JP6641725B2 - X-ray equipment - Google Patents

Description

  The present invention relates to an X-ray imaging apparatus that captures an X-ray image of a subject in the medical field or the like, and particularly to an X-ray imaging apparatus that can capture an X-ray phase image.

  When diagnosing the inside of a subject in the medical field or the like, an X-ray imaging apparatus that irradiates X-rays and generates an X-ray image is widely used. An X-ray image that is widely used is generated by an absorption imaging method in which a difference in X-ray intensity attenuation is imaged as contrast.

  The X-rays radiated to the subject are absorbed and attenuated according to the substances constituting each part of the subject when transmitting through the subject. The X-ray transmitted through the subject is detected by the X-ray detector as an X-ray absorption image and output as an X-ray detection signal. Since the X-ray detection signal varies depending on the absorption rate of the X-ray, various image processing is performed on the X-ray detection signal, so that the difference in attenuation of the X-ray intensity is represented as a contrast (difference in density). Is generated. For example, since bone tissue has a high X-ray absorption rate, an image of bone tissue with high contrast can be acquired by the absorption imaging method.

  However, the X-ray absorptance varies greatly depending on the elements constituting the subject, and an element having a small atomic number has a small X-ray absorptivity. X-rays are hardly absorbed in soft tissues, such as cartilage, which contain many elements having low atomic numbers. Therefore, it is difficult to obtain an image of a soft tissue with a sufficient contrast formed by an X-ray image by the absorption imaging method.

  Therefore, in recent years, there has been proposed an X-ray imaging apparatus that generates an X-ray image by a phase imaging method, which images an object using a phase difference of X-rays (for example, see Patent Documents 1 and 2). X-rays, which are a type of electromagnetic waves, shift in phase when transmitting through a subject. That is, since the propagation speed of the X-ray varies depending on the substance, the position of the peak of the wave of the X-ray shifts by transmitting through the subject, and a phase shift occurs. Since the effect of the phase shift of the X-ray is much larger than the effect of the attenuation of the X-ray, an X-ray image with high contrast can be obtained by the phase imaging method even for a soft tissue having a low X-ray absorption rate.

  An X-ray imaging apparatus that captures an X-ray image by the phase imaging method will be described. As an X-ray imaging method using a phase imaging method (X-ray phase imaging), an X-ray imaging apparatus using a Talbot interference method using Talbot interference will be described as an example.

  In the conventional X-ray imaging apparatus 101 used for X-ray phase imaging, the subject M is irradiated with X-rays 103a having the same phase from the X-ray tube 103 as shown in FIG. A phase grating 107 having an interdigital grating R1 is provided between the subject M and the X-ray detector 105. The grating R1 extends in the y direction, and shifts the phase of the X-ray 103a. Therefore, by transmitting the phase grating 107, the phase is modulated between the X-ray 103a transmitting the grating R1 and the X-ray 103a transmitting the gap (slit) of the grating R1.

  By transmitting the X-rays through the phase grating 107, an image of the phase grating 107 is projected at a predetermined distance (Talbot distance) from the phase grating 107 by the Talbot interference effect. The image of the phase grating 107 projected by Talbot interference is called a self-image. In the self-image, an image (interference fringe) of a stripe-like X-ray intensity distribution generated by interference of X-rays is displayed. Each of the interference fringes is parallel to the direction in which the grating R1 extends (the y direction).

  The interference fringe projected on the self image is modulated by the phase shift of the X-ray transmitted through the subject M. That is, when the subject M exists, the phase of the X-ray 103a is shifted by transmitting through the subject M, so that the interference fringes are disturbed in a direction different from the y direction. Since the disturbance of the interference fringes depends on the shape of the subject M and the substance constituting the subject M, the phase information of the subject M can be obtained by analyzing the interference fringes reflected in the self-image.

  In order for the Talbot interference effect to occur, the pitch of the grating provided on the phase grating 107 needs to be a small distance of about several μm, so that the period of the interference fringes reflected in the self-image is the same. Since it is relatively difficult to directly analyze such narrow-period fringes with an X-ray detector, it is common to further provide an absorption grating 109 at a position separated from the phase grating 107 by a Talbot distance. The absorption grating 109 is constituted by an interdigital grating R2 made of an X-ray absorber.

  In this case, in the self-image formed behind the absorption grating 109, fringe-like moire occurs due to a shift in the period between the interference fringe based on the phase grating 107 and the interference fringe of the absorption grating 109. The period of the moire fringes is larger than the period of the interference fringes, and the shape of the moire fringes changes according to the disturbance of the interference fringes reflected in the self-image. Therefore, the structure of the subject M can be relatively easily analyzed based on the shape of the moire fringes generated in the self image.

  Here, the X-ray detector 105 that detects the X-ray intensity distribution will be described. As the X-ray detector 105, a flat panel detector (FPD) or the like is used. Here, an indirect conversion type X-ray detector that converts X-rays into light using a scintillator element or the like, and further converts light into electric charges as electric signals will be described as an example. The X-ray detector 105 has a configuration in which a scintillator layer 105a and an output layer 105b are stacked in the z direction as shown in FIG. The scintillator layer 105a is composed of a scintillator element that absorbs X-rays and converts them into light.

  The output layer 105b includes a substrate 111 and pixels 113 arranged in a two-dimensional matrix. Each of the pixels 113 includes a photoelectric conversion element and an output element (not shown). X-rays incident on the X-ray detector 105 are converted into light in the scintillator layer 105a and emit light as scintillator light. The scintillator light is converted into electric charge as an electric signal by a photoelectric conversion element provided in the pixel 113, and is output from the output element as an X-ray detection signal. Then, an X-ray image showing a self-image is generated based on the output X-ray detection signal.

  When performing X-ray imaging using the Talbot interference method, a plurality of X-ray images are captured while scanning the absorption grating 109 in the periodic direction (x direction) of the grating R2. Then, an image (X-ray phase image) showing a phase contrast image of the subject M is obtained by analyzing a change in moiré fringes generated in each of the plurality of X-ray images. Unlike an absorption contrast image, a phase contrast image is clearly seen even in a soft tissue or the like. Therefore, by using an X-ray phase image, highly accurate diagnosis can be performed on a soft tissue or the like.

International Publication WO2004 / 058070 JP-A-2524068

However, the conventional example having such a configuration has the following problem.
That is, in the X-ray detector 105 used in the conventional X-ray imaging apparatus, since the scintillator element forming the scintillator layer 105a is thin, X-rays having relatively high energy among incident X-rays cannot be converted into scintillator light. . Therefore, an X-ray phase image acquired based on an X-ray detection signal has low accuracy of phase information. However, when the thickness of the scintillator layer 105a is increased so that high-energy X-rays can be detected, scintillator light is easily scattered inside the scintillator layer 105a. As a result, there is a concern about a new problem that the resolution of the X-ray phase image is reduced.

  On the other hand, for the purpose of improving the resolution of an X-ray image, a configuration in which a scintillator element is partitioned by a partition in an X-ray detector has been proposed (see Reference 1: International Publication 2012/161304). In the X-ray detector 201 having such a configuration, a scintillator layer 203 and an output layer 205 are stacked, and the output layer 205 includes a substrate 207 and pixels 209 (FIG. 9A). The scintillator layer 203 has a shape in which a large number of scintillator elements 211 arranged in a two-dimensional matrix are partitioned by a lattice-shaped light shielding wall 213 (FIG. 9B).

