JP2022006401A - X-ray image photographing apparatus and x-ray image generation method - Google Patents

Abstract

To provide an X-ray image photographing apparatus capable of suppressing deterioration in the quality of an acquired image when generating at least one of a phase contrast image and a dark field image.SOLUTION: An X-ray image photographing apparatus 100 includes: an X-ray source 1; a first grid 6 in which a first grid pattern is formed; a detector 2 for detecting a first X-ray that has arrived through the first grid 6 and a second X-ray that has arrived without passing through the first grid 6; a relative position moving part 3; and an image processing part 4 for correcting a plurality of first images 30 generated on the basis of the first X-ray acquired at a plurality of relative positions with respect to a subject 90 on the basis of a plurality of second images 31 generated on the basis of the second X-ray acquired at a plurality of relative positions with respect to the subject 90, and generating at least one of a phase contrast image 21 or a dark field image 23 on the basis of a plurality of first images 32 after correction.SELECTED DRAWING: Figure 1

Description

The present invention relates to an X-ray imaging apparatus and an X-ray image having a grid in which a grid pattern is formed so as to diffract X-rays emitted from an X-ray source or to shield a part of the irradiated X-rays. Regarding the generation method.

Conventionally, an X-ray phase imaging system including a grid in which a grid pattern is formed so as to diffract X-rays emitted from an X-ray source or to block a part of the irradiated X-rays is known (for example). , Patent Document 1).

The X-ray phase imaging system disclosed in Patent Document 1 includes an X-ray source, a grid group including a first grid, a second grid, and a third grid, a detection unit, and a transport unit for moving a subject. , A pixel calculation unit and an image calculation unit are provided. The X-ray phase imaging system disclosed in Patent Document 1 captures a plurality of images while moving the subject in the periodic direction of the moire fringes generated by the plurality of grids irradiated with X-rays. It is configured to generate an absorption image, a phase contrast image, and a dark field image. The absorption image is an image imaged based on the attenuation of the X-rays generated when the X-rays pass through the subject. The phase contrast image is an image imaged based on the phase shift of the X-rays generated when the X-rays pass through the subject. The dark field image is a Visibility image obtained by a change in Visibility based on small-angle scattering (refraction) of X-rays by an object. The dark field image is also called a small-angle scattered image. "Visibility" is sharpness.

Japanese Unexamined Patent Publication No. 2017-44603

However, in X-ray phase imaging using an X-ray phase imaging system (X-ray imaging apparatus) as in Patent Document 1, changes in the temporal brightness of X-rays emitted from the X-ray source and the lattice. Depending on the angle of the X-rays to be irradiated (irradiation angle) and the like, a false image (artifact) may occur in the generated phase contrast image and dark field image. When a false image occurs in the phase contrast image and the dark field image, there is a problem that the image quality of each image is deteriorated.

The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to obtain image quality when at least one of a phase contrast image and a dark field image is generated. It is an object of the present invention to provide an X-ray image taking apparatus which can suppress the decrease.

In order to achieve the above object, the X-ray imaging apparatus according to the first aspect of the present invention diffracts or a part of the X-ray source emitted from the X-ray source and the X-ray emitted from the X-ray source. The first lattice in which the first lattice pattern is formed so as to shield the image, the first X-rays arriving through the first lattice, and the second X-rays arriving without passing through the first lattice are detected. A plurality of first images generated based on a detector, a relative position moving unit for moving the relative position of the detector with respect to the subject, and first X-rays acquired at a plurality of relative positions with respect to the subject, and a plurality of first images with respect to the subject. Corrected based on a plurality of second images generated based on the second X-rays acquired at relative positions, and at least one of a phase contrast image or a dark field image is generated based on the corrected first images. An image processing unit is provided.

Further, in order to achieve the above object, in the method for generating an X-ray image according to the second aspect of the present invention, the X-ray source and the lattice pattern so as to diffract or shield the X-rays emitted from the X-ray source are used. An X-ray image using an X-ray imaging apparatus including a formed lattice, a detector that detects a first X-ray that arrives through the lattice, and a second X-ray that arrives without passing through the lattice. The step of acquiring a plurality of first images generated based on the first X-rays acquired at a plurality of shooting positions while changing the relative position of the detector with respect to the subject, and the detector for the subject. A step of acquiring a plurality of second images generated based on the second X-rays acquired in a plurality of shootings while changing the relative position of the image, and each of the plurality of first images based on the plurality of second images. A step of generating at least one of a phase contrast image or a dark field image based on a plurality of corrected first images.

In the X-ray imaging apparatus in the first aspect, as described above, the plurality of first images are corrected based on the plurality of second images, and the phase contrast image is corrected based on the corrected plurality of first images. Alternatively, it includes an image processing unit that generates at least one of the dark field images. Here, the irradiation intensity of the X-rays emitted from the X-ray source changes with time due to the rotation of the target of the X-ray source and the like. Therefore, the brightness of the X-rays detected by the detector also changes with time. If this change in brightness is faster than the image acquisition frame rate of the detector, striped artifacts will occur in the detected image. The temporal change in the brightness of X-rays occurs in both the first X-ray and the second X-ray. Since the first X-rays pass through the grid, in addition to the temporal change in the brightness of the X-rays, the X-rays pass through the grid, causing different X-ray attenuations and spectral changes in the regions within the grid. On the other hand, since the second X-ray does not pass through the grid, the X-ray does not change due to the grid. Therefore, by configuring as described above, the X-ray attenuation due to the lattice occurs by estimating the temporal luminance change of the X-ray based on the plurality of second images generated based on the second X-ray. Compared with the configuration in which the temporal luminance change of X-rays is estimated based on a plurality of first images, the temporal luminance change of X-rays can be estimated more accurately.

Further, since the plurality of first images are generated based on the X-rays after passing through the lattice, a false image due to the lattice may occur. On the other hand, since the plurality of second images are generated based on the X-rays detected without passing through the grid, no false image due to the grid occurs. Therefore, when a false image due to the grid is generated in the plurality of first images, it is caused by the angle of the X-rays applied to the grid based on the plurality of first images and the plurality of second images. It is possible to estimate the false image that occurs. Therefore, since the phase contrast image or the dark field image is generated based on the plurality of first images corrected based on the plurality of second images, a false image (artifact) may occur in the phase contrast image or the dark field image. Can be suppressed. As a result, when at least one of the phase contrast image and the dark field image is generated, it is possible to suppress the deterioration of the image quality of the obtained image.

Further, in the method of generating an X-ray image in the second aspect, as described above, a step of correcting each of the plurality of first images based on the plurality of second images, and a plurality of corrected first images. It comprises a step of generating at least one of a phase contrast image or a darkfield image based on the image. Thereby, similarly to the X-ray imaging apparatus in the first aspect, it is possible to suppress deterioration of the image quality of the obtained image when at least one of the phase contrast image and the dark field image is generated. A method for generating an X-ray image can be provided.

It is a schematic diagram which showed the whole structure of the X-ray image taking apparatus by one Embodiment. It is a schematic diagram for demonstrating the arrangement of the grid of the X-ray image taking apparatus by one Embodiment. It is a schematic diagram for demonstrating the false image (artifact) caused by the 1st luminance change. It is a schematic diagram for demonstrating the structure which the image processing part by one Embodiment generates a phase contrast image based on a plurality of first images and a plurality of third images. It is a schematic diagram for demonstrating the structure which the image processing part by one Embodiment corrects a plurality of first images based on a plurality of second images. It is a schematic diagram for demonstrating the structure which the image processing part by one Embodiment corrects a plurality of third images based on a plurality of fourth images. A schematic for explaining a configuration in which an image processing unit according to an embodiment generates a phase contrast image based on a first image corrected based on a second image and a third image corrected based on a fourth image. It is a figure. It is a schematic diagram for demonstrating the structure which the image processing part by one Embodiment acquires the 1st luminance change. It is a graph which shows the 1st luminance change. It is a schematic diagram for demonstrating the structure which the image processing part by this embodiment corrects a 1st image based on a 1st luminance change. It is a schematic diagram which showed the phase contrast image generated by the image processing part by this embodiment. It is a schematic diagram for demonstrating the false image (artifact) caused by the 2nd luminance change which occurred in the absorption image. It is a schematic diagram for demonstrating the false image (artifact) caused by the 2nd luminance change which occurred in the dark field image. It is a schematic diagram for demonstrating the structure which the image processing part by one Embodiment acquires the 2nd luminance change. It is a schematic diagram for demonstrating the structure which the image processing part by one Embodiment corrects a false image (artifact) generated in a dark field image. It is a flowchart for demonstrating the process which the image processing part by one Embodiment generates a phase contrast image. It is a flowchart for demonstrating the process which the image processing part by one Embodiment generate a dark field image.

