Image processing device, radiographic system, control method of image processing device, and program

Abstract

To inhibit a situation in which re-imaging of a subject image and a gain correction image is required, from occurring, and to improve operability.MEANS FOR SOLVING THE PROBLEM: An image processing device includes: an image acquisition unit for acquiring a plurality of subject images obtained using a plurality of different radiation energies and a plurality of gain correction images obtained using a plurality of different radiation energies; a positional relationship acquisition unit for acquiring first positional relationship information between a radiation generator and a radiation detector on the basis of an image obtained when capturing the plurality of subject images, and acquiring second positional relationship information between the radiation generator and the radiation detector on the basis of an image obtained when capturing the plurality of gain correction images; a correction unit for correcting one of the plurality of subject images and the plurality of gain correction images on the basis of the first and second positional relationship information, and performing gain correction for the plurality of subject images using the corrected one and the other of the subject images and the gain correction images; and an image generation unit for generating a material discrimination image using the plurality of subject images for which the gain correction is performed.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to an image processing device, a radiation imaging system, a control method for an image processing device, and a program. [Background technology]

[0002] Conventionally, a measurement method called BMD (Bone Mineral Density) measurement has been used for the diagnosis of osteoporosis. In BMD measurement, it is necessary to measure the amount of bone mineral in the bone (bone density). The DXA (Dual-energy X-ray Absorptiometry) method is used to measure bone density.

[0003] DXA is a method that uses two X-rays with different energy distributions to measure bone density based on the difference in X-ray absorption coefficient (linear attenuation coefficient) between soft tissue and bone tissue. Devices dedicated to bone density measurement using DXA include devices equipped with a line sensor that irradiates high-energy X-rays and low-energy X-rays alternately at a fixed interval, and filter-type devices that place a filter in front of the X-ray tube to change the irradiation energy to a different level.

[0004] In recent years, digital image diagnosis using X-ray images taken with general radiography equipment has become widespread, and attempts have begun to apply such X-ray images to bone density measurement. When bone density imaging is performed using a general radiography FPD (Flat Pannel Detector), X-rays are irradiated onto the entire surface of the sensor (cone beam imaging) to obtain an image, which has the advantage of shortening the time required for each imaging session and reducing the burden on the patient.

[0005] However, there are also issues with BMD measurement using cone beam imaging. When using equipment dedicated to bone density measurement, the relative position of the tube and FPD does not change significantly from one scan to the next. In contrast, when using an FPD for general imaging, the tube and FPD may be moved, which may cause the relative position of the tube and FPD to change.

[0006] In the DXA method, in addition to an image of a subject photographed using two different X-rays, an image (gain correction image) obtained by irradiating an X-ray without a subject placed on the imaging device must be used in order to correct the conversion coefficient when converting the dose to pixel values. Specifically, the transmittance of each pixel of the high-energy X-ray image is calculated from the pixel values ​​of the gain correction image obtained by high-energy photography and the pixel values ​​of the X-ray image of the subject. Similarly, the transmittance of each pixel of the low-energy X-ray image is calculated from the pixel values ​​of the gain correction image obtained by low-energy photography and the pixel values ​​of the X-ray image of the subject. Then, the X-ray absorption coefficients of the soft tissues and bone tissues are derived from the two transmittances to generate a DXA image. An example of the timing for acquiring the gain correction image is the timing for imaging a bone density calibration phantom for calculating the bone density calibration value.

[0007] Here, in order to calculate the accurate transmittance at each pixel, the dose distribution irradiated to the FPD must be consistent when acquiring the gain correction image and when acquiring the X-ray image of the subject. To achieve this, the SID (Source Image Receptor Distance), which indicates the distance between the radiation generator and the radiation detector, as well as geometric conditions such as the position, size, and angle of the irradiation field, tube voltage, etc. must be consistent.

[0008] Therefore, when imaging using an FPD for general imaging, the accurate transmittance at each pixel cannot be calculated due to changes in the relative position between the tube and the FPD, and accurate measurements may not be possible. Although the DXA method has been described here, the same problem exists even when performing simple imaging using a general imaging device, in which the relative position between the tube and the FPD can change between acquiring the radiation image of the subject and acquiring the image for gain correction.

[0009] Patent Document 1 discloses a technique for calculating an evaluation value indicating the measurement accuracy of bone density from the degree of misalignment of the FPD when capturing correction data (gain correction image) or the amount of misalignment of the tube voltage, SID, irradiation field size, etc., in BMD measurement using cone beam imaging. Patent Document 1 also discloses a technique for notifying a user of the need to re-capture the subject or re-perform the gain correction image by displaying the evaluation value when deriving bone density. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2018-192054 A Summary of the Invention [Problem to be solved by the invention]

[0011] In the medical field, gain correction images may be acquired daily. In the technology described in Patent Document 1, an evaluation value is calculated, and the evaluation value or a guidance using the evaluation value is displayed on the screen to notify the user. However, if the evaluation value is to be increased, re-imaging or re-acquisition of gain correction images is required each time. Therefore, considering the frequency of imaging as described above, this places a burden and effort on the user. In addition, whether re-imaging the subject image or re-imaging the gain correction image, the user must take the time and effort to position the tube in centimeters. [Means for solving the problem]

[0012] An image processing device according to an embodiment of the present disclosure includes an image acquisition unit that acquires a plurality of subject images obtained by imaging a subject using a plurality of different radiation energies and a plurality of gain correction images obtained by imaging the subject using the plurality of different radiation energies without passing through the subject; a positional relationship acquisition unit that acquires first positional relationship information between a radiation generating device and a radiation detector based on an image obtained when the plurality of subject images are imaged, and acquires second positional relationship information between the radiation generating device and the radiation detector based on an image obtained when the plurality of gain correction images are imaged; a correction unit that corrects one of the plurality of subject images and the plurality of gain correction images based on the first positional relationship information and the second positional relationship information, and performs gain correction on the multiple subject images using the corrected one and the others of the multiple subject images and the multiple gain correction images; and an image generation unit that generates a material decomposition image using the multiple subject images that have been gain-corrected. Effect of the Invention

[0013] According to the present disclosure, it is possible to prevent the occurrence of a situation in which it is necessary to recapture a subject image or a gain correction image, thereby improving operability. [Brief description of the drawings]

[0014] [Figure 1] 1 shows an outline of an example of a radiation imaging system according to a first embodiment. [Diagram 2] 1 is a diagram illustrating an example of a configuration of an information processing device according to a first embodiment. [Diagram 3] 1 shows images and values ​​obtained in Example 1. [Figure 4] 3 shows a flowchart of subject imaging according to the first embodiment. [Diagram 5] 1 shows an outline of an example of a radiation generating apparatus according to a first embodiment. [Figure 6] 3 shows an example of a subject image and a gain correction image according to the first embodiment, and histograms of pixel values ​​for a certain pixel row in these images. [Figure 7] 4 shows a flowchart of bone density calibration imaging according to the first embodiment. [Figure 8] 3 shows a flowchart of bone mineral density calculation according to the first embodiment. [Figure 9] 13 shows a flowchart of subject imaging according to the second embodiment. [Figure 10] 13 shows a flowchart of subject imaging according to the third embodiment. [Figure 11] 13 shows a flowchart of bone density calibration imaging according to the third embodiment. [Figure 12] 13 shows a flowchart of bone mineral density calculation according to the third embodiment. [Figure 13] 13 shows a flowchart of bone mineral density calculation according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, exemplary embodiments for carrying out the present disclosure will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of components described in the following embodiments are arbitrary and can be changed according to the configuration of the device to which the present disclosure is applied or various conditions. In addition, the same reference numerals are used in the drawings to indicate elements that are the same or functionally similar.

[0016] In the following embodiments, a radiography system using X-rays as an example of radiation will be described, but the radiography system according to the present disclosure may use other types of radiation. Here, the term radiation includes electromagnetic radiation such as X-rays and gamma rays, as well as particle radiation such as alpha rays, beta rays, particle beams, proton beams, heavy ion beams, and meson beams.

[0017] In the following examples, the term "imaging conditions" refers to conditions necessary for performing radiation irradiation, including at least tube voltage, tube current, and irradiation time. In the following examples, the term "during imaging" refers to a series of periods including not only a period during which an image is captured, but also a period during which an image captured consecutively to the image is captured, or a period during which an image captured substantially simultaneously in relation to the image is captured. The energy subtraction process refers to a process of obtaining a difference using images (energy images) related to different radiation energies to obtain, for example, material decomposition images of bone and soft tissue, contrast agent and water, and information on effective atomic number and surface density. In the following, an example is described in which a bone image and a soft tissue image in which bone and soft tissue are differentiated as material decomposition images are generated, but the object of material decomposition is not limited to this, and may be contrast agent and water, solder and a material other than solder, and the like. In the energy subtraction process, two images with different radiation energies are used, but the number of images used in the energy subtraction process may be two or more depending on the purpose of material decomposition.

[0018] Example 1 A radiography system for performing bone density measurement or bone mineral quantitative measurement using energy subtraction, an image processing device, and a control method thereof according to a first embodiment will be described below with reference to Figs. 1 to 8. Fig. 1 shows an outline of an example of a radiography system according to this embodiment. As shown in Fig. 1, a radiography system 100 includes a radiation generating device 101 that generates radiation to be irradiated onto a subject P, and a radiation detector 102 that detects radiation generated from the radiation generating device 101 and transmitted through the subject P to obtain a radiographic image.

[0019] The radiation generating device 101 can be configured using a tube or the like that generates radiation. In this embodiment, as an example, the radiation generating device 101 is fixed to a gantry 103 or the like, and a radiation detector 102 is fixed inside the gantry 103. A subject P is placed on a placement section 104 of the gantry 103. When acquiring a bone density calibration image used to calibrate bone density, a phantom 107 having a predetermined bone density is placed on the placement section 104 instead of the subject P. An optical image acquiring section 106 can be attached to the radiation generating device 101. The optical image acquiring section 106 may include, for example, an optical camera.

[0020] The radiation detector 102 can be configured using an FPD, etc. Note that the radiation detector 102 may be an indirect conversion type detector that converts radiation into visible light using a scintillator, etc., and then converts the visible light into an electrical signal using a photoelectric conversion element, or may be a direct conversion type detector that directly converts incident radiation into an electrical signal.

