X-ray phase difference imaging system and image processing method

Abstract

To provide an X-ray phase difference imaging system and an image processing method, capable of suppressing a moire artifact in a phase contrast image generated, even with a large deviation between a set value of a movement of a grating and an actual movement of the grating.SOLUTION: An X-ray phase difference imaging system 100 includes: an X-ray source 11; a plurality of gratings 20; a detector 12 configured to detect X-ray; a grating movement mechanism 40; and a control part 30 configured to generate a phase contrast image. The control part 30 acquires, to reduce a moire artifact, an analysis cycle showing a cycle of an intensity change showing a change in a pixel value of each detected pixel, and adjusts a set value of a movement of a second grating 22 to generate a phase contrast image, according to the acquired analysis cycle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an X-ray phase-contrast imaging system and an image processing method, and more particularly to an X-ray phase-contrast imaging system that performs imaging using a plurality of gratings. [Background technology]

[0002] 2. Description of the Related Art Conventionally, an X-ray phase-contrast imaging system that performs imaging using a plurality of gratings is known (see, for example, Patent Document 1).

[0003] The X-ray phase-contrast imaging system disclosed in the above Patent Document 1 performs X-ray imaging using a Talbot-Lau interferometer that uses multiple gratings to perform imaging, and generates a phase contrast image by a fringe scanning method. In the Talbot-Lau interferometer, imaging is performed multiple times while translating one of the multiple gratings in a direction perpendicular to the direction in which the grating pattern extends. In the fringe scanning method, a phase contrast image is generated based on the intensity change of the pixel value of each pixel of the X-ray image captured multiple times while translating the grating. In the fringe scanning method, the intensity change of the pixel value of each pixel of the X-ray image is regarded as data at each phase of a function whose waveform changes depending on the period of the grating pattern, and the waveform of the function is determined, and a phase contrast image is generated based on the function whose waveform has been determined.

[0004] Here, due to changes in the relative position of the grating caused by thermal fluctuations and the movement accuracy of the grating movement mechanism, the period of the intensity change of the acquired pixel value may differ from the period of the grating pattern. In that case, the waveform of the function deviates from the actual data, and artifacts occur as noise components in the obtained image. In contrast, the X-ray phase contrast imaging system disclosed in the above Patent Document 1 uses the period of the function representing the intensity change of the pixel value as a variable and obtains an optimal solution of the period by approximation, thereby suppressing the occurrence of artifacts in the obtained phase contrast image even if there is a discrepancy between the period of the intensity change of the pixel value at each pixel and the period of the grating. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6743983 Summary of the Invention [Problem to be solved by the invention]

[0006] Here, not only the change in the relative position of the grating due to thermal fluctuation, or the deviation between the period of the intensity change and the period of the grating pattern due to the movement accuracy of the grating movement mechanism, but also the deviation may occur between the set value for the movement of the grating and the actual movement of the grating based on the set value. For example, the actual movement amount of the grating and the actual angular position of the grating may deviate from the set value of the movement amount of the grating and the set angle of the angular position of the grating. In that case, in the fringe scanning method for generating a phase contrast image, the period of the intensity change of the acquired pixel value is different in magnitude from the period of the grating pattern, so that artifacts occur in the acquired phase contrast image. Therefore, as in the X-ray phase contrast imaging system described in the above Patent Document 1, it is considered to generate a phase contrast image by determining the waveform of a function from the intensity change of the pixel value of each pixel of the X-ray image by obtaining an optimal solution of the period of the intensity change of the acquired pixel value. However, in the X-ray phase contrast imaging system described in the above Patent Document 1, the phase contrast image is generated by determining the waveform of a function representing the intensity change by approximation for the intensity change of the pixel value detected in a state where there is a deviation from the set value of the movement of the grating. Therefore, when there is a large deviation between the set value in the movement of the grating and the actual movement of the grating based on the set value, even if a phase contrast image is generated by determining the waveform of a function from the intensity change of the pixel value of each pixel of an X-ray image as in the X-ray phase contrast imaging system described in the above Patent Document 1, the phase contrast image is generated based on the intensity change of the pixel value detected in a state where there is a deviation from the set value, so that artifacts (moiré artifacts) contained in the phase contrast image cannot be sufficiently suppressed. Therefore, it is desired to suppress moiré artifacts in the generated phase contrast image even when there is a large deviation between the set value in the movement of the grating and the actual movement of the grating.

[0007] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide an X-ray phase contrast imaging system and an image processing method that are capable of suppressing moiré artifacts in the generated phase contrast image even when there is a large discrepancy between the set value for the movement of the grating and the actual movement of the grating. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, an X-ray phase contrast imaging system in a first aspect of the present invention includes an X-ray source, a plurality of gratings including a first grating for forming a self-image by X-rays irradiated from the X-ray source and a second grating for interfering with the self-image of the first grating, a detector for detecting X-rays irradiated from the X-ray source, a grating movement mechanism for moving at least one of the plurality of gratings, and a control unit for generating a phase contrast image based on an intensity change representing a change in pixel value of each pixel detected by the detector while moving a scanning grating, which is at least one of the plurality of gratings, by the grating movement mechanism, and the control unit acquires an analysis period representing a period of intensity change in order to reduce moiré artifacts, which are noise components included in the phase contrast image, and adjusts a setting value for the movement of the scanning grating for generating the phase contrast image based on the acquired analysis period.

[0009] In order to achieve the above-mentioned object, an image processing method in a second aspect of the present invention includes the steps of: detecting X-rays irradiated from an X-ray source and passing through multiple gratings while moving a scanning grating, which is at least one of multiple gratings including a first grating for forming a self-image by X-rays irradiated from an X-ray source and a second grating for interfering with the self-image of the first grating; generating a phase contrast image based on intensity changes that represent changes in pixel values ​​of each detected pixel; acquiring an analysis period that represents the period of intensity changes in order to reduce moiré artifacts, which are noise components included in the generated phase contrast image; and adjusting a setting value for the movement of the scanning grating for generating the phase contrast image based on the acquired analysis period. Effect of the Invention

