JP2008224661A - X-ray imaging element, device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new X-ray imaging element capable of imaging surely moire fringes, while attaining thinning. <P>SOLUTION: This X-ray imaging element 11 is arranged on a position separated from a diffraction grating for a talbot approximately as long as a talbot distance L, and images an X-ray diffracted by the diffraction grating for the talbot. The X-ray imaging element 11 includes an X-ray conversion element 111 having a pattern equivalent to a diffraction grating formed of a material generating visible light by absorbing the X-ray, and an imaging element 112 for imaging the visible light. To put it concretely, the X-ray conversion element 111 comprises a fluorescence part 111a including a material emitting fluorescence by absorbing X-ray energy, and a non-fluorescence part 111b not including such a fluorescent material. The fluorescence part 111a is formed of a pattern equivalent to the diffraction grating. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for imaging X-rays.

  Conventionally, in X-ray imaging, an image having an X-ray absorption contrast, that is, an X-ray absorption level by a subject is obtained as a contrast. X-ray absorption generally increases as the atomic number increases, that is, the heavier the element. When a living body is a subject, the elements constituting the living body are mainly elements having a relatively small atomic number, such as hydrogen (H), carbon (C), nitrogen (N), and oxygen (O), that is, light elements. Therefore, the X-ray image of the living body does not have much contrast. Therefore, a substance containing an element with a large atomic number is used as a contrast agent in X-ray imaging of a living body. For example, barium sulfate is used as a contrast agent in X-ray imaging of digestive organs such as the stomach and colon. However, the contrast medium cannot be used for all tissues, and the burden on the living body is large.

  Therefore, in recent years, a phase contrast method has been studied and developed in which X-rays are treated as waves and an image is obtained in which the difference in the speed with which the waves travel through the subject is taken as contrast. In the phase contrast method, for example, an X-ray interferometer is used, and a transmission image of a subject is obtained by detecting an X-ray phase shift caused by passing through the subject. This phase contrast method is expected to improve the sensitivity by about 1000 times compared to the case where a transmission image of a subject is obtained by the X-ray absorption contrast, thereby reducing the X-ray irradiation amount to, for example, 1/100 to 1/1000. There is also an advantage that it becomes possible.

  As one of such phase contrast methods, for example, a method using a Talbot interferometer has been proposed in, for example, Patent Document 1 and Non-Patent Document 1.

FIG. 7 is an explanatory diagram showing a schematic configuration of the X-ray imaging apparatus described in Patent Document 1. As shown in FIG. 7, an X-ray imaging apparatus 1000 described in Patent Document 1 includes an X-ray source 1001, a phase-type first diffraction grating 1002 that diffracts X-rays emitted from the X-ray source 1001, and a first diffraction grating. An amplitude type second diffraction grating 1003 that forms an image contrast by diffracting the X-rays diffracted by 1002, and an X-ray image detector 1004 that detects X-rays in which image contrast is generated by the second diffraction grating 1003, And the first and second diffraction gratings 1002 and 1003 are set to the conditions that constitute the Talbot interferometer. This condition is expressed by the following equations 1 and 2. Equation 2 assumes that the first diffraction grating 1002 is a phase type diffraction grating.
l = λ / (a / (L + Z1 + Z2)) (Expression 1) Z1 = (m + 1/2) × (d ² / λ) (Expression 2)

  Here, l is a coherent distance, λ is an X-ray wavelength (usually a center wavelength), and a is an aperture diameter of the X-ray source 1001 in a direction substantially perpendicular to the diffraction member of the diffraction grating. Yes, L is the distance from the X-ray source 1001 to the first diffraction grating 1002, Z1 is the distance from the first diffraction grating 1002 to the second diffraction grating 1003, and Z2 is from the second diffraction grating 1003. The distance to the X-ray image detector 1004, m is an integer, and d is the period of the diffractive member (the period of the diffraction grating, the grating constant, the distance between the centers of adjacent diffractive members).

In the X-ray imaging apparatus 1000 having such a configuration, the subject 1010 is disposed between the X-ray source 1001 and the first diffraction grating 1002, and X-rays are irradiated from the X-ray source 1001 toward the first diffraction grating 1002. Is done. This irradiated X-ray produces a Talbot effect at the first diffraction grating 1002 to form a Talbot image. This Talbot image is acted on by the second diffraction grating 1003 to form an image contrast of moire fringes. This image contrast is detected by the X-ray image detector 1004. The moire fringes are modulated by the subject 1010, and the amount of modulation is proportional to the angle at which the X-ray is bent by the refraction effect of the subject 1010. For this reason, the subject 1010 and its internal structure can be detected by analyzing the moire fringes.

