WO2011001705A1 - 放射線画像撮影装置 - Google Patents
放射線画像撮影装置 Download PDFInfo
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- WO2011001705A1 WO2011001705A1 PCT/JP2010/052840 JP2010052840W WO2011001705A1 WO 2011001705 A1 WO2011001705 A1 WO 2011001705A1 JP 2010052840 W JP2010052840 W JP 2010052840W WO 2011001705 A1 WO2011001705 A1 WO 2011001705A1
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
- A61B6/4208—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
- A61B6/4233—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector using matrix detectors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
- A61B6/4283—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by a detector unit being housed in a cassette
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/30—Transforming light or analogous information into electric information
- H04N5/32—Transforming X-rays
Definitions
- the present invention relates to a radiographic image capturing apparatus, and more particularly to a radiographic image capturing apparatus capable of detecting the start of radiation irradiation and the like.
- a so-called direct type radiographic imaging device that generates electric charges by a detection element in accordance with the dose of irradiated radiation such as X-rays and converts it into an electrical signal, or other radiation such as visible light with a scintillator or the like.
- Various so-called indirect radiographic imaging devices have been developed that convert charges to electromagnetic waves after being converted into electrical signals by generating electric charges with photoelectric conversion elements such as photodiodes in accordance with the energy of the converted and irradiated electromagnetic waves. Yes.
- the detection element in the direct type radiographic imaging apparatus and the photoelectric conversion element in the indirect type radiographic imaging apparatus are collectively referred to as a radiation detection element.
- This type of radiographic imaging device is known as an FPD (Flat Panel Detector) and has been conventionally formed integrally with a support base (or a bucky apparatus) (see, for example, Patent Document 1).
- FPD Full Panel Detector
- a portable radiographic imaging device in which an element or the like is housed in a housing has been developed and put into practical use (see, for example, Patent Documents 2 and 3).
- the radiation image capturing apparatus may be configured to read image data from each radiation detection element after the radiation irradiation ends.
- a sensor or the like in the radiographic imaging apparatus so that the start or end of radiation irradiation is detected by the sensor, but the sensor is arranged in the radiographic imaging apparatus. Space is required, and the apparatus becomes large. Further, when the sensor is provided, there is a problem that a large amount of electric power is consumed for driving the sensor, and in particular, a portable radiographic imaging apparatus consumes a built-in battery.
- JP-A-9-73144 JP 2006-58124 A Japanese Patent Laid-Open No. 6-342099 US Pat. No. 7,211,803
- the radiation detection element is connected via the bias line.
- the noise generated by the current detecting means is superimposed on the applied bias voltage and applied.
- the noise of the voltage generated by the current detection means is superimposed as the noise charge on the charge generated in the radiation detection element due to the irradiation of radiation, so that the image quality of the finally obtained radiation image is affected by the influence of the noise charge.
- problems such as deterioration of the graininess may occur.
- each radiation detection element itself is formed small in order to increase the resolution of the radiographic image.
- the light condensing surface such as a photodiode is designed to be as wide as possible in a limited space. Therefore, the parasitic capacitance of the radiation detection element is relatively large.
- the capacitance C is amplified to a relatively large noise charge, which is superimposed on the charge generated in the radiation detection element due to the irradiation of radiation, so that the image quality of the finally obtained radiation image is further reduced. There is a fear.
- the radiographic imaging apparatus When the image quality of radiographic images deteriorates, especially when the granularity deteriorates, for example, when making a diagnosis using such radiographic images, the lesion may be overlooked or the normal part may be mistaken for the lesion. There is a risk of inconvenience such as misdiagnosis. For this reason, it is desirable for the radiographic imaging apparatus to obtain a radiographic image with an appropriate image quality in which the influence of noise is eliminated as much as possible.
- the present invention has been made in view of the above-described problems, and reduces the influence of noise generated by a current detection unit that detects a current for detecting the start of radiation irradiation.
- An object of the present invention is to provide a radiographic imaging apparatus that can be obtained.
- the radiographic imaging device of the present invention includes: A plurality of scanning lines and a plurality of signal lines arranged so as to intersect with each other; a plurality of radiation detecting elements arranged in a two-dimensional manner in each region partitioned by the plurality of scanning lines and the plurality of signal lines; , An off state and an on state are switched according to a voltage applied to the connected scanning line, arranged for each radiation detection element, and in the off state, the charge generated in the radiation detection element is retained, Switch means for releasing the charge from the radiation detection element in the ON state; Scan driving means comprising: a gate driver that applies an on-voltage and an off-voltage to the switch means via the scanning line; and a power supply circuit that supplies the on-voltage and the off-voltage to the gate driver; Current detection means for detecting a current flowing between the power supply circuit and the gate driver or a current flowing through the scanning line; Control means for detecting at least the start of radiation irradiation based on
- the current detection means for detecting the start of radiation irradiation is provided between the power supply circuit of the scanning drive means and the gate driver, or in each scanning line. A current flowing between them and a current flowing through each scanning line are detected.
- the parasitic capacitance formed in the switch means is much smaller than the large parasitic capacitance of the photodiode portion, and the switch means portion is caused by the noise of the voltage generated in the current detection means. It becomes possible to make the noise charge generated in the case of very small.
- the noise with respect to the bias voltage by the current detection means provided on the bias line is much smaller than when the noise is amplified by the large parasitic capacitance of the radiation detection element and a large noise charge is superimposed.
- the noise Since it is possible to superimpose the influence of the voltage noise generated by the current detection means on the image data finally read out from each radiation detection element, the noise It is possible to reliably reduce the influence of electric charges, and it is possible to accurately prevent problems such as deterioration of the image quality of the finally obtained radiographic image, particularly the granularity thereof.
- FIG. 2 is a cross-sectional view taken along line AA in FIG. It is a top view which shows the structure of the board
- FIG. 5 is a sectional view taken along line XX in FIG. 4. It is a side view explaining the board
- the radiographic imaging device is a so-called indirect radiographic imaging device that includes a scintillator or the like and converts the irradiated radiation into electromagnetic waves of other wavelengths such as visible light to obtain an electrical signal.
- the present invention can also be applied to a direct radiographic imaging apparatus.
- the radiographic image capturing apparatus is portable will be described, the present invention is also applicable to a radiographic image capturing apparatus formed integrally with a support base or the like.
- FIG. 1 is an external perspective view of the radiographic image capturing apparatus according to the present embodiment
- FIG. 2 is a cross-sectional view taken along the line AA in FIG.
- the radiographic imaging apparatus 1 according to the present embodiment is configured as a portable (cassette type) apparatus in which a scintillator 3, a substrate 4, and the like are housed in a housing 2. .
- the housing 2 is formed of a material such as a carbon plate or plastic that transmits radiation at least on a surface R (hereinafter referred to as a radiation incident surface R) that receives radiation.
- a radiation incident surface R a surface that receives radiation.
- 1 and 2 show a case in which the housing 2 is a so-called lunch box type formed by the frame plate 2A and the back plate 2B.
- the housing 2 is integrally formed in a rectangular tube shape. It is also possible to use a so-called monocoque type.
- the side surface of the housing 2 is opened and closed to replace a power switch 36, an indicator 37 composed of LEDs and the like, and a battery 40 (not shown) (see FIG. 7 described later).
- a possible lid member 38 and the like are arranged.
- an antenna device 39 that is a communication unit for wirelessly communicating with an external device is embedded in the side surface of the lid member 38.
- a base 31 is disposed inside the housing 2 via a thin lead plate or the like (not shown) on the lower side of the substrate 4.
- the disposed PCB substrate 33, the buffer member 34, and the like are attached.
- a glass substrate 35 for protecting the substrate 4 and the radiation incident surface R of the scintillator 3 is disposed.
- the scintillator 3 is affixed to a detection part P (described later) of the substrate 4.
- the scintillator 3 is, for example, a phosphor whose main component is converted into an electromagnetic wave having a wavelength of 300 to 800 nm, that is, an electromagnetic wave centered on visible light when it receives radiation, and that is output.
- the substrate 4 is formed of a glass substrate. As shown in FIG. 3, a plurality of scanning lines 5 and a plurality of signal lines are provided on a surface 4 a of the substrate 4 facing the scintillator 3. 6 are arranged so as to cross each other. In each small region r defined by the plurality of scanning lines 5 and the plurality of signal lines 6 on the surface 4 a of the substrate 4, radiation detection elements 7 are respectively provided.
- the region is a detection unit P.
- a photodiode is used as the radiation detection element 7, but other than this, for example, a phototransistor or the like can also be used.
- Each radiation detection element 7 is connected to the source electrode 8s of the TFT 8 serving as a switch means, as shown in the enlarged views of FIGS.
- the drain electrode 8 d of the TFT 8 is connected to the signal line 6.
- the TFT 8 is turned on when a turn-on voltage is applied to the connected scanning line 5 by the scanning drive means 15 described later and applied to the gate electrode 8g, and is generated and accumulated in the radiation detection element 7. The charged electric charge is discharged to the signal line 6.
- the TFT 8 is turned off when the off voltage is applied to the connected scanning line 5 and the off voltage is applied to the gate electrode 8g, and the discharge of the charge from the radiation detecting element 7 to the signal line 6 is stopped. Electric charges generated in the radiation detection element 7 are held and accumulated in the radiation detection element 7.
- FIG. 5 is a sectional view taken along line XX in FIG.
- a gate electrode 8g of a TFT 8 made of Al, Cr or the like is formed on the surface 4a of the substrate 4 so as to be integrally laminated with the scanning line 5, and silicon nitride (laminated on the gate electrode 8g and the surface 4a).
- An upper portion of the gate electrode 8g on the gate insulating layer 81 made of SiN x ) or the like is connected to the first electrode 74 of the radiation detection element 7 via a semiconductor layer 82 made of hydrogenated amorphous silicon (a-Si) or the like.
- the formed source electrode 8s and the drain electrode 8d formed integrally with the signal line 6 are laminated.
- the source electrode 8s and the drain electrode 8d are divided by a first passivation layer 83 made of silicon nitride (SiN x ) or the like, and the first passivation layer 83 covers both electrodes 8s and 8d from above.
- ohmic contact layers 84a and 84b formed in an n-type by doping hydrogenated amorphous silicon with a group VI element are stacked between the semiconductor layer 82 and the source electrode 8s and the drain electrode 8d, respectively.
- the TFT 8 is formed as described above.
- an auxiliary electrode 72 is formed by laminating Al, Cr, or the like on the insulating layer 71 formed integrally with the gate insulating layer 81 on the surface 4 a of the substrate 4.
- a first electrode 74 made of Al, Cr, Mo or the like is laminated on the auxiliary electrode 72 with an insulating layer 73 formed integrally with the first passivation layer 83 interposed therebetween.
- the first electrode 74 is connected to the source electrode 8 s of the TFT 8 through the hole H formed in the first passivation layer 83.
- a p layer 77 formed by doping a group III element into silicon and forming a p-type layer is formed by laminating sequentially from below.
- the electromagnetic wave When radiation enters from the radiation incident surface R of the housing 2 of the radiographic imaging apparatus 1 and is converted into an electromagnetic wave such as visible light by the scintillator 3, and the converted electromagnetic wave is irradiated from above in the figure, the electromagnetic wave is detected by radiation.
- the electron hole pair is generated in the i layer 76 by reaching the i layer 76 of the element 7. In this way, the radiation detection element 7 converts the electromagnetic waves irradiated from the scintillator 3 into electric charges.
- a second electrode 78 made of a transparent electrode such as ITO is laminated and formed so that the irradiated electromagnetic wave reaches the i layer 76 and the like.
- the radiation detection element 7 is formed as described above. The order of stacking the p layer 77, the i layer 76, and the n layer 75 may be reversed. Further, in the present embodiment, a case where a so-called pin-type radiation detection element formed by sequentially stacking the p layer 77, the i layer 76, and the n layer 75 as described above is used as the radiation detection element 7. However, it is not limited to this.
