Radiation detector

Abstract

To easily reduce erroneous detection of radiation irradiation due to disturbance.SOLUTION: A radiation detector 1 comprises: an X-ray sensor substrate 40 on which an X-ray sensor 41 for detecting X-ray irradiation is mounted; and a metal base 30 on which the X-ray sensor substrate 40 is disposed and is connected to GND. The metal base 30 includes a bottom 31 and a rib 32 erected on a peripheral edge of the bottom 31. On the X-ray sensor substrate 40, the X-ray sensor 41 is covered with the bottom 31 and rib 32 of the metal base 30 and is disposed on the metal base 30 so as to be separated from the metal base 30.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Conventionally, a lightweight and thin radiation detector called a flat panel detector (FPD) has been used to capture radiation (hereinafter also referred to as X-ray) images. Regarding this radiation detector, a technology has been disclosed that reduces false detection of radiation exposure caused by disturbances by offsetting vibration noise values ​​superimposed on signals for determining the radiation exposure state with correction values ​​calculated from the output of an acceleration sensor, etc. (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-173902 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology disclosed in Patent Document 1 has problems such as an increase in the number of parts due to the use of an acceleration sensor, and also has problems such as a complicated control system because a correction value must be calculated from the output of the acceleration sensor, etc., and a process must be performed to offset the vibration noise value with the correction value in order to reduce false detection of radiation irradiation.

[0005] The present invention has been made in consideration of the above problems, and has an object to easily reduce erroneous detection of radiation irradiation due to disturbances. [Means for solving the problem]

[0006] In order to solve the above problems, the radiation detector according to the present invention comprises: A substrate equipped with an X-ray sensor for detecting X-ray irradiation; A metal base connected to GND on which the substrate is disposed; Equipped with The metal base is The container has a bottom and a rib extending around the bottom. The substrate is The X-ray sensor is covered by the bottom and ribs of the metal base and is disposed on the metal base in a spaced-apart state. It is characterized by: Effect of the Invention

[0007] According to the present invention, it is possible to easily reduce erroneous detection of radiation irradiation due to disturbances. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view showing an external appearance of a radiation detector according to an embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view across an X-ray sensor built into the radiation detector shown in FIG. 1. [Diagram 3] FIG. 2 is a plan view illustrating a configuration of a TFT substrate. [Figure 4] FIG. 2 is a block diagram showing an equivalent circuit of a radiation detector. [Diagram 5] 13 is a cross-sectional view showing an X-ray sensor built into a radiation detector according to a modified example. FIG. [Figure 6] 13 is a cross-sectional view showing an X-ray sensor built into a radiation detector according to a modified example. FIG. [Figure 7] 13 is a cross-sectional view showing an X-ray sensor built into a radiation detector according to a modified example. FIG. [Figure 8] 1 is a cross-sectional view of an X-ray sensor incorporated in a conventional radiation detector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0010] [Radiation detector configuration] First, the configuration of a radiation detector 1 according to this embodiment will be described.

[0011] FIG. 1 is a perspective view showing the appearance of a radiation detector 1 according to this embodiment. As shown in Fig. 1, a power switch 51, a changeover switch 52, a connector 53, an indicator 54, etc. are arranged on one side of the housing 2 of the radiation detector 1. Although not shown, an antenna 55 (see Fig. 4) for wireless communication with the outside is provided on the opposite side of the housing 2. The radiation detector 1 has a built-in X-ray sensor 41 that detects X-rays irradiated to the radiation detector 1 from an X-ray irradiation device (not shown). The X-ray sensor 41 is composed of a sensor element (e.g., a photodiode) that converts X-ray energy into an electric charge, etc.

[0012] Fig. 2 is a cross-sectional view across the X-ray sensor 41 built into the radiation detector 1 shown in Fig. 1. Fig. 2 is a schematic cross-sectional view that locally shows the X-ray sensor 41 and its surroundings, omitting other parts.

