JP7297826B2 - Radiation imaging device and radiography system - Google Patents

Description

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

BACKGROUND ART Currently, radiation imaging apparatuses using a flat panel detector (hereinafter abbreviated as FPD) made of a semiconductor material as a radiation detection unit are widely used as imaging apparatuses for medical image diagnosis and non-destructive inspection using radiation. there is Such a radiation imaging apparatus is used in a radiation imaging system, for example, in medical image diagnosis as a digital imaging apparatus capable of still image imaging such as general radiography and moving image imaging such as fluoroscopic imaging.

A radiation imaging apparatus generates a radiographic image by converting radiation emitted from a radiation generating apparatus into electrical signals by an FPD arranged inside the radiation imaging apparatus. At this time, part of the irradiated radiation can become scattered radiation (backscattered radiation) that passes through the FPD, is reflected by the structure on the opposite side of the FPD to the incident side of the radiation, and reenters the FPD. Such backscattered rays pass through the components arranged on the side opposite to the radiation incident side of the FPD and enter the FPD, and the components appear in the radiographic image, causing artifacts. may be lost.

For example, Patent Literature 1 discloses a technique of reducing the effects of artifacts by using attenuation members with different radiation transmittances in different regions so that the amount of backscattered radiation reaching the FPD is generally uniform. In general, the lower the radiation transmittance of the attenuation member, the heavier the weight of the attenuation member. can be made lighter. By reducing the weight of the radiation imaging apparatus, it is possible to reduce the workload of the user when carrying the apparatus for setting a subject.

JP 2004-294114 A

However, in the technique of Patent Document 1, the radiation transmittance is low at the location where the component with high radiation transmittance is arranged on the side opposite to the radiation incident side of the FPD, that is, the heavy attenuation member must be used. For example, when downsizing parts with low radiation transmittance in order to reduce the weight of a radiographic imaging device, an attenuation member with low radiation transmittance is arranged in a region where the radiation transmittance is high due to the downsizing of the part. , there is a problem that it is difficult to further reduce the weight of the radiation imaging apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for reducing artifacts that occur in a radiographic image due to backscattered rays while reducing the weight of a radiographic imaging apparatus.

The above-described problem is a radiation imaging apparatus that generates a radiographic image based on radiation emitted from a radiation generating apparatus and that has passed through a subject. a radiation detection unit having one surface and a second surface facing the first surface; a plurality of components provided on the side of the second surface with respect to the radiation detection unit; an attenuation member provided on the second surface side with respect to the detection unit and for attenuating backscattered rays incident on the radiation detection unit from the second surface side, the attenuation member is made of a material having a higher radiation transmittance than any one of the parts included in the plurality of parts, and covers an end of the outer shape of the part that overlaps the radiation detection unit in orthogonal projection onto the second surface. Further, the problem is solved by a radiation imaging apparatus characterized by having an area smaller than that of the radiation detection section.

According to the present invention, it is possible to provide a radiation imaging apparatus that is lightweight while reducing artifacts caused by backscattered radiation generated behind the radiation imaging apparatus.

1 is a diagram showing the configuration of a radiation imaging system 10 according to a first embodiment; FIG. 1 is a diagram showing the configuration of a radiation imaging apparatus 102 according to a first embodiment; FIG. FIG. 3 is a schematic diagram for explaining backscattered rays according to the first embodiment; FIG. 3 is a schematic diagram showing the arrangement of damping members 210 according to the first embodiment; FIG. 5 is a diagram showing the relationship between the position on FIG. 4 and the incident amount of scattered radiation according to the first embodiment; FIG. 5 is a schematic diagram showing the arrangement of damping members 210 according to the second embodiment;

Preferred embodiments to which the present invention is applied will now be described in detail with reference to the accompanying drawings. In addition, the following embodiments do not limit the invention according to the scope of claims. Although multiple features are described in the embodiments, not all of these multiple features are essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant description is omitted. In addition, although the term radiation can typically be X-rays, it is not limited to X-rays, and other radiations (eg, α-rays, β-rays, γ-rays, etc.) can also be applied.