[0010] As described above, the X-ray phase-contrast imaging system according to the first aspect and the image processing method according to the second aspect of the present invention acquire an analysis period that represents a period of intensity change in order to reduce moiré artifacts, which are noise components included in a phase contrast image. The X-ray phase-contrast imaging system according to the first aspect and the image processing method according to the second aspect adjust a set value of the movement of the scanning grating for generating a phase contrast image based on the acquired analysis period. In this way, by adjusting the set value of the movement of the grating based on the acquired analysis period, the set value can be adjusted so as to reduce the deviation of the actual movement of the grating from the set value of the movement of the grating. Therefore, a phase contrast image can be generated based on the intensity change of pixel values ​​detected in a state in which the deviation from the set value of the movement of the grating is reduced. As a result, even when the deviation between the set value of the movement of the grating and the actual movement of the grating is large, the moiré artifacts in the generated phase contrast image can be suppressed. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of an X-ray phase-contrast imaging system according to an embodiment of the present invention viewed from the Y direction. [Diagram 2] 5A and 5B are schematic diagrams for explaining the configuration of a grating moving mechanism. [Diagram 3] 11A and 11B are schematic diagrams for explaining a process of acquiring an intensity change of a pixel value in a pixel. [Figure 4] 11A and 11B are diagrams for explaining shifts in the period of intensity changes of pixel values ​​in each pixel. [Diagram 5] 1A and 1B are schematic diagrams for explaining moire artifacts that occur in a phase contrast image. [Figure 6] 11A and 11B are schematic diagrams for explaining changes in artifacts when the period is varied. [Figure 7]11A and 11B are diagrams for explaining a comparison between a state in which a setting value is not adjusted and a state in which the setting value is adjusted according to the present embodiment. [Figure 8] 2 is a flowchart illustrating an image processing method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0013] The configuration of an X-ray phase-contrast imaging system 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0014] (Configuration of X-ray phase contrast imaging system) First, a configuration of an X-ray phase-contrast imaging system 100 according to an embodiment of the present invention will be described with reference to Fig. 1. The X-ray phase-contrast imaging system 100 is a system that uses a phase difference of X-rays that have passed through the subject 101 to image the inside of the subject 101. The X-ray phase-contrast imaging system 100 is also a system that uses a Talbot-Lau interferometer to image the inside of the subject 101 by a fringe scanning method. The X-ray phase-contrast imaging system 100 is used, for example, in non-destructive inspection applications to image the inside of the subject 101 as an object.

[0015] FIG. 1 is a view of the X-ray phase-contrast imaging system 100 as viewed from the Y direction. As shown in FIG. 1, the X-ray phase-contrast imaging system 100 includes an X-ray source 11, a detector 12, a plurality of gratings 20, a control unit 30, and a grating movement mechanism 40. The plurality of gratings 20 include a first grating 21, a second grating 22, and a third grating 23. In this specification, the direction from the X-ray source 11 toward the first grating 21 is defined as the X2 direction, and the opposite direction is defined as the X1 direction. The X direction is the direction of the irradiation axis of the X-rays from the X-ray source 11, and is the direction from the X-ray source 11 toward the detector 12. The left-right direction in a plane perpendicular to the X direction is defined as the Y direction, the direction toward the back of the paper is defined as the Y2 direction, and the direction toward the front of the paper is defined as the Y1 direction. The up-down direction in a plane perpendicular to the X direction is defined as the Z direction, the upward direction is defined as the Z1 direction, and the downward direction is defined as the Z2 direction. In the X-ray phase-contrast imaging system 100, the X-ray source 11, the third grating 23, the first grating 21, the second grating 22, and the detector 12 are arranged in this order along the X-ray irradiation axis direction (X direction). That is, the first grating 21, the second grating 22, and the third grating 23 are arranged between the X-ray source 11 and the detector 12. The second grating 22 is an example of a "scanning grating" in the claims. The Y direction and the Z direction are examples of a "first direction" and a "second direction" in the claims, respectively.

[0016] The X-ray source 11 irradiates the subject 101 with X-rays. The X-ray source 11 includes an X-ray tube that generates X-rays when a high voltage is applied from a power supply device (not shown) based on a signal from the control unit 30. The X-ray source 11 is configured to irradiate the generated X-rays toward the detector 12 (in the X2 direction).

[0017] The detector 12 detects X-rays irradiated from the X-ray source 11. The detector 12 is configured to convert the detected X-rays into an electric signal and read the converted electric signal as an image signal. The detector 12 is, for example, a flat panel detector (FPD). The detector 12 is configured to include 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 Y direction and the Z direction in the YZ plane at a predetermined period (pixel pitch). The detector 12 is also configured to output the acquired image signal to the control unit 30. The YZ plane is an example of the "orthogonal plane" in the claims.

[0018] The first grating 21 has a predetermined period (pitch) p 1 The X-ray phase shifter 21b has a plurality of slits 21a and X-ray phase shifters 21b arranged at a period (pitch) p 1 is the sum of the widthwise sizes of one slit 21a and one X-ray phase shift portion 21b in the width direction of the grating pattern. Each slit 21a and each X-ray phase shift portion 21b are formed so as to extend linearly. Also, each slit 21a and each X-ray phase shift portion 21b are formed so as to extend parallel to each other. The first grating 21 is disposed between the X-ray source 11 and the second grating 22, and X-rays are irradiated from the X-ray source 11. When coherent X-rays pass through the grating in which the slits are formed, an image of the grating (self-image 50) is formed at a position a predetermined distance (Talbot distance) away from the grating. This is called the Talbot effect. The first grating 21 is a phase grating for forming a self-image 50 of the first grating 21 (see FIG. 3) by the Talbot effect.

[0019] The second grating 22 has a predetermined period (pitch) p 2 The X-ray transmitting portion 22a and the X-ray absorbing portion 22b are arranged at a period (pitch) p 2is the sum of the widthwise sizes of one X-ray transparent portion 22a and one X-ray absorbing portion 22b in the width direction of the grating pattern. Each X-ray transparent portion 22a and each X-ray absorbing portion 22b are formed so as to extend linearly. Also, each X-ray transparent portion 22a and each X-ray absorbing portion 22b are formed so as to extend parallel to each other. The second grating 22 is an absorption grating for interfering with the self-image 50 of the first grating 21. The first grating 21 and the second grating 22 are gratings having different roles, but the slit 21a and the X-ray transparent portion 22a each transmit X-rays. Also, the X-ray absorbing portion 22b plays a role of blocking X-rays, and the X-ray phase change portion 21b changes the phase of X-rays due to the difference in refractive index with the slit 21a. The second grating 22 is disposed between the first grating 21 and the detector 12, and is irradiated with X-rays that have passed through the first grating 21. In addition, the second grating 22 is disposed at a position separated by the Talbot distance from the first grating 21. The second grating 22 interferes with a self-image 50 of the first grating 21 to form Moiré fringes (not shown) on the detection surface of the detector 12.

[0020] The third grating 23 has a predetermined period (pitch) p 3 The X-ray absorbing portion 23b has a plurality of slits 23a and X-ray absorbing portions 23b arranged at a period (pitch) p 3 is the sum of the widthwise sizes of one slit 23a and one X-ray absorbing portion 23b in the width direction of the grating pattern. Each slit 23a and each X-ray absorbing portion 23b are formed to extend linearly. Each slit 23a and each X-ray absorbing portion 23b are formed to extend parallel to each other. The third grating 23 is disposed between the X-ray source 11 and the first grating 21, and X-rays are irradiated from the X-ray source 11. The third grating 23 is configured to make the X-rays that have passed through each slit 23a into a line light source corresponding to the position of each slit 23a. This increases the coherence of the X-rays irradiated from the X-ray source 11 by the third grating 23. That is, the third grating 23 is a multi-slit that increases the coherence of the X-rays from the X-ray source 11.

[0021] The grating movement mechanism 40 moves at least one of the plurality of gratings 20 based on a signal from the control unit 30. For example, the grating movement mechanism 40 is configured to step-move the second grating 22 in a scanning direction, which is the width direction of the grating pattern of the second grating 22, within a grating plane (within the YZ plane) that is a plane perpendicular to the irradiation axis of the X-rays. The scanning direction is a direction perpendicular to the extension direction of the grating pattern within the grating plane, and is the direction in which the X-ray transparent portions 22a and the X-ray absorbing portions 22b of the second grating 22 are arranged (period p 2 The grating movement mechanism 40 moves the second grating 22 in a direction parallel to the period p 2 is divided into N parts, and p 2 The second lattice 22 is moved so as to move in steps of 1 / N, where N is a positive integer, for example, N=4.

