Radiographic imaging system, radiographic imaging device, radiographic imaging device control method, and program storage medium

A radiographic imaging system includes plural radiographic imaging devices that image a same subject. The radiographic imaging device includes: a radiation detector; