radiation detector

Abstract

To suppress noise inflow from peripheral parts to an X-ray sensor while taking into account the thickness constraints of a cassette device.SOLUTION: A radiation detector 1 includes an X-ray sensor 26 that detects X-ray irradiation, a shield 28 that reduces electro-magnetic noise to the X-ray sensor 26, and a base 31 on which the X-ray sensor 26 is assembled. The X-ray sensor 26, the shield 28, and the base 31 are respectively arranged so that a distance (H1) between the X-ray sensor 26 and the shield 28 in the thickness direction of the radiation detector 1 is larger than a distance (H2) between the shield 28 and the base 31.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a radiation detector. [Background technology]

[0002] Conventionally, lightweight and thin radiation detectors called flat panel detectors (FPDs) have been used to capture radiation (hereinafter also referred to as X-ray) images. Regarding this radiation detector, for example, Patent Document 1 discloses a technology for forming a shield that protects internal components from external electrical noise using a housing that covers the internal components. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5580971 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the technology disclosed in Patent Document 1, when the thickness of the cassette device (15 mm (+1 / -2 mm; for a cassette size of 14 inches x 17 inches)) standardized by ISO 4090 and JIS Z 4905 is taken into consideration, the space available for storing the internal components within the housing is limited. As a result, for example, the X-ray sensor, which is an internal component, is prone to capacitive coupling with surrounding components (surrounding internal components), and if the distance between the X-ray sensor and the surrounding components fluctuates due to vibration, the capacitive component fluctuates, causing noise to flow into the X-ray sensor and resulting in false detection of X-ray irradiation.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to suppress the inflow of noise from peripheral components into an X-ray sensor while taking into consideration the constraints on the thickness of the cassette device. [Means for solving the problem]

[0006] In order to solve the above problems, the radiation detector according to the present invention comprises: an X-ray sensor for detecting X-ray irradiation; a shield for reducing electromagnetic noise to the X-ray sensor; a base on which the X-ray sensor is assembled; A radiation detector comprising: The X-ray sensor, the shield, and the base are arranged so that the distance between the X-ray sensor and the shield in the thickness direction of the radiation detector is greater than the distance between the shield and the base. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress the inflow of noise from peripheral components into the X-ray sensor while taking into consideration the constraints on the thickness of the cassette device. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view showing the appearance of a radiation detector according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line XX in FIG. [Figure 3] FIG. 2 is a plan view showing the configuration of a substrate. [Figure 4] FIG. 2 is a block diagram showing an equivalent circuit of a radiation detector. [Figure 5] 3 is a partial schematic cross-sectional view showing an enlarged portion of the X-ray sensor unit in FIG. 2. FIG. [Figure 6] 10 is a diagram showing an example of an X-ray sensor unit in which a capacitance component occurs between the base and the shield. FIG. [Figure 7] 10A and 10B are diagrams illustrating an example of equal potential processing in which the base and the shield are set to the same potential. [Figure 8] 10A and 10B are diagrams illustrating an example of equal potential processing in which the base and the shield are set to the same potential. [Figure 9] 10 is a diagram showing an example of an X-ray sensor unit in which an opening provided in the ceiling of a shield is blocked with a conductor having a higher X-ray transmittance than the shield. FIG. [Figure 10] FIG. 10 is a diagram showing an example of a radiation detector in which a plurality of X-ray sensor units are provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the technical scope of the present invention is not limited to the following embodiments and illustrated examples.

[0010] [Radiation detector configuration] First, the radiation detector according to this embodiment will be described. Fig. 1 is a perspective view showing the appearance of the radiation detector according to this embodiment, and Fig. 2 is a cross-sectional view taken along line XX in Fig. 1. Note that the following description of the up-down direction in the radiation detector 1 will be based on the case where the radiation detector 1 is positioned as shown in Fig. 2.

[0011] 1, a power switch 37, a selector switch 38, a connector 39, an indicator 40, etc. are arranged on one side of the housing 2 of the radiation detector 1. Although not shown, an antenna 41 (see FIG. 4 described later) for wireless communication with the outside is provided on the opposite side of the housing 2.

[0012] 2, a base 31 is disposed inside the housing 2, and a substrate 4 is disposed on the upper surface of the base 31 via a thin lead plate or the like (not shown). X-ray detection elements 7 and the like are provided on the upper surface of the substrate 4, which will be described later. Then, above the substrate 4, the scintillator 3 and the scintillator substrate 34 are disposed in a state in which the scintillator 3 formed on the scintillator substrate 34 and the X-ray detection elements 7 and the like of the substrate 4 face each other.

[0013] A PCB board 33 on which electronic components 32 and the like are arranged, a built-in power supply 24, and the like are attached to the underside of the base 31. An X-ray sensor unit 25 is also attached to the underside of the base 31. The configuration of the X-ray sensor unit 25 will be described later. In this embodiment, the sensor panel SP is formed in this manner. In this embodiment, a buffer material 35 is also provided between the sensor panel SP and the side surface of the housing 2 to prevent them from colliding with each other.

[0014] 3, a plurality of scanning lines 5 and a plurality of signal lines 6 are arranged so as to intersect with each other on the upper surface 4a of the substrate 4 (i.e., the surface facing the scintillator 3). Furthermore, an X-ray detection element 7 is provided in each region r partitioned by the plurality of scanning lines 5 and the plurality of signal lines 6. In this embodiment, the X-ray detection elements 7 are thus arranged two-dimensionally (in a matrix).

[0015] In this embodiment, a plurality of bias lines 9 are arranged in parallel to the signal lines 6, and each bias line 9 is connected to a connection 10. A plurality of input / output terminals 11 are provided on the periphery of the substrate 4, and each input / output terminal 11 is connected to each scanning line 5, each signal line 6, and each connection 10. Although not shown, each input / output terminal 11 is connected to a flexible circuit board on which a chip such as a readout IC 16 (described later) is mounted on a film, and the flexible circuit board is routed to the back side of the substrate 4 and connected to the aforementioned PCB board 33, etc.

[0016] Here, the circuit configuration of the radiation detector 1 will be described. Fig. 4 is a block diagram showing an equivalent circuit of the radiation detector 1 according to this embodiment. Each X-ray detection element 7 generates an electric charge according to the dose of X-rays irradiated through a subject (not shown) (or the amount of electromagnetic waves converted by the scintillator 3). Note that, although the following describes a case where the X-ray detection element 7 is configured as a photodiode, it is also possible to use, for example, a phototransistor or a CCD (Charge Coupled Device) as the X-ray detection element 7.

[0017] A bias line 9 is connected to one electrode 7a of each X-ray detection element 7, and a reverse bias voltage is applied to each X-ray detection element 7 from a bias power supply 14 via the bias line 9 and a connection 10. A TFT 8 is connected as a switching element to the other electrode 7b of each X-ray detection element 7, and the TFT 8 is connected to a signal line 6.

[0018] Furthermore, when an on voltage is applied from the scan driving means 15 (described later) via the scanning line 5, the TFT 8 is turned on, causing the charge accumulated in the X-ray detection element 7 to be discharged to the signal line 6. When an off voltage is applied via the scanning line 5, the TFT 8 is turned off, causing the discharge of charge from the X-ray detection element 7 to the signal line 6 to be stopped, causing the charge to be accumulated in the X-ray detection element 7.

[0019] Each scanning line 5 is connected to a gate driver 15b of the scanning driving means 15. In the scanning driving means 15, an on voltage and an off voltage are supplied from a power supply circuit 15a to the gate driver 15b via wiring 15c, and the gate driver 15b switches the voltage applied to each line L1 to Lx of the scanning lines 5 between the on voltage and the off voltage.

[0020] Each signal line 6 is connected to a corresponding readout circuit 17 built into the readout IC 16. In this embodiment, the readout circuit 17 is composed of an integration circuit 18, a correlated double sampling circuit 19, etc. The readout IC 16 further includes an analog multiplexer 21 and an A / D converter 20. In FIG. 4, the correlated double sampling circuit 19 is abbreviated as CDS.

