JP6141488B2 - Subject information acquisition device - Google Patents

Description

  The present invention relates to a photoacoustic wave imaging apparatus that reconstructs a three-dimensional image inside a subject based on photoacoustic waves.

  Conventionally, an X-ray mammography apparatus is widely known as a powerful diagnostic imaging apparatus for early detection of breast cancer. In an X-ray mammography apparatus, a breast is compressed and held by an imaging table in which a radiation detector is housed and a compression plate disposed opposite to the imaging table, and radiation is irradiated to the breast through the compression plate. The reason why the breast is compressed with the compression plate at this time is for the purpose of minimizing the exposure amount of the radiation used by reducing the thickness at the time of imaging of the breast as much as possible. Further, since the breast is compressed, the load applied to the compression plate has been measured and displayed in order to ensure safety for the subject and prevent an excessive load from being applied to the subject. However, in general, a load (force) applied to the compression plate is measured and displayed, and the pressure applied to the breast itself has not been considered due to the size of the breast on the compression plate.

  On the other hand, Patent Document 1 discloses an X-ray mammography apparatus that uses a two-dimensional pressure sensor provided on an imaging stand to detect and display a compression pressure distribution during breast compression by a compression plate.

  On the other hand, there is known a method for acquiring a wide range of three-dimensional image data using an ultrasonic echo with low invasiveness instead of X-rays accompanied by exposure. Furthermore, in recent years, a subject (breast) is irradiated with light in the infrared band such as a laser beam having a low bioabsorption rate, and a photoacoustic wave generated inside the subject is detected, and three-dimensional image data based on the photoacoustic wave is detected. There has been proposed a photoacoustic mammography apparatus that acquires and displays the above. The photoacoustic mammography device detects an photoacoustic wave generated as a result of a specific substance in the subject absorbing the energy of the irradiation light, and forms an image. The specific substance is, for example, glucose or hemoglobin contained in blood. is there. Therefore, the photoacoustic mammography apparatus can image the oxygenated state of hemoglobin by detecting blood distribution in the subject, hemoglobin concentration distribution in the blood, and photoacoustic waves from irradiation light of different wavelengths. For this reason, the conventional X-ray mammography apparatus displays the internal structure of the subject in which the X-ray transmittance generated mainly due to the difference in tissue density is displayed, whereas the new blood vessels generated around the cancer tissue It is expected as a modality that can estimate cancer density and blood oxygen level, and can perform cancer diagnosis with higher accuracy and reliability.

  Patent Document 2 describes that, in a photoacoustic mammography apparatus, a photoacoustic wave is acquired by irradiating a subject with light while the subject is pressed by a holding plate in order to allow light to reach a deep portion of the subject. ing.

JP Patent Publication No. 2009-285345 Japanese Patent Laid-Open No. 2010-017426

  In the photoacoustic mammography apparatus described in Patent Document 2, a photoacoustic mammography apparatus that enables a more reliable diagnosis is required.

The photoacoustic apparatus of the present invention that solves the above problems is a photoacoustic apparatus that acquires information inside the subject based on an acoustic wave generated from the subject irradiated with light,
A holding member that holds the subject, a pressure information obtaining unit that obtains pressure information applied to the subject by the holding member, and a control that causes the display unit to display the pressure information and information inside the subject. And the control means displays, on the display means, a cross-sectional image of a cross section inside the subject as information inside the subject, and pressure information on the cross section as the pressure information. It is displayed on the display means .

  It is possible to provide a subject information acquisition apparatus that enables a more reliable diagnosis.

The figure showing 1st embodiment of this invention The figure explaining other structures of 1st embodiment of this invention The figure showing 2nd embodiment of this invention The figure showing 3rd embodiment of this invention The figure explaining arrangement | positioning of the load sensor in connection with 3rd embodiment of this invention. The other figure explaining arrangement | positioning of the pressure sensor in connection with 3rd embodiment of this invention. The figure which shows the outline of the ultrasonic echo signal in connection with 2nd embodiment of this invention The figure explaining the detail of the control means in connection with embodiment of this invention The figure showing the example of the display image structure of this invention

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

(First embodiment)
FIG. 1 shows the configuration of the first embodiment of the present invention. The subject information acquisition apparatus of this embodiment includes a holding plate 101 (101a, 101b) that is a compression plate that holds and compresses a subject, a laser light source 104 that is an irradiation unit, and a transducer array 105 that is a photoacoustic wave detection unit. A photoacoustic signal processing unit 106 and an image reconstruction unit 107 that are image signal generation units, a pressure calculation unit 114 that is a pressure information acquisition unit, and a control unit 128. Here, the laser light source 104 as an irradiation unit irradiates the subject with irradiation light, and the transducer array 105 as an acoustic wave detection unit receives an acoustic wave generated inside the subject by the irradiation light and receives an electrical signal. Is output. The photoacoustic signal processing unit 106 and the image reconstruction unit 107 that are image signal generation units generate signals for forming an acoustic wave image based on the electrical signals output from the transducer array 105 that is an acoustic wave detection unit. To do. The pressure calculation unit 114 serving as a pressure information acquisition unit acquires pressure information applied to the subject by the holding plate 101 serving as a compression plate. The control unit 128 displays the acoustic wave image and the pressure information on the display unit 115. It is what is displayed. These improve the reliability of diagnosis using an acoustic wave image. More specifically, in the photoacoustic mammography apparatus, which is an object information acquisition apparatus, it is possible to obtain effective image information for the distribution of blood and blood components in the object. Can be used as auxiliary information during diagnosis. In other words, the pressure information applied to the subject is information useful for determining the reliability of the photoacoustic image because the subject information acquisition device acquires a photoacoustic image that images information about the blood of the subject. . Moreover, since the pressure may affect the blood flow and the reproducibility of photoacoustic wave measurement may be impaired, it can be expected to use pressure information as information for confirmation.

  In the configuration shown in FIG. 1, as a preferred form, the laser is transmitted to the subject via the light transmission means 103 made of an optical fiber that transmits light from the laser light source 104 that is an irradiation means, and the holding plate 101b that is a compression plate. A light irradiating unit 102 for irradiating light, a load sensor 108 for detecting a load applied to the compression plate 101a (sometimes referred to as a load sensor), and a column 109 for holding the holding plate 101 as a compression plate. Yes. Also, information necessary for pressure calculation by the pressure calculation unit 114 as pressure information acquisition means, specifically, a CCD camera 110 and a CCD camera for calculating the contact area between the holding plate 101 as a compression plate and the subject. An image generation unit 111, a contour extraction unit 112, a contact area calculation unit 113 as an area detection unit, and an illumination unit 116 are further provided. The control means 128 also serves as control of the laser light source 104, the ultrasonic transducer array 105, and the like as a preferred form.

  The configuration shown in FIG. 1 and the configurations shown in FIG. 2, FIG. 3, and FIG. 4 to be described later can be said to be a preferable form in a subject information acquisition apparatus that acquires a photoacoustic image. This will be described below.

  In the configuration in which the pressure sensor is arranged on the entire surface of the holding plate as described in Patent Document 1, a photoacoustic image is obtained that the laser light irradiation and the photoacoustic signal cannot be satisfactorily performed when the photoacoustic image is acquired. There is a new problem peculiar to the subject information acquiring apparatus.

  That is, since the photoacoustic wave is a kind of ultrasonic wave, the subject, the holding plate, and the ultrasonic transducer for detecting the photoacoustic wave need to be arranged in acoustic contact with each other. In particular, in order to detect the weak photoacoustic signal generated inside the subject, if the attenuation or reflection of the photoacoustic wave occurs at these contact surfaces, the intensity of the received photoacoustic signal decreases and the SNR deteriorates. It is not preferable to sandwich a material or structure other than the acoustic matching material. In addition, in order to efficiently irradiate laser light, it is necessary to have a structure with high laser light transmission between the subject and the holding plate, and the irradiation unit for irradiating the laser light is close to the holding plate and is irradiated with light. It is not preferable to provide a material or structure that causes light absorption or reflection between the portion and the holding plate.

  In addition, a pressure sensor such as a piezoelectric element needs to be placed in contact with the surface of the subject or the holding plate in order to directly measure the pressure. However, a solid-type pressure measuring element such as a piezoelectric element generally has a high acoustic impedance, and the subject When sandwiched between holding plates and the like, strong reflection of photoacoustic waves tends to occur.

