CN116491964A - Radiation imaging apparatus and radiography system - Google Patents

Abstract

The invention discloses a radiation imaging apparatus and a radiography system. The radiation imaging apparatus includes an attenuation member for reducing reflection of a component disposed on a back side of the radiation imaging apparatus, the reflection of the component being generated by back-scattered radiation that has been reflected on a structure of the back side of the radiation imaging apparatus, the attenuation member being provided on the back side of a radiation incidence plane of the radiation detection unit, wherein the attenuation member is made of a material having an atomic number higher than a material having a highest atomic number among materials of the component, and a material having an atomic number lower than the material having the highest atomic number among materials of the component, covers an end portion of an outline of the component overlapping the radiation detection unit in orthogonal projection onto the second plane, and is smaller in area than the radiation detection unit.

Description

Radiation imaging apparatus and radiography system

Technical Field

The present invention relates to a radiation imaging apparatus and a radiography system.

Background

Radiographic medical image diagnosis and nondestructive inspection are currently being widely performed using a radiation imaging apparatus in which a flat panel detector (hereinafter abbreviated as FPD) formed of a semiconductor material is used as a radiation detector. These radiation imaging apparatuses are used in a radiographic system for medical image diagnosis as digital imaging apparatuses capable of still image capturing such as normal imaging or moving image capturing such as fluoroscopic imaging, for example.

The radiation imaging apparatus generates a radiographic image by converting radiation from the radiation generating apparatus into an electrical signal through an FPD disposed in the radiation imaging apparatus. At this time, a part of the radiation passes through the FPD, and then may become scattered radiation (back-scattered radiation) by being reflected on a structure of a side of the FPD opposite to the side on which the radiation is incident and then reentering the FPD. Such back-scattered radiation may enter the FPD through an assembly disposed on a side of the FPD opposite to the side on which the radiation is incident, and the assembly may be reflected in the radiographic image to generate artifacts.

For example, japanese patent application laid-open No.2004-294114 discusses a technique for reducing the influence of artifacts by using attenuation members having different radiation transmittances in the corresponding areas so that the amount of back-scattered radiation reaching the FPD becomes almost uniform. The attenuation member is generally heavier in weight as the radiation transmittance is lower. However, according to the technique discussed in japanese patent application laid-open No.2004-294114, an attenuation member having a high radiation transmittance, that is, an attenuation member having a low weight is used in a region that does not affect the image quality, so that the radiation imaging apparatus can be made light in weight. Making the radiation imaging apparatus lighter in weight reduces the workload of a user carrying the radiation imaging apparatus to set the radiation imaging apparatus for the subject.

However, in the technique discussed in japanese patent application laid-open No.2004-294114, it is necessary to use an attenuation member having a low radiation transmittance, i.e., a heavy attenuation member, at a position where a component having a high radiation transmittance is arranged at a side of the FPD opposite to the side where radiation is incident. For example, if an assembly having a low radiation transmittance is made lighter in weight for the purpose of weight reduction of the radiation imaging apparatus, an attenuation member having a low radiation transmittance is arranged in a region having a high radiation transmittance. This causes a disadvantage that it is difficult to further reduce the weight of the radiation imaging apparatus.

Disclosure of Invention

The present invention has been made in view of the above-described disadvantages. An aspect of the present invention is to provide a technique for reducing artifacts that may occur in radiographic images due to back-scattered radiation while suppressing the weight of a radiation imaging apparatus.

According to an aspect of the present invention, a radiation imaging apparatus that performs radiographic imaging based on radiation that has been emitted by a radiation generating apparatus and passed through a subject includes: a radiation detection unit including a plurality of pixels for converting radiation into an electric signal and having a first plane on a side of the radiation detection unit on which radiation from the radiation generating apparatus is incident and a second plane on a side opposite to the first plane; an assembly provided at a second plane of the radiation detection unit; and an attenuation member provided on a second plane of the radiation detection unit to attenuate back-scattered radiation incident on the radiation detection unit from a side of the second plane, wherein the attenuation member is made of a material having an atomic number higher than a material having a highest atomic number among materials of the components and a material having an atomic number lower than a material having a highest atomic number among materials of the components, covers an end of an outer shape of the component overlapping the radiation detection unit in orthogonal projection onto the second plane, and is smaller in area than the radiation detection unit.

Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1 is a diagram illustrating a configuration of a radiography system according to a first exemplary embodiment.

Fig. 2A and 2B are diagrams illustrating a configuration of a radiation imaging apparatus according to the first exemplary embodiment.

Fig. 3 is a schematic diagram illustrating back-scattered radiation according to the first exemplary embodiment.

Fig. 4A and 4B are schematic diagrams illustrating an arrangement of the attenuation members according to the first exemplary embodiment.

Fig. 5A and 5B are diagrams illustrating a relationship between the position in fig. 4 and the incident amount of scattered radiation according to the first exemplary embodiment.

Fig. 6A and 6B are schematic diagrams illustrating an arrangement of the attenuation member according to the second exemplary embodiment.

Detailed Description

Hereinafter, exemplary embodiments to which the present invention is applied will be described in detail with reference to the accompanying drawings.

The following exemplary embodiments are not intended to limit the invention according to the claims. Exemplary embodiments include a number of features as described below. However, all of these features are not necessarily essential to the invention, and the features may be arbitrarily combined. In the drawings, the same or similar components are denoted by the same reference numerals, and repetitive description thereof will be omitted. The term radiation herein may typically refer to, but is not limited to, X-rays. For example, other radiation (e.g., alpha rays, beta rays, gamma rays, etc.) may also be applied.

Fig. 1 is a diagram illustrating an overall configuration of a radiography system 10 according to a first exemplary embodiment of the present invention. The radiography system 10 includes a control apparatus 100, a radiation generating apparatus 101, and a radiation imaging apparatus 102. The control apparatus 100 includes an imaging condition setting unit 103, an imaging control unit 104, an image processing unit 105, and a display unit 106. The control apparatus 100 may be a general-purpose computer that includes a Central Processing Unit (CPU), a main storage device, an auxiliary storage device, and a display, and that implements the functions of the components of the control apparatus 100.

The radiation generating apparatus 101 emits radiation to the subject P. The radiation generating apparatus 101 includes an X-ray tube that generates radiation, a collimator that defines an expansion angle of a beam of the generated radiation, and a radiation dosimeter attached to the collimator.

The radiation imaging apparatus 102 performs radiographic imaging based on radiation that has been emitted by the radiation generating apparatus 101 and passed through the subject P. Image data generated by radiographic imaging is transferred to the image processing unit 105, so that the image data undergoes various types of image processing to form a radiographic image. The radiation imaging apparatus 102 also transmits information about the dose of the detected radiation to the imaging control unit 104. The internal structure of the radiation imaging apparatus 102 will be described in detail with reference to fig. 2.

The imaging condition setting unit 103 has an imaging condition input unit for an operator to input imaging conditions such as X-ray voltage, X-ray current, and imaging target portion. Imaging conditions input by the operator are transmitted to the imaging control unit 104. The imaging control unit 104 controls the radiation generating apparatus 101, the radiation imaging apparatus 102, and the image processing unit 105 based on the input imaging conditions.

The image processing unit 105 performs image processing such as offset correction, gain correction, and noise reduction on the radiographic image transmitted from the radiation imaging apparatus 102. The image processing unit 105 transfers the radiographic image that has undergone image processing to the display unit 106. The display unit 106 is a general-purpose display or the like and outputs image information transmitted from the image processing unit 105.

Fig. 2A and 2B are diagrams illustrating the configuration of the radiation imaging apparatus 102 in the present exemplary embodiment. Fig. 2A is an external perspective view of the radiation imaging apparatus 102 seen from the incident plane, and fig. 2B is a sectional view of the radiation imaging apparatus 102 taken along a line A-A' in fig. 2A and seen from the direction indicated by the arrow. An arrow X in fig. 2B schematically indicates the direction of radiation incident on the radiation imaging apparatus 102.

The radiation imaging apparatus 102 has a substantially rectangular parallelepiped shape, and the housing 201 contains components of the radiation imaging apparatus 102. The case 201 includes a front cover 202 having a chest plate portion 202a and a frame portion 202b, a rear cover 203, and a cover 213 of the secondary battery 209.

