JP7040625B2 - X-ray phase imaging system - Google Patents

Description

The present invention relates to an X-ray phase imaging system, and relates to an X-ray phase imaging system including a plurality of grids including a grid for enhancing the coherence of X-rays emitted from an X-ray source.

Conventionally, an X-ray phase imaging system including a plurality of grids including a grid for enhancing the coherence of X-rays emitted from an X-ray source is known. Such an X-ray phase imaging system is disclosed, for example, in Japanese Patent No. 5548085 and International Publication No. 2018/016369.

The X-ray phase imaging system of Patent No. 5548085 and International Publication No. 2018/016369 is for diffracting X-rays with an X-ray source, a detector, a G0 lattice for enhancing the coherence of X-rays, and an X-ray. The G1 lattice and the G2 lattice for interfering with the lattice image of the G1 lattice are provided. The X-ray phase imaging system of Patent No. 5548085 and International Publication No. 2018/016369 has one of a plurality of lattices in a state where moire fringes are generated by interfering the lattice image of the G1 lattice with the G2 lattice. A phase contrast image is acquired by a fringe scanning method in which one is imaged while moving in the direction of the pitch of the grid. The fringe scanning method is a method of imaging the inside of a subject based on the phase difference of X-rays passing through the subject and the small-angle scattering of X-rays.

Here, when the relative positions of the plurality of grids are misaligned, unintended moire fringes are detected. When unintended moire fringes are detected, the image quality of the generated phase contrast image deteriorates. Therefore, in Japanese Patent No. 5548085 and International Publication No. 2018/016369, the positional deviation of the relative positions of the plurality of lattices is adjusted.

In Japanese Patent No. 5548085, after adjusting the position of the G0 grid, the positions of the G1 grid and the G2 grid are adjusted. In the configuration disclosed in Japanese Patent No. 5548085, the grids are arranged so that moire fringes occur when the positions of the G1 grid and the G2 grid are adjusted. Then, according to the shape of the moire fringes, the positional deviation of the grid in the rotation direction around the axes in the two directions orthogonal to each other is adjusted in the plane orthogonal to the optical axis of the X-ray. After that, the relative position of each grid is adjusted so that the period of the unintended moire fringes becomes large (or small) so that the unintended moire fringes cannot be detected by the detector. In addition, in International Publication No. 2018/016369, the relative positions of the G1 grid and the G2 grid are adjusted in the optical axis direction of X-rays and the rotation direction around the optical axis of X-rays so that moire fringes are not detected. conduct.

Japanese Patent No. 5548085 International Publication No. 2018/016369

However, in the configuration disclosed in Japanese Patent No. 5548085, the relative position of each grid is adjusted so as to increase (or decrease) the period of the moire fringes. However, the moiré fringe is a pattern formed by superimposing the self-image which is the shadow of the G1 lattice and the G2 lattice, and adjusting by judging from the period of the moiré fringe is the relative relationship between the G1 lattice and the G2 lattice. I'm just adjusting the position. That is, even if the adjustment described in Japanese Patent No. 5548085 is performed, there may be a positional shift in the relative position of the G0 grid and the G1 grid in the rotation direction around the optical axis of the X-ray. Further, International Publication No. 2018/016369 discloses a configuration for adjusting the positional deviation between the G1 grid and the G2 grid, but does not disclose a configuration for adjusting the relative position between the G0 grid and the G1 grid. .. When the relative positions of the G0 grid and the G1 grid are displaced in the rotation direction around the optical axis of the X-ray, the grid image becomes unclear. When the grid image is unclear, there is a problem that the image quality of the obtained phase contrast image is deteriorated.

The present invention has been made to solve the above-mentioned problems, and it is possible to suppress deterioration of the image quality of the obtained phase contrast image due to the unclear lattice image. It is to provide an X-ray phase imaging system.

In order to achieve the above object, the X-ray phase imaging system in one aspect of the present invention includes an X-ray source that irradiates a subject with X-rays, a detector that detects X-rays emitted from the X-ray source, and a detector. A first lattice placed between the X-ray source and the detector to increase the coherence of X-rays emitted from the X-ray source, and X-rays from the first lattice are irradiated to form a lattice image. A plurality of grids including a second grid for performing X-rays, an image processing unit that generates a phase contrast image based on a signal detected by a detector, and a first grid and a first grid in the rotation direction around the optical axis of X-rays. A grid position adjustment mechanism that adjusts the relative position with the two grids, and a grid position adjustment mechanism that adjusts the position shift of the relative position so that the grid image becomes clear based on the sharpness of the grid image detected by the detector. The second grid is a phase grid for forming a self-image as a grid image, and the control unit is a relative position position based on the sharpness of the self-image. It is configured to control to adjust the deviation. The relative position deviations of the plurality of lattices are the position deviation of the lattice in the optical axis direction of the X-ray, the positional deviation of the lattice in the rotation direction around the optical axis of the X-ray, and orthogonality to the optical axis of the X-ray. Includes the misalignment of the grid in the direction of rotation around the axes in two directions orthogonal to each other in the plane.

In the X-ray phase imaging system according to one aspect of the present invention, as described above, the grid image is sharpened based on the sharpness of the grid image detected by the detector around the optical axis of the X-ray. It is provided with a control unit that controls the position deviation of the relative position between the first grid and the second grid in the rotation direction by the grid position adjusting mechanism. As a result, it is possible to suppress the positional deviation between the first grid and the second grid in the rotation direction of the X-ray around the optical axis and make the grid image clear. As a result, the lattice image becomes unclear, and it is possible to suppress deterioration of the image quality of the obtained phase contrast image. The phase contrast image includes an absorption image based on X-ray attenuation, a phase differential image based on X-ray phase shift, and a dark field image obtained by a change in visibility based on small-angle X-ray scattering. Is done. Since the absorption image is calculated based on the average intensity of the grid image, the image quality of the obtained image does not deteriorate even if the grid image is unclear. On the other hand, for the phase differential image and the dark field image, an image is generated based on the change between the lattice image when the subject is imaged without being arranged and the lattice image when the subject is arranged and imaged. Therefore, by making the lattice image clear, it is possible to suppress deterioration of the image quality of the obtained image.
Further, the second grid is a phase grid for forming a self-image as a grid image, and the control unit controls to adjust the positional deviation of the relative position based on the sharpness of the self-image. With the configuration, it is possible to suppress the self-image from becoming unclear in the Talbot interference in which the image of the subject is acquired by using the self-image. As a result, it is possible to suppress deterioration of the image quality of the phase contrast image due to the unclear self-image.

In the X-ray phase imaging system in the above one aspect, preferably, the control unit adjusts the positional deviation of the relative position by the grid position adjusting mechanism so that the sharpness of the grid image becomes larger than a predetermined threshold value. It is configured to provide control. With this configuration, the position adjustment of the grid can be completed when the sharpness of the grid image becomes larger than a predetermined threshold value. As a result, it is possible to suppress an increase in the number of grid adjustments as compared with the case where the relative positions between the grids of a plurality of grids are adjusted so that the sharpness of the grid image is maximized. The grid adjustment time can be shortened.

In the configuration in which the control for adjusting the positional deviation of the relative position is performed based on the sharpness of the self-image, the control unit preferably sets the self-image based on the maximum and minimum pixel values of the self-image. It is configured to acquire the visibility representing the contrast or the amplitude representing the intensity difference between the bright part and the dark part of the self-image as the sharpness of the self-image. With this configuration, it is possible to acquire the sharpness of the self-image by acquiring the visibility or amplitude, so the sharpness of the self-image can be determined by visually observing the image of the self-image. By comparison, the sharpness of the self-image can be obtained accurately. As a result, it is possible to accurately acquire the positional deviation between the first grid and the second grid in the rotation direction around the optical axis of X-rays, so that the first grid in the rotation direction around the optical axis of X-rays can be obtained. The misalignment with the second grid can be adjusted accurately.