  As described above, in an apparatus that fixes a subject (breast) with a holding plate that holds the subject and detects light irradiation and photoacoustic waves through the holding plate, the device can cover a wide area on the surface of the holding plate. The structure in which the pressure sensor is provided is not preferable, and improvement has been required.

  For these reasons, the subject information acquisition apparatus having the configuration shown in FIG. 1 as an example of the present embodiment and the subject information acquisition apparatus having the configuration shown in FIGS.

  Next, the operation of the subject information acquiring apparatus configured as shown in FIG. 1 will be described.

  First, acquisition and display of a photoacoustic wave image will be described. Two holding plates 101 (101a, 101b), which are compression plates, are held by a support 109, and the distance between the holding plates 101 (101a and 101b) is adjusted manually or by motor drive to compress and hold the subject. The holding plate 101b is formed of a resin material (for example, PC, PMMA, etc.) having high light transmissivity in at least the wavelength of the laser pulse light generated by the laser light source 104 serving as the irradiation unit and the emission wavelength band (visible range) of the illumination unit 116. The The holding plate 101a is formed of a material having a high photoacoustic wave permeability and a small difference in acoustic impedance from the subject to prevent reflection of the photoacoustic wave at the boundary, for example, polymethylpentene polymer TPX (R). It is preferable. The sonic laser light source 104, which is an irradiating means, generates laser pulse light having a specific wavelength of 650 nm to 1100 nm in response to a drive command from the control means 128, and the generated pulse light propagates through the optical transmission means 103 and is held by the light irradiation unit 102. The subject is irradiated through the plate 101b. The photoacoustic wave generated in the subject by the irradiated light pulse is received by the ultrasonic transducer array 105 which is an acoustic wave detecting means via the holding plate 101a. The ultrasonic transducer array 105 is opposed to the light irradiation unit 103 and the holding plate 101, and is preferably composed of a two-dimensional array. The ultrasonic transducer array 105 and the light irradiation unit 102 may be scanned on the holding plate 101 while maintaining the facing relationship. The photoacoustic signal received by each element of the ultrasonic transducer array 105 is subjected to signal processing such as amplification and digitization by the photoacoustic signal processing unit 106 that constitutes the image signal generation unit, and the photoacoustic signal that also constitutes the image signal generation unit. The image reconstruction unit 107 converts the image data into three-dimensional image data. In the photoacoustic image reconstruction unit 107, based on the signal from each element on the ultrasonic transducer array 105, the arrival time of the photoacoustic wave from the arrival time of the photoacoustic wave and the position of each element, that is, the light intensity An acoustic wave generation intensity distribution is calculated and stored as three-dimensional image data. For the calculation of the photoacoustic wave generation intensity distribution, a delay and sum method, a back projection method, a migration method, or the like can be used.

  Since the photoacoustic wave generation intensity is proportional to the absorption rate of the irradiation pulsed light at each point, the blood in the subject is made to match the wavelength of the pulsed light generated by the laser light source 104 as the irradiation means with the absorption wavelength of blood. Distribution image data can be calculated. Similarly, image data of hemoglobin concentration distribution can be created by matching the wavelength of pulsed light with the absorption wavelength of hemoglobin. Alternatively, pulsed light generated by the laser light source 104 may be pulsed light having a plurality of wavelengths, and spectroscopic image data may be created by comparing photoacoustic wave generation intensity distributions with respect to irradiation pulsed light of each wavelength. For example, distribution image data of blood oxygen concentration can be created by comparing photoacoustic wave generation intensity distributions by a plurality of wavelength pulse lights in accordance with the difference in absorption wavelengths of oxyhemoglobin and deoxyhemoglobin.

  The ultrasonic transducer array 105 that is an acoustic wave detection unit and the light irradiation unit 102 are scanned by a scanning unit (not shown) on the holding plate 101 that is a compression plate, so that the tertiary of the entire area in contact with the holding plate 101 is obtained. Original image data can be acquired. The three-dimensional image data created by the photoacoustic image reconstruction unit 107 constituting the image signal generation unit is sent to the control unit 128.

  The compression pressure is measured as follows.

  Preferably, when the subject is held and fixed using the holding plate 101 that is a compression plate, the ultrasonic transducer array 105 that is an acoustic wave detecting unit and the light irradiation unit 102 are moved to the retracted position by a scanning unit (not shown). Moving. The retreat position may be outside the imaging field angle of the CCD camera 110.

  An illuminating unit 116 made of, for example, an LED light source is disposed at the peripheral edge of the holding plate 101b, and illuminates the holding plate 101b by transmitting illumination light. The CCD camera 110 images the holding plate 101b surface. At this time, most of the irradiation light from the illuminating means 116 propagates while being substantially totally reflected inside the holding plate 101b. However, the optical refractive index is different between the contact surface and the non-contact surface of the subject with respect to the holding plate 101b. Therefore, a contrast difference is likely to occur on the imaging screen of the CCD camera 110. For this reason, in particular, the subject contact surface can be detected based on the contrast difference between the contact surface and the non-contact surface, and the boundary edge is particularly emphasized.

  The CCD camera image generation unit 111 generates a captured image of the CCD camera 110. At this time, contrast enhancement of image luminance may be performed. The created captured image information is subjected to contour extraction by the contour extraction unit 112, and an area inside the boundary is calculated by a contact area calculation unit 113 which is a region detection means. Specifically, the contour extraction unit 112 may perform contour extraction using a spatial differential filter. Preferably, the boundary between the contact region and the non-contact region is interpolated with a single connection boundary line by determining whether the contour is connected or not. The contact area calculation unit 113, which is a region detection unit, may count pixels within the boundary (subject contact portion). In addition to this, various methods used in normal image processing may be used to calculate the subject contact area from the image captured by the CCD camera 110. In particular, the image captured by the CCD camera 110 without performing contour extraction may be used. The image may be directly binarized.

  Further, the image data from the CCD camera image generation unit 111 may be input to the control unit 128 and displayed together with the photoacoustic image as will be described later.

  The load sensor 108 may be a load cell element such as a magnetostrictive load cell, a capacitance load cell, a gyro load cell, or a strain gauge load cell. The pressing force applied to the holding plate is detected by placing it on the holding plate 101 holding portion of the column 109, and the value is sent to the compression pressure calculation unit 114 which is a pressure information acquisition unit. The compression pressure calculation unit 114 calculates the compression pressure from the compression force measured by the load sensor 108 and the subject contact area calculated by the contact area calculation unit 113 which is a region detection unit. The calculated compression pressure is converted to a unit of mmHg that can be easily compared with blood pressure and the like, and is sent to the control means 128.

  Next, the control means 128 will be described. FIG. 8 shows the control means 128 in more detail. The control unit 128 includes a main control unit 132, an input unit 133, an image processing unit 134, and a storage unit 135.

  The main control unit 132 controls acquisition of photoacoustic waves including driving of the laser light source 104 serving as the irradiation unit described above. Prior to the acquisition of the photoacoustic image data, control for measuring the compression pressure is performed. Furthermore, when acquiring the photoacoustic image data while scanning the ultrasonic transducer array 105 and the light irradiation unit 102 as acoustic wave detecting means, the photoacoustic wave including the driving of the scanning unit (not shown) and the laser light source 104 is used. Control acquisition. The imaging conditions are input from the input unit 133, and the photoacoustic image data is acquired according to the conditions. At the same time, the display image data to be displayed on the display unit 115 is generated by the input from the input unit 133 as follows. Take control. The main control unit 132 includes a microprocessor such as a CPU and MPU for performing these controls, a RAM, a ROM, various buses for data transfer, a communication interface, and the like.

