JP2013172810A - Photoacoustic image processing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide information useful for diagnosis or the like by combining an acoustic velocity distribution and information obtained by photoacoustics.SOLUTION: A laser unit 13 emits light to be irradiated to a subject. A probe 11 detects an acoustic wave from inside the subject. An acoustic velocity distribution generation means 27 obtains an acoustic velocity distribution of the acoustic wave progressing inside the subject based on the acoustic wave detected by the probe 11. A photoacoustic image generation means 25 generates a photoacoustic image based on a photoacoustic signal. A malignancy distribution image generation means 28 generates a malignancy distribution image indicating a distribution of a region where malignancy is considered to be high based on the photoacoustic image and the acoustic velocity distribution inside the subject.

Description

  The present invention relates to a photoacoustic image processing apparatus and method, and more particularly, photoacoustic image processing for generating a photoacoustic image by irradiating a subject with light and detecting an acoustic wave generated in the subject by the light irradiation. The present invention relates to an apparatus and a 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. By receiving the reflected sound wave with the ultrasonic probe and calculating the distance based on the time until the reflected ultrasonic wave returns to the ultrasonic probe, the internal state can be imaged.

  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 signals) are generated by adiabatic expansion due to the energy. By detecting this photoacoustic signal with an ultrasonic probe or the like and constructing a photoacoustic image based on the detection signal, in-vivo visualization based on the photoacoustic signal is possible.

  Here, several various measurement methods for measuring the sound velocity of the subject using ultrasonic waves have been proposed so far. Attempts have also been made to measure sound velocity values (hereinafter referred to as local sound velocity values) in a part of the subject. The speed of sound is acoustic information that is effective for diagnosing a living tissue, a lesion, its progress, and the like when a doctor performs an ultrasonic diagnosis.

  For example, in Patent Document 1, a plurality of ultrasonic transducers for transmission and reception are used, and by changing their angles and intervals, the intersecting region (region of interest) of the ultrasonic beam is moved in the depth direction in the living body. And obtaining a local sound velocity value. By moving the intersection region in the direction along the body surface of the living body and obtaining the local sound speed value at each position, the two-dimensional distribution of the local sound speed value in the living body can be obtained.

  Further, in Patent Document 2, based on the virtual sound velocity distribution, the sound ray path is set by changing the irradiation angle and the incident angle for each of the transmitting transducer and the receiving transducer, and the actual elapsed time measured. It has been proposed to obtain error data from the set time required for the sound ray path, correct the sound ray distribution so as to minimize the error data, and obtain the sound velocity from the corrected sound ray distribution.

  Patent Document 3 uses the Huygens principle to determine lattice points set in a region shallower than the region of interest in the subject and the optimum sound speed value in the region of interest, and based on the optimum sound speed value in the region of interest. Each grid obtained from the optimum sound speed value at each grid point based on the assumed sound speed by calculating the received wave received from the target area when the ultrasonic wave is transmitted to the target area and assuming the assumed sound speed in the target area An ultrasonic diagnostic apparatus is disclosed in which a received wave from a point is synthesized to obtain a synthesized received wave, and a local sound velocity value in a region of interest is determined based on the received wave and the synthesized received wave.

  Regarding the provision of the obtained sound speed distribution to the user, Patent Document 4 describes generating a color sound speed map in which a difference in sound speed value is represented by a change in color based on the sound speed of each small area. . Since the sound speed changes depending on the component of the medium through which the ultrasonic wave propagates, it can be said that the color sound speed map makes it possible to visually recognize the distribution of the tissue component of the imaging target cross section by color. Patent Document 4 also describes that a color sound velocity map and an ultrasonic image (B mode image) are displayed side by side.

JP 62-254740 A Japanese Patent Laid-Open No. 5-95946 JP 2010-99452 A JP 2008-264531 A

  However, in Patent Document 4, an ultrasonic image and a sound velocity map are merely displayed side by side, and a user such as a doctor must read the ultrasonic image and the sound velocity map. Although it is conceivable to display the photoacoustic image and the sound velocity map side by side, even in that case, the user needs to perform interpretation while comparing the photoacoustic image and the sound velocity map. Conventionally, an apparatus that provides information useful for diagnosis or the like by combining information obtained by photoacoustics with a distribution of sound velocity has not been known.

  In view of the above, an object of the present invention is to provide a photoacoustic measurement apparatus and method that provide information useful for diagnosis and the like by combining information obtained by photoacoustics and sound velocity distribution.

  In order to achieve the above object, the present invention provides a light source that emits light to be irradiated on a subject, an acoustic wave detection unit that detects an acoustic wave from within the subject, and an acoustic wave detected by the acoustic wave detection unit. A sound velocity distribution generating means for obtaining a sound velocity distribution of an acoustic wave traveling in the subject based on the wave, and an acoustic wave detection signal detected by the acoustic wave detecting means after the light emitted from the light source is irradiated on the subject. A photoacoustic image generation means for generating a photoacoustic image based on the photoacoustic signal, and a malignancy distribution image generation means for generating a malignancy distribution image based on the photoacoustic image and the sound velocity distribution in the subject. A photoacoustic image processing apparatus characterized by comprising:

  Here, the “acoustic wave detected by the acoustic wave detection means” used when generating the sound velocity distribution is transmitted to the subject with the photoacoustic wave generated in the subject by irradiating the subject with light. And a reflected acoustic wave with respect to the acoustic wave.

  The malignancy distribution image generation means identifies a location where the sound velocity is higher than the surrounding area or higher than a predetermined value and the signal intensity of the photoacoustic image is a predetermined value or more as a high malignancy location. May be.

  The malignancy distribution image generation means changes at least one of the luminance and the display color of the pixel corresponding to the location specified as the location with high malignancy according to at least one of the sound speed and the signal intensity of the photoacoustic image. May be.

  It is preferable that the photoacoustic image generation means delay-adds the photoacoustic signals detected by the plurality of acoustic wave detection elements of the acoustic wave detection means with a delay time based on the sound speed distribution.

  The photoacoustic image processing apparatus of the present invention can employ a configuration further including an acoustic wave transmission unit that transmits an acoustic wave to a subject. In this case, the sonic velocity generation unit transmits an acoustic wave from the acoustic wave transmission unit. Then, the sound velocity distribution may be generated based on the reflected acoustic wave with respect to the transmitted acoustic wave detected by the acoustic wave detecting means.

  The photoacoustic image processing apparatus of the present invention can employ a configuration further comprising reflected acoustic wave image generation means for generating a reflected acoustic wave image based on a reflected acoustic signal that is a reflected acoustic wave detection signal.

  You may further provide the image synthetic | combination means which synthesize | combines a malignancy distribution image and a reflected acoustic wave image. In addition to the malignancy distribution image and the reflected acoustic wave image, a photoacoustic image may be further synthesized.

