JP2013103022A - Acoustic wave acquisition device and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique to understand and correct the variation of reception characteristics among receiving elements of a probe used for photoacoustic measurement.SOLUTION: An acoustic wave acquisition device, which receives an acoustic wave generated from a subject irradiated with light and calculates subject information, includes: a light source; the plurality of receiving elements which receive the acoustic wave and generate the reception signal; a correction unit which obtains the reception characteristic of the plurality of receiving elements from the plurality of reception signals generated from the acoustic wave generated when the light is irradiated to the plurality of receiving elements from the light source, and corrects the plurality of reception signals, generated from the acoustic wave generated when the light is irradiated to the subject from the light source, by using the reception characteristics; and a processing unit which calculates the subject information by using the corrected reception signal.

Description

  The present invention relates to an acoustic wave acquisition apparatus and a control method thereof.

  Research in optical imaging technology for generating information in a subject obtained by irradiating the subject with light from a light source as image data is in progress in the medical field. As one of the optical imaging techniques, there is a photoacoustic measurement using a photoacoustic tomography (PAT) technique.

  According to Non-Patent Document 1, in photoacoustic measurement, a subject is irradiated with pulsed light generated from a light source. Then, the probe detects changes with time of the acoustic wave generated from the living tissue that has absorbed the energy of light propagated and diffused in the subject at a plurality of locations surrounding the subject. Then, the information processing apparatus performs mathematical analysis processing (image reconstruction processing) on the obtained signal to visualize information related to the optical characteristic value inside the subject. Thereby, it is possible to obtain subject information in the subject, such as initial sound pressure, optical characteristic values (especially light energy absorption density and absorption coefficient) and their distribution, and distribution of the absorber in the living body and location of the malignant tumor It can be used for identification.

In photoacoustic tomography, an initial sound pressure p ₀ generated at an initial sound pressure generation point (light absorber) inside the subject is expressed by the following equation (1).
p ₀ = (βc ² / C _p ) μ _a F = ΓA (1)
Here, β is the volume expansion coefficient [K ⁻¹ ], c is the speed of sound in the subject [cm / sec], and Cp is the specific heat [J / K · kg]. Further, μ _a is a light absorption coefficient [cm ⁻¹ ], F is a light intensity (fluence) [J / cm ² ], and A is an accumulated energy [J / cm ³ ] per unit volume. Γ is a Gruneisen coefficient, and Γ = βc ² / Cp.

As can be seen from Equation (1), in the photoacoustic tomography, the initial sound pressure p ₀ is proportional to the light intensity F.
Further, in Non-Patent Document 2, blood and organs in a mouse body are observed by a multi-probe arranged on an arc by photoacoustic tomography.

M, Xu, L.V.Wang “Photoacoustic imaging in biomedicine”, Review of scientific instruments, 77, 041101 (2006) Fairway Medical, A.A.Oraevsky “Whole-body three-dimensional optoacoustic tomography system for small animals” Journal of Biomedical Optics 146, 064007 (2009)

  In photoacoustic tomography, an ultrasonic probe is generally used to receive an acoustic wave. Specifically, a multi-probe in which a plurality of receiving elements are arranged is generally used for the purpose of efficiently detecting signals from a plurality of locations. Here, the receiving element of the probe is formed of a piezoelectric element or the like, and each receiving element has variations in receiving characteristics depending on the working accuracy. Even in an ultrasonic receiving element using the MEMS technology, even if it is manufactured using a semiconductor process, the receiving characteristics of each receiving element vary.

  Further, even when measurement using a receiving element is performed on a subject such as a living body, the receiving characteristics of each receiving element may vary. In general photoacoustic measurement, in order to suppress reflection of acoustic waves, an acoustic matching agent such as gel or water may be filled between the subject and the receiving probe. For example, in Non-Patent Document 2, a subject and a probe are placed in a water tank, and photoacoustic measurement is performed in water. In this case, it is inevitable that the probe surface always comes into contact with the acoustic matching agent. Therefore, the probe surface is deteriorated due to use over time, and the reception characteristics of each receiving element vary.

