JP2016043064A - Photoacoustic imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a more accurate photoacoustic image that can clearly identify a real image of a light absorber to be acquired.SOLUTION: A photoacoustic imaging apparatus includes: a light source drive control unit which performs photo-driven control of a light source including first and second light sources that are provided opposite on both sides of a detection part outputting detection signals of photoacoustic waves generated by a light absorber in a subject; a tomographic image generation part which generates a tomographic image on the basis of the detection signal of the photoacoustic wave generated every time pulse light irradiated to the subject from the light source is absorbed by the light absorber; and an image forming part forming a photoacoustic image displayed to a display on the basis of the tomographic image. The tomographic image generation part generates a differential signal between first signal intensity of a first detection signal when the pulse light is irradiated from the first light source and second signal intensity of a second detection signal when the pulse light is irradiated from the second light source, and generates a tomographic image on the basis of a detection signal component corresponding an effective differential signal component where the differential signal intensity is within a prescribed numerical value range.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a photoacoustic imaging apparatus.

  In recent years, development of a photoacoustic imaging apparatus (see Patent Document 1) for inspecting a specific object inside a living body in a nondestructive manner has been advanced. This photoacoustic imaging apparatus irradiates a living body with light of a predetermined wavelength, and detects a photoacoustic wave that is an elastic wave emitted from a specific object (light absorber) inside the living body when the light is absorbed. Then, by generating a tomographic image based on the detection result of the photoacoustic wave, a photoacoustic image showing the light absorber inside the living body in the region immediately below the photoacoustic wave detector is formed.

JP 2013-188311 A

  However, since the light incident on the living body diffuses, the light is irradiated to a region other than the plane region directly under the photoacoustic wave detector. Therefore, for example, the detector also detects a photoacoustic wave generated in the light absorber in the external region that is shifted in the normal direction from the plane region immediately below. In this case, in the photoacoustic image, a light absorber that is not in the plane area directly under the detector appears as a virtual image (so-called artifact). Furthermore, the depth of the actual position where the light absorber in the external region exists in the living body is different from the distance from the light absorber in the external region to the detector. For this reason, the virtual image appears in the photoacoustic image at a position deeper from the surface of the living body than the actual position.

  With respect to such a problem, in Patent Document 1, a photoacoustic image is obtained when the irradiation direction and irradiation position of light, the position of a detector, and the like are changed. Then, by acquiring the similarity distribution of each photoacoustic image, it is possible to determine whether the light absorber reflected in the photoacoustic image is a real image or a virtual image. However, since light easily diffuses in the living body, even if it is a light absorber that is not in the plane area directly under the detector, the detection level of the generated photoacoustic wave becomes strong if it is close to the light irradiation position. Therefore, in a photoacoustic image in which the irradiation direction and irradiation position of light are changed, the virtual image of the light absorber that is not in the plane area directly under the detector is more than the real image of the light absorber in the plane area directly under the detector. May appear clearly. Therefore, there is a possibility that the real image cannot be accurately identified by the similarity distribution acquired from such a photoacoustic image. Further, since the tomographic image changes when the position of the photoacoustic wave detector is changed, the similarity distribution of the photoacoustic image cannot be obtained accurately.

  The present invention has been made in view of such a situation, and an object thereof is to provide a photoacoustic imaging apparatus capable of acquiring a more accurate photoacoustic image that can clearly identify a real image of a light absorber. And

  In order to achieve the above object, a photoacoustic imaging apparatus according to an aspect of the present invention is provided so as to face each other with a detection unit that outputs a detection signal of a photoacoustic wave generated by a light absorber in a subject. A light source drive control unit that performs light drive control of a light source including the first light source and the second light source, and light generated each time pulse light irradiated from the light source to the subject is absorbed by the light absorber in the subject A tomographic image generation unit comprising: a tomographic image generation unit that generates a tomographic image of a subject based on an acoustic wave detection signal; and an image forming unit that forms a photoacoustic image to be displayed on a display unit based on the tomographic image. The first signal intensity of the first detection signal output from the detection unit when pulse light is irradiated on the subject from the first light source, and detection when pulse light is irradiated on the subject from the second light source A difference signal with the second signal strength of the second detection signal output from the unit is generated. Difference signal strength of said difference signal is configured to generate a tomographic image based on the detection signal component of the detection signal corresponding to the effective difference signal component falls within a predetermined numerical range (first configuration).

  According to the first configuration, the first signal intensity of the first detection signal when the subject is irradiated with pulsed light from the first light source, and the second when the subject is irradiated with pulsed light from the second light source. A difference signal from the second signal strength of the detection signal is generated. The difference signal intensity corresponds to the difference between the distance from the first light source to the light absorber and the distance from the second light source facing the detection unit to the light absorber. Therefore, if the difference signal intensity is within a predetermined numerical range, it can be determined that the light absorber is directly below the detection unit and corresponds to a real image. Therefore, if a tomographic image is generated based on a detection signal component corresponding to an effective differential signal component in which the differential signal intensity is within a predetermined numerical range among the differential signals, the real image of the light absorber can be more accurately identified. A simple photoacoustic image can be acquired.

  Further, in the photoacoustic imaging apparatus having the first configuration, the tomographic image generation unit includes a detection signal component corresponding to an effective difference signal component among the addition combined signal obtained by adding and combining the first detection signal and the second detection signal. It is good also as a structure (2nd structure) which produces | generates a tomogram based on this.

  According to the second configuration, the signal strength of the addition combined signal is higher than that of the first detection signal and the second detection signal. In addition, since the tomographic image is generated based on the detection signal component corresponding to the effective difference signal component in the added composite signal, the virtual image can be excluded from the tomographic image. Therefore, the photoacoustic image formed based on the tomographic image can be made clearer.

  In the photoacoustic imaging apparatus having the first configuration, the tomographic image generation unit includes a third detection signal output from the detection unit when the subject is irradiated with pulsed light from the first light source and the second light source. The tomographic image may be generated based on the detection signal component corresponding to the effective difference signal component (third configuration).

  According to the third configuration, the signal intensity of the third detection signal is higher than that of the first and second detection signals because light is emitted from the first and second light sources. Further, since the tomographic image is generated based on the detection signal component corresponding to the effective difference signal component in the third detection signal, the virtual image can be excluded from the tomographic image. Therefore, the photoacoustic image formed based on the tomographic image can be made clearer.

  In the photoacoustic imaging apparatus having any one of the first to third configurations, the tomographic image generation unit includes an invalid detection signal component of a detection signal corresponding to an invalid difference signal component other than an effective difference signal component of the difference signal. And generating an offset tomogram based on the tomogram, and the image forming unit forms a photoacoustic image for displaying the offset tomogram in a display format different from the tomogram based on the tomogram and the offset tomogram (fourth configuration) ).

  According to the fourth configuration, in the photoacoustic image, the shifted tomographic image generated based on the invalid detection signal component is displayed in a display format different from the tomographic image. Therefore, the presence of the light absorber at a position shifted from directly below the detection unit can be visually recognized by displaying the shifted tomographic image. In other words, the three-dimensional position of the light absorber can be simply displayed on the photoacoustic image.