  The malignancy distribution image generation means may extract a predetermined lesion from the reflected acoustic wave image and generate a malignancy distribution image for a portion of a region corresponding to the extracted lesion.

  It is preferable that the reflected acoustic wave image generating means delay-adds the reflected acoustic signals detected by the plurality of acoustic wave detecting elements of the acoustic wave detecting means with a delay time based on the sound speed distribution.

  The acoustic wave detecting element of the acoustic wave detecting means may also serve as the acoustic wave transmitting element of the acoustic wave transmitting means.

  The light source emits light having a plurality of different wavelengths, and the photoacoustic image generation unit detects each of the plurality of wavelengths detected by the acoustic wave detection unit with respect to the light of the plurality of wavelengths irradiated on the subject. 2 wavelength data calculation means for extracting the relative magnitude of the relative signal intensity between the photoacoustic signals corresponding to, and intensity for generating intensity information indicating the signal intensity based on the photoacoustic signals corresponding to each of a plurality of wavelengths Including an information extraction means, and the gradation value of each pixel of the photoacoustic image may be determined based on the intensity information, and the display color of each pixel may be determined based on the relative relationship of the signal intensity. .

  The present invention also includes a step of irradiating the subject with light, a step of detecting a photoacoustic wave from the subject after the subject is irradiated with light, and a photoacoustic image based on the detected photoacoustic wave. Based on the acoustic wave detected in the subject, the step of generating the sound velocity distribution of the acoustic wave traveling in the subject, the photoacoustic image and the sound velocity distribution in the subject A photoacoustic image processing method comprising: generating a malignancy distribution image.

  The photoacoustic image processing method of the present invention further includes a step of transmitting an acoustic wave to the subject prior to the step of generating the sound velocity distribution, and in the step of generating the sound velocity distribution, the reflection of the transmitted acoustic wave is performed. A sound velocity distribution may be generated based on the acoustic wave.

  In the present invention, a malignancy distribution image is generated based on the sound velocity distribution and the photoacoustic image. The present invention can provide information useful for diagnosis and the like by combining information obtained by photoacoustics and sound velocity distribution. In particular, the part where the sound velocity is fast corresponds to the part where the tissue is hard, and the part where the signal intensity of the photoacoustic signal is strong corresponds to the part where the blood vessels such as light absorbers are densely packed. Such a location should be identified as a location with high malignancy.

The block diagram which shows the photoacoustic image processing apparatus of one Embodiment of this invention. FIG. 4 is a diagram showing an example of a data acquisition sequence. The figure which shows the reflected acoustic signal detected with the aperture element corresponding to each line of US mode. The figure which shows the ultrasonic image after a reconstruction. The figure which shows the photoacoustic signal detected with the aperture element corresponding to each area of PA mode. The figure which shows the photoacoustic signal after a reconstruction. The figure which shows the ultrasonic transducer | vibrator of a probe, and the light absorber in a subject. The figure shown in the time distribution of the reflected acoustic signal detected with the aperture element. The figure which shows the data for 1 line reconfigure | reconstructed. The figure which shows the time distribution of the reflected acoustic signal when the sound speed in a subject is not constant. The flowchart which shows the operation | movement procedure at the time of calculating | requiring sound speed distribution. The flowchart which shows the operation | movement procedure of a photoacoustic image processing apparatus. The block diagram which shows the structural example of the photoacoustic image generation means in the case of irradiating the subject with the light of a some wavelength.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a photoacoustic image processing apparatus according to an embodiment of the present invention. The photoacoustic image processing apparatus (photoacoustic image diagnostic apparatus) 10 includes an ultrasonic probe (probe) 11, an ultrasonic unit 12, and a light source (laser unit) 13. The photoacoustic image processing apparatus 10 can generate both an ultrasonic image and a photoacoustic image.

  The laser unit 13 is a light source and generates light (laser light) to be irradiated on the subject. What is necessary is just to set the wavelength of a laser beam suitably according to an observation target object. For example, the laser unit 13 emits light having a wavelength with a large absorption of hemoglobin, specifically, light having a wavelength of 750 nm or 800 nm. Laser light emitted from the laser unit 13 is guided to the probe 11 using light guide means such as an optical fiber, and is irradiated from the probe 11 to the subject. Alternatively, light irradiation may be performed from a place other than the probe 11.

  The probe 11 includes an acoustic wave transmission unit that outputs (transmits) an acoustic wave (ultrasonic wave) to the subject, and an acoustic wave detection unit that detects an acoustic wave (ultrasonic wave) from within the subject. The acoustic wave detecting element of the acoustic wave detecting means may also serve as the acoustic wave transmitting element of the acoustic wave transmitting means. For example, one ultrasonic transducer (element) may be used for both transmission and detection of ultrasonic waves. The probe 11 has, for example, a plurality of ultrasonic transducers arranged in a one-dimensional manner, outputs ultrasonic waves from the plurality of ultrasonic transducers, and reflects reflected acoustic waves (hereinafter referred to as “acoustic waves”) to the output ultrasonic waves. Are also detected by a plurality of ultrasonic transducers. In addition, the probe 11 detects a photoacoustic wave (hereinafter also referred to as a photoacoustic signal) generated by the measurement object in the subject absorbing light from the laser unit 13 by using a plurality of ultrasonic transducers. Note that it is not necessary for one probe 11 to have both the ultrasonic transmission means and the ultrasonic detection means. The ultrasonic transmission means and the ultrasonic detection means are separated to transmit ultrasonic waves and ultrasonic waves. Reception may be performed at a different location.

  The ultrasonic unit 12 includes a reception circuit 21, an AD conversion unit 22, a reception memory 23, a data separation unit 24, a photoacoustic image generation unit 25, an ultrasonic image generation unit 26, a sound velocity distribution generation unit 27, and a malignancy distribution image generation unit. 28, an image composition unit 29, a trigger control circuit 30, a transmission control circuit 31, and a control unit 32. The control means 32 controls each part in the ultrasonic unit 12. The receiving circuit 21 receives an acoustic wave detection signal (a photoacoustic signal or a reflected acoustic signal) detected by the probe 11. The AD converter 22 samples the photoacoustic signal and the reflected acoustic signal received by the receiving circuit 21 and converts them into a digital signal. The AD conversion means 22 samples the acoustic wave detection signal at a predetermined sampling period, for example, in synchronization with the AD clock signal.