  In such a configuration, the scattered scintillator light is blocked by the light shielding wall 213, so that the scattered light generated in the scintillator element 211 can be prevented from reaching the adjacent scintillator element 211. Therefore, by applying the configuration of the X-ray detector 201 having the light-shielding wall to the X-ray imaging apparatus 101 based on the Talbot interference method, even if the scintillator element 211 is made thicker, a decrease in the resolution of the X-ray phase image is avoided. Can be expected.

  However, in the X-ray detector 201, since each of the scintillator elements 211 is partitioned by the light shielding wall 213, the X-ray incident on the light shielding wall 213 is not converted into light. Therefore, among the X-rays irradiated to the X-ray detector 201, an X-ray detection signal is not output to the portion of the light shielding wall 213, so that the X-ray sensitivity of the X-ray detector 201 as a whole is reduced. Is concerned. In particular, since the X-ray sensitivity of the X-ray detector 201 is further reduced as the light-shielding wall becomes thicker, the diagnostic performance of the X-ray phase image is reduced.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an X-ray imaging apparatus with higher X-ray sensitivity that enables imaging of an X-ray phase image with high diagnostic performance. .

The present invention has the following configuration to achieve such an object.
That is, in the X-ray imaging apparatus according to the present invention, the X-ray tube for irradiating the subject with X-rays and the diffractive member extending in the first direction are arranged in parallel in a second direction orthogonal to the first direction. A first diffraction grating for forming interference fringes extending in the first direction by diffracting the X-rays; and a moiré for diffracting the X-rays forming the interference fringes and extending in a third direction. A second diffraction grating that forms fringes, a scintillator element that is arranged in a two-dimensional matrix and detects the X-rays that form the moiré fringes and converts the X-rays into light, and partitions the scintillator element to block the light An X-ray detector including a scintillator layer including a light-shielding wall and an output layer in which pixels that convert light converted by each of the scintillator elements into electric charges and output an X-ray detection signal are arranged in a two-dimensional matrix. And the X-ray An image generation unit that generates an X-ray image using the X-ray detection signal output by the output unit; and an X-ray that displays an X-ray phase contrast image of the subject based on the X-ray image generated by the image generation unit. A reconstructing unit for reconstructing a phase image, wherein a period of the light shielding wall in a direction in which the moiré fringes are deformed by a change in the phase of the X-rays is equal to the light shielding in the third direction in which the moiré fringes extend. than the period of the wall is kept short, at least a part of the portion to be deformed of the moire fringes, intersects with the light-shielding wall, is detected at said different scintillator element from said scintillator element for detecting a portion which is not deformed That is, it is characterized.

  [Operation and Effect] According to the X-ray imaging apparatus of the present invention, the scintillator layer of the X-ray detector has a configuration in which the light shielding wall partitions the scintillator element. Therefore, scattering of light converted in the scintillator element is avoided by the light shielding wall. Therefore, the resolution of the X-ray image and the X-ray phase image can be improved even when the scintillator layer is made thick to detect high-energy X-rays.

  The period of the light shielding wall in the direction in which the moire fringes are deformed by the change in the phase of the X-rays is shorter than the period of the light shielding wall in the direction in which the moiré stripes extend. Since the period of the light shielding wall in the direction in which the moiré fringes are deformed is short, the X-rays based on the moiré fringe portions deformed by the change in the phase of the X-rays and the moiré fringe portions that are not deformed are surely transmitted to different scintillator elements. Incident.

  Since the scintillator elements are separated from each other by the light-shielding walls, it is possible to preferably prevent the light converted by the different scintillator elements from scattering in the direction in which the moire fringes are deformed. Therefore, the resolution of the X-ray image is particularly high in the direction in which the moiré fringes are deformed, so that the moiré fringe portions deformed by the phase change of the X-ray and the moiré fringe portions that are not deformed in the X-ray image have high accuracy. Can be distinguished. As a result, the phase contrast image of the subject is clearly reflected in the reconstructed X-ray phase image, so that the diagnostic performance of the X-ray phase image can be improved.

  On the other hand, the period of the light-shielding wall in the direction in which the moiré stripes extend becomes longer. Therefore, on the X-ray detection surface of the X-ray detector, the area where the light shielding wall is provided can be reduced. That is, since the region where the X-ray detector cannot detect X-rays is further reduced, the diagnostic performance of the X-ray phase image can be improved, and a decrease in the X-ray sensitivity of the X-ray detector can be suitably avoided.

  In the above-described invention, it is preferable that the light-shielding wall and the scintillator element extend in the third direction, and are alternately arranged in a direction in which the moiré stripes are deformed.

  [Operation and Effect] According to the X-ray imaging apparatus of the present invention, the light shielding wall and the scintillator element extend in the third direction, and are arranged in parallel in the direction in which the moire fringes are deformed. In this case, the light-shielding wall extends only in the third direction in which the moiré stripes extend, and no light-shielding wall extending in a direction intersecting the third direction is formed. Therefore, in the scintillator layer of the X-ray detector, the area where the light shielding wall is provided can be further reduced. Therefore, the X-ray insensitive region of the X-ray detector can be narrowed, so that the X-ray sensitivity can be further improved.

  Since the light-shielding walls and the scintillator elements are alternately arranged in the direction in which the moire fringes are deformed, the pitch of the light-shielding walls in the direction in which the moiré fringes are deformed becomes shorter. Therefore, the resolution of the X-ray image becomes higher in the direction in which the moiré fringes are deformed by the phase change of the X-ray. Therefore, in the X-ray image, the moiré fringe portion deformed by the phase change of the X-ray and the moiré fringe portion that is not deformed can be distinguished with particularly high accuracy. As a result, the phase contrast image of the subject is more clearly reflected in the reconstructed X-ray phase image, so that the diagnostic performance of the X-ray phase image can be further improved.

The present invention may have the following configuration in order to achieve such an object.
That is, in the X-ray imaging apparatus according to the present invention, the X-ray tube for irradiating the subject with X-rays and the diffractive member extending in the first direction are arranged in parallel in a second direction orthogonal to the first direction. A first diffraction grating that forms interference fringes extending in the first direction by diffracting the X-rays, and detects the X-rays that are arranged in a two-dimensional matrix and form the interference fringes. A scintillator element that converts light into light, a scintillator layer that partitions the scintillator element and includes a light-shielding wall that blocks the light, and a pixel that converts the light converted by each of the scintillator elements into an electric charge and outputs an X-ray detection signal. An X-ray detector including an output layer arranged in a two-dimensional matrix; an image generation unit configured to generate an X-ray image using the X-ray detection signal output from the X-ray detector; X generated by the part A reconstruction unit for reconstructing an X-ray phase image showing an X-ray phase contrast image of the subject based on an image, wherein the interference fringes are deformed by a change in the phase of the X-rays. period, the first and the shielding wall period than the short Kuna' in direction, at least a part of the portion to be deformed of the interference fringes, the scintillator in which the light shielding wall and intersect to detect the portion is not deformed And detecting by the scintillator element different from the element.