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

The configuration of the X-ray imaging apparatus 100 according to the embodiment will be described with reference to FIGS. 1 and 2. The X-ray imaging apparatus 100 is an imaging apparatus that can be used for diagnosing breast cancer in mammography. Further, the X-ray imaging apparatus 100 is an imaging apparatus that can be used for diagnosis in medical examinations other than breast cancer, evaluation in nondestructive examinations, and the like.

(Configuration of X-ray imaging device)
As shown in FIG. 1, the X-ray image capturing apparatus 100 includes an X-ray source 1, a detector 2, a plurality of grids, a relative position moving unit 3, an image processing unit 4, a control unit 5, and a collimator. 60 and.

In the X-ray imaging apparatus 100, the X-ray source 1, the collimator 60, the plurality of grids, and the detector 2 are arranged in this order in the X-ray irradiation axis 70 direction (optical axis direction, Z direction). Have been placed. In the present specification, the optical axis direction (Z direction) of X-rays is the horizontal direction. Further, the horizontal direction and the vertical direction orthogonal to the optical axis direction of the X-ray are defined as the X direction and the Y direction, respectively.

The plurality of grids include a first grid group and a second grid group. The first grid group includes a first grid 6, a second grid 7, and a source grid 8. The second grid group includes a third grid 9, a fourth grid 10, and a source grid 11. In the first grid group, each grid of the source grid 8, the first grid 6, and the second grid 7 in the direction from the X-ray source 1 toward the detector 2 (direction from the Z1 side to the Z2 side). They are lined up in order. Further, in the second grid group, each grid is arranged in the order of the radiation source grid 11, the third grid 9, and the fourth grid 10 in the direction from the X-ray source 1 to the detector 2. The details of the configuration of each grid will be described later.

The X-ray source 1 generates X-rays by applying a high voltage. The X-rays generated by the X-ray source 1 are configured to be emitted in the direction in which the detector 2 is arranged (Z2 direction). In the example shown in FIG. 1, the X-ray source 1 irradiates a region surrounded by a straight line 71 and a straight line 72 with X-rays.

The detector 2 detects the X-rays emitted from the X-ray source 1 and converts the detected X-rays into an electric signal. The detector 2 detects the first X-ray that arrived through the first grid 6 and the second X-ray that arrived without passing through the first grid 6. In the present embodiment, as shown in FIG. 1, the region 76 irradiated with the first X-ray and the region 77 irradiated with the second X-ray are in a predetermined direction intersecting the direction of the irradiation axis 70 of the X-ray. They are arranged side by side. In this embodiment, the predetermined direction is the X direction. The detector 2 is, for example, an FPD (Flat Panel Detector). The detector 2 includes a plurality of conversion elements (not shown) arranged on the detection surface on the X-ray source 1 side (Z1 side), and pixel electrodes (not shown) arranged on the plurality of conversion elements. It is composed of. The plurality of conversion elements and pixel electrodes are arranged side by side in the X direction and the Y direction with a predetermined period (pixel pitch). The detection signal (image signal) of the detector 2 is sent to the image processing unit 4.

The relative position moving unit 3 is configured to move the relative position of the detector 2 with respect to the subject 90. In the present embodiment, the relative position moving unit 3 is configured to move the relative positions of the region 76 irradiated with the first X-ray and the region 77 irradiated with the second X-ray with respect to the subject 90. In the present embodiment, the relative position moving unit 3 is configured to move the subject 90 in a predetermined direction (X direction) under the control of the control unit 5, as shown by the thick arrow in FIG. That is, in the present embodiment, the relative position moving unit 3 moves the subject 90 so that the detector 2 (the region 76 irradiated with the first X-ray and the region 77 irradiated with the second X-ray) with respect to the subject 90. It is configured to move the relative position.

The image processing unit 4 is configured to generate at least one of the phase contrast image 20 (see FIG. 3) and the dark field image 23 (see FIG. 13) based on the detection signal sent from the detector 2. .. In the present embodiment, the image processing unit 4 is configured to generate both the phase contrast image 20 and the dark field image 23. Further, in the present embodiment, the image processing unit 4 generates an absorption image 22 (see FIG. 12). The image processing unit 4 includes, for example, a processor such as a GPU (Graphics Processing Unit) or an FPGA (Field-Programmable Gate Array) configured for image processing. The details of the configuration in which the image processing unit 4 generates the phase contrast image 20, the absorption image 22, and the dark field image 23 will be described later.

The control unit 5 is configured to control the operation of the relative position moving unit 3. The control unit 5 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

The collimator 60 is arranged between the first grid 6 and the third grid 9 and the source grid 8 and the source grid 11. The collimator 60 is composed of a shielding member that shields X-rays, and has a collimator hole 60a and a collimator hole 60b that are openable and closable. The X-rays that have passed through the collimator hole 60a are applied to the area surrounded by the straight lines 73 and 74. The collimator hole 60a can adjust the irradiation range of the X-rays emitted from the X-ray source 1, passing through the first lattice group and the second lattice group and irradiating the detector 2. be. The X-rays that have passed through the collimator hole 60b are applied to the area surrounded by the straight lines 75 and 76. The collimator hole 60b can adjust the range of X-rays emitted to the detector 2 without passing through the first grid group and the second grid group. As shown in FIG. 1, the region where the X-rays that have passed through the collimator hole 60a and reached the detector 2 are irradiated is the region 76 where the first X-rays are irradiated. Further, the region where the X-rays that have passed through the collimator hole 60b and reached the detector 2 are irradiated is the region 77 where the second X-rays are irradiated.

(Composition of multiple grids)
As shown in FIG. 2, in the first grid 6, the first grid pattern is formed so as to diffract the X-rays emitted from the X-ray source 1 or to shield a part of the irradiated X-rays. .. In the present embodiment, the first grid 6 has a grid pattern formed so as to diffract the X-rays emitted from the X-ray source 1. Specifically, the first grid 6 is configured as a diffraction grating (phase grid) that changes the phase of the passing X-rays. As shown in FIG. 2, the first grid 6 has slits 6a and an X-ray absorbing portion 6b arranged in a substantially Y direction with a predetermined period (lattice pitch) 6c. Each slit 6a and the X-ray absorbing portion 6b are formed so as to extend in the substantially X direction.

The first grid 6 is arranged between the X-ray source 1 and the second grid 7, and is provided to form a self-image (by the Talbot effect) by the X-rays emitted from the X-ray source 1. There is. The Talbot effect is that when X-rays with interfering properties pass through a grid on which slits are formed, a grid image (self-image) is formed at a position separated from the grid by a predetermined distance (Talbot distance). Means that.

Similar to the first grid 6, the second grid 7 has a plurality of slits 7a and an X-ray absorbing portion 7b arranged in a substantially Y direction with a predetermined period (lattice pitch) 7c. Each slit 7a and the X-ray absorbing portion 7b are formed so as to extend in the substantially X direction.