Here, the Talbot effect means that when light enters the diffraction grating, the same image as the diffraction grating (self-image of the diffraction grating) is formed at a certain distance. It is called a distance L, and this self-image is called a Talbot image. When the diffraction grating is a phase type diffraction grating, the Talbot distance L is Z1 represented by the above formula 2 (L = Z1). In the Talbot image, an inverted image appears at an odd multiple of L (= (2m + 1) L, m is an integer), and a normal image appears at an even multiple of L (= 2 mL).
International Publication No. WO2004 / 058070 Pamphlet Kaoru Hyakusei, “Recent Developments of X-ray Phase Imaging”, Medical Imaging Technology, Vol. 24, No. 5, November 2006

The first diffraction grating 1002 used in the X-ray imaging apparatus 1000 is a grating that is sufficiently coarser than the wavelength of the X-ray to form an X-ray Talbot image, for example, the lattice constant is about the X-ray wavelength. It needs to be 20 times or more. Since the wavelength of X-rays is generally about 10 ⁻¹² m to 10 ⁻⁸ m, the grating constant of the first diffraction grating 1002 is about 10 ⁻¹¹ m to 10 ⁻⁷ m. It becomes several μm. Since the Talbot image is a self-image of the first diffraction grating 1002, that is, when the incident X-ray is parallel light, it is an image having the same pattern as the grating pattern of the first diffraction grating 1002. When it can be regarded as a point light source, the grating of the first diffraction grating 1002 expanded according to the ratio of the distance from the X-ray source 1001 to the first diffraction grating 1002 and the distance from the X-ray source 1001 to the second diffraction grating 1003. This is a pattern image, and the Talbot image is also a striped pattern with a period of several μm. For this reason, in order for the Talbot image to generate moire fringes by the second diffraction grating 1003, the grating constant of the second diffraction grating 1003 is also several μm.

  On the other hand, when the second diffraction grating 1003 is formed of an amplitude type (absorption type) diffraction grating, in order to absorb sufficient X-rays that function as an amplitude type diffraction grating, the diffraction member of the second diffraction grating 1003 is used. Even when a heavy element such as gold (Au) is used, a thickness of several tens to several hundreds μm is required.

  Therefore, as shown in FIG. 8, the diffraction member of the second diffraction grating 1003 has a thickness of several tens to several hundreds μm (for example, 100 μm) with respect to a width of several μm (for example, 4 μm). For this reason, it is necessary to form the diffractive member with a high aspect ratio, and it is not easy to manufacture the second diffraction grating 1003.

  Even if the second diffraction grating 1003 can be manufactured, the X-rays emitted from the X-ray source 1001 spread radially because the X-ray source 1001 is a substantially point light source. For this reason, as shown in FIG. 8, in the central region of the second diffraction grating 1003, the X-rays of the Talbot image are incident substantially parallel to the diffraction member, so that a moire is generated by the Talbot image and the second diffraction grating 1003. However, in both side regions of the second diffraction grating 1003, the X-rays of the Talbot image are obliquely incident on the diffractive member, so that the moire image by the Talbot image and the second diffraction grating 1003 is blurred or completely moire. Does not occur.

On the other hand, even when the second diffraction grating 1003 is formed of a phase diffraction grating, the second diffraction grating 1003 can be used to give a sufficient phase change that functions as a phase diffraction grating to the X-ray.
Even when a heavy element such as gold (Au) is used for the diffraction member, a thickness of several tens of μm is required. For this reason, the same inconvenience as in the amplitude type diffraction grating occurs in the phase type diffraction grating.

  Further, in order to avoid such inconvenience due to the second diffraction grating 1003, a method of directly capturing a Talbot image without using the second diffraction grating 1003 can be considered. For a chest X-ray, a digital imaging device such as a CCD having a size of 17 inches × 14 inches and a resolution of 4000 dots × 3000 dots is known, but the pixel size is about 110 μm, Even with such an image sensor, a Talbot image with a period of several μm cannot be captured.

  In order to overcome various problems that occur when imaging X-rays via an amplitude-type or phase-type diffraction grating, the present invention provides a new X-ray that can reliably capture moiré fringes while achieving a reduction in thickness. An object of the present invention is to provide a line imaging device, an apparatus, and a method.

  An X-ray imaging device according to an aspect of the present invention includes a first X-ray conversion device having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates secondary energy, and the first Pattern detection means for detecting the generation pattern of the secondary energy by the X-ray conversion element, wherein the first X-ray conversion element has an incident surface on which an X-ray image is incident. (Claim 1).