  [Operation / Effect] According to the X-ray imaging apparatus according to the present invention, the period of the light shielding wall in the direction in which the interference fringes are deformed by the change in the phase of the X-ray is determined by the period of the light shielding wall in the first direction in which the interference fringes extend. It is shorter than the period. Since the period of the light shielding wall in the direction in which the interference fringes are deformed is short, the X-rays based on the interference fringe portions deformed by the change in the phase of the X-rays and the X-rays based on the non-deformed interference fringe portions are surely different scintillators Light enters the element.

  Since the scintillator elements are separated from each other by the light-shielding walls, it is possible to preferably prevent the light converted by the different scintillator elements from scattering in the direction in which the interference fringes are deformed. Therefore, the resolution of the X-ray image is particularly high in the direction in which the interference fringes are deformed. Therefore, in the X-ray image, the portions of the interference fringes deformed by the phase change of the X-rays and the portions of the non-deformed interference fringes are highly accurately determined. Can be distinguished. As a result, the phase contrast image of the subject is clearly reflected in the reconstructed X-ray phase image, so that the diagnostic performance of the X-ray phase image can be improved.

  On the other hand, the period of the light-shielding wall in the direction in which the interference fringes extend becomes longer. Therefore, on the X-ray detection surface of the X-ray detector, the area where the light shielding wall is provided can be reduced. That is, since the region where the X-ray detector cannot detect X-rays is further reduced, the diagnostic performance of the X-ray phase image can be improved, and a decrease in the X-ray sensitivity of the X-ray detector can be suitably avoided.

  Further, since the X-ray detector directly detects the interference fringes formed by the first diffraction grating, the second diffraction grating can be omitted. It is difficult to manufacture the second diffraction grating with a large area corresponding to the X-ray detector. Therefore, by omitting the second diffraction grating, the manufacturing cost of the X-ray imaging apparatus can be reduced.

  In the above-described invention, it is preferable that the light-shielding wall and the scintillator element extend in the first direction, and are alternately arranged in a direction in which the interference fringes are deformed.

  [Operation and Effect] According to the X-ray imaging apparatus of the present invention, the light shielding wall and the scintillator element extend in the first direction and are arranged in parallel in the direction in which the interference fringes are deformed. In this case, the light shielding wall extends only in the first direction, and no light shielding wall extending in a direction intersecting with the first direction is formed. Therefore, in the scintillator layer of the X-ray detector, the area where the light shielding wall is provided can be further reduced. Therefore, the X-ray insensitive region of the X-ray detector can be narrowed, so that the X-ray sensitivity can be further improved.

  Since the light-shielding walls and the scintillator elements are alternately arranged in the direction in which the interference fringes are deformed, the pitch of the light-shielding walls in the direction in which the interference fringes are deformed becomes shorter. Therefore, the resolution of the X-ray image becomes higher in the direction in which the interference fringes are deformed by the phase change of the X-ray. Therefore, in the X-ray image, the portion of the interference fringe deformed by the phase change of the X-ray and the portion of the interference fringe that are not deformed can be distinguished with particularly high accuracy. As a result, the phase contrast image of the subject is more clearly reflected in the reconstructed X-ray phase image, so that the diagnostic performance of the X-ray phase image can be further improved.

  According to the X-ray imaging apparatus of the present invention, the scintillator layer of the X-ray detector has a configuration in which the light shielding wall partitions the scintillator element. Therefore, scattering of light converted in the scintillator element is avoided by the light shielding wall. Therefore, the resolution of the X-ray image and the X-ray phase image can be improved even when the scintillator layer is made thick to detect high-energy X-rays.

  The period of the light shielding wall in the direction in which the moire fringes are deformed by the change in the phase of the X-rays is shorter than the period of the light shielding wall in the direction in which the moiré stripes extend. Since the period of the light shielding wall in the direction in which the moiré fringes are deformed is short, the X-rays based on the moiré fringe portions deformed by the change in the phase of the X-rays and the moiré fringe portions that are not deformed are surely transmitted to different scintillator elements. Incident.

  Since the scintillator elements are separated from each other by the light-shielding walls, it is possible to preferably prevent the light converted by the different scintillator elements from scattering in the direction in which the moire fringes are deformed. Therefore, the resolution of the X-ray image is particularly high in the direction in which the moiré fringes are deformed, so that the moiré fringe portions deformed by the phase change of the X-ray and the moiré fringe portions that are not deformed in the X-ray image have high accuracy. Can be distinguished. As a result, the phase contrast image of the subject is clearly reflected in the reconstructed X-ray phase image, so that the diagnostic performance of the X-ray phase image can be improved.

  On the other hand, the period of the light-shielding wall in the direction in which the moiré stripes extend becomes longer. Therefore, on the X-ray detection surface of the X-ray detector, the area where the light shielding wall is provided can be reduced. That is, since the region where the X-ray detector cannot detect X-rays is further reduced, the diagnostic performance of the X-ray phase image can be improved, and a decrease in the X-ray sensitivity of the X-ray detector can be suitably avoided.

FIG. 1 is a diagram illustrating a configuration of an X-ray imaging apparatus according to an embodiment. (A) is a schematic diagram illustrating the entire configuration of the X-ray imaging apparatus, (b) is a diagram illustrating the configuration of the diffraction grating, and (c) is a schematic diagram illustrating interference fringes reflected in a self-image. (D) is a schematic diagram showing moire fringes reflected in a self-image. FIG. 2 is a diagram illustrating a configuration of an X-ray detector according to an embodiment. FIG. 3A is a cross-sectional view illustrating a configuration of an X-ray detector, FIG. 3B is a plan view illustrating an array of pixels, and FIG. 3C is a plan view illustrating an array of scintillator elements partitioned by light-shielding walls. FIG. FIG. 4 is a diagram illustrating a direction in which interference fringes are deformed in the example. (A) is a figure which shows the interference fringe in the state without a phase shift of X-ray, (b) is a figure which shows the interference fringe in the state deformed by the phase shift of X-ray. FIG. 4 is a diagram illustrating a positional relationship between a detection surface of an X-ray detector and moiré fringes according to an example. (A) is a figure which shows the positional relationship between each of the moire fringes deformed according to the deformation of the interference fringes and the moire fringes which are not deformed, and the scintillator element, and (b) is an X-ray detector in the direction in which the moire fringes are deformed. 4A is a cross-sectional view taken along the line AA in FIG. 4A, and FIG. 4C is a cross-sectional view taken along the line BB in FIG. It is. FIG. 14 is a diagram illustrating a positional relationship between a detection surface of an X-ray detector and moiré fringes according to a modification (2). FIG. 14 is a diagram illustrating a positional relationship between a detection surface of an X-ray detector and moiré fringes according to a modification (3). (A) is a figure which shows the positional relationship between each of the moire fringes deformed according to the deformation of the interference fringes and the moire fringes which are not deformed, and the scintillator element, and (b) is a cross-sectional view taken along the line AA of FIG. (C) is a plan view of the X-ray detector showing the arrangement of the scintillator element and the light shielding wall according to the comparative example. It is a figure showing composition of a Moire fringe concerning modification (4). FIG. 2 is a diagram illustrating a configuration of an X-ray imaging apparatus according to a conventional example. FIG. 1A is a schematic diagram illustrating the entire configuration of an X-ray imaging apparatus, and FIG. 2B is a cross-sectional view illustrating the configuration of an X-ray detector. It is a figure showing the composition of the conventional X-ray detector which has the composition divided by the shading wall. (A) is sectional drawing which shows the structure of an X-ray detector, (b) is overhead view explaining the structure of a scintillator layer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a schematic diagram illustrating the entire configuration of the X-ray imaging apparatus according to the embodiment.

