JP2016118527A - Radiation detection device and radiographic imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detection device that features reduced image noise caused by an AC magnetic field of unknown frequency and amplitude coming from a horizontal direction.SOLUTION: A radiation detection device includes: a planar detection unit having two-dimensionally arrayed elements for obtaining radiation-based electrical signals thereon to detect irradiated radiation; a drive circuit configured to drive switches for outputting electrical signals from respective elements; an acquisition circuit configured to acquire an electrical signal from each of the elements when a switch corresponding thereto is driven; a support base having the drive circuit and acquisition circuit arranged thereon; and a conductive member disposed partially in front of the detection unit viewing from a radiation source that emits radiation for imaging, and electrically connected to the ground of the drive circuit and the ground of the acquisition circuit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radiation detection apparatus that detects radiation, and a radiation imaging system that captures a radiation image using the radiation detection apparatus.

  In recent years, flat panel type radiation detection apparatuses using a sensor array in which conversion elements for converting radiation into electrical signals are arranged in a two-dimensional array have become widespread. Such a sensor array generally has a conversion element formed on a glass substrate for each pixel and a switch element such as a TFT for transferring an electric signal converted by the conversion element to the outside. Arranged and configured as an array. Patent Document 1 describes a method for obtaining an image using such a sensor array. In this method, a plurality of gate drivers are arranged outside or on the glass substrate, and the gate drivers drive the switch elements via the drive signal lines. Similar to the gate driver, a plurality of sense amplifiers for charge detection are arranged outside or on the glass substrate, and the sense amplifier detects an electrical signal taken out through the image signal line. An image is formed from the detected electrical signal.

  Such a radiation detection apparatus has the following problems because the conversion element detects minute charges. For example, in a radiographing room such as a hospital, a radiation detecting device and a device for emitting radiation or other diagnostic devices are installed, and these devices may use high power. That is, an environment in which a device that detects a weak charge and a device that uses high power coexist can occur. In such an environment, unnecessary electromagnetic energy from the high-power device becomes magnetic field noise for other devices, which may cause malfunctions and performance degradation in these devices. Regarding the radiation detection apparatus, when AC magnetic field noise is applied from the outside, horizontal stripe-like image noise called a line artifact appears in the captured image. These noises are generated particularly from high-power devices, inverters of X-ray generators, etc., and have a relatively low frequency band of about 1 kHz to 100 kHz. Further, these AC magnetic field noises can come from various directions depending on the installation status or usage status of the radiation detection apparatus and the high power equipment. Noise countermeasures against such AC magnetic field noise are generally difficult.

  Conventionally, various methods have been proposed to reduce image noise due to such an alternating magnetic field. Patent Document 2 adjusts the readout time of a dark image and a radiographic image with respect to an AC magnetic field arriving at a specific frequency and a specific amplitude from the outside, and erases the influence of the AC magnetic field from the final image by subtraction processing. The method is described. Patent Document 3 describes a method of reducing the influence of electromagnetic noise by arranging a conductive member, a photoelectric conversion unit, and a scintillator in this order from the radiation irradiation side of the radiation detection apparatus.

Japanese Patent No. 4018725 JP 2012-119770 A JP 2012-112726 A

  However, with the technique of Patent Document 2, if the frequency or amplitude of the alternating magnetic field changes during dark image acquisition and radiological image acquisition, image noise cannot be removed in the subtraction process. Furthermore, in order to make the time from the start of dark image acquisition to the start of radiological image acquisition an integer multiple of the external magnetic field period, it is necessary to delay the image acquisition interval according to the period of the external magnetic field, and the imaging speed is reduced. There was a problem. Moreover, in patent document 3, although the electromagnetic noise from the radiation incident direction can be reduced, there is a problem that it is difficult to obtain an effect with respect to the alternating magnetic field that arrives at the radiation detection device from the horizontal direction.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce image noise caused by an alternating magnetic field arriving from the horizontal direction with unknown frequency and amplitude in a radiation detection apparatus.

