JP2019042002A - Photoacoustic apparatus - Google Patents

Abstract

To provide a photoacoustic apparatus capable of widening a frequency bandwidth of a detected acoustic wave by irradiating a subject with pulse lights whose pulse waveforms are different at least partially a plurality of times.SOLUTION: A photoacoustic apparatus includes a control part for controlling a light irradiation part so that a subject is irradiated with pulse lights a plurality of times, and an acquisition part for acquiring information on the subject based on a plurality of electric signals converted from acoustic waves generated when the subject is irradiated with pulse lights a plurality of times. The control part controls the light irradiation part so that at least part of the pulse lights irradiated with a plurality of times become pulse waveforms different from each other.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a photoacoustic apparatus.

  In recent years, as an imaging technology using light, a photoacoustic apparatus for imaging the inside of a subject using a photoacoustic effect has been researched and developed. A photoacoustic apparatus is an apparatus which acquires the information regarding a subject based on the ultrasonic wave (photoacoustic wave) generated by the photoacoustic effect from the light absorber which absorbed the energy of the light irradiated to the subject.

  In Patent Document 1, photoacoustic imaging is performed in which the ratio of the rising slope to the falling slope of the light pulse waveform emitted from the light source unit is set so as to be compatible with the frequency band of the detection unit that detects acoustic waves. The device is disclosed.

JP 2017-46823 A

  In the method of Patent Document 1, the parameter for changing the detection frequency is only the slope ratio, and there is a limit to broadening the detection frequency.

A photoacoustic apparatus according to the present invention comprises: a light irradiation unit that irradiates a subject with pulsed light; and a reception unit that receives an acoustic wave generated by irradiating the subject with pulsed light and converts the acoustic wave into an electrical signal. A control unit configured to control the light emitting unit such that the subject is irradiated with the pulsed light multiple times; and a plurality of the electric waves converted from acoustic waves generated by applying the pulsed light multiple times to the subject An acquisition unit configured to acquire information on the subject based on a signal;
The control unit controls the light emitting unit such that at least a part of the pulsed light irradiated a plurality of times has different pulse waveforms.

  According to the photoacoustic apparatus according to the present invention, the frequency band of the acoustic wave to be detected can be broadened by irradiating the object with pulse light different in at least part of the pulse waveform multiple times. As a result, it is possible to acquire information on a substance having a size corresponding to a low frequency among substances having a size corresponding to a low frequency among light absorbers distributed in a subject. In addition, by increasing the types of pulse waveforms, the frequency band of the detected acoustic wave can be further broadened.

The figure for demonstrating the effect of the photoacoustic apparatus which concerns on embodiment of this invention. Block diagram for explaining a photoacoustic apparatus according to an embodiment of the present invention The figure which shows the structure of the probe concerning the embodiment of the present invention A figure showing an example of composition of a drive part in an embodiment of the present invention The figure which shows an example of the computer structure in embodiment of this invention. A figure for explaining an example of control of a photoacoustic apparatus in an embodiment of the present invention

  Embodiments of the present invention will be described below with reference to the drawings. However, the dimensions, materials, shapes and relative positions of the components described below should be suitably changed according to 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 embodiment relates to a technique for detecting an acoustic wave propagating from a subject, generating characteristic information inside the subject, and acquiring the characteristic information. Therefore, the present embodiment can be understood as an object information acquisition apparatus or a control method thereof, or an object information acquisition method or a signal processing method. The present embodiment can also be grasped as a display method for generating and displaying an image indicating characteristic information inside the subject. The present embodiment can also be regarded as a program that causes an information processing apparatus having hardware resources such as a CPU and a memory to execute these methods, and a non-transitory computer-readable storage medium storing the program. .

  The subject information acquiring apparatus according to the present embodiment irradiates light (electromagnetic wave) a plurality of times to the subject, and receives an acoustic wave generated in the subject for each irradiation. And the photoacoustic imaging apparatus using the photoacoustic effect which acquires the characteristic information of a test object as image data based on the received photoacoustic signal is included. In this case, the characteristic information is information of characteristic values corresponding to each of a plurality of positions in the subject, generated using a signal derived from the received photoacoustic wave.

  The photoacoustic image data according to the present embodiment is a concept including all image data derived from the photoacoustic wave generated by light irradiation. For example, the photoacoustic image data includes at least one object such as a generated sound pressure of a photoacoustic wave (initial sound pressure), an absorbed energy density, an absorption coefficient, and a concentration of a substance constituting the object (such as oxygen saturation). Image data representing the spatial distribution of information. It should be noted that photoacoustic image data showing spectral information such as the concentration of a substance constituting an object is obtained based on signals (photoacoustic signals) derived from photoacoustic waves generated by light irradiation of a plurality of different wavelengths. Be The photoacoustic image data indicating spectral information may be oxygen saturation, a value obtained by weighting the oxygen saturation with an intensity such as an absorption coefficient, total hemoglobin concentration, oxyhemoglobin concentration, or deoxyhemoglobin concentration. Further, photoacoustic image data indicating spectral information may be glucose concentration, collagen concentration, melanin concentration, or a volume fraction of fat or water.

  A two-dimensional or three-dimensional characteristic information distribution is obtained based on the characteristic information of each position in the subject. Distribution data may 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 acoustic wave referred to in the present embodiment is typically an ultrasonic wave, and includes an acoustic wave and an elastic wave called an acoustic wave. An electrical signal converted from an acoustic wave by a transducer or the like is also referred to as an acoustic signal. However, the description of ultrasonic wave or acoustic wave in the present specification is not intended to limit the wavelength of the elastic wave. The acoustic wave generated by the photoacoustic effect is called photoacoustic wave or photoacoustic wave. An electrical signal derived from a photoacoustic wave is also referred to as a photoacoustic signal. The distribution data is also called photoacoustic image data or reconstructed image data.

  In the following embodiment, as an object information acquisition apparatus, the object is irradiated with pulsed light for a plurality of times, and photoacoustic waves from the object are received, and information in the object (for example, a blood vessel image (structure Take up the photoacoustic device to get the image)). Although the following embodiments also deal with an optoacoustic apparatus having a hand-held probe, the present invention can also be applied to an optoacoustic apparatus in which a stage is provided with a probe and mechanically scanned. Furthermore, in the following embodiments, a device in which a plurality of semiconductor light emitting elements are mounted inside a hand-held type probe and connected to a photoacoustic apparatus main body by wiring will be described. However, the present embodiment can also be applied to a photoacoustic apparatus that has a power supply such as a battery in a hand-held type probe and wirelessly transmits the photoacoustic signal of the hand-held type probe to the main body of the photoacoustic apparatus. Thus, when the hand-held probe has the function of the present invention, the photoacoustic apparatus of the present invention can be said to mean the hand-held probe itself.

First Embodiment
First, the basic concept of the present embodiment will be described below.

