JP2019005560A - Information processing apparatus and system - Google Patents

Abstract

Highly accurate object information is acquired in an apparatus for processing a photoacoustic signal generated due to light irradiated through an interchangeable optical member. An information processing apparatus according to an embodiment of the present invention includes an acoustic wave generated by irradiating a subject with light through a light irradiation unit in which a positional relationship with an acoustic wave probe is defined. An information processing apparatus for processing image data indicating characteristic information at a plurality of positions in the subject based on the image data acquisition means for acquiring the image data and identifying the type of the acoustic wave probe Information acquisition means for acquiring the identification information to be performed, and based on the identification information for identifying the type of the acoustic wave probe, the light irradiated through the light irradiation unit at a plurality of positions in the subject Correction means for correcting the influence of the image data on the image value caused by the variation in the amount of light. [Selection] Figure 1

Description

  The present invention relates to an apparatus for acquiring information on a subject using acoustic waves.

Photoacoustic imaging is known as a technique for imaging structural information in a subject and physiological information, that is, functional information.
When light such as laser light is irradiated on a living body that is a subject, an acoustic wave (typically, an ultrasonic wave) is generated when the light is absorbed by a living tissue in the subject. This phenomenon is called a photoacoustic effect, and an acoustic wave generated by the photoacoustic effect is called a photoacoustic wave. Since tissues constituting the subject have different optical energy absorption rates, the sound pressures of the generated photoacoustic waves are also different. In photoacoustic imaging (PAI), the generated photoacoustic waves are received by a probe, and the received signal is mathematically analyzed to obtain characteristic information in the subject.

  On the other hand, ultrasonic imaging is known as a method for acquiring structural information in a subject. In ultrasonic imaging, ultrasonic waves are transmitted to a subject from a plurality of acoustic elements (transducers) arranged on a probe. Then, a reflected wave generated at an interface having different acoustic impedance in the subject is received, and image data is generated.

  As a technique related to this, for example, Patent Document 1 describes a technique for acquiring an image by photoacoustic imaging and an image by ultrasonic imaging using the same handheld probe.

JP 2017-000660 A

  Patent Document 1 describes a configuration in which a member (light irradiation unit) that irradiates light to a subject can be attached to and detached from the probe. However, when the combination of the light irradiating unit and the probe is changed, the positional relationship between the acoustic element and the light irradiating unit and the characteristics of the light irradiated to the subject change. Further, due to this, there has been a problem that the distribution of the amount of light in the subject changes and the visibility when the subject information is imaged changes.

  The present invention has been made in view of the above-described problems of the prior art. In an apparatus for processing a photoacoustic signal generated due to light irradiated through a replaceable optical member, the present invention is highly accurate. The purpose is to obtain specimen information.

  The information processing apparatus according to the present invention is based on an acoustic wave generated by irradiating a subject with light through a light irradiating unit in which a positional relationship with the acoustic wave probe is defined. An information processing apparatus for processing image data indicating characteristic information at a plurality of positions, wherein the image data acquisition means for acquiring the image data and the information acquisition for acquiring the identification information for identifying the type of the acoustic wave probe And the image resulting from variations in the amount of light at a plurality of positions in the subject of the light irradiated through the light irradiation unit based on the identification information identifying the type of the means and the acoustic probe Correction means for correcting the influence of the data on the image value.

  In addition, the system according to the present invention includes a light irradiation unit that irradiates a subject with light, an acoustic probe that converts an acoustic wave generated by light irradiation onto the subject into an electrical signal, and the light irradiation unit. And at least one of the light irradiation unit and the acoustic wave probe so as to define a positional relationship between the acoustic wave probe and a plurality of the acoustic wave probes, and a plurality of components in the subject based on the electrical signal. An information processing device that generates image data indicating characteristic information at a position, wherein the information processing device acquires identification information for identifying a type of the acoustic wave probe, and the acoustic wave Based on the identification information for identifying the type of probe, the influence of the light irradiated through the light irradiation unit on the image value of the image data caused by the variation in the amount of light at a plurality of positions in the subject Correction means for correcting Including.

  In addition, the information processing apparatus according to the second aspect of the present invention is adapted to detect acoustic waves generated by irradiating a subject with light through a light irradiation unit whose positional relationship with the acoustic wave probe is defined. An information processing apparatus for processing image data indicating characteristic information at a plurality of positions in the subject based on image data acquisition means for acquiring the image data, and irradiation unit information that is information on the light irradiation unit To the image value of the image data resulting from the variation in the amount of light at a plurality of positions in the subject of the light irradiated through the light irradiation unit based on the information on the irradiation unit Correction means for correcting the influence of the above.

  An information processing method according to a second aspect of the present invention includes a light irradiation unit that irradiates light to a subject, and an acoustic wave probe that converts an acoustic wave generated by light irradiation to the subject into an electrical signal. And a mounting portion for attaching at least one of the light irradiation unit and the acoustic wave probe so as to define a positional relationship between the light irradiation unit and the acoustic wave probe based on the electrical signal. An information processing device that generates image data indicating characteristic information at a plurality of positions in the subject, wherein the information processing device acquires irradiation unit information that is information relating to the light irradiation unit. And correction for correcting the influence of the light irradiated through the light irradiation unit on the image value of the image data caused by the variation in the light amount at a plurality of positions in the subject based on the irradiation unit information Means.

  According to the present invention, highly accurate object information can be acquired in an apparatus that processes a photoacoustic signal generated due to light irradiated through an interchangeable optical member.

The block diagram of the photoacoustic apparatus which concerns on embodiment. The perspective view which showed the probe which concerns on embodiment. The processing flow figure which the photoacoustic apparatus which concerns on embodiment performs. The figure which showed the effect of embodiment typically. The example of the display screen output via a display apparatus.

