Radiation imaging device, radiation imaging system, radiation imaging method and program

Abstract

A suitable bias power supply is essential to obtain good radiation image data. [Solution] The FPD 1 includes photodiodes 412, a readout circuit 43, bias power supplies 46 and 51, a switch 50, and a control unit 10. The photodiodes 412 are arranged in a matrix so as to generate electric charges when exposed to radiation. The readout circuit 43 reads out signals from the photodiodes 412 for generating radiation image data. The bias power supplies 46 and 51 apply bias voltages to the photodiodes 412 via bias lines connected to the photodiodes 412. The switch 50 switches between the bias power supplies 46 and 51. The control unit 10 controls the switching timing of the switch 50.

Description

[Technical Field]

[0001] The present invention relates to a radiation imaging apparatus, a radiation imaging system, a radiation imaging method, and a program. [Background technology]

[0002] Conventionally, radiation imaging devices such as FPDs (Flat Panel Detectors) are known that receive radiation irradiated from a radiation irradiator via a subject and generate radiation image data. Non-coordinated imaging, which does not depend on a user such as a doctor turning on an exposure switch, is also known. Non-coordinated imaging is an imaging method in which the radiation irradiator and the radiation imaging device are not synchronized. In non-coordinated imaging, an exposure determination unit of the radiation imaging device detects the current flowing through the bias line and determines exposure when the amount of change in the detected current exceeds a threshold. A readout circuit of the radiation imaging device reads out an image signal corresponding to the irradiated radiation.

[0003] There is also known a radiation imaging device that monitors the current in a bias line and determines exposure (see Patent Document 1). This radiation imaging device includes a bias power supply having an integrating circuit using an operational amplifier, and an irradiation detection unit.

[0004] There is also known a radiographic imaging device that monitors the current in a bias line and determines whether exposure should be initiated (see Patent Document 2). This radiographic imaging device includes a detection unit that detects the bias current, a bias power supply, and a control unit that integrates the detected bias current and compares it with a threshold value to determine whether exposure should be initiated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-192062 [Patent Document 2] International Publication No. 2010 / 150569 Summary of the Invention [Problem to be solved by the invention]

[0006] Furthermore, when data signals are read out from the pixel section of a radiation imaging device, a through-charge occurs. This through-charge is noise that is transmitted to the signal line through the parasitic capacitance of the TFT (Thin Film Transistor) when the gate of the pixel TFT is switched on / off. For this reason, a configuration in which a charge injection circuit is implemented inside the readout circuit of a radiation imaging device is being considered. The charge injection circuit operates when data signals are read out from the pixel, and corrects the through-charge by injecting an opposite-phase charge.

[0007] FIG. 6 is a circuit diagram showing a detection unit 400. Consider the detection unit 400 of a radiation imaging device as shown in FIG. 6. The detection unit 400 includes a radiation detection unit 41, a gate drive circuit 42, a readout circuit 43, and a bias power supply 46. The radiation detection unit 41 includes a plurality of pixel units 410, a plurality of scanning lines 413, signal lines 414, and bias lines 415. The pixel units 410 are arranged in a two-dimensional matrix. Each pixel unit 410 includes a TFT 411 and a photodiode 412.

[0008] The readout circuit 43 reads out a data signal from a signal line 414 of each pixel unit 410. The readout circuit 43 has an integration circuit 44 and a charge injection circuit 45 corresponding to each signal line 414. The integration circuit 44 has an operational amplifier 441, a capacitor 442, a switch 443, and a constant voltage source 444. The charge injection circuit 45 has a capacitor 451, a switch 452, a resistor 453, a constant voltage source 454, a resistor 455, and a ground unit 456. The resistor 453 and the constant voltage source 454 are defined as E1. The resistor 455 and the ground unit 456 are defined as E2. The switch 452 switches the connection destination of the capacitor 451 between E1 and E2.

[0009] The bias power supply 46 supplies a bias voltage to the bias line 415 via the bias line 416, monitors the current flowing through the bias line 416, and determines whether radiation has been irradiated. The bias power supply 46 has an integrating circuit 47, an AD (Analog to Digital) converter 48, and an exposure determining unit 49. The integrating circuit 47 has an operational amplifier 471, a capacitor 472, a switch 473, and a constant voltage source 474.

[0010] In non-coordinated imaging, when the readout circuit 43 reads out a data signal from the pixel unit 410, the gate terminal of the target TFT 411 is turned on, generating a through charge. At this time, the charge injection circuit 45 operates. Specifically, the connection destination of the capacitor 451 is switched to E2 by the switch 452, and the through charge is corrected by injecting an opposite-phase charge.

