JP6475175B2 - Photoacoustic image generation apparatus, system, and method - Google Patents

Description

  The present invention relates to a photoacoustic image generation apparatus, system, and method, and more specifically, generates a photoacoustic image based on a detection signal of a photoacoustic wave generated when a light absorber in a subject absorbs light. The present invention relates to a photoacoustic image generation apparatus, system, and method.

  An ultrasonic inspection method is known as a kind of image inspection method capable of non-invasively examining the state inside a living body. In the ultrasonic inspection, an ultrasonic probe capable of transmitting and receiving ultrasonic waves is used. When ultrasonic waves are transmitted from the ultrasonic probe to the subject (living body), the ultrasonic waves travel inside the living body and are reflected at the tissue interface. The reflected ultrasound is received by the ultrasound probe, and the internal state can be imaged by calculating the distance based on the time it takes for the reflected ultrasound to return to the ultrasound probe. .

  In addition, photoacoustic imaging is known in which the inside of a living body is imaged using a photoacoustic effect. In general, in photoacoustic imaging, a living body is irradiated with pulsed laser light. Inside the living body, the living tissue absorbs the energy of the pulsed laser light, and ultrasonic waves (photoacoustic waves) are generated by adiabatic expansion due to the energy. By detecting this photoacoustic wave with an ultrasonic probe or the like and constructing a photoacoustic image based on the detection signal, in vivo visualization based on the photoacoustic wave is possible.

  Here, since the reflected ultrasonic wave and the photoacoustic wave are attenuated when propagating in the subject, the intensity of the detection signal of the reflected ultrasonic wave and the photoacoustic wave generated in the deep part of the subject becomes weak. STC (Sensitivity Time) in which the gain (sensitivity) of an amplifier that amplifies a detection signal is changed according to time (depth) as processing for compensating for attenuation of reflected ultrasonic waves and photoacoustic waves traveling in the subject. Control) processing is known. STC is also called TGC (Time Gain Control).

  Patent Document 1 discloses STC processing in an apparatus that generates both an ultrasonic image and a photoacoustic image. In the apparatus described in Patent Literature 1, a first image is generated using a photoacoustic wave generated from a subject irradiated with light and received by a probe. In addition, a second image is generated by using the ultrasonic wave received by the probe after being transmitted to the subject and reflected inside the subject. The first correction unit corrects the luminance of the first image with a gain corresponding to the position in the depth direction. The second correction unit corrects the luminance of the second image with a gain corresponding to the position in the depth direction independently of the first correction unit. In Patent Document 1, by providing independent brightness correction means for the photoacoustic image and the ultrasonic image, the brightness correction is performed so that the user can easily observe without depending on the attenuation characteristics based on the respective measurement principles. It is described that can be performed.

JP 2004-163257 A

  In Japanese Patent Laid-Open No. 2004-260260, the photoacoustic wave and the ultrasonic wave have a difference in image characteristics in the depth direction due to a difference in attenuation characteristics of the respective measurement principles, and thus correction control is performed independently. For this reason, in order to obtain an ultrasonic image having a uniform luminance level regardless of the measurement depth, even if the relationship between the depth and the gain is adjusted with respect to the ultrasonic image, the depth and the gain with respect to the photoacoustic image are adjusted. The relationship is maintained independently of that for the ultrasound image. In order to obtain an image having a uniform luminance level regardless of the measurement depth in the photoacoustic image, it is necessary to separately adjust the relationship between the depth and the gain with respect to the photoacoustic image. Therefore, an observer of the image such as a doctor has to adjust the relationship between the depth and the gain for both the photoacoustic image and the ultrasonic image, which is troublesome.

  In view of the above circumstances, the present invention provides a photoacoustic image generation apparatus, system, and the like that can suppress the trouble of adjusting the relationship between depth and gain in STC processing when both a photoacoustic image and an ultrasonic image are displayed. And a method.

  In order to achieve the above object, the present invention provides a reflected acoustic wave image generation unit that generates a reflected acoustic wave image based on a detection signal of a reflected acoustic wave with respect to an acoustic wave transmitted into a subject, and a light emitted from a light source. A photoacoustic image generation unit that generates a photoacoustic image based on a photoacoustic wave detection signal generated due to absorption of light by a light absorber in the subject, and a reflected acoustic wave image generation unit. In accordance with first gain definition information that defines a correspondence relationship between each of a plurality of positions in the depth direction and a gain at each position, at least one of the reflected acoustic wave detection signal and the signal value of the reflected acoustic wave image. At least one of a first amplification unit that amplifies with a gain according to a position in the depth direction, a photoacoustic wave detection signal input to the photoacoustic image generation unit, and a signal value of the photoacoustic image is output to a plurality of depths. With each position A second amplifying unit that amplifies with a gain according to a position in the depth direction according to second gain definition information that defines a correspondence relationship with a gain at the position; and a second gain based on the first gain definition information There is provided a photoacoustic image generation apparatus including a gain calculation unit that calculates definition information.

  It is preferable that the photoacoustic image generation apparatus of the present invention further includes a gain determination unit that determines the first gain definition information.

  It is preferable that the photoacoustic image generation apparatus of the present invention further includes a gain operation unit for changing the first gain definition information in accordance with a user operation. The gain determination unit preferably determines the first gain definition information according to the operation of the gain operation unit.

  In the photoacoustic image generating apparatus of the present invention, it is preferable that the gain operation unit has a plurality of gain changing knobs corresponding to respective positions in the depth direction in the first gain definition information. It is also preferable that the gain determination unit determines the gain at each position in the depth direction according to the operation amount of each knob.

  In the photoacoustic image generation device of the present invention, the gain determination unit stores a plurality of first gain definition information, and the first amplification unit is selected from the plurality of first gain definition information according to a user operation. The first gain definition information used in step 1 may be selected.

  In the photoacoustic image generation apparatus of the present invention, the gain determination unit may determine the first gain definition information based on the detection signal of the reflected acoustic wave.

  In the photoacoustic image generation device of the present invention, the gain calculation unit obtains a gain defined by the second gain definition information by multiplying a gain at each position in the depth direction by the conversion coefficient in the first gain definition information. May be calculated as

  The conversion coefficient may be set in advance.

  The gain calculation unit may determine the conversion coefficient based on the reception frequency of the photoacoustic wave and the reception frequency of the reflected acoustic wave.

  The photoacoustic image generation apparatus of the present invention may be configured to further include a coefficient determination unit that compares the detection signal of the photoacoustic wave and the detection signal of the reflected acoustic wave and determines a conversion coefficient.

  In the photoacoustic image generation device of the present invention, the coefficient determination unit compares the detection signal of the photoacoustic wave and the detection signal of the reflected acoustic wave in each of the range of positions in the depth direction, and determines the plurality of depths. A transform coefficient may be determined for each of the range of directional positions. In that case, the gain calculation unit preferably multiplies the gain at each position in the depth direction in the first gain definition information by a conversion coefficient determined for the range of positions in the depth direction to which each position belongs.

