JP6091235B2 - Subject information acquisition device - Google Patents

Description

  The present invention relates to a subject information acquisition apparatus.

  One of apparatuses that use light to image a subject such as a living body is a photoacoustic imaging apparatus using a photoacoustic effect. The photoacoustic imaging apparatus is expected as a medical device that replaces an ultrasonic diagnostic apparatus, an X-ray apparatus, an MRI apparatus, and the like that have been conventionally used particularly in the diagnosis of skin cancer and breast cancer.

  In general, in breast cancer diagnosis in the mammary gland department, benign and malignant diagnosis is comprehensively performed based on palpation and the results of using the above-described modalities. Among them, the photoacoustic imaging apparatus has a great advantage in terms of patient burden because it can perform non-exposure and non-invasive image diagnosis by using light during imaging. Therefore, it is expected to be used in screening for breast cancer and early diagnosis instead of an X-ray apparatus that is difficult to repeatedly diagnose.

  The photoacoustic effect is that when a living tissue is irradiated with measurement light such as visible light or near-infrared light, a light-absorbing substance (such as hemoglobin in the blood) inside the living body absorbs light energy and instantly expands. It is a phenomenon that generates acoustic waves. The acoustic wave generated at this time is called a photoacoustic wave. In the photoacoustic imaging apparatus, information on a living tissue is visualized by measuring the photoacoustic wave. Such a tomographic technique using the photoacoustic effect is also referred to as photoacoustic tomography (PAT). According to photoacoustic imaging, the light energy absorption density distribution, that is, the density distribution of the light absorbing substance in the living body can be measured quantitatively and three-dimensionally.

According to Non-Patent Document 1, in PAT, the sound pressure (P) of a photoacoustic wave is expressed by the following equation (1).
P = Γ · μ _a · Φ (1)
Here, Γ is a Gruneisen coefficient which is an elastic characteristic value, which is obtained by dividing the product of the square of the volume expansion coefficient (β) and the speed of sound (c) by the specific heat (C _p ). μ _a is an absorption coefficient of the absorber (light absorbing material). Φ is the amount of light in the local region (the amount of light irradiated to the absorber).

  As shown in the above equation, the sound pressure is proportional to the local light amount reaching the absorber. Since the light irradiated to the living body is rapidly attenuated in the body due to scattering and absorption, the sound pressure of the photoacoustic wave generated in the deep tissue in the living body is greatly attenuated according to the distance from the light irradiation site. Therefore, in order to increase the signal intensity of the photoacoustic wave in order to obtain a good image, it is necessary to increase the amount of light applied to the living body.

  However, from the viewpoint of safety with respect to a living body, when a laser is used as a light source, attention must be paid to the irradiation density (irradiation light amount per unit area) irradiated to the living body. It is necessary that the maximum value of the irradiation density does not exceed the maximum allowable exposure (MPE: Maximum Permissible Exposure) defined by the laser safety standards (JIS standards C6802 and IEC 60825-1).

Photoacoustic waves are generally received by a probe in which receiving elements that convert electricity and acoustic waves are arranged one-dimensionally or two-dimensionally. In order to image a relatively large internal structure of a subject such as a breast by photoacoustic imaging, laser light emission and light at each position where the probe is mechanically scanned along the surface of the subject. It is necessary to repeat reception of acoustic waves. In order to improve the S / N ratio, it is preferable that the photoacoustic wave is received a plurality of times at the same location and averaged. Thus, during imaging for a long time, the breast as the subject is stretched and fixed thinly by the two holding plates, which is a burden on the subject.

  Patent Document 1 describes a technique for reducing the burden on the subject. In this method, the probe stage moves at a constant speed and receives a photoacoustic wave in synchronization with the oscillation period of the laser pulse light. This eliminates the need to start and stop the probe stage for each measurement position, thereby reducing the measurement time.