The second grid 7 is arranged between the first grid 6 and the detector 2 and is provided to interfere with the self-image formed by the first grid 6. The second grid 7 is arranged at a position separated from the first grid 6 by the Talbot distance in order to interfere with the self-image and the second grid 7. By interfering between the self-image formed by the first grid 6 and the second grid 7, moire (not shown) having a period larger than the grid pitch of the self-image is formed on the detection surface. To.

The radiation source grid 8 is arranged between the X-ray source 1 and the first grid 6. The radiation source lattice 8 has a plurality of slits 8a and an X-ray absorption unit 8b arranged in a substantially Y direction with a predetermined period (lattice pitch) 8c. Each slit 8a and the X-ray absorbing portion 8b are formed so as to extend in the substantially X direction. The radiation source grid 8 is configured as a grid (multi-slit) capable of microfocusing the X-rays emitted from the X-ray source 1. In other words, the radiation source grid 8 is configured to improve the coherence of X-rays emitted from the X-ray source 1.

Further, as shown in FIG. 2, in the third grid 9, a second grid pattern is formed so as to diffract the X-rays emitted from the X-ray source 1 or to shield a part of the irradiated X-rays. ing. In the present embodiment, the third grid 9 has a grid pattern formed so as to diffract the X-rays emitted from the X-ray source 1. Specifically, the third grid 9 is configured as a diffraction grating (phase grid) that changes the phase of the passing X-rays. As shown in FIG. 2, the third grid 9 has slits 9a and X-ray absorbing portions 9b arranged in a substantially X direction with a predetermined period (lattice pitch) 9c. Each slit 9a and the X-ray absorbing portion 9b are formed so as to extend in the substantially Y direction. That is, the third grid 9 is arranged so that the direction of the second grid pattern is orthogonal to the direction of the first grid pattern.

The third grid 9 is arranged between the X-ray source 1 and the fourth grid 10, and is provided to form a self-image (by the Talbot effect) by the X-rays emitted from the X-ray source 1. There is.

Similar to the third grid 9, the fourth grid 10 has a plurality of slits 10a and an X-ray absorbing portion 10b arranged in a substantially X direction with a predetermined period (lattice pitch) 10c. Each slit 10a and the X-ray absorbing portion 10b are formed so as to extend in the substantially Y direction.

The fourth grid 10 is arranged between the third grid 9 and the detector 2 and is provided to interfere with the self-image formed by the third grid 9. The fourth grid 10 is arranged at a position separated from the third grid 9 by a Talbot distance in order to interfere with the self-image and the fourth grid 10. By interfering between the self-image formed by the third grid 9 and the fourth grid 10, moire (not shown) having a period larger than the grid pitch of the self-image is formed on the detection surface. To.

The radiation source grid 11 is arranged between the X-ray source 1 and the third grid 9. The radiation source lattice 11 has a plurality of slits 11a and an X-ray absorption unit 11b arranged in a substantially Y direction with a predetermined period (lattice pitch) 11c. Each slit 11a and the X-ray absorbing portion 11b are formed so as to extend in the substantially X direction. The radiation source grid 11 is configured as a grid (multi-slit) capable of microfocusing the X-rays emitted from the X-ray source 1. In other words, the radiation source grid 11 is configured to improve the coherence of X-rays emitted from the X-ray source 1.

Here, since the phase contrast image 20 and the dark field image 23 are sensitive to changes in X-rays in the direction orthogonal to the lattice pattern, the portion of the subject 90 that extends in the direction orthogonal to the lattice pattern. Is imaged, and the portion extending in the direction along the lattice pattern is not imaged. Therefore, in the present embodiment, each lattice included in the first lattice group and the direction of the lattice pattern in the second lattice group are orthogonal to each other so that the direction of the lattice pattern in the first lattice group and the direction of the lattice pattern in the second lattice group are orthogonal to each other. , Each grid included in the second grid group is arranged.

(Generation of phase contrast image)
Next, with reference to FIGS. 3 to 11, the configuration in which the image processing unit 4 generates the phase contrast image 21 (see FIG. 7) will be described.

In the present embodiment, as shown in FIG. 3, the image processing unit 4 generates the phase contrast image 20. Specifically, as shown in FIG. 4, the image processing unit 4 is imaged while moving the subject 90 by the relative position moving unit 3 in a state where moire fringes (not shown) are generated by a plurality of grids. Based on the plurality of first images 30, the first intensity signal curve of X-rays is acquired. The plurality of first images 30 include four first images 30 of the first image 30a to the first image 30d taken at different relative positions in the region 76 irradiated with the first X-ray.

Further, the image processing unit 4 acquires a second intensity signal curve based on a plurality of third images 33 (third images 33a to 33d) captured in a state where the subject 90 is not arranged. The plurality of third images 33 are the four third images 33a to 33d taken at different relative positions in the region 76 irradiated with the first X-ray in a state where the subject 90 is not arranged. 3 Includes image 33. The image processing unit 4 generates a phase contrast image 20 based on the acquired first intensity signal curve and second intensity signal curve. In the example shown in FIG. 4, for convenience, the image processing unit 4 uses four first images 30 to form a first intensity signal curve, and uses four third images 33 to form a second intensity signal curve. An example of acquisition is shown, but in reality, the first intensity signal curve is acquired using four or more first images 30, and the second intensity signal curve is acquired using four or more third images 33. To get. For example, the image processing unit 4 acquires the first intensity signal curve using about 600 first images 30, and acquires the second intensity signal curve using about 600 third images 33.

Here, the brightness of the X-rays emitted from the X-ray source 1 changes with time due to the rotation of the target generated in the X-ray source 1 and the like. Therefore, a false image (artifact) 80 (see FIG. 3) is generated in the phase contrast image 20. The false image 80 is a bright and dark striped pattern caused by a change in the brightness of X-rays.

Therefore, in the present embodiment, the image processing unit 4 is configured to suppress the occurrence of a false image 80 in the generated phase contrast image 20.

Specifically, as shown in FIG. 5, the image processing unit 4 has a plurality of first images 30 (first images 30a to 30a) generated based on the first X-rays acquired at a plurality of relative positions with respect to the subject 90. The first image 30d) is configured to be corrected based on a plurality of second images 31 generated based on the second X-rays acquired at a plurality of relative positions with respect to the subject 90. The plurality of second images 31 include four second images 31 of the second image 31a to the second image 31d taken at different relative positions in the region 77 irradiated with the second X-ray. The details of the configuration in which the image processing unit 4 corrects the first image 30 based on the second image 31 will be described later.

Further, in the present embodiment, as shown in FIG. 6, a plurality of third images 33 (third images 33a to third images) generated based on the first X-rays acquired in a state where the subject 90 is not arranged. 33d) is configured to be corrected based on a plurality of fourth images 34 generated based on the second X-rays acquired in a state where the subject 90 is not arranged. The plurality of fourth images 34 are the four fourth images 34a to 34d of the fourth image 34a to the fourth image 34d taken at different relative positions in the region 77 irradiated with the second X-ray in a state where the subject 90 is not arranged. 4 includes image 34. The image processing unit 4 corrects the third image 33 based on the first luminance change 41. The details of the configuration in which the image processing unit 4 corrects the third image 33 based on the fourth image 34 will be described later.

In the present embodiment, as shown in FIG. 7, the image processing unit 4 is configured to generate the phase contrast image 21 based on the plurality of corrected first images 32. Specifically, the image processing unit 4 generates at least one of the phase contrast image 21 and the dark field image 23 based on the corrected first image 32 and the corrected third image 35. It is configured as follows. In the present embodiment, the image processing unit 4 generates the phase contrast image 21 based on the corrected first image 32 and the corrected third image 35.

In the present embodiment, the first image 30a and the second image 31a are images captured at the same timing. Similarly, the first image 30b and the second image 31b, the first image 30c and the second image 31c, and the first image 30d and the second image 31d are images taken at the same timing, respectively. The same applies to the third image 33 and the fourth image 34.