  The present invention also provides a photoacoustic wave generated due to a light source, an acoustic wave transmitting unit that transmits an acoustic wave in the subject, and a light absorber in the subject absorbing light emitted from the light source. And an acoustic wave receiving unit that detects a reflected acoustic wave with respect to the acoustic wave transmitted from the acoustic wave transmitting unit, a reflected acoustic wave image generating unit that generates a reflected acoustic wave image based on a detection signal of the reflected acoustic wave, and light At least one of a photoacoustic image generation unit that generates a photoacoustic image based on an acoustic wave detection signal, a reflected acoustic wave detection signal input to the reflected acoustic wave image generation unit, and a signal value of the reflected acoustic wave image A first amplifying section that amplifies with a gain according to a position in the depth direction according to first gain definition information that defines a correspondence relationship between each of the positions in the depth direction and the gain at each position; Photoacoustic wave input to the acoustic image generator At least one of the detection signal and the signal value of the photoacoustic image is moved to the position in the depth direction according to the second gain definition information that defines the correspondence between each of the positions in the depth direction and the gain at each position. There is provided a photoacoustic image generation system including a second amplification unit that amplifies with a corresponding gain and a gain calculation unit that calculates second gain definition information based on the first gain definition information.

  The present invention further includes a step of generating a reflected acoustic wave image based on a detection signal of a reflected acoustic wave with respect to an acoustic wave transmitted into the subject, and a light absorber in the subject absorbs light emitted from the light source. A step of generating a photoacoustic image based on a photoacoustic wave detection signal generated due to the detection, a reflected acoustic wave detection signal used for generating a reflected acoustic wave image, and a signal value of the reflected acoustic wave image At least one of the plurality of positions in the depth direction and a gain corresponding to the position in the depth direction according to first gain definition information that defines a correspondence relationship between each of the positions in the depth direction and the gain at each position; A photo-acoustic wave detection signal used for generating an acoustic image and / or a signal value of the photoacoustic image is defined by defining a correspondence relationship between each of a plurality of positions in the depth direction and a gain at each position. A photoacoustic image generation method comprising: amplifying with a gain according to a position in the depth direction according to the gain definition information; and calculating second gain definition information based on the first gain definition information To do.

  INDUSTRIAL APPLICABILITY The photoacoustic image generation apparatus, system, and method of the present invention can reduce the effort of adjusting the relationship between depth and gain in STC processing when displaying both a photoacoustic image and an ultrasonic image. .

1 is a block diagram showing a photoacoustic image generation system according to a first embodiment of the present invention. The block diagram which shows the one part detailed structure in an ultrasonic unit. The figure which shows the specific example of a gain operation part. The graph which shows the gain curve used for amplification of an ultrasonic image signal. The graph which shows the attenuation characteristic of an acoustic wave. The graph which shows the gain curve used for amplification of a photoacoustic image signal. The flowchart which shows an operation | movement procedure. The figure which shows the ultrasonic image and photoacoustic image before gain operation. The figure which shows the ultrasonic image photoacoustic image after gain operation. The block diagram which shows a part of photoacoustic image generating apparatus which concerns on 2nd Embodiment of this invention. The flowchart which shows the operation | movement procedure in 2nd Embodiment. The flowchart which shows the procedure of the 1st gain definition information determination based on an ultrasonic image signal. The block diagram which shows a part of photoacoustic image generating apparatus which concerns on 3rd Embodiment of this invention. The graph which shows the attenuation characteristic of an acoustic wave.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a photoacoustic image generation system according to the first embodiment of the present invention. The photoacoustic image generation system 10 includes a probe (ultrasonic probe) 11, an ultrasonic unit 12, and a laser unit 13. In the embodiment of the present invention, an ultrasonic wave is used as an acoustic wave. However, the ultrasonic wave is not limited to an ultrasonic wave, and is audible as long as an appropriate frequency is selected according to a test object, measurement conditions, and the like. An acoustic wave having a frequency may be used.

  The laser unit 13 is a light source and emits measurement light. The measurement light emitted from the laser unit 13 is guided to the probe 11 using light guide means such as an optical fiber, and is emitted from the probe 11 toward the subject. The laser unit 13 is a solid-state laser light source using, for example, YAG (yttrium / aluminum / garnet) or alexandrite. The laser unit 13 includes, for example, a flash lamp that is an excitation light source, and a Q switch for causing the laser to oscillate. The type of light source in the laser unit 13 is not particularly limited, and the laser unit 13 may be a laser diode light source (semiconductor laser light source), or an optically amplified laser light source using a laser diode light source as a seed light source. Also good. A light source other than the laser light source may be used.

  The wavelength of the laser light emitted from the laser unit 13 is appropriately determined according to the light absorption characteristics of the substance in the subject to be measured. For example, when the measurement target is hemoglobin in a living body (that is, when imaging blood vessels), the wavelength of the laser light is preferably a wavelength belonging to the near-infrared wavelength region. The near-infrared wavelength region means a wavelength region of about 700 to 850 nm. The laser unit 13 may emit laser light having a single wavelength, or may emit laser light having a plurality of wavelengths. When the laser unit 13 can emit laser beams having a plurality of wavelengths, the laser unit 13 may emit laser beams having a plurality of wavelengths at the same time, or may switch and emit laser beams having a plurality of wavelengths.

  The probe 11 has, for example, a plurality of ultrasonic transducers arranged one-dimensionally. The probe 11 detects a photoacoustic wave emitted from a light absorber in the specimen after the subject is irradiated with the laser light emitted from the laser unit 13. In addition to detecting the photoacoustic wave, the probe 11 transmits an acoustic wave (ultrasonic wave) to the subject and receives a reflected acoustic wave (reflected ultrasonic wave) with respect to the transmitted ultrasonic wave. In that case, the probe 11 serves as an acoustic wave transmission part and an acoustic wave reception part. You may perform transmission / reception of an ultrasonic wave in the separated position. For example, ultrasonic waves may be transmitted from a position different from the probe 11, and reflected ultrasonic waves with respect to the transmitted ultrasonic waves may be received by the probe 11. The probe 11 is not limited to a linear probe, and may be a convex probe or a sector probe.

  The ultrasonic unit 12 constitutes a photoacoustic image generation apparatus. The ultrasonic unit 12 includes a reception circuit 21, an AD converter (Analog to Digital converter) 22, a reception memory 23, a photoacoustic image generation unit 24, an ultrasonic image generation unit 25, an image synthesis unit 26, a control unit 28, and transmission control. A circuit 29, a gain operation unit 30, a gain determination unit 31, and a gain calculation unit 32 are included. The ultrasonic unit 12 typically includes a processor, a memory, a bus, and the like. The ultrasonic unit 12 incorporates a program related to photoacoustic image generation, and the processor operates according to the program, thereby realizing at least some functions of each unit in the ultrasonic unit 12.

