JP6942847B2 - Subject information acquisition device and signal processing method - Google Patents

Description

The present invention relates to a subject information acquisition device and a signal processing method.

Photoacoustic imaging is one of the optical imaging techniques using light. In photoacoustic imaging, pulsed light is irradiated to a living body as a subject, and acoustic waves generated at a test site such as a tumor due to energy absorption of the pulsed light are received by a transducer. Then, by analyzing the received signal output from the transducer, the optical characteristic distribution in the living body is acquired as image data.

Patent Document 1 discloses a device in which a holding member holds a breast from both sides and a transducer two-dimensionally scans the holding member to receive an acoustic wave. By scanning the transducer two-dimensionally, it is possible to acquire characteristic information of a plurality of positions in the subject.

Japanese Unexamined Patent Publication No. 2010-022812

The subject information is obtained by performing image reconstruction processing on the signal data of the acoustic waves received by the plurality of acoustic wave receiving elements. The image reconstruction process is, for example, data processing such as back projection in the time domain or Fourier domain generally used in tomography technology, or phasing addition processing. These processes generally require a large amount of calculation. Therefore, when the subject information is generated following the reception of the acoustic wave, the subject information is visualized following the reception of the acoustic wave in response to the demand for higher definition of the image and higher frequency of light irradiation. It was difficult to do.

The present invention has been made in view of the above problems. An object of the present invention is to improve the followability to signal data acquisition when visualizing subject information in photoacoustic measurement.

The present invention adopts the following configuration. That is, an input unit that accepts input of information regarding the region of interest of the subject, and a plurality of photoacoustic waves from different measurement positions of the subject are received in parallel with a plurality of light irradiations of the subject based on the information. based on the plurality of signals obtained by, said processing unit for generating a unit reconstructs image data representing the characteristic information about the region of interest, a display control unit for displaying on the display unit an image based on the image data has, before Symbol processor, the image reconstruction processing performed in parallel with reception of the photoacoustic wave generates a first image data in the first reconstruction unit that is set based on the information the In the image reconstruction process performed after the reception of the photoacoustic wave in the region of interest is completed by updating the first image data with the change of the measurement position, the size is smaller than that of the first reconstruction unit. This is a subject information acquisition device that generates a second image data in the second reconstruction unit set as described above.

The present invention also employs the following configuration. That is, the step of accepting the input of information regarding the region of interest of the subject, the step of setting the reconstruction unit based on the information, and the step of irradiating the subject with a plurality of times of light are different in the region of interest. A step of receiving a plurality of photoacoustic waves from the measurement position, a step of generating image data showing characteristic information regarding the region of interest based on the signal obtained by the receiving step, and an image based on the image data. A signal processing method including a step of displaying on a display unit , wherein the display step generates first image data in a set first reconstruction unit and responds to a change in the measurement position. The image reconstruction process is performed in parallel with the reception of the photoacoustic wave so as to update the first image data, and the first reconstruction is performed after the reception of the photoacoustic wave corresponding to the region of interest is completed. The image reconstruction process is performed so as to generate the second image data in the second reconstruction unit set to be smaller in size than the unit, and the display step is the first step based on the first image data. Display control was performed in parallel with the reception of the photoacoustic wave so as to display and update the first display with the change of the measurement position, and the reception of the photoacoustic wave corresponding to the region of interest was completed. This is a signal processing method that controls the display so that the second display is performed later based on the second image data.

According to the present invention, in photoacoustic measurement, it is possible to improve the followability to signal data acquisition when visualizing subject information.

Block diagram of the subject information acquisition device Image diagram showing the area that is the basis of image data generation in sequential display A flowchart showing an example of dividing the reconstruction region for each of a plurality of wavelengths. Image of drive control pattern of transducer and light emission end Flowchart showing an example of resizing a voxel

A preferred embodiment 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 appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions. Therefore, it is not intended to limit the scope of the present invention to the following description.

The present invention relates to a technique for detecting an acoustic wave propagating from a subject and generating and acquiring characteristic information inside the subject. Therefore, the present invention can be regarded as a subject information acquisition device or a control method thereof, or a subject information acquisition method or a signal processing method. The present invention can also be regarded as a program for executing these methods in an information processing device having hardware resources such as a CPU and a memory, and a storage medium for storing the program.

The subject information acquisition device of the present invention has a photoacoustic effect of receiving acoustic waves generated in a subject by irradiating the subject with light (electromagnetic waves) and acquiring characteristic information of the subject as image data. Includes devices that utilize. In this case, the characteristic information is information on characteristic values corresponding to each of a plurality of positions in the subject, which is generated by using the received signal obtained by receiving the photoacoustic wave.

