JP7131625B2 - X-ray phase imaging system - Google Patents

Description

The present invention relates to an X-ray phase imaging apparatus, and more particularly to an X-ray phase imaging apparatus having a grating that enhances the coherence of X-rays.

Conventionally, an X-ray phase imaging apparatus is known that includes a grating that enhances the coherence of X-rays. Such an X-ray phase imaging apparatus is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2012-16370.

The X-ray phase imaging apparatus disclosed in Japanese Patent Application Laid-Open No. 2012-16370 includes an X-ray source, a detector arranged in the irradiation direction of the X-ray source, and an X-ray image detector between the X-ray source and the X-ray image detector. A plurality of gratings including a multi-slit near the source and a grating positioned between the multi-slit and the detector. A multi-slit is provided to enhance the coherence of X-rays emitted from the X-ray source. The X-ray imaging apparatus disclosed in Japanese Patent Application Laid-Open No. 2012-16370 uses a plurality of gratings to interfere X-rays emitted from an X-ray source while moving one of the plurality of gratings in the direction of the grating pitch. , to obtain an intensity-modulated signal representing the intensity variation of the X-rays detected at the detector.

The X-ray imaging apparatus disclosed in Japanese Patent Application Laid-Open No. 2012-16370 detects an object based on the phase difference between an intensity-modulated signal when the object is not placed between a plurality of gratings and an intensity-modulated signal when the object is placed. It is configured to generate a phase-contrast image of the interior. A conventional X-ray imaging apparatus as disclosed in Japanese Patent Application Laid-Open No. 2012-16370 utilizes the phase difference of X-rays rather than the amount of absorption of X-rays to image the inside of a subject, thereby capturing X-rays. It is possible to image hard-to-absorb light element objects and biological soft tissues. Note that the phase contrast image includes an absorption image, a phase differential image, and a dark field image. An absorption image is an image formed based on attenuation of X-rays that occur when X-rays pass through an object. A phase differential image is an image formed based on the phase shift of X-rays generated when the X-rays pass through a subject. A dark-field image is a visibility image obtained by changes in visibility based on small-angle scattering of an object. A dark-field image is also called a small-angle scattering image. "Visibility" is definition.

Japanese Unexamined Patent Application Publication No. 2012-16370

Here, in order to check the detailed structure of the subject, it may be desired to take an enlarged image of the subject. In this case, there is a problem that the image quality of the obtained image is degraded if the subject is magnified and imaged without increasing the definition. Therefore, by capturing an image with increased sharpness, it is possible to suppress deterioration in image quality even when capturing an enlarged image. In order to improve definition, it is conceivable to reduce the focal size of the X-ray source. However, in Japanese Unexamined Patent Application Publication No. 2012-16370, the X-ray source is provided with multi-slits in order to increase the coherence of the X-ray source. When the focal size of the X-ray source is reduced in a configuration in which the X-ray source is provided with multi-slits, the grid pattern of the multi-slits is resolved and detected as stripes on the image. Therefore, there is a problem that the image quality of the obtained image is degraded by the striped pattern of the grid pattern of the multi-slits.

The present invention has been made to solve the above-described problems. An object of the present invention is to provide an X-ray phase imaging apparatus capable of suppressing .

To achieve the above object, an X-ray phase imaging apparatus according to a first aspect of the present invention comprises an X-ray source that irradiates an object with X-rays, and a detector that detects the X-rays emitted from the X-ray source. , a first grating which is a multi-slit arranged between an X-ray source and a detector and uses the X-ray emitted from the X-ray source as a line source to increase the coherence of the X-ray; A plurality of gratings including a second grating that is a phase grating that is irradiated with X-rays and forms a self-image, and an image processing unit that generates a phase contrast image based on the signal detected by the detector, When the focus size of the X-ray source is changed to be smaller in order to increase the sharpness of the phase-contrast image, the X-ray source is irradiated with X-rays due to the smaller focus size. The first grating and the X-ray source are combined so that the enlarged and projected grating pattern of the first grating is not detected by the detector when the enlarged and projected grating pattern of the first grating is detected by are adjusted, or the focus size of the x-ray source is adjusted such that the focal size of the x-ray source is increased .

In the X-ray phase imaging apparatus according to the first aspect of the present invention, as described above, when the focus size of the X-ray source is changed to be smaller in order to increase the clarity of the phase contrast image, the X-ray source is due to the reduction of the focal spot size, when the grid pattern of the first grid magnified and projected is detected by irradiation with X-rays, the magnified and projected first grid The relative placement of the first grating and the X-ray source is adjusted so that the grating pattern is not detected by the detector, or the focus size of the X-ray source is increased so that the focus size of the X-ray source is increased. is adjusted. As a result, it is possible to prevent the enlarged and projected grid pattern of the first grid from being detected by the detector, even when imaging is performed with increased definition by reducing the focal size of the X-ray source. . As a result, it is possible to suppress the deterioration of the image quality of the obtained image even when the focus size of the X-ray source is reduced to increase the definition.

In the X-ray phase imaging apparatus according to the first aspect, preferably, the X-ray source is resolved by the detector so that the fringe pattern of the enlarged and projected grid pattern of the first grid is not detected. Then, the relative placement of the first grating and the X-ray source or the focus size of the X-ray source is adjusted. With this configuration, by adjusting the relative arrangement of the first grating and the X-ray source or the focal size of the X-ray source, the enlarged and projected grid pattern of the first grating is detected. resolution by the instrument can be suppressed. As a result, for example, it is possible to suppress the stripe pattern of the enlarged and projected grid pattern of the first grid from being detected by the detector at a definition that cannot be recognized by the naked eye. It is possible to further suppress the deterioration of the image quality of the image due to the grid pattern of the first grid.

In the X-ray phase imaging apparatus according to the first aspect, preferably, the X-ray source is positioned in the optical axis direction of the X-ray at a position where the magnified and projected grating pattern of the first grating is not detected by the detector, It is spaced apart from the first grid. With this configuration, even if the grid pattern of the first grid is detected as being magnified and projected due to the irradiation of the X-rays due to the reduction in the focus size, the grid pattern is magnified and projected. In addition, the magnification of the grid pattern of the first grid can be reduced. As a result, the enlarged and projected grid pattern of the first grid is not resolved, so that it is possible to suppress the detector from detecting the enlarged and projected grid pattern of the first grid, It is possible to suppress deterioration of the image quality of the image due to detection of the grid pattern of the first grid projected in an enlarged manner.

In the X-ray phase imaging apparatus according to the first aspect, preferably, the X-ray source is enlarged such that one period of the enlarged and projected grating pattern of the first grating is smaller than the pixel size of the detector. It is placed in a position that becomes a rate. With this configuration, it is possible to make the size of one period of the enlarged and projected grid pattern of the first grid smaller than the pixel size of the detector. It is possible to further suppress detection of the grid pattern of one grid by the detector. As a result, it is possible to further suppress deterioration in image quality due to detection of the grid pattern of the first grid projected in an enlarged manner.

ここで、ｍは、拡大されて投影された第１格子の格子パターンの拡大率である。また、Ｒは、Ｘ線源と検出器との間の距離である。また、ｒ_０は、Ｘ線源と第１格子との間の距離である。また、ｐ_１は、拡大されて投影された第１格子の格子パターンの周期である。また、ｐ_０は、第１格子の格子周期である。また、ｎは、拡大されて投影された第１格子の格子パターンに含まれる画素数である。また、ｐ_２は、検出器の画素サイズである。
このように構成すれば、上記式（４）を満たす位置にＸ線源を配置することにより、拡大されて投影された第１格子の格子パターンの１周期の大きさを、検出器の画素サイズよりも容易に小さくすることができる。その結果、拡大されて投影された第１格子の格子パターンが検出されることに起因して画像の画質が劣化することを、より容易に抑制することができる。In this case, the X-ray source is preferably placed at a position that satisfies the following equation (4) when the following equations (1) to (3) are defined.