JP 2011-125571 A

M. XU, L. V. "WANG, PHOTOACOUSTIC IMAGING IN BIOMEDICINE", REVIEW OF SCIENTIFIC INSTRUMENTS, 77, 041101 (2006)

  As described above, the energy of the light irradiated to the subject attenuates according to the distance from the light irradiation site. Therefore, when imaging the deepest part of the subject, it is necessary to increase the amount of irradiation light as the holding distance of the subject (distance between the holding plates) increases. Conversely, the shorter the holding distance (that is, the thinner the subject), the weaker the irradiation light quantity. From the viewpoint of safety, if the irradiation light quantity can be reduced, the oscillation frequency of the laser pulse light (hereinafter referred to as the laser oscillation frequency) can be increased.

  As a method of shortening the restraint time of the subject, there is a method of increasing the laser oscillation frequency and shortening the photoacoustic wave reception interval. However, in the prior art, there is no means for controlling the irradiation light quantity and the laser oscillation frequency in accordance with the holding distance. Therefore, in the photoacoustic imaging apparatus that receives a plurality of photoacoustic waves at the same location, there is a problem that the restraint time of the subject is determined uniformly regardless of the holding distance.

  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 controlling an irradiation light amount and a laser oscillation frequency according to a holding distance in photoacoustic imaging so as to shorten a restraint time of a subject. To do.

The present invention employs the following configuration. That is,
A holding unit for holding the subject;
An irradiation unit that irradiates the subject with pulsed light through the holding unit;
A probe for receiving an acoustic wave generated from the subject irradiated with the pulsed light;
A processing unit for acquiring characteristic information in the subject using the acoustic wave;
A position acquisition unit that acquires information regarding the position of the holding unit;
Based on information on the position acquired by the position acquisition unit, a control unit for controlling the light amount and oscillation frequency of the pulsed light emitted from the irradiation unit;
A subject information acquisition apparatus characterized by comprising:

  According to the present invention, in photoacoustic imaging, it is possible to provide a technique for shortening the restraint time of the subject by controlling the amount of irradiation light and the laser oscillation frequency according to the holding distance.

The figure which shows the relationship between the distance from a light irradiation site | part, and the light quantity in the distance. The figure which shows the relationship between the distance from a light irradiation site | part, and the irradiation light quantity to a biological body. The figure which shows the relationship between the input energy to a light source, and the irradiation light quantity from a light source. The figure which shows the relationship between the input voltage to a light source, and the input energy to a light source. The figure which shows the relationship between time and the voltage thrown into a light source. The figure which shows the structure of a photoacoustic imaging device. FIG. 3 is a diagram illustrating a flow of photoacoustic imaging in the first embodiment. The figure which shows the mechanical scanning of a probe. FIG. 6 is a diagram illustrating a flow of photoacoustic imaging in the second embodiment.

  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 changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the following description.

  In the present invention, the acoustic wave includes an elastic wave called a sound wave, an ultrasonic wave, a photoacoustic wave, and an optical ultrasonic wave. The receiver (probe) receives the acoustic wave propagated through the subject. The subject information acquisition apparatus of the present invention utilizes a photoacoustic effect that receives acoustic waves generated in a subject by irradiating the subject with light (electromagnetic waves) and acquires characteristic information in the subject. Device.

  The characteristic information in the subject acquired by the device is the initial sound pressure of the acoustic wave generated by light irradiation, the light energy absorption density derived from the initial sound pressure, the absorption coefficient, and the substance constituting the tissue. The subject information reflecting the concentration and the like is shown. The concentration of the substance is, for example, oxygen saturation or oxy / deoxyhemoglobin concentration. Further, the characteristic information may be acquired not as numerical data but as distribution information indicating the characteristics of each position in the subject. That is, distribution information such as an absorption coefficient distribution and an oxygen saturation distribution may be acquired as image data.

  In the following description, a photoacoustic imaging apparatus that acquires and images characteristic information in a subject by photoacoustic tomography will be described as an example of the subject information acquisition apparatus. A typical subject is a living body breast, but is not limited thereto.