[0022] As shown in FIG. 2, the grating movement mechanism 40 includes a first movement mechanism 41, a second movement mechanism 42, and a rotation mechanism 43. The first movement mechanism 41 moves the second grating 22 in the Y direction. The second movement mechanism 42 moves the second grating 22 in the Z direction perpendicular to the Y direction. The rotation mechanism 43 rotates the second grating 22 in the YZ plane. That is, the rotation mechanism 43 rotates the second grating 22 so as to change the direction in which the grating pattern of the second grating 22 extends in the YZ plane perpendicular to the irradiation axis of the X-rays by changing the angular position of the second grating 22. That is, the rotation mechanism 43 changes the angular position of the second grating 22 in the YZ plane, thereby changing the scanning direction of the second grating 22. Note that the first movement mechanism 41 and the second movement mechanism 42 linearly move the second grating 22 in the Y direction and the Z direction, respectively, regardless of the angular position of the second grating 22 in the YZ plane.

[0023] In this embodiment, the grating movement mechanism 40 moves the second grating 22 by a set amount of scanning along a predetermined movement direction, which is either the Y direction or the Z direction, regardless of the angular position of the second grating 22 in the YZ plane, thereby moving the second grating 22 in the scanning direction by one period p 2For example, when the second grating 22 is disposed at an angle position inclined by 45 degrees from the Y direction, the first moving mechanism 41 moves the second grating 22 by p 2 By stepping the second grating 22 by √2 times / N, the second grating 22 moves in the scanning direction corresponding to the angular position p 2 The first moving mechanism 41, the second moving mechanism 42, and the rotating mechanism 43 each include, for example, a stepping motor or a piezoelectric actuator.

[0024] Furthermore, the grating movement mechanism 40 is configured to change the angular positions of the first grating 21 and the third grating 23 to align them with the angular position of the second grating 22 when the rotation mechanism 43 changes the angular position of the second grating 22. Each of the multiple gratings 20 (the first grating 21, the second grating 22, and the third grating 23) has a grating pattern arranged along a common YZ plane. Even when the angular position of the second grating 22 is changed by the rotation mechanism 43, the multiple gratings 20 are arranged such that the extending directions of their grating patterns are in a common direction.

[0025] As shown in Fig. 1, the control unit 30 includes an apparatus control unit 31 and an image processing unit 32. The control unit 30 controls the operation of each unit of the X-ray phase-contrast imaging system 100. The control unit 30 is a computer including an arithmetic unit (processor) such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit) or an FPGA (Field-Programmable Gate Array) configured for image processing, a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and a storage device including a non-volatile memory such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The control unit 30 controls the operation of each unit of the X-ray phase-contrast imaging system 100 based on parameters and various programs stored in the storage device.

[0026] The device control unit 31 is configured to control the operation of the X-ray source 11 and the grating movement mechanism 40. For example, the device control unit 31 controls the operation of the grating movement mechanism 40 to move the second grating 22 so that the second grating 22 moves stepwise in the scanning direction. The device control unit 31 is configured in software as a functional block realized by the arithmetic device of the control unit 30 executing various programs stored in a storage device. The device control unit 31 may be configured in hardware by providing a dedicated processor (processing circuit). The image processing unit 32 is configured to generate a phase contrast image 52 based on the intensity distribution of the X-rays detected by the detector 12. Specifically, the image processing unit 32 is configured to generate an X-ray image (not shown) based on an image signal output from the detector 12. The image processing unit 32 is also configured to generate a phase contrast image 52 (see FIG. 4) based on the generated X-ray image. The generated phase contrast image 52 is stored in the storage device. The image processing unit 32 is configured in software as a functional block realized by the arithmetic device (processor) executing various programs. The image processing unit 32 may be configured by hardware including a dedicated processor (processing circuit). Details of the configuration in which the image processing unit 32 generates the phase contrast image 52 will be described later. In addition, the control unit 30 stores in advance in a storage device as set values ​​for the movement of the second grating 22, a set angle in which the angular position of the second grating 22 in the YZ plane is set, and a scanning amount in which the movement amount of the second grating 22 by the grating movement mechanism 40 is set, as set values ​​for the movement of the second grating 22.

[0027] (Generation of phase contrast images) As shown in Fig. 3, the control unit 30 acquires an intensity change 51 of the pixel value of each pixel of X-ray image data (X-ray image) detected by the detector 12. In this embodiment, the control unit 30 generates a phase contrast image 52 (see Fig. 4) by the fringe scanning method based on the intensity change 51 that represents the change in pixel value of each pixel detected by the detector 12 while moving the second grating 22 by a predetermined scanning amount set in advance using the grating moving mechanism 40. The control unit 30 calculates one period p of the second grating 22 in the scanning direction based on the set angle. 2 3 shows schematic diagrams (A) to (D) illustrating the positional relationship between the self-image 50 of the first grating 21 and the second grating 22 when the second grating 22 is translated in the scanning direction by the grating moving mechanism 40 in the case where a phase contrast image 52 is generated by the fringe scanning method, and a graph showing an intensity change 51 of the pixel value at each pixel of the X-ray image captured by translating the second grating 22.

[0028] As shown in (A) to (D) of FIG. 3, the control unit 30 controls the scanning direction, which is the width direction of the grid pattern, to be p 2 The control unit 30 is configured to perform imaging while stepping the second grating 22 in a predetermined moving direction by the grating moving mechanism 40 so that the second grating 22 is translated four times by p / 4 each. 2 / 4 for one period of the lattice (period p 2 3 is obtained as the intensity change of the pixel value of each pixel when imaging is performed while moving the second grating 22 at a period p 2 A predetermined scanning amount is preset as the movement amount of the second grating 22 by the grating movement mechanism 40 so that the second grating 22 moves by a distance equal to

[0029] In the fringe scanning method, a phase contrast image 52 is generated based on the intensity change 51 in an X-ray image captured without placing the subject 101 and the intensity change 51 in an X-ray image captured with the subject 101 placed.

[0030] As shown in FIG. 4, the phase contrast image 52 includes, for example, a phase differential image 52a, an absorption image 52b, and a scattering image 52c. The phase differential image 52a is an image created based on the phase shift of X-rays that occurs when X-rays pass through the subject 101. The absorption image 52b is an image created based on the attenuation of X-rays that occurs when X-rays pass through the subject 101. The scattering image 52c (small-angle scattering image) is a visibility image obtained by a change in visibility based on small-angle scattering of an object. The scattering image 52c is also called a dark-field image. "Visibility" refers to clarity.