In the X-ray phase imaging system in the above aspect, preferably, the control unit performs the intensity of the 0th-order peak and the intensity of the 1st-order peak in the first Fourier transform spectrum obtained by Fourier transforming the image of the self-image, or , Based on the intensity of the first-order peak in the first Fourier transform spectrum, the visibility representing the contrast of the self-image or the amplitude representing the intensity difference between the bright and dark parts of the self-image is acquired as the sharpness of the self-image. It is configured as follows. With this configuration, it is possible to obtain the sharpness of the self-image based on the intensity of the 0th-order peak and the intensity of the 1st-order peak of the 1st Fourier transform spectrum or the intensity of the 1st-order peak of the 1st Fourier transform spectrum. Therefore, the sharpness of the self-image can be accurately acquired as compared with the case where the sharpness of the self-image is visually acquired. As a result, in the configuration of acquiring the first Fourier transform spectrum as well as the configuration of acquiring the visibility or the amplitude based on the maximum value and the minimum value of the pixel value of the self-image, the rotation direction of the X-ray around the optical axis. It is possible to accurately adjust the positional deviation between the first grid and the second grid in.

In the configuration in which the control for adjusting the positional deviation of the relative position is performed based on the sharpness of the self-image, it is preferably arranged between the second grid and the detector, and due to the interference with the self-image of the second grid. It further includes a third grid for producing moire fringes. With this configuration, even if the size of the pixel size of the detector is larger than the size of one cycle of the self-image of the second grid, the moire fringes caused by arranging the third grid are detected. This makes it possible to generate a phase contrast image. As a result, even when the pixel size of the detector is larger than the size of one cycle of the self-image, it is possible to generate a phase contrast image, so that the degree of freedom in selecting the detector can be improved.

In this case, preferably, the control unit is configured to acquire the visibility representing the contrast of the moire fringes or the amplitude representing the intensity difference between the bright part and the dark part of the moire fringes as the sharpness of the self-image. .. Here, the moire fringes are generated by interfering the self-image of the second lattice with the third lattice. The third grid is a grid designed so that the cycle of the grid almost coincides with the cycle of the self-image of the second grid. Therefore, if the moire fringes are clear, it is considered that the self-image of the second lattice is clear. Further, if the intensity difference between the bright part and the dark part of the moire fringe is large, it is considered that the moire fringe is clear. That is, the amplitude of the moire fringes is also an index showing the sharpness of the moire fringes. Therefore, with the above configuration, the sharpness of the self-image can be indirectly acquired by acquiring the visibility or amplitude of the moire fringes. As a result, by adjusting a plurality of grids based on the visibility or amplitude of the moire fringes, it becomes possible to sharpen the self-image and suppress the deterioration of the image quality due to the blurring of the self-image. be able to.

In the configuration further including the third lattice, the control unit preferably performs the intensity of the 0th-order peak and the intensity of the 1st-order peak in the second Fourier transform spectrum obtained by Fourier transforming the image of the moire fringes, or the first-order peak. 2 Based on the intensity of the first-order peak in the Fourier transform spectrum, the visibility representing the contrast of the moiré fringes or the amplitude representing the intensity difference between the bright and dark parts of the moiré fringes should be acquired as the sharpness of the self-image. It is configured. With this configuration, in the configuration for acquiring the second Fourier transform spectrum as in the configuration for acquiring the first Fourier transform spectrum, the first lattice and the second lattice in the rotation direction around the optical axis of the X-ray are It is possible to accurately adjust the misalignment of.

In a configuration in which the visibility representing the contrast of the moire fringes or the amplitude representing the intensity difference between the bright part and the dark part of the moire fringes is acquired as the sharpness of the self-image, the control unit is preferably any of a plurality of lattices. It is configured to acquire the visibility of moiré fringes or the amplitude of moiré fringes based on the maximum and minimum values of the signal intensity of the intensity signal curve acquired by imaging while translating one of them. .. With this configuration, it is possible to acquire the intensity signal curve of the moire fringes based on the change in the signal intensity of a predetermined pixel in a plurality of moire fringe images captured while moving the lattice in translation. In one moire fringe image, the pixel values of the moire fringes are compared with the configuration in which the pixels of the bright part and the dark part are selected and the pixel values of the selected pixels are set to the maximum and minimum values of the pixel values of the moire fringes. The maximum and minimum values of can be obtained accurately. Therefore, the sharpness of the moire fringes can be obtained with high accuracy. As a result, it becomes possible to accurately acquire the sharpness of the self-image, so it is necessary to accurately adjust the positional deviation between the first grid and the second grid in the rotation direction around the optical axis of the X-ray. Can be done.

In a configuration in which the visibility representing the contrast of the moire fringes or the amplitude representing the intensity difference between the bright part and the dark part of the moire fringes is acquired as the sharpness of the self-image, the control unit is preferably any of a plurality of lattices. The intensity of the 0th-order peak and the intensity of the 1st-order peak in the 3rd Fourier transform spectrum obtained by Fourier transforming the intensity signal curve obtained by imaging while translating one of them, or the 3rd Fourier transform spectrum. Based on the intensity of the first-order peak in, the visibility representing the contrast of the moiré fringes or the amplitude representing the intensity difference between the bright part and the dark part of the moiré fringes is configured to be acquired as the sharpness of the self-image. .. With this configuration, the rotation of the X-ray around the optical axis is performed in the configuration for acquiring the third Fourier transform spectrum as in the configuration for acquiring the first Fourier transform spectrum and the configuration for acquiring the second Fourier transform spectrum. The positional deviation between the first grid and the second grid in the direction can be accurately adjusted.

In the X-ray phase imaging system in the above one aspect, preferably, the second grid is an absorption grid that forms a striped pattern generated by shielding a part of X-rays as a grid image, and the control unit is a striped image. It is configured to control the position shift of the relative position based on the sharpness of the pattern. With this configuration, a part of the X-rays is shielded by the second lattice, similar to an interferometer that generates a phase-contrast image based on the self-image generated by the interference of the X-rays diffracted by the second lattice. Even in a non-interferometer that images a subject based on the striped pattern of the second grid, the deterioration of the image quality of the phase contrast image due to the blurring of the striped pattern of the second grid can be suppressed. Can be done. Further, the striped pattern of the second grid is generated by shielding a part of X-rays. Therefore, unlike the Talbot interferometer that produces a self-image of the second grid, it is not necessary to arrange the second grid at a predetermined distance (Talbot distance) from the first grid. As a result, the degree of freedom in the arrangement position of the second grid can be improved.

According to the present invention, as described above, it is possible to provide an X-ray phase imaging system capable of suppressing deterioration of the image quality of the obtained phase contrast image due to the blurring of the lattice image. Can be done.

It is a schematic diagram which looked at the X-ray phase imaging system by 1st Embodiment from the Y direction. It is a perspective view of the grid position adjustment mechanism provided in the X-ray phase imaging system by 1st Embodiment. It is a schematic diagram (A) of the absorption image, the schematic diagram (B) of the phase differential image, and the schematic diagram (C) of the dark field image generated by the X-ray phase imaging system according to the first comparative example. It is a schematic diagram of the image of the self-image of the second grid detected by the detector according to the first embodiment. It is a schematic diagram for demonstrating the positional deviation of the 1st grid and the 2nd grid in the rotation direction around the optical axis of X-rays by 1st Embodiment. It is a schematic diagram (A)-(C) for demonstrating the sharpness of the self-image of the 1st grid. It is a flowchart for demonstrating the grid position adjustment processing by 1st Embodiment. It is a schematic diagram for demonstrating the 1st Fourier transform spectrum of the self-image of the 2nd lattice by 2nd Embodiment. It is a flowchart for demonstrating the grid position adjustment process by 2nd Embodiment. It is a schematic diagram which looked at the X-ray phase imaging system by 3rd Embodiment from the Y direction. It is a schematic diagram for demonstrating the intensity signal curve acquired by the X-ray phase imaging system by 3rd Embodiment. It is a flowchart for demonstrating the grid position adjustment process by 3rd Embodiment. It is a schematic diagram for demonstrating the 2nd Fourier transform spectrum by 1st modification of 3rd Embodiment. It is a schematic diagram for demonstrating the 3rd Fourier transform spectrum by the 2nd modification of 3rd Embodiment.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

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

(Configuration of X-ray phase imaging system)
First, with reference to FIG. 1, the configuration of the X-ray phase imaging system 100 according to the present embodiment of the present invention will be described.

As shown in FIG. 1, the X-ray phase imaging system 100 is a device that images the inside of the subject Q by utilizing the Talbot effect. The X-ray phase imaging system 100 is configured to image the subject Q while moving one of the plurality of grids in translation in the periodic direction (X direction) of the grids.

As shown in FIG. 1, the X-ray phase imaging system 100 controls an X-ray source 1, a detector 2, a plurality of grids including a first grid 3 and a second grid 4, an image processing unit 5, and a control unit. A unit 6, a storage unit 7, a grid position adjusting mechanism 8, and a grid moving mechanism 9 are provided. In the present specification, the direction from the X-ray source 1 toward the first grid 3 is the Z2 direction, and the direction opposite to the direction is the Z1 direction. Further, the left-right direction in the plane orthogonal to the Z direction is the X direction, the upper direction of the paper surface of FIG. 1 is the X1 direction, and the lower direction of the paper surface of FIG. 1 is the X2 direction. Further, the vertical direction in the paper surface orthogonal to the Z direction is the Y direction, the direction toward the front side of the paper surface in FIG. 1 is the Y1 direction, and the direction toward the back of the paper surface in FIG. 1 is the Y2 direction.

The X-ray source 1 is configured to generate X-rays by applying a high voltage and to irradiate the generated X-rays toward the subject Q.

The detector 2 is configured to detect X-rays, convert the detected X-rays into an electric signal, and read the converted electric signal as an image signal. 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. The plurality of conversion elements and pixel electrodes are arranged in an array in the X direction and the Y direction at a predetermined period. Further, the detector 2 is configured to output the acquired image signal to the image processing unit 5.

The first grid 3 has a plurality of slits 3a arranged in the X direction with _a predetermined period (pitch) p1 and an X-ray absorption unit 3b. Each of the slits 3a and the X-ray absorbing portion 3b is formed so as to extend linearly along the Y direction. Further, each of the slits 3a and the X-ray absorbing portion 3b is formed so as to extend in parallel with each other. The first grid 3 is a so-called absorption grid. The first grid 3 is irradiated with X-rays from the X-ray source 1. The first grid 3 is configured to use X-rays that have passed through each slit 3a as a line light source corresponding to the position of each slit 3a. That is, the first grid 3 is a grid for increasing the coherence of X-rays emitted from the X-ray source 1.

The second grid 4 is arranged between the first grid 3 and the detector 2, and is irradiated with X-rays that have passed through the first grid 3. The second grid 4 is provided to form a grid image (self-image 40 (see FIG. 5)) of the second grid 4 by the Talbot effect. When X-rays having coherence pass through the lattice in which the slit is formed, a lattice image (self-image 40) is formed at a position separated from the lattice by a predetermined distance (Talbot distance). This is called the Talbot effect.

The _second grid 4 has a plurality of slits 4a arranged in the X direction with a predetermined period (pitch) p2, and an X-ray phase changing portion 4b. Each of the slits 4a and the X-ray phase changing portion 4b is formed so as to extend linearly along the Y direction. Further, each of the slits 4a and the X-ray phase changing portion 4b is formed so as to extend in parallel with each other. The second grid 4 is a so-called phase grid. The first grid 3 and the second grid 4 are grids having different roles, but the slit 3a and the slit 4a each allow X-rays to pass through. Further, the X-ray absorbing unit 3b plays a role of shielding X-rays, and the X-ray phase changing unit 4b changes the phase of X-rays depending on the difference in refractive index from the slit 4a.

The image processing unit 5 is configured to generate a phase contrast image 10 (see FIG. 3) 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 10a (see FIG. 3), a phase differential image 10b (see FIG. 3), and a dark field image 10c (see FIG. 4) as the phase contrast image 10. do. The image processing unit 5 includes, for example, a processor such as a GPU (Graphics Processing Unit) or an FPGA (Field-Programmable Gate Array) configured for image processing.

The control unit 6 is configured to control the grid position adjusting mechanism 8 to adjust the relative positions of the first grid 3 and the second grid 4. The details of the adjustment processing of the relative positions between the first grid 3 and the second grid 4 by the control unit 6 will be described later. Further, the control unit 6 is configured to control the grid movement mechanism 9 to translate the second grid 4. The 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 10 and the like generated by the image processing unit 5. The storage unit 7 includes, for example, an HDD (Hard Disk Drive), a non-volatile memory, and the like.

The grid position adjusting mechanism 8 is configured to adjust the relative positions of the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays under the control of the control unit 6. In the first embodiment, the grid position adjusting mechanism 8 holds the first grid 3. The grid position adjusting mechanism 8 is configured to adjust the relative position between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays by adjusting the position of the first grid 3. ing.

The grid movement mechanism 9 is configured to translate any one of the plurality of grids in the periodic direction (X direction) of the grids under the control of the control unit 6. In the first embodiment, the grid moving mechanism 9 holds the second grid 4 and is configured to translate the second grid 4. That is, in the first embodiment, the X-ray phase imaging system 100 is configured to generate a phase contrast image 10 by a fringe scanning method in which imaging is performed while the second grid 4 is translated and moved by the grid moving mechanism 9. There is.

(Lattice position adjustment mechanism and grid movement mechanism)
As shown in FIG. 2, the grid position adjusting mechanism 8 has a rotation direction Rz around the X-direction, Y-direction, Z-direction, and Z-direction axes, a rotation direction Rx around the X-direction axis, and around the Y-direction axis. The first lattice 3 is configured to be movable in the rotation direction Ry of. Specifically, the grid position adjusting 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 connection unit 83, and a stage support unit drive unit 84. A stage support unit 85, a stage drive unit 86, and a stage 87 are included. The X-direction linear motion mechanism 80 is configured to be movable in the X-direction. The X-direction linear motion mechanism 80 includes, for example, a motor and the like. The Y-direction linear motion mechanism 81 is configured to be movable in the Y-direction. The Y-direction linear motion mechanism 81 includes, for example, a motor and the like. 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 and the like.

The grid position adjusting mechanism 8 is configured to move the first grid 3 in the X direction by the operation of the linear motion mechanism 80 in the X direction. Further, the grid position adjusting mechanism 8 is configured to move the first grid 3 in the Y direction by the operation of the Y-direction linear motion mechanism 81. Further, the grid position adjusting mechanism 8 is configured to move the first grid 3 in the Z direction by the operation of the Z-direction linear motion mechanism 82.

The stage support portion 85 supports the stage 87 from below (Y1 direction). The stage drive unit 86 is configured to reciprocate the stage 87 in the X direction. The bottom of the stage 87 is formed in a convex curved surface shape toward the stage support portion 85, and is configured to rotate around the optical axis of X-rays (Rz direction) by being reciprocated in the X direction. ing. Further, the stage support unit drive unit 84 is configured to reciprocate the stage support unit 85 in the Z direction. Further, the bottom of the stage support portion 85 is formed in a convex curved surface shape toward the linear motion mechanism connecting portion 83, and by being reciprocated in the Z direction, the stage support portion 85 rotates around the axis in the X direction (Rx direction). It is configured as follows. 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 axis in the Y direction (Ry direction). Therefore, the grid position adjusting mechanism 8 can rotate the grid around the central axis in the Y direction.