Here, m is the magnification of the enlarged and projected grid pattern of the first grid. Also, R is the distance between the X-ray source and the detector. Also, r ₀ is the distance between the X-ray source and the first grating. Also, p1 is the period of the grid pattern of the _first grid projected in an enlarged manner. Also, _p0 is the grating period of the first grating. Also, n is the number of pixels included in the grid pattern of the first grid projected in an enlarged manner. Also, _p2 is the pixel size of the detector.
With this configuration, by arranging the X-ray source at a position that satisfies the above formula (4), the size of one period of the enlarged and projected grid pattern of the first grid can be changed to the pixel size of the detector. can be easily made smaller. As a result, it is possible to more easily suppress the deterioration of the image quality of the image due to the detection of the grid pattern of the first grid projected in an enlarged manner.

In the X-ray phase imaging apparatus according to the first aspect, preferably, the amount of blurring of the enlarged and projected grating pattern of the first grating caused by the focal size of the X-ray source is enlarged. The focal spot size of the X-ray source is set such that the grid pattern of the first grid projected by 1 is a blur amount that is not detected by the detector. With this configuration, even if the grid pattern of the first grid is detected as being magnified and projected due to the irradiation of the X-rays due to the reduction in the focus size, the grid pattern is magnified and projected. The grid pattern of the first grid can be blurred. As a result, the enlarged and projected grid pattern of the first grid can be blurred until it cannot be detected by the detector. deterioration of image quality can be suppressed.

Here, as a result of intensive studies by the inventors of the present application, when the amount of blur is 3.0 times or more of one period of the grid pattern of the enlarged and projected first grid, the enlarged and projected It was found that the grid pattern of the first grid was not detected by the detector. Based on this knowledge, the X-ray phase imaging apparatus according to the second aspect of the present invention provides an X-ray source so that the magnified and projected grid pattern of the first grid has a blur amount that is not detected by the detector. focal size is set . That is, the X-ray phase imaging apparatus according to the second aspect of the present invention comprises: an X-ray source for irradiating an object with X-rays; a detector for detecting the X-rays irradiated from the X-ray source; a plurality of gratings disposed between the vessel and including a first grating for enhancing the coherence of X-rays emitted from the X-ray source and a second grating for receiving X-rays from the first grating; an image processor that generates a phase-contrast image based on the signals detected by the detector, wherein the X-ray source is magnified by being irradiated with X-rays due to the reduction of the focal spot size. The relative relationship between the first grating and the X-ray source is such that when the grating pattern of the first grating projected as an enlarged projection is not detected by the detector, or the focal size of the X-ray source is adjusted, and the amount of blurring of the enlarged and projected grid pattern of the first grating caused by the size of the focal size of the X-ray source is enlarged and projected. The focal size of the X-ray source is set such that the grid pattern of the first grid is not detected by the detector, and the X-ray source is projected with an enlarged blur amount. The focal size of the X-ray source is set to a range of 3.0 times or more of one period of the grating pattern. With this configuration, the enlarged and projected grid pattern of the first grid can be easily blurred until it is no longer detected by the detector. As a result, it is possible to easily suppress deterioration in the image quality of the image due to the grid pattern of the first grid projected in an enlarged manner.

ここで、ｂは、上記ぼけ量である。また、ｓは、Ｘ線源の焦点サイズである。
このように構成すれば、拡大されて投影された第１格子の格子パターンの１周期の大きさを、検出器の画素サイズよりも小さくすることが困難な場合でも、拡大されて投影された第１格子の格子パターンが検出器によって検出されることを容易に抑制することができる。その結果、Ｘ線源の焦点サイズｓを、上記式（６）を満たす焦点サイズに調整することにより、拡大されて投影された第１格子の格子パターンに起因して画像の画質が劣化することを容易に抑制することができる。In the configuration in which the focal size of the X-ray source is set such that the enlarged and projected grid pattern of the first grid is a blur amount that is not detected by the detector, the X-ray source is preferably magnified. When one period of the grid pattern of the first grid projected by the following equation is larger than the pixel size of the detector, the magnitude of the blur amount defined by the following equation (5) is given by the following equation (6) The focal spot size of the X-ray source is set so as to satisfy

Here, b is the blur amount. Also, s is the focal spot size of the X-ray source.
With this configuration, even if it is difficult to make the size of one period of the enlarged and projected grid pattern of the first grid smaller than the pixel size of the detector, the enlarged and projected first grid can be used. It is possible to easily suppress detection of a grid pattern of one grid by the detector. As a result, by adjusting the focus size s of the X-ray source to a focus size that satisfies the above formula (6), the image quality of the image is degraded due to the enlarged and projected grid pattern of the first grid. can be easily suppressed.

The X-ray phase imaging apparatus according to the first aspect preferably further includes a third grating arranged between the second grating and the detector. With this configuration, even when the pixel size of the detector is larger than the size of one period of the self-image of the second grating, a phase contrast image can be generated by detecting moire fringes. can. As a result, a phase-contrast image can be generated without depending on the pixel size of the detector, so the degree of freedom in selecting detectors can be improved.

According to the present invention, as described above, X-rays capable of suppressing deterioration in image quality of an obtained image even when imaging is performed with increased definition by reducing the focal size of the X-ray source. A phase imaging device can be provided.

1 is a schematic diagram of the X-ray phase imaging apparatus according to the first embodiment viewed from the X direction; FIG. 1 is a perspective view of a grating moving mechanism included in the X-ray phase imaging apparatus according to the first embodiment; FIG. FIG. 10 is a schematic diagram for explaining a grid pattern of an enlarged projected first grid detected by a detector according to a first comparative example; FIG. 4A is a schematic diagram of an absorption image, (B) is a schematic diagram of a differential phase image, and (C) is a schematic diagram of a dark field image obtained by the X-ray phase imaging apparatus according to the first comparative example. FIG. 4 is a schematic diagram for explaining the grid pattern of the enlarged projected first grid detected by the detector according to the first embodiment; FIG. 4A is a schematic diagram of an absorption image, (B) is a schematic diagram of a differential phase image, and (C) is a schematic diagram of a dark field image obtained by the X-ray phase imaging apparatus according to the first embodiment; FIG. 11 is a schematic diagram for explaining the amount of blurring of the grid pattern of the enlarged and projected first grid detected by the detector according to the second embodiment; FIG. 10 is a schematic diagram for explaining the amount of blurring of the grid pattern of the enlarged and projected first grid detected by the detector according to the second comparative example; FIG. 10 is a schematic diagram for explaining changes in the grid pattern of the enlarged and projected first grid and changes in the Fourier transform image when the focus size of the X-ray source is changed; FIG. 11 is a schematic diagram of an X-ray phase imaging apparatus according to a modification as viewed from the X direction;

Embodiments embodying the present invention will be described below with reference to the drawings.

[First embodiment]
The configuration of an X-ray phase imaging apparatus 100 according to the first embodiment will be described with reference to FIGS. 1 to 6. FIG.

(Configuration of X-ray phase imaging device)
First, referring to FIG. 1, the configuration of an X-ray phase imaging apparatus 100 according to this embodiment of the present invention will be described.

