X-ray diagnostic apparatus and tomosynthesis image generating method

Abstract

To reduce an artifact of a tomosynthesis image.SOLUTION: An X-ray diagnostic apparatus comprises an X-ray irradiation unit, a diffusion unit, a detection unit, and an image generation unit. The X-ray irradiation unit applies X-rays. The diffusion unit diffuses the applied X-rays. The detection unit detects an incident direction of incident X-rays made incident through a subject after being diffused by the diffusion unit. The image generation unit generates a tomosynthesis image of the subject based on the incident direction of the incident X-rays detected by the detection unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray diagnostic apparatus and a tomosynthesis image generating method. [Background technology]

[0002] In recent years, some X-ray diagnostic equipment is capable of using tomosynthesis technology to obtain various cross-sectional images and three-dimensional images (hereinafter referred to as tomosynthesis images) by reconstructing multiple image data obtained by irradiating a subject with X-rays from multiple discrete incident directions within a predetermined range of incident angles.

[0003] An example of tomosynthesis imaging involves irradiating a subject with X-rays from each incidence direction, in the order of -15 degrees, -14 degrees, ..., +15 degrees, in 1 degree increments within an incidence angle range of ±15 degrees around the X-ray irradiation axis, to obtain multiple image data.

[0004] However, tomosynthesis requires multiple X-ray captures, which results in long acquisition times. As a result, the tomosynthesis images obtained by reconstruction may have strong motion artifacts, making it difficult for users to interpret the images correctly.

[0005] In addition, tomosynthesis imaging involves taking X-ray images at discrete angles, and although the acquisition time can be reduced by taking coarser angles, the resulting tomosynthesis image is highly artifact-prone. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-024097 A [Patent Document 2] International Publication No. 2017 / 209059 Summary of the Invention [Problem to be solved by the invention]

[0007] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to reduce artifacts in tomosynthesis images. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0008] An X-ray diagnostic apparatus according to an embodiment includes an X-ray irradiator, a scattering unit, a detector, and an image generator. The X-ray irradiator irradiates X-rays. The scattering unit scatters the irradiated X-rays. The detector detects the incidence direction of the incident X-rays that are scattered by the scattering unit and then penetrate the subject. The image generator generates a tomosynthesis image of the subject based on the incidence direction of the incident X-rays detected by the detector. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram showing an example of the configuration of an X-ray diagnostic apparatus according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of the configuration of an X-ray detector. [Diagram 3] FIG. 2 is an explanatory diagram showing an example of the positional relationship between a scatterer, a grid, and a subject as viewed from an X-ray irradiator. [Figure 4] 1A is an xz cross-sectional view showing an example of a grid configuration in which the opening shape of each of the multiple holes in the grid is a square, FIG. 1B is an xy cross-sectional view, and FIG. [Diagram 5] 1A is an xz cross-sectional view showing an example of a grid configuration in which the opening shape of each of the multiple holes in the grid is rectangular, FIG. 1B is an xy cross-sectional view, and FIG. [Figure 6]10 is an xz cross-sectional view showing an example of a grid configuration in which the opening shape of each of a plurality of holes in the grid is circular. FIG. [Figure 7] 4 is a flowchart showing an example of a procedure for reducing artifacts in a tomosynthesis image using the X-ray diagnostic apparatus shown in FIG. 1. [Figure 8] FIG. 13 is an explanatory diagram showing a modified example of the X-ray irradiator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of an X-ray diagnostic apparatus and a tomosynthesis image generating method will be described in detail with reference to the drawings. The X-ray diagnostic apparatus according to the present embodiment may be any apparatus capable of X-ray imaging, and may include, for example, a breast X-ray imaging apparatus (mammography apparatus), an X-ray TV apparatus, a general imaging apparatus, an X-ray angiography apparatus, etc.

[0011] Fig. 1 is a block diagram showing an example of the configuration of an X-ray diagnostic apparatus 10 according to an embodiment. In this embodiment, the y-axis direction is parallel to the X-ray irradiation axis and normal to the scatterer, grid, and X-ray detector. In the example shown in Fig. 1, the y-axis direction is parallel to the front-rear direction of the subject. The x-axis direction is perpendicular to the y-axis direction and parallel to the left-right direction of the subject, and the z-axis direction is perpendicular to the x-axis direction and parallel to the axial direction of the subject (see Fig. 1).

[0012] The X-ray diagnostic apparatus 10 includes an imaging device 11 and a console 12. The imaging device 11 and the console 12 may be integrally configured, or a portion of the configuration of the console 12 may be provided as a separate device.

[0013] The imaging device 11 includes an X-ray irradiator 21 , an X-ray detector 22 , a scatterer 23 , and a grid 24 .

[0014] The X-ray irradiator 21 is disposed opposite the X-ray detector 22 with the subject in between, and irradiates the subject with X-rays. The X-ray irradiator 21 and the X-ray detector 22 may be supported at both ends of a support member such as an arm. When the X-ray diagnostic apparatus 10 is a mammography apparatus, for example, the X-ray irradiator 21 is provided at the upper end of an arm whose lower end is supported on an imaging table that holds the X-ray detector 22 therein.

[0015] The X-ray irradiator 21 has an X-ray tube and an X-ray aperture. The X-ray tube is a vacuum tube that irradiates thermoelectrons from a cathode (filament) to an anode (target) by application of high voltage from a high-voltage power supply. The X-ray aperture is, for example, a movable X-ray aperture made up of multiple lead blades. The X-ray irradiator 21 is an example of an X-ray irradiation unit.

[0016] The X-ray detector 22 detects the direction of incidence of the incident X-rays which are scattered by the scatterer 23 and then pass through the subject.

[0017] As the X-ray detector 22 capable of detecting the incident direction of X-rays, for example, an electron track detection type detector using Compton scattering can be used. The configuration and operation of the X-ray detector 22 will be described in detail later with reference to FIG.

[0018] The scatterer 23 is provided between the X-ray irradiator 21 and the subject, and scatters the X-rays irradiated from the X-ray irradiator 21. The scatterer 23 is made of a material that has a function of scattering X-rays, such as PMMA or water. The scatterer 23 is an example of a scattering section.

[0019] The grid 24 is provided between the scatterer 23 and the subject, and has a plurality of holes that transmit X-rays, and the holes limit the angle of incidence of the X-rays scattered by the scatterer 23 to the subject within a predetermined angle of incidence. The grid 24 is an example of a transmitting portion.

[0020] Specifically, the grid 24 is a parallel multi-hole collimator in which a large number of holes that transmit X-rays are provided in a metal such as lead or tungsten that has a high radiation source attenuation coefficient and a high X-ray shielding ability. When the X-rays irradiated from the X-ray irradiator 21 collide with the metal constituting the grid 24, a photoelectric effect occurs and the X-rays disappear. Only the X-rays that can pass through the small holes in the grid 24 reach the X-ray detector 22 through the subject and are detected as photons. The predetermined angle of incidence (for example, ±15 degrees) limited by the grid 24 and the spatial resolution of the grid 24 change depending on the type of the grid 24. The type of the grid 24 differs depending on the opening shape of the holes, the arrangement of the openings, the thickness of the partitions, etc. The holes in the grid 24 are aligned perpendicular to the scatterer 23 and the X-ray detector 22 (see FIG. 1).

[0021] The grid 24 is preferably detachably provided on the subject side of the scatterer 23. In this case, the grid 24 can be easily replaced, and a grid 24 of a type appropriate for the purpose of the examination can be quickly and appropriately used. The configuration and operation of the grid 24 will be described in detail later with reference to Figs. 3-6. The X-ray diagnostic apparatus 10 does not have to include the grid 24.

[0022] On the other hand, the console 12 has an input interface 31, a display 32, a memory circuit 33, and a processing circuit .

[0023] The input interface 31 is configured with, for example, a general pointing device such as a joystick, a trackball, a trackball mouse, a keyboard, a touch panel, or a numeric keypad, or a hand switch for instructing the timing of X-ray exposure, and provides an operation signal corresponding to a user's operation to the processing circuit 34. For example, the input interface 31 accepts settings of X-ray imaging conditions including ON / OFF of X-ray imaging, as well as settings of a classification width (incident angle width, for example, every 0.5 degrees) of X-ray detection data in generating a tomosynthesis image according to this embodiment. Note that some or all of the functions of the input interface 31 may be provided in the imaging device 11.