The image processing unit 4 acquires the corrected first image 32a to the first image 32d by correcting each of the first image 30a to the first image 30d with each of the second image 31a to the second image 31d. do. Further, the image processing unit 4 generates the phase contrast image 21 based on the corrected first image 32a to the first image 32d.

(Acquisition of first brightness change)
As shown in FIG. 8, the image processing unit 4 is configured to acquire the first luminance change 40 of X-rays based on a plurality of second images 31 (second images 31a to 31d). There is. Here, the brightness of the X-rays emitted from the X-ray source 1 changes with time. Further, the first luminance change 40 is a luminance change such that the dark part and the bright part repeat in a predetermined cycle. Therefore, as shown in FIG. 8, different first luminance changes 40a to first luminance changes 40d occur in each of the plurality of second images 31a to 31d. Each of the first luminance change 40a to the first luminance change 40d has a different period between the dark portion (dark portion 43a to dark portion 43d) and the bright portion (bright portion 44a to bright portion 44d).

Therefore, in the present embodiment, the image processing unit 4 is configured to acquire the first luminance change 40 that occurs in each of the plurality of second images 31. However, since the subject 90 is captured in each second image 31, it may be difficult to acquire the first luminance change 40 depending on how the subject 90 is captured when acquiring the first luminance change 40. be. Therefore, in the present embodiment, the image processing unit 4 is determined based on the relative movement of the subject 90 in the plurality of second images 31 in order to suppress the influence of the subject 90 reflected in the second image 31. It is configured to acquire the first luminance change 40 (first luminance change 40a to first luminance change 40d) that occurs in each of the plurality of second images 31 based on the region.

As shown in FIG. 8, the predetermined area is the area 42 in which the same portion of the subject 90 is captured in each of the plurality of second images 31. The image processing unit 4 acquires the average value of the pixel values of the region 42 in which the same portion of the subject 90 is captured, and divides each of the plurality of second images 31 by the acquired average value to obtain the plurality of second images. It is configured to acquire the first luminance change 40 of the X-ray generated in each of the 31. Specifically, the image processing unit 4 generates an average image (not shown) in each region 42 based on each region 42 of each second image 31. Then, the image processing unit 4 removes the subject 90 reflected in each region 42 by dividing each region 42 of the plurality of second images 31 from the acquired average image, thereby removing the subject 90 reflected in each region 42 of the plurality of second images 31. It is configured to acquire the first luminance change 40 of the X-ray generated in each.

If the subject 90 is not shown in the second image 31, it is not necessary to remove the subject 90. Therefore, the image processing unit 4 acquires the luminance change of a predetermined line in the Y direction of each second image 31 as the first luminance change 40.

Further, in the detector 2, the sensitivity may be uneven for each detected pixel. Therefore, in the present embodiment, the image processing unit 4 performs sensitivity correction on each of the plurality of second images 31, and based on the plurality of second images 31 after the sensitivity correction, X-rays are obtained. It is configured to acquire the first luminance change 40.

The graph 45 shown in FIG. 9 is a graph of the first luminance change 40. In the graph 45, the vertical axis is the luminance value and the horizontal axis is the position of the pixel in the Y direction. As shown in the graph 45, a portion having a large luminance value and a portion having a small luminance value are periodically generated in the first luminance change 40. Further, as shown in the graph 45, the first luminance change 40 includes noise. Therefore, in the present embodiment, the image processing unit 4 is configured to perform smoothing processing on the first luminance change 40.

Here, in the first luminance change 40, the luminance in the direction along the Y direction changes periodically, but the luminance value does not change periodically in the X direction. Therefore, in the second image 31, a change in the brightness of a predetermined line in the Y direction of the region 42 can be regarded as a change in the brightness of the entire second image 31. Therefore, it is possible to acquire the first luminance change 40 of the second image 31 by acquiring the luminance change occurring in the region 42 in which the same portion of the subject 90 is captured.

As described above, each of the plurality of first images 30 and each of the plurality of second images 31 are imaged at the same timing. Since the first luminance change 40 is caused by the change in the output of the X-rays emitted from the X-ray source 1, as shown by the arrow 12 in FIG. 10, the region where the first X-rays are irradiated at the same time point. It is commonly detected in the area 77 where the 76 and the second X-ray are irradiated. That is, the first luminance change 40 that occurs in each of the plurality of second images 31 also occurs in each of the plurality of first images 30 at the same time point. For example, the first luminance change 40a that occurs in the second image 31a also occurs in the first image 30a. Therefore, the change in the luminance of the X-rays that occurs in the first image 30a can be corrected by the first luminance change 40a. Similarly, the first image 30b to the first image 30d can be corrected by the second image 31b to the second image 31d.

In the present embodiment, the image processing unit 4 generates X in a direction (Y direction) orthogonal to a predetermined direction (X direction) in the plane of the plurality of second images 31 based on the plurality of second images 31. It is configured to acquire the first luminance change 40 of the line and correct each of the plurality of first images 30 based on the acquired first luminance change 40 of the X-ray. The image processing unit 4 corrects a change in luminance that occurs in a direction orthogonal to a predetermined direction in the plane of a plurality of first images 30 in a direction along a predetermined direction based on the first luminance change 40. Is configured to correct each of the plurality of first images 30.

As a method of correcting the first image 30, each pixel of the first luminance change 40 with respect to each pixel in the direction (Y direction) orthogonal to the predetermined direction (X direction) in the plane of the first image 30. A method of subtracting or dividing the value can be considered, but any method can be used as long as the change in brightness generated in the first image 30 can be corrected by using the first brightness change 40. good.

Further, the configuration in which the image processing unit 4 acquires the corrected third image 35 by correcting the first brightness change 41 generated in the plurality of third images 33 by the plurality of fourth images 34 is an image. Since the processing unit 4 corrects the first brightness change 40 generated in the plurality of first images 30 by the plurality of second images 31, the configuration is similar to the configuration in which the corrected first images 32 are acquired. , Detailed explanation is omitted. If the plurality of corrected third images 35 are acquired in advance and stored in a storage unit (not shown) or the like, it is not necessary to acquire the corrected third image 35 each time the subject 90 is imaged.

As described above, the image processing unit 4 has the phase contrast image 21 based on the corrected first image 32 (see FIG. 7) and the corrected third image 35 (see FIG. 7). (See FIG. 7) is acquired. In the plurality of corrected first images 32, the first luminance change 40 is corrected. Further, in the plurality of corrected third images 35, the first luminance change 41 is corrected. Therefore, as shown in FIG. 11, the phase contrast image 21 generated based on the corrected first image 32 and the corrected third image 35 is an image from which the false image 80 is removed. ..

(2nd brightness change)
The X-ray imaging apparatus 100 according to the present embodiment includes at least the first grid 6 as a plurality of grids. The angle at which the X-rays are incident on the first lattice 6 increases as the distance from the irradiation axis 70 increases in the X direction. Depending on the angle incident on the first grid 6, the number of X-rays passing through the X-ray absorbing portion 6b of the first grid 6 is reduced.

When the X-rays are reduced in the X-ray absorption unit 6b of the first grid 6, as shown in FIG. 12, a false image 81 due to the second luminance change 46 is generated in the absorption image 22. The second luminance change 46 is, for example, a luminance change in which a bright portion 48 is generated in the central portion of the absorption image 22 in the Y direction and a dark portion 47 is generated at both ends in the Y direction. The image processing unit 4 generates an absorption image 22 and a dark field image 23 based on the first intensity signal curve and the second intensity signal curve.

(False image generated in dark field image)
Further, when the false image 81 caused by the second luminance change 46 is generated in the absorption image 22, the false image 82 is also generated in the dark field image 23 as shown in FIG. In the false image 82, for example, in the Y direction, a dark portion 50 is formed in the central portion of the dark field image 23, and bright portions 49 are formed at both ends in the Y direction. That is, the change in luminance that occurs in the dark field image 23 is a symmetrical change in luminance in which the bright portion 48 and the dark portion 47 of the second luminance change 46 are inverted.