(First embodiment)
FIG. 1 is a diagram showing the overall configuration of a radiation imaging system 10 according to the first embodiment of the invention. The radiation imaging system 10 includes a control device 100 , a radiation generation device 101 and a radiation imaging device 102 . The control device 100 includes an imaging condition setting unit 103 , an imaging control unit 104 , an image processing unit 105 and a display unit 106 . A general-purpose computer having a CPU, a main storage device, an auxiliary storage device, and a display is preferably used as the control device 100 to implement the functions of each section of the control device 100 .

The radiation generator 101 irradiates the subject P with radiation. The radiation generator 101 is composed of a tube that generates radiation, a collimator that defines the spread angle of the generated radiation beam, and a radiation dosimeter attached to the collimator.

The radiation imaging device 102 generates a radiation image based on the radiation emitted from the radiation generation device 101 and passed through the subject P. FIG. The generated radiation image is transmitted to the image processing unit 105 . The radiation imaging apparatus 102 also transmits information on the detected radiation dose to the imaging control unit 104 . The internal structure of the radiation imaging apparatus 102 will be described in detail with reference to FIG.

The imaging condition setting unit 103 has imaging condition input means for the operator to input imaging conditions such as tube voltage, tube current, and imaging site. be done. The imaging control unit 104 controls the radiation generation device 101, the radiation imaging device 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 processing, gain correction processing, and noise reduction processing on the radiation image transmitted from the radiation imaging apparatus 102 . The image processing unit 105 transmits the radiographic image after image processing to the display unit 106 . A general-purpose display or the like is used as the display unit 106 and outputs the image information transmitted from the image processing unit 105 .

FIG. 2 is a diagram showing the configuration of the radiation imaging apparatus 102 according to this embodiment. FIG. 2(a) is an external perspective view of the radiation imaging device 102 viewed from the incident surface side, and FIG. 2(b) cuts the radiation imaging device 102 along the line AA' shown in FIG. 2(a). and FIG. 10 is a cross-sectional view seen from the direction of the arrow. An arrow X in FIG. 2B schematically indicates the incident direction of radiation incident on the radiation imaging apparatus 102 .

The radiation imaging apparatus 102 has a substantially rectangular parallelepiped shape, and each component constituting the radiation imaging apparatus 102 is enclosed by a housing 201 . The housing 201 has a front cover 202 having a breastplate portion 202 a and a frame portion 202 b , a rear cover 203 and a cover 213 for a secondary battery 209 .

The breastplate 202a is a plate-shaped member arranged on the surface of the housing 201 on which radiation is incident. A high-rigidity member is suitable for the chest support 202a because the radiation imaging apparatus 102 may be subjected to a load when it is used for imaging. Moreover, since the breastplate 202a is a surface on which the radiation from the radiation generator 101 is incident, a material with high radiation transmittance is suitable. From these points of view, for example, CFRP (Carbon Fiber Reinforced Plastic) is used for the breastplate 202a. A magnesium alloy is used for the frame portion 202b located on the periphery of the breastplate portion 202a.

The rear cover 203 is a plate-like member arranged on the surface of the housing 201 opposite to the surface on which the radiation is incident. As described above, since a load may be applied to the radiation imaging apparatus 102 , a highly rigid member is suitable for the back cover 203 . In addition, a material with high radiation transmittance is suitable for suppressing reflection of radiation within the housing. From these points of view, for example, CFRP is used for the back cover 203 .

In the housing 201, a shock absorbing sheet 204, a radiation detector 205, and a base 206 are laminated in order from the radiation incident surface side. The shock absorbing sheet 204 protects the radiation detecting section 205 from shocks received from the outside of the housing 201 .

The radiation detection unit 205 consists of a plurality of scintillator crystals that convert the wavelength of radiation into light that can be sensed by the photoelectric conversion elements on a plurality of pixels 205a each having a photoelectric conversion element and arranged in a two-dimensional array. It is an FPD having a scintillator layer 205b. Radiation emitted from the radiation generating device 101 is converted into light by the scintillator layer 205b, and further converted into electrical signals by the photoelectric conversion elements of the plurality of pixels 205a. An electric signal from each pixel of the plurality of pixels 205a is read out by a driving circuit and a readout circuit, and generated as a radiographic image.

