JP2018143764A - Image generation device, image generation method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image generation apparatus capable of suppressing artifacts. The present invention is based on a plurality of received signals corresponding to a plurality of times of light irradiation obtained by receiving photoacoustic waves generated from a subject by a plurality of times of light irradiation on the subject. An image generation device for generating image data, wherein a signal processing means for performing signal processing including time differentiation processing and inversion processing for inverting the sign of a signal level for each of a plurality of received signals, and signal processing are performed. Image data generating means for generating a plurality of image data based on a plurality of received signals, weighting processing means for performing a weighting process for making negative weights of the plurality of image data larger than positive weights, and weighting Synthesizing means for generating first image data by synthesizing a plurality of processed image data. [Selection] Figure 9

Description

  The present invention relates to an image generation apparatus that generates image data derived from photoacoustic waves generated by light irradiation.

  A photoacoustic apparatus is known as an apparatus that generates image data based on a reception signal obtained by receiving an acoustic wave. A photoacoustic device irradiates a subject with pulsed light generated from a light source, and absorbs the energy of pulsed light that has propagated and diffused within the subject (typically ultrasonic waves generated from the subject tissue). , Also called a photoacoustic wave). Then, the photoacoustic apparatus images subject information based on the received signal.

  Non-Patent Document 1 discloses Universal Back-Projection (UBP), which is one of back projection methods, as a method for imaging an initial sound pressure distribution from a photoacoustic wave reception signal.

“Universal back-projection algorithm for photocou” “stick computed tomography”, Mingua Xu and Lihong V. Wang, PHYSICAL REVIEW E 71,016706

  By the way, when the image data is generated by back projecting the reception signal of the acoustic wave by the method described in Non-Patent Document 1, the reception signal is back projected other than the generation position of the acoustic wave and appears as an artifact in the image. This artifact causes a reduction in the image quality (contrast, etc.) of the reconstructed image.

  SUMMARY An advantage of some aspects of the invention is that it provides an image generation apparatus that can suppress artifacts.

  The present invention generates image data based on a plurality of received signals corresponding to a plurality of times of light irradiation obtained by receiving photoacoustic waves generated from the subject by a plurality of times of light irradiation on the subject. An image generating apparatus that performs signal processing including time differentiation processing and inversion processing that inverts the sign of a signal level for each of a plurality of reception signals, and a plurality of receptions that have undergone signal processing Based on the signal, image data generating means for generating a plurality of image data, weighting processing means for performing a weighting process for making negative weights of the plurality of image data larger than positive weights, and weighting processing are performed. And combining means for generating first image data by combining the plurality of image data.

  According to the image generation apparatus according to the present invention, artifacts can be suppressed.

The figure for demonstrating the time differentiation process and positive / negative inversion process by UBP The figure for demonstrating the back projection process by UBP The figure which shows the fluctuation | variation of the image value obtained by UBP The figure which shows the image obtained by the process which concerns on a comparative example and this invention The block diagram which shows the photoacoustic apparatus which concerns on 1st Embodiment. The schematic diagram which shows the probe which concerns on 1st Embodiment 1 is a block diagram showing a configuration of a computer and its peripherals according to a first embodiment 1 is a flowchart of an image generation method according to the first embodiment. Flowchart of a process for generating photoacoustic image data according to the first embodiment Graph showing the relationship between weight and image data contrast The figure which shows the fluctuation | variation of the image value for every light irradiation which concerns on 3rd Embodiment. The figure which shows the display screen of the viewer which concerns on 4th Embodiment

  Embodiments of the present invention will be described below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the following description.

  The present invention relates to generation of image data representing a two-dimensional or three-dimensional spatial distribution derived from a photoacoustic wave generated by light irradiation. The photoacoustic image data includes at least one subject such as a sound pressure (initial sound pressure) generated by a photoacoustic wave, a light absorption energy density, a light absorption coefficient, and a concentration of a substance constituting the subject (such as oxygen saturation). It is image data representing the spatial distribution of information.

  By the way, a living body, which is a main subject of photoacoustic imaging, has a characteristic of scattering and absorbing light. For this reason, the light intensity exponentially attenuates as the light travels deeper into the living body. As a result, typically, a photoacoustic wave having a large amplitude is generated in the vicinity of the subject surface, and a photoacoustic wave having a small amplitude tends to be generated in the deep part of the subject. In particular, a photoacoustic wave having a large amplitude is likely to be generated from a blood vessel existing near the surface of the subject.

  In a reconstruction method called UBP (Universal Back-Projection) described in Non-Patent Document 1, a received signal is back-projected onto an arc centered on a transducer. At this time, a received signal of a photoacoustic wave having a large amplitude near the surface of the subject is back-projected to the subject deep portion, resulting in an artifact in the subject deep portion. For this reason, when imaging a living tissue existing in the deep part of the subject, the image quality (contrast, etc.) may be reduced due to artifacts caused by photoacoustic waves generated from the subject surface.

  The present invention is an invention that can suppress a deterioration in image quality of a photoacoustic image due to an artifact. Hereinafter, processing according to the present invention will be described.

  It is known that a photoacoustic wave reception signal generally has a waveform called N-Shape as shown in FIG. In UBP, time differentiation processing is performed on the N-Shape signal shown in FIG. 1A to generate a time differentiation signal shown in FIG. Subsequently, a positive / negative inversion process for inverting the positive / negative of the signal level of the time differential signal is performed to generate a positive / negative inversion signal shown in FIG. A signal (also referred to as a projection signal) generated by performing time differentiation processing and positive / negative inversion processing on the N-Shape signal has a negative value as indicated by arrows A and C in FIG. Then, a portion having a positive value as shown by an arrow B in FIG.

  FIG. 2 shows an example in which UBP is applied when photoacoustic waves generated from the target 10, which is a microspherical light absorber inside the subject, are received by the transducer 21 and the transducer 22. When the target 10 is irradiated with light, a photoacoustic wave is generated, and the photoacoustic wave is sampled as an N-Shape signal by the transducer 21 and the transducer 22. FIG. 2A is a diagram showing an N-Shape-shaped received signal sampled by the transducer 21 superimposed on the target 10. For convenience, only the reception signal output from the transducer 21 is shown, but the reception signal is also output from the transducer 22 in the same manner.

  FIG. 2B is a diagram in which a projection signal obtained by performing time differentiation processing and positive / negative inversion processing on the N-Shape-shaped reception signal shown in FIG.

  FIG. 2C shows a state in which the projection signal obtained using the transducer 21 is back-projected by UBP. In UBP, a projection signal is projected on an arc centered on the transducer 21. In this case, the projection signal is back-projected in the range of the directivity angle (for example, 60 °) of the transducer 21. As a result, the image is as if the target 10 exists over the regions 31, 32, and 33. Here, the regions 31 and 33 are regions having negative values, and the region 32 is a region having positive values. In FIG. 2C, the areas 31 and 33 having negative values are filled with gray.

  FIG. 2D shows a case where the projection signal obtained using the transducer 22 is backprojected by UBP. As a result, the image is as if the target 10 exists over the areas 41, 42, and 43. Here, the regions 41 and 43 are regions having negative values, and the region 42 is a region having positive values. In FIG. 2D, the areas 41 and 43 having negative values are filled with gray.

  FIG. 2E shows a diagram in the case where the projection signals corresponding to the plurality of transducers 21 and 22 are backprojected by UBP. Photoacoustic image data is generated by synthesizing a plurality of projection signals back-projected in this way.

  As shown in FIG. 2E, at the position 51 inside the target 10, the positive value region 32 of the projection signal corresponding to the transducer 21 and the positive value region 42 of the projection signal corresponding to the transducer 22 overlap. . That is, in a region where the target 10 is typically present (also referred to as a target region), positive value regions predominately overlap each other. Therefore, in the area of the target 10, image data for each light irradiation typically tends to be a positive value.