  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 acoustic waves propagating from a subject, generating characteristic information inside the subject, and acquiring the characteristic information. Therefore, the present invention can also be understood as a subject information acquisition apparatus, a control method thereof, or a subject information acquisition method. The present invention can also be understood as an information processing apparatus that generates object information based on acoustic waves, a control method thereof, or an information 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 and a memory to execute these methods, and a non-transitory storage medium that stores the program and is readable by a computer.

  An information processing apparatus according to the present invention processes a signal obtained by receiving an acoustic wave generated in a subject by irradiating the subject with light (electromagnetic waves), and acquires characteristic information of the subject as image data. It is a device to do. In this case, the characteristic information is characteristic value information corresponding to each of a plurality of positions in the subject, which is generated using a reception signal obtained by receiving a photoacoustic wave.

The characteristic information acquired by photoacoustic imaging is a value reflecting the absorption rate of light energy. For example, a generation source of an acoustic wave generated by light irradiation, an initial sound pressure in a subject, a light energy absorption density or absorption coefficient derived from the initial sound pressure, and a concentration of a substance constituting a tissue are included.
Further, the oxygen saturation distribution can be calculated by obtaining the oxygenated hemoglobin concentration and the reduced hemoglobin concentration as the substance concentration. In addition, glucose concentration, collagen concentration, melanin concentration, fat and water volume fraction, and the like are also required. Furthermore, a substance having a characteristic light absorption spectrum, such as a contrast agent administered into the body, can also be mentioned.

  An information processing apparatus according to the present invention includes an apparatus that processes a signal obtained by receiving an ultrasonic wave (ultrasonic echo) reflected inside a subject and acquires characteristic information of the subject as image data. In this case, the acquired characteristic information is information reflecting the difference in acoustic impedance of the tissue inside the subject.

  A two-dimensional or three-dimensional characteristic information distribution is obtained based on the characteristic information of each position in the subject. The distribution data can be generated as image data. The characteristic information may be obtained not as numerical data but as distribution information of each position in the subject. That is, distribution information such as initial sound pressure distribution, energy absorption density distribution, absorption coefficient distribution, and oxygen saturation distribution. The image data is data indicating characteristic information at a plurality of positions in the subject.

  The acoustic wave in this specification is typically an ultrasonic wave, and includes an elastic wave called a sound wave and an acoustic wave. An electric signal converted from an acoustic wave by a probe or the like is also called an acoustic signal. However, the description of ultrasonic waves or acoustic waves in this specification is not intended to limit the wavelength of those elastic waves. An acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave. An electrical signal derived from a photoacoustic wave is also called a photoacoustic signal. In this specification, the photoacoustic signal is a concept including both an analog signal and a digital signal. The distribution data is also called photoacoustic image data or reconstructed image data.

(Description of Embodiment)
<Device configuration>
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of a photoacoustic apparatus (system) according to the present embodiment. The photoacoustic apparatus (system) according to the present embodiment includes an acoustic probe 21 including an acoustic element 17, a light source 11, an optical system 13, a light irradiation unit 18 that can be attached to and detached from the acoustic probe 21, and information processing. A unit 23 and a display control unit 24 are included. The information processing unit 23 and the display control unit 24 may be collectively referred to as an information processing apparatus. That is, it can be said that the information processing apparatus according to the present invention includes the information processing unit 23 and the display control unit 24.

Here, an outline of photoacoustic imaging for a subject will be described.
Light emitted from the light source 11 is guided to the light irradiation unit 18 through the optical system 13 including an optical transmission path such as an optical fiber, and is desired by an optical system such as a lens or a diffusion plate incorporated in the light irradiation unit 18. And is finally irradiated to the subject 15.
When a part of the energy of the light 12 propagating through the subject 15 is absorbed by the light absorber 14 such as a blood vessel, an acoustic wave 16 (typically an ultrasonic wave) is generated due to thermal expansion. The acoustic wave 16 is detected by the acoustic element 17 in the acoustic wave probe, and amplified and digitally converted by the signal acquisition unit 20. The converted signal is converted into photoacoustic image data representing the characteristics of the subject by the information processing unit 23 and the display control unit 24 and displayed as an image on the display device 25.

Next, details of each component will be described.
<< Light source 11 >>
The light source 11 is a device that generates pulsed light that irradiates a subject. The light source may be a laser light source in order to obtain a large output, but a light emitting diode, a flash lamp, a microwave source, or the like may be used instead of the laser. Note that when an electromagnetic wave having a wavelength different from that of light such as a microwave or a radio wave is used, the light source can also be referred to as an electromagnetic wave source.
When a laser is used as the light source, various lasers such as a solid laser, a gas laser, a dye laser, and a semiconductor laser can be used. For example, a pulse laser such as an Nd: YAG laser or an alexandrite laser may be used as the light source. In addition, a Ti: sa laser that uses Nd: YAG laser light as excitation light or an optical parametric oscillator (OPO) laser may be used as a light source.

Further, the wavelength of the pulsed light may be a specific wavelength that is absorbed by a specific component among the components constituting the subject, and may be a wavelength at which the light propagates to the inside of the subject. Specifically, when the subject is a living body, it may be 500 nm or more and 1400 nm or less.
In order to effectively generate photoacoustic waves, light must be irradiated in a sufficiently short time according to the thermal characteristics of the subject. When the subject is a living body, the pulse width of the pulsed light generated from the light source can be 1 nanosecond to 1000 nanoseconds.

