JP2012132793A - Grid for taking radiation image, manufacturing method for the same and radiation image taking system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grid without a defect such as a void and a gap inside X-ray absorption parts.SOLUTION: X-ray absorption parts 24 are formed by filling the inside of grooves 27a provided in an X-ray transmissive substrate 27 composing an X-ray transmission part 25 with an X-ray absorber made of a metal having a melting point lower than a temperature at which a grid structure composed of the X-ray absorption parts 24 and the X-ray transmission part 25 may be deformed. When a defect such as a void 34 and a gap 35 is produced inside the X-ray absorption parts 24, the defect such as the void 34 and the gap 35 is eliminated by melting the X-ray absorption parts 24 and a recess 24a produced by the defect elimination is re-filled with the X-ray absorber.

Description

  The present invention relates to a grid used for radiographic imaging, a method for manufacturing the grid, and a radiographic imaging system using the grid.

  It is known that X-rays change in intensity and phase due to interaction when incident on an object, and the change in phase exhibits an interaction higher than the change in intensity. Using this X-ray property, based on the phase change (angle change) of the X-ray by the subject, a high-contrast image (hereinafter referred to as a phase contrast image) is obtained from the subject having a low X-ray absorption capability. Research on line phase imaging has been actively conducted.

  An X-ray imaging system that performs X-ray phase imaging using the Talbot interference effect by two transmission diffraction gratings (grids) has been devised (see, for example, Patent Document 1 and Non-Patent Document 1). In this X-ray imaging system, as viewed from the X-ray source, the first grid is arranged behind the subject, and the second grid is arranged downstream from the first grid by the Talbot interference distance. Behind the second grid, an X-ray image detector (FPD: Flat Panel Detector) that detects X-rays and generates an image is arranged. The first grid and the second grid are striped one-dimensional grids in which X-ray absorbing portions and X-ray transmitting portions extended in one direction are alternately arranged along an arrangement direction orthogonal to the extending direction. . The Talbot interference distance is a distance at which the X-rays that have passed through the first grid form a self image (a fringe image) due to the Talbot interference effect.

  In the above X-ray imaging system, a fringe image generated by superposition (intensity modulation) of the self-image of the first grid and the second grid is detected by the fringe scanning method, and the object is detected from the change in the fringe image by the subject. Obtain sample phase information. The fringe scanning method is a method in which the second grid with respect to the first grid is substantially parallel to the plane of the first grid and in a direction substantially perpendicular to the lattice direction (strip direction) of the first grid. The image is taken a plurality of times while being translated at a scanning pitch obtained by equally dividing the lattice pitch, and the angle distribution of X-rays refracted by the subject (differentiating the phase shift) from the change in each pixel value obtained by the X-ray image detector. Image), and a phase contrast image of the subject is obtained based on this angular distribution. This fringe scanning method is also used in an imaging apparatus using laser light (see, for example, Non-Patent Document 2).

  The first and second grids require a fine structure in which the width and pitch of the X-ray absorption part are several μm. Moreover, the X-ray absorption part of the first and second grids is required to have high X-ray absorption. In particular, the second grid requires higher X-ray absorption than the first grid in order to surely modulate the intensity of the fringe image. Therefore, the X-ray absorption parts of the first and second grids are made of heavy atomic weight gold (Au), and the X-ray absorption part of the second grid has a relatively large thickness with respect to the X-ray traveling direction. And so-called aspect ratio (a value obtained by dividing the thickness of the portion that absorbs X-rays by the width) is required.

  In Patent Document 1, as a method of manufacturing the first and second grids, a groove is formed in a photosensitive resin layer provided on a substrate by X-ray lithography, and an X such as Au is formed in the groove by electrolytic plating or the like. A method of filling a line absorber is disclosed.

JP 2009-282322 A

C. David, et al., Applied Physics Letters, Vol. 81, No. 17, October 2002, p. 3287 Hector Canabal, et al., Applied Optics, Vol.37, No.26, September 1998, 6227

  4A shows, for example, a groove provided in the X-ray transparent substrate 27 by electrolytic plating using the sheath layer 22 provided between the support substrate 21 and the X-ray transparent substrate 27 as an electrode. An X-ray absorbing material is filled in 27a and an X-ray absorbing portion 24 is formed. As described above, the X-ray absorbing portion 24 requires a very high aspect ratio such that the width W2 and the pitch P2 are several μm and the thickness T2 is several tens to several tens of μm, for example. It is difficult to fill the material without gaps. Therefore, a void 34 that is a void generated in the X-ray absorbing portion 24, and a filling defect such as a shim 35 that is a void generated at the center of the groove 27a when the X-ray absorbing material is filled along the inner wall of the groove 27a. May occur.

