Image processing device, radiation image capturing system, image processing method, and image processing program

Abstract

To provide an image processing device, a radiation imaging system, an image processing method, and an image processing program capable of deriving an amount of positional deviation between projection images with a high degree of precision.SOLUTION: In an image processing device, a processor acquires a plurality of projection images; acquires a plurality of tomographic images generated using the plurality of projection images, which correspond to each of a plurality of tomographic surfaces of a subject; generates a plurality of reference material presence pseudo projection images including reference material images by performing pseudo projection from an irradiation position in settings corresponding to the irradiation position of each of the plurality of projection images using the tomographic image including the reference material image indicating the reference material used as a reference for deriving the amount of positional deviation between the projection images of the plurality of tomographic images; and derives the amount of positional deviation between the projection images on the basis of the plurality of projection images and the plurality of reference material presence pseudo projection images.SELECTED DRAWING: Figure 10

Description

[Technical Field]

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

[0002] 2. Description of the Related Art So-called tomosynthesis imaging is known, in which a radiation source irradiates a subject with radiation from a plurality of irradiation positions each having a different irradiation angle, and a plurality of projection images of the subject are captured at different irradiation positions.

[0003] In tomosynthesis imaging, multiple projection images are captured, and therefore positional deviations may occur between the projection images due to the effects of the subject's body movement, deviations in the position of the radiation source at each irradiation position, etc. A problem has been that a tomographic image generated using multiple projection images with positional deviations results in a blurred image.

[0004] Therefore, there are known techniques for correcting the positional deviation between projected images. For example, Patent Document 1 discloses a technique for deriving the amount of positional deviation between a plurality of projected images on a tomographic plane corresponding to a tomographic image on which a feature point is detected, using the feature point as a reference. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 067475 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, a projection image is an image of structures aligned in the direction of radiation irradiation and contains a large amount of information. Therefore, the projection image may contain image information of structures that interferes with deriving the amount of misalignment between the projection images. In the above-described conventional technology, the influence of unnecessary information may reduce the accuracy of deriving the amount of misalignment between the projection images.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide an image processing device, a radiographic image capturing system, an image processing method, and an image processing program that can accurately derive the amount of positional deviation between projected images. [Means for solving the problem]

[0008] In order to achieve the above object, an image processing device of a first aspect of the present disclosure is an image processing device that processes a plurality of projection images obtained by irradiating a subject with radiation from a radiation source from each of a plurality of irradiation positions with different irradiation angles, and includes a processor. The processor acquires the plurality of projection images, acquires a plurality of tomographic images generated using the plurality of projection images and corresponding to each of a plurality of tomographic planes of the subject, and uses a tomographic image among the plurality of tomographic images that includes a reference object image representing a reference object to be used as a basis for deriving the amount of positional deviation between the projection images, and generates a plurality of pseudo-projection images with a reference object that include the reference object image by pseudo-projecting from a set irradiation position that corresponds to each of the irradiation positions of the plurality of projection images, and derives the amount of positional deviation between the projection images based on the plurality of projection images and the plurality of pseudo-projection images with a reference object.

[0009] An image processing device according to a second aspect of the present disclosure is the image processing device according to the first aspect, wherein the processor generates a pseudo projection image with a reference object using only a tomographic image in which the reference object is depicted.

[0010] An image processing device of a third aspect of the present disclosure is an image processing device of the first or second aspect that generates a partial pseudo-projection image as a pseudo-projection image with reference object by pseudo-projecting onto a reference object region in a tomographic image that includes a reference object image.

[0011] An image processing device according to a fourth aspect of the present disclosure is the image processing device according to any one of the first to third aspects, wherein the processor generates a plurality of tomographic images based on the plurality of projection images and the amount of positional deviation. The corresponding misalignment is corrected. A plurality of tomographic images are also generated.

[0012] An image processing device according to a fifth aspect of the present disclosure is the image processing device according to any one of the first to fourth aspects, wherein the processor issues a notification when the amount of positional deviation exceeds a preset threshold.

[0013] An image processing device according to a sixth aspect of the present disclosure is the image processing device according to any one of the first to fifth aspects, wherein the subject is a breast and the reference object is a calcification or a mammary gland.

[0014] In addition, in order to achieve the above object, a radiographic imaging system according to a seventh aspect of the present disclosure includes a radiation source that generates radiation, a radiographic imaging device that performs tomosynthesis imaging by irradiating a subject with radiation from the radiation source from each of a plurality of irradiation positions having different irradiation angles and capturing a projection image of the subject at each irradiation position, and an image processing device according to the present disclosure.

[0015] Furthermore, in order to achieve the above object, an image processing method according to an eighth aspect of the present disclosure is an image processing method for processing a plurality of projection images obtained by irradiating a subject with radiation from a radiation source from each of a plurality of irradiation positions having different irradiation angles, the image processing method comprising the steps of: acquiring a plurality of projection images; acquiring a plurality of tomographic images generated using the plurality of projection images and corresponding to each of a plurality of tomographic planes of the subject; using a tomographic image among the plurality of tomographic images including a reference object image representing a reference object used as a basis for deriving the amount of positional deviation between the projection images; generating a plurality of pseudo projection images with reference object including the reference object image by pseudo-projecting from a set irradiation position corresponding to each of the irradiation positions of the plurality of projection images; and deriving the amount of positional deviation between the projection images based on the plurality of projection images and the plurality of pseudo projection images with reference object, the image processing method is performed by a computer.

[0016] Furthermore, in order to achieve the above object, an image processing program of a ninth aspect of the present disclosure is an image processing program that processes a plurality of projection images obtained by irradiating a subject with radiation from a radiation source from each of a plurality of irradiation positions having different irradiation angles, and that acquires a plurality of projection images, acquires a plurality of tomographic images that are generated using the plurality of projection images and correspond to each of a plurality of tomographic planes of the subject, and uses a tomographic image among the plurality of tomographic images that includes a reference object image representing a reference object used as a basis for deriving the amount of positional deviation between the projection images, and generates a plurality of pseudo projection images with reference object that include the reference object image by pseudo-projecting from a set irradiation position that corresponds to each of the irradiation positions of the plurality of projection images, and causes a computer to execute a process of deriving the amount of positional deviation between the projection images based on the plurality of projection images and the plurality of pseudo projection images with reference object. [Effects of the Invention]

[0017] According to the present disclosure, the amount of positional deviation between projected images can be derived with high accuracy. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a configuration diagram schematically illustrating an example of the overall configuration of a radiation image capturing system according to an embodiment; [Figure 2] FIG. 1 is a diagram illustrating an example of tomosynthesis imaging. [Figure 3] 1 is a block diagram showing an example of the configuration of a mammography apparatus and a console according to a first embodiment. [Figure 4] FIG. 2 is a functional block diagram illustrating an example of functions of the console according to the first embodiment. [Figure 5] 10A and 10B are diagrams illustrating the correspondence between a projection image and a tomographic image generated from a plurality of projection images. [Figure 6] 10A and 10B are diagrams for explaining generation of a reference object-free pseudo projection image by a pseudo projection image generation unit. [Figure 7] 10A and 10B are diagrams for explaining generation of a component-removed image by a component-removed image generating unit. [Figure 8] 4 is a flowchart showing an example of the flow of image processing by the console of the first embodiment. [Figure 9] FIG. 10 is a block diagram showing an example of the configuration of a control unit of a console according to a second embodiment. [Figure 10] FIG. 10 is a functional block diagram illustrating an example of functions of a console according to a second embodiment. [Figure 11] 10A and 10B are diagrams for explaining generation of a reference object-included pseudo projection image in the second embodiment. [Figure 12] 10A and 10B are diagrams for explaining generation of a pseudo projection image with a reference object by a pseudo projection image generation unit. [Figure 13] 10 is a flowchart showing an example of the flow of image processing by the console of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the embodiment.

[0020] [First embodiment] First, an example of the overall configuration of the radiation image capturing system of this embodiment will be described. Fig. 1 shows a configuration diagram illustrating an example of the overall configuration of the radiation image capturing system 1 of this embodiment. As shown in Fig. 1, the radiation image capturing system 1 of this embodiment includes a mammography apparatus 10 and a console 12.

[0021] First, the mammography device 10 of this embodiment will be described. Figure 1 shows a side view of an example of the appearance of the mammography device 10 of this embodiment. Note that Figure 1 shows an example of the appearance of the mammography device 10 when viewed from the left side of the subject.

[0022] The mammography device 10 of this embodiment operates under the control of the console 12 and is a device that takes a radiographic image of a subject's breast by irradiating the breast with radiation R (e.g., X-rays). Note that the mammography device 10 may be a device that takes images of the subject's breast not only when the subject is standing (standing position) but also when the subject is sitting in a chair (including a wheelchair) or the like (seated position).

[0023] In addition, the mammography device 10 of this embodiment has the function of performing normal imaging, in which imaging is performed by positioning the radiation source at an irradiation position along the normal direction of the detection surface 20A of the radiation detector, and so-called tomosynthesis imaging, in which imaging is performed by moving the radiation source 29 to each of multiple irradiation positions.