[0031] The control unit 30 generates a phase contrast image 52 by fitting the waveform shape of the intensity change 51 acquired when the second grating 22 is translated N times and imaged (see FIG. 3 ) to a trigonometric function with a period p. For example, the fitting function is set as shown in Equation (1).

number

[0032] The control unit 30 determines coefficients a to c of the function of formula (1) for N data points on the acquired intensity change 51 by fitting using the least squares method, and generates a phase contrast image 52. When calculating each pixel value of the phase contrast image 52, the above formula (1) is rewritten as the following formula (2) and used.

number

number

[0033] Using the coefficients A, B, and C in the above formula (2), the pixel values ​​of each of the differential phase image 52a, the absorption image 52b, and the scattering image 52c can be expressed by the following formulas (6) to (8), respectively.

number

[0034] In the fringe scanning method, the period p of the second grating 22 is 2 The phase contrast image 52 is generated based on a value calculated on the assumption that the laser beam moves by a value obtained by dividing the period of the intensity change 51 by the number of steps. In other words, the above formula (1) is expressed by dividing the period p of the second grating 22 by the value p set as the period of the intensity change 51. 2 The values ​​of the coefficients a, b, and c are determined by applying the values ​​of a, b, and c. Therefore, when N=4, the image acquired at each step has a period p 2 Since it is assumed that the images are at 1 / 4, 2 / 4, 3 / 4, and 4 / 4 of the phase, it is necessary to reliably obtain images at each of the phases 1 / 4 to 4 / 4 by capturing images while translating the second grating 22. Here, the period p of the acquired intensity change 51 and the period p of the second grating 22 are 2 When there is a shift between the first and second gratings 22 and the second grating 23, the calculation is performed using images (pixel values) at phases shifted from 1 / 4 to 4 / 4, and therefore the generated phase contrast image 52 contains moire artifacts 53 as noise components. 2 Since the phase contrast image 52 is generated by fitting the period p of the intensity change 51 to a trigonometric function having the same period as that of the second grating 22, 2When a phase contrast image 52 is generated by the fringe scanning method in a state where a misalignment occurs, stripe-like moiré artifacts 53 are formed in each image, as shown in FIG.

[0035] <Shift in the period of intensity change> As shown in FIG. 5, the actual period p of the intensity variation 51 and the period p of the second grating 22 2 In FIG. 5, the period p of the intensity change 51 and the period p of the second grating 22 are different. 2 The intensity change 51a (solid line in FIG. 5) and the period p of the intensity change 51 and the period p of the second grating 22 when 2 5 is a schematic diagram showing an intensity change 51b (dashed line in FIG. 5) when there is a deviation between the intensity change 51 and the period p of the second grating 22. Note that, although the intensity change 51 is actually data for N points, in the example shown in FIG. 5, each of the data for the N points is regarded as data for a k / N period. In this way, the total amount of movement in the direction (scanning direction) perpendicular to the direction in which the grating pattern of the second grating 22 extends and the period p of the second grating 22 are 2 When a deviation occurs, the period p of the intensity change 51 acquired by the control unit 30 becomes equal to the period p of the second grating 22. 2 Displaced.

[0036] For example, there may be a deviation between a preset angle and the actual angular position of second grating 22. Since second grating 22 moves by a predetermined movement amount (one period p2 of second grating 22) in the scanning direction of second grating 22, the actual movement amount f of second grating 22 by first moving mechanism 41 or second moving mechanism 42 is expressed by the following equation (9).

number

[0037] <Adjusting the setting value> Therefore, in this embodiment, the control unit 30 acquires an analysis period Ap (see FIG. 6) representing the period p of the intensity change 51 in order to reduce the moiré artifacts 53. Then, the control unit 30 adjusts a setting value for the movement of the second grating 22 for generating the phase contrast image 52 based on the acquired analysis period Ap. Specifically, the control unit 30 adjusts a preset setting value prior to generating the phase contrast image 52 obtained by capturing an image of the subject 101. In this embodiment, the control unit 30 adjusts the setting angle as a setting value by acquiring an angle deviation amount of the second grating 22 with respect to the setting angle set as a setting value based on the acquired analysis period Ap.

[0038] Specifically, the control unit 30 adjusts the set angle when the X-ray phase-contrast imaging system 100 is installed or when regular maintenance is performed before imaging the subject 101. The adjustment of the set angle is performed based on the pixel value of the scattered image 52c in the phase contrast image 52 generated by the intensity change 51 detected when the subject 101 is not placed. As shown in formula (8), the pixel value D of the scattered image 52c is obtained by comparing the case where the image is captured with the subject 101 and the case where the image is captured without the subject 101. In the adjustment of the set angle, the front and back of two images captured without the subject 101 are compared as the case where the image is captured with the subject 101 and the case where the image is captured without the subject 101.

[0039] In adjusting the set angle, the control unit 30 acquires an appropriate value of the period p in formula (1) based on the amplitude of pixel values ​​in the background region of the generated scattered image 52c, thereby acquiring an analysis period Ap (see FIG. 6). Specifically, the control unit 30 searches for an appropriate value of the period p based on the amplitude of pixel values ​​in the background region of the scattered image 52c by changing the value of the period p in formula (1). The control unit 30 acquires a value that minimizes the amplitude of pixel values ​​in the background region of the scattered image 52c as an optimal period. Note that the background region means a region in the scattered image 52c that does not include the subject 101. When imaging is performed without placing the subject 101, the entire image becomes the background region. Since the subject 101 is not placed, the pixel values ​​in the background region become values ​​that represent the pixel values ​​of the moiré artifact 53. The control unit 30 calculates the magnitude of the amplitude value of the moiré artifacts 53 in the scattered image 52c while changing the value of the period p in formula (1), and searches for the value of the period p with the smallest amplitude value, thereby acquiring the value of the analysis period Ap (see FIG. 6) that represents an appropriate period p. For example, the control unit 30 acquires the amplitude value of the moiré artifacts 53 by acquiring the standard deviation of each pixel value of the scattered image 52c generated in adjusting the set angle (set value). Then, the control unit 30 acquires the value of the period p with which the amplitude value of the moiré artifacts 53 is the smallest, as the value of the period of the intensity variation 51. The analysis period Ap that represents the period p of the intensity variation 51 is calculated by subtracting the value representing the period of the intensity variation 51 from the period p of the second grating 22. 2 This is expressed as a ratio to

[0040] As shown in Fig. 6, as the analysis period Ap is reduced from 1.00 to 0.95, the moire artifacts 53 occurring in each image are reduced. Also, when the analysis period Ap is further reduced from 0.95, the moire artifacts 53 increase. For example, in Fig. 6, when the analysis period Ap is 0.95, the period p 2 The period obtained by multiplying 2 ) is obtained as the period p of the intensity change 51. In other words, the appropriate value of the analysis period Ap is the period p of the second grating 22. 26 shows the ratio of the period p of the intensity change 51 to the period p of the second grating 22. 2 4 shows an example in which a scattering image 52c is generated using a plurality of periods smaller than the period shown in FIG.

[0041] In this embodiment, the control unit 30 adjusts the set angle by acquiring an appropriate value of the analysis period Ap, which represents the period p of the intensity change 51. For example, the set angle of the second grating 22 is adjusted to θ 2 Then, the set scanning amount f 2 is expressed as the following equation (10).

number

number

number

[0042] The control unit 30 adjusts the set angle by changing the amount of rotation of the second grating 22 by the rotation mechanism 43 based on the angle deviation amount Δθ acquired as described above. That is, the control unit 30 adjusts the set angle θ 2 The set angle is adjusted by changing the control amount for controlling the operation of rotation mechanism 43 in response to the set angle. Before capturing an image of subject 101, control unit 30 adjusts the set angle, and stores the amount of rotation of rotation mechanism 43 corresponding to the adjusted set angle in the storage device. In other words, control unit 30 updates the amount of rotation of rotation mechanism 43 stored as the set angle by adjusting the set angle.