[0024] The display 32 is configured with a general display output device such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display, and displays various information under the control of the processing circuit .

[0025] The memory circuit 33 has a configuration including a processor-readable recording medium, such as a magnetic or optical recording medium or a semiconductor memory, and some or all of the programs and data in these storage media may be configured to be downloaded via an electronic network.

[0026] The processing circuitry 34 realizes a function of overall control of the X-ray diagnostic apparatus 10. The processing circuitry 34 is also a processor that reads out and executes a tomosynthesis image generating program stored in the storage circuitry 33, thereby executing a process for reducing artifacts in a tomosynthesis image.

[0027] 1, the processor of the processing circuitry 34 realizes an imaging control function 341, an incident direction calculation function 342, a classification function 343, and an image generation function 344. Each of these functions is stored in the memory circuitry 33 in the form of a program.

[0028] The imaging control function 341 controls X-ray imaging of a subject by controlling the imaging device 11 according to an imaging protocol selected by a user via, for example, the input interface 31. The imaging protocol defines a series of procedures for collecting desired image data, and includes information on the imaging site, X-ray imaging conditions including the tube current and tube voltage applied to the X-ray irradiator 21, and the setting of the incidence angle width in generating a tomosynthesis image according to this embodiment.

[0029] The incident direction calculation function 342 determines the incident direction of X-rays based on the X-ray detection data output by the X-ray detector 22. The incident direction calculation function 342 and the X-ray detector 22 are an example of a detection unit. The incident direction calculation function 342 is an example of a calculation unit. The incident direction calculation function 342 may be provided in the X-ray detector 22. In this case, the X-ray detector 22 may have a processor that realizes the incident direction calculation function 342.

[0030] The classification function 343 classifies, for each predetermined incident angle width, the X-ray detection data for each X-ray photon incident at an incident angle limited by the multiple holes in the grid 24. The classification function 343 is an example of a classification unit.

[0031] The image generation function 344 generates a tomosynthesis image of the subject based on the X-ray detection data classified for each predetermined incident angle width. The image generation function 344 reconstructs a tomosynthesis image from the classified X-ray detection data, for example, by a filtered back projection method (FBP) or an iterative reconstruction method (IR). Incident angle information of the classified X-ray detection data is used for back projection and back projection in the reconstruction process.

[0032] Here, a tomosynthesis image generating method using the X-ray diagnostic apparatus 10 according to this embodiment will be described.

[0033] Typically, in X-ray photography to generate a tomosynthesis image, the positions of the X-ray source and X-ray detection unit are changed within a specified range of incidence angles (e.g., ±15 degrees), and X-rays are irradiated onto the subject from each incidence direction at discrete angles (e.g., 1 degree).

[0034] However, this type of tomosynthesis imaging requires multiple X-rays, which results in a long collection time. As a result, the condition of the subject may change between the first X-ray imaging (X-ray imaging from -15 degrees in the above example) and the last X-ray imaging (X-ray imaging from +15 degrees in the above example), such as the subject's body movement or the concentration of the contrast agent in the observation area changing. In this case, the tomosynthesis image obtained by reconstruction will have strong motion artifacts, making it difficult for the user to interpret the image correctly.

[0035] Furthermore, in this type of tomosynthesis imaging, X-ray imaging is performed at each discrete angle. If the angle increments are made coarse (e.g., from 1 degree to 3 degrees in the above example), the acquisition time can be shortened, but the tomosynthesis image obtained by reconstruction will be an image with strong artifacts. On the other hand, if the angle increments are made finer (e.g., from 1 degree to 0.5 degrees or 0.25 degrees in the above example), the acquisition time will be longer. One possible method for shortening the acquisition time is to increase the frame rate of X-ray imaging (e.g., from 15 fps to 30 fps), but there are performance limits for each component, such as the X-ray detector 22, and increasing the frame rate is not realistic. For this reason, if the angle increments are made finer, the acquisition time will inevitably be longer, and the tomosynthesis image obtained by reconstruction will still be an image with strong motion artifacts.