  When the void 34 is generated in the X-ray absorption unit 24, the X-ray absorption performance of the X-ray absorption unit 24 is degraded, and the image quality of the phase contrast image photographed using the grid is degraded. Further, when the shim 35 is generated in the X-ray absorber 24, not only the X-ray absorption performance of the X-ray absorber 24 is degraded, but the shim 35 disturbs the pitch of the X-ray absorber 24. As a result, the formation of moire used to generate a phase contrast image is hindered.

  An object of the present invention is to provide a grid having no defects such as voids and shims in the X-ray absorbing portion.

  In order to solve the above-described problems, a radiographic imaging grid according to the present invention is a radiographic imaging grid having a plurality of radiation transmitting portions and radiation absorbing portions, and includes a radiation absorbing portion and a radiation transmitting portion in the radiation absorbing portion. A metal having a melting point lower than the temperature at which the grid structure composed of the parts may change is used.

  When having a grid layer composed of a radiation absorbing portion and a radiation transmitting portion, and a support substrate joined to support the grid layer, the melting point of the radiation absorbing portion is such that the radiation transmissive substrate and the support substrate constituting the grid layer are It is preferable that the temperature is lower than the temperature applied to the radiation transmissive substrate and the support substrate during bonding to the substrate. The melting point of the radiation absorbing portion is, for example, 400 ° C. or less, and an alloy such as AuSn, AuSi, AuGe, AuIn, AuInPb, SnInPb, AgSn, SnPb, SnBi, BiCd, SnBiPb, BiPbSnCd, BiPbSnSb is preferably used.

  The method for manufacturing a radiographic imaging grid according to the present invention includes a step of bonding a radiation transmissive substrate and a support substrate that supports the radiation transmissive substrate, and a plurality of grooves in which radiation absorbing portions are formed in the radiation transmissive substrate. Forming a radiation transmitting portion between the grooves, and forming a radiation absorbing portion by filling the groove with a metal having a melting point lower than the heating temperature at the time of joining the radiation transmitting substrate and the support substrate. And a step of heating and melting the radiation absorbing portion to repair a defect generated in the radiation absorbing portion.

  Moreover, you may replenish a radiation absorbing material to the recessed part produced in the radiation absorption part by the defect repair of the radiation absorption part. Further, diffusion bonding may be used for bonding the radiation transmissive substrate and the support substrate. Furthermore, it is preferable to use the melting point, material, etc. of the radiation absorbing portion similar to the grid for radiographic imaging of the present invention.

  In the radiographic imaging system of the present invention, a grid structure including a portion that transmits radiation and a portion that absorbs radiation is periodically arranged, and the first periodic pattern image is formed by passing the radiation irradiated from the radiation source. A first grid, intensity modulation means for applying intensity modulation to the first periodic pattern image at at least one relative position having a phase different from that of the first periodic pattern, and a first generated by the intensity modulation means at the relative position. A radiation image detector comprising: a radiation image detector that detects two periodic pattern images; and an arithmetic processing unit that images phase information based on at least one second periodic pattern image detected by the radiation image detector. In this imaging system, the radiation image capturing grid is used as the first grid.

  The intensity modulation means includes a second grid in which a grid structure including a portion that transmits the first periodic pattern and a portion that absorbs the first periodic pattern is periodically arranged, and one of the first and second grids. In the case of a radiographic imaging system that includes a scanning unit that moves at a predetermined pitch in the periodic direction of the grid structure of the first and second grids, each position moved by the scanning unit corresponds to a relative position. The grid for radiographic imaging may be used as the grid.

  In the case of a radiographic imaging system having a third grid that is arranged between the radiation source and the first grid and that partially shields the radiation emitted from the radiation source and serves as a number of line light sources. The radiographic imaging grid may be used as the third grid.

  According to the present invention, the radiation absorbing portion is made of a metal having a melting point lower than the temperature at which the grid structure may change, so that the radiation absorbing portion can be changed without changing the structure of the completed grid. Only defects such as voids and shims existing in the radiation absorbing portion can be repaired. Moreover, after the defect repair of the radiation absorbing portion, the concave portion generated in the radiation absorbing portion by the defect repair can be repaired. As a result, a grid free from defects such as voids and shims can be obtained, and a high-quality phase contrast image can be taken.