  The trigger control circuit 30 outputs an optical trigger signal that instructs the laser unit 13 to emit light. The laser unit 13 includes a flash lamp 41 that excites a laser medium (not shown) such as YAG or titanium-sapphire, and a Q switch 42 that controls laser oscillation. When the trigger control circuit 30 outputs a flash lamp trigger signal, the laser unit 13 turns on the flash lamp 41 and excites the laser medium. For example, when the flash lamp 41 sufficiently excites the laser medium, the trigger control circuit 30 outputs a Q switch trigger signal. The Q switch 42 is turned on when a Q switch trigger signal is received, and emits laser light from the laser unit 13. The time required from when the flash lamp 41 is turned on until the laser medium is sufficiently excited can be estimated from the characteristics of the laser medium.

  Instead of controlling the Q switch from the trigger control circuit 30, the Q switch 42 may be turned on after the laser medium is sufficiently excited in the laser unit 13. In that case, a signal indicating that the Q switch 42 is turned on may be notified to the ultrasonic unit 12 side. Here, the light trigger signal is a concept including at least one of a flash lamp trigger signal and a Q switch trigger signal. When outputting the Q switch trigger signal from the trigger control circuit 30, the Q switch trigger signal corresponds to the optical trigger signal. When the laser unit 13 generates the timing of the Q switch trigger, the flash lamp trigger signal is used as the optical trigger signal. It may correspond. By outputting the optical trigger signal, the subject is irradiated with laser light and the photoacoustic signal is detected.

  In addition, the trigger control circuit 30 outputs an ultrasonic transmission trigger signal that instructs ultrasonic transmission to the transmission control circuit 31. When receiving the ultrasonic transmission trigger signal, the transmission control circuit 31 transmits ultrasonic waves from the probe 11. By outputting the ultrasonic transmission trigger signal, transmission of ultrasonic waves to the subject and detection of reflected acoustic signals are performed.

  Further, the trigger control circuit 30 outputs a sampling trigger signal for instructing the AD conversion means 22 to start sampling. The trigger control circuit 30 outputs a sampling trigger signal at a predetermined timing after outputting the optical trigger signal or the ultrasonic transmission trigger signal. For example, when detecting a photoacoustic signal, the trigger control circuit 30 preferably outputs a sampling trigger signal after the output of the optical trigger signal, preferably at a timing when the subject is actually irradiated with the laser light. For example, the trigger control circuit 30 outputs a sampling trigger signal in synchronization with the output of the Q switch trigger signal. The trigger control circuit 30 outputs a sampling trigger signal in synchronization with the ultrasonic transmission trigger signal when detecting a reflected acoustic signal. When receiving the sampling trigger signal, the AD conversion unit 22 starts sampling the photoacoustic signal or the reflected acoustic signal detected by the probe 11.

  The AD conversion unit 22 stores the sampled photoacoustic signal and reflected acoustic signal in the reception memory 23. As the reception memory 23, for example, a semiconductor memory device can be used. Alternatively, other storage devices such as a magnetic storage device may be used for the reception memory 23. The reception memory 23 stores photoacoustic signal sampling data (photoacoustic data) and reflected acoustic signal sampling data (reflected ultrasound data). The data separation unit 24 separates the photoacoustic signal and the reflected acoustic signal stored in the reception memory 23. The data separation unit 24 passes the separated photoacoustic signal to the photoacoustic image generation unit 25. The separated reflected acoustic signal is passed to the ultrasonic image generation means 26 and the sound speed distribution generation means 27.

  The sound velocity distribution generating means 27 receives the reflected acoustic signal from the data separating means 24, and generates the sound velocity distribution of the acoustic wave traveling in the subject based on the received reflected acoustic signal. The method of generating the sound speed distribution is not particularly limited. For generating the sound velocity distribution, any method for estimating the sound velocity distribution based on the acoustic wave can be used.

  The photoacoustic image generation means 25 generates a photoacoustic image based on the photoacoustic signal. The photoacoustic image generation unit 25 includes a photoacoustic image reconstruction unit 251, a detection / logarithm conversion unit 252, and a photoacoustic image construction unit 253. The ultrasonic image generating means 26 generates an ultrasonic image (reflected acoustic image) based on the reflected acoustic signal. The ultrasonic image generation means (reflected acoustic wave image generation means) 26 includes an ultrasonic image reconstruction means 261, a detection / logarithm conversion means 262, and an ultrasonic image construction means 263.

  The photoacoustic image reconstruction unit 251 receives the photoacoustic signal from the data separation unit 24 and reconstructs the photoacoustic signal. The photoacoustic image reconstruction unit 251 generates data of each line of the photoacoustic image that is a tomographic image based on the photoacoustic signal. Here, the reconstructed photoacoustic signal can be regarded as a photoacoustic image. The photoacoustic image reconstruction means 251 reconstructs a photoacoustic signal by a delay addition method (synonymous with delay and sum, phase matching addition, and phasing addition). The photoacoustic image reconstruction unit 251 adds, for example, photoacoustic signals for 64 elements with a delay time corresponding to the position of each element (each ultrasonic transducer) to generate data for one line. At this time, the photoacoustic image reconstruction means 251 delays and adds the photoacoustic signal detected by each element while correcting the delay time of each element using the sound speed distribution generated by the sound speed distribution generation means 27.

  The detection / logarithm conversion unit 252 generates an envelope of the data of each line output by the photoacoustic image reconstruction unit 251 and logarithmically converts the envelope to widen the dynamic range. The photoacoustic image construction unit 253 generates a photoacoustic image based on the data of each line subjected to logarithmic transformation. The photoacoustic image construction unit 253 generates a photoacoustic image by converting, for example, the position in the time axis direction of the photoacoustic signal (peak portion) into the position in the depth direction in the tomographic image.

  The ultrasonic image reconstruction unit 261 receives the reflected acoustic signal from the data separation unit 24 and reconstructs the reflected acoustic signal. The ultrasonic image reconstruction unit 261 generates data of each line of the ultrasonic image that is a tomographic image based on the received reflected acoustic signal. Here, the reconstructed reflected acoustic signal can be regarded as an ultrasonic image. The ultrasonic image reconstruction means 261 adds, for example, reflected acoustic signals for 64 elements with a delay time corresponding to the position of each element, and generates data for one line. At this time, the ultrasonic image reconstructing unit 261 delays and adds the reflected acoustic signal detected by each element while correcting the delay time of each element using the sound speed distribution generated by the sound speed distribution generating unit 27.

  The detection / logarithm conversion unit 262 generates an envelope of the data of each line output from the ultrasonic image reconstruction unit 261, and logarithmically converts the envelope to widen the dynamic range. The ultrasonic image construction unit 263 generates an ultrasonic image based on the data of each line subjected to logarithmic transformation. The generation of the ultrasonic image in the ultrasonic image generation unit 26 may be the same as the generation of the photoacoustic image in the photoacoustic image generation unit 25 except that the signal is a reflected acoustic signal.