[0036] Therefore, in the X-ray diagnostic apparatus 10 according to this embodiment, the X-ray irradiator 21 irradiates X-rays toward the subject without changing its position relative to the subject and the X-ray detector 22, and without moving from one position directly facing the X-ray detector 22. The X-rays irradiated from the X-ray irradiator 21 are scattered by the scatterer 23 and proceed toward the subject at various angles of incidence, and then pass through the subject and proceed toward the X-ray detector 22. The X-ray detector 22 and the incidence direction calculation function 342 associate an incidence angle with each X-ray photon incident on the X-ray detector 22. In addition, when the grid 24 is used, the X-rays scattered by the scatterer 23 are limited by the grid 24 to X-rays within a predetermined incidence angle (for example, within ±15 degrees).

[0037] Therefore, even without moving the X-ray source to change the X-ray incidence direction, the X-ray irradiator 21 can irradiate the subject with photons within a predetermined incidence angle and obtain X-ray detection data for each desired incidence angle range by simply irradiating X-rays from one position. Therefore, tomosynthesis images with fine angle intervals can be generated in a very short time.

[0038] For this reason, the X-ray diagnostic apparatus 10 according to this embodiment has an X-ray detector 22 capable of detecting the incident direction (incident angle) of X-rays, and a grid 24 that limits the incident direction of X-rays so that photons within a predetermined incident angle are irradiated onto the subject.

[0039] First, the configuration and operation of the X-ray detector 22 will be described with reference to FIG.

[0040] Fig. 2 is a cross-sectional view showing an example of the configuration of the X-ray detector 22. In Fig. 2, a yz cross section of the X-ray detector 22 is shown.

[0041] The X-ray detector 22 according to this embodiment has a configuration capable of detecting the incident direction (incident angle) of X-rays. Fig. 2 shows an example of the X-ray detector 22 in the case where the X-ray detector 22 and the incident direction calculation function 342 constitute an electron track detection type detector using Compton scattering. As an example of this type of electron track detection type detector, an electron track detection type Compton camera (ETCC, Electron-Tracking Compton Camera) described in Patent Document 2 is known.

[0042] The X-ray detector 22 has a rectangular parallelepiped shape and has a chamber 41 in the center that is filled with gas. The gas in the chamber 41 is, for example, argon gas at one to several atmospheres.

[0043] X-rays scattered by the scatterer 23 and transmitted through the grid 24 within a certain angle of incidence enter the chamber 41 from above in the y-axis direction. A part of the incident X-rays causes Compton scattering due to interaction with electrons of gas atoms in the chamber 41. Compton scattering changes the traveling direction of the incident X-rays, and the incident X-rays become scattered X-rays. An X-ray corresponding to one Compton scattering is one photon. Furthermore, electrons that receive energy from the incident X-rays fly out of the gas atoms as recoil electrons.

[0044] A two-dimensional gas amplification position detector 42 is installed on the bottom surface of the chamber 41. For example, a μPIC (Micro Pixel Chamber) can be used as the two-dimensional gas amplification position detector 42. The two-dimensional gas amplification position detector 42 according to this embodiment is a type of micropattern gas detector (MPGD) and acquires the incident position of a charged particle. A drift plane 43 is disposed above the chamber 41.

[0045] Furthermore, an electric field is formed in chamber 41, directed from two-dimensional gas amplification position detector 42 to drift plane 43. The recoil electrons ionize electrons from the gas in chamber 41, forming an electron cloud. The electron cloud is guided by the electric field to two-dimensional gas amplification position detector 42 and detected by two-dimensional gas amplification position detector 42.

[0046] A scattered X-ray detector 44 is disposed on each of the outside of the four side surfaces of the chamber 41 and below the two-dimensional gas amplification position detector 42. The scattered X-ray detector 44 includes a scintillator array 441 in which scintillators are arranged two-dimensionally, and a detection circuit 442 using a photomultiplier tube or the like that detects fluorescence from each scintillator. The scintillator array 441 is disposed between the chamber 41 and the detection circuit 442. When a scattered X-ray from the chamber 41 is absorbed by any of the scintillators, the detection circuit 442 detects the light emitted from the scintillator, thereby obtaining the detection position of the scattered X-ray.