  The subject is held by two substantially parallel holding plates. The distance between the two holding plates is the holding distance. On the first holding plate, a one-dimensional or two-dimensional array probe is arranged so as to face the subject. The two holding plates correspond to the holding portion of the present invention.

  The optical device is disposed so as to illuminate the living body from the second holding plate side. For the transmission of light from the light source to the optical device, a spatial transmission system using an optical waveguide such as an optical fiber, a lens, or a mirror can be used. As the light source, a YAG laser, a titanium sapphire laser, a dye laser or the like is used.

First, the control of the irradiation light amount according to the holding distance will be described. The relationship between the amount of light applied to the living body and the distance from the light irradiation site is expressed by the following equation (2).
Φ = Φ ₀ × exp (−Meff × Z) (2)
here,
Φ: Light intensity at depth Z [J / mm ² ]
Φ ₀ : Amount of light irradiated to the living body [J / mm ² ]
Meff: attenuation coefficient Z: distance [mm] from the light irradiation site.

1, [Phi ₀ to 0.05 to always constant irradiation light amount to the living body, when substituting 0.1 to Meff, the distance from the light irradiation site Z (horizontal axis), in the depth Z It is the figure which showed the relationship of the light quantity Φ (vertical axis).
Also, FIG. 2 shows the distance Z (horizontal axis) from the light irradiation site and the living body when 0.02 is substituted for Φ and 0.1 is set for Meff so that the light quantity at the depth Z is always constant. It is the figure which showed the relationship of irradiation light quantity (PHI) ₀ (vertical axis).

FIG. 1 shows that the light quantity Φ at the depth Z becomes weaker as the distance Z from the light irradiation site becomes larger. In addition, FIG. 2 shows that in order to make the light quantity Φ at the depth Z constant regardless of the distance Z from the light irradiation site, it is necessary to increase the irradiation light quantity Φ ₀ applied to the living body.
Therefore, the light quantity (corresponding to Φ in the equation (2)) for obtaining the photoacoustic wave having the intensity necessary for obtaining a good image in terms of the S / N ratio is set in advance and maintained. The amount of light irradiated on the living body can be determined according to the distance (corresponding to Z in Expression (2)). Here, the amount of light for obtaining a photoacoustic wave having a required intensity is measured in advance and set as an ideal value.

Next, control of the laser oscillation frequency according to the amount of pulsed light irradiation will be described. FIG. 3 is a diagram showing the relationship between the energy (J) input to the light source indicated on the horizontal axis and the output irradiation light amount (J / mm ² ) indicated on the vertical axis. FIG. 4 is a graph showing the relationship between energy (J) input to the light source on the vertical axis and voltage (V) input to the light source on the horizontal axis. When the energy input to the light source and the voltage input to the light source are considered as a macro, the following equation (3) holds.
Laser input energy ^{= CV 2/2 ... (3} )
here,
C: capacitor,
V: voltage applied to the light source.

  FIG. 5 is a diagram showing the relationship between the time shown on the horizontal axis and the voltage applied to the light source shown on the vertical axis. When boosting with a boosting chopper or the like, a linear relationship as shown in FIG. In the example of FIG. 5, energy is input to the light source at a laser oscillation frequency of 1 Hz and 1000 V, so that the voltage level is 0 in a 1 second cycle.

  FIG. 3 shows that in order to increase the energy output from the light source, the energy input to the light source must be increased. FIG. 4 shows that in order to increase the energy input to the light source, the voltage input to the light source must be increased. FIG. 5 shows that in order to increase the voltage applied to the light source, it is necessary to charge the voltage over a longer time.

  Further, FIG. 5 shows that the laser oscillation frequency decreases as the time required for charging the voltage increases. For example, when the voltage applied to the light source in FIG. 5 is 500 V, the laser oscillation frequency can be 2 Hz. Therefore, from the relationship between the charge voltage and the amount of irradiation light, it can be said that the laser oscillation frequency decreases as the amount of irradiation light output from the light source increases.