<< Optical system 13 >>
The light emitted from the light source 11 propagates through the optical system 13 and is irradiated on the subject surface. An optical element such as a mirror or an optical fiber can be used for the optical system 13. In order to make the irradiation pattern of the pulsed light have a desired shape, the optical system 13 may be configured using a diffusion plate, a lens, or the like. The optical system 13 may be incorporated in a light irradiation unit 18 described later.

<< Subject 15 (light absorber 14) >>
The subject 15 does not constitute the present invention, but will be described below. The photoacoustic apparatus according to the present embodiment can be used for the purpose of diagnosing malignant tumors, vascular diseases, etc. of humans and animals, and monitoring the progress of chemical treatment. Therefore, the subject 15 is assumed to be a target site for diagnosis such as a living body, specifically breasts of human bodies or animals, each organ, blood vessel network, head, neck, abdomen, extremities including fingers and toes. The For example, if the human body is a measurement target, oxyhemoglobin or deoxyhemoglobin, a blood vessel containing many of them, or a new blood vessel formed in the vicinity of a tumor, or the like may be used as a light absorber. Further, a plaque of the carotid artery wall or the like may be a target of the light absorber. In addition, a dye such as methylene blue (MB) or indocyanine green (ICG), gold fine particles, or a substance introduced from the outside, which is accumulated or chemically modified, may be used as the light absorber.

<< Acoustic element 17 >>
The acoustic element 17 is means for detecting an acoustic wave and converting it into an analog electrical signal. The acoustic wave probe is also called a probe, an acoustic element, an acoustic wave detection element, an acoustic wave detector, an acoustic wave receiver, or a transducer. Since the acoustic wave generated from the living body is an ultrasonic wave of 100 KHz to 100 MHz, an element capable of receiving the above frequency band is used as the acoustic element 17. Specifically, a transducer using a piezoelectric phenomenon, a transducer using optical resonance, a transducer using a change in capacitance, or the like can be used.
In addition, when the photoacoustic apparatus according to the present embodiment has a function of performing ultrasonic imaging, the acoustic element 17 may have a function of transmitting an acoustic wave formed on an arbitrary wavefront. .

  An acoustic element having high sensitivity and a wide frequency band may be used. Specifically, piezoelectric elements using PZT (lead zirconate titanate), polymer piezoelectric film materials such as PVDF (polyvinylidene fluoride), CMUT (capacitive micromachined ultrasonic transducer), and Fabry-Perot interferometer were used. Things. However, the present invention is not limited to those listed here, and any one may be used as long as it satisfies the function as a probe.

As the acoustic element 17, a plurality of elements that transmit and receive acoustic waves may be arranged in an array, or a single element may be employed. The arrangement shape may be any configuration. In particular, it is preferable in terms of the principle of image reconstruction to arrange in a planar shape, a cylindrical shape, a spherical shape, or a part thereof. The example of FIG. 1 shows an example in which a plurality of acoustic elements 17 are arranged in a one-dimensional or secondary dimension.
By using such multidimensionally arranged acoustic wave detection elements, acoustic waves can be detected at a plurality of locations at the same time, and the measurement time can be shortened. As a result, it is possible to reduce the influence of the swing of the subject. However, when the acoustic elements can be scanned, it is not always necessary to have an array arrangement. Further, when only the change of the acoustic wave signal at a specific location is observed, that is, when imaging is not required, there is one acoustic element and scanning is not necessary.
In addition, you may further scan the acoustic element which is a multidimensional array, and may detect an acoustic wave in more various positions.

<< Acoustic wave probe 21 >>
The acoustic wave probe 21 is a probe that has a grip portion for the operator to grip and houses the acoustic element 17. The gripping part also functions as a housing that holds the components of the probe. The shape of the gripping part may be a cylindrical shape, an elliptical column shape, a rectangular column shape, or the like. Moreover, you may provide an unevenness | corrugation so that an operator may hold | grip easily. The acoustic wave probe 21 has an acoustic wave detection surface, and at least one acoustic element 17 (transducer) is provided on the detection surface. The acoustic probe 21 can be detached from and exchanged with a signal acquisition unit 20 described later, and various characteristics (number of elements and frequency) and shapes (linear, sector) are selected from a plurality of types according to the measurement purpose. (Three-dimensional etc.) may be selectable. Basically, those having characteristics and shapes that can be used in a normal ultrasonic apparatus can also be used in the present invention.

<< Light irradiation part 18 >>
The light irradiation unit 18 can be attached to and detached from the acoustic probe 21 and is a means for irradiating the subject 15 with the light propagated through the optical system 13. The light irradiation unit 18 may include an optical system such as a diffusion plate, a lens, and a prism that processes the transmitted light into a desired shape. Further, when the light source 11 is a small one such as a semiconductor laser or LED, the light source 11 may be incorporated in the light irradiation unit 18.
In the present embodiment, the light irradiation unit 18 can be attached to and detached from the acoustic probe 21 having various shapes.