- a bias line 9 for applying a bias voltage to the radiation detection element 7 is connected to the upper surface of the second electrode 78 of the radiation detection element 7 via the second electrode 78.
- the second electrode 78 and the bias line 9 of the radiation detection element 7, the first electrode 74 extended to the TFT 8 side, the first passivation layer 83 of the TFT 8, that is, the upper surfaces of the radiation detection element 7 and the TFT 8 are A second passivation layer 79 made of silicon nitride (SiN x ) or the like is covered from above.
- one bias line 9 is connected to a plurality of radiation detection elements 7 arranged in rows, and each bias line 9 is connected to a signal line 6. Are arranged in parallel with each other.
- each bias line 9 is bound to one connection 10 at a position outside the detection portion P of the substrate 4.
- each scanning line 5, each signal line 6, and connection 10 of the bias line 9 are input / output terminals (also referred to as pads) provided near the edge of the substrate 4. 11 is connected.
- each input / output terminal 11 has a COF (ChipCOn Film) 12 in which a chip such as a gate IC 12 a functioning as a gate driver 15 b of the scanning drive means 15 described later is incorporated. They are connected via an anisotropic conductive adhesive material 13 such as a film (Anisotropic Conductive Film) or an anisotropic conductive paste (Anisotropic Conductive Paste).
- the COF 12 is routed to the back surface 4b side of the substrate 4 and connected to the PCB substrate 33 described above on the back surface 4b side.
- substrate 4 part of the radiographic imaging apparatus 1 is formed.
- illustration of the electronic component 32 and the like is omitted.
- FIG. 7 is a block diagram illustrating an equivalent circuit of the radiographic imaging apparatus 1 according to the present embodiment
- FIG. 8 is a block diagram illustrating an equivalent circuit for one pixel constituting the detection unit P.
- each radiation detection element 7 of the detection unit P of the substrate 4 has the bias line 9 connected to the second electrode 78, and each bias line 9 is bound to the connection 10 to the bias power supply 14. It is connected.
- the bias power supply 14 applies a bias voltage to the second electrode 78 of each radiation detection element 7 via the connection 10 and each bias line 9.
- the bias line 9 is connected to the p-layer 77 side (see FIG. 5) of the radiation detection element 7 via the second electrode 78
- a voltage lower than the voltage applied to the first electrode 74 side of the radiation detection element 7 (that is, a so-called reverse bias voltage) is applied to the second electrode 78 of the radiation detection element 7 as a bias voltage via the bias line 9. Yes.
- the bias power source 14 is connected to a main control unit 22 and a sub control unit 23 described later, and the main control unit 22 and the sub control unit 23 apply each radiation detection element 7 from the bias power source 14.
- the bias voltage is made variable as necessary.
- the first electrode 74 of each radiation detection element 7 is connected to the source electrode 8s of the TFT 8 (indicated as S in FIGS. 7 and 8), and the gate electrode 8g of each TFT 8 (FIGS. 7 and 8). Are respectively connected to the lines L1 to Lx of each scanning line 5 extending from a gate driver 15b of the scanning driving means 15 described later. Further, the drain electrode 8 d (denoted as D in FIGS. 7 and 8) of each TFT 8 is connected to each signal line 6.
- the scanning drive unit 15 includes a power supply circuit 15a and a gate driver 15b, and an on-voltage applied to the gate electrode 8g of the TFT 8 via each scanning line 5 connected to the gate driver 15b.
- the off voltage is controlled.
- the power supply circuit 15a supplies an on voltage and an off voltage to be applied to the gate electrode 8g of the TFT 8 via each scanning line 5 to the gate driver 15b.
- the gate driver 15b is formed by juxtaposing a plurality of the gate ICs 12a described above, and can modulate the pulse width of the on-voltage applied to each scanning line 5 by pulse width modulation (PWM) or the like. It is like that.
- PWM pulse width modulation
- the current detection means 41 for detecting the current flowing between the power supply circuit 15a and the gate driver 15b of the scanning drive means 15 is provided on the wiring 15c.
- the current detection means 41 can also be configured to detect a current flowing through one or more scanning lines 5 among the lines L1 to Lx of the scanning line 5. The configuration of the current detection unit 41 will be described later.
- Each signal line 6 is connected to each readout circuit 17 formed in the readout IC 16. Note that a predetermined number of readout circuits 17 are provided in the readout IC 16, and by providing a plurality of readout ICs 16, readout circuits 17 corresponding to the number of signal lines 6 are provided.
- the readout circuit 17 includes an amplification circuit 18, a correlated double sampling circuit 19, an analog multiplexer 21, and an A / D converter 20. 7 and 8, the correlated double sampling circuit 19 is represented as CDS. In FIG. 8, the analog multiplexer 21 is omitted.
- the amplifier circuit 18 is configured by a charge amplifier circuit, and is configured by connecting a capacitor 18b and a charge reset switch 18c in parallel to the operational amplifier 18a and the operational amplifier 18a. Further, the signal line 6 is connected to the inverting input terminal on the input side of the operational amplifier 18 a of the amplifier circuit 18, and the reference potential V 0 is applied to the non-inverting input terminal on the input side of the amplifier circuit 18. ing. Note that the reference potential V 0 is set to an appropriate value, and in this embodiment, for example, 0 [V] is applied.
- the charge reset switch 18c of the amplifier circuit 18 is connected to the main control means 22 and the sub control means 23, and is controlled to be turned on / off by the main control means 22 and the like.
- the charge reset switch 18c is off and the TFT 8 of the radiation detection element 7 is turned on (that is, when an on-voltage is applied to the gate electrode 8g of the TFT 8 via the scanning line 5)
- the radiation The electric charge discharged from the detection element 7 flows into the capacitor 18b and is accumulated, and a voltage value corresponding to the accumulated electric charge is output from the output terminal of the operational amplifier 18a.