  FIG. 2 shows a detailed configuration of a part of the ultrasonic unit 12. The receiving circuit 21 receives a detection signal output from the probe 11. The reception circuit 21 includes a low noise amplifier 211, a variable gain amplifier 212, and a low pass filter 213. The detection signal of the probe 11 is amplified by the low noise amplifier 211, and then the gain is adjusted according to the depth by the variable gain amplifier 212, and the high frequency component is cut by the low pass filter 213.

  The AD converter 22 converts the detection signal received by the reception circuit 21, that is, the photoacoustic wave detection signal and the reflected ultrasonic detection signal detected by the probe 11, from an analog signal to a digital signal. The AD converter 22 stores the detection signal (sampling data) of the photoacoustic wave and the reflected ultrasonic wave subjected to AD conversion in the reception memory 23. The receiving circuit 21 and the AD converter 22 may be configured as one IC (Integrated Circuit), for example, or may be configured as individual ICs.

  The photoacoustic image generation unit 24 reads sampling data of a photoacoustic wave detection signal from the reception memory 23. The photoacoustic image generation unit 24 generates a photoacoustic image based on a photoacoustic wave detection signal (its sampling data). The ultrasonic image generation unit (reflected acoustic wave image generation unit) 25 reads the sampling data of the detection signal of the reflected ultrasonic wave from the reception memory 23. The ultrasonic image generation unit 25 generates an ultrasonic image (reflected acoustic wave image) based on the detection signal (the sampling data) of the reflected ultrasonic wave.

  The ultrasonic image generation unit 25 includes an ultrasonic image reconstruction unit 251, a detection / logarithm conversion unit 252, a first amplification unit 253, and an ultrasonic image construction unit 254. The ultrasonic image reconstruction unit 251 reconstructs a reflected ultrasonic wave detection signal (reflected ultrasonic signal), and generates data for each line of the ultrasonic image. The reconstructed reflected ultrasound signal can be regarded as an ultrasound image. For example, the ultrasonic image reconstruction unit 251 adds data from 64 acoustic detection elements of the probe 11 with a delay time corresponding to the position of the acoustic detection element, and generates data for one line (delay addition method). ).

  The detection / logarithm conversion unit 252 performs, for example, envelope detection on the reconstructed reflected ultrasonic signal (ultrasonic image signal), and logarithmically converts the detected signal. The first amplifying unit 253 performs STC processing on the ultrasonic image. The first amplifying unit 253 amplifies the ultrasonic image signal (the signal value) subjected to logarithmic conversion with a gain corresponding to the position in the depth direction. In other words, the first amplifying unit 253 amplifies the reflected ultrasonic signal with a gain corresponding to the time elapsed from the time when ultrasonic transmission is started (the time when sampling is started). In particular, in the present embodiment, the first amplifying unit 253 amplifies the ultrasonic image signal with a gain corresponding to the position in the depth direction in accordance with the first gain definition information determined by the gain determining unit 31.

  The gain determination unit 31 determines first gain definition information. The first gain definition information is information that defines a correspondence relationship between each of the positions in the depth direction and the gain at each position. In the ultrasonic image, a plurality of control points are set discretely in the depth direction of the subject. The first gain definition information defines the gain at each of the plurality of control points. The gain defined by the first gain definition information is defined as, for example, a change (difference) from the default value. The gain operation unit 30 has a user interface for changing the first gain definition information in accordance with a user operation. The gain determination unit 31 determines first gain definition information according to the operation of the gain operation unit 30.

  FIG. 3 shows a specific example of the gain operation unit 30. The gain operation unit 30 includes, for example, a plurality of gain changing knobs corresponding to a plurality of positions (control points) in the depth direction in the first gain definition information. In the example of FIG. 3, the gain operation unit 30 includes six gain changing knobs T1 to T6 corresponding to six control points. The intervals between adjacent control points are set, for example, at equal intervals. The number of control points is arbitrary and may be set as appropriate according to the measurement depth. The gain changing knob may be a physical means such as a slide bar or a dial, or may be configured with a GUI (graphical user interface).

  In FIG. 3, a knob T1 is a gain changing knob corresponding to the control point at the shallowest position, and a knob T6 is a gain changing knob corresponding to the control point at the deepest value. The user can change the first gain definition information by moving the knobs T1 to T6 in the horizontal direction of the paper. For example, when the user moves the knob T1 to the right side toward the paper surface, the gain determination unit 31 increases the gain for the control point corresponding to the knob T1. Conversely, when the user moves the knob T1 to the left side toward the paper surface, the gain determination unit 31 weakens the gain for the control point corresponding to the knob T1. The center position of the knob T1 is a “neutral” position, and when the knob T1 is positioned at the center, the gain remains unchanged from the default value.

  FIG. 4 shows a gain curve used for amplification of the ultrasonic image signal. In the graph shown in FIG. 4, the horizontal axis represents the magnitude of the gain, and the vertical axis represents the position in the depth direction. Control points C1 to C6 in FIG. 4 represent control points corresponding to the knobs T1 to T6 in FIG. The first amplifying unit 253 uses the gain defined by the first gain definition information at the positions of the control points C1 to C6 defined by the first gain definition information to gain the ultrasound image signal. And The first amplifying unit 253 linearly interpolates the gains of the two control points at the position in the depth direction between the two adjacent control points, and uses the linearly interpolated gains of the ultrasonic image signal. The gain used for amplification. Interpolation is not limited to linear interpolation, and higher-order interpolation may be used.

  In place of or in addition to the above, when the gain determination unit 31 stores a plurality of pieces of the first gain definition information, the gain determination unit 31 selects the first gain definition information from among the plurality of first gain definition information according to the user operation. The first gain definition information used in one amplifying unit 253 may be selected. For example, the gain determination unit 31 stores first gain definer information corresponding to each of a plurality of observation target parts. When the user operates an input unit such as a button, a trackball, or a touch panel provided on the console to select the observation target region, the gain determination unit 31 selects the first gain corresponding to the selected observation target region. The setting information is selected as first gain definition information used in the first amplifying unit 253.

  Returning to FIG. 2, the ultrasonic image construction unit 254 converts the ultrasonic image signal amplified by the first amplification unit 253 into a pixel value of the display image, and generates an ultrasonic image (B-mode image). The ultrasonic image construction unit 254 generates an ultrasonic image by converting, for example, the signal intensity within a certain range of the ultrasonic image signal into a display gradation in a range from the highest luminance to the lowest luminance. The ultrasonic image construction unit 254 transmits the generated ultrasonic image to the image composition unit 26.

