JP2023032611A - Radiation imaging apparatus and radiation imaging system - Google Patents

Abstract

To provide a radiation imaging apparatus that can reduce artifacts resulting from a back scattering beam and has a weight reduced compared to before.SOLUTION: An attenuation member for attenuating radiation is provided on a side of a surface facing a detection surface of a radiation detector, the attenuation member having the area smaller than that of the detection surface and having an outer shape having a tapered end in orthogonal projection on the detection surface, and provided apart from a radiation detection unit and a control board.SELECTED DRAWING: Figure 2

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. may be lost.

Japanese Patent Application Laid-Open No. 2002-200000 discloses a radiation imaging apparatus in which an attenuation member for attenuating radiation larger than the detection surface of the detection panel is provided on the back side of a detection panel for detecting radiation.

Japanese Patent Application Laid-Open No. 2002-214352

However, when the technique described in Patent Document 1 is used, the amount of backscattered rays incident on the detection surface is reduced, so artifacts can be reduced, but the attenuation member needs to cover the entire detection surface, and the attenuation member is heavy. There was a problem.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a radiation imaging system that can reduce artifacts caused by backscattered radiation and that can be made lighter than before.

The above problem is to solve the above problem in a radiation imaging apparatus that irradiates a subject with radiation emitted from a radiation generating means and generates a radiographic image based on the radiation that has passed through the subject. a radiation detection unit having a first surface arranged in an array and a second surface facing the first surface; and a plurality of radiation detection units provided on the side of the second surface of the radiation detection unit. and an attenuation member provided on the side of the second surface of the radiation detection unit for attenuating incident radiation in order to reduce reflection of the component in a radiographic image, the attenuation member , an area smaller than that of the radiation detection unit in orthogonal projection onto the second surface, an end portion of an outer shape of the radiation detection unit being tapered, and provided apart from the second surface of the radiation detection unit. It is solved by a radiation imaging device.

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. 5 is a diagram showing the relationship between the shadow difference and the distance to the shield according to the first 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 generator 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 an image based on the irradiated radiation. 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. 1(b) cuts the radiation imaging device 102 along the line AA' shown in FIG. 1(a). and FIG. 10 is a cross-sectional view seen from the direction of the arrow. An arrow X in FIG. 1B 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 and a back cover 203 having a breastplate portion 202a and a frame portion 202b.

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 absorption sheet 204, a radiation image detection panel 205, a holding layer 206, and a base 207 are laminated in this order from the radiation incident surface side. The impact absorbing sheet 204 protects the radiation image detection panel 205 from impacts received from the outside of the housing 201 .

The radiation detection unit 205 is an FPD, and has a plurality of pixels 205a each having a photoelectric conversion element and arranged in a two-dimensional array on an insulating substrate 205c. Furthermore, on the plurality of pixels 205a, a scintillator layer 205b composed of a plurality of scintillator crystals for wavelength-converting radiation into light that can be sensed by the photoelectric conversion element is provided.

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.

The radiation detector 205 is connected to the control board 209 via the flexible circuit board 208 . The control board 209 is mounted with electronic components that function as the drive circuit and the readout circuit described above, and performs control for reading out signals from the photoelectric conversion elements.

The base 207 is a flat member for supporting the radiation image detection panel 205 . The base 207 is preferably made of a magnesium alloy in consideration of ensuring rigidity, weight reduction, and the influence of electrical noise. A radiation image detection panel 205 is arranged on the first surface of the base 207, which is the surface on which the radiation is incident, with a holding layer 206 having an adhesive function interposed on both surfaces. A control board 209, a secondary battery (not shown), a wireless module, an antenna section, and the like are held on the second surface, which is the back surface of the first surface. The secondary battery supplies power for driving. 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 on the side of the radiation detection unit 205 opposite to the radiation incident surface, and the control board provided on the second surface of the base 207 is reflected in the radiographic image by backscattered rays. It is a member for preventing this. Backscatter rays will be described in detail in the description of FIG. Materials that absorb radiation such as bismuth, lead, SUS, iron, and tungsten are used as materials for the attenuation member 210 .

In this embodiment, the weight of the attenuation member 210 is reduced by making the attenuation member 210 smaller in area than the detection surface in orthogonal projection onto the detection surface of the radiation detection unit 205 . Further, the attenuation member 210 is provided at a position away from the radiation detection unit 205 in order to prevent the attenuation member 210 arranged in this way from appearing in the radiographic image due to backscattered radiation. The damping member 210 is used, for example, by turning these materials into particles or powder, dispersing them in an organic substance such as resin or rubber, and processing them into a sheet.