[0011] At this time, an inrush current E1 generated in the readout circuit 43 is transmitted to the bias power supply 46 via the pixel unit 410 and bias lines 415 and 416. The inrush current causes the exposure determination unit 49 to oscillate. The oscillation of the exposure determination unit 49 affects the data signal readout value of the readout circuit 43 via the bias line 416 again, resulting in image noise in the radiation image data.

[0012] An object of the present invention is to obtain good radiation image data by using an appropriate bias power supply. [Means for solving the problem]

[0013] In order to solve the above problem, the radiation imaging apparatus of the invention described in claim 1 comprises: a plurality of radiation detection elements arranged in a matrix so as to generate electric charges when exposed to radiation; a readout unit that reads out signals for generating radiation image data from the radiation detection elements; a plurality of bias power supplies that apply bias voltages to the radiation detection elements via bias lines connected to the radiation detection elements; a switching unit that switches the bias power supply; and a control unit that controls the switching timing of the switching unit.

[0014] The invention described in claim 2 is the radiation imaging apparatus described in claim 1, The control unit switches the switching unit at any timing.

[0015] The invention described in claim 3 is the radiation imaging apparatus described in claim 1, A first bias power supply among the plurality of bias power supplies is The device has an exposure determination unit that determines whether radiation exposure has started based on whether the amount of change in the current flowing through the bias line has exceeded a threshold value.

[0016] The invention described in claim 4 is the radiation imaging apparatus described in claim 3, The readout section has a charge injection section that injects charge into the through charge to correct it when the radiation detection element is switched.

[0017] The invention described in claim 5 is the radiation imaging apparatus described in claim 3, The control unit switches to the first bias power supply using the switching unit when monitoring the amount of change in the current, and switches to a second bias power supply among the plurality of bias power supplies that does not have the exposure determination unit using the switching unit when reading out a signal in the reading unit.

[0018] The invention described in claim 6 is the radiation imaging apparatus described in claim 1, The switching unit has a current fluctuation in the bias line that does not affect the image of the radiation image data before and after the switching.

[0019] The invention described in claim 7 is the radiation imaging apparatus described in claim 6, The switching unit is an FET, a photo MOS relay, or a mechanical relay.

[0020] The radiation imaging system of the invention described in claim 8 comprises: a radiation imaging device according to any one of claims 1 to 7; and a radiation irradiation device that irradiates the plurality of radiation detection elements with radiation through the subject.

[0021] The radiation imaging method of the invention described in claim 9 comprises: a reading step of reading signals for generating radiation image data from a plurality of radiation detection elements arranged in a matrix so as to generate charges in response to radiation exposure; and a control step of controlling the switching timing of a switching unit that switches between a plurality of bias power supplies that apply bias voltages to the plurality of radiation detection elements via bias lines connected to the radiation detection elements.

[0022] The program of the invention described in claim 10 is a plurality of radiation detection elements arranged in a matrix so as to generate electric charges when exposed to radiation; a readout unit that reads out signals for generating radiation image data from the radiation detection elements; a plurality of bias power supplies that apply bias voltages to the radiation detection elements via bias lines connected to the radiation detection elements; a switching unit that switches the bias power supply; a control unit that controls the switching timing of the switching unit; Function as. [Effects of the Invention]

[0023] According to the present invention, good radiation image data can be obtained by using an appropriate bias power supply. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram showing the overall configuration of a radiation imaging system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing the functional configuration of an FPD. [Figure 3] FIG. 2 is a circuit diagram showing a detection unit according to the embodiment. [Figure 4] 10 is a time chart showing an imaging sequence of non-cooperative imaging processing of an FPD. [Figure 5] 5 is a time chart showing a readout circuit sequence of the non-cooperative imaging process of the FPD for one scanning line in the actual reading imaging sequence of FIG. 4. [Figure 6] FIG. 10 is a circuit diagram showing a detection unit of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0025] Advantages and features provided by one or more embodiments of the present invention will be more fully understood from the following detailed description and the accompanying drawings. However, these drawings are for illustrative purposes only and are not intended to define the limits of the present invention. Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the disclosed embodiments.

[0026] (Embodiment) An embodiment of the present invention will be described with reference to Figs. 1 to 5. First, the device configuration of this embodiment will be described with reference to Figs. 1 to 3. Fig. 1 is a diagram showing the overall configuration of a radiation imaging system 100 of this embodiment. Fig. 2 is a block diagram showing the functional configuration of an FPD 1. Fig. 3 is a circuit diagram showing a detection unit 40 of this embodiment.