  FIG. 1 is a graph showing the relationship between an optical pulse waveform and a photoacoustic wave (photoacoustic signal) for explaining the basic concept of the present embodiment in an easily understandable manner. FIGS. 1 (a) and 1 (c) are graphs showing light pulse waveforms, in which the vertical axis is light intensity and the horizontal axis is time. 1 (b) and 1 (d) are graphs respectively simulating the frequency characteristics (frequency spectrum) of the photoacoustic wave obtained when the object is irradiated with the light pulse waveform shown in FIGS. 1 (a) and 1 (c). The vertical axis represents the intensity of the photoacoustic wave, and the horizontal axis represents the frequency. As shown in FIG. 1 (a), when the light pulse having a short pulse width (100 nsec) is irradiated, as shown in FIG. 1 (b), the peak value of the photoacoustic wave frequency spectrum is about 7 It will be .5 MHz. On the other hand, as shown in FIG. 1 (c), when the light pulse having a long pulse width (200 nsec) is irradiated, as shown in FIG. 1 (d), the peak value of the photoacoustic wave frequency spectrum is It will be about 3.75 MHz.

  In the first embodiment, such light pulses having different light pulse waveforms are irradiated to the subject a plurality of times, and information based on the photoacoustic signal is obtained from the photoacoustic signal obtained for each irradiation. For example, the light emission of a plurality of times is 12 times, of which 6 times are irradiated with the light pulse of the light pulse waveform shown in FIG. 1A, and the remaining 6 times are light shown in FIG. A subject is illuminated with light pulses of a pulse waveform. Then, the photoacoustic signals obtained for each irradiation are averaged. As a result, the photoacoustic signal which becomes the frequency spectrum of the photoacoustic wave which averaged the frequency spectrum of the photoacoustic wave shown in FIG.1 (b) and the frequency spectrum of the photoacoustic wave shown in FIG.1 (d) is obtained. be able to.

  As another method, the frequency spectrum of the photoacoustic wave can be easily changed by controlling the number of times of light emission. For example, multiple times of light emission is 12 times, and 4 times of them are irradiated with the light pulse of the light pulse waveform shown in FIG. 1A, and the remaining 8 times are light shown in FIG. 1C. A subject is illuminated with light pulses of a pulse waveform. Then, the photoacoustic signals obtained for each irradiation are averaged. As a result, the frequency spectrum of the photoacoustic wave shown in FIG. 1B and the frequency spectrum of the photoacoustic wave shown in FIG. It is possible to obtain a synthesized photoacoustic signal that is a spectrum. In this case, since the number of times the object is irradiated with the light pulse having the light pulse waveform shown in FIG. 1C increases, the frequency characteristic of the combined photoacoustic signal is high compared to the case where the number of times of light emission is the same. The range component can be made relatively large.

  As another method, it is possible to easily change the frequency spectrum of the photoacoustic wave by controlling the light intensity. For example, the light emission of a plurality of times is 12 times, of which 6 times are irradiated with the light pulse of the light pulse waveform shown in FIG. 1A, and the remaining 6 times are light shown in FIG. The subject is illuminated with a light pulse having a light intensity twice that of the pulse waveform. Then, the photoacoustic signals obtained for each irradiation are averaged. As a result, the frequency spectrum of the photoacoustic wave obtained by averaging the frequency spectrum of the photoacoustic wave illustrated in FIG. 1B and the frequency spectrum of the photoacoustic wave illustrated in FIG. The combined photoacoustic signal can be obtained. In this case, since the light intensity for irradiating the object with the light pulse of the light pulse waveform shown in FIG. 1C is increased, the frequency characteristics of the combined photoacoustic signal are compared with the case where the respective light intensities are the same. The high frequency component can be made relatively large. In addition, as another method of controlling the light intensity, when the light irradiation unit has a light source unit and the light source unit includes a plurality of semiconductor light emitting elements, the number of semiconductor light emitting elements that emit pulsed light Control may be performed by increasing or decreasing the

  As another method, the frequency spectrum of the photoacoustic wave can be easily changed by controlling the amplification degree of the amplifier that amplifies the received photoacoustic signal for each light emission. For example, the light emission of a plurality of times was 12 times, 6 times of which were irradiated with the light pulse of the light pulse waveform shown in FIG. 1A, and the remaining 6 times were shown in FIG. 1C. The subject is illuminated with a light pulse of light pulse waveform. Then, the photoacoustic signal obtained by irradiating the object with the light pulse of the light pulse waveform shown in FIG. 1 (a) is amplified by, for example, a double amplification factor, and the light pulse waveform shown in FIG. 1 (c) The photoacoustic signal obtained by irradiating the object with the light pulse of (1) is amplified by, for example, an amplification factor of 1. Such amplification may be realized by changing the amplification degree of the analog amplifier or may be realized by performing digital operation with a CPU or the like after digitizing the photoacoustic signal. Then, the photoacoustic signals obtained and amplified for each irradiation are added and averaged. As a result, the frequency spectrum of the photoacoustic wave shown in FIG. 1 (b) and the frequency spectrum of the photoacoustic wave obtained by averaging the frequency spectrum of the photoacoustic wave shown in FIG. 1 (d) with a weight of 2: 1 The combined photoacoustic signal can be obtained. In this case, since the photoacoustic signal obtained by irradiating the object with the light pulse of the light pulse waveform shown in FIG. 1A becomes large, compared with the case where the amplification degree is not changed, The low frequency component of the frequency characteristic can be made relatively large.

  As another method, three or more types of light pulse waveforms can be used. For example, the waveform of the third light pulse is shown in FIG. The graph which simulated the frequency spectrum of the photoacoustic wave obtained when a test object is irradiated with the light pulse waveform shown in FIG.1 (e) is shown in FIG.1 (f). The vertical axis of the graph of FIG. 1 (e) is light intensity, and the horizontal axis is time. The vertical axis of the graph in FIG. 1 (f) is the intensity of the photoacoustic wave, and the horizontal axis is the frequency. As shown in FIG. 1 (e), when an optical pulse with a pulse width of 300 nsec is irradiated, the peak value of the photoacoustic wave frequency spectrum is about 2.5 MHz as shown in FIG. 1 (f). Become. The object is irradiated with light pulses of the light pulse waveform shown in FIG. 1A with light emission of a plurality of times being 12 times. Furthermore, the subject is irradiated with the light pulse of the light pulse waveform shown in FIG. 1 (c) four times, and the object is irradiated with the light pulse of the light pulse waveform shown in FIG. 1 (e) for the remaining four times. . Then, the photoacoustic signals obtained for each irradiation are averaged. As a result, the frequency spectrum of the photoacoustic wave shown in FIG. 1 (b), the frequency spectrum of the photoacoustic wave shown in FIG. 1 (d), and the frequency spectrum of the photoacoustic wave shown in FIG. 1 (f) A combined photoacoustic signal can be obtained which results in the frequency spectrum of the averaged photoacoustic wave. As described above, irradiation of three or more types of light pulse waveforms is performed, and as a result, it is possible to make the frequency characteristic of the combined photoacoustic signal a higher band.