In the first embodiment, the grid moving mechanism 9 has the same configuration as the grid position adjusting mechanism 8. Therefore, like the grid position adjusting mechanism 8, the grid moving mechanism 9 has a rotation direction Rx around the central axis in the X direction, a Y direction, a Z direction, and an X direction, a rotation direction Ry around the central axis in the Y direction, and The subject Q is configured to be movable in the rotation direction Rz around the optical axis of the X-ray. The grid moving mechanism 9 is different from the grid position adjusting mechanism 8 that adjusts the relative positions of the first grid 3 and the second grid 4 in the rotation direction around the optical axis of X-rays under the control of the control unit 6. The second grid 4 is configured to be translated in the X direction.

In the first embodiment, the control unit 6 controls the grid movement mechanism 9 to perform image capture while moving the second grid 4 in translation. The image processing unit 5 generates an absorption image 10a, a phase differential image 10b, and a dark field image 10c shown in FIGS. 3A to 3C.

(Self-image of the second grid)
In the first embodiment, the second grid 4 is arranged at a position separated from the first grid 3 by a certain distance. Therefore, as shown in FIG. 4, the detector 2 detects the self-image 40 of the second grid 4. The self-image 40 has a bright portion 41 and a dark portion 42. A bright portion 41 is formed at a position where the X-rays diffracted by the second lattice 4 are intensified. Further, the dark portion 42 is formed at a position where the X-rays diffracted by the second lattice 4 weaken each other. The bright portion 41 and the dark portion 42 of the self-image 40 are formed at predetermined intervals p3 _, respectively.

The example shown in FIG. 5 is an arrangement when there is no positional deviation between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays. Specifically, in FIG. 5, the position shifts between the relative position of the first grid 3 in the rotation direction Rz ₀ around the optical axis of X-rays and the second relative position in the rotation direction Rz ₁ around the optical axis of X-rays. Shows the arrangement when is not occurring. In the example shown in FIG. 5, since there is no positional deviation between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of the X-ray, the self-image 40 is clear in the detector 2. Is detected in. In the first embodiment, the pixel size of the detector ₂ is a size capable of resolving one cycle p3 of the self-image 40.

Here, if a positional shift occurs between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of the X-ray, the self-image 40 becomes unclear. Hereinafter, the cause of the unclear self-image 40 will be described with reference to FIG.

FIG. 6A is an example in which there is no positional deviation between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays. The first grid 3 is configured to use X-rays that have passed through each slit 3a as a line light source corresponding to the position of each slit 3a. Therefore, attention is paid to one of the slits 3a, the slit 3a. Consider X-ray R1 and X-ray R2 emitted from two line light sources (line light source 1a and line light source 1b) having different positions in the Y direction in the slit 3a. Since the line light source 1a and the line light source 1b have the same position in the X direction, there is no path difference between the X-ray R1 and the X-ray R2 in the X direction. Therefore, the self-image 40a generated by the X-ray R1 irradiated from the line light source 1a to the second grid 4 and the self-image 40b generated by the X-ray R2 irradiated from the line light source 1b to the second grid 4 are the detector 2. Is detected at the same position. Therefore, the self-image 40 of the second grid 4 becomes clear. In the example shown in FIG. 6A, the self-image 40a and the self-image 40b are shown with a slight shift for convenience.

FIG. 6B is an example in which the first grid 3 and the second grid 4 are misaligned in the rotation direction Rz around the optical axis of the X-ray. The example shown in FIG. 6B is a case where the misalignment of the angle θ ₁ occurs between the first grid 3 and the second grid 4 as the misalignment. When a positional deviation of an angle θ ₁ occurs between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays, the positions of the line light source 1a and the line light source 1b are moved to a distance d1 in the X direction. Just shift. When the positions of the line light source 1a and the line light source 1b deviate by the distance d1 in the X direction, a difference occurs between the path of the X-ray R1 and the path of the X-ray R2 in the X direction. Therefore, as shown in FIG. 6B, the positions of the self-image 40a and the self-image 40b in the X direction are deviated by a distance d2. Since the position of the self-image 40a and the position of the self-image 40b deviate by a distance d2, the self-image 40a and the self-image 40b are detected in an overlapping state. Therefore, the self-image 40 becomes unclear.

FIG. 6C is an example in which the first grid 3 and the second grid 4 are displaced more than the example shown in FIG. 6B in the rotation direction Rz around the optical axis of X-rays. Is. Specifically, in the example shown in FIG. 6C, in the rotation direction Rz around the optical axis of X-rays, only an angle θ ₂ larger than the angle θ ₁ is located at the first grid 3 and the second grid 4. There is a gap. Therefore, in the example shown in FIG. 6C, the positions of the line light source 1a and the line light source 1b are displaced by the distance d3 in the X direction. The distance d3 is a value larger than the distance d1. Since the positions of the line light source 1a and the line light source 1b are displaced by the distance d3 in the X direction, the self-image 40a and the self-image 40b are displaced by a distance d4 in the X direction. Therefore, in the example shown in FIG. 6 (C), the self-image 40 is less clear than in the example shown in FIG. 6 (B). The distance d4 is a value larger than the distance d2. Further, in the example shown in FIG. 6C, the self-image 40a and the self-image 40b are displaced by approximately half a cycle in the X direction, so that the self-image 40 cannot be resolved.

Therefore, in the first embodiment, the control unit 6 is relative so as to sharpen the grid image (self-image 40) based on the sharpness C of the grid image (self-image 40) detected by the detector 2. It is configured to control the position deviation by the grid position adjusting mechanism 8. Specifically, in the first embodiment, the control unit 6 is configured to perform control for adjusting the positional deviation of the relative position based on the sharpness C of the self-image 40.

The control unit 6 has visibility V representing the contrast of the self-image 40 based on the maximum value I _max and the minimum value I _min of the pixel value of the self-image 40, or the bright part 41 and the dark part 42 of the self-image 40. The amplitude A representing the intensity difference is configured to be acquired as the sharpness C of the self-image 40. The maximum value I _max of the pixel value of the self-image 40 is the pixel value of the bright portion 41 of the self-image 40. Further, the minimum value I _min of the pixel value of the self-image 40 is the pixel value of the dark portion 42 of the self-image 40.

Visibility V can be expressed as the following equation (1) by using the maximum value I _max and the minimum value I _min of the pixel value of the self-image 40.

Further, the amplitude A can be expressed by the following equation (2) by using the maximum value I _max and the minimum value I _min of the pixel value of the self-image 40.

In the first embodiment, the control unit 6 acquires the visibility V acquired by the above equation (1) or the amplitude A acquired by the above equation (2) as the sharpness C of the self-image 40. It is configured. Further, the control unit 6 controls the grid position adjusting mechanism 8 to adjust the positional deviation of the relative position so that the sharpness C of the grid image (self-image 40) becomes larger than the predetermined threshold value Cth. It is configured in. The predetermined threshold value Cth is a value set by the arrangement of the X-ray source 1, the detector 2, and a plurality of grids. The predetermined threshold Cth is, for example, 0.3. As the sharpness C of the self-image 40, the visibility V may be used or the amplitude A may be used.

Next, with reference to FIG. 7, the processing of the grid position adjustment by the X-ray phase imaging system 100 according to the first embodiment will be described. The grid position adjustment process is started by inputting a signal for starting the grid position adjustment process to the control unit 6 by an input operation by a user or the like.

In step S1, the control unit 6 adjusts the position of the first grid 3 by controlling the grid position adjusting mechanism 8. Specifically, the control unit 6 moves the first grid 3 in a predetermined first direction by a predetermined distance (a predetermined angle) in the rotation direction Rz around the optical axis of the X-ray by the grid position adjusting mechanism 8. By letting it adjust the position.

Next, in step S2, the X-ray phase imaging system 100 acquires an image 43 (see FIG. 4) of the self-image 40. After that, the process proceeds to step S3.

In step S3, the control unit 6 acquires the sharpness C of the self-image 40. Specifically, the control unit 6 acquires the sharpness C of the self-image 40 by the above formula (1) or the above formula (2). After that, in step S4, the control unit 6 determines whether or not the sharpness C of the self-image 40 is larger than the predetermined threshold value Cth. When the sharpness C of the self-image 40 is larger than the predetermined threshold value Cth, the grid adjustment process is terminated. When the sharpness C of the self-image 40 is equal to or less than the predetermined threshold value Cth, the process proceeds to step S5.