  Here, if reception characteristics of each receiving element, for example, sensitivity characteristics in the frequency band of acoustic waves, vary, the signal intensity of the photoacoustic wave received by each receiving element varies. In Non-Patent Document 2, there is no description that sensitivity characteristics between the receiving elements are corrected, and image reconstruction is performed on the assumption that the receiving characteristics between the receiving elements are uniform. If the reception characteristics of the receiving element vary, as a result, intensity unevenness occurs on the screen after reconstruction, which causes a loss of measurement reproducibility.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for grasping and correcting variations in reception characteristics between receiving elements of a probe used for photoacoustic measurement.

The present invention employs the following configuration. That is,
An acoustic wave acquisition apparatus that acquires an acoustic wave generated from a subject irradiated with light and calculates subject information representing characteristics inside the subject,
A light source;
A plurality of receiving elements that receive acoustic waves and generate received signals;
While obtaining the reception characteristics of the plurality of reception elements from a plurality of reception signals generated from acoustic waves generated from the plurality of reception elements when light from the light source is irradiated onto the plurality of reception elements, Correction that corrects a plurality of reception signals generated from acoustic waves generated from the subject and received by the plurality of receiving elements when the light from the light source is irradiated on the subject using the reception characteristics And
A processing unit that calculates the subject information using the reception signal corrected by the correction unit;
It is an acoustic wave acquisition device characterized by having.

The present invention also employs the following configuration. That is,
A control method of an acoustic wave acquisition apparatus having a light source, a plurality of receiving elements that receive an acoustic wave and generate a reception signal, a correction unit, and a processing unit,
The light source irradiates light to the plurality of receiving elements;
The correction unit obtains reception characteristics of the plurality of reception elements from a plurality of reception signals generated from acoustic waves generated from the plurality of reception elements;
The light source irradiates the subject with light; and
The correction unit corrects a plurality of reception signals generated from acoustic waves generated from the subject and received by the plurality of reception elements, using the reception characteristics;
The processing unit calculates subject information representing characteristics inside the subject using the reception signal corrected by the correction unit;
It is a control method of the acoustic wave acquisition apparatus characterized by having.

  ADVANTAGE OF THE INVENTION According to this invention, the technique for grasping | ascertaining and correct | amending the dispersion | variation in the receiving characteristic between the receiving elements of the probe used for a photoacoustic measurement can be provided.

The figure which shows the structure of the acoustic wave acquisition apparatus in this invention. The figure which shows the structure of the signal processing part in this invention. The flowchart of the calculation of the receiving characteristic in this invention. The flowchart of the correction | amendment of the signal in this invention. The figure which shows the structure of the acoustic wave acquisition apparatus in Embodiment 8 of this invention. The figure which shows the structure of the acoustic wave acquisition apparatus in Embodiment 3 and 4 of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to these. The acoustic wave acquisition apparatus of the present invention has an initial sound pressure generated at each initial sound pressure generation point (light absorber) in the subject due to the photoacoustic effect when the subject is irradiated with light (electromagnetic wave). The acoustic wave is received by the receiving element of the probe and converted into a reception signal that is an analog electric signal. Then, the received signal is amplified and AD converted by the signal processing unit and digitized. Therefore, the reception signal of the present invention is a concept including an analog electric signal and a digital electric signal, and if it is necessary to distinguish both, they are called “analog reception signal” or “digital reception signal”. The signal processing unit also performs image reconstruction on the digital received signal and generates subject information for each initial sound pressure generation point. The acoustic wave includes an elastic wave called a sound wave, an ultrasonic wave, etc., and the acoustic wave generated by the photoacoustic effect is particularly called a photoacoustic wave or an optical ultrasonic wave.

The subject information includes initial sound pressure, “optical characteristic values” such as “light absorption coefficient value”, “oxygen saturation value”, and “light energy absorption density” based on the initial sound pressure, and concentration information of biological components. The concentration information includes, for example, oxygen saturation, oxidized / reduced hemoglobin concentration, glucose concentration, and the like. Also, an “image” representing “characteristic distribution” such as “initial sound pressure distribution”, “light absorption coefficient distribution”, “oxygen saturation distribution”, and image data for generating an image are obtained. Alternatively, it may include a concentration distribution of a photoacoustic contrast agent administered from outside the body for the purpose of visualizing a living tissue by photoacoustic measurement.
These pieces of subject information are information related to the inside of the subject. Therefore, the acoustic wave acquisition apparatus of the present invention can also be called a subject information acquisition apparatus.