As shown in FIG. 1, the X-ray phase imaging apparatus 100 is an apparatus that images the inside of a subject Q using the Talbot effect. The X-ray phase imaging apparatus 100 is configured to image the subject Q while translating any one of a plurality of gratings in the periodic direction (Y direction) of the gratings.

As shown in FIG. 1, the X-ray phase imaging apparatus 100 includes an X-ray source 1, a detector 2, a plurality of gratings including a first grating 3 and a second grating 4, an image processing unit 5, a control A unit 6 , a storage unit 7 , and a grid moving mechanism 8 are provided. In this specification, the direction from the X-ray source 1 to the first grating 3 is the Z2 direction, and the opposite direction is the Z1 direction. The left-right direction in the plane of the paper perpendicular to the Z direction is the X direction, the direction toward the back of the plane of FIG. 1 is the X2 direction, and the direction toward the front side of the plane of FIG. 1 is the X1 direction. The vertical direction in a plane perpendicular to the Z direction is the Y direction, the upward direction is the Y1 direction, and the downward direction is the Y2 direction.

The X-ray source 1 is configured to generate X-rays and irradiate a subject Q with the generated X-rays by applying a high voltage thereto. The sharpness of the obtained image is adjusted by adjusting the focus size s of the X-ray source 1 . If the focal spot size s is reduced, the definition of the resulting image can be enhanced.

The first grating 3 has a plurality of slits 3a and X-ray absorbing portions 3b arranged at a predetermined period (pitch) p0 in the Y direction. Each slit 3a and X-ray absorbing portion 3b are formed to extend linearly along the X direction. Each slit 3a and X-ray absorbing portion 3b are formed to extend parallel to each other. The first grating 3 is a so-called absorption grating. The first grating 3 is irradiated with X-rays from the X-ray source 1 . The first grating 3 is configured to turn the X-rays passing through each slit 3a into a line light source corresponding to the position of each slit 3a.

The second grating 4 is arranged between the first grating 3 and the detector 2 and is irradiated with the X-rays passing through the first grating 3 . The second grating 4 is provided to form a self-image (not shown) of the second grating 4 by the Talbot effect. When coherent X-rays pass through a slit-formed grating, an image of the grating (self-image) is formed at a predetermined distance (Talbot distance) from the grating. This is called the Talbot effect.

The second grating 4 has a plurality of slits 4a arranged at a predetermined period ₍ pitch) p3 in the Y direction, and an X-ray phase changing portion 4b. Each of the slits 4a and the X-ray phase changing portions 4b are formed to extend linearly along the X direction. Each slit 4a and the X-ray phase changing portion 4b are formed so as to extend parallel to each other. The second grating 4 is a so-called phase grating. The first grating 3 and the second grating 4 are gratings having different roles, but the slits 3a and 4a transmit X-rays, respectively. The X-ray absorbing portion 3b plays a role of shielding X-rays, and the X-ray phase changing portion 4b changes the phase of the X-rays due to the difference in refractive index from that of the slit 4a.

The detector 2 is configured to detect X-rays, convert the detected X-rays into electrical signals, and read the converted electrical signals as image signals. The detector 2 is, for example, an FPD (Flat Panel Detector). The detector 2 is composed of a plurality of conversion elements (not shown) and pixel electrodes (not shown) arranged on the plurality of conversion elements. A plurality of conversion elements and pixel electrodes are arranged in an array in the X and Y directions with a predetermined period (pixel size p ₂ ). The detector 2 is also configured to output the acquired image signal to the image processing section 5 .

The image processing section 5 is configured to generate a phase contrast image 15 (see FIG. 4) based on the image signal output from the detector 2 . In the first embodiment, the image processing unit 5 generates, for example, an absorption image 15a (see FIG. 4), a phase differential image 15b (see FIG. 4), and a dark field image 15c (see FIG. 4) as the phase contrast image 15. do. The image processing unit 5 includes a processor such as a GPU (Graphics Processing Unit) or an FPGA (Field-Programmable Gate Array) configured for image processing.

The controller 6 is configured to control the grid moving mechanism 8 to move the second grid 4 . Control unit 6 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

The storage unit 7 is configured to store the phase contrast image 15 generated by the image processing unit 5 and the like. Storage unit 7 includes, for example, an HDD (Hard Disk Drive), a nonvolatile memory, and the like.

The grid moving mechanism 8 is configured to move the second grid 4 under the control of the controller 6 . Also, the grid moving mechanism 8 holds the second grid 4 .

(Grid moving mechanism)
As shown in FIG. 2, the grating moving mechanism 8 can rotate in the X direction, the Y direction, the Z direction, the rotation direction Rz about the Z direction axis, the rotation direction Rx about the X direction axis, and the rotation direction Rx about the Y direction axis. The first grating 3 is configured to be movable in the rotational direction Ry. Specifically, the grating moving mechanism 8 includes an X-direction linear motion mechanism 80 , a Y-direction linear motion mechanism 81 , a Z-direction linear motion mechanism 82 , a linear motion mechanism connecting portion 83 , and a stage support portion driving portion 84 . , a stage supporting portion 85 , a stage driving portion 86 , and a stage 87 . The X-direction linear motion mechanism 80 is configured to be movable in the X-direction. X-direction linear motion mechanism 80 includes, for example, a motor. The Y-direction linear motion mechanism 81 is configured to be movable in the Y-direction. Y-direction direct-acting mechanism 81 includes, for example, a motor. The Z-direction linear motion mechanism 82 is configured to be movable in the Z-direction. The Z-direction linear motion mechanism 82 includes, for example, a motor.

The grating moving mechanism 8 is configured to move the first grating 3 in the X direction by the operation of the X direction linear motion mechanism 80 . Also, the grating moving mechanism 8 is configured to move the first grating 3 in the Y direction by the operation of the Y-direction direct-acting mechanism 81 . Also, the grating moving mechanism 8 is configured to move the first grating 3 in the Z direction by the operation of the Z-direction direct-acting mechanism 82 .

The stage support portion 85 supports the stage 87 from below (Y1 direction). The stage driving section 86 is configured to reciprocate the stage 87 in the X direction. The stage 87 has a bottom portion formed in a convex curved shape facing the stage support portion 85, and is configured to rotate about an axis in the Z direction (Rz direction) by reciprocating in the X direction. there is Further, the stage support portion driving portion 84 is configured to reciprocate the stage support portion 85 in the Z direction. In addition, the bottom of the stage support portion 85 is formed in a convex curved shape toward the linear motion mechanism connection portion 83, and is rotated about the axis in the X direction (Rx direction) by reciprocating in the Z direction. is configured as Further, the linear motion mechanism connecting portion 83 is provided in the X-direction linear motion mechanism 80 so as to be rotatable around the Y-direction axis (Ry direction). Therefore, the grid moving mechanism 8 can rotate the grid around the central axis in the Y direction.

Here, when the object Q is imaged by enlarging it, if it is imaged by enlarging it without increasing the definition, the obtained phase contrast image 15 may become unclear. Therefore, it is conceivable to increase the definition of the obtained phase contrast image 15 . By reducing the focal spot size s of the X-ray source 1, the sharpness of the obtained phase contrast image 15 can be enhanced. However, when the focus size s of the X-ray source 1 is reduced, the resolution of the first grating 3 causes the grating pattern 9 (see FIG. 1) of the first grating 3 to be enlarged and projected on the detector 2. be done. Depending on the size of the period p ₁ (see FIG. 1) of the enlarged and projected grating pattern 9 of the first grating 3, the enlarged and projected grating pattern 9 of the first grating 3 may be detected by the detector 2. may occur. A case where the grid pattern 9 of the first grid 3 projected in an enlarged manner is detected by the detector 2 will be described below with reference to FIG.