  On the other hand, at the position 52 outside the target 10, the positive value region 32 of the projection signal corresponding to the transducer 21 and the negative value region 43 of the projection signal corresponding to the transducer 22 overlap. Further, at a position 53 outside the target 10, the negative value region 31 of the projection signal corresponding to the transducer 21 and the positive value region 41 of the projection signal corresponding to the transducer 22 overlap. Thus, in the area other than the target 10, the positive value area and the negative value area tend to overlap in a complicated manner. That is, in the area other than the target 10, the image data tends to be a positive value or a negative value for each light irradiation. A possible reason for this tendency is that the relative position between the transducer 22 and the target 10 changes with each light irradiation.

  Next, fluctuations in image data values (image values) for each light irradiation when the light irradiation is performed by changing the combination of the photoacoustic wave receiving positions for each light irradiation will be described. FIG. 3A shows the fluctuation of the image data value (image value) when the area of the target 10 is reconstructed by the UBP described in Non-Patent Document 1. The horizontal axis indicates the light irradiation number, and the vertical axis indicates the image value. On the other hand, FIG. 3B shows the fluctuation of the image data value (image value) when the area other than the target 10 is reconstructed by the UBP described in Non-Patent Document 1. The horizontal axis indicates the light irradiation number, and the vertical axis indicates the image value.

  According to FIG. 3A, it can be seen that the image value of the region of the target 10 is always a positive value, although there is a variation for each light irradiation. On the other hand, according to FIG.3 (b), it turns out that the image value of area | regions other than the target 10 becomes a positive value and a negative value for every light irradiation.

  Here, when image data is generated by combining image data corresponding to all the light irradiations, a positive value is combined in the region of the target 10, so that the final image value becomes large. On the other hand, in the area other than the target 10, the positive value and the negative value of the image data cancel each other, and the final image value becomes smaller than the area of the target 10. As a result, the presence of the target 10 can be visually recognized on the image based on the photoacoustic image data.

  However, in an area other than the target 10, the image value does not become 0 despite the absence of the target, and the final image value may be a positive value. In this case, artifacts are generated at positions other than the target 10 and the visibility of the target is reduced.

  Therefore, in order to solve the above-described problem, the present inventor typically has a positive image data for each light irradiation in the target area, and a positive value for each light irradiation in the area other than the target. Inspired by the fact that it tends to be one of negative values. That is, the inventor has conceived a process of combining a plurality of pieces of image data with a negative weight greater than a positive weight. The idea is that, according to this process, the final image value of the area other than the target can be made smaller, and artifacts can be suppressed. Details of the processing according to the present invention will be described later in the first embodiment.

  Here, the effect when the process according to the present invention is applied in the simulation will be described. FIG. 4A shows an object model 1000 used in the simulation. As the object model 1000, a model in which a blood vessel 1010 exists near the surface and a blood vessel 1011 of 0.2 [mm] running in the Y-axis direction exists at a depth of 20 [mm] from the surface was created. . Then, the received signal when the receiving unit provided on the lower side of the subject model 1000 receives photoacoustic waves generated from the blood vessels 1010 and 1011 in the subject model 1000 when the light is irradiated a plurality of times is simulated. Created by. In addition, the received signal was created by changing the position of the photoacoustic wave receiving unit for each light irradiation. Subsequently, reconstruction processing was performed using the received signal obtained by the simulation, and image data corresponding to each of a plurality of times of light irradiation was created.

  FIG. 4B is an image according to a comparative example obtained by synthesizing image data for each light irradiation obtained by reconstruction with UBP described in Non-Patent Document 1. On the other hand, FIG. 4C is obtained by performing weighting processing for making the negative weight of image data for each light irradiation obtained by UBP larger than the positive weight and combining the weighted image data. It is the image which concerns on this invention. In both FIG. 4B and FIG. 4C, the image data of the projection area 1020 (including the blood vessel 1011) having a thickness of 2 [mm] is projected in the Z-axis direction to the maximum value (MIP: Maximum Intensity Projection). It is the obtained MIP image. Further, in both FIG. 4B and FIG. 4C, the brightness at the position where the image value is 0 or less is displayed as 0. Further, the image data of the projection area also includes an artifact based on a reception signal derived from the blood vessel 1010 near the surface.

  4 that the visibility of the blood vessel 1011 in the image of FIG. 4C according to the present invention is higher than that of the blood vessel 1011 in the image of FIG. 4B according to the comparative example. This is considered to be because the positive value component causing the artifact is canceled by relatively increasing the weight of the negative value component by the processing according to the present invention. As a result, according to the processing according to the present invention, artifacts can be suppressed, and the visibility of blood vessels (targets) in the image is improved.

[First Embodiment]
In the first embodiment, an example in which photoacoustic image data is generated by a photoacoustic apparatus will be described. Hereinafter, the configuration and information processing method of the photoacoustic apparatus of the present embodiment will be described.

  The configuration of the photoacoustic apparatus according to the present embodiment will be described with reference to FIG. FIG. 3 is a schematic block diagram of the entire photoacoustic apparatus. The photoacoustic apparatus according to the present embodiment includes a probe 180 including a light irradiation unit 110 and a reception unit 120, a drive unit 130, a signal collection unit 140, a computer 150, a display unit 160, and an input unit 170.

  FIG. 5 is a schematic diagram of the probe 180 according to the present embodiment. The measurement object is the subject 100. The drive unit 130 drives the light irradiation unit 110 and the reception unit 120 to perform mechanical scanning. The light irradiation unit 110 irradiates the subject 100 with light, and an acoustic wave is generated in the subject 100. An acoustic wave generated by the photoacoustic effect due to light is also called a photoacoustic wave. The receiving unit 120 outputs an electric signal (photoacoustic signal) as an analog signal by receiving a photoacoustic wave.

  The signal collection unit 140 converts the analog signal output from the reception unit 120 into a digital signal and outputs the digital signal to the computer 150. The computer 150 stores the digital signal output from the signal collection unit 140 as signal data derived from ultrasonic waves or photoacoustic waves.

  The computer 150 generates photoacoustic image data representing a two-dimensional or three-dimensional spatial distribution of information about the subject 100 (subject information) by performing signal processing on the stored digital signal. Further, the computer 150 causes the display unit 160 to display an image based on the obtained image data. A doctor as a user can make a diagnosis by confirming the image displayed on the display unit 160. The display image is stored in a memory in the computer 150 or a memory such as a data management system connected to the modality via a network based on a storage instruction from the user or the computer 150.

  The computer 150 also performs drive control of the configuration included in the photoacoustic apparatus. The display unit 160 may display a GUI or the like in addition to the image generated by the computer 150. The input unit 170 is configured so that a user can input information. The user can use the input unit 170 to perform operations such as measurement start and end, and instructions for saving a created image.

  Hereafter, the detail of each structure of the photoacoustic apparatus which concerns on this embodiment is demonstrated.

(Light irradiation unit 110)
The light irradiation unit 110 includes a light source 111 that emits light and an optical system 112 that guides the light emitted from the light source 111 to the subject 100. The light includes pulsed light such as a so-called rectangular wave and triangular wave.

  The pulse width of light emitted from the light source 111 may be 1 ns or more and 100 ns or less. Further, the wavelength of light may be in the range of about 400 nm to 1600 nm. When a blood vessel is imaged with high resolution, a wavelength (400 nm or more and 700 nm or less) having a large absorption in the blood vessel may be used. When imaging a deep part of a living body, light having a wavelength (700 nm or more and 1100 nm or less) that is typically less absorbed in the background tissue (water, fat, etc.) of the living body may be used.