<Embodiment 1>
First, the configuration of the acoustic wave acquisition apparatus according to the present embodiment will be described with reference to FIG. The acoustic wave acquisition apparatus of the present embodiment is an apparatus that images the inside of a subject with image data based on the subject information acquired from photoacoustic waves. When the subject is a living body, the acoustic wave acquisition device is used for the purpose of diagnosing malignant tumors, vascular diseases, etc., follow-up of chemotherapy, and grasping the distribution of the photoacoustic contrast agent administered into the living body. Image information.

(Device configuration)
The acoustic wave acquisition apparatus of the present embodiment includes a light source 100, an optical system 101, a probe 103, a reception characteristic calculation unit 104, a signal processing unit 105, an image display unit 106, and a control unit 107 as hardware configurations. Light (diffused pulsed light) 102 is irradiated from the optical system 101 to the subject or the probe. An object (not shown) such as a living body is placed at a position where it contacts the probe. A holding plate for holding the subject may be provided as necessary.

(light source)
When the subject is a living body, the light source emits light of a specific wavelength that is absorbed by a specific component (for example, a light absorber such as blood or a contrast medium for photoacoustics) in the living body. As the light source, a pulse light source capable of generating pulsed light on the order of several nanometers to several hundred nanoseconds is preferable. A laser is preferable as the light source, but a light emitting diode or the like may be used instead of the laser. As the laser, various lasers such as a solid laser, a gas laser, a dye laser, and a semiconductor laser can be used.
In the present embodiment, an example of a single light source is shown, but a plurality of light sources may be used. As a situation where a plurality of light sources are used, first, there are cases where a plurality of light sources that oscillate the same wavelength are used in order to increase the irradiation intensity of the light irradiating the living body. In addition, in order to measure the difference in the optical characteristic value distribution depending on the wavelength, a plurality of light sources having different oscillation wavelengths may be used. Note that if a laser using a dye capable of converting the oscillation wavelength or a laser using OPO (Optical Parametric Oscillators) is used as the light source, it is also possible to measure the difference in the optical characteristic value distribution depending on the wavelength. Regarding the wavelength to be used, a region of 700 nm to 1100 nm, which is less absorbed in the living body, is preferable. However, when obtaining the optical characteristic value distribution of the living tissue relatively near the surface of the living body, it is also possible to use a wavelength range wider than the above wavelength range, for example, a wavelength range of 400 nm to 1600 nm.
The time width of the light pulse at this time is preferably set to such an extent that the heat / stress confinement condition is satisfied in order to efficiently confine the absorbed energy in the light absorber. Typically, it is about 1 nanosecond to 200 nanoseconds.
When the light absorber absorbs light energy, the temperature of the light absorber rises, volume expansion occurs due to the temperature rise, and an acoustic wave is generated.

(Optical system)
The optical system is an optical component such as a lens, a mirror, or an optical fiber that guides pulsed light from a light source to a subject. When there are multiple light sources, it is possible to guide the light to the surface of the living body using an optical fiber for each light source, or to guide the light from each light source to a single optical fiber, All light may be guided to the living body. In addition, optical components such as a mirror that reflects light and a lens that collects and enlarges light and changes its shape can also be used. As such an optical component, any optical component may be used as long as light emitted from the light source is irradiated in a desired shape onto the light irradiation region of the subject surface.

(Probe)
The probe 103 receives an acoustic wave and converts it into an electrical signal. For measurement of photoacoustic waves generated from a living body, an ultrasonic band of 100 KHz to 100 MHz is generally used. Therefore, it is desirable to use an ultrasonic detector capable of receiving the above frequency band for the probe 103. Specifically, a transducer using a piezoelectric phenomenon such as PZT (lead zirconate titanate) or PVDF (PolyVinyllineDiFluoride) can be preferably used. In addition, any probe may be used as long as it can detect an acoustic wave, such as a transducer using light resonance and a transducer using change in capacitance. In addition to the above probe, a probe surface protective film, an acoustic matching agent, and the like are formed, thereby generating an acoustic wave corresponding to the intensity of irradiated light and detecting the probe. If so, it can be used for correction of sensitivity characteristics in the present invention.
The probe 103 according to this embodiment uses a plurality of receiving elements arranged two-dimensionally. By using such a two-dimensional array element, acoustic waves can be detected at a plurality of locations simultaneously, and part or all of the mechanical scanning of the measurement region of the subject can be omitted. Therefore, the detection time can be shortened and the influence of the vibration of the subject can be reduced. Further, it is desirable to use an acoustic matching agent such as gel or water for suppressing reflection of sound waves between the acoustic wave detector 103 and the subject.
An object of the present invention is to deal with variations in reception characteristics among the respective reception elements due to a decrease in sensitivity characteristics over time during use.

(Signal processing unit, image display unit and control unit)
The signal processing unit 105 performs amplification processing when the intensity of the reception signal generated by the probe 103 is small. Further, the analog reception signal is converted into a digital reception signal by the AD converter. The signal processing unit 105 further performs image reconstruction processing on the digital received signal to generate image data representing the subject information inside the subject. As described above, the signal processing unit has a signal processing function and an image reconstruction function for the received signal. The signal processing unit may be a set of circuits that implement each function, or may be configured as software that implements each function on the information processing apparatus.
The image display unit 110 displays an image inside the subject formed based on the image data.
Further, all the components of the acoustic wave acquisition apparatus are controlled by the control unit 107 via a control line (not shown).

(Outline of reception characteristics calculation)
The outline of the procedure for calculating the receiving characteristics for each receiving element of the probe is as follows. First, the probe is irradiated with light having a known intensity distribution. The photoacoustic wave generated from the piezoelectric body of the probe or the protective film on the surface of the probe or the acoustic matching agent upon receiving the light is received by the receiving element of the probe.

The intensity distribution of the irradiated light is measured in advance by a photoelectric conversion element such as a beam profiler or a laser power meter.
Diffused pulse light used for photoacoustic measurement can also be used as the light directly irradiated to the probe. However, since the optical energy of the diffusion pulse light generally has a Gaussian distribution, it is desirable to perform a uniform process such as diffusion using a diffusion plate or flat top molding in the optical system. By uniformly irradiating the surface of the probe with the uniform light, it is possible to irradiate a plurality of receiving elements with light having the same intensity.

Based on the acoustic wave generated from the probe irradiated with the uniformed light, a reception signal is generated by each receiving element, transferred to the reception characteristic calculation unit 104 through processing in the signal processing unit. The reception characteristic calculation unit calculates reception characteristics for each reception element from the reception signal.
Here, examples of the “reception characteristics” include sensitivity characteristics and frequency characteristics of each receiving element. In the present embodiment, a case where the reception characteristic calculation unit 104 calculates sensitivity characteristics will be described. In the case of the sensitivity characteristic, the maximum amplitude of the received signal with respect to light having a known intensity is calculated. Since each pulse light has a known intensity distribution and is irradiated with an equal amount of light especially when uniform light is used, the sound pressure of the acoustic wave received by each probe is equal. Therefore, variations in sensitivity characteristics can be grasped by comparing the maximum amplitudes of received signals derived from the respective receiving elements.
Thereby, the dispersion | variation in the receiving characteristic of a some receiving element can be grasped | ascertained with the simple structure peculiar to an acoustic wave acquisition apparatus.

(Outline of received signal correction)
An outline of processing for correcting a received signal based on the acquired reception characteristics will be described. The basic idea is that if the sensitivity characteristics vary between receiving elements, the intensity of the received signal will not be accurate, and the subject information cannot be acquired accurately, so the received signal intensity of the receiving element with low sensitivity will be amplified. Thus, correction is performed to reduce variation.
Specifically, a correction value for the received signal is obtained based on the reception characteristic calculated by the reception characteristic calculation unit. Then, a calculation for correcting the received signal by the correction value is performed. For example, when the sensitivity characteristic is obtained as the reception characteristic, the reception signal of the reception element is multiplied by the reciprocal of the sensitivity of the reception element as a correction value. In the present invention, a collection of correction values for individual receiving elements is referred to as correction data.

(Specific steps)
The measurement of reception characteristics, generation of correction data, and correction of received signals will be specifically described with reference to the operation flow.
FIG. 2 shows an internal block of the signal processing unit 105 in the present embodiment. Signal processing unit 105
Includes an amplifier 201, an A / D converter 202, a correction unit 203, and a reconstruction unit 204.