The characteristic information acquired by the photoacoustic measurement is a value that reflects the absorption rate of light energy. For example, it includes the source of the acoustic wave generated by light irradiation, the initial sound pressure in the subject, or the light energy absorption density and absorption coefficient derived from the initial sound pressure, and the concentration of substances constituting the tissue. In addition, the oxygen saturation distribution can be calculated by obtaining the oxidized hemoglobin concentration and the reduced hemoglobin concentration as the substance concentration. In addition, glucose concentration, collagen concentration, melanin concentration, volume fraction of fat and water, etc. are also required.

A two-dimensional or three-dimensional characteristic information distribution can be obtained based on the characteristic information of each position in the subject. Distribution data can be generated as image data. The characteristic information may be obtained not as numerical data but as distribution information of each position in the subject. That is, it is distribution information such as initial sound pressure distribution, energy absorption density distribution, absorption coefficient distribution, and oxygen saturation distribution.

The acoustic wave referred to in the present invention is typically an ultrasonic wave, and includes an elastic wave called a sound wave or an acoustic wave. An electric signal converted from an acoustic wave by a transducer or the like is also called an acoustic signal. However, the description of ultrasonic waves or acoustic waves in the present specification is not intended to limit the wavelengths of these elastic waves. The acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave. An electric signal derived from a photoacoustic wave is also called a photoacoustic signal.

Although the details will be described in each embodiment, the present invention is characterized in that the subject information acquisition device that visualizes the subject information by following the acquisition of the signal data of the acoustic wave improves the followability of the visualization. In principle, the same components are designated by the same reference numerals, and the description thereof will be omitted.

<Embodiment 1>
In the present embodiment, a method of improving the followability of subject information visualization by following the acquisition of signal data of acoustic waves in a device using a photoacoustic effect will be described.

(Basic configuration of the device)
FIG. 1 is a block diagram showing a configuration of a subject information acquisition device according to the first embodiment. The device includes a subject holding means 102 that holds a living body 101 that is a subject, an irradiation unit 103 that irradiates light, and a transducer 104 that receives an acoustic wave and converts it into a received signal. The device also provides a signal processing means 105 that amplifies the received signal and converts it into a digital signal, a support 106 that directs at least a portion of the plurality of transducers 104 to intersect the most sensitive directions of their respective receive directivities. Have. The apparatus also generates image data of a region different for each wavelength of the light emitted from the irradiation unit 103 by using the signals from the scanning control means 107 and the signal processing means 105 that scan and control the irradiation unit 103 and the support 106. It has an image reconstruction means 108. The apparatus also includes an image display means 109 for displaying the generated images in total, and an input means 110 for setting shooting conditions and the like to start shooting. Hereinafter, the details of each configuration will be described, and finally, the steps for improving the followability will be described.

(Subject holding means)
As the living body 101, for example, a breast can be considered. Since the subject holding means 102 is located on the optical path of light, a material having a high transmittance for the light to be used, such as polymethylpentene, is preferable. Further, it is preferable to reduce the thickness of the subject holding means 102 in order to increase the transparency of ultrasonic waves and reduce harmful noise. Therefore, as the subject holding means 102, it is preferable to use a member having strength enough to withstand the weight of the subject even if it is thin. Further, it is preferable that the member has high acoustic consistency with the transducer 104. Specifically, a bowl-shaped or dish-shaped member using PET can be used. Alternatively, a stretchable film-like member may be used.

It is preferable to fill a matching liquid between the subject holding means 102 and the subject in order to match the acoustic impedance. The matching liquid is preferably one that is close to the acoustic impedance of the human body and has a small ultrasonic attenuation. For example, water, gel, castor oil, etc. can be used.

(Irradiation unit)
The irradiation unit 103 that irradiates the living body 101 with light is composed of a light source that generates light and an irradiation unit that guides the light from the light source to the subject and irradiates the subject. As the light source, a solid-state laser capable of generating pulsed light (pulse width 100 nsec or less) having a central wavelength in the near infrared region of 530 to 1300 nm is preferable. For example, Yttrium-Aluminium-Garnet lasers and Titan-Sapphire lasers are used. The wavelength of the measurement light is selected from 530 nm to 1300 nm depending on the light absorbing substance (for example, hemoglobin, glucose, cholesterol, etc.) in the living body to be measured.

In this embodiment, two Titan-Sapphire lasers are used to alternately irradiate light having a short wavelength of 756 nm and a long wavelength of 797 nm at 10 Hz. More preferably, the wavelength of the pulsed light is about 700 nm to 1200 nm, which is a near-infrared region called a window of a living body. Since the light in this region reaches a relatively deep part of the living body, information on the deep part of the living body can be acquired. If it is limited to the measurement of the surface portion of the living body, a visible light to near infrared region of about 500 to 700 nm may also be used. Further, it is desirable that the wavelength of the pulsed light has a high absorption coefficient depending on the observation target.