  In order to solve the above-described problems, a radiation detection apparatus according to the present invention includes a planar detection unit that arranges elements for acquiring an electrical signal based on radiation in a two-dimensional array, and detects irradiated radiation, and A driving circuit for driving a switch for outputting a detection result in each of the elements; an acquisition circuit for acquiring the detection result in each of the elements in response to driving of the switch; the driving circuit; and A support base on which the acquisition circuit is disposed, a part of the support base disposed in front of the detection unit as viewed from a radiation source that emits radiation, and a ground of the drive circuit and a ground of the acquisition circuit; And a conductive member electrically connected.

  According to the present invention, in the radiation detection apparatus, it is possible to reduce image noise caused by an alternating magnetic field that is unknown in frequency and amplitude and arrives from the horizontal direction.

The figure which shows the 1st example of the structure of a radiation detection apparatus. The figure which shows the example of a structure of a radiation detection apparatus in case the electroconductive member is not connected to a radiation detection apparatus in FIG. The figure which shows the 2nd example of the structure of a radiation detection apparatus. The figure which shows the 3rd example of the structure of a radiation detection apparatus.

  Hereinafter, a specific configuration and operation principle of a radiation detection apparatus according to the present invention will be described with reference to the drawings. This radiation detection apparatus is, for example, in a radiation imaging system that forms a radiation imaging image from a radiation source that emits radiation and an electrical signal corresponding to a detection result of radiation output by the radiation detection apparatus that has detected the emitted radiation. Used. The radiation imaging system may be a single device that includes all the radiation sources and the radiation imaging image forming functions described above, or may have a configuration in which at least a part thereof is independently present as another device. . The radiation may be X-rays or other radiation.

<< Embodiment 1 >>
1A and 1B show a first example of the structure of a radiation detection apparatus. 1A is a perspective view of the radiation detection apparatus, and FIG. 1B is a cross-sectional view taken along the line aa ′ in FIG. In FIGS. 1A and 1B, it is assumed that three-dimensional coordinates are designated as XYZ by a one-way arrow, and radiation is emitted from the lower side in the figure, that is, from the origin side of the Z axis. As for the AC magnetic field that becomes a noise source, what comes from the Z direction is called a vertical AC magnetic field, and what comes from the X or Y direction is called a horizontal AC magnetic field.

  The radiation detection apparatus is configured by, for example, stacking the conductive member 13, the sensor array 2, and the support base 12 when viewed from the direction in which the radiation is irradiated.

  The sensor array 2 is composed of a substrate having an insulating surface such as glass, and is a planar radiation detector in which a plurality of conversion elements 1 and switch elements 3 each corresponding to one pixel are arranged in a two-dimensional array. Part. The sensor array 2 is wired with a drive signal line 4 for driving the switch element 3 and an image signal line 5 for outputting a detection result of radiation by the conversion element 1. In the sensor array 2, there is a parasitic capacitance 14 as a capacitance formed unintentionally due to the structure of the switch element 3 and the intersection of the drive signal line 4 and the image signal line 5. obtain.

  The conversion element 1 is an element that converts radiation into an electrical signal. The switch element 3 is composed of a TFT or the like. As described above, the conversion element 1 and the switch element 3 correspond to one pixel in a pair, and the pair is arranged in a two-dimensional array form in the sensor array 2, thereby forming radiation composed of a plurality of pixels. It functions as a radiation detection unit for acquiring a captured image. The drive signal line 4 is arranged corresponding to each row in the two-dimensional array in which the combination of the conversion element 1 and the switch element 3 is arranged, and the drive on bias and the drive off are applied to the switch element 3 in each row. Supply one of the biases. The drive off bias may be any potential that can turn off the switch element 3, and in this embodiment, for example, is the same potential as the ground. The image signal line 5 is arranged for each column in the above-described two-dimensional array, and the electrical signal of the conversion element 1 corresponding to the switch element 3 to which the drive on-bias is supplied by the drive signal line 4, that is, the detection of radiation. The result is transmitted to the reading circuit 6. The conversion element 1 includes a direct conversion type that directly converts radiation into an electric signal, and an indirect conversion type that converts light emitted when a phosphor (not shown) is irradiated with radiation into an electric signal. Any of them may be used.