  The malignancy distribution image generation unit 28 has a malignancy based on the photoacoustic signal (photoacoustic image) reconstructed by the photoacoustic image reconstruction unit 251 and the sound velocity distribution generated by the sound velocity distribution generation unit 27. A malignancy distribution image showing a distribution of a portion considered to be high is generated. Here, it is considered that the place where the signal intensity is high in the photoacoustic image is a place where light absorbers such as blood vessels are densely packed. On the other hand, the part where the sound speed is high in the sound speed distribution is considered to be a place where the tissue is hardened. Therefore, in the present embodiment, in particular, a portion where the intensity of the photoacoustic image is high and the sound speed is high is estimated as a portion considered to be high in malignancy, and a malignancy distribution image obtained by imaging the portion is generated. .

  The image synthesis means 29 synthesizes the malignancy distribution image generated by the malignancy distribution image generation means 28 and the ultrasonic image generated by the ultrasonic image generation means 26. The image synthesis unit 29 may further synthesize the photoacoustic image generated by the photoacoustic image generation unit 25. The image composition unit 29 performs image composition, for example, by superimposing a photoacoustic image and a malignancy distribution image on an ultrasonic image. The image display unit 14 displays the image synthesized by the image synthesis unit 29 on a display monitor or the like. The image display unit 14 may switch and display the malignancy distribution image, the photoacoustic image, and the ultrasonic image without performing image synthesis. Alternatively, the malignancy distribution image, the photoacoustic image, and the ultrasonic image may be displayed side by side.

  An acquisition sequence of the photoacoustic signal and the reflected acoustic signal will be described. FIG. 2 shows an example of a data acquisition sequence. In the figure, mode “US” represents acquisition of reflected acoustic signals, and mode “PA” represents acquisition of photoacoustic signals. Here, the probe 11 has 128 ultrasonic transducers arranged one-dimensionally as an acoustic wave detector element and an acoustic wave transmission element.

  In the acquisition of the photoacoustic signal, after the subject is irradiated with light from the laser unit 13, the photoacoustic signal is captured 64 elements at a time. That is, data for a total of 128 elements is acquired in two steps. For example, a photoacoustic signal detected by an ultrasonic transducer having an element number of 1 to 64 elements is acquired after the first laser emission, and an ultrasonic transducer having an element number of 65 to 128 elements is acquired after the second laser emission. The detected photoacoustic signal is acquired. On the other hand, in the acquisition of the reflected acoustic signal, after transmitting ultrasonic waves from the 64-element ultrasonic transducer, the reflected acoustic signal is acquired by the 64-element ultrasonic transducer. It should be noted that ultrasonic waves are transmitted and received with fewer elements than 64 elements at the ends of the ultrasonic transducers arranged one-dimensionally. In the acquisition of the reflected acoustic signal, the reflected acoustic signal is acquired by the line by line while shifting the range (opening position) of the ultrasonic transducer that transmits and receives the ultrasonic wave one element at a time.

  In the sequence example of FIG. 2, the reflected acoustic wave signal is performed 128 times with respect to the acquisition of the photoacoustic signal twice. As described above, the photoacoustic wave is divided into two areas of 64 elements and data is acquired, whereas the reflected acoustic wave is 128 lines in order to generate one line in one transmission and reception. This is because the generation requires 128 transmissions / receptions. At that time, since it is the repetition of the laser light source that becomes the time-determining rate, there are more than 64 times between the photoacoustic data acquisition of the first area and the photoacoustic data acquisition of the second area. By transmitting and receiving sound waves, both data can be acquired most efficiently. More specifically, the apparatus starts operating in the US mode, shifting the opening position from line 1 to line 31 one element at a time (since line 1 to line 31 is an end, in fact one element at a time ) Transmit and receive ultrasonic waves and obtain reflected acoustic signals. Next, the mode is changed to the PA mode, and the subject is irradiated with the laser beam from the laser unit 13, and the photoacoustic signal is detected by 64 elements corresponding to the first area. Next, in the US mode, ultrasonic waves are transmitted and received while shifting the opening position from the line 32 to the line 95 one element at a time, and a reflected acoustic signal is acquired. Thereafter, the PA mode is entered and the subject is irradiated with the laser light from the laser unit 13, and a photoacoustic signal is acquired with 64 elements corresponding to the second area. Subsequently, in the US mode, transmitting and receiving ultrasonic waves while shifting the opening position from line 96 to line 128 one element at a time (since line 95 to line 128 is an end, the opening element is actually narrowed one element at a time) To obtain a reflected acoustic signal.

  FIG. 3 shows reflected acoustic signals detected by aperture elements corresponding to each line in the US mode of FIG. 2, and FIG. 4 shows an ultrasonic image after reconstruction. In FIG. 3, the vertical axis indicates the elapsed time from ultrasonic transmission. Data of each line from line 1 to line 128 is generated by delay-adding (phase matching addition) the reflected acoustic signals of 64 elements in each line (however, the opening elements are fewer than 64 elements at the end). Can generate one frame of ultrasound image shown in 4 ・

  FIG. 5 shows a photoacoustic signal detected by an aperture element corresponding to each area of the PA mode in FIG. 2, and FIG. 6 shows a photoacoustic signal (photoacoustic image) after reconstruction. In FIG. 5, the vertical axis indicates the elapsed time from the irradiation of the laser beam on the subject. The photoacoustic image shown in FIG. 6 can be generated by reconstructing the photoacoustic signals for a total of 128 elements in the two areas.

  In the above description, it has been described that the ultrasonic wave is a line by line and the photoacoustic signal is divided into two areas to detect the photoacoustic signal, but the ultrasonic wave is also transmitted and received in each of the two areas. The reflected acoustic signal may be detected. For example, after a photoacoustic signal is detected by the ultrasonic transducer of element number 1-64 corresponding to area 1 by irradiating light to the subject, the ultrasonic transducer of element number 1-64 is not focused. An ultrasonic wave may be transmitted to the subject to detect a reflected acoustic signal. Similarly, in area 2, after the light irradiation, a photoacoustic signal is detected by the ultrasonic transducer of element number 65-128 corresponding to area 2, and then the ultrasonic transducer of element number 65-128 is applied to the subject. Then, the reflected acoustic signal may be detected by transmitting an ultrasonic wave. Either the photoacoustic signal or the reflected acoustic signal may be detected first.

  In the above description, the photoacoustic signal is detected by being divided into two areas, but the area division may not be performed. For example, photoacoustic signals may be detected by all 128 elements after irradiating the subject with light. In this case, only one light irradiation is required. Similarly, for reflected acoustic signals, for example, ultrasonic waves may be transmitted from all 128 elements without focus, and reflected acoustic signals may be detected by 128 elements.

