KR101967499B1

KR101967499B1 - Radiation detection apparatus and radiation imaging system

Info

Publication number: KR101967499B1
Application number: KR1020150177853A
Authority: KR
Inventors: 야스히코 사노
Original assignee: 캐논 가부시끼가이샤
Priority date: 2014-12-22
Filing date: 2015-12-14
Publication date: 2019-04-09
Also published as: KR20160076446A; JP2016118527A; PH12015000445B1; PH12015000445A1; SG10201509711PA; JP6714332B2

Abstract

The radiation detection apparatus includes a planar detection unit having a two-dimensional array of elements for acquiring an electric signal based on radiation and detecting the irradiated radiation, a drive circuit for driving a switch for causing the element to output an electric signal, An acquisition circuit for acquiring the electric signal from the element as the drive circuit is driven, a support base on which the drive circuit and the acquisition circuit are disposed, and a radiation source for irradiating the radiation used for imaging, And a conductive member having a portion electrically connected to the ground of the drive circuit and the ground of the acquisition circuit.

Description

TECHNICAL FIELD [0001] The present invention relates to a radiation detection apparatus and a radiation imaging system,

The present invention relates to a radiation detecting apparatus for detecting radiation and a radiation imaging system for obtaining a radiation image using the radiation detecting apparatus.

Recently, a flat panel type radiation detecting apparatus using a sensor array arranged in a two-dimensional array having conversion elements each designed to convert radiation into an electric signal has been popular. Such a sensor array generally includes a conversion element formed on a glass substrate for each pixel and a switching element such as a TFT for transferring an electric signal converted by the conversion element to the outside. These elements are arranged two-dimensionally in the array. Japanese Patent No. 4018725 discloses a technique for acquiring an image using such a sensor array. According to this technique, a plurality of gate drivers are disposed on an external or glass substrate to drive the switch elements through drive signal lines. In addition, like the gate driver, a plurality of charge detection amplifiers are disposed on an external or glass substrate to detect electric signals taken out through image signal lines. Then, an image is formed from the detected electric signal.

Such a radiation detecting apparatus has the following problems because the converting element detects minute charges. For example, in a radiographic room of a hospital or the like, an apparatus for radiating radiation or another diagnostic apparatus and the like are provided together with a radiation detecting apparatus. These devices often use high power. That is, there may be an environment where a device for detecting a weak electric charge and an device using a high electric power coexist. In such an environment, unnecessary electromagnetic energy from the high power device becomes a magnetic field noise to other devices. This often causes malfunctions or performance degradation in these devices. When AC magnetic field noise is externally applied to the radiation detection apparatus, image noise of a horizontal stripe pattern called a line artifact appears in the acquired image. Such noise is generated, in particular, from a high-power device, an inverter of an X-ray generator, and the like, and has a frequency band of about 1 kHz to about 100 kHz. Such AC magnetic field noise can be reached from various directions depending on the installation situation or use situation of the radiation detection device and the high power device. It is generally difficult to establish a countermeasure against noise of AC magnetic field noise.

Conventionally, various techniques for reducing image noise caused by such AC magnetic fields have been proposed. Japanese Laid-Open Patent Publication No. 2012-119770 discloses a technique of eliminating the influence of an alternating magnetic field externally reaching a specific frequency and a specific amplitude from a final image by adjusting a read time for a dark image and a radiographic image . Further, Japanese Patent Laid-Open Publication No. 1-12726 discloses a technique in which the influence of electromagnetic noise is reduced by arranging a conductive member, a photoelectric conversion unit, and a scintillator in a named order from one side of a radiation detecting apparatus to which radiation is irradiated And a reduction technique.

However, the technique disclosed in Japanese Laid-Open Patent Publication No. 2012-119770 can not remove the image noise by the subtraction processing when the frequency or amplitude of the AC magnetic field changes at the time of acquiring the dark image and the radiographic image. In order to make the time from the start of acquisition of the dark image to the start of acquisition of the radiographic image an integral multiple of the external magnetic field period, it is necessary to delay the image acquisition interval according to the external magnetic field period, which lowers the imaging speed. Although the technique disclosed in Japanese Patent Laid-Open Publication No. 1-12726 can reduce the electromagnetic noise from the radiation incidence direction, it is difficult to obtain an effect on the AC magnetic field which reaches the radiation detection device from the horizontal direction.