  In the image processing unit 134, based on the three-dimensional image data created by the photoacoustic image reconstruction unit 107 constituting the image signal generation means, a cross-sectional two-dimensional image of the photoacoustic image specified by the input of the input unit 133, Display images such as projected two-dimensional images and rendered images are created. From the input unit 133, the position and direction of the cross section of the cross-sectional two-dimensional image, the direction of the projection plane of the projected two-dimensional image, the viewpoint direction of the rendering image, and the like can be designated. The image processing unit 134 creates desired display image data in accordance with the input from the input unit 133. Further, noise removal, filter processing, contrast and color correction are performed on the display image data. The image processing unit 134 can be used in combination with the same microprocessor as the main control unit 132, but can preferably be configured using a GPU dedicated to image processing. The storage unit 135 stores various parameters input from the input means for the drive control and display control, and parameters originally fixed to the apparatus. Further, the storage unit 135 stores various data. As stored data, photoacoustic image data created by the photoacoustic image reconstruction unit 107 constituting the image signal generation unit, pressure value data calculated by the compression pressure calculation unit 114 as pressure information acquisition unit, patient ID Examinee information such as name and name. Furthermore, various diagnostic information useful for diagnosis is recorded. Diagnostic information includes blood pressure history (past maximum / minimum blood pressure, etc.), body fat percentage, BMI (body mass index), age, cup size (difference between top bust and under bust). Further, an image by another modality such as X-ray mammography or MRI image or a photoacoustic image captured in the past can be transferred and recorded in the storage unit 135 through a communication interface of the main control unit 132 or the like. More preferably, when displaying the image data of these other modalities with the photoacoustic display image using the image processing unit 134, for example, when displaying the photoacoustic image as a cross-sectional two-dimensional image, the other modality image Also, it is preferable that other modality image data is generated by converting the coordinates of other modality image data so that an image of the same cross section can be displayed as a two-dimensional cross-sectional image. Furthermore, image data from the CCD camera image generation unit 111 may be stored, and various display images displayed on the display unit may be stored. The storage unit 135 can be composed of various storage devices, but is preferably composed of a large-capacity storage device such as an HDD in order to store various image data.

  The main control unit 132 displays the display image data of the photoacoustic image created by the image processing unit 134 and various data recorded in the storage unit 135 on the display unit 115. FIG. 9 shows a configuration example of various display data displayed on the display unit 115. 136 is a subject information display area, 137 is a photoacoustic image display area, 138 is a photoacoustic image control parameter display area, 139 is another modality image display area, and 140 is a pressure value display area. In the subject information display area 136, information on the subject such as patient ID, name, past maximum / minimum blood pressure, body fat percentage, BMI, age, and cup size is displayed. In the photoacoustic image display area 137, photoacoustic display images such as a cross-sectional two-dimensional image, a projected two-dimensional image, and a rendering image of the photoacoustic image designated by the input of the input unit 133 are based on the three-dimensional image data. Is displayed. In the photoacoustic image control parameter display area 138, various conditions of the photoacoustic display image designated by the input of the input unit 133, for example, which of the cross-sectional two-dimensional image, the projected two-dimensional image, and the rendering image are selected, The position and direction of the cross section of the cross-sectional two-dimensional image, the direction of the projection plane of the projected two-dimensional image, the viewpoint direction of the rendering image, and the like are displayed. Further, image processing for the photoacoustic display image, for example, the type and conditions of the used image filter, and conditions for contrast and color correction are displayed. In the other modality image display area 139, images such as X-ray mammography and MRI images and their imaging conditions are displayed so that they can be compared with the photoacoustic image. In the pressure value display area 140, the pressure value calculated by the compression pressure calculation unit 114, which is a pressure information acquisition unit, is displayed in mmHg units.

  In addition, the other modality image display area 139 does not display the image of the other modality, but uses the image data from the CCD camera image generation unit 111 to confirm the fixed state of the subject, and the subject captured by the CCD camera 110 is used. A sample outline image may be displayed. This configuration has an advantage that the fixed state of the subject at the time of imaging can be confirmed by displaying the subject outline image in parallel with the photoacoustic image.

  The display image and various data displayed on the display unit 115 are recorded in the storage unit 135 or transferred to the outside via the communication interface of the main control unit 132. Thereby, it is possible to compare the photoacoustic images when performing the follow-up observation of the subject. In addition, by recording an object outline image captured by the CCD camera 110, it is possible to confirm the object fixed state for imaging at different points in time.

  Here, the photoacoustic image reconstruction unit 107 constituting the image signal generation unit, the CCD camera image generation unit 111, the contour extraction unit 112, the contact area calculation unit 113 which is a region detection unit, and the compression pressure calculation which is a pressure information acquisition unit. Although the unit 114 and the control unit 128 have been described as individual blocks, in actuality, the processing of each of the above blocks can be performed on software using a PC.

  Further, the measurement of the compression pressure may be performed before or after the acquisition of the photoacoustic image as described above, and further according to the scanning of the ultrasonic transducer array 105 which is an acoustic wave detection means and the light irradiation unit 102. The CCD camera 110 may be performed during acquisition of the photoacoustic image as long as the entire area of the subject contact surface can be imaged.

  In the present embodiment, the illumination means 116 is provided on the peripheral edge of the holding plate 101b, which is a compression plate, and the illumination light propagates inside the holding plate 101b. It is sufficient that the subject contact area is detected by imaging and the configuration is not particularly limited. For example, the loss of the incidence of pulsed light from the light irradiation unit 103 to the inside of the subject can be suppressed by configuring the holding plate 101b to be thin and illuminating from the CCD camera 110 side of the holding plate 101b.

  In the above configuration, the area of the subject contact area is obtained from the imaging of the CCD camera 110, but the contact area can also be calculated using a different optical imaging device. FIG. 2 shows a configuration using a time-of-flight camera. In the figure, reference numerals 101 to 115 denote the same components as described above, and in particular, the acquisition and display of the photoacoustic wave image are performed in the same manner as described above, and thus the description thereof is omitted.

Reference numeral 117 denotes a time-of-flight camera, 118 denotes a three-dimensional shape processing unit, and 119 denotes a contact area calculation unit that is a region detection unit. The time-of-flight camera 117 measures a three-dimensional shape of the subject surface sandwiched between holding plates 101 that are compression plates. The light source that emits the modulated irradiation light, the light receiving sensor, and the output of the light receiving sensor are phase-detected, and the flight time (delay time) and speed of light (3 × 10) until the irradiation light is reflected by the object and reaches the sensor. ⁸ m / s), and a processing means for measuring the distance to the subject.

  The three-dimensional shape data of the subject surface calculated by the time-of-flight camera 117 is input to the three-dimensional shape processing unit 118. The three-dimensional shape processing unit 118 extracts the subject contact area based on the position information of the time-of-flight camera 117 and the holding plate 101 measured in advance and the three-dimensional shape data of the subject surface. That is, the contact area is optically detected using an optical three-dimensional measurement technique. That is, the intersecting curved surface of the subject surface and the surface of the holding plate 101 is obtained as boundary line data between the contact area and the non-contact area of the subject, and is input to the contact area calculation unit 119 which is an area detection unit. The contact area calculation unit, which is an area detection means, calculates the contact area area of the subject on the holding plate 101 based on the boundary line data. The calculated subject contact area is used for the compression pressure calculation together with the compression force measured by the load sensor 108 in the compression pressure calculation unit 114 which is a pressure information acquisition unit as in the configuration of FIG.

  In the present configuration using the time-of-flight camera 117, the subject contact area on the holding plate 101 is calculated from the three-dimensional shape of the subject surface sandwiched between the holding plates 101 and the surface position of the holding plate 101. For this reason, the time-of-flight camera 117 can be placed at a position where the space between the holding plates 101 can be seen, and the contact area measurement can be performed regardless of the positions of the ultrasonic transducer array 105 and the light irradiation unit 102 as acoustic wave detecting means on the holding plate 101. And the compression pressure at the time of acquiring the photoacoustic image can be calculated on time. Further, since the contact area measurement is not performed through the holding plate 101 as compared with the configuration of FIG. 1, the influence of the contact area detection error due to dirt on the holding plate 101 is small. Even in the case of this configuration, the three-dimensional shape processing unit 118, the contact area calculation unit 119 that is a region detection means, and the like are built on the processing configuration as software on the PC and do not need to be configured as actual circuit blocks. The configuration is the same as that of FIG.

  Although the time-of-flight camera 117 is used here, the same effect can be obtained by using a laser scanning three-dimensional measuring apparatus capable of optically three-dimensionally measuring the subject surface.

  Further, in this configuration, the three-dimensional shape at the time of fixation of the breast, which is the subject, obtained using the time-of-flight camera 117 and the three-dimensional shape processing unit 118 is stored in the storage unit 135 in the control unit 128 and displayed. Can be displayed. For example, in the display configuration example shown in FIG. 9, the three-dimensional shape when the subject is fixed is displayed in the other modality image display area 139 using the data from the three-dimensional shape processing unit 118 according to the display input setting from the input unit 133. The rendered image can be displayed simultaneously with the photoacoustic image. Further, when the photoacoustic display image is displayed as a cross-sectional two-dimensional image, a projected two-dimensional image, or a rendered image, the subject displaying the cross-sectional position, the projected plane direction, the viewpoint direction of the rendered image, etc. in the other modality image display area 139 The image is superimposed on the shape image. In this configuration, since the positional relationship between the outer shape when the subject is fixed and the photoacoustic display image are associated with each other, there is an advantage that the positional relationship between the imaging region and the entire subject becomes clear. In addition, the three-dimensional shape data at the time of fixing the subject is recorded in the storage unit 135 or transferred to the outside via the communication interface of the main control unit 132 and stored, so that the subject fixed state can be obtained for imaging at different times. The comparison and confirmation are possible as in the case described above.

  As another configuration example, contact area measurement may be performed using an optical sensor that scans together with the ultrasonic transducer array 105 and the light irradiation unit 102 as acoustic wave detection means. The optical sensor is disposed adjacent to the light irradiation unit 102 so as to face the subject via the holding plate 101, and is directed to the subject from a light pulse emitted from the light irradiation unit 102 toward the subject or from a separately provided light source. The reflected light from the object surface of the irradiated light is detected. A position where a change in the amount of reflected light by the optical sensor scanned simultaneously with the light irradiation unit 102 is detected as a boundary line between the contact area and the non-contact area of the subject with respect to the holding plate 101, and similarly from the boundary line position, as described above. The subject contact area may be calculated. The optical sensor can be configured to form a plurality of arrays according to the opening width of the light irradiation unit 102 and detect a boundary line by using each optical sensor position on the array and the scanning position of the light irradiation unit 102. . In this configuration, the subject contact area can be calculated with a simple configuration compared to the above configuration.

  As described above, in this embodiment, the area of the subject region optically imaged is detected, and the pressure value applied to the holding plate is calculated from the load measurement value of the load sensor disposed on the holding plate holding portion of the support column 109. Therefore, the laser irradiation unit and the ultrasonic transducer array that receives the photoacoustic signal can be arranged in contact with the holding plate. As a result, it is possible to calculate pressure in a manner that does not hinder laser irradiation on the subject and acquisition of photoacoustic waves from the subject. Further, when scanning the laser irradiation unit and the ultrasonic transducer array, it is possible to make the imaging field angle of an imaging means such as a CCD camera or a time-of-flight camera out of the scanning range. It can be set as the structure which does not become.

(Second embodiment)
A second embodiment will be described with reference to FIG. In the figure, 101 to 109, 113 to 115, and 128 are the same constituent elements as those of the previous embodiment, and thus the description thereof is omitted or simplified. Further, the details of acquisition and display of the photoacoustic wave image are performed in the same manner as in the previous embodiment, and thus description thereof is omitted. However, the photoacoustic signal processing unit 106 performs signal processing such as amplification and digitization on the received ultrasonic signal in addition to the received photoacoustic wave signal. In FIG. 3, 120 is a transmitted wave detecting means, and 121 is an ultrasonic transmitting means.

  Prior to acquisition of the photoacoustic wave signal at each position of the ultrasonic transducer array 105, ultrasonic waves are transmitted and received from the ultrasonic transducer array 105 to contact the holding plate 101a in a region facing the ultrasonic transducer array 105 of the subject. The area to be detected is detected. Although details of this will be described later, that is, the contact area between the subject and the holding plate which is the compression plate is acoustically detected. Specifically, the contact area is detected based on whether or not ultrasonic waves are received by the ultrasonic transducer array. Then, as described above, the photoacoustic wave signal is acquired by irradiating the pulsed light from the light irradiation unit 102. When scanning and acquiring a photoacoustic wave image, the ultrasonic transducer array 105 and the light irradiation unit 102 are moved by a scanning unit (not shown), and then the contact area is detected and the photoacoustic wave signal is acquired at the next position. By repeating this, detection of the contact area of the subject with the holding plate 101a and acquisition of the photoacoustic wave image are performed. Note that either the detection of the contact portion by ultrasonic transmission / reception or the order of the photoacoustic wave signal by pulse light irradiation may be performed first.

  The ultrasonic wave is transmitted from all or a part of the elements in the ultrasonic transducer array 105 toward the subject by the drive signal from the ultrasonic transmission unit 121. The transmitted ultrasonic wave passes through the holding plate 101a, enters the subject in an area in contact with the holding plate 101a, and generates an ultrasonic echo or an ultrasonic wave reflected by the opposing holding plate 101b in the subject. The generated ultrasonic echo inside the subject and the ultrasonic reflected wave of the holding plate 101b are received by an element below the contact area on the ultrasonic transducer array 105. On the other hand, in the element located at a position where the subject does not contact the holding plate 101a, the transmitted ultrasonic wave does not enter the subject, and the reflected ultrasonic wave that has caused multiple reflections in the holding plate 101a is received. Therefore, an area in contact with the holding plate 101a can be detected in the reception area of the ultrasonic transducer array 105 from the reception signal of each element in the ultrasonic transducer array 105 for ultrasonic transmission.

  FIG. 7 shows a schematic diagram of the received signal of the ultrasonic echo at the ultrasonic transducer array 105. FIG. 7A shows a received ultrasonic signal at an element in contact with the subject, and FIG. 7B shows a received ultrasonic signal at an element not in contact with the subject. Reference numeral 132 denotes an ultrasonic reflection signal at the interface of the holding plate 101 a opposite to the ultrasonic transducer array 105, 133 denotes an ultrasonic echo signal within the subject, and 134 denotes multiple reflection from the interface between the holding plate 101 a and the ultrasonic transducer array 105. Signal.

  In the element located in the region where the subject and the holding plate are in contact with each other as shown in FIG. 7A, the transmission ultrasonic wave is caused by the difference in acoustic impedance between the holding plate 101a and the subject at the interface between the holding plate 101a and the subject. The resulting reflected signal 132 is received. Thereafter, an ultrasonic echo signal 133 is received from the tissue inside the subject. The reflected signal 132 is received at the time when the transmitted ultrasonic wave propagates through the holding plate 101a after ultrasonic transmission, and thus appears at a time position determined from the reception start time for each element. The ultrasonic echo signal 133 continues to be received after the reflected signal 132 for a time that substantially propagates through the thickness of the subject.

  In the element in the region where the subject is not in contact with the holding plate shown in FIG. 7B, air or the like is generally in contact with the interface on the side opposite to the arrangement side of the ultrasonic transducer array 105 of the holding plate 101a. Therefore, a larger reflected signal 132 is generated than when the subject is in contact. Furthermore, the ultrasonic waves reflected at this interface run backward through the holding plate 101a, and a multiple reflection signal 134 due to multiple reflection at the interface between the holding plate 101a and the ultrasonic transducer array 105 is received. The time interval between the multiple reflection signal 134 and the ultrasonic reflection signal 132 is determined by the sound velocity of the ultrasonic waves in the holding plate 101a and the holding plate 101a. A signal does not appear at a timing other than the arrival timing of the multiple reflection signal 134.

  As described above, the transmitted wave detection unit 120 uses the compression plate 132 based on the signal strength of the reflected signals 133 and 134 at the interface opposite to the arrangement side of the ultrasonic transducer array 105 of the holding plate 101a 132 that appears at a specific position of the received signal. The contact or non-contact between a certain holding plate and the subject can be determined. That is, using the difference in reflection intensity caused by the difference in acoustic impedance between the subject and air, the element whose reflection intensity of the received signal is below a certain value is determined as an element located in the area where the holding plate and the object are in contact it can.

  Further, the presence or absence of the multiple reflection signal 134 is determined at a fixed time after the reception of the reflection signal 132, and an element where the multiple reflection signal 134 does not appear can be determined as an element located in a region where the holding plate and the subject are in contact with each other.