Therefore, in the present embodiment, the image processing unit 4 has a second luminance change 46 of the X-rays caused by the X-rays passing through the plurality of lattices based on the plurality of first images 30 and the plurality of second images 31. Is acquired, and the dark field image 23 is corrected based on the acquired second luminance change 46.

Specifically, as shown in FIG. 14, the image processing unit 4 generates the first absorption image 22 based on the plurality of first images 30, and the second absorption image 24 based on the plurality of second images 31. Is generated, and the second luminance change 46 is acquired based on the first absorption image 22 and the second absorption image 24.

Here, the second luminance change 46 is a change in the luminance of the X-rays caused by the incident angle when the X-rays are applied to the grid. Therefore, unlike the first luminance change 40, it is considered that the change over time is small. Therefore, the image processing unit 4 generates the second absorption image 24 by selecting one of the plurality of second images 31 as the second absorption image 24. When the second luminance change 46 is acquired based on the first absorption image 22 and the second absorption image 24, it is preferable that the position where the subject 90 is captured in each absorption image is the same. Therefore, the image processing unit 4 aligns the position where the subject 90 in the second absorption image 24 is captured with the position where the subject 90 is captured in the first absorption image 22.

The plurality of first images 30 are images generated based on the X-rays detected by the detector 2 after passing through the plurality of grids. Therefore, the plurality of first images 30 have both a change in luminance due to the passage of X-rays through the subject 90 and a second luminance change 46 caused by the passage of X-rays through the grid. Therefore, in the first absorption image 22 generated based on the plurality of first images 30, a false image is caused by the change in luminance caused by the passage of X-rays through the subject 90 and the change in second luminance 46. 81 occurs.

The plurality of second images 31 are images generated based on the X-rays detected by the detector 2 without passing through the plurality of grids. Therefore, in the plurality of second images 31, the change in luminance caused by the passage of X-rays through the subject 90 occurs, but the change in luminance 46 caused by the passage of X-rays through the grid does not occur. That is, since the second absorption image 24 is generated based on the X-rays detected without passing through the grid, the change in the brightness of the X-rays caused by the subject 90 is generated in the second absorption image 24. Is included.

Therefore, as shown in FIG. 14, by subtracting or dividing the second absorption image 24 from the first absorption image 22, the change in the luminance of the X-rays caused by the subject 90 is removed, and the X-rays pass through the grid. The second luminance change 46 caused by the above can be acquired.

In the present embodiment, as shown in FIG. 15, the image processing unit 4 corrects the dark field image 23 based on the second luminance change 46 to generate the dark field image 25 from which the false image 82 is removed. .. Since the false image 82 generated in the dark field image 23 is a brightness change in contrast to the second luminance change 46, the image processing unit 4 can, for example, add the second luminance change 46 to the dark field image 23. The dark field image 23 is corrected. Any method may be used as the correction method as long as the false image 82 can be removed from the dark field image 23 by using the second luminance change 46.

Next, with reference to FIG. 16, the process in which the image processing unit 4 according to the present embodiment generates the phase contrast image 21 will be described.

In step 101, the image processing unit 4 acquires a plurality of first images 30 generated based on the first X-rays acquired at the plurality of shooting positions while changing the relative position of the detector 2 with respect to the subject 90.

In step 102, the image processing unit 4 acquires a plurality of second images 31 generated based on the second X-rays acquired in the plurality of shootings while changing the relative position of the detector 2 with respect to the subject 90.

In step 103, the image processing unit 4 acquires a plurality of third images 33 generated based on the first X-rays acquired at a plurality of shooting positions in a state where the subject 90 is not arranged.

In step 104, the image processing unit 4 acquires a plurality of fourth images 34 generated based on the second X-rays acquired at a plurality of shooting positions in a state where the subject 90 is not arranged.

In step 105, the image processing unit 4 performs sensitivity correction on the plurality of second images 31 and the plurality of fourth images 34.

In step 106, the image processing unit 4 corrects each of the plurality of first images 30 based on the plurality of second images 31.

In step 107, the image processing unit 4 corrects each of the plurality of third images 33 based on the plurality of fourth images 34.

In step 108, at least one of the phase contrast image 21 and the dark field image 23 is generated based on the corrected first image 32. In the present embodiment, in the process of step 107, the image processing unit 4 generates the phase contrast image 21 based on the corrected first image 32 and the corrected third image 35. do. After that, the process ends.

The processes of steps 101 to 104 may be performed in any order. Further, when the third image 35 corrected by the plurality of fourth images 34 is acquired in advance, the processing of step 103, the processing of step 104, and the processing of step 107 are omitted.

Next, with reference to FIG. 17, a process in which the image processing unit 4 according to the present embodiment generates a dark field image 25 will be described. A detailed description of the same process as the step in the process of generating the phase contrast image 21 will be omitted.

In step 101, the image processing unit 4 is. A plurality of first images 30 are acquired.

In step 201, the image processing unit 4 acquires the first absorption image 22 based on the plurality of first images 30.

In step 102, the image processing unit 4 acquires a plurality of second images 31.

In step 202, the image processing unit 4 acquires the second absorption image 24 based on the plurality of second images 31.

In step 203, the image processing unit 4 acquires the second luminance change 46 based on the first absorption image 22 and the second absorption image 24.

In step 204, the image processing unit 4 generates a dark field image 23 based on the plurality of first images 30.

In step 205, the image processing unit 4 corrects the dark field image 23 based on the second luminance change 46 to generate the dark field image 25 from which the false image 82 is removed. After that, the process ends. Either the process of step 101 and step 201 and the process of step 102 and step 202 may be performed first.

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

In the present embodiment, as described above, in the X-ray imaging apparatus 100, the X-ray source 1 and the X-rays emitted from the X-ray source 1 are diffracted or a part of the irradiated X-rays is shielded. The first lattice 6 in which the first lattice pattern is formed, the first X-rays arriving through the first lattice 6 and the second X-rays arriving without passing through the first lattice 6 are detected. The detector 2, the relative position moving unit 3 that moves the relative position of the detector 2 with respect to the subject 90, and a plurality of first images 30 generated based on the first X-rays acquired at the plurality of relative positions with respect to the subject 90. Is corrected based on the plurality of second images 31 generated based on the second X-rays acquired at the plurality of relative positions with respect to the subject 90, and the phase contrast image is corrected based on the corrected plurality of first images 32. An image processing unit 4 that generates at least one of 21 or a dark field image 23 is provided. Here, the irradiation intensity of the X-rays emitted from the X-ray source 1 changes with time due to the rotation of the target of the X-ray source 1 and the like. Therefore, the brightness of the X-rays detected by the detector 2 also changes with time. If this luminance change is faster than the image acquisition frame rate of the detector 2, striped artifacts are generated in the detected image. The temporal change in the brightness of X-rays occurs in both the first X-ray and the second X-ray. Since the first X-rays pass through the grid, in addition to the temporal change in the brightness of the X-rays, the X-rays pass through the grid, causing different X-ray attenuations and spectral changes in the regions within the grid. On the other hand, since the second X-ray does not pass through the grid, the X-ray does not change due to the grid. Therefore, by configuring as described above, by estimating the temporal luminance change of the X-ray based on the plurality of second images 31 generated based on the second X-ray, the attenuation of the X-ray by the lattice is reduced. The temporal luminance change of X-rays can be estimated more accurately as compared with the configuration of estimating the temporal luminance change of X-rays based on a plurality of generated first images 30.