[0021] During imaging, when X-rays are irradiated onto the radiation detector 1 from an X-ray irradiator (not shown) with each TFT 8, which is a switching element, in an OFF state, electric charges generated in each X-ray detection element 7 by the X-ray irradiation are accumulated in the X-ray detection element 7. Then, during the readout process of image data d from each X-ray detection element 7, an ON voltage is sequentially applied from the gate driver 15b of the scan drive means 15 to each line L1 to Lx of the scanning line 5, and electric charges are released from each X-ray detection element 7 to the signal line 6.

[0022] The electric charges then flow into and are accumulated in the integrating circuit 18 of each readout circuit 17, and a voltage value corresponding to the amount of accumulated electric charge is output. The correlated double sampling circuit 19 outputs the difference between the output values ​​output from the integrating circuit 18 before and after the electric charges flow from each X-ray detection element 7 as analog image data d.

[0023] Then, each output image data d is sequentially transmitted to the A / D converter 20 via the analog multiplexer 21, and is sequentially converted into digital image data d by the A / D converter 20, output to the storage means 23, and sequentially stored. In this manner, the readout process of the image data d is carried out.

[0024] The control means 22 is configured by a computer having a central processing unit (CPU), read only memory (ROM), random access memory (RAM), input / output interface, etc. connected to a bus (not shown), a field programmable gate array (FPGA), etc. It may also be configured by a dedicated control circuit.

[0025] The control means 22 is connected to a storage means 23 configured with an SRAM (Static RAM), an SDRAM (Synchronous DRAM), a NAND flash memory, etc., a built-in power supply 24 configured with a lithium ion capacitor, etc., and the X-ray sensor 26 of the X-ray sensor unit 25 described above. Also connected to the control means 22 is a communication unit 42 for communicating with the outside wirelessly or via a wired system via the antenna 41 and connector 39 described above.

[0026] In addition, appropriate measures are taken, such as shielding the wiring connecting the X-ray sensor 26 and the control means 22 to prevent noise from being picked up, or not providing a thin lead plate in the part of the base 31 (see Figure 5) corresponding to the X-ray sensor 26 to make it easier for X-rays to reach the X-ray sensor 26.

[0027] Meanwhile, the control means 22 detects the start of X-ray irradiation based on the output of the X-ray sensor 26. When the start of X-ray irradiation is detected, an off voltage is applied from the gate driver 15b of the scan drive means 15 to each of the lines L1 to Lx of the scanning line 5, turning off each TFT 8 and shifting to a charge accumulation state in which charges generated in the X-ray detection elements 7 by X-ray irradiation are accumulated in each X-ray detection element 7.

[0028] Then, when a predetermined time has elapsed since the transition to the charge accumulation state, the control means 22 causes the gate driver 15b to sequentially apply an ON voltage to each line L1 to Lx of the scanning line 5, causes each readout circuit 17 to perform a readout operation, and performs the readout process of the image data d from each X-ray detection element 7 as described above.

[0029] [X-ray sensor unit configuration] Next, a description will be given of the X-ray sensor unit 25. Fig. 5 is a partial schematic cross-sectional view showing an enlarged portion of the X-ray sensor unit 25 in Fig. 2.

[0030] 5, the X-ray sensor unit 25 includes an X-ray sensor 26 and a shield 28. In the X-ray sensor unit 25, an X-ray sensor substrate 27 (described later) is fixed to a rib (not shown) extending downward from the underside of the base 31.

[0031] The X-ray sensor 26 is a sensor for detecting X-rays irradiated from an X-ray irradiation device (not shown) to the radiation detector 1. The X-ray sensor 26 is configured by a sensor element (e.g., a photodiode) that converts X-ray energy into an electric charge. The X-ray sensor 26 is configured in a state where it is incorporated into an X-ray sensor board 27.

[0032] The shield 28 is a shield for reducing electromagnetic noise to the X-ray sensor 26, and is formed in a box shape that covers the top and side surfaces of the X-ray sensor 26. More specifically, the shield 28 covers the top and side surfaces of the X-ray sensor 26 while leaving gaps between the shield 28 and the top and side surfaces of the X-ray sensor 26. The shield 28 is made of copper, aluminum, or the like, which has high electrical conductivity.