In the following description, the surface on which the plurality of pixels of the radiation detection unit 205 are provided is called a first surface, and the surface opposite to the first surface is called a second surface.

The radiation detector 205 is connected to the control board 208 via the flexible circuit board 207 . The control board 208 has the aforementioned driving circuit and reading circuit, and controls driving signals and the like for reading out signals from the photoelectric conversion elements.

The base 206 is a plate-like member for supporting the radiation detection section 205 . A radiation detection unit 205 is arranged on the surface of the base 206 on which radiation is incident, and a control board 208, a secondary battery 209, a wireless module (not shown), and a radio module (not shown) are provided on the surface opposite to the surface on which the radiation is incident. An antenna section and the like are provided and supported by a base 206 . The surface of the base 206 opposite to the surface on which the radiation is incident may be provided with unevenness for supporting various parts. The base 206 is preferably made of a magnesium alloy in consideration of securing rigidity, weight reduction, and the influence of electrical noise.

A secondary battery 209 supplies driving power. The wireless module and antenna section function as a wireless communication section that wirelessly transmits image signals to an external device.

The attenuation member 210 is provided to attenuate the backscattered radiation incident on the radiation detection section 205 . Backscattered radiation refers to the side opposite to the radiation incident side of the radiation detection unit 205 when part of the radiation irradiated to the radiation detection unit 205 is transmitted or when the irradiation field is wider than the radiation detection unit 205. is a component that the radiation is reflected by the structure and enters the radiation detection unit 205 again. Backscatter rays will be described in detail in the description of FIG. The damping member 210 is made of radiation absorbing material such as bismuth, lead, SUS, iron, and tungsten.

Attenuating member 210 is a member for attenuating backscattered radiation incident on radiation detection unit 205 , and is provided on the second surface side of radiation detection unit 205 . For example, it is provided between the radiation detection unit 205 and the base 206 and inside and outside the back cover 203 of the housing 201 , but it is not limited to this, and may be provided on the second surface side of the radiation detection unit 205 .

Next, the backscattered radiation will be described with reference to FIG. FIG. 3 is a diagram showing the situation of backscattered rays in the radiation generating apparatus 101 and radiation imaging apparatus 102 in FIG. Radiation emitted from the radiation generating apparatus 101 enters a radiation detection unit 205 arranged inside the radiation imaging apparatus 102 .

A portion of the radiation that has entered the radiation detection unit 205 is transmitted without being absorbed by the scintillator layer 205b of the radiation detection unit 205, and is reflected and scattered by structures such as the wall surface and floor on the back side of the radiation imaging device 102. , re-incident from the back side of the radiation detection unit 205 . The backscattered rays incident from the back side include those that are attenuated by the components of the radiation imaging apparatus 102 installed on the back side and those that enter the phosphor. A difference in the transmittance of radiation between a portion where a component is present and a portion where it is not causes the component to appear in the radiographic image, that is, artifacts.

When the attenuation member 210 is provided so as to cover the entire surface of the radiation detection unit 205 from backscattered radiation, the absolute amount of backscattered radiation incident on the radiation detection unit 205 can be reduced, thereby reducing artifacts. can. However, when the damping member 210 is provided on the entire surface in this way, the weight of the radiation imaging apparatus 102 increases. Due to the nature of the device, the radiation imaging device 102 has to be carried and used by the user in many tasks such as setting for a subject, so it is necessary to reduce the weight as much as possible.

Therefore, in the present invention, the artifact caused by reflection of components caused by the backscattered radiation generated outside the housing of the radiation imaging apparatus 102 is reduced by arranging an attenuation member smaller than the area of the radiation detection unit 205. We will reduce it while striving to

FIG. 4 is a diagram simply showing the configuration of the radiation imaging apparatus 102 according to this embodiment. FIG. 4(a) is a view of the radiographic imaging apparatus 102 from the side opposite to the incident side (arrow X in FIG. 2) when no damping member is provided, and FIG. ) with a damping member added. A control board 208a, a control board 208b, and a secondary battery 209 are provided in the radiation imaging apparatus 102 shown in FIG.