FIG. 3 shows an operation flow of reception characteristic calculation in this embodiment. Here, data used for correcting the sensitivity characteristic among the reception characteristics is acquired.
(Step S301) The acoustic wave acquisition device is activated. This operation flow is usually executed in a preparatory stage after the apparatus is started and before actual photoacoustic measurement is performed. However, this operation flow can also be performed during photoacoustic measurement.
(Step S302) The probe is directly irradiated with light having a known intensity distribution. Then, an acoustic wave is generated by the photoacoustic effect on the member on the probe surface, the acoustic matching layer, or the protective film. This acoustic wave is received by the probe and converted into an analog received signal. In this operation flow, uniform light with a known light intensity distribution is uniformly applied to the probe surface. In this way, correction data for sensitivity characteristics can be calculated with a single laser irradiation.
(Step S <b> 303) The signal processing unit 105 amplifies the analog reception signal by the signal amplifier 201 and then converts the analog reception signal into a digital reception signal by the AD converter 202. The converted reception signal is sent to reception characteristic calculation section 104.
(Step S304) The reception characteristic calculation unit 104 detects the maximum value of the amplitude for each reception signal corresponding to each reception element of the probe. Thereby, the maximum intensity of the received signal obtained by each receiving element is calculated.
(Step S305) The reception characteristic calculation unit 104 calculates the reciprocal of the maximum intensity in each reception signal and stores it as reception characteristic data (sensitivity characteristic in this embodiment) (the storage unit is not shown). The reception characteristic calculation unit may communicate with an external memory to store information. Further, the reception characteristic calculation unit 104 may be configured such that only the maximum intensity is obtained, and the correction unit 203 and the reconstruction unit 204 are provided with arithmetic processing means and a storage unit for sensitivity correction. In this procedure, the signal processing unit and the reception characteristic calculation unit cooperate to realize the function of the correction unit of the present invention.

FIG. 4 shows an operation flow for correcting an actual measurement signal using the reception characteristics measured above in the present embodiment.
(Step S401) The subject is irradiated with light having a known light intensity distribution from the light source. Then, the probe receives the acoustic wave generated by the light absorber inside the subject and converts it into a reception signal that is an analog electric signal.
(Step S402) After the signal amplifier 201 of the signal processing unit amplifies the analog reception signal, the AD converter 202 converts it into a digital reception signal.
(Step S403) The correction unit 203 acquires the reception characteristic data stored in the reception characteristic calculation unit 104. Then, correction data is generated based on the reception characteristic data, in this case, the sensitivity characteristic for each reception element. Then, the received signal is corrected using the correction data. Specifically, for each receiving element, the signal intensity is multiplied by a correction value. Since the correction value is the reciprocal of the sensitivity, the multiplier having a lower sensitivity has a larger multiplier. As a result, the difference in sensitivity between the receiving elements is corrected, and variations are reduced. The corrected received signal is sent to the reconstruction unit 204.
(Step S404) The reconstruction unit 204 performs image reconstruction based on the received signal. In the reconstruction, a known method such as phasing addition or a back projection method can be applied. The reconstruction unit corresponds to the processing unit of the present invention.
(Step S405) The image display unit 106 displays the reconstructed image.

  As described above, according to the method of the present embodiment, the influence of the sensitivity variation of the probe can be reduced, and more accurate subject information can be acquired by photoacoustic measurement. Therefore, when this is imaged, an image with higher accuracy is obtained, and diagnosis with high accuracy is possible.

<Embodiment 2>
In the present embodiment, an example will be described in which the reception characteristic calculation unit obtains the frequency characteristic as the reception characteristic of the reception element. In the first embodiment, the correction value is calculated using the maximum signal strength, but in the present embodiment, the reception characteristic calculation unit 104 does not calculate the maximum strength of the received signal, but performs frequency analysis such as FFT, The signal intensity (power spectrum) for each frequency of the received signal is calculated. By calculating the reciprocal of this power spectrum, a correction value is obtained for each frequency, so that correction data considering frequency characteristics can be obtained.

  This frequency-dependent correction data is applied to actual measurement results as follows. In the first embodiment, in S403 of FIG. 4, there is one sensitivity correction value for each receiving element, and this is multiplied by the signal intensity of each receiving element. On the other hand, the reception characteristic of this embodiment is a frequency characteristic, and the correction data also depends on the frequency. Thus, frequency analysis such as FFT is performed on the acquired received signal, and correction data is obtained by taking the reciprocal of the power spectrum. Then, the received signal subjected to frequency analysis and the correction data are multiplied for each corresponding frequency. The obtained reception signal data subjected to frequency-dependent sensitivity correction is returned to reception signal data on the time axis by inverse FFT or the like. Accordingly, it is possible to reduce the variation of the received signal by correcting the frequency-dependent sensitivity characteristic, and to generate accurate subject information.