[0033] [Positional relationship between the X-ray sensor unit and the base] Next, the positional relationship between the X-ray sensor unit 25 and the base 31 in the thickness direction of the radiation detector 1 will be described. As shown in FIG. 5 , if the height from the ceiling 28a of the shield 28 to the X-ray sensor 26 (the upper surface of the X-ray sensor substrate 27) is H1 and the height from the lower surface of the base 31 to the ceiling 28a of the shield 28 is H2, the X-ray sensor unit 25 is disposed on the lower surface of the base 31 so that H1 > H2. Here, a capacitance component C1 generated between the X-ray sensor 26 and the shield 28 decreases in inverse proportion to the above-mentioned H1. Therefore, by disposing the X-ray sensor unit 25 on the lower surface of the base 31 so that H1 > H2, the above-mentioned H1 can be increased, and the capacitance component C1 generated between the X-ray sensor 26 and the shield 28 can be reduced. As a result, electromagnetic noise generated due to the above-mentioned capacitance component C1 can be reduced, and erroneous detection of X-ray irradiation by the X-ray sensor 26 can be suppressed.

[0034] Note that if the base 31 is made of a dielectric material (e.g., a hard foam material), the base 31 is likely to become charged. As shown in FIG. 6, when the base 31 is charged, a capacitance component C2 is generated between the base 31 and the shield 28. Therefore, when the base 31 is charged, the capacitance component Cshunt (=C1 / / C2) is coupled (capacitively coupled) to the X-ray sensor 26. Here, if the value of H1+H2 is constant, the value of the capacitance component Cshunt does not change. However, if the value of H1+H2 changes due to vibration, the value of the capacitance component Cshunt also changes. This may generate electromagnetic noise, which may lead to erroneous detection of X-ray irradiation by the X-ray sensor 26. Therefore, it is preferable to arrange the X-ray sensor unit 25 on the underside of the base 31 so that H1>H2 as described above and to prevent the generation of the capacitance component C2. In other words, it is preferable to perform an equal potential treatment to equalize the potentials of the base 31 and the shield 28. Here, one method for making the base 31 and the shield 28 have the same potential is to add a conductive material (e.g., carbon) to the base 31 to prevent it from becoming charged, thereby making the base 31 and the shield 28 have the same potential. This prevents the generation of the capacitance component C2, and only capacitance component C1 couples (capacitively couples) with the X-ray sensor 26. However, since the X-ray sensor unit 25 is disposed on the underside of the base 31 so that H1 > H2, as described above, this capacitance component C1 can be reduced. As a result, electromagnetic noise caused by the capacitance component C1 can be reduced, and erroneous detection of X-ray irradiation by the X-ray sensor 26 can be suppressed.

[0035] (Variation) Next, a description will be given of another example of equal potential processing in which the base 31 and the shield 28 are set to the same potential. Fig. 7 is a diagram showing an example of equal potential processing in which the base 31 and the shield 28 are set to the same potential. Fig. 7, like Fig. 5, is a partial schematic cross-sectional view in which the X-ray sensor unit 25 is enlarged.

[0036] 7, at least the area of ​​the underside of base 31 facing X-ray sensor 26 is covered with conductor 29, such as a copper plate or aluminum plate, and this conductor 29 is connected to shield 28, thereby making base 31 and shield 28 at the same potential. Note that the method for fixing conductor 29 is not limited to the above method. As shown in FIG. 8, conductor 29 may be fixed to X-ray sensor board 27 by inserting an end of conductor 29, which has a substantially L-shaped cross section, into clip CL, which is used to fix shield 28 to X-ray sensor board 27.

[0037] [effect] As described above, the radiation detector 1 of this embodiment is a radiation detector 1 that includes an X-ray sensor 26 that detects X-ray irradiation, a shield 28 that reduces electromagnetic noise to the X-ray sensor 26, and a base 31 on which the X-ray sensor 26 is mounted, and the X-ray sensor 26, the shield 28, and the base 31 are each arranged so that the distance (H1) between the X-ray sensor 26 and the shield 28 in the thickness direction of the radiation detector 1 is greater than the distance (H2) between the shield 28 and the base 31. Therefore, according to the radiation detector 1, by disposing the X-ray sensor 26 on the underside of the base 31 so that H1>H2, H1 can be increased, thereby reducing the capacitance component C1 generated between the X-ray sensor 26 and the shield 28. As a result, it is possible to suppress the inflow of noise from peripheral components into the X-ray sensor 26 while taking into consideration the constraints on the thickness of the cassette device.