  The X-ray imaging apparatus 1 according to the embodiment, which is used for the Talbot interference X-ray phase imaging, irradiates the subject M with the X-rays 3a, and detects the X-rays 3a to generate an X-ray detection signal. X-ray detector 5, which outputs the following, first diffraction grating 7, second diffraction grating 9, moving mechanism 11, X-ray irradiation control unit 12, image generation unit 13, reconstruction unit 15, It has.

  The first diffraction grating 7 is disposed such that the direction (z direction) along the central axis 3b of the X-ray 3a emitted from the X-ray tube 3 is orthogonal to the X-ray incident surface of the first diffraction grating 7. Is done. In the first diffraction grating 7, diffraction members R1 extending in the y direction and diffracting X-rays are arranged at a predetermined pitch (period) T1 in the x direction (see the left diagram in FIG. 1B). An X-ray transmitting portion R2 is provided in the gap between the diffraction members R1 in a slit shape. The y direction is one direction in the X-ray incidence plane of the first diffraction grating 7, and the x direction is a direction orthogonal to each of the z direction and the y direction. Generally, a phase grating that modulates the phase of X-rays is used as the first diffraction grating 7. In this case, it is preferable to use a material that modulates the phase of X-rays as the diffraction member R1.

  When the X-rays 3a pass through the first diffraction grating 7, the X-rays 3a that have passed through the first diffraction grating 7 overlap and interfere with each other by being diffracted. Then, as shown in FIG. 1C, the self-image S appears at a position separated by a predetermined distance (Talbot distance) so as to satisfy the condition that the phases of the diffracted X-rays 3a are aligned. In the self-image S, an interference fringe R, which is an image of a stripe-like X-ray intensity distribution generated by X-ray interference, is displayed. The pattern of the interference fringes R reflects the shape of the diffraction member R1 provided on the first diffraction grating 7. That is, the interference fringes R extend in the y direction and appear as a plurality of fringe patterns arranged in parallel in the x direction with a period of the length T3.

  The second diffraction grating 9 is provided between the first diffraction grating 7 and the X-ray detector 5, and its X-ray incident surface is configured to be orthogonal to the z direction. The configuration of the second diffraction grating 9 is the same as that of the first diffraction grating 7, in which diffraction members R3 extending in the y direction and further diffracting X-rays are arranged at a predetermined pitch T2 in the x direction (FIG. 1). (B) See right figure). An X-ray transmitting portion R4 is provided in a gap between the diffraction members R3 in a slit shape. The distance between the second diffraction grating 9 and the first diffraction grating 7 is adjusted to be the Talbot distance. Therefore, the X-ray 3a transmits through the first diffraction grating 7 and the second diffraction grating 9 and forms a self-image S behind the second diffraction grating 9. As the second diffraction grating 9, an X-ray absorption type shielding grating (absorption grating) that generally modulates the intensity of X-rays is used. In this case, it is preferable to use a material that appropriately absorbs X-rays as the diffraction member R2.

  When the X-ray 3a passes through the first diffraction grating 7 and the second diffraction grating 9, the X-ray 3a that has passed through the first diffraction grating 7 is partially shielded by passing through the second diffraction grating 9. And diffract further. Therefore, the moire fringes P appear on the self-image S due to the superposition of the pattern of the interference fringes R and the pattern of the diffractive member R3 (FIG. 1D).

  In the embodiment, each of the diffraction members R1 and R3 extends in the y direction. That is, the moiré fringes P appearing due to the superposition of the interference fringes R extending in the y direction and the diffraction member R3 are so-called parallel moirés extending in the y direction, and the period D of the moiré fringes P is (T3 · T2) / (T3- T2). Since the value of the period D of the moire fringes P is much larger than the period T3 of the interference fringes R, the pitch of the pixel 27 is adjusted by adjusting the values of the period T2 of the diffraction member R3 and the period T3 of the interference fringes R, respectively. Is large, the change in the shape of the moiré fringes P can be easily detected.

  The moving mechanism 11 is connected to the second diffraction grating 9, and moves the second diffraction grating 9 to relatively displace the positional relationship between the first diffraction grating 7 and the second diffraction grating 9. Let it. An X-ray irradiation control unit 12 is connected to the X-ray tube 3, and the X-ray irradiation control unit 12 controls the timing of irradiating the X-ray 3 a from the X-ray tube 3, the dose of the X-ray 3 a, and the like. The X-ray irradiation control unit 12 irradiates the X-ray 3a at an appropriate timing while the moving mechanism 11 displaces the relative position between the first diffraction grating 7 and the second diffraction grating 9 in the x-direction. An X-ray image showing the image S is taken.

  The moving mechanism 11 photographs a plurality of self-images S in which the moire fringes P are generated while moving the second diffraction grating 9 in the periodic direction (x direction) of the grating R2. The distance by which the second diffraction grating 9 is moved generally corresponds to the pitch length T2 of the diffraction member R3. By placing the subject M between the X-ray tube 3a and the first diffraction grating 7, the phase of the X-ray 3a passing through the subject M is shifted. As a result, since the interference fringes R in the self-image S are deformed, the shape of the moire fringes P is also changed.

  The image generation unit 13 is provided at a stage subsequent to the X-ray detector 5 and generates an X-ray image showing the self-image S based on the X-ray detection signal output from the X-ray detector 5. The reconstruction unit 15 is provided at a subsequent stage of the image generation unit 13, performs various arithmetic processing on the X-ray image generated by the image generation unit 13, and based on information on the moire fringes P reflected on the self image S, An X-ray image (X-ray phase image) showing a phase contrast image of the subject M is reconstructed.

  The X-ray detector 5 is arranged so that the X-ray detection surface is orthogonal to the z direction, and detects information of the self image S. Further, in order to avoid blurring of the self-image S, it is preferable that the X-ray detector 5 and the second diffraction grating 9 are configured to be as close as possible. In the embodiment, an indirect conversion flat panel detector (FPD) is used as the X-ray detector 5. As shown in FIG. 2A, the X-ray detector 5 has a configuration in which a scintillator layer 17 and an output layer 19 are stacked in the z direction. The scintillator layer 17 has a configuration in which the scintillator element 21 is partitioned by a lattice-shaped light-shielding wall 23 (see Reference 1: International Publication 2012/161304).

  The scintillator element 21 absorbs the irradiated X-rays and emits light such as fluorescent light as scintillator light according to the irradiated X-rays. As a material for forming the scintillator element 21, an X-ray phosphor such as cesium iodide may be used. As a material of the light shielding wall 23, for example, glass powder containing an alkali metal oxide is used. The details of the material of the scintillator element 15, the material of the light-shielding wall 23, the process of forming the light-shielding wall 23 on the output layer 19, and the like are described in detail in Reference Document 1 and the like. Omitted.