INDUSTRIAL APPLICABILITY The present invention reduces the image noise due to the AC magnetic field which reaches from the horizontal direction at an unknown frequency and amplitude in the radiation detecting apparatus.

According to an aspect of the invention there is provided a lithographic apparatus comprising a planar detection unit having a two-dimensional array of elements for acquiring an electrical signal based on radiation, the planar detection unit being configured to detect the irradiated radiation; A driving circuit for driving a switch for causing the device to output the electric signal; An acquisition circuit that acquires the electrical signal from the element as the switch is driven; A support base on which the drive circuit and the acquisition circuit are disposed; And a conductive member which is disposed in proximity to the front of the detection unit as viewed from the radiation source for irradiating the radiation and has a portion electrically connected to the ground of the drive circuit and the ground of the acquisition circuit.

According to another aspect of the present invention, there is provided a lithographic apparatus comprising: a radiation detection device; An irradiating unit configured to irradiate the radiation detecting apparatus with radiation; And a forming unit configured to form a radiographic image, wherein the radiation detecting apparatus has a two-dimensional array of elements for acquiring an electrical signal based on the radiation, the radiation detecting apparatus being configured to detect the irradiated radiation A planar detection unit, a drive circuit for driving a switch for causing the element to output an electric signal, an acquisition circuit for acquiring the electric signal from the element as the switch is driven, And a conductive member disposed in proximity to the front of the detection unit and having a portion electrically connected to the ground of the drive circuit and the ground of the acquisition circuit when viewed from a radiation source that irradiates the radiation, The forming unit may be configured so that the pre- The radiation imaging system on the basis of the signal to form the radio graphic image is provided.

Additional features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the accompanying drawings).

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1A and 1B are views showing a first example of the structure of a radiation detecting apparatus.
Figs. 2A and 2B are diagrams showing examples of the structure of a radiation detecting apparatus when the conductive member is not connected to the radiation detecting apparatus in Figs. 1A and 1B. Fig.
3 is a diagram showing a second example of the structure of the radiation detecting apparatus.
4 is a diagram showing a third example of the structure of the radiation detecting apparatus.

Exemplary embodiment (s) of the present invention will now be described in detail with reference to the drawings. The relative arrangement, numerical representations, and numerical values of the components described in this embodiment do not limit the scope of the present invention unless it is specifically described otherwise.

A radiation detection apparatus according to the present invention is a radiation detection apparatus that includes a radiation source that emits radiation, for example, a radiation imaging apparatus that forms a radio graphic image from an electrical signal corresponding to a radiation detection result output from a radiation detection apparatus that detects a radiation emitted, Used in the system. It should be noted that the radiation imaging system may be a single device that includes both the radiation source and the radio graphic imaging function, or that at least some of the systems may exist as separate and independent devices. The radiation may also be X-rays or other types of radiation.

&Lt; First Embodiment >

1A and 1B show a first example of the structure of a radiation detecting apparatus. 1A is a perspective view of a radiation detection apparatus. 1B is a cross-sectional view taken along line a-a 'in FIG. 1A. 1A and 1B, the one-way arrow specifies three-dimensional coordinates as the X-, Y-, and Z-axes, and the apparatus is placed in a direction from below in FIGS. 1A and 1B, &Lt; / RTI > The AC magnetic field as a noise source arriving from the Z direction is called a vertical AC magnetic field, and the AC magnetic field as a noise source arriving from the X or Y direction is called a horizontal AC magnetic field.

The radiation detecting device is formed by laminating the conductive member 13, the sensor array 2 and the supporting base 12, for example, as viewed from the direction in which the radiation is irradiated to the device.

The sensor array 2 is formed of a substrate having an insulating surface such as a glass substrate and has a plurality of conversion elements 1 and switch elements 3 respectively corresponding to one pixel arranged two- Detection unit. The sensor array 2 is wired to the drive signal line 4 for driving the switch element 3 and the image signal line 5 for outputting the detection result of the radiation acquired by the conversion element 1. [ The sensor array 2 is an inexpensive capacitive capacitor formed by the structure of each switch element 3 and the intersection of the drive signal line 4 and the image signal line 5, &Lt; / RTI > may exist.

Each conversion element 1 is an element that converts radiation into an electric signal. Each switch element 3 is formed of a TFT or the like. As described above, each pair of the conversion element 1 and the switch element 3 corresponds to one pixel. These pairs are arranged two-dimensionally from the sensor array 2 to the array. And the resulting structure functions as a radiation detection unit for obtaining a radio graphic image composed of a plurality of pixels. The driving signal line 4 is arranged corresponding to each row of the two-dimensional array in which the pair of the conversion element 1 and the switching element 3 are arranged, and the driving- Or a drive off-bias. Note that the drive off-bias is required to be at least a potential capable of turning off each switch element 3, and is the same potential as the ground. The image signal lines 5 are arranged corresponding to the respective columns of the two-dimensional array described above and are connected to the conversion element 1 corresponding to the switching element 3 to which the driving on-bias is supplied from the driving signal line 4 That is, the result of radiation detection, to the reading circuit 6. The conversion element 1 is a direct conversion type which converts radiation directly into an electric signal or an indirect conversion type which converts light emitted from a phosphor (not shown) into an electric signal in accordance with irradiation of radiation Note that it can be either.

The readout circuit 6 and the output circuit 9 are arranged in the support base 12. The support base 12 is a base for fixing and supporting the sensor array 2, the reading circuit 6, and the output circuit 9. As the support base 12, a base formed by inserting a metal mesh into a conductive metal material or a lightweight high strength carbon fiber reinforced plastic (CFRP) material according to a recent demand for weight reduction, or a CFRP material alone is used. The support base 12 is configured to emit light from the drive signal line 4 and the image signal line 5 through a shielding member for shielding a member for impact mitigation and various circuits from radiation, Lt; RTI ID = 0.0 > h. &Lt; / RTI >

Each readout circuit 6 includes a sense amplifier 7 and a readout substrate 8 and functions as an acquisition circuit for acquiring a radiation detection result. Each of the sense amplifiers 7 converts an electric signal from the corresponding image signal line 5 into a digital signal by using an A / D converter or the like, and transfers the signal to the readout substrate 8. [ The readout substrate 8 inputs / outputs control signals to / from each of the sense amplifiers 7, for example, and often supplies power.

Each output circuit 9 includes a gate driver 10 and an output substrate 11 and functions as a drive circuit for driving each of the switch elements 3 described above. Each gate driver 10 applies either a driving on-bias for turning on the corresponding switching element 3 to the corresponding driving signal line 4 or a driving off-bias for turning off the switching element 3 One is selectively applied. In each gate driver 10, both the driving on-bias and the driving off-bias may be input. The output substrate 11 inputs / outputs a control signal to each gate driver 10 and supplies power to the gate driver 10. [

The sense amplifier 7 and the gate driver 10 are generally constituted by an integrated circuit and mounted on a flexible substrate such as TCP (Tape Carrier Package) and COF (Chip On Film). The sense amplifier 7 and the gate driver 10 can be mounted on the sensor array 2 by a mounting method called COG (Chip On Glass).

The conductive member 13 is disposed closer to the irradiation side of the radiation than the sensor array 2 and is provided for one of purposes including prevention of detection of visible light other than radiation, protection of a phosphor (not shown), and measures for preventing electric field noise . The conductive member 13 is disposed in proximity to the conversion element 1, the driving signal line 4 and the image signal line 5 for the above purpose, , With an interval h '. Note that the conductive member 13 needs to have a thickness, for example, a radiation transmittance of 99% or more because it is necessary to transmit radiation at the time of imaging. The conductive member 13 is, for example, a thin film containing aluminum and covering the sensor array 2. This film has a thickness of, for example, about 0.1 탆 to 100 탆. Note that the conductive member 13 is not limited to this, but may be formed of another material, or may have a thickness outside the above range, if the conductive material has a radiation transmittance of 99% or more.

Further, in the present embodiment, as described later, the conductive member 13 is also used as a part of the closed loop for receiving AC magnetic field noise, that is, as part of a propagation path for induction current. The portions 13-1 and 13-2 of the conductive member 13 are electrically connected to the ground of the reading circuit 6 and the ground of the output circuit 9, respectively.

The connection point 15 is used for connection of the ground of the reading circuit 6 and the ground of the output circuit 9 to the supporting base 12. As the connection point 15, a conductive screw or the like is used. In this embodiment, for example, at least one of the ground of the reading circuit 6 and the ground of the output circuit 9 may be a configuration that is not electrically connected to the supporting base 12, that is, have.