  The readout circuit 6 and the output circuit 9 are disposed on the support base 12. The support base 12 is a base for fixing and supporting the sensor array 2, the readout circuit 6, and the output circuit 9. The support base 12 is made of a conductive metal, or a metal mesh sandwiched between carbon fiber reinforced plastics (CFRP) that is light and strong in response to the recent demand for weight reduction, or a single CFRP. The support base 12, the drive signal line 4, and the image signal line 5 are surfaces facing the radiation irradiation direction, that is, the Z direction by a member for shock buffering or a shielding member for shielding various circuits from radiation. In FIG. 2, they are arranged at an interval h.

  The 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. The sense amplifier 7 converts an electrical signal from the image signal line 5 into a digital signal by an A / D converter or the like and transmits the digital signal to the readout substrate 8. For example, the reading substrate 8 inputs / outputs a control signal to / from the sense amplifier 7 and also supplies power in some cases.

  The output circuit 9 includes a gate driver 10 and an output substrate 11 and functions as a drive circuit that drives each of the switch elements 3 described above. The gate driver 10 selectively applies either a drive on bias for turning on the switch element 3 or a drive off bias for turning off to the drive signal line 4. A drive on bias and a drive off bias can be input to the gate driver 10. The output board 11 inputs and outputs control signals to the gate driver 10 and supplies power.

  The sense amplifier 7 and the gate driver 10 are generally constituted by an integrated circuit, and are mounted on a flexible substrate such as TCP (Tape Carrier Package) or COF (Chip On Film) (not shown). Further, the sense amplifier 7 and the gate driver 10 may be mounted on the sensor array 2 by a mounting method called COG (Chip On Glass).

  The conductive member 13 is disposed on the radiation irradiation side of the sensor array 2 and is used for at least one of the purposes of preventing detection of visible light other than radiation, protecting phosphors not shown, and countermeasures against electric field noise. Is done. For the above purpose, the conductive member 13 is usually disposed in the vicinity of the conversion element 1, the drive signal line 4 and the image signal line 5, and is located at a position spaced apart by a distance h 'in the radiation irradiation direction, that is, the Z direction. Be placed. In addition, since it is necessary for the conductive member 13 to transmit radiation at the time of imaging, for example, it is necessary that the thickness be such that the radiation transmittance is 99% or more. The conductive member 13 is a thin film that covers the sensor array 2 including, for example, aluminum, and the thickness thereof is, for example, about 0.1 to 100 μm. The conductive member 13 is not limited to this, and may be formed of other materials or have a thickness outside the above range as long as the conductive material has a radiation transmittance of 99% or more. There may be.

  In this embodiment, the conductive member 13 is also used as a part of a closed loop that receives AC magnetic field noise, that is, a part of a propagation path of induced current, as will be described later. For this reason, the parts 13-1 and 13-2 of the conductive member 13 are electrically connected to the ground of the readout circuit 6 and the ground of the output circuit 9, respectively.

  The connection point 15 is a connection for electrically connecting the ground of the readout circuit 6 and the output circuit 9 to the support base 12 and uses conductive screws or the like. In the present embodiment, for example, at least one of the grounds of the readout circuit 6 and the output circuit 9 may be configured not to be electrically connected to the support base 12, that is, not electrically connected.

  Hereinafter, the operation principle of the radiation detection apparatus of this embodiment will be described. FIGS. 2A and 2B are portions 13-1 for electrically connecting the conductive member 13 and the ground of the readout circuit 6 and the output circuit 9 from the radiation detection apparatus of FIG. 1 as a comparative example. It is a figure which shows the structure of the radiation detection apparatus when 13-2 is abbreviate | omitted. FIG. 2A is a perspective view of a comparative example of the radiation detection apparatus, and FIG. 2B is a cross-sectional view taken along line b-b ′ in FIG. 2A and 2B, the same components as those in FIGS. 1A and 1B are denoted by the same reference numerals.

  In the radiation detection apparatus, an induced electromotive force is generated by an alternating magnetic field, that is, a changing magnetic flux, passing through a closed circuit in the radiation detection apparatus according to the law of electromagnetic induction. Further, the induced electromotive force is converted into an induced current by the impedance of the closed circuit, and the induced current is superimposed on the electric signal detected by the sense amplifier 7, thereby generating image noise. It is known that this induced current is proportional to the magnetic flux density of the alternating magnetic field noise and the cross-sectional area of the closed circuit that penetrates, and inversely proportional to the impedance of the closed circuit. That is, the smaller the cross-sectional area of the closed circuit through which the AC magnetic field noise penetrates and the higher the impedance of the closed circuit, the less the image noise is generated.

  In the radiation detection apparatus, according to the law of electromagnetic induction, an induced electromotive force is generated by passing an alternating magnetic field, that is, a changing magnetic flux, through a closed circuit in the radiation detection apparatus, and the induced electromotive force is detected by the sense amplifier 7. Image noise is generated by superimposing the electric signal. This induced electromotive force is known to be proportional to the magnetic flux density of the alternating magnetic field noise and the cross-sectional area of the closed circuit that penetrates. That is, the larger the cross-sectional area of the closed circuit through which AC magnetic field noise penetrates, the more image noise is generated.

  In FIG. 2B, a closed circuit C2 through which horizontal AC magnetic field noise penetrates is indicated by a dotted line. In this closed circuit C2, the path of the output substrate 11 to the gate driver 10 to the drive signal line 4 to the parasitic capacitance 14 to the image signal line 5 to the sense amplifier 7 to the readout substrate 8 is connected to the ground of the output circuit 9 and the readout circuit 6. And a route passing through the support base 12. Therefore, the image noise generated by the alternating magnetic field noise in the horizontal direction has a magnitude proportional to the cross-sectional area shown by the oblique lines in FIG. In addition, the part which is not shown with the oblique line in the closed circuit C2 is a part which exists on the same plane as the support base 12 when it sees in a cross section. That is, although it is drawn above the support base 12 for explanation, it is actually a portion formed on the same plane as the support base 12. Therefore, this part has no cross-sectional area in the horizontal direction or is very small even if it has a cross-sectional area. Therefore, the horizontal direction AC magnetic field noise does not penetrate, or even if it penetrates, it has only a minute effect. It becomes. In the following description, a portion not shown by hatching in the closed circuit indicates a portion that does not penetrate the AC magnetic field noise for the same reason or has only a minute influence even if it does not penetrate.

  2A and 2B, the conductive member 13 does not have portions 13-1 and 13-2 that are electrically connected to the grounds of the readout circuit 6 and the output circuit 9, respectively. An example that does not function as a part is shown. 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 readout circuit 6, the conductive member 13 does not function as a closed circuit. The same applies even if only a part 13-2 of the conductive member 13 is connected to the ground of the output circuit 9. That is, in other words, unless both the parts 13-1 and 13-2 of the conductive member 13 are connected, the conductive member 13 does not function as a closed circuit.