  The output layer 19 includes a substrate 25 and pixels 27 arranged in a two-dimensional matrix as shown in FIG. Each of the pixels 27 includes a photoelectric conversion element that converts light into electric charge, and an output element that outputs an X-ray detection signal based on the converted electric charge, and detects the scintillator light emitted from the scintillator element 21 by X-ray detection. Convert to a signal and output. The image generation unit 13 is connected to each of the pixels 27, and performs various image processing on the X-ray detection signal output from the pixel 27 to generate an image showing the self image S. As described above, the pattern of the moire fringes P reflected on the self-image S is detected by the X-ray detector 5.

  Note that, as shown in FIG. 2A, each of the scintillator elements 21 partitioned by the light shielding wall 23 and each of the pixels 27 are arranged so as to have a one-to-one positional relationship in the x direction. Is preferred. That is, the pitch (period) of the pixels 27 is preferably configured to be substantially the same as the pitch of the scintillator elements 21 in the x direction. With such a configuration, an X-ray image with higher resolution in the x direction can be obtained.

  As described above, the scintillator layer 17 has a configuration in which each of the cells partitioned by the lattice-shaped light-shielding walls 23 is filled with the scintillator element 21. With such a configuration, even if the scintillator light emitted by the scintillator element 21 is scattered inside the scintillator layer 17, the scattered scintillator light is blocked by the light shielding wall 23.

  Therefore, it is possible to prevent the scattered light generated in the scintillator element 21 from entering the adjacent scintillator element 21. Therefore, even if the scintillator element 21 is thickened in the z direction to improve the X-ray sensitivity of the X-ray detector 5 by dividing the scintillator element 21 by the light shielding wall 23, the resolution of the X-ray image is reduced. Can be avoided. In the X-ray detector 5 according to the embodiment, the pitch of the light shielding walls 17 can be set to a short distance of about 60 to 100 μm. Therefore, even when an X-ray image with a finer pixel pitch is required, a decrease in the resolution of the X-ray image can be avoided.

<Arrangement of scintillator elements and their effects>
Here, an arrangement of the scintillator elements 21 partitioned by the light shielding wall 23, which is characteristic of the embodiment, will be described. The X-ray detector 5 has a configuration in which a plurality of scintillator elements 21 extending in one predetermined direction are arranged in a direction orthogonal to the extending direction. The direction in which each of the light-shielding wall 23 and the scintillator element 21 extends is parallel to the direction in which the moiré fringes P extend, and is set to be orthogonal to the direction in which the moiré fringes P deform (disturb). In the embodiment, the moire fringes P reflected on the self image S extend in the y direction. That is, as shown in FIG. 2C, in the X-ray imaging apparatus 1 according to the embodiment, in the X-ray detector 5, the light shielding walls 23 and the scintillator elements 21 extending in the y direction are alternately arranged in the x direction. Are arranged.

  By placing the subject M between the X-ray tube 3 and the first diffraction grating 7, the interference fringes R in the self image S are deformed. That is, when the X-ray 3a does not pass through the subject M, the interference fringes R have a shape extending in the y direction (FIG. 3A). On the other hand, when the X-rays 3a pass through the subject M, the interference fringes R are deformed so as to be distorted in a wave shape by shifting the phase of the X-rays 3a. Such deformation of the interference fringes R is caused by the movement of each of the components (points) constituting the interference fringes R in the x direction (see FIG. 3B, symbols N1 to N3). That is, the symbols N1 to N3 indicate the amount of change in the x direction in each component of the interference fringe R.

  Therefore, when the diffraction member R1 of the first diffraction grating 7 extends in the y direction, the direction in which the interference fringes R are deformed can be regarded as the x direction orthogonal to the y direction. Then, as a result of the interference fringes R being deformed (disturbed) in the x direction, the moire fringes P extending in the y direction are also deformed in the x direction according to the amount of change of the interference fringes R. That is, the phase information of the X-ray 3a that changes depending on the subject M is detected based on the amount of change in the moire fringes P in the x direction.

  The scintillator layer 17 has a configuration in which the light shielding walls 23 and the scintillator elements 21 extending in the y direction are alternately arranged in the direction (x direction) in which the interference fringes R are deformed. Therefore, the pitch length of the light shielding wall 23 in the x direction becomes shorter. The direction in which the scintillator element 23 extends and the direction in which the moiré fringes P extend are substantially the same.

  Accordingly, the position where the moiré fringes P of the self-image S are reflected on the X-ray detection surface of the X-ray detector 5 is as shown in FIG. When the phase shift of the X-ray 3a does not occur, the moiré fringes P have a shape extending in the y direction without being deformed. Such moire fringes P1 are reflected on the same scintillator element 21c in all components. When the X-ray 3a passes through the subject M and the phase shifts, the moire fringes P are deformed due to the deformation of the interference fringes R. The moiré fringes P deformed by the phase shift of the X-ray 3a are referred to as moiré fringes P2.

  Of the moiré fringes P2 deformed by the phase shift of the X-rays 3a, a portion that is not deformed in the x direction is reflected on the same scintillator element 21a. On the other hand, since the pitch length of the light shielding wall 23 in the x direction is short, a portion of the moire fringes P that deforms in the x direction crosses the light shielding wall 23 and is reflected on a scintillator element 21b different from the scintillator element 21a.

  Since the scintillator element 21a and the scintillator element 21b are separated by the light shielding wall 23, the scattering of the scintillator light in the x direction is preferably avoided. That is, the scintillator light W obtained by converting the X-ray 3a by the scintillator element 21a surely enters the pixel 27a, and the scintillator light W converted by the scintillator element 21a surely enters the pixel 27b (FIG. 4B).

  As described above, since the X-ray detector 5 is configured so that the pitch of the light shielding wall 23 in the x direction becomes shorter, the moire fringe P component that does not change in the x direction and the moire fringe P component that changes in the x direction Are surely detected at pixels 27 different from each other. Therefore, the amount of change in each of the moiré fringes P in the x direction can be accurately detected, so that the resolution of the X-ray phase image in the x direction can be improved. In order to improve the accuracy of the information on the subject M based on the change in the phase of the X-rays, it is necessary to accurately detect the amount of change in the moire fringes P. Therefore, by improving the resolution in the x direction, the diagnostic ability of an X-ray phase image showing a phase contrast image of the subject M can be greatly improved.

  Further, in the X-ray detector 5 according to the embodiment, since each of the light shielding wall 23 and the scintillator element 21 is configured to extend in the y direction, the pitch of the light shielding wall 23 in the y direction becomes longer (FIG. 4C). ). When a lattice-shaped light shielding wall is provided on the scintillator layer of the X-ray detector, a generally conceivable configuration is a configuration in which the scintillator elements 21 are arranged in a grid pattern as shown in FIG.

  In the configuration of the X-ray detector 201 according to the comparative example as shown in FIG. 6C, since the pitch of the light shielding walls 213 is short not only in the x direction but also in the y direction, the area where the light shielding walls 213 are provided is small. Become wider. X-rays incident on the light shielding wall 213 pass through the X-ray detector 201 without being converted into scintillator light. Therefore, the region where the light shielding wall 213 is provided in the X-ray detector 201 is a region that can be called a blind spot where X-rays cannot be detected. Therefore, the X-ray sensitivity of the X-ray detector decreases when the area where the light shielding wall is provided increases.