[0043] In addition, when a stepping motor is used as the grating movement mechanism 40, the set scanning amount f, which is the scanning amount of the movement set by the resolution r and the number of pulses s in the movement of the stepping motor, is set. 3 is expressed as the following equation (14). In that case, the set f 3 The appropriate setting angle θ for 3 is calculated.

number

[0044] In this embodiment, the control unit 30 has a plurality of preset angles. The control unit 30 rotates the second grating 22 by the rotation mechanism 43 to generate a phase contrast image 52 based on the intensity change 51 of the pixel value detected while moving the second grating 22 by a set scanning amount at each of the plurality of preset set angles. For example, the control unit 30 pre-sets and stores four set angles of +90 degrees, +45 degrees, 0 degrees, and -45 degrees, with the scanning direction along the Z direction being 0 degrees. In this embodiment, the control unit 30 adjusts each of the plurality of set angles by acquiring an appropriate value of the analysis period Ap as described above at each of the plurality of set angles. The control unit 30 is configured to translate (scan) the second grating 22 at each of the adjusted plurality of set angles to generate a phase contrast image 52 for each of the plurality of set angles. For example, when the subject 101 is made of a fiber-reinforced resin material, the fiber orientation of the fibers contained in the subject 101 can be visually recognized from the phase contrast images 52 generated at each of the multiple set angles.

[0045] <Generation of adjusted phase contrast image> The control unit 30 captures an image of the subject 101 with the set angle adjusted as a set value, thereby generating a phase contrast image 52 of the subject 101. The control unit 30 adjusts the set angle as a set value in advance as described above, and while moving the second grating 22 by the adjusted set value (set angle), acquires an intensity change 51 representing a change in pixel value of each pixel detected again by the detector 12. Here, the adjusted intensity change 51 acquired after adjusting the set angle may also include a period shift. For example, an angle shift with respect to the set angle may occur due to the operating accuracy of the rotation mechanism 43, and thus a period shift may be included in the adjusted intensity change 51. Therefore, in this embodiment, the control unit 30 acquires an analysis period Ap representing the period p of the intensity change 51 detected again. Then, the control unit 30 generates an adjusted phase contrast image 52 by changing the analysis period so as to eliminate the period shift amount based on the reacquired analysis period Ap. Note that the angle shift caused by the operating accuracy of the rotation mechanism 43 is smaller than the angle shift adjusted by adjusting the set angle.

[0046] Specifically, the control unit 30 acquires an intensity change 51 of the pixel value of each pixel of the detector 12 when the object 101 is imaged, similar to the adjustment of the set angle before the image of the object 101 is captured. Then, similar to the adjustment of the set angle, the control unit 30 acquires an appropriate value of the analysis period Ap in the intensity change 51 at the adjusted set angle based on the pixel value in the background region not including the object 101. Then, the control unit 30 performs calculations according to the formulas (6) to (8) in a state in which the period of the intensity change 51 acquired by the appropriate analysis period Ap is applied to the value of the period p in the formulas (1) and (2), thereby generating an adjusted phase contrast image 52 including a differential phase image 52a, an absorption image 52b, and a scattering image 52c. In this way, the control unit 30 generates an adjusted phase contrast image 52 generated in a state in which the set angle (set value) is adjusted in advance and the period deviation caused by the operation accuracy of the grating moving mechanism 40 is corrected.

[0047] (Comparison with comparative examples) As shown in FIG. 7, in the X-ray phase-contrast imaging system 100 in this embodiment, the set angle (set value) is adjusted by acquiring the analysis period Ap, thereby suppressing the moiré artifacts 53 in the phase contrast image 52. In FIG. 7, a solid line shows an example of a graph indicating the amount of the moiré artifacts 53 included in the phase contrast image 52 generated with the set angle adjusted. In FIG. 7, a dashed line shows an example of a graph indicating the amount of the moiré artifacts 53 included in the phase contrast image 52 generated with the set angle not adjusted. In the graph of FIG. 7, the vertical axis indicates the amount of the moiré artifacts 53 (for example, the amplitude of the moiré artifacts 53). In the graph of FIG. 7, the horizontal axis indicates the number of times the phase contrast image 52 is generated. In the example shown in FIG. 7, for example, after the angular position of the second grating 22 is moved from 0 degrees to 45 degrees a plurality of times, the phase contrast image 52 is generated based on the intensity change 51 detected while the second grating 22 is translated in the scanning direction. In the phase contrast image 52 generated when the set angle is not adjusted, the amount of moiré artifacts 53 is large. On the other hand, in the phase contrast image 52 generated when the set angle is adjusted, although there are moiré artifacts 53 due to the operational accuracy of the grating moving mechanism 40, the moiré artifacts 53 are reduced compared to when the set angle is not adjusted.

[0048] (Image processing method) Next, the image processing method according to the present embodiment will be described with reference to Fig. 8. Note that the control processes in steps 201 to 207 are executed by the control unit 30.

[0049] In step 201, X-rays irradiated from the X-ray source 11 and passing through multiple gratings 20 (first grating 21, second grating 22, and third grating 23) are detected while the second grating 22 is moved based on a predetermined scanning amount set in advance.

[0050] Next, in step 202, an intensity change 51 representing a change in pixel value of each detected pixel is obtained. Specifically, the intensity change 51 of the pixel value of each pixel in a plurality of image data in which X-rays are continuously detected while the second grating 22 is moved is obtained.

[0051] Next, in step 203, a phase contrast image 52 is generated based on the acquired intensity change 51. Specifically, by changing the value of the period p in equations (1) and (2), a phase contrast image 52 is generated for each value of p.

[0052] Next, in step 204, an analysis period Ap representing the period p of the intensity change 51 is obtained in order to reduce moiré artifacts 53, which are noise components included in the generated phase contrast image 52. Specifically, an appropriate value of the analysis period Ap is obtained based on the amplitude of the moiré artifacts 53 in the phase contrast image 52 (scattered image 52c) generated in step 203 by changing the value of the period p in equations (1) and (2).

[0053] Next, in step 205, a setting value for the movement of the second grating 22 for generating the phase contrast image 52 is adjusted based on the acquired analysis period Ap. Specifically, the setting angle is adjusted by adjusting the amount of rotation of the rotation mechanism 43 corresponding to the setting angle set as the setting value.

[0054] Next, in step 206, an X-ray image of the subject 101 is obtained while moving the second grid 22 according to the adjusted setting value (setting angle), thereby again obtaining data on the intensity change 51 of the pixel value at each pixel of the X-ray image of the subject 101.

[0055] Next, in step 207, an appropriate value of the analysis period Ap, which represents the period p of the re-detected intensity variation 51, is obtained, thereby determining the period p of the function according to equation (1) and the coefficients a, b, and c, to generate an adjusted phase contrast image 52. Then, the control process of the image processing method according to this embodiment is terminated.

[0056] [Effects of this embodiment] In this embodiment, the following effects can be obtained.