FIG. 2 is a schematic diagram illustrating an example of the light irradiation unit 18 that can be attached to and detached from the acoustic probe 21. For example, as shown in FIG. 2A, it is possible to attach the light irradiation unit to the acoustic probe 21 having a different shape by integrating the light irradiation unit with the clip. Further, as shown in FIG. 2B, a dedicated attachment portion 22 may be provided for each acoustic wave probe 21, and the light irradiation portion 18 may be attached to the attachment portion. Note that the method of attaching to and detaching from the acoustic wave probe 21 is not limited to the method shown in FIG. 2, and any method such as fixing with a screw or a pin or using a fastener may be adopted. By attaching at least one of the light irradiation unit 18 and the acoustic wave probe 21 to the attachment unit 22, the positional relationship between the light irradiation unit 18 and the acoustic wave probe 21 is defined. The clip in FIG. 2A also corresponds to the attachment portion. The attachment part for defining the positional relationship between the light irradiation part and the acoustic wave probe may be provided in the light irradiation part or in the acoustic wave probe. Moreover, the attachment part may be comprised independently of the light irradiation part and the acoustic wave probe. That is, the attachment unit only needs to be able to attach at least one of the light irradiation unit and the acoustic wave probe as long as the positional relationship between the light irradiation unit and the acoustic wave probe can be defined. Moreover, the attachment part may be able to attach a plurality of types of light irradiation parts in a replaceable manner. Moreover, the attachment part may be able to attach a plurality of types of acoustic wave probes in a replaceable manner.

<< Signal acquisition unit 20 >>
The signal acquisition unit 20 is means for amplifying an analog electrical signal obtained by the acoustic element 17 and converting it into a digital signal. The signal acquisition unit 20 is typically configured by an amplifier, an A / D converter, an FPGA (Field Programmable Gate Array) chip, and the like. When there are a plurality of signals obtained from the acoustic wave probe, a plurality of signals may be processed simultaneously. Thereby, the time until the image is formed can be shortened. In addition, the photoacoustic signal in this specification is the concept including the analog signal acquired from the acoustic element 17 and the digital signal after that A / D-converted. In the case where the acoustic element 17 has a function of transmitting ultrasonic waves to the subject, an electric circuit that transmits ultrasonic waves via the acoustic elements may be incorporated in the signal acquisition unit 20.

<< Information Processing Unit 23 >>
The information processing unit 23 is means for converting the digital signal obtained by the signal acquisition unit 20 into image data (photoacoustic image data) representing the characteristic information of the subject. The characteristic information of the subject is generally an initial sound pressure distribution, a light absorption energy density distribution, or information related thereto. The information processing unit 23 is an example of an image data acquisition unit in the present invention.

  The information processing unit 23 applies an image reconstruction algorithm generally used in photoacoustic imaging to the digital signal acquired by the signal acquisition unit 20 to obtain information on the optical characteristics inside the subject (photoacoustic image). Data). As an image reconstruction algorithm, back projection by the time domain method is generally used, but a method such as an inverse problem analysis method by iterative processing can also be used. As another typical image reconstruction method, there is a time domain reconstruction method such as a universal back projection method or a filtered back projection method.

On the other hand, when combined with ultrasonic imaging, beam forming technology (phasing addition) commonly used in ultrasonic imaging equipment is applied to the signal received from the reflected wave (ultrasonic echo) reflected from the subject. And subject information is acquired as image data.
When photoacoustic imaging is performed, subject information can be formed without image reconstruction by using a focused acoustic probe. In such a case, it is not necessary to perform signal processing using an image reconstruction algorithm.

  For the information processing unit 23, a general-purpose computer or a dedicated electronic circuit board is used. The signal acquisition unit 20 and the information processing unit 23 may be integrated. In this case, the image data of the subject can be generated not by software processing performed by a computer but by hardware processing.

<< Display control unit 24 >>
The display control unit 24 as information acquisition means acquires information regarding the light irradiation unit 18. And the display control part 24 as a correction | amendment means correct | amends the photoacoustic image data (henceforth 1st photoacoustic image data) which the information processing part 23 produced | generated based on the information regarding the light irradiation part 18, and a user. Image data (hereinafter referred to as second photoacoustic image data) to be provided to the (operator) is generated.
Specifically, image processing is performed based on the photoacoustic image data generated by the information processing unit 23 and information on the light irradiation unit 18 attached to the acoustic wave probe, and the second photoacoustic image data is obtained. Generate. The image processing includes, for example, luminance conversion according to the light amount distribution in the subject, extraction of a region of interest, blood vessel extraction processing, arterial and vein separation processing, logarithmic compression processing, and the like, but is not limited thereto.

The “information about the light irradiation unit” described here is information for calculating the light amount distribution in the subject, and typically indicates an identifier for identifying the individual or type of the light irradiation unit. Although it is identification information, you may use other information. For example, the type of probe to which the light irradiation unit is attached, the type and shape of the attachment unit that connects the light irradiation unit and the probe, and the region where light is irradiated on the subject (hereinafter referred to as the light irradiation region) It may be information that identifies the shape of the light irradiation unit and whether or not the light irradiation unit is mounted.
Hereinafter, the information regarding the light irradiation unit is referred to as irradiation unit information. By using the irradiation unit information, it is possible to correct a difference in light amount distribution that occurs for each type of light irradiation unit.

Further, the display control unit 24 as display control means generates information accompanying the subject information and outputs it simultaneously with an image representing the subject information. For example, an image or display representing the attached / detached state of the light irradiation unit, the type of the light irradiation unit used, the wavelength of the laser light, the light irradiation position, and the like are output together with the first and second photoacoustic image data.
In addition, the display control part 24 may record 1st photoacoustic image data and irradiation part information temporarily, and may produce | generate 2nd photoacoustic image data by post-processing.
Further, the display control unit 24 may output image data other than the photoacoustic image data (for example, ultrasonic image data). In this case, additional image processing may be performed.

<< Display device 25 >>
The display device 25 is a device that displays an image output from the display control unit 24, and typically uses a liquid crystal display or the like. The display device 25 may be provided separately from the photoacoustic device according to the present embodiment.