- the amplifying circuit 18 outputs a voltage in accordance with the amount of charge output from each radiation detection element 7 to perform charge voltage conversion and amplify the voltage.
- the charge reset switch 18c When the charge reset switch 18c is turned on, the input side and the output side of the amplifier circuit 18 are short-circuited, and the charge accumulated in the capacitor 18b is discharged to reset the amplifier circuit 18. ing.
- the amplifier circuit 18 may be configured to output a current in accordance with the charge output from the radiation detection element 7. Further, as shown in FIG. 8, power is supplied from the power supply unit 42 to the amplifier circuit 18. In FIG. 7, the power supply unit 42 is not shown.
- a correlated double sampling circuit (CDS) 19 is connected to the output side of the amplifier circuit 18.
- the correlated double sampling circuit 19 has a sample and hold function.
- the sample and hold function in the correlated double sampling circuit 19 is turned on / off by a pulse signal transmitted from the main control means 22. Is to be controlled.
- the correlated double sampling circuit 19 is emitted from the radiation detection element 7 when the image data is read from each radiation detection element 7 after the amplifier circuit 18 is reset and the charge reset switch 18c is turned off.
- the first pulse signal is received from the main control means 22 at the time when the accumulated electric charge flows into the capacitor 18b and starts to be accumulated, the voltage value output from the amplifier circuit 18 at that time is held.
- the image data of each radiation detection element 7 output from the correlated double sampling circuit 19 is transmitted to the analog multiplexer 21 and sequentially transmitted from the analog multiplexer 21 to the A / D converter 20. Then, the A / D converter 20 sequentially converts the image data into digital values, which are output to the storage means 43 and sequentially stored.
- the main control means 22 is a computer or FPGA (Field Programmable) in which a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, and the like (not shown) are connected to the bus. Gate Array) etc.
- CPU Central Processing Unit
- ROM Read Only Memory
- RAM Random Access Memory
- the sub-control means 23 is constituted by a microcomputer (also referred to as a microprocessor) in this embodiment.
- the sub-control unit 23 uses less power than the main control unit 22.
- the main control unit 22 and the sub control unit 23 are provided as control units for controlling the functional units of the radiographic image capturing apparatus 1, and images from the radiation detection elements 7 are provided.
- both the main control means 22 and the sub control means 23 are configured such that the operating state is switched between the activated state and the activated stopped state.
- the activation stop state is a slight energization, that is, activation from the other side, that is, from the sub control unit 23 in the main control unit 22 and from the main control unit 22 in the sub control unit 23.
- a sleep state in which only an activation signal for instructing can be received.
- the radiographic imaging apparatus 1 is turned off by an operator such as a radiographer, the main control unit 22 and the sub control unit 23 are in a so-called off state in which energization is completely stopped.
- the sub-control unit 23 when the operator depresses the power switch 36 (see FIG. 1) and the radiographic imaging apparatus 1 is turned on, the sub-control unit 23 is activated, and the main control unit 22 stops activation. It is configured to enter a state, that is, a sleep state. Then, when the sub-control unit 23 detects the start or end of radiation irradiation to the radiographic imaging apparatus 1 based on the current value detected by the current detection unit 41, the sub-control unit 23 transmits an activation signal to the main control unit 22 to The control means 22 is activated, and after the main control means 22 is activated, the sub-control means 23 itself stops activation.
- an activation signal is transmitted from the main control unit 22 to the sub-control unit 23. While the control means 23 is activated, the main control means 22 itself returns to the state where the activation is stopped.
- the main control means 22 is awakened only when image data reading processing from each radiation detection element 7 is performed, image data transmission to an external device, or the like. Otherwise, activation is stopped. It is supposed to be in the sleep state.
- the sub-control means 23 is connected to the bias power supply 14 and the charge reset switch 18c of the amplifier circuit 18, and although not shown in FIG.
- the control means 23 is also connected to the power supply section 42, the power supply circuit 15a of the scanning drive means 15, the gate driver 15b, and the like.
- the sub-control unit 23 supplies power to the amplifier circuit 18 from the power supply unit 42 to activate the amplifier circuit 18.
- the control means 23 is configured to turn on the charge reset switch 18c. At this stage, power is not supplied to the other functional units of the readout circuit 17, that is, the correlated double sampling circuit 19, the A / D converter 20, the analog multiplexer 21, and the like, and is not activated.
- the sub-control unit 23 is connected to the scanning drive unit 15.
- the sub-control unit 23 starts up the bias power source 14 and applies a bias voltage to each radiation detection element 7 via the bias line 9. Then, an on-voltage is applied to each scanning line 5 from the scanning drive means 15, an on-voltage is applied to the gate electrode 8 g of each TFT 8 connected to each scanning line 5, all the TFTs 8 are turned on, and the gates of all TFTs 8 are turned on. Is in an open state.
- each functional unit When each functional unit is activated in this way, excess charge accumulated in each radiation detection element 7 passes through the TFT 8 and the charge reset switch 18c, and is output from the output terminal side of the operational amplifier 18a of the amplifier circuit 18 to the operational amplifier. It passes through the interior 18 a and is discharged to the power supply unit 42. In this way, the reset processing of each radiation detection element 7 is performed.
- the sub-control unit 23 supplies power only to the functional units necessary for the reset processing of each radiation detection element 7 and the detection of current by the current detection unit 41 described later. By not supplying power, unnecessary power consumption is avoided.
- the sub-control unit 23 is further connected to the above-described current detection unit 41, and the sub-control unit 23 detects the start of radiation irradiation based on the current value detected by the current detection unit 41. It has become.
- the current detection means 41 is provided in the wiring 15c that connects the power supply circuit 15a of the scanning drive means 15 and the gate driver 15b, and the power supply circuit 15a is associated with the start of radiation irradiation. The current flowing between the gate driver 15b and the gate driver 15b is detected.
- the current detection unit 41 has a predetermined resistance value connected in series to the wiring 15c connecting the power supply circuit 15a and the gate driver 15b of the scanning drive unit 15.