  From the above, it can be seen that the irradiation light quantity can be determined according to the holding distance, and the laser oscillation frequency can be determined according to the irradiation light quantity.

Here, it is preferable that the relationship between the holding distance, the irradiation light amount, the input energy to the light source, the input voltage to the light source, the charging time of the voltage, and the laser oscillation frequency is previously measured and tabulated. Accordingly, the irradiation light quantity, the input energy to the light source, the input voltage to the light source, the charging time of the voltage, and the laser oscillation frequency can be determined by referring to the table based on the holding distance during actual photoacoustic imaging. From the viewpoint of safety, it is necessary to set the irradiation light amount within a range that does not exceed the maximum allowable exposure amount (MPE).
A more detailed configuration will be described in the embodiments described below.

<Example 1>
Hereinafter, the configuration and function of the photoacoustic imaging apparatus according to Embodiment 1 of the present invention will be described.

(Device configuration)
The apparatus includes holding plates 601A and 601B that hold the subject 600, and a holding plate driving mechanism 602 that moves the positions of the holding plates 601 and acquires the positions. The apparatus also includes a power source 604 that inputs energy to a light source 603 that generates measurement light, and an optical device 605 that converts the generated irradiation light into a desired form. The apparatus also controls a probe 606 that detects a photoacoustic wave propagating through the subject 600, a probe drive mechanism 607 that moves the position of the probe 606, subject holding, light irradiation, and acoustic wave reception. A control unit 611 is included. The apparatus also includes an information processing unit 608 that receives the acquired photoacoustic wave from the control unit 611 and generates a photoacoustic image and the like, and a display unit 609 that displays the generated photoacoustic image and the like. The subject 600 is, for example, a breast that contains a light-absorbing substance 610 such as a tumor inside.

  The subject 600 to be imaged is held and fixed by a pair of holding plates 601A and 601B from both sides. Thereby, the measurement error due to the movement of the subject 600 can be reduced. Further, by extending the subject 600 thinly, light can easily reach a deep part in the subject, and the amount of irradiation light can be suppressed. When the holding plate driving mechanism 602 controls the position of the holding plate 601, the distance (holding distance) between the two holding plates is changed. As a result, the pressure applied to the subject is also changed. Hereinafter, when it is not necessary to distinguish between the holding plates 601A and 601B, they are collectively referred to as the holding plate 601.

  Since the holding plate 601 is located on the optical path of the irradiation light, the holding plate 601 preferably has a high transmittance with respect to the irradiation light. In particular, the holding plate 601A on the probe side preferably has high acoustic matching with the probe 606. For example, a member such as polymethylpentene can be suitably used.

  The light source 603 generates irradiation light for the subject 600. For example, a solid-state laser (such as a Yttrium-Aluminum-Garnet laser or a Titanium-Sapphire laser) that can emit pulsed light having a center wavelength in the near-infrared region can be used as the light source 603.

  The wavelength of the irradiation light is selected between 530 nm and 1300 nm according to the type of the light absorbing material 610 in the subject to be imaged. As the light absorbing substance 610, hemoglobin, glucose, cholesterol or the like can be assumed. For example, hemoglobin in a new blood vessel of breast cancer absorbs light having a wavelength of 600 nm to 1000 nm, and the light absorption of water constituting the living body is minimized around a wavelength of 830 nm. Therefore, when hemoglobin is used as an imaging target, light having a wavelength of 750 nm to 850 nm is preferable. Moreover, the oxygen saturation in blood can also be calculated | required by using the light of the wavelength corresponding to each of oxyhemoglobin and reduced hemoglobin.

  The light irradiation direction is not limited from the side facing the probe. Light may be irradiated from the same side as the probe, or light may be irradiated from both sides of the subject. In the case of both-side irradiation, a plurality of light sources 603 may be prepared, or light may be branched.

  The power source 604 inputs energy necessary for creating desired irradiation light to the light source 603.