Further, since the plurality of first images 30 are generated based on the X-rays after passing through the lattice, a false image 82 due to the lattice may occur. On the other hand, since the plurality of second images 31 are generated based on the X-rays detected without passing through the grid, the false image 82 caused by the grid does not occur. Therefore, when the false image 82 caused by the grid is generated in the plurality of first images 30, it is caused by the angle of the X-rays applied to the grid based on the first image 30 and the second image 31. The false image 82 generated by the above can be estimated. Therefore, since the phase contrast image 21 or the dark field image 23 is generated based on the plurality of first images 32 corrected based on the plurality of second images 31, the phase contrast image 21 or the dark field image 23 is a false image. It is possible to suppress the occurrence of (artifact) 80 and false image 82. As a result, when at least one of the phase contrast image 21 and the dark field image 23 is generated, it is possible to suppress the deterioration of the image quality of the obtained image.

Further, in the above embodiment, the following further effects can be obtained by configuring as follows.

That is, in the present embodiment, as described above, the region 76 to be irradiated with the first X-ray and the region 77 to be irradiated with the second X-ray are arranged in a predetermined direction intersecting the direction of the irradiation axis 70 of the X-ray. The image processing unit 4 is arranged with, and based on the plurality of second images 31, the first brightness change 40 of X-rays generated in a direction orthogonal to a predetermined direction in the plane of the plurality of second images 31. Is obtained, and each of the plurality of first images 30 is corrected based on the acquired first brightness change 40 of the X-ray. As a result, even when the first luminance change 40 of the X-ray, which is the temporal luminance change of the X-ray caused by the rotation of the target from the X-ray source 1, occurs, it is acquired based on the plurality of second images 31. The first luminance change 40 can correct the luminance change in each of the plurality of first images 30 in the direction orthogonal to the predetermined direction. As a result, each of the plurality of first images 30 is corrected, so that the phase contrast image 21 or the dark field image 23 generated based on the plurality of first images 30 is false due to the temporal brightness change of the X-ray. It is possible to suppress the formation of the image 80.

Further, in the present embodiment, as described above, the image processing unit 4 determines the change in luminance that occurs in the plane of the plurality of first images 30 in the direction orthogonal to the predetermined direction based on the first luminance change 40. , Each of the plurality of first images 30 is corrected by correcting in a direction along a predetermined direction. Here, the first luminance change 40 of the X-ray occurs in the direction (Y direction) orthogonal to the predetermined direction (X direction), and the luminance in the direction along the predetermined direction does not change. Therefore, by configuring as described above, in each of the first images 30, the luminance change that occurs in the direction orthogonal to the predetermined direction is corrected along the predetermined direction by the first luminance change 40. , The change in brightness that occurs in the entire first image 30 can be easily corrected.

Further, in the present embodiment, as described above, the image processing unit 4 has a plurality of second images 31 based on a predetermined region determined based on the relative movement of the subject 90 in the plurality of second images 31. It is configured to acquire the first luminance change 40 that occurs in each of the above. As a result, a predetermined area determined based on the relative movement of the subject 90 is determined, so that the positions of the subject 90 in the predetermined area of the second image 31 can be aligned between the second images 31. Therefore, since it is possible to align the positions where the subject 90 is captured in a predetermined area, the subject 90 captured in each second image 31 can be removed. As a result, the subject 90 is removed from each of the second images 31, so that the first luminance change 40 that occurs in each of the plurality of second images 31 can be acquired.

Further, in the present embodiment, as described above, the predetermined area is the area 42 in which the same part of the subject 90 is captured in each of the plurality of second images 31, and the image processing unit 4 is the same part of the subject 90. By acquiring the average value of the pixel values of the region 42 in which the image is captured and dividing each of the plurality of second images 31 by the acquired average value, the first luminance of the X-ray generated in each of the plurality of second images 31 It is configured to acquire change 40. Thereby, by dividing each of the plurality of second images 31 by the acquired average value, the subject 90 reflected in each second image 31 can be easily removed. As a result, the subject 90 is removed from each of the second images 31, so that the first luminance change 40 that occurs in each of the plurality of second images 31 can be easily obtained.

Further, in the present embodiment, as described above, the image processing unit 4 corrects the sensitivity of each of the plurality of second images 31, and is based on the plurality of second images 31 after the sensitivity correction. Therefore, it is configured to acquire the first luminance change 40 of the X-ray. Thereby, the noise caused by the detector 2 generated in the plurality of second images 31 can be removed. Therefore, it is possible to suppress the deterioration of the image quality of the corrected first image 32 due to the noise caused by the detector 2. As a result, it is possible to further suppress the deterioration of the image quality of the phase contrast image 21 or the image quality of the dark field image 23 generated based on the corrected first image 32.

Further, in the present embodiment, as described above, the image processing unit 4 is configured to perform smoothing processing on the first luminance change 40. Thereby, the high frequency noise included in the first luminance change 40 can be removed by the smoothing process. Therefore, by correcting the plurality of first images 30 by the corrected first luminance change, the image quality of the corrected first image 32 deteriorates due to the noise included in the first luminance change 40. It can be suppressed. As a result, it is possible to further suppress the deterioration of the image quality of the corrected first image 32, so that the image quality of the phase contrast image 21 generated based on the corrected first image 32 or the darkness is achieved. It is possible to further suppress the deterioration of the image quality of the field image 23.

Further, in the present embodiment, as described above, the image processing unit 4 uses the subject 90 as a plurality of third images 33 generated based on the first X-rays acquired in a state where the subject 90 is not arranged. A plurality of corrected first images 32 and a plurality of corrected third images are corrected based on a plurality of fourth images 34 generated based on the second X-rays acquired in a non-arranged state. It is configured to generate at least one of the phase contrast image 21 and the darkfield image 23 based on 35. As a result, the phase contrast image 21 or the phase contrast image 21 or the plurality of corrected first images 32 in which the first luminance change 40 is corrected and the plurality of corrected third images 35 in which the first luminance change 41 is corrected are used. Since the dark field image 23 is generated, it is possible to further suppress the occurrence of the false image 80 in the phase contrast image 21 or the dark field image 23.

Further, in the present embodiment, as described above, the region 76 to be irradiated with the first X-ray and the region 77 to be irradiated with the second X-ray are arranged side by side in a predetermined direction, and the image processing unit 4 is arranged. Based on the plurality of first images 30 and the plurality of second images 31, the second luminance change 46 of the X-rays caused by the passage of the X-rays through the first lattice 6 is acquired, and the acquired second luminance change is acquired. It is configured to correct the dark field image 23 based on 46. As a result, the dark field image 23 is corrected by the second luminance change 46 acquired based on the plurality of first images 30 and the plurality of second luminance 31, so that the false image 82 generated by the second luminance change 46 is generated. The removed dark field image 25 can be easily obtained.

Further, in the present embodiment, as described above, the image processing unit 4 generates the first absorption image 22 based on the plurality of first images 30, and the second absorption image 24 based on the plurality of second images 31. Is generated, and the second luminance change 46 is acquired based on the first absorption image 22 and the second absorption image 24. As a result, the second luminance change 46 is based on the first absorption image 22 including the X-ray luminance change caused by the subject 90 and the grid and the second luminance image 24 including the X-ray luminance change caused by the subject 90. By acquiring, only the luminance change (second luminance change 46) of the X-ray caused by the grid can be easily acquired.

Further, in the present embodiment, as described above, a second grid 7 is further provided, which is arranged between the first grid 6 and the detector 2 and for interfering with the self-image of the first grid 6. As a result, by interfering the self-image of the first grid 6 with the second grid 7, it is possible to form an interference fringe having a period larger than the period (pitch) of the self-image of the first grid 6. As a result, the detector 2 required to generate the phase contrast image 21 or the dark field image 23 is required to generate the phase contrast image 21 or the dark field image 23 as compared with the case where the self-image of the first grid 6 is directly detected by detecting the formed interference fringes. It is possible to suppress an increase in detection accuracy.