[0021] The radiation imaging system 100 is also provided with an information processing device 110 (image processing device) that controls the radiation generation device 101, the radiation detector 102, and the like. The information processing device 110 is communicatively connected to the radiation generation device 101 and the radiation detector 102, and may be, for example, wired to the radiation generation device 101 and wirelessly connected to the radiation detector 102. However, the method of connection is not limited thereto, and the information processing device 110 may be wirelessly connected to the radiation generation device 101 or wired to the radiation detector 102. The information processing device 110 is also communicatively connected to the optical image acquisition unit 106, and can control the optical image acquisition unit 106. The information processing device 110 may be wired or wirelessly connected to the optical image acquisition unit 106.

[0022] Further, a display unit 111 and an input unit 112 are communicatively connected to the information processing device 110. The display unit 111 includes, for example, any monitor, and can display information and images output from the information processing device 110, and information input by the input unit 112, etc. The input unit 112 includes input devices such as a keyboard, a mouse, a trackball, a touch panel, etc., and can input instructions to the information processing device 110 by being operated by an operator. Note that the information processing device 110 can function as an example of a display control unit that controls display by the display unit 111.

[0023] Furthermore, an exposure switch 105 for instructing irradiation of radiation is connected to the information processing device 110. A technician G (user) can instruct the radiation generation device 101 to irradiate radiation via the information processing device 110 by operating the exposure switch 105. After irradiation of radiation, the technician G can check the radiation image that has been acquired by the radiation detector 102, image-processed by the information processing device 110, and displayed on the display unit 111.

[0024] The imaging region of the subject P placed on the mounting section 104 may be, for example, the vicinity of the femur, but is not limited thereto and may be any other region. In the following, an example in which the subject is a human body is described, but the subject is not limited thereto. For example, the subject may be a product, and the image processing device and the radiation imaging system according to the present disclosure may be used for non-destructive testing, etc.

[0025] Next, the configuration of the information processing device 110 will be described with reference to Fig. 2. Fig. 2 is a configuration diagram of the information processing device 110 that controls each component of the radiation imaging system 100. Solid arrows indicate the exchange of information. The information processing device 110 includes an imaging condition setting unit 201, an image acquisition unit 202, a positional relationship calculation unit 203, a storage unit 204, a correction unit 205, a bone image generation unit 206, and a bone density calculation unit 207.

[0026] The imaging condition setting unit 201 sets imaging conditions for radiography in response to an instruction from the technician G via the input unit 112. The imaging condition setting unit 201 may also set imaging conditions based on information on the subject, such as the imaging site, patient ID, and case, and environmental information, such as the imaging location. When bone density measurement is performed by the DXA method, imaging is performed using imaging conditions using low-energy radiation and imaging conditions using high-energy radiation. In the following, the imaging conditions using low-energy radiation are referred to as first imaging conditions, and the imaging conditions using high-energy radiation are referred to as second imaging conditions. However, the imaging conditions using high-energy radiation may be referred to as the first imaging conditions, and the imaging conditions using low-energy radiation may be referred to as the second imaging conditions.

[0027] The image acquiring unit 202 can acquire radiation images acquired by the radiation detector 102 and transmitted to the information processing device 110. As the radiation images, a subject image acquired by imaging the subject P, a calibration image acquired by imaging the phantom 107 instead of the subject P, and a gain correction image acquired by imaging without placing the subject P or the phantom 107 are acquired. As for the radiation images used for calculating bone density, an image captured under a first imaging condition and an image captured under a second imaging condition are acquired. The image acquiring unit 202 can also acquire optical images captured by the optical image acquiring unit 106.

[0028] The positional relationship calculation unit 203 calculates first positional relationship information using the subject image, and calculates second positional relationship information using the gain correction image. Here, the positional relationship refers to the positional relationship between the tube of the radiation generation device 101 and the radiation detector 102, and in this embodiment, the SID value and information indicating the position of the center of the irradiation field on the radiation detector 102 are collectively referred to as positional relationship information. A method for calculating the positional relationship information will be described later in detail.

[0029] The storage unit 204 stores various radiographic images acquired by the image acquisition unit 202, positional relationship information calculated by the positional relationship calculation unit 203, the amount of correction calculated by the correction unit 205 and various corrected radiographic images, bone images generated by the bone image generation unit 206, etc. The storage unit 204 can also store bone density calculated by the bone density calculation unit 207, optical images acquired by the optical image acquisition unit 106, etc. The storage unit 204 can also store other information such as information on imaging conditions input by the technician G, subject information, and environmental information.

[0030] The storage unit 204 can also store programs for implementing various application software including an operating system (OS), device drivers for peripheral devices, and programs for performing processes described below. Note that the storage medium for storing these may be provided separately from the storage unit 204.

[0031] The correction unit 205 performs gain correction on the calibration image using the gain correction image, and generates gain-corrected calibration data. The correction unit 205 also calculates a correction amount for correcting the gain correction image from the first positional relationship information and the second positional relationship information, and corrects the gain correction image using the calculated correction amount. Thereafter, the correction unit 205 performs gain correction on the subject image using the corrected gain correction image, and generates gain-corrected subject data. The method of gain correction and the method of calculating the correction value of the gain correction image will be described later in detail.

[0032] The bone image generating unit 206 generates a bone image from gain-corrected first object data and gain-corrected second object data obtained by performing gain correction on a first object image acquired with low-energy radiation and a second object image acquired with high-energy radiation. The bone image generating unit 206 also generates a bone image from gain-corrected first calibration data and gain-corrected second calibration data obtained by performing gain correction on a first calibration image acquired with low-energy radiation and a second calibration image acquired with high-energy radiation. A known energy subtraction method may be used as a method for generating the bone image. The method for generating the bone image according to this embodiment will be described later in detail.

[0033] The bone density calculation unit 207 calculates a bone density calibration value based on a bone image generated from the gain-corrected first calibration data and the gain-corrected second calibration data and a predetermined bone density of the phantom 107. The bone density calibration value may be calculated from a correspondence relationship between a pixel value in the bone image generated from the gain-corrected first calibration data and the gain-corrected second calibration data and the bone density of the phantom 107 corresponding to the pixel of the pixel value. The bone density calculation unit 207 calculates a calibrated bone density value based on the bone image generated from the gain-corrected first subject data and the gain-corrected second subject data and the calculated bone density calibration value. A method for calculating the bone density calibration value and a method for calculating the calibrated bone density value will be described in detail later.

[0034] The information processing device 110 can be configured by a computer provided with a processor and a memory. The information processing device 110 may be configured by a general computer or a computer dedicated to a radiation imaging system.

[0035] Each component of the information processing device 110 other than the storage unit 204 can be configured using, for example, one or more processors such as CPUs (Central Processing Units) and programs read from the storage unit 204. The processor may be, for example, an MPU (Micro Processing Unit), a GPU (Graphical Processing Unit), or an FPGA (Field-Programmable Gate Array). Each component of the information processing device 110 other than the storage unit 204 may be configured using an integrated circuit performing a specific function such as an ASIC. The internal configuration of the information processing device 110 may include a graphics control unit such as a GPU, a communication unit such as a network card, an input / output control unit such as a keyboard, a display, or a touch panel, and the like.

[0036] In this embodiment, the information processing device 110, the display unit 111, and the input unit 112 are described as separate devices, but they may be configured as an integrated unit. For example, the display unit 111 may be configured as a touch panel display, and in this case, the display unit 111 can also be used as the input unit 112.

[0037] A series of processes related to the bone density calculation process according to this embodiment will be described below with reference to Fig. 3 to Fig. 8. Fig. 3 shows images and values ​​acquired in this embodiment. Fig. 4 shows a flowchart of the subject imaging according to this embodiment.

[0038] First, in step S401, the technician G starts imaging the subject. In step S402, the technician G places the subject P on the placement unit 104. The imaging condition setting unit 201 sets the first imaging condition. The first imaging condition may be set in advance based on instructions from the technician G, information about the subject, and the like. Thereafter, when the technician G presses the irradiation switch 105 or a button for issuing an irradiation instruction (not shown), the radiation generating device 101 irradiates radiation under the first imaging condition.

[0039] In step S403, the radiation detector 102 detects radiation transmitted through the subject P, and generates and acquires a first subject image 301. The radiation detector 102 also transmits the acquired first subject image 301 to the information processing device 110, and the image acquisition unit 202 acquires the first subject image 301, which is an image of the subject P and which is transmitted from the radiation detector 102.

[0040] In step S404, the imaging condition setting unit 201 sets second imaging conditions while the subject P is placed on the placement unit 104. The second imaging conditions may be set in advance based on instructions from the technician G, information on the subject, etc. Thereafter, the radiation generating device 101 irradiates radiation under the second imaging conditions.

[0041] In step S405, radiation detector 102 detects radiation transmitted through subject P, and generates and acquires second subject image 302. Radiation detector 102 also transmits the acquired second subject image 302 to information processing device 110, and image acquisition unit 202 acquires second subject image 302 of subject P transmitted from radiation detector 102. Here, it is assumed that first subject image 301 and second subject image 302 are radiation images of the same subject.

[0042] In step S406, the positional relationship calculation unit 203 calculates the SID value and the position on the radiation detector of the center of the irradiation field from the first subject image 301 or the second subject image 302. Here, in steps S402 to S405, the subject P is imaged so that the first imaging condition and the second imaging condition are instantly switched. This makes it possible to acquire the first subject image 301 and the second subject image 302 in a state that is not affected by the body movement of the subject P, that is, in a state in which the positional relationship between the tube or irradiation field and the radiation detector 102 remains the same.

[0043] The process of calculating the SID value and the position of the center of the irradiation field on the radiation detector by the positional relationship calculation unit 203 in step S406 will be described in detail below. Hereinafter, the position of the center of the irradiation field on the radiation detector and the SID value in step S406 will be collectively referred to as the "first positional relationship".

[0044] In a general radiation imaging apparatus, a metal filter for fixing the aperture ratio in radiation irradiation may be installed in front of the collimator. Hereinafter, this filter is referred to as a fixed aperture mask. Hereinafter, the fixed aperture mask will be described with reference to FIG. 5. In this embodiment, an example in which an X-ray tube is used as an example of the radiation generating apparatus 101 is shown. A conceptual diagram of an X-ray tube is shown in FIG.

[0045] The tube 501 according to this embodiment is provided with a target 502 for generating radiation, a collimator 503, and a fixed aperture mask 504. The collimator 503 can limit the irradiation range of the X-rays irradiated from the target 502 of the tube 501. The collimator 503 may be manually or automatically adjustable depending on the imaging conditions. The fixed aperture mask 504 is installed under the collimator 503, and can ensure that the aperture ratio does not change for each irradiation. FIG. 5 shows an example in which the aperture of the collimator 503 is sufficiently large compared to the aperture of the fixed aperture mask 504. On the other hand, the size of the aperture of the collimator 503 may be limited to the aperture of the fixed aperture mask 504, and the aperture ratio may be fixed.

[0046] An example of calculating the positional relationship in step S406 will be described below with reference to Fig. 6, on the assumption that the irradiation field size for a certain SID is kept constant by, for example, attaching a fixed aperture mask 504 to the radiation generating device 101. Fig. 6 shows an example of a subject image and a gain correction image according to this embodiment, and histograms of pixel values ​​for a certain pixel row in these images.

[0047] 6 indicates the first object image 301. In this case, the positional relationship calculation unit 203 calculates the irradiation field R A The pixel column M on the long side of A For the pixel value I A Let the pixel position be Y A The histogram (Y A -I A ) and the pixel value I A Maximum value of IAMAX Pixel position Y corresponding to AMAX Get the.

[0048] In addition, the positional relationship calculation unit 203 designates a pixel row in which the object is not shown in the object image A as a pixel row M A The pixel column M A As a method for identifying a pixel row not showing an object, for example, a known edge detection algorithm, threshold processing, etc. may be used to identify the pixel row not showing an object. Note that in the threshold processing, a pixel row having a predetermined number of consecutive pixels whose pixel value is smaller than a predetermined threshold may be identified as a pixel row not showing an object.

[0049] The positional relationship calculation unit 203 calculates the histogram (X A -I A ) (not shown) is obtained, and the pixel value I A Maximum value of I AMAX Pixel position X corresponding to AMAX (not shown). The positional relationship calculation unit 203 obtains the pixel position Y AMAX , and pixel position X with respect to the short side of the illumination AMAX The pixel position (X AMAX , Y AMAX ) is obtained as the position on the radiation detector of the center of the irradiation field.

[0050] When the fixed opening mask 504 is attached, the positional relationship calculation unit 203 calculates the SID value as SID1=L 1p / 2tan(θ / 2). Here, the opening of the fixed opening mask 504 is expressed in θ (rad). 1p (pixel) represents the side length of the irradiation field, L 1p =L 1m ×S. Here, the irradiation field is expressed based on the pixel value of each pixel of the image obtained by the radiation detector 102. In addition, the irradiation field R AIf the coordinates of the four corners (X1, Y1), (X2, Y2), (X3, Y3), and (X4, Y4) are known in advance, the side length of the irradiation field can be calculated from each of the four points. For example, if the side connecting the coordinates (X1, Y1) and (X2, Y2) is the short side, the length of the short side is the distance between the coordinates (X1, Y1) and (X2, Y2). The length of the long side can also be calculated in a similar manner.

[0051] S is L 1p (pixel) to L 1m This represents a scale amount for converting the effective pixel length (mm) of the sensor and the side length (pixel) of the radiation image in advance, and can be obtained by measuring the side length (mm) of the effective pixel length (mm) of the radiation image in advance. Here, the process of calculating the first positional relationship from the first object image 301 has been described, but the positional relationship calculation unit 203 may calculate the first positional relationship from the second object image 302 in a similar manner.

[0052] In step S407, positional relationship information indicating the calculated first positional relationship is stored in the storage unit 204. When the positional relationship information is stored in the storage unit 204 in step S407, imaging of the subject ends in step S408.

[0053] Thereafter, before starting bone density measurement, technician G performs bone density calibration imaging. FIG. 7 shows a flowchart of bone density calibration imaging according to this embodiment. Note that bone density calibration imaging may be performed before subject imaging. When bone density calibration imaging is started in step S701, the process proceeds to step S702. In step S702, technician G places the phantom 107 on the placement unit 104. The radiation generating device 101 irradiates radiation under the first imaging condition in response to an instruction from technician G. Note that the setting of imaging conditions, irradiation instructions, etc. may be the same as in step S402.

[0054] In step S703, the radiation detector 102 detects radiation that has passed through the phantom 107, and generates and acquires the first calibration image 303. The radiation detector 102 also transmits the acquired first calibration image 303 to the information processing device 110, and the image acquisition unit 202 acquires the first calibration image 303, which is an image of the phantom 107 and which has been transmitted from the radiation detector 102.

[0055] In step S704, the radiation generating device 101 irradiates radiation under the second imaging condition with the phantom 107 placed on the placement unit 104. Note that the imaging condition settings and the like may be the same as those in step S404.

[0056] In step S705, the radiation detector 102 detects the radiation that has passed through the phantom 107, and generates and acquires the second calibration image 304. The radiation detector 102 also transmits the acquired second calibration image 304 to the information processing device 110, and the image acquisition unit 202 acquires the second calibration image 304, which is an image of the phantom 107 and which has been transmitted from the radiation detector 102.

[0057] In step S706, the radiation generating device 101 irradiates radiation under the imaging conditions used in step S702 without placing the subject P and the phantom 107. The settings of the imaging conditions and the irradiation instructions may be the same as those in step S702.

[0058] In step S707, the radiation detector 102 detects the irradiated radiation and generates and acquires the first gain correction image 305. The radiation detector 102 also transmits the acquired first gain correction image 305 to the information processing device 110, and the image acquisition unit 202 acquires the first gain correction image 305 transmitted from the radiation detector 102.

[0059] In step S708, the radiation generating device 101 irradiates radiation under the imaging conditions used in step S704 without placing the subject P and the phantom 107. The imaging conditions may be set in the same manner as in step S704.

[0060] In step S709, the radiation detector 102 detects the irradiated radiation and generates and acquires the second gain correction image 306. The radiation detector 102 also transmits the acquired second gain correction image 306 to the information processing device 110, and the image acquisition unit 202 acquires the second gain correction image 306 transmitted from the radiation detector 102.

[0061] In step S710, the positional relationship calculation unit 203 calculates the SID value and the position on the radiation detector of the center of the irradiation field from the first gain correction image 305 or the second gain correction image 306. Hereinafter, the position on the radiation detector of the center of the irradiation field and the SID value in step S710 are collectively referred to as the "second positional relationship." Note that in steps S702 to S709, it is assumed that the positional relationship between the tube of the radiation generation device 101 and the radiation detector 102 does not change.

[0062] Hereinafter, a process will be described in which the positional relationship calculation unit 203 calculates the second positional relationship from the first gain correction image 305 or the second gain correction image 306. It is assumed that the gain correction image B in FIG. 6 represents the first gain correction image 305. In this case, the positional relationship calculation unit 203 calculates the second positional relationship from the pixel row M B For the pixel value I B Let the pixel position be Y B The histogram (Y B -I B ) and the pixel value I B Maximum value of I BMAX Pixel position Y corresponding to BMAX Here, the gain correction image B is obtained by imaging without placing either the subject P or the phantom 107. Therefore, the positional relationship calculation unit 203 calculates an arbitrary pixel row of the gain correction image B as a pixel row M B For example, a given pixel column may be identified as pixel column M B may be specified as

[0063] The positional relationship calculation unit 203 calculates the histogram (X B -I B) (not shown) is obtained, and the pixel value I B Maximum value of I BMAX Pixel position X corresponding to BMAX (not shown). The positional relationship calculation unit 203 obtains the pixel position Y BMAX , and pixel position X with respect to the short side of the illumination BMAX The pixel position (X BMAX , Y BMAX ) is obtained as the position on the radiation detector of the center of the irradiation field.

[0064] The positional relationship calculation unit 203 acquires the SID value related to the second positional relationship in the same manner as the calculation method of the SID value related to the first positional relationship in step S406.

[0065] In step S711, the storage unit 204 stores positional relationship information indicating the calculated second positional relationship.

[0066] In step S712, the correction unit 205 performs gain correction on the first calibration image 303 captured under the first shooting condition by using the first gain correction image 305 captured under the first shooting condition, and generates gain-corrected first calibration data 311. Similarly, the correction unit 205 performs gain correction on the second calibration image 304 captured under the second shooting condition by using the second gain correction image 306 captured under the second shooting condition, and generates gain-corrected second calibration data 312. Here, a known method may be used for the gain correction. For example, when a pixel value at coordinates (x, y) of the calibration image is I(x, y) and a pixel value at coordinates (x, y) of the gain correction image is I0(x, y), the correction unit 205 may perform gain correction for each pixel of the calibration image according to the following formula:

number

[0067] In step S713, the bone image generating unit 206 performs energy subtraction processing on the gain-corrected first calibration data 311 and the gain-corrected second calibration data 312 acquired in step S712 to generate a bone image 313. Here, the energy subtraction processing may be performed using a known method. For example, the bone image generating unit 206 subtracts the pixel value d bone may be calculated according to the following formula:

number

number

number

[0068] Next, in step S714, the bone density calculation unit 207 calculates a bone density calibration value 314 based on the bone image 313 and a predetermined bone density of the phantom 107. The bone density calculation unit 207 can calculate a correspondence relationship between the bone density of the bone image 313 and the bone density of the phantom 107, for example, from pixel values ​​of a plurality of pixels of the bone image 313 corresponding to a plurality of locations of the phantom 107 having different bone densities, and the bone density of the plurality of locations of the phantom 107. More specifically, the bone density calculation unit 207 can calculate an approximation line between the pixel values ​​of the bone image 313 and the bone density of the phantom 107, from the pixel values ​​of a plurality of pixels of the bone image 313 and the bone density of the corresponding plurality of locations of the phantom 107. The bone density calculation unit 207 acquires parameters including the slope and intercept of the calculated approximation line as the bone density calibration value 314. The bone density calculation unit 207 can store the bone density calibration value 314 in the storage unit 204 .

[0069] When the bone mineral density calibration value 314 is calculated in step S714, the bone mineral density calibration imaging ends in step S715.

[0070] Next, with reference to FIG. 8, the calculation of bone density for a subject will be described. As described above, when performing radiation imaging using a general imaging device, the positional relationship between the tube of the radiation generating device 101 and the radiation detector 102 may change between the time when the gain correction image is acquired and the time when the radiation image of the subject is acquired. In this case, it is possible that the gain correction cannot be performed appropriately and appropriate measurement of bone density and the like cannot be performed. Therefore, the information processing device 110 according to this embodiment performs gain correction after correcting the gain correction image based on the positional relationship related to the subject image and the positional relationship related to the gain correction image. Thereafter, the information processing device 110 generates a bone image using the gain-corrected subject image, and calculates bone density based on the bone image.

[0071] 8 shows a flow of bone mineral density value calculation according to this embodiment. In step S801, when bone mineral density calculation for the subject is started, the process proceeds to step S802. Note that bone mineral density calculation for the subject may be started after bone mineral density calibration imaging is completed, or may be started according to an instruction from technician G, etc.