The chest plate portion 202a is a plate-like member arranged on the side of the housing 201 on which radiation is incident. Since the radiation imaging apparatus 102 is subjected to a load when used for image capturing, the chest plate portion 202a is preferably a high-rigidity member. Further, since the chest plate portion 202a is located on the incident side of the radiation from the radiation generating apparatus 101, the chest plate portion 202a is preferably made of a material having high radiation transmittance. From these viewpoints, the chest plate portion 202a is made of, for example, carbon Fiber Reinforced Plastic (CFRP). The frame portion 202b positioned at the peripheral edge of the chest plate portion 202a is made of magnesium alloy.

The rear cover 203 is a plate-like member arranged on the opposite side of the housing 201 from the side on which radiation is incident. Since the radiation imaging apparatus 102 is subjected to a load as described above, the rear cover 203 is preferably a high-rigidity member. The rear cover 203 is also preferably made of a material having high radiation transmittance. From these viewpoints, the rear cover 203 is made of CFRP, for example.

In the case 201, an impact absorbing sheet 204, a radiation detecting unit 205, and a base 206 are stacked in order from the incident side of radiation. The impact absorbing sheet 204 protects the radiation detection unit 205 from an impact from the outside of the housing 201.

The radiation detection unit 205 is a Flat Panel Detector (FPD) including a plurality of pixels 205a and a scintillator layer 205b on the plurality of pixels 205 a. The plurality of pixels 205a each have a photoelectric conversion element and are aligned in a two-dimensional array on a substrate. The scintillator layer 205b is composed of a plurality of crystals of a scintillator that wavelength-converts radiation into light that can be sensed by the photoelectric conversion element. The radiation emitted from the radiation generating apparatus 101 is converted into light by the scintillator layer 205b, and further converted into an electrical signal by the photoelectric conversion elements of the plurality of pixels 205 a. The electric signals from the plurality of pixels 205a are read by the drive circuit and the read circuit to generate a radiographic image.

The radiation detection unit 205 shown in fig. 2B is configured such that the scintillator layer 205B and the plurality of pixels 205a are stacked in order from the incident side of radiation, but the stacking order in this structure may be reversed. The following description is based on a case where the radiation detection unit 205 is configured such that the scintillator layer 205B and the plurality of pixels 205a are stacked in order from the incident side of radiation as shown in fig. 2B.

The plane of the radiation detection unit 205 on the side where radiation from the radiation generating apparatus 101 is incident will be referred to as a first plane, and the plane on the side opposite to the first plane will be referred to as a second plane. In the following description, a plane of a side where the plurality of pixels 205a are provided is a first plane, and a plane opposite to the first plane is a second plane.

The radiation detection unit 205 is connected to a control board 208 via a flexible circuit board 207. The control board 208 has the above-described drive circuit and read circuit, and controls a drive signal or the like for reading a signal from the photoelectric conversion element.

The base 206 is a plate-like member for supporting the radiation detection unit 205. The radiation detection unit 205 is arranged on the side of the base 206 on which radiation is incident. A control board 208, a secondary battery 209, and a wireless module and an antenna unit, not shown, are provided on the opposite side of the base 206 from the side on which radiation is incident, and these components are supported by the base 206. The control plate 208 (208 a,208 b) is secured to the base 206, for example, by securing members (e.g., bolts) 212. Concave and convex portions (steps) for supporting various components may be formed by the spacer 211 on the opposite side of the base 206 from the side on which radiation is incident. The base 206 is preferably made of magnesium alloy in view of ensuring rigidity, reducing weight, and avoiding the influence of electric noise.

The secondary battery 209 supplies electric power for driving. The wireless module and the antenna portion function as a wireless communication unit that wirelessly transmits an image signal to an external device.