  According to this configuration, instead of using an amplitude type or phase type diffraction grating, the first X-ray conversion element having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates secondary energy. Is used. When an X-ray fringe image is incident on the incident surface of the first X-ray conversion element, secondary energy is generated at a portion where the X-ray stripe pattern and the pattern of the first X-ray conversion element coincide with each other. Is done. Therefore, by detecting this secondary energy generation pattern, it is possible to substantially capture the moire fringes.

  In the above configuration, the first X-ray conversion element includes a first surface on which an X-ray image is incident and a second surface facing a pattern detection unit that detects the generation pattern of the secondary energy. Desirable (Claim 2). In this case, the secondary energy may be visible light, and the pattern detection unit may be an image sensor that captures visible light. Alternatively, the secondary energy may be electrons or holes, and the pattern detection unit may be a charge detection unit capable of detecting a charge distribution charged by electrons or holes.

  In any one of the configurations described above, it is desirable that the X-ray image is an X-ray Talbot image. The pattern corresponding to the diffraction grating is preferably a one-dimensional periodic pattern. Furthermore, it is desirable that the pattern corresponding to the diffraction grating is a two-dimensional periodic pattern.

  When adopting a two-dimensional period, it is desirable that the periodic structure is a square lattice arrangement or a triangular lattice arrangement.

  An X-ray imaging device according to another aspect of the present invention includes a second X-ray conversion device having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates visible light, and visible light. The second X-ray conversion element includes a first surface on which an X-ray image is incident and a second surface facing the image sensor. Item 9).

According to this configuration, instead of using an amplitude type or phase type diffraction grating, the second X-ray conversion element having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates visible light is provided. Used. Then, when an X-ray fringe image is incident on the first surface of the second X-ray conversion element, the X-ray fringe pattern becomes visible light only at a portion where the X-ray stripe pattern and the pattern of the second X-ray conversion element coincide. As a result, a moire fringe of visible light is generated as a result. By capturing the visible moire fringes with an image sensor arranged on the second surface of the second X-ray conversion element, the moire fringes can be captured.

  An X-ray imaging device according to still another aspect of the present invention includes a third X-ray conversion device having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates electrons or holes; Charge detecting means capable of detecting a charge distribution charged by electrons or holes generated by the third X-ray conversion element, wherein the X-ray image is incident on the third X-ray conversion element An incident surface is provided (claim 10).

  According to this configuration, instead of using an amplitude type or phase type diffraction grating, the third X-ray conversion having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates electrons or holes. An element is used. Then, when an X-ray fringe image is incident on the incident surface of the third X-ray conversion element, electrons or holes only at a portion where the X-ray stripe pattern coincides with the pattern of the third X-ray conversion element. As a result, moiré fringes of the charge distribution are generated. Therefore, the moire fringes can be substantially imaged by detecting this charge distribution.

  An X-ray imaging apparatus according to another aspect of the present invention includes an X-ray source that emits X-rays, a Talbot diffraction grating that generates a Talbot effect by the X-rays emitted from the X-ray source, and the Talbot diffraction grating. An X-ray imaging device that images X-rays diffracted by the X-ray imaging device, wherein the X-ray imaging device is the X-ray imaging device according to any one of claims 1 to 10, The element is arranged at a position substantially separated from the Talbot diffraction grating by a Talbot distance (claim 11).

  Moreover, the X-ray imaging method which concerns on the further another situation of this invention produces | generates an X-ray Talbot image, and uses this X-ray Talbot image for the X-ray image sensor of any one of Claims 1-10. It is made to enter (claim 12).

  According to these configurations, the Talbot image generated by the Talbot diffraction grating is incident on the X-ray imaging device. Then, moire fringes are imaged in the X-ray image sensor. Therefore, moire fringes can be imaged without using an amplitude type diffraction grating.

  According to the X-ray imaging device, apparatus, and method of the present invention, instead of generating moire fringes in the diffraction grating, an X-ray conversion element having a pattern corresponding to the diffraction grating is used. In this configuration, moire fringes are generated at portions where the pattern matches. Accordingly, moire fringes can be generated reliably and the X-ray conversion element does not need to be thickened, so that the X-ray imaging element and the X-ray imaging apparatus can be thinned.

(First embodiment)
FIG. 1 is an explanatory diagram showing a configuration of an X-ray imaging apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram illustrating the configuration of the X-ray imaging device according to the first embodiment.