[0072] In step S802, the correction unit 205 calculates the correction amount of the first gain correction image 305 and the second gain correction image 306 based on the positional relationship information stored in the storage unit 204. The positional relationship information used here includes the SID value and the position on the radiation detector at the center of the irradiation field when the subject image is acquired (first positional relationship information), and the SID value and the position on the radiation detector at the center of the irradiation field when the gain correction image is acquired (second positional relationship information). As described above, the positional relationship when the first subject image 301 and the second subject image 302 are captured is the same. The positional relationship when the first gain correction image 305 and the second gain correction image 306 are captured is also the same. Therefore, the correction amount calculated based on the first positional relationship information and the second positional relationship information can be applied to both the first gain correction image 305 and the second gain correction image 306.

[0073] In step S802, the correction unit 205 calculates the SID correction amount (SID1 / SID2) 2 This is because the dose is proportional to the square of the SID. Here, SID1 represents the SID in the first positional relationship, and SID2 represents the SID in the second positional relationship.

[0074] Furthermore, the correction unit 205 calculates a position correction amount ΔY based on the position related information. AMAX -(Y BMAX -Y BC ) / √R to calculate the position correction amount ΔY. BC is the pixel row M of the gain correction image B B Pixel position Y B R represents the magnification ratio of the subject image A to the gain correction image B, and the SID correction amount (SID1 / SID2)2 It is.

[0075] In step S803, the correction unit 205 corrects the first gain correction image 305 and the second gain correction image 306 based on the correction amount calculated in step S802, and generates a corrected first gain correction image 307 and a corrected second gain correction image 308. First, the correction unit 205 corrects the difference in the dose due to the difference in the SID related to the first positional relationship and the second positional relationship. Here, the pixel value I B The pixel value obtained by multiplying the SID correction amount by I B ´.

[0076] Next, the correction unit 205 detects a pixel position Y B Pixel value at I B ´, Y B+ΔY Pixel value at I B+ΔY '. Note that, although an example of correcting pixel values ​​of columns positioned vertically in the image has been shown here, pixel values ​​of columns positioned horizontally in the image may be corrected using a similar method, or pixel values ​​of columns positioned both vertically and horizontally may be corrected. In these cases, in step S802, the amount of position correction can be calculated using a similar calculation method for the pixel values ​​of the columns to be corrected.

[0077] The correction unit 205 can obtain a corrected first gain correction image 307 and a corrected second gain correction image 308 by performing such correction processing.

[0078] In step S804, the correction unit 205 performs gain correction on the first object image 301 captured under the first imaging condition by using the corrected first gain correction image 307, and generates gain-corrected first object data 309. Similarly, the correction unit 205 performs gain correction on the second object image 302 captured under the second imaging condition by using the corrected second gain correction image 308, and generates gain-corrected second object data 310. The method of gain correction may be the same as that in step S712.

[0079] In step S805, the bone image generating unit 206 performs energy subtraction processing on the gain-corrected first object data 309 and the gain-corrected second object data 310 acquired in step S804 to generate a bone image 315. The energy subtraction processing may be the same processing as in step S713.

[0080] In step S806, the bone density calculation unit 207 uses the bone image 315 and the bone density calibration value 314 to calculate and obtain the calibrated bone density value 316. For example, the pixel values ​​of the bone image 315 can be substituted into an approximation line having the parameters of the bone density calibration value 314 to obtain the calibrated bone density value 316. When the calibrated bone density value 316 is obtained in step S806, the bone density calculation ends in step S807.

[0081] As described above, the radiation imaging system 100 according to this embodiment includes a radiation generating device 101 that irradiates radiation, a radiation detector 102 that detects radiation, and an information processing device 110 that functions as an example of an image processing device that processes images. The information processing device 110 includes an image acquiring unit 202, a positional relationship calculating unit 203, a correction unit 205, and a bone image generating unit 206. The image acquiring unit 202 acquires a plurality of subject images obtained by imaging a subject using a plurality of different radiation energies, and a plurality of gain correction images obtained by imaging the subject using the plurality of different radiation energies without passing through the subject. The positional relationship calculating unit 203 functions as an example of a positional relationship acquiring unit that acquires first positional relationship information between the radiation generating device 101 and the radiation detector 102 based on images acquired when the plurality of subject images are captured, and acquires second positional relationship information between the radiation generating device 101 and the radiation detector 102 based on images acquired when the plurality of gain correction images are captured. The correction unit 205 corrects the multiple gain correction images based on the first positional relationship information and the second positional relationship information, and performs gain correction on the multiple subject images using the corrected multiple gain correction images and the multiple subject images. The bone image generation unit 206 functions as an example of an image generation unit that generates a material decomposition image using the multiple gain-corrected subject images. The first positional relationship information and the second positional relationship information may include at least one of the inclination or distance of the radiation detector 102 with respect to the radiation generation device 101, the size of the radiation irradiation field, and the position of the irradiation field on the radiation detector 102.

[0082] According to the above configuration, it is possible to prevent the occurrence of situations requiring re-imaging of the subject image or the gain correction image, and it is expected to improve operability. In addition, since the occurrence of situations requiring re-imaging is prevented, the burden on the subject during positioning is reduced, and there is also a safety benefit of reduced radiation exposure. Furthermore, since the positional relationship is corrected based on the captured image, the effort required for positioning the tube can be reduced.

[0083] Furthermore, the positional relationship calculation unit 203 can acquire first positional relationship information based on the subject image, and acquire second positional relationship information based on the gain correction image. More specifically, the positional relationship calculation unit 203 can acquire first positional relationship information based on the size and position of the radiation irradiation field in the subject image, and acquire second positional relationship information based on the size and position of the radiation irradiation field in the gain correction image. According to the above configuration, since the image is aligned based on the radiation image, it is not necessary to use an imaging device for positioning, and the radiation imaging system 100 can be further simplified. Furthermore, since the image is aligned based on the radiation image, it is possible to reduce the effort of installing a marker or the like during positioning.

[0084] The subject may be a human body, and the material decomposition image may be a bone image. In this case, the information processing device 110 may further include a bone density acquisition unit that acquires the bone density of the subject based on the bone image. With this configuration, in an apparatus that performs bone density measurement using a radiation detector for general imaging, it is possible to suppress the occurrence of a situation in which it is necessary to retake a subject image or a gain correction image, and it is expected to improve operability.

[0085] Moreover, the image acquisition unit 202 can further acquire a plurality of calibration images obtained by imaging the phantom 107 having a predetermined bone density using a plurality of different radiation energies. Furthermore, the correction unit 205 can perform gain correction on the plurality of calibration images using a plurality of gain correction images and a plurality of calibration images. Furthermore, the bone image generation unit 206 can generate a bone image using a plurality of gain-corrected calibration images. In this case, the bone density calculation unit 207 can acquire a calibration value using a bone image generated using a plurality of gain-corrected calibration images. Furthermore, the bone density calculation unit 207 can acquire a bone density using a bone image and a calibration value generated using a plurality of gain-corrected subject images. According to such a configuration, the information processing device 110 can acquire the bone density of the subject with higher accuracy.

[0086] The calibration images may be images obtained by capturing the gain correction images in succession. In this case, the positional relationship calculation unit 203 may obtain the second positional relationship information by using the calibration images as images obtained when capturing the gain correction images.

[0087] In this embodiment, an example is described in which two shooting conditions (a first shooting condition and a second shooting condition) are used, but three or more shooting conditions may be used to calculate the positional relationship in a similar manner and correct the gain correction image.

[0088] In this embodiment, the correction unit 205 corrects the multiple gain correction images based on the first positional relationship information and the second positional relationship information, and then performs gain correction on the multiple subject images. Alternatively, the correction unit 205 may correct the multiple subject images based on the first positional relationship information and the second positional relationship information, and perform gain correction on the multiple subject images using the multiple gain correction images and the corrected multiple subject images.

[0089] In this embodiment, the positional relationship between the tube of the radiation generating device 101 and the radiation detector 102 is not changed in steps S702 to S709. In contrast, the positional relationship between the tube of the radiation generating device 101 and the radiation detector 102 may change between steps S702 to S705 for acquiring the calibration image and steps S706 to S709 for acquiring the gain correction image. In this case, when performing gain correction on the calibration image, the gain correction image may be corrected based on the positional relationship of the calibration image and the positional relationship of the gain correction image, as in steps S802 and S803, and then the calibration image may be gain-corrected. In this case, too, the correction unit 205 may perform gain correction after correcting the calibration image, rather than the gain correction image, based on each positional relationship.

[0090] In this embodiment, after the calibration image is acquired in steps S702 to S705, the gain correction image is acquired in steps S706 to S709. Alternatively, the calibration image may be acquired after the gain correction image is acquired.

[0091] In this embodiment, the case where the correction is performed in step S803 by simply shifting the position of the center of the irradiation field on the radiation detector has been described, but the correction process is not limited to this. For example, the information processing device 110 may obtain the inclination of the tube of the radiation generating device 101 with respect to the radiation detector 102, obtain the SID value, and perform the correction process. Specifically, the positional relationship calculation unit 203 can obtain the first positional relationship information by trapezoidally approximating the radiation irradiation field in the image obtained when the subject image is captured, and can obtain the second positional relationship information by trapezoidally approximating the radiation irradiation field in the image obtained when the gain correction image is captured.

[0092] In this case, the positional relationship calculation unit 203 calculates, for example, the irradiation field R B After obtaining the center of the irradiation field from the coordinates (X1, Y1), (X2, Y2), (X3, Y3), and (X4, Y4) of the four corners, a trapezoid approximation can be performed using each of the four points. The positional relationship calculation unit 203 obtains the inclination of the tube of the radiation generating device 101 with respect to the radiation detector 102 from the ratio of the length of the upper side and the lower side of the trapezoid obtained by the approximation, and can obtain the SID value. Here, a correspondence table between the ratio of the length of the upper side and the lower side of the trapezoid and the inclination of the tube with respect to the radiation detector 102 can be obtained in advance by measurement or the like. The correction unit 205 performs the correction process in steps S802 and S803 using the SID obtained in this way, thereby making it possible to perform a correction process that takes into account the inclination of the tube with respect to the radiation detector 102, and to perform a more appropriate gain correction.