Examples of the irradiation unit include a mirror that reflects light, a lens that collects, magnifies, and changes the shape of light, a prism that disperses, refracts, and reflects light, an optical fiber that propagates light, and a diffuser plate. Can be mentioned. Any type of irradiation unit may be used as long as the light emitted from the light source irradiates the desired region of the subject with a desired shape. In the present embodiment, the emission end of the light from the irradiation unit is located at the bottom of the support 106, which will be described later, and the support 106 is moved by movement control by the scanning control means 107. However, the position of the exit end is not limited to this as long as the living body 101 can be irradiated with light.

(Transducer)
The transducer 104 is an element that receives an acoustic wave and converts it into an electric signal (received signal). One transducer 104 may include a plurality of elements. As the element included in the transducer 104, a conversion element using a piezoelectric phenomenon, a conversion element using light resonance, a conversion element using a change in capacitance, and the like can be considered. However, any element may be used as long as it can receive the acoustic wave and convert it into an electric signal.

(Signal processing means)
The signal processing means 105 includes a signal amplification unit that amplifies an analog signal (analog reception signal) input from the transducer 104, and an A / D conversion unit that converts an analog signal into a digital signal. The signal amplification unit controls to increase or decrease the amplification gain according to the time from light irradiation to the arrival of the acoustic wave at the transducer element in order to obtain image data with uniform contrast regardless of the depth in the living body. And so on. In addition, it also corrects the sensitivity variation of the element with respect to the digital received signal, complements the physically or electrically missing element, and performs the recording operation on a recording medium (not shown). The signal processing means 105 can be configured by a processing circuit or the like using FPGA or the like.

(Support)
The support 106 is a container-shaped member that supports the transducer 104. The transducer is preferably arranged in a spiral shape on the inner surface of the container. By forming the transducer support surface into a curved surface, it is possible to form a high resolution region in which the directions (direction axes) of each transducer with high reception sensitivity are gathered. The high resolution region can be defined, for example, as a range having a resolution of 50% or more of the maximum resolution, centering on the place where the resolution is the highest. The container can be, for example, hemispherical, spherically crowned, part of an ellipsoid, bowl-shaped, or a combination of multiple planes or curved surfaces.

It is preferable to fill a matching liquid between the inside of the support 106 and the subject holding means 102 in order to match the acoustic impedance. As the matching liquid, the same material as that used in the subject holding means 102 may be used, or another material may be used. For example, the subject may be coated with ultrasonic gel and the inside of the support may be filled with water.

(Scanning control means)
The scanning control means 107 changes the relative positions of the light emitting end and the support 106 with respect to the subject. For example, a stage equipped with a stepping motor, a ball screw, or the like and capable of horizontal scanning in the XY direction can be used. A dedicated processing circuit may be used for controlling the stage, or an information processing device described later may be used for controlling the stage. In addition to horizontal scanning in the XY direction, it is preferable to be able to scan in the Z direction as well. Information can be acquired from a wide range of subjects by scanning control. In particular, when a hemispherical support that forms a high-resolution region is used, high-definition image data of the entire subject can be acquired by scanning control. However, scanning control is not always necessary when the region of interest is narrow. Scanning control is not essential to the present invention. The present invention is applicable in all cases where an image needs to be displayed in real time during a photoacoustic measurement.

In the present embodiment, the center position of the support 106 at the timing of irradiating light is set as the measurement position. Generally, the propagation speed of the acoustic wave is faster than the speed at which the scanning control means 107 moves the support 106. Therefore, it may be considered that the acoustic wave is received at the position of the transducer 104 at the time of light irradiation. Therefore, in the present embodiment, the timing of irradiating the light is the timing of measuring the acoustic wave. Also, the positions of the plurality of transducers 104 on the support 106 are known. Therefore, it is possible to reconstruct an image of an arbitrary region based on the position of the support 106 and the light irradiation timing. Regarding the relationship between scanning control, light irradiation, and acoustic wave reception, continuous scanning or step-and-repeat may be used. The scanning control means corresponds to the scanning control unit of the present invention.

(Image reconstruction means)
The image reconstructing means 108 acquires optical characteristic information of each position in the living body 101 by using the signal output from the signal processing means 105. The characteristic information distribution (absorption coefficient distribution, oxygen saturation distribution, etc.) can be generated as image data. Further, various correction processes such as brightness adjustment, distortion correction, and cutting out of a region of interest may be applied to the generated image data to generate image data preferable for diagnosis. As the image reconstructing means 108, an information processing device (PC, workstation, etc.) that includes resources such as a CPU, a memory, and a communication device and operates according to a program can be used. The image reconstructing means 108 functions as a processing unit and a display control unit of the present invention.