The operation principle of the radiation detecting apparatus according to the present embodiment will be described below. 2A and 2B show a comparative example in which a portion for electrically connecting the conductive member 13 to the ground of the readout circuit 6 and the ground of the output circuit 9 from the radiation detection device of Figs. In portions 13-1 and 13-2 of the radiation detecting apparatus shown in FIG. 2A is a perspective view of a comparative example of a radiation detecting apparatus. FIG. 2B is a cross-sectional view taken along the line b-b 'in FIG. 2A. FIG. In Figs. 2A and 2B, the same reference numerals denote the same components as in Figs. 1A and 1B.

In the radiation detecting apparatus, an induced electromotive force is generated when an alternating magnetic field, that is, a fluctuating magnetic flux passes through a closed circuit in a radiation detecting apparatus in accordance with an electromagnetic induction law. Also, the induced electromotive force is converted to the induced current by the impedance of the closed circuit. This induced current is superimposed on the electrical signal detected by the sense amplifier 7. This causes image noise. It is known that the induced current is proportional to the magnetic flux density of the AC magnetic field noise and the cross-sectional area of the closed circuit, and inversely proportional to the impedance of the closed circuit. That is, as the cross-sectional area of the closed circuit through which AC magnetic field noise passes decreases and the impedance of the closed circuit increases, image noise becomes less likely to occur.

In the radiation detecting apparatus, an induced electromotive force is generated when an alternating magnetic field, that is, a fluctuating magnetic flux passes through a closed circuit in a radiation detecting apparatus in accordance with an electromagnetic induction law. This induced electromotive force is superimposed on the electrical signal detected by the sense amplifier 7. This causes image noise. It is known that the induced electromotive force is proportional to the magnetic flux density of the AC magnetic field noise and the cross sectional area of the closed circuit. That is, as the cross-sectional area of the closed circuit through which AC magnetic field noise passes increases, more image noise is generated.

Referring to FIG. 2B, a closed circuit C2 through which horizontal AC magnetic field noise passes is indicated by a dotted line. The closed circuit C2 includes an output substrate 11, a gate driver 10, a driving signal line 4, a parasitic capacitor 14, an image signal line 5, a sense amplifier 7, And a path extending through the support base 12 to which the ground of the output circuit 9 and the ground of the readout circuit 6 are connected. Therefore, the magnitude of the image noise generated by the horizontal AC magnetic field noise is proportional to the cross-sectional area shown by oblique lines in Fig. 2B. Note that the portion not shown in the oblique line in the closed circuit C2 is a portion existing in the same plane as the support base 12 in cross section. That is, this portion is shown on the support base 12 for convenience of explanation. In practice, however, this portion is formed on the same plane as the support base 12. Therefore, this portion has no cross-sectional area in the horizontal direction or only a small cross-sectional area, and therefore, the horizontal AC magnetic noise does not pass through it. Even if this noise passes through that portion, there is only a small effect. In the following description, it is noted that, for the same reason, a portion not shown by the slant line in the closed circuit is a portion not passing the AC magnetic field noise or a portion having only a small influence even if such noise passes therethrough.

2A and 2B show that the conductive member 13 does not have the portions 13-1 and 13-2 electrically connected to the ground of the reading circuit 6 and the ground of the output circuit 9, And the member 13 does not function as a part of the closed circuit. On the other hand, for example, even when only a part 13-1 of the conductive member 13 is connected to the ground of the reading circuit 6, the conductive member 13 does not function as a part of the closed circuit. The same applies to the case where only the part 13-2 of the conductive member 13 is connected to the ground of the output circuit 9. [ That is, as long as both of the portions 13-1 and 13-2 of the conductive member 13 are not connected to the ground, the conductive member 13 does not function as a part of the closed circuit.