(First comparative example)
FIG. 3 is a schematic diagram of an X-ray phase imaging apparatus 200 according to a comparative example when the grid pattern 9 of the first grid 3 projected in an enlarged manner is detected by the detector 2, viewed from the X direction. As shown in FIG. 3, the X-ray phase imaging apparatus 200 includes an X-ray source 11, a detector 12, a first grating 13, a control unit (not shown), a storage unit (not shown), and a grid moving mechanism (not shown). Note that the X-ray source 11, the detector 12, and the first grating 13 shown in FIG. It has the same configuration as 1 grating 3 .

In the example shown in FIG. 3, the first grating 13 is arranged at a position where the distance between the X-ray source ₁ and the first grating 13 is the distance R1. Further, in the example shown in FIG. 3, the detector 14 is arranged at a position where the distance between the X-ray source 11 and the detector 14 is the distance _R2 .

In FIG. 3, the first grating 13 is an example in which the size of one period p4 of the grating pattern 19 of the enlarged and projected first grating ₃ is larger _than the size of the pixel size p2 of the detector 12. showing. If the size of one period p4 of the grid pattern 19 of the enlarged projected first grating ₁₃ is larger _than the pixel size p2 of the detector 12, the enlarged projected grating of the first grating 3 The pattern 19 is resolved, and in the generated phase-contrast image 15, the grid pattern 9 of the enlarged projected first grid 3 is detected as a striped pattern SP (see FIG. 4).

FIG. 4A is a schematic diagram of an absorption image 15a obtained by the X-ray phase imaging apparatus 200 according to the first comparative example. FIG. 4B is a schematic diagram of a differential phase image 15b obtained by the X-ray phase imaging apparatus 200 according to the first comparative example. FIG. 4C is a schematic diagram of a dark field image 15c obtained by the X-ray phase imaging apparatus 200 according to the first comparative example. In each phase-contrast image 15 shown in FIGS. 4A to 4C, a striped pattern SP caused by the enlarged and projected lattice pattern 9 of the first lattice 3 is detected. Therefore, the image quality of the phase contrast image 15 is degraded.

Therefore, in the first embodiment, the X-ray source 1 detects the grid pattern 9 of the first grid 3 that is enlarged and projected by irradiating the X-ray due to the reduction of the focus size s. The relative placement of the first grating 3 and the X-ray source 1 is adjusted so that the enlarged and projected grating pattern 9 of the first grating 3 is not detected by the detector 2 when the first grating 3 is projected. Specifically, the X-ray source 1 is resolved by the detector 2 so that the stripe pattern SP of the grid pattern 9 of the first grid 3 projected in an enlarged manner is not detected. and the X-ray source 1 are adjusted.

なお、ｍは、拡大されて投影された第１格子３の格子パターン９の拡大率である。また、Ｒは、Ｘ線源１と検出器２との間の距離である。また、ｒ_０は、Ｘ線源１と第１格子３との間の距離である。また、ｐ_１は、拡大されて投影された第１格子３の周期である。また、ｐ_０は、第１格子３の周期である。また、ｎは、拡大されて投影された第１格子３の格子パターン９に含まれる画素数である。また、ｐ_２は、検出器２の画素サイズである。As shown in FIG. 5, in the first embodiment, in the X-ray source 1, the grid pattern 9 of the first grid 3 projected in an enlarged manner is detected by the detector 2 in the X-ray optical axis direction (Z direction). It is arranged away from the first grating 3 at a position where it is not detected. Specifically, the X-ray source 1 has an enlargement factor m such that one period p1 of the enlarged and projected grating pattern 9 of the _first grating 3 is smaller than the pixel size p2 of the detector ₂ . placed in a certain position. More specifically, the X-ray source 1 is placed at a position that satisfies the following formula (4) when the following formulas (1) to (3) are defined. In addition, in FIG. 5, for comparison, the X-ray source 11 in the X-ray phase imaging apparatus 200 according to the first comparative example is illustrated by a broken line.

Note that m is the magnification of the grid pattern 9 of the first grid 3 projected in an enlarged manner. Also, R is the distance between the X-ray source 1 and the detector 2 . Also, r ₀ is the distance between the X-ray source 1 and the first grating 3 . Also, p1 is the period of the enlarged projected _first grating 3 . Also, p ₀ is the period of the first grating 3 . Also, n is the number of pixels included in the grid pattern 9 of the first grid 3 projected in an enlarged manner. Also, p ₂ is the pixel size of the detector 2 .

As shown in FIG. 5, when the X-ray source 1 is placed at a position that satisfies the above formula (4), one period p ₁ of the grid pattern 9 of the first grid 3 projected in an enlarged manner corresponds to that of the detector 2. smaller _than the pixel size p2. Therefore, the grid pattern 9 of the first grid 3 that is enlarged and projected by the detector 2 is not detected. When the distance _r0 between the X-ray source 1 and the first grating 3 is increased, the dose of X-rays reaching the detector 2 is reduced. Therefore, the imaging time must be lengthened in order to suppress deterioration of the image quality of the phase contrast image 15 due to insufficient dose of X-rays. However, if the imaging time is lengthened, the amount of radiation exposure increases, which is not preferable.

Therefore, in the first embodiment, the above formula (4 ), the X-ray source 1 and the first grating 3 are placed at relative positions such that n approaches one. Preferably, the X-ray source 1 and the first grating 3 are arranged at relative positions where n=1. Further, when it is desired to further suppress the deterioration of the image quality of the phase contrast image 15 caused by the grid pattern 9 of the first grid 3 projected in an enlarged manner, the relative position is set to a position where n is 0.8 to 0.9. , the X-ray source 1 and the first grating 3 may be arranged. That is, the X-ray source 1 and the first grating 3 may be placed at relative positions such that the value of n satisfies the following equation (7).

FIG. 6A is a schematic diagram of an absorption image 15a obtained by the X-ray phase imaging apparatus 100 according to the first embodiment. FIG. 6B is a schematic diagram of a differential phase image 15b obtained by the X-ray phase imaging apparatus 100 according to the first embodiment. FIG. 6C is a schematic diagram of a dark field image 15c obtained by the X-ray phase imaging apparatus 100 according to the first embodiment. In each phase-contrast image 15 shown in FIGS. 6A to 6C, unlike each phase-contrast image 15 shown in FIGS. The striped pattern SP caused by the lattice pattern 9 of 3 is not detected. Therefore, by arranging the X-ray source 1 at a position that satisfies the above formula (4), deterioration of the image quality of the phase contrast image 15 can be suppressed even when the definition is increased.

(Effect of the first embodiment)
The following effects can be obtained in the first embodiment.

In the first embodiment, as described above, the X-ray phase imaging apparatus 100 includes the X-ray source 1 that irradiates the subject Q with X-rays, and the detector 2 that detects the X-rays emitted from the X-ray source 1. , a first grating 3 arranged between the X-ray source 1 and the detector 2 to enhance the coherence of the X-rays emitted from the X-ray source 1, and the X-rays from the first grating 3 being emitted. a second grating 4, and an image processor 5 for generating a phase-contrast image 15 based on the signals detected by the detector 2, the X-ray source 1 reducing the focal spot size s As a result, when the enlarged and projected lattice pattern 9 of the first grating 3 is detected by X-ray irradiation, the enlarged and projected lattice pattern 9 of the first grating 3 is detected. is not detected by the detector 2, the relative placement of the first grating 3 and the X-ray source 1 is adjusted. As a result, the detector 2 detects the enlarged and projected grid pattern 9 of the first grid 3 even when the focus size s of the X-ray source 1 is reduced to increase the definition of the image. can be suppressed. As a result, it is possible to suppress the deterioration of the image quality of the obtained phase contrast image 15 even when imaging is performed with the sharpness increased by reducing the focus size s of the X-ray source 1 .