[0057] In this embodiment, as described above, the X-ray phase-contrast imaging system 100 acquires an analysis period Ap representing the period of the intensity change 51 in order to reduce the moiré artifacts 53, which are noise components included in the phase contrast image 52. Then, the X-ray phase-contrast imaging system 100 adjusts the set value of the movement of the second grating 22 (scanning grating) for generating the phase contrast image 52 based on the acquired analysis period Ap. In this way, by adjusting the set value of the movement of the grating based on the acquired analysis period Ap, the set value can be adjusted so as to reduce the deviation of the actual movement of the grating from the set value of the movement of the grating. Therefore, the phase contrast image 52 can be generated based on the intensity change 51 of the pixel value detected in a state in which the deviation from the set value of the movement of the grating is reduced. As a result, even when the deviation between the set value of the movement of the grating and the actual movement of the grating is large, the moiré artifacts 53 in the generated phase contrast image 52 can be suppressed.

[0058] Furthermore, in the X-ray phase-contrast imaging system 100 according to the present embodiment, the following further effects can be obtained by being configured as follows.

[0059] That is, in this embodiment, the control unit 30 adjusts at least one of the set angle of the second grating 22 in a plane perpendicular to the irradiation axis of the X-rays from the X-ray source 11 and the set amount of scanning of the movement as a set value of the movement of the second grating 22 (scanning grating) for generating the phase contrast image 52 based on the analysis period Ap. With this configuration, the set angle, which is at least one of the set angle of the second grating 22 and the set amount of scanning, can be adjusted to adjust the set value of the movement of the second grating 22, so that the deviation of the actual angular position of the second grating 22 from the set value of the set angle of the second grating 22 can be reduced. As a result, even if the deviation of the actual angular position of the second grating 22 from the set value of the set angle of the second grating 22 is large, the moiré artifacts 53 in the generated phase contrast image 52 can be suppressed.

[0060] In this embodiment, the control unit 30 adjusts the set angle by acquiring the angle deviation amount Δθ of the second grating 22 (scanning grating) relative to the set angle based on the analysis period Ap. Here, when the actual angular position of the second grating 22 is deviated from the set angle, not only the moire artifact 53 caused by the deviation of the set movement value of the second grating 22 from the set value, but also the moire artifact 53 caused by the deviation of the angular positions of each of the plurality of gratings 20 may occur. In that case, even if the waveform of the function is determined from the intensity change 51 of the pixel value to generate the phase contrast image 52, the moire artifact 53 included in the phase contrast image 52 cannot be sufficiently suppressed. Therefore, by adjusting the set angle so as to reduce the angle deviation amount Δθ indicating the magnitude of deviation of the actual angular position of the second grating 22 relative to the set angle, the deviation of the angular positions of each of the plurality of gratings 20 can be suppressed, so that the moire artifact 53 included in the phase contrast image 52 can be effectively suppressed.

[0061] In this embodiment, the grating movement mechanism 40 includes a rotation mechanism 43 that rotates the second grating 22 (scanning grating) in an orthogonal plane. The control unit 30 adjusts the set angle by changing the rotation amount of the second grating 22 by the rotation mechanism 43 based on the acquired angle deviation amount Δθ. With this configuration, when the angular position of the second grating 22 is changed by rotating the second grating 22 by the rotation mechanism 43, it is possible to effectively suppress deviation of the angular position from the set angle. Therefore, it is possible to effectively suppress moiré artifacts 53 included in the phase contrast image 52 caused by deviation of the angular position when the second grating 22 is rotated by the rotation mechanism 43.

[0062] In this embodiment, the control unit 30 also calculates one period p of the second grating 22 in the scanning direction, which is the width direction of the grating pattern of the second grating 22 (scanning grating), based on the set angle. 2 The second grating 22 is moved by the grating movement mechanism 40 so that the second grating 22 moves by a set scanning amount, thereby acquiring an intensity change 51 representing a change in the pixel value of each pixel detected by the detector 12. The grating movement mechanism 40 moves the second grating 22 by a set scanning amount along a predetermined movement direction, regardless of the angular position of the second grating 22 in the orthogonal plane, thereby moving the second grating 22 in the scanning direction over one period p of the second grating 22. 2 Here, when the scanning direction of the second grating 22 and the predetermined movement direction (Y direction or Z direction) in which the second grating 22 is actually moved by the grating movement mechanism 40 are different from each other, the period p 2 Therefore, when the second grating 22 is moved along a predetermined moving direction regardless of the angular position of the second grating 22, the control unit 30 is configured to adjust the set angle based on the acquired analysis period Ap, whereby the moiré artifacts 53 can be effectively suppressed.

[0063] In this embodiment, the grating movement mechanism 40 includes a first movement mechanism 41 that moves the second grating 22 in the Y direction (first direction) along the orthogonal plane, regardless of the angular position of the second grating 22 (scanning grating) in the orthogonal plane, and a second movement mechanism 42 that moves the second grating 22 in the Z direction (second direction) orthogonal to the Y direction in the orthogonal plane. The control unit 30 controls the movement of the second grating 22 in the scanning direction by the operation of either the first movement mechanism 41 or the second movement mechanism 42. 2 By configuring in this way, by operating only one of the first moving mechanism 41 and the second moving mechanism 42 to move the second grating 22, the amount of movement of the second grating 22 (scanning grating) can be controlled with higher precision than when controlling the operations of both the first moving mechanism 41 and the second moving mechanism 42. Therefore, even when the second grating 22 is moved in the Y direction or the Z direction regardless of the angular position of the second grating 22, the amount of movement can be controlled with higher precision, and the moiré artifacts 53 can be effectively suppressed by adjusting the set angle based on the acquired analysis period Ap. As a result, the moiré artifacts 53 included in the phase contrast image 52 can be further suppressed.

[0064] In this embodiment, the control unit 30 generates a phase contrast image 52 including an X-ray scattered image 52c. The control unit 30 then acquires an analysis period Ap based on the amplitude of pixel values ​​in a background region of the generated scattered image 52c. With this configuration, it is possible to effectively suppress the moire artifacts 53 in the scattered image 52c. Therefore, it is possible to effectively improve the visibility of the subject 101 in the scattered image 52c.

[0065] In addition, in this embodiment, the control unit 30 adjusts the set value of the movement of the second grating 22 (scanning grating) for generating the phase contrast image 52, and while moving the second grating 22 by the adjusted set value, acquires the intensity change 51 representing the change in pixel value of each pixel detected again by the detector 12. Then, the control unit 30 acquires an analysis period Ap representing the period of the intensity change 51 detected again, thereby generating the adjusted phase contrast image 52. With this configuration, by adjusting the set value of the movement in advance, it is possible to suppress the moiré artifacts 53 in the acquired phase contrast image 52, and by acquiring the analysis period Ap representing the period of the intensity change 51 detected again based on the adjusted set value, it is possible to further suppress the moiré artifacts 53 in the adjusted phase contrast image 52 generated from the intensity change 51 detected again based on the adjusted set value.