In step S5, the control unit 6 determines whether or not the position of the grid is adjusted for the first time. In the case of the first grid position adjustment, the process proceeds to step S1. In the case of the second and subsequent grid position adjustments, the process proceeds to step S6.

In step S6, the control unit 6 determines whether or not the sharpness C of the self-image 40 is larger than the previous value. If the sharpness C of the self-image 40 is larger than the previous value, the process proceeds to step S1. If the sharpness C of the self-image 40 is equal to or less than the previous value, the process proceeds to step S7.

In step S7, the control unit 6 moves the first grid 3 by a predetermined distance (predetermined angle) in the second direction opposite to the first direction in which the position of the first grid 3 is adjusted in step S1. As a result, the position of the first grid 3 is adjusted. After that, the process proceeds to step S2.

The first direction and the second direction in steps S1 and S7 may be opposite to each other. That is, in the rotation direction Rz around the optical axis of X-rays, when the clockwise direction is the first direction, the second direction is the counterclockwise direction. Further, in the rotation direction Rz around the optical axis of X-rays, when the counterclockwise direction is the first direction, the second direction is the clockwise direction. Further, the position adjustment of the first grid 3 may be performed in a state where the subject Q is not arranged, or may be performed in a state where the subject Q is arranged. When the subject Q is arranged, the sharpness C of the self-image 40 may be obtained by using the maximum value I _max and the minimum value I _min of the pixel values of the background portion where the subject Q is not shown.

(Effect of the first embodiment)
In the first embodiment, the following effects can be obtained.

In the first embodiment, as described above, the X-ray phase imaging system 100 includes an X-ray source 1 that irradiates the subject Q with X-rays, and a detector 2 that detects the X-rays emitted from the X-ray source 1. , The first grid 3 arranged between the X-ray source 1 and the detector 2 to increase the coherence of the X-rays emitted from the X-ray source 1 and the X-rays from the first grid 3 are irradiated. A plurality of grids including a second grid 4 for forming a grid image (self-image 40), an image processing unit 5 that generates a phase contrast image 10 based on a signal detected by the detector 2, and an image processing unit 5. The grid position adjustment mechanism 8 that adjusts the relative position between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays, and the clear grid image (self-image 40) detected by the detector 2. A control unit 6 for controlling the positional deviation of the relative position by the grid position adjusting mechanism 8 is provided so as to make the lattice image (self-image 40) clear based on the degree C. As a result, the lattice image (self-image 40) can be made clear by suppressing the positional deviation between the first lattice 3 and the second lattice 4 in the rotation direction Rz around the optical axis of the X-ray. As a result, the lattice image (self-image 40) becomes unclear, and it is possible to suppress deterioration of the image quality of the obtained phase contrast image 10.

The phase contrast image 10 includes an absorption image 10a based on X-ray attenuation, a phase differential image 10b based on X-ray phase shift, and a dark field image obtained by a change in visibility based on small-angle X-ray scattering. 10c and is included. Since the absorption image 10a is calculated based on the average intensity of the lattice image, the image quality of the obtained image does not deteriorate even if the lattice image (self-image 40) is unclear. On the other hand, regarding the phase differential image 10b and the dark field image 10c, a grid image (self-image 40) when the subject Q is not arranged and an image is taken, and a grid image (self-image 40) when the subject Q is arranged and imaged. ) And the image is generated based on the change. Therefore, by making the lattice image (self-image 40) clear, it is possible to suppress deterioration of the image quality of the obtained image.

Further, in the first embodiment, as described above, the control unit 6 grids the positional deviation of the relative positions so that the sharpness C of the grid image (self-image 40) becomes larger than the predetermined threshold value Cth. It is configured to control the adjustment by the position adjusting mechanism 8. As a result, the position adjustment of the grid can be completed when the sharpness C of the grid image (self-image 40) becomes larger than the predetermined threshold value Cth. As a result, it is possible to suppress an increase in the number of grid adjustments as compared with the case where the relative positions between the grids of a plurality of grids are adjusted so that the sharpness C of the grid image (self-image 40) is maximized. Therefore, the grid adjustment time can be shortened.

Further, in the first embodiment, as described above, the second grid 4 is a phase grid for forming the self-image 40 as a grid image, and the control unit 6 is based on the sharpness C of the self-image 40. Therefore, it is configured to control to adjust the positional deviation of the relative position. As a result, it is possible to prevent the self-image 40 from becoming unclear in the Talbot interference in which the image of the subject Q is acquired using the self-image 40. As a result, it is possible to suppress deterioration of the image quality of the phase contrast image 10 due to the unclearness of the self-image 40.

Further, in the first embodiment, as described above, the control unit 6 has visibility V representing the contrast of the self-image 40 based on the maximum value I _max and the minimum value I _min of the pixel values of the self-image 40, or The amplitude A representing the intensity difference between the bright portion 41 and the dark portion 42 of the self-image 40 is configured to be acquired as the sharpness C of the self-image 40. As a result, it is possible to acquire the sharpness C of the self-image 40 by acquiring the visibility V or the amplitude A. Therefore, the sharpness C of the self-image 40 can be obtained by visually observing the image 43 of the self-image 40. The sharpness C of the self-image 40 can be accurately acquired as compared with the case of determination. As a result, it is possible to accurately acquire the positional deviation between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays, so that in the rotation direction Rz around the optical axis of X-rays. The positional deviation between the first grid 3 and the second grid 4 can be accurately adjusted.

[Second Embodiment]
Next, the configuration of the X-ray phase imaging system 200 (see FIG. 1) according to the second embodiment will be described with reference to FIGS. 1 and 8. The X-ray phase imaging system 200 according to the second embodiment is different from the first embodiment in which the sharpness C of the self-image 40 is acquired based on the maximum value I _max and the minimum value I _min of the pixel values of the self-image 40. The control unit 60 is configured to acquire the sharpness C of the self-image 40 based on the first Fourier transform spectrum 44 (see FIG. 8) obtained by Fourier transforming the image 43 of the self-image 40. .. The first Fourier transform spectrum 44 is a spectrum obtained by calculating the absolute value of the value (complex number) obtained by Fourier transforming the image of the self-image 40. The same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 1, the X-ray phase imaging system 200 includes an X-ray source 1, a detector 2, a first grid 3, a second grid 4, an image processing unit 5, a control unit 60, and storage. A unit 7, a grid position adjusting mechanism 8, and a grid moving mechanism 9 are provided. The X-ray phase imaging system 200 has the same configuration as the X-ray phase imaging system 100 according to the first embodiment, except that the control unit 60 is provided.

In the second embodiment, the control unit 60 has an intensity I ₀ and a first-order peak 46 of the 0th-order peak 45 (see FIG. 8) in the first Fourier transform spectrum 44 obtained by Fourier transforming the image 43 of the self-image 40. With the visibility V _FFT representing the contrast of the self-image 40 based on the intensity I ₁ of (see FIG. 8) or the intensity I ₁ of the primary peak 46, or the bright portion 41 of the self-image 40 (see FIG. 8). The amplitude A _FFT representing the intensity difference from the dark portion 42 (see FIG. 8) is configured to be acquired as the sharpness C of the self-image 40.

FIG. 8 is a schematic diagram showing an image 43 of the self-image 40 and a first Fourier transform spectrum 44 obtained by Fourier transforming the image 43 of the self-image 40. As shown in FIG. 8, the control unit 60 is configured to acquire the first Fourier transform spectrum 44 by Fourier transforming the image 43 of the self-image 40. Further, the control unit 60 is configured to acquire the intensity I ₀ of the 0th-order peak 45 and the intensity I ₁ of the 1st-order peak 46 in the acquired first Fourier transform spectrum 44. Here, the 0th-order peak 45 is a peak having a frequency of 0. Further, the primary peak 46 is a peak corresponding to the frequency of the self-image 40.