At this time, there is a large difference in the amount of incident backscattered radiation in the in-plane direction of the second surface of the radiation detection unit 205 between the outer edge portions of these components and the locations where there are no components. Artifacts appear in the image at locations where there is such a large difference in the amount of backscattered radiation.

In the present embodiment, in the orthogonal projection onto the second surface of the radiation detection unit 205, the edge of the outline of the part provided on the side of the second surface of the radiation detection unit 205, which is the target for which reflection is desired to be reduced, is A damping member 210 is provided to cover the portion. At this time, it is assumed that the attenuation member 210 has a higher radiation transmittance than the part whose reflection is to be reduced.

By doing so, the difference in the amount of backscattered rays reaching the second surface of the radiation detection unit 205 that occurs between the edge of the outline of the part whose reflection is to be reduced and the part without the part. can be gradual, artifacts can be reduced.

Hereinafter, description will be made with reference to FIGS. 4 and 5. FIG. FIG. 5 is a diagram showing the amount of scattered radiation incident on the radiation detector 205 at the position of line BB' in FIG. 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 the radiation is incident, parts (in FIG. 4, the control board 208a and the control board 208b) are not provided and there are regions provided with components. FIG. 5 shows the scattered radiation incident amount for each region.

5(a) corresponds to the case where the damping member 210 of FIG. 4(a) is not provided, and FIG. 5(b) corresponds to the case where the damping member 210 of FIG. 4(b) is provided. In FIG. 5(a), there is a large difference in the amount of incident scattered radiation between the area where the component is not provided and the area where the component is provided, and the component is reflected, causing artifacts. On the other hand, in FIG. 5B where the damping member 210 is provided, the damping member 210 divides the area covered with the part and the damping member 210, the area covered only with the damping member 210, and both the part and the shielding member. There will be uncovered areas.

The difference in the amount of incident scattered radiation in each region in FIG. 5B is smaller than the difference between the region where the component is not provided and the region where the component is provided when the damping member 210 is not arranged. Therefore, parts are less likely to be reflected, and artifacts can be reduced.

The damping member 210 uses a material having a higher radiation transmittance than the part whose reflection is to be reduced. This is because, if the radiation transmittance of the attenuation member 210 is lower than that of the part whose reflection is to be reduced, the attenuation member 210 causes reflection. In FIG. 4, damping member 210 is arranged to cover control board 208 a , control board 208 b and secondary battery 209 . As described with reference to FIG. 5, the difference in the amount of backscattered radiation between these regions is moderate compared to the case where the damping member 210 is not arranged.

In addition, in the above description of FIG. 4B, the control board 208 and the secondary battery 209 are the components for which reflection is desired to be reduced, but this is not the only option. For example, the ends of the contours of the uneven portion provided on the base 206, the antenna for communication of the radiation imaging apparatus 102, the cable for connecting various electric parts, the fastening member for fastening various parts, etc. A damping member 210 may be provided to cover.

Also, the damping member 210 may have a thickness that varies continuously at the ends of the profile. By doing so, the difference in the amount of backscattered radiation reaching the second surface of the radiation detection unit 205 at the end of the attenuation member 210 can be reduced, so that the outer shape of the attenuation member 210 is reflected in the radiographic image. can make it harder to get into.

Also, the attenuation member 210 may be configured to be detachable from the radiation imaging apparatus 102 . By doing so, it becomes easy to dispose the damping member 210 at an appropriate position after observing the situation of reflection in an actually captured radiographic image. Further, by making the damping member 210 removable, it becomes easy to change the material of the damping member 210 according to the situation of reflection of the radiographic image.

(Second embodiment)
Next, a second embodiment of the invention will be described. The difference from the first embodiment is that the damping member 210 does not cover the entire part whose reflection is to be reduced, but only the outer edge of the part.

FIG. 6 is a diagram simply showing the configuration of the radiation imaging apparatus 102 according to this embodiment. FIG. 6(a) is a view without an attenuation member, viewed from the side opposite to the incident side of the radiation imaging apparatus 102, and FIG. 6(b) is a view with an attenuation member 210 added to FIG. 6(a). be.