It is the schematic which shows typically the structure of the X-ray imaging system of this invention. It is the top view and sectional drawing which show the structure of a 2nd grid. It is sectional drawing which shows the manufacturing process of a 2nd grid. It is sectional drawing which shows the defect repair process of a 2nd grid.

  FIG. 1 is a conceptual diagram showing a configuration of an X-ray imaging system 10 of the present invention. The X-ray imaging system 10 includes an X-ray source 11, a source grid 12, a first grid 13, a second grid 14, and an X-ray image detector arranged along the z direction that is the X-ray irradiation direction. 15 is provided. The X-ray source 11 includes, for example, a rotary anode type X-ray tube and a collimator that limits the X-ray irradiation field, and emits cone beam-shaped X-rays to the subject H. The X-ray image detector 15 is, for example, a flat panel detector (FPD) using a semiconductor circuit, and is disposed behind the second grid 14. The X-ray image detector 15 is connected to a phase contrast image generation unit 16 that generates a phase contrast image from the image data detected by the X-ray image detector 15.

  The radiation source grid 12, the first grid 13, and the second grid 14 are absorption grids that absorb X-rays, and are disposed to face the X-ray source 11 in the z direction. Between the radiation source grid 12 and the first grid 13, an interval at which the subject H can be arranged is provided. Further, the distance between the first grid 13 and the second grid 14 is set to be equal to or shorter than the minimum Talbot interference distance. That is, the X-ray image capturing system 10 of the present embodiment captures a phase contrast image by projecting X-rays without using the Talbot interference effect.

  The second grid 14 and the scanning mechanism 18 constitute intensity modulation means of the present invention. The scanning mechanism 18 is a mechanism that translates the grating pitch of the second grid 14 in the grating pitch direction (x direction) at a scanning pitch obtained by equally dividing the grating pitch of the second grid 14 (for example, five divisions) when capturing a phase contrast image.

  The structure of the grid will be described using the second grid 14 as an example. 2A is a front view of the second grid 14 as viewed from the X-ray image detector 15 side, and FIG. 2B is a cross-sectional view taken along the line AA in FIG. The second grid 14 is provided between the grid layer 20 functioning as a grid, the support substrate 21 provided on the surface of the grid layer 20 on the X-ray source 11 side, and the grid layer 20 and the support substrate 21. And the seeds layer 22.

  The grid layer 20 includes a plurality of X-ray absorbing parts 24 and X-ray transmitting parts 25 that are extended in the y direction within a plane orthogonal to the z direction. The X-ray absorption unit 24 and the X-ray transmission unit 25 are alternately arranged along the x direction orthogonal to the z direction and the y direction, and form a striped grid. The X-ray absorption unit 24 and the X-ray transmission unit 25 absorb (shield) and transmit X-rays emitted from the X-ray source 11 to form a striped image.

  The X-ray absorber 24 is made of a low melting point metal having high X-ray absorption. The reason why the low melting point metal is used for the X-ray absorbing portion 24 is that the X-ray absorbing portion 24 is melted after the second grid 14 is manufactured, and defects such as voids and shims generated in the X-ray absorbing portion 24 are obtained. This is so that it can be repaired. The low melting point in the present invention is a temperature lower than the temperature at which the grid structure composed of the X-ray absorption part 24 and the X-ray transmission part 25 may change.

  The X-ray transmission part 25 is made of a material having lower X-ray absorption than the X-ray absorption part 24. The support substrate 21 is made of a material having low X-ray absorption like the X-ray transmission part and having rigidity for supporting the grid layer 20. The seed layer 22 is made of a conductive material, and is used as an electrode when the X-ray absorbing portion 24 is formed by electrolytic plating. Since the seed layer 22 is thinner than the grid layer 20 and the support substrate 21, there is little influence on the X-ray transparency.

  The width W2 and the pitch P2 of the X-ray absorber 24 are the distance between the source grid 12 and the first grid 13, the distance between the first grid 13 and the second grid 14, and the first The width W2 is about 2 to 20 μm, and the pitch P2 is about 4 to 40 μm, depending on the pitch of the X-ray absorbing portion of the grid 13 and the like. Further, the thickness T2 in the z direction of the X-ray absorber 24 is preferably as thick as possible to obtain high X-ray absorption, but considering the vignetting of cone-beam X-rays emitted from the X-ray source 11, For example, it is about 100 μm. In the present embodiment, for example, the width W2 is 2.5 μm, the pitch P2 is 5 μm, the thickness T2 is 100 μm, and the aspect ratio of the X-ray absorber 24 is 40.