  The photoacoustic image generation unit 24 includes a photoacoustic image reconstruction unit 241, a detection / logarithm conversion unit 242, a second amplification unit 243, and a photoacoustic image construction unit 244. The photoacoustic image reconstruction unit 241 reconstructs a photoacoustic wave detection signal (photoacoustic signal) and generates data of each line of the photoacoustic image. The reconstructed photoacoustic signal can be regarded as a photoacoustic image. The photoacoustic image reconstruction unit 241 reconstructs a photoacoustic signal using, for example, a delay count method. The photoacoustic image reconstruction unit 241 may perform reconstruction by the CBP method (Circular Back Projection) instead of the delay addition method. Alternatively, the photoacoustic image reconstruction unit 241 may perform reconstruction using the Hough transform method or the Fourier transform method.

  The detection / logarithm conversion unit 242 performs, for example, envelope detection on the reconstructed photoacoustic signal (photoacoustic image signal), and logarithmically converts the detected signal. The second amplifying unit 243 performs STC processing on the photoacoustic image. The second amplifying unit 243 amplifies the photoacoustic image signal (the signal value) subjected to logarithmic conversion with a gain according to the position in the depth direction. In particular, in the present embodiment, the second amplifying unit 243 amplifies the photoacoustic image signal with a gain corresponding to the position in the depth direction according to the second gain definition information calculated by the gain calculating unit 32.

  The gain calculation unit 32 calculates second gain definition information based on the first gain definition information determined by the gain determination unit 31. The gain calculation unit 32 calculates, for example, a gain obtained by multiplying the gain at each position in the depth direction in the first gain definition information by the conversion coefficient as a gain defined by the second gain definition information. The conversion coefficient is set in advance, and may be stored in a storage unit (not shown) in the ultrasonic unit 12. The conversion coefficient may be determined by acquiring a test screen having no subject in both the ultrasonic image and the photoacoustic image and calculating a ratio thereof. The conversion coefficient may be determined, for example, before the ultrasonic unit 12 is shipped from the factory, and the determined conversion coefficient may be preset in the storage unit as a conversion coefficient unique to the apparatus.

  FIG. 5 is a graph showing attenuation of acoustic waves. In the graph shown in FIG. 5, the horizontal axis represents the position in the depth direction, and the vertical axis represents the attenuation of the acoustic wave. The attenuation rate of the portion through which the acoustic wave passes is 0.5 [bB / cm / MHz], and the case where the frequency of the acoustic wave is 10 MHz is considered. In FIG. 5, a graph B shows the attenuation characteristic of the reflected ultrasonic wave, and a graph PA shows the attenuation characteristic of the photoacoustic wave. The reflected ultrasonic attenuation is expressed as the ratio of the received ultrasonic intensity to the transmitted ultrasonic intensity, and the photoacoustic wave attenuation is the detected photoacoustic wave intensity relative to the generated photoacoustic wave intensity. Expressed as a ratio of intensities.

  Comparing the graph B and the graph PA, it can be seen that the attenuation of the photoacoustic wave is half that of the reflected ultrasonic wave. The reason why the attenuation of photoacoustic waves is halved is that ultrasonic waves are attenuated in the reciprocal path between transmission and reception, whereas photoacoustic waves are attenuated in one way only for detection (reception). It is done.

  Specifically, the attenuation characteristic of ultrasonic waves in the living body is 0.5 [dB / cm / MHz] to 1 [dB / cm / MHz], and the attenuation is roughly proportional to the propagation distance and frequency of the ultrasonic waves. . For example, when considering a depth position of 3 cm, an ultrasonic wave propagates 6 cm in a reciprocating manner, whereas a photoacoustic wave propagates as an acoustic wave (ultrasonic wave) only 3 cm in one way. For example, consider a case where the user is observing an ultrasonic image having a depth of 3 cm. Further, it is assumed that the ultrasonic image can be properly observed when the gain is increased by 10 dB at the control point at the depth position of 3 cm. In this case, it is considered that the photoacoustic image can be appropriately observed by increasing the gain by 5 dB at the control point at the depth position of 3 cm.

  The present inventor, when performing an amplification of an ultrasonic image signal with a certain gain in order to compensate for the attenuation accompanying the progress of the ultrasonic wave with respect to the reflected ultrasonic wave (ultrasonic image), at a gain that is half that gain. It has been found that if the photoacoustic image signal is amplified, the attenuation accompanying the progression of the photoacoustic wave can be compensated. Therefore, it is preferable that the conversion coefficient used when calculating the second gain definition information setting is set to 0.5. The gain calculation unit 32 uses this conversion coefficient to calculate a gain that is half the gain at each position in the depth direction in the first gain definition information as a gain defined by the second gain definition information.

  FIG. 6 shows a gain curve used for amplification of the photoacoustic image signal. In the graph shown in FIG. 6, the horizontal axis indicates the magnitude of the gain, and the vertical axis indicates the position in the depth direction. Control points C1 to C6 in FIG. 6 represent control points corresponding to the knobs T1 to T6 in FIG. The second amplifying unit 243 obtains the gain defined by the second gain definition information at the position in the depth direction of each of the control points C1 to C6 defined by the second gain definition information. The gain used for amplification. At the position in the depth direction between two adjacent control points, the second amplifying unit 243 performs a linear interpolation operation on the gains of the two control points, and the linearly interpolated gains are obtained from the photoacoustic image signal. The gain used for amplification. Interpolation is not limited to linear interpolation, and higher-order interpolation may be used. Comparing FIG. 4 with FIG. 6, it can be seen that the gain for the photoacoustic image signal is half the gain for the ultrasonic image signal.

  Returning to FIG. 2 again, the photoacoustic image construction unit 244 converts the photoacoustic image signal amplified by the second amplification unit 243 into a pixel value of the display image, and generates a photoacoustic image. For example, the photoacoustic image construction unit 244 generates a photoacoustic image by converting the signal intensity within a certain range of the photoacoustic image signal into a display gradation in a range from the highest luminance to the lowest luminance. The photoacoustic image construction unit 244 transmits the generated photoacoustic image to the image composition unit 26.

  The image synthesis unit 26 synthesizes the photoacoustic image and the ultrasonic image. The image composition unit 26 performs image composition by superimposing a photoacoustic image and an ultrasonic image, for example. The image composition unit 26 may assign different display colors to the photoacoustic image and the ultrasonic image. The synthesized image is displayed on an image display device 14 (see FIG. 1) such as a display device. It is also possible to display the photoacoustic image and the ultrasonic image side by side on the image display device 14 without performing image synthesis, or to switch between the photoacoustic image and the ultrasonic image.

  The control unit 28 illustrated in FIG. 1 controls each unit in the ultrasonic unit 12. For example, when acquiring a photoacoustic image, the control unit 28 transmits a trigger signal to the laser unit 13 to emit laser light from the laser unit 13. The trigger signal includes, for example, an excitation trigger signal for emitting excitation light to the laser medium in the laser unit 13 and a Q switch trigger signal for causing the laser to perform Q switch oscillation. The control unit 28 transmits a sampling trigger signal to the receiving circuit 21 in accordance with the emission of the laser light, and controls the photoacoustic wave sampling start timing and the like.