[0024] The radiation detector 20 detects radiation R that has passed through the breast, which is the subject. In detail, the radiation detector 20 detects radiation R that has entered the breast of the subject and the imaging table 24 and reached the detection surface 20A of the radiation detector 20, generates a radiographic image based on the detected radiation R, and outputs image data representing the generated radiographic image. Hereinafter, the series of operations of irradiating radiation R from the radiation source 29 and generating a radiographic image by the radiation detector 20 may be referred to as "imaging." The type of radiation detector 20 in this embodiment is not particularly limited, and may be, for example, an indirect conversion type radiation detector that converts radiation R into light and then converts the converted light into electric charges, or a direct conversion type radiation detector that directly converts radiation R into electric charges.

[0025] 1, the radiation detector 20 is disposed inside the imaging table 24. In the mammography apparatus 10 of this embodiment, when imaging is performed, the breast of the subject is positioned on the imaging surface 24A of the imaging table 24 by the user.

[0026] The compression plate 38 used to compress the breast when imaging is attached to a compression unit 36 ​​provided on the imaging table 24. More specifically, the compression unit 36 ​​is provided with a compression plate drive section (not shown) that moves the compression plate 38 in a direction toward or away from the imaging table 24 (hereinafter referred to as the "up and down direction"). A support section 39 of the compression plate 38 is detachably attached to the compression plate drive section and is moved in the up and down direction by the compression plate drive section, compressing the breast of the subject between the compression plate 38 and the imaging table 24. The compression plate 38 of this embodiment is an example of a compression member of the present disclosure.

[0027] As shown in Figure 1, the mammography device 10 of this embodiment includes an imaging table 24, an arm unit 33, a base 34, and a shaft unit 35. The arm unit 33 is held by the base 34 so that it can move up and down (in the Z-axis direction). The shaft unit 35 also allows the arm unit 33 to rotate relative to the base 34. The shaft unit 35 is fixed to the base 34, and the shaft unit 35 and the arm unit 33 rotate together.

[0028] Gears are provided on the shaft 35 and the compression unit 36 ​​of the imaging table 24, and by switching between an engaged state and a non-engaged state of these gears, it is possible to switch between a state in which the compression unit 36 ​​of the imaging table 24 and the shaft 35 are connected and rotate together, and a state in which the shaft 35 is separated from the imaging table 24 and rotates freely. Note that the switching between transmission and non-transmission of power to the shaft 35 is not limited to the gears, and various other mechanical elements can be used.

[0029] The arm unit 33 and the imaging table 24 are independently rotatable relative to the base 34, with the shaft 35 serving as a rotation axis. In this embodiment, the base 34, the arm unit 33, and the compression unit 36 ​​of the imaging table 24 are each provided with an engagement portion (not shown), and by switching the state of this engagement portion, the arm unit 33 and the compression unit 36 ​​of the imaging table 24 are each connected to the base 34. Either or both of the arm unit 33 and the imaging table 24 connected to the shaft 35 rotate together around the shaft 35.

[0030] When performing tomosynthesis imaging in the mammography device 10, the radiation source 29 of the radiation irradiation unit 28 is moved sequentially to each of a plurality of irradiation positions with different irradiation angles by the rotation of the arm unit 33. The radiation source 29 has a radiation tube (not shown) that generates radiation R, and the radiation tube is moved to each of the plurality of irradiation positions in accordance with the movement of the radiation source 29. FIG. 2 is a diagram for explaining an example of tomosynthesis imaging. Note that the compression paddle 38 is not shown in FIG. 2. In this embodiment, as shown in FIG. 2, the radiation source 29 is moved sequentially to each of the irradiation positions 19 with irradiation angles that differ by a predetermined angle θ. k (k=1, 2, . . . , the maximum value is 7 in FIG. 2), in other words, the radiation detector 20 is moved to a position where the irradiation angle of the radiation R with respect to the detection surface 20A of the radiation detector 20 is different. k In the radiation imaging system 1, radiation R is irradiated from the radiation source 29 toward the breast W in response to an instruction from the console 12, and a radiation image is captured by the radiation detector 20. k and move to each of the irradiation positions 19 k In the example of Fig. 2, when tomosynthesis imaging is performed to capture radiation images at each irradiation position 19, 13 radiation images are obtained. In the following, in tomosynthesis imaging, the radiation images captured at each irradiation position 19 are referred to as "projection images" when they are to be distinguished from other radiation images. Furthermore, when referring to radiation images collectively regardless of the type of projection image or tomographic image, which will be described later, they are simply referred to as "radiation images." Furthermore, in the following, when referring to radiation images captured at each irradiation position 19, k When collectively referring to the irradiation positions, the symbol k for distinguishing each irradiation position is omitted and they are referred to as "irradiation positions 19." k Projection images taken at irradiation position 19 k The images corresponding to the above will be described by adding the symbol "k" representing the irradiation position 19k to the symbol representing each image.

[0031] As shown in Fig. 2, the irradiation angle of radiation R refers to the angle α formed between a normal CL to the detection surface 20A of the radiation detector 20 and a radiation axis RC. The radiation axis RC is an axis connecting the focal point of the radiation source 29 at each irradiation position 19 and a predetermined position such as the center of the detection surface 20A. Hereinafter, the detection surface 20A of the radiation detector 20 is assumed to be a plane substantially parallel to the imaging surface 24A. Hereinafter, the predetermined range within which the irradiation angle is varied in tomosynthesis imaging, as shown in Fig. 2, will be referred to as the "irradiation angle range."

[0032] On the other hand, when performing normal imaging in the mammography device 10, the radiation source 29 of the radiation irradiation unit 28 is positioned at the irradiation position 19 where the irradiation angle α is 0 degrees. k (Irradiation position along the normal direction 19 k 2) remains at the irradiation position 194). In response to an instruction from the console 12, the radiation source 29 irradiates the subject with radiation R, and the radiation detector 20 captures a radiological image.

[0033] 3 is a block diagram showing an example of the configuration of the mammography apparatus and console of this embodiment. As shown in FIG. 3, the mammography apparatus 10 of this embodiment further includes a control unit 40, a memory unit 42, an I / F (Interface) unit 44, an operation unit 46, and a radiation source movement unit 47. The control unit 40, the memory unit 42, the I / F unit 44, the operation unit 46, and the radiation source movement unit 47 are connected via a bus 49 such as a system bus or a control bus so that various information can be exchanged between them.

[0034] The control unit 40 controls the overall operation of the mammography apparatus 10 in accordance with the control of the console 12. The control unit 40 includes a CPU (Central Processing Unit) 40A, a ROM (Read Only Memory) 40B, and a RAM (Random Access Memory) 40C. The ROM 40B stores various programs in advance, including an imaging program 41 executed by the CPU 40A to control the imaging of radiographic images. The RAM 40C temporarily stores various data.

[0035] The memory unit 42 stores image data of radiographic images captured by the radiation detector 20, as well as various other information. Specific examples of the memory unit 42 include a hard disk drive (HDD) and a solid state drive (SSD). The I / F unit 44 communicates various information with the console 12 via wireless or wired communication. Image data of radiographic images captured by the radiation detector 20 in the mammography apparatus 10 is transmitted to the console 12 via the I / F unit 44 via wireless or wired communication.

[0036] The control unit 40 , storage unit 42 , and I / F unit 44 of this embodiment are each provided inside the imaging stand 24 .

[0037] The operation unit 46 is provided as a plurality of switches on the imaging table 24 of the mammography apparatus 10. The operation unit 46 may be provided as a touch panel switch or as a foot switch that is operated by a user such as a doctor or technician.

[0038] As described above, when tomosynthesis imaging is performed, the radiation source moving unit 47 has a function of moving the radiation source 29 to each of the plurality of irradiation positions 19 under the control of the control unit 40. Specifically, the radiation source moving unit 47 moves the radiation source 29 to each of the plurality of irradiation positions 19 by rotating the arm unit 33 relative to the imaging table 24. The radiation source moving unit 47 in this embodiment is provided inside the arm unit 33.

[0039] On the other hand, the console 12 of this embodiment has the function of controlling the mammography device 10 using imaging orders and various information obtained from a RIS (Radiology Information System) or the like via a wireless communication LAN (Local Area Network) or the like, and instructions given by the user via the operation unit 56 or the like.

[0040] 3, the console 12 includes a control unit 50, a storage unit 52, an I / F unit 54, an operation unit 56, and a display unit 58. The control unit 50, the storage unit 52, the I / F unit 54, the operation unit 56, and the display unit 58 are connected via a bus 59 such as a system bus or a control bus so as to be able to exchange various information with each other.

[0041] The control unit 50 of this embodiment controls the overall operation of the console 12. The control unit 50 includes a CPU 50A, a ROM 50B, and a RAM 50C. The ROM 50B pre-stores various programs, including an image generation program 51 executed by the CPU 50A. The RAM 50C temporarily stores various data. In this embodiment, the CPU 50A is an example of a processor of the present disclosure, and the console 12 is an example of an image processing device of the present disclosure. Furthermore, the image generation program 51 of this embodiment is an example of an image processing program of the present disclosure.

[0042] The storage unit 52 stores image data of radiographic images captured by the mammography apparatus 10, as well as various other information. Specific examples of the storage unit 52 include an HDD and an SSD.