  As the light source 111, a laser or a light emitting diode can be used. Moreover, when measuring using the light of several wavelengths, the light source which can change a wavelength may be sufficient. When irradiating a subject with a plurality of wavelengths, it is also possible to prepare a plurality of light sources that generate light of different wavelengths and alternately irradiate from each light source. When multiple light sources are used, they are collectively expressed as light sources. As the laser, various lasers such as a solid laser, a gas laser, a dye laser, and a semiconductor laser can be used. For example, a pulsed laser such as an Nd: YAG laser or an alexandrite laser may be used as the light source. Further, a Ti: sa laser or an OPO (Optical Parametric Oscillators) laser using Nd: YAG laser light as excitation light may be used as a light source. Further, a flash lamp or a light emitting diode may be used as the light source 111. Further, a microwave source may be used as the light source 111.

  For the optical system 112, optical elements such as a lens, a mirror, a prism, an optical fiber, a diffusion plate, and a shutter can be used.

  The maximum permissible exposure (MPE) is determined by the safety standard shown below for the intensity of light allowed to irradiate the living tissue. (IEC 60825-1: Safety of laser products, JIS C 6802: Laser product safety standards, FDA: 21 CFR Part 1040.10, ANSI Z136.1: Laser Safety Standards, etc.). The maximum allowable exposure amount defines the intensity of light that can be irradiated per unit area. For this reason, a large amount of light can be guided to the subject E by collectively irradiating the surface of the subject E over a wide area, so that a photoacoustic wave can be received with a high S / N ratio. In the case where a biological tissue such as a breast is used as the subject 100, the emission unit of the optical system 112 may be configured with a diffusion plate or the like for diffusing light in order to irradiate with a wide beam diameter of high energy light. On the other hand, in the photoacoustic microscope, in order to increase the resolution, the light emitting portion of the optical system 112 may be configured with a lens or the like, and the beam may be focused and irradiated.

  Note that the light irradiation unit 110 may directly irradiate the subject 100 with light from the light source 111 without including the optical system 112.

(Receiver 120)
The receiving unit 120 includes a transducer 121 that outputs an electrical signal by receiving an acoustic wave, and a support body 122 that supports the transducer 121. The transducer 121 may be a transmission unit that transmits an acoustic wave. The transducer as the reception means and the transducer as the transmission means may be a single (common) transducer or may have different configurations.

  As a member constituting the transducer 121, a piezoelectric ceramic material typified by PZT (lead zirconate titanate), a polymer piezoelectric film material typified by PVDF (polyvinylidene fluoride), or the like can be used. Further, an element other than the piezoelectric element may be used. For example, a capacitive transducer (CMUT: Capacitive Micro-machined Ultrasonic Transducers), a transducer using a Fabry-Perot interferometer, or the like can be used. Any transducer may be adopted as long as it can output an electrical signal by receiving an acoustic wave. The signal obtained by the transducer is a time-resolved signal. That is, the amplitude of the signal obtained by the transducer represents a value based on the sound pressure received by the transducer at each time (for example, a value proportional to the sound pressure).

  The frequency component constituting the photoacoustic wave is typically 100 KHz to 100 MHz, and a transducer capable of detecting these frequencies can be employed as the transducer 121.

  The support body 122 may be made of a metal material having high mechanical strength. In order to make a large amount of irradiation light incident on the subject, the surface of the support 122 on the subject 100 side may be subjected to a mirror surface or light scattering process. In the present embodiment, the support body 122 has a hemispherical shell shape, and is configured to support a plurality of transducers 121 on the hemispherical shell. In this case, the directivity axes of the transducers 121 arranged on the support 122 are gathered around the center of curvature of the hemisphere. Then, when imaged using signals output from the plurality of transducers 121, the image quality near the center of curvature is improved. The support 122 may have any configuration as long as it can support the transducer 121. The support 122 may have a plurality of transducers arranged side by side in a plane or curved surface called a 1D array, 1.5D array, 1.75D array, or 2D array. The plurality of transducers 121 correspond to a plurality of receiving means.

  Further, the support body 122 may function as a container for storing the acoustic matching material 210. That is, the support 122 may be a container for arranging the acoustic matching material 210 between the transducer 121 and the subject 100.

  The receiving unit 120 may include an amplifier that amplifies the time-series analog signal output from the transducer 121. The receiving unit 120 may include an A / D converter that converts a time-series analog signal output from the transducer 121 into a time-series digital signal. That is, the receiving unit 120 may include a signal collecting unit 140 described later.

  In order to be able to detect acoustic waves at various angles, the transducer 121 may be ideally arranged so as to surround the subject 100 from the entire periphery. However, when the subject 100 is large and the transducer cannot be disposed so as to surround the entire periphery, the transducer may be disposed on the hemispherical support 122 so as to approximate the entire periphery.

  Note that the arrangement and number of transducers and the shape of the support may be optimized according to the subject, and any receiving unit 120 can be employed in the present invention.

  The space between the receiving unit 120 and the subject 100 is filled with a medium through which photoacoustic waves can propagate. For this medium, a material that can propagate an acoustic wave, has matching acoustic characteristics at the interface with the subject 100 and the transducer 121, and has a photoacoustic wave transmittance as high as possible is used. For example, water, ultrasonic gel, or the like can be used as this medium.

  6A shows a side view of the probe 180, and FIG. 6B shows a top view of the probe 180 (viewed from above in FIG. 6A). A probe 180 according to this embodiment shown in FIG. 6 includes a receiving unit 120 in which a plurality of transducers 121 are three-dimensionally arranged on a hemispherical support body 122 having an opening. In the probe 180 shown in FIG. 6, the light emitting part of the optical system 112 is arranged at the bottom of the support 122.

  In the present embodiment, the shape of the subject 100 is held by contacting the holding unit 200 as shown in FIG. In the present embodiment, when the subject 100 is a breast, an embodiment is provided in which an opening for inserting the breast is provided in a bed that supports a subject in a prone position, and a breast that is suspended vertically from the opening is measured. Assumed.

  The space between the receiving unit 120 and the holding unit 200 is filled with a medium (acoustic matching material 210) through which photoacoustic waves can propagate. For this medium, a material that can propagate a photoacoustic wave, has matching acoustic characteristics at the interface with the subject 100 and the transducer 121, and has a high photoacoustic wave transmittance as much as possible is adopted. For example, water, castor oil, ultrasonic gel, or the like can be used as this medium.

  A holding unit 200 as a holding unit is used to hold the shape of the subject 100 during measurement. By holding the subject 100 by the holding unit 200, the movement of the subject 100 can be suppressed and the position of the subject 100 can be held in the holding unit 200. A resin material such as polycarbonate, polyethylene, or polyethylene terephthalate can be used as the material of the holding unit 200.

  The holding unit 200 is preferably a material having a hardness capable of holding the subject 100. The holding unit 200 may be a material that transmits light used for measurement. The holding unit 200 may be made of a material having the same impedance as that of the subject 100. When the subject 100 has a curved surface such as a breast, the holding unit 200 molded into a concave shape may be used. In this case, the subject 100 can be inserted into the concave portion of the holding unit 200.

  The holding part 200 is attached to the attachment part 201. The attachment unit 201 may be configured such that a plurality of types of holding units 200 can be exchanged according to the size of the subject. For example, the attachment portion 201 may be configured to be exchangeable with a different holding portion such as a curvature radius or a curvature center.

  The holding unit 200 may be provided with a tag 202 in which information on the holding unit 200 is registered. For example, information such as the radius of curvature, the center of curvature, the speed of sound, and the identification ID of the holding unit 200 can be registered in the tag 202. Information registered in the tag 202 is read by the reading unit 203 and transferred to the computer 150. In order to easily read the tag 202 when the holding unit 200 is attached to the attachment unit 201, the reading unit 203 may be installed in the attachment unit 201. For example, the tag 202 is a barcode, and the reading unit 203 is a barcode reader.