  In the photoacoustic imaging apparatus having any one of the first to fourth configurations, the shifted tomographic image has an upper limit threshold value in which the difference signal intensity of the difference signal obtained by subtracting the second signal intensity from the first signal intensity is a numerical value range. A first shift tomogram generated based on a first invalid detection signal component of a detection signal corresponding to a larger differential signal component and a detection corresponding to a differential signal component whose differential signal intensity is smaller than a lower limit threshold of a numerical range A second shifted tomogram generated based on a second invalid detection signal component of the signal, and the image forming unit displays the tomographic image, the first shifted tomographic image, and the second shifted tomographic image in different display formats. The photoacoustic image to be displayed may be formed based on the tomographic image, the first shifted tomographic image, and the second shifted tomographic image (fifth configuration).

  According to the fifth configuration, in the photoacoustic image, the tomographic image, the first shifted tomographic image, and the second shifted tomographic image are displayed in different display formats. Therefore, the light absorber displayed in the photoacoustic image is directly under the detection unit, is in a position shifted from directly under the detection unit to the first light source side, or is shifted from directly under the detection unit to the second light source side. It is possible to make it visible. In other words, a more accurate three-dimensional position of the light absorber can be simply displayed on the photoacoustic image.

  In the photoacoustic imaging apparatus having the fourth or fifth configuration, the correction information in which the positional information in the depth direction of the shifted tomogram and the deviation ratio of the positional information are associated with each difference signal intensity of the difference signal. A tomographic image generation unit may further include a storing memory, and the tomogram generation unit may correct the positional information in the depth direction of the shifted tomogram based on the correction information (sixth configuration).

  According to the sixth configuration, it is possible to correct the position information in the depth direction of the shifted tomogram according to the difference signal intensity using the correction information. Therefore, an accurate photoacoustic image of position information can be acquired even for a virtual image.

  In the photoacoustic imaging apparatus having any one of the first to sixth configurations, the first light source and the second light source may each be a light emitting diode element light source (seventh configuration).

  Alternatively, in the photoacoustic imaging apparatus having any one of the first to sixth configurations, the first light source and the second light source may each be a semiconductor laser element light source (eighth configuration).

  Alternatively, in the photoacoustic imaging apparatus having any one of the first to sixth configurations, the first light source and the second light source may be organic light emitting diode element light sources (ninth configuration).

  According to any of the seventh to ninth configurations, the first light source and the second light source can be miniaturized, and the subject can be irradiated with pulsed light having a high emission frequency with a simple configuration. Therefore, since more tomographic images can be formed per unit time, a clearer and higher-definition photoacoustic image can be acquired.

  ADVANTAGE OF THE INVENTION According to this invention, the photoacoustic imaging device which can acquire the more exact photoacoustic image which can identify the real image of a light absorber clearly can be provided.

It is an external appearance perspective view of a photoacoustic imaging device. It is a block diagram which shows the example of an internal structure of a photoacoustic imaging device. It is a schematic front view of an ultrasonic probe. It is a schematic side view of an ultrasonic probe. It is the example of arrangement | positioning of the light source in the light source part provided in a 1st and 2nd light irradiation part. It is a figure for demonstrating the principle displayed on the photoacoustic image which imaged the photoacoustic wave. It is a figure which shows the photoacoustic wave which generate | occur | produces in the light absorber which received the pulsed light irradiated from a 1st light irradiation part. It is a figure which shows the photoacoustic wave which generate | occur | produces in the light absorber which received the pulsed light irradiated from a 2nd light irradiation part. It is a flowchart for demonstrating an example of the imaging procedure of the photoacoustic wave detected in 1st Embodiment. It is an example of each signal which a photoacoustic imaging device generates in a 1st embodiment. The distribution of the light absorber in the XZ plane in the subject in 2nd Embodiment is shown. It is a flowchart for demonstrating an example of the imaging procedure of the photoacoustic wave detected in 2nd Embodiment. It is an example of each signal which a photoacoustic imaging device generates in a 2nd embodiment. It is an example of the display screen of the photoacoustic image displayed on LCD in 2nd Embodiment. It is a flowchart for demonstrating an example of the imaging procedure of the photoacoustic wave detected in 3rd Embodiment. It is an example of each signal which a photoacoustic imaging device generates in a 3rd embodiment. It is an example of the display screen of the photoacoustic image displayed on LCD in 3rd Embodiment. The example of distribution of the light absorber P in the XZ plane in the subject in 4th Embodiment is shown. It is a flowchart for demonstrating an example of the imaging procedure of the photoacoustic wave detected in 4th Embodiment. It is an example of each signal which a photoacoustic imaging device generates in a 4th embodiment. It is an example of the display screen of the photoacoustic image displayed on LCD in 4th Embodiment. It is the schematic diagram which looked at the puncture needle inserted in the subject from the Y direction. It is a photoacoustic image of a puncture needle. It is a figure which shows the positional relationship of the light absorber in the position which shifted | deviated to the Z direction from right under the ultrasonic probe, and its virtual image. It is a graph which shows an example of the correction information of the positional information of the X direction of a shift | offset | difference tomogram.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an external perspective view of the photoacoustic imaging apparatus 100. FIG. 2 is a block diagram illustrating an internal configuration example of the photoacoustic imaging apparatus 100. The photoacoustic imaging apparatus 100 includes an ultrasonic probe 20 for acquiring tomographic image information in the subject 150, an image generation unit 30, and an image display unit 40.

  The ultrasonic probe 20 irradiates the subject 150 that is a living body with light and detects photoacoustic waves generated in the subject 150. The ultrasonic probe 20 transmits ultrasonic waves to the subject 150 and detects ultrasonic waves that are reflected waves.

  As shown in FIG. 2, the ultrasonic probe 20 includes a drive power supply unit 101, a light source drive unit 102, a first light irradiation unit 201A, a second light irradiation unit 201B, and an acoustoelectric conversion unit 202. Yes. The light source drive unit 102 is supplied with power from the drive power supply unit 101. Each of the first and second light irradiation units 201 </ b> A and 201 </ b> B has a light source unit 103. The light source unit 103 includes light sources 103A and 103B including LED (Light Emitting Diode) elements (not shown). The light source 103A is driven by the light source driving circuit 102A in the light source driving unit 102, and the light source 103B is driven by the light source driving circuit 102B.

  In addition, the ultrasonic probe 20 includes a lens member that collects light emitted from the light source unit 103, and a light guide unit (for example, made of acrylic resin) that guides the light collected by the lens member to the subject 150. (Light guide plate, optical fiber) or the like.

  Here, a schematic front view of the ultrasonic probe 20 is shown in FIG. 3A, and a schematic side view thereof is shown in FIG. 3B. As shown in FIGS. 3A and 3B, the first and second light irradiation units 201A and 201B are arranged side by side in the Z direction so as to face each other with an ultrasonic vibration element 202A described later interposed therebetween. In the first and second light irradiation units 201A and 201B, the light source unit 103 is provided so as to be positioned in the vicinity of the subject 150 when the ultrasonic probe 20 is brought into contact with the subject 150.