  When the acoustic signal and the reflected acoustic signal are detected in the same area, after the detection of one signal is started, the other signal is detected while the sampling by the AD conversion means 22 is continued, and both signals are continuously detected. You may make it acquire. For example, when the photoacoustic signal is detected first, the trigger control circuit 30 outputs the optical trigger signal (flash lamp trigger signal or Q switch trigger signal), and then transmits the ultrasonic wave at a timing to end the detection of the photoacoustic signal. Outputs a trigger signal. At this time, the AD conversion means 22 continues sampling without interrupting sampling. In other words, the trigger control circuit 30 outputs an ultrasonic transmission trigger signal in a state where the AD conversion means 22 continues sampling. When the probe 11 performs ultrasonic transmission in response to the ultrasonic transmission trigger signal, the acoustic wave detected by the probe 11 changes from a photoacoustic wave to a reflected acoustic wave. Since the AD conversion means 22 continues sampling, the photoacoustic signal and the reflected acoustic signal can be sampled continuously. In this case, the time from the start of detection of the photoacoustic wave to the end of detection of the reflected acoustic wave can be shortened as compared to the case of sampling separately, and when both images are superimposed and displayed, A positional shift between images can be suppressed.

  Here, when the AD conversion means 22 samples the photoacoustic signal and the reflected acoustic signal at the same sampling rate, it is preferable to provide a resampling means for resampling the reflected acoustic signal to ½. The ½ resampling unit compresses the reflected acoustic signal to ½ in the time axis direction, for example. The reason for resampling is that if the photoacoustic signal and the reflected acoustic signal are generated at the same position in the depth direction in the subject, in the case of the reflected acoustic signal, the ultrasonic wave transmitted from the probe 11 reaches that position. This is because the time required to proceed is necessary, and the time from ultrasonic transmission to reflected acoustic signal detection is twice the time from light irradiation to photoacoustic signal detection. That is, the photoacoustic signal is detected in one-way time, whereas the reflected acoustic signal takes time for a round trip. Instead of performing resampling, the sampling rate of the AD conversion means 22 at the time of detecting the reflected acoustic signal may be controlled to half the sampling rate at the time of detecting the photoacoustic signal.

  Next, generation of the sound speed distribution will be described. FIG. 7 shows the ultrasonic transducer of the probe and the light absorber in the subject. In the figure, the horizontal axis direction represents the arrangement direction of the ultrasonic transducers arranged one-dimensionally, and the vertical axis represents the depth direction of the subject. A region indicated by diagonal lines represents an aperture element when a reflected acoustic signal is detected. A reflector 45 exists immediately below the aperture element. Consider, for example, that ultrasonic waves are transmitted from the 64 elements forming the aperture elements in the depth direction of the subject and the reflected acoustic waves from the reflector 45 are detected.

  FIG. 8 shows the time distribution of the reflected acoustic signal detected by the aperture element. In the figure, the vertical axis represents the elapsed time from ultrasonic transmission. As shown in the figure, the detection time of the reflected acoustic signal from the reflector 45 (FIG. 7) detected by each element in the opening is the position of the reflector 45 in the opening and each ultrasonic transducer. It changes according to the positional relationship. FIG. 9 shows the reconstructed data for one line. By delay-adding the reflected acoustic signals for 64 elements shown in FIG. 8, data for one line of the ultrasonic image in which the reflected acoustic signal converges to one point is obtained. By performing a series of processes on each line, an ultrasonic image of one frame can be generated.

  FIG. 10 shows the time distribution of the reflected acoustic signal when the speed of sound in the subject is not constant. When reconstructing the reflected acoustic signal shown in FIG. 8, if the sound speed in the subject matches the assumed sound speed and the sound speed does not change depending on the position in the subject, the reflected acoustic signal is The delay time given to each element when performing delay addition is uniquely determined from the positional relationship between the reflector and each element. However, when the sound speed is not uniform, the time distribution of the detected reflected acoustic signal deviates from the case where the sound speed indicated by the solid line is uniform, as indicated by the broken line in FIG. In that case, even if the delay is added with an ideal delay curve assuming a uniform assumed sound speed, the reflected acoustic signal cannot be converged to one point. Therefore, a virtual sound speed value is calculated so that the detected reflected acoustic signal is reconstructed into one point. By calculating the virtual sound speed value for each pixel, the sound speed distribution in the subject can be determined.

  FIG. 11 shows an example of an operation procedure when obtaining the sound velocity distribution. Here, the reflected acoustic signal is described as an image in which the time axis is replaced with a position in the depth direction. The sound velocity distribution generation means 27 determines whether or not the signal intensity of the reflected acoustic signal at a position in a certain time axis direction (a certain pixel) of a certain element is equal to or higher than a predetermined value (step A1). When the signal intensity is equal to or higher than a predetermined value, the sound velocity distribution generation unit 27 calculates a phase for the pixel (target pixel) (step A2). In step A2, for example, the sound velocity distribution generation unit 27 assumes a sound velocity distribution in the subject, and based on the assumption, performs a delay addition for each of the aperture elements that substantially include the element corresponding to the target pixel. Set the delay time when performing.

  The sound velocity distribution generation means 27 evaluates the luminance value (signal intensity of the reconstructed signal) of the pixel when the reflected acoustic signal in the aperture element is delayed and added based on the phase calculated in step A2 (step A3). ). The sound velocity distribution generation means 27 determines whether or not the luminance value evaluated in step A3 is the maximum value (step A4). If it is not the maximum value, the process returns to step A2, and the phase is recalculated assuming a different sound velocity distribution. The sound velocity distribution generation means 27 repeatedly executes step A2 and step A3 until it determines that the luminance value has become maximum in step A4, and obtains the phase that gives the maximum luminance value.

  When determining that the luminance value is the maximum in step A4, the sound velocity distribution generation means 27 stores the phase data (phase distribution) at the target pixel in a storage means such as a memory (step A5). The sound velocity distribution generation means 27 stores, for example, information on the delay time given to each aperture element when the luminance value is maximized in the storage means as phase data in the pixel of interest. Instead of the delay time information, sound speed data in a direction from the target pixel toward each element may be stored as phase data. Further, function parameters obtained by approximating a delay time given to each element or sound speed data in a direction toward each element by a predetermined function (for example, a function of a quadratic function or more) may be stored in the storage means as phase data. Good.

  The sound speed distribution generation means 27 determines whether all the pixels have been processed (step A6). If unprocessed pixels remain, the process returns to step A1, and it is determined whether or not the luminance value of the next pixel is equal to or greater than a predetermined value. Here, a pixel whose luminance value is determined to be smaller than a predetermined value cannot evaluate a change in luminance value with respect to a phase change. Therefore, when it is determined in step A1 that the luminance value is smaller than the predetermined value, step A1 is repeated until a pixel having a luminance value equal to or higher than the predetermined value is selected without performing phase calculation.