[0043] The operation unit 56 is used by the user to input instructions regarding radiographic image capture, including instructions for irradiating radiation R, and various types of information. The operation unit 56 is not particularly limited, and examples thereof include various switches, a touch panel, a touch pen, and a mouse. The display unit 58 displays various types of information. The operation unit 56 and the display unit 58 may be integrated into one unit to form a touch panel display.

[0044] The I / F unit 54 communicates various types of information between the mammography apparatus 10, the RIS, and a PACS (Picture Archiving and Communication Systems) via wireless or wired communication. In the radiation image capturing system 1 of this embodiment, the console 12 receives image data of a radiation image captured by the mammography apparatus 10 from the mammography apparatus 10 via the I / F unit 54 via wireless or wired communication.

[0045] The console 12 of this embodiment has a function for correcting misalignment between multiple projection images obtained by tomosynthesis imaging. FIG. 4 shows a functional block diagram of an example of the configuration of the console 12 of this embodiment, related to the function for correcting misalignment between multiple projection images obtained by tomosynthesis imaging. As shown in FIG. 4 , the console 12 includes an image acquisition unit 60, a tomographic image acquisition unit 62, a pseudo projection image generation unit 64, a misalignment amount deriving unit 66, a notification unit 68, a tomographic image generation unit 70, and a display control unit 72. As an example, in the console 12 of this embodiment, the CPU 50A of the control unit 50 executes an image generation program 51 stored in the ROM 50B, so that the CPU 50A functions as the image acquisition unit 60, the tomographic image acquisition unit 62, the pseudo projection image generation unit 64, the misalignment amount deriving unit 66, the notification unit 68, the tomographic image generation unit 70, and the display control unit 72.

[0046] The image acquisition unit 60 has a function of acquiring multiple projection images. Specifically, the image acquisition unit 60 of this embodiment acquires image data representing multiple projection images obtained by tomosynthesis imaging in the mammography apparatus 10. The image acquisition unit 60 outputs the image data representing the acquired multiple projection images to the tomographic image acquisition unit 62 and the positional deviation amount derivation unit 66.

[0047] The tomographic image acquisition unit 62 has a function of acquiring a plurality of tomographic images corresponding to a plurality of tomographic planes of the breast, which is the subject. Specifically, the tomographic image acquisition unit 62 of this embodiment acquires a plurality of tomographic images by generating a plurality of tomographic images corresponding to a plurality of tomographic planes of the breast, using a plurality of projection images acquired by the image acquisition unit 60.

[0048] The method by which the tomographic image acquisition unit 62 generates the multiple tomographic images is not particularly limited, and known techniques can be used. For example, reconstruction may be performed using a back projection method such as the FBP (Filter Back Projection) method or an iterative reconstruction method, and known techniques can be applied. The tomographic planes of the multiple tomographic images generated by the tomographic image acquisition unit 62 are planes approximately parallel to the detection plane 20A of the radiation detector 20, and in this embodiment, are planes approximately parallel to the imaging plane 24A of the imaging table 24. The positions of the tomographic planes of the multiple tomographic images generated by the tomographic image acquisition unit 62, in other words, the heights of the tomographic planes from the imaging plane 24A of the imaging table 24, are not particularly limited. The heights of the tomographic planes can be determined, for example, depending on the size of the object of interest, the image quality of the radiation image, the processing load of the calculation process for generating the tomographic images, instructions from the user, etc. The tomographic image acquisition unit 62 outputs image data representing the multiple acquired tomographic images to the pseudo projection image generation unit 64.

[0049] The pseudo projection image generating unit 64 has a function of generating a plurality of pseudo projection images that do not include a reference object image representing the reference object by using a group of tomographic images among the plurality of tomographic images other than the tomographic image that includes the reference object used as a reference for deriving the amount of positional deviation between the projection images and performing pseudo projection from a set irradiation position corresponding to each irradiation position of the plurality of projection images. In this embodiment, a pseudo projection image that does not include a reference object image is called a "reference object-free pseudo projection image."

[0050] An example of a method for generating a reference-object-free pseudo projection image in the pseudo projection image generating unit 64 of this embodiment will be described with reference to Figures 5 and 6. Note that Figure 5 shows the correspondence between a projection image 801 captured when the radiation source 29 is located at the irradiation position 191 and a tomographic image 82 generated from a plurality of projection images 80 including the projection image 801. The projection image 801 is used to generate the tomographic image 82. The projection image 801 includes a structure image 93A1 representing a structure 92A located at a height corresponding to the tomographic image 822, a reference object image 911 representing a reference object 90 located at a height corresponding to the tomographic image 823, and a structure image 93B1 representing a structure 92B located at a height corresponding to the tomographic image 825.

[0051] First, referring to FIG. 5 , the pseudo projection image generating unit 64 extracts a reference object 90 from a plurality of tomographic images 82 (seven images 821 to 827 in FIG. 5 ). Specifically, the pseudo projection image generating unit 64 extracts a reference object image 91 representing the reference object 90 from the plurality of tomographic images 82. The method for extracting the reference object image 91 by the pseudo projection image generating unit 64 will be described. In the case of tomosynthesis imaging, as described above, a plurality of projection images 80 are captured by performing imaging at each irradiation position 19. Therefore, positional deviations may occur between the projection images 80 due to the influence of the subject's body movement or the positional deviation of the radiation source 29 at each irradiation position 19. In the console 12 of this embodiment, the reference object 90 is used as a reference to derive the amount of positional deviation between the projection images 80. It is preferable that the reference object 90 has a distinctive structure so that an image representing the reference object 90 can be easily extracted from each of the tomographic images 82 and the projection images 80. Furthermore, it is preferable that the reference object 90 is included in all of the multiple projection images 80 acquired by the image acquisition unit 60. As described above, the reference object 90 is used as a reference for deriving the amount of positional deviation due to the subject's body movement, etc., and is therefore preferably a structure present inside the subject. When the subject is a breast, such a reference object 90 may be at least one of calcification and mammary glands. As an example, in this embodiment, it is predetermined that the mammary glands are used as the reference object 90.

[0052] The method by which the pseudo projection image generating unit 64 extracts the reference object 90 from the multiple tomographic images 82 is not particularly limited. The pseudo projection image generating unit 64 first identifies, in each of the multiple tomographic images 82, an area that is included in all of the projection images 80 acquired by the image acquiring unit 60 as a common area. The method by which the pseudo projection image generating unit 64 identifies the common area is not particularly limited. As an example, in this embodiment, the multiple projection images 80 acquired by tomosynthesis imaging are assigned with imaging information that indicates the irradiation angle range and irradiation field, and a correspondence relationship between the irradiation angle range and irradiation field in tomosynthesis imaging and the common area is determined in advance. The pseudo projection image generating unit 64 identifies the common area from the correspondence relationship based on the imaging information assigned to the multiple projection images 80 acquired by the image acquiring unit 60.

[0053] Once the common region is identified, the pseudo projection image generating unit 64 extracts mammary glands from the common region in each of the multiple tomographic images 82. The method by which the pseudo projection image generating unit 64 extracts mammary glands is not particularly limited. The pseudo projection image generating unit 64 of this embodiment extracts specific structures representing mammary glands from the common region in each of the tomographic images 82, for example, using a known computer-aided diagnosis (CAD) (hereinafter referred to as CAD) algorithm. The CAD algorithm preferably derives a probability (e.g., likelihood) that a pixel in the common region is a mammary gland, and if the probability is equal to or greater than a predetermined threshold, the pixel is detected as a pixel constituting an image of the mammary gland. Alternatively, for example, the pseudo projection image generating unit 64 may use a method for extracting mammary glands from the common region, such as filtering using a filter for extracting mammary glands. When there are multiple extracted mammary glands, for example, when mammary glands are extracted from each of specific regions in multiple tomographic images 82, the pseudo projection image generating unit 64 extracts one mammary gland as a reference object 90 based on the feature amount of the mammary gland. Fig. 5 shows an example in which the pseudo projection image generating unit 64 extracts the reference object 90 from a tomographic image 823. The tomographic image 823 in this embodiment is an example of a first tomographic image of the present disclosure, and the tomographic images 821, 822, 824 to 827 are examples of second tomographic images of the present disclosure.

[0054] Next, the pseudo projection image generating unit 64 specifies a reference object region 831 in a portion of the tomographic image 823 that includes a reference object image 91 representing the reference object 90. Note that the method by which the pseudo projection image generating unit 64 specifies the reference object region 831 is not particularly limited. In this embodiment, in a projection image 804 captured at an irradiation position 194 (see FIG. 2) where the irradiation angle α is 0 degrees, an area having a size that is a predetermined proportion to the size of the projection image 804 and that is centered on the reference object image 91 of the reference object 90 is set as the reference object region 831. Furthermore, as shown in FIG. 5, the pseudo projection image generating unit 64 specifies, as partial regions 832, regions in each of the tomographic images 821, 822, 824 to 827 that correspond to the reference object region 831.