  FIG. 4 is an arrangement example of the light sources 103A and 103B in the light source unit 103 provided in the first and second light irradiation units 201A and 201B. In the light source unit 103, as shown in FIG. 4, for example, the light sources 103A and 103B are alternately arranged in the Y direction. Each of the light sources 103A and 103B includes three rows of LED elements in the Y direction and six rows (that is, 3 × 6 = 18) of LED elements in the Z direction.

  As described above, if the light sources 103A and 103B are LED light sources, respectively, the light sources 103A and 103B can be downsized, and the subject can be irradiated with pulsed light having a high emission frequency with a simple configuration. Accordingly, since more tomographic image information can be acquired per unit time (for example, a period required for updating the display of the LCD 401 described later), the photoacoustic image I described later can be made clearer and higher in definition.

  Further, the light emission wavelengths of the LED elements are different between the light sources 103A and 103B. Here, the light source 103A and the light source 103B emit light having different wavelengths. Regarding the setting of the wavelength, a wavelength having a high absorptance with respect to the measurement target (light absorber P) may be selected. For example, the wavelength of light emitted from the light source 103A may be 760 nm, which has a high absorption rate for oxyhemoglobin in blood, and the wavelength of light emitted from the light source 103B may be 850 nm, which has a high absorption rate for reduced hemoglobin in blood. it can. In this case, for example, when the light source 103A emits light and the subject 150 is irradiated with light having a wavelength of 760 nm, light is absorbed by oxyhemoglobin in blood contained in arterial blood vessels or tumors in the subject 150. An acoustic wave is generated, and a photoacoustic image I including an arterial blood vessel and a tumor is generated in a photoacoustic image construction unit 307 described later.

  The LED element of the light source 103A is controlled to emit light by the light source driving circuit 102A and irradiates the subject 150 with light (see FIG. 2). Similarly, the LED element of the light source 103B is controlled to emit light by the light source driving circuit 102B and irradiates the subject 150 with light. The LED element is an LED light source that is driven to emit pulsed light. The PRF (Pulse Repetition Frequency) of the pulsed light is not particularly limited, but can be, for example, 1000 [times / sec].

  The acoustoelectric conversion unit 202 is configured to include a plurality of ultrasonic vibration elements 202A disposed in the Y direction between the first and second light irradiation units 201A and 201B. The ultrasonic vibration element 202A is a piezoelectric element that generates an ultrasonic wave by vibration when a voltage is applied and generates a voltage when vibration (ultrasonic wave) is applied. An adjustment layer (not shown) for adjusting the difference in acoustic impedance is interposed between the acoustoelectric conversion unit 202 and the surface of the subject 150. This adjustment layer efficiently propagates the ultrasonic wave generated from the ultrasonic vibration element 202 </ b> A into the subject 150. Further, the adjustment layer has a function of efficiently transmitting ultrasonic waves (including photoacoustic waves) from within the subject 150 to the ultrasonic vibration element 202A. The acoustoelectric conversion unit 202 is an example of the detection unit of the present invention.

  As shown in FIGS. 3A and 3B, the pulsed light emitted from the first and second light irradiation units 201A and 201B is incident on the subject 150 while being scattered, and the light absorber P ( Absorbed by living tissue). When the light absorber P absorbs light, a photoacoustic wave (ultrasonic wave) that is an elastic wave is generated by adiabatic expansion. This photoacoustic wave propagates through the subject 150 and is converted into a voltage signal by the ultrasonic vibration element 202A.

  Further, the ultrasonic vibration element 202A generates an ultrasonic wave to propagate the ultrasonic wave into the subject 150, detects the ultrasonic wave reflected in the subject 150, and generates a voltage signal. That is, the photoacoustic imaging apparatus 100 of the present embodiment can also perform ultrasonic imaging in addition to photoacoustic imaging.

  Next, the image generation unit 30 will be described. The image generation unit 30 processes the signal detected by the ultrasonic probe 20 and performs imaging. For example, the image generation unit 30 generates an acoustic wave image based on a photoacoustic wave detection signal, and generates an ultrasonic image based on the ultrasonic detection signal. As shown in FIG. 2, the image generation unit 30 includes a reception circuit 301, an A / D converter 302, a reception memory 303, a data processing unit 304, a photoacoustic image reconstruction unit 305, a detection / logarithmic converter 306, and a photoacoustic image construction. A unit 307, an ultrasonic image reconstruction unit 308, a detection / logarithmic converter 309, an ultrasonic image construction unit 310, an image synthesis unit 311, a control unit 312, a transmission control circuit 313, and an operation unit 314.

  The reception circuit 301 selects a part of the ultrasonic vibration elements 202A from the plurality of ultrasonic vibration elements 202A and performs a process of amplifying a voltage signal (detection signal) for the selected ultrasonic vibration element 202A.

  In the case of photoacoustic imaging, for example, a plurality of ultrasonic transducer elements 202A are divided into two regions adjacent in the Y direction, and one region is selected for the first light irradiation, and the second light irradiation is performed. The remaining one area is selected at the time. In the case of ultrasonic imaging, for example, an ultrasonic wave is generated while switching a group composed of a part of adjacent ultrasonic vibration elements 202A among a plurality of ultrasonic vibration elements 202A (so-called linear electronic scan), and a reception circuit. In 301, the above group is selected while being switched.

  The A / D converter 302 converts the amplified detection signal from the reception circuit 301 into a digital signal. The reception memory 303 stores the digital signal from the A / D converter 302. The data processing unit 304 has a function of distributing the signal stored in the reception memory 303 to the photoacoustic image reconstruction unit 305 or the ultrasonic image reconstruction unit 308.

  The photoacoustic image reconstruction unit 305 performs phase matching addition processing based on the photoacoustic wave detection signal to reconstruct photoacoustic wave data. The detection / logarithmic converter 306 performs logarithmic compression processing and envelope detection processing on the reconstructed photoacoustic wave data. Then, the photoacoustic image construction unit 307 converts the data processed by the detection / logarithmic converter 306 into luminance value data for each pixel. That is, photoacoustic image data (for example, gray scale) is generated as luminance value data for each pixel on the XY plane. The photoacoustic image reconstruction unit 305, the detection / logarithmic converter 306, the photoacoustic image construction unit 307, and the image synthesis unit 311 are examples of the tomographic image generation unit and the image formation unit of the present invention. Perform imaging processing.

  The photoacoustic image data is data indicating a photoacoustic image I formed by performing an averaging process on tomographic images of photoacoustic waves generated in the XY plane region immediately below the ultrasonic probe 20 in the subject 150. It is. The pixel size of the photoacoustic image I is, for example, vertical 2048 [pixel] × horizontal 128 [pixel]. Each pixel represents the detection level of the photoacoustic wave after the averaging process in 256 gray scales. The horizontal width of the photoacoustic image I corresponds to the width of the tomographic image (distance in the Y direction), and the vertical width corresponds to the detection depth (distance in the X direction) starting from the surface of the subject 150. The size of the tomographic image (that is, the actual size in the XY plane region) is, for example, width × detection depth = 5 [cm] × 5 [cm]. Further, the data amount of the tomographic image generated from the detection signal of the photoacoustic wave generated by one light irradiation is, for example, 32 [MB].