  In order to avoid such a problem of a decrease in X-ray sensitivity, the X-ray detector 5 according to the embodiment has a configuration in which the pitch of the light shielding wall 23 is increased in the y direction in which the moire fringes P extend. With such a configuration, the area where the light shielding wall 23 is provided in the X-ray detector 5 can be further reduced as compared with the configuration of the comparative example in which the scintillator elements 21 are arranged in a grid pattern ( FIG. 6 (c)). As a result, the area of the light shielding wall 23 which is the X-ray insensitive area is reduced, so that a decrease in the X-ray sensitivity of the X-ray detector 5 can be preferably avoided.

  When the moire fringes P extend in the y direction, the moiré fringes P do not deform in the y direction but deform in the x direction. Therefore, since it is not necessary to accurately detect the amount of change in the moiré fringes P in the y direction, the influence of the resolution in the y direction on the X-ray phase image contributing to the diagnostic performance of the X-ray phase image is small. Therefore, by making the direction in which the light shielding wall 23 and the scintillator element 21 extend parallel to the direction in which the moire stripes P extend, the area in which the light shielding wall 23 is attached is reduced, and the direction in which the moiré stripes P are deformed is reduced. The detection accuracy of the X-ray detector 5 can be improved. As a result, it is possible to suitably avoid a decrease in the X-ray sensitivity of the X-ray detector 5, and to greatly improve the diagnostic capability of the X-ray phase image.

  An operation of capturing an X-ray phase image using the X-ray imaging apparatus 1 will be described. First, as shown in FIG. 1A, the X-ray tube 3 emits X-rays 3a. In this case, the X-rays 3a passing through the X-ray transmitting portion R2 of the first diffraction grating 7 and the X-ray transmitting portion R4 of the second diffraction grating 9 cause the self-image S behind the second diffraction grating 9 to be formed. It is formed. Moire fringes P appear in the self-image S by the pattern of the interference fringes R and the pattern of the diffractive member R3 overlapping each other (FIG. 1D).

  When the subject M does not exist, the moire fringes P extend in the y direction. On the other hand, when the subject M is placed between the X-ray tube 3 and the first diffraction grating 7, the phase of the X-ray 3a changes (shifts) when passing through the subject M. As a result, the shape of the interference fringes R extending in the y direction is disturbed in the x direction with the border of the subject M as a boundary, so that the shape of the moire fringes P in the self-image S changes in the x direction.

  The X-ray detector 5 detects the pattern of the moire fringes P with respect to the self-image S formed by the irradiation of the X-rays 3a and outputs an X-ray detection signal. The image generation unit 13 performs various image processing on the X-ray detection signal to form an image, thereby generating an X-ray image (moire image) showing the moire fringes P. In the X-ray detector 5, the period of the light shielding wall 23 and the scintillator element 21 in the x direction is shorter than the period in the y direction. In such a configuration, since the scattering of the scintillator light in the x direction is suitably prevented, the resolution of the moire image in the x direction is improved. The light-shielding wall 23 is configured to preferably intersect with the direction in which the moiré fringes P deform (the x direction).

  Therefore, the component of the moiré fringes P deformed by the phase shift of the X-rays is displaced from the position intersecting the light shielding wall 23 and overlapping the scintillator element 21a to the position overlapping the scintillator element 21b (FIG. 4A). Therefore, the component of the moire fringe P that is not deformed and the component of the moire fringe P that is deformed in the x direction are converted into scintillator light by the different scintillator elements 21 and output as X-ray detection signals by the different pixels 27. As a result, information on the deformation pattern of the moiré fringes P based on the X-ray phase shift is displayed on the moiré image generated by the image generator 13 with high accuracy.

  Then, the moving mechanism 11 moves the second diffraction grating 9 in the x direction, and the X-ray irradiation controller 12 sends the X-ray from the X-ray tube 3 every time the second diffraction grating 9 moves a predetermined distance in the x direction. The line 3a is irradiated. The distance that the second diffraction grating 9 moves is the pitch length T2 of the diffraction member R3, and the X-ray irradiation control unit 12 determines that the distance of the second diffraction grating 9 is T2 / m (m is an integer) in the x direction. An X-ray irradiation is performed every time it moves.

  By performing m times of X-ray irradiation in this manner, m moiré images are generated. The reconstruction unit 15 analyzes the m moiré images generated by the image generation unit 13 and reconstructs an X-ray phase image based on the phase information of the moiré fringes P reflected in each moiré image.

  Specifically, a change in the luminance value of each of the pixels 27 is calculated for the m moiré images, and a differential phase is calculated based on the change in the luminance value. The luminance value of the pixel 27 shows a periodic change that draws a sine curve in the m moiré images. However, the period of the luminance value change of the moiré fringe P deformed based on the phase shift of the X-ray is changed. shift. Therefore, the reconstruction unit 15 calculates the differential phase based on the period of the luminance value change in the m moiré images, and further reconstructs the X-ray phase image representing the shape of the subject M based on the differential phase information. Can be.

  The present invention is not limited to the above embodiment, but can be modified as follows.

  (1) In each of the embodiments described above, two diffraction gratings including the first diffraction grating 7 and the second diffraction grating 9 are provided. However, the number of diffraction gratings may be one. That is, the second diffraction grating 9 may be omitted, and the X-ray detector 5 may be configured to directly detect the interference fringes R reflected on the self-image S of the first diffraction grating 7. In this case, in the X-ray detector 5, the direction in which the scintillator element 21 and the light shielding wall 23 extend is parallel to the direction in which the interference fringes R extend, that is, the direction in which the diffraction member R1 of the first diffraction grating 7 extends. It is composed of

  In such a modified example (1), as an example, the positions of the first diffraction grating 7 and the X-ray detector 5 are such that the diffraction member R1, the scintillator element 21, and the light shielding wall 23 all extend in the y direction. The relationship is set. In this case, the interference fringes R reflected on the self image S are deformed in the x direction due to the phase shift of the X-ray. Since the pitch length of the light shielding wall 23 in the X-ray detector 5 is short in the x direction, the deformation amount of the interference fringes R deforming in the x direction can be detected with high accuracy.

  In the y direction in which the interference fringes R are not deformed, the pitch of the light shielding walls 23 is long, so that the X-ray insensitive area in the X-ray detector 5 can be further reduced. Therefore, a decrease in the X-ray sensitivity of the X-ray detector 5 can be avoided, and the diagnostic performance of the X-ray phase image can be improved. Furthermore, it is very difficult to form the second diffraction grating 9 having a configuration in which the diffraction gratings R3 are arranged at a pitch length of several μm with a wide area corresponding to the detection surface of the X-ray detector 5. is there. Therefore, the manufacturing cost of the X-ray imaging apparatus 1 can be significantly reduced by omitting the second diffraction grating 9.

  (2) In the above-described embodiments and modified examples, the configuration in which the direction in which the moiré fringes P extend and the direction in which the light-shielding wall 23 extends is described as an example, but is not limited thereto. That is, as long as the direction in which the moiré fringes P deform and the direction in which the light-shielding wall 23 extends intersect, the direction in which each of the moiré fringe P and the light-shielding wall 23 extend may be different.