- the differential amplifier 41c is supplied with power from the power supply means 45.
- the current detection means 41 measures the voltage V between both terminals of the resistor 41a with the differential amplifier 41c, and determines the current flowing through the resistor 41a, that is, the current flowing between the power supply circuit 15a and the gate driver 15b as a voltage. It is converted into a value V, detected, and output to the sub-control means 23.
- the resistor 41a provided in the current detection means 41 a resistor having a resistance value capable of converting the current flowing in the wiring 15c into an appropriate voltage value V is used.
- the diode 41b is provided so that it can be detected even in a wide dynamic range such as a radiographic imaging device, and may be configured to include only the diode 41b or only the resistor 41a.
- the current detection means 41 In cases other than the case where the start or end of radiation irradiation is detected, it is not necessary for the current detection means 41 to detect the current flowing between the power supply circuit 15a and the gate driver 15b, and conversely the current detection means 41.
- the resistor 41a obstructs the supply of the on-voltage and off-voltage from the power supply circuit 15a to the gate driver 15b, so that the current detection means 41 has a connection between both terminals of the resistor 41a when current detection is unnecessary.
- a switch 41d for short-circuiting is provided as necessary.
- the sub-control unit 23 increases the voltage value V output from the current detection unit 41, for example, when it exceeds a preset threshold value Vth (see time tc in FIG. 10), When the increasing rate of the voltage value V exceeds a preset threshold value (see time td), it is detected that radiation irradiation has started.
- the current detection means 41 may output a voltage value Va that is a small amount but not 0 [V].
- an off voltage is applied from the gate driver 15 b to each gate electrode 8 g of each TFT 8 via each scanning line 5.
- the TFT 8 is turned off, as will be described later, at least when the start of radiation irradiation is detected, an on voltage is applied to the gate electrode 8g of each TFT 8 to turn on each TFT 8. It is also possible to configure as described above.
- each TFT 8 is in an OFF state, when radiation irradiation is started, a current flows between the power supply circuit 15a and the gate driver 15b of the scanning drive means 15, for the following reason.
- the radiation incident on the radiographic imaging device 1 is converted into electromagnetic waves such as visible light by the scintillator 3, and the converted electromagnetic waves are directly below.
- a predetermined negative bias voltage Vbias is applied to the second electrode 78 from the bias power supply 14 via the bias line 9, and the potential is fixed, and electrons generated in the i layer 76 are generated.
- the hole pairs holes move to the second electrode 78 side and electrons move to the first electrode 74 side, so that the potential on the first electrode 74 side decreases.
- the potential on the source electrode 8s (denoted as S in FIG. 8) side of the TFT 8 shown in FIG. 8 is lowered accordingly.
- a kind of capacitor is formed by the gate electrode 8g, the source electrode 8s, and the insulating layer 71 (see FIG. 5) between them, and there is a parasitic capacitance between the gate electrode 8g and the source electrode 8s. Existing.
- the potential on the source electrode 8s side of the TFT 8 falls with respect to the gate electrode 8g of the TFT 8 to which the predetermined off voltage is applied and the potential does not change, the potential difference between the gate electrode 8g and the source electrode 8s of the TFT 8 changes. To do.
- the current detection unit 41 is not necessarily connected to the power supply circuit 15a and the gate driver 15b as in the present embodiment. There is no need to provide the wiring 15c to be connected, and as described above, a current flowing through one or a plurality of scanning lines 5 among the lines L1 to Lx of the scanning line 5 may be detected. Even with this configuration, the current flowing through each scanning line 5 can be detected to detect the start or end of radiation irradiation.
- the power supply circuit 15a of the scanning drive means 15 and the gate driver 15b are connected.
- the value of the current flowing through the wiring 15c is a relatively large value. Therefore, when the current detection means 41 is provided on the wiring 15c as in the present embodiment, the voltage value V corresponding to the current detected by the current detection means 41 has a good S / N ratio, and increases or decreases. It becomes possible to detect accurately.
- the current that flows along with the irradiation of radiation not only flows between the power supply circuit 15a and the gate driver 15b and each scanning line 5, but also the equivalent amount of current flows to the source electrode 8s of the TFT 8 (in FIG. 8). S) and the radiation detection element 7 and also between the radiation detection element 7 and the bias power source 14.
- the sub-control unit 23 decreases the voltage value V corresponding to the current output from the current detection unit 41 and falls below a preset threshold value Vth.
- the rate of decrease of the voltage value V falls below a preset threshold value (see time tg)
- the end of radiation irradiation is detected.
- the radiation irradiation start time is time tc in FIG. 10 and the radiation irradiation end time is time tf.
- the radiation incident on the i layer 76 of the radiation detection element 7 or the incident radiation is converted by the scintillator 3 and is proportional to the number of photons of the electromagnetic wave incident on the i layer 76 of the radiation detection element 7. Electron hole pairs are generated in the i layer 76, and the potential difference between the first electrode 74 and the second electrode 78 of the radiation detection element 7 and the potential difference between the source electrode 8s and the gate electrode 8g of the TFT 8 change accordingly. Thus, a current flows through the wiring 15c that connects the power supply circuit 15a of the scanning drive means 15 and the gate driver 15b.
- the dose of radiation irradiated to the radiation image detection apparatus 1 from the start of irradiation to the end of irradiation is calculated. Can do.
- a frequency band in a predetermined range is further provided between the output terminal of the differential amplifier 41c of the current detection unit 41 and the integration circuit.
- a band pass filter (band pass filter) that passes only data and does not pass data of other frequencies attenuated is additionally arranged and banded to a voltage value V corresponding to the current value output from the current detecting means 41. It is also possible to perform a pass filter process and integrate it to calculate the radiation dose.
- the sub-control unit 23 is configured to have a peak hold function, and the sub-control unit 23 sets the time interval tf-tc between the start and end of radiation irradiation. It is also possible to calculate the dose of the irradiated radiation based on the peak value of the current flowing through the wiring 15c detected by the current detection means 41.