Image reconstruction can be performed by any known algorithm (phase-aligned addition method, Fourier transform method, iterative calculation method, etc.). More specifically, in image reconstruction, the image reconstruction means 108 acquires characteristic information for each of a plurality of reconstruction units inside the subject by performing image reconstruction based on a digital electrical signal. The reconstruction unit is a region in which the region of interest to be imaged inside the subject is divided into arbitrary sizes. The reconstruction unit is called a voxel when generating 3D image data, and a pixel when generating 2D image data. Three-dimensional (or two-dimensional) image data represents the distribution of characteristic information of reconstruction units arranged in a three-dimensional (two-dimensional) space. In the sequential display described later, the amount of calculation may be reduced by setting a reconstruction unit having a size larger than that of the high-definition display. Further, in the sequential display, a method with a small amount of calculation may be used, and in the high-definition display, a repetitive calculation with a relatively large amount of calculation may be used. In the present specification, the sequential display is also referred to as a first display, and the high-definition display is also referred to as a second display.

(Switching reconstruction mode)
In the present embodiment, it is possible to select and determine whether the image reconstruction is performed in the sequential display mode or the high-definition display mode. In the sequential display, the image is displayed in parallel with the irradiation of light and the reception of acoustic waves. Sequential display is suitable for real-time display performed in parallel with photoacoustic measurement. In the sequential display, image data is generated at high speed based on a relatively small number of electric signals, but there are problems that the image quality is low and the image does not reflect the overall composition of the subject. On the other hand, in the high-definition display, image data is generated based on a larger number of electric signals than in the sequential display, so that an image in a wide area can be generated with high quality. That is, in high-definition display, image data is generated by increasing the total amount of electrical signal data used for image generation as compared with the case of sequential display. It can be said that even when the same electric signal as the electric signal used in the sequential display is repeatedly used, an image based on a larger number of electric signals is generated than in the case of the sequential display.

In the case of high-definition display, the characteristic information of the reconstruction unit in a wide range of the subject (for example, the entire region of interest) is acquired, and the three-dimensional image data is reconstructed. On the other hand, in the case of sequential display, characteristic information in a smaller range (for example, a part of the region of interest specified by the user) is acquired. Further, at the time of sequential display, the three-dimensional image data may be projected by a predetermined method and displayed as a two-dimensional image. For example, a maximum value projection method (MIP) may be applied to the reconstructed characteristic information to generate a MIP image. The projection direction is arbitrary. For example, when scanning the support in the XY direction, a two-dimensional image can be generated by projecting in the Z direction orthogonal to the scanning direction. Even in the high-definition display, the three-dimensional image data may be displayed as a two-dimensional image by projecting it by a predetermined method.

Further, the type of characteristic information may be switched between sequential display and high-definition display. In this case, in the case of sequential display, the initial sound pressure distribution that can be obtained by simple reconstruction and the light energy absorption density distribution that can be obtained by using the Grunaisen coefficient that takes a predetermined value for each subject are displayed. On the other hand, in the case of high-definition display, it is possible to display an absorption coefficient distribution that requires an operation based on the light amount distribution. Further, in the case of high-definition display, the computational resources required to display the oxygen saturation distribution can be easily secured.

Further, in the sequential display, electric signals derived from light having a plurality of wavelengths can be used for image reconstruction having different depths. Here, it is assumed that the light source can irradiate light having a first wavelength and light having a second wavelength different from the first wavelength. Then, since the light transmittance inside the subject differs depending on the wavelength, the first region inside the subject is imaged by using the electric signal derived from the light of the first wavelength, and the light of the second wavelength is used. A second region different from the first region can be imaged by using the electric signal derived from. Typically, the longer the wavelength of light, the deeper it reaches the subject, so by setting the second wavelength longer than the first wavelength, it is deeper than the first region and the first region. The second region (long distance from the light source) can be suitably imaged.

The amount of calculation in the sequential display differs depending on conditions such as the calculation time determined by the scanning speed, the size of the reconstruction unit, and the size of the subject area which is the basis for acquiring the characteristic information. Therefore, if these conditions permit, the initial sound pressure may be standardized based on the light amount distribution in the sequential display, and the absorption coefficient and oxygen saturation may be obtained. The value of the initial sound pressure varies greatly depending on the length of the distance from the light source (in other words, the amount of light attenuation after irradiation). Therefore, when the maximum value is extracted to generate a MIP image, or when electric signals derived from light of a plurality of wavelengths are used for image reconstruction of different depths, the correctness of the calculated value is lowered. There is a problem to do. Therefore, this problem can be solved by performing the above standardization. However, since standardization involves an increase in the amount of calculation, it should be decided whether or not to perform standardization, especially in consideration of the relationship with the scanning speed.