  Next, a method for manufacturing the second grid 14 will be described. FIG. 3 shows a manufacturing procedure of the second grid 14 and is a cross-sectional view along the xz plane defined by the x direction and the z direction in FIGS. 1 and 2. As shown in FIG. 3A, in the first step, an X-ray transmissive substrate 27 constituting the X-ray transmissive portion 25 of the grid layer 20, and a support substrate 21 provided with a sheath layer 22 on one surface, Are joined.

  The material of the X-ray transmissive substrate 27 needs to have low X-ray absorption, high strength, and easy processing. As a material satisfying such characteristics, for example, silicon (Si) is desirable, but GaAs, Ge, quartz, or the like may be used. The thickness L1 of the X-ray transparent substrate 27 corresponds to the thickness T2 in the z direction of the X-ray absorber 24 described above, and is, for example, 20 to 150 μm.

  The support substrate 21 is made of a material having a low X-ray absorption and a small difference in thermal expansion coefficient from the X-ray transmission substrate 27. The material of the support substrate 21 is preferably borosilicate glass, soda lime glass, quartz, alumina, GaAs, Ge or the like, and more preferably the same silicon as the X-ray transparent substrate 27. As the borosilicate glass, for example, Pyrex (registered trademark) glass, Tempax (registered trademark) glass, or the like can be used. The reason why the support substrate 21 is made of a material having a small difference in thermal expansion coefficient from that of the X-ray transparent substrate 27 is to prevent distortion due to thermal stress at the time of joining and use with the X-ray transparent substrate 27. .

  The seed layer 22 is made of, for example, Au or Ni, or a metal film made of Al, Ti, Cr, Cu, Ag, Ta, W, Pb, Pd, Pt, or a metal film made of an alloy thereof. preferable. Further, the seed layer 22 may be provided on the X-ray transparent substrate 27, or may be provided on both the X-ray transparent substrate 27 and the support substrate 21. Since the seed layer 22 has a thickness of about several μm, it does not affect the X-ray transmission even when a material having high X-ray absorption such as Au is used.

  A thickness L2 of the support substrate 21 including the seeds layer 22 is thicker than the X-ray transmissive substrate 27, and is about 100 to 700 μm, for example. Note that the support substrate 21 may be thickened before bonding, and may be polished to be adjusted to a desired thickness after bonding.

  For bonding the X-ray transparent substrate 27 and the support substrate 21, diffusion bonding in which bonding is performed while applying heat and pressure, or room temperature bonding in which surfaces are activated in a high vacuum is used. In addition, the X-ray transparent substrate 27 and the support substrate 21 are bonded to each other using an anodic bonding performed while applying an electric field and heat in a vacuum, or a method of bonding via a material that melts by heating, such as In or AuSn. May be. In the case where diffusion bonding is performed with a combination of the seed layer 22 being Au, the X-ray transparent substrate 27 and the support substrate 21 being silicon, for example, a bonding apparatus capable of applying a temperature of 300 to 400 ° C. and a pressure of 5 to 40 kN is used. . The time required for this diffusion bonding is about 10 minutes.

  In the present embodiment, the temperature at which the X-ray transmissive substrate 27 and the support substrate 21 are bonded is 400 ° C. as the temperature at which the grid structure described above may change, and the X-ray absorber 24 is applied. The low melting point metal used has a melting point of 400 ° C. or lower. That is, since it is clear that the change in the grid structure does not occur until the temperature at which the X-ray transmissive substrate 27 and the support substrate 21 are bonded, the melting point of the X-ray absorbing portion 24 is set to be equal to or lower than the bonding temperature. Yes.

  In the next step, an etching mask is formed on the upper surface of the X-ray transparent substrate 27 by using a general photolithography technique. As shown in FIG. 3B, a resist layer 29 is formed on the upper surface of the X-ray transparent substrate 27. The resist layer 29 is formed, for example, through a step of applying a liquid resist to the X-ray transparent substrate 27 by a coating method such as spin coating and a step of pre-baking for evaporating an organic solvent from the applied liquid resist.

