described above, in the acoustic wave receiving apparatus capable of both photoacoustic imaging and ultrasonic echo imaging, it is possible to improve the comfort of the posture of the subject while improving the workability of the auxiliary work by the assistant. it can.

<Other embodiments>
The present invention can also be implemented by a computer (or a device such as a CPU or MPU) of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device. For example, the present invention can be implemented by a method including steps executed by a computer of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device. . It can also be realized by a circuit (for example, ASIC) that realizes one or more functions. For this purpose, the program is stored in the computer from, for example, various types of recording media that can serve as the storage device (ie, computer-readable recording media that holds data non-temporarily). Provided to. Therefore, the computer (including devices such as CPU and MPU), the method, the program (including program code and program product), and the computer-readable recording medium that holds the program non-temporarily are all present. It is included in the category of the invention.

  100: light source, 300: receiving array, 310: receiving element, 1300: transmitting / receiving array, 1310: transmitting / receiving element, 400: array supporting unit, 500: scanner, 700: computer, 1200: supporting member

Claims (16)

A light irradiator optically connected to the light source and irradiating the subject's subject with light; and
A receiving array comprising a plurality of receiving elements for receiving a photoacoustic wave generated by irradiating the test portion with light irradiated from the light irradiation unit and outputting a photoacoustic signal;
A transmission / reception array including a plurality of transmission / reception elements that transmit ultrasonic waves to the test part, receive ultrasonic waves reflected by the test part and output ultrasonic signals;
An array support unit comprising: a first part that supports the reception array so that an effective reception area where at least a part of the directivity axes of the reception array gathers is formed; and a second part that supports the transmission / reception array When,
A scanning unit that integrally scans the reception array and the transmission / reception array with respect to the test unit by moving the array support unit;
Have
The acoustic wave receiving apparatus according to claim 1, wherein the array support unit is configured such that an effective reception area formed by the reception array and a focusing area of the transmission / reception array do not overlap. The acoustic wave receiving apparatus according to claim 1, wherein the second portion has a bottom surface portion and a side surface portion, and the transmission / reception array is disposed on the bottom surface portion. The acoustic wave receiving apparatus according to claim 1, further comprising acoustic wave focusing means for focusing the ultrasonic waves transmitted by the transmission / reception array to the same depth as the effective reception area. The said array support part accommodates the acoustic matching fluid which acoustically couples the said test part, the said receiving array, the said test part, and the said transmission / reception array, respectively. The acoustic wave receiver according to any one of 1 to 3. 5. The acoustic wave receiving apparatus according to claim 1, wherein the scanning unit changes a relative position in a rotation direction of the array support unit and the test unit. The acoustic wave receiving apparatus according to claim 1, wherein the array support unit arranges the transmission / reception array on a head side with respect to the reception array. The acoustic wave receiving apparatus according to claim 1, wherein the array support unit arranges the transmitting / receiving array on either the left side or the right side of the receiving array. The array support section is arranged on the left side and the right side of the reception array so that the transmission / reception array can be subjected to ultrasonic echo imaging of the test section in half.
The acoustic wave receiving apparatus according to claim 1, wherein the acoustic wave receiving apparatus is provided. While supporting the subject, further has a support member provided with an insertion port into which the subject portion of the subject is inserted,
9. The height of the support member on the tail side of the subject is lower than the height of the support member on the head side of the subject. Acoustic wave receiver. The acoustic wave receiving apparatus according to claim 1, further comprising a shape holding part that holds the test part. When the incident angle at which the receiving sensitivity of the photoacoustic wave is 50% of the maximum value in the receiving area of the receiving array is α, the transmitting / receiving array is an angle formed between the photoacoustic wave and the receiving surface of the receiving element. The acoustic wave receiving apparatus according to claim 1, wherein the acoustic wave receiving apparatus is disposed in a range such that is less than or equal to −α or greater than or equal to α. The acoustic wave receiving apparatus according to claim 1, wherein the second portion of the array support portion is different from the first portion.   The acoustic wave receiving apparatus according to claim 1, wherein the second portion of the array support section supports the transmission / reception array in a linear array. The acoustic wave receiving apparatus according to claim 1, wherein the effective reception area is an isocenter in which a plurality of directivity axes intersect each other. The acoustic wave receiving apparatus according to claim 1, further comprising an information processing unit that acquires characteristic information of the test unit using the photoacoustic signal and the ultrasonic signal. . 16. The acoustic according to claim 1, wherein normal directions of the effective reception area formed by the plurality of receiving elements and a common receiving surface of the transmitting and receiving elements do not overlap each other. Wave receiver.