[0047] The scattered X-ray detector 44 may be provided only on the bottom surface of the chamber 41. The four scattered X-ray detectors 44 on the side surfaces are effective in improving the detection efficiency.

[0048] When the scattered X-rays are incident on any of the five scattered X-ray detectors 44 (see FIG. 2), the detection position and detection time are acquired by the scattered X-ray detector 44. The scattered X-ray detector 44 is an example of a scattered X-ray detection unit.

[0049] Meanwhile, the recoil electrons ionize electrons from gas atoms in the chamber 41 and move forward while losing energy. The electron cloud of the ionized electrons moves toward the two-dimensional gas amplification position detector 42 due to the electric field formed in the chamber 41. The two-dimensional gas amplification position detector 42 has micro detectors arranged two-dimensionally. Each micro detector detects the entering ionized electrons. This allows the detection position and detection time of the ionized electrons to be obtained. The two-dimensional gas amplification position detector 42 is an example of an electron detection unit.

[0050] The detection information of the scattered X-rays and ionized electrons is provided to an incident direction calculation function 342 of the processing circuit 34.

[0051] The incident direction calculation function 342 uses the Compton scattering equation to determine the incident angle (incident direction) of the incident X-rays to the X-ray detector 22 based on these X-ray detection data (detection information of scattered X-rays and ionized electrons), which are the detection results of the X-ray detector 22.

[0052] In addition, the incident direction calculation function 342 may calculate the energy of the incident X-ray based on the law of conservation of energy, which states that the sum of the energy of the scattered X-ray and the energy of the recoil electrons is equal to the sum of the energy of the incident X-ray and the energy of electrons that can be considered to be stationary, and may exclude from the imaging target X-rays that are incident on the chamber 41 of the X-ray detector 22 and have an energy smaller than a predetermined value.

[0053] Next, the configuration and operation of the grid 24 according to this embodiment will be described with reference to FIGS.

[0054] Fig. 3 is an explanatory diagram showing an example of the positional relationship between the subject and the scatterer 23 and grid 24 as viewed from the X-ray irradiator 21. Fig. 3 shows an example in which the observation target site is the lung field.

[0055] Moreover, Figure 4(a) is an xz cross-sectional view showing an example of the configuration of grid 24 when the opening shape of each of multiple holes 241 in grid 24 is square, (b) is an xy cross-sectional view, and (c) is a yz cross-sectional view.

[0056] 4(a)-(c) show an example in which the opening of each hole 241 in the grid 24 has a side of length dx in the x direction and a side of length dz in the z direction, where the lengths dx and dz are the same.

[0057] In this case, the incidence angle ±θx (e.g., ±15 degrees) and its angular width θX (e.g., 30 degrees) in the x direction defined by the grid 24 (see Figure 4(b)) are equal to the incidence angle ±θz and its angular width θZ in the z direction (see Figure 4(c)).

[0058] The classification function 343 classifies the X-ray detection data based on the X-ray photons incident at the incident angles limited by the multiple holes 241 of the grid 24 into a predetermined incident angle range.

[0059] At this time, unlike typical tomosynthesis imaging in which X-ray imaging is repeated while changing the position of the X-ray source at a specified incident angle increment (for example, every 1 degree), the X-ray detection data in this embodiment can be classified at any angle increment.

[0060] Then, the image generation function 344 can generate a tomosynthesis image of the subject based on the X-ray detection data classified by the classification function 343 into a predetermined incident angle width (for example, 0.25 degrees), and display the image on the display 32.

[0061] In the X-ray diagnostic apparatus 10 according to this embodiment, the X-ray irradiator 21 can irradiate the subject with X-rays within the incident angle limited by the grid 24 almost simultaneously by simply irradiating the subject with X-rays without changing its position relative to the subject and the X-ray detector 22 and without moving from one position. This makes it possible to collect X-ray detection data in a very short time. Therefore, the X-ray diagnostic apparatus 10 can generate a high-quality tomosynthesis image with extremely few motion artifacts.