The image reconstructing means 108 of the present embodiment acquires characteristic information of different regions for each wavelength emitted from the irradiation unit 103. That is, the characteristic information of the first region is acquired based on the electric signal derived from the photoacoustic wave obtained when the subject is irradiated with the light of the first wavelength, and the light of the second wavelength is used as the subject. The characteristic information of the second region is acquired based on the electric signal derived from the photoacoustic wave obtained when the light is irradiated.

In this embodiment, light having a short wavelength of 756 nm and light having a long wavelength of 797 nm are alternately irradiated at 10 Hz. FIG. 2A is a schematic view of an image forming region of the present embodiment. The image reconstruction area 201 corresponds to the entire target area (area of interest) for photoacoustic measurement. The light is emitted from above the paper surface along the Z axis. The image reconstruction region 201 is divided into voxels at a desired pitch (not shown). The short wavelength reconstruction region 202 is a region (first region) that is reconstructed using a received signal derived from light having a short wavelength (first wavelength). The long wavelength reconstruction region 203 is a region (second region) that is reconstructed using a received signal derived from long wavelength light (second wavelength) that can reach a deeper part. In the real-time display, the images of the entire reconstructed first region and the second region may be displayed, or the maximum value projection method may be applied to each region.

Here, as a preferable signal processing method, in high-definition display, oxygen saturation is performed in a portion where the short wavelength reconstruction region corresponding to the first wavelength and the long wavelength reconstruction region corresponding to the second wavelength overlap. There is a method to calculate and display the degree. This is because a relatively long processing time can be taken in a high-definition display. On the other hand, in the sequential display, there are few (or no) overlapping regions between wavelengths. Therefore, since it is difficult to acquire oxygen saturation using two wavelengths, it is preferable to display information that can be acquired even with a single wavelength, such as initial sound pressure distribution, light energy absorption density, or absorption coefficient distribution.

By limiting the reconstruction region for each wavelength by the image reconstruction means 108 of the present embodiment, the amount of calculation in the reconstruction for each light irradiation is reduced. As a result, the calculation time can be shortened, and the followability of the acoustic wave of the image display to the signal data acquisition is improved. Therefore, real-time display that generates an image while performing photoacoustic measurement and probe scanning can be preferably performed. At this time, by narrowing the short wavelength reconstruction area 202 and the long wavelength reconstruction area 203, an image can be displayed at a higher speed.

Generally, it is said that long-wavelength light reaches a deep position for a living body. Therefore, by allocating the region to be reconstructed for each wavelength according to the measurement depth, the image quality of the image displayed by the image display means 109 described later can be improved. The setting here is a setting value for speeding up the tracking property when the signal data acquisition of the acoustic wave is followed and imaged. Therefore, after the scanning is completed, it is preferable to perform image reconstruction on the entire region of the subject. At the very least, characteristic information is acquired for a larger number of reconstruction units than the real-time display.

The depth from the body surface of the first region and the second region (in other words, the length of the distance from the light source) can be arbitrarily set. Typically, if the subject is the breast, it is advisable to set the depth at which breast cancer is likely to occur. The depth of breast cancer varies depending on the type and degree of breast cancer, breast size, fat thickness, etc., but for example, if the area is set a few cm below the body surface (typically 2-3 cm below), good.

In the present embodiment, images in different regions are reconstructed for light of two wavelengths, but different regions can be reconstructed even when light of three or more wavelengths is handled.

(Image display means)
The image display means 109 displays an image based on the image data input from the image reconstruction means 108. The image display means 109 corresponds to the display unit of the present invention. At the time of sequential display, the amount of information in the sequential display can be increased by displaying the image data by adding up the short wavelength reconstruction area 202 and the long wavelength reconstruction area 203. Here, the summing of image data means generating image data that displays a wide range of images based on images of different regions generated based on each wavelength. When the regions partially overlap each other, it is preferable to perform weighting average value processing or the like so as not to give a sense of discomfort to the user.

(Input means)
The input means 110 receives an instruction given by the user to the device. The input instructions include a shooting start command, designation of a region of interest, a reconstructed range or reconstructed image quality in sequential display, a scanning region in scanning control, a wavelength of light, and the like. As the input means 110, a pointing device such as a mouse or a keyboard, a pen tablet, a keyboard, a voice input device, or the like can be used. Further, if the image display means 109 has a touch input function, it can also be used as an input means 110 for receiving an instruction input. The input means corresponds to the input unit of the present invention.