  On the other hand, in the radiation detection apparatus according to this embodiment, a part 13-1 of the conductive member 13 is connected to the ground of the readout circuit 6, and a part 13-2 of the conductive member 13 is connected to the output circuit 9. Connected to ground. As a result, the closed circuit C1 through which the horizontal AC magnetic field noise penetrates is as shown by the dotted line in FIG. In the closed circuit C1, the path of the output board 11 to the gate driver 10 to the drive signal line 4 to the parasitic capacitance 14 to the image signal line 5 to the sense amplifier 7 to the readout board 8 is connected to the ground of the output circuit 9 and the readout circuit 6. And the conductive member 13 to be formed. In other words, in this embodiment, the parts 13-1 and 13-2 of the conductive member 13 are electrically connected to the ground of the output circuit 9 and the readout circuit 6, so that a closed circuit via the conductive member 13 is obtained. C1 is formed. The closed circuit C1 uses a conductive member 13 which has not been used as a path so far and is disposed close to the drive signal line 4 and the image signal line 5 as a part of the path. Therefore, it can be seen that the cross-sectional area where the alternating magnetic field noise indicated by the oblique lines is significantly smaller than the conventional one. As a result, part of the induced current induced by the horizontal AC magnetic field noise flows through the closed circuit C1 having a small cross-sectional area, so that the image noise can be greatly reduced.

  Further, the relationship of the distance h between 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 and the conductive member 13. May be h ′ <h. By doing in this way, the cross-sectional area of the closed circuit C1 formed in the present embodiment is significantly smaller than the cross-sectional area of the conventional closed circuit C2. That is, the induced current induced by the horizontal AC magnetic field noise becomes smaller, and the image noise can be reduced more effectively.

  Next, attention is paid to the impedance of each member calculated from the physical shape such as the electrical conductivity or the sheet resistance value, the area, the thickness, and the physical shape such as the aperture ratio when the shape is a mesh. Image noise can be further reduced by making the impedance of the conductive member 13 lower than the impedance of the support base 12 in the support base 12 and the conductive member 13. This is considered to be an effect obtained by reducing the induced current induced in the closed circuit C2 having a large cross-sectional area and flowing the induced current to the closed circuit C1 having a smaller cross-sectional area.

<< Embodiment 2 >>
FIG. 3 shows a second example of the structure of the radiation detection apparatus. FIG. 3 shows only a cross-sectional view of the structure, but the basic structure is the same as in FIGS. 1 (a) and 1 (b). In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The radiation detection apparatus according to the present embodiment is different from that according to the first embodiment in that a power supply 16 serving as a driving off bias is applied to the gate driver 10 via a power supply substrate 17. The driving off bias is a ground potential in the first embodiment, but in this embodiment, the driving off bias is set to a potential at which the potential difference between the driving on bias and the driving off bias becomes larger. This is to prevent the switch element 3 from being turned on unintentionally when the drive off bias fluctuates due to various noises, and to reduce the leakage current of the switch element 3. The radiation detection apparatus of the present embodiment is further different from that of the first embodiment in that the drive off bias is connected to the ground via the capacitor 18 on the output circuit 9. Note that the capacitance value of the capacitor 18 is, for example, 1.3 μF to 1.0 mF in view of the impedance of the power supply 16 serving as a driving off bias.

  In FIG. 3, the closed circuit C3 through which the horizontal AC magnetic field noise penetrates is indicated by a dotted line as in the description of the first embodiment. The closed circuit C3 includes a path from the output substrate 11 to the gate driver 10 to the drive signal line 4 to the parasitic capacitance 14 to the image signal line 5 to the sense amplifier 7 to the readout substrate 8. In addition, a propagation path is formed from the output circuit 9 to the ground of the output circuit 9 from the output circuit 9 via the capacitor 18 with respect to the gate driver 10 that is driving off bias in the closed circuit C3. Then, by electrically connecting these paths and the conductive member 13 by the portions 13-1 and 13-2 of the conductive member 13 to which the ground of the output circuit 9 and the readout circuit 6 are connected, the conductive member 13 A closed circuit C3 is formed via the sexual member 13.

  As described above, in the radiation detection apparatus according to the present embodiment, as in the first embodiment, it can be seen that the cross-sectional area where the alternating magnetic field noise indicated by the oblique lines is significantly smaller than the conventional one. As a result, part of the induced current induced by the horizontal AC magnetic field noise flows through the closed circuit C3 having a small cross-sectional area, so that the image noise can be greatly reduced.