In FIG. 1, an X-ray imaging apparatus 1 includes an X-ray imaging element 11, a diffraction grating 12 (Talbot diffraction grating), and an X-ray source 13, and in this embodiment, the X-ray source 13 is powered on. Of the X-ray power supply unit 14, the camera control unit 15 that controls the imaging operation of the X-ray imaging device 11, the processing unit 16 that controls the overall operation of the X-ray imaging apparatus X, and the X-ray power supply unit 14 An X-ray control unit 17 that controls the X-ray emission operation in the X-ray source 13 by controlling the operation is provided.

  The X-ray source 13 is a device that emits X-rays and emits X-rays toward the diffraction grating 12. The X-ray source 13 emits X-rays when, for example, a high voltage supplied from the X-ray power supply unit 14 is applied between the cathode and the anode, and electrons emitted from the cathode filament collide with the anode. Device.

  The diffraction grating 12 is a transmission type diffraction grating that generates a Talbot effect by X-rays emitted from the X-ray source 13. The diffraction grating 12 includes a flat substrate made of a material that transmits X-rays and a plurality of diffraction members formed on one surface of the substrate. Each of the plurality of diffractive members has a linear shape extending in one direction (in FIG. 1, the normal direction to the paper surface), and is disposed at a predetermined interval in a direction orthogonal to the one direction. This predetermined interval is fixed in this embodiment. That is, the plurality of diffractive members are arranged at equal intervals in a direction orthogonal to the one direction. For example, glass is used for the substrate of the diffraction grating 12, and gold (Au) is used for the diffraction member. The diffraction grating 12 is configured to satisfy the conditions for causing the Talbot effect, and has a grating sufficiently coarser than the wavelength of X-rays emitted from the X-ray source 13, for example, a grating constant (diffraction grating period) d. It is a phase type diffraction grating which is about 20 times or more the wavelength of the X-ray. The first diffraction grating 12 may be an amplitude (absorption) diffraction grating that performs the same function.

  The X-ray imaging element 11 is an apparatus that is disposed at a position approximately L Talbot distance L away from the diffraction grating 12 and images X-rays diffracted by the diffraction grating. As shown in FIG. 2, the X-ray imaging element 11 includes an X-ray conversion element 111 (second X-ray conversion) having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates visible light. Element) and an image sensor 112 that captures visible light. An X-ray Talbot image T (X-ray image) is incident on the surface (first surface) facing the subject S of the X-ray conversion element 111. The imaging element 112 has a light receiving surface opposed to a surface (second surface) opposite to the first surface of the X-ray conversion element 111.

  The X-ray conversion element 111 includes a fluorescent part 111a containing a substance that emits fluorescence by absorbing X-ray energy, and a non-fluorescent part 111b that does not contain such a fluorescent substance. The fluorescent part 111a can be composed of, for example, a scintillator. The scintillator is a layer having a phosphor as a main component, and emits fluorescence having a visible light wavelength by incident X-rays.

Phosphors used in the fluorescent part 111a include tungstate phosphors, terbium activated rare earth oxysulfide phosphors, terbium activated rare earth phosphate phosphors, terbium activated rare earth oxyhalide phosphors, thulium activated phosphors. Rare earth oxyhalide phosphor, gadolinium activated rare earth oxyhalide phosphor, cerium activated rare earth oxyhalide phosphor, barium sulfate phosphor, divalent europium activated alkaline earth metal phosphate phosphor, 2 Examples thereof include valent europium activated alkaline earth metal fluoride halide phosphors, iodide phosphors, sulfide phosphors, hafnium phosphate phosphors, tantalate phosphors, and the like. In particular, cesium iodide (CsI: X, X is an activator) and gadolinium oxysulfide (Gd ₂ O ₂ S: X, X is an activator) having high X-ray absorption and emission efficiency are preferable.

The diameter of the phosphor particles is preferably 7 μm or less, particularly 4 μm or less. This is because, as the diameter of the phosphor particles is smaller, light scattering in the scintillator can be prevented and high sharpness can be obtained. Further, the phosphor particles may be dispersed in a binder. As the binder, polyurethane, polyester, vinyl chloride copolymer, polyvinyl butyral, nitrocellulose and the like are preferable. If such a binder is used, it is possible to improve the dispersibility of the phosphor and increase the filling rate of the phosphor.

  The fluorescent part 111a is formed in a pattern of a one-dimensional periodic structure (striped structure) corresponding to a diffraction grating. That is, the fluorescent portions 111a are provided with a width and an interval corresponding to the slits of the diffraction grating. For example, the X-ray conversion element 111 is configured with a periodic structure in which fluorescent portions 111a having a width of several μm to several tens of μm and non-fluorescent portions 111b having a width of several μm to several tens of μm are alternately arranged.