In the present embodiment, the radiographic imaging apparatus 102 is provided with a control board 208a, a control board 208b, and a secondary battery 209 as parts whose reflection is to be reduced, and an attenuation member 210 is attached to each end of the outer shape of each part. Deploy. By arranging the attenuation member 210 as shown in FIG. 6, the area of the attenuation member 210 becomes smaller than that in the first embodiment, so that the weight of the radiation imaging apparatus 102 can be further reduced.

102 Radiation imaging apparatus 205 Radiation detector 210 Shielding member P Subject

Claims (14)

A radiation imaging device for generating a radiographic image based on radiation emitted from a radiation generating device and passing through a subject,
a radiation detection unit having a first surface provided with a plurality of pixels each for converting radiation into an electrical signal, and a second surface facing the first surface;
a plurality of components provided on the second surface side with respect to the radiation detection unit;
an attenuation member provided on the second surface side with respect to the radiation detection unit for attenuating backscattered radiation incident on the radiation detection unit from the second surface side;
The attenuating member is made of a material having a higher radiation transmittance than any one of the parts included in the plurality of parts, and the outer edge of the part overlaps the radiation detection unit in orthogonal projection onto the second surface. A radiation imaging apparatus covering a portion and having an area smaller than that of the radiation detection portion. The plurality of parts includes a part composed of a plurality of component parts,
2. The radiation imaging apparatus according to claim 1, wherein the attenuation member covers an outer edge of the component that overlaps with the detection unit in orthogonal projection onto the second plane. the plurality of components includes a control board for reading out signals from the radiation detection unit;
2. The radiation imaging apparatus according to claim 1, wherein the attenuation member covers an edge of the outer shape of the control board that overlaps the detection unit in orthogonal projection onto the second surface. the plurality of components includes a secondary battery that supplies power to the radiation imaging device;
2. The radiation imaging apparatus according to claim 1, wherein the attenuation member covers an outer edge of the secondary battery that overlaps the detection unit in orthogonal projection onto the second surface. the plurality of components includes an antenna for the radiation imaging device to communicate with an external device;
2. The radiation imaging apparatus according to claim 1, wherein the attenuation member covers an outer edge of the antenna that overlaps the detection unit in orthogonal projection onto the second plane. The plurality of components includes a base supporting the detection unit on the second surface side of the detection unit;
2. The radiation imaging apparatus according to claim 1, wherein the attenuation member covers an end portion of the unevenness of the base that overlaps with the detection section in orthogonal projection onto the second surface. The plurality of parts includes fastening members that fasten parts of the radiation imaging device,
2. The radiation imaging apparatus according to claim 1, wherein the damping member covers an end portion of the outer shape of the fastening member that overlaps the detection section in orthogonal projection onto the second surface. the plurality of components include cables connected to components of the radiation imaging device;
2. The radiation imaging apparatus according to claim 1, wherein the attenuation member covers an outer end of the cable that overlaps the detection unit in orthogonal projection onto the second plane. 9. The radiation imaging apparatus according to any one of claims 1 to 8, wherein the attenuation member has a thickness that varies continuously at the edges of the outer shape. The radiation imaging apparatus according to any one of claims 1 to 9, wherein the attenuation member is detachable with respect to the radiation imaging apparatus. 11. The radiation imaging apparatus according to claim 1, wherein said attenuation member is made of at least one of bismuth, lead, SUS, iron, and tungsten. Having a housing that encloses the radiation detection unit and the component,
12. The radiation imaging apparatus according to claim 1, wherein the surface of the housing opposite to the surface on which the radiation is incident is made of CFRP. 13. The pixel according to claim 1, wherein each of said plurality of pixels has a photoelectric conversion element, and said radiation detection section has a scintillator that converts radiation into light that can be detected by said photoelectric conversion element. 10. The radiographic imaging apparatus according to 1. a radiation imaging apparatus according to any one of claims 1 to 13;
and an image processing unit that processes the radiation detected by the radiation imaging device as a radiographic image.

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