  Further, the relationship of the distance h between 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 and the conductive member 13. May be h ′ <h. By doing so, the cross-sectional area of the closed circuit C3 formed in this embodiment is significantly smaller than the cross-sectional area of the conventional closed circuit C2. That is, the induced current induced by the horizontal AC magnetic field noise becomes smaller, and the image noise can be reduced more effectively.

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

<< Embodiment 3 >>
FIG. 4 shows a third example of the structure of the radiation detection apparatus. Note that FIG. 4 shows only a cross-sectional view of the structure, but the basic structure is the same as FIGS. 1 (a) and 1 (b). In addition, in this embodiment, about the structure similar to Embodiment 1 or 2, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the radiation detection apparatus of the present embodiment, the conductive member 13 is connected on the output circuit 9 with the power supply 16 that is a driving off bias via a part 13-2 of the conductive member 13, and the conductive member 13 is driven. It differs from the first and second embodiments in that it has the same potential as the off bias. In addition, the radiation detection apparatus according to the present embodiment is further connected to the ground via the capacitor 18 on the readout circuit 6 by the part 13-1 of the conductive member 13, as described in the first and second embodiments. And different. For the capacitance value of the capacitor 18, for example, 1.3 μF to 1.0 mF is used in view of the impedance of the power supply 16 that is a driving off bias.

  In FIG. 4, similarly to the description of the first and second embodiments, the closed circuit C4 through which the horizontal AC magnetic field noise penetrates is indicated by a dotted line. The closed circuit C4 includes paths of the gate driver 10 to the drive signal line 4 to the parasitic capacitance 14 to the image signal line 5 to the sense amplifier 7. In the closed circuit C4, a current flowing into or out of the driving off bias of the gate driver 10 passes through a part 13-2 of the conductive member 13 connected on the output circuit 9, and the conductive members 13 to The readout circuit 6 is reached through a path of a part 13-1 of the conductive member 13. This current reaches the ground of the readout circuit 6 via the capacitor 18 on the readout circuit 6. By the above path, a closed circuit C4 through which horizontal AC magnetic field noise penetrates is formed.

  Thus, also in the radiation detection apparatus according to the present embodiment, the cross-sectional area of the closed circuit through which the horizontal AC magnetic field noise penetrates can be reduced as in the first and second embodiments. For this reason, the radiation detection apparatus according to the present embodiment can significantly reduce image noise caused by horizontal AC magnetic field noise.

  In each of the above embodiments, the closed circuit through which the horizontal AC magnetic field noise penetrates only one wiring passing through one drive signal line 4 and one image signal line 5 is shown by a dotted line. A similar closed circuit exists for the combination of the drive signal line 4 and the image signal line 5. Then, the integration of the induced electromotive force generated by the horizontal AC magnetic field noise penetrating all these closed circuits is detected by the sense amplifier 7 to generate image noise. However, in the case of the radiation detection apparatus according to each of the above-described embodiments, the cross-sectional area of the closed circuit is reduced with respect to all the closed circuits corresponding to the combinations of all these drive signal lines 4 and image signal lines 5. Image noise caused by AC electromagnetic noise can be reduced.

  In addition, according to the radiation detection apparatus according to each of the above-described embodiments, the induced electromotive force due to the AC magnetic field noise is reduced by reducing the cross-sectional area of the closed circuit. This special control is unnecessary. Further, since the effect of reducing the induced electromotive force is obtained by reducing the amount of magnetic field noise interlinked, it is possible to obtain the effect regardless of the amplitude and frequency of the AC magnetic field noise. As described above, according to the radiation detection apparatus of each of the above-described embodiments, even when the frequency and amplitude of the AC magnetic field noise coming from the outside are unknown, the horizontal electromagnetic noise does not occur without causing a reduction in the imaging operation speed. It is possible to reduce the influence on the captured image due to.