  When acquiring an ultrasonic image, the control unit 28 transmits an ultrasonic transmission trigger signal to the transmission control circuit 29 to instruct ultrasonic transmission. When receiving the ultrasonic transmission trigger signal, the transmission control circuit 29 causes the probe 11 to transmit ultrasonic waves. The control unit 28 transmits a sampling trigger signal to the reception circuit 21 in synchronization with the timing of ultrasonic transmission, and starts sampling of reflected ultrasonic waves.

  FIG. 7 shows an operation procedure. A user such as a doctor operates the gain operation unit 30 to adjust the gain in the STC process for the ultrasound image (step S21). The gain determination unit 31 determines first gain definition information based on the operation in the gain operation unit 30 (step S22). The gain determination unit 31 transmits the determined first gain definition information to the first amplification unit 253 (see FIG. 2) and the gain calculation unit 32.

  The gain calculation unit 32 determines second gain definition information based on the first gain definition information (step S23). In step S23, the gain calculation unit 32 determines, for example, a gain that is half of the gain defined by the first gain definition information as the second gain definition information. The gain calculation unit 32 transmits the determined second gain definition information to the second amplification unit 243.

  The control unit 28 (see FIG. 1) transmits an ultrasonic transmission trigger signal to the transmission control circuit 29, and transmits ultrasonic waves from the probe 11 to the subject via the transmission control circuit 29 (step S11). The probe 11 detects reflected ultrasonic waves with respect to the transmitted ultrasonic waves (step S12). The detected reflected ultrasound is converted into a digital signal by the AD converter 22 through the receiving circuit 21 and stored in the receiving memory 23.

  The ultrasonic image generation unit 25 reads the reflected ultrasonic signal from the reception memory 23 and generates an ultrasonic image based on the read reflected ultrasonic signal (step S13). The first amplifying unit 253 amplifies the ultrasonic image signal with a gain corresponding to the depth position according to the first gain definition information determined in step S22 (step S14).

  In FIG. 2, the first amplifying unit 253 amplifies the ultrasonic image signal that has been detected and logarithmically converted by the detection and logarithmic conversion unit 252, but is not limited thereto. The first amplifying unit 253 amplifies the ultrasonic image signal reconstructed by the ultrasonic image reconstructing unit 251 or the ultrasonic image signal converted to the pixel value of the display image by the ultrasonic image constructing unit 254. May be.

  Further, the operation of the gain operation unit 30 in step S21 may be performed in a state where the image generated in step S13 is displayed on the image display device 14. In that case, by repeatedly performing the operation of the gain operation unit 30 and the generation and display of the ultrasonic image, the user adjusts the gain in the STC processing while confirming the ultrasonic image subjected to the STC processing. Can be implemented.

  The control unit 28 transmits an excitation trigger signal to the laser unit 13 and then transmits a Q switch trigger signal. The laser unit 13 lights an excitation light source such as a flash lamp in response to the excitation trigger signal, turns on the Q switch in response to the Q switch trigger signal, and emits pulsed laser light (step S15).

  In the subject, a photoacoustic wave is generated by absorbing the energy of the pulsed laser light irradiated by the light absorber. The probe 11 detects a photoacoustic wave generated in the subject (step S16). The detected photoacoustic wave is converted into a digital signal by the AD converter 22 through the reception circuit 21 and stored in the reception memory 23. It is also possible to divide the region of the subject irradiated with laser light into a plurality of partial regions, and perform light irradiation and photoacoustic signal detection for each partial region.

  The photoacoustic image reconstruction unit 241 reads a photoacoustic signal from the reception memory 23, and generates a photoacoustic image based on the read photoacoustic signal (step S17). The second amplifying unit 243 amplifies the photoacoustic image signal with a gain corresponding to the depth position in accordance with the second gain definition information determined in step S23 (step S18). For example, the second amplifying unit 243 amplifies the photoacoustic image with a gain that is half of the ultrasonic image amplified by the first amplifying unit 253 at each depth position. The image composition unit 26 displays the ultrasonic image, the photoacoustic image, and the image display device 14 (step S19).

  FIG. 8 shows an ultrasonic image and a photoacoustic image before gain operation. Since the reflected ultrasonic wave and the photoacoustic wave are attenuated as they go deeper, the luminance is extremely lowered at a deep position, and it is difficult to observe the deep part as it is.

  FIG. 9 shows an ultrasonic image photoacoustic image after gain operation. The user operates the gain operation unit 30 and adjusts the gain of the STC process so that the deep portion can be observed in the ultrasonic image by increasing or decreasing the gain of each control point from the default value, for example. When the first gain definition information is changed in the gain adjustment of the STC process for the ultrasonic image, the second gain definition information is also changed accordingly, and the gain adjustment of the STC process for the photoacoustic image is performed. By adjusting the gain of the STC process for the photoacoustic image, for example, as indicated by a white arrow in FIG. 9, the light absorber present in the deep portion that cannot be observed in FIG. 8 is observed. It becomes possible.

  In the present embodiment, second gain definition information for the photoacoustic image is determined based on the first gain definition information for the ultrasonic image. Photoacoustic measurement and ultrasonic (reflected ultrasonic) measurement are different in the principle of measurement, but there is a similarity in attenuation received by a photoacoustic wave passing through the same part of the subject and a reflected ultrasonic wave. In the present embodiment, the gain of the STC process for the photoacoustic image is set to, for example, half of the gain of the STC process for the ultrasonic image. By setting in this way, the user can perform gain adjustment of STC processing on the photoacoustic image only by performing gain operation of STC processing on the ultrasound image. For example, by adjusting the gain of the STC process so that the deep portion can be observed in the ultrasonic image, the deep portion can be observed also in the photoacoustic image, and the adjustment work can be saved.

  Next, a second embodiment of the present invention will be described. FIG. 10 shows a part of the photoacoustic image generation apparatus according to the second embodiment of the present invention. The configuration of the photoacoustic image generation apparatus (ultrasonic unit) according to the present embodiment is a configuration in which the gain operation unit 30 is omitted from the configuration of the ultrasonic unit described in the first embodiment shown in FIG. In the present embodiment, the gain determination unit 31 determines first gain definition information based on the reflected ultrasonic signal. Other points may be the same as in the first embodiment.

  The gain determination unit 31 receives the ultrasonic image signal subjected to detection / logarithmic conversion from the detection / logarithmic conversion unit 252 of the ultrasonic image generation unit 25. The gain determination unit 31 determines a gain for each control point in the first gain definition information based on the received ultrasonic image signal. In other words, the gain determination unit 31 automatically adjusts the gain of STC processing based on the ultrasonic image signal. The method for adjusting the gain of the STC process based on the ultrasonic image signal is not particularly limited. As such a technique, for example, a technique described in Japanese Patent Application Laid-Open No. 2007-117168 can be used.