[0055] Next, as shown in FIG. 6, the pseudo projection image generating unit 64 uses the tomographic images 821, 822, 824 to 827 to generate a pseudo projection image corresponding to each of the irradiation positions 19 in the plurality of projection images 80. V (In Figure 6, the irradiation position is 19 V1 ) to generate multiple pseudo-projection images without the reference object 90. V The actual irradiation position 19 of the radiation source 29 when the projection image 80 is captured in the tomosynthesis imaging may change depending on the time and the like. V In this embodiment, what is known is the irradiation position 19 in the setting. V Therefore, the pseudo projection image generating unit 64 calculates the actual irradiation position 19 for the partial region 832 of each of the tomographic images 821, 822, and 824 to 827. V By performing pseudo projection from the projection plane 80A, a pseudo projection image 86 without a reference object is generated on the projection plane 80A similar to the projection image 80. Note that, if it is considered that there is no positional deviation of the irradiation position 19 of the radiation source 29 in the tomosynthesis imaging, the irradiation position 19 in the setting Vis the same as the actual irradiation position 19. The reference object-free pseudo-projection image 86 of this embodiment is an example of a reference object-free pseudo-projection image of the present disclosure, and is also an example of a partial pseudo-projection image.

[0056] The reference object-free pseudo projection image 861 includes a structure image representing a structure other than the reference object 90. In the example shown in FIG. 6, the reference object-free pseudo projection image 861 includes a structure image 93A1 representing a structure 92A existing at a height corresponding to the tomographic image 822, and a structure image 93B1 representing a structure 92B existing at a height corresponding to the tomographic image 825. Furthermore, the reference object-free pseudo projection image 861 does not include a reference object image 91 representing the reference object 90 existing at a height corresponding to the tomographic image 823. In this way, the pseudo projection image generating unit 64 generates a pseudo projection image based on the set irradiation position 19. V For each, a reference object pseudoprojection-free image 86 is generated.

[0057] The pseudo projection image generating unit 64 outputs image data representing the generated multiple reference object-free pseudo projection images 86 to the positional deviation amount deriving unit 66 .

[0058] The misalignment amount derivation unit 66 has a function of deriving the amount of misalignment between the projection images 80. As shown in Fig. 4, the misalignment amount derivation unit 66 of this embodiment includes a component-removed image generation unit 67. The component-removed image generation unit 67 has a function of generating a component-removed image including the reference object by removing the components of the multiple reference-object-free pseudo projection images 86 from the multiple projection images 80.

[0059] First, as shown in Fig. 5, the component-removed image generating unit 67 of this embodiment extracts an image of a portion corresponding to the reference object-free pseudo projection image 86 from the projection image 80 as a partial image 84. Furthermore, as shown in Fig. 7, the component-removed image generating unit 67 subtracts the pixel value of the reference object-free pseudo projection image 86 from the pixel value of the extracted partial image 84 for each corresponding pixel, thereby generating a component-removed image 88 (component-removed images 881 to 887 in Fig. 7) that represents the difference between the partial image 84 and the reference object-free pseudo projection image 86.

[0060] 7 , the component-removed image generating unit 67 generates a component-removed image 881 by subtracting, for each corresponding pixel, the pixel value of the reference-object-free pseudo-projection image 861 from the pixel value of the partial image 841 for a projection image 801 corresponding to irradiation position 191, which is the first irradiation position 19. The component-removed image generating unit 67 also generates a component-removed image 882 by subtracting, for each corresponding pixel, the pixel value of the reference-object-free pseudo-projection image 862 from the pixel value of the partial image 842 for a projection image 802 corresponding to irradiation position 192. The component-removed image generating unit 67 also generates a component-removed image 883 by subtracting, for each corresponding pixel, the pixel value of the reference-object-free pseudo-projection image 863 from the pixel value of the partial image 843 for a projection image 803 corresponding to irradiation position 193. In this way, the component-removed image generating unit 67 generates a component-removed image 88 from the partial images 84 of the projection image 80 corresponding to each irradiation position 19 and the reference-object-free pseudo-projection image 86, and then generates a component-removed image 887 by subtracting the pixel value of the reference-object-free pseudo-projection image 867 from the pixel value of the partial image 847 for each corresponding pixel in the projection image 807 corresponding to irradiation position 197, which is the last irradiation position 19.

[0061] The projection image 80 is an image showing structures lined up in the direction of irradiation with radiation R, and contains a large amount of information. Therefore, as shown in FIGS. 5 to 7, the projection image 80 of this embodiment includes a reference object image 91 and structure images 93A and 93B superimposed according to the heights at which the reference object 90 and structures 92A and 92B are located. In the example shown in FIGS. 5 and 6, the structure 92A is located above the reference object 90. Therefore, the partial images 841 to 847 shown in FIG. 7 include structure images 93A1 to 93A7 superimposed on the reference object images 911 to 917, respectively. In this way, when an image of another structure, such as the structure image 93A, is superimposed on the reference object image 91, the image of the other structure, such as the structure image 93A, becomes an obstacle, making it difficult to extract the contour of the reference object image 91.

[0062] In contrast, the component-removed images 881 to 887 have structure images 93A and 93B, which are images of other structures, removed, so that the reference object image 91 does not overlap with other structure images and is an image in which the reference object image 91 clearly appears. In particular, the component-removed images 881 to 887 have structure image 93A, which represents structure 92A, which is located above the reference object 90, in other words, closer to the radiation source 29, and therefore would be superimposed on the reference object image 91, removed, so that the reference object image 91 clearly appears.

[0063] As described above, the component-removed image generating unit 67 of this embodiment generates the component-removed image 88 by subtracting the pixel value of the reference object-free pseudo-projection image 86 from the pixel value of the partial image 84 for each corresponding pixel, but the method by which the component-removed image generating unit 67 generates the component-removed image 88 is not limited to this embodiment. For example, the component-removed image generating unit 67 may generate the component-removed image 88 by reducing the pixel values ​​of pixels in each partial image 84 that correlate with the reference object-free pseudo-projection image 86.

[0064] The misalignment amount derivation unit 66 derives the amount of misalignment between the projection images 80 based on the component-removed images 881 to 887 generated by the component-removed image generation unit 67. The method by which the misalignment amount derivation unit 66 derives the amount of misalignment between the projection images 80 is not limited. As an example, the misalignment amount derivation unit 66 of this embodiment derives the amount of misalignment between the projection images 80 based on the component-removed images 881 to 887 and the tomographic image 823. As a specific example of the method, the misalignment amount derivation unit 66 of this embodiment derives the amount of misalignment between the projection images 80 by applying the technology described in International Publication No. 2020 / 067475. International Publication No. 2020 / 067475 discloses a technology for deriving the amount of misalignment between a plurality of projection images based on feature points on a tomographic plane corresponding to a tomographic image on which feature points are detected. When the present technology is applied to the present embodiment, the positional deviation amount derivation unit 66 assumes that each projection image 80 is a tomographic plane projection image when projected onto the tomographic plane of the tomographic image 823, and derives the positional deviation amount between each projection image 80 based on the positional deviation amount between the multiple tomographic plane projection images derived using feature points of the reference object 90 as a reference. Note that the positional deviation amount derivation unit 66 may be configured to derive, for example, the positional deviation amount for each partial image 84 as the positional deviation amount between each projection image 80. Furthermore, the positional deviation amount derivation unit 66 may derive, for example, the positional deviation amount of the entire breast, which is the subject included between each projection image 80, as the positional deviation amount between each projection image 80. When deriving the positional deviation amount of the entire breast between each projection image 80, for example, a method may be applied in which a parameter representing the degree of positional deviation of the entire breast is set and the parameter is optimized according to the positional deviation of the reference object 90.

[0065] The amount of misalignment between the projection images 80 derived by the misalignment amount deriving unit 66 is output to the notifying unit 68 and the tomographic image generating unit 70.

[0066] When the amount of misalignment between the projection images 80 is relatively large, the misalignment between the projection images 80 may not be sufficiently corrected, or the image quality of the tomographic image 82 generated from the projection images 80 may be degraded. For example, if the subject moves significantly during tomosynthesis imaging, the body movement of the breast, which is the subject, may become large, resulting in a relatively large amount of misalignment between the projection images 80. In such a case, it may be preferable to recapture the projection images 80. Therefore, the notification unit 68 of this embodiment has a function of issuing a warning when the amount of misalignment derived by the misalignment amount derivation unit 66 exceeds a predetermined threshold. The predetermined threshold used to determine whether to issue a warning may be predetermined based on, for example, the desired image quality of the tomographic image 82, diagnostic accuracy, etc., or may be user-configurable. As an example, in this embodiment, the amount of misalignment at which recapture is preferable is set as the predetermined threshold. The method of notification by the notification unit 68 is not particularly limited, and may be, for example, at least one of a visual display and an audible display on the display unit 58 of the console 12. The content of the notification by the notification unit 68 is not limited to a warning, and may be, for example, at least one of a visual and an audible notification method, such as displaying a warning message on the display unit 58 of the console 12 or issuing a warning sound from a speaker (not shown) of the console 12. The content of the notification by the notification unit 68 is not limited to a warning, and may be, for example, information indicating that the amount of positional deviation is large or the derived amount of positional deviation itself, and the specific content is not limited.