  As shown in FIG. 3C, the resist layer 29 is irradiated with light such as ultraviolet rays through a striped exposure mask 31 having a pitch P2 of several μm. Next, as shown in FIG. 4D, the exposed portion of the resist layer 29 is removed by the developer. As a result, a striped etching mask 32 having a plurality of line patterns extending in the y direction and arranged along the x direction is formed on the X-ray transparent substrate 27. The width of each line pattern and opening portion of the etching mask 32 is, for example, 2.5 μm. A known aligner or stepper is used for this photolithography. The resist layer 29 is a positive resist, but a negative resist in which an exposed portion is left may be used. Further, instead of using an etching mask made of a resist layer, SiO2 or metal may be formed and etched to form an etching mask.

  As shown in FIG. 3E, in the next step, a plurality of grooves 27a extending in the y direction and arranged in the x direction are formed on the X-ray transparent substrate 27 by dry etching through the etching mask 32. A plurality of X-ray transmission portions 25 arranged between the grooves 27a are formed. For the dry etching, dry etching for deep trenching capable of forming the groove 27a having a high aspect ratio is used. For dry etching for deep trenching, for example, a method called a Bosch process in which etching and protective film formation are alternately repeated is used.

  In the Bosch process, for example, etching is performed using a gas SF6 for etching silicon and a gas C4F8 for forming a protective film. When etching is performed with SF6 gas, etching proceeds not only in the depth direction but also in the lateral direction, so that it is impossible to form deep holes or grooves. Therefore, in the Bosch process, after etching for a certain time, the gas is switched to C4F8, thereby depositing the CFn polymer generated by the plasma in the etched groove to form a film. Then, etching is again performed using SF6 gas for etching. When etching the inside of the groove, the etching rate of the side surface is lower than that of the bottom surface, so that only the bottom surface is etched. By repeating this, a deep groove with a high aspect can be formed.

  The etching conditions of the Bosch process are, for example, a gas pressure of 1 to 10 Pa, an interval for switching the gas of SF6 and C4F8 is about 5 to 10 s, and power is 600 w. The etching rate under these conditions is, for example, 2 μm / min, and the groove depth is 100 μm. For this etching, it is important to generate plasma with high density, and there are various methods such as ICP (Inductive Coupling Plasma) and helicon wave.

  As the deep etching for dry etching, dry etching by a cryo process may be used in addition to the Bosch process. Dry etching by a cryo process is a technique in which a substrate to be etched is cooled to −100 ° C. or lower, and dry etching is performed with SF 6 gas. The reason why it is difficult to form a shape with a high aspect ratio by ordinary dry etching is that isotropic etching due to chemical reaction occurs, and in the cryo process, the etching substrate is lowered to suppress chemical etching. This enables high aspect ratio etching.

  The dry etching is performed until the seed layer 22 is exposed at the bottom of the groove 27a. The seed layer 22 made of metal functions as an etching stop layer because the etching rate is slower than the X-ray transparent substrate 27 made of silicon. Therefore, even if there is in-plane unevenness of the groove depth due to the etching rate difference in the X-ray transparent substrate 27, it is possible to improve the in-plane uniformity of the groove depth finally. In addition, although the Bosch process was used for etching, you may perform by anisotropic etching by wet etching resulting from the plane orientation of a silicon single crystal, for example.

  As shown in FIG. 3 (F), in the next step, an X-ray absorber made of a low melting point metal is embedded in the groove 27a by an electrolytic plating method, and the X-ray absorber 24 is formed. As described above, the X-ray absorbing material is an X-ray absorbing metal having a melting point of 400 ° C. or lower, which is the fracture temperature of the second grid 14. Examples of the X-ray absorber include AuSn (80: 20%, melting point 280 ° C.), AuSi (97: 3%, melting point 363 ° C.), AuGe, AuIn, AuInPb, SnInPb, AgSn, SnPb, SnBi, BiCd. (60: 40%, melting point 144 ° C.), SnBiPb, BiPbSnCd (50: 26.7: 13.3: 10%, melting point 70 ° C., changed from 60 to 130 ° C. depending on the composition), BiPbSn (50:25 : 25%, melting point 93 ° C.), BiPbSnSb (47.7: 33.2: 18.8: 0.3%, melting point 130 ° C.), etc. Alternatively, a low melting point metal having X-ray absorption such as Pb can be used.