In addition, the user can specify the region of interest for photoacoustic measurement by using the input means 110 with reference to the living body 101. In that case, the scanning control means 107 controls the scanning position of the support 106 so that the acoustic wave in the region of interest can be acquired.

The input means 110 also receives information on which region is to be reconstructed at which wavelength and input of a range of reconstruction by each wavelength. The image reconstructing means 108 reconstructs an electric signal derived from a photoacoustic wave generated by light of each wavelength based on the information. However, the image reconstructing means 108 may store the reconstructed region at which wavelength and the reconstructed range as a set value. Upon receiving a photographing instruction from the user, the scanning control means 107 starts scanning control, and the irradiation unit 103 starts laser irradiation. Further, when the reconstruction region at the time of sequential display is specified, the image reconstruction means may determine the wavelength according to the depth of the reconstruction region.

(Flow of this embodiment)
This embodiment is performed according to the flow shown in FIG. This flow starts from the place where the living body 101 is held by the subject holding means 102.

In step S301, the measurement conditions are set. For example, using the input means, the user inputs information on the test portion, the type of the subject holding means 102, the imaging region, the region for each wavelength reconstructed by the image reconstructing means 108, and the like among the imaging regions. .. Alternatively, the conditions may be read from the memory.

In step S302, the scanning control means 107 calculates the driving conditions of the support 106 based on the measurement conditions input in step 301. It is desirable to move the support 106 so that the high resolution region where the reception directivity of the transducer 104 intersects covers the entire imaging region. In the present embodiment, as shown in FIG. 4, the region of interest is spirally horizontally scanned in the XY directions. In FIG. 4, reference numeral 402 indicates a locus of a central portion of the support, and reference numeral 401 indicates a position at which light irradiation and acoustic wave reception start are performed.

By such driving, the fluctuation of the liquid level of the matching liquid can be reduced. Moreover, even if the region of interest is changed, it can be dealt with by changing the size of the circle when driving in a spiral shape. If the relative positions of the support 106 and the subject can be changed, the scanning control method is not limited to the above. For example, the side of the subject may be moved, or both the subject and the support may be moved.

In the present embodiment, the support 106 is continuously moved, but a step-and-repeat method may be used in which the support 106 is repeatedly moved and stopped to irradiate light and receive acoustic waves at the stop position. Moreover, it is not limited to the spiral drive. Any path may be driven as long as the support 106 can be driven so that the high resolution region covers the entire region of interest. For example, a raster scan method in which the main scan and the sub scan are repeated may be used.

In step S303, the input means 110 receives a command to start imaging. As a result, the scan set in S302 is started. Further, along with scanning, light irradiation of a plurality of wavelengths from the irradiation unit 103, reception of photoacoustic waves by the transducer 104, and digital conversion and amplification processing by the signal processing means 105 are performed. The method of synchronizing these processes is arbitrary. For example, there are a method of storing a digital signal in response to light detection using a photodetector and a method of storing a digital signal in conjunction with a control signal of light irradiation. Further, it is preferable that the coordinate information of the scanning control means 107 is acquired based on the control information of the XY stage and the like, and the position when each digital signal is acquired is stored.

In step S304, the image reconstructing means 108 reconstructs the region corresponding to each wavelength. The signal of which wavelength is determined based on the irradiation control information of the light of each wavelength by the irradiation unit 103. Further, index information indicating the wavelength may be added to the signal sent from the signal processing means 105. The image reconstructing means 108 images a region determined according to the wavelength, and transmits the data to the image displaying means 109.

In step S305, the image display means 109 displays the image data for each wavelength sent from the image reconstruction means 108. This makes it possible to display the image data so as to follow the drive of the support 106. In this step, it is preferable that an image corresponding to the high resolution region is gradually added as the scan progresses, and the image is enlarged. In this case, an image based on the newly generated image data is added to the images that have been displayed so far according to the change in the relative position.

In step S306, it is determined whether the signal can be acquired at all the measurement positions in the region of interest. If the signal acquisition is not completed, the process from step S303 is repeated. When the acquisition of all the signals is completed, the process proceeds to step S307 and the scanning is completed. This completes the photoacoustic measurement. This completes the sequential display mode, and thereafter the high-definition display mode starts.

In step S308, the image reconstruction means 108 performs image reconstruction for the entire region of interest. However, it is not always necessary to reconfigure the entire area of interest immediately after the end of scanning, and all the acquired data is transferred to an external storage device such as an HDD or flash memory or a server, and reconfigured at any time and place of the user. You may. In this step, it is sufficient to obtain at least more information than the sequential display.