  Further, as in the above description, the number of light emission times and the light intensity of three or more types of light pulse waveforms are controlled, or the amplification degree for amplifying the photoacoustic signal received for each light emission is controlled, thereby being synthesized more finely. It is possible to control the frequency characteristics of the photoacoustic signal.

  In the embodiment of the present invention, as described above, the shape of the light pulse waveform is set such that the frequency of the peak value of the frequency spectrum of the photoacoustic wave obtained by the light pulse having two or more types of light pulse waveforms is different. Do. Such a configuration is preferable because the frequency characteristics of the photoacoustic signal can be adjusted more easily. In order to make the frequency of the peak value of the frequency spectrum of the photoacoustic wave different, when the light pulse waveform is a triangular wave, it is preferable to make the pulse width different. Specifically, the light pulse waveform may be selected from pulse widths of 100 nsec to 1000 nsec. For example, a triangular wave having a pulse width of 100 nsec and a pulse width of 200 nsec may be used, or a triangular wave having a pulse width of 100 nsec and 300 nsec may be used. Also, the three triangular waves may be used.

  Alternatively, as shown in FIG. 1G, an optical pulse having an asymmetric light pulse waveform with a rise time of 100 nsec and a fall time of 50 nsec may be used. In this case, the frequency spectrum of the photoacoustic wave as shown in FIG. 1 (h) is obtained. It goes without saying that the present invention can be applied in consideration of such characteristics. The light pulse waveform that can be applied in the present invention may have any shape.

  In the above, it has been described that control of the frequency characteristic of the combined photoacoustic signal is possible. According to the present invention, for example, as disclosed in Patent Document 1, the number of times of light emission, the light intensity, the amplification degree, etc. are controlled so that the frequency characteristic of the combined photoacoustic signal is adapted to the frequency band of the receiving unit. You may In the case of a photoacoustic apparatus which can exchange a probe, it is preferable to control the number of times of light emission, the light intensity, the amplification degree, etc. so that the frequency characteristic of the combined photoacoustic signal matches the frequency characteristic of the probe. In addition, the number of times of light emission, the light intensity, the amplification degree, and the like may be determined so that the intensity of the frequency spectrum of the photoacoustic wave determined by the thickness of the blood vessel in the region of the object to be noticed becomes large. In addition, the number of times of light emission, the light intensity, the amplification degree, and the like may be controlled so that the frequency characteristics of the photoacoustic signal can be controlled by the instruction of the user. For example, when the user wants to gaze at a fine blood vessel, it is preferable to make settings such as increasing the number of times of light pulse emission with a short light pulse width so as to raise the high band of the frequency characteristic of the photoacoustic signal. When the user wants to gaze at a thick blood vessel, it is preferable to perform setting such as increasing the number of times of light pulse emission with a long light pulse width so as to raise the low frequency range of the photoacoustic signal. Furthermore, when the region of the object to be noticed is in the deep part of the object, the attenuation of the high frequency of the photoacoustic wave becomes large, so the computer automatically raises the high frequency characteristic of the photoacoustic signal. The configuration of the light pulse waveform and the number of times of light emission may be set. Alternatively, a pressure sensor or the like may be provided on the hand-held probe, the pressing force of the probe on the subject may be measured, and the computer may change the frequency characteristic of the photoacoustic signal according to the magnitude of the pressing force. For example, when the user observes details, he may press the probe unconsciously and strongly. When the pressing force is large, it is preferable to increase the number of times of light pulse emission with a short light pulse width, increase the light intensity, or increase the amplification to raise the high frequency band of the frequency spectrum of the photoacoustic wave.

  In the example described above, the light pulse having different light pulse waveforms is irradiated to the subject a plurality of times, and the photoacoustic signals obtained for each irradiation are added and averaged to obtain an averaged characteristic of the frequency spectrum of the photoacoustic wave. The photoacoustic signal was obtained. The following methods are also effective as synthesis methods that can be used in the present invention. For example, weighting may be performed on the acquired photoacoustic signal in proportion to the light intensity of the frequency spectrum of the photoacoustic wave obtained by the irradiated light pulse waveform, and averaging may be performed. In this way, since the average is obtained by weighting with a good S / N component having a large light intensity, the S / N ratio can be made good. In addition, a portion where the light intensity of the frequency spectrum of the photoacoustic wave according to the light pulse waveform is large may be selected and synthesized. Specifically, the frequency band of the photoacoustic wave according to two or more types of different light pulse waveforms may be determined and the band in which the photoacoustic signal is synthesized may be synthesized. For example, when using the light pulse waveforms of FIG. 1 (a) and FIG. 1 (c), the photoacoustic signal obtained by irradiating the light pulse waveform of FIG. 1 (a) is averaged for frequencies of 5 MHz or less. Use the signal that And about the frequency of 5 MHz or more, it is good to use the signal which added and averaged the photoacoustic signal obtained by irradiation of the waveform of the optical pulse of FIG.1 (c). Of course, in order to prevent the connection from becoming unnatural at the switching frequency, weighted combining processing may be performed rather than just switching.

  In addition, a filter having a characteristic to flatten the frequency spectrum of the photoacoustic wave according to the light pulse waveform is used to flatten the frequency spectrum of the photoacoustic wave obtained by emission of two or more different light pulse waveforms. After averaging, it may be averaged. In this case, although the S / N ratio is not improved, there is an advantage that the frequency characteristic of the obtained combined photoacoustic signal becomes flat.

  As described above, in the photoacoustic apparatus that acquires information based on photoacoustic signals generated by light emission of multiple times of pulsed light emitted from the light emitting unit, among the multiple light emissions emitted from the light emitting unit, Light is emitted with at least two or more types of light pulse waveforms. Then, by driving the semiconductor light emitting element included in the light irradiation unit so as to emit light as described above, it is possible to obtain information based on the frequency characteristics of the written (desired) photoacoustic signal. Although the following description shows an embodiment in which photoacoustic signals obtained by two types of light pulse waveforms are added and averaged, it goes without saying that photoacoustic signals obtained by irradiating an object with three or more types of pulse waveforms. The above-described processing of signals can be applied to the configuration.