  In the electrolytic plating, a current terminal is attached to the seed layer 22. The substrate to which the X-ray transmissive substrate 27 and the support substrate 21 are bonded is immersed in the plating solution, and the other electrode (anode) is disposed at the opposite position. Then, when a current is passed between the seed layer 22 and the other electrode, metal ions in the plating solution are deposited on the patterned substrate, and the X-ray absorber is embedded in the groove 27a. After the formation of the X-ray absorption part 24, the etching mask 32 is removed from above the X-ray transmission part 25, and the second grid 14 composed of the grid layer 20 and the support substrate 21 is completed.

  As shown in FIG. 4A, the groove 27a of the X-ray transparent substrate 27 has a very high aspect ratio of several μm in width and pitch and several tens to several tens of μm. Then, the groove 27 a cannot be completely filled with the X-ray absorber, and defects such as voids 34 and shims 35 may occur in the X-ray absorber 24. In order to repair such a defect, the second grid 14 is heated to the melting temperature of the X-ray absorber by, for example, a hot plate or a muffle furnace, and the X-ray absorber 24 is melted. As a result, as shown in FIG. 5B, the void 34 and the shim 35 disappear from the X-ray absorber 24, and the X-ray absorber 24 is filled with a tight X-ray absorber.

  In the upper part of the X-ray absorption part 24 where the void 34 and the shim 35 existed, a concave part 24a is formed by these volume fractions. Therefore, as shown in FIG. 4C, the concave portion 24a of the X-ray absorbing portion 24 is filled with a supplemental X-ray absorbing material 37 made of gold ink or the like. Thereby, the thickness of each X-ray absorption part 24 can be made equal.

  Similarly to the second grid 14, the radiation source grid 12 and the first grid 13 are configured by a grid layer and a support substrate. Similarly to the grid layer 20 of the second grid 14, the grid layers of the source grid 12 and the first grid 13 are extended in the y direction and alternately arranged along the x direction. A transmission part is provided. Thus, the source grid 12 and the first grid 13 are the second except that the X-ray absorption part and the X-ray transmission part of each small grid differ in the width and pitch in the y direction, the thickness in the z direction, and the like. Since the configuration is almost the same as that of the grid 14, detailed description is omitted. Further, since the source grid 12 and the first grid 13 are manufactured in the same manner as the second grid 14, a detailed description thereof is omitted.

  Next, the operation of the X-ray imaging system 10 will be described. The X-rays emitted from the X-ray source 11 are partially shielded by the X-ray absorber of the source grid 12, thereby reducing the effective focal size in the x direction, and a large number of line light sources in the x direction. (Dispersed light source) is formed. The X-rays of a large number of line light sources formed by the radiation source grid 12 cause a phase difference when passing through the subject H, and the X-rays pass through the first grid 13 to refract the subject H. A fringe image (first periodic pattern image) reflecting the transmission phase information of the subject H determined from the rate and the transmission optical path length is formed. The fringe image of each line light source is projected onto the second grid 14 and coincides (overlaps) at the position of the second grid 14, so that the image quality of the phase contrast image can be improved without reducing the X-ray intensity. it can.

  The fringe image is intensity-modulated by the second grid 14. The intensity-modulated fringe image (second periodic pattern image) is detected by, for example, a fringe scanning method. In the fringe scanning method, the grid pitch is equally divided (for example, divided into 5) into the direction along the lattice plane with the X-ray focal point as the center by the scanning mechanism 18 with respect to the first grid 13. While translating at the scanning pitch, the X-ray source 11 irradiates the subject H with X-rays, performs multiple imaging, detects with the X-ray image detector 15, and detects the X-rays with the phase-contrast image generator 16. Corresponds to the phase differential image (angle distribution of X-rays refracted by the subject) from the phase shift amount (the amount of phase shift with and without the subject H) of the pixel data of each pixel of the image detector 15 ). A phase contrast image of the subject H can be obtained by integrating the phase differential image along the above-described fringe scanning direction by the phase contrast image generation unit 16.

  As described above, the source grid 12, the first grid 13, and the second grid 14 of the present embodiment are formed by the low melting point metal having the X-ray absorption property of the X-ray absorption part 24. By heating the completed grid, defects such as voids and shims in the X-ray absorber 24 can be repaired. Thereby, in the X-ray imaging system 10 using the radiation source grid 12, the first grid 13, and the second grid 14 of the present embodiment, the image quality of the phase contrast image can be improved. In addition, since the melting point of the X-ray absorption unit 24 is set to a breakdown temperature or less that may change the structure of the grid, even if the grid is heated for defect repair, the grid is not damaged by the heat. .