  In the X-ray detector 5A according to such a modification (2), as shown in FIG. 5, the direction (F direction) in which the light shielding wall 23 and the scintillator element 21 extend is the direction in which the moire fringes P extend (y direction). ). On the X-ray detection surface of the X-ray detector 5A, each of the moire fringes P extends so as to be inclined with respect to the arrangement of the scintillator elements 21 and the pixels 27. The angle at which the extending direction y of the moire fringes P is inclined with respect to the extending direction F of the scintillator element 21 is defined as θ1. Note that the inclination angle θ1 of the moiré fringes P is such that the direction in which the moiré fringes P deform (the x direction) intersects the light shielding wall 23. In addition, the inclination angle θ1 is appropriately set so that the cycle Vx of the light shielding wall 23 in the x direction in which the moire fringes P deform is shorter than the cycle Vy of the light shielding wall 23 in the y direction in which the moire fringes P extend. preferable.

  As described above, in the configuration according to the modified example (2), even when the shape of the moire fringes P does not change, the moire fringes P are positioned so as to straddle the plurality of scintillator elements 21. On the other hand, in the configuration according to the embodiment, the direction in which the moiré fringes P extend and the direction in which the light shielding wall 23 extends are parallel. Therefore, depending on the combination of the period of the light shielding wall 23 and the period of the moiré stripe P, the moiré stripe P may overlap the light shielding wall 23 (see FIG. 4A, moiré stripe P3).

  Since the X-rays incident on the light-shielding wall 23 pass through the X-ray detector 5 without being detected by the scintillator element 21, the region where the light-shielding wall 23 is provided can be said to be an X-ray insensitive region. Therefore, the X-ray detector 5 cannot detect any moire fringes P3 overlapping the light shielding wall 23.

  In the configuration of the embodiment in which the moiré fringes P and the light-shielding wall 23 extend in parallel, the period of the light-shielding wall 23 in the x direction in which the moiré fringe P changes is the shortest. In particular, detection can be performed with high accuracy. On the other hand, in the configuration of the embodiment, when the moiré fringes P and the light shielding wall 23 overlap as described above, there is a concern that the sensitivity of the X-ray detector to the moiré fringes P decreases.

  On the other hand, in the X-ray detector 5A according to the modification (2), the y-direction in which the moire fringes P extend is inclined with respect to the F-direction in which the light-shielding wall 23 and the scintillator element 21 extend. The portion surely overlaps the area of the scintillator element 21. As an example, in the configuration shown in FIG. 5, the moire fringes P overlap with each of the scintillator elements 21a to 21c. Therefore, since the pixels 27 corresponding to each of the scintillator elements 21a to 21c detect the moiré fringes P, the X-ray detector 5A according to the modification can surely detect the moiré fringes P with more pixels 27. As a result, the X-ray sensitivity of the X-ray detector 5A can be further improved.

  Then, of the moire fringes P, with respect to the moire fringes P2 deformed by the phase shift of the X-ray 3a, the x direction in which the moire fringes P are deformed is set so as to intersect the light shielding wall 23. Therefore, the component of the moiré fringes P2 that is deformed in the x direction due to the phase shift of the X-rays intersects with the light shielding wall 23 and is detected by the scintillator element 21 that is different from the non-deformed component of the moiré fringes P2.

  Since the period of the light shielding wall 23 in the x direction is short, the light shielding wall 23 suitably shields the scattering of the scintillator light in the x direction. Therefore, the moiré image generated by the image generation unit 13 is an image having a high resolution in the x direction, which is the direction in which the moiré fringes P2 change due to the phase change of the X-rays. Therefore, the reconstruction unit 15 can accurately detect the amount of change in the moire fringes P2 caused by the change in the phase of the X-ray, and can reconstruct an X-ray phase image with high diagnostic performance.

  When the cycle D of the moire fringes P is larger than the cycle V of the light-shielding wall 23, the direction in which the scintillator element 23 and the light-shielding wall 23 extend is inclined from the direction in which the moire fringe P extends. Can be reduced. As a result, the moiré fringes P can be detected by more scintillator elements 21 and pixels 27, so that the X-ray imaging apparatus according to the modification (2) can further improve the X-ray sensitivity of the X-ray detector 5A. . Therefore, it is possible to improve the X-ray sensitivity of the X-ray detector and the diagnostic capability of the X-ray phase image at the same time.

  (3) In the above-described embodiments and the modifications, the configuration in which the light shielding wall 23 extends only in the y direction has been described as an example, but the invention is not limited to this. That is, as shown in FIG. 6A, in the X-ray detector 5, the light shielding wall 23 may be configured to extend not only in the y direction but also in the x direction. In the configuration according to the modified example (3), the pitch V1 of the light shielding walls 23 in the y direction is shorter than the pitch V2 of the light shielding walls 23 in the x direction. The length of the pitch V1 is preferably substantially equal to the pitch length Y of the pixels 27, and the length of the pitch V2 is particularly preferably about 4 to 6 times the pitch length Y of the pixels 27 (see FIG. b)). FIG. 6B is a cross-sectional view taken along line AA of the X-ray detector 5B shown in FIG.

  In such a configuration, the scattering of the scintillator light can be preferably avoided not only in the x direction but also in the y direction, so that the resolution of the moiré image and the X-ray phase image can be further improved, and the diagnostic performance of the image can be further improved. . Further, since the cycle of the light shielding wall 23 is long in the y direction, the scintillator elements 211 which are conventionally considered as the X-ray detector 201 having the light shielding wall are arranged in a grid pattern (FIGS. 6C and 9B). )), The area where the light shielding wall 213 is provided can be reduced. Therefore, in the modification (3), the X-ray sensitivity of the X-ray detector 5B can be improved as compared with the configuration according to the comparative example as shown in FIG.

  Since the moiré fringes P do not deform in the y direction, the X-ray phase image does not require a high resolution in the y direction. Therefore, even if the pitch V2 of the light shielding wall 23 in the y direction is increased, it is possible to avoid a decrease in diagnostic performance of the X-ray phase image. Therefore, by making the pitch V1 shorter than the pitch V2, it is possible to achieve both an improvement in the X-ray sensitivity of the X-ray detector and an improvement in the diagnostic capability of the X-ray phase image.

  When the configuration according to the modification (3) is applied to the configuration according to the modification (2), the pitch of the light shielding walls 23 in the direction (y direction) in which the moiré stripes P are deformed is determined by changing the pitch (y The grid pattern of the light shielding wall 23 is configured so as to be shorter than the pitch of the light shielding wall 23 in the (direction). With such a configuration, a portion of the moiré fringes P that is deformed in the x direction due to a change in the phase of the X-ray and a portion that is not deformed are reliably detected by different scintillator elements 21. As a result, it is possible to accurately detect the amount of change in the moire fringes P in the moire image. Further, the area of the light shielding wall 23 can be reduced as compared with the configuration according to the comparative example as shown in FIG. Therefore, it is possible to improve the X-ray sensitivity of the X-ray detector and the diagnostic capability of the X-ray phase image at the same time.