[0062] Furthermore, since the X-ray diagnostic apparatus 10 can easily acquire X-ray detection data classified at any angle increment, it is possible to significantly reduce artifacts associated with the coarse angle increments in tomosynthesis images.

[0063] Furthermore, the X-ray diagnostic apparatus 10 according to this embodiment can obtain X-ray detection data with an incidence angle of ±θx in the x direction and X-ray detection data with an incidence angle of ±θz in the z direction almost simultaneously in an extremely short time by simply irradiating X-rays from one position with the X-ray irradiator 21. Furthermore, the angle intervals for classifying the X-ray detection data can be freely set for each of the x direction and the z direction.

[0064] FIG. 5(a) is an xz cross-sectional view showing an example of a configuration of grid 24 in which the opening shape of each of multiple holes 241 in grid 24 is rectangular, (b) is an xy cross-sectional view, and (c) is a yz cross-sectional view.

[0065] 5(a)-(c) show an example in which the opening of each hole 241 in the grid 24 has sides with a length dx in the x direction and sides with a length dz in the z direction, where dz is longer than dx.

[0066] When observing a lesion in a lung field, the ribs may hinder the visibility of the lesion. The ribs extend in the left-right direction of the subject.

[0067] In this case, it is preferable to use the grid 24 having a long opening in the body axis direction (z direction) as shown in FIGS. 5(a)-(c).

[0068] By using a grid 24 having an opening longer in the body axis direction (z direction) than in the left-right direction (x direction), the body axis direction of the subject can be blurred in a tomosynthesis image generated from X-ray detection data with an incidence angle of ±θz (e.g., ±30 degrees) in the body axis direction. This reduces the visibility of ribs in the tomosynthesis image, making it easier to observe lesions.

[0069] FIG. 6 is an xz cross-sectional view showing an example of the configuration of grid 24 in which each of a plurality of holes 241 in grid 24 has a circular opening shape.

[0070] When observing a paranasal sinus or an eye socket, bones are not in a specific direction within the field of view but are in multiple directions. In this case, X-ray imaging can be performed using a grid 24 having circular or elliptical openings. In this case, X-ray detection data equivalent to that obtained by X-ray imaging while moving an X-ray source along a circular orbit in general tomosynthesis imaging can be collected.

[0071] In this way, by changing the opening shape of the holes 241 in the grid 24, the X-ray irradiator 21 can easily mimic the linear, circular, or elliptical orbit of the X-ray source in general tomosynthesis imaging simply by irradiating X-rays from one position.

[0072] Next, an example of the operation of the X-ray diagnostic apparatus 10 and the tomosynthesis image generating method according to this embodiment will be described.

[0073] Fig. 7 is a flowchart showing an example of a procedure for reducing artifacts in a tomosynthesis image by the X-ray diagnostic apparatus 10 shown in Fig. 1. In Fig. 7, the reference characters S followed by numbers indicate each step of the flowchart.

[0074] This procedure starts when the X-ray irradiator 21 is positioned directly opposite the subject and the X-ray detector 22, with the X-ray irradiator 21 and the X-ray detector 22 facing each other with the subject in between.

[0075] First, in step S1, the scatterer 23 and the grid 24 are placed on the X-ray irradiator 21 side of the subject in the order of the scatterer 23 and the grid 24 from the X-ray irradiator 21 side. At this time, it is preferable that the scatterer 23 and the grid 24 are adjacent to each other. It is also preferable that the grid 24 and the subject are close to each other, and more preferably, the grid 24 and the subject are in close contact with each other (see FIG. 1).

[0076] Next, in step S2, the X-ray irradiator 21 irradiates the subject with X-rays from one position.

[0077] X-rays irradiated from the X-ray irradiator 21 toward the subject are scattered by the scatterer 23 (step S3), and only X-rays within an incident angle limited according to the opening shape of the holes 241 in the grid 24 pass through the grid 24 (step S4), then pass through the subject and proceed toward the X-ray detector 22 (step S5).