<Process flowchart>
Next, processing performed by the photoacoustic apparatus according to the present embodiment will be described. The following processing is characterized in that the display control unit 24 acquires the irradiation unit information and corrects the first photoacoustic image data generated by the information processing unit 23 based on the information. .
Note that the processing shown below is started in a state where a photoacoustic signal resulting from light irradiated on the subject is stored in a memory (not shown) in the apparatus, and the information processing unit 23 or the display control unit 24 is started. Shall be executed by

  First, in step S301, the information processing unit 23 acquires the photoacoustic signal digitally converted by the signal acquisition unit 20 and temporarily stores it.

  Next, in step S302, the information processing unit 23 uses the stored photoacoustic signal to generate first photoacoustic image data representing the distribution of optical characteristic values in the subject. For example, as first photoacoustic image data, image data representing an initial sound pressure distribution, a light absorption energy density distribution, or a distribution related thereto is generated. The image data is data depending on the light irradiation method.

Next, in step S303, the display control unit 24 acquires irradiation unit information.
The irradiation unit information is typically identification information indicating an identifier for identifying the individual or type of the light irradiation unit, but other information may be used. For example, the type of the probe to which the light irradiation unit is attached, the type and shape of the attachment unit that connects the light irradiation unit and the probe, the shape of the light irradiation region, information for identifying whether or not the light irradiation unit is attached, Information on the wavelength and intensity of light may be used.

  The irradiation unit information is information necessary for calculating a light amount distribution of light reaching a plurality of positions in the subject. As such information, for example, information electrically recorded on the acoustic probe 21 may be acquired via the signal acquisition unit 20. Further, information electrically recorded in the light irradiation unit 18 may be acquired via a control circuit in the light source 11. Further, the information electrically recorded in the light irradiation unit 18 may be acquired by the information processing unit 23 or the display control unit 24 via wireless. Thus, the information may be acquired by any method regardless of wired or wireless.

Next, in step S304, the display control unit 24 performs image processing on the first photoacoustic image data based on the acquired irradiation unit information.
As described above, the first photoacoustic image data is data representing the initial sound pressure distribution in the subject, the light absorption energy density distribution, and the like. Here, the light absorption energy density distribution will be described as an example.
The light absorption energy density distribution H (r) is proportional to the absorption coefficient distribution μ _a (r) in the subject and the light quantity Φ (r) reaching the subject, as represented by the equation (1). .

As can be seen from Equation (1), H (r) is greatly affected by the amount of light Φ (r) reaching the subject. Light irradiated to a subject that is a living body is diffused and absorbed, and is greatly attenuated as the propagation distance of the light increases. A general biological equivalent attenuation coefficient of 1.74 cm ⁻¹ represents that when light propagates 1.74 cm in the living body, the energy is at least 37% or less. That is, since the amount of light decreases exponentially according to the distance from the light irradiation unit, the brightness of the first photoacoustic image data varies greatly depending on the location. That is, the dynamic range to be displayed is widened. On the other hand, when the dynamic range is widened, the visibility is remarkably lowered, and it is easy to overlook a light absorber having a low luminance.

A specific example is shown in FIG. FIG. 4 is a diagram illustrating a state in which two light irradiation units are mounted on both sides of the acoustic probe 21. As shown in the figure, the distance d between the two light irradiation parts varies depending on the shape of the acoustic wave probe 21.
Reference numeral 41 is an example of the first photoacoustic image data obtained using the acoustic probe shown in FIG. 4A, and reference numeral 42 is the acoustic probe shown in FIG. 4B. It is an example of the 1st photoacoustic image data obtained using a child.
In the first photoacoustic image data, the luminance of the pixel decreases as the distance from the light irradiation region increases. In this example, since the interval between the light irradiation parts is narrower in FIG. 4A than in FIG. 4B, the amount of light reaching the deep part of the subject is reduced in the case of FIG. The brightness at the top is reduced. In FIG. 4B, the light amount distribution is described so as to change according to the depth. However, even if the depth is the same, if the horizontal position is different, a difference occurs in the light amount.
As described above, depending on the arrangement and type of the light irradiation unit, the distribution of light reaching the inside of the subject changes, and thus the visibility of the light absorber changes. In the present embodiment, in order to solve this problem, the first photoacoustic image data is corrected using the irradiation unit information.

In general, the light amount distribution in the subject (variation in the amount of light at a plurality of positions in the subject) can be calculated by solving the following light diffusion equation (or transport equation).

Here, D (r) is the diffusion coefficient distribution, φ (r) is the light quantity distribution in the subject, ν is the speed of light, μ _a (r) is the absorption coefficient distribution, S (r) is the distribution of irradiation light, and r is Represents a three-dimensional position within the subject. When the measurement site of the subject is determined, the average diffusion coefficient and absorption coefficient can be obtained. Therefore, if the distribution of the irradiation light as S (r) is known, the light amount distribution in the subject can be calculated.

As can be seen from FIG. 4, the light amount distribution of the irradiation light can be estimated based on the type (shape) of the probe to which the light irradiation unit is attached and the position to which the light irradiation unit is attached. That is, if the relative positional relationship between the acoustic wave probe and the light irradiation unit is known, the light amount distribution in the subject can be estimated, and the first photoacoustic image data can be corrected.
The relative positional relationship between the acoustic wave probe and the light irradiation unit can be known by acquiring the irradiation unit information described above.
For example, by acquiring the type of the acoustic wave probe and the type of the light irradiation unit, it is possible to specify the position where the light is irradiated on the subject, and as a result, as described above, Can be calculated. The light amount distribution may be stored in association with the irradiation unit information or may be calculated each time. In other words, the display control unit 24 may include a memory as a storage unit in which a plurality of irradiation unit information (identification information and the like) and information indicating variations in light quantity at a plurality of positions in the subject are associated. Further, the display control unit 24 may read information indicating the variation in the light amount at a plurality of positions in the subject corresponding to the irradiation unit information acquired in step 303 from the memory and use the information for correction processing for correcting the variation in the light amount. .