(Configuration of photoacoustic apparatus)
FIG. 2 shows a block diagram of the photoacoustic apparatus 1 according to the present embodiment. Hereinafter, using the block diagram of FIG. 2, in the photoacoustic apparatus 1 according to the present embodiment, the light irradiation unit 200 that irradiates the subject 100 with pulse light generated from the light source and the subject 100 are irradiated with the pulse light And a receiver 120 for receiving and converting an acoustic wave generated by the conversion into an electrical signal. Furthermore, the control unit 153 that controls the light emitting unit 200 so that the subject 100 is irradiated with the pulse light a plurality of times is provided. The acquisition unit 151 is configured to acquire information on the subject 100 based on a plurality of electrical signals converted from an acoustic wave generated by irradiating the subject 100 with the pulsed light multiple times. Then, the control unit 153 is characterized in that the light emitting unit 200 is controlled such that at least a part of the pulsed light irradiated a plurality of times has different pulse waveforms. As described above, the frequency of the acoustic wave to be detected changes because the pulse waveform of the pulsed light irradiated to the subject is different. Therefore, the frequency band of the acoustic wave to be detected can be broadened by increasing the types of pulse waveforms of the pulsed light irradiated to the object. As a result, it is possible to acquire information on a substance having a size corresponding to a low frequency acoustic wave among light absorbers distributed in a subject, to a substance having a small size corresponding to a high frequency acoustic wave.

  In the present embodiment, the pulse waveforms being different are typically cases where the pulse widths are different, but it is not limited thereto.

  Further, in the present embodiment, the control unit controls the light emitting unit so that the number of times of emission of pulse light having different pulse waveforms differs from each other, and the light intensity of pulse light having pulse waveforms different from each other is The light emitters can be controlled to be different from one another. With such a configuration, as described above, when a large acoustic wave of a specific frequency is generated, the number of times of emission of pulse light having a pulse waveform for generating the frequency is increased, or the light intensity of pulse light is increased. It can be strong.

  The photoacoustic apparatus according to the present embodiment includes a probe 180, a signal collection unit 140, a computer 150, a display unit 160, and an input unit 170. The probe 180 includes a light irradiator 200, a driver 210, and a receiver 120. The computer 150 includes an acquisition unit 151, a storage unit 152, and a control unit 153. In addition, the part connected by the cable except the probe 180 can also be described as a photoacoustic apparatus main body.

  In the present embodiment, the light irradiation unit 200 includes a light source unit that generates pulsed light. The light source unit is configured to include a plurality of semiconductor light emitting elements (semiconductor light emitting elements). Although it is necessary to increase the light intensity in order to improve the S / N ratio of the photoacoustic signal, and the number of semiconductor light emitting devices is preferably plural, the number of semiconductor light emitting devices is required to realize the effects of the present invention. May be one configuration. The driving unit 210 drives the light emission of the plurality of semiconductor light emitting elements of the light emitting unit 200 so as to have the above-described light pulse waveform. The driver 210 controls the light pulse waveform of the light source 200 for each light emission to emit light. The light pulse waveform may be determined as described above.

  The driver 210 causes the semiconductor light emitting element of the light source 200 to emit light a plurality of times with at least two or more types of light pulse waveforms. Then, the light source 200 irradiates the subject 100 with two or more types of light pulse waveforms. The receiving unit 120 receives the photoacoustic wave generated from the subject 100 in each light emission, and outputs an electrical signal (photoacoustic signal) that is an analog signal. The signal collecting unit 140 converts an analog signal output from the receiving unit 120 at each light emission into a digital signal, and outputs the digital signal to the computer 150.

  The computer 150 uses the acquisition unit 151, the storage unit 152, and the control unit 153 to combine the digital signals output from the signal collection unit 140 in each light emission, and generates an electrical signal derived from the photoacoustic wave (combined It stores in the storage unit 152 as a photoacoustic signal). Here, the synthesis is not limited to the simple addition averaging, but includes the processing described above. The following description will be mainly made on the case of averaging, but the above-described combining method other than averaging can be applied. The computer 150 performs processing such as image reconstruction on the digital signals stored in the storage unit 152 to generate photoacoustic image data. The photoacoustic image data is then displayed on the display unit 160. The computer 150 also controls the overall operation of these devices and performs setting of light pulse waveforms, light emission control, and reception control. Although not shown, the computer 150 may perform image processing for display and processing for synthesizing a graphic for a GUI on the obtained photoacoustic image data as necessary.

  The user (a doctor, an engineer, etc.) can carry out a diagnosis by confirming the photoacoustic image displayed on the display unit 160. The display image may be stored in a memory in the computer 150, a data management system connected to the photoacoustic apparatus via a network, or the like based on a storage instruction from a user or the computer 150. The input unit 170 receives an instruction from the user.

(Detailed configuration of each block)
Subsequently, the preferred configuration of each block will be described in detail.

(Probe 180)
FIG. 3 is a diagram showing the structure of the probe 180 of the first embodiment.

  In FIG. 3, the probe 180 includes a light irradiator 200, a driver 210, a receiver 120, and a housing 181. The housing 181 is a housing that encloses the light emitting unit 200, the driving unit 210, and the receiving unit 120. The user can use the probe 180 as a handheld probe by gripping the housing 181.

  The light irradiation unit 200 irradiates the light pulse to the subject. As described above, the light emitting unit 200 causes the drive unit 210 to emit light pulses with a desired light pulse waveform for each light pulse emission.

  The XYZ axes in the figure indicate coordinate axes when the probe is left stationary, and do not limit the direction when using the probe.

  The probe 180 shown in FIG. 3 is connected to the signal collecting unit 140 via the cable 182. The cable 182 includes a wire for supplying power to the light emitting unit 200, a light emission control signal wire, and a wire for outputting an analog signal output from the receiving unit 120 to the signal collecting unit 140. The cable 182 may be provided with a connector so that the probe 180 and the other configuration of the photoacoustic apparatus can be separated.

(Light irradiation unit 200)
The light irradiation unit in the present embodiment irradiates the subject with pulsed light generated from the light source.

  The light irradiation part 200 is comprised, for example by 16 semiconductor light emitting elements (for example, laser diode). The type of semiconductor light emitting element is not limited to the laser diode (LD), and may be a light emitting diode (LED). The type and number of semiconductor light emitting devices are determined from the required light intensity. Eight laser diodes (200a to 200h) and eight laser diodes (200i to 200p) are disposed to face each other with the receiving unit 120 interposed therebetween. Then, the sample is irradiated with light. Each laser diode is mounted in the direction of maximum sensitivity of the receiver 200. That is, as shown in FIG. 3, the laser diodes (200a to 200h) and the laser diodes (200i to 200p) are mounted at an angle so as to be directed to the receiving unit 120. Further, FIG. 3 shows a mounting arrangement in which the receiving unit 200 is sandwiched, but may be an arrangement in which light sources are collected on one side. Furthermore, more laser diodes may be used. Although FIG. 3 shows a mounting form in which discrete components are arranged, a configuration in which a plurality of dies from which a semiconductor wafer is cut out may be mounted on a metal base or a printed board may be used. The configuration of the light irradiation unit 200, that is, the arrangement of the laser diodes is not limited to this arrangement. As long as the object can be irradiated with the light pulse satisfactorily, it may be mounted in any arrangement depending on conditions such as the shape of the probe.