[0067] The tomographic image generating unit 70 has a function of generating multiple tomographic images for each of the multiple tomographic planes based on the multiple projection images 80 acquired by the image acquiring unit 60 and the amount of misalignment derived by the misalignment amount deriving unit 66. The method by which the tomographic image generating unit 70 generates multiple tomographic images for each of the multiple tomographic planes based on the multiple projection images 80 and the amount of misalignment is not limited. For example, when the tomographic image generating unit 70 reconstructs a tomographic image from the multiple projection images 80 using a back projection method, the multiple tomographic images may be generated by reconstructing the tomographic image using the back projection positions of the projection images 80 corrected based on the amount of misalignment. Alternatively, for example, the tomographic image generating unit 70 may correct the projection images 80 based on the amount of misalignment to generate multiple projection images assuming no misalignment occurs. The tomographic image generating unit 70 may then generate multiple tomographic images using the multiple projection images 80 with the misalignment corrected.

[0068] Furthermore, the height of the multiple tomographic planes generated by the tomographic image generating unit 70 is not limited. For example, the height of the tomographic planes may be the same as or different from the height of the multiple tomographic images 82 acquired by the tomographic image acquiring unit 62. Furthermore, the height of the tomographic planes may be a height specified by the user.

[0069] The tomographic image generating unit 70 outputs image data representing the generated multiple tomographic images to the display control unit 72.

[0070] The display control unit 72 has a function of displaying the multiple tomographic images generated by the tomographic image generating unit 70 on the display unit 58. The display destination of the multiple tomographic images is not limited to the display unit 58. For example, the display destination may be an image reading device or the like external to the radiation image capturing system 1.

[0071] Next, the operation of the console 12 in tomosynthesis imaging will be described with reference to the drawings. After tomosynthesis imaging is performed by the mammography apparatus 10, the console 12 generates multiple tomographic images using multiple projection images obtained by tomosynthesis imaging and displays them on the display unit 58, etc.

[0072] As an example, when tomosynthesis imaging is completed, the mammography apparatus 10 of this embodiment outputs image data of the captured multiple projection images 80 to the console 12. The console 12 stores the image data of the multiple projection images 80 input from the mammography apparatus 10 in the memory unit 52.

[0073] After storing the image data of the multiple projection images 80 in the storage unit 52, the console 12 executes the image processing shown in Fig. 8. Fig. 8 shows a flowchart illustrating an example of the flow of image processing by the console 12 of this embodiment. As an example, the console 12 of this embodiment executes the image processing example shown in Fig. 8 by causing the CPU 50A of the control unit 50 to execute the image generation program 51 stored in the ROM 50B.

[0074] 8, the image acquisition unit 60 acquires a plurality of projection images 80. As described above, the image acquisition unit 60 of this embodiment acquires image data of a plurality of projection images from the storage unit 52.

[0075] In the next step S102, the tomographic image acquisition unit 62 acquires a plurality of tomographic images 82. As described above, the plurality of projection images 80 acquired in step S100 are used to generate a plurality of tomographic images 82 corresponding to the plurality of cross-sectional planes of the breast, thereby acquiring the plurality of tomographic images 82.

[0076] In the next step S104, the pseudo projection image generating unit 64 extracts a reference object 90 to be used as a reference for deriving the amount of positional deviation between the projection images 80 from the plurality of tomographic images 82. As described above, the pseudo projection image generating unit 64 extracts the reference object 90, which is a mammary gland, from the common region of the plurality of projection images 80 based on the feature amount.

[0077] In the next step S106, the pseudo projection image generating unit 64 identifies a partial region 83 in the tomographic image 82 that does not include the reference object image 91 representing the reference object 90. As described above, the pseudo projection image generating unit 64 identifies the reference object region 831 that includes the reference object image 91 representing the reference object 90 extracted in step S104, and identifies a partial region 832 in another tomographic image 82 that corresponds to the identified reference object region 831. In this embodiment, as described above, the pseudo projection image generating unit 64 identifies the reference object region 831 in the tomographic image 823. Furthermore, the pseudo projection image generating unit 64 identifies the region corresponding to the reference object region 831 in each of the tomographic images 821, 822, 824 to 827 as the partial region 832.

[0078] In the next step S108, the pseudo projection image generating unit 64 generates a reference object-free pseudo projection image 86. As described above, the pseudo projection image generating unit 64 generates a pseudo projection image 86 by setting the irradiation position 19 on the setting for the partial region 832 of each of the tomographic images 821, 822, 824 to 827. V By performing pseudo projection from the reference object, a reference object-free pseudo projection image 86 on the projection plane 80A of the projection image 80 is generated.

[0079] In the next step S110, the component-removed image generating unit 67 of the positional deviation amount derivation unit 66 generates a component-removed image 88. As described above, the component-removed image generating unit 67 extracts an image of a portion corresponding to the reference object-free pseudo-projection image 86 from the multiple projection images 80 as a partial image 84. Furthermore, the component-removed image generating unit 67 subtracts the pixel value of the reference object-free pseudo-projection image 86 from the pixel value of the extracted partial image 84 for each corresponding pixel, thereby generating a component-removed image 88 that represents the difference between the partial image 84 and the reference object-free pseudo-projection image 86.

[0080] In the next step S112, the misalignment amount deriving unit 66 derives the amount of misalignment between the multiple projection images 80. As described above, the misalignment amount deriving unit 66 derives the amount of misalignment between the projection images 80 based on the component-removed image 88 generated in step S110.

[0081] In the next step S114, the notification unit 68 determines whether or not the amount of positional deviation between the plurality of projected images 80 exceeds a predetermined threshold. In other words, as described above, the notification unit 68 determines whether or not a positional deviation has occurred to an extent that makes it desirable to perform re-imaging. If the amount of positional deviation derived in step S112 above is equal to or less than the predetermined threshold, the determination in step S114 is negative, and the process proceeds to step S118. On the other hand, if the amount of positional deviation derived in step S112 above exceeds the predetermined threshold, the determination in step S114 is positive, and the process proceeds to step S116.

[0082] In step S116, the notification unit 68 displays a warning on the display unit 58. As described above, the notification unit 68 of the present embodiment uses the display unit 58 to notify the user of a warning indicating that the amount of positional deviation is large and that it is preferable to perform re-imaging.

[0083] In the next step S118, the tomographic image generating unit 70 generates a plurality of tomographic images in which the positional deviation has been corrected. As described above, the tomographic image generating unit 70 generates a plurality of tomographic images for each of a plurality of tomographic planes based on the plurality of projection images 80 acquired in step S100 and the amount of positional deviation derived in step S112.

[0084] In the next step S120, the display control unit 72 displays the tomographic image generated in step S118 on the display unit 58. When the process of step S120 ends, the image processing shown in FIG.

[0085] As described above, the console 12 of this embodiment processes a plurality of projection images 80 obtained by irradiating the breast with radiation R from the radiation source 29 from each of a plurality of irradiation positions 19 with different irradiation angles α. The console 12 includes a CPU 50A. The CPU 50A acquires the plurality of projection images 80, acquires a plurality of tomographic images 82 generated using the plurality of projection images 80 and corresponding to each of a plurality of tomographic planes of the breast, and uses a group of tomographic images 82 (821, 822, 824 to 827) among the plurality of tomographic images 82 other than the tomographic image 821 including the reference object image 91 representing the reference object 90 used as a reference for deriving the amount of positional deviation between the projection images 80 to calculate the set irradiation positions 19 corresponding to each of the irradiation positions 19 of the plurality of projection images 80. V By performing pseudo projection from the reference object, a plurality of reference-object-free pseudo-projection images 86 that do not include a reference object image 91 representing the reference object 90 are generated, and the amount of positional deviation between the projection images 80 is derived based on a component-removed image 88 that includes a reference object image 91 obtained by removing the components of the plurality of reference-object-free pseudo-projection images 86 from the plurality of projection images 80.

[0086] The console 12 of this embodiment derives the amount of misalignment between the projection images 80 using a reference object 90 that serves as a reference for deriving the amount of misalignment between the projection images 80. The projection image 80 is an image of structures lined up in the direction in which the radiation R is irradiated and contains a large amount of information. Therefore, the projection image 80 includes a reference object image 91 representing the reference object 90 as well as structure images representing structures other than the reference object 90. The projection image 80 shown in FIG. 5 includes, in addition to the reference object image 91, a structure image 93A representing a structure 92A and a structure image 93B representing a structure 92B. When images of other structures are superimposed on the reference object image 91, the outline of the reference object image 91 becomes unclear. In particular, a structure image representing a structure located above the reference object 90, in other words, closer to the radiation source 29 (in this embodiment, the structure image 93A representing the structure 92A) is superimposed on the reference object image 91, and therefore the outline of the reference object image 91 becomes unclear.

[0087] Therefore, the console 12 of this embodiment derives the amount of positional deviation between the projection images 80 based on the component-removed image 88 generated by subtracting, for each corresponding pixel, the pixel values ​​of a plurality of reference-object-free pseudo projection images 86 that do not include the reference object image 91 from the pixel values ​​of the partial image 84 of the projection image 80. In this way, the console 12 of this embodiment derives the amount of positional deviation between the projection images 80 using the component-removed image 88 in which the reference object image 91 representing the reference object 90 is clearly shown. Therefore, the console 12 of this embodiment can accurately derive the amount of positional deviation between the projection images 80.