  When determining that there is no unprocessed pixel in Step A6, the sound speed distribution generation unit 27 generates a sound speed distribution based on the phase data stored in Step A5 (Step A7). A known method can be used to generate (estimate) the sound velocity distribution based on the phase data.

  The sound speed distribution generation means 27 outputs phase data based on the sound speed distribution to the photoacoustic image reconstruction means 251 and the ultrasonic image reconstruction means 261 as a sound speed correction table. The photoacoustic image reconstruction means 251 delays and adds the photoacoustic signal with a delay time based on the sound speed correction table. Further, the ultrasonic image reconstruction unit 261 reconstructs the reflected acoustic signal with a delay time based on the sound speed correction table. Instead of outputting the sound speed correction table from the sound speed distribution generating means 27, the sound speed distribution data is output to the photoacoustic image reconstruction means 251 and the ultrasonic image reconstruction means 261, and based on the sound speed distribution data in these means. You may make it perform delay addition by delay time.

  The method for obtaining the sound velocity distribution is not limited to the above. For example, the local sound velocity value may be calculated by a method similar to the method described in Patent Document 3, and the distribution may be obtained. That is, using Huygens' principle, the optimum sound speed value at the lattice point set in the region shallower than the region of interest in the subject and the region of interest is determined, and the ultrasonic wave is determined based on the optimum sound speed value in the region of interest. Calculates the received wave received from the region of interest when transmitted to the region of interest, assumes the assumed sound speed in the region of interest, and receives from each lattice point obtained from the optimum sound speed value at each lattice point based on the assumed sound speed A synthesized reception wave may be obtained by synthesizing waves, and a local sound velocity value may be obtained by determining a local sound velocity value in the region of interest based on the reception wave and the synthesized reception wave, and the distribution thereof may be obtained.

  Subsequently, the operation procedure will be described. FIG. 12 shows an operation procedure of the photoacoustic image processing apparatus. The trigger control circuit 30 outputs an ultrasonic transmission trigger signal to the transmission control circuit 31. When receiving the ultrasonic transmission trigger signal, the transmission control circuit 31 transmits ultrasonic waves from the probe 11 (step B1). After transmitting the ultrasonic wave, the probe 11 detects a reflected acoustic signal for the transmitted ultrasonic wave (step B2). The reflected acoustic signal detected by the probe 11 is input to the AD conversion means 22 via the receiving circuit 21. The AD conversion means 22 samples the reflected acoustic signal, converts it into digital data, and stores it in the reception memory 23.

  Subsequently, the trigger control circuit 30 outputs a flash lamp trigger signal to the laser unit 13. In the laser unit 13, the flash lamp 41 is turned on in response to the flash lamp trigger signal, and excitation of the laser medium is started. The trigger control circuit 30 sends a Q switch trigger signal to the laser unit 13 and turns on the Q switch 42 to emit pulsed laser light from the laser unit 13 (step B3). The trigger control circuit 30 outputs the Q switch trigger signal at a timing that is in a predetermined time relationship with the timing at which the flash lamp trigger signal is output, for example. For example, the trigger control circuit 30 outputs a Q switch trigger signal 150 seconds after the flash lamp emission.

  Laser light emitted from the laser unit 13 is irradiated to the subject. In the subject, a photoacoustic signal is generated by the irradiated pulsed laser beam. The probe 11 detects a photoacoustic signal generated in the subject (step B4). The photoacoustic signal detected by the probe is input to the AD conversion means 22 via the receiving circuit 21. The AD conversion means 22 samples the photoacoustic signal, converts it into digital data, and stores it in the reception memory 23. Note that either the reflected acoustic signal or the photoacoustic signal may be detected first. Further, for example, the reflected acoustic signal and the photoacoustic signal may be detected alternately according to the sequence shown in FIG.

  The data separation unit 24 reads the photoacoustic signal from the reception memory 23, and gives the read photoacoustic signal to the photoacoustic image generation unit 25. Further, the reflected acoustic signal is read from the reception memory 23, and the read reflected acoustic signal is given to the ultrasonic image generating unit 26 and the sound speed distribution generating unit 27. The sound speed distribution generation means 27 generates a sound speed distribution based on the reflected acoustic signal received from the data separation means 24 (step B5).

  The photoacoustic image generation unit 25 generates a photoacoustic image based on the photoacoustic signal received from the data separation unit 24 (step B6). At that time, the photoacoustic image generation means 25 delays and adds the photoacoustic signals of the respective elements with a delay time based on the sound speed distribution generated in step B5. By performing reconstruction in consideration of the difference in sound speed according to the position inside the subject, even if the sound speed distribution is not uniform, the photoacoustic signal emitted from one photoacoustic wave source is displayed on the photoacoustic image. It can be converged to one point.

  The ultrasonic image generation unit 26 generates an ultrasonic image based on the reflected acoustic signal received from the data separation unit 24 (step B7). At that time, the ultrasonic image generating means 26 delay-adds the reflected acoustic signals of the respective elements with a delay time based on the sound speed distribution generated in step B5. By performing reconstruction in consideration of the difference in sound speed depending on the position inside the subject, even if the sound speed distribution is not uniform, the reflected acoustic signal from one reflected acoustic wave source is displayed on the ultrasound image. It can be converged to one point.

  The malignancy distribution image generation unit 28 inputs a photoacoustic image representing the distribution of the light absorber from the photoacoustic image generation unit 25 and inputs a sound speed distribution (sound speed map) representing the distribution of the sound speed from the sound speed distribution generation unit 27. . In FIG. 1, the photoacoustic signal reconstructed by the photoacoustic image reconstruction unit 251 is input to the malignancy distribution image generation unit 28 as data representing the distribution of the light absorber. The photoacoustic signal after detection / logarithmic conversion output by the logarithmic conversion unit 252 or the photoacoustic image generated by the photoacoustic image construction unit 253 may be input as data representing the distribution of the light absorber. .

  The malignancy distribution image generation means 28 generates a malignancy distribution image indicating a distribution of a portion considered to have a high malignancy based on the photoacoustic image and the sound velocity distribution in the subject (step B8). For example, the malignancy distribution image generation means 28 has a sound speed that is faster than the surrounding area or higher than a predetermined value, and the signal intensity of the reconstructed photoacoustic signal (photoacoustic image) is equal to or higher than a predetermined value. The location is identified as a portion having a high malignancy, and a malignancy distribution image indicating the distribution of the portion is generated. The malignancy distribution image generation means 28 changes at least one of the luminance or the display color of the pixel corresponding to the location specified as the location with the high malignancy according to at least one of the sound speed and the signal intensity of the photoacoustic image. You may let them.