  As a result, for example, the first photoacoustic image data indicated by reference numeral 41 and reference numeral 42 is divided by the calculated light amount distribution to reduce the influence of the light amount distribution, as indicated by reference numeral 43, and after correction. Image data (second photoacoustic image data) can be obtained. That is, this correction process can correct variations in the image values of the first photoacoustic image data caused by variations in the amount of light at a plurality of positions in the subject. As a result, image data with high visibility can be provided to the user regardless of the shape of the acoustic wave probe attached to the light irradiation unit.

  In this example, the same light irradiation unit is mounted on the acoustic probe having a different shape. However, the light irradiation unit having different characteristics is mounted on the acoustic probe having the same shape. Even if it is a case, the same effect is acquired. In the former case, the identification information of the acoustic wave probe may be the irradiation unit information, and in the latter case, the identification information of the light irradiation unit may be the irradiation unit information. Of course, when both can be exchanged, both the identification information of the light irradiation unit and the identification information of the acoustic wave probe may be used as the irradiation unit information.

  Next, in step S305, the display control unit 24 arranges various display items related to the irradiation unit information along with the first or second photoacoustic image data as shown in FIG. Display above. In this example, the type of the light irradiation unit and the type of the acoustic wave probe are displayed together with the corrected photoacoustic image data (second photoacoustic image data).

  In addition, if the information to display is the information regarding a light irradiation part, it will not be restricted to these. For example, the type and shape of the light irradiation unit, the type and shape of the acoustic probe to which the light irradiation unit is attached, the type and shape of the attachment unit, the shape of the light irradiation region, whether or not the light irradiation unit is attached, You may display a light irradiation position. Moreover, when the light irradiation part has a light source, you may display the wavelength of light, irradiation light quantity, etc. In addition, the display regarding irradiation part information does not necessarily need to be performed.

In the example of FIG. 3, the second photoacoustic image data is generated in step S304 and displayed in step S305. However, the irradiation unit information is stored together with the first photoacoustic image data, and the second process is performed by post-processing. Photoacoustic image data may be generated.
In this case, the image data may be stored using a format (for example, DICOM format) that can hold information related to measurement separately from the image. For example, an image can be preserve | saved in the state which stored irradiation part information in the header.
This also makes it possible to perform image data correction processing using image processing software or the like installed in another computer. Of course, the processing in steps S304 and S305 may be performed after the information is stored.

Example 1
Next, an example of a photoacoustic apparatus to which the above-described embodiment is applied will be described.
In the present embodiment, a Ti: sa laser system excited by a double wave YAG laser is used as the light source 11. The Ti: sa laser can irradiate the subject with light having a wavelength between 700 and 900 nm. The laser light is guided to a light irradiation unit 18 incorporating a magnifying optical system using an optical fiber that is an optical transmission path. Further, the laser beam is expanded to 5 × 20 mm in the light irradiation unit. The light irradiator is attached to an acoustic probe (15 mm × 50 mm) used in a normal ultrasonic diagnostic apparatus. The acoustic wave probe is a linear probe having a center frequency of 7.5 MHz.

As shown in FIG. 2A, the light irradiator is attached with a clip, and can be attached to a probe of any shape. The acoustic wave probe is connected to the signal acquisition unit 20 and can receive data in synchronization with light irradiation.
The subject 15 is a rectangular parallelepiped phantom that simulates a living body, and includes titanium oxide as a scatterer and urethane rubber mixed with ink as an absorber. In addition, a wire that strongly absorbs light is embedded as the light absorber 14 in the rectangular parallelepiped urethane phantom.

The phantom is irradiated with light having a wavelength of 756 nm from a Ti: sa laser, and the obtained analog detection signal is stored as a digital signal in a memory in a computer that is the information processing unit 23. Next, image reconstruction is performed by software corresponding to the information processing unit 23 using the digital detection signal. Note that the UBP method in the time domain is used as the image reconstruction method. Thereby, the 1st photoacoustic image data which is light absorption energy density distribution is obtained.
In the first photoacoustic image data, the luminance of the wire target away from the light irradiation region is significantly smaller than that of the wire target near the light irradiation region due to light attenuation in the phantom.

  Next, image processing is performed on the first photoacoustic image data with software corresponding to the display control unit 24 installed in the same computer as the information processing unit 23 to correct the image with higher visibility. .

First, the computer acquires the ID (identification information) of the acoustic wave probe through the signal acquisition unit 20.
In the first embodiment, the light irradiation unit is common, and the light amount distribution in the subject varies depending on the type of acoustic probe to which the light irradiation unit is attached. Therefore, the ID of the acoustic wave probe is used as the irradiation unit information. In the present embodiment, the positional relationship among the ID, the light irradiation position, and the detection element is recorded in advance in a table (LUT) format in a memory in the computer, and the LUT data is used to store the ID in the subject. Estimate a rough light distribution.
Then, the first photoacoustic image is divided by the estimated light amount distribution to generate corrected second photoacoustic image data. As a result, the second photoacoustic image data with high visibility in which the luminance change of the target was reduced as indicated by reference numeral 43 was obtained.

Even if the acoustic wave probe is changed to a convex type having a different shape, the same processing is performed based on the ID (identification information) of the acoustic wave probe, and a similar highly visible image is obtained. I was able to.
As described above, according to Example 1, it was confirmed that a highly visible photoacoustic image can be generated even when the removable light irradiation unit is attached to various handheld probes having different shapes.