Further, in the present embodiment, as described above, a second lattice pattern is formed so as to diffract the X-rays emitted from the X-ray source 1 or to shield a part of the irradiated X-rays, and the second grid pattern is formed. The third grid 9 is arranged so that the direction of the grid pattern is orthogonal to the direction of the first grid pattern, and the third grid 9 is arranged between the third grid 9 and the detector 2, and the third grid 9 is self. A fourth grid 10 for interfering with the image is further provided. As a result, in the region 76 where the first X-ray is irradiated, since each grid is arranged so that the first grid pattern and the second grid pattern are orthogonal to each other, the region 76 where the first X-ray is irradiated By photographing at a plurality of relative positions in the above, the subject 90 can be imaged in a lattice pattern orthogonal to each other without changing the arrangement direction of the lattice. As a result, unlike the configuration in which the direction of the grid pattern is changed to image the subject 90, it is possible to take an image in a grid pattern orthogonal to each other without changing the arrangement direction of the grid, so that the imaging time is increased. It can be suppressed.

Further, in the present embodiment, as described above, in the method of generating an X-ray image, a lattice pattern is formed so as to diffract or shield the X-ray source 1 and the X-rays emitted from the X-ray source 1. An X-ray imaging apparatus including 1 grid 6 and a detector 2 for detecting first X-rays arriving through the first grid 6 and second X-rays arriving without passing through the first grid 6. In the X-ray image generation method used, a plurality of first images 30 generated based on the first X-rays acquired at a plurality of shooting positions are acquired while changing the relative position of the detector 2 with respect to the subject 90. A step of acquiring a plurality of second images 31 generated based on the second X-rays acquired in a plurality of shootings while changing the relative position of the detector 2 with respect to the subject 90, and a plurality of second images. A step of correcting each of the plurality of first images 30 based on 31 and a step of generating at least one of the phase contrast image 21 or the dark field image 23 based on the corrected plurality of first images 32 are provided. .. This makes it possible to suppress deterioration of the image quality of the obtained image when at least one of the phase contrast image 21 and the dark field image 23 is generated, similarly to the X-ray image capturing apparatus 100 in the above embodiment. It is possible to provide a method for generating an X-ray image.

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

For example, in the above embodiment, the relative position moving unit 3 has shown an example in which the relative position of the detector 2 with respect to the subject 90 is changed by moving the subject 90, but the present invention is not limited to this. In the present invention, the relative position moving unit 3 changes the relative position of the detector 2 with respect to the subject 90 by moving the image pickup system including the X-ray source 1, a plurality of grids, and the detector 2. You may.

Further, in the above embodiment, an example of a configuration in which a plurality of lattices include both a first lattice group and a second lattice group is shown, but the present invention is not limited to this. For example, the X-ray imaging apparatus 100 may be configured to include only one of the first grid group and the second grid group.

Further, in the above embodiment, an example including the radiation source grid 8 and the radiation source grid 11 is shown, but the present invention is not limited to this. In the present invention, the X-ray imaging apparatus 100 may be configured not to include the radiation source grid 8 and the radiation source grid 11. In that case, since the X-rays cannot be micro-focused by the radiation source grid 8 and the radiation source grid 11, it is preferable that the X-ray source 1 has a configuration capable of irradiating X-rays having high coherence.

Further, in the above embodiment, an example in which a grid for diffracting X-rays is used as the first grid 6 and the third grid 9, but the present invention is not limited to this. In the present invention, a grid that shields X-rays may be used as the first grid 6 and the third grid 9.

Further, in the above embodiment, as a method of detecting the X-rays diffracted by the first grid 6 (third grid 9), a second for interfering with the self-image generated by the first grid 6 (third grid 9). Although the method of providing the grid 7 (fourth grid 10) is shown, the present invention is not limited to this. In the present invention, a method of directly detecting a self-image using a detector having fine pixels may be used, or a method of interfering with the self-image using a detector having a grid-like scintillator may be used. ..

Further, in the above embodiment, an example of the configuration in which the image processing unit 4 acquires four images as a plurality of second images 31 is shown, but the present invention is not limited to this. For example, the image processing unit 4 may be configured to acquire eight second images 31. The number of the plurality of second images 31 acquired by the image processing unit 4 may be any number as long as it is four or more.

Further, in the above embodiment, an example of the configuration in which the image processing unit 4 generates the phase contrast image 21 based on the plurality of first images 32 corrected based on the first luminance change 40 is shown. Is not limited to this. For example, the image processing unit 4 may be configured to generate a dark field image based on a plurality of first images 32 corrected based on the first luminance change 40.

Further, in the above embodiment, an example of a configuration in which the image processing unit 4 performs sensitivity correction on a plurality of second images 31 is shown, but the present invention is not limited to this. For example, the image processing unit 4 does not have to perform sensitivity correction on the plurality of second images 31. However, in a configuration in which the sensitivity correction is not performed on the plurality of second images 31, the image quality of the obtained phase contrast image or dark field image may deteriorate. Therefore, the image processing unit 4 may perform the plurality of second images 31. It is preferable that the sensitivity is corrected.

Further, in the above embodiment, an example of the configuration in which the image processing unit 4 performs smoothing processing on the first luminance change 40 is shown, but the present invention is not limited to this. For example, the image processing unit 4 does not have to perform smoothing processing on the first luminance change 40. However, when the image processing unit 4 does not perform the smoothing process on the first luminance change 40, the image quality of the obtained phase contrast image or dark field image is improved due to the high frequency noise included in the first luminance change 40. Since the image processing unit 4 may be lowered, it is preferable that the image processing unit 4 is configured to perform smoothing processing on the first luminance change 40.

[Aspect]
It will be understood by those skilled in the art that the above-mentioned exemplary embodiments are specific examples of the following embodiments.

(Item 1)
X-ray source and
A first grid in which a first grid pattern is formed so as to diffract X-rays emitted from the X-ray source or to shield a part of the irradiated X-rays.
A detector that detects the first X-ray that arrived through the first grid and the second X-ray that arrived without passing through the first grid.
A relative position moving unit that moves the relative position of the detector with respect to the subject,
A plurality of first images generated based on the first X-rays acquired at a plurality of the relative positions with respect to the subject are generated based on the second X-rays acquired at the plurality of the relative positions with respect to the subject. In addition to making corrections based on multiple second images
An X-ray imaging apparatus including an image processing unit that generates at least one of a phase contrast image or a dark field image based on the corrected first image.

(Item 2)
The region irradiated with the first X-ray and the region irradiated with the second X-ray are arranged side by side in a predetermined direction intersecting the direction of the irradiation axis of the X-ray.
The image processing unit
Based on the plurality of second images, the first luminance change of X-rays occurring in a direction orthogonal to the predetermined direction in the plane of the plurality of second images is acquired, and at the same time.
The X-ray imaging apparatus according to item 1, which is configured to correct each of the plurality of first images based on the acquired first luminance change of the X-ray.

(Item 3)
The image processing unit corrects a change in brightness that occurs in a direction orthogonal to the predetermined direction in the plane of the plurality of first images in a direction along the predetermined direction based on the first brightness change. Item 2. The X-ray imaging apparatus according to item 2, which is configured to correct each of the plurality of first images.

(Item 4)
The image processing unit acquires the first luminance change that occurs in each of the plurality of second images based on a predetermined region determined based on the relative movement of the subject in the plurality of second images. The X-ray imaging apparatus according to item 2 or 3, which is configured as described above.

(Item 5)
The predetermined area is an area in which the same portion of the subject is captured in each of the plurality of second images.
The image processing unit acquires the average value of the pixel values of the region in which the same portion of the subject is captured, and divides each of the plurality of second images by the acquired average value to obtain the plurality of second images. The X-ray imaging apparatus according to item 4, which is configured to acquire the first luminance change that occurs in each of the images.

(Item 6)
The image processing unit corrects the sensitivity of each of the plurality of second images, and acquires the first luminance change based on the plurality of second images after the sensitivity correction. The X-ray image capturing apparatus according to any one of items 3 to 5, which is configured.

(Item 7)
The X-ray image capturing apparatus according to any one of items 3 to 6, wherein the image processing unit is configured to perform smoothing processing on the first luminance change.