[0013] 2, the radiation detector 1 is provided with, in order from the top (the side irradiated with X-rays) to the bottom in the figure, an upper cover 2a constituting a housing 2, a TFT assembly 3, a lead sheet LS, a metal base 30, an X-ray sensor board 40, and a lower cover 2b constituting the housing 2. An adhesive Ad is interposed between the upper cover 2a and the TFT assembly 3. In addition, a PET sheet PS is interposed between the lower cover 2b and the metal base 30.

[0014] The TFT assembly 3 is composed of a TFT substrate 4, a scintillator substrate (not shown), etc. In the TFT assembly 3, a scintillator and a scintillator substrate are arranged above the TFT substrate 4 in a state in which a scintillator formed on the scintillator substrate faces the X-ray detection elements 7 of the TFT substrate 4, etc.

[0015] FIG. 3 is a plan view showing the configuration of the TFT substrate 4. As shown in FIG. 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 TFT substrate 4 (i.e., the surface facing the scintillator). 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).

[0016] In this embodiment, a plurality of bias lines 9 are disposed in parallel to each signal line 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 TFT substrate 4, and each input / output terminal 11 is connected to each scanning line 5, each signal line 6, and each connection 10. Each input / output terminal 11 is connected to a flexible circuit board having chips such as a readout IC 16 (described later) mounted on a film, and the flexible circuit board is routed to the back side of the TFT substrate 4 and connected to a PCB board (not shown) on which electronic components and the like are arranged.

[0017] 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. In each X-ray detection element 7, an electric charge corresponding to the dose of X-rays irradiated through a subject (not shown) (or the amount of electromagnetic waves converted by a scintillator) is generated within each X-ray detection element 7. Note that, although the following describes a case where the X-ray detection element 7 is configured with a photodiode, it is also possible to use, for example, a phototransistor or a CCD (Charge Coupled Device) for the X-ray detection element 7.

[0018] 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.

[0019] When an on-voltage is applied from a 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, and causing the charge to be accumulated in the X-ray detection element 7.

[0020] Each scanning line 5 is connected to a gate driver 15b of the scanning drive means 15. In the scanning drive 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. In the scanning drive means 15, the gate driver 15b switches the voltage applied to each line L1 to Lx of the scanning lines 5 between an on voltage and an off voltage.

[0021] Each signal line 6 is connected to a corresponding readout circuit 17 built in 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 represented as CDS.

[0022] During imaging, when X-rays are irradiated from an X-ray irradiator (not shown) to the radiation detector 1 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 a process of reading 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 discharged from each X-ray detection element 7 to the signal line 6.

[0023] The electric charges then flow into and are accumulated in the integrating circuit 18 of each readout circuit 17, and a voltage value according 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.

[0024] Then, each output image data d is sequentially transmitted to the A / D converter 20 via the analog multiplexer 21, sequentially converted into digital value image data d by the A / D converter 20, and sequentially output to and stored in the storage means 23. In this manner, the readout process of the image data d is performed.

[0025] The control means 22 is composed of a computer in which a central processing unit (CPU), read only memory (ROM), random access memory (RAM), input / output interface, etc. are connected to a bus (not shown), a field programmable gate array (FPGA), etc. It may be composed of a dedicated control circuit.

[0026] The control means 22 is connected to a storage means 23 configured with an SRAM, SDRAM, NAND type flash memory, etc., a built-in power source 24 configured with a lithium ion capacitor, etc., an X-ray sensor 41 mounted on an X-ray sensor board 40, etc. Also, the control means 22 is connected to a communication unit 56 for communicating with the outside wirelessly or wired via the above-mentioned antenna 55 and connector 53.

[0027] The control means 22 detects the start of X-ray irradiation based on the output of the X-ray sensor 41. When the start of X-ray irradiation is detected, an off voltage is applied to each of the lines L1 to Lx of the scanning lines 5 from the gate driver 15b of the scan driving means 15. Then, the control means 22 turns off each TFT 8, and transitions 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] 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. Then, the control means 22 causes each readout circuit 17 to perform a readout operation, and causes the image data d from each X-ray detection element 7 to be read out as described above.

[0029] [X-ray sensor and surrounding structure] Next, the structure surrounding the X-ray sensor 41 will be described with reference to FIG. As shown in FIG. 2, an X-ray sensor substrate 40 on which an X-ray sensor 41 is mounted is attached to a metal base 30 via an adhesive Ad.

[0030] Specifically, the metal base 30 is composed of a substantially rectangular bottom 31 and a rib 32 standing on the periphery of the bottom 31. The rib 32 has a step 33 formed on its inner periphery. The step 33 is formed at a position that is a predetermined distance above the end 32a of the rib 32 in the figure. The above-mentioned adhesive Ad is provided on the step 33, and the X-ray sensor board 40 is attached via the adhesive Ad so that the X-ray sensor 41 faces the bottom 31. That is, the X-ray sensor board 40 is disposed on the metal base 30 in a state in which the X-ray sensor 41 is covered by the bottom 31 and the rib 32 of the metal base 30 and is spaced from the metal base 30. The step 33 functions as a pedestal for disposing the X-ray sensor board 40. Here, the metal base 30 is formed of, for example, magnesium, which is a metal material, and is connected to GND (not shown) inside the housing 2. Therefore, the metal base 30 functions as an electromagnetic wave shield that protects the X-ray sensor 41 from electromagnetic waves. Therefore, in this embodiment, as shown in FIG. 8, the conventional electromagnetic wave shield SH that is provided to protect the X-ray sensor 41 from electromagnetic waves is not necessary. Also, in this embodiment, the distance D1 between the metal base 30 and the X-ray sensor 41 can be made larger than the distance D2 (see FIG. 8) between the electromagnetic wave shield SH and the X-ray sensor 41 in the conventional radiation detector 101. As a result, the parasitic capacitance C between the metal base 30 and the X-ray sensor 41 can be made smaller, so that electromagnetic wave noise caused by fluctuations in the parasitic capacitance C due to disturbances such as vibrations can be suppressed. Therefore, according to the radiation detector 1, it is possible to easily reduce erroneous detection of X-ray irradiation due to disturbances without increasing the number of parts or complicating the control system. Note that FIG. 8 is a cross-sectional view crossing the X-ray sensor 41 built into the conventional radiation detector 101. The conventional radiation detector 101 has a structure generally similar to that of the radiation detector 1 of this embodiment, except that it uses a base 130 formed from a resin material or a foam material.

[0031] [effect] As described above, the radiation detector 1 according to this embodiment includes the X-ray sensor board 40 having the X-ray sensor 41 mounted thereon for detecting irradiation of X-rays, and the metal base 30 connected to GND and on which the X-ray sensor board 40 is disposed. The metal base 30 includes a bottom 31 and ribs 32 standing on the periphery of the bottom 31. The X-ray sensor board 40 is disposed on the metal base 30 in a state in which the X-ray sensor 41 is covered by the bottom 31 and the ribs 32 of the metal base 30 and is spaced apart from the metal base 30. This allows the metal base 30 to function as an electromagnetic wave shield that protects the X-ray sensor 41 from electromagnetic waves, making it possible to easily reduce erroneous detection of irradiation of radiation due to disturbances such as impacts without complicating the control system.

[0032] Furthermore, the radiation detector 1 according to this embodiment is not provided with an electromagnetic wave shield for protecting the X-ray sensor 41 from electromagnetic waves. Therefore, the radiation detector 1 can easily reduce erroneous detection of radiation irradiation caused by disturbances such as impacts, without increasing the number of parts.

[0033] Furthermore, the rib 32 of the metal base 30 has a step portion (pedestal portion) 33 that holds the X-ray sensor substrate 40. The step portion 33 is formed so that the distance D1 between the X-ray sensor 41 and the bottom portion 31 is larger than the distance D2 between the X-ray sensor 41 and the electromagnetic shield SH when the electromagnetic shield SH is disposed on the X-ray sensor substrate 40. This allows the distance D1 between the metal base 30 and the X-ray sensor 41 to be larger than the distance D2 between the conventional electromagnetic shield SH and the X-ray sensor 41. As a result, the parasitic capacitance between the metal base 30 and the X-ray sensor 41 can be reduced, thereby suppressing electromagnetic noise caused by fluctuations in the parasitic capacitance C due to disturbances such as vibrations.