[0027] As shown in FIG. 1, the radiography system 100 is a system for making rounds in a hospital ward to perform radiography on patients who have difficulty moving around. The radiography system 100 includes an FPD 1, a main body 2, and a radiation source 3. The main body 2 and the radiation source 3 function as a radiation irradiation device. The radiography system 100 has wheels on the main body 2, and is configured as a mobile medical cart. The main body 2 is provided with a storage unit 201 for storing the FPD 1. The storage unit 201 is provided with a connector (not shown) for connecting to the stored FPD 1. The connector allows the main body 2 to be transported while charging the battery 80 (FIG. 2) of the stored FPD 1.

[0028] The main body 2 has a console (control device) function that controls radiography, such as wireless communication with the FPD 1 and confirmation of a radiographic image displayed on the display unit 203 after radiography.

[0029] It should be noted that the radiation imaging system 100 is not limited to a configuration in which the main body 2 is a medical cart. The radiation imaging system can also be applied to a configuration in which an FPD 1 is used to image a subject placed on an imaging table in a general imaging room. The FPD 1 wirelessly transmits the generated radiation image data to a console instead of the main body 2.

[0030] The radiation imaging system 100 is brought into an operating room, an intensive care unit, a hospital room 1000, or the like. The FPD 1 is inserted, for example, between a subject (examinee) 5 lying on a bed 4 and the bed 4, or into an insertion port (not shown) provided on the side of the bed 4 opposite the subject 5. In this state, the radiation imaging system 100 irradiates the subject 5 with radiation from the radiation source 3 to capture still images or video of the subject 5. Capturing a still image refers to acquiring radiation image data of a single still image of the subject in response to an imaging trigger. Capturing video refers to continuously acquiring multiple radiation image data of the subject in response to an imaging trigger. In video imaging, the subject is irradiated with pulsed radiation such as X-rays repeatedly at predetermined time intervals (pulse irradiation), or is irradiated continuously and without interruption at a low dose (continuous irradiation).

[0031] The radiation imaging system 100 has an apparatus-cooperative imaging mode and a non-cooperative imaging mode. Apparatus-cooperative imaging is an imaging method in which the FPD1 images a subject in cooperation with a radiation irradiation apparatus in response to a user pressing the exposure switch 202 as an imaging trigger. The user is a doctor, technician, or the like. Non-cooperative imaging is an imaging method in which the radiation irradiation apparatus and the FPD1 are not synchronized. In non-cooperative imaging, the FPD1 itself detects radiation exposure as a trigger to start imaging. In this embodiment, a case will be described in which the radiation imaging system 100 operates in the non-cooperative imaging mode.

[0032] 2, the FPD 1 includes a control unit 10, an operation unit 20, a display unit 30, a detection unit 40, a storage unit 60, a communication unit 70, and a battery 80. The various units of the FPD 1 are connected via a bus 90.

[0033] The control unit 10 is configured, for example, with an FPGA (Field Programmable Gate Array) and controls each unit of the FPD 1. The control unit 10 performs various processes using programmed logic circuits in the FPGA. The control unit 10 may also be configured to include a CPU (Central Processing Unit) and RAM (Random Access Memory). The CPU of the control unit 10 reads out various processing programs stored in the storage unit 60, loads them into the RAM, and executes various processes in cooperation with the loaded programs.

[0034] For example, the control unit 10 controls the detection unit 40 to detect radiation exposure and generate and acquire radiation image data. The control unit 10 transmits the acquired radiation image data to the main body 2 via the communication unit 70.

[0035] The operation unit 20 is a switch for turning on / off the power supply of the FPD 1 and switching modes, etc. The operation unit 20 receives operation input from the user and outputs the operation information to the control unit 10.

[0036] The display unit 30 is configured with an LED (Light Emitting Diode) etc. The display unit 30 performs various displays under the control of the control unit 10.

[0037] The detection unit 40, under the control of the control unit 10, converts radiation emitted from the radiation source 3 and transmitted through the subject 5 into an electrical signal in accordance with its intensity using the radiation detection unit 41 (FIG. 4). The detection unit 40 reads out data signals (pixel signals), which are analog electrical signals, to generate radiation image data. FPDs are of an indirect conversion type and a direct conversion type, and either may be used as the FPD 1. The indirect conversion type is a system in which radiation is converted into an electrical signal by a photoelectric conversion element such as a photodiode via a scintillator. The direct conversion type is a system in which radiation is directly converted into an electrical signal by a photoelectric conversion element. The detection unit 40 will be described in detail below.