  The material of the non-fluorescent portion 111b is not particularly limited, and can be formed of various X-ray transmissive substances or various substances that absorb X-rays but do not generate visible light. For example, the non-fluorescent portion 111b may be formed of an air layer instead of the binder material that does not include phosphor particles or a solid substance.

  The X-ray conversion element 111 having such a one-dimensional periodic structure includes, for example, a substrate on which a stripe mask with a pitch of several μm to several tens of μm is applied, and a concave groove processing with a width of several μm to several tens of μm is several μm to several It can be formed by selectively growing the scintillator material constituting the fluorescent part 111a in a stripe shape on a substrate applied at a pitch of 10 μm.

  The arrangement positions of the X-ray conversion element 111 and the diffraction grating 12 are set under the conditions that constitute the Talbot interferometer represented by the above-described Expression 1 and Expression 2.

  The imaging element 112 is an apparatus that images visible light converted by the X-ray conversion element 111. The image sensor 112 is an element that converts an image of visible light into an electric signal, and includes a plurality of photoelectric conversion elements arranged in a two-dimensional matrix and a peripheral circuit for generating a charge corresponding to the amount of received light. Is done. For example, a visible light CCD (charge coupled device) image sensor or a CMOS (complementary metal oxide semiconductor) image sensor is used as the image sensor 112.

  The processing unit 16 is a device that controls the entire operation of the X-ray imaging apparatus 1 by controlling each unit of the X-ray imaging apparatus 1. For example, the processing unit 16 includes a microprocessor and its peripheral circuits, and is functionally An image processing unit 161 and a system control unit 162 are provided.

  The system control unit 162 controls the X-ray emission operation in the X-ray source 13 via the X-ray power source unit 14 by transmitting and receiving control signals to and from the X-ray control unit 17, and the camera control unit 15 The imaging operation of the X-ray imaging device 11 is controlled by transmitting and receiving control signals between the X-ray imaging device 11 and the X-ray imaging device 11. Under the control of the system control unit 162, X-rays are emitted toward the subject S, and an image generated thereby is captured by the X-ray image sensor 11, and an image signal is input to the processing unit 16 via the camera control unit 15. The

  The image processing unit 161 processes the image signal generated by the X-ray image sensor 11 and generates an image of the subject S.

  Next, the operation of the first embodiment will be described. When the subject S is disposed between the X-ray source 13 and the diffraction grating 12 and the user of the X-ray imaging apparatus 1 instructs the imaging of the subject S from an operation unit (not shown), the system control unit 162 of the processing unit 16. Outputs a control signal to the X-ray control unit 17 to irradiate X toward the subject S. With this control signal, the X-ray control unit 17 causes the X-ray power supply unit 14 to supply power to the X-ray source 13, and the X-ray source 13 emits X-rays and irradiates the subject S with X-rays.

  The irradiated X-ray passes through the diffraction grating 12, is diffracted by the diffraction grating 12, and forms a Talbot image T that is a self-image of the diffraction grating 12 at a position away from the Talbot distance L (= Z1).

  This X-ray Talbot image is incident on the first surface of the X-ray conversion element 111 of the X-ray imaging element 11. Then, the X-rays are absorbed by the fluorescent part 111a and converted into visible light only at the part where the striped pattern of the Talbot image matches the stripe pattern of the fluorescent part 111a of the X-ray conversion element 111. As a result, visible moire fringes appear on the second surface of the X-ray conversion element 111.

  The visible moire fringe image is picked up by the image sensor 112 whose exposure time is controlled by the system controller 162, for example. Although the non-fluorescent portion 111b transmits X-rays as they are, the imaging device 112 does not have sensitivity to the wavelength of the X-rays, and thus the X-rays are not imaged.

  Here, in order to increase the conversion efficiency into visible light, the thickness of the fluorescent portion 111a in the X-ray incident direction may be increased. However, if it is too thick, a problem similar to the problem described above with reference to FIG. 8 may occur. However, in the present embodiment, since the contrast is easily obtained by the difference in wavelength between the X-ray and the visible light, it is not necessary to make the fluorescent portion 111a so thick. That is, even if the intensity of the visible light generated by the fluorescent part 111a is weak, X-rays that do not pass through the fluorescent part 111a are not detected by the image sensor 112, so that the contrast can be regarded as large. .

  The image sensor 112 outputs the image signal of the moire fringe image to the processing unit 16 via the camera control unit 15. This image signal is processed by the image processing unit 161 of the processing unit 16.