- the sub-control unit 23 detects the peak value Vp (see FIG. 10) of the voltage value detected from the irradiation start time tc to the irradiation end time tf, and the peak value Vp according to the following equation (1).
- an approximate value M of the dose of radiation irradiated to the radiation image detection apparatus 1 is calculated based on a value obtained by multiplying a value obtained by subtracting a constant ⁇ from the time interval tf ⁇ tc from the start to the end of radiation irradiation. It has become.
- the approximate value M of the radiation dose is a value proportional to the area of the voltage value V from the rising portion after the irradiation start time tc to the falling portion before the irradiation end time tf in FIG.
- a is a preset coefficient.
- the constant ⁇ is a constant set in advance for adjusting an error caused by actually considering the transition of the trapezoidal voltage value V as a rectangular shape.
- the sub-control unit 23 when the operator depresses the power switch 36 (see FIG. 1) and the radiographic image capturing apparatus 1 is turned on, the sub-control unit 23 is activated to perform main control.
- the means 22 enters a stop state of activation, that is, a sleep state.
- the sub-control means 23 When activated, the sub-control means 23 performs a predetermined reset process for each radiation detection element 7. That is, in the readout circuit 17, only the amplifier circuit 18 is activated by supplying power from the power supply unit 42 (see FIG. 8), and the charge reset switch 18c is turned on. Further, the sub-control unit 23 activates the bias power supply 14 and applies a bias voltage to each radiation detection element 7 via the bias line 9, and causes the scanning drive unit 15 to apply an on-voltage to each scanning line 5. Then, each TFT 8 connected to each scanning line 5 is turned on, and excess electric charge accumulated in each radiation detection element 7 is discharged to the power supply unit 42 via the TFT 8 and the amplifier circuit 18. In this way, predetermined reset processing of each radiation detection element 7 is performed without supplying power to the correlated double sampling circuit 19 and the A / D converter 20 of the readout circuit 17 and preventing wasteful power consumption. I do.
- the scan driving unit 15 applies the off voltage to the gate electrode 8 g of each TFT 8 via each scanning line 5 to turn off each TFT 8. To do. Then, power is supplied from the power supply means 45 (see FIG. 9) to the differential amplifier 41c of the current detection means 41, the switch 41d is turned off to activate the current detection means 41, and the differential amplifier 41c outputs the power.
- the voltage value V that is, the voltage value V corresponding to the current flowing through the wiring 15c connecting the power supply circuit 15a and the gate driver 15b of the scanning drive unit 15 is monitored.
- the sub-control means 23 detects the decrease in the voltage value V as described above and detects that the radiation irradiation has been completed.
- the current detection means 41 when the current detection means 41 is provided to detect the current flowing through the wiring 15c (or the voltage value V corresponding thereto), the current detection means is conventionally used as the bias line 9 or the connection line 10.
- noise is generated in the current detection means 41 and is applied from the power supply circuit 15a of the scanning drive means 15 to each scanning line 5 via the gate driver 15b and applied to the gate electrode 8g of each TFT 8.
- the noise generated by the current detection means 41 is superimposed on the off-voltage that is applied.
- the noise of the voltage generated by the current detection means is amplified by the relatively large parasitic capacitance C of the radiation detection element 7 and compared. Large noise charge, which was superposed on the charge generated in the radiation detection element by irradiation of radiation.
- the area of the portion where the source electrode 8s and the gate electrode 8g of the TFT 8 overlap is very small compared to the area of the condensing surface of the photodiode constituting the radiation detection element 7. For this reason, the parasitic capacitance C in the photodiode portion of the radiation detection element 7 is increased, whereas the parasitic capacitance c in the portion constituted by the source electrode 8s and the gate electrode 8g of the TFT 8 is very small.
- the voltage noise generated in the current detection unit 41 is a parasitic that is very small.
- the capacitance c is only slightly amplified and the generated noise charge is very small.
- the sub-control unit 23 When the sub-control unit 23 detects the start or end of radiation irradiation, the sub-control unit 23 stops supplying power from the power supply unit 45 to the differential amplifier 41c of the current detection unit 41, turns on the switch 41d, and turns on the resistor 41a. The function of the current detection means 41 is stopped by short-circuiting both terminals. Further, if it is configured to calculate the dose of radiation irradiated to the radiation image detection apparatus 1 from the start of irradiation to the end of irradiation, the sub-control unit 23 calculates the dose of radiation as described above. To do.
- the sub-control unit 23 transmits an activation signal to the main control unit 22 to activate the main control unit 22 to wake it up in order to perform processing for reading image data from each radiation detection element 7 and the like. . Then, if the main control means 22 is activated, it is not necessary to activate the sub control means 23. Therefore, when the main control means 22 is activated, the sub control means 23 stops its activation. That is, the sleep state is entered.
- the main control means 22 activated and awakened is configured to transmit a stop signal to the sub-control means 23 so that the sub-control means 23 receives the stop signal from the main control means 22 and stops the start-up. You may comprise. In this way, by configuring the sub-control unit 23 to stop when the main control unit 22 is activated, unnecessary power is supplied to the sub-control unit 23 and power is wasted. It becomes possible to prevent.
- the main control unit 22 When activated, the main control unit 22 activates the remaining functional units of the readout circuit 17, that is, the correlated double sampling circuit 19, the A / D converter 20, the analog multiplexer 21, and the like, and other necessary functional units. As described above, the readout process for reading out the image data by discharging the charge from each radiation detection element 7 is performed.
- the main control unit 22 transmits a pulse signal to the scanning drive unit 15, and sets the voltage applied from the scanning drive unit 15 to the gate electrode 8 g of each TFT 8 via each scanning line 5 between the on voltage and the off voltage. Switch between.
- on / off of the charge reset switch 18c of the amplifier circuit 18 of the readout circuit 17 is controlled, or a pulse signal is transmitted to the correlated double sampling circuit 19 to turn on / off the sample hold function.