  The optical device 605 irradiates the subject 600 with the irradiation light from the light source 603 in a desired shape. The optical device 605 includes an optical system such as a lens, a mirror, and an optical fiber, and a scanning mechanism that moves a light irradiation portion relative to the holding plate 601. Any optical system may be used as long as irradiation light emitted from the light source 603 is irradiated on the subject 601 in a desired shape. When irradiation light generated by the light source 603 is irradiated onto the subject 600 through the optical device 605, the light absorbing material 610 absorbs light and emits photoacoustic waves. In this case, the light absorbing material 610 corresponds to the sound source.

  The probe 606 detects the photoacoustic wave generated in the light absorbing material 610 and converts it into an electrical signal. A photoacoustic wave generated from a living body is an ultrasonic wave of 100 KHz to 100 MHz. Therefore, a probe that can receive the above frequency band is used as the probe 606. Any probe may be used as long as it can detect a photoacoustic wave, such as a transducer using a piezoelectric phenomenon, a transducer using optical resonance, and a transducer using a change in capacitance.

  In the probe 606 of this embodiment, a plurality of receiving elements are two-dimensionally arranged. By using such a two-dimensional array element, photoacoustic waves can be detected simultaneously at a plurality of locations, the detection time can be shortened, and the influence of vibration of the subject can be reduced. In this embodiment, the subject 600 is irradiated with irradiation light on the front surface of the probe 606. Therefore, the optical device 605 and the probe 606 are disposed at positions facing each other with the subject 600 interposed therebetween. Then, scanning control is performed in which the optical device 605 and the probe driving mechanism 607 are interlocked so as to maintain the positional relationship.

  The holding plate drive mechanism 602 operates the holding plate 602 based on information input from the user. Further, the position information of the holding plate 602 at this time is transmitted to the control unit 611. At this time, the holding plate driving mechanism and the control unit correspond to the position acquisition unit of the present invention.

  The control unit 611 amplifies the photoacoustic wave electrical signal obtained from the probe 606 and converts the analog signal (analog electrical signal) into a digital signal (digital electrical signal). Hereinafter, this signal is also referred to as a photoacoustic signal. The control unit 611 also performs integration processing between digital signals for noise reduction. The control unit 611 also controls the holding plate driving mechanism 602, the light source 603, the power source 604, the optical device 605, the probe 606, and the probe driving mechanism 607.

  In the present invention, the control unit 611 receives the position of the holding plate 601 from the holding plate driving mechanism 602, and calculates the holding distance based on the position. Based on the calculated holding distance, the control unit 611 determines the irradiation light amount, the input energy to the light source, the input voltage to the light source, the charging time of the voltage, and the laser oscillation frequency with reference to the above table. Alternatively, these numerical values may be determined by calculation instead of the table reference.

  The integration processing refers to performing measurement of the same part of the subject 600 repeatedly and performing addition averaging processing. Thereby, system noise can be reduced and the S / N ratio of the photoacoustic signal can be improved. At this time, the necessary number of times of integration processing (hereinafter, the number of integration times) is measured in advance and set to an ideal value.

  The control performed by the control unit 611 on the optical device 605 and the probe drive mechanism 607 includes movement control of the position of the light irradiation site and the position of the probe 606 relative to the subject. Such movement is performed in order to image a wide area by two-dimensionally scanning the subject. For example, full breast imaging is possible in mammography. The probe driving mechanism corresponds to the scanning unit of the present invention.

  The information processing unit 608 generates a photoacoustic image based on the photoacoustic signal received from the control unit 611 and displays it on the display unit 609. As the information processing unit 608, a device having a high-performance arithmetic processing function or a graphics display function such as a personal computer or a workstation can be used.

  With the photoacoustic imaging apparatus having the above configuration, the optical characteristic distribution of the subject 600 can be imaged and a photoacoustic image can be presented.