[0093] Example 2 In the first embodiment, a configuration for performing bone density measurement using a general imaging device has been described. In contrast, even when performing plain radiography using a general imaging device, if the positional relationship between the tube of the radiation generator and the radiation detector changes between taking an image of the subject and taking an image for gain correction, accurate gain correction may not be possible. Therefore, in the second embodiment of the present disclosure, the correction process according to the present disclosure is applied when taking a plain radiographic image using a general imaging device.

[0094] In the first embodiment, the positional relationship between the tube of the radiation generating device and the radiation detector is calculated using a radiation image, but the method of calculating the positional relationship is not limited to this. In the present embodiment, the positional relationship between the tube of the radiation generating device and the radiation detector is calculated using an optical image captured during radiation image capture.

[0095] Hereinafter, subject imaging according to this embodiment will be described with reference to Fig. 9. Since the radiation imaging system and information processing device according to this embodiment have the same configurations as the radiation imaging system 100 and information processing device 110 according to the first embodiment, the same reference numerals are used and the description will be omitted. Note that the information processing device 110 according to this embodiment does not necessarily have to include the bone image generating unit 206 and the bone density calculating unit 207.

[0096] 9 is a flowchart showing the procedure for imaging a subject according to this embodiment. In step S901, when the technician G starts radiography, the process proceeds to step S902.

[0097] In step S902, the technician G places the subject P on the placement unit 104. The first imaging condition may be set in advance based on instructions from the technician G, information on the subject, etc. After that, when the technician G presses the irradiation switch 105 or a button for issuing an irradiation instruction (not shown), the radiation generating device 101 irradiates radiation under the first imaging condition.

[0098] In step S903, the radiation detector 102 detects radiation transmitted through the subject P, and generates and acquires a first subject image. The radiation detector 102 also transmits the acquired first subject image to the information processing device 110, and the image acquisition unit 202 acquires the first subject image. In step S903, the information processing device 110 further controls the optical image acquisition unit 106 to capture a first optical image of the subject P. The optical image acquisition unit 106 transmits the acquired first optical image to the information processing device 110, and the image acquisition unit 202 acquires the first optical image.

[0099] In step S904, the positional relationship calculation unit 203 obtains positional relationship information indicating the SID value and the position on the radiation detector of the center of the irradiation field from the first optical image. Any known method may be used to obtain the SID value and the position on the radiation detector of the center of irradiation based on the first optical image. For example, the positional relationship calculation unit 203 performs image processing such as edge detection and corner detection on the first optical image to detect feature points of the collimator lamp that indicate the irradiation range of radiation and are shown in the first optical image, and can obtain the SID, etc. based on the detected feature points.

[0100] The positional relationship calculation unit 203 may detect, as the feature points of the collimator lamp, feature points of the collimator lamp corresponding to the four corner points of the irradiation field, or may detect feature points of a cross-shaped area of ​​the collimator lamp where light is not irradiated, for example. The positional relationship calculation unit 203 may detect, as the feature points of the collimator lamp, feature points of the collimator lamp corresponding to the four corner points of the irradiation field and feature points of a cross-shaped area of ​​the collimator lamp where light is not irradiated. Here, the positional relationship calculation unit 203 may detect the corner points of the cross-shaped area as the feature points of the cross-shaped area. The positional relationship calculation unit 203 may obtain the SID, etc., based on some of the feature points of the collimator lamp corresponding to the four corner points of the irradiation field and some of the feature points of the cross-shaped area.

[0101] In addition, the positional relationship calculation unit 203 may detect a feature point indicating a specific location on the mounting unit 104 or a feature point indicating a marker attached to the mounting unit 104, which is shown in the first optical image, and calculate the SID, etc. based on the detected feature point.

[0102] In addition, to calculate the positional relationship information, the positional relationship calculation unit 203 may use the positional information of the radiation generation device 101 and the optical image acquisition unit 106. Hereinafter, the position on the radiation detector at the center of the irradiation field and the SID value in step S904 will be collectively referred to as the "first positional relationship", and information indicating the first positional relationship will be referred to as the "first positional relationship information".

[0103] In step S905, the first positional relationship information calculated in step S904 is stored in the storage unit 204.

[0104] In step S906, the radiation generating device 101 irradiates radiation under the imaging conditions used in step S902 without placing the subject P and the phantom 107. The settings of the imaging conditions and the irradiation instructions may be the same as those in step S902.

[0105] In step S907, the radiation detector 102 detects the irradiated radiation and generates and acquires a first image for gain correction. The radiation detector 102 also transmits the acquired first image for gain correction to the information processing device 110, and the image acquisition unit 202 acquires the first image for gain correction from the radiation detector 102. In step S907, the information processing device 110 further controls the optical image acquisition unit 106 to capture a second optical image of the subject P. The optical image acquisition unit 106 transmits the acquired second optical image to the information processing device 110, and the image acquisition unit 202 acquires the second optical image.

[0106] In step S908, the positional relationship calculation unit 203 obtains, from the second optical image, positional relationship information indicating the SID value and the position on the radiation detector of the center of the irradiation field. The positional relationship calculation unit 203 can obtain the second positional relationship information based on the second optical image by a method similar to that of step S904. Hereinafter, the position on the radiation detector of the center of the irradiation field and the SID value in step S908 are collectively referred to as the "second positional relationship", and the information indicating the second positional relationship is referred to as the "second positional relationship information".

[0107] In step S909, the second positional relationship information calculated in step S908 is stored in the storage unit 204.

[0108] In step S910, the correction unit 205 calculates the correction amount of the first gain correction image by using the first positional relationship information acquired in step S904 and the second positional relationship information acquired in step S908. More specifically, the correction unit 205 can calculate the correction amount of the first gain correction image by using the first positional relationship information and the second positional relationship information in the same manner as in step S802.

[0109] In step S911, the correction unit 205 can correct the first gain correction image using the calculated correction amount in the same manner as in step S803, and obtain a corrected first gain correction image.

[0110] In step S912, the correction unit 205 performs gain correction on the first object image acquired in step S903 by using the corrected first gain correction image acquired in step S911, and generates and acquires gain-corrected first object data. Note that the method of gain correction may be the same as that in step S712. When the gain-corrected first object data is acquired in step S912, the object imaging ends in step S913.

[0111] As described above, the radiation imaging system 100 according to this embodiment includes a radiation generating device 101 that irradiates radiation, a radiation detector 102 that detects radiation, and an information processing device 110 that functions as an example of an image processing device that processes images. The information processing device 110 includes an image acquiring unit 202, a positional relationship calculating unit 203, and a correction unit 205. The image acquiring unit 202 acquires a subject image obtained by imaging a subject, and a gain correction image obtained by imaging without the subject. The positional relationship calculating unit 203 functions as an example of a positional relationship acquiring unit that acquires first positional relationship information between the radiation generating device 101 and the radiation detector 102 based on an image obtained when the subject image is captured, and acquires second positional relationship information between the radiation generating device 101 and the radiation detector 102 based on an image obtained when the gain correction image is captured. The correction unit 205 corrects one of the subject image and the gain correction image based on the first positional relationship information and the second positional relationship information, and performs gain correction on the subject image using the corrected one and the other of the subject image and the gain correction image.

[0112] According to the above configuration, it is possible to prevent the occurrence of situations requiring re-imaging of the subject image or the gain correction image, and it is expected to improve operability. In addition, since the occurrence of situations requiring re-imaging is prevented, the burden on the subject during positioning is reduced, and there is also a safety benefit of reduced radiation exposure. Furthermore, since the positional relationship is corrected based on the captured image, the effort required for positioning the tube can be reduced.

[0113] The image acquisition unit 202 can further acquire a first optical image, which is an example of an image obtained when capturing an object image, and a second optical image, which is an example of an image obtained when capturing an image for gain correction. In this case, the positional relationship calculation unit 203 can acquire first positional relationship information based on the first optical image, and acquire second positional relationship information based on the second optical image. Even in such a configuration, since the positional relationship is corrected based on the captured optical image, the effort required for positioning the tube can be reduced.

[0114] The correction unit 205 may use the trapezoidal approximation calculation method exemplified in the first embodiment. For example, the correction unit 205 may obtain the four corner points of the irradiation field from the feature points of the collimator lamp in the optical image, perform trapezoidal approximation, obtain the inclination of the tube of the radiation generating device 101 with respect to the radiation detector 102, and obtain the SID value. The correction unit 205 may perform trapezoidal approximation using the feature points of the cross region of the collimator lamp in the optical image where no light is irradiated. The correction unit 205 may also perform trapezoidal approximation using the feature points indicating a specific location on the placement unit 104 in the optical image or the feature points indicating a marker attached on the placement unit 104. In these cases, the correction unit 205 can perform a correction process taking into account the inclination of the tube with respect to the radiation detector 102, and can perform more appropriate gain correction.

[0115] In this embodiment, the change in the positional relationship is corrected using an optical image. However, similar to the first embodiment, the change in the positional relationship may be corrected using a radiation image.

[0116] Example 3 In Example 1, the positional relationship between the tube of the radiation generating device and the radiation detector is calculated using a radiation image for bone density measurement by DXA method. In contrast, in Example 3, the positional relationship between the tube of the radiation generating device and the radiation detector is calculated using an optical image captured during radiation image capture, similar to Example 2, for bone density measurement by DXA method.

[0117] 10 to 12, a subject imaging according to this embodiment will be described below. Since the radiation imaging system and the information processing device according to this embodiment have the same configuration as the radiation imaging system 100 and the information processing device 110 according to the first embodiment, the same reference numerals are used and the description will be omitted.

[0118] 10 is a flowchart showing the procedure for imaging a subject according to this embodiment. In step S1001, when the technician G starts radiography, the process proceeds to step S1002.

[0119] In step S1002, the technician G places the subject P on the placement unit 104. The imaging condition setting unit 201 sets a first imaging condition. The first imaging condition may be set in advance based on instructions from the technician G, information on the subject, and the like. After that, when the technician G presses the irradiation switch 105 or a button for issuing an irradiation instruction (not shown), the radiation generating device 101 irradiates radiation under the first imaging condition.

[0120] In step S1003, the radiation detector 102 detects radiation transmitted through the subject P, and generates and acquires a first subject image 301. The radiation detector 102 also transmits the acquired first subject image 301 to the information processing device 110, and the image acquisition unit 202 acquires the first subject image 301 of the subject P transmitted from the radiation detector 102. In step S1003, the information processing device 110 further controls the optical image acquisition unit 106 to capture a first optical image of the subject P. The optical image acquisition unit 106 transmits the acquired first optical image to the information processing device 110, and the image acquisition unit 202 acquires the first optical image. Note that the first optical image may be acquired in step S1005.