[0088] It should be noted that there are cases where the correction of the positional deviation in step S118 is insufficient. In other words, there are cases where the image quality of the multiple tomographic images generated by the tomographic image generating unit 70 in step S118 is lower than the image quality of the multiple tomographic images generated from the projection images 80 when it is considered that no positional deviation has occurred. In such cases, the process returns to step S106 after step S118 and repeats the processes of steps S106 to S116 until the amount of positional deviation derived in step S112 becomes equal to or less than the level at which it is considered that no positional deviation has occurred.

[0089] In this embodiment, the pseudo projection image generating unit 64 generates the reference object-free pseudo projection image 86 by performing pseudo projection onto the partial region 832 of the tomographic image 82 corresponding to the reference object region 831, but the region on which the pseudo projection is performed is not limited to this embodiment. For example, the pseudo projection image generating unit 64 may generate the reference object-free pseudo projection image 86 by performing pseudo projection onto the entire tomographic image 82.

[0090] [Second embodiment] The overall configuration of the radiographic imaging system 1 of this embodiment is similar to that of the radiographic imaging system 1 of the first embodiment (see FIG. 1), so a detailed description thereof will be omitted. Also, the configuration of the mammography apparatus 10 is similar to that of the mammography apparatus 10 of the first embodiment (see FIGS. 1 to 3), so a detailed description thereof will be omitted.

[0091] In addition, the hardware configuration of the console 12 of this embodiment is the same as that of the first embodiment, except that an image generation program 51A stored in the ROM 50B of the control unit 50 is stored instead of the image generation program 51 as shown in FIG. 9, so a description thereof will be omitted.

[0092] Meanwhile, the console 12 of this embodiment has a different functional configuration from the console 12 of the first embodiment (see FIG. 4 ), and therefore the functional configuration of the console 12 of this embodiment will be described below. FIG. 10 shows a functional block diagram of an example of a configuration related to a function of correcting misalignment between multiple projection images 80 obtained by tomosynthesis imaging in the console 12 of this embodiment. As shown in FIG. 10 , the console 12 includes an image acquisition unit 60, a tomographic image acquisition unit 62, a pseudo projection image generation unit 63, a misalignment amount deriving unit 65, a notification unit 68, a tomographic image generation unit 71, and a display control unit 72. As an example, in the console 12 of this embodiment, the CPU 50A of the control unit 50 executes an image generation program 51A stored in the ROM 50B, so that the CPU 50A functions as the image acquisition unit 60, the tomographic image acquisition unit 62, the pseudo projection image generation unit 63, the misalignment amount deriving unit 65, the notification unit 68, the tomographic image generation unit 71, and the display control unit 72.

[0093] The image acquisition unit 60, like the image acquisition unit 60 of the first embodiment (see FIG. 4), has the function of acquiring a plurality of projection images 80. Specifically, the image acquisition unit 60 of this embodiment acquires image data representing a plurality of projection images 80 obtained by tomosynthesis imaging in the mammography apparatus 10. The image acquisition unit 60 outputs the image data representing the acquired plurality of projection images 80 to the tomographic image acquisition unit 62 and the positional deviation amount derivation unit 65.

[0094] Similar to the tomographic image acquisition unit 62 of the first embodiment (see FIG. 4), the tomographic image acquisition unit 62 has a function of acquiring a plurality of tomographic images 82 corresponding to a plurality of tomographic planes of the breast, which is the subject. Specifically, the tomographic image acquisition unit 62 of this embodiment acquires a plurality of tomographic images 82 by reconstructing a plurality of projection images 801 to 807 acquired by the image acquisition unit 60 to generate a plurality of tomographic images 821 to 827 corresponding to a plurality of tomographic planes of the breast, as shown in FIG. 11 . The tomographic image acquisition unit 62 outputs image data representing the generated plurality of tomographic images 82 to the pseudo projection image generation unit 63.

[0095] The pseudo projection image generating unit 63 uses the tomographic image 82, among the multiple tomographic images 82 acquired by the tomographic image acquiring unit 62, including the reference object image 95 representing the reference object 90 used as a reference for deriving the amount of positional deviation between the projection images 80, to generate a pseudo projection image corresponding to the irradiation positions 19 on the setting of the multiple projection images 80. V 97. In this embodiment, the pseudo projection image including the reference object image 97 is referred to as a "pseudo projection image with reference object."

[0096] An example of a method for generating a reference object-included pseudo projection image in the pseudo projection image generating unit 63 of this embodiment will be described with reference to FIG. 5 shown in the first embodiment, and FIGS.

[0097] First, the pseudo projection image generating unit 63 extracts a reference object 90 from the plurality of tomographic images 82. Specifically, the pseudo projection image generating unit 63 extracts a reference object image 95 representing the reference object 90 from the plurality of tomographic images 82. In this embodiment, the reference object 90 used as a reference for deriving the amount of positional deviation between the projection images 80 is the same as the reference object 90 in the first embodiment. Furthermore, the method by which the pseudo projection image generating unit 63 extracts the reference object 90 from the plurality of tomographic images 82 is the same as the method by which the pseudo projection image generating unit 64 in the first embodiment extracts the reference object 90 from the plurality of tomographic images 82, and therefore a description thereof will be omitted. Furthermore, in this embodiment, similar to the reference object 90 in the first embodiment, a case will be described in which the pseudo projection image generating unit 63 extracts the reference object 90 present at a height corresponding to the tomographic image 823 from among the tomographic images 821 to 827.

[0098] 11, the pseudo projection image generating unit 63 identifies a reference object region 831 in a portion of the tomographic image 823 that includes a reference object image 95 representing the reference object 90. Note that the method by which the pseudo projection image generating unit 63 identifies the reference object region 831 is similar to the method by which the pseudo projection image generating unit 64 of the first embodiment identifies the reference object region 831, and therefore a description thereof will be omitted.

[0099] Next, as shown in FIGS. 11 and 12, the pseudo projection image generating unit 63 uses the reference object region 831 to generate the pseudo projection image 19 on the setting corresponding to the irradiation positions 191 to 197 of the projection images 801 to 807. V1 ~19 V7 12, pseudo projection images 891 to 897 with reference object including the reference object image 97 are generated by performing pseudo projection from the projection position 191. V1 8 shows a pseudo projection image 891 with a reference object pseudo-projected onto a projection surface 80A similar to the projection image 80 from the perspective of the user.

[0100] The images representing structures included in the reference-object-included pseudo projection image 89 are determined depending on the images representing structures included in the tomographic image 823. In the example shown in Figures 11 and 12, the tomographic image 823 includes a reference object image 95 representing the reference object 90, but does not include a structure image representing the structure 92A or a structure image representing the structure 92B. Therefore, the reference-object-included pseudo projection image 89 includes the reference object image 95, but does not include structure images representing the structures 92A and 92B. Therefore, the reference-object-included pseudo projection image 89 is an image that does not include structure images representing structures that are located at positions different from the reference object 90.

[0101] A tomographic image 82 generated from multiple projection images 80 in which misalignment occurs may be blurred or otherwise affected by the misalignment. For example, in the example shown in FIG. 11 , the reference object image 95 included in the tomographic image 823 is blurred or larger in size than the reference object image 91 included in the projection image 80. Furthermore, because a reference object region 831 including the reference object image 95 affected by the misalignment is pseudo-projected, the reference object image 97 included in the pseudo-projection image with reference object 89 is also blurred or larger in size than the reference object image 91 included in the projection image 80. In this way, the pseudo-projection image with reference object 89 includes the reference object image 97 in which the misalignment between the projection images 80 is apparent.

[0102] The pseudo projection image generating unit 63 outputs image data representing the generated plurality of pseudo projection images 89 with reference object to the positional deviation amount deriving unit 65 .

[0103] The positional deviation amount deriving unit 65 has a function of deriving the positional deviation amount between the projection images 80 based on the projection images 801-807 and the reference-object-included pseudo projection images 891-897. As described above, the reference-object-included pseudo projection image 89 includes a reference object image 97 that reflects the positional deviation between the projection images 80. For example, the reference object image 97 in the reference-object-included pseudo projection image 89 is larger than the reference object image 91 in the projection image 80. The positional deviation amount deriving unit 65 of this embodiment derives the positional deviation amount between the projection images 80 by comparing the reference object image 97 included in the reference-object-included pseudo projection image 89 with the reference object image 91 included in the projection image 80. As an example, the positional deviation amount deriving unit 65 derives the positional deviation amount between the projection images 80 based on the difference between the size and position of the reference object image 97 included in the reference-object-included pseudo projection image 89 and the size and position of the reference object image 91 included in the projection image 80. When it is considered that no positional deviation occurs between the projection images 80, the size and position of the reference object image 97 included in the reference object-included pseudo projection image 89 will be similar to the size and position of the reference object image 91 included in the projection image 80. Note that the method by which the positional deviation amount derivation unit 65 of this embodiment derives the amount of positional deviation between the projection images 80 based on the projection images 801 to 807 and the reference object-included pseudo projection images 891 to 897 is not limited to this embodiment.