  (4) In the above-described embodiment and each modified example, the configuration in which the diffraction member R1 of the first diffraction grating 7 and the diffraction member R3 of the second diffraction grating 9 extend in the same direction has been described as an example. The directions in which the diffractive members R1 and R3 extend may be different from each other. In this case, while the diffractive member R1 extends in the y direction, the extending direction (J direction) of the diffractive member R3 is shifted from the y direction by an angle θ2 (upper part in FIG. 7). In the embodiment, since the diffractive member R1 and the diffractive member R3 extend in the same direction, the moire fringes P, which are parallel moire, appear in the self-image S so as to extend in the y direction.

  On the other hand, in the modification (4), since the diffractive member R1 and the diffractive member R3 extend in different directions, moire fringes Pa, which are so-called rotational moire, appear in the self-image S. The direction in which the moire fringes Pa extend is a direction substantially orthogonal to the J direction (K direction), and the period Da of the moiré fringes Pa is obtained by the formula of T1 / θ (lower part in FIG. 7). The angle θ2 can be adjusted by rotating the second diffraction grating 9 about the axis in the z direction by the moving mechanism 11. Therefore, each of the direction K in which the moiré fringes Pa extend and the cycle Da of the moiré fringes Pa can be appropriately adjusted by the moving mechanism 11.

  In the X-ray detector 5 according to the modification (4), the direction in which the scintillator element 21 and the light-shielding wall 23 extend intersects with the direction in which the moire fringes Pa deform. In this case, when the X-ray 3a passes through the subject M and a phase shift occurs, the moiré fringes Pa are deformed in a direction intersecting with the light shielding wall 23.

  Since the deformed moiré fringes Pa preferably intersect with the light shielding wall 23 and are displaced to the position of the adjacent scintillator element 21, the components of the undeformed moiré fringes Pa and the components of the deformed moiré fringes Pa are more reliably different. It is detected by the scintillator element 21. As a result, an X-ray detection signal is output from each of the different pixels 27, so that the phase information of the moiré fringes Pa that changes based on the phase shift of the X-ray 3a can be detected with high accuracy.

  (5) In the above-described embodiment and each modified example, the X-ray of the subject M is obtained based on a plurality of X-ray images that are obtained by relatively moving the first diffraction grating 7 and the second diffraction grating 9 in the x direction. The description is made by taking an example of X-ray phase imaging by a fringe scanning method for acquiring a line phase image. However, the method of performing X-ray phase imaging by the Talbot interference method is not limited to the fringe scanning method, and another method such as a Fourier transform method may be used as appropriate. In the Fourier transform method, it is not necessary to move the second diffraction grating 9 in order to reconstruct an X-ray phase image, so that the number of X-ray irradiations can be suppressed to one.

  (6) In the above-described embodiment and each of the modifications, a phase grating that modulates the phase of X-rays is used as the first diffraction grating 7. An amplitude type diffraction grating that modulates the intensity of X-rays may be used. Although the second diffraction grating 9 uses an absorption grating, that is, an X-ray absorption type shielding grating, the X-ray reflection type shielding grating, which shields X-rays by reflecting X-rays, is used as the second diffraction grating 9. May be used. In addition, a phase grating may be used as the second diffraction grating 9 instead of the shielding grating as long as the configuration can diffract X-rays.

  (7) In the above-described embodiment and each modified example, the configuration using an indirect conversion type X-ray detector that converts X-rays into light with a scintillator element or the like and further converts light into an electric signal has been described as an example. The configuration of the X-ray detector according to the present invention can also be applied to a direct conversion type X-ray detector that directly converts X-rays into an electric signal. That is, in the configuration according to each embodiment, an X-ray conversion element configured of a-Se (amorphous selenium) or the like and converting X-rays into electric charges is used instead of the scintillator element.

  By forming the grooves for shielding the scattering of electric charges in a lattice shape instead of the light shielding walls, the effect of the present invention can be obtained also in the direct conversion type X-ray detector. Note that, in the indirect conversion type X-ray detector, a configuration in which the scintillator element 21 is partitioned by a groove instead of the light shielding wall 23 may be used.

DESCRIPTION OF SYMBOLS 1 ... X-ray imaging device 3 ... X-ray tube 5 ... X-ray detector 7 ... 1st diffraction grating 9 ... 2nd diffraction grating 11 ... Moving mechanism 12 ... X-ray irradiation control unit 13 ... Image generation unit 15 ... Re Structural unit 17: scintillator layer 19: output layer 21: scintillator element 23: light-shielding wall 27: pixel

Claims (4)

An X-ray tube that irradiates the subject with X-rays;
A diffractive member extending in a first direction is arranged in a second direction orthogonal to the first direction, and diffracts the X-ray to form an interference fringe extending in the first direction. A diffraction grating;
A second diffraction grating that diffracts the X-rays that form the interference fringes to form Moiré fringes extending in a third direction;
A scintillator element that is arranged in a two-dimensional matrix and detects the X-rays that form the moiré fringes and converts the X-ray into light, a scintillator layer including a light-shielding wall that partitions the scintillator element and blocks the light, and the scintillator element An X-ray detector configured by an output layer in which pixels each converting the converted light into an electric charge and outputting an X-ray detection signal are arranged in a two-dimensional matrix;
An image generation unit that generates an X-ray image using the X-ray detection signal output by the X-ray detector;
A reconstruction unit for reconstructing an X-ray phase image showing an X-ray phase contrast image of the subject based on the X-ray image generated by the image generation unit,
Cycle of the light shielding wall in a direction in which the moire fringes is deformed by the phase change of the X-ray is kept short than the period of the shielding wall in the third direction in which the moire fringes is extended, the moire fringes at least a part of the portion which deforms out of the shielding wall and intersect, X-rays imaging apparatus characterized by, detected by said different scintillator element from said scintillator element for detecting a portion which is not deformed. The X-ray imaging apparatus according to claim 1,
The X-ray imaging apparatus, wherein the light shielding wall and the scintillator element extend in the third direction, and are alternately arranged in a direction in which the moiré fringes are deformed. An X-ray tube that irradiates the subject with X-rays;
A diffractive member extending in a first direction is arranged in a second direction orthogonal to the first direction, and diffracts the X-ray to form an interference fringe extending in the first direction. A diffraction grating;
A scintillator element that is arranged in a two-dimensional matrix and detects the X-rays that form the interference fringes and converts the X-ray into light; a scintillator layer including a light-shielding wall that partitions the scintillator element and blocks the light; and the scintillator element An X-ray detector configured by an output layer in which pixels each converting the converted light into an electric charge and outputting an X-ray detection signal are arranged in a two-dimensional matrix;
An image generation unit that generates an X-ray image using the X-ray detection signal output by the X-ray detector;
A reconstruction unit for reconstructing an X-ray phase image showing an X-ray phase contrast image of the subject based on the X-ray image generated by the image generation unit,
Cycle of the light shielding wall in a direction in which the interference fringes are deformed by the phase change of the X-rays, said first and kept short than the period of the shielding wall in the direction of the portion that deforms out of the interference fringes at least in part, the light shielding wall and intersect, X-rays imaging apparatus characterized by, detected by said different scintillator element from said scintillator element for detecting a portion which is not deformed. The X-ray imaging apparatus according to claim 3,
The X-ray imaging apparatus, wherein the light shielding wall and the scintillator element extend in the first direction, and are alternately arranged in a direction in which the interference fringes are deformed.

Images