Further, in the first embodiment, as described above, the X-ray source 1 is resolved by the detector 2 to detect the enlarged and projected stripe pattern SP of the grid pattern 9 of the first grid 3. The relative placement of the first grating 3 and the X-ray source 1 is adjusted so that it does not occur. Accordingly, by adjusting the relative arrangement of the first grating 3 and the X-ray source 1, the enlarged and projected stripe pattern SP of the grating pattern 9 of the first grating 3 is resolved by the detector 2. can be suppressed. As a result, for example, it is possible to suppress the detector 2 from detecting the striped pattern SP of the grid pattern 9 of the first grid 3 that has been enlarged and projected at a definition that cannot be recognized by the naked eye. It is possible to further suppress the deterioration of the image quality of the phase contrast image 15 due to the grid pattern 9 of the first grid 3 projected in an enlarged manner.

In the first embodiment, as described above, the X-ray source 1 uses the detector 2 to project the enlarged grid pattern 9 of the first grid 3 in the X-ray optical axis direction (Z direction). It is arranged away from the first grating 3 at a position where it is not detected. As a result, even when the grid pattern 9 of the first grid 3 that is enlarged and projected by X-ray irradiation is detected due to the reduction of the focal spot size s, the enlarged and projected grid pattern 9 is detected. The magnification m of the grid pattern 9 of the first grid 3 can be reduced. As a result, the enlarged and projected grid pattern 9 of the first grating 3 is not resolved, so that the detection of the enlarged and projected grid pattern 9 of the first grating 3 by the detector 2 is suppressed. This makes it possible to suppress deterioration in the image quality of the image due to detection of the grid pattern 9 of the first grid 3 projected in an enlarged manner.

In addition, in the first embodiment, as described above, the X-ray source 1 is such that one period p ₁ of the grid pattern 9 of the first grid 3 projected in an enlarged manner is larger than the pixel size p ₂ of the detector 2. It is arranged at a position where the enlargement ratio m becomes small. As a result, it is possible to make the size of _one period p1 of the grid pattern 9 of the first grating 3 projected in an enlarged manner smaller than the pixel size p2 of the detector ₂ . Detecting the grid pattern 9 of the first grid 3 thus detected by the detector 2 can be further suppressed. As a result, deterioration of the image quality of the phase contrast image 15 due to detection of the grid pattern 9 of the first grid 3 projected in an enlarged manner can be further suppressed.

Further, in the first embodiment, as described above, the X-ray source 1 is arranged at a position that satisfies the above equation (4) when the above equations (1) to (3) are defined. As a result, by arranging the X-ray source 1 at a position that satisfies the above formula (4), the size of _one period p1 of the enlarged and projected grating pattern 9 of the first grating 3 is It can easily be smaller _than the pixel size p2. As a result, deterioration of the image quality of the phase contrast image 15 due to detection of the grid pattern 9 of the first grid 3 projected in an enlarged manner can be more easily suppressed.

[Second embodiment]
Next, the configuration of the X-ray phase imaging apparatus 300 (see FIG. 1) according to the second embodiment will be described with reference to FIGS. 1 and 7 to 9. FIG. Unlike the first embodiment in which the distance _r0 between the X-ray source 1 and the first grating 3 is adjusted so that the enlarged projected grating pattern 9 of the first grating 3 is no longer detected by the detector 2, In the X-ray phase imaging apparatus 300 according to the second embodiment, the X-ray source 1 is arranged so that the detector 2 does not detect the grating pattern 9 of the first grating 3 that is magnified and projected by irradiation with X-rays. is adjusted for the focal size s. In addition, the same code|symbol is attached|subjected about the structure similar to the said 1st Embodiment, and description is abbreviate|omitted.

As shown in FIG. 1, the X-ray phase imaging apparatus 300 includes an X-ray source 1, a detector 2, a first grating 3, a second grating 4, an image processing unit 5, a control unit 6, a storage A unit 7 and a grid moving mechanism 8 are provided. The X-ray phase imaging apparatus 300 is the X-ray phase imaging apparatus according to the first embodiment, except that the distance r ₀ between the X-ray source 1 and the first grating 3 and the focus size s of the X-ray source 1 are different. It has the same configuration as 100.

In the second embodiment, the focal size s of the X-ray source 1 is adjusted so that the grid pattern 9 of the first grid 3, which is enlarged and projected by irradiation with X-rays, is not detected by the detector 2. be. Specifically, the blur amount b of the enlarged and projected grating pattern 9 of the first grating 3 caused by the size of the focal point size s of the X-ray source 1 is the enlarged and projected first The focal size s of the X-ray source 1 is set so that the grid pattern 9 of the grid 3 has a blur amount b that is not detected by the detector 2 .

Here, the blur amount b will be described with reference to FIG. As shown in FIG. 7, the X-ray XR1 emitted from the X-ray source 1 in the Y1 direction and the X-ray XR2 emitted from the X-ray source 1 in the Y2 direction are at the same location on the first grating 3. Even when the light is directed toward the target, the position in the Y direction that the light reaches on the detector 2 is different. Since the positions reached on the detector 2 are different, the outline of the enlarged and projected grid pattern 9 of the first grid 3 is blurred. The blur amount b is the amount by which the outline of the grid pattern 9 of the first grid 3 that is enlarged and projected is blurred. When the amount of blur b is small, the outline of the striped pattern SP of the grid pattern 9 of the first grid 3 projected in an enlarged manner becomes clear, and the striped pattern SP is clearly detected. On the other hand, when the amount of blur b is large, the outline of the grid pattern 9 of the enlarged and projected first grid 3 becomes unclear, and the striped pattern SP cannot be clearly detected. , is no longer detected as a striped pattern SP.

The blur amount b of the enlarged and projected grid pattern 9 of the first grid 3 is obtained by the following equation (5).

When acquiring the phase contrast image 15 by imaging with increased definition, it is conceivable to reduce the focal size s of the X-ray source 1 . The blur amount b when the focus size of the X-ray source is reduced will be described below with reference to FIG.

(Second comparative example)
An X-ray phase imaging apparatus 400 shown in FIG. 8 includes an X-ray source 21 , a detector 22 and a first grating 33 . The X-ray source 21 has the same configuration as the X-ray source 1 except that the focus size sc is smaller than the focus size s of the X-ray source 1 according to the first embodiment. Moreover, the detector 22 and the first grating 33 have the same configurations as the detector 2 and the first grating 3 according to the first embodiment, respectively.

The example shown in FIG. 8 shows the case where the focus size sc of the X-ray source 21 is smaller than the focus size s of the X-ray source 1 . Also in the configuration shown in FIG. 8, the relationship between the focal spot size sc of the X-ray source 21 and the amount of blur bc is the same as the above formula (5). Therefore, when the focal spot size sc of the X-ray source 21 becomes smaller, the blur amount bc of the enlarged projected grid pattern 9 of the first grating 13 becomes smaller. When the blur amount bc of the enlarged and projected grid pattern 9 of the first grating 13 becomes smaller, the striped pattern SP (not shown) of the enlarged and projected grid pattern 9 of the first grating 13 becomes sharper. , in the phase-contrast image 15, the stripe pattern SP of the grid pattern 9 of the first grid 13 projected in an enlarged manner is detected.