  The pulse width of the light emitted from the light irradiation unit 200 is, for example, 10 ns or more and 1 μs or less. More preferably, 100 nsec to 800 nsec are preferable. Moreover, as a wavelength of the light of the light irradiation part 200, although 400 nm or more and 1600 nm or less are suitable, it is good to determine a wavelength according to the light absorption characteristic of the light absorber which you want to image. In the case of imaging blood vessels with high resolution, wavelengths (400 nm or more and 800 nm or less) in which absorption in blood vessels is large may be used. In the case of imaging a deep part of a living body, light of a wavelength (700 nm or more and 1100 nm or less) with less absorption in background tissue (water, fat and the like) of the living body may be used. In the present invention, structural information of a blood vessel can be acquired as a predetermined wavelength, and it is 975 nm, which is a wavelength that reaches the deep part of the subject, and is simultaneously irradiated with light sources of a plurality of other wavelengths that satisfy the above conditions. A photoacoustic wave equivalent to the photoacoustic wave by irradiation can be obtained.

(Drive unit 210)
FIG. 4A and FIG. 4B show the configuration of the drive unit 210 according to the first embodiment. Either of the configurations can preferably correspond to the present invention. First, the configuration of the drive unit 210 shown in FIG. 4A will be described. In FIG. 4A, in the light irradiation unit 200, a plurality of semiconductor light emitting elements (laser diodes) are connected in series. Reference numeral 210 a denotes, for example, a transistor such as a MOSFET, which controls the current flowing to the laser diode of the light irradiation unit 200. A power supply 210 b supplies power to the laser diode of the light emitting unit 200. Here, in the case of the hand-held type probe, the power supply 210 b may be mounted on the photoacoustic apparatus main body outside the probe 180 and supply power. In this case, in order to reduce the impedance (inductance component) of the power supply, a bypass capacitor (not shown) or the like may be mounted in the probe. By controlling the gate voltage of the transistor 210a, it is possible to obtain a current waveform flowing through the laser diode of the light emitting unit 200 corresponding to a predetermined light pulse waveform. The light pulse waveform described above can be realized by realizing such a drive unit 210.

  Another configuration of the drive unit 210 is shown in FIG. Also in FIG. 4B, in the light irradiation unit 200, a plurality of semiconductor light emitting elements (laser diodes) are connected in series. Reference numeral 210 a denotes, for example, a transistor such as a MOSFET, which turns on / off the current flowing through the laser diode of the light emitting unit 200. Reference numeral 210 c denotes an inductor, which is realized by, for example, a coil, wiring of a printed board, or the like. A diode 210d returns a current when the transistor 210a is turned off to the inductor 210c. 210e is a variable voltage power supply. In the case of a hand-held probe, the variable voltage power supply 210e outside the probe may be mounted on the photoacoustic apparatus body. In this case, in order to reduce the impedance (inductance component) of the power supply, a bypass capacitor (not shown) or the like is mounted in the probe. In the configuration of FIG. 4B, the case where the transistor 210a is turned on is considered. At this time, the voltage of the sum of the forward voltage of the laser diode of the light irradiation unit 200, the voltage of the sum of the drain-source voltage when the transistor 210a is ON, and the voltage of the difference between the output voltage of the variable voltage power supply 210e. Is applied to the inductor 210c. The slope of the current flowing through the inductor 210c can be determined by the voltage applied to the inductor 210c and the inductance of the inductor 210c. That is, if the inductance is fixed, the slope of the current flowing through the inductor 210c can be increased by increasing the voltage of the variable voltage power supply 210e. That is, the inclination of the current flowing to the laser diode of the light irradiation unit 200 can be controlled. Then, the slope of the rising waveform of the light pulse waveform can be determined. When the transistor 210a is turned off, the voltage applied to the inductor 210c is the sum of the forward voltage of the laser diode of the light emitting unit 200 and the total voltage of the forward voltage of the diode 210d. The slope of the current flowing through the inductor 210c is determined by this voltage and the inductance of the inductor 210c. That is, the slope of the falling waveform of the light pulse waveform is determined. A case is considered in which the drain-source voltage when the transistor 210a is on and the forward voltage of the diode 210d are sufficiently smaller than the sum voltage of the forward voltages of the laser diode of the light emitting unit 200. In that case, if the output voltage of the variable voltage power supply 210e is set to a voltage twice the voltage of the sum of forward voltages of the laser diode of the light irradiation unit 200, the rising waveform of the current flowing in the laser diode of the light irradiation unit 200 The slope of the falling waveform can be made the same. Therefore, the rising waveform and the falling waveform of the light pulse waveform can have the same slope. Further, by connecting the anode of the diode 210d to the other electrode of the inductor 210c, the fall time of the current flowing to the laser diode of the light irradiation unit 200 can be further shortened when the transistor 210a is turned off. As described above, it is possible to obtain a predetermined light pulse waveform by using the inductor 210c and the variable power supply 210e.

(Receiver 120)
The receiving unit 120 includes a transducer that receives a photoacoustic wave generated as a result of the light emission of the light emitting unit 200 and outputs an electrical signal, and a support that supports the transducer. For example, a piezoelectric material, a capacitive transducer, a transducer using a Fabry-Perot interferometer, or the like can be used as a member constituting the transducer. Examples of the piezoelectric material include piezoelectric ceramic materials such as PZT (lead zirconate titanate) and polymeric piezoelectric film materials such as PVDF (polyvinylidene fluoride). In addition, a capacitive type transducer may be called CMUT (Capacitive Micro-machined Ultrasonic Transducers).

  The electrical signal obtained by the transducer for each light emission of the light emitting unit 200 is a time-resolved signal. Therefore, the amplitude of the electrical signal represents a value based on the sound pressure received by the transducer at each time (for example, a value proportional to the sound pressure). In addition, as a transducer, what can detect the frequency component (typically 100 KHz to 10 MHz) which comprises a photoacoustic wave is preferable. It is also preferable to arrange a plurality of transducers side by side on the support to form a flat surface or a curved surface called 1D array, 1.5D array, 1.75D array, or 2D array. Note that FIG. 3 schematically shows a 1D array transducer as an example.

  The receiver 120 may include an amplifier that amplifies the time-series analog signal output from the transducer. Also, the receiving unit 120 may include an A / D converter that converts a time-series analog signal output from the transducer into a time-series digital signal. That is, the receiving unit 120 may include the signal collecting unit 140.

  In addition, in order to detect an acoustic wave from various angles and to improve an image precision, the transducer arrangement | positioning which encloses the test object 100 from the whole circumference is preferable. Also, if the subject 100 is large enough to not surround the entire circumference, the transducer may be placed on a hemispherical support. The probe 180 including the receiving unit 120 having such a shape is not a handheld type, but is suitable for a mechanical scanning type photoacoustic apparatus that moves the probe relative to the subject 100. A scanning unit such as an XY stage may be used to move the probe. The arrangement and number of transducers, and the shape of the support are not limited to the above, and may be optimized according to the subject 100.