[0038] The storage unit 60 is configured with a non-volatile semiconductor memory, etc. The storage unit 60 stores various programs to be executed when the control unit 10 is a CPU and RAM, parameters required for executing processes, and data such as radiation image data.

[0039] The communication unit 70 transmits and receives information to and from the main body 2 via wireless communication. That is, the control unit 10 transmits and receives information to and from external devices such as the main body 2 and a console via the communication unit 70. The wireless communication method of the communication unit 70 is a wireless local area network (LAN), etc. Note that the communication unit 70 may also include a communication unit for wired communication.

[0040] The battery 80 is a power storage unit that serves as a drive source for the FPD 1 and supplies power to each component of the FPD 1 .

[0041] Next, the configuration of the detection unit 40 will be described with reference to Fig. 3. As shown in Fig. 3, the detection unit 40 includes a radiation detection unit 41, a gate drive circuit 42, a readout circuit 43, bias power supplies 46 and 51, and a switch 50. The readout circuit 43 functions as a readout unit. The switch 50 functions as a switching unit.

[0042] The radiation detection unit 41 has a plurality of pixel units 410, a plurality of scanning lines 413, signal lines 414, and bias lines 415. The plurality of scanning lines 413 and the plurality of signal lines 414 are arranged so as to intersect with each other. Small regions defined by the plurality of scanning lines 413 and the plurality of signal lines 414 on the surface of the radiation detection unit 41 correspond to the pixel units 410. The pixel units 410 are arranged in a two-dimensional matrix and correspond to each pixel of the radiographic image. Each pixel unit 410 has a TFT 411 and a photodiode 412.

[0043] The TFT 411 is a switching element that turns on and off drain-source conduction by turning on and off a gate terminal. The photodiode 412 is a radiation detection element that generates a photocurrent as a data signal for the pixel section 410 when radiation is incident directly or as visible light via a scintillator.

[0044] The radiation detection unit 41 has a plurality of pixel units 410 arranged on a substrate. The substrate is a plate-like substrate made of glass, a base film, a semiconductor material such as silicon, or the like. When a scintillator is present, the substrate is arranged parallel to the scintillator. In each pixel unit 410, the gate terminal of the TFT 411 is electrically connected to a scanning line 413. As shown in FIG. 3, the radiation detection unit 41 is taken as the X-axis and the Y-axis. The gate terminals of the plurality of TFTs 411 at the same position on the Y-axis are connected to one scanning line 413. The gate drive circuit 42 is connected to the plurality of scanning lines 413.

[0045] In each pixel unit 410, the source terminal of the TFT 411 is electrically connected to a signal line 414. The source terminals of multiple TFTs 411 at the same position on the X axis are connected to one signal line 414. The readout circuit 43 is connected to multiple signal lines 414.

[0046] In each pixel unit 410, the drain terminal of the TFT 411 is electrically connected to the cathode of the photodiode 412. The anode of the photodiode 412 is connected to a bias line 415. The multiple bias lines 415 are connected in a grid pattern and electrically connected to one bias line 416 on the bias power supply 46 side.

[0047] The gate drive circuit 42 selects each of the multiple scan lines 413 and turns on and off the gates of the multiple TFTs 411 connected to the selected scan line 413. The gate drive circuit 42 is composed of a power supply circuit, a gate driver, etc. The power supply circuit generates different on-voltages and off-voltages and supplies them to the gate driver. The gate driver switches the voltage applied to each of the scan lines 413 between the on-voltage and the off-voltage.

[0048] 3, the pixel units 410, signal lines 414, and bias lines 415 are shown as representative examples. The numbers of pixel units 410, signal lines 414, and bias lines 415 are not limited to those shown in the figure.

[0049] The readout circuit 43 is a ROIC (Read Out Integrated Circuit) and reads out a data signal from a signal line 414 of each pixel unit 410. The readout circuit 43 has an integrating circuit 44 and a charge injection circuit 45 as a charge injection unit corresponding to each signal line 414. The integrating circuit 44 time-integrates the voltage of the data signal from the signal line 414 and outputs the result. The integrating circuit 44 has an operational amplifier 441, a capacitor 442, a switch 443, and a constant voltage source 444.

[0050] The signal line 414 is connected to the inverting input terminal of the operational amplifier 441. The constant voltage source 444 is a voltage source that outputs a constant voltage. The constant voltage source 444 is connected to the non-inverting input terminal of the operational amplifier 441. The capacitor 442 is connected between the output terminal and the inverting input terminal of the operational amplifier 441. The on / off of the switch 443 is controlled by the control unit 10, and the switch 443 is connected in parallel to the capacitor 442. The integrating circuit 44 charges the capacitor 442 when the switch 443 is turned off, and discharges the capacitor 442 when the switch 443 is turned on.