[0034] [others] The above embodiment is merely an example of the radiation detector according to the present invention, and the present invention is not limited to this embodiment.

[0035] For example, as shown in FIG. 5, a portion of the bottom 31 of the metal base 30 facing the X-ray sensor 41 may be perforated to provide a space 31a. At this time, a lead sheet LS is disposed on the top of the bottom 31, so that the shielding effect is not lost even if the space 31a is provided. In addition, at this time, the distance between the lead sheet LS functioning as a shield and the X-ray sensor 41 can be made even greater than in the above embodiment, so that the parasitic capacitance C can be further reduced. As a result, electromagnetic noise caused by fluctuations in parasitic capacitance due to disturbances such as vibrations can be further suppressed, so that erroneous detection of X-ray irradiation by the X-ray sensor 41 can be effectively reduced.

[0036] 6, when the X-ray sensor substrate 40 is attached to the step portion 33, a gap OP may be formed between the X-ray sensor substrate 40 and the rib 32 in the left-right direction in the figure so that they do not come into contact with each other even when vibration occurs. In other words, the X-ray sensor substrate 40 may be formed so as not to come into contact with parts of the rib 32 other than the step portion 33. To prevent contact, the area (region) of the step portion 33 of the metal base 30 is made large and / or the area (region) of the peripheral edge of the X-ray sensor substrate 40 is made narrow.

[0037] 7, the bottom 31 of the metal base 30 may be formed in a curved shape to maximize the distance between the bottom 31 and the X-ray sensor 41. This can further reduce the parasitic capacitance C compared to the above embodiment. The bottom 31 of the metal base 30 is not limited to a curved shape as long as it has a shape that maximizes the distance from the X-ray sensor 41. For example, a recess (not shown) may be formed in the portion of the bottom 31 of the metal base 30 directly above the X-ray sensor 41 on the side facing the X-ray sensor 41.

[0038] In the above embodiment, the metal base 30 is described as being made of magnesium, but is not limited thereto. The metal base 30 only needs to have an effect as an electromagnetic wave shield that protects the X-ray sensor 41 from electromagnetic waves, and may be made of, for example, aluminum or the like. [Explanation of symbols]

[0039] 1. Radiation detector 30 Metal Base 31 Bottom 32 Ribs 33 Step section (base section) 40 X-ray sensor board 41 X-ray sensor

Claims

1. a substrate having an X-ray sensor mounted thereon for detecting X-ray irradiation; a metal base connected to GND on which the substrate is placed; Equipped with The metal base is The container has a bottom and a rib extending from a periphery of the bottom. The substrate is the X-ray sensor is covered by the bottom and ribs of the metal base and is disposed on the metal base in a spaced-apart state; A radiation detector comprising:

2. No electromagnetic shield is provided to protect the X-ray sensor from electromagnetic waves.

2. The radiation detector according to claim 1 .

3. the rib includes a base portion for holding the substrate, the base is formed such that a distance between the X-ray sensor and the bottom in a thickness direction of the device when the substrate is held thereon is greater than a distance between the X-ray sensor and the electromagnetic shield in a thickness direction of the device when the electromagnetic shield is disposed on the substrate.

3. The radiation detector according to claim 2.

4. the substrate and the rib are formed such that, when the substrate is held on the base portion, the substrate does not come into contact with any portion of the rib other than the base portion; 4. The radiation detector according to claim 3.

5. the bottom portion is formed such that a thickness of a portion facing the X-ray sensor is thinner than a thickness of other portions; 2. The radiation detector according to claim 1 .

6. The bottom portion is perforated at a portion facing the X-ray sensor.

2. The radiation detector according to claim 1 .

Images