  In the space between the receiving unit 120 and the subject 100, a medium for propagating the photoacoustic wave may be disposed. This matches the acoustic impedance at the interface between the subject 100 and the transducer. Examples of the medium include water, oil, ultrasonic gel and the like.

  The photoacoustic apparatus 1 may include a holding member that holds the subject 100 and stabilizes the shape. It is preferable that the holding member be high in both light transmission and acoustic wave transmission. For example, polymethylpentene, polyethylene terephthalate, acrylic and the like can be used.

  When the apparatus according to the present embodiment generates an ultrasonic image by transmitting and receiving acoustic waves in addition to the photoacoustic image, the transducer may function as a transmitting unit that transmits the acoustic waves. The transducer as the receiving means and the transducer as the transmitting means may be a single (common) transducer or may be separate configurations.

(Signal collecting unit 140)
The signal collecting unit 140 includes an amplifier for amplifying an electric signal which is an analog signal output from the receiving unit 120 generated for each light emission of the light emitting unit 200, and an A / D for converting the analog signal output from the amplifier to a digital signal. And a converter. The signal collection unit 140 may be configured by an FPGA (Field Programmable Gate Array) chip or the like.

  The operation of the signal processing unit 140 will be described in more detail. Analog signals output from a plurality of transducers arranged in an array of the receiving unit 120 are amplified by a plurality of amplifiers corresponding to each, and converted into digital signals by a plurality of A / D converters corresponding to each. The A / D conversion rate is performed at least twice or more of the band of the input signal. As described above, if the frequency component of the photoacoustic wave is 100 KHz to 10 MHz, conversion is performed at a frequency of 20 MHz or more, preferably 40 MHz. Note that the signal collection unit 140 synchronizes the timing of the light irradiation and the timing of the signal collection process by using the light emission control signal. That is, A / D conversion is started at the above-described A / D conversion rate based on the light emission time for each light emission of the light emitting unit 200, and an analog signal is converted into a digital signal. As a result, it is possible to acquire, for each of the plurality of transducers, digital data strings for each time interval (A / D conversion interval) of 1 / A / D conversion rate from the light emission time for each light emission of the light emitting unit 200. At this time, the light emission time may be determined based on the time when the light pulse waveform peaks.

  The signal acquisition unit 140 is also called a data acquisition system (DAS). In the present specification, an electrical signal is a concept that includes both an analog signal and a digital signal.

  As described above, the signal collection unit 140 may be disposed inside the housing 181 of the probe 180. With such a configuration, the information between the probe 180 and the computer 150 is transmitted as a digital signal, so the noise resistance is improved. Further, the number of wires can be reduced by using a high-speed digital signal as compared with the case of transmitting an analog signal, and the operability of the probe 180 is improved.

  Also, the signal acquisition unit 140 may perform an addition averaging described later. In this case, it is preferable to perform averaging using hardware such as an FPGA.

(Computer 150)
The computer 150 includes an acquisition unit 151, a storage unit 152, and a control unit 153. The unit responsible for the arithmetic function as the acquisition unit 151 can be configured by a processor such as a CPU or a graphics processing unit (GPU), or an arithmetic circuit such as a field programmable gate array (FPGA) chip. These units may be composed of a single processor or arithmetic circuit, or may be composed of a plurality of processors or arithmetic circuits.

  For example, for each of the plurality of transducers, the computer 150 performs combining processing such as the above-described averaging on the photoacoustic signals acquired for each of the plurality of light pulse irradiations. The computer 150 is also filter means for changing the frequency characteristic of the photoacoustic signal when performing weighting processing in proportion to the intensity of the frequency spectrum of the photoacoustic wave obtained by the above-described irradiated light pulse waveform. The filter means in the present embodiment can change the frequency characteristics of the electrical signal based on the peak frequency of the acoustic wave. As the filter means, for example, one having characteristics substantially the same as the frequency spectrum of the acoustic wave, or one changing the frequency spectrum of the acoustic wave to the substantially flat characteristic can be used.

  In the following embodiments, among these combining processes, the case of performing simple addition averaging will be described.

  The computer 150 adds and averages each of the data of the same time from the light emission time of the above-mentioned digital data string output from the signal collection unit 140 for each light emission of the light emission unit 200. Then, the computer 150 stores the arithmetically averaged digital data string in the storage unit 152 as an arithmetically averaged electrical signal (synthesized photoacoustic signal) derived from the photoacoustic wave. Then, based on the combined photoacoustic signal stored in the storage unit 152, the acquisition unit 151 executes generation of photoacoustic image data (structural image or functional image) by image reconstruction and various other arithmetic processing. Do. The acquisition unit 151 may receive input of various parameters such as the sound velocity of the object and the configuration of the holding unit from the input unit 170, and may use them for calculation.

  As a reconstruction algorithm when the acquisition unit 151 converts an electrical signal into three-dimensional volume data, any method such as back projection in the time domain, back projection in the Fourier domain, model-based method (repeated operation method), etc. Method can be adopted. As back projection methods in the time domain, Universal back-projection (UBP), Filtered back-projection (FBP), Delay-and-Sum, etc. may be mentioned.

  The storage unit 152 is configured of a volatile memory such as a random access memory (RAM), a read only memory (ROM), and a non-temporary storage medium such as a magnetic disk or a flash memory. The storage medium in which the program is stored is a non-temporary storage medium. In addition, the storage unit 152 is configured of a plurality of storage media.

  The storage unit 152 can store various data such as a combined photoacoustic signal, photoacoustic image data generated by the acquisition unit 151, and reconstructed image data based on the photoacoustic image data.

  The control unit 153 is configured of an arithmetic element such as a CPU. The control unit 153 controls the operation of each component of the photoacoustic apparatus. The control unit 153 sends, to the drive unit 210, emission control control signals of a plurality of light pulses and setting signals of light pulse waveforms. Then, the laser diode emits light with the designated light pulse waveform to irradiate the subject. The controller 153 is also an optical pulse waveform setting unit that sets an optical pulse waveform.

  Further, as described above, the control unit 153 controls the light pulse waveform, the light intensity of the light pulse, the number of times of light emission, the amplification degree of the photoacoustic signal, etc. by the user's instruction or automatically. That is, the control unit 153 is also light intensity setting means for setting the light intensity of each of the at least two or more types of light pulse waveforms described above. It is also a light emission number setting means for setting the light emission number of each of two or more types of light pulse waveforms.

  Further, the control unit 153 reads out the program code stored in the storage unit 152, and controls the operation of each component of the photoacoustic apparatus. Further, the control unit 153 performs adjustment of the image on the display unit 160 and the like. As a result, an oxygen saturation distribution image is sequentially displayed along with the movement of the probe and the photoacoustic measurement.

  Computer 150 may be a workstation specifically designed for the present invention. The computer 150 may also operate a general-purpose PC or a work station according to an instruction of a program stored in the storage unit 152. Also, each configuration of the computer 150 may be configured by different hardware. Also, at least a part of the configuration of the computer 150 may be configured by a single piece of hardware.

  FIG. 5 shows a specific configuration example of the computer 150 according to the present embodiment. The computer 150 according to the present embodiment includes a CPU 154, a GPU 155, a RAM 156, a ROM 157, and an external storage device 158. Further, a liquid crystal display 161 as the display unit 160, a mouse 171 as the input unit 170, and a keyboard 172 are connected to the computer 150.

  Also, the computer 150 and the receiving unit 120 may be provided in a configuration housed in a common housing. Alternatively, part of the signal processing may be performed by a computer housed in a housing, and the remaining signal processing may be performed by a computer provided outside the housing. In this case, the computers provided inside and outside the housing can be collectively referred to as the computer according to the present embodiment. That is, the hardware constituting the computer may not be housed in one housing. As the computer 150, an information processing apparatus installed at a remote place provided by a cloud computing service or the like may be used.

  The computer 151 corresponds to the processing unit of the present invention. In particular, the acquisition unit 151 mainly implements the function of the processing unit.

(Display unit 160)
The display unit 160 is a display such as a liquid crystal display or an organic EL (Electro Luminescence). This is an apparatus for displaying an image based on object information (for example, structure information or function information) obtained by the computer 150 or a numerical value of a specific position. The display unit 160 may display an image or a GUI for operating the device. Image processing (adjustment of luminance value, etc.) may be performed on the display unit 160 or the computer 150.

(Input unit 170)
As the input unit 170, an operation console that can be operated by the user and configured with a mouse, a keyboard, and the like can be adopted. In addition, the display unit 160 may be configured by a touch panel, and the display unit 160 may be used as the input unit 170. The input unit 170 receives an instruction from a user, an input such as a numerical value, and the like, and transmits the input to the computer 150.

  Each configuration of the photoacoustic apparatus may be configured as a separate apparatus, or may be configured as one integrated apparatus. Further, at least a part of the configuration of the photoacoustic apparatus may be configured as one integrated device.

  The computer 150 also performs drive control of the configuration included in the photoacoustic apparatus by the control unit 153. In addition to the image generated by the computer 150, the display unit 160 may display a GUI or the like. The input unit 170 is configured to allow the user to input information. The user can use the input unit 170 to perform operations such as measurement start and end, designation of an irradiation mode to be described later, and an instruction to save a created image.

(Subject 100)
The subject 100 does not constitute a photoacoustic apparatus, but will be described below. The photoacoustic apparatus according to the present embodiment can be used for the purpose of diagnosis of malignant tumors and vascular diseases of humans and animals and follow-up of chemical treatment. Therefore, the object 100 is assumed to be an object of diagnosis of a living body, specifically a breast or each organ of a human body or an animal, a blood vessel network, a head, a neck, an abdomen, an extremity including a finger and a toe. Ru. For example, if the human body is to be measured, oxyhemoglobin or deoxyhemoglobin, or a blood vessel containing many of them or a neovascular formed in the vicinity of a tumor may be used as the light absorber. In addition, plaque or the like of the carotid artery wall may be a target of the light absorber. In the case of the human body as a subject, melanin, which is a pigment contained in the skin, can be a light absorber that generates the above-mentioned interference. In addition, a pigment such as methylene blue (MB) or indosine green (ICG), gold fine particles, or a substance introduced from the outside obtained by accumulating or chemically modifying them may be used as the light absorber. In addition, a puncture needle or a light absorber attached to the puncture needle may be an observation target. The subject may be an inanimate object such as a phantom or a test object.

(Operation of the embodiment)
Next, the subject information acquiring apparatus according to the present invention irradiates the subject with light pulses of at least two or more types of light pulse waveforms multiple times, receives an acoustic wave generated in the subject for each irradiation, and receives Characteristic information of the object is acquired based on the photoacoustic signal. In the first embodiment, a detailed description will be given below of an embodiment in which two types of light pulse waveforms are alternately emitted and the obtained photoacoustic signals are averaged.

  FIG. 6 is a timing chart for easily explaining the operation in the first embodiment. In FIG. 6, the horizontal axis is a time axis. The control is performed by the computer 150 or an FPGA or dedicated hardware. Acquisition of the photoacoustic signal of the photoacoustic apparatus of this invention and the method of producing | generating the photoacoustic image based on the acquired photoacoustic signal are demonstrated in detail using FIG.

  FIG. 6 is a timing chart of alternately emitting light pulses of two types of light pulse waveforms and obtaining structural information from the obtained photoacoustic signal. In addition, when acquiring the structural information of a blood vessel, it is good for the wavelength of the light irradiation part 200 to select about 795 nm from which the absorption coefficient of oxyhemoglobin and deoxyhemoglobin becomes equal.

  Since the light intensity of the laser diode is small, the photoacoustic apparatus repeatedly emits light at an irradiation cycle: tw1 interval, as shown in FIG. 6T1, to improve the S / N, as shown in FIG. And acquire a photoacoustic signal. The length of the irradiation cycle: tw1 is set in consideration of the Maximum Permissible Exposure (MPE) to the skin. For example, 0.1 mSec may be selected as the irradiation cycle tw1.

  In FIG. 6T1, the light pulse waveform of FIG. 1 (a) and the light pulse waveform of FIG. 1 (c) are alternately emitted, and the photoacoustic signal is acquired 168 times at the irradiation cycle: tw1 ((1) to (4) ...), averaging and obtaining the averaged photoacoustic signal A1 every imaging frame rate cycle: tw2. That is, the 83 photoacoustic signals obtained by the light pulse waveform of FIG. 1A and the light pulse waveform of FIG. 1C are added and averaged. Here, the averaging is an example, and the other combining process described above may be used.

  Next, as shown in FIG. 6T3, based on the averaged photoacoustic signal A1, the above-described processing for reconstruction is performed to obtain reconstructed image data R1. Then, the reconstructed image data R1 is sequentially output to the display unit 160 and displayed as structure information S1 with a period tw2 of an imaging frame rate of 16.6 msec (FIG. 6T4). The frequency of the imaging frame rate is approximately 60 Hz.

  When the photoacoustic signal is acquired 166 times and averaging is performed, the frequency of the imaging frame rate is about 60 Hz, which matches the display frame rate of the display unit 160, but when the number of averaging times is different, the imaging frame rate and display Frame rates may not match. In this case, the imaging frame rate may be converted to a display frame rate using a frame rate converter (not shown) and displayed on the display unit 160.

  As described above, it is possible to obtain information based on the frequency characteristic of a predetermined photoacoustic signal by emitting light with at least two or more types of light pulse waveforms among multiple times of light emission of the light irradiation unit 200 .

  As a result, it is possible to obtain information that is more optimal for the photoacoustic signal frequency characteristics.