  In FIG. 10, the gain determination unit 31 determines the first gain definition information based on the ultrasonic image signal that has been detected and logarithmically converted by the detection and logarithm conversion unit 252. It is not limited. The gain determination unit 31 performs the first operation based on the ultrasound image signal reconstructed by the ultrasound image reconstruction unit 251 or the ultrasound image signal converted to the pixel value of the display image by the ultrasound image construction unit 254. 1 gain definition information may be determined.

  FIG. 11 shows an operation procedure in the present embodiment. The control unit 28 (see FIG. 1) transmits an ultrasonic transmission trigger signal to the transmission control circuit 29, and transmits ultrasonic waves from the probe 11 to the subject via the transmission control circuit 29 (step S31). The probe 11 detects reflected ultrasonic waves with respect to the transmitted ultrasonic waves (step S32). The detected reflected ultrasound is converted into a digital signal by the AD converter 22 through the receiving circuit 21 and stored in the receiving memory 23.

  The ultrasonic image generation unit 25 reads the reflected ultrasonic signal from the reception memory 23 and generates an ultrasonic image based on the read reflected ultrasonic signal (step S33). The gain determination unit 31 determines the gain for each control point in the first gain definition information based on the received ultrasonic image signal (step S34). The gain determination unit 31 transmits the determined first gain definition information to the first amplification unit 253 (see FIG. 10) and the gain calculation unit 32.

  FIG. 12 shows a procedure for determining first gain definition information based on the ultrasonic image signal. The gain determination unit 31 divides the ultrasonic image into a plurality of regions in the depth direction (step S51). Each of the divided depth regions includes a control point. The control point preferably coincides with the center of each depth region. The gain determination unit 31 generates a histogram in each divided depth region (step S52). The gain determination unit 31 obtains a histogram peak (class value of the class with the highest frequency) and an intensity width (class width at which the frequency exceeds a certain value) for the histogram of each depth region (step) S53).

  The gain determination unit 31 calculates the average signal strength within the histogram strength of each depth region (step S54). The gain determination unit 31 calculates the difference between the average signal strength within the strength of each depth region and the target average signal strength preset in each depth region (step S55). The gain determination unit 31 determines first gain definition information based on the difference value (difference value) calculated in step S55 (step S56). In step S56, the gain determination unit 31 obtains a correction gain for the ultrasonic image at the center depth of each depth region based on the difference value calculated in step S55. The method of determining the first gain definition based on the above-described ultrasonic image is an example, and is not limited to the above.

  Returning to FIG. 11, the gain calculator 32 determines second gain definition information based on the first gain definition information determined in step S34 (step S35). In step S35, the gain calculation unit 32 determines, for example, a gain that is half of the gain defined by the first gain definition information as the second gain definition information. The gain calculation unit 32 transmits the determined second gain definition information to the second amplification unit 243. The first amplifying unit 253 amplifies the ultrasonic image signal with a gain corresponding to the depth position according to the first gain definition information determined in step S34 (step S36).

  The control unit 28 transmits an excitation trigger signal to the laser unit 13 and then transmits a Q switch trigger signal. The laser unit 13 turns on an excitation light source such as a flash lamp in response to the excitation trigger signal, turns on the Q switch in response to the Q switch trigger signal, and emits pulsed laser light (step S37). In the subject, a photoacoustic wave is generated by absorbing the energy of the pulsed laser light irradiated by the light absorber. The probe 11 detects the photoacoustic wave generated in the subject (step S38). The detected photoacoustic wave is converted into a digital signal by the AD converter 22 through the reception circuit 21 and stored in the reception memory 23.

  The photoacoustic image reconstruction unit 241 reads a photoacoustic signal from the reception memory 23, and generates a photoacoustic image based on the read photoacoustic signal (step S39). The second amplifying unit 243 amplifies the photoacoustic image signal with a gain corresponding to the depth position according to the second gain definition information determined in step S35 (step S40). For example, the second amplifying unit 243 amplifies the photoacoustic image with a gain that is half of the ultrasonic image amplified by the first amplifying unit 253 at each depth position. The image composition unit 26 displays the ultrasonic image, the photoacoustic image, and the image display device 14 (step S41).

  In the present embodiment, the gain determination unit 31 determines first gain definition information based on the ultrasonic image signal. By determining the first gain definition information based on the ultrasonic image, the gain in the STC process can be automatically adjusted. In this embodiment, the gain in the STC process for the photoacoustic image can be automatically adjusted using the result of the automatic adjustment in the ultrasonic image. For this reason, it is possible to further reduce the labor of the user. In the present embodiment, a configuration having the gain operation unit 30 (see FIG. 1) may be employed as in the first embodiment. In that case, the gain automatically adjusted based on the ultrasonic image signal and the gain manually adjusted by the user may be switchable.

  Subsequently, a third embodiment of the present invention will be described. FIG. 13 shows a part of the photoacoustic image generation apparatus according to the third embodiment of the present invention. The photoacoustic image generation apparatus (ultrasonic unit) according to the present embodiment includes a coefficient determination unit 33 in addition to the configuration of the ultrasonic unit described in the first embodiment illustrated in FIG. The coefficient determination unit 33 compares the detection signal of the photoacoustic wave and the detection signal of the reflected acoustic wave, and determines a conversion coefficient used by the gain calculation unit 32. Other points may be the same as in the first embodiment or the second embodiment.

  The coefficient determination unit 33 receives the photoacoustic signal reconstructed by the photoacoustic image reconstruction unit 241 and the ultrasonic signal reconstructed by the ultrasonic image reconstruction unit 251. The coefficient determination unit 33 integrates the photoacoustic signal in the depth direction for a certain sound ray (line). Similarly, the coefficient determination unit 33 integrates the ultrasonic signal in the depth direction for a certain sound ray. The range to be integrated need not be the entire range in the depth direction. Since the detection signal of the photoacoustic wave generated in the deep part of the subject is weak, the coefficient determination unit 33 may integrate within a certain range from the surface side of the subject.

  The coefficient determination unit 33 calculates the ratio between the photoacoustic signal integrated in the depth direction and the ultrasonic signal integrated in the depth direction. The coefficient determination unit 33 determines the calculated ratio as a conversion coefficient used when calculating the second gain definition information. The coefficient determination unit 33 may integrate the photoacoustic signal and the ultrasonic signal with each of the plurality of sound rays, and may determine the conversion coefficient based on the total or average thereof. The coefficient determination unit 33 notifies the gain calculation unit 32 of the determined conversion coefficient. The gain calculation unit 32 determines a gain obtained by multiplying the gain in the first gain definition information by the notified conversion coefficient as the gain in the second gain definition information. The coefficient determination unit 33 may be configured as one IC, or may be configured as a part of ICs of other components.

  The coefficient determination unit 33 may divide the depth direction into a plurality of blocks and integrate the photoacoustic signal and the ultrasonic signal with each of them. In that case, the ratio between the photoacoustic signal integrated for each block and the integrated ultrasonic signal may be calculated to determine the conversion coefficient for each block. That is, the coefficient determination unit 33 compares the photoacoustic wave detection signal and the reflected acoustic wave detection signal in each of the plurality of depth-direction position ranges, and each of the plurality of depth-direction position ranges. A conversion coefficient may be determined for. In that case, the gain calculation unit 32 multiplies the gain at each position in the depth direction in the first gain definition information by the conversion coefficient determined for the range of the position in the depth direction to which each position belongs. 2 gain definition information may be calculated.

  The photoacoustic signal and the ultrasonic signal received by the coefficient determination unit 33 are not limited to those reconstructed. For example, the detection / logarithmically converted photoacoustic signal output from the detection / logarithmic conversion unit 242 and the detection / logarithmically converted ultrasonic signal output from the detection / logarithmic conversion unit 252 may be received. Alternatively, the photoacoustic image generated by the photoacoustic image construction unit 244 in a state where the second amplification unit 243 does not perform the STC process, and the ultrasonic image construction unit 254 in a state where the first amplification unit 253 does not perform the STC process. And an ultrasonic image generated by.

  In the present embodiment, the coefficient determination unit 33 determines a conversion coefficient based on the photoacoustic signal and the reflected ultrasonic signal. In this way, the conversion coefficient can be changed according to the subject, and the subject dependency is eliminated compared with the case where a constant conversion coefficient is used, and a more appropriate gain of STC processing is applied to the photoacoustic image. Can be set. Other effects are the same as those of the first embodiment or the second embodiment.

  As described above, the attenuation of reflected ultrasonic waves and the attenuation of photoacoustic waves are also proportional to the frequency. For example, consider using a probe 11 with a probe bandwidth of 5 MHz to 10 MHz. This band is a typical band of a shallow probe that can be used for photoacoustic measurement. When a probe having such a band is used, the reception frequency may be different between the photoacoustic wave and the reflected ultrasonic wave. For example, the sensitivity of the photoacoustic wave is emphasized, the photoacoustic wave reception frequency may be 5 MHz, and the reflected ultrasonic wave reception frequency may be 10 MHz.

  FIG. 14 is a graph showing attenuation of acoustic waves. In the graph shown in FIG. 14, the horizontal axis represents the position in the depth direction, and the vertical axis represents the attenuation of the acoustic wave. The attenuation rate of the portion through which the acoustic wave passes is 0.5 [bB / cm / MHz]. In FIG. 14, a graph B shows the attenuation characteristic of the reflected ultrasonic wave, and a graph PA shows the attenuation characteristic of the photoacoustic wave. The reception frequency of the photoacoustic wave is 5 MHz, and the reception frequency of the reflected ultrasonic wave is 10 MHz.

  Since the propagation distance of the reflected ultrasonic wave is twice the propagation distance of the photoacoustic wave, the attenuation of the reflected ultrasonic wave is twice the attenuation of the photoacoustic wave when it is assumed that the reception frequency is the same ( (See also FIG. 4). When the reception frequency of the reflected ultrasonic wave is twice the reception frequency of the photoacoustic wave, the attenuation of the reflected ultrasonic wave is further doubled, and as shown in FIG. 4 times the attenuation of the photoacoustic wave of 2.

  When calculating the second gain definition information based on the first gain definition information, the gain calculation unit 32 determines the conversion coefficient based on the reception frequency of the photoacoustic wave and the reception frequency of the reflected ultrasonic wave. Also good. For example, in the above case, since the attenuation of the reflected ultrasonic wave having the reception frequency of 10 MHz is four times the attenuation of the photoacoustic wave having the reception frequency of 5 MHz, the conversion coefficient is determined to be 0.25. The gain calculation unit 32 calculates a gain obtained by multiplying a gain at each position in the depth direction in the first gain definition information by a conversion coefficient 0.25 as a gain defined by the second gain definition information. In this way, when the reception frequency of the reflected ultrasonic wave is 10 MHz and the reception frequency of the photoacoustic wave is 5 MHz, the gain adjustment of the STC process is performed so that the deep portion can be observed in the ultrasonic image. Thus, it is possible to observe deep portions of the photoacoustic image.

  Contrary to the above, it is also conceivable that the sensitivity of reflected ultrasonic waves is emphasized, the reception frequency of reflected ultrasonic waves is 5 MHz, and the reception frequency of photoacoustic waves is 10 MHz. In that case, the attenuation of the photoacoustic wave is the same as the attenuation of the reflected acoustic wave whose reception frequency is half. In such a case, the gain calculation unit 32 may determine the conversion coefficient as 1.

  In each of the above embodiments, the first amplifying unit 253 is a part of the ultrasonic image generating unit 25, and the first amplifying unit 253 performs the STC processing by amplifying the ultrasonic image signal. Although described, it is not limited to this. For example, the first amplifying unit 253 may be disposed before the ultrasonic image generating unit 25, and the reflected ultrasonic signal input to the ultrasonic image generating unit 25 may be amplified with a gain corresponding to the depth position. Similarly for the second amplification unit 243, the second amplification unit 243 is arranged in front of the photoacoustic image generation unit 24, and the photoacoustic signal input to the photoacoustic image generation unit 24 is set in accordance with the depth position. You may amplify with a gain. The first amplifying unit 253 and the second amplifying unit 243 are omitted, and the variable gain amplifier 212 of the receiving circuit 21 detects the reflected ultrasound detection signal based on the first gain definition information when detecting the reflected ultrasound. It is good also as amplifying and amplifying the detection signal of a photoacoustic wave based on 2nd gain definition information at the time of the detection of a photoacoustic wave.

  In the flowcharts shown in FIGS. 7 and 11, the ultrasonic image is generated first and the photoacoustic image is generated later, but either the generation of the ultrasonic image or the generation of the photoacoustic image may be performed first. Further, the operation of the gain operation unit 30 in step S21 in FIG. 7 can be performed at an arbitrary timing. For example, it may be performed after the ultrasonic image and the photoacoustic image are displayed on the image display device 14 in step S19. In that case, an ultrasonic image amplified according to the newly determined first gain definition information and a photoacoustic image amplified according to the second gain definition information may be displayed on the image display device 14. The ultrasonic image and the photoacoustic image are not necessarily generated at the same frame rate. For example, one photoacoustic image may be generated while a plurality of ultrasonic images are generated.