  Further, the presence / absence of the ultrasonic echo signal 133 is determined by calculating the signal amplitude intensity over a specific time region of a certain time or more, and the region where the ultrasonic echo signal 133 is received is in contact with the holding plate and the subject. It can be determined that the element is located at. The presence / absence of the ultrasonic echo signal 133 may be obtained by using the average of the signal amplitude intensity over a fixed time, but the ultrasonic echo signal 133 is received continuously unlike the reflected signal 132 and the multiple reflected signal 134. Therefore, it is determined using a time when a signal with a constant intensity continues, or when the time dispersion of the signal amplitude intensity with respect to the average signal amplitude intensity is equal to or less than a predetermined value, it is determined that the ultrasonic echo signal 133 is present The statistical processing may be used.

  All or any of the above determinations can be combined.

  The ultrasonic reception signals of the respective elements of the ultrasonic transducer array 105 are subjected to signal processing such as amplification and digitization by the photoacoustic signal processing unit 106 and input to the transmitted wave detection means 120. The transmitted wave detection means 120 determines whether each element has received an ultrasonic echo in the subject or an ultrasonic wave reflected by the holding plate 101b from the digitized ultrasonic reception signal. Subsequently, the element identification number of the element that has received the ultrasonic echo or the ultrasonic reflected wave, or the positional information on the ultrasonic transducer array 105 is input to the contact area calculation unit 113 that is the area detection means.

  The contact area calculation unit 113, which is an area detection means, calculates the subject contact area in the reception area of the ultrasonic transducer array 105 based on the identification number or position information of the element that has received the ultrasonic echo or ultrasonic reflected wave. To do. For example, when the ultrasonic transducer array 105 is composed of elements having an equal reception area, the element area may be multiplied by the number of elements that have received an ultrasonic echo or an ultrasonic reflected wave. When the element areas are different, the integration may be performed taking into account the corresponding element area based on the element identification number or position information. When scanning the ultrasonic transducer array 105, the subject contact area at the position of each ultrasound transducer array 105 is added to obtain the subject contact area for the entire scanning region. In this way, the contact area is detected acoustically.

  The calculated subject contact area is used for the compression pressure calculation together with the compression force measured by the load sensor 108 in the compression pressure calculation unit 114 as in the configuration of FIG. And pressure information are displayed on the display unit 115 at the same time (displayed simultaneously).

  In the above description, the configuration in which the acquisition of the photoacoustic wave signal and the transmission / reception of the ultrasonic wave for measuring the contact area of the subject are performed by the same ultrasonic transducer array 105 has been described. In the case of acquisition, photoacoustic wave signal reception and ultrasonic transmission / reception can be performed by separate transducer arrays. It is also possible to perform photoacoustic wave signal reception processing and ultrasonic transmission / reception processing as separate components.

  A photoacoustic signal is a type of ultrasonic wave, but generally requires a wide-band transducer and receiving means, while a transducer that performs both transmission and reception of ultrasonic waves has high reception sensitivity and resistance to high voltage applied during transmission. It is desirable to have.

  In order to avoid crosstalk between acquisition of photoacoustic wave signals and transmission / reception of ultrasonic waves, it is preferable to acquire signals for the necessary propagation times of photoacoustic waves and ultrasonic waves at independent timings. On the other hand, the time required for the entire photoacoustic wave image and contact area detection by making the use band of transmission / reception ultrasonic waves different from that of photoacoustic waves, eliminating crosstalk and simultaneously performing photoacoustic wave signal acquisition and ultrasonic transmission / reception Can be shortened.

  When photoacoustic wave signal acquisition and ultrasonic transmission / reception are performed at the same time, each signal processing band and transducer characteristics are individually set by performing photoacoustic wave reception and ultrasonic transmission / reception with different elements. It is possible and preferable.

  In addition, when a photoacoustic wave image is acquired by scanning and photoacoustic wave signal reception and ultrasonic transmission / reception are performed by separate transducer arrays, the position of each transducer is determined, and the photoacoustic wave signal acquisition region and the contact area are measured. By making the detection areas different, the crosstalk can be spatially separated. In particular, the scanning of the photoacoustic wave receiving transducer array and the light irradiating unit and the scanning of the ultrasonic receiving transducer array can be performed simultaneously and independently.

  The above configuration can shorten the time required for the entire photoacoustic wave image and contact area detection, and is therefore a suitable configuration for reducing the total time for holding the subject and suppressing the load on the subject.

  In this embodiment, the ultrasonic wave is transmitted from the ultrasonic transducer array 105 or a separately prepared transducer, and the echo reflected in the subject is received, thereby detecting the contact area between the holding plate 101a and the subject. However, as a method for acoustically detecting the contact area, the contact area can be detected using a photoacoustic wave reception signal. That is, when the contact area between the subject and the holding plate as the compression plate is acoustically detected, the contact area is detected based on whether or not the photoacoustic wave is received by the ultrasonic transducer array. In this case, the photoacoustic wave signal received by each element on the ultrasonic transducer array 105 is determined by the photoacoustic signal processing unit 106 and contacted on the ultrasonic transducer array 105 as in the case of the ultrasonic wave reception signal. The area to be detected is detected. When scanning the ultrasonic transducer array 105, the contact area of the subject with respect to the entire region of the holding plate 101a is calculated by overlapping the contact regions at each position of the ultrasonic transducer array 105. This configuration has the advantage that the ultrasonic wave transmitting means is not required, and the subject contact area can be calculated simultaneously when the photoacoustic wave image is acquired.

  As described above, in the present embodiment, the area of the subject region is detected based on whether or not the ultrasonic wave or photoacoustic wave detected using the reception signal of the ultrasonic transducer array is transmitted through the holding plate, and this and the holding plate of the support 109 The pressure value applied to the holding plate is calculated from the load measurement value of the load sensor arranged in the holding unit. For this reason, the area of the subject region is detected at the same time as scanning for acquiring the photoacoustic image, and the configuration does not hinder the acquisition of the photoacoustic image.

(Third embodiment)
In the present embodiment, the pressure distribution on the holding plate in the subject contact area is detected, and the pressure distribution inside the subject is estimated using this, and displayed with the photoacoustic image at the same time (simultaneously). At this time, a configuration is adopted in which the pressure distribution in the subject contact area is detected so as not to hinder acquisition of the photoacoustic signal.

  FIG. 4 shows the configuration of the third embodiment of the present invention. Among the reference numerals in the drawings, those described in FIGS. 1 and 3 indicate the same components as those described for the first and second embodiments, respectively. The operations from the reception of the photoacoustic signal at the time of acquiring the photoacoustic image data to the creation of the three-dimensional image data by the photoacoustic image reconstruction unit 107 are the same as those in the first embodiment, and thus a part of the description is omitted. 122 is a holding frame, 123 is a weighted distribution calculating unit, 124 is a light-projecting-side pressure distribution calculating unit, 125 is an ultrasonic transducer array pressure measuring unit, 126 is a photoacoustic wave receiving-side pressure distribution calculating unit, and 127 is pressure information acquisition An object pressure distribution calculation unit as a means, 128 is a control means, and 129 is an array type load sensor in which load sensor elements are arranged.

  Photoacoustic image data is acquired in the same manner as in the first embodiment. However, it is assumed that the ultrasonic transducer array 105 and the light irradiation unit 103 are positioned to face each other, scan the holding plate 101 by a scanning unit (not shown), and acquire an image of the entire subject.

  First, the measurement of the pressure distribution in the contact area of the photoacoustic wave receiving side holding plate 101a in contact with the subject will be described. In this embodiment, photoacoustic image data acquisition and pressure distribution measurement of the subject contact area on the photoacoustic wave receiving side holding plate 101a side are performed simultaneously.

  The ultrasonic transducer array 105 is additionally provided with an array type load sensor array 129. The array type load sensor 129 has a size capable of measuring a load distribution in a range covering the opening area of the ultrasonic transducer array 105, and preferably detects a load value at a point corresponding to the array arrangement of each element of the ultrasonic transducer array 105. To do. Further, the relative position between the ultrasonic transducer array 105 and the array type load sensor 129 is set by the scanning direction of the ultrasonic transducer array 105.

  FIGS. 6A and 6B show specific examples of the element configuration of the ultrasonic transducer array 105, the element configuration of the array type load sensor 129, and the arrangement of each.