The attenuation member 210 can be placed either on the radiation entrance side of the back cover 203 (ie inside the housing) or on the opposite side of the radiation entrance side (ie outside the housing). Installation on the rear cover 203 is suitable for weight reduction of the radiation imaging apparatus if an adhesive layer is used. For the adhesive layer, acrylic, epoxy, or rubber adhesives can be used. Use of a sheet-like double-sided adhesive improves installation workability.

In addition, in a portable radiographic imaging apparatus, the radiation attenuation member may come off due to rubbing against the bed or sheets during round imaging. It should be placed on the incident surface side.

When the damping member 210 is processed into a sheet shape, it is preferable to apply heat and pressure to shape the sheet end portion into a tapered shape. The tapered ends are expected to have the following effects.

For example, artifacts due to reflection of the damping member 210 can be reduced. When the backscattered rays are attenuated by the attenuation member 210, there is a large difference in the amount of backscattered rays that reach the area near the detection surface where the attenuation member 210 is provided and the area where it is not provided. Due to this difference, the end portion of the damping member 210 is reflected in the radiographic image. Since the end portion of the damping member 210 is tapered, the end portion of the damping member 210 can be prevented from being clearly reflected, thereby reducing artifacts.

In addition, since the end portion of the damping member is tapered, it is possible to prevent stress from concentrating on the end portion due to temperature change, friction, etc., and to prevent the damping member 210 from being turned over or peeled off.

Next, backscattered radiation, which is a problem in the present invention, 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 generator 101 enters a radiation detector 205 arranged inside the radiation imaging apparatus 102 .

A portion of the radiation irradiated to 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 the floor on the back side of the radiation imaging apparatus 102. and enters from the rear side of the radiation detection unit 205 . Some of the backscattered rays that enter the radiation detection unit 205 from the back side are shielded by components installed on the back side of the radiation imaging apparatus 102, and some enter the scintillator layer 205b. A difference in shadow occurs between a portion shielded by the radiographic image and a portion incident on the radiation detection unit 205, so that parts appear as reflections on the radiographic image, and artifacts occur.

In order to quantitatively evaluate this artifact amount, let A be the average pixel value in the area where the part is captured, and let B be the average pixel value in the vicinity of the part where the part is not captured. can ask.
Shadow difference=(B−A)/A (1)

In FIG. 4, the attenuation member 210 is arranged in an area covering the control substrate 209 in orthogonal projection onto the detection surface, and the distance from the interface between the scintillator layer 205b and the plurality of pixels 205a to the attenuation member 210 is x. It evaluates and expresses the relationship with the distance x. As shown in FIG. 4, the difference in shading decreases as the distance x increases. This is because the larger the distance x, the backscattered radiation wraps around the damping member 210 and reaches the scintillator layer 205b, so that the end of the damping member 210 is not clearly reflected.

The dotted line indicated as the reference value is the reference value of the shadow difference obtained from a plurality of radiographic images, which is considered to have no effect in actual use of the image. The intersection point between this reference value and the shadow difference data was 5 mm. From this result, it can be seen that the distance from the interface between the scintillator layer 205b and the plurality of pixels 205a to the radiation attenuation member 210 falls below the reference value if the distance is 5 mm or more. In order to obtain a more suitable image, the separation may be 8 mm or more.

As described above, in this embodiment, the attenuation member 210 has a smaller area than the detection surface in orthogonal projection onto the detection surface of the radiation detection unit 205 . Furthermore, in order to reduce reflection of the attenuation member 210 that occurs at this time, the attenuation member 210 is provided away from the radiation detection unit 205 . In addition, by making the ends of the outer shape of the damping member 210 tapered, reflection of the damping member 210 can be further reduced.

With the above configuration, it is possible to reduce the amount of artifacts caused by backscattered radiation while reducing the weight of the radiation imaging apparatus 102 .

In the above description, the control board 209 is used as the component for which reflection is desired to be reduced, but this is not the only option. For example, the damping member 210 may be provided so as to cover the secondary battery that supplies power to the radiation imaging apparatus 102 , the uneven portion provided on the base 207 , and the outer edge of the antenna section for communication of the radiation imaging apparatus 102 . can be Components for which reflection is desired to be reduced also include cables for connecting various electrical components, fastening members for fastening various components, and the like.