(Item 8)
The image processing unit
A plurality of third images generated based on the first X-rays acquired in a state where no subject is placed, and a plurality of images generated based on the second X-rays acquired in a state where no subject is placed. While making corrections based on the 4th image of
Items 1 to 6 configured to generate at least one of the phase contrast image or the dark field image based on the corrected first image and the corrected third image. The X-ray imaging apparatus according to any one of the above items.

(Item 9)
The region irradiated with the first X-ray and the region irradiated with the second X-ray are arranged side by side in a predetermined direction.
The image processing unit acquires and acquires the second luminance change of the X-ray caused by the X-ray passing through the first lattice based on the plurality of first images and the plurality of second images. The X-ray imaging apparatus according to item 1, which is configured to correct the dark field image based on the second luminance change.

(Item 10)
The image processing unit generates a first absorption image based on the plurality of first images, generates a second absorption image based on the plurality of second images, and generates the first absorption image and the second absorption image. Item 9. The X-ray image photographing apparatus according to item 9, which is configured to acquire the second luminance change based on an image.

(Item 11)
Item 6. X-ray imaging according to any one of items 1 to 10, further comprising a second grid arranged between the first grid and the detector to interfere with the self-image of the first grid. Device.

(Item 12)
A second grid pattern is formed so as to diffract the X-rays emitted from the X-ray source or shield a part of the irradiated X-rays, and the direction of the second grid pattern is the direction of the first grid pattern. A third grid arranged so as to be orthogonal to the direction of
The X-ray image according to any one of items 1 to 11, further comprising a fourth grid arranged between the third grid and the detector to interfere with the self-image of the third grid. Shooting device.

(Item 13)
X-ray source and
A grid in which a grid pattern is formed so as to diffract or shield X-rays emitted from the X-ray source, and
A method for generating an X-ray image using an X-ray imaging apparatus including a detector for detecting a first X-ray that has passed through the grid and a second X-ray that has arrived without passing through the grid. There,
A step of acquiring a plurality of first images generated based on the first X-rays acquired at a plurality of shooting positions while changing the relative position of the detector with respect to the subject.
A step of acquiring a plurality of second images generated based on the second X-rays acquired in a plurality of shootings while changing the relative position of the detector with respect to the subject.
A step of correcting each of the plurality of first images based on the plurality of second images, and a step of correcting each of the plurality of first images.
A method for generating an X-ray image, comprising a step of generating at least one of a phase contrast image or a dark field image based on the corrected first image.

1 X-ray source 2 Detector 3 Relative position moving part 4 Image processing part 6 1st grid 7 2nd grid 9 3rd grid 10 4th grid 21 Phase contrast image 22 1st absorption image 24 2nd absorption image 25 Dark field image 30, 30a, 30b, 30c, 30d First image 31, 31a, 31b, 31c, 31d Second image 32 Corrected first image 33, 33a, 33b, 33c, 33d Third image 34, 34a, 34b, 34c , 34d 4th image 35 3rd image after correction 40 1st brightness change of X-ray 42 Area where the same part of the subject is captured 46 2nd brightness change of X-ray 76 Area where 1st X-ray is irradiated 77 2nd X-ray Irradiated area 90 Subject 100 X-ray imaging device

Claims (13)

X-ray source and
A first grid in which a first grid pattern is formed so as to diffract X-rays emitted from the X-ray source or to shield a part of the irradiated X-rays.
A detector that detects the first X-ray that arrived through the first grid and the second X-ray that arrived without passing through the first grid.
A relative position moving unit that moves the relative position of the detector with respect to the subject,
A plurality of first images generated based on the first X-rays acquired at a plurality of the relative positions with respect to the subject are generated based on the second X-rays acquired at the plurality of the relative positions with respect to the subject. In addition to making corrections based on multiple second images
An X-ray imaging apparatus including an image processing unit that generates at least one of a phase contrast image or a dark field image based on the corrected first image. The region irradiated with the first X-ray and the region irradiated with the second X-ray are arranged side by side in a predetermined direction intersecting the direction of the irradiation axis of the X-ray.
The image processing unit
Based on the plurality of second images, the first luminance change of X-rays occurring in a direction orthogonal to the predetermined direction in the plane of the plurality of second images is acquired, and at the same time.
The X-ray imaging apparatus according to claim 1, wherein each of the plurality of first images is corrected based on the acquired first luminance change of the X-ray. The image processing unit corrects a change in brightness that occurs in a direction orthogonal to the predetermined direction in the plane of the plurality of first images in a direction along the predetermined direction based on the first brightness change. The X-ray imaging apparatus according to claim 2, which is configured to correct each of the plurality of first images. The image processing unit acquires the first luminance change that occurs in each of the plurality of second images based on a predetermined region determined based on the relative movement of the subject in the plurality of second images. The X-ray imaging apparatus according to claim 2 or 3, which is configured as described above. The predetermined area is an area in which the same portion of the subject is captured in each of the plurality of second images.
The image processing unit acquires the average value of the pixel values of the region in which the same portion of the subject is captured, and divides each of the plurality of second images by the acquired average value to obtain the plurality of second images. The X-ray imaging apparatus according to claim 4, which is configured to acquire the first luminance change that occurs in each of the images. The image processing unit corrects the sensitivity of each of the plurality of second images, and acquires the first luminance change based on the plurality of second images after the sensitivity correction. The X-ray imaging apparatus according to any one of claims 3 to 5, which is configured. The X-ray image photographing apparatus according to any one of claims 3 to 6, wherein the image processing unit is configured to perform smoothing processing on the first luminance change. The image processing unit
A plurality of third images generated based on the first X-rays acquired in a state where no subject is placed, and a plurality of images generated based on the second X-rays acquired in a state where no subject is placed. While making corrections based on the 4th image of
Claims 1 to 1, wherein at least one of the phase contrast image and the dark field image is generated based on the corrected first image and the corrected third image. 6. The X-ray imaging apparatus according to any one of 6. The region irradiated with the first X-ray and the region irradiated with the second X-ray are arranged side by side in a predetermined direction.
The image processing unit acquires and acquires the second luminance change of the X-ray caused by the X-ray passing through the first lattice based on the plurality of first images and the plurality of second images. The X-ray imaging apparatus according to claim 1, which is configured to correct the dark field image based on the second luminance change. The image processing unit generates a first absorption image based on the plurality of first images, generates a second absorption image based on the plurality of second images, and generates the first absorption image and the second absorption image. The X-ray imaging apparatus according to claim 9, which is configured to acquire the second luminance change based on an image. The X-ray image according to any one of claims 1 to 10, further comprising a second grid arranged between the first grid and the detector to interfere with the self-image of the first grid. Shooting device. A second grid pattern is formed so as to diffract the X-rays emitted from the X-ray source or shield a part of the irradiated X-rays, and the direction of the second grid pattern is the direction of the first grid pattern. A third grid arranged so as to be orthogonal to the direction of
The X-ray according to any one of claims 1 to 11, further comprising a fourth grid, which is arranged between the third grid and the detector and for interfering with the self-image of the third grid. Imaging device. X-ray source and
A grid in which a grid pattern is formed so as to diffract or shield X-rays emitted from the X-ray source, and
A method for generating an X-ray image using an X-ray imaging apparatus including a detector for detecting a first X-ray that has passed through the grid and a second X-ray that has arrived without passing through the grid. There,
A step of acquiring a plurality of first images generated based on the first X-rays acquired at a plurality of shooting positions while changing the relative position of the detector with respect to the subject.
A step of acquiring a plurality of second images generated based on the second X-rays acquired in a plurality of shootings while changing the relative position of the detector with respect to the subject.
A step of correcting each of the plurality of first images based on the plurality of second images, and a step of correcting each of the plurality of first images.
A method for generating an X-ray image, comprising a step of generating at least one of a phase contrast image or a dark field image based on the corrected first image.

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