In step S309, the image reconstructed in S308 is displayed on the image display means 109. In S309, since the image reconstruction process is performed on all the received signals, a higher definition image than in S305 can be obtained. In addition, images with a large amount of calculation such as absorption coefficient distribution and oxygen saturation distribution can be obtained.

By executing the above flow in the apparatus of the present invention, it is possible to display an image with high followability in the sequential display performed in real time in parallel with the scanning, and it is possible to display a high-definition image after the scanning is completed. Therefore, in the photoacoustic measurement, the followability to the signal data acquisition in the visualization of the subject information is improved.

<Modification example>
In the above flow, light having a plurality of wavelengths was used. However, as shown in FIG. 2B, the present invention can also be applied to imaging using light of one wavelength. Even in this case, the amount of calculation in the real-time image display can be reduced by reconstructing the image in a relatively narrow area (reference numeral 204) in the sequential display. On the other hand, in high-definition display, image reconstruction is performed on the entire region of interest (image reconstruction region 201). As a result, the followability to signal data acquisition is improved.

Further, the first region and the second region may be set at distant positions as shown in FIG. 2 (C). The position of each region can be flexibly set according to the wavelength of light and the imaging region desired by the user.

<Embodiment 2>
In the second embodiment, the image is displayed in a shorter time by distinguishing the region to be reconstructed for each wavelength and further changing the size of the voxel at the time of reconstructing. In the present embodiment, the time from driving the support 106 to displaying the image is further shortened. The apparatus configuration of the present embodiment is the same as that of the first embodiment, but the functions of the image reconstructing means 108 and the input means 110 are different. Therefore, the description of the configuration similar to that of the first embodiment will be omitted, and only the parts different from the first embodiment will be described in detail.

In the present embodiment, the input means 110 accepts the voxel size for image reconstruction for each wavelength. The image reconstructing means 108 reconstructs the image data with the set size. As a result, the transmission time of the image data to the image display means 109 can be further shortened.

FIG. 5 is a flowchart of the operation in the second embodiment. Steps S502 to S509 are the same as steps S302 to S309 of the first embodiment. In step S501, the input means 110 receives input of the voxel size at the time of reconstruction from the user. At this time, the size of the voxel may be changed according to the wavelength. Further, the voxel size of each of the sequential display and the high-definition display may be set. Further, the user may specify the image quality, and the image reconstruction means 108 may calculate the voxel size for realizing the specified image quality.

In the present embodiment, a large voxel size can be set in the sequential display. As a result, the amount of calculation is reduced, and the real-time property of the reconstructed image display can be improved.

(Other Examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

103: Irradiation unit, 104: Transducer, 108: Image reconstruction means, 109: Image display means

Claims (28)