In addition, when a plurality of component parts forming a certain component have different radiation shielding rates, the attenuation member 210 may be provided so as to cover the outer edge of the component part. For example, consider a case in which a plurality of battery cells with a high radiation shielding rate are mounted in one secondary battery unit. In this case, even within a single secondary battery unit, the shielding rate of radiation differs greatly between locations with battery cells and locations without them. can be reduced.

Although the embodiments according to the present invention have been shown above, the present invention is not limited to the above-described embodiments, and the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. be.

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

Claims (16)

In a radiation imaging apparatus that irradiates a subject with radiation emitted from a radiation generating means and generates a radiation image based on the radiation that has passed through the subject,
a radiation detection unit having a first surface on which a plurality of conversion elements for detecting radiation transmitted through a subject are arranged in a two-dimensional array, and a second surface facing the first surface;
a plurality of components provided on the second surface side of the radiation detection unit;
an attenuating member provided on the second surface side of the radiation detection unit and attenuating incident radiation to reduce reflection of the component in a radiographic image;
The attenuating member has an area smaller than that of the radiation detection section when orthogonally projected onto the second surface, has a tapered outer edge, and is provided apart from the second surface of the radiation detection section. A radiation imaging device characterized by: 2. The radiation imaging apparatus according to claim 1, wherein said damping member covers an edge of the outline of said component in orthogonal projection onto said second surface. The component has a plurality of component parts for configuring the component,
3. The radiation imaging apparatus according to claim 2, wherein the attenuating member covers an outer edge of the component that overlaps with the radiation detection section in orthogonal projection onto the second surface. the part is a control board mounted with an electronic part for reading a signal from the radiation detection unit;
3. The radiation imaging apparatus according to claim 2, wherein the attenuating member covers an outer edge of the control board that overlaps with the radiation detector in orthogonal projection onto the second surface. the component is a secondary battery that supplies power to the radiation imaging device;
3. The radiation imaging apparatus according to claim 2, wherein the attenuating member covers an outer edge of the secondary battery that overlaps with the radiation detector in orthogonal projection onto the second surface. the part is an antenna for the radiation imaging device to communicate with an external device;
3. The radiation imaging apparatus according to claim 2, wherein the attenuation member covers an outer edge of the antenna that overlaps the radiation detection section in orthogonal projection onto the second plane. the component is a base supporting the detection unit on the second surface side of the detection unit;
3. The radiation imaging apparatus according to claim 2, wherein the attenuating member covers an end portion of the unevenness of the base that overlaps with the radiation detection section in orthogonal projection onto the second surface. the component is a fastening member for fastening a component of the radiation imaging device;
3. The radiation imaging apparatus according to claim 2, wherein the attenuating member covers an outer edge of the fastening member that overlaps the radiation detection section in orthogonal projection onto the second surface. the component is a cable connected to a component of the radiation imaging device;
3. The radiation imaging apparatus according to claim 2, wherein the attenuating member covers an end portion of the outer shape of the cable that overlaps the radiation detection section in orthogonal projection onto the second plane. a housing that encloses the radiation detection unit, the component, and the attenuation member;
3. The radiation imaging apparatus according to claim 1, wherein the attenuation member is provided outside the housing. a housing containing the radiation detection unit, the control board, and the attenuation member;
3. The radiation imaging apparatus according to claim 1, wherein the attenuation member is provided inside the housing. 12. A radiation imaging apparatus according to claim 10, wherein said damping member is adhered to said housing via an adhesive layer. The radiation detection unit has a scintillator layer that converts radiation into light,
13. The radiation imaging apparatus according to claim 1, wherein the attenuation member is provided at a distance of 5 mm or more from an interface between the second surface and the scintillator layer. 14. The radiation imaging apparatus according to any one of claims 1 to 13, wherein the attenuation member is made of at least one of bismuth, lead, SUS, iron, and tungsten. The radiation imaging apparatus according to any one of claims 1 to 14, wherein the surface of the housing opposite to the surface on which radiation is incident is made of CFRP. a radiation imaging apparatus according to any one of claims 1 to 15;
an image processing unit that processes the radiation detected by the radiation imaging device as a radiographic image;
A radiation imaging system comprising:

Images