The attenuation member 210 is provided to attenuate back-scattered radiation incident on the radiation detection unit 205. The back-scattered radiation is a component of the radiation emitted to the radiation detection unit 205. If a part of the radiation passes through the radiation detecting unit 205 or the irradiation field is wider than the radiation detecting unit 205, the back-scattered radiation is reflected on a structure of a side of the radiation detecting unit 205 opposite to the side on which the radiation is incident, and enters the radiation detecting unit 205 again. The back-scattered radiation will be described in detail with reference to fig. 3. The attenuation member 210 is made of, for example, a material that absorbs radiation, such as tungsten, molybdenum, lead, stainless steel (SUS), iron, bismuth, or cerium.

Since the attenuation member 210 is a member that attenuates back-scattered radiation incident on the radiation detection unit 205, the attenuation member 210 is provided on the second plane of the radiation detection unit 205. For example, the attenuation member 210 is provided between the radiation detection unit 205 and the base 206, inside and outside the rear cover 203 of the housing 201. However, the position of the attenuation member 210 is not limited thereto, and it is sufficient if the attenuation member is provided on the second plane of the radiation detection unit 205.

Next, the back-scattered radiation will be described with reference to fig. 3. Fig. 3 is a diagram illustrating a state of back-scattered radiation in the radiation generating apparatus 101 and the radiation imaging apparatus 102. The radiation 500 emitted from the radiation generating apparatus 101 enters a radiation detecting unit 205 disposed inside the radiation imaging apparatus 102.

A part of the radiation 500 incident on the radiation detection unit 205 passes through the radiation detection unit 205 without being absorbed by the scintillator layer 205b of the radiation detection unit 205, and is reflected and scattered on the structure 300 such as the wall surface and the floor of the rear side of the radiation detection unit 205, and enters the radiation detection unit 205 again from the rear side. If radiation is emitted in a wider range than the radiation detection unit 205, the radiation is similarly reflected and scattered on the structure 300 such as the wall surface and the floor of the rear side of the radiation imaging apparatus 102, and then enters the radiation detection unit 205 again from the rear side.

The back-scattered radiation incident from the rear side may be partially attenuated by components of the radiation imaging apparatus 102 arranged at the rear side (501) or may partially enter the phosphor (502). The difference in radiation transmittance between the places with components and the places without components causes reflection of the components, i.e., the occurrence of artifacts in radiographic images. The energy E' of the back-scattered radiation is determined by Compton scattering expressed by the following equation 1:

[ equation 1]

In this equation, E is the energy of incident radiation [ keV ], E' is the energy of radiation that has undergone compton scattering [ keV ], and θ is the angle formed by the incident direction of radiation and the scattering direction of compton scattered radiation. Back-scattered radiation refers to radiation that has undergone Compton scattering in the range of 90 deg. to 180 deg..

If the attenuation member 210 is provided so as to shield the entire surface of the radiation detection unit 205 from the back-scattered radiation, the absolute amount of the back-scattered radiation incident on the radiation detection unit 205 may be reduced, thereby reducing the artifact. However, providing the attenuation member 210 on the entire surface of the radiation detection unit 205 increases the weight of the radiation imaging apparatus 102. It is necessary to make the radiation imaging apparatus 102 as light weight as possible, because the radiation imaging apparatus 102 is often carried by a user to set for a subject.

In the present invention, attenuation members smaller in area than the radiation detection unit 205 are arranged to reduce artifacts due to reflection of components caused by back-scattered radiation outside the housing of the radiation imaging apparatus 102, while making the radiation imaging apparatus 102 lightweight.

Fig. 4A and 4B are diagrams simply illustrating the configuration of the radiation imaging apparatus 102 in the present exemplary embodiment. Fig. 4A is a diagram of the radiation imaging apparatus 102 without the attenuation member as seen from the side opposite to the incident side (arrow X in fig. 2) of the radiation imaging apparatus 102, and fig. 4B is a diagram illustrating the radiation imaging apparatus 102 with the attenuation member. The radiation imaging apparatus 102 shown in fig. 4A and 4B is provided with a control board 208a, a control board 208B, and a secondary battery 209.

In this configuration, a large difference occurs in the amount of back-scattered radiation incident on the second plane of the radiation detection unit 205 in the in-plane direction between the end portions of the outer shapes of the components and the places where the components are not present. Artifacts may appear where the difference in the amount of backscattered radiation in the image is large.