  In the flowcharts shown in FIGS. 7 and 11, the detection of reflected ultrasonic waves and the detection of photoacoustic waves are performed, but these detections are not necessarily performed. For example, in a storage device (not shown), a photoacoustic wave detection signal and a reflected ultrasonic detection signal detected in the past, or a photoacoustic image and an ultrasonic image generated in the past are stored, and the storage device A photoacoustic wave detection signal and a reflected ultrasonic wave detection signal, or a photoacoustic image and an ultrasonic image may be read out. The storage device only needs to be configured to be readable from the ultrasonic unit 12. For example, the storage device and the ultrasonic unit 12 may be connected via a network such as the Internet.

  As mentioned above, although this invention was demonstrated based on the suitable embodiment, the photoacoustic image generation apparatus of this invention, a system, and a method are not limited only to the said embodiment, From the structure of the said embodiment. Various modifications and changes are also included in the scope of the present invention.

10: Photoacoustic image generation system 11: Probe 12: Ultrasonic unit 13: Laser unit 14: Image display device 21: Reception circuit 22: AD converter 23: Reception memory 24: Photoacoustic image generation unit 25: Ultrasonic image generation Unit 26: Image composition unit 28: Control unit 29: Transmission control circuit 30: Gain operation unit 31: Gain determination unit 32: Gain calculation unit 33: Coefficient determination unit 21: Low noise amplifier 212: Variable gain amplifier 213: Low pass filter 241 : Photoacoustic image reconstruction unit 242: Detection / logarithm conversion unit 243: Second amplification unit 244: Photoacoustic image construction unit 251: Ultrasound image reconstruction unit 252: Logarithm conversion unit 253: First amplification unit 254: Ultrasound image construction unit T1 to T6: Knob

Claims (13)

A reflected acoustic wave image generation unit that generates a reflected acoustic wave image based on a detection signal of the reflected acoustic wave with respect to the acoustic wave transmitted into the subject;
A photoacoustic image generation unit that generates a photoacoustic image based on a detection signal of a photoacoustic wave generated due to absorption of light emitted from a light source by a light absorber in the subject;
Correspondence between at least one of a detection signal of a reflected acoustic wave input to the reflected acoustic wave image generation unit and a signal value of the reflected acoustic wave image and a gain at each position in a plurality of depth directions A first amplifying unit that amplifies with a gain according to a position in the depth direction in accordance with first gain definition information that defines
At least one of a photoacoustic wave detection signal and a signal value of the photoacoustic image input to the photoacoustic image generation unit is defined as a correspondence relationship between each of a plurality of positions in the depth direction and a gain at each position. A second amplifying unit that amplifies the gain according to the position in the depth direction according to the second gain definition information
A photoacoustic image generation apparatus comprising: a gain calculation unit that calculates the second gain definition information based on the first gain definition information.   The photoacoustic image generating apparatus according to claim 1, further comprising a gain determination unit that determines the first gain definition information.   The apparatus further includes a gain operation unit for changing the first gain definition information in response to a user operation, and the gain determination unit determines the first gain definition information in accordance with an operation of the gain operation unit. The photoacoustic image generating apparatus according to claim 2.   The gain operation unit has a plurality of gain changing knobs corresponding to the positions in the depth direction in the first gain definition information, and the gain determination unit determines the depth according to the operation amount of each knob. The photoacoustic image generating apparatus of Claim 3 which determines the gain in each position of a direction.   The gain determination unit stores a plurality of the first gain definition information, and a first gain used in the first amplification unit in accordance with a user operation from the plurality of first gain definition information. The photoacoustic image generating device according to claim 2 which selects definition information.   The photoacoustic image generation apparatus according to claim 2, wherein the gain determination unit determines the first gain definition information based on a detection signal of the reflected acoustic wave.   The gain calculation unit calculates a gain obtained by multiplying a gain at each position in the depth direction in the first gain definition information by a conversion coefficient as a gain defined by the second gain definition information. 6. The photoacoustic image generating apparatus according to any one of claims 6 to 6.   The photoacoustic image generation apparatus according to claim 7, wherein the conversion coefficient is set in advance.   The photoacoustic image generation apparatus according to claim 7, wherein the gain calculation unit determines the conversion coefficient based on a reception frequency of the photoacoustic wave and a reception frequency of the reflected acoustic wave.   The photoacoustic image generation apparatus according to claim 7, further comprising a coefficient determination unit that compares the detection signal of the photoacoustic wave and the detection signal of the reflected acoustic wave and determines the conversion coefficient. The coefficient determination unit compares the photoacoustic wave detection signal and the reflected acoustic wave detection signal in each of a plurality of depth direction position ranges, and each of the plurality of depth direction position ranges. Determining the conversion factor for
The gain calculation unit multiplies the gain at each position in the depth direction in the first gain definition information by the conversion coefficient determined for the range of positions in the depth direction to which each position belongs. The photoacoustic image generating apparatus of description. A light source;
An acoustic wave transmitter that transmits acoustic waves into the subject;
An acoustic wave for detecting a photoacoustic wave generated due to absorption of light emitted from the light source by the light absorber in the subject and a reflected acoustic wave for the acoustic wave transmitted from the acoustic wave transmission unit A receiver,
A reflected acoustic wave image generation unit that generates a reflected acoustic wave image based on the detection signal of the reflected acoustic wave;
A photoacoustic image generation unit that generates a photoacoustic image based on the detection signal of the photoacoustic wave;
Correspondence between at least one of a detection signal of a reflected acoustic wave input to the reflected acoustic wave image generation unit and a signal value of the reflected acoustic wave image and a gain at each position in a plurality of depth directions A first amplifying unit that amplifies with a gain according to a position in the depth direction in accordance with first gain definition information that defines
At least one of a photoacoustic wave detection signal and a signal value of the photoacoustic image input to the photoacoustic image generation unit is defined as a correspondence relationship between each of a plurality of positions in the depth direction and a gain at each position. A second amplifying unit that amplifies the gain according to the position in the depth direction according to the second gain definition information
A photoacoustic image generation system comprising: a gain calculation unit that calculates the second gain definition information based on the first gain definition information. Generating a reflected acoustic wave image based on a detection signal of the reflected acoustic wave with respect to the acoustic wave transmitted into the subject;
Generating a photoacoustic image based on a detection signal of a photoacoustic wave generated due to absorption of light emitted from a light source by a light absorber in the subject;
At least one of the detection signal of the reflected acoustic wave used for generation of the reflected acoustic wave image and the signal value of the reflected acoustic wave image has a correspondence relationship between each of the positions in the depth direction and the gain at each position. Amplifying with a gain according to the position in the depth direction according to the first gain definition information to be defined;
At least one of a photoacoustic wave detection signal used for generating the photoacoustic image and a signal value of the photoacoustic image defines a correspondence relationship between each of a plurality of positions in the depth direction and a gain at each position. Amplifying with a gain according to the position in the depth direction according to the second gain definition information;
And a step of calculating the second gain definition information based on the first gain definition information.