  FIG. 6A shows a configuration example when the ultrasonic transducer array 105 is scanned in the y-direction. Similar to the two-dimensional array of ultrasonic transducer arrays 105, array type load sensors 129 are two-dimensionally arranged, and the load sensor elements 131 of the array type load sensor 129 are arranged at the same pitch intervals as the transducer elements 130 on the ultrasonic transducer array 105. Has been placed. Further, the ultrasonic transducer array 105 and the array type load sensor 129 are set to have the same number of transducer elements in the vertical (x direction) and horizontal (y direction) of the ultrasonic transducer array 105 and the number of load sensor elements of the array type load sensor 129. Are arranged in the y direction. Each transducer element 130 on the ultrasonic transducer array 105 and each load sensor element on the array type load sensor 129 are scanned by the ultrasonic transducer array 105 by the width in the y direction as the photoacoustic image data is acquired. The positions of 131 overlap, and the load at each transducer element 130 before scanning can be detected by each load sensor element 131.

  Specifically, photoacoustic waves are received by the ultrasonic transducer array 105 in synchronization with the irradiation from the light irradiation unit 102. Based on the received signal of each transducer element 130 amplified and digitized by the photoacoustic signal processing unit 106, the transmitted wave detection means 120 determines whether the subject is in contact with or not in contact with each transducer element 130. At the same time, each load sensor element 131 of the array type load sensor 129 performs load measurement. The measured load value is stored in the ultrasonic transducer array pressure measurement unit 125 for the time required for scanning. The ultrasonic transducer array upper pressure measurement unit 125 stores and holds the load value measured by the array type load sensor 129 with the width in the y direction of the ultrasonic transducer array 105 as a scanning unit, and also stores the load stored before one scanning unit. Based on the value and the determination of the transmitted wave detection means 120, the pressure value of the transducer element 130 located in the contact area between the holding plate and the subject is calculated and output to the photoacoustic wave reception side pressure distribution calculation unit 126. Here, the pressure value of the transducer element 130 located in the contact area between the holding plate and the subject is the load value measured by the load sensor element 131 of the array type load sensor 129, and the corresponding ultrasonic transducer element 130 has the same value. Calculate by dividing by area. In the photoacoustic wave reception side pressure distribution calculation unit 126, the position of each transducer element 130 in contact with the photoacoustic wave reception side holding plate 101a based on the scanning position information of the ultrasonic transducer array 105 scanning accompanying the acquisition of the photoacoustic image data. The pressure value at is calculated as the pressure distribution in the contact area.

  Here, according to the scanning direction, the load measurement value from the array type load sensor 129 is first stored for one scanning unit, and the contact element pressure value is determined using the contact / non-contact determination from the transmitted wave detecting means 120. However, if the scanning direction is reversed, contact / non-contact determination from the transmitted wave detecting means 120 is stored for one scanning unit, and this is calculated using the load measurement value from the array type load sensor 129. You can also When the ultrasonic transducer array 105 is scanned in the x direction, the ultrasonic transducer array 105 and the array type load sensor 129 may be arranged side by side in the x direction.

  Further, when the scanning unit is set to the width of each transducer element 130, an array type load sensor 129 having a one-dimensional array can be used as shown in FIG. In FIG. 6B, the array type load sensor 129 is arranged with a width corresponding to one element of the transducer element 130 in both the x direction and the y direction, and the pressure of the transducer element 130 for one line each time the scanning unit moves in each direction. We will continue to measure. In particular, when the photoacoustic wave signal is weak in the acquisition of photoacoustic image data, when the SNR is improved by scanning the transducer elements in width and integrating the photoacoustic wave signals of the elements in the overlapping region, With this configuration, the pressure distribution in the contact area can be measured simultaneously with the photoacoustic image data acquisition. Furthermore, by selecting the number of element arrangements of the array type load sensor 129, it is possible to measure the pressure distribution suitable for the scanning method of the ultrasonic transducer array 105.

  Further, in the above description, the arrangement of the transducer elements 130 on the ultrasonic transducer array 105 and the arrangement of the load sensor elements 131 on the array-type load sensor 129 are made to coincide with each other for simplicity of explanation. In addition, the pressure value at the position of each transducer element 130 on the ultrasonic transducer array 105 can be obtained by interpolating each value of the load value measured by the array type load sensor 129 using the geometric relationship between the two. Is possible. Further, when interpolation is used, the transducer elements 130 and the load sensor elements 131 do not have to be uniform, and may be converted into a pressure distribution by interpolation according to the size and arrangement of the elements. By using the measured pressure value and the contact / non-contact determination from the transmitted wave detecting means 120, the same pressure distribution can be measured.

  As described above, the load sensor element 131 is juxtaposed with the ultrasonic transducer array 105, and simultaneously with the scanning of the ultrasonic transducer array 105 at the time of photoacoustic image acquisition, pressure distribution measurement is performed at the same time. It becomes the composition which does not become.

  Next, measurement of the pressure distribution in the contact area of the irradiation-side holding plate 101b that contacts the subject will be described.

  The holding frame 122 holds the periphery of the holding plate 101 b via a plurality of load sensors 108 and is movably fixed to the column 109. The load sensor 108 is disposed around the holding plate 101 b so as to be outside the scanning area of the light irradiation unit 102 and the imaging area of the CCD camera 110. The holding frame 122 moves on the support column 109 manually or by motor drive, and holds the subject by adjusting the interval between the holding plates 101a and 101b. FIG. 5 shows an example of the arrangement of the load sensor 108, the holding frame 122, and the support column 109 that hold the holding plate 101b. The holding frame 122 is desirably a U-shaped body with an empty body side in order to secure and hold an imaging region of the breast that is the subject. A plurality of, for example N, load sensors 108 are arranged along the holding frame 122, preferably at equal intervals, and measure the load distribution on the holding plate 101b.

  The subject image captured by the CCD camera 110 is processed by the CCD camera image generation unit 111 and the contour extraction unit 112 in the same manner as in the first embodiment, and the subject contact area on the holding plate 101b is detected.

  The weight distribution calculation unit 123 calculates the load distribution on the holding plate 101b based on the outputs from the plurality of load sensors 108 arranged along the holding frame 122 as follows.

  A subject contact area on the holding plate 101b is detected from the output of the contour extraction unit 112. M sampling points are set in the subject contact area. The sampling point number M is preferably equal to or less than the number N−1 of the load sensors 108 arranged along the holding frame 122. Based on the positional relationship between the M sampling points and the N load sensors 108 and the outputs from the N load sensors 108, the loads at the M sampling points are calculated.

  For example, when the holding plate 101b has a high rigidity, the number N of the load sensors 108 is obtained as a formula of a moment with each load sensor 108 as a fulcrum. Further, an equation for balancing the load of M sampling points and the load balance of N load sensors 108 is obtained, and the load values at M sampling points may be obtained as unknowns for N + 1 conditional expressions. When M = N + 1, the contact load value of the subject at each sampling point can be obtained by solving the equation. Otherwise, it can be obtained by fitting using a regression method such as the least square method. You may obtain | require using statistical methods, such as a maximum likelihood method.

In the case of M = N + 1, specifically, the following simultaneous linear equations with the load values P _i (i = 1, 2,..., M) at M sampling points as unknowns may be solved. .