In the present exemplary embodiment, the attenuation member 210 is provided so as to cover an end of the outer shape of the component provided on the second plane of the radiation detection unit 205 to reduce reflection in orthogonal projection onto the second plane of the radiation detection unit 205. The attenuation member 210 is higher in radiation transmittance than the component whose reflection is to be reduced.

In this way, it is possible to alleviate the difference in the amount of the back-scattered radiation reaching the second plane of the radiation detection unit 205 between the end of the outer shape of the component whose reflection is to be reduced and the place where the component is not present, thereby reducing the occurrence of artifacts.

Hereinafter, description will be provided with reference to fig. 4A, 4B, 5A, and 5B. Fig. 5A and 5B are diagrams illustrating the incident amount of scattered radiation to the radiation detection unit 205 at a position taken along the line B-B' in fig. 4. In the radiation imaging apparatus 102 shown in fig. 4A, on the side of the radiation detection unit 205 opposite to the side on which radiation is incident, there are areas where components (the control board 208a and the control board 208B in fig. 4A) at positions taken along the line B-B' are provided, and areas where no components are provided. Fig. 5A and 5B illustrate the incident amounts of scattered radiation in the respective areas.

Fig. 5A corresponds to a case where the attenuation member 210 is not provided as shown in fig. 4A, and fig. 5B corresponds to a case where the attenuation member 210 is provided as shown in fig. 4B. In the case of fig. 5A, a large difference occurs in the incident amount of scattered radiation between the region without the component and the region with the component, so that the component can be reflected to cause an artifact.

On the other hand, in the case of fig. 5B in which the attenuation member 210 is provided, the attenuation member 210 creates an area covered by the component and the attenuation member 210, an area covered only by the attenuation member 210, and an area not covered by the component or the attenuation member 210.

The difference in the incident amount of scattered radiation between the regions shown in fig. 5B is smaller than that between the region having no component and the region having the component without the attenuation member 210 arranged, so that the component is less likely to be reflected in the image, thereby reducing the artifact.

The attenuation member 210 is higher in radiation transmittance than the component whose reflection is to be reduced. This is because if the attenuation member 210 is lower in radiation transmittance than the component whose reflection is to be reduced, the attenuation member 210 will be reflected in the image.

Referring to fig. 4A and 4B, the attenuation member 210 is arranged so as to cover the control board 208a, the control board 208B, and the secondary battery 209. As described above with reference to fig. 5A and 5B, the difference in the amount of back-scattered radiation between these areas is relaxed compared to the case without the attenuation member 210, so that the component is less likely to be reflected in the image, thereby reducing the artifact.

Next, the radiation transmittance of the attenuation member 210, particularly, the energy focused on the X-rays will be described in detail.

In general, interactions between X-rays that do not carry a charge and a substance include photoelectric absorption, compton scattering, and electron pair generation. The primary interaction that attenuates X-rays is the photoelectric effect. The photoelectric effect becomes pronounced for higher atomic number species. An approximate expression of the atomic number of a substance and the broad radiation energy as in the following equation 2 is known:

[ equation 2]

In this equation, τ represents the probability of occurrence of the photoelectric effect, E represents the energy of radiation, and Z represents the atomic number of the substance. The known index n varies between 4 and 5 depending on the range of E. According to equation 2, as the atomic number Z of the substance constituting the attenuation member 210 is higher, the radiation transmittance becomes lower, which makes it possible to reduce the absolute amount of the back-scattered radiation incident on the radiation detection unit 205.

On the other hand, if the substance constituting the attenuation member 210 is higher in atomic number Z than the substance constituting the assembly, the attenuation member 210 is lower in radiation transmittance than the assembly.

In this case, as shown in fig. 5B, there is a larger difference in the incident amount of scattered radiation between the region covered only by the attenuation member 210 and the region not covered by the assembly or the attenuation member 210 than in the assembly, which may cause an artifact. In order to prevent the occurrence of such an artifact, it is desirable to mix a substance having a higher radiation transmittance than the assembly (i.e., a low atomic number substance) into the attenuation member 210.