[0104] The amount of positional deviation between the projection images 80 derived by the positional deviation amount deriving unit 65 is output to the notifying unit 68 and the tomographic image generating unit 71.

[0105] The notifying unit 68 has a function of issuing a notification when the amount of positional deviation derived by the positional deviation amount deriving unit 65 exceeds a preset threshold value, similar to the notifying unit 68 in the first embodiment (see FIG. 4).

[0106] Similar to the tomographic image generating unit 70 of the first embodiment (see FIG. 4), the tomographic image generating unit 71 has a function of generating a plurality of tomographic images for each of a plurality of tomographic planes based on a plurality of projection images 80 acquired by the image acquiring unit 60 and the amount of misalignment derived by the misalignment amount deriving unit 66. The tomographic image generating unit 71 outputs image data representing the generated plurality of tomographic images to the display control unit 72.

[0107] The display control unit 72 has a function of causing the display unit 58 to display a plurality of tomographic images generated by the tomographic image generating unit 70, similar to the display control unit 72 of the first embodiment (see FIG. 4).

[0108] Next, the operation of the console 12 during tomosynthesis imaging will be described with reference to the drawings. As an example, when tomosynthesis imaging is completed, the mammography apparatus 10 of this embodiment outputs image data of the captured multiple projection images 80 to the console 12. The console 12 stores the image data of the multiple projection images 80 input from the mammography apparatus 10 in the memory unit 52.

[0109] After storing the image data of the plurality of projection images 80 in the storage unit 52, the console 12 executes the image processing shown in Fig. 13. Fig. 13 shows a flowchart illustrating an example of the flow of image processing by the console 12 of this embodiment. As an example, the console 12 of this embodiment executes the image processing example shown in Fig. 12 by causing the CPU 50A of the control unit 50 to execute the image generation program 51A stored in the ROM 50B.

[0110] 13, the image acquisition unit 60 acquires a plurality of projection images 80. The image acquisition unit 60 acquires image data of the plurality of projection images from the storage unit 52, similar to step S100 of the image processing in the first embodiment (see FIG. 8).

[0111] In the next step S102, the tomographic image acquisition unit 62 acquires a plurality of tomographic images 82. As in step S102 (see FIG. 8 ) of the image processing in the first embodiment, the tomographic image acquisition unit 62 acquires the plurality of tomographic images 82 by generating a plurality of tomographic images 82 corresponding to each of a plurality of tomographic planes of the breast using the plurality of projection images 80 acquired in step S100.

[0112] In the next step S104, the pseudo projection image generating unit 63 extracts a reference object 90 to be used as a reference for deriving the amount of positional deviation between the projection images 80 from the multiple tomographic images 82. Similar to step S104 (see FIG. 8) of the image processing in the first embodiment, the pseudo projection image generating unit 63 extracts the reference object 90, which is a mammary gland, from the common region of the multiple projection images 80 based on the feature amount.

[0113] In the next step S107, the pseudo projection image generating unit 63 identifies the reference object region 831 in the tomographic image 82 including the reference object image 95 representing the reference object 90. As described above, the pseudo projection image generating unit 63 identifies the reference object region 831 including the reference object image 95 in the tomographic image 823 including the reference object image 95 representing the reference object 90 extracted in step S104 above.

[0114] In the next step S109, the pseudo projection image generating unit 63 generates a pseudo projection image with reference object 89. As described above, the pseudo projection image generating unit 63 generates a pseudo projection image with reference object 89 by projecting the reference object region 831 of the tomographic image 823 onto the set irradiation position 19. V By performing pseudo projection from the projection plane 80A, a pseudo projection image 89 with a reference object is generated on the projection plane 80A of the projection image 80.

[0115] In the next step S113, the positional deviation amount derivation unit 65 derives the positional deviation amount between the plurality of projection images 80. As described above, the positional deviation amount derivation unit 65 derives the positional deviation amount between the projection images 80 based on the reference object image 97 included in the reference object-included pseudo projection image 89 generated in step S109 and the reference object image 91 included in the projection images 80.

[0116] In the next step S114, the notification unit 68 determines whether or not the amount of positional deviation between the plurality of projected images 80 exceeds a predetermined threshold. As in step S114 of the image processing in the first embodiment (see FIG. 8), the notification unit 68 determines whether or not a positional deviation has occurred that is greater than or equal to a degree that makes it preferable to perform re-imaging. If the amount of positional deviation derived in step S112 above is equal to or less than the predetermined threshold, the determination in step S114 is negative, and the process proceeds to step S118. On the other hand, if the amount of positional deviation derived in step S112 above exceeds the predetermined threshold, the determination in step S114 is positive, and the process proceeds to step S116.

[0117] In step S116, the notification unit 68 displays a warning on the display unit 58. As in step S116 of the image processing in the first embodiment (see FIG. 8), the notification unit 68 uses the display unit 58 to notify the user of a warning indicating that it is preferable to re-shoot the image because the amount of positional deviation is large.

[0118] In the next step S118, the tomographic image generating unit 70 generates a plurality of tomographic images in which the positional deviation has been corrected. Similar to step S118 (see FIG. 8) of the image processing in the first embodiment, the tomographic image generating unit 70 generates a plurality of tomographic images for each of a plurality of tomographic planes based on the plurality of projection images 80 acquired in step S100 and the amount of positional deviation derived in step S113.

[0119] In the next step S120, the display control unit 72 displays the tomographic image generated in step S118 on the display unit 58. When the processing in step S120 ends, the image processing shown in FIG.

[0120] As described above, the console 12 of this embodiment processes a plurality of projection images 80 obtained by irradiating the breast with radiation R from the radiation source 29 from each of a plurality of irradiation positions 19 with different irradiation angles α. The console 12 includes a CPU 50A. The CPU 50A acquires the plurality of projection images 80, acquires a plurality of tomographic images 82 generated using the plurality of projection images 80 and corresponding to each of a plurality of tomographic planes of the breast, and uses a tomographic image 823 among the plurality of tomographic images 82, which includes a reference object image 95 used as a reference for deriving the amount of positional deviation between the projection images 80, to calculate the set irradiation positions 19 corresponding to each of the irradiation positions 19 of the plurality of projection images 80. V By performing pseudo projection from the reference object, a plurality of pseudo projection images with a reference object including the reference object image 97 are generated, and the amount of positional deviation between the projection images 80 is derived based on the plurality of projection images 80 and the plurality of pseudo projection images with a reference object.

[0121] The console 12 of this embodiment derives the amount of misalignment between the projected images 80 using a reference object 90 that serves as a reference for deriving the amount of misalignment between the projected images 80. The projected image 80 is an image of structures lined up in the direction in which the radiation R is irradiated, and contains a large amount of information. Therefore, the projected image 80 includes not only a reference object image 91 that represents the reference object 90, but also images that represent structures other than the reference object 90. When images of other structures are superimposed on the reference object image 91, the contour of the reference object image 91 becomes unclear. In particular, an image that represents a structure located above the reference object 90, in other words, closer to the radiation source 29 (structure image 93A representing structure 92A in FIG. 11 ), is superimposed on the reference object image 91, and therefore the contour of the reference object image 91 becomes unclear.

[0122] Therefore, the console 12 of this embodiment uses a tomographic image 823 including the reference object image 95 among the plurality of tomographic images 82, and calculates the irradiation positions 19 on the setting corresponding to the respective irradiation positions 19 of the plurality of projection images 80. VBy performing pseudo projection from the reference object 90, a plurality of reference-object-included pseudo projection images 89 including a reference object image 97 are generated. As a result, the reference-object-included pseudo projection images 89 do not include structure images that represent structures that exist in positions different from the reference object 90, and the reference object image 97 is clearly displayed. In this way, the console 12 of this embodiment derives the amount of positional deviation between the projection images 80 using the reference-object-included pseudo projection images 89 that show the positional deviation between the projection images 80 and include clear reference object images 97. Therefore, the console 12 of this embodiment can accurately derive the amount of positional deviation between the projection images 80.

[0123] It should be noted that there are cases where the correction of the positional deviation in step S118 is insufficient. In other words, there are cases where the image quality of the multiple tomographic images generated by the tomographic image generating unit 70 in step S118 is lower than the image quality of the multiple tomographic images generated from the projection images 80 when it is considered that no positional deviation has occurred. In such cases, after step S118, the process returns to step S107, and the processes of steps S107 to S116 are repeated until the amount of positional deviation derived in step S113 becomes equal to or less than the level at which it is considered that no positional deviation has occurred.

[0124] In this embodiment, the pseudo projection image generating unit 63 generates the reference object-included pseudo projection image 89 by performing pseudo projection onto the reference object region 831, but the region on which the pseudo projection is performed is not limited to this embodiment. For example, the pseudo projection image generating unit 63 may generate the reference object-included pseudo projection image 89 by performing pseudo projection onto the entire tomographic image 82.

[0125] As described above, according to the console 12 of each of the above embodiments, the reference object 90 is used as a reference for deriving the amount of positional deviation between the projection images 80, and the amount of positional deviation between the projection images 80 is derived using the component-removed image 88 or the reference-object-included pseudo projection image 89 that does not include structural images representing structures other than the reference object 90. Therefore, according to the console 12 of each of the above embodiments, the amount of positional deviation between the projection images 80 can be derived with high accuracy.