On the other hand, in the radiation detecting apparatus according to the present embodiment, a part 13-1 of the conductive member 13 is connected to the ground of the reading circuit 6, and a part 13-2 of the conductive member 13 is connected to the ground. Is connected to the ground of the output circuit (9). As a result, the closed circuit C1 across which the horizontal AC magnetic field noise crosses is represented by a dotted line in Fig. 1B. The closed circuit C1 is connected to the output substrate 11, the gate driver 10, the driving signal line 4, the parasitic capacitor 14, the image signal line 5, the sense amplifier 7, And a conductive member 13 to which the ground of the output circuit 9 and the ground of the reading circuit 6 are connected. That is, in this embodiment, portions 13-1 and 13-2 of the conductive member 13 are electrically connected to the ground of the output circuit 9 and the ground of the readout circuit 6, To form a closed circuit (C1). This closed circuit C1 uses the conductive member 13 disposed close to the drive signal line 4 and the image signal line 5 which are not used as a path as a part of the path. Obviously, this greatly reduces the cross-sectional area of alternating-field magnetic noise shown by diagonal lines compared to the conventional art. This causes a part of the induced current induced by the horizontal AC magnetic field noise to flow in the closed circuit C1 having a small cross sectional area, thereby greatly reducing the image noise.

The distance h between both the drive signal line 4 and the image signal line 5 and the support base 12 and both the drive signal line 4 and the image signal line 5, The relationship between the distance h 'and the distance h' can be set so as to satisfy h '<h. With this setting, the sectional area of the closed circuit C1 formed in the present embodiment becomes much smaller than the conventional closed path C2. That is, this reduces the induced current induced by the horizontal AC magnetic field noise, thereby effectively reducing the image noise.

When the conductivity or the sheet resistance, the area, the thickness, and the shape are a mesh shape, the impedance of each member calculated from physical form such as opening is taken into consideration. Referring to the support base 12 and the conductive member 13, reducing the impedance of the conductive member 13 to a value smaller than the impedance of the support base 12 reduces image noise. It can be considered that this is an effect obtained by reducing an induced current induced in the closed circuit C2 having a large cross-sectional area and flowing an induced current in the closed circuit C1 having a smaller cross-sectional area.

&Lt; Embodiment 2 >

Fig. 3 shows a second example of the structure of the radiation detecting apparatus. Although Fig. 3 shows only a cross-sectional view of the structure, the basic structure is the same as that shown in Figs. 1A and 1B. Note that the same reference numerals as in the first embodiment denote the same components, and a description thereof is omitted.

The radiation detecting apparatus according to the present embodiment is different from the first embodiment in that a power source 16 serving as a driving off-bias is applied to the gate driver 10 through the power source substrate 17. [ The driving off-bias is the ground potential in the first embodiment. In contrast, in the second embodiment, the driving on-bias is set to a potential that further increases the potential difference between the driving on-bias and the driving off-bias. This setting is made in order to prevent the switching element 3 from being turned on and reduce the leakage current of the switching element 3 when the driving off-bias is varied by various noises. Further, the radiation detecting apparatus according to the present embodiment is different from the first embodiment in that the driving off-bias is connected to the ground via the capacitor 18 on the output circuit 9. [ Note that, as the capacitance value of the capacitor 18, a capacitance of, for example, 1.3 占 내지 to 1.0 占 F is used in consideration of the impedance of the power source 16 as a drive off-bias.

Referring to Fig. 3, as shown in the description of the first embodiment, the dotted line indicates the closed circuit C3 through which the horizontal AC magnetic field noise passes. The closed circuit C3 includes an output substrate 11, a gate driver 10, a driving signal line 4, a parasitic capacitor 14, an image signal line 5, a sense amplifier 7, As shown in Fig. A propagation path is formed in the closed circuit C3 from the output circuit 9 to the ground of the output circuit 9 via the capacitor 18 with respect to the gate driver 10 serving as a drive off-bias . Portions 13-1 and 13-2 of the conductive member 13 to which the ground of the output circuit 9 and the ground of the reading circuit 6 are electrically connected are electrically connected to the conductive member 13 , And the closed circuit (C3) via the conductive member (13) is formed.

As described above, in the radiation detecting apparatus according to the present embodiment, as in the first embodiment, it is clear that the cross-sectional area of alternating-current magnetic noise shown by diagonal lines is significantly reduced as compared with the prior art. This causes a part of the induced current induced by the horizontal AC magnetic field noise to flow through the closed circuit C3 having a small cross-sectional area, thereby greatly reducing the image noise.

The distance h between both the drive signal line 4 and the image signal line 5 and the support base 12 and the distance h between the drive signal line 4 and the image signal line 5 both of the conductive member 13) can be set so as to satisfy h '<h. With this setting, the sectional area of the closed circuit C3 formed in the present embodiment becomes smaller than the sectional area of the conventional closed circuit C2. That is, this further reduces the induced current induced by the horizontal AC magnetic field noise, thereby effectively reducing the image noise.

Further, referring to the support base 12 and the conductive member 13, reducing the impedance of the conductive member 13 to a value smaller than the impedance of the support base 12 can further reduce the image noise. This can be considered to be an effect obtained by reducing an induced current induced in the closed circuit C2 having a large cross-sectional area and flowing an induced current in the closed circuit C3 having a smaller cross-sectional area.

&Lt; Third Embodiment >

Fig. 4 shows a third example of the structure of the radiation detecting apparatus. Fig. 4 shows only a sectional view of the structure, but the basic structure is the same as that shown in Figs. 1A and 1B. Note that the same reference numerals as in the first embodiment and the second embodiment denote the same components, and a description thereof will be omitted.

The radiation detecting apparatus according to the present embodiment is configured such that the conductive member 13 is connected to the power source 16 serving as a drive off-bias in the output circuit 9 through the part 13-2 of the conductive member 13 And is different from the radiation detecting apparatus according to the first and second embodiments in that the conductive member 13 is set at the same potential as the driving off-bias. The radiation detecting apparatus according to the present embodiment is different from the radiation detecting apparatus according to the first and second embodiments in that a part 13-1 of the conductive member 13 is connected to the ground via the capacitor 18 on the reading circuit 6. [ Is different from the radiation detecting apparatus according to the first embodiment. Note that a capacitance of, for example, 1.3 占 내지 to 1.0 占 F is used as the capacitance value of the capacitor 18 in consideration of the impedance of the power supply 16 as a drive off-bias.

Referring to Fig. 4, as shown in the description of the first and second embodiments, the dotted line indicates the closed circuit C4 through which the horizontal AC magnetic field noise passes. The closed circuit C4 includes a path constituted by the gate driver 10, the driving signal line 4, the parasitic capacitor 14, the image signal line 5, and the sense amplifier 7. The current flowing into or out of the drive off-bias of the gate driver 10 in the closed circuit C4 is also supplied to the portion 13-2 of the conductive member 13 connected to the output circuit 9 and the conductive member 13 and a part 13-1 of the conductive member 13. The reading circuit 6 is a part of the conductive member 13, This current reaches the ground of the readout circuit 6 through the capacitor 18 on the readout circuit 6. The path forms a closed circuit C4 across which horizontal AC magnetic noise crosses.

As described above, as in the first and second embodiments, the radiation detecting apparatus according to the third embodiment can reduce the cross-sectional area of the closed circuit through which the horizontal alternating-current magnetic field noise passes. This enables the radiation detecting apparatus according to the present embodiment to significantly reduce the image noise caused by the horizontal AC magnetic field noise.

In each of the above embodiments, the closed circuit through which horizontal alternating-current magnetic field noise passes is shown by a dotted line only for one wiring line passing through one driving signal line 4 and one image signal line 5, Note that there is a similar closed circuit for the combination of line 4 and image signal line 5. Each of the sense amplifiers 7 detects the integrated value of the induced electromotive force generated when the horizontal alternating-current magnetic field noise passes through all these closed circuits, thus generating image noise. The radiation detecting apparatus according to each of the above embodiments can reduce the image noise due to the AC magnetic field noise by reducing the cross sectional areas of all the closed circuits corresponding to the combination of all the drive signal lines 4 and all the image signal lines 5 have.

It is noted that the radiation detecting apparatus according to each of the above embodiments does not need to provide any specific control for noise reduction at the time of imaging because it reduces the induced electromotive force caused by the AC magnetic field noise by reducing the cross sectional area of each closed circuit do it. Moreover, this is an effect of reducing the induced electromotive force by reducing the amount of magnetic field noise applied to the chain, so that the effect can be obtained irrespective of the amplitude and the frequency of the AC magnetic noise. As described above, in the radiation detecting apparatus according to each of the above-described embodiments, even when the frequency or the amplitude of the AC magnetic field noise arriving from the outside is not known, The influence can be reduced.

In the above embodiment, the portion 13-1 of the conductive member 13 is linearly connected to the ground at one point of the reading circuit 6, but this is not restrictive. The conductive member 13 may be connected to the ground of the reading circuit 6, for example, at a plurality of points or two-dimensionally. Likewise, the portion 13-2 of the conductive member 13 can be connected to the ground of the output circuit 9 at a plurality of points or two-dimensionally.

Each of the embodiments described above can be configured such that at least one of the ground of the reading circuit 6 and the ground of the output circuit 9 is not electrically connected to the supporting base 12. [ This can also be achieved by changing the support base 12 to a non-conductive material such as CFRP or a non-conductive material. That is, increasing (or increasing) the impedance of the closed circuit through the support base 12 infinitely can achieve an effect equivalent to greatly increasing the impedance of each closed circuit through the conductive member 13. This makes it possible to further reduce image noise by preventing the formation of a closed circuit through the support base 12 by the radiation detecting device.

The following is a noise amount evaluation result obtained by using the radiation detecting apparatus according to each of the above-described embodiments as a cassette type X-ray digital imaging apparatus used for imaging of a human body in order to demonstrate the effects of each of the above-described embodiments. In this evaluation, an X-ray digital imaging device having external dimensions of 384 mm (width) x 460 mm (depth) x 15 mm (thickness) was used. Further, the conversion element has about 2800 x 3400 pixels. The following evaluation result shows a case where a sine wave current of 25.04 kHz is applied by using a 1 m square loop coil as external horizontal AC magnetic field noise.

[Evaluation 1]

In the radiation detecting apparatus according to the first embodiment, the intervals h and h 'in FIGS. 1A and 1B are set to h = about 3 mm and h' = about 500 μm, respectively. Further, the conductive member 13 was made of aluminum with a thickness of 30 mu m. The conductive member 13 is electrically connected to the ground by a conductive screw at one point on the reading board 8 of the reading circuit 6 and one point on the output board 11 of the output circuit 9 .

In this configuration, the image noise amount at the time of image capturing was compared with the image noise amount in Figs. 2A and 2B as a comparative example. By using the radiation detecting apparatus according to the first embodiment, it is possible to reduce the image noise due to the AC magnetic field noise from the X direction to 58% when the image noise amount in Figs. 2A and 2B is 100% It is possible to reduce the image noise caused by the AC magnetic field noise to 87%. That is, it was confirmed that the radiation detecting apparatus according to the first embodiment was able to obtain the effect of reducing the AC magnetic field noise from the X and Y directions by 42% and 13%, respectively.

[Evaluation 2]

In this evaluation, unlike the evaluation 1, in the radiation detecting apparatus according to the first embodiment, the connection point 15 is made of a non-conductive resin screw or the like, and the ground of the reading circuit 6 and the ground of the output circuit 9 At least one of them is not electrically connected to the support base 12. This can be achieved by significantly increasing the impedance of the closed loop through the support base 12 relative to the impedance of the closed loop through the conductive member 13 by infinitely increasing (or increasing greatly) the impedance of the closed loop through the support base 12 Equal. This configuration is the same as that shown in Figs. 1A and 1B in that the closed circuit C1 is formed, but all of the induced current does not flow to the conductive base member 12 To the closed circuit (C1). Therefore, the cross sectional area reduction effect should be further increased.

In such a configuration, the image noise amount obtained by image pickup is compared with the image noise amount in Figs. 2A and 2B showing a comparative example. As a result, with the above arrangement, when the image noise amount in Figs. 2A and 2B is set to 100%, the image noise due to the AC magnetic field noise from the X direction is reduced to 45% The image noise caused by the magnetic field noise could be reduced to 87%. That is, the radiation detecting apparatus according to the first embodiment has the effect of reducing the image noise caused by the AC magnetic field noise from the X direction and the Y direction by 55% and 13%, respectively.

[Evaluation 3]

Evaluation was made as to the case where the radiation detecting apparatus according to the second embodiment was used in an X-ray digital imaging apparatus. In this evaluation, when the part 13-1 of the conductive member 13 is not electrically connected to the reading circuit 6 or the part 13-2 of the conductive member 13 is electrically connected to the output circuit 9 And a case where a radiation detector having a capacitor 18 mounted on the power supply board 17 is used as a comparative object.

As a result, when the comparative example is 100% and the capacitor 18 is 1.3 占,, the image noise due to the AC magnetic field noise from the X direction is reduced to 90% and the image noise due to the AC magnetic field noise from the Y direction is reduced 97%. That is, the radiation detecting apparatus according to the second embodiment has the effect of reducing the image noise caused by the AC magnetic field noise from the X and Y directions by 10% and 3%, respectively, as compared with the comparative example Respectively.

When the capacitor 18 is 69.3 mu F, the image noise due to the AC magnetic field noise from the X direction is reduced to 75%, and the image noise due to the AC magnetic field noise from the Y direction can be reduced to 71% there was. That is, the radiation detecting apparatus according to the second embodiment has the effect of reducing the image noise caused by the AC magnetic field noise from the X and Y directions by 25% and 29%, respectively, as compared with the comparative example Respectively.

INDUSTRIAL APPLICABILITY The present invention can reduce the image noise due to the AC magnetic field which reaches from the horizontal direction at an unknown frequency and amplitude in the radiation detecting apparatus.

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

Claims

A radiation detection device comprising:
A planar detection unit having a two-dimensional array of elements for acquiring an electrical signal based on the radiation and configured to detect the irradiated radiation,
A drive circuit for driving a switch for causing the element to output the electric signal through a drive signal line,
An acquisition circuit for acquiring the electric signal from the element through an image signal line as the switch is driven,
A support base on which the drive circuit and the acquisition circuit are disposed,
And a conductive member having a portion electrically connected to the ground of the drive circuit and a ground of the acquisition circuit,
The radiation detecting device is formed by laminating the conductive member, the two-dimensional array and the support base from the viewpoint of a radiation source for irradiating the radiation,
Wherein the drive circuit, the acquisition circuit, the drive signal line, the image signal line, and the conductive member form a closed circuit.

The radiation detection apparatus according to claim 1, wherein the support base is disposed at a position where the distance between the support base and the planar detection unit is longer than the distance between the planar detection unit and the conductive member.

The radiation detection apparatus according to claim 1, wherein an impedance of the support base is higher than an impedance of the conductive member.

The driving circuit according to claim 1, wherein a driving off-bias for turning off the switch is inputted to the driving circuit,
A capacitor is connected between the driving off-bias and the ground of the driving circuit, and the conductive member is electrically connected to the ground of the driving circuit and the ground of the acquisition circuit.

The driving circuit according to claim 1, wherein a driving off-bias for turning off the switch is inputted to the driving circuit,
Wherein the conductive member is electrically connected to the ground of the acquisition circuit via a capacitor disposed between the drive off-bias of the drive circuit and the ground of the acquisition off- .

5. The radiation detection apparatus of claim 4, wherein the capacitor has a capacitance of 1.3 [mu] F to 1.0 mF.

The radiation detection apparatus according to claim 1, wherein the support base is disposed behind the planar detection unit when viewed from the radiation source.

The radiation detecting apparatus according to claim 1, wherein at least one of the ground of the driving circuit and the ground of the obtaining circuit is not electrically connected to the supporting base.

The radiation detection apparatus according to claim 1, wherein a part of the conductive member comprises a thin film covering the planar detection unit.

The radiation detection apparatus according to claim 1, wherein the conductive member is electrically connected to at least one of a ground of the drive circuit and a ground of the acquisition circuit at a plurality of positions.

A radiation imaging system comprising:
Radiation detector,
An irradiation unit configured to irradiate the radiation detection device with radiation, and
A forming unit configured to form a radiographic image,
The radiation detecting apparatus includes:
A planar detection unit having a two-dimensional array of elements for acquiring an electrical signal based on the radiation and configured to detect the irradiated radiation,
A drive circuit for driving a switch for causing the element to output the electric signal through a drive signal line,
An acquisition circuit for acquiring the electric signal from the element through an image signal line as the switch is driven,
A support base on which the drive circuit and the acquisition circuit are disposed,
And a conductive member having a portion electrically connected to the ground of the drive circuit and a ground of the acquisition circuit,
Wherein the forming unit forms the radio graphic image based on the electric signals acquired by the acquisition circuit,
The radiation detecting device is formed by laminating the conductive member, the two-dimensional array and the support base from the viewpoint of a radiation source for irradiating the radiation,
Wherein the drive circuit, the acquisition circuit, the drive signal line, the image signal line, and the conductive member form a closed circuit.