[0051] In each integration circuit 44, the integrated data signal of each pixel unit 410 output from the output terminal of each operational amplifier 441 is input to a CDS (Correlated Double Sampling) circuit (not shown). Each CDS circuit subtracts the voltage value of the integrated data signal at the reference hold (SHR) from the voltage value of the integrated data signal at the sample hold (SHS) for the target pixel unit 410. The reference hold is a data signal reading sequence during exposure when the gate of the TFT 411 of the pixel unit 410 is not turned on. The sample hold is a data signal reading sequence during exposure when the gate of the TFT 411 of the pixel unit 410 is turned on. The sample hold voltage value contains not only the desired signal value but also switching noise of the switch 443 of the readout circuit 43 and an offset component. The reference hold voltage value does not contain the desired signal value but contains switching noise of the switch 443 of the readout circuit 43 and an offset component. Therefore, the CDS circuit obtains the desired signal value by taking the difference between the sample hold voltage value and the reference hold voltage value.

[0052] Each CDS circuit outputs a difference value (desired signal value) as a pixel signal to a multiplexer (not shown). The multiplexer combines pixel signals input from multiple CDS circuits and outputs the combined signal to an AD conversion unit (not shown) as analog radiation image data. The AD conversion unit converts the analog radiation image data input from the multiplexer into AD data and outputs the digital radiation image data to the control unit 10. The control unit 10 obtains the final desired radiation image data by subtracting the dark reading radiation image data from the actual reading radiation image data (described later). The actual reading is an imaging sequence in which data signals are read during radiation exposure. The dark reading is an imaging sequence in which data signals are read without radiation exposure.

[0053] When a through charge occurs in the signal line 414 during data signal readout, the charge injection circuit 45 corrects the through charge by injecting charge. The charge injection circuit 45 includes a capacitor 451, a switch 452, a resistor 453, a constant voltage source 454, a resistor 455, and a ground 456.

[0054] Capacitor 451 is connected to the inverting input terminal (signal line 414) of operational amplifier 441 and switch 452. Switch 452 switches the connection destination of capacitor 451 between E1 (resistor 453, constant voltage source 454) and E2 (resistor 455, ground 456) under the control of control unit 10. Resistor 453 is connected to switch 452 and constant voltage source 454. Constant voltage source 454 is a voltage source that outputs a constant voltage. The output voltage values ​​of constant voltage source 444 and constant voltage source 454 are different.

[0055] Resistor 455 is connected to switch 452 and ground 456. Ground 456 is grounded. When a through charge occurs in signal line 414 due to the gate of TFT 411 being turned on during data signal readout, charge injection circuit 45 switches switch 452 to E2. When switch 452 is switched to E2, charge injection circuit 45 injects an opposite-phase charge into the through charge of signal line 414 to correct it.

[0056] The switch 50, under the control of the control unit 10, switches the connection destination via the bias line 416 of the radiation detection unit 41 between the bias power supply 46 and 51. The switch 50 has the characteristic of being able to suppress bias voltage fluctuations that do not affect the image of the radiation image data before and after switching. The switch 50 is composed of a FET (Field Effect Transistor), a photo MOS (Metal Oxide Semiconductor) relay, a mechanical relay, or the like.

[0057] The bias power supply 46 supplies a bias voltage to the bias line 415 via the bias line 416, monitors the current flowing through the bias line 416, and determines whether or not radiation has been irradiated. The bias power supply 46 has an integrating circuit 47, an AD conversion unit 48, and an exposure determination unit 49.

[0058] The integrating circuit 47 integrates the voltage of the signal on the bias line 416 over time and outputs the result to the AD conversion unit 48. The integrating circuit 47 includes an operational amplifier 471, a capacitor 472, a switch 473, and a constant voltage source 474. The bias line 416, via the switch 50, is connected to the inverting input terminal of the operational amplifier 471. The constant voltage source 474 is a voltage source that outputs a constant voltage. The constant voltage source 474 is connected to the non-inverting input terminal of the operational amplifier 471. The capacitor 472 is connected between the output terminal and the inverting input terminal of the operational amplifier 471. The on / off of the switch 473 is controlled by the control unit 10 and is connected in parallel to the capacitor 472. The integrating circuit 47 charges the capacitor 472 when the switch 473 is turned off, and discharges the capacitor 472 when the switch 473 is turned on.

[0059] The AD conversion unit 48 is connected to the output terminal of the operational amplifier 471 and performs AD conversion on the signal of the bias line 416 integrated by the integration circuit 47. The exposure determination unit 49 compares the digital integrated signal converted by the AD conversion unit 48 with a predetermined threshold. The exposure determination unit 49 determines that radiation exposure has occurred if the signal is equal to or greater than a predetermined threshold. The exposure determination unit 49 determines that radiation exposure has not occurred if the signal is less than the predetermined threshold. The exposure determination unit 49 outputs the exposure determination result to the control unit 10.

[0060] Next, the operation of the FPD 1 of the radiation imaging system 100 will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a time chart showing an imaging sequence of non-cooperative imaging processing of the FPD 1. Fig. 5 is a time chart showing a readout circuit sequence of non-cooperative imaging processing of the FPD 1 for one scan line in the actual reading imaging sequence of Fig. 4.

[0061] A user performs non-coordinated imaging of a subject 5 using the radiation imaging system 100. The control unit 10 of the FPD 1 performs non-coordinated imaging processing based on an embedded program or a program stored in the storage unit 60. As shown in FIG. 4, in an exposure standby imaging sequence, the control unit 10 switches the switch 50 to the bias power supply 46 in advance. This causes the control unit 10 to supply a bias voltage to the bias line 415 and determine exposure. At this time, the control unit 10 sequentially selects multiple scanning lines 413 one by one using the gate drive circuit 42 and turns on the gate of the corresponding TFT 411. The control unit 10 switches on and off the switch 473 within one scanning line 413 whose gate is turned on, resetting (discharging) the capacitor 472.

[0062] The exposure standby imaging sequence is a period in which the readout circuit 43 does not read out data signals. Therefore, the control unit 10 may switch the switch 452 to either E1 or E2. Similarly, the control unit 10 may switch the switch 443 to either on or off.

[0063] Then, when the exposure determination unit 49 of the bias power supply 46 determines that radiation exposure has occurred, the process proceeds to an accumulation imaging sequence for the photodiodes 412 in each pixel unit 410. At this time, the control unit 10 turns on the switch 473 to fix the bias voltage supplied by the integration circuit 47. The accumulation imaging sequence continues as a period in which the readout circuit 43 does not read out data signals. Therefore, the control unit 10 may switch the switches 452 and 443 to either position.

[0064] Then, the control unit 10 switches the switch 50 to the bias power supply 51, and proceeds to an imaging sequence for reading (main reading) a data signal corresponding to the exposure. By switching to the bias power supply 51 without an exposure determination circuit, a bias voltage is supplied from the bias power supply 51 to the bias line 415 via the bias line 416. At the same time, oscillation of the bias power supply 51 due to the occurrence of an inrush current of E1 in the readout circuit 43 is prevented. Since the bias power supply 51 is switched to, the control unit 10 may switch the switch 473 of the unused bias power supply 46 to either position.

[0065] In the actual reading imaging sequence, the control unit 10 sequentially selects the multiple scanning lines 413 one by one using the gate drive circuit 42 and turns on the gate of the corresponding TFT 411. The data signal of the signal line of the pixel unit 410 whose TFT 411 has been gated on is read out by the readout circuit 43. Thus, with reference to FIG. 5, in the actual reading imaging sequence, the control unit 10 sequentially selects the multiple scanning lines 413 one by one. Here, with reference to FIG. 5, multiple sequences (readout circuit sequences) of the readout circuit 43 corresponding to one selected scanning line 413 in the actual reading imaging sequence will be described.

[0066] First, in the readout circuit sequence of the charge amplifier reset, the control unit 10 turns off the gate of the TFT 411 in one scanning line 413 selected by the gate drive circuit 42. At this time, the control unit 10 switches the switch 452 to E1 to charge the capacitor 451. At this time, the control unit 10 also turns on the switch 443 to discharge the capacitor 442 of the integration circuit 44.

[0067] Then, in the reference hold readout circuit sequence, the control unit 10 turns off the switch 443 to prevent the capacitor 442 of the integration circuit 44 from being discharged. At this time, the control unit 10 continues to turn off the gate of the selected one scan line 413 and to switch the switch 452 to E1.

[0068] Then, in the sample-and-hold readout circuit sequence, the control unit 10 causes the gate drive circuit 42 to turn on the gate of the TFT 411 in the one scan line 413 being selected. At this time, the control unit 10 keeps the switch 443 off to prevent the capacitor 442 from discharging. The integration circuit 44 outputs the integral value of the data signal on the signal line 414 during readout. At this time, the control unit 10 also switches the switch 452 to E2, discharges the capacitor 451, and injects an opposite-phase charge into the through charge generated by turning on the gate of the TFT 411.