  In the above embodiment, the defect repair is performed after the grid is completed, but the defect repair may not be performed for all the grids. For example, the completed grid may be subjected to X-ray transmission inspection and the like, and defect repair may be performed according to the result. Moreover, in the said embodiment, although X-ray absorption material is replenished to the X-ray absorption part after defect repair, for example, the upper surface of a grid layer is grind | polished and the thickness of all the X-ray absorption parts is made uniform. Also good.

  In the above embodiment, a striped one-dimensional grid having X-ray absorbing portions and X-ray transmitting portions that are stretched in one direction and alternately arranged along the arrangement direction orthogonal to the stretching direction has been described as an example. However, the present invention can also be applied to a two-dimensional grid in which an X-ray absorption part and an X-ray transmission part are arranged in two directions. Furthermore, in the above-described embodiment, the subject H is disposed between the X-ray source and the first grid. However, when the subject H is disposed between the first grid and the second grid. Similarly, a phase contrast image can be generated. Moreover, although the X-ray imaging system provided with the source grid has been described, the present invention can also be applied to an X-ray imaging system that does not use the source grid. The above embodiments can be combined with each other within a consistent range.

  In the above embodiment, the first and second grids are configured to linearly project the X-rays that have passed through the X-ray transmission part, but the present invention is not limited to this configuration. A configuration in which a so-called Talbot interference effect is generated by diffracting X-rays with the first and second grids (configuration described in International Publication WO 2004/058070) may be employed. In this case, it is necessary to set the distance between the first and second grids to the Talbot interference distance. Further, the type of the first grid may be a phase type grid having a relatively low aspect ratio instead of the absorption type grid.

  Moreover, in the said embodiment, the fringe image intensity-modulated by the 2nd grid is detected by the fringe scanning method, and the phase contrast image is produced | generated, However, The X-ray image which produces | generates a phase contrast image by one imaging | photography Imaging systems are also known. For example, in the X-ray imaging system described in International Publication WO2010 / 050484, the moire generated by the first and second grids is detected by the X-ray image detector, and the intensity of the detected moire is detected. A spatial frequency spectrum is acquired by performing Fourier transform on the distribution, and a differential phase image is obtained by separating the spectrum corresponding to the carrier frequency from this spatial frequency spectrum and performing inverse Fourier transform. You may use the grid of this invention for at least one of the 1st and 2nd grids of such an X-ray imaging system.

  In addition, in an X-ray imaging system that generates a phase contrast image by one imaging, a conversion layer that converts X-rays into electric charges and a conversion layer are used as intensity modulation means instead of the second grid. Some use a direct conversion type X-ray image detector having a charge collecting electrode for collecting the collected charges. This X-ray imaging system, for example, electrically connects linear electrodes in which the charge collection electrodes of each pixel are arranged with a period substantially matching the period pattern of the striped image formed by the first grid. The linear electrode groups are arranged so that their phases are different from each other, and each stripe electrode group is individually controlled to collect charges, thereby acquiring a plurality of fringe images by one photographing. A phase contrast image is generated on the basis of the plurality of fringe images (configuration described in JP 2009-133823 A). You may use the grid of this invention for the 1st grid of such an X-ray imaging system.

  Further, as another X-ray imaging system for generating a phase contrast image by one imaging, the first and second grids are arranged such that the extending directions of the X-ray absorption part and the X-ray transmission part are relatively at a predetermined angle. By dividing and capturing the section of the moire cycle that occurs in the stretching direction due to this inclination, a plurality of fringe images with different relative positions of the first and second grids are acquired, and these It is also possible to generate a phase contrast image from a plurality of fringe images. You may use the grid of this invention for at least one of the 1st and 2nd grids of such an X-ray imaging system.

  Further, an X-ray imaging system in which the second grid is omitted by using an optical reading type X-ray image detector can be considered. In this system, a first electrode layer that transmits a periodic pattern image formed by a first grid, a photoconductive layer that generates charges upon irradiation of the periodic pattern image transmitted through the first electrode layer, A charge accumulation layer for accumulating charges generated in the photoconductive layer and a second electrode layer in which a large number of linear electrodes that transmit the reading light are arranged in this order, and each linear shape is scanned by the reading light. An optical reading X-ray image detector from which an image signal for each pixel corresponding to the electrode is read is used as the intensity modulation means, and the charge storage layer is formed in a grid pattern with a pitch finer than the arrangement pitch of the linear electrodes. Thus, the charge storage layer can function as the second grid. You may use the grid of this invention for the 1st grid of such an X-ray imaging system.