[0038] Furthermore, in the radiation detector 1 according to this embodiment, when an equal potential treatment is performed on the base 31 to make it have the same potential as the shield 28, it is possible to prevent the generation of a capacitance component C2 (see FIG. 6) between the base 31 and the shield 28, so that the capacitance component coupled (capacitively coupled) to the X-ray sensor 26 can be limited to the capacitance component C1 generated between the X-ray sensor 26 and the shield 28. As a result, by performing an equal potential treatment to make the base 31 and the shield 28 have the same potential, and by arranging the X-ray sensor unit 25 on the underside of the base 31 so that H1>H2 as described above, it is possible to further suppress the inflow of noise from peripheral components into the X-ray sensor 26.

[0039] [others] It goes without saying that the present invention is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present invention.

[0040] For example, in the above embodiments, a so-called indirect type radiation detector has been described as an example of a radiation detector that includes a scintillator or the like and converts emitted X-rays into electromagnetic waves of other wavelengths, such as visible light, to obtain an electrical signal. However, the present invention can also be applied to a so-called direct type radiation detector that detects X-rays directly with a detection element without passing through a scintillator or the like.

[0041] In addition, in the above-described embodiments, in order to allow X-rays to easily reach the X-ray sensor 26, an opening may be provided in the area of ​​the ceiling portion 28a of the shield 28 facing the X-ray sensor 26, as shown in FIG. 9, and the opening may be blocked with a conductor 30 having a higher X-ray transmittance than the shield 28.

[0042] Furthermore, in the above-described embodiments, the radiation detector 1 is provided with only one X-ray sensor unit 25. However, as shown in FIG. 10, it is also possible to provide a plurality of X-ray sensor units 25. That is, it is possible to configure the X-ray sensor unit 25 so that it is located not only at the center of the underside of the base 31, but also at a position other than the center. Although FIG. 10 illustrates the configuration in which two X-ray sensor units 25 are provided, three or more may be provided. With this configuration, even when X-rays are irradiated onto the radiation detector 1 with a narrowed irradiation field, any of the plurality of X-ray sensor units 25 can detect the X-rays. [Explanation of symbols]

[0043] 1. Radiation detector 25 X-ray sensor unit 26 X-ray sensors 27 X-ray sensor board 28 Shield 29 Conductor 30 Conductors 31 Foundation

Claims

1. an X-ray sensor for detecting X-ray irradiation; a shield for reducing electromagnetic noise to the X-ray sensor; a base on which the X-ray sensor is mounted; A radiation detector comprising: the X-ray sensor, the shield, and the base are arranged so that the distance between the X-ray sensor and the shield in the thickness direction of the radiation detector is greater than the distance between the shield and the base. A radiation detector characterized by:

2. The base is subjected to an equipotential treatment to make the base and the shield have the same potential.

2. The radiation detector according to claim 1.

3. The base is doped with a conductive material.

3. The radiation detector according to claim 2.

4. The surface of the base is covered with a conductor.

3. The radiation detector according to claim 2.

5. The base is a dielectric material.

5. The radiation detector according to claim 4.

6. The base is made of a foam material.

6. The radiation detector according to claim 5.

7. A plurality of the X-ray sensors are provided.

7. The radiation detector according to claim 1, wherein the radiation detector is a radiation detector having a wavelength of 100 nm or less.

8. the X-ray sensor is a photodiode; 8. The radiation detector according to claim 7.

9. the shield has an opening at a position facing the X-ray sensor in the thickness direction; The opening is filled with a conductor having a higher radiation transmittance than the shield.

7. The radiation detector according to claim 1, wherein the radiation detector is a radiation detector having a wavelength of 100 nm or less.

10. A plurality of the X-ray sensors are provided.

10. The radiation detector according to claim 9.

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