  On the other hand, the ultrasound image reconstruction unit 308 performs phase matching addition processing based on the ultrasound detection signal to reconstruct the ultrasound data. The detection / logarithmic converter 309 performs logarithmic compression processing and envelope detection processing on the reconstructed ultrasonic data. Then, the ultrasonic image construction unit 310 converts the data processed by the detection / logarithmic converter 309 into luminance value data for each pixel. That is, ultrasonic image data (for example, gray scale) is generated as luminance value data for each pixel on the XY plane.

  The image synthesizing unit 311 synthesizes the photoacoustic image data and the ultrasonic image data to generate synthesized image data. Here, for image synthesis, a photoacoustic image may be superimposed on an ultrasonic image, or a photoacoustic image and an ultrasonic image may be arranged in parallel. The image display unit 40 displays an image based on the combined image data generated by the image combining unit 311. Note that the image composition unit 311 may output either the photoacoustic image data or the ultrasonic image data to the image display unit 40 as it is.

  The control unit 312 controls each component of the photoacoustic imaging apparatus 100 using a program and control information stored in a non-transitory storage medium (memory) (not shown). For example, the control unit 312 transmits a wavelength control signal to the light source driving circuit 102. The light source driving circuit 102 that has received the wavelength control signal selects either the light source 103A or the light source 103B. When the light trigger signal is transmitted from the control unit 31 to the light source driving circuit 102, the light source driving circuit 102 transmits a driving signal to the selected light source 103A or 103B.

  The transmission control circuit 313 transmits a drive signal to the acoustoelectric conversion unit 202 according to an instruction from the control unit 312 to generate an ultrasonic wave. In addition, the control unit 312 controls the receiving circuit 301 and the like.

  The operation unit 314 accepts a user operation input and outputs an input signal corresponding to the operation input to the control unit 312.

  Next, the image display unit 40 will be described. The image display unit 40 is a display device having a touch panel, and includes an LCD (Liquid Crystal Display) 401 and an input detection unit 402. The LCD 401 displays an image (for example, a photoacoustic image) based on the image signal generated by the image generation unit 30. The input detection unit 402 receives user operation input. When the display screen of the LCD 401 is touch-inputted by a user's finger or a touch pen, the input detection unit 402 outputs an input signal corresponding to the touch input to the control unit 312.

  Next, the principle that a virtual image (so-called artifact) of the light absorber Pa is displayed in the photoacoustic image I obtained by imaging a photoacoustic wave will be described with reference to FIG. In FIG. 5, the alternate long and short dash line indicates the XY plane region immediately below the ultrasonic probe 20. Consider the case where the light absorber P is located at a position shifted in the −Z direction from directly below the ultrasonic vibration element 202 </ b> A of the ultrasonic probe 20 as shown in FIG. 5. In this case, when the pulsed light is irradiated from the first and second light irradiation units 201A and 201B, the pulsed light is received by the light absorber P, so that a photoacoustic wave is generated in the light absorber P. It is detected by the ultrasonic vibration element 202A. Here, the ultrasonic vibration element 202A cannot detect the propagation direction of the photoacoustic wave to be detected. Therefore, the acoustoelectric conversion unit 202 detects the photoacoustic wave generated by the light absorber P as the photoacoustic wave generated by the virtual light absorber Pf immediately below the ultrasonic vibration element 202A. As a result, the virtual light absorber Pf appears as a virtual image in the tomographic image generated based on the detection signal of the acoustoelectric conversion unit 202 and its photoacoustic image.

  Further, the depth (that is, the position in the X direction) of the virtual light absorber Pf is the same as the shortest distance L between the light absorber P and the ultrasonic vibration element 202A. Therefore, it becomes deeper than the actual depth of the light absorber P (that is, the shortest distance between the light absorber P and the surface of the object 150). Therefore, in the tomographic image, the virtual light absorber Pf is shifted in the X direction.

  FIG. 5 shows an example in which the first and second light irradiation units 201A and 201B both radiate pulsed light. However, when either one of the first and second light irradiation units 201A or 201B irradiates pulsed light. Similarly, the virtual light absorber Pf appears in the tomographic image and its photoacoustic image as a virtual image. FIG. 6 is a diagram showing photoacoustic waves generated by the light absorber P that has received the pulsed light emitted from the second light irradiation unit 201B. FIG. 7 is a diagram illustrating photoacoustic waves generated by the light absorber P that has received the pulsed light emitted from the first light irradiation unit 201A. As shown in FIGS. 6 and 7, a photoacoustic wave is generated in the light absorber P by the pulsed light emitted from the first or second light irradiation unit 201A or 201B, and the photoacoustic wave is generated by the ultrasonic vibration element 202A. Detected.

  However, since the light absorber P is closer to the second light irradiation unit 201B than the first light irradiation unit 201A, the pulsed light received by the light absorber P in FIG. It becomes stronger than the received pulsed light. Therefore, the photoacoustic wave generated in the light absorber Pa in FIG. 6 is stronger than the photoacoustic wave generated in the light absorber P in FIG. The photoacoustic imaging apparatus 100 uses this phenomenon to acquire a more accurate photoacoustic image I that can clearly identify the real image of the light absorber P.

  Next, photoacoustic wave imaging processing of the photoacoustic imaging apparatus 100 will be described.

<First Embodiment>
FIG. 8 is a flowchart for explaining an example of a procedure for imaging a photoacoustic wave detected in the first embodiment. FIG. 9 is an example of each signal generated by the photoacoustic imaging apparatus 100 in the first embodiment.

  First, the light source unit 103 of the first light irradiation unit 201A is caused to emit light to irradiate the subject 150 with pulsed light, and the first detection signal output from the acoustoelectric conversion unit 202 is acquired (S101). Hereinafter, the process of acquiring the first detection signal by irradiating the pulsed light from the first light irradiation unit 201A on one side of the ultrasonic probe 20 is referred to as a first imaging mode.

  Next, the light source unit 103 of the second light irradiation unit 201B is caused to emit light to irradiate the subject 150 with pulse light of substantially the same level, and a second detection signal output from the acoustoelectric conversion unit 202 is acquired (S102). . In the following, the process of acquiring the second detection signal by irradiating pulse light of substantially the same level as the first imaging mode from the second light irradiation unit 201B on the other side of the ultrasonic probe 20 is referred to as the second imaging mode. Call.

  Then, the first and second detection signals are differentially combined to generate a differential signal (S103). In FIG. 9, the signal level (difference signal strength) of the difference signal is the difference between the signal level (first signal strength) A1 of the first detection signal and the signal level (second signal strength) A2 of the second detection signal. The absolute value | A1-A2 |

  Next, an invalid extraction signal is generated based on the comparison result between the signal level | A1-A2 | and the threshold level S (S104). The invalid extraction signal is a light absorption in which each signal component of the first and second detection signals indicates a real image of the light absorber P immediately below the ultrasonic probe 20 or is shifted in the Z direction from directly below the ultrasonic probe 20. It is a signal for determining whether to show a virtual image of the body P.

  First, it is determined whether or not the signal level | A1-A2 | of the difference signal is equal to or lower than the threshold level S (S104a). That is, it is determined whether or not the signal level | A1-A2 | is within a numerical range of 0 or more and the threshold level S or less. In addition, since the photoacoustic wave diffuses as the distance to the ultrasonic probe 20 increases, the detection level thereof decreases. Therefore, the threshold level S has a negative correlation with the photoacoustic wave detection distance (that is, the depth of the photoacoustic wave generation position). The threshold level S is determined based on, for example, experimental results, but can be arbitrarily changed by, for example, user input.

  As shown in FIG. 9, when the signal level | A1-A2 | is equal to or lower than the threshold level S (YES in S104a), the signal level of the invalid extraction signal is set to H (S104b). If the signal level | A1-A2 | is greater than the threshold level S (NO in S104a), the signal level of the invalid extraction signal is set to L (S104c).

  Next, the first and second detection signals are added and combined to generate an added combined signal (S105), and an effective detection signal obtained by filtering the added combined signal based on the invalid extraction signal is generated (S106). For example, the signal section corresponding to the invalid extracted signal having a signal level of H among the added combined signals is recognized as indicating a virtual image and is set to a reference level (for example, signal level (A1 + A2) = 0). Note that the signal section corresponding to the invalid extraction signal with the signal level of L is recognized as showing a real image, and the signal level (A1 + A2) is not changed.

  Then, a photoacoustic image is formed from the tomographic image generated based on the effective detection signal (S107). Thus, the imaging process of the photoacoustic image I is completed, and the photoacoustic image I is displayed on the LCD 401.

  According to the above-described photoacoustic wave imaging process, an added composite signal corresponding to an effective differential signal component whose signal level is within a predetermined numerical range (0 ≦ | A1−A2 | ≦ S) in the differential signal. By generating a tomographic image based on the signal component, it is possible to exclude a virtual image from the tomographic image. Therefore, a more accurate photoacoustic image I that can clearly identify the real image of the light absorber P can be acquired and displayed on the LCD 401.

Second Embodiment
Next, a second embodiment will be described. In the second embodiment, the photoacoustic image I is formed based on the third detection signal acquired when the first and second light irradiation units 201A and 201B emit light simultaneously. The rest is the same as in the first embodiment. Hereinafter, a configuration different from the first embodiment will be described. Moreover, the same code | symbol is attached | subjected to the component similar to 1st Embodiment, and the description is abbreviate | omitted.

  FIG. 10 shows the distribution of the light absorbers Pa and Pb on the XZ plane in the subject 150 in the second embodiment. In FIG. 10, the alternate long and short dash line indicates the XY plane region immediately below the ultrasonic probe 20. 10 is parallel to the thickness direction (Z direction) of the ultrasonic probe 20, and is orthogonal to the XY plane corresponding to the tomographic image. As shown in FIG. 10, in the XZ plane immediately below the ultrasonic probe 20, there are three light absorbers Pa immediately below the ultrasonic probe 20, and at a position shifted in the Z direction from directly below the ultrasonic probe 20. There are three light absorbers Pb.

  FIG. 11 is a flowchart for explaining an example of a procedure for imaging a photoacoustic wave detected in the second embodiment. FIG. 12 is an example of each signal generated by the photoacoustic imaging apparatus 100 in the second embodiment.

  Since S101 to S104 are the same as those in the first embodiment (see FIG. 8), description thereof is omitted. In addition, each peak of the 1st and 2nd detection signal acquired by S101 and S102 respond | corresponds to the detection of the photoacoustic wave which generate | occur | produced in light absorber Pa or Pb, respectively.

  Next, the light sources 103 of the first and second light irradiation units 201A and 201B are caused to emit light at the same time to irradiate the subject 150 with the pulsed light, and the third detection signal output from the acoustoelectric conversion unit 202 is acquired. (S205). Each peak of the third detection signal corresponds to detection of a photoacoustic wave generated by the light absorber Pa or Pb. In the following, a third detection signal is obtained by irradiating pulse light at substantially the same level as in the first and second imaging modes from the first and second light irradiation units 201A and 201B on both sides of the ultrasonic probe 20, respectively. This process is called a third imaging mode.

  And a valid detection signal is produced | generated by filtering a 3rd detection signal based on an invalid extraction signal (S206). In this effective detection signal, for example, a signal section corresponding to an invalid extraction signal having a signal level of H in the third detection signal is recognized as indicating a virtual image of the light absorber Pb, and a reference level (for example, signal level A3a) is determined. = 0). Note that the signal section corresponding to the invalid extraction signal having a signal level of L is recognized as indicating a real image of the light absorber Pa, and the signal level A3a is not changed.

  Then, a photoacoustic image I is formed from the tomographic image generated based on the effective detection signal (S107). Thus, the imaging process of the photoacoustic image I is completed, and the photoacoustic image I is displayed on the LCD 401 as shown in FIG.

  According to the above-described photoacoustic wave imaging process, the third detection corresponding to the effective differential signal component of which the signal level is within a predetermined numerical range (0 ≦ | A1−A2 | ≦ S) among the differential signals. By generating the tomographic image based on the signal component of the signal, the virtual image of the light absorber Pb can be excluded from the tomographic image. Therefore, a more accurate photoacoustic image I that can clearly identify the real image of the light absorber Pa can be acquired and displayed on the LCD 401.

<Third Embodiment>
Next, a third embodiment will be described. In the third embodiment, the display color in which the real image of the light absorber Pa immediately below the ultrasonic probe 20 and the virtual image of the light absorber Pb in which the photoacoustic image is shifted from directly below the ultrasonic probe 20 are different from each other. Is displayed. The rest is the same as in the second embodiment. Hereinafter, a configuration different from the first and second embodiments will be described. Moreover, the same code | symbol is attached | subjected to the structure part similar to 1st and 2nd embodiment, and the description is abbreviate | omitted.

  The distribution of the light absorber P in the XZ plane in the subject 150 in the third embodiment is the same as that in the second embodiment (see FIG. 10). In the XZ plane immediately below the ultrasonic probe 20, there are three light absorbers Pa immediately below the ultrasonic probe 20, and the three light absorbers Pb are located at positions shifted in the Z direction from directly below the ultrasonic probe 20. Existing.

  FIG. 14 is a flowchart for explaining an example of an imaging procedure of photoacoustic waves detected in the third embodiment. FIG. 15 is an example of each signal generated by the photoacoustic imaging apparatus 100 in the third embodiment.

  Since S101 to S104 and S205 are the same as those in the second embodiment (see FIG. 11), description thereof will be omitted. Each peak of the first to third detection signals acquired in S101, S102, and S205 corresponds to detection of a photoacoustic wave generated in the light absorber Pa or Pb, respectively.

  Next, an effective detection signal and an invalid detection signal are generated by filtering the third detection signal acquired in the third imaging mode based on the invalid extraction signal (S306).