Here, since the subject S is disposed between the X-ray source 13 and the diffraction grating 12, the X-rays that have passed through the subject S are out of phase with the X-rays that do not pass through the subject S. For this reason, the X-ray incident on the diffraction grating 12 includes distortion in its wavefront, and the Talbot image is deformed accordingly. For this reason, the visible moire fringes generated by superimposing the X-ray Talbot image incident on the first surface of the X-ray conversion element 111 and the one-dimensional periodic structure of the fluorescent part 111a are modulated by the subject S. Yes. This modulation amount is proportional to the angle at which the X-ray is bent by the refraction effect by the subject S. Therefore, the subject S and its internal structure can be detected by analyzing the moire fringes. Further, by imaging the subject S from a plurality of angles, a tomographic image of the subject S can be formed by X-ray phase CT (computed tomography).

  As described above, according to the X-ray imaging apparatus 1 according to the first embodiment, instead of arranging the amplitude type diffraction grating at the position of the Talbot distance, the X-ray imaging apparatus 1 is formed by the fluorescent part 111a that absorbs X-rays and generates visible light. Visible light moire fringes can be generated by the X-ray conversion element 111 having a pattern corresponding to the diffraction grating having a one-dimensional period. Therefore, moire fringes can be generated reliably and the X-ray conversion element 111 does not need to be thickened, so that the X-ray imaging element 11 can be thinned.

  That is, according to the above configuration, moire fringes are substantially generated by superimposing the stripe pattern of the X-ray Talbot image and the stripe pattern of the fluorescent part 111a. The stripes of the X-ray Talbot image T are very fine stripes and cannot be resolved by the image sensor 112 having a general pixel pitch, but the fluorescent portions 111a arranged at a fine pitch as described above are arranged in the front. Therefore, the striped pattern of the X-ray Talbot image T can be enlarged using moire. Therefore, the X-ray Talbot image T can be substantially captured even when the image sensor 112 having a large pixel pitch that cannot normally resolve the stripe pattern is used.

  In the above-described embodiment, the X-ray conversion element 111 and the diffraction grating 12 may be disposed so as to be relatively rotated by an angle θ around the optical axis passing through the X-ray source 13 and the imaging element 112. When the X-ray conversion element 111 and the diffraction grating 12 having the lattice constant d are rotated and arranged by an angle θ, the moire fringe spacing becomes d / θ. Is expanded and the analysis of moire fringes becomes easier.

  In the above-described embodiment, the X-ray conversion element 111 and the diffraction grating 12 may have different lattice constants. Assuming that the grating constant of the diffraction grating 12 is d1 and the grating constant of the periodic structure of the fluorescent part 111a formed in the X-ray conversion element 111 is d2, a moire fringe of d1 × d2 / (d2−d1) appears and is the same as described above. In addition, the subject S and its internal structure can also be detected by analyzing the moire fringes.

  In the above-described embodiment, the subject is disposed between the X-ray source 13 and the diffraction grating 12, but the subject may be disposed between the diffraction grating 12 and the X-ray conversion element 111.

  Furthermore, although the X-ray conversion element 111 has shown the example in which the fluorescence part 111a was formed in the pattern of the diffraction grating of a one-dimensional period in the above-mentioned embodiment, it is not limited to this. FIG. 3 is an explanatory view showing a diffraction grating pattern having a two-dimensional period of a square lattice arrangement. FIG. 4 is a diagram for explaining moire generated from a Talbot image by the pattern shown in FIG. 4A shows a Talbot image, and FIG. 4B shows a moire image. The pattern of the fluorescent part 111a of the X-ray conversion element 111 may thus be a two-dimensional diffraction grating pattern, and the periodic structure may be a square lattice arrangement or a triangular lattice arrangement. In short, the pattern of the fluorescent part 111a may be a pattern having a structure in which moire is generated by capturing a Talbot image.

  For example, a two-dimensional periodic diffraction grating pattern is configured by arranging dots serving as diffraction members at equal intervals in two linearly independent directions. As shown in FIG. 3, the square lattice arrangement is configured by arranging dots serving as diffraction members at equal intervals in two orthogonal directions so that the unit lattice is square. Although not shown in the figure, the triangular lattice arrangement is configured by arranging dots serving as diffractive members at equal intervals in two directions that are 60 degrees from each other so that the unit lattice is a regular triangle. What is necessary is just to comprise such a dot part by the fluorescence part 111a or the non-fluorescence part 111b.

  In such a two-dimensional periodic X-ray conversion element 111, for example, as shown in FIG. 4A, a plurality of shadows extending linearly in one direction are formed at equal intervals in a direction orthogonal to the one direction. For example, as shown in FIG. 3, when an X-ray conversion element 111 having a periodic structure of fluorescent portions 111a having a square lattice arrangement is applied to the striped Talbot image that is tilted slightly from the one direction, Visible light moire fringes shown in FIG. 4B can be generated.