[0069] Then, the control unit 10 turns off the gate of the TFT 411 in the one scanning line 413 being selected by the gate drive circuit 42. At this time, the control unit 10 switches the switch 452 to E1 to charge the capacitor 451. Also, at this time, the control unit 10 continues to keep the switch 443 off to continue not to discharge the capacitor 442.

[0070] The readout circuit sequence corresponding to the selected one scanning line 413 is executed for all scanning lines 413 in order, and the actual reading imaging sequence is completed.

[0071] Returning to FIG. 4, the control unit 10 proceeds to an imaging sequence for resetting the photodiode 412 of each pixel unit 410. The control unit 10 continues to switch the switch 50 to the bias power supply 51. The control unit 10 sequentially selects the multiple scanning lines 413 one by one using the gate drive circuit 42. The control unit 10 resets the photodiode 412 by switching on and off the gate of the TFT 411 of the selected scanning line 413. The reset imaging sequence is a period during which the readout circuit 43 does not read out data signals. Therefore, the control unit 10 may switch the switch 452 to either E1 or E2. Similarly, the control unit 10 may switch the switch 443 to either on or off.

[0072] Then, the control unit 10 transitions to an accumulation imaging sequence, which is a period for waiting for charge to accumulate in the photodiode 412 of each pixel unit 410. The control unit 10 continues to switch the switch 50 to the bias power supply 51. The control unit 10 accumulates charge in the photodiode 412 without selecting the scanning line 413 or operating the TFT 411. The control unit 10 may also switch the switch 452 to either E1 or E2. Similarly, the control unit 10 may also switch the switch 443 to either on or off.

[0073] The control unit 10 then transitions to an imaging sequence for reading out (dark reading) data signals during a period when there is no exposure. The dark read data signals are acquired to calculate the difference from the actual read data signals. The dark reading imaging sequence is the same as the actual reading imaging sequence during a period when there is no exposure.

[0074] Then, to wait for the next exposure, the control unit 10 switches the switch 50 to the bias power supply 46, turns off the switch 473, and turns off the switch 443. This starts the exposure standby imaging sequence, and the imaging sequence in FIG.

[0075] As described above, the final desired radiation image data is generated from the data signals obtained in the above imaging sequence by the CDS, multiplexer, and control unit 10. The final desired radiation image data is generated based on the signal value of the main reading (sample hold voltage value - reference hold voltage value) - the signal value of the dark reading (similar difference value).

[0076] As described above, according to this embodiment, the FPD 1 includes the photodiodes 412, the readout circuit 43, the bias power supplies 46 and 51, the switch 50, and the control unit 10. The photodiodes 412 are arranged in a matrix so as to generate electric charges when exposed to radiation. The readout circuit 43 reads out signals from the photodiodes 412 for generating radiation image data. The bias power supplies 46 and 51 apply bias voltages to the plurality of photodiodes 412 via bias lines 415 and 416 connected to the photodiodes 412. The switch 50 switches between the bias power supplies 46 and 51. The control unit 10 controls the switching timing of the switch 50.

[0077] Therefore, by selecting an appropriate bias power supply according to each imaging sequence of the radiation imaging, it is possible to obtain good radiation image data with low noise.

[0078] The control unit 10 switches the switch 50 at any timing, so that the bias power supply can be switched at an appropriate timing according to each imaging sequence.

[0079] The bias power supply 46 has an exposure determination unit 49 that determines whether radiation exposure has started based on whether the amount of change (integral value) of the current flowing through the bias line 416 has exceeded a threshold value. Therefore, the bias power supply 46 can determine whether radiation exposure has started.

[0080] The readout circuit 43 has a charge injection circuit 45 that injects charge into the through charge to correct it when the photodiode 412 is switched. This makes it possible to correct the through charge that occurs when the TFT 411 switches the photodiode 412, thereby obtaining good radiation image data.

[0081] When monitoring the amount of change in current, the control unit 10 switches to the bias power supply 46 using the switch 50. When reading out a signal in the readout circuit 43, the control unit 10 switches to the bias power supply 51 using the switch 50. The bias power supply 51 does not have an exposure determination unit. Therefore, it can determine radiation exposure. However, when the readout circuit 43 reads out a data signal, the exposure determination unit 49 of the bias power supply 46 oscillates due to the inrush current of E1. Therefore, by switching to the bias power supply 51, it is possible to prevent the exposure determination unit 49 from oscillating.