(Example 2)
In Example 2, an alexandrite laser that generates 755 nm light, which is a solid-state laser, is used as the light source 11. As a phantom, a urethane phantom simulating a breast shape is used. Inside the phantom, a light absorber similar to that of the first embodiment is disposed.
In this embodiment, a linear probe for three-dimensional images (outer shape 50 mm × 50 mm) is used as the acoustic wave probe 21. The oscillated laser beam is guided through a bundle type optical fiber to a light irradiation unit that can be connected to the acoustic wave probe. The light irradiation unit is configured to branch a plurality of fibers and to irradiate light from a plurality of locations.
As shown in FIG. 1, the light irradiation unit is connected to the linear probe for a three-dimensional image with a screw so that light can be irradiated from two directions.

In the second embodiment, both the light irradiation unit and the acoustic wave probe are interchangeable. Therefore, both the ID of the light irradiation unit and the ID of the acoustic wave probe are used as irradiation unit information.
A wireless IC tag is built in the light irradiation unit, and the ID of the light irradiation unit can be wirelessly transmitted to a computer that is an information processing unit and a display control unit. In addition, the signal acquisition unit can transmit the ID of the acoustic wave probe to a computer that is an information processing unit and a display control unit.

  In Example 2, the phantom is irradiated with light having a wavelength of 755 nm from an alexandrite laser, and the obtained photoacoustic signal is stored in a memory in a computer that is the information processing unit 23. Next, image reconstruction is performed by software corresponding to the information processing unit 23 using the photoacoustic signal. Note that a model-based reconstruction method is used as the image reconstruction method. Thereby, the first photoacoustic image data that is the initial sound pressure distribution is obtained.

Next, as in Example 1, image processing is performed on the first photoacoustic image data to correct the image with higher visibility.
In the present embodiment, the computer that is the display control unit acquires the ID (identification information) of the light irradiation unit from the light irradiation unit, and acquires the ID (identification information) of the acoustic wave probe from the signal acquisition unit. Then, the initial sound pressure distribution, which is the first photoacoustic image data, is corrected based on the positional relationship between the acoustic element and the light irradiation unit acquired based on each identification information. As a result, the second photoacoustic image data with high visibility in which the luminance change of the target was reduced as indicated by reference numeral 43 was obtained.

Even if the acoustic wave probe is changed to a convex type having a different shape, the same processing is performed based on the ID (identification information) of the acoustic wave probe, and a similar highly visible image is obtained. I was able to.
In this embodiment, in order to make the operator recognize what kind of light irradiation unit is attached, the light irradiation unit is attached and detached together with the corrected second photoacoustic image data. The type of light irradiation part was output.
As described above, according to Example 2, it was confirmed that a highly visible photoacoustic image can be generated even when the replaceable light irradiation unit is mounted on various handheld probes having different shapes. .

Example 3
The configuration of the apparatus in the third embodiment is almost the same as that in the second embodiment, but the light irradiation unit is connected to a computer that is a display control unit through an electric cable, and the light irradiation unit and the acoustic wave probe are It is different in that it is connected by a dedicated mounting portion as shown in FIG.

In the third embodiment, the light irradiating unit is replaceable along with the mounting unit. Therefore, the ID of the light irradiation unit is used as irradiation unit information.
In the third embodiment, image reconstruction is performed based on the photoacoustic signal in the same manner as in the second embodiment, and the light energy absorption density distribution that is the first photoacoustic image data is calculated. Moreover, the information regarding an attaching part is acquired through an electric cable from a light irradiation part.
Next, a computer that is an information processing unit or a display control unit generates and stores a DICOM image in which the first photoacoustic image data and information related to the attachment unit are simultaneously recorded.

  Next, the computer which is a display control part reads the information regarding an attachment part from the preserve | saved DICOM image, and correct | amends 1st photoacoustic image data by the method similar to Example 2. FIG. As a result, the second photoacoustic image data with high visibility in which the luminance change of the target was reduced as indicated by reference numeral 43 was obtained.

Moreover, even if the type of the light irradiation part was changed, the same processing was performed based on the ID (identification information) of the attachment part, and a similar highly visible image could be obtained.
In this example, in order to make the user recognize what kind of light irradiation unit is attached, the rough irradiation position of light on the subject is displayed together with the corrected second photoacoustic image data.
As described above, according to Example 3, it was confirmed that a highly visible photoacoustic image can be generated even when various light irradiation units having different characteristics are attached to the same probe.

(Other embodiments)
The description of each embodiment is an exemplification for explaining the present invention, and the present invention can be implemented with appropriate modifications or combinations without departing from the spirit of the invention.
For example, the present invention can be implemented as an information processing apparatus that performs at least a part of the above processing. The present invention can also be implemented as an information processing method including at least a part of the above processing. Also, the present invention can be executed as a system (subject information acquisition device) including the information processing device and a subject information acquisition method for executing the information processing method. The above processes and means can be freely combined and implemented as long as no technical contradiction occurs.

For example, in the description of the embodiment, the display control unit 24 corrects the image, but the image correction may be performed by the information processing unit 23.
In the description of the embodiment, the information indicating the identifier of the light irradiation unit or the acoustic wave probe is electrically read. However, for example, the image information obtained by encoding the identifier may be optically read. Good. Such electrical / optical information may be provided to the light irradiation unit or the acoustic wave probe, or may be provided to an attachment unit integrated with the light irradiation unit or the acoustic wave probe. . Further, information indicating an identifier may be acquired by an input operation performed by the operator.

The present invention is also realized by executing the following processing. That is, a program that realizes one or more functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and one or more processors in the computer of the system or apparatus read the program. It can also be realized by processing to be executed. It can also be realized by a circuit (for example, FPGA or ASIC) that realizes one or more functions.