(Second Embodiment)
FIG. 5 is a schematic diagram showing an X-ray image sensor 11A according to the second embodiment. Since parts other than the X-ray image sensor 11A are the same as those in the first embodiment, description thereof will be omitted. The X-ray imaging element 11A includes an X-ray conversion element 113 (third X-ray conversion element) having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates electrons or holes. Charge detecting means capable of detecting a charge distribution charged by electrons or holes generated by the X-ray conversion element 113. An X-ray Talbot image T is incident on the incident surface of the X-ray conversion element 113 facing the subject S.

  The X-ray conversion element 113 includes a photoelectric conversion unit 114 having a semiconductor that absorbs X-ray energy and generates electrons or holes, and a non-conversion unit 115 that does not have such an electron or hole generation function. Consists of. The photoelectric conversion unit 114 is formed in a pattern corresponding to an amplitude type diffraction grating as in the first embodiment. For example, in a pattern of a one-dimensional periodic structure (striped pattern structure) in which stripes of photoelectric conversion units 114 having a width of several μm to several tens of μm and non-conversion units 115 having a width of several μm to several tens of μm are alternately arranged. A line conversion element 113 is configured. The pattern may be a two-dimensional periodic pattern such as a square lattice arrangement or a triangular lattice arrangement.

  FIG. 6 is a diagram schematically showing a detailed configuration of the X-ray conversion element 113. The X-ray conversion element 113 includes an alternating arrangement layer 114a composed of the photoelectric conversion unit 114 and the non-conversion unit 115, a bias electrode 114b that is solid on the surface on the X-ray incident side of the alternating arrangement layer 114a, and an alternating arrangement layer. And a plurality of pixel electrodes 114c provided on the other surface of 114a.

  One pixel electrode 114c covers a plurality (here, four layers are exemplified) of the photoelectric conversion units 114. That is, the photoelectric conversion units 114 are arranged at a finer pitch than the arrangement pitch of the pixel electrodes 114c.

  A charge detection unit 20 (charge detection means) is attached to such an alternating layer 114a with electrodes. The charge detection unit 20 includes an FET as a switching element and a capacitor C that accumulates charge for each pixel electrode 114c. The drain of the FET is connected to the pixel electrode 114c, the gate is connected to the control lines g1, g2, and g3, and the source is connected to the signal line s. The capacitor C is connected to the pixel electrode 114c.

  In the above configuration, a high voltage is applied to the bias electrode 114b, and an accelerating electric field is formed inside the alternating layer 114a. When X-rays enter the photoelectric conversion unit 114, the X-rays eject electrons bonded to the atoms. The ejected electrons e go to the bias electrode 114b, while the holes h go to the corresponding pixel electrode 114c to charge the capacitor C. This charged charge is read from the signal line s by the operation of the FET.

  The non-converting portion 115 is formed of an appropriate material that does not have such a photoelectric conversion function. Or the non-conversion part 115 may be comprised not with a solid substance but with an air layer.

  When an X-ray Talbot image is incident on such an X-ray imaging device 11A (X-ray conversion device 113), a portion where the striped pattern of the Talbot image matches the stripe pattern of the photoelectric conversion unit 114 of the X-ray conversion device 113 Only when the charge is generated. This electric charge is accumulated in the capacitor C and read out at a predetermined timing. An image corresponding to moire fringes can be obtained by obtaining a two-dimensional distribution of the read charges.

  That is, according to the above configuration, moire fringes are substantially generated by overlapping the striped pattern of the Talbot image with the striped pattern of the photoelectric conversion unit 114. The stripes of the X-ray Talbot image T are very fine stripes. For example, the stripes of the pixel electrodes 114c cannot be resolved, but the photoelectric conversion units 114 arranged at a finer pitch than the arrangement pitch of the pixel electrodes 114c Since it is provided, the striped pattern of the X-ray Talbot image T can be enlarged using moire. For this reason, the X-ray Talbot image T can be substantially captured even if the pixel electrodes 114c are arranged at a large pitch that cannot normally resolve the stripe pattern.

  In the case where X-ray energy is converted into fluorescence using a phosphor as in the X-ray conversion element 111 of the first embodiment described above, each phosphor emits light upon receiving X-ray incidence. Therefore, secondary energy that is essentially diffusible is generated. For this reason, it cannot be denied that diffusion in the X-ray conversion element 111 tends to blur the image before the fluorescence reaches the image sensor 112. However, since the X-ray conversion element 113 of the second embodiment uses a charge conversion type material that absorbs X-rays and generates electrons or holes, a secondary that has essentially no diffusivity. Generate energy.