(Processing flow)
Next, the flow from the implementation of photoacoustic imaging to the display of a photoacoustic image will be described using the flow of FIG. The numbers in the figure indicate process step numbers or data used for the processes.

In FIG. 7A, after the user appropriately holds the subject 600, photoacoustic imaging is started (step 700).
In step 701, the control unit 611 calculates a holding distance based on the holding position information received from the holding plate driving mechanism 602.
In step 702, the control unit 611 refers to a lookup table (reference numeral 703) prepared in advance. Then, the irradiation light amount corresponding to the holding distance calculated in step 701, the input energy to the light source, the input voltage to the light source, the time for charging the input voltage to the light source, and the laser oscillation frequency are determined.

In step 704, a photoacoustic signal is acquired. Details of this processing will be described with reference to FIG. When the process starts (step 7040), first, the control unit 611 moves the optical device and the probe to the initial imaging position (step 7041).
In step 7042, the subject 600 is irradiated with the irradiation light amount determined in step 702.
In step 7043, the probe 606 receives the photoacoustic wave generated from the subject, and the control unit 611 converts it into a digital electric signal. Thereby, a photoacoustic signal is acquired.

In step 7044, it is determined whether the number of integration has reached a predetermined value. If the predetermined value has been reached (Yes), the process proceeds to step 7045. On the other hand, if not reached (No), the process proceeds to Steps 7042 to 7043 and the photoacoustic signal acquisition is continued.
Next, in step 7045, it is determined that the acquisition of the photoacoustic signal for the entire imaging region has been completed. The imaging region is, for example, a range on the subject set in advance by the user.

When Step 7045 is No, the optical device and the probe are moved to the next photographing position (Step 7046). A method of repeatedly moving and stopping the probe and the optical device and performing photoacoustic imaging at the stop position is called a step-and-repeat method. Steps 7042 to 7044 are repeated again.
On the other hand, if Step 7045 is Yes, the acquisition of the photoacoustic signal is terminated (Step 7047).

In step 705, the information processing unit 608 generates a photoacoustic image from the photoacoustic signal and displays it on the display unit 609.
A photoacoustic image is generated and displayed by the above flow.

According to this embodiment, the irradiation light quantity, the input energy to the light source, the input voltage to the light source, the time for charging the input voltage to the light source, and the laser oscillation frequency are controlled in accordance with the holding distance. As a result, the holding distance varies depending on the degree and size of pain felt by the subject. However, by using a suitable condition according to the holding distance, it is possible to shorten the restraint time of the subject.

<Example 2>
In the second embodiment, a case where the optical device 605 and the probe 606 operate at a constant speed when acquiring a photoacoustic wave will be described. The configuration of the apparatus in the present embodiment is the same as that in the first embodiment.

  FIG. 8 is a diagram illustrating an example of a state in which the probe 606 mechanically scans the surface of the holding plate 601. The probe 606 moves along a path 800 indicated by an arrow.

  First, the probe 606 performs photoacoustic imaging at each measurement position while moving at a constant speed in the main scanning direction (lateral direction 8000 in FIG. 8). Here, the region where the probe 606 is moved in the main scanning direction and the photoacoustic measurement is performed is defined as a stripe. When the measurement of one stripe is completed, the probe 606 moves in the sub-scanning direction (vertical direction 8001 in FIG. 8), and performs photoacoustic imaging at each measurement position while moving again at a constant speed in the main scanning direction. In this way, it is possible to scan the entire surface of the imaging region 801 on the surface of the holding plate at high speed and obtain a photoacoustic signal.