  In the valid detection signal, for example, the signal section corresponding to the invalid extraction signal having a signal level of H in the third detection signal is recognized as indicating a virtual image of the light absorber Pb, and the reference level (for example, the signal level) is determined. A3a = 0). Note that the signal section corresponding to the invalid extraction signal having a signal level of L is recognized as indicating a real image of the light absorber Pa, and the signal level A3a is not changed.

  In the invalid detection signal, for example, the signal section corresponding to the invalid extraction signal having a signal level of L among the third detection signals is recognized as indicating a real image of the light absorber Pa, and the reference level (for example, signal level A3b = 0). Note that the signal section corresponding to the invalid extraction signal having a signal level of H is recognized as indicating a virtual image of the light absorber Pb, and the signal level A3b is not changed.

  Then, a tomographic image is generated based on the valid detection signal (S307), and a shifted tomographic image is generated based on the invalid detection signal (S308).

  Next, the tomographic image and the shifted tomographic image generated per unit time are subjected to the addition averaging process, and the photoacoustic image I is formed from the tomographic image and the shifted tomographic image after the averaging process (S310). Then, the imaging process of the photoacoustic image I ends, and the photoacoustic image I is displayed on the LCD 401.

  FIG. 16 is an example of a display screen of the photoacoustic image I displayed on the LCD 401 in the third embodiment. In this photoacoustic image I, the tomographic image and the shifted tomographic image after the averaging process are superimposed and displayed, and the tomographic image is displayed in a normal color (for example, gray scale), but the shifted tomographic image is different from the normal color. Displayed in display color (for example, yellow). Accordingly, the light absorber Pa (that is, a real image) immediately below the ultrasonic probe 20 is displayed in a normal color, but the light absorber Pb (that is, a virtual image) that is shifted from directly below the ultrasonic probe 20 is a normal color. Displayed in a different display color.

  In FIG. 16, in the photoacoustic image I, the shifted tomographic image (and the light absorber Pb) is displayed in a display color different from the normal color, but the present invention is not limited to this example. The shifted tomographic image (and light absorber Pb) only needs to be displayed in a display format different from that of the tomographic image (and light absorber Pa). For example, the shifted tomographic image (and light absorber Pb) may be painted with a predetermined pattern, color, etc., unlike the tomographic image (and light absorber Pa).

  According to the above-described photoacoustic wave imaging processing, in the photoacoustic image I, the shifted tomographic image generated based on the invalid detection signal component is displayed in a display format (particularly, display color) different from that of the tomographic image. Therefore, the presence of the light absorber Pb at a position shifted from directly below the ultrasonic probe 20 can be visually recognized by displaying a shifted tomographic image. In other words, the three-dimensional positions of the light absorbers Pa and Pb can be simply displayed on the photoacoustic image I.

<Fourth embodiment>
Next, a fourth embodiment will be described. In the fourth embodiment, in the photoacoustic image I, a real image of the light absorber Pa, light absorbers Pc1 and Pc2 on the first light irradiation unit 201A side, and light absorber Pd1 on the second light irradiation unit 201B side. , Pd2 virtual images are displayed in different display colors. The rest is the same as in the third embodiment. Below, a different structure from 1st-3rd embodiment is demonstrated. Moreover, the same code | symbol is attached | subjected to the component similar to 1st-3rd embodiment, and the description is abbreviate | omitted.

  FIG. 17 shows a distribution example of the light absorber P on the XZ plane in the subject 150 in the fourth embodiment. In FIG. 17, the alternate long and short dash line indicates the XY plane region immediately below the ultrasonic probe 20. 17 is parallel to the thickness direction (Z direction) of the ultrasonic probe 20, and is orthogonal to the XY plane corresponding to the tomographic image. As shown in FIG. 17, in the XZ plane immediately below the ultrasonic probe 20, one light absorber Pa exists immediately below the ultrasonic probe 20. In addition, two light absorbers Pc1 and Pc2 are present at positions shifted in the Z direction from directly below the ultrasonic probe 20 toward the first light irradiation unit 201A. In addition, two light absorbers Pd1 and Pd2 exist at a position shifted in the −Z direction from directly below the ultrasonic probe 20 toward the second light irradiation unit 201B.

  FIG. 18 is a flowchart for explaining an example of a procedure for imaging a photoacoustic wave detected in the fourth embodiment. FIG. 19 is an example of each signal generated by the photoacoustic imaging apparatus 100 in the fourth embodiment.

  Since S101 and S102 are the same as in the third embodiment (see FIG. 14), description thereof is omitted. Each peak of the first and second detection signals acquired in S101 and S102 corresponds to detection of photoacoustic waves generated in the light absorbers Pc2, Pc1, Pa, Pd1, and Pd2, respectively.

  Next, a differential signal is generated from the first and second detection signals (S403). Note that the signal level (difference signal intensity) of the difference signal is different from the first to third embodiments in FIG. 19 in the difference between the signal level A1 of the first detection signal and the signal level A2 of the second detection signal ( A1-A2) is shown.

  Then, an invalid extraction signal is generated based on the comparison result between the signal level (A1-A2) of the difference signal and the upper threshold level S1 and the lower threshold level S2 (S404). That is, it is determined whether or not the signal level (A1-A2) is within a numerical range not less than the lower threshold level S2 and not more than the upper threshold level S1. In addition, since the photoacoustic wave diffuses as the distance to the ultrasonic probe 20 increases, the detection level thereof decreases. Therefore, the upper threshold level S1 has a negative correlation with the photoacoustic wave detection distance (that is, the depth of the photoacoustic wave generation position), and the lower threshold level S2 has a positive correlation with the photoacoustic wave detection distance. . The upper threshold level S1 and the lower threshold level S2 are determined based on, for example, experimental results, but can be arbitrarily changed by, for example, user input.

  First, it is determined whether or not the signal level (A1-A2) of the difference signal is equal to or lower than the upper threshold level S1 (S404a). When the signal level (A1-A2) is higher than the upper threshold level S1 (NO in S104a), the signal level of the invalid extraction signal is set to A + (S404b).

If the signal level (A1-A2) is equal to or lower than the upper threshold level S1 (YES in S404a), it is determined whether the signal level (A1-A2) is equal to or higher than the lower threshold level S2 (S404c). When the signal level (A1-A2) is equal to or higher than the lower threshold level S2 (YES in S404c), the signal level of the invalid extraction signal is set to A0 (S404d).
When the signal level (A1-A2) is lower than the lower threshold level S2 (NO in S404c), the signal level of the invalid extraction signal is set to A- (S404e).

  Each signal level of the invalid extraction signal is A− <A0 <A +, and is set to A0 = 0, for example.

  Next, a third detection signal is acquired in the third imaging mode (S205). In addition, each peak of the 3rd detection signal acquired by S205 respond | corresponds to the detection of the photoacoustic wave which each generate | occur | produced in light absorber Pc2, Pc1, Pa, Pd1, and Pd2.

  Then, by filtering the third detection signal based on the invalid extraction signal, a valid detection signal, a first invalid detection signal, and a second invalid detection signal are generated (S406).