(Driver 130)
The driving unit 130 is a part that changes the relative position between the subject 100 and the receiving unit 120. In the present embodiment, the drive unit 130 is a device that moves the support 122 in the XY directions, and is an electric XY stage equipped with a stepping motor. The driving unit 130 includes a motor such as a stepping motor that generates a driving force, a driving mechanism that transmits the driving force, and a position sensor that detects position information of the receiving unit 120. As the drive mechanism, a lead screw mechanism, a link mechanism, a gear mechanism, a hydraulic mechanism, or the like can be used. In addition, as the position sensor, a potentiometer using an encoder, a variable resistor, a linear scale, a magnetic sensor, an infrared sensor, an ultrasonic sensor, or the like can be used.

  The driving unit 130 is not limited to changing the relative position between the subject 100 and the receiving unit 120 in the XY direction (two-dimensional), and may be changed to one-dimensional or three-dimensional. The movement path may be scanned in a spiral or line & space plane, or may be tilted three-dimensionally along the body surface. Further, the probe 180 may be moved so as to keep the distance from the surface of the subject 100 constant. At this time, the driving unit 130 may measure the amount of movement of the probe by monitoring the number of rotations of the motor.

  The driving unit 130 may fix the receiving unit 120 and move the subject 100 as long as the relative position between the subject 100 and the receiving unit 120 can be changed. When the subject 100 is moved, a configuration in which the subject 100 is moved by moving a holding unit that holds the subject 100 may be considered. Further, both the subject 100 and the receiving unit 120 may be moved.

  The drive unit 130 may move the relative position continuously or may be moved by step-and-repeat. The drive unit 130 may be an electric stage that moves along a programmed trajectory, or may be a manual stage. That is, the photoacoustic apparatus may be a handheld type in which the user holds and operates the probe 180 without having the driving unit 130.

  In this embodiment, the drive unit 130 drives the light irradiation unit 110 and the reception unit 120 simultaneously to perform scanning. However, the drive unit 130 drives only the light irradiation unit 110 or only the reception unit 120. May be.

(Signal collection unit 140)
The signal collection unit 140 includes an amplifier that amplifies an electrical signal that is an analog signal output from the transducer 121 and an A / D converter that converts the analog signal output from the amplifier into a digital signal. The signal collection unit 140 may be configured by an FPGA (Field Programmable Gate Array) chip or the like. The digital signal output from the signal collection unit 140 is stored in the storage unit 152 in the computer 150. The signal collection unit 140 is also referred to as a data acquisition system (DAS). In this specification, an electric signal is a concept including both an analog signal and a digital signal. Note that a light detection sensor such as a photodiode may detect light emission from the light irradiation unit 110, and the signal collection unit 140 may start the above process in synchronization with the detection result. In addition, the signal collection unit 140 may start the process in synchronization with an instruction given using a freeze button or the like.

(Computer 150)
A computer 150 serving as a display control device includes a calculation unit 151, a storage unit 152, and a control unit 153. The function of each component will be described when the processing flow is described.

  The unit responsible for the calculation function as the calculation unit 151 can be configured by a processor such as a CPU or a GPU (Graphics Processing Unit), or an arithmetic circuit such as an FPGA (Field Programmable Gate Array) chip. These units are not only composed of a single processor and arithmetic circuit, but may be composed of a plurality of processors and arithmetic circuits. The computing unit 151 may process the received signal by receiving various parameters such as the subject sound speed and the configuration of the holding unit from the input unit 170.

  The storage unit 152 can be configured by a non-temporary storage medium such as a ROM (Read only memory), a magnetic disk, or a flash memory. Further, the storage unit 152 may be a volatile medium such as a RAM (Random Access Memory). Note that the storage medium storing the program is a non-temporary storage medium. Note that the storage unit 152 may be configured not only from one storage medium but also from a plurality of storage media.

  The storage unit 152 can store image data indicating a photoacoustic image generated by the calculation unit 151 by a method described later.

  The control unit 153 includes an arithmetic element such as a CPU. The control unit 153 controls the operation of each component of the photoacoustic apparatus. The control unit 153 may control each component of the photoacoustic apparatus in response to instruction signals from various operations such as measurement start from the input unit 170. In addition, the control unit 153 reads out the program code stored in the storage unit 152 and controls the operation of each component of the photoacoustic apparatus. For example, the control unit 153 may control the light emission timing of the light source 111 via a control line. When the optical system 112 includes a shutter, the control unit 153 may control opening and closing of the shutter via a control line.

  The computer 150 may be a specially designed workstation. Each configuration of the computer 150 may be configured by different hardware. Further, at least a part of the configuration of the computer 150 may be configured by a single hardware.

  FIG. 7 shows a specific configuration example of the computer 150 according to the present embodiment. A computer 150 according to this embodiment includes a CPU 154, a GPU 155, a RAM 156, a ROM 157, and an external storage device 158. In addition, a liquid crystal display 161 as a display unit 160, a mouse 171 and a keyboard 172 as input units 170 are connected to the computer 150.

  The computer 150 and the plurality of transducers 121 may be provided in a configuration housed in a common housing. However, a part of signal processing may be performed by a computer housed in the housing, and the remaining signal processing may be performed by a computer provided outside the housing. In this case, the computers provided inside and outside the housing can be collectively referred to as the computer according to the present embodiment. That is, the hardware constituting the computer may not be housed in a single housing.

(Display unit 160)
The display unit 160 is a display such as a liquid crystal display, an organic EL (Electro Luminescence) FED, a glasses-type display, or a head-mounted display. This is an apparatus for displaying an image based on volume data obtained by the computer 150, a numerical value at a specific position, and the like. The display unit 160 may display a GUI for operating an image or device based on the volume data. Note that the subject information can be displayed after image processing (such as adjustment of luminance values) is performed on the display unit 160 or the computer 150. The display unit 160 may be provided separately from the photoacoustic apparatus. The computer 150 can transmit the photoacoustic image data to the display unit 160 in a wired or wireless manner.

(Input unit 170)
As the input unit 170, an operation console that can be operated by a user and configured with a mouse, a keyboard, or the like can be employed. The display unit 160 may be configured with a touch panel, and the display unit 160 may be used as the input unit 170.

  The input unit 170 may be configured to be able to input information on a position or depth to be observed. As an input method, numerical values may be input, or input may be performed by operating a slider bar. Further, the image displayed on the display unit 160 may be updated according to the input information. Thereby, the user can set to an appropriate parameter while confirming the image generated by the parameter determined by his / her operation.

  Moreover, the user may operate the input unit 170 provided remotely from the photoacoustic apparatus, and information input using the input unit 170 may be transmitted to the photoacoustic apparatus via a network.

  In addition, each structure of a photoacoustic apparatus may be comprised as a respectively different apparatus, and may be comprised as one apparatus united. Moreover, you may comprise as one apparatus with which at least one part structure of the photoacoustic apparatus was united.

  Information transmitted and received between the components of the photoacoustic apparatus is exchanged by wire or wirelessly.

(Subject 100)
The subject 100 does not constitute a photoacoustic apparatus, but will be described below. The photoacoustic apparatus according to the present embodiment can be used for the purpose of diagnosing malignant tumors, vascular diseases, etc. of humans and animals, and monitoring the progress of chemical treatment. Therefore, the subject 100 is assumed to be a target site for diagnosis such as a living body, specifically breasts of human bodies or animals, each organ, blood vessel network, head, neck, abdomen, extremities including fingers and toes. The For example, if the human body is an object to be measured, oxyhemoglobin or deoxyhemoglobin, a blood vessel containing many of them, a new blood vessel formed in the vicinity of a tumor, or the like may be used as a light absorber. Further, a plaque of the carotid artery wall or the like may be a target of the light absorber. In addition, melanin, collagen, lipid, and the like contained in the skin or the like may be targeted for the light absorber. In addition, a dye such as methylene blue (MB) or indocyanine green (ICG), gold fine particles, or a substance introduced from the outside, which is accumulated or chemically modified, may be used as the light absorber. A phantom that simulates a living body may be used as the subject 100.

  Next, an image display method including information processing according to the present embodiment will be described with reference to FIG. Each step is executed by the computer 150 controlling the operation of the configuration of the photoacoustic apparatus.

(S100: Step of setting control parameters)
The user designates control parameters such as the irradiation condition (repetition frequency, wavelength, etc.) of the light irradiation unit 110 and the position of the probe 180 necessary for acquiring the subject information using the input unit 170. The computer 150 sets control parameters determined based on user instructions.

(S200: Step of moving the probe to the designated position)
The control unit 153 causes the drive unit 130 to move the probe 180 to a specified position based on the control parameter specified in step S100. When imaging at a plurality of positions is designated in step S100, the drive unit 130 first moves the probe 180 to the first designated position. Note that the driving unit 130 may move the probe 180 to a preprogrammed position when an instruction to start measurement is given. In the case of the handheld type, the user may hold the probe 180 and move it to a desired position.

(S300: Step of irradiating light)
The light irradiation unit 110 irradiates the subject 100 with light based on the control parameter specified in S100.

  Light generated from the light source 111 is irradiated to the subject 100 as pulsed light through the optical system 112. Then, the pulsed light is absorbed inside the subject 100, and a photoacoustic wave is generated by the photoacoustic effect. The light irradiation unit 110 transmits a synchronization signal to the signal collection unit 140 together with the transmission of the pulsed light.

(S400: Step of receiving photoacoustic wave)
When the signal collection unit 140 receives the synchronization signal transmitted from the light irradiation unit 110, the signal collection unit 140 starts a signal collection operation. That is, the signal collection unit 140 generates an amplified digital electric signal by amplifying and AD converting the analog electric signal derived from the acoustic wave output from the receiving unit 120 and outputs the amplified digital electric signal to the computer 150. The computer 150 stores the signal transmitted from the signal collection unit 140 in the storage unit 152. When imaging at a plurality of scanning positions is designated in step S100, the steps S200 to S400 are repeatedly executed at the designated scanning positions, and the generation of digital signals derived from irradiation with pulsed light and acoustic waves is repeated. The computer 150 may acquire and store the position information of the receiving unit 120 at the time of light emission based on the output from the position sensor of the driving unit 130 using light emission as a trigger.

(S500: Step of generating photoacoustic image data)
The computing unit 151 of the computer 150 serving as image data generating means generates photoacoustic image data based on the signal data stored in the storage unit 152 and stores it in the storage unit 152.

  Reconstruction algorithms for converting signal data into volume data as a spatial distribution include analytical reconstruction methods such as back projection in the time domain and back projection in the Fourier domain, and model-based methods (repetitive computation). Can be adopted. For example, as a back projection method in the time domain, Universal back-projection (UBP), Filtered back-projection (FBP), or delay-and-sum (Delay-and-Sum) can be cited.

  In addition, the calculation unit 151 obtains absorption coefficient distribution information by calculating a light fluence distribution inside the subject 100 of light irradiated on the subject 100 and dividing the initial sound pressure distribution by the light fluence distribution. May be. In this case, absorption coefficient distribution information may be acquired as photoacoustic image data. The computer 150 can calculate the spatial distribution of the light fluence inside the subject 100 by a method of numerically solving a transport equation and a diffusion equation indicating the behavior of light energy in a medium that absorbs and scatters light. As a numerical solution method, a finite element method, a difference method, a Monte Carlo method, or the like can be employed. For example, the computer 150 may calculate the spatial distribution of the light fluence inside the subject 100 by solving the light diffusion equation shown in Expression (1).

  Here, D is the diffusion coefficient, μa is the absorption coefficient, S is the incident intensity of the irradiated light, φ is the reaching fluence, r is the position, and t is the time.

  Moreover, the process of S300 and S400 may be performed using light of a plurality of wavelengths, and the calculation unit 151 may acquire absorption coefficient distribution information corresponding to each of the lights of a plurality of wavelengths. Then, the calculation unit 151 acquires, as photoacoustic image data, spatial distribution information of the concentration of the substance constituting the subject 100 as spectroscopic information based on the absorption coefficient distribution information corresponding to each of a plurality of wavelengths of light. May be. That is, the calculation unit 151 may acquire spectral information using signal data corresponding to light having a plurality of wavelengths.

(S600: Step of generating / displaying an image based on photoacoustic image data)
The computer 150 as display control means generates an image based on the photoacoustic image data obtained in S500 and causes the display unit 160 to display the image. The image value of the image data may be used as the brightness value of the display image as it is. Further, the luminance of the display image may be determined by applying a predetermined process to the image value of the image data. For example, a display image in which the image value is assigned to the luminance when the image value is positive and the luminance is 0 when the image value is negative may be generated.

  Next, the characteristic image generation method of the present invention in S500 will be described using the flowchart of the image generation method shown in FIG.

(S510: Step of performing time differential signal and inversion processing on received signal)
The computer 150 as signal processing means performs signal processing including time differentiation processing and inversion processing that inverts the sign of the signal level on the received signal stored in the storage unit 152. A reception signal subjected to these signal processings is also called a projection signal. In this step, these signal processes are executed for each received signal stored in the storage unit 152. As a result, a plurality of light irradiations and projection signals corresponding to the plurality of transducers 121 are generated.

  For example, the computer 150 performs time differentiation processing and inversion processing (adding a minus to the time differentiation signal) on the received signal p (r, t), as shown in Expression (2), and the projection signal b (r, t t) and the projection signal b (r, t) is stored in the storage unit 152.

  Here, r is a receiving position, t is an elapsed time from light irradiation, p (r, t) is a received signal indicating a sound pressure of an acoustic wave received at the receiving position r at an elapsed time t, and b (r, t ) Is a projection signal. In addition to time differentiation processing and inversion processing, other signal processing may be performed. For example, the other signal processing is at least one of frequency filtering (low pass, high pass, band pass, etc.), deconvolution, envelope detection, and wavelet filtering.

  Note that the reversal process may not be executed in this step. In this case, the effect of this embodiment is not impaired by substituting the negative component enhancement processing in S540 described later with the positive component enhancement processing.

(S520: Step of generating image data based on the received signal after the signal processing)
The computer 150 as image data generation means generates a plurality of photoacoustic image data based on a plurality of light irradiations generated in S510 and reception signals (projection signals) corresponding to the plurality of transducers 121, respectively. As long as a plurality of photoacoustic image data can be generated, the photoacoustic image data may be generated for each light irradiation, or one photoacoustic image data may be generated from a projection signal derived from a plurality of times of light irradiation. .

For example, the computer 150 generates image data indicating the spatial distribution of the initial sound pressure p ₀ for each light irradiation, based on the projection signal b (r _i , t) as shown in Expression (3). As a result, image data corresponding to each of a plurality of times of light irradiation is generated, and a plurality of image data can be acquired.

Here, r ₀ is a position vector indicating a position to be reconstructed (also referred to as a reconstructed position or a target position), p ₀ (r ₀ ) is the initial sound pressure at the position to be reconstructed, and c is the sound velocity of the propagation path. . Further, ΔΩ _i is a solid angle at which the i-th transducer 121 is viewed from the position to be reconstructed, and N is the number of transducers 121 used for reconstruction. Equation (3) indicates that the projection signal is subjected to phasing addition by applying a solid angle weight (back projection).

  In the present embodiment, as described above, image data can be generated by an analytical reconstruction method or a model-based reconstruction method. In particular, the present invention can be suitably applied when an analytical reconstruction method is employed. In the analytical reconstruction method, when an acoustic wave is received under the conditions of the limited view, the sound source cannot be accurately reproduced, and the region other than the target may be reconstructed with a negative value.