[0126] Although the above embodiments have been described with reference to a single reference object 90, a plurality of reference objects 90 may be provided. In this case, the console 12 may perform pseudo projection for each of the plurality of reference objects 90. Specifically, in the first embodiment, the pseudo projection image generating unit 64 identifies a reference object region 831 and a partial region 832 for each of the plurality of reference objects 90. Furthermore, the pseudo projection image generating unit 64 generates a reference-object-free pseudo projection image 86 by performing pseudo projection using the partial region 832 for each of the plurality of reference objects 90. The positional deviation amount deriving unit 66 may derive the positional deviation amount for each reference object 90 using a component-removed image 88 generated using the reference-object-free pseudo projection image 86. Furthermore, in the second embodiment, the pseudo projection image generating unit 63 generates a reference-object-included pseudo projection image 89 by performing pseudo projection using the reference object region 831 for each of the plurality of reference objects 90. Furthermore, the pseudo projection image generating unit 63 may be configured to derive the amount of positional deviation for each reference object 90 using the pseudo projection image with reference object 89. When a plurality of reference objects 90 are provided in this manner, for example, the amount of positional deviation for a region determined for each reference object 90 may be derived, or the amount of positional deviation for the entire projection image 80 may be derived by averaging the amount of positional deviation for each reference object 90, etc.

[0127] In the above embodiment, the console 12 is an example of the image processing device of the present disclosure. However, a device other than the console 12 may have the functions of the image processing device of the present disclosure. In other words, some or all of the functions of the image acquisition unit 60, the tomographic image acquisition unit 62, the pseudo-projection image generation unit 64, the positional deviation amount derivation unit 66, the notification unit 68, the tomographic image generation unit 70, and the display control unit 72 may be provided by a device other than the console 12, such as the mammography device 10 or an external device. Furthermore, the image processing device of the present disclosure may be configured by multiple devices. For example, some of the functions of the image processing device may be provided by a device other than the console 12.

[0128] In the above embodiment, a breast is used as an example of a subject of the present disclosure, and mammography device 10 is used as an example of a radiological imaging device of the present disclosure. However, the subject is not limited to a breast, and the radiological imaging device is not limited to a mammography device. For example, the subject may be a chest or abdomen, or the radiological imaging device may be a radiological imaging device other than a mammography device.

[0129] In the above embodiment, the following various processors may be used as the hardware structure of the processing units that perform various processes, such as the image acquisition unit 60, tomographic image acquisition unit 62, pseudo projection image generation unit 64, positional deviation amount deriving unit 66, notification unit 68, tomographic image generation unit 70, and display control unit 72, or the image acquisition unit 60, tomographic image acquisition unit 62, pseudo projection image generation unit 63, positional deviation amount deriving unit 65, notification unit 68, tomographic image generation unit 71, and display control unit 72. As described above, the various processors include a CPU, which is a general-purpose processor that executes software (programs) and functions as various processing units, as well as dedicated electrical circuits that are processors having a circuit configuration specifically designed to perform specific processes, such as a programmable logic device (PLD), a processor whose circuit configuration can be changed after manufacture, such as an FPGA (Field Programmable Gate Array), and an application specific integrated circuit (ASIC).

[0130] A single processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same or different types (for example, a combination of multiple FPGAs, or a combination of a CPU and an FPGA). Also, multiple processing units may be configured with a single processor.

[0131] Examples of configuring multiple processing units with a single processor include, first, a form in which one processor is configured with a combination of one or more CPUs and software, and this processor functions as multiple processing units, as typified by computers such as client and server. Second, a form in which a processor is used to realize the functions of the entire system including multiple processing units with a single IC (Integrated Circuit) chip, as typified by systems on chips (SoCs). In this way, various processing units are configured using one or more of the above-mentioned various processors as a hardware structure.

[0132] Furthermore, more specifically, the hardware structure of these various processors can be an electric circuit that combines circuit elements such as semiconductor elements.

[0133] In the above embodiments, the photographing program 41 is pre-stored (installed) in ROM 40B, and the image generating program 51 or the image generating program 51A is pre-stored (installed) in ROM 50B. However, the present invention is not limited to this. Each of the photographing program 41, the image generating program 51, and the image generating program 51A may be provided in a form recorded on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory. Each of the photographing program 41, the image generating program 51, and the image generating program 51A may be downloaded from an external device via a network. [Explanation of symbols]

[0134] 1. Radiography system 10 Mammography equipment 12 Console 191~197 irradiation position, 19 V , 19V1 Irradiation position in settings 20 Radiation detector, 20A detection surface 24 imaging table, 24A imaging surface 28 Radiation Irradiation Unit 29 Radiation source 33 Arm section 34 Foundation 35 Shaft 36 Compression Unit 38 Compression Plate 39 Support part 40A, 50A CPU, 40B, 50B ROM, 40C, 50C RAM 41 Filming Program 42, 52 Storage section 44, 54 I / F section 46, 56 Operation section 47 Source moving part Buses 49 and 59 51, 51A Image generation program 58 Display section 60 Image acquisition unit 62 Tomographic image acquisition unit 63, 64 Pseudo projection image generation unit 65, 66 Position deviation amount derivation section 67 Component removal image generation unit 68 Information Department 70, 71 Tomographic image generation unit 72 Display control unit 80, 801 projection image, 80A projection surface 82 821~827 Tomographic images 831 reference object area, 832 partial area 84, 841-847 partial images 86, 861~867 Pseudo projection image without reference object 881~887 component removed image 90 Reference object 91, 911-917, 95, 971-977 Reference object images 92A, 92B structures 93A, 93B, 93A1-93A7, 93B1-93B7 structure images CL normal R radiation, RC radiation axis W breast α, θ angles

Claims

1. 1. An image processing device that processes a plurality of projection images obtained by irradiating a subject with radiation from a radiation source from each of a plurality of irradiation positions having different irradiation angles, the image processing device comprising: a processor; The processor: acquiring the plurality of projection images; acquiring a plurality of tomographic images generated using the plurality of projection images and corresponding to a plurality of tomographic planes of the subject, respectively; generating a plurality of pseudo projection images including the reference object image by using a tomographic image including a reference object image representing a reference object used as a reference for deriving the amount of positional deviation between the projection images among the plurality of tomographic images and performing pseudo projection from a set irradiation position corresponding to each of the irradiation positions of the plurality of projection images; Deriving a positional deviation amount between the projection images based on the plurality of projection images and the plurality of pseudo projection images with reference object. Image processing device.

2. The processor: A pseudo-projection image including the reference object is generated using only the tomographic image in which the reference object is depicted. The image processing device according to claim 1 .

3. The processor: A partial pseudo-projection image is generated as the reference object pseudo-projection image by pseudo-projecting the reference object region including the reference object image in the tomographic image.

3. The image processing device according to claim 1.

4. The processor: Further, a plurality of tomographic images, the positional deviations of which have been corrected and corresponding to the plurality of tomographic planes, are generated based on the plurality of projection images and the amount of positional deviation. The image processing device according to any one of claims 1 to 3.

5. The processor: When the amount of positional deviation exceeds a preset threshold, a notification is given. The image processing device according to any one of claims 1 to 4.

6. the subject is a breast, The fiducial is a calcification or a mammary gland The image processing device according to any one of claims 1 to 5.

7. a radiation source that generates radiation; a radiation image capturing apparatus that performs tomosynthesis imaging by irradiating a subject with radiation from a radiation source from each of a plurality of irradiation positions having different irradiation angles and capturing a projection image of the subject for each of the irradiation positions; The image processing device according to any one of claims 1 to 6, A radiation imaging system comprising:

8. 1. An image processing method for processing a plurality of projection images obtained by irradiating a subject with radiation from a radiation source from each of a plurality of irradiation positions having different irradiation angles, the method comprising: acquiring the plurality of projection images; generated using the plurality of projection images and for each of the plurality of tomographic planes of the subject, acquiring a plurality of corresponding tomographic images; generating a plurality of pseudo projection images including the reference object image by using a tomographic image including a reference object image representing a reference object used as a reference for deriving the amount of positional deviation between the projection images among the plurality of tomographic images and performing pseudo projection from a set irradiation position corresponding to each of the irradiation positions of the plurality of projection images; Deriving a positional deviation amount between the projection images based on the plurality of projection images and the plurality of pseudo projection images with reference object. An image processing method in which processing is performed by a computer.

9. An image processing program for processing a plurality of projection images obtained by irradiating a subject with radiation from a radiation source from each of a plurality of irradiation positions having different irradiation angles, the program comprising: acquiring the plurality of projection images; acquiring a plurality of tomographic images generated using the plurality of projection images and corresponding to a plurality of tomographic planes of the subject, respectively; generating a plurality of pseudo projection images including the reference object image by using a tomographic image including a reference object image representing a reference object used as a reference for deriving the amount of positional deviation between the projection images among the plurality of tomographic images and performing pseudo projection from a set irradiation position corresponding to each of the irradiation positions of the plurality of projection images; Deriving a positional deviation amount between the projection images based on the plurality of projection images and the plurality of pseudo projection images with reference object. An image processing program that causes a computer to perform the processing.

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