[0121] In step S1004, the imaging condition setting unit 201 sets second imaging conditions while the subject P is placed on the placement unit 104. The second imaging conditions may be set in advance based on instructions from the technician G, information on the subject, etc. Thereafter, the radiation generating device 101 irradiates radiation under the second imaging conditions.

[0122] In step S1005, the radiation detector 102 detects radiation transmitted through the subject P, and generates and acquires a second subject image 302. The radiation detector 102 also transmits the acquired second subject image 302 to the information processing device 110, and the image acquisition unit 202 acquires the second subject image 302 of the subject P transmitted from the radiation detector 102.

[0123] In step S1006, the positional relationship calculation unit 203 calculates the SID value and positional relationship information indicating the position on the radiation detector of the center of the irradiation field from the first optical image. The positional relationship calculation unit 203 can acquire the first positional relationship information based on the first optical image by the same method as in step S904. Here, in steps S1002 to S1005, the subject P is imaged so that the first imaging condition and the second imaging condition are instantly switched. This makes it possible to acquire the first subject image 301 and the second subject image 302 in a state that is not affected by the body movement of the subject P, that is, in a state where the positional relationship between the tube or irradiation field and the radiation detector 102 is the same. Hereinafter, the position on the radiation detector of the center of the irradiation field and the SID value in step S1006 are collectively referred to as the "first positional relationship", and the information indicating the first positional relationship is referred to as the "first positional relationship information".

[0124] In step S1007, the first positional relationship information calculated in step S1006 is stored in storage unit 204. After the first positional relationship information is stored in storage unit 204 in step S1007, imaging of the subject ends in step S1008.

[0125] Thereafter, before starting bone density measurement, technician G performs bone density calibration imaging. Fig. 11 shows a flowchart of bone density calibration imaging according to this embodiment. Here, imaging for calculating bone density calibration values ​​may be performed before imaging the subject. When bone density calibration imaging is started in step S1101, the process proceeds to step S1102.

[0126] In step S1102, the technician G places the phantom 107 on the placement unit 104. The radiation generating device 101 irradiates radiation under the first imaging condition. Note that the settings of the imaging condition, the irradiation instructions, and the like may be the same as those in step S1002.

[0127] In step S1103, the radiation detector 102 detects radiation that has passed through the phantom 107, and generates and acquires a first calibration image 303. The radiation detector 102 also transmits the acquired first calibration image 303 to the information processing device 110, and the image acquisition unit 202 acquires the first calibration image 303, which is an image of the phantom 107 and which has been transmitted from the radiation detector 102.

[0128] In step S1104, the radiation generating device 101 irradiates radiation under the second imaging condition with the phantom 107 placed on the placement unit 104. Radiation is irradiated under the second imaging condition. Note that the imaging condition settings and the like may be the same as those in step S1004.

[0129] In step S1105, the radiation detector 102 detects radiation that has passed through the phantom 107, and generates and acquires a second calibration image 304. The radiation detector 102 also transmits the acquired second calibration image 304 to the information processing device 110, and the image acquisition unit 202 acquires the second calibration image 304, which is an image of the phantom 107 and which has been transmitted from the radiation detector 102.

[0130] In step S1106, the radiation generating device 101 irradiates radiation under the imaging conditions used in step S1102 without placing the subject P and the phantom 107. The settings of the imaging conditions and the irradiation instructions may be the same as those in step S1102.

[0131] In step S1107, the radiation detector 102 detects the irradiated radiation and generates and acquires the first gain correction image 305. The radiation detector 102 also transmits the acquired first gain correction image 305 to the information processing device 110, and the image acquisition unit 202 acquires the first gain correction image 305 transmitted from the radiation detector 102. In step S1107, the information processing device 110 further controls the optical image acquisition unit 106 to capture a second optical image. The optical image acquisition unit 106 transmits the acquired second optical image to the information processing device 110, and the image acquisition unit 202 acquires the second optical image. Note that the timing for acquiring the second optical image may be step S1103, S1104, S1109, or step S1110.

[0132] In step S1108, the radiation generating device 101 irradiates radiation under the imaging conditions used in step S1104 without placing the subject P and the phantom 107. The imaging conditions may be set in the same manner as in step S1104.

[0133] In step S1109, the radiation detector 102 detects the irradiated radiation and generates and acquires the second gain correction image 306. The radiation detector 102 also transmits the acquired second gain correction image 306 to the information processing device 110, and the image acquisition unit 202 acquires the second gain correction image 306 transmitted from the radiation detector 102.

[0134] In step S1110, the positional relationship calculation unit 203 calculates, from the second optical image, the SID value and positional relationship information indicating the position on the radiation detector of the center of the irradiation field. The positional relationship calculation unit 203 can acquire the second positional relationship information based on the second optical image by the same method as in step S908. Hereinafter, the position on the radiation detector of the center of the irradiation field and the SID value in step S1110 are collectively referred to as the "second positional relationship", and the information indicating the second positional relationship is referred to as the "second positional relationship information". Note that in steps S1102 to S1109, it is assumed that the positional relationship between the tube of the radiation generation device 101 and the radiation detector 102 does not change.

[0135] In step S1111, the calculated second positional relationship information is stored in storage unit 204.

[0136] In step S1112, the correction unit 205 performs gain correction on the first calibration image 303 captured under the first shooting condition, using the first gain correction image 305 captured under the first shooting condition, to generate gain-corrected first calibration data 311. Similarly, the correction unit 205 performs gain correction on the second calibration image 304 captured under the second shooting condition, using the second gain correction image 306 captured under the second shooting condition, to generate gain-corrected second calibration data 312. The method of gain correction may be the same as that in step S712.

[0137] In step S1113, the bone image generating unit 206 performs energy subtraction processing on the gain-corrected first calibration data 311 and the gain-corrected second calibration data 312 acquired in step S1112 to generate a bone image 313. The energy subtraction processing may be the same processing as in step S713.

[0138] In step S1114, the bone density calculation section 207 calculates the bone density calibration value 314 based on the bone image 313 and the known bone density of the phantom 107. Here, the method of calculating the bone density calibration value may be the same as that in step S714.

[0139] When the bone mineral density calibration value is calculated in step S1114, the bone mineral density calibration imaging ends in step S1115.

[0140] Next, the bone density calculation for the subject will be described with reference to Fig. 12. Fig. 12 shows a flow of bone density value calculation according to this embodiment. When the bone density calculation for the subject is started in step S1201, the process proceeds to step S1202. Note that the bone density calculation for the subject may be started after the bone density calibration imaging is completed, or may be started in response to an instruction from the technician G, etc.

[0141] In step S1202, the correction unit 205 calculates the correction amount of the first gain correction image and the second gain correction image based on the positional relationship information stored in the storage unit 204, similarly to step S802. Here, the positional relationship information used includes the SID value when the subject image is acquired and the position on the radiation detector at the center of the irradiation field (first positional relationship information), and the SID value when the gain correction image is acquired and the position on the radiation detector at the center of the irradiation field (second positional relationship information). As described above, the positional relationship when the first subject image 301 and the second subject image 302 are captured is the same. Also, the positional relationship when the first gain correction image and the second gain correction image are captured is the same. Therefore, the correction amount calculated based on the first positional relationship information and the second positional relationship information can be applied to both the first gain correction image and the second gain correction image.

[0142] In step S1203, the correction unit 205 corrects the first gain correction image 305 and the second gain correction image 306 based on the correction amount calculated in step S1202, and generates a corrected first gain correction image 307 and a corrected second gain correction image 308. Note that the correction method may be the same as the correction method in step S803.

[0143] In step S1204, the correction unit 205 performs gain correction on the first object image 301 captured under the first imaging condition by using the corrected first gain correction image 307, and generates gain-corrected first object data 309. Similarly, the correction unit 205 performs gain correction on the second object image 302 captured under the second imaging condition by using the corrected second gain correction image 308, and generates gain-corrected second object data 310. The method of gain correction may be the same as that in step S804.

[0144] In step S1205, the bone image generating unit 206 performs energy subtraction processing on the gain-corrected first object data 309 and the gain-corrected second object data 310 acquired in step S1204 to generate a bone image 315. The energy subtraction processing may be the same processing as in step S805.

[0145] In step S1206, the bone density calculation unit 207 uses the bone image 315 and the bone density calibration value 314 to calculate and obtain the calibrated bone density value 316. For example, the bone density calculation unit 207 can obtain the calibrated bone density value 316 by substituting the pixel values ​​of the bone image 315 into an approximation line having the parameters of the bone density calibration value 314. When the calibrated bone density value 316 is obtained in step S1206, the bone density measurement ends in step S1207.

[0146] As described above, the image acquisition unit 202 can further acquire a first optical image, which is an example of an image obtained when capturing an object image, and a second optical image, which is an example of an image obtained when capturing an image for gain correction. Furthermore, the positional relationship calculation unit 203 can acquire first positional relationship information based on the first optical image, and acquire second positional relationship information based on the second optical image. Even in such a configuration, the positional relationship is corrected based on the captured optical image, so that the effort required for positioning the tube can be reduced.

[0147] In this embodiment, the positional relationship is determined based on the SID and the position of the center of the irradiation field on the radiation detector, and in step S1202, the correction amount is calculated in the same manner as in step S802 in embodiment 1. Alternatively, the position of the feature point in the optical image may be determined based on the positional relationship, and the correction amount may be calculated based on the positional deviation between the feature point in the first optical image and the feature point in the second optical image.

[0148] Here, an example of the correction amount calculation will be described on the assumption that the irradiation field size for a certain SID is kept constant by, for example, attaching a fixed aperture mask to the radiation generating device 101. First, in step S1006, the positional relationship calculation unit 203 calculates the characteristic point Q C In step S1110, the positional relationship calculation unit 203 calculates a feature point Q D The method for detecting the feature points in the optical image may be the same as the method for detecting the feature points described in step S904. C ,Q D may be, for example, a feature point indicating a specific location on the mounting portion 104, or may be a feature point indicating a marker attached to the mounting portion 104.

[0149] In step S1202, the correction unit 205 corrects the feature point Q in the first optical image C. C and feature point Q C A feature point Q in the second optical image D corresponding to D Then, the correction unit 205 performs scale conversion from the coordinate system on the optical image to the coordinate system of the radiation detector 102, and calculates offset amounts ΔX and ΔY. However, the scale amount used in this scale conversion is assumed to be acquired in advance by performing measurements or the like. Then, in step S1203, the correction unit 205 calculates the position deviation of the pixel positions (X A , Y A ) pixel value I A , the pixel position (X A+ΔX , Y A+ΔY ) pixel value I A+ΔXY The pixel value is changed to .