In the second embodiment, the visibility _VFFT representing the contrast of the self-image 40 can be expressed by the following equation (3).

Further, in the second embodiment, the amplitude _AFFT representing the intensity difference between the bright portion 41 and the dark portion 42 of the self-image 40 can be expressed by the following equation (4).

In the second embodiment, the control unit 60 acquires the visibility V _FFT acquired by the above equation (3) or the amplitude A _FFT acquired by the above equation (4) as the sharpness C of the self-image 40. Is configured to

Next, with reference to FIG. 9, the processing of the grid position adjustment performed by the control unit 60 according to the second embodiment will be described. A detailed description of the step of performing the same processing as that of the control unit 6 according to the first embodiment will be omitted.

In steps S1 and S2, the control unit 60 acquires the image 43 of the self-image 40 after adjusting the position of the first grid 3. After that, the process proceeds to step S8.

In step S8, the control unit 60 acquires the first Fourier transform spectrum 44 by Fourier transforming the image 43 of the self-image 40. Then, in step S9, the control unit 60 is based on the intensity I ₀ of the 0th-order peak 45 and the intensity I ₁ of the 1st-order peak 46 or the intensity I ₁ of the 1st-order peak 46 in the first Fourier transform spectrum 44. The sharpness C of the self-image 40 is acquired.

After that, the processing performs the processing of steps S3 to S7 in the same manner as in the first embodiment, and ends the grid position adjustment processing.

The other configurations of the second embodiment are the same as those of the first embodiment.

(Effect of the second embodiment)
In the second embodiment, the following effects can be obtained.

In the second embodiment, as described above, the control unit 60 has the intensity I ₀ of the 0th-order peak 45 and the 1st-order peak 46 in the 1st Fourier transform spectrum 44 obtained by Fourier transforming the image 43 of the self-image 40. Intensity I ₁ of the self-image 40, or the visibility V _FFT representing the contrast of the self-image 40 based on the intensity I ₁ of the first-order peak 46 in the first Fourier transform spectrum 44, or the bright and dark areas 42 of the self-image 40. The amplitude A _FFT representing the intensity difference of the self-image 40 is configured to be acquired as the sharpness C of the self-image 40. As a result, the self-image 40 is based on the intensity I ₀ of the 0th-order peak 45 of the first Fourier transform spectrum 44 and the intensity I ₁ of the first-order peak 46 or the intensity I ₁ of the first-order peak 46 of the first Fourier transform spectrum 44. Since the sharpness C can be acquired, the sharpness C of the self-image 40 can be accurately acquired as compared with the case where the sharpness C of the self-image 40 is visually acquired. As a result, in the configuration of acquiring the first Fourier transform spectrum 44 as well as the configuration of acquiring the visibility V or the amplitude A based on the maximum value I _max and the minimum value I _min of the pixel value of the self-image 40, X It is possible to accurately adjust the positional deviation between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of the line.

The other effects of the second embodiment are the same as those of the first embodiment.

[Third Embodiment]
Next, the X-ray phase imaging system 300 (see FIG. 10) according to the third embodiment will be described with reference to FIGS. 10 and 11. Unlike the first embodiment, which includes the first grid 3 and the second grid 4 as the plurality of grids, the X-ray phase imaging system 300 in the third embodiment has the first grid 3 and the second grid as the plurality of grids. In addition to the grid 4, it further includes a third grid 20 (see FIG. 10) disposed between the second grid 4 and the detector 2. The same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the third embodiment, the X-ray phase imaging system 300 controls the X-ray source 1, the detector 2, the first grid 3, the second grid 4, the third grid 20, and the image processing unit 5. A unit 61, a storage unit 7, a grid position adjusting mechanism 8, and a grid moving mechanism 9 are provided.

The third grid 20 has a plurality of X-ray transmitting portions 20a and X-ray absorbing portions 20b arranged in the X direction with a predetermined period ₍ pitch) p4. Each of the X-ray transmitting portion 20a and the X-ray absorbing portion 20b is formed so as to extend linearly along the Y direction. Further, the X-ray transmitting portion 20a and the X-ray absorbing portion 20b are each formed so as to extend in parallel with each other. The third grid 20 is a so-called absorption grid. The first grid 3, the second grid 4, and the third grid 20 are grids having different roles, but the slit 3a, the slit 4a, and the X-ray transmitting portion 20a each transmit X-rays. Further, the X-ray absorbing unit 3b and the X-ray absorbing unit 20b each play a role of shielding X-rays, and the X-ray phase changing unit 4b changes the phase of X-rays depending on the difference in the refractive index from the slit 4a. Let me.

The third grid 20 is arranged between the second grid 4 and the detector 2, and is irradiated with X-rays that have passed through the second grid 4. Further, the third grid 20 is arranged at a position separated from the second grid 4 by the Talbot distance. The third grid 20 interferes with the self-image 40 of the second grid 4 to form moire fringes M (see FIG. 11) on the detection surface of the detector 2.

Here, the moire fringe M is generated by interfering the self-image 40 of the second grid 4 with the third grid 20. The _third grid 20 is a grid designed so that the cycle p4 of the grid substantially coincides with the cycle p3 of the self-image 40 of the second grid ₄ . Therefore, if the moire fringes M are clear, it is considered that the self-image 40 of the second grid 4 is clear. Further, if the intensity difference between the bright portion M1 and the dark portion M2 of the moire fringe M is large, it is considered that the moire fringe M is clear. That is, the amplitude A of the moire fringes M is also an index showing the sharpness of the moire fringes M. Therefore, in the third embodiment, the control unit 61 sharpens the visibility V representing the contrast of the moire fringes M or the amplitude A representing the intensity difference between the bright portion M1 and the dark portion M2 of the moire fringes M in the self-image 40. It is configured to be acquired as degree C.

In the third embodiment, as shown in FIG. 11, the X-ray phase imaging system 300 acquires a plurality of moire fringe images 21 by imaging while moving the second grid 4 in translation. In the third embodiment, the moiré fringe image 21a, the moiré fringe image 21b, the moiré fringe image 21c, and the moiré fringe image 21d in each step are acquired by taking an image while moving the second grid 4 in translation four times (4 steps). do. The control unit 61 pays attention to the pixel P in each moire fringe image 21 and acquires the pixel value (signal strength) of the pixel P in each moire fringe image 21. Specifically, the control unit 61 acquires the signal strength of the pixel P1 in the moire fringe image 21a. Further, the control unit 61 acquires the signal strength of the pixel P2 in the moire fringe image 21b. Further, the control unit 61 acquires the signal strength of the pixel P3 in the moire fringe image 21c. Further, the control unit 61 acquires the signal strength of the pixel P4 in the moire fringe image 21c. The pixels P1 to P4 are pixels having the same coordinates in each moire fringe image 21.

The graph G shown in FIG. 11 is a graph of the intensity signal curve 22 in which the horizontal axis is the translation amount (translation distance) of the second grid 4 and the vertical axis is the signal intensity. The control unit 61 plots the pixel values (signal intensities) of the pixels P (pixels P1 to P4) in each moire fringe image 21 and performs fitting with a sine wave to acquire an intensity signal curve 22. In the third embodiment, the control unit 61 acquires the maximum value of the acquired signal intensity of the intensity signal curve 22 as I _max and the minimum value as I _min .

In the third embodiment, the control unit 61 performs a moire fringe M based on the maximum value I _max and the minimum value I _min of the signal intensity of the intensity signal curve 22 acquired by imaging while moving the second grid 4 in translation. It is configured to acquire the visibility V of the above or the amplitude A of the moire fringe M. Specifically, the maximum value I _max and the minimum value I _min of the signal strength of the intensity signal curve 22, and the control unit 61, according to the above equation (1) or the above equation (2), the visibility V of the moire fringe M. Alternatively, it is configured to acquire the amplitude A of the moire fringe M.