In particular, it is desirable to reduce the radiation transmittance in the energy band of the back-scattered radiation described in equation 1 to be lower than that of the assembly. This makes it possible to alleviate the difference in the amount of back-scattered radiation between the regions as shown in fig. 5B, thereby reducing the occurrence of artifacts.

In the attenuation member 210, among the energies of the radiation emitted from the radiation generating apparatus 101, the ratio of the radiation transmittance between the component of the energy band higher than the energy of the back-scattered radiation and the component of the energy band of the back-scattered radiation is preferably lower than the ratio of the radiation transmittance in the assembly.

For example, in general X-ray imaging, the maximum value of the energy of emitted radiation is in the range of 100kV to 140 kV. The maximum value of the energy of the back-scattered radiation expressed by equation 1 is in the range of about 70kV to 90 kV. In this case, with 80kV as a boundary, the attenuation member 210 is preferably higher than the assembly in transmittance of radiation having an energy of 80kV or less, and the attenuation member 210 is preferably lower than the assembly in transmittance of radiation having an energy of higher than 80 kV. Specifically, the attenuation member 210 is preferably formed by mixing a substance having an atomic number higher than that of the component whose reflection is to be prevented and a substance having an atomic number lower than that of the component whose reflection is to be prevented.

In the foregoing description with reference to fig. 4B, the components whose reflection is to be reduced are the control board 208 and the secondary battery 209. However, the present invention is not limited thereto. For example, the attenuation member 210 may be provided so as to cover concave and convex portions on the base 206, a communication antenna for the radiation imaging apparatus 102, a cable for connection with various electric components, an end of an outer shape of a fastening member for fastening various components.

There may be a difference in radiation transmittance between constituent parts of the assembly. For example, the secondary battery 209 includes a plurality of battery cells in the exterior package, and there is a difference in radiation transmittance between the exterior package of the secondary battery 209 and the battery cells. In this case, the attenuation member 210 may be provided so as to cover the end portions of the constituent parts of the assembly. The material for the attenuation member 210 in this case may be formed of a substance having an atomic number higher than that of the constituent portion whose reflection is to be prevented and a substance having an atomic number lower than that of the constituent portion whose reflection is to be prevented.

For example, to reduce the reflection of the control plate 208, the main reason for the reflection is copper (Cu, having an atomic number of 29). Accordingly, the attenuation member 210 is preferably formed of a substance having an atomic number higher than 29 and a substance having an atomic number lower than 29. In another example, the attenuation member 210 may be formed of a substance having an atomic number higher than that of iron (Fe, having an atomic number 26) for the fastening member and a substance having an atomic number lower than that of iron (Fe, having an atomic number 26) for the fastening member. The present invention is not limited to these examples. The material used for the damping member 210 may be determined according to the substance whose influence is to be reduced.

The attenuation member 210 may vary continuously in thickness at the ends of the profile. This reduces the difference in the amount of back-scattered radiation reaching the second plane of the radiation detection unit 205 at the end of the attenuation member 210, so that the outer shape of the attenuation member 210 is less likely to be reflected in the radiographic image.

The attenuation member 210 may be detachably attached to the radiation imaging apparatus 102.

This facilitates arranging the attenuation member 210 in an appropriate position in view of the state of reflection in the actually captured radiographic image. Removably attaching the attenuation member 210 facilitates changing the material used for the attenuation member 210 according to the state of reflection in the radiographic image.

Next, a second exemplary embodiment of the present invention will be described. The second exemplary embodiment is different from the first exemplary embodiment in that the attenuation member 210 covers only an end portion of a member whose reflection is to be reduced, not the entire member.

Fig. 6A and 6B are schematic diagrams illustrating the radiation imaging apparatus 102 according to the present exemplary embodiment. Fig. 6A illustrates the radiation imaging apparatus 102 without the attenuation member as seen from the side opposite to the incident side, and fig. 6B illustrates the radiation imaging apparatus 102 with the attenuation member 210 added.