[0150] Furthermore, when the irradiation field size for the SID is kept constant, the correction unit 205 can also obtain the correction amount for the SID based on the feature amount in the optical image. In this case, the correction unit 205 may calculate the deviation of the SID when the subject image is acquired and when the gain correction image is acquired from a plurality of feature points on the first optical image C and a plurality of feature points on the second optical image D corresponding to the plurality of feature points, and calculate the correction amount from the deviation amount of the SID.

[0151] The above-described correction process can also prevent the gain correction from being unable to be performed appropriately due to a change in the positional relationship between the tube of the radiation generating device 101 and the radiation detector 102. This can prevent the occurrence of a situation where it is necessary to recapture a radiographic image or a gain correction image, thereby improving operability.

[0152] The correction unit 205 may use the trapezoidal approximation calculation method exemplified in the first embodiment. For example, the correction unit 205 may obtain the four corner points of the irradiation field from the feature points of the collimator lamp in the optical image, perform trapezoidal approximation, obtain the inclination of the tube of the radiation generating device 101 with respect to the radiation detector 102, and obtain the SID value. The correction unit 205 may perform trapezoidal approximation using the feature points of the cross region of the collimator lamp in the optical image where no light is irradiated. The correction unit 205 may also perform trapezoidal approximation using the feature points indicating a specific location on the placement unit 104 in the optical image or the feature points indicating a marker attached on the placement unit 104. In these cases, the correction unit 205 can perform a correction process taking into account the inclination of the tube with respect to the radiation detector 102, and can perform more appropriate gain correction.

[0153] Example 4 In the first to third embodiments, the change in the positional relationship between the tube of the radiation generator and the radiation detector when capturing an image of the subject and when capturing an image for gain correction is corrected by image processing. However, if the change in the positional relationship is significant, it may not be possible to correct the change in the positional relationship by image processing. Therefore, in the information processing device according to the fourth embodiment of the present disclosure, if the change (deviation) in the positional relationship is greater than a threshold, a warning is issued to prompt re-imaging.

[0154] Hereinafter, the bone density calculation according to this embodiment will be described with reference to Fig. 13. Since the radiation imaging system and the information processing device according to this embodiment have the same configuration as the radiation imaging system 100 and the information processing device 110 according to the first embodiment, the same reference numerals are used and the description will be omitted. In this embodiment, the description will be given on the premise that the subject imaging shown in Fig. 4 and the bone density calibration imaging shown in Fig. 7 have been completed.

[0155] In this embodiment, when bone density calculation is started in step S1301, the process proceeds to step S1302. In step S1302, the correction unit 205 determines whether the deviation amount between the irradiation field center when the subject image is captured and the irradiation field center when the gain-corrected image is captured is equal to or less than a threshold value. If it is determined that the deviation amount of the irradiation center is equal to or less than the threshold value, the process proceeds to step S1303. Here, the position of the irradiation field center when the subject image is captured may be, for example, the position on the radiation detector of the irradiation field center included in the positional relationship when the subject image is captured, calculated in step S406. In addition, the position of the irradiation field center when the gain-corrected image is captured may be, for example, the position on the radiation detector of the irradiation field center included in the positional relationship when the gain-corrected image is captured, calculated in step S710. The processes of steps S1303 to S1308 are the same as steps S802 to S807, and therefore will not be described.

[0156] On the other hand, if it is determined in step S1302 of Fig. 13 that the deviation amount of the irradiation field center is greater than the threshold value, the process proceeds to step S1309. In step S1309, the information processing device 110 prompts the technician G to retake the image of the subject or the image for gain correction by displaying a warning on the display unit 111. After the warning is displayed in step S1309, the process proceeds to step S1308, and the bone density calculation ends. Note that the warning is not limited to being displayed on the display unit 111, and may be displayed on another display device (not shown). The warning may also be displayed in a manner that prompts the technician G to retake the image by issuing a sound using a speaker (not shown), for example.

[0157] As described above, the information processing device 110 according to this embodiment can issue a warning to prompt the user to recapture the subject image or the gain correction image when the correction amount for correcting one of the subject image and the gain correction image is greater than a threshold value. In this configuration, the efficiency of the examination can be improved by prompting the user to recapture the subject image when there is a significant change in the positional relationship between the tube of the radiation generating device 101 and the radiation detector 102 when capturing the subject image and the gain correction image. Furthermore, when the subject is recaptured, the subject's radiation exposure increases. In response to this, when the subject is recaptured, the gain correction image is recaptured, thereby preventing the subject's radiation exposure from increasing.

[0158] In this embodiment, in the bone density calculation process after the subject imaging and the bone density calibration imaging according to the first embodiment are completed, a warning is displayed to prompt the user to perform imaging again if the deviation in the positional relationship is greater than a threshold value. However, the timing of the determination of the deviation in the positional relationship (step S1302) and the warning to prompt the user to perform imaging again (step S1309) are not limited to this. These processes may be performed after the positional relationship of the subject image and the positional relationship of the gain correction image are acquired. Therefore, these processes may be performed after step S710, step S908, or step S1110, and may be performed after step S909 or step S1201, for example.

[0159] (Variation 1) In the above first to fourth embodiments, when calculating the correction amounts of the first and second gain correction images, the correction amounts of the images due to the influence of a grid or scattered rays attached to the radiation detector 102 may be taken into consideration. For this reason, the correction unit 205 may correct one of the subject image and the gain correction image based on at least one of the scattered rays or the grid attached to the radiation generating device 101. Note that the influence of the grid or scattered rays on the image may be calculated by any known calculation method, and the correction amount may be calculated based on the difference between the influence of the grid or scattered rays when the subject image is captured and the influence of the gain correction image when the gain correction image is captured.

[0160] Furthermore, the correction amounts of the first and second gain correction images may be acquired based on actual values ​​measured in advance. For example, when calculating the correction amounts (step S802, step S910, or step S1303), the correction unit 205 may calculate the correction amounts using a conversion table that receives the first and second positional relationship information as inputs and outputs the correction amounts. In this case, for example, the table can be created by capturing the subject image and the gain correction image in various positional relationships in advance and calculating the correction amounts corresponding to each positional relationship. Note that the correction amounts when creating the table may be calculated by the calculation method described above, or may be correction amounts determined by an engineer or the like while checking the images.

[0161] (Variation 2) In the above-described first to fourth embodiments, the information processing device 110 may display the acquired gain-corrected object image and bone density on the display unit 111. Furthermore, the information processing device 110 may display the obtained bone density and gain-corrected object image on the display unit 111 side by side, or may display them in a switching manner, or may display them in a superimposed manner.

[0162] Furthermore, the correction unit 205 may correct the amount of correction when correcting one of the gain correction image and the subject image based on the positional relationship information according to an instruction from the technician G. In this case, the information processing device 110 can support the technician G in inputting an instruction to correct the amount of correction by displaying the amount of correction on the display unit 111. Note that the instruction to correct the amount of correction by the technician G may be given via the input unit 112, and may be given, for example, by inputting a numerical value or by operating a display such as a bar. Furthermore, the information processing device 110 can support the technician G in checking the result of the correction amount correction by displaying, on the display unit 111, a gain-corrected subject image obtained by using the gain correction image corrected using the corrected amount of correction.

[0163] Furthermore, the information processing device 110 may preset a plurality of different correction amount candidates. In this case, the technician G can instruct the correction of the correction amount by selecting one of the plurality of correction amount candidates. Furthermore, the information processing device 110 may display, on the display unit 111, a plurality of gain-corrected subject images obtained by using a gain correction image corrected with a correction amount corrected using a plurality of correction amount candidates. In this case, the technician G can instruct the correction amount corresponding to the selected gain-corrected subject image by selecting a desired gain-corrected subject image from the plurality of displayed gain-corrected subject images.

[0164] (Variation 3) In the above first to fourth embodiments, the image acquiring unit 202 of the information processing device 110 acquired a radiation image from the communicatively connected radiation detector 102. In contrast, the image acquiring unit 202 may acquire a radiation image from an external storage device connected to the information processing device 110, or a radiation detection device or an external storage device connected to the information processing device 110 via an arbitrary network.

[0165] (Other Examples) The present disclosure can also be realized by a process in which a program for implementing one or more functions of the above-described embodiments is provided to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) for implementing one or more functions. A computer may have one or more processors or circuits, and may include separate computers or a network of separate processors or circuits for reading and executing computer-executable instructions.

[0166] The processor or circuitry may include a central processing unit (CPU), a microprocessing unit (MPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), or a field programmable gateway (FPGA), and the processor or circuitry may include a digital signal processor (DSP), a data flow processor (DFP), or a neural processing unit (NPU).