ここで、Ｒ_ｉ，ｊはｉ番目（ｉ＝１，・・・，Ｍ）のサンプリング点から、ｊ番目（ｊ＝１，・・・，Ｎ）の荷重センサ１０８までの距離、Ｒ’_ｊ，ｋはｊ番目（ｊ＝１，・・・，Ｎ）の荷重センサ１０８から、ｋ番目（ｋ＝１，・・・，Ｎ）の荷重センサ１０８までの距離をあらわす。またＱ_ｊはｊ番目（ｊ＝１，・・・，Ｎ）の荷重センサ１０８の計測した荷重値、

Here, R _{i, j} is the distance from the i-th (i = 1,..., M) sampling point to the j-th (j = 1,..., N) load sensor 108, and R ′ _{j , K} represents the distance from the jth (j = 1,..., N) load sensor 108 to the kth (k = 1,..., N) load sensor 108. Q _j is a load value measured by the jth (j = 1,..., N) load sensor 108,

はｊが１からＮまでのうちｊ＝ｋとなるものを除いた和をとることを表す。右辺はＮ＋１＝Ｍ行のベクトルであり、左辺は（Ｎ＋１）行Ｍ列、即ちＭ行Ｍ列の正方行列にＭ行のベクトルをかけたものであるので連立方程式として解くことができる。なおここでサンプリング点での荷重値Ｐ_ｉと荷重センサ１０８の計測した荷重値Ｑ_ｊは、保持板１０１ｂの表面法線に沿ってそれぞれ逆方向（例えば図４で各々上下方向）に働く荷重方向を正にとることとする。また保持板１０１ｂの重量を補正するために、荷重センサ１０８の計測した荷重値Ｑ_ｊは、保持板１０１で被検体を保持する以前の値を基準に、保持圧迫による増加分をとることが好ましい。

Represents taking the sum excluding those where j = k from 1 to N. The right side is a vector of N + 1 = M rows, and the left side is (N + 1) rows and M columns, that is, a square matrix of M rows and M columns multiplied by a vector of M rows, so that it can be solved as a simultaneous equation. Here, the load value P _i at the sampling point and the load value Q _j measured by the load sensor 108 are respectively applied in the opposite directions (for example, the vertical direction in FIG. 4) along the surface normal of the holding plate 101b. Is taken positively. In order to compensate the weight of the holding plate 101b, the load value Q _j measured load sensors 108, based on the previous value for holding the object by the holding plate 101, it is preferable to adopt the increase by the holding pressure .

When M ≠ N, the matrix on the left side does not become a square matrix, so the equation cannot be solved. However, the above equation becomes the maximum likelihood using the least square method or other statistical methods as a fitting equation for Q _j. it may be calculated the value of the Q _j. In this case, it is preferable that M ≦ N.

  If the sampling point number M is larger than the number N of the load sensors 108, the measurement accuracy is lowered. Therefore, the subject contact on the holding plate 101b based on the load values at the M sampling points obtained as described above. It is preferable to calculate the load distribution value at each point in the region by using an interpolation method such as linear interpolation, polynomial interpolation, wavelet interpolation or the like.

  The light projection side pressure distribution calculation unit 124 calculates the pressure distribution in the subject contact area on the holding plate 101b based on the load distribution value. In this embodiment, the load distribution value at the pixel position of the image data created by the CCD camera image generation unit 111 is calculated by interpolation, and this is divided by the area of the area element on the holding plate 101b corresponding to each pixel. Then, the pressure value in the vertical direction of the holding plate 101b at that point is calculated. By performing this for the pixels in the subject contact area, the pressure distribution in the subject contact area on the holding plate 101b is calculated. If necessary, the load value at the center position may be calculated by interpolation using a plurality of pixels as a unit, and the pressure distribution may be calculated using the average pressure value divided by the area of the plurality of pixels.

  When the rigidity of the holding plate 101b is not so high and distortion occurs, the above rigid body moment relationship is not established, but when the degree of distortion is small, the load distribution can be calculated as follows.

  Sampling points are taken over the entire holding plate 101b, and the measured values of the load sensors 108 when a certain point is loaded are approximately linearly related when the degree of distortion is small. That is, there is a linear relationship between the load value applied to a specific sample point and the measurement value obtained from a specific load sensor among the load sensors 108, and there is a load value applied to a different sample point. The effect on the measured value is also additive. Using this fact, the following load distribution is calculated.

  The measured value of each load sensor 108 when a unit load is independently applied to each sampling point spread over the entire holding plate 101b is stored as a table. This table may be created by actual measurement, or may be calculated by the finite element method using the elastic characteristic value of the holding plate 101b. The value of each element in this table is a linear constant proportional constant that the load applied to the specific sample point gives to the measurement value of a certain load sensor.

  Using this table, which is related to the sampling points included in the subject contact area on the holding plate 101b, an equation for giving a measurement value of each load sensor 108 using the above-described linear relationship is established as follows. Become. However, the number of sampling points included in the subject contact area is M ′, and the number of load sensors 108 is N.

ここでＰ_ｉ（ｉ＝１，２，・・・，Ｍ’）は被検体接触領域内の含まれるサンプリング点での荷重値、Ｑ_ｊはｊ番目（ｊ＝１，・・・，Ｎ）の荷重センサ１０８の計測した荷重値、Ｃ_ｉ，ｊはｉ番目のサンプリング点に与えた荷重値とｊ番目の荷重センサ１０８での計測値の 比例定数で、上記テーブルの要素である。

Here, P _i (i = 1, 2,..., M ′) is a load value at a sampling point included in the subject contact area, and Q _j is jth (j = 1,..., N). The load value C _{i, j} measured by the load sensor 108 is a proportional constant between the load value applied to the i-th sampling point and the measurement value obtained by the j-th load sensor 108, and is an element of the table.

When M ′ ≦ N, similarly to the case of using the rigid body moment relationship, the load value Q _j measured by the load sensor 108 using simultaneous equations or fitting is used to obtain a sampling point included in the subject contact area. The load value _Pi is calculated, and the pressure distribution in the subject contact area is obtained by performing interpolation in the same manner as described above.

  When the number of sampling points included in the subject contact area is larger than the number N of the load sensors 108, the sampling point for obtaining the load distribution is selected, the sampling point to be obtained is set to N or less, the load distribution is calculated, and interpolation is performed. The light side pressure distribution calculation unit 124 obtains the pressure distribution in the subject contact area.

  The measurement amount of the load sensor 108 has been described as a load, that is, a normal stress in the surface normal direction of the holding plate 101b. Stress, various strains, etc. can be taken. Also in these cases, there is a linear relationship between the measured value of each sensor and the load at the sampling point, and a linear relationship using a matrix similar to the above is established, so that the load distribution can be calculated by the same calculation. . In particular, the number N of measurement quantities can be increased by using a plurality of independent strains and stresses. Thereby, the number M ′ of sampling points for calculating the load distribution can be increased, and the calculation accuracy of the pressure distribution calculated by interpolation can be improved.

  With the configuration as described above, the pressure distribution inside the subject contact area of the holding plate 101b is calculated from the load sensor 108 arranged outside the scanning area of the light irradiation unit 102 and the imaging area of the CCD camera 110. In other words, the pressure distribution is measured using the measurement value of the load sensor 108 installed in the region that does not hinder the scanning of the light irradiation unit 102 for photoacoustic image acquisition, and pressure distribution measurement that does not hinder photoacoustic image acquisition is enabled. ing.

  The pressure distribution in the subject contact surface on the holding plates 101a and 101b calculated as described above is input to the subject pressure distribution calculation unit 127 serving as pressure information acquisition means. And the distribution information of the pressure which the holding board which is a compression board applies to a subject is acquired.

  On the other hand, the three-dimensional photoacoustic image data configured by the photoacoustic image reconstruction unit 107 is converted into photoacoustic display image data according to the display image format selected by the control unit 128 as described in the first embodiment. Converted. Here, the display image format is, for example, a MIP (maximum intensity projection) image with respect to a designated direction, a tomographic image with respect to a designated section, surface rendering with respect to a designated threshold, and volume rendering. Projection plane according to the display image format specified based on any one of the photoacoustic wave generation intensity, laser light absorption intensity, hemoglobin concentration, blood oxygen concentration, or distribution of each calculated by the photoacoustic image reconstruction unit 107 Create brightness or color value data at the coordinates on the cross-section and rendering coordinates.

  In the object pressure distribution calculation unit 127 that is a pressure information acquisition unit, the object contact surface on the holding plates 101a and 101b obtained by the light projection side pressure distribution calculation unit 124 and the photoacoustic wave reception side pressure distribution calculation unit 126 is obtained. Pressure distribution image data at points inside the subject is calculated in accordance with the display image format selected by the control means 128 based on the pressure distribution inside the subject. The display image format may be the same as or different from the display image format used for the photoacoustic display image data. In particular, by taking the same format as the display image format used for the photoacoustic display image data, the pressure distribution image and the photoacoustic image can be easily compared. For example, when a specific cross section is designated as the photoacoustic display image, the cross-sectional pressure distribution data on the same cross section is calculated by the subject pressure distribution calculating unit 127 which is a pressure information acquisition unit. The calculation is performed using interpolation methods such as linear interpolation, polynomial interpolation, and wavelet interpolation at points on the specified cross section based on the pressure distribution in the object contact surface on the holding plates 101a and 101b.