<Embodiment 3>
In the present embodiment, a description will be given of a case where a second light source different from the laser light source for photoacoustic measurement is provided to directly irradiate the probe with light having an arbitrary light intensity distribution when obtaining reception characteristics. . In this case, the light source for irradiating the subject with light is referred to as a first light source.
As shown in FIG. 6, the acoustic wave acquisition apparatus of the present embodiment is different from the photoacoustic measurement light source 100 for irradiating the probe surface with light when acquiring reception characteristic information. A second light source 108 is included. As the second light source, in addition to the above-described light source, laser diode, holocathode lamp, etc., a light source capable of irradiating uniform light such as an integrating sphere light source can be used. In addition, the light having a known light intensity distribution can also be used by using a photoelectric conversion element such as a beam profiler. By irradiating the probe surface with light having a known light intensity distribution, a signal corresponding to the light intensity distribution irradiated to each receiving element can be received. As a result, the receiving characteristics of each receiving element are obtained, and the sensitivity correction value can be obtained based on the receiving characteristics.

<Embodiment 4>
In the present embodiment, a description will be given of a case where light having an arbitrary intensity is sequentially irradiated to each receiving element when obtaining reception characteristics.
As shown in FIG. 6, the acoustic wave acquisition apparatus according to the present embodiment includes a probe moving unit 109. By moving the probe by the probe moving means, it is possible to irradiate light having a known light intensity in order to a plurality of receiving elements of the probe and receive photoacoustic waves. By using the probe moving means a plurality of times in accordance with the probe and the size of light, it is possible to receive photoacoustic waves when light having a known light intensity is irradiated to all the receiving elements.
The moving means may be any means that can move the probe position relative to the irradiation light. For example, it is possible to adopt a configuration in which the position of the probe is fixed and the optical system for guiding the irradiation light is driven. Furthermore, a second light source for calculating reception characteristics may be provided as in the third embodiment, and the second light source may be moved relative to the probe.
As a result, the receiving characteristics of each receiving element are obtained, and the sensitivity correction value can be obtained based on the receiving characteristics.

<Embodiment 5>
In the present embodiment, a method for equalizing the amount of light irradiated per unit time on the probe surface when obtaining reception characteristics will be described.
That is, the surface of the probe is scanned for an arbitrary time from a laser light source used for photoacoustic measurement or a light source provided for evaluating reception characteristics in Embodiment 3 using a known optical scanning method such as a beam scanner. While irradiating with light. Thereby, the light quantity irradiated per unit time on the probe surface can be made uniform. The reception signals detected during an arbitrary time are integrated, and the reception characteristic data in each reception element is obtained from the magnitude of the integrated value, and the sensitivity can be corrected based on the reception characteristic data.

<Embodiment 6>
In the present embodiment, a method for obtaining more accurate subject information by arbitrarily setting a threshold value of a reception signal in each reception element will be described. A method for confirming the deterioration of the probe over time will also be described.
In this embodiment, an arbitrary threshold is set for the intensity of the received signal obtained by each receiving element when the probe is directly irradiated with light having a known intensity distribution to grasp the reception characteristics. In the image reconstruction, receiving elements whose received signal strength is smaller than a set threshold value are excluded and are not used for obtaining object information. Then, a receiving element having a sensitivity characteristic lower than a predetermined threshold is excluded from the calculation of the subject information.
As a result, only the received signal generated by the receiving element having a certain degree of sensitivity is used for the image reconstruction, so that it is possible to reduce the intensity unevenness of the optical characteristic value distribution after the reconstruction. Further, by performing this operation at an arbitrary time interval, it is possible to confirm the deterioration in performance of the receiving element over time. The time interval of the operation for obtaining the reception characteristics may be a predetermined interval or may be performed according to a user instruction.