[0167] The above disclosure includes the following configurations, methods, and programs. (Configuration 1) an image acquisition unit that acquires a plurality of subject images obtained by imaging a subject using a plurality of different radiation energies and a plurality of gain correction images obtained by imaging the subject using the plurality of different radiation energies without passing through the subject; a positional relationship acquisition unit that acquires first positional relationship information between a radiation generation device and a radiation detector based on images obtained when the plurality of subject images are captured, and acquires second positional relationship information between the radiation generation device and the radiation detector based on images obtained when the plurality of gain correction images are captured; a correction unit that corrects one of the plurality of object images and the plurality of gain correction images based on the first positional relationship information and the second positional relationship information, and performs gain correction on the plurality of object images using the corrected one and the other of the plurality of object images and the plurality of gain correction images; an image generating unit that generates a material decomposition image using the plurality of gain-corrected object images; An image processing device comprising: (Configuration 2) an image acquisition unit that acquires a subject image obtained by imaging a subject and a gain correction image obtained by imaging without passing through the subject; a positional relationship acquisition unit that acquires first positional relationship information between a radiation generation device and a radiation detector based on an image obtained when the object image is captured, and acquires second positional relationship information between the radiation generation device and the radiation detector based on an image obtained when the gain correction image is captured; a correction unit that corrects one of the object image and the gain correction image based on the first positional relationship information and the second positional relationship information, and performs gain correction on the object image using the corrected one and the other of the object image and the gain correction image; An image processing device comprising: (Configuration 3) 3. The image processing device according to configuration 1 or 2, wherein the positional relationship acquisition unit acquires the first positional relationship information based on the object image, and acquires the second positional relationship information based on the gain correction image. (Configuration 4) the image acquisition unit further acquires a first optical image which is an image obtained when the object image is captured, and a second optical image which is an image obtained when the gain correction image is captured; 3. The image processing device according to configuration 1 or 2, wherein the positional relationship acquisition unit acquires the first positional relationship information based on the first optical image, and acquires the second positional relationship information based on the second optical image. (Configuration 5) The image processing device according to any one of configurations 1 to 4, wherein the positional relationship acquisition unit acquires the first positional relationship information based on a size and position of the radiation irradiation field in an image obtained when the subject image is captured, and acquires the second positional relationship information based on the size and position of the radiation irradiation field in an image obtained when the gain correction image is captured. (Configuration 6) The image processing device according to any one of configurations 1 to 4, wherein the positional relationship acquisition unit acquires the first positional relationship information by trapezoidally approximating the radiation irradiation field in an image obtained when capturing the subject image, and acquires the second positional relationship information by trapezoidally approximating the radiation irradiation field in an image obtained when capturing the gain correction image. (Configuration 7) The image processing device according to any one of configurations 1 to 6, wherein the first positional relationship information and the second positional relationship information include at least one of an inclination or distance of the radiation detector relative to the radiation generation device, a size of a radiation irradiation field, and a position of the irradiation field on the radiation detector. (Configuration 8) 8. The image processing device according to any one of configurations 1 to 7, wherein the correction unit corrects one of the object image and the gain correction image based on at least one of scattered radiation or a grid attached to the radiation generating device. (Configuration 9) The image processing device according to any one of configurations 1 to 8, wherein, when a correction amount when correcting one of the object image and the gain correction image is greater than a threshold value, the image processing device issues a warning to prompt the user to re-capture the object image or the gain correction image. (Configuration 10) 10. The image processing device according to any one of configurations 1 to 9, wherein the correction unit modifies an amount of correction when correcting one of the object image and the gain correction image in response to an instruction from an operator. (Configuration 11) the subject is a human body, 2. The image processing device according to configuration 1, wherein the material decomposition image is a bone image. (Configuration 12) 12. The image processing device according to configuration 11, further comprising a bone density acquisition unit that acquires a bone density of the subject based on the bone image. (Configuration 13) the image acquisition unit further acquires a plurality of calibration images obtained by imaging a phantom having a predetermined bone density using the plurality of different radiation energies; the correction unit performs gain correction on the calibration images by using the gain correction images and the calibration images; the image generating unit generates a bone image using the gain-corrected calibration images; The bone density acquisition unit includes: obtaining a calibration value using a bone image generated using the gain-corrected calibration images; acquiring the bone density using a bone image generated using the plurality of gain-corrected subject images and the calibration value; 13. The image processing device according to configuration 12. (Configuration 14) the plurality of calibration images are a plurality of images obtained by capturing the plurality of gain correction images consecutively, 14. The image processing device according to configuration 13, wherein the positional relationship acquisition unit acquires the second positional relationship information by using the plurality of calibration images as images obtained when the plurality of gain correction images are captured. (Configuration 15) A radiation generating device that irradiates radiation; a radiation detector for detecting the radiation; An image processing device according to any one of configurations 1 to 14, A radiography system comprising: (Method 1) Obtaining a plurality of object images obtained by imaging the object using a plurality of different radiation energies, and a plurality of gain correction images obtained by imaging the object using the plurality of different radiation energies without passing through the object; acquiring first positional relationship information between a radiation generation device and a radiation detector based on images obtained during capture of the plurality of subject images, and acquiring second positional relationship information between the radiation generation device and the radiation detector based on images obtained during capture of the plurality of gain correction images; correcting one of the plurality of object images and the plurality of gain correction images based on the first positional relationship information and the second positional relationship information, and performing gain correction on the plurality of object images using the corrected one and the other of the plurality of object images and the plurality of gain correction images; generating a material decomposition image using the gain-corrected object images; A control method for an image processing device comprising: (Method 2) Obtaining an object image obtained by imaging the object and a gain correction image obtained by imaging without the object; acquiring first positional relationship information between a radiation generation device and a radiation detector based on an image obtained when capturing the object image, and acquiring second positional relationship information between the radiation generation device and the radiation detector based on an image obtained when capturing the gain correction image; correcting one of the object image and the gain correction image based on the first positional relationship information and the second positional relationship information, and performing gain correction on the object image using the corrected one and the other of the object image and the gain correction image; A control method for an image processing device comprising: (Program 1) A program that, when executed by a computer, causes the computer to execute each step of the method for controlling an image processing device according to the first or second method.

[0168] Although the present disclosure has been described above with reference to the examples and modifications, the present disclosure is not limited to the above examples and modifications. Inventions modified within the scope of the present disclosure and inventions equivalent to the present disclosure are also included in the present disclosure. In addition, the above-mentioned examples and modifications can be appropriately combined within the scope of the present disclosure. [Explanation of symbols]

[0169] 110: information processing device (image processing device), 202: image acquisition unit, 203: positional relationship calculation unit, 205: correction unit

Claims

1. an image acquisition unit that acquires a plurality of subject images obtained by imaging a subject using a plurality of different radiation energies and a plurality of gain correction images obtained by imaging the subject using the plurality of different radiation energies without passing through the subject; a positional relationship acquisition unit that acquires first positional relationship information between a radiation generation device and a radiation detector based on images obtained during capture of the plurality of subject images, and acquires second positional relationship information between the radiation generation device and the radiation detector based on images obtained during capture of the plurality of gain correction images; a correction unit that corrects one of the plurality of object images and the plurality of gain correction images based on the first positional relationship information and the second positional relationship information, and performs gain correction on the plurality of object images using the corrected one and the other of the plurality of object images and the plurality of gain correction images; an image generating unit that generates a material decomposition image using the plurality of gain-corrected object images; An image processing device comprising:

2. an image acquisition unit that acquires a subject image obtained by imaging a subject and a gain correction image obtained by imaging without passing through the subject; a positional relationship acquisition unit that acquires first positional relationship information between a radiation generation device and a radiation detector based on an image obtained when the subject image is captured, and acquires second positional relationship information between the radiation generation device and the radiation detector based on an image obtained when the gain correction image is captured; a correction unit that corrects one of the object image and the gain correction image based on the first positional relationship information and the second positional relationship information, and performs gain correction on the object image using the corrected one and the other of the object image and the gain correction image; An image processing device comprising:

3. The image processing apparatus according to claim 1 , wherein the positional relationship acquisition unit acquires the first positional relationship information based on the subject image, and acquires the second positional relationship information based on the gain correction image.

4. the image acquisition unit further acquires a first optical image which is an image obtained when the object image is captured, and a second optical image which is an image obtained when the gain correction image is captured, The image processing device according to claim 1 , wherein the positional relationship acquisition unit acquires the first positional relationship information based on the first optical image, and acquires the second positional relationship information based on the second optical image.

5. 3. The image processing device according to claim 1, wherein the positional relationship acquisition unit acquires the first positional relationship information based on a size and position of the radiation irradiation field in an image obtained when the subject image is captured, and acquires the second positional relationship information based on a size and position of the radiation irradiation field in an image obtained when the gain correction image is captured.

6. 3. The image processing device according to claim 1, wherein the positional relationship acquisition unit acquires the first positional relationship information by trapezoidally approximating a radiation irradiation field in an image obtained when the subject image is captured, and acquires the second positional relationship information by trapezoidally approximating a radiation irradiation field in an image obtained when the gain correction image is captured.

7. 3 . The image processing device according to claim 1 , wherein the first positional relationship information and the second positional relationship information include at least one of an inclination or a distance of the radiation detector relative to the radiation generation device, a size of an irradiation field of radiation, and a position of the irradiation field on the radiation detector.

8. The image processing apparatus according to claim 1 , wherein the correction unit corrects one of the object image and the gain correction image based on at least one of scattered radiation or a grid attached to the radiation generating device.

9. 3. The image processing device according to claim 1, wherein the image processing device issues a warning to prompt the user to re-capture the object image or the gain correction image when a correction amount for correcting one of the object image and the gain correction image is greater than a threshold value.

10. The image processing apparatus according to claim 1 , wherein the correction unit modifies an amount of correction used when correcting one of the object image and the gain correction image in response to an instruction from an operator.

11. the subject is a human body, The image processing apparatus according to claim 1 , wherein the material decomposition image is a bone image.

12. The image processing apparatus according to claim 11 , further comprising a bone density acquisition unit that acquires a bone density of the subject based on the bone image.

13. the image acquisition unit further acquires a plurality of calibration images obtained by imaging a phantom having a predetermined bone density using the plurality of different radiation energies; the correction unit performs gain correction on the calibration images by using the gain correction images and the calibration images; the image generating unit generates a bone image using the gain-corrected calibration images; The bone density acquisition unit includes: obtaining a calibration value using a bone image generated using the gain-corrected calibration images; acquiring the bone density using a bone image generated using the plurality of gain-corrected subject images and the calibration value; The image processing device according to claim 12.

14. the plurality of calibration images are a plurality of images obtained by capturing the plurality of gain correction images consecutively, The image processing device according to claim 13 , wherein the positional relationship acquisition unit acquires the second positional relationship information by using the plurality of calibration images as images obtained when the plurality of gain correction images are captured.

15. A radiation generating device that irradiates radiation; a radiation detector for detecting the radiation; The image processing device according to claim 1 or 2, A radiography system comprising:

16. Obtaining a plurality of object images obtained by imaging the object using a plurality of different radiation energies, and a plurality of gain correction images obtained by imaging the object using the plurality of different radiation energies without passing through the object; acquiring first positional relationship information between a radiation generation device and a radiation detector based on images obtained during capture of the plurality of subject images, and acquiring second positional relationship information between the radiation generation device and the radiation detector based on images obtained during capture of the plurality of gain correction images; correcting one of the plurality of object images and the plurality of gain correction images based on the first positional relationship information and the second positional relationship information, and performing gain correction on the plurality of object images using the corrected one and the other of the plurality of object images and the plurality of gain correction images; generating a material decomposition image using the gain-corrected object images; A control method for an image processing device comprising:

17. Obtaining an object image obtained by imaging the object and a gain correction image obtained by imaging without the object; acquiring first positional relationship information between a radiation generation device and a radiation detector based on an image obtained when capturing the subject image, and acquiring second positional relationship information between the radiation generation device and the radiation detector based on an image obtained when capturing the gain correction image; correcting one of the object image and the gain correction image based on the first positional relationship information and the second positional relationship information, and performing gain correction on the object image using the corrected one and the other of the object image and the gain correction image; A control method for an image processing device comprising:

18. A program that, when executed by a computer, causes the computer to execute each step of the method for controlling an image processing apparatus according to claim 16 or 17.

Images