[0066] In this embodiment, the control unit 30 rotates the second grating 22 (scanning grating) by the rotation mechanism 43 to generate a phase contrast image 52 based on an intensity change 51 detected while moving the second grating 22 at each of a plurality of preset set angles. The control unit 30 then adjusts each of the plurality of set angles by acquiring an analysis period Ap at each of the plurality of set angles. With this configuration, since each of the plurality of set angles is adjusted, even when a phase contrast image 52 is captured at each of the plurality of set angles, it is possible to effectively suppress moiré artifacts 53 in each of the plurality of phase contrast images 52 generated for each set angle.

[0067] Moreover, in this embodiment, the multiple gratings 20 include a third grating 23 disposed between the X-ray source 11 and the first grating 21. With this configuration, the third grating 23 can increase the coherence of the X-rays irradiated from the X-ray source 11. As a result, it becomes possible to form a self-image 50 of the first grating 21 without depending on the focal diameter of the X-ray source 11, thereby improving the degree of freedom in selecting the X-ray source 11.

[0068] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications (variations) within the meaning and scope of the claims.

[0069] For example, in the above embodiment, an example was shown in which the phase contrast image 52 is generated by moving the second grating 22 (scanning grating) in the scanning direction to cause interference with the self-image 50 from the first grating 21 of the multiple gratings 20, but the present invention is not limited to this. In the present invention, a phase contrast image may be generated by moving the first grating or the third grating of the multiple gratings. That is, the first grating or the third grating of the multiple gratings may be the scanning grating. In addition, the multiple gratings may be moved to obtain intensity changes in pixel values ​​and generate a phase contrast image. In addition, the third grating may not be disposed by using an X-ray source that irradiates highly coherent X-rays.

[0070] In the above embodiment, the set value of the movement of the second grating 22 is adjusted by adjusting the set angle of the second grating 22 (scanning grating), but the present invention is not limited to this. In the present invention, the set value may be adjusted by adjusting the scanning amount of the set movement of the scanning grating. For example, the set scanning amount f 2 or f 3 is expressed by the formula (11), the optimal scanning amount f 0 In this case, if the grating movement mechanism includes a stepping motor, the resolution r in formula (14) is reduced by a driving method called microstepping, which reduces the step angle (resolution r) of the stepping motor, and the optimal scanning amount f 0By changing the number of pulses s so that it is equal to the set scan amount f 3 The scanning amount as a set value may be adjusted by changing the microstep. As an example, when the microstep of the stepping motor included in the grating movement mechanism is 4, the resolution r is 0.0625 μm / pulse, whereas when the microstep is changed to 8, the resolution r is 0.0125 μm / pulse. The optimal scanning amount f 0 Depending on the value of f, more appropriate setting of scanning amount f 3 The optimal scanning amount f 0 When becomes an infinitesimal, the set scan amount f 3 The microstep may be changed to make the value closer to the set angle. Note that in the present invention, both the set angle and the set scanning amount (set scanning amount) may be configured to be adjustable. In that case, it is possible to selectively adjust either the set angle or the scanning amount, whichever is easier to adjust or has the greater effect.

[0071] In the above embodiment, the grating movement mechanism 40 moves the second grating 22 along a predetermined movement direction (Y direction or Z direction) regardless of the angular position of the second grating 22 (scanning grating), but the present invention is not limited to this. In the present invention, the grating movement mechanism may be configured to change the direction in which the scanning grating is moved depending on the angular position of the scanning grating.

[0072] In the above embodiment, an example was shown in which the analysis period Ap representing the period p of the intensity change 51 was acquired based on the amplitude of pixel values ​​in the background region of the scattering image 52c of the phase contrast image 52, but the present invention is not limited to this. In the present invention, the analysis period may be acquired based on a differential phase image or an absorption image, rather than a scattering image. In addition, in fitting a function representing the intensity change, the analysis period representing the period of the intensity change may be acquired based on a function with a small fitting error. In addition, the detected intensity change of pixel values ​​may be fitted to a periodic function other than a trigonometric function.

[0073] In the above embodiment, an example has been shown in which the period p of the function representing the intensity change 51 is changed by reacquiring the analysis period Ap representing the intensity change 51 due to the adjusted set value after adjusting the set value, but the present invention is not limited to this. In the present invention, a phase contrast image may be generated assuming that the period of the intensity change of the pixel value acquired using the adjusted set value is the period of a preset grating. In other words, a phase contrast image may be generated assuming that the intensity change of the image data acquired by imaging the subject after adjusting the movement set value is represented by a function having a period that matches the period of the scanning grating.

[0074] In addition, in the above embodiment, an example in which a plurality of set angles are set has been shown, but the present invention is not limited to this. In the present invention, only one set angle may be set in advance.

[0075] In the above embodiment, the controller 30 is configured to control the operation of the grating movement mechanism 40, the operation of the X-ray source 11, the generation of the phase contrast image 52, and the adjustment of the set values ​​by acquiring the analysis period Ap, but the present invention is not limited to this. In the present invention, the operation of the grating movement mechanism, the operation of the X-ray source, the generation of the phase contrast image, and some of the adjustment of the set values ​​by acquiring the analysis period Ap may be configured to be executed by control devices (hardware) configured separately from each other.

[0076] [Aspects] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0077] (Item 1) An X-ray source; a plurality of gratings including a first grating for forming a self-image by X-rays emitted from the X-ray source and a second grating for interfering with the self-image of the first grating; a detector for detecting X-rays irradiated from the X-ray source; a grating movement mechanism that moves at least one of the plurality of gratings; and a control unit that generates a phase contrast image based on an intensity change that represents a change in pixel value of each pixel detected by the detector while moving a scanning grating, which is at least one of the plurality of gratings, by the grating moving mechanism, The control unit is obtaining an analysis period that represents a period of the intensity change in order to reduce a moiré artifact that is a noise component included in the phase contrast image; An X-ray phase contrast imaging system that adjusts a setting value of the movement of the scanning grating for generating the phase contrast image based on the acquired analysis period.

[0078] (Item 2) 2. The X-ray phase contrast imaging system according to item 1, wherein the control unit adjusts at least one of a set angle of the scanning grating in a plane perpendicular to an irradiation axis of X-rays from the X-ray source and a set scanning amount of the movement as the set value of the movement of the scanning grating for generating the phase contrast image based on the analysis period.

[0079] (Item 3) 3. The X-ray phase contrast imaging system according to item 2, wherein the control unit adjusts the set angle by acquiring an angle deviation amount of the scanning grating from the set angle based on the analysis cycle.

[0080] (Item 4) the grating moving mechanism includes a rotation mechanism that rotates the scanning grating in the orthogonal plane; 4. The X-ray phase contrast imaging system according to item 3, wherein the control unit adjusts the set angle by changing the amount of rotation by which the scanning grating is rotated by the rotation mechanism based on the acquired amount of angular deviation.

[0081] (Item 5) the control unit acquires the intensity change representing a change in pixel value of each pixel detected by the detector by moving the scanning grating by the grating movement mechanism so that the scanning grating moves by one period of the scanning grating in a scanning direction that is a width direction of a grating pattern of the scanning grating based on the set angle; 5. The X-ray phase-contrast imaging system according to item 3 or 4, wherein the grating movement mechanism moves the scanning grating by one period of the scanning grating in the scanning direction by moving the scanning grating by the set scanning amount along a predetermined movement direction regardless of the angular position of the scanning grating in the orthogonal plane.