<Embodiment 7>
In this embodiment, each receiving element is irradiated with light whose output is changed within an arbitrary light intensity range, and the received signal between the receiving elements is corrected from the received signal intensity at that time, and the output change is also corrected. A method for confirming the probe response will be described.
In this case, when the probe is directly irradiated with light with a known intensity distribution and the reception characteristics at each receiving element are grasped, the output characteristics of the light intensity of the irradiation light can be changed arbitrarily, so that the reception characteristics are detailed. Can be measured. Specifically, since each receiving element receives an acoustic wave having an intensity corresponding to the directly irradiated light intensity distribution, the received signal of each receiving element is changed by changing the light intensity of the irradiated light in an arbitrary range. Can acquire information on sensitivity characteristics having linearity. As a result, only receiving elements having reception characteristics in an arbitrary range can be used for image reconstruction, so that it is possible to reduce intensity unevenness of the optical characteristic value distribution after reconstruction. Further, by performing this operation at an arbitrary time interval, it is possible to check the performance deterioration of the probe over time.

<Eighth embodiment>
In the present embodiment, a method for correcting reception characteristics between receiving elements via a calibration probe will be described.
FIG. 5 is a diagram illustrating an acoustic wave acquisition apparatus according to the present embodiment. A second probe 503 for calibration different from the first probe 103 to be corrected is provided, and the received signal of the probe 103 is corrected based on the signal response of the calibration probe 503. Specifically, a part or all of the light 102 whose light intensity distribution is directly irradiated onto the first probe 103 is guided to the second probe 503 for calibration by the optical system 501. Then, the signal response of the probe corresponding to the light intensity is normalized and corrected based on the signal response of the calibration probe. Reference numeral 502 denotes irradiation light whose intensity distribution is known, and reference numeral 505 denotes a signal processing unit of the calibration probe.

  100: light source, 103: probe, 104: reception characteristic calculation unit, 105: signal processing unit, 203: correction unit, 204: reconstruction unit

Claims (8)

An acoustic wave acquisition apparatus that acquires an acoustic wave generated from a subject irradiated with light and calculates subject information representing characteristics inside the subject,
A light source;
A plurality of receiving elements that receive acoustic waves and generate received signals;
While obtaining the reception characteristics of the plurality of reception elements from a plurality of reception signals generated from acoustic waves generated from the plurality of reception elements when light from the light source is irradiated onto the plurality of reception elements, Correction that corrects a plurality of reception signals generated from acoustic waves generated from the subject and received by the plurality of receiving elements when the light from the light source is irradiated on the subject using the reception characteristics And
A processing unit that calculates the subject information using the reception signal corrected by the correction unit;
An acoustic wave acquisition apparatus comprising: The acoustic characteristic according to claim 1, wherein the reception characteristic is a sensitivity characteristic obtained based on the intensity of reception signals generated by the plurality of reception elements when irradiated with light having a known intensity. Wave acquisition device. The acoustic wave acquisition apparatus according to claim 2, wherein the processing unit does not use a reception signal generated by a receiving element having a sensitivity characteristic lower than a predetermined threshold for calculation of subject information. The acoustic wave acquisition apparatus according to claim 1, wherein the reception characteristic is a frequency characteristic obtained based on a power spectrum of reception signals generated by the plurality of reception elements. The light source includes a first light source that irradiates light to the subject and a second light source that irradiates light to the plurality of receiving elements in order to obtain the reception characteristics. The acoustic wave acquisition apparatus according to any one of 1 to 4. The light applied to the plurality of receiving elements in order to obtain the reception characteristics is subjected to a uniform light intensity distribution process, according to any one of claims 1 to 5. Acoustic wave acquisition device. The acoustic wave acquisition apparatus according to claim 1, wherein the correction unit obtains reception characteristics of the plurality of reception elements at predetermined time intervals. A control method of an acoustic wave acquisition apparatus having a light source, a plurality of receiving elements that receive an acoustic wave and generate a reception signal, a correction unit, and a processing unit,
The light source irradiates light to the plurality of receiving elements;
The correction unit obtains reception characteristics of the plurality of reception elements from a plurality of reception signals generated from acoustic waves generated from the plurality of reception elements;
The light source irradiates the subject with light; and
The correction unit corrects a plurality of reception signals generated from acoustic waves generated from the subject and received by the plurality of reception elements, using the reception characteristics;
The processing unit calculates subject information representing characteristics inside the subject using the reception signal corrected by the correction unit;
A method for controlling an acoustic wave acquisition apparatus comprising:

Images