  In the valid detection signal, the signal section corresponding to the invalid extraction signal having the signal level of A + or A− in the third detection signal is recognized as indicating a virtual image of the light absorbers Pc1, Pc2, Pd1, and Pd2. The Therefore, the signal level of these signal sections is set to a reference level (for example, A3a = 0). Note that the signal section corresponding to the invalid extraction signal having a signal level of A0 is recognized as indicating a real image of the light absorber Pa. Therefore, the signal level A3a is not changed.

  In the first invalidity detection signal, the signal section corresponding to the invalid extraction signal whose signal level is A0 or A− in the third detection signal is set to the reference level (for example, signal level A3c = 0). The signal section corresponding to the invalid extraction signal with the signal level of A + is a virtual image of the light absorbers Pc1 and Pc2 located in a position shifted in the Z direction from directly below the ultrasonic probe 20 toward the first light irradiation unit 201A. Certified to show. Therefore, the signal level A3c is not changed.

  In the second invalidity detection signal, the signal section corresponding to the invalid extraction signal whose signal level is A + or A0 in the third detection signal is set to the reference level (for example, signal level A3d = 0). Note that the signal section corresponding to the invalid extraction signal with the signal level of A + is a virtual image of the light absorbers Pd1 and Pd2 at a position shifted in the Z direction from directly below the ultrasonic probe 20 toward the second light irradiation unit 201B. Certified to show. Therefore, the signal level A3d is not changed.

  Then, a tomographic image is generated based on the valid detection signal (S407), a first shifted tomographic image is generated based on the first invalid detection signal (S408), and a second shifted tomographic image is generated based on the second invalid detection signal. Is generated (S409). Note that the first misaligned tomogram is a virtual image of the light absorbers Pc1 and Pc2 located at positions displaced in the Z direction from directly below the ultrasonic probe 20 toward the first light irradiation unit 201A. Further, the second shifted tomographic image shows virtual images of the light absorbers Pd1 and Pd2 located at positions shifted in the Z direction from directly below the ultrasonic probe 20 toward the second light irradiation unit 201B.

  Next, the tomographic image generated per unit time, the first misaligned tomographic image, and the second misaligned tomographic image are each subjected to an averaging process, and the tomographic image after the averaging process, the first misaligned tomographic image, A photoacoustic image I is formed from the two shifted tomographic images (S410). Then, the imaging process of the photoacoustic image I ends, and the photoacoustic image I is displayed on the LCD 401.

  FIG. 20 is an example of a display screen of the photoacoustic image I displayed on the LCD 401 in the fourth embodiment. In FIG. 20, the change in display color according to the position of the virtual image shifted in the Z direction from directly below the ultrasonic probe 20 is expressed by the type of hatched lines and the pitch thereof. Further, in FIG. 20, for the sake of convenience, the change in display color is expressed by changing the type of hatched line and its pitch stepwise. The change in the display color may be changed in stages, but it is preferable to change the display color in an inclined manner.

  In this photoacoustic image I, the tomographic image after the averaging process, the first shifted tomographic image, and the second shifted tomographic image are displayed in an overlapping manner. In addition, the tomographic image, the first shifted tomographic image, and the second shifted tomographic image are displayed in different display colors. For example, the tomographic image is displayed in gray scale. Further, the first shifted tomographic image is displayed in yellow, and the second shifted tomographic image is displayed in red. In the first shift tomogram, the shift in the Z direction from directly below the ultrasonic probe 20 toward the first light irradiation unit 201A is larger in the light absorber Pc2 than in the light absorber Pc1. For this reason, the light absorber Pc2 is displayed in a display color having a stronger yellow hue than the light absorber Pc1. Further, in the second shift tomogram, the shift in the Z direction from directly below the ultrasonic probe 20 toward the second light irradiation unit 201B is larger in the light absorber Pd2 than in the light absorber Pd1. Therefore, the light absorber Pd2 is displayed in a display color having a stronger red hue than the light absorber Pd1.

  In the photoacoustic image I of FIG. 20, the display colors of the tomographic image, the first shifted tomographic image, and the second shifted tomographic image are changed, but the present invention is not limited to this example. The tomographic image, the first shifted tomographic image, and the second shifted tomographic image may be displayed in different display formats.

  According to the above-described photoacoustic wave imaging process, in the photoacoustic image I, the tomographic image, the first shifted tomographic image, and the second shifted tomographic image after the averaging process are displayed in different display formats (particularly, display colors). Is displayed. Therefore, the light absorber P displayed in the photoacoustic image I is directly below the ultrasonic probe 20, or is located at a position shifted from the bottom of the ultrasonic probe 20 toward the first light irradiation unit 201A, or It is possible to visually recognize whether or not the position is shifted from the position immediately below the ultrasonic probe 20 toward the second light irradiation unit 201B. In other words, a more accurate three-dimensional position of the light absorber P can be simply displayed on the photoacoustic image I.

  Further, as in the above-described photoacoustic wave imaging processing, if the hue of the display color is increased in accordance with the amount of deviation in the Z direction, light indicating a cross-sectional image in the XY plane region immediately below the ultrasonic probe 20. From the display of the acoustic image I, the inclination of the light absorber P with respect to the XY plane region can also be visually recognized. FIG. 21 is a schematic view of the puncture needle N inserted into the subject 150 as seen from the Y direction. In FIG. 21, the alternate long and short dash line indicates the XY plane region immediately below the ultrasonic probe 20.

  FIG. 22 is a photoacoustic image I of the puncture needle N. According to this photoacoustic image I, the tip of the puncture needle N inserted into the subject 150 is shifted from the position immediately below the ultrasonic probe 20 to the second light irradiation unit 201B side. It can be seen that the X-Y plane region is inclined from the first light irradiation unit 201A side to the second light irradiation unit 201B side.

<Fifth Embodiment>
Next, a fifth embodiment will be described. As described above (see FIG. 5), the virtual image is shifted in the X direction in the tomographic image. Therefore, in the fifth embodiment, the correction information for correcting the position of the virtual image in the X direction is used to correct the position information of the shifted tomographic image in the X direction according to the signal level | A1-A2 | of the difference signal. . The rest is the same as in the third embodiment. Below, a different structure from 1st-4th embodiment is demonstrated. Moreover, the same code | symbol is attached | subjected to the component similar to 1st-4th embodiment, and the description is abbreviate | omitted.

  FIG. 23 is a diagram illustrating a positional relationship between the light absorber P located at a position shifted in the Z direction from directly below the ultrasonic probe 20 and its virtual image Pf. In FIG. 23, the alternate long and short dash line indicates the XY plane region immediately below the ultrasonic probe 20. L1 is the actual depth of the light absorber P in the X direction, and is the shortest distance between the surface of the subject 150 and the light absorber P. L2 (L2> L1) is the detection distance of the light absorber P, and is the shortest distance between the ultrasonic probe 20 and the light absorber P. Furthermore, the detection distance L2 is the same distance as the depth of the virtual image of the light absorber P in the tomographic image.