(S530: Step of performing negative component enhancement processing on a plurality of image data)
The computer 150 as the weighting means performs a negative component enhancement process (weighting process) that makes the weight for the negative values of the plurality of image data acquired in S520 larger than the weight for the positive values.

  Here, consider a case where four image data are generated in S520, and the image values of each image data at a position where there is a region other than the target are D1, -D2, D3, and -D4.

  For example, the computer 150 performs weighting processing by multiplying positive values D1 and D3 by a weight of 1, and negative values -D2 and -D4 by a weight greater than 1. Negative components may be emphasized. Note that D1 and D3 may be regarded as having been subjected to a weighting process of multiplying a weight of 1 by performing no process.

  In addition, the computer 150 performs weighting processing of multiplying positive values D1 and D3 by weights smaller than 1, and negative values -D2 and -D4 by weights greater than 1. Thus, the negative component may be emphasized.

  In addition, as long as the weights for the negative values of the plurality of image data are made larger than the weights for the positive values, any weighting process may be applied.

  The image data to which the weighting process in this step is applied may be image data obtained by one light irradiation, or based on data (signal data or image data) obtained by two or more light irradiations. It may be image data.

  The computer 150 may read information on the weight of at least one of a positive value and a negative value stored in the storage unit 152 in advance, and set the weight based on the information. Alternatively, the user may use the input unit 170 to instruct information regarding at least one of the positive value and the negative value, and the computer 150 may set the weight based on the information regarding the weight received from the input unit 170.

  The computer 150 may set a weight for each position of the image data. That is, the computer 150 may divide the image data into a plurality of areas and set the weights independently for each of the divided areas.

  The computer 150 may change the weight according to the image value of the image data. For example, the computer 150 may decrease the weight of the negative value as the magnitude (absolute value) of the negative value of the image data increases. Further, the computer 150 makes the weight when the negative value size (absolute value) of the image data is larger than the threshold value smaller than the weight when the negative value size (absolute value) of the image data is smaller than the threshold value. May be. By performing such weight control, the enhancement degree of the negative component can be adjusted. In particular, it is possible to prevent the target image value from being canceled by overemphasizing the negative component.

  The computer 150 may change the weight for each light irradiation or for each group of two or more light irradiations.

(S540: Step of synthesizing a plurality of image data subjected to negative component enhancement processing)
The computer 150 as the synthesis unit generates new image data (corresponding to the first image data) by synthesizing the plurality of pieces of image data on which the negative component enhancement processing acquired in S530 is performed, and the storage unit Store in 152. The computer 150 may synthesize a plurality of image data by simple addition or addition processing for averaging.

  While the image data in the target area has a dominant positive value, the image data in the area other than the target includes a negative value. Therefore, in the negative component enhancement processing in S530, the negative value of the image data in the area other than the target is It is emphasized by superiority. For this reason, in the region other than the target, the positive value of the image data that causes the artifact can be canceled with the emphasized negative value by the combining process in S540. On the other hand, in the target area, since the positive value is dominant in the image data, the influence of the negative component enhancement processing is limited. As described above, according to the image generation method according to the present embodiment, the image contrast between the target area and the other areas is increased.

  The image based on the image data obtained as a result of the negative component enhancement may be displayed alone or may be displayed side by side with the image based on the image data obtained without performing the negative component enhancement. Note that when displaying the images side by side, the display colors of the images may be different. In the case of displaying side by side, a label may be provided with characters or symbols, or the display window may have a different shape and size so that the presence or absence of negative component emphasis can be distinguished.

  Further, an image based on the image data obtained as a result of the negative component enhancement and an image based on the image data obtained without performing the negative component enhancement may be superimposed and displayed. At this time, the images may be displayed with different colors. That is, display colors may be distinguished by making the saturation of one image lower than the saturation of the other image. In addition, display colors may be distinguished by displaying a plurality of images with different hues. For example, one image may be displayed in gray scale (achromatic color) and the other image may be displayed in color (chromatic color). Further, an area having a difference between images may be displayed in color.

  Further, an image based on image data obtained as a result of negative component enhancement and an image based on image data obtained without performing negative component enhancement may be switched and displayed at the same display position.

  As long as it is possible to distinguish between an image based on image data obtained as a result of negative component enhancement and an image based on image data obtained without performing negative component enhancement, it is not limited to parallel, superimposition, and switching. It may be a display mode.

  Further, when the first image when the negative component enhancement is performed with the predetermined weight or the weight set based on the user's instruction is displayed, the new weight is based on the new instruction from the user. May be set. In this case, the display image may be updated from the first image to the second image to which the new weight is applied. Further, the first image and the second image may be displayed in parallel or superimposed.

  Note that images to which different weights are applied may be displayed in parallel, superimposed, or switched in order of weights (ascending or descending).

  In this embodiment, the example in which the signal level positive / negative inversion processing is performed after the time differentiation processing is performed on the photoacoustic wave reception signal has been described, but the inversion processing may not be performed. When the inversion process is not performed, instead of the negative component enhancement process, a positive component enhancement process (weighting process) for making the positive value weights of the plurality of image data larger than the negative value weights may be performed. Even when the positive component emphasis process is performed instead of the negative component emphasis process, the positive component can be emphasized by the same method as the method of emphasizing the negative component by the negative component emphasis process described above.

[Second Embodiment]
This embodiment is different from the first embodiment in that an optimum weight is determined based on image data obtained by applying a plurality of different weights. In the second embodiment, the same apparatus as the photoacoustic apparatus described in the first embodiment is used. The components already described are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 10 shows an example of contrast fluctuation of image data obtained by applying a plurality of different weights to the received signal created by the simulation using the model shown in FIG. The graph shown in FIG. 10 represents the contrast fluctuation between the blood vessel 1011 in the MIP image of the projection area 1020 shown in FIG. 4 and the surrounding area. Here, the contrast is defined as the difference between the average value of the image values of the blood vessel 1011 and the average value of the image values around the blood vessel 1011. As the weight, a positive value weight of the image data for each light irradiation is set to 1, and a negative value weight of the image data is changed. That is, the horizontal axis of the graph shown in FIG. 10 represents the weight for the negative value of the image data.

  As shown in FIG. 10, the contrast may have a maximum point when the weight is changed. This is because there are cases where the artifact suppression effect by the negative component enhancement processing is superior to the effect of canceling the target image value (positive value) and when it is not. Therefore, the computer 150 generates a plurality of image data by applying a plurality of different weights, and calculates the contrast of each image data. Then, the computer 150 may determine the weight applied to the image data having the maximum contrast as the optimum weight value. Further, the computer 150 may determine and display the image data having the maximum contrast among the plurality of image data as the optimum image data. Further, the computer 150 may determine the weight that optimizes the contrast, that is, the optimized image data, by solving the optimization problem using the weight as an argument.

  Further, the computer 150 may obtain the optimum value of the weight at each position in the image data. That is, the computer 150 may divide the image data into a plurality of areas and determine an optimum weight (optimum image data) in each divided area. In addition, the computer 150 may obtain an optimum weight for each light irradiation or for each group including two or more light irradiations.

  According to the image generation method according to the present embodiment, even when the optimum weight is unknown, the optimum weight or the image data to which the optimum weight is applied can be determined adaptively.

[Third Embodiment]
In the present embodiment, the computer 150 serving as a weighting unit weights a plurality of pieces of image data acquired by the method described in the first or second embodiment with a weighting coefficient M for negative image values. An image generation method when performing the above will be described. The first embodiment is that, prior to the weighting process, data obtained by accumulatively adding negative values of image values in the same region is generated and stored, and the negatively-added negative image values are used for the weighting process. Or, it is different from the second embodiment. Hereinafter, the contents of the present embodiment will be specifically described.