Receiving an input unit for accepting input of information about the region of interest of the subject, a plurality of photoacoustic waves from different measurement positions of the subject in parallel with the light irradiation a plurality of times with respect to the subject on the basis of the information based on the plurality of signals obtained by, said processing unit for generating a unit reconstructs image data representing the characteristic information about the region of interest, a display control unit for displaying on the display unit an image based on the image data, the Have and
Pre Symbol processing unit, the first change of the first generation and the measurement position of image data in the reconstruction units set on the basis of the information in the image reconstruction process performed in parallel with reception of the photoacoustic wave Along with this, the first image data is updated, and in the image reconstruction process performed after the reception of the photoacoustic wave in the region of interest is completed, the size is set to be smaller than the first reconstruction unit. A subject information acquisition device that generates a second image data in two reconstruction units. The processing unit generates the characteristic information corresponding to the reconstruction unit arranged three-dimensionally, and projects the characteristic information acquired in the first reconstruction unit to obtain the first image data. The subject information acquisition device according to claim 1 to be generated. A transducer for outputting said signal by receiving the light acoustic Nami, subject information obtaining apparatus according to claim 1 or 2 further have a scan controller for scanning the said transducer in a predetermined direction. The subject information acquisition device according to claim 3, wherein the processing unit generates the first image data by projecting the characteristic information in a direction orthogonal to the predetermined direction. The subject information acquisition device according to claim 3 or 4, further comprising a support that supports the transducer. The subject information acquisition device according to claim 5, further comprising an exit end for irradiating the subject with light. The subject information acquisition device according to claim 6, wherein the scanning control unit changes the measurement position by changing the relative positions of the transducer and the exit end with respect to the subject via the support. Wherein the processing unit, before Symbol characteristic information object information acquiring apparatus according to any one of the first image data from the 請Motomeko 2 that generates a 7 by applying the maximum intensity projection method. Wherein the processing unit, before Symbol Examples characteristic information first initial sound pressure in the reconstruction unit, claims 1 to generate the first image data indicative of at least one of the optical energy absorption density and the absorption coefficient 8 The subject information acquisition device according to any one of the items. The subject information acquisition device according to any one of claims 1 to 9 , wherein the processing unit generates the second image data indicating the oxygen saturation in the second reconstruction unit as the characteristic information. .. The exit end, the light of the first wavelength, the so capable of emitting light of a second wavelength different from the first wavelength, according to claim 6 or 7 is optically coupled to a light source Subject information acquisition device. The processing unit uses the signal derived from the light of the first wavelength to generate the first image data of the first region of the subject, and the processing unit generates the first image data derived from the light of the second wavelength. The subject information acquisition device according to claim 11, wherein the first image data in a second region different from the first region is generated by using a signal. The subject information acquisition according to claim 12 , wherein the second wavelength is longer than the first wavelength, and the second region has a deeper depth from the body surface of the subject than the first region. Device. Wherein the processing unit on the basis of the venlafaxine No. Before from each light before Symbol first wavelength and the second wavelength, the first region and the second region each first Kion pressure, light energy absorption density and subject information obtaining apparatus according to請Motomeko 12 or 13 that generates the first image data indicative of at least one of the absorption coefficient. The subject information acquisition device according to any one of claims 11 to 14 , wherein the processing unit generates the second image data indicating the oxygen saturation of the subject. The processing unit according to any one of claims 11 to 15, which sets the size of the reconstruction unit depending on whether or not the image reconstruction processing is performed in parallel with the reception of the photoacoustic wave. Subject information acquisition device. The processing unit sets the number of the reconstruction units in which the region of interest is divided according to whether or not the image reconstruction processing is performed in parallel with the reception of the photoacoustic wave. The subject information acquisition device according to any one of the items. 16. The processing unit sets in claim 16 whether to use the signal corresponding to the first wavelength or the second wavelength when generating the first image data based on the information. Described subject information acquisition device. The subject information acquisition device according to claim 6 or 7 , wherein the transducer includes a plurality of conversion elements, and the plurality of conversion elements are supported by the support so that the directivity axes of each of the transducers are gathered. In the display control performed in parallel with the irradiation of the light and the reception of the photoacoustic wave, the display control unit performs the first display based on the first image data, and the first display is performed with the change of the measurement position. In the display control performed after the light irradiation and the reception of the photoacoustic wave are completed, the second display is performed based on the second image data. Any one of claims 1 to 19. The subject information acquisition device described in. The display control unit adds a display based on the first image data newly generated in response to a change in the measurement position to the displayed first display , thereby causing the first display. The subject information acquisition device according to claim 20 , wherein the display is updated. Wherein the input unit, subject information obtaining apparatus according to claim 20 or 21 receives an input of the image quality of the images of the first display. Before Symbol wherein the size of the reconstruction unit, subject information obtaining apparatus according to any one of claims 1 to 22 which is set based on the input received via the input unit. The subject information acquisition device according to any one of claims 11 to 18, further comprising the light source. Any one of claims 1 to 24, wherein the processing unit generates the first image data for each of the first reconstruction units, and generates the second image data for each of the second reconstruction units. The subject information acquisition device according to item 1. A step of accepting input of information about the region of interest of the subject, a step of setting a reconstruction unit based on the information, and different measurement positions in the region of interest in parallel with a plurality of light irradiations of the subject. A step of receiving a plurality of photoacoustic waves from the above, a step of generating image data indicating characteristic information regarding the region of interest based on the signal obtained by the receiving step, and a display unit displaying an image based on the image data. It is a signal processing method having a step to be displayed in.
The display step is the reception of the photoacoustic wave so as to generate the first image data in the set first reconstruction unit and update the first image data in response to the change in the measurement position. The image reconstruction process is performed in parallel, and after the reception of the photoacoustic wave corresponding to the region of interest is completed, the second reconstruction unit set to be smaller in size than the first reconstruction unit is used. Perform image reconstruction processing so as to generate the image data of 2.
In the display step, display control is performed in parallel with reception of the photoacoustic wave so that the first display is performed based on the first image data and the first display is updated when the measurement position is changed. A signal processing method for performing display control so as to perform a second display based on the second image data after the reception of the photoacoustic wave corresponding to the region of interest is completed. The signal according to claim 26, wherein the generation step generates the first image data for each of the first reconstruction units, and generates the second image data for each of the second reconstruction units. Processing method. A program that causes an information processing apparatus to execute each step of the signal processing method according to claim 26 or 27.

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