  In the positional relationship as shown in FIG. 23, the signal level | A1-A2 | of the differential signal increases as the light absorber P moves away from directly below the ultrasonic probe 20. Therefore, although it can be seen that the light absorber P is displaced in the Z direction from directly below the ultrasonic probe 20 by the signal level | A1-A2 |, the light absorber P is detected by the detection distance of the light absorber P in the shifted tomographic image. It appears at a depth position in the X direction corresponding to L2 and appears at a position shifted from the actual depth position L1.

  FIG. 24 is a graph illustrating an example of correction information of positional information in the X direction of a shifted tomographic image. This correction information is created in advance based on, for example, experimental results, and stored in a non-transitory storage medium (not shown). As shown in FIG. 24, in the correction information, the ratio (L1 / L2) of the deviation of the depth of the light absorber P that appears in the shifted tomographic image corresponds to the signal level | A1-A2 | of the difference signal. It is associated with the P detection distance L2.

  Accordingly, when generating a shifted tomogram based on the invalid detection signal (see S308 in FIG. 14), the signal level | A1-A2 of the difference signal is used for each signal section of the invalid detection signal using the correction information in FIG. If the ratio of the shift in depth (L1 / L2) corresponding to the position L2 in the X direction of each region (for example, the light absorber P) of the shifted tomographic image is obtained according to |, the actual depth position L1 is obtained. be able to. Note that position information in the X direction of each region of the shifted tomographic image can be obtained from each peak of the invalid detection signal. For example, the depth of the light absorber P can be obtained from the peak of the invalid detection signal corresponding to the light absorber P.

  Then, based on the information on the actual depth position L1 obtained for each signal section of the invalid detection signal, the position information in the X direction of each region of the shifted tomographic image corresponds to the signal level | A1-A2 | of the difference signal. Can be corrected. Therefore, an accurate photoacoustic image of position information can be acquired even for a virtual image.

  Note that the above configuration is applicable not only to the configuration of the third embodiment (see FIG. 16) but also to the configuration of the fourth embodiment (see FIG. 20).

  The embodiment of the present invention has been described above. Note that the above-described embodiment is an exemplification, and various modifications can be made to each component and combination of processes, and it will be understood by those skilled in the art that they are within the scope of the present invention.

  For example, in the above-described embodiment, the light sources 103A and 103B are LED light sources, but the present invention is not limited to this example. The light sources 103A and 103B only need to include a light emitting unit that can emit pulsed light, and more preferably a light emitting unit that can emit more pulsed light in a short period of time. For example, the light sources 103A and 103B may be light sources including semiconductor laser elements (semiconductor laser element light sources) or light sources including organic light emitting diode elements (organic light emitting diode element light sources). Alternatively, the light sources 103A and 103B may be light sources including at least one of a light emitting element among an LED element, a semiconductor laser element, and an organic light emitting diode element. In this way, the light sources 103A and 103B can be downsized. Furthermore, the subject 150 can be irradiated with pulsed light having a high emission frequency with a simple configuration. Therefore, since more tomographic images can be formed per unit time, a clearer and higher-definition photoacoustic image can be acquired.

DESCRIPTION OF SYMBOLS 100 Photoacoustic imaging apparatus 150 Subject 20 Ultrasonic probe 101 Drive power supply part 102 Light source drive part 102A, 102B Light source drive circuit 201A 1st light irradiation part 201B 2nd light irradiation part 103 Light source part 103A, 103B Light source 202 Acoustoelectric conversion Unit 202A ultrasonic vibration element 30 image generation unit 301 reception circuit 302 A / D converter 303 reception memory 304 data processing unit 305 photoacoustic image reconstruction unit 306 detection / logarithmic converter 307 photoacoustic image construction unit 308 ultrasonic image reconstruction unit 309 Detection / logarithmic converter 310 Ultrasound image construction unit 311 Image composition unit 312 Control unit 313 Transmission control circuit 314 Operation unit 40 Image display unit 401 LCD
402 Input detector P Light absorber I Photoacoustic image

Claims (9)

A light source drive control unit that performs light drive control of the light source including a first light source and a second light source provided opposite to each other with a detection unit that outputs a detection signal of a photoacoustic wave generated by a light absorber in the subject interposed therebetween When,
A tomographic image that generates a tomographic image of the subject based on a detection signal of the photoacoustic wave that is generated each time pulse light irradiated from the light source to the subject is absorbed by a light absorber in the subject. A generator,
An image forming unit that forms a photoacoustic image to be displayed on a display unit based on the tomographic image;
With
The tomographic image generation unit includes a first signal intensity of a first detection signal output from the detection unit when the pulsed light is emitted from the first light source to the subject, and the pulsed light is the second light. When the subject is irradiated from a light source, a difference signal with the second signal intensity of the second detection signal output from the detection unit is generated, and the difference signal intensity of the difference signal is within a predetermined numerical range. A photoacoustic imaging apparatus that generates the tomographic image based on a detection signal component of the detection signal corresponding to an effective difference signal component.   2. The tomographic image generation unit generates the tomographic image based on a detection signal component corresponding to the effective difference signal component of an addition combined signal obtained by adding and combining the first detection signal and the second detection signal. 2. The photoacoustic imaging apparatus described in 1.   The tomographic image generation unit outputs the effective difference signal component of the third detection signal output from the detection unit when the subject is irradiated with the pulsed light from the first light source and the second light source. The photoacoustic imaging apparatus according to claim 1, wherein the tomographic image is generated based on a corresponding detection signal component. The tomographic image generation unit generates the shifted tomographic image based on an invalid detection signal component of the detection signal corresponding to an invalid differential signal component other than the effective differential signal component of the difference signal of the difference signal,
The said image formation part forms the said photoacoustic image which displays the said shift | offset | difference tomogram in the display format different from the said tomogram based on the said tomogram and the said shift | offset | difference tomogram. 2. The photoacoustic imaging apparatus described in 1. The misaligned tomogram is obtained by subtracting the second signal intensity from the first signal intensity and the difference signal intensity of the difference signal that is greater than an upper limit threshold of the numerical range. Based on a first shifted tomogram generated based on one invalid detection signal component and a second invalid detection signal component of the detection signal corresponding to a difference signal component whose difference signal intensity is smaller than a lower limit threshold of the numerical range. A second tomographic image generated by
The image forming unit displays the photoacoustic image displaying the tomographic image, the first shifted tomographic image, and the second shifted tomographic image in different display formats, the tomographic image, the first shifted tomographic image, and The photoacoustic imaging apparatus according to claim 1, wherein the photoacoustic imaging apparatus is formed based on the second shifted tomographic image. A memory for storing correction information in which position information in the depth direction of the shifted tomographic image and a displacement ratio of the position information are associated with each difference signal intensity of the difference signal;
The photoacoustic imaging apparatus according to claim 4 or 5, wherein the tomographic image generation unit corrects position information in the depth direction of the shifted tomographic image according to the difference signal intensity based on the correction information. .   The photoacoustic imaging apparatus according to claim 1, wherein each of the first light source and the second light source is a light emitting diode element light source.   The photoacoustic imaging apparatus according to claim 1, wherein each of the first light source and the second light source is a semiconductor laser element light source.   The photoacoustic imaging apparatus according to claim 1, wherein each of the first light source and the second light source is an organic light emitting diode element light source.

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