Next, with reference to FIG. 12, the processing of the grid position adjustment performed by the control unit 61 according to the third embodiment will be described. A detailed description of the step of performing the same processing as that of the control unit 6 according to the first embodiment will be omitted.

In step S1, the control unit 60 adjusts the position of the first grid 3 by controlling the grid position adjusting mechanism 8. After that, the process proceeds to step S10.

In step S10, the control unit 61 acquires an intensity signal curve 22 based on a plurality of moire fringe images 21 imaged while moving the second grid 4 in translation. After that, in step S11, the control unit 61 acquires the maximum value I _max and the minimum I _min of the signal intensity from the intensity signal curve 22. After that, the processing performs the processing of steps S3 to S7 in the same manner as in the first embodiment, and ends the grid position adjustment processing.

The other configurations of the third embodiment are the same as those of the first embodiment.

(Effect of the third embodiment)
In the third embodiment, the following effects can be obtained.

In the third embodiment, as described above, the third grid 20 is arranged between the second grid 4 and the detector 2 to generate moire fringes M by interference with the self-image 40 of the second grid 4. Including further. As a result, even when the size of the pixel size of the detector ₂ is larger than the size of one cycle p3 of the self-image 40 of the second grid 4, the moire fringes M generated by arranging the third grid 20 By detecting the above, the phase contrast image 10 can be generated. As a result, even when the pixel size of the detector ₂ is larger than the size of one cycle p3 of the self-image 40, the phase contrast image 10 can be generated, so that the degree of freedom of selection of the detector 2 is improved. Can be made to.

Further, in the third embodiment, as described above, the control unit 61 sets the visibility V representing the contrast of the moire fringes M or the amplitude A representing the intensity difference between the bright portion M1 and the dark portion M2 of the moire fringes M. It is configured to be acquired as the sharpness C of the self-image 40. As a result, the sharpness C of the self-image 40 can be indirectly acquired by acquiring the visibility V or the amplitude A of the moire fringe M. As a result, by adjusting a plurality of grids based on the visibility V or the amplitude A of the moire fringe M, the self-image 40 can be made clear, and the phase contrast image caused by the self-image 40 becoming unclear. It is possible to suppress the deterioration of the image quality of 10.

Further, in the third embodiment, as described above, the control unit 61 has the maximum value I _max and the minimum value I _min of the signal intensity of the intensity signal curve 22 acquired by imaging while moving the second grid 4 in translation. Based on the above, it is configured to acquire the visibility V of the moire fringe M or the amplitude A of the moire fringe M. This makes it possible to acquire the intensity signal curve 22 of the moire fringes M based on the change in the signal intensity of a predetermined pixel P in the plurality of moire fringe images 21 captured while the second lattice 4 is translated and moved. Therefore, in one moire fringe image 21, the pixels of the bright part M1 and the dark part M2 are selected, and the pixel values of the selected pixels are set to the maximum value I _max and the minimum value I _min of the pixel values of the moire fringe M. The maximum value I _max and the minimum value I _min of the pixel value of the moire fringe M can be accurately obtained. Therefore, the sharpness of the moire fringes M can be obtained with high accuracy. As a result, it is possible to accurately acquire the sharpness C of the self-image 40, so that the positional deviation between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of the X-ray can be obtained. It can be adjusted accurately.

The other effects of the third embodiment are the same as those of the first embodiment.

(Modification example)
It should be noted that the embodiments disclosed this time are exemplary in all respects and are not considered to be restrictive. The scope of the present invention is shown by the scope of claims, not the description of the above-described embodiment, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims.

For example, in the first to third embodiments, the second grid 4 shows an example of a phase grid as a plurality of grids, but the present invention is not limited to this. For example, the second grid 4 is an absorption grid that forms a striped pattern generated by shielding a part of X-rays as a grid image, and the control unit 6 has the relative position based on the sharpness of the striped pattern. It may be configured to perform control for adjusting the misalignment of. With this configuration, the X-rays are generated by the second lattice 4 in the same manner as the interferometer that generates the phase contrast image 10 based on the self-image 40 generated by the interference of the X-rays diffracted by the second lattice 4. Even in a non-interferometer that images the subject Q based on the striped pattern of the second grid 4 caused by being partially shielded, the phase contrast image 10 caused by the striped pattern of the second grid 4 becoming unclear. Deterioration of image quality can be suppressed. Further, the striped pattern of the second grid 4 is generated by shielding a part of X-rays. Therefore, unlike the Talbot interferometer that produces the self-image 40 of the second grid 4, the second grid 4 does not have to be arranged at a predetermined distance (Talbot distance) from the first grid 3. As a result, the degree of freedom in the arrangement position of the second lattice 4 can be improved.

Further, in the first to third embodiments, an example of the configuration in which the grid position adjusting mechanism 8 moves the second grid 4 is shown, but the present invention is not limited to this. For example, the grid position adjusting mechanism 8 may be configured to move the first grid 3 in the X direction for imaging. Further, when the third grid 20 (see FIG. 10) is provided as the plurality of grids, the grid position adjusting mechanism 8 may be configured to move the third grid 20 in the X direction for imaging.

Further, in the first to third embodiments, the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays are adjusted by adjusting the position of the first grid 3 by the grid position adjusting mechanism 8. Although an example of the configuration for adjusting the relative position with the above is shown, the present invention is not limited to this. For example, the grid position adjusting mechanism 8 adjusts the position of the second grid 4 to adjust the relative position between the first grid 3 and the second grid 4 in the rotation direction Rz around the optical axis of X-rays. It may be.

Further, in the first to third embodiments, the control unit 6 (60, 61) adjusts the position of the grid when the sharpness C of the grid image (self-image 40) becomes larger than the predetermined threshold value Cth. Although an example of the configuration for terminating the above is shown, the present invention is not limited to this. For example, the control unit 6 (60, 61) may be configured to adjust the position of the grid so that the sharpness C of the grid image (self-image 40) is maximized. However, when the control unit 6 (60, 61) adjusts the position of the grid so that the sharpness C of the grid image (self-image 40) is maximized, the time required for the adjustment increases. Therefore, it is preferable that the grid position adjustment is completed when the sharpness C of the grid image (self-image 40) becomes larger than the predetermined threshold value Cth.

Further, in the first to third embodiments, the control unit 6 (60, 61) has a self-image 40 based on the visibility V (visibility V _FFT ) or the amplitude A (amplitude A _FFT ) of the self-image 40. Although an example of the configuration for acquiring the sharpness C of is shown, the present invention is not limited to this. For example, the control unit 6 (60, 61) sharpens the self-image 40 based on an index that can be acquired from the image 43 of the self-image 40 other than the visibility V (visibility _{VFFT) or the amplitude A (amplitude A FFT )} . It may be configured to acquire the degree C. For example, the control unit 6 (60, 61) acquires the vibration value of the self-image 40 as an RMS (Root Mean Square), and acquires the sharpness C of the self-image 40 using the acquired RMS. It may be configured as follows.

Further, in the first to third embodiments, an example of the configuration in which the X-ray phase imaging system 100 (200, 300) includes the grid position adjusting mechanism 8 and the grid moving mechanism 9 is shown. Not limited to. For example, the X-ray phase imaging system 100 (200, 300) may be configured to include only the grid position adjusting mechanism 8. When the X-ray phase imaging system 100 (200, 300) is configured to include only the grid position adjusting mechanism 8, the grid position adjusting mechanism 8 adjusts the position of the second grid 4, and the second grid 4 is moved in translation. It may be configured to take an image.