Next, the flow of photoacoustic imaging in the present embodiment will be described with reference to FIG. However, steps that are the same as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
In step 900, which is the difference between FIG. 9A and FIG. 7A, the control unit 611 calculates the scanning speed in the main scanning direction. Assume that the number of elements in the X direction of the probe is Enxa (pieces), the element pitch is Epicha (mm), the number of photoacoustic measurements is Mn (times), and the laser emission frequency is LHz (Hz). In order to simplify the explanation, it is assumed that the integration number Mn is a multiple of the element number Enxa. At this time, the scanning speed V _ax (mm / sec) in the main scanning direction of the probe and the optical device is calculated by the following equation (4).
V _ax = Epitcha × LHz (4)

  From equation (4), it can be seen that the scanning speed is proportional to the laser oscillation frequency. In other words, if the laser oscillation frequency can be increased, the scanning speed can be increased. Also, it can be seen that the integration can be performed Enxa times with one stripe.

  Under more complicated conditions, if the number of integrations is smaller than the number of elements Enxa in the main scanning direction or a multiple of a value smaller than Enxa, the number of integrations per stripe must be reduced. In this case, the probe movement amount can be scanned while shifting by 2 pixels or more per unit time, so that it is understood that the setting of the scanning speed becomes high.

  The moving speed of the probe is not limited to the method exemplified in this embodiment. Various algorithms for adjusting the scanning speed can be applied according to the measurement conditions and the apparatus configuration. That is, as long as the probe moving speed for obtaining the photoacoustic signal can be obtained, the reference parameter and the algorithm are not limited to those of the present embodiment.

Photoacoustic signal acquisition (step 704) will be described with reference to FIG. In step 901, the probe 606 scans the entire surface of the imaging region 801 in FIG. 8 in order to acquire photoacoustic waves over the entire imaging region. At this time, light is emitted from the light source 603 at a cycle of the laser frequency LHz. The probe 606 scans while receiving a photoacoustic wave generated by light irradiation. The generation and display of image data based on photoacoustic waves is the same as in the above embodiment.
A photoacoustic image is generated and displayed by the above flow.

According to the present embodiment, the scanning speed is calculated according to the laser oscillation frequency determined according to the holding distance. As a result, since a suitable scanning speed corresponding to the holding distance is used, it is possible to shorten the subject's restraint time.

  As described above, when photoacoustic imaging is performed by the method of the present invention, the amount of irradiation light and the laser oscillation frequency are controlled according to the holding distance, and the restraint time of the subject can be shortened.

  601A, 601B: holding plate, 602: holding plate driving mechanism, 603: light source, 605: optical device, 606: probe, 607: probe driving mechanism, 611: control unit

Claims (7)

A holding unit for holding the subject;
An irradiation unit that irradiates the subject with pulsed light through the holding unit;
A probe for receiving an acoustic wave generated from the subject irradiated with the pulsed light;
A processing unit for acquiring characteristic information in the subject using the acoustic wave;
A position acquisition unit that acquires information regarding the position of the holding unit;
Based on information on the position acquired by the position acquisition unit, a control unit for controlling the light amount and oscillation frequency of the pulsed light emitted from the irradiation unit;
A subject information acquisition apparatus characterized by comprising: The holding unit is to hold the subject by two holding plates,
The subject information acquisition apparatus according to claim 1, wherein the position acquisition unit acquires a holding distance, which is a distance between the two holding plates, as information related to the position. The said control part controls the said light quantity so that the said acoustic wave of the intensity | strength required in order to acquire the said characteristic information may generate | occur | produce from the said test object based on the said holding distance. 2. The subject information acquisition apparatus according to 2. The irradiation unit irradiates a laser from a light source as the pulsed light,
The subject information acquisition apparatus according to claim 3, wherein the control unit controls the light amount so as not to exceed a maximum allowable exposure amount for the subject. The object information acquiring apparatus according to claim 3, wherein the control unit controls the oscillation frequency based on a charge voltage to the light source necessary for irradiating the light amount. A scanning unit that moves the probe along the holding plate;
The object information acquiring apparatus according to claim 2, wherein the control unit controls a scanning speed of the scanning unit based on the oscillation frequency. The probe includes a plurality of receiving elements for receiving the acoustic wave,
The object information acquiring apparatus according to claim 6, wherein the control unit controls a scanning speed of the scanning unit based on an element pitch of the receiving element.

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