  That is, as shown in FIG. 6, in the charge conversion type, charge cannot flow through the non-conversion unit 115, and an electric field is applied through the bias electrode 114b and the pixel electrode 114c. The charge proceeds without diffusing in the photoelectric conversion unit 114. For this reason, the phenomenon that the image is blurred cannot occur. In this aspect, the X-ray conversion element 113 of the second embodiment has an advantage over the X-ray conversion element 111 of the first embodiment.

  Although two embodiments of the present invention have been described above, the present invention is not limited to these. For example, the X-ray conversion element that absorbs X-rays and generates visible light and the X-ray conversion element that absorbs X-rays and generates electrons or holes are illustrated above. Any X-ray conversion element (first X-ray conversion element) formed of a material that generates some secondary energy can be applied to the present invention. In this case, pattern detection means for detecting the generation pattern of the secondary energy by the X-ray conversion element may be provided.

In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

It is explanatory drawing which shows the structure of the X-ray imaging device in 1st Embodiment. It is explanatory drawing which shows the structure of the X-ray image sensor in 1st Embodiment. It is explanatory drawing which shows the diffraction grating of the two-dimensional period of a square lattice arrangement | sequence. It is a figure for demonstrating the moire produced from a Talbot image by the diffraction grating shown in FIG. It is explanatory drawing which shows the structure of the X-ray image sensor in 2nd Embodiment. It is a schematic diagram which shows the structure of the photoelectric conversion part in 2nd Embodiment. It is explanatory drawing which shows schematic structure of the X-ray imaging device of patent document 1. FIG. It is a top view for demonstrating the 2nd diffraction grating and moire image in the X-ray imaging device which concerns on background art.

Explanation of symbols

1 X-ray imaging device 11, 11A X-ray imaging device 12 Diffraction grating (Talbot diffraction grating)
13 X-ray source 111 X-ray conversion element (second X-ray conversion element)
111a Fluorescent part 111b Non-fluorescent part 112 Imaging element 113 X-ray conversion element (third X-ray conversion element)
114 photoelectric conversion unit 115 non-conversion unit 20 charge detection unit (charge detection means)

Claims (12)

A first X-ray conversion element having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates secondary energy;
Pattern detection means for detecting a generation pattern of the secondary energy by the first X-ray conversion element,
The first X-ray conversion element includes an incident surface on which an X-ray image is incident. The first X-ray conversion element is:
A first surface on which an X-ray image is incident;
The X-ray imaging device according to claim 1, further comprising a pattern detection unit that detects the generation pattern of the secondary energy and a second surface facing the pattern detection unit. The secondary energy is visible light;
The X-ray imaging device according to claim 1, wherein the pattern detection unit is an imaging device that captures visible light. The secondary energy is an electron or a hole;
The X-ray imaging device according to claim 1, wherein the pattern detection unit is a charge detection unit capable of detecting a charge distribution charged with electrons or holes.   The X-ray imaging device according to claim 1, wherein the X-ray image is an X-ray Talbot image.   The X-ray imaging device according to claim 1, wherein the pattern corresponding to the diffraction grating is a one-dimensional periodic pattern.   The X-ray imaging device according to claim 1, wherein the pattern corresponding to the diffraction grating is a two-dimensional periodic pattern.   The X-ray imaging device according to claim 7, wherein the two-dimensional periodic structure is a square lattice arrangement or a triangular lattice arrangement. A second X-ray conversion element having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates visible light;
An imaging device for imaging visible light,
The X-ray imaging device, wherein the second X-ray conversion device includes a first surface on which an X-ray image is incident and a second surface facing the imaging device. A third X-ray conversion element having a pattern corresponding to a diffraction grating formed of a material that absorbs X-rays and generates electrons or holes;
Charge detection means capable of detecting a charge distribution charged by electrons or holes generated by the third X-ray conversion element,
The X-ray imaging element, wherein the third X-ray conversion element includes an incident surface on which an X-ray image is incident. An X-ray source emitting X-rays;
A Talbot diffraction grating that produces a Talbot effect by X-rays emitted from the X-ray source;
An X-ray imaging device that images X-rays diffracted by the Talbot diffraction grating,
The X-ray imaging device is the X-ray imaging device according to any one of claims 1 to 10,
The X-ray imaging device, wherein the X-ray conversion element is disposed at a position substantially away from the Talbot diffraction grating. Generate an X-ray Talbot image,
An X-ray imaging method, wherein the X-ray Talbot image is incident on the X-ray imaging device according to claim 1.

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