[0078] Next, in step S5, the X-ray detector 22 detects and outputs the detection position and detection time of the scattered X-rays due to Compton scattering for each photon of the X-rays incident on the chamber 41, and also detects and outputs the detection position and detection time of the ionized electrons due to the recoil electrons due to Compton scattering. The incident direction calculation function 342 determines the incident direction of the X-rays incident on the chamber 41 for each photon based on these X-ray detection data.

[0079] Next, in step S6, the classification function 343 classifies the X-ray detection data based on the X-ray photons incident at the incident angles limited by the multiple holes in the grid 24 into a predetermined incident angle range.

[0080] Then, in step S7, the image generating function 344 reconstructs the X-ray detection data classified for each predetermined incident angle width to generate a tomosynthesis image of the subject.

[0081] Note that calibration image data reconstructed based on X-ray detection data of the ambient gas without placing a subject may be stored in advance in the storage circuitry 33. In this case, the image generating function 344 may perform so-called air calibration, in which a tomosynthesis image of the subject is calibrated with the calibration image data.

[0082] By following the above procedure, the X-ray irradiator 21 can simply irradiate X-rays from a single position to generate a tomosynthesis image based on X-ray detection data at fine angular intervals, thereby significantly reducing artifacts in the tomosynthesis image.

[0083] The X-ray diagnostic apparatus 10 according to this embodiment can generate a tomosynthesis image based on X-ray detection data with fine angular intervals by simply irradiating X-rays toward a subject without moving the X-ray irradiator 21 from one position. This makes it possible to collect the required X-ray detection data in a very short time, and generate a high-quality tomosynthesis image with extremely few motion artifacts. In addition, artifacts due to the roughness of the angular intervals in the tomosynthesis image can be significantly reduced.

[0084] Furthermore, the X-ray diagnostic apparatus 10 according to this embodiment does not require the X-ray irradiator 21 and the X-ray detector 22 to be moved during tomosynthesis imaging. This makes it possible to prevent the X-ray irradiator 21 and the X-ray detector 22 from interfering with the subject or with devices such as an injector installed around the X-ray diagnostic apparatus 10. Therefore, the X-ray diagnostic apparatus 10 allows for extremely safe tomosynthesis imaging.

[0085] FIG. 8 is an explanatory diagram showing a modified example of the X-ray irradiator 21. As shown in FIG. 8, the X-ray diagnostic apparatus 10 may include an X-ray irradiator group 50 consisting of a plurality of small X-ray irradiators 51 arranged in a plane perpendicular to the X-ray irradiation axis. In this case, the distance between the X-ray irradiator 51 that can irradiate the entire area of ​​the observation target part of the subject with X-rays and the X-ray detector 22 (the distance between the X-ray tube focus and the X-ray image receiving surface (SID: Source Image Receptor Distance)) can be significantly shortened. Therefore, the X-ray diagnostic apparatus 10 can be made compact, and the X-ray diagnostic apparatus 10 can be installed in a small room, a medical cart, or the like. In addition, the aperture of each X-ray irradiator 51 can be narrowed to reduce the viewing angle, thereby reducing image distortion around the X-ray viewing field.

[0086] According to at least one of the embodiments described above, artifacts in tomosynthesis images can be reduced.

[0087] In the above embodiment, the term "processor" refers to a circuit such as a dedicated or general-purpose CPU (Central Processing Unit), GPU (Graphics Processing Unit), or an Application Specific Integrated Circuit (ASIC), a programmable logic device (for example, a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a Field Programmable Gate Array (FPGA)). When the processor is a CPU, for example, the processor realizes various functions by reading and executing a program stored in a memory circuit. When the processor is an ASIC, for example, instead of storing a program in a memory circuit, a function corresponding to the program is directly built into the processor circuit as a logic circuit. In this case, the processor realizes various functions by hardware processing that reads and executes the program built into the circuit. Alternatively, the processor can realize various functions by combining software processing and hardware processing.

[0088] In the above embodiment, an example was shown in which a single processor of the processing circuit realizes each function, but a processing circuit may be configured by combining multiple independent processors, and each processor may realize each function. In addition, when multiple processors are provided, a memory circuit for storing a program may be provided for each processor, or one memory circuit may collectively store programs corresponding to the functions of all the processors.