  The image synthesizing unit 29 synthesizes the ultrasonic image and the malignancy distribution image (step B9), and displays the synthesized image on the display screen of the image display unit 14. For example, the malignancy distribution image generation unit 28 generates a malignancy distribution image that displays a portion identified as a high malignancy portion in red, and superimposes such a malignancy distribution image on the ultrasound image. Thus, a portion having a high malignancy may be clearly indicated to the user. At that time, for example, depending on the sound speed and the signal intensity of the photoacoustic image, the higher the sound speed or the greater the signal intensity of the photoacoustic image, the higher the luminance value in the malignancy distribution image, the more malignancy. You may make it stand out the part considered high. Alternatively, the color of the pixel in the malignancy distribution image may be determined using a color map in which the display color changes stepwise from blue to red according to the sound speed and the signal intensity of the photoacoustic image. .

  In the present embodiment, a malignancy distribution image is generated based on the photoacoustic image and the sound velocity distribution. The user can know the distribution of the light absorber by observing the photoacoustic image, and can know the place where the sound speed in the subject is high and low by observing the sound speed distribution. By combining the photoacoustic image and the sound velocity distribution, a portion where the distribution of the light absorber and the sound velocity satisfy a certain standard is specified as a portion considered to have a high malignancy, and the portion is displayed as a malignancy distribution image. In the present embodiment, in particular, a portion where the signal intensity of the photoacoustic image is high and the sound speed is high can be specified as a portion having a high malignancy. In this case, a user such as a doctor can easily find a portion where the light absorbers are dense and the tissue is hardened by observing the malignancy distribution image. Thus, in this embodiment, information obtained by photoacoustics and sound velocity distribution can be combined to provide useful information for diagnosis and the like to a user such as a doctor.

  The user identifies a lesion such as a tumor on an ultrasound image, for example. By superimposing the malignancy distribution image on the ultrasonic image, the user can grasp the malignancy of the portion corresponding to the lesion. Extraction of a lesion from an ultrasound image may be performed by the ultrasound unit 12. For example, the malignancy distribution image generation means 28 inputs an ultrasonic image from the ultrasonic image generation means 26 and extracts a lesion such as a tumor from the ultrasonic image. The tumor extraction method is not particularly limited. For example, a tumor is extracted from an ultrasonic image by combining pattern recognition and luminance. The malignancy distribution image generation means 28 generates a malignancy distribution image for the region corresponding to the extracted lesion. In this case, the user can determine the malignancy of a portion where a tumor or the like is recognized in the ultrasonic image by observing the malignancy distribution image.

  In generating the photoacoustic image, the laser unit 13 may be configured to emit light having a plurality of wavelengths, and the subject may be irradiated with laser beams having a plurality of different wavelengths from the laser unit 13. In this case, the photoacoustic image generation means 25 may generate a photoacoustic image that can distinguish, for example, an artery and a vein, using the wavelength dependence of the light absorption characteristics of the light absorber in the subject.

  For example, the subject is irradiated with light having a wavelength of about 750 nm and light having a wavelength of about 800 nm. Molecular absorption coefficient at a wavelength of 750 nm of oxygenated hemoglobin (oxy-Hb combined with oxygen) contained in a large amount of human arteries is higher than a molecular absorption coefficient at a wavelength of 800 nm. On the other hand, the molecular absorption coefficient at a wavelength of 750 nm of deoxygenated hemoglobin (hemoglobin deoxy-Hb not bound to oxygen) contained in a large amount in veins is lower than the molecular absorption coefficient at a wavelength of 800 nm. Using this property, by examining whether the photoacoustic signal obtained at a wavelength of 750 nm is relatively large or small with respect to the photoacoustic signal obtained at a wavelength of 800 nm, the photoacoustic signal from the artery and the vein From the photoacoustic signal.

  FIG. 13 shows a configuration example of the photoacoustic image generation means when the subject is irradiated with light of two wavelengths. The photoacoustic image generation unit 25 a includes a two-wavelength data calculation unit 254 and an intensity information extraction unit 255 in addition to the photoacoustic image reconstruction unit 251, the detection / logarithm conversion unit 252, and the photoacoustic image construction unit 253. The photoacoustic image reconstruction means 251 is a photoacoustic signal (first photoacoustic signal) when the subject is irradiated with light of the first wavelength and light when the light of the second wavelength is irradiated. An acoustic signal (second photoacoustic signal) is reconstructed. The photoacoustic image reconstruction unit 251 passes the reconstructed first and second photoacoustic signals to the two-wavelength data calculation unit 254 and the intensity information extraction unit 255.

The two-wavelength data calculation means 254 generates data indicating the relative magnitude of the relative signal intensity between the photoacoustic signals corresponding to each of a plurality of wavelengths of light irradiated on the subject. The two-wavelength data calculation unit 254 generates, for example, a ratio between the first photoacoustic signal and the second photoacoustic signal as data indicating the relative relationship between the signal intensities. For example, when the signal intensity of the first photoacoustic signal is X and the signal intensity of the second photoacoustic signal is Y, Y / X is data indicating the relative magnitude of the signal intensity. Instead of using the ratio (Y / X) of the two photoacoustic signals as data indicating the relative magnitude of the relative signal intensity, tan ⁻¹ (Y / X) indicates the relative magnitude of the signal intensity. It may be used as data.

The intensity information extraction unit 255 generates intensity information indicating the signal intensity based on the photoacoustic signal corresponding to each wavelength. The intensity information extraction unit 255 generates, for example, (X ² + Y ² ) ^1/2 as the intensity information. The detection / logarithm conversion means 252 generates an envelope of data indicating the intensity information extracted by the intensity information extraction means 255, and then logarithmically converts the envelope to widen the dynamic range.

  The photoacoustic image construction means 253 is based on the relative magnitude relationship information of the two-wavelength data generated by the two-wavelength data calculation means 254 and the intensity information generated by the intensity information extraction means 255. Is generated. For example, the photoacoustic image construction unit 253 determines the luminance (gradation value) of each pixel in the distribution image of the light absorber based on the input intensity information. The photoacoustic image construction unit 253 determines the color (display color) of each pixel in the light absorber distribution image based on, for example, phase information. The photoacoustic image construction unit 253 determines the color of each pixel based on the input data indicating the magnitude relationship using, for example, a color map in which the range of data indicating the relative magnitude relationship is associated with a predetermined color. To do.

When the photoacoustic image construction unit 253 uses, for example, tan ⁻¹ (Y / X) as data indicating a relative magnitude relationship between the photoacoustic signals, for example, 0 ° is red and colorless as the angle approaches 45 ° ( A photoacoustic image is generated using a color map that gradually changes so that the color gradually changes so that 90 ° is blue and approaches 45 ° as white approaches 45 °. . A portion where the first photoacoustic signal is larger than the second photoacoustic signal corresponds to an artery, and a portion where the second photoacoustic signal is larger than the first photoacoustic signal corresponds to a vein. By using the color map, the portion corresponding to the artery can be represented in red and the portion corresponding to the vein can be represented in blue on the photoacoustic image.