  When the photoacoustic image is an MIP image, pressure MPI image data that is easy to compare with the photoacoustic image is created by calculating an MPI image of the pressure distribution in the same direction by interpolation or the like. When displaying a rendered photoacoustic image, pressure surface rendering data and pressure volume rendering data are created. However, the display image format of the distribution image is not necessarily matched with the photoacoustic image.

  The calculated cross-sectional pressure distribution data is sent to the control means 128, and the pressure value at each point is converted into luminance or color value data for display in the same manner as the photoacoustic image, and the display means 115 simultaneously with the photoacoustic display image. Is displayed. Although the photoacoustic image and the pressure distribution image have the advantage of being able to compare the pressure and photoacoustic information at substantially the same position by displaying the photoacoustic image and the pressure distribution image at the same time, especially in a superimposed manner, they are displayed in different display image formats for comparison Needless to say, the photoacoustic image and the pressure distribution image can be displayed separately (temporarily) separately, or at different times. As shown in FIG. 8, the control unit 128 includes a main control unit 132, an input unit 133, an image processing unit 134, and a storage unit 135. As shown in FIG. 9, 136 displayed on the display means 115 is a subject information display area, 137 is a photoacoustic image display area, 138 is a photoacoustic image control parameter display area, 139 is another modality image display area, and 140 is a pressure value. It is a display area.

  These cross-sectional pressure distribution data are stored in the storage unit 135 in the control means 128 as in the first embodiment, and are processed by the image processing unit 134 according to the display image format specified by the display control input from the input unit 133. And displayed on the display means 115. For example, in the display configuration exemplified with reference to FIG. 9, the pressure distribution can be displayed with a constant pressure line superimposed on the photoacoustic display image displayed in the photoacoustic image display area or a color area display. Further, a pressure distribution display image may be displayed in a color area display or the like in parallel with the photoacoustic display image in the other modality image display area 139. At this time, it is preferable to match the positions and viewpoint directions of the cross sections of the photoacoustic display image and the pressure distribution display image displayed in parallel, but this is the case of the photoacoustic display image and the other modality display image in the first embodiment. It can be done in the same way as matching. The pressure value display area 140 may display an average pressure value.

  In the above description, the calculation of the (two-dimensional) pressure distribution of the subject contact area on each holding plate in the photoacoustic wave receiving side holding plate 101a and the light projecting side holding plate 101b is respectively performed with a plurality of loads arranged on the holding frame 122. The calculation from the sensor and the calculation using an array type load sensor that scans simultaneously with the ultrasonic transducer array 105 were performed. For this reason, in this configuration, the object contact area is optically acquired with respect to the light projecting side holding plate 101b and the object contact area is detected acoustically with respect to the photoacoustic wave receiving side holding plate 101a. The apparatus configuration can be highly compatible with the image acquisition operation.

  However, both of the photoacoustic wave receiving side holding plate 101a and the light projecting side holding plate 101b can be performed using calculations from a plurality of load sensors arranged in the holding frame 122.

  Further, the calculation of the (two-dimensional) pressure distribution in the specimen contact area on the light-projecting side holding plate 101b is scanned by combining an ultrasonic probe capable of transmitting and receiving and an array type load sensor, and receiving echo ultrasonic waves, detecting transmitted waves, It can also be obtained by measuring pressure on the ultrasonic transducer.

  Furthermore, the (two-dimensional) pressure distribution obtained by scanning the ultrasonic probe and the array type load sensor that can be transmitted and received is compared with the specimen contact area obtained using the CCD camera 110 to obtain the (two-dimensional) specimen contact area. A pressure distribution can also be obtained.

  As another configuration, the CCD camera 110 can detect the polarization, and a relative elastic stress distribution on the projection side holding plate 101b is obtained by taking a photoelastic image of the projection side holding plate 101b. A (two-dimensional) pressure distribution in the subject contact area on the light projecting side holding plate 101b may be calculated from a load sensor that measures force.

  In the present embodiment, since the (two-dimensional) pressure distribution in the subject contact area on the photoacoustic wave receiving side holding plate 101a and the light projecting side holding plate 101b is separately calculated, each holding plate is used when holding and pressing the subject. The in-subject pressure can be measured even when the areas of the subject contact areas are different. Especially when the holding plate surface is arranged in the horizontal direction perpendicular to gravity, the subject contact area of the upper and lower holding plates is different due to the subject's own gravity, or the subject contact area is uneven due to pressure during holding This configuration is also effective when there is a difference in area. In particular, even when there is a difference in the pressure on the holding plate due to the difference in the contact area of the subject on the holding plate, the pressure value at the collection position of the photoacoustic signal such as the cross section of the photoacoustic image to be displayed is simultaneously distributed. Can be displayed. For this reason, the pressure distribution information inside the subject can be effectively used for image diagnosis such as blood distribution, hemoglobin concentration distribution, blood oxygen concentration distribution using photoacoustic images.

  In any of the above embodiments, blood pressure information may be displayed instead of or in addition to the pressure information. Specifically, the blood pressure of the subject may be measured using existing blood pressure information acquisition means (blood pressure monitor) and displayed together with the acoustic wave image. At that time, the same effect can be obtained even if the blood pressure information of the subject is acquired in a state where the holding plate which is the compression plate presses the subject, and the acoustic wave image and the blood pressure information are displayed on the display means. I can do it. The blood pressure information of the subject in a state where the holding plate that is the compression plate is compressing the subject is not limited to the blood pressure during the compression, but the blood pressure information during the compression and the blood pressure before and after the compression. If the relationship with the information can be grasped, the acoustic wave image and the blood pressure information before and after the compression are displayed on the display means, which is sufficiently useful information for determining the reliability of the acoustic image. And like pressure information, it is preferable to display an acoustic wave image and blood pressure information on a display means at a time.

  The present invention relates to a diagnostic apparatus for imaging blood information in a subject using photoacoustic waves, and more particularly to photoacoustic mammography using a breast as a subject.

DESCRIPTION OF SYMBOLS 101 Holding plate 102 Laser light source 103 Light transmission means 104 Light irradiation part 105 Ultrasonic transducer array 106 Photoacoustic signal processing part 107 Photoacoustic image reconstruction part 108 Load sensor 110 CCD camera 111 CCD camera image generation part 112 Contour extraction part 113 Contact Area calculation unit 114 Compression pressure calculation unit 115 Display unit 119 Contact area calculation unit 128 Control unit

Claims (8)

A photoacoustic apparatus for acquiring information inside the subject based on an acoustic wave generated from the subject irradiated with light,
A holding member for holding the subject;
Pressure information acquisition means for acquiring pressure information applied to the subject by the holding member;
Control means for displaying on the display means the pressure information and information inside the subject,
The control means causes the display means to display a cross-sectional image in a cross section inside the subject as information inside the subject, and causes the display means to display pressure information in the cross section as the pressure information. about
A photoacoustic apparatus. The photoacoustic apparatus according to claim 1, wherein the pressure information acquisition unit calculates the pressure information as distribution image data inside the subject. The photoacoustic apparatus according to claim 1, further comprising an input unit that receives designation of the cross section. A load sensor for measuring a load applied to the holding member;
A contact area detecting means for detecting a contact area between the holding member and the subject;
The pressure information acquisition means acquires the pressure information using a measured load and a detected contact area.
The photoacoustic apparatus of any one of Claims 1-3 characterized by these. The photoacoustic apparatus according to claim 1, wherein the control unit causes the display unit to display information on the subject. The photoacoustic apparatus according to claim 5, wherein the information on the subject includes any one of patient ID, name, age, body fat percentage, BMI, cup size, and blood pressure information.
A light irradiation unit for irradiating the subject with the light;
A receiving unit for receiving an acoustic wave generated from the subject;
A scanning unit that moves the light irradiation unit and the receiving unit relative to the subject;
The photoacoustic apparatus of any one of Claims 1-6 characterized by these. The photoacoustic apparatus according to claim 1, wherein the control unit displays an image based on information inside the subject and an image based on the pressure information in a superimposed manner. .

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