  The embodiment described above can be applied not only to a radiographic imaging system for medical diagnosis but also to other radiographic systems for industrial use and nondestructive inspection. The present invention is also applicable to a scattered radiation removal grid that removes scattered radiation in X-ray imaging. Furthermore, in the present invention, gamma rays or the like can be used in addition to X-rays as radiation.

DESCRIPTION OF SYMBOLS 10 X-ray imaging system 11 X-ray source 12 Source grid 13 1st grid 14 2nd grid 15 X-ray image detector 18 Operation mechanism 20 Grid layer 21 Support substrate 24 X-ray absorption part 34 Void 35 Shim 37 Supplement X-ray absorber

Claims (12)

A radiographic imaging grid having a plurality of radiation transmitting portions and radiation absorbing portions,
The radiation imaging grid according to claim 1, wherein the radiation absorbing portion is made of a metal having a melting point lower than a temperature at which a grid structure including the radiation absorbing portion and the radiation transmitting portion may change. A grid layer composed of the radiation absorbing portion and the radiation transmitting portion, and a support substrate bonded to support the grid layer;
The melting point of the radiation absorbing portion is lower than a temperature applied to the radiation transmissive substrate and the support substrate when the radiation transmissive substrate constituting the grid layer and the support substrate are bonded. The grid for radiographic imaging according to claim 1.   The radiation image capturing grid according to claim 2, wherein a melting point of the radiation absorbing portion is 400 ° C. or less.   4. The radiographic imaging according to claim 3, wherein the radiation absorbing portion is made of an alloy such as AuSn, AuSi, AuGe, AuIn, AuInPb, SnInPb, AgSn, SnPb, SnBi, BiCd, SnBiPb, BiPbSnCd, BiPbSnSb. grid. Bonding a radiation transmissive substrate and a support substrate supporting the radiation transmissive substrate;
Forming a plurality of grooves in which a radiation absorbing portion is formed in the radiation transmissive substrate, and providing a radiation transmitting portion between the grooves;
Filling the groove with a metal having a melting point lower than the heating temperature at the time of joining the radiation transmissive substrate and the support substrate, and forming the radiation absorbing portion;
Heating and melting the radiation absorbing portion, repairing defects occurring in the radiation absorbing portion; and
The manufacturing method of the grid for radiographic imaging characterized by including these.   6. The method of manufacturing a grid for radiographic imaging according to claim 5, wherein a radiation absorbing material is replenished in a concave portion generated in the radiation absorbing portion due to defect repair of the radiation absorbing portion.   The method of manufacturing a grid for radiographic imaging according to claim 5 or 6, wherein the step of bonding the radiation transmissive substrate and the support substrate includes diffusion bonding.   The method for manufacturing a grid for radiographic imaging according to claim 7, wherein the melting point of the radiation absorbing portion is 400 ° C. or less.   9. The radiographic imaging according to claim 8, wherein the radiation absorbing portion is made of an alloy such as AuSn, AuSi, AuGe, AuIn, AuInPb, SnInPb, AgSn, SnPb, SnBi, BiCd, SnBiPb, BiPbSnCd, BiPbSnSb. Grid manufacturing method. A grid structure including a portion that transmits radiation and a portion that absorbs radiation is periodically arranged, and a first grid that forms a first periodic pattern image by passing radiation emitted from a radiation source; Intensity modulating means for applying intensity modulation to the first periodic pattern image at at least one relative position having a phase different from that of the periodic pattern, and a second periodic pattern image generated at the relative position by the intensity modulating means. A radiographic imaging system comprising: a radiological image detector for detecting phase information; and an arithmetic processing means for imaging phase information based on at least one second periodic pattern image detected by the radiographic image detector. Because
The radiographic imaging system characterized by using the radiographic imaging grid according to any one of claims 1 to 4 as the first grid. The intensity modulating means includes a second grid in which a grid structure including a portion that transmits and absorbs the first periodic pattern is periodically arranged, and one of the first and second grids. In a radiographic imaging system in which each position moved by the scanning means corresponds to the relative position. There,
The radiographic imaging system according to claim 10, wherein the radiographic imaging grid according to claim 1 is used as the second grid.   A third grid disposed between the radiation source and the first grid and partially shielding the radiation emitted from the radiation source to form a plurality of line light sources; The radiographic imaging system according to claim 10 or 11, wherein the radiographic imaging grid according to any one of claims 1 to 4 is used.

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