  In the first embodiment, two or more different light pulse waveforms are controlled to emit light alternately. However, the present invention is not limited to the configuration emitting light alternately. For example, control is performed such that the light pulse of the light pulse waveform of FIG. 1A is emitted 83 consecutive times, and then the light pulse of FIG. 1C is continuously emitted 83 times. I don't care. In the configuration in which control is performed so as to emit light alternately, the time when the light pulse of the light pulse waveform of FIG. 1A emits light and the time when the light pulse of the light pulse waveform of FIG. Therefore, it is possible to reduce the influence of the movement of the object of the synthesis portion of the photoacoustic signal obtained by the light irradiation of each light pulse waveform. In addition, if the configuration is such that each light is emitted continuously, the time for light irradiation of each light pulse waveform becomes short, so each photoacoustic signal obtained by light irradiation of each light pulse waveform is affected by the movement of the subject. It has the advantage of becoming less receptive.

(Other embodiments)
In the first embodiment described above, the embodiment in which the photoacoustic signals obtained by the irradiation of the light pulse of each light pulse waveform are averaged is described. As described above, the number of irradiations of the light pulse of each light pulse waveform may be changed, and the obtained photoacoustic signal may be averaged. Also, the light intensity of the light pulse of each light pulse waveform may be changed, and the obtained photoacoustic signal may be averaged. Further, the number of light emission of the semiconductor light emitting element of the light pulse of each light pulse waveform may be changed, and the obtained photoacoustic signal may be averaged. Further, in accordance with the irradiation of the light pulse of each light pulse waveform, the amplification degree for amplifying the photoacoustic signal may be changed, and the amplified photoacoustic signal may be added and averaged. Alternatively, weighting may be performed on the acquired photoacoustic signal in proportion to the intensity of the frequency spectrum of the photoacoustic wave obtained by the irradiated light pulse waveform, and averaging may be performed. In addition, after the frequency spectrum of the obtained photoacoustic wave is made flat by a filter having a characteristic that flattens the frequency spectrum of the photoacoustic wave obtained by the irradiated light pulse waveform, the value is also obtained by averaging. It is also good.

  As another embodiment, when processing for obtaining reconstructed image data is performed, the above-described processing is not performed on the photoacoustic signal, but reconstruction processing is performed for each light pulse to acquire reconstructed image data, The composition processing described above may be performed on the reconstructed image data. However, in the case of performing synthesis processing with such reconstructed image data, it is necessary to carry out reconstruction processing for each light emission, and there is a drawback that the amount of calculation increases.

  Moreover, the wavelength of the light which light irradiation part 200 light-emits may use several wavelength. When a plurality of wavelengths are used, for example, the oxygen saturation as function information can be calculated. In the present invention, for example, two wavelengths are alternately switched for each imaging frame rate, photoacoustic signals are acquired, reconstructed image data is calculated, and oxygen saturation is calculated from reconstructed image data calculated at two imaging frame rates. It can be calculated. The calculation of the oxygen saturation is described in detail in JP-A-2015-142740. Furthermore, when obtaining structural information, the light pulse waveforms of the two or more types of the present invention are sequentially irradiated to obtain information of wide frequency characteristics. Then, the light pulse waveform of the other wavelength for obtaining the function information may have a shape of one light pulse waveform in which the pulse width is extended. By doing this, the structural information can be clearly detected regardless of the thickness of the blood vessel, and the functional information can obtain information without high frequency components. The function information can be made detailed information by masking it with the structure information.

  In addition, the plurality of embodiments shown in the present invention may be realized by one photoacoustic apparatus so that they can be switched and used. Furthermore, the photoacoustic apparatus of the present invention may be additionally realized with the function of transmitting ultrasonic waves from a transducer and performing measurement using a reflected wave. In this case, of course, the light emitting unit 200 does not emit light.

DESCRIPTION OF SYMBOLS 1 photoacoustic apparatus 120 receiving part 151 acquisition part 153 control part 200 light irradiation part

Claims (14)

A light irradiation unit that irradiates a subject with pulsed light;
A receiving unit that receives an acoustic wave generated by irradiating the subject with pulsed light and converts the acoustic wave into an electrical signal;
A control unit configured to control the light emitting unit such that the subject is irradiated with pulsed light a plurality of times;
An acquisition unit configured to acquire information on the subject based on a plurality of electrical signals converted from an acoustic wave generated by irradiating the subject with pulsed light multiple times;
A photoacoustic device having
The photoacoustic apparatus, wherein the control unit controls the light emitting unit such that at least a part of the pulsed light irradiated a plurality of times has different pulse waveforms.   The photoacoustic apparatus according to claim 1, wherein the control unit controls the light emitting unit such that at least a part of the pulse lights irradiated a plurality of times have different pulse widths. .   The photoacoustic apparatus according to claim 1, wherein the control unit controls the light emitting unit such that the number of times of emission of the pulse light having the pulse waveforms different from each other is different from each other.   The photoacoustic apparatus according to any one of claims 1 to 3, wherein the control unit controls the light emitting unit such that light intensities of the pulse lights having different pulse waveforms are different from each other. apparatus.   The photoacoustic apparatus according to any one of claims 1 to 4, wherein the acquisition unit performs a process of averaging the plurality of electrical signals.   The photoacoustic apparatus according to any one of claims 1 to 5, wherein the acquisition unit selects an electric signal having a predetermined frequency component among the plurality of electric signals and performs averaging. .   7. The apparatus according to claim 1, wherein the acquisition unit acquires a plurality of reconstructed images by performing image reconstruction of each of the plurality of electrical signals, and adds and averages the plurality of reconstructed images. The photoacoustic apparatus as described in any one.   The acquisition unit acquires a plurality of reconstructed images by performing image reconstruction of each of the plurality of electrical signals, and the re-corresponding to an electrical signal of a predetermined frequency component among the plurality of reconstructed images. The photoacoustic apparatus according to any one of claims 1 to 7, wherein a component image is selected and the averaging is performed.   A first acoustic wave generated by irradiating the subject with a first pulse light having a first pulse waveform among the pulse lights irradiated a plurality of times, and a second different from the first pulse waveform 9. The second acoustic wave generated by irradiating the object with a second pulse light having a pulse waveform at a peak frequency that is different from each other in any one of claims 1 to 8. Photoacoustic apparatus as described.   The photoacoustic apparatus according to any one of claims 1 to 9, further comprising filter means for changing frequency characteristics of the electric signal based on a peak frequency of the acoustic wave.   11. The photoacoustic apparatus according to claim 10, wherein the filter means has substantially the same characteristics as the frequency spectrum of the acoustic wave. 12. The photoacoustic apparatus according to claim 10, wherein the filter means changes the frequency spectrum of the acoustic wave to a substantially flat characteristic.   The photoacoustic apparatus according to any one of claims 1 to 12, wherein the light irradiation unit includes a light source unit that generates pulse light.   The photoacoustic apparatus according to claim 13, wherein the light source unit includes a plurality of semiconductor light emitting elements.

Images