[0082] The switch 50 has the characteristic of being able to accommodate bias voltage fluctuations that do not affect the image quality of the radiation image data before and after switching. The switch 50 is an FET, photoMOS relay, or mechanical relay. Therefore, good radiation image data can be obtained without image quality being affected by switching the switch 50.

[0083] The radiation imaging system 100 includes an FPD 1 and a radiation irradiation device (a main body 2 and a radiation source 3). The main body 2 and the radiation source 3 irradiate radiation to a plurality of photodiodes 412 via a subject 5. Therefore, by selecting an appropriate bias power supply according to each imaging sequence of radiation imaging, it is possible to obtain good radiation image data with low noise.

[0084] In the above description, an example has been disclosed in which a semiconductor memory is used as a computer-readable medium for the program according to the present invention, but this is not limiting. Other computer-readable media include non-volatile memory such as flash memory and portable recording media such as CD-ROMs. Furthermore, a carrier wave is also applicable to the present invention as a medium for providing data for the program according to the present invention via a communication line.

[0085] The above-described embodiments are merely examples of the radiation imaging apparatus, radiation imaging system, radiation imaging method, and program according to the present invention, and the present invention is not limited to these.

[0086] Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only, and not limitation, and the scope of the present invention should be construed by the terms of the appended claims. [Explanation of symbols]

[0087] 100 Radiography System 1 FPD 10 Control Unit 20 Control section 30 Display section 40,400 detector 41 Radiation detection unit 410 pixel section 411 TFT 412 Photodiode 413 scan lines 414 Signal Line 415,416 Bias wire 42 Gate drive circuit 43 Readout circuit 44,47 Integrating circuit 441,471 operational amplifiers 442,451,472 capacitors 443,452,50,473 Switches 444,454,474 Constant voltage source 45 Charge injection circuit 453,455 Resistance 456 Grounding part 46,51 Bias power supply 48 AD conversion section 49 Exposure Judgment Department 60 Storage section 70 Communications Department 80 Battery 90 Bus 2 Main unit 201 Storage section 202 Exposure switch 203 Display section 3 Radiation source 4 beds 5. Subject

Claims

1. a plurality of radiation detection elements arranged in a matrix so as to generate electric charges when exposed to radiation; a readout unit that reads out signals for generating radiation image data from the radiation detection elements; a plurality of bias power supplies that apply bias voltages to the radiation detection elements via bias lines connected to the radiation detection elements; a switching unit that switches the bias power supply; a control unit that controls the switching timing of the switching unit.

2. The radiation imaging apparatus according to claim 1 , wherein the control unit switches the switching unit at an arbitrary timing.

3. A first bias power supply among the plurality of bias power supplies is 2. The radiation imaging apparatus according to claim 1, further comprising an exposure determination unit that determines whether radiation exposure has started based on whether a change in current flowing through the bias line has exceeded a threshold value.

4. 4. The radiation imaging apparatus according to claim 3, wherein the readout section includes a charge injection section that injects charges into the through charges to correct them when the radiation detection elements are switched.

5. 4. The radiation imaging device according to claim 3, wherein the control unit switches to the first bias power supply using the switching unit when monitoring the amount of change in the current, and switches to a second bias power supply among the plurality of bias power supplies that does not have the exposure determination unit using the switching unit when reading out a signal in the readout unit.

6. The radiation imaging apparatus according to claim 1 , wherein the switching unit has a characteristic that bias voltage fluctuations before and after the switching do not affect the image of the radiation image data.

7. 7. The radiation imaging apparatus according to claim 6, wherein the switching unit is an FET, a photo MOS relay, or a mechanical relay.

8. The radiation imaging device according to any one of claims 1 to 7; a radiation irradiation device that irradiates the plurality of radiation detection elements with radiation via a subject.

9. a reading step of reading signals for generating radiation image data from a plurality of radiation detection elements arranged in a matrix so as to generate charges in response to radiation exposure; a control step of controlling the switching timing of a switching unit that switches between a plurality of bias power supplies that apply bias voltages to the plurality of radiation detection elements via bias lines connected to the radiation detection elements.

10. a plurality of radiation detection elements arranged in a matrix so as to generate electric charges when exposed to radiation; a readout unit that reads out signals for generating radiation image data from the radiation detection elements; a plurality of bias power supplies that apply bias voltages to the radiation detection elements via bias lines connected to the radiation detection elements; a switching unit that switches the bias power supply; a control unit that controls the switching timing of the switching unit; A program to function as a

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