  11: Light source, 20: Signal acquisition unit, 21: Acoustic wave probe, 23: Signal processing unit, 24: Display control unit

Claims (17)

An image showing characteristic information at a plurality of positions in the subject based on an acoustic wave generated by irradiating the subject with light through a light irradiating unit in which a positional relationship with the acoustic wave probe is defined. An information processing apparatus for processing data,
Image data acquisition means for acquiring the image data;
Information acquisition means for acquiring identification information for identifying the type of the acoustic wave probe;
Based on the identification information for identifying the type of the acoustic wave probe, the image of the image data resulting from variations in the amount of light emitted from the light irradiation unit at a plurality of positions within the subject. Correction means for correcting the influence on the value;
An information processing apparatus. The plurality of positions in the subject of the identification information for identifying the type of the acoustic wave probe and the light irradiated through the light irradiation unit in which the positional relationship with the acoustic wave probe is defined Storage means for associating and storing information indicating the variation in the amount of light in
Based on the identification information, the correction unit reads information indicating the variation in the amount of light corresponding to the identification information from the storage unit, and performs correction processing on the image data using the information indicating the variation in the amount of light. The information processing apparatus according to claim 1, wherein the information processing apparatus performs the processing.   The information processing apparatus according to claim 1, further comprising display control means for outputting the identification information and the image data as an image.   4. The information processing apparatus according to claim 1, wherein the information acquisition unit acquires the identification information electrically stored in the acoustic wave probe. 5.   The said information acquisition means acquires the said identification information by optically reading the image information attached | subjected to the said acoustic probe, The any one of Claim 1 to 3 characterized by the above-mentioned. Information processing device. The information processing apparatus according to claim 1, wherein the information acquisition unit acquires the identification information based on an input operation performed by a user.   The said image data acquisition means produces | generates the said image data based on the electrical signal converted from the said acoustic wave with the said acoustic wave probe, The any one of Claim 1 to 6 characterized by the above-mentioned. The information processing apparatus described. A light irradiation unit for irradiating the subject with light;
An acoustic wave probe for converting an acoustic wave generated by light irradiation to the subject into an electrical signal;
A mounting part for attaching at least one of the light irradiation part and the acoustic wave probe so as to define a positional relationship between the light irradiation part and the acoustic wave probe;
An information processing device that generates image data indicating characteristic information at a plurality of positions in the subject based on the electrical signal;
Have
The information processing apparatus includes:
Information acquisition means for acquiring identification information for identifying the type of the acoustic wave probe;
Based on the identification information for identifying the type of the acoustic wave probe, the image value of the image data resulting from the variation in the amount of light at the plurality of positions in the subject of the light irradiated through the light irradiation unit Correction means for correcting the influence on
The system characterized by including. An image showing characteristic information at a plurality of positions in the subject based on an acoustic wave generated by irradiating the subject with light through a light irradiating unit in which a positional relationship with the acoustic wave probe is defined. An information processing apparatus for processing data,
Image data acquisition means for acquiring the image data;
Information acquisition means for acquiring irradiation unit information which is information relating to the light irradiation unit;
Correction means for correcting the influence of the light irradiated through the light irradiation unit on the image value of the image data caused by the variation in the amount of light at a plurality of positions in the subject based on the irradiation unit information; ,
An information processing apparatus comprising: The irradiation unit information includes information on a relative position between the acoustic wave probe and the light irradiation unit,
The correction means corrects an influence on the image value of the image data caused by the variation in the light amount based on information on a relative position between the acoustic wave probe and the light irradiation unit. The information processing apparatus according to claim 9. The irradiation unit information includes identification information for identifying the type of the light irradiation unit,
The information processing apparatus further includes a storage unit that stores the identification information and information indicating variations in the light amount at the plurality of positions in the subject of light irradiated on the subject via the light irradiation unit in association with each other. ,
Based on the identification information, the correction unit reads information indicating the variation in the amount of light corresponding to the identification information from the storage unit, and performs correction processing on the image data using the information indicating the variation in the amount of light. The information processing device according to claim 9, wherein the information processing device is performed. The information processing apparatus according to claim 11, wherein the information acquisition unit acquires the identification information based on an input operation performed by a user.   The information processing apparatus according to claim 9, further comprising display control means for outputting the irradiation unit information and the image data as an image. The information processing apparatus according to any one of claims 9 to 13, wherein the information acquisition unit acquires the irradiation unit information electrically stored in the light irradiation unit. The information according to any one of claims 9 to 13, wherein the information acquisition means acquires the irradiation unit information by optically reading image information attached to the light irradiation unit. Processing equipment. The said image data acquisition means produces | generates the said image data based on the electrical signal converted from the said acoustic wave with the said acoustic wave probe, The any one of Claim 9 to 15 characterized by the above-mentioned. The information processing apparatus described. A light irradiation unit for irradiating the subject with light;
An acoustic wave probe for converting an acoustic wave generated by light irradiation to the subject into an electrical signal;
A mounting part for attaching at least one of the light irradiation part and the acoustic wave probe so as to define a positional relationship between the light irradiation part and the acoustic wave probe;
An information processing device that generates image data indicating characteristic information at a plurality of positions in the subject based on the electrical signal;
Have
The information processing apparatus includes:
Information acquisition means for acquiring irradiation unit information which is information relating to the light irradiation unit;
Correction means for correcting the influence of the light irradiated through the light irradiation unit on the image value of the image data caused by the variation in the amount of light at a plurality of positions in the subject based on the irradiation unit information; ,
A system characterized by including.

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