In the present exemplary embodiment, the radiation imaging apparatus 102 is provided with a control board 208a, a control board 208b, and a secondary battery 209 as components whose reflection is to be reduced, and an attenuation member 210 is disposed at the outer ends of these components. The arrangement of the attenuation member 210 as shown in fig. 6 reduces the area of the attenuation member 210 to be smaller than that in the first exemplary embodiment, thereby further reducing the weight of the radiation imaging apparatus 102.

According to at least one exemplary embodiment of the present invention, a radiation imaging apparatus that reduces artifacts caused by backscattered radiation while suppressing an increase in weight of the radiation imaging apparatus may be provided.

While the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims (17)

1. A radiation imaging apparatus that performs radiographic imaging based on radiation that has been emitted by a radiation generating apparatus and passed through a subject, the radiation imaging apparatus comprising:

a radiation detection unit including a plurality of pixels for converting radiation into an electric signal and having a first plane on a side of the radiation detection unit on which radiation from the radiation generating apparatus is incident and a second plane on a side opposite to the first plane;

an assembly provided at a second plane of the radiation detection unit; and

an attenuation member provided on a second plane of the radiation detection unit to attenuate back-scattered radiation incident on the radiation detection unit from one side of the second plane,

wherein the attenuation member is made of a material having an atomic number higher than that of a material having a highest atomic number among materials of the components, and a material having an atomic number lower than that of a material having a highest atomic number among materials of the components, covers an end of an outer shape of the component overlapping the radiation detection unit in orthogonal projection onto the second plane, and is smaller in area than the radiation detection unit.

2. The radiation imaging apparatus according to claim 1, wherein, in the attenuation member, a ratio of radiation transmittance between a component of an energy band higher than that of the backscattered radiation and a component of an energy band of the backscattered radiation is lower than that in the assembly, among energies of radiation emitted from the radiation generating apparatus.

3. The radiation imaging apparatus according to claim 1, wherein the attenuation member is higher than the assembly in transmittance of radiation having an energy of 80kV or less, and the attenuation member is lower than the assembly in transmittance of radiation having an energy of higher than 80 kV.

4. The radiation imaging apparatus according to any one of claims 1 to 3, wherein the component is a control board for reading a signal from the radiation detection unit.

5. The radiation imaging apparatus according to any one of claims 1 to 3, wherein the component is a secondary battery that supplies electric power to the radiation imaging apparatus.

6. The radiation imaging apparatus according to any one of claims 1 to 3, wherein the component is an antenna for the radiation imaging apparatus to communicate with an external apparatus.

7. The radiation imaging apparatus according to any one of claims 1 to 3, wherein the component is a base that supports the radiation detection unit on a side of a second plane of the radiation detection unit.

8. The radiation imaging apparatus according to any one of claims 1 to 3, wherein the component is a fastening member that fastens a component of the radiation imaging apparatus.

9. The radiation imaging apparatus according to any one of claims 1 to 3, wherein the component is a cable connected to a component of the radiation imaging apparatus.

10. The radiation imaging apparatus according to any one of claims 1 to 3, wherein the assembly has a plurality of constituent parts for constituting the assembly.

11. The radiation imaging apparatus according to claim 1, wherein the component includes at least one selected from the group of copper and iron.

12. The radiation imaging apparatus according to claim 1, wherein the attenuation member continuously changes in thickness at an end of the outer shape.

13. The radiation imaging apparatus according to claim 1, wherein the attenuation member is detachably attached to the radiation imaging apparatus.

14. The radiation imaging apparatus according to claim 1, wherein the attenuation member includes at least one selected from the group of tungsten, molybdenum, lead, stainless steel (SUS), iron, bismuth, and cerium.

15. The radiation imaging apparatus according to claim 1, comprising a housing accommodating the radiation detection unit and the assembly,

wherein a plane of the housing opposite to a plane of radiation incidence is made of Carbon Fiber Reinforced Plastic (CFRP).

16. The radiation imaging apparatus according to claim 1, wherein each of the plurality of pixels has a photoelectric conversion element, and the radiation detection unit has a scintillator that converts radiation into light that the photoelectric conversion element can sense.

17. A radiography system, the radiography system comprising:

the radiation imaging apparatus according to any one of claims 1 to 16; and

an image processing unit configured to process radiation detected by the radiation imaging apparatus into a radiographic image.