  First, the calculation unit 151 refers to a plurality of image data, determines the negative value of the image value when examining the fluctuation of the image value in a certain area, and displays information indicating the accumulated value Dn of all the negative image values. Generated and stored in the storage unit 152. Further, when referring to a plurality of image data, the calculation unit 151 generates information indicating the number of effective image values related to a certain region, in other words, information indicating the number N of additions of image values related to a certain region, and the storage unit Save to 152.

  Next, the calculation unit 151 generates information indicating an average value Da of image values in a certain region of a plurality of image data obtained by all light irradiation, and stores the information in the storage unit 152. FIG. 11 is a plot of changes in pixel values corresponding to a certain area when 10 pieces of image data are obtained by performing light irradiation 10 times. Here, it is shown that the pixel value of a certain region in the first light irradiation is P1, the pixel value of a certain region in the second light irradiation is P2, and the like, and the image value varies with each light irradiation. . In this case, the number of effective image values related to a certain area, in other words, the number N of additions of image values related to a certain area is 10. Further, the cumulative value of the negative image values is Dn = P3 + P5 + P6 + P8 + P10. The average value Da of the image values is Da = (P1 + P2 +... + P10) / N = (P1 + P2 +. + P10) / 10. In this way, by generating information indicating the cumulative value Dn of negative image values, the number N of additions, and the average value Da in advance, the negative values are weighted by an arbitrary weighting coefficient using these pieces of information. Negative component enhancement processing can be performed. Hereinafter, a calculation method when the negative component weighting coefficient is M will be described. Note that the negative component portion enhancement processing when the negative component weighting coefficient is M is referred to as M-fold negative component enhancement. The calculation unit 151 reads out the cumulative value Dn of negative image values, the number of additions N, and the average value Da from the storage unit 152, and the image value Dm = {Da * N + (M−1) * Dn at the time of M-fold negative component enhancement. } / N is calculated. The image value Dm when the M-fold negative component is emphasized corresponds to weighted image data. By performing the M-fold negative component enhancement processing using information calculated in advance in this way, it is not necessary to store all of a plurality of image data, so a memory capacity for storing data necessary for processing Can be reduced.

  Further, once information about the cumulative value Dn of negative image values, the number N of additions, and the average value Da is generated when imaging is performed, it is not necessary to perform imaging again to re-acquire a plurality of image data. In addition, the process of emphasizing the M-fold negative component can be performed, and an extra imaging effort can be omitted.

  Up to this point, the cumulative value Dn has been defined as a cumulative value of negative image values, but may be a cumulative value of positive image values. Even in such a case, the accumulated value Dn of negative image values can be obtained by Da * N- (accumulated value of positive image values), and therefore M-fold negative component enhancement processing can be performed. That is, performing negative component enhancement using the cumulative value of positive image values, the number of additions N, and the average value Da means that negative component enhancement is performed using the cumulative value Dn of negative image values, the number of additions N, and the average value Da. Is substantially equivalent to

  As described above, according to the image generation method according to the present embodiment, it is possible to perform negative component enhancement processing using an arbitrary weighting coefficient with a small amount of data by using information indicating a cumulative value of image values calculated in advance.

  In the case where the positive / negative inversion processing is not performed as the signal processing, the image data in which the artifact component is suppressed can be generated by switching the negative value and the positive value in the description of the present embodiment. That is, similarly to the M-fold negative component enhancement processing, M-fold positive component enhancement processing can be performed when the positive component weighting coefficient is M.

[Fourth Embodiment]
In the present embodiment, a display mode of a negative component emphasized image performed by the computer 150 as a display control unit will be described. FIG. 12 shows an example of the viewer 300 that displays a negative component emphasized image. In the viewer 300, there are an image display area 310, a negative component emphasis parameter setting area 320, and an image characteristic information display area 330.

  In the image display area 310, a photoacoustic image is displayed. The display mode is not limited to a specific mode as long as it is suitable for diagnosis, such as a one-dimensional image, a two-dimensional image, a three-dimensional image, and a moving image. Furthermore, the image processing method is not limited to a specific one, and an image generated by any method such as volume rendering, surface rendering, MIP (MAXIMUM INTERNITY PROJECTION) can be displayed. In the present embodiment, the photoacoustic image is divided into an XY cross-sectional image 311, an XZ cross-sectional image 312, and a YZ cross-sectional image 313, and three cross-sections are displayed in the image display area 310. It is also possible for the user to select and display an arbitrary plane.

  In the parameter setting area 320, parameters necessary for performing negative component enhancement processing are set. For example, as shown in FIG. 12, in the parameter setting area 320, the user can input ON / OFF of the negative component enhancement processing, the negative gain, and the offset value to be added to the image value. The parameters that can be input may be any parameters that are related to the negative component enhancement processing. The input mode is not necessarily limited to that shown in FIG. Instead of inputting the negative value amplification factor and the offset value to be added to the image value as numerical values, the input value may be designated with a slider or dial, and is not limited to a specific format. In addition, the parameter value may be performed from the input unit 170 from an operation console including a mouse and a keyboard that can be operated by the user. The parameter value may be provided by a slider or dial that is provided on the operation console of the input unit 170 and that can be adjusted by contact with the user. The display unit 160 may be configured with a touch panel, and the display unit 160 may be used as the input unit 170.

  In the image characteristic information display area 330, the characteristic information of the image value regarding the depth direction of the living body is displayed. In photoacoustic images, the intensity of light emitted decreases from the irradiation position to the deep part of the living body due to the influence of diffusion and attenuation of light in the living tissue, so that the image values of blood vessels and the like in the deep part of the living body tend to decrease. . Therefore, the variation characteristic of the image value in the depth direction of the living body may be displayed in the image characteristic information display area 330 so that the user can arbitrarily correct the image value. Thereby, a photoacoustic image with improved visibility can be displayed.

  For example, with respect to the subject image 350, the user designates an area 334-1 (hereinafter referred to as “characteristic confirmation area”) on the XY cross-sectional image 311 where the fluctuation characteristic of the image value in the depth direction of the living body is to be confirmed. When the characteristic confirmation area 334-1 is designated, areas 334-2 and 334-3 corresponding to the characteristic confirmation area 334-1 are also displayed in the XZ cross-sectional image 312 and the YZ cross-sectional image 313. The user adjusts the range of the designated area 334-2 in the XZ cross-sectional image 312 or the designated area 334-3 in the YZ cross-sectional image 313, thereby specifying the area that the user wants to check in the depth direction, that is, the Z direction. May be. The user may be able to specify numerical values.

  The user designation area 334 need not be one, and a plurality of user designation areas 334 may be set.

  When a plurality of settings are set, the characteristic information of the image values of the plurality of areas may be superimposed and displayed on the image characteristic information display area 330, or only the characteristic information on the area selected by the user may be displayed on the image characteristic information display area 330. May be.

  Once the user sets the characteristic confirmation region 334, the photoacoustic apparatus of the present invention displays the fluctuation characteristic 331 of the image value in the Z direction from Z1, which is the Z coordinate value of the surface of the subject image 350. The calculation method of the fluctuation characteristic is not limited to a specific one, and an index that can grasp the fluctuation characteristic of the image value in the Z direction of the living body may be used. For example, the maximum value of the image data of the area included in the characteristic confirmation area 334 may be used on the XY plane at a certain Z coordinate value. Then, the luminance value of the image can be corrected to match the attenuation correction curve 332 specified by the user or the luminance value level 333 of the surface of the subject image 350. A line segment 335 indicates the Z coordinate value of the surface of the subject image 350. In the parameter setting area 320, whether or not to execute the attenuation correction may be set by selecting whether or not the attenuation coefficient correction is turned ON / OFF. In the parameter setting area 320, it is possible to select whether the correction is performed according to the attenuation correction curve 332 specified by the user or the luminance value level 333 of the surface of the subject 350.