Here, the inventors of the present invention found that the blur amount b of the enlarged and projected lattice pattern 9 of the first grating 3 is one period p ₁ of the enlarged and projected lattice pattern 9 of the first grating 3 It has been found that the grid pattern 9 of the first grid 3 projected in an enlarged manner is not detected by the detector 2 when the range is 3.0 times or more of .

Based on the above knowledge, in the second embodiment, the X-ray source 1 has a blur amount b in a range of 3.0 times or more of one period p ₁ of the enlarged and projected grating pattern 9 of the first grating 3. The focus size s of the X-ray source 1 is set so that Specifically, the X _- ray source ₁ uses the above formula ( The focus size s of the X-ray source 1 is set so that the magnitude of the blur amount b defined by 5) satisfies the following equation (6).

Depending on the arrangement of the X-ray source 1 and the plurality of gratings, the X-ray source may be adjusted such that the amount of blur b is 3.0 times the one period p ₁ of the grating pattern 9 of the first grating 3 projected by enlarging it. Even if the focus size s of 1 is adjusted, the grating pattern 9 of the first grating 3 may still be detected. In such a case, the focus size s of the X-ray source 1 should be adjusted so that the amount of blur b is such that the grid pattern 9 of the first grid 3 is not detected. For example, the focal size of the X-ray source 1 is such that the magnitude of the blur amount b is 6.5 times as large as _one period p1 of the grating pattern 9 of the first grating 3 projected with the blur amount b enlarged. s should be adjusted. The upper limit of the blur amount b is not particularly limited. The focus size s of the X-ray source 1 should be adjusted to .

In the first embodiment, by increasing the distance _r0 between the X-ray source 1 and the first grating 3, the enlarged and projected grating pattern 9 of the first grating 3 is not detected by the detector 2. It was configured to However, for example, when the focus size s of the X-ray source 1 is set small in order to improve definition, the X-ray source 1 and the first grating 3 are placed at a position that satisfies the above formula (4). 1 may not be placed. Even in that case, by setting the focus size s that satisfies the above formula (6), the sharpness of the phase contrast image 15 is increased, and the phase Degradation of the image quality of the contrast image 15 can be suppressed.

The X-ray source 1 shown in FIG. 7 has a focal size s (see FIG. 1) of the X-ray source 1 in the first embodiment and a focal size sc (see FIG. 8) of the X-ray source 21 in the second comparative example. also shows the focal point size s enlarged. This is because the focal size s of the X-ray source 1 in the first embodiment and the focal size sc of the X-ray source 21 in the second comparative example are reduced to increase the sharpness. It is from. Note that the focal size s of the X-ray source 1 in the second embodiment is set smaller than the focal size of the X-ray source when general X-ray imaging is performed. That is, the focal size s of the X-ray source 1 in the second embodiment is set to be smaller than the focal size for normal X-ray imaging in order to improve definition, and the amount of blur b is defined by the above formula ( 6), it is set larger than the focal size s of the X-ray source 1 in the first embodiment.

(Experimental example)
Next, with reference to FIG. 9, an experiment for obtaining the above knowledge will be described.

FIG. 9 shows an X-ray image 17 and an X-ray image captured by changing the focus size s of the X-ray source 1 in order to acquire the range of the amount of blur b of the grid pattern 9 of the first grid 3 projected in an enlarged manner. It is a Fourier transform image 18 obtained by Fourier transforming (FT) the line image 17 . Note that the Fourier transform image 18 includes a 0th-order peak 30 and a 1st-order peak 31 . Of the 0th-order peak 30 and the 1st-order peak 31 in the Fourier transform image 18, the 1st-order peak 31 is caused by the striped pattern SP of the grid pattern 9 of the first grating 3 projected in an enlarged manner.

In the experimental example shown in FIG. 9, the presence or absence of the striped pattern SP of the grid pattern 9 of the first grid 3 projected in an enlarged manner in the X-ray image 17 was checked to see if the primary peak 31 in the Fourier transform image 18 was detected. is judged by That is, even if the striped pattern SP of the grid pattern 9 of the first grid 3 projected in an enlarged manner cannot be confirmed with the naked eye, if the primary peak 31 is produced in the Fourier transform image 18, the X-ray image 17 It is assumed that the striped pattern SP of the grid pattern 9 of the first grid 3 that has been enlarged and projected in is detected.

In the example shown in FIG. 9, the experiment was conducted with the X-ray source 1 and the detector 2 arranged at a position where the distance R between the X-ray source 1 and the detector 2 was 1120 mm. Further, in the example shown in FIG. 9, the X-ray source 1 and the first grating 3 are placed at a position where the distance _r0 between the X-ray source 1 and the first grating 3 is 100 mm, and the experiment is performed. rice field. Also, in the example shown in FIG. 9, the experiment was conducted using the first grating 3 having a grating period _p0 of 9 μm. Moreover, in the example shown in FIG. 9, the experiment was conducted using the detector 2 having a pixel size p2 of 75 μm. Based on the above conditions, in the example shown in FIG. 9, the period p1 of the enlarged and projected grating pattern 9 of the _first grating 3 is 100.8 μm, and n in the above formula (4) is 1.34. Experiments were conducted under the following conditions.

The example shown in FIG. 9A is a schematic diagram of an X-ray image 17a captured with the focus size s of the X-ray source 1 set to 10 μm. Since the focus size s of the X-ray source 1 is set to 10 μm, the blur amount b of the enlarged and projected grid pattern 9 of the first grid 3 is 102 μm. That is, in the X-ray image 17a, the blur amount b of the enlarged and projected grid pattern 9 of the first grating 3 is 1.1 of one period p ₁ of the enlarged and projected grid pattern 9 of the first grid 3. This is an example in which the focus size s of the X-ray source 1 is adjusted to 01 times. In the X-ray image 17a, the striped pattern SP of the grid pattern 9 of the first grid 3 projected in an enlarged manner was confirmed.

A 0th-order peak 30 and a 1st-order peak 31 were confirmed in the Fourier transform image 18a obtained by Fourier transforming the X-ray image 17a. Therefore, when the focus size s of the X-ray source 1 was set to 10 μm, the stripe pattern SP of the enlarged and projected lattice pattern 9 of the first lattice 3 could be confirmed in the X-ray image 17a. Also in the Fourier transform image 18a, a primary peak 31 caused by the grid pattern 9 of the first grid 3 projected in an enlarged manner was confirmed.

In the example shown in FIG. 9(B), since the focus size s of the X-ray source 1 is set to 12 μm, the blur amount b of the enlarged and projected lattice pattern 9 of the first grating 3 is 122 μm. It is a schematic diagram of the image 17b. That is, in the X-ray image 17b, the blur amount b of the enlarged and projected lattice pattern 9 of the first lattice 3 is 1.1 of one period p ₁ of the enlarged and projected lattice pattern 9 of the first lattice 3. This is an example in which the focus size s of the X-ray source 1 is adjusted to be 21 times. Also in the X-ray image 17b, the striped pattern SP of the grid pattern 9 of the first grid 3 projected in an enlarged manner could be confirmed.

A 0th order peak 30 and a 1st order peak 31 were confirmed in a Fourier transform image 18b obtained by Fourier transforming the X-ray image 17b. Therefore, when the focus size s of the X-ray source 1 was set to 12 μm, the stripe pattern SP of the enlarged projected lattice pattern 9 of the first lattice 3 could be confirmed in the X-ray image 17b. Also in the Fourier transform image 18b, a primary peak 31 caused by the grid pattern 9 of the first grid 3 projected in an enlarged manner was confirmed.