[0082] (Item 6) the grating movement mechanism includes a first movement mechanism that moves the scanning grating in a first direction along the orthogonal plane regardless of an angular position of the scanning grating in the orthogonal plane, and a second movement mechanism that moves the scanning grating in a second direction orthogonal to the first direction in the orthogonal plane, 6. The X-ray phase contrast imaging system according to item 5, wherein the control unit moves the scanning grating in the scanning direction by one period of the scanning grating by operating either the first moving mechanism or the second moving mechanism.

[0083] (Item 7) The control unit is generating the phase contrast image including an X-ray scattering image; 7. The X-ray phase-contrast imaging system according to any one of items 1 to 6, wherein the analysis period is acquired based on an amplitude of pixel values ​​in a background region of the generated scattered image.

[0084] (Item 8) The control unit is by adjusting the set value of the movement of the scanning grating for generating the phase contrast image, while moving the scanning grating by the adjusted set value, acquiring the intensity change representing the change in pixel value of each pixel detected by the detector again; 8. The X-ray phase contrast imaging system according to any one of claims 1 to 7, wherein the adjusted phase contrast image is generated by acquiring the analysis period that represents a period of the intensity change that is detected again.

[0085] (Item 9) The set angle includes a plurality of the set angles, The control unit is generating the phase contrast image based on the intensity change detected while moving the scanning grating at each of the plurality of preset angles by rotating the scanning grating with the rotation mechanism; 5. The X-ray phase contrast imaging system according to item 4, wherein each of the plurality of set angles is adjusted by acquiring the analysis period at each of the plurality of set angles.

[0086] (Item 10) 10. The X-ray phase-contrast imaging system according to any one of claims 1 to 9, wherein the plurality of gratings further includes a third grating disposed between the X-ray source and the first grating.

[0087] (Item 11) a step of detecting X-rays emitted from the X-ray source and passing through the plurality of gratings while moving a scanning grating which is at least one of a plurality of gratings including a first grating for forming a self-image by X-rays emitted from the X-ray source and a second grating for interfering with the self-image of the first grating; generating a phase contrast image based on the detected intensity changes representing changes in pixel values ​​of each pixel; obtaining an analysis period that represents a period of the intensity change in order to reduce a moiré artifact that is a noise component included in the generated phase contrast image; An image processing method comprising adjusting a setting value of the movement of the scanning grating for generating the phase contrast image based on the acquired analysis period. [Explanation of symbols]

[0088] 11 X-ray source 12 Detector 20 Multiple Grids 21 1st grid 22 Second grating (scanning grating) 23 Third grid 30 Control section 40 Lattice movement mechanism 41 1st movement mechanism 42 Second movement mechanism 43 Rotation mechanism 50 Self-image 51 Intensity change 52 Phase contrast images 52c Scattered image 53 Moire Artifacts 100 X-ray phase contrast imaging system

Claims

1. An X-ray source; a plurality of gratings including a first grating for forming a self-image by X-rays emitted from the X-ray source and a second grating for interfering with the self-image of the first grating; a detector for detecting X-rays emitted from the X-ray source; a grating movement mechanism that moves at least one of the plurality of gratings; and a control unit that generates a phase contrast image based on an intensity change that represents a change in pixel value of each pixel detected by the detector while moving a scanning grating, which is at least one of the plurality of gratings, by the grating moving mechanism, The control unit is obtaining an analysis period that represents a period of the intensity change in order to reduce a moiré artifact that is a noise component included in the phase contrast image; An X-ray phase contrast imaging system that adjusts settings of the movement of the scanning grating for generating the phase contrast image based on the acquired analysis period.

2. 2. The X-ray phase contrast imaging system according to claim 1, wherein the control unit adjusts at least one of a set angle of the scanning grating in a plane perpendicular to an irradiation axis of X-rays from the X-ray source and a set scanning amount of the movement as the set value of the movement of the scanning grating for generating the phase contrast image based on the analysis period.

3. The X-ray phase-contrast imaging system according to claim 2 , wherein the control unit adjusts the set angle by acquiring an angle deviation amount of the scanning grating from the set angle, which is set, based on the analysis cycle.

4. the grating moving mechanism includes a rotation mechanism that rotates the scanning grating in the orthogonal plane; The X-ray phase-contrast imaging system according to claim 3 , wherein the control unit adjusts the set angle by changing an amount of rotation by which the scanning grating is rotated by the rotation mechanism based on the acquired amount of angular deviation.

5. the control unit acquires the intensity change representing a change in pixel value of each pixel detected by the detector by moving the scanning grating by the grating movement mechanism so that the scanning grating moves by one period of the scanning grating in a scanning direction that is a width direction of a grating pattern of the scanning grating based on the set angle; 5. The X-ray phase-contrast imaging system according to claim 3, wherein the grating movement mechanism moves the scanning grating by one period of the scanning grating in the scanning direction by moving the scanning grating by the set scanning amount along a predetermined movement direction regardless of an angular position of the scanning grating in the orthogonal plane.

6. the grating movement mechanism includes a first movement mechanism that moves the scanning grating in a first direction along the orthogonal plane regardless of an angular position of the scanning grating in the orthogonal plane, and a second movement mechanism that moves the scanning grating in a second direction orthogonal to the first direction in the orthogonal plane, The X-ray phase-contrast imaging system according to claim 5 , wherein the control unit moves the scanning grating in the scanning direction by one period of the scanning grating by operating either the first moving mechanism or the second moving mechanism.

7. The control unit is generating the phase contrast image including an X-ray scattering image; 5. The X-ray phase-contrast imaging system according to claim 1, wherein the analysis period is acquired based on an amplitude of pixel values ​​in a background region of the generated scattered image.

8. The control unit is by adjusting the set value of the movement of the scanning grating for generating the phase contrast image, while moving the scanning grating by the adjusted set value, acquiring the intensity change representing the change in pixel value of each pixel detected by the detector again; 5. The X-ray phase contrast imaging system according to claim 1, further comprising: a phase contrast image generation unit configured to generate an adjusted phase contrast image by obtaining an analysis period that represents a period of the intensity change detected again.

9. The set angle includes a plurality of the set angles, The control unit is generating the phase contrast image based on the intensity change detected while moving the scanning grating at each of the plurality of preset angles by rotating the scanning grating with the rotation mechanism; The X-ray phase contrast imaging system according to claim 4 , wherein each of the plurality of set angles is adjusted by acquiring the analysis period at each of the plurality of set angles.

10. The X-ray phase-contrast imaging system according to any one of claims 1 to 4, wherein the plurality of gratings further includes a third grating disposed between the X-ray source and the first grating.

11. a step of detecting X-rays emitted from the X-ray source and passing through the plurality of gratings while moving a scanning grating which is at least one of a plurality of gratings including a first grating for forming a self-image by X-rays emitted from the X-ray source and a second grating for interfering with the self-image of the first grating; generating a phase contrast image based on the detected intensity changes representing changes in pixel values ​​of each pixel; obtaining an analysis period that represents a period of the intensity change in order to reduce a moiré artifact that is a noise component included in the generated phase contrast image; An image processing method comprising adjusting a setting value of the movement of the scanning grating for generating the phase contrast image based on the acquired analysis period.

Images