[0089] Although some embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0090] 10. X-ray diagnostic equipment 21 X-ray irradiator 22 X-ray detector 23 Scatterer 24 Grid 241 holes 34 Processing circuit 342 Incident direction calculation function 343 Classification function 344 Image Generation Function 41 Chamber 42 Two-dimensional gas amplified position sensitive detector 43 Drift Plane 44 Scattered X-ray Detector 50 X-ray irradiator group 51 X-ray irradiator

Claims

1. an X-ray irradiation unit that irradiates X-rays; A scattering unit that scatters the irradiated X-rays; a detection unit that detects the direction of incidence of incident X-rays that are scattered by the scattering unit and then transmitted through a subject; an image generating unit that generates a tomosynthesis image of the subject based on the incident direction of the incident X-rays detected by the detection unit; An X-ray diagnostic device comprising:

2. a transmission section that transmits X-rays having an incident angle within a predetermined range among the X-rays scattered by the scattering section; Further equipped with The detection unit is detecting the incident direction of the X-rays transmitted through the transmission portion and the subject; 2. The X-ray diagnostic apparatus according to claim 1.

3. The transmission portion is a plurality of holes provided between the scattering section and the subject, the holes allowing X-rays to pass therethrough, the holes limiting an angle of incidence of the X-rays scattered by the scattering section with respect to the subject to within the predetermined angle of incidence; 3. The X-ray diagnostic apparatus according to claim 2.

4. The opening shape of each of the plurality of holes in the transmission portion is square.

4. The X-ray diagnostic apparatus according to claim 3.

5. an opening shape of each of the plurality of holes of the transmission section is a rectangle having a different length of a side along the body axis direction of the subject and a side perpendicular to the body axis direction; 4. The X-ray diagnostic apparatus according to claim 3.

6. The opening shape of each of the plurality of holes of the transmission portion is circular or elliptical.

4. The X-ray diagnostic apparatus according to claim 3.

7. The X-ray irradiation unit includes: irradiating the subject with X-rays without moving from one position; a sorting unit that sorts X-ray detection data for each X-ray photon incident at a limited incidence angle within the predetermined incidence angle by the plurality of holes in the transmission unit, into a predetermined incidence angle range within the predetermined incidence angle; Further equipped with The image generating unit includes: generating a tomosynthesis image of the subject based on the X-ray detection data classified for each predetermined incident angle width; 7. An X-ray diagnostic apparatus according to claim 3.

8. The detection unit is a detector that utilizes Compton scattering, A chamber; a scattered X-ray detection unit that detects a detection position and a detection time of scattered X-rays due to Compton scattering of the incident X-rays that are scattered by the scattering unit, pass through a subject, and enter the chamber; an electron detector for detecting a detection position and a detection time of ionization electrons based on the recoil electrons caused by Compton scattering; a calculation unit that calculates the incident direction of the incident X-rays based on detection results of the scattered X-ray detection unit and the electron detection unit; Including, 8. An X-ray diagnostic apparatus according to claim 1.

9. a storage unit in which a calibration image based on X-ray detection data of X-rays transmitted through an atmospheric gas instead of the subject and detected by the detection unit is stored; Further equipped with The image generating unit includes: calibrating the tomosynthesis image of the subject with the calibration image and obtaining the calibrated tomosynthesis image; 9. An X-ray diagnostic apparatus according to claim 1.

10. The X-ray irradiation unit includes: a plurality of X-ray irradiators for irradiating X-rays; The plurality of X-ray irradiators include Arranged in a plane perpendicular to the X-ray irradiation axis, 10. An X-ray diagnostic apparatus according to claim 1.

11. an X-ray irradiation unit irradiating X-rays; A step of scattering the irradiated X-rays by a scattering portion; detecting an incidence direction of incident X-rays which are scattered by the scattering unit and then pass through the subject; generating a tomosynthesis image of the subject based on the incident direction of the detected incident x-rays; A tomosynthesis image generating method comprising:

Images