In the example shown in FIG. 9(C), since the focus size s of the X-ray source 1 is set to 14 μm, the blur amount b of the enlarged and projected lattice pattern 9 of the first grating 3 is 143 μm. Fig. 17c is a schematic diagram of an image 17c; That is, in the X-ray image 17c, the blur amount b of the enlarged and projected grid pattern 9 of the first grating 3 is 1.1 of one period p ₁ of the enlarged and projected grid pattern 9 of the first grid 3. This is an example in which the focus size s of the X-ray source 1 is adjusted to 42 times. Also in the X-ray image 17c, the striped pattern SP of the grid pattern 9 of the first grid 3 projected in an enlarged manner could be confirmed.

A 0th order peak 30 and a 1st order peak 31 were confirmed in a Fourier transform image 18c obtained by Fourier transforming the X-ray image 17c. Therefore, when the focus size s of the X-ray source 1 was set to 14 μm, the stripe pattern SP of the enlarged and projected grid pattern 9 of the first grid 3 could be confirmed in the X-ray image 17c. Also in the Fourier transform image 18C, a primary peak 31 caused by the grid pattern 9 of the first grid 3 projected in an enlarged manner was confirmed.

In the example shown in FIG. 9(D), since the focus size s of the X-ray source 1 is set to 16 μm, the blur amount b of the enlarged and projected grating pattern 9 of the first grating 3 is 163 μm. 17d is a schematic diagram of an image 17d; FIG. That is, in the X-ray image 17d, the blur amount b of the enlarged and projected grid pattern 9 of the first grating 3 is 1.1 of one period p ₁ of the enlarged and projected grid pattern 9 of the first grid 3. This is an example in which the focus size s of the X-ray source 1 is adjusted to 62 times. In the X-ray image 17d, the striped pattern SP of the grid pattern 9 of the first grid 3 projected in an enlarged manner could not be confirmed.

A 0th order peak 30 and a 1st order peak 31 were confirmed in a Fourier transform image 18d obtained by Fourier transforming the X-ray image 17d. When the focus size s of the X-ray source 1 was set to 16 μm, the stripe pattern SP of the enlarged and projected grid pattern 9 of the first grid 3 could not be confirmed in the X-ray image 17d. However, in the Fourier transform image 18b, a primary peak 31 caused by the grid pattern 9 of the first grid 3 projected in an enlarged manner was confirmed.

In the example shown in FIG. 9(E), the focus size s of the X-ray source 1 is set to 30 μm, so the blur amount b of the enlarged and projected grid pattern 9 of the first grid 3 is 306 μm. X-ray image 17e. Therefore, in the X-ray image 17e, the blur amount b of the enlarged and projected lattice pattern 9 of the first grating 3 is 3.1 of one period p ₁ of the enlarged and projected lattice pattern 9 of the first grating 3. This is an example in which the focus size s of the X-ray source 1 is adjusted to 04 times.

In the Fourier transform image 18e obtained by Fourier transforming the X-ray image 17e, the 0th-order peak 30 could be confirmed, but the 1st-order peak 31 could not be confirmed. When the focus size s of the X-ray source 1 was set to 30 μm, the stripe pattern SP of the enlarged and projected grid pattern 9 of the first grid 3 could not be confirmed in the X-ray image 17e. , the primary peak 31 due to the grid pattern 9 of the first grid 3 projected in an enlarged manner could not be confirmed either in the Fourier transform image 18e.

As shown in FIGS. 9A to 9E, as the blur amount b of the enlarged and projected grid pattern 9 of the first grid 3 increases, the striped pattern SP in the X-ray image 17 becomes unclear. became. When the blur amount b was 1.6 times or more of _one period p1 of the enlarged and projected grating pattern 9 of the first grating 3, it became impossible to confirm with the naked eye. In addition, in the Fourier transform image 18, the intensity (signal intensity) of the primary peak 31 decreased as the blur amount b of the grid pattern 9 of the enlarged and projected first grid 3 increased. The primary peak 31 was no longer detected when the amount of blur b was three times or more the _one period p1 of the grid pattern 9 of the enlarged projected first grid 3 . In the example shown in FIG. 9, for convenience, the intensity (signal intensity) of the primary peak 31 is represented by the size of the primary peak 31 and the thickness of the line shown. As a result, an experimental result was obtained that the enlarged and projected grid pattern 9 of the first grid 3 was not detected when the range of the amount of blur b was the range shown in the above formula (6).

Other configurations of the second embodiment are the same as those of the first embodiment.

(Effect of Second Embodiment)
The following effects can be obtained in the second embodiment.

In the second embodiment, as described above, the X-ray source 1 that irradiates the subject Q with X-rays, the detector 2 that detects the X-rays emitted from the X-ray source 1, the X-ray source 1 and the detector 2 and includes a first grating 3 for enhancing the coherence of X-rays emitted from the X-ray source 1 and a second grating 4 to which the X-rays emitted from the first grating 3 are applied. and an image processing unit 5 for generating a phase-contrast image 15 based on the signals detected by the detector 2, the X-ray source 1 having a small focal spot size s, the X When the enlarged and projected grid pattern 9 of the first grating 3 is detected by irradiating the line, the enlarged and projected grid pattern 9 of the first grid 3 is not detected by the detector 2. so that the focal spot size s of the X-ray source 1 is adjusted. As a result, in the same manner as the X-ray phase imaging apparatus 100 according to the first embodiment, even when the focus size s of the X-ray source 1 is reduced to increase the definition and the imaging is performed, the image quality of the obtained phase contrast image 15 can be suppressed from deteriorating.

Further, in the second embodiment, as described above, the blur amount b of the enlarged and projected grid pattern 9 of the first grid 3 caused by the size of the focal point size s of the X-ray source 1 is The focal point size s of the X-ray source 1 is set so that the grid pattern 9 of the first grid 3 projected in an enlarged manner has a blur amount b that is not detected by the detector 2 . As a result, even when the grid pattern 9 of the first grid 3 is detected as being magnified and projected by X-ray irradiation due to the reduction of the focal spot size s, the magnified and projected grid pattern 9 is detected. The grid pattern 9 of the first grid 3 can be blurred. As a result, the enlarged and projected grid pattern 9 of the first grating 3 can be blurred until the detector 2 cannot detect it. As a result, it is possible to suppress deterioration of the image quality of the phase contrast image 15 .

Further, in the second embodiment, as described above, the X-ray source 1 has a blur amount b of 3.0 times or more of _one period p1 of the grid pattern 9 of the first grid 3 projected in an enlarged manner. A focus size s of the X-ray source 1 is set so as to be within the range. This makes it possible to easily blur the enlarged and projected grid pattern 9 of the first grid 3 until it is no longer detected by the detector 2 . As a result, it is possible to easily suppress deterioration of the image quality of the phase contrast image 15 due to the grid pattern 9 of the first grid 3 projected in an enlarged manner.

In addition, in the second embodiment, as described above, the X-ray source 1 is such that one period p ₁ of the grid pattern 9 of the first grid 3 projected in an enlarged manner is larger than the pixel size p ₂ of the detector 2. The focal size s of the X-ray source 1 is set so that the magnitude of the blur amount b defined by the above equation (5) satisfies the above equation (6) when the focal point size s increases. As a result, even when it is difficult to make the size of _one period p1 of the enlarged and projected grating pattern 9 of the first grating 3 smaller than the pixel size p2 of the detector ₂ , the enlarged and projected Detecting the grid pattern 9 of the first grid 3 thus detected by the detector 2 can be easily suppressed. As a result, by adjusting the focus size s of the X-ray source 1 to a focus size s that satisfies the above equation (6), the phase-contrast image is obtained due to the enlarged and projected grating pattern 9 of the first grating 3. 15 can easily be prevented from deteriorating.