  In the above description, an example in which light of two wavelengths is irradiated has been described. However, the number of wavelengths of pulsed laser light irradiated on a subject when generating a photoacoustic image is not limited to two. The subject may be irradiated with three or more pulsed laser beams, and a photoacoustic image may be generated based on a photoacoustic signal corresponding to each wavelength.

  In the above embodiment, the sound speed distribution generation unit 27 generates the sound speed distribution based on the reflected acoustic wave. However, the present invention is not limited to this. A sound velocity distribution may be generated based on at least one of the acoustic waves. For example, the sound speed distribution generation unit 27 receives a photoacoustic signal (photoacoustic data) from the data separation unit 24 and generates a sound speed distribution based on the photoacoustic signal. As an algorithm for generating the sound velocity distribution, an algorithm similar to that for generating the sound velocity distribution based on the reflected acoustic wave can be used.

  The acoustic wave detection signal used when generating the sound velocity distribution is not limited to a reflected acoustic signal detected for one acoustic wave transmission or a photoacoustic signal generated by one light irradiation. For example, the sound speed distribution may be generated by performing ultrasonic transmission a plurality of times and averaging the reflected acoustic signals for a plurality of times. Moreover, light irradiation may be performed a plurality of times, and the sound speed distribution may be generated by averaging the photoacoustic signals for a plurality of times. Similarly, the generation of the ultrasonic image and the photoacoustic image may be performed based on the reflected acoustic signal and the photoacoustic signal which are averaged.

  Although the present invention has been described based on the preferred embodiment, the photoacoustic image processing apparatus and method of the present invention are not limited to the above embodiment, and various modifications can be made from the configuration of the above embodiment. Further, modifications and changes are also included in the scope of the present invention.

10: Photoacoustic image processing apparatus 11: Probe 12: Ultrasound unit 13: Laser unit 14: Image display means 21: Reception circuit 22: AD conversion means 23: Reception memory 24: Data separation means 25: Photoacoustic image generation means 26 : Ultrasonic image generation means 27: Sound velocity distribution generation means 28: Malignancy distribution image generation means 29: Image composition means 30: Trigger control circuit 31: Transmission control circuit 32: Control means 41: Flash lamp 42: Q switch 251: Light Acoustic image reconstruction means 252: detection / logarithm conversion means 253: photoacoustic image construction means 254: 2-wavelength data calculation means 255: intensity information extraction means 261: ultrasonic image reconstruction means 262: detection / logarithm conversion means 263: super Sound image construction means

Claims (13)

A light source that emits light to be applied to the subject;
Acoustic wave detection means for detecting acoustic waves from within the subject;
Based on the acoustic wave detected by the acoustic wave detecting means, a sound speed distribution generating means for obtaining a sound speed distribution of the acoustic wave traveling in the subject;
A photoacoustic image generating means for generating a photoacoustic image based on a photoacoustic signal which is a detection signal of an acoustic wave detected by the acoustic wave detecting means after the light emitted from the light source is irradiated on the subject;
A photoacoustic image processing apparatus comprising: a malignancy distribution image generation unit configured to generate a malignancy distribution image based on the photoacoustic image and the sound velocity distribution in the subject.   Where the malignancy distribution image generation means has a high malignancy where the sound velocity is faster than the surroundings or higher than a predetermined value and the signal intensity of the photoacoustic image is equal to or higher than a predetermined value. The photoacoustic image processing apparatus according to claim 1, characterized by:   The malignancy distribution image generation means, at least of the luminance or display color of a pixel corresponding to a location identified as a location with a high malignancy, according to at least one of the sound speed and the signal intensity of the photoacoustic image 3. The photoacoustic image processing apparatus according to claim 2, wherein one of the two is changed.   The photoacoustic image generation means delay-adds photoacoustic signals detected by a plurality of acoustic wave detection elements of the acoustic wave detection means with a delay time based on the sound velocity distribution. The photoacoustic image processing apparatus in any one. An acoustic wave transmitting means for transmitting an acoustic wave to the subject;
The sound velocity distribution generating means generates the sound velocity distribution based on the reflected acoustic wave with respect to the transmitted acoustic wave detected by the acoustic wave detecting means after the acoustic wave is transmitted from the acoustic wave transmitting means. The photoacoustic image processing apparatus according to any one of claims 1 to 4.   6. The photoacoustic image processing apparatus according to claim 5, further comprising reflected acoustic wave image generation means for generating a reflected acoustic wave image based on a reflected acoustic signal that is a detection signal of the reflected acoustic wave.   The photoacoustic image processing apparatus according to claim 6, further comprising an image synthesis unit that synthesizes the malignancy distribution image and the reflected acoustic wave image.   The malignancy distribution image generation means extracts a predetermined lesion from the reflected acoustic wave image, and generates the malignancy distribution image for a portion of a region corresponding to the extracted lesion. 8. The photoacoustic image processing apparatus according to 7.   The reflected acoustic wave image generation means delay-adds the reflected acoustic signals detected by a plurality of acoustic wave detection elements of the acoustic wave detection means with a delay time based on the sound velocity distribution. 8. The photoacoustic image processing apparatus according to any one of 8.   The photoacoustic image processing apparatus according to claim 5, wherein the acoustic wave detection element of the acoustic wave detection unit also serves as the acoustic wave transmission element of the acoustic wave transmission unit. The light source emits light having a plurality of different wavelengths;
Relative signal intensity between photoacoustic signals corresponding to each of a plurality of wavelengths detected by the acoustic wave detecting unit with respect to light of a plurality of wavelengths irradiated on the subject by the photoacoustic image generation unit Two-wavelength data calculating means for extracting the magnitude relationship between the two, and intensity information extracting means for generating intensity information indicating signal intensity based on photoacoustic signals corresponding to each of a plurality of wavelengths, The gradation value of a pixel is determined based on the intensity information, and the display color of each pixel is determined based on the relative relationship between the relative signal intensities. Photoacoustic image processing apparatus. Irradiating the subject with light; and
Detecting photoacoustic waves from the subject after the light is irradiated on the subject;
Generating a photoacoustic image based on the detected photoacoustic wave;
Generating a sound velocity distribution of acoustic waves traveling in the subject based on the acoustic waves detected from within the subject;
And a step of generating a malignancy distribution image based on the photoacoustic image and a sound velocity distribution in the subject. Prior to the step of generating the sound velocity distribution, further comprising transmitting an acoustic wave to the subject;
13. The photoacoustic image processing method according to claim 12, wherein in the step of generating the sound speed distribution, a sound speed distribution is generated based on a reflected acoustic wave with respect to the transmitted acoustic wave.