- Various processes such as control are executed to read image data from each radiation detection element 7.
- Each read image data is stored in the storage means 43 (see FIG. 7 and the like).
- the main control unit 22 transmits the image data stored in the storage unit 43 to the external device via the antenna device 39 when a series of radiographic image capturing is completed.
- the image data may be configured to be transmitted by a wired method such as a cable.
- the main control means 22 When the main control means 22 completes the transmission of the image data to the external device, the main control means 22 activates the sub-control means 23, stops itself, or activates by a stop signal from the activated sub-control means 23. To stop. That is, the sleep state is entered. At that time, necessary information is transmitted from the main control means 22 to the sub-control means 23.
- the activated sub-control means 23 when returning to the state where the power of the radiographic imaging apparatus 1 is turned on as described above, the activated sub-control means 23 performs a predetermined reset of each radiation detection element 7 as described above. While performing the process, the current detection means 41 and the like are activated to continue monitoring whether or not radiation irradiation has started.
- the main control unit 22 performs only processing that consumes a relatively large amount of power, such as image data reading processing and image data transmission, and other processing such as radiation exposure monitoring is performed. Since it is possible not to be performed by the main control unit 22 but to be performed by the sub-control unit 23 that operates with low power consumption, it is possible to suppress power consumption of the battery 40.
- the main control means 22 is awakened at an appropriate timing. Further, other processing is also performed as appropriate, and at that time, the main control means 22 is appropriately awakened and performed as necessary.
- the current detection unit 41 for detecting the start of radiation irradiation is provided between the power supply circuit 15a of the scanning drive unit 15 and the gate driver 15b. The current flowing between them and the current flowing through each scanning line 5 are detected.
- the parasitic capacitance c formed by the source electrode 8s and the gate electrode 8g of the TFT (switch means) 8 is inevitably large because the area of the condensing surface is large.
- the noise with respect to the bias voltage by the current detecting means provided on the bias line 9 is much smaller than when the noise is amplified by the large parasitic capacitance C of the radiation detecting element 7 and a large noise charge is superimposed. .
- the image data read from each radiation detection element 7 and finally obtained is greatly affected by the noise of the voltage generated by the current detection means 41. Since it is possible to superimpose only slightly, it is possible to reliably reduce the influence of noise charges, and there are problems such as deterioration of the image quality of the radiographic image finally obtained, in particular its granularity. It is possible to accurately prevent the occurrence.
- the current detection unit 41 is continuously operated even after the start of radiation irradiation to the radiographic imaging device 1 is detected, and the current value (voltage) detected by the current detection unit 41 is detected.
- the case of detecting until the end of radiation irradiation based on the value V) has been described.
- the influence of noise generated by the current detection means 41 is further reduced when the operation of the current detection means 41 is stopped after the start of radiation irradiation is detected.
- the power supply means 45 (see FIG. 9). It is possible to stop the function of the current detection means 41 by stopping the supply of power from the current detection means 41 to the differential amplifier 41c and turning on the switch 41d.
- the end of radiation irradiation cannot be detected based on the current value (or voltage value V) from the current detection means 41.
- a predetermined time is set in advance and the sub-control is performed.
- the means 23 determines that the irradiation of radiation has ended when the predetermined time has elapsed after the value of the current detected by the current detection means 41 (or voltage value V) has increased and the start of irradiation has been detected. It can be configured to do so.
- an off voltage is applied from the gate driver 15 b to each gate electrode 8 g of each TFT 8 via each scanning line 5.
- the case where the TFT 8 is kept off has been described.
- dark charges generated due to thermal excitation of the radiation detection element 7 due to heat or the like. May increase in the amount accumulated in each radiation detection element 7.
- Each TFT 8 can be configured to be slightly open.
- the voltage applied to the gate electrode 8g of each TFT 8 is determined from the voltage value at the boundary when the applied voltage is lowered, that is, the boundary voltage value when the current flowing through the TFT 8 is exactly 0. The voltage is adjusted so that a slightly higher voltage by a predetermined value is applied.
- each TFT 8 is slightly opened. For this reason, even if a dark charge is generated in each radiation detection element 7, it can be accurately removed from the radiation detection element 7, and the adverse effect of the dark charge being accumulated in each radiation detection element 7. Can be avoided accurately.
- each TFT 8 instead of slightly opening each TFT 8 until the start of radiation irradiation is detected as described above, an on-voltage is applied to the gate electrode 8g of each TFT 8 until the start of radiation irradiation is detected. It is also possible to configure each TFT 8 to be actively opened. If comprised in this way, it will become possible to remove the dark charge which generate
- each radiation detection element 7 is irradiated by radiation if the TFT 8 is left open thereafter. All the charges generated in the inside flow out from each radiation detection element 7 via the TFT 8, and the charge (image data) is not accumulated in each radiation detection element 7.
- the sub-control unit 23 when the sub-control unit 23 detects that the voltage value V has increased and radiation irradiation has started, the sub-control unit 23 applies an off-voltage from the scanning drive unit 15 to each scanning line 5. All the TFTs 8 are turned off by applying an off voltage to the gate electrodes 8g of the TFTs 8 connected to the scanning lines 5.
- the operation of the current detection means 41 is performed when the voltage applied to the gate electrode 8g of each TFT 8 is switched to the off voltage. It is also possible to determine that the irradiation of radiation has been completed when a predetermined time has elapsed after stopping the operation.
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Abstract
Description
互いに交差するように配設された複数の走査線および複数の信号線と、前記複数の走査線および複数の信号線により区画された各領域に二次元状に配列された複数の放射線検出素子と、
前記放射線検出素子ごとに配置され、接続された前記走査線に印加される電圧に応じてオフ状態とオン状態とが切り替えられ、前記オフ状態では前記放射線検出素子内で発生した電荷を保持し、前記オン状態では前記放射線検出素子から前記電荷を放出させるスイッチ手段と、
前記走査線を介して前記スイッチ手段にオン電圧およびオフ電圧を印加するゲートドライバと、前記ゲートドライバに前記オン電圧および前記オフ電圧を供給する電源回路とを備える走査駆動手段と、
前記電源回路と前記ゲートドライバとの間を流れる電流、または前記走査線を流れる電流を検出する電流検出手段と、
前記電流検出手段が検出した前記電流の値に基づいて少なくとも放射線の照射の開始を検出する制御手段と、
を備えることを特徴とする。
この放射線の線量の近似値Mは、図10における照射開始時刻tc以後の立ち上がり部分から照射終了時刻tf以前の立ち下がり部分までの電圧値Vを矩形状に近似してその面積に比例する値として求めるものであり、照射開始時刻tcおよび照射終了時刻tfを検出し、ピーク値Vpを検出するだけで簡単に算出できるという利点を有する。なお、上記(1)式においてaは予め設定された係数である。また、定数αは、実際には台形状の電圧値Vの推移を矩形状と見なすことにより生じる誤差を調整するために予め設定された定数である。
5 走査線
6 信号線
7 放射線検出素子
8 TFT(スイッチ手段)
15 走査駆動手段
15a 電源回路
15b ゲートドライバ
23 サブ制御手段(制御手段)
41 電流検出手段
41a 抵抗器
41d スイッチ
r 領域
V 電圧値(電流に相当する電圧値)
Vp ピーク値
Claims (10)
- 互いに交差するように配設された複数の走査線および複数の信号線と、前記複数の走査線および複数の信号線により区画された各領域に二次元状に配列された複数の放射線検出素子と、
前記放射線検出素子ごとに配置され、接続された前記走査線に印加される電圧に応じてオフ状態とオン状態とが切り替えられ、前記オフ状態では前記放射線検出素子内で発生した電荷を保持し、前記オン状態では前記放射線検出素子から前記電荷を放出させるスイッチ手段と、
前記走査線を介して前記スイッチ手段にオン電圧およびオフ電圧を印加するゲートドライバと、前記ゲートドライバに前記オン電圧および前記オフ電圧を供給する電源回路とを備える走査駆動手段と、
前記電源回路と前記ゲートドライバとの間を流れる電流、または前記走査線を流れる電流を検出する電流検出手段と、
前記電流検出手段が検出した前記電流の値に基づいて少なくとも放射線の照射の開始を検出する制御手段と、
を備えることを特徴とする放射線画像撮影装置。 - 前記電流検出手段は、前記電源回路と前記ゲートドライバとを結ぶ配線に直列に接続された抵抗器と、前記抵抗器の両端子間を短絡可能なスイッチとを備え、放射線の照射の開始を検出する際には前記スイッチの短絡が解除され、それ以外の場合には前記スイッチにより前記抵抗器の両端子間が短絡されるように構成されていることを特徴とする請求項1に記載の放射線画像撮影装置。
- 前記制御手段は、前記電流検出手段が検出した前記電流の値が増加した場合に放射線の照射の開始を検出することを特徴とする請求項1または請求項2に記載の放射線画像撮影装置。
- 前記制御手段は、前記電流検出手段が検出した前記電流の値が増加して放射線の照射の開始を検出した後、所定時間が経過した時点で放射線の照射が終了したと判断することを特徴とする請求項3に記載の放射線画像撮影装置。
- 前記制御手段は、前記電流検出手段が検出した前記電流の値が減少した場合に放射線の照射の終了を検出することを特徴とする請求項1から請求項3のいずれか一項に記載の放射線画像撮影装置。
- 前記制御手段は、照射された前記放射線の線量を、前記放射線の照射の開始および終了の時間間隔と、前記電流検出手段により検出された前記電流のピーク値とに基づいて算出することを特徴とする請求項5に記載の放射線画像撮影装置。
- 前記制御手段は、前記電流検出手段により検出された前記電流の、前記放射線の照射の開始および終了の時間間隔における積分値として、照射された前記放射線の線量を算出することを特徴とする請求項5に記載の放射線画像撮影装置。
- 前記制御手段は、前記電流検出手段により検出された前記電流の値に対してバンドパスフィルタ処理を施した値の、前記放射線の照射の開始および終了の時間間隔における積分値として、照射された前記放射線の線量を算出することを特徴とする請求項5に記載の放射線画像撮影装置。
- 前記スイッチ手段は、放射線の照射の開始を検出する際はオフ状態とされていることを特徴とする請求項1から請求項8のいずれか一項に記載の放射線画像撮影装置。
- 前記スイッチ手段は、放射線の照射の開始を検出する際は、印加される電圧を低下させた場合にオフ状態となる境界の電圧値から所定値だけ高い電圧が印加されていることを特徴とする請求項1から請求項8のいずれか一項に記載の放射線画像撮影装置。
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Cited By (5)
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JP2012152235A (ja) * | 2011-01-21 | 2012-08-16 | Fujifilm Corp | 放射線画像撮影装置およびプログラム |
JP2014020880A (ja) * | 2012-07-17 | 2014-02-03 | Fujifilm Corp | 放射線画像撮影装置、放射線画像撮影システム、放射線の照射開始の検出感度制御方法およびプログラム |
EP2716224A1 (en) * | 2011-06-02 | 2014-04-09 | Konica Minolta, Inc. | Radiation imaging system |
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JP5673558B2 (ja) * | 2010-01-14 | 2015-02-18 | コニカミノルタ株式会社 | 放射線画像撮影装置 |
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EP2716224A4 (en) * | 2011-06-02 | 2014-11-26 | Konica Minolta Inc | RADIOGRAPHY SYSTEM |
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JP2014020880A (ja) * | 2012-07-17 | 2014-02-03 | Fujifilm Corp | 放射線画像撮影装置、放射線画像撮影システム、放射線の照射開始の検出感度制御方法およびプログラム |
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US20120097860A1 (en) | 2012-04-26 |
JPWO2011001705A1 (ja) | 2012-12-13 |
US8866095B2 (en) | 2014-10-21 |
JP5447519B2 (ja) | 2014-03-19 |
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