Further, in the third embodiment, the control unit 61 sets the visibility V, which represents the contrast of the moire fringes M, or the amplitude A, which represents the intensity difference between the bright portion M1 and the dark portion M2 of the moire fringes M, of the self-image 40. Although an example of the configuration to be acquired as the sharpness C is shown, the present invention is not limited to this. For example, the control unit 161 (see FIG. 10) has the intensity of the 0th-order peak 51 and the intensity of the 1st-order peak 52 in the second Fourier transform spectrum 50 obtained by Fourier transforming the moire fringe image 21 as shown in FIG. Based on the intensity or the intensity of the first-order peak 52 in the second Fourier transform spectrum 50, the visibility _VFFT representing the contrast of the moire fringes M or the intensity difference between the bright part M1 and the dark part M2 of the moire fringes M is shown. The amplitude A _FFT may be configured to be acquired as the sharpness C of the self-image 40. Since the configuration in which the control unit 61 acquires the V _FFT or the A _FFT based on the second Fourier transform spectrum 50 is the same as that in the second embodiment, detailed description thereof will be omitted. With the above configuration, in the configuration for acquiring the second Fourier transform spectrum 50 as in the configuration for acquiring the first Fourier transform spectrum 44, the first lattice 3 in the rotation direction Rz around the optical axis of the X-rays 3 And the position deviation between the second lattice 4 and the second lattice 4 can be accurately adjusted. Further, the moire fringe image 21 is an example of the "image of moire fringes" in the claims.

Further, in the third embodiment, the control unit 61 determines the visibility V of the moire fringe M or the amplitude A of the moire fringe M based on the maximum value I _max and the minimum value I _min of the signal intensity of the intensity signal curve 22. Although an example of the configuration is shown so as to obtain, the present invention is not limited to this. For example, as shown in FIG. 14, the control unit 261 (see FIG. 10) is obtained by Fourier transforming the intensity signal curve 22 obtained by imaging while moving any one of the plurality of lattices in translation. Visibility _VFFT representing the contrast of the moire fringes M based on the intensity of the 0th-order peak 54 and the intensity of the 1st-order peak 55 in the 3rd Fourier transform spectrum 53, or the intensity of the 1st-order peak 55 in the 3rd Fourier transform spectrum 53. Alternatively, the amplitude A _FFT representing the intensity difference between the bright portion M1 and the dark portion M2 of the moire fringe M may be configured to be acquired as the sharpness C of the self-image 40. Since the configuration in which the control unit 61 acquires the V _FFT or the A _FFT based on the third Fourier transform spectrum 53 is the same as that in the second embodiment, detailed description thereof will be omitted. With the above configuration, X-ray light is also used in the configuration for acquiring the third Fourier transform spectrum 53, as in the configuration for acquiring the first Fourier transform spectrum 44 and the configuration for acquiring the second Fourier transform spectrum 50. The positional deviation between the first lattice 3 and the second lattice 4 in the rotation direction Rz around the axis can be accurately adjusted.

Further, in the first to third embodiments, for convenience of explanation, an example in which the control processing of the control unit 6 (60, 61) is described by using a flow-driven flowchart in which the processing is sequentially performed along the processing flow. However, the present invention is not limited to this. In the present invention, the control processing of the control unit 6 (60, 61) may be performed by an event-driven type (event-driven type) processing in which the processing is executed in event units. In this case, it may be completely event-driven, or it may be a combination of event-driven and flow-driven.

1 X-ray source 2 Detector 3 1st grid 4 2nd grid 5 Image processing unit 6, 60, 61, 161, 261 Control unit 8 Grid position adjustment mechanism 10 Phase contrast image 20 3rd grid 21 Moire fringe image (moire fringe) Image of)
40, 40a, 40b Self-image 41 Bright part of self-image 42 Dark part of self-image 43 Image of self-image 44 1st Fourier transformation spectrum 45, 51, 54 0th peak 46, 52, 55 1st peak 50 2nd Fourier transformation Spectrum 53 Third Fourier transform spectrum 100, 200, 300 X-ray phase imaging system A, A FFT Intensity representing the difference in intensity between the bright and dark areas of the _FFT self-image (moire fringes) C Self-image sharpness Cth Predetermined threshold I ₀ 0th-order peak intensity I ₁ 1st-order peak intensity I _max Maximum pixel value of self-image image (or moire fringe image) I _min Minimum pixel value of self-image image (or moire fringe image) M Moire fringe M1 Moire fringe bright part M2 Moire fringe dark part Q Subject Rz, Rz ₀ , Rz ₁ Visibility showing the contrast of the rotation direction V, V _FFT self-image (moire fringe) around the optical axis of X-rays.

Claims (10)

An X-ray source that irradiates the subject with X-rays,
A detector that detects X-rays emitted from the X-ray source, and
A first grid, which is arranged between the X-ray source and the detector to increase the coherence of X-rays emitted from the X-ray source, and X-rays from the first grid are irradiated. Multiple grids, including a second grid for forming the grid image, and
An image processing unit that generates a phase contrast image based on the signal detected by the detector, and an image processing unit.
A grid position adjusting mechanism that adjusts the relative position between the first grid and the second grid in the direction of rotation around the optical axis of X-rays, and
A control unit that controls adjustment of the positional deviation of the relative position by the grid position adjusting mechanism so as to make the grid image clear based on the sharpness of the grid image detected by the detector is provided. ,
The second grid is a phase grid for forming a self-image as the grid image.
The control unit is an X-ray phase imaging system configured to control the positional deviation of the relative position based on the sharpness of the self-image . The control unit is configured to control the position deviation of the relative position by the grid position adjusting mechanism so that the sharpness of the grid image becomes larger than a predetermined threshold value. The X-ray phase imaging system according to 1. The control unit determines the visibility representing the contrast of the self-image or the amplitude representing the intensity difference between the bright part and the dark part of the self-image based on the maximum value and the minimum value of the pixel value of the self-image. The X-ray phase imaging system according to claim 1 , which is configured to acquire the sharpness of the self-image. The control unit performs the intensity of the 0th-order peak and the intensity of the 1st-order peak in the 1st Fourier transform spectrum obtained by Fourier transforming the image of the self-image, or the intensity of the 1st-order peak in the 1st Fourier transform spectrum. Based on the above, it is configured to acquire the visibility representing the contrast of the self-image or the amplitude representing the intensity difference between the bright part and the dark part of the self-image as the sharpness of the self-image. The X-ray phase imaging system according to 1 . The X-ray phase according to claim 1 , further comprising a third grid arranged between the second grid and the detector to cause moire fringes due to interference of the second grid with the self-image. Imaging system. The control unit is configured to acquire the visibility representing the contrast of the moire fringes or the amplitude representing the intensity difference between the bright part and the dark part of the moire fringes as the sharpness of the self-image. Item 5. The X-ray phase imaging system according to Item 5. The control unit performs the intensity of the 0th-order peak and the intensity of the 1st-order peak in the 2nd Fourier transform spectrum obtained by Fourier transforming the image of the moire fringes, or the intensity of the 1st-order peak in the 2nd Fourier transform spectrum. Based on the above, it is configured to acquire the visibility representing the contrast of the moire fringes or the amplitude representing the intensity difference between the bright part and the dark part of the moire fringes as the sharpness of the self-image. 5. The X-ray phase imaging system according to 5. The control unit has the visibility of the moire fringes or the visibility based on the maximum value and the minimum value of the signal intensity of the intensity signal curve obtained by imaging while moving any one of the plurality of lattices in translation. The X-ray phase imaging system according to claim 6 , which is configured to acquire the amplitude of the moire fringes. The control unit transfers the intensity and the first-order peak of the 0th-order peak in the third Fourier transform spectrum obtained by Fourier-transforming the intensity signal curve obtained by imaging while translating any one of the plurality of lattices. Based on the intensity of the first-order peak in the third Fourier transform spectrum, the visibility representing the contrast of the moire fringes, or the amplitude representing the intensity difference between the bright part and the dark part of the moire fringes is described above. The X-ray phase imaging system according to claim 6 , which is configured to acquire the sharpness of a self-image. The second grid is an absorption grid that forms a striped pattern generated by shielding a part of X-rays as the grid image.
The X-ray phase imaging system according to claim 1, wherein the control unit controls to adjust the positional deviation of the relative position based on the sharpness of the striped pattern.

Images