  In the display mode of the negative component emphasized image, it is not always necessary to display only the image display area 310, the negative component emphasized parameter setting area 320, and the image characteristic information display area 330. Any item displayed on the viewer of the conventional ultrasonic diagnostic apparatus and photoacoustic diagnostic apparatus can be displayed together, and the item that the user wants to display can be arbitrarily selected and displayed.

  Further, in the display mode of the negative component emphasized image, it is not always necessary to display all of the image display area 310, the negative component emphasized parameter setting area 320, and the characteristic information display area 330. The user may arbitrarily select and display an area to be displayed. That is, at least one of the image display area 310, the negative component emphasis parameter setting area 320, and the image characteristic information display area 330 may be displayed.

  Note that in the viewer described in the fourth embodiment of the present invention, image display may be performed in the manner described in the first and second embodiments of the present invention. Further, the areas and item layouts displayed in the viewer shown in FIG. 12, the wordings and fonts displayed in the viewer are not necessarily limited to those shown in FIG.

  Thus, according to the image generation method according to the present embodiment, it is possible to perform negative component enhancement with a processing parameter desired by the user.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

150 Computer 160 Display unit

Claims (20)

An image for generating image data based on a plurality of reception signals corresponding to the plurality of times of light irradiation obtained by receiving photoacoustic waves generated from the subject by a plurality of times of light irradiation on the subject. A generating device,
Signal processing means for performing signal processing including time differentiation processing and inversion processing for inverting the sign of the signal level for each of the plurality of received signals;
Image data generating means for generating a plurality of image data based on the plurality of received signals subjected to the signal processing;
Weighting processing means for performing weighting processing for making negative weights of the plurality of image data larger than positive weights;
Synthesizing means for generating first image data by synthesizing the plurality of image data subjected to the weighting processing;
An image generation apparatus comprising: An image for generating image data based on a plurality of reception signals corresponding to the plurality of times of light irradiation obtained by receiving photoacoustic waves generated from the subject by a plurality of times of light irradiation on the subject. A generating device,
Signal processing means for performing signal processing including time differentiation on each of the plurality of received signals;
Image data generating means for generating a plurality of image data based on the plurality of received signals subjected to the signal processing;
Weighting processing means for performing weighting processing for making positive weights of the plurality of image data larger than negative weights;
Synthesizing means for generating first image data by synthesizing the plurality of image data subjected to the weighting processing;
An image generation apparatus comprising: The image generation apparatus according to claim 1, wherein the weighting processing unit changes the weight of the negative value according to the magnitude of the negative value. The image generating apparatus according to claim 3, wherein the weighting processing unit reduces the weight of the negative value as the magnitude of the negative value increases. The image generating apparatus according to claim 2, wherein the weighting processing unit changes the weight of the positive value of the plurality of image data in accordance with the size of the positive value. The image generating apparatus according to claim 5, wherein the weighting processing unit decreases the weight of the positive value as the size of the positive value increases. The weighting processing means determines at least one weight of the positive value and the negative value based on a user instruction, and performs the weighting processing according to the weight. The image generating apparatus according to claim 1. Display control means for causing the display means to display a first image based on the first image data;
The weighting processing unit determines a weight of at least one of the positive value and the negative value based on a user instruction while the first image is displayed on the display unit, and the weighting processing unit determines the weight according to the weight. Perform weighting,
The synthesizing unit generates second image data by synthesizing the plurality of image data subjected to the weighting process according to the weight determined based on a user instruction,
The image according to claim 7, wherein the display control unit updates the image displayed on the display unit from the first image to a second image based on the second image data. Generator. Display control means for causing the display means to display a first image based on the first image data;
The weighting processing unit determines a weight of at least one of the positive value and the negative value based on a user instruction while the first image is displayed on the display unit, and the weighting processing unit determines the weight according to the weight. Perform weighting,
The synthesizing unit generates second image data by synthesizing the plurality of image data subjected to the weighting process according to the weight determined based on a user instruction,
8. The display control unit according to claim 7, wherein the display control unit causes the display unit to display the first image and a second image based on the second image data in parallel or superimposed. Image generation device. The weighting processing means includes
The weights different from each other are set for each of a plurality of positions of the plurality of image data, and the weighting process is performed on the plurality of image data according to the weights. The image generation apparatus according to item. 11. The image generation apparatus according to claim 1, wherein the weighting processing unit performs the weighting processing to increase a weight of at least one of the positive value and the negative value to be greater than 1. 11. A light irradiation means for irradiating the subject with the light multiple times;
By receiving the photoacoustic wave generated by the multiple times of light irradiation, a receiving unit that outputs the plurality of received signals;
The image generating apparatus according to claim 1, wherein the image generating apparatus includes: The image generating apparatus according to claim 12, further comprising a moving unit configured to move the receiving unit so that the position of the receiving unit with respect to the subject is changed by each of the plurality of times of light irradiation. The said image data production | generation means produces | generates the said several image data comprised from the image data corresponding to each of these said multiple times of light irradiation, The one of Claim 1 to 13 characterized by the above-mentioned. Image generation device. An image for generating image data based on a plurality of reception signals corresponding to the plurality of times of light irradiation obtained by receiving photoacoustic waves generated from the subject by a plurality of times of light irradiation on the subject. A generating device,
Signal processing means for performing signal processing including time differentiation processing and inversion processing for inverting the sign of the signal level for each of the plurality of received signals;
Image data generating means for generating a plurality of image data based on the plurality of received signals subjected to the signal processing;
Generating information indicating the number of additions of the plurality of image data, information indicating a cumulative positive or negative value of the plurality of image data, and information indicating an average value of the image values of the plurality of image data;
Weighting means for generating weighted image data using information indicating the number of additions, information indicating the cumulative value, and information indicating the average value;
An image generation apparatus characterized by that. In the case where the number of additions is N, the cumulative value is Dn, the average value is Da, the weighting coefficient is M, and the weighted image data is the image value Dm, the weighting means is Dm = {Da * N + ( 16. The image generation apparatus according to claim 15, wherein the weighted image data is generated according to M-1) * Dn} / N. Information for generating image data based on a plurality of reception signals corresponding to the plurality of times of light irradiation obtained by receiving photoacoustic waves generated from the subject by a plurality of times of light irradiation on the subject. A processing method,
Perform signal processing including time differentiation processing and inversion processing to invert the signal level for each of the plurality of received signals,
Based on the plurality of received signals subjected to the signal processing, generate a plurality of image data,
Performing a weighting process for making negative weights of the plurality of image data larger than positive weights,
An image generation method, wherein the first image data is generated by combining the plurality of image data subjected to the weighting process. Information for generating image data based on a plurality of reception signals corresponding to the plurality of times of light irradiation obtained by receiving photoacoustic waves generated from the subject by a plurality of times of light irradiation on the subject. A processing method,
Perform signal processing including time differentiation processing for each of the plurality of received signals,
Based on the plurality of received signals subjected to the signal processing, generate a plurality of image data,
Performing a weighting process for making the positive weight of the plurality of image data larger than the negative weight;
An image generation method, wherein the first image data is generated by combining the plurality of image data subjected to the weighting process. Information for generating image data based on a plurality of reception signals corresponding to the plurality of times of light irradiation obtained by receiving photoacoustic waves generated from the subject by a plurality of times of light irradiation on the subject. A processing method,
Perform signal processing including time differentiation processing and inversion processing to invert the signal level for each of the plurality of received signals,
Based on the plurality of received signals subjected to the signal processing, generate a plurality of image data,
Generating information indicating the number of additions of the plurality of image data, information indicating a cumulative positive value or negative value of the plurality of image data, and information indicating an average value of the image values of the plurality of image data;
A weighted image data is generated using information indicating the number of additions, information indicating the cumulative value, and information indicating the average value.   A program for causing a computer to execute the image generation method according to any one of claims 17 to 19.