  In the above embodiment, the part 13-1 of the conductive member 13 is linear and connected to the ground at one point of the readout circuit 6, but is not limited thereto. For example, the conductive member 13 may be connected to the ground of the readout circuit 6 at a plurality of locations, or may be connected in a planar shape. Similarly, a part 13-2 of the conductive member 13 may be connected to the ground of the output circuit 9 at a plurality of locations, or may be connected in a planar shape.

  In each of the above-described embodiments, at least one of the ground of the readout circuit 6 and the ground of the output circuit 9 can be configured not to be electrically connected to the support base 12. This can also be achieved by changing the support base 12 to a material having little conductivity such as CFRP or a non-conductive material. That is, by making the impedance of the closed circuit via the support base 12 infinite (or a very large value), an effect equivalent to making it significantly higher than the impedance of the closed circuit via the conductive member 13 is achieved. Can be obtained. Thereby, in the radiation detection apparatus, it is possible to further reduce image noise by preventing the formation of a closed circuit via the support base 12.

  Hereinafter, in order to verify the effect of each embodiment described above, the evaluation result of the noise amount when the radiation detection apparatus according to each embodiment described above is used for the cassette type X-ray digital image capturing apparatus used for imaging the human body Indicates. In this evaluation, an X-ray digital image pickup apparatus having an outer dimension of 384 (width) × 460 (depth) × 15 (thickness) mm was used. The conversion element has approximately 2800 × 3400 pixels. In the following example of evaluation results, an example in which a sine wave current of 25.04 kHz is applied as a horizontal AC magnetic field noise from the outside using a 1 m square loop coil is shown.

[Evaluation 1]
In the X-ray digital imaging apparatus using the radiation detection apparatus of Embodiment 1, the intervals h and h ′ in FIGS. 1A and 1B are set to h = about 3 mm and h ′ = about 500 μm, respectively. The material of the conductive member 13 is aluminum and the thickness is 30 μm. In addition, the conductive member 13 is electrically connected to the ground with a conductive screw at one point on each of the readout substrate 8 of the readout circuit 6 and the output substrate 11 of the output circuit 9.

  In such a configuration, the captured image noise amount was compared with the image noise amount in FIG. 2 as a comparative example. By using the radiation detection apparatus of the first embodiment, when the amount of image noise in FIG. 2 is 100%, the image noise due to the AC magnetic field noise from the X direction is 58%, and the AC magnetic field noise from the Y direction is It was possible to reduce the image noise caused by the noise to 87%. That is, it was confirmed that the radiation detection apparatus according to the first embodiment has an effect of reducing the AC magnetic field noise from the X direction and the Y direction by 42% and 13%, respectively.

[Evaluation 2]
In this evaluation, unlike the evaluation 1, in the radiation detection apparatus according to the first embodiment, a non-conductive resin screw or the like is used for the connection point 15 and at least one of the grounds of the readout circuit 6 and the output circuit 9 is a support base. 12 was not electrically connected. This is equivalent to making the impedance of the closed circuit through the support base 12 infinite (or a very large value) to be significantly higher than the impedance of the closed circuit through the conductive member 13. is there. Thereby, the point where the closed circuit C1 is formed is the same as in FIG. 1, but a part of the induced current does not flow through the support base 12 but all flows into the closed circuit C1 via the conductive member 13. It should be possible to increase the cross-sectional area reduction effect.

  In such a configuration, the captured image noise amount was compared with the image noise amount in FIG. 2 as a comparative example. As a result, with the configuration as described above, when the amount of image noise in FIG. 2 is 100%, the image noise caused by the AC magnetic field noise from the X direction is 45%, and the AC magnetic field noise from the Y direction is caused. Image noise can be reduced to 87%. That is, it was confirmed that the radiation detection apparatus according to the first embodiment has an 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]
The case where the radiation detection apparatus of Embodiment 2 was used in the X-ray digital imaging device was evaluated. In this evaluation, at least one of the part 13-1 of the conductive member 13 and the readout circuit 6 or the part 13-2 of the conductive member 13 and the output circuit 9 is not electrically connected, and the capacitor 18 is connected to the power source. The case where a radiation detection device mounted on the substrate 17 was used was set as a comparison target.