(Modification)
It should be noted that the embodiments and experimental examples disclosed this time should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments and experimental examples, and includes all changes (modifications) within the meaning and scope equivalent to the scope of the claims.

For example, in the above-described first and second embodiments, examples of configurations including the first grating 3 and the second grating 4 are shown as the plurality of gratings, but the present invention is not limited to this. For example, as in an X-ray phase imaging apparatus 500 shown in FIG. 10, a configuration in which a third grating 25 is provided between the second grating 4 and the detector 2 may be employed. The third grating 25 has a plurality of slits 25a and X-ray absorbing portions 25b arranged at a predetermined period ₍ pitch) p5 in the Y direction. Each slit 25a and X-ray absorbing portion 25b are formed to extend linearly along the X direction. Each slit 25a and the X-ray absorbing portion 25b are formed so as to extend parallel to each other. Also, the third grating 25 is arranged between the second grating 4 and the detector 2, and the X-rays passing through the second grating 4 are irradiated. Also, the third grating 25 is arranged at a position separated from the second grating 4 by the Talbot distance. The third grating 25 interferes with the self-image of the second grating 4 to form moiré fringes (not shown) on the detection surface of the detector 2 . As a result, even when the pixel size p2 of the detector ₂ is larger than the size of one cycle of the self-image of the second grating 4, the phase contrast image 15 (absorption image 15a , a phase differential image 15b and a dark field image 15c). As a result, the phase contrast image 15 (absorption image 15a, phase differential image 15b and dark field image 15c) can be generated without depending on the pixel size p2 of the detector ₂ . degree of freedom can be improved.

Further, in the above-described first and second embodiments, an example of a configuration in which the grid moving mechanism 8 moves the second grid 4 is shown, but the present invention is not limited to this. For example, the grating moving mechanism 8 may be configured to move the first grating 3 in the Y direction for imaging. Moreover, when the third grating 25 (see FIG. 10) is provided as the plurality of gratings, the grating moving mechanism 8 may be configured to move the third grating 25 in the Y direction for imaging.

Also, in the above-described first and second embodiments, the second grating 4 is a phase grating, but the present invention is not limited to this. For example, the second grating 4 may be an absorbing grating.

Further, in the above-described first and second embodiments, an example of a configuration in which an image is captured while the second grating 4 is moved by the grating moving mechanism 8 has been shown, but the present invention is not limited to this. For example, the present invention can also be applied to a moire single-shot technique using moire fringes generated by slightly rotating the second grating 4 around the optical axis direction of X-rays.

REFERENCE SIGNS LIST 1 X-ray source 2 detector 3 first grating 4 second grating 6 image processor 9 enlarged and projected grating pattern of first grating 15 phase contrast image 25 third grating 100, 300, 500 X-ray phase imaging device b amount of blur m enlargement ratio of the first grid n number of pixels included in the grid pattern of the first grid that has been enlarged and projected p ₀ grid period of the first grid p ₁ grid pattern of the first grid that has been enlarged and projected p Pixel size of ₂ detectors Q Object R Distance between X-ray source and detector r ₀ Distance between X-ray source and first grating s Focus size of X-ray source SP Enlarged projection striped pattern of the grid pattern of the first grid

Claims (9)

an X-ray source that irradiates an object with X-rays;
a detector that detects X-rays emitted from the X-ray source;
a first grating which is a multi-slit arranged between the X-ray source and the detector and is arranged between the X-ray source and the X-ray source to make the X-ray emitted from the X-ray source a linear light source and enhance the coherence of the X-ray; a plurality of gratings including a second grating that is a phase grating that is irradiated with X-rays from the grating to form a self-image ;
an image processing unit that generates a phase contrast image based on the signal detected by the detector;
When the focus size of the X-ray source is modified to reduce the focus size to increase the sharpness of the phase-contrast image, the X-ray source emits X-rays due to the reduction of the focus size. When the grid pattern of the first grid magnified and projected is detected, the grid pattern of the first grid magnified and projected is not detected by the detector. 1. An X-ray phase imaging apparatus wherein the relative placement of the grating and the X-ray source is adjusted, or the focal size of the X-ray source is adjusted such that the focal size of the X-ray source is increased. . The X-ray source is resolved by the detector so that the stripe pattern of the enlarged projected grid pattern of the first grid is not detected. 2. The X-ray phase imaging apparatus of claim 1, wherein the relative placement or focus size of the X-ray source is adjusted. The X-ray source is arranged at a position apart from the first grating in the direction of the optical axis of X-rays so that the enlarged projected grating pattern of the first grating is not detected by the detector. Item 3. The X-ray phase imaging apparatus according to Item 1 or 2. 1. The X-ray source is arranged at a position having an enlargement ratio such that one period of the enlarged and projected grid pattern of the first grid is smaller than the pixel size of the detector. 4. The X-ray phase imaging apparatus according to any one of 3. 5. The X-ray phase imaging apparatus according to claim 4, wherein the X-ray source is arranged at a position that satisfies the following formula (4) when the following formulas (1) to (3) are defined.

here,
m: magnification of the grid pattern of the first grid projected in an enlarged manner;
R: distance between the X-ray source and the detector;
r ₀ : distance between the X-ray source and the first grating;
p ₁ : the period of the enlarged projected grating pattern of the first grating;
p ₀ : grating period of the first grating;
n: the number of pixels included in the grid pattern of the first grid projected in an enlarged manner;
p ₂ : pixel size of the detector;
is. The amount of blurring of the magnified and projected grid pattern of the first grid caused by the focal size of the X-ray source is detected by the magnified and projected grid pattern of the first grid. 3. The X-ray phase imaging apparatus according to claim 1, wherein the focal size of said X-ray source is set such that said blur amount is no longer detected by the detector. an X-ray source that irradiates an object with X-rays;
a detector that detects X-rays emitted from the X-ray source;
a first grating disposed between the X-ray source and the detector to enhance the coherence of X-rays emitted from the X-ray source; and a second grating irradiated with X-rays from the first grating. a plurality of grids, including a grid;
an image processing unit that generates a phase contrast image based on the signal detected by the detector;
The X-ray source is magnified and projected when the grid pattern of the first grid, which is magnified and projected by irradiation with X-rays, is detected due to the reduction of the focus size. adjusting the relative arrangement of the first grating and the X-ray source or the focus size of the X-ray source so that the grating pattern of the first grating is not detected by the detector;
The amount of blurring of the magnified and projected grid pattern of the first grid caused by the focal size of the X-ray source is detected by the magnified and projected grid pattern of the first grid. a focal size of the X-ray source is set such that the amount of blur is no longer detected by the instrument;
The focal size of the X-ray source is set such that the amount of blur is in the range of 3.0 times or more one period of the enlarged and projected grating pattern of the first grating. An X -ray phase imaging device. In the X-ray source, when one period of the enlarged and projected grid pattern of the first grid is larger than the pixel size of the detector, the blur amount defined by the following equation (5) 8. The X-ray phase imaging apparatus according to claim 7, wherein the focal size of the X-ray source is set such that the magnitude satisfies the following equation (6).

here,
b: the blur amount;
s: focal spot size of the X-ray source;
is. An X-ray phase imaging apparatus according to any one of claims 1 to 8, further comprising a third grating arranged between said second grating and said detector.

Images