  As a result, when the comparative example is 100%, when the capacitor 18 is 1.3 μF, the image noise caused by the AC magnetic field noise from the X direction is set to 90%, and the image noise caused by the AC magnetic field noise from the Y direction is set. Can be reduced to 97%. That is, the radiation detection apparatus according to the second embodiment can reduce the image noise caused by the AC magnetic field noise from the X direction and the Y direction by 10% and 3%, respectively, as compared with the comparative example. It could be confirmed.

  Further, when the capacitor 18 is 69.3 μF, the image noise caused by the AC magnetic field noise from the X direction can be reduced to 75%, and the image noise caused by the AC magnetic field noise from the Y direction can be reduced to 71%. . That is, the radiation detection apparatus according to the second embodiment can reduce the image noise caused by the AC magnetic field noise from the X direction and the Y direction by 25% and 29%, respectively, as compared with the comparative example. It could be confirmed.

  1: conversion element, 2: sensor array, 3: switch element, 4: drive signal line, 5: image signal line, 6: readout circuit, 7: sense amplifier, 8: readout substrate, 9: output circuit, 10: gate Driver 11: Output board 12: Support base 13: Conductive member

Claims (11)

A radiation detection device comprising:
Planar detection means for detecting the irradiated radiation by arranging the elements for acquiring the electrical signal based on the radiation in a two-dimensional array,
A drive circuit for driving a switch for outputting the electrical signal in each of the elements;
An acquisition circuit for acquiring the electrical signal in each of the elements in response to the switch being driven;
A support base on which the drive circuit and the acquisition circuit are disposed;
A conductive member that is partly disposed in front of the detection means as viewed from a radiation source that emits radiation, and that is electrically connected to the ground of the drive circuit and the ground of the acquisition circuit;
A radiation detection apparatus comprising: The support base is disposed at a position where a distance between the support base and the detection means is larger than a distance between the detection means and the conductive member.
The radiation detection apparatus according to claim 1. The impedance of the support base is higher than the impedance of the conductive member,
The radiation detection apparatus according to claim 1, wherein: A driving off bias for turning off the switch is input to the driving circuit,
A capacitor is connected between the drive off bias and the ground of the drive circuit, and the conductive member is electrically connected to the ground of the drive circuit and the ground of the acquisition circuit.
The radiation detection apparatus according to any one of claims 1 to 3, wherein A driving off bias for turning off the switch is input to the driving circuit,
The conductive member is connected to the drive off bias in the drive circuit, and the conductive member is further connected to the acquisition circuit via a capacitor disposed between the drive off bias and the ground of the acquisition circuit. Electrically connected to the ground,
The radiation detection apparatus according to any one of claims 1 to 3, wherein The capacitor has a capacitance of 1.3 μF to 1.0 mF;
The radiation detection apparatus according to claim 4 or 5, wherein The support base is disposed after the detection means when viewed from the radiation source;
The radiation detection apparatus according to claim 1, wherein At least one of the ground of the drive circuit and the ground of the acquisition circuit is configured not to be electrically connected to the support base.
The radiation detection apparatus according to claim 1, wherein The part of the conductive member has a thin film portion covering the detection means,
The radiation detection apparatus according to claim 1, wherein the radiation detection apparatus is a radiation detection apparatus. The conductive member is electrically connected at a plurality of locations with at least one of the ground of the drive circuit and the ground of the acquisition circuit.
The radiation detection apparatus according to any one of claims 1 to 9, wherein: The radiation detection apparatus according to any one of claims 1 to 10,
Irradiating means for irradiating the radiation detecting device with radiation;
Forming means for forming a radiation image based on the electrical signal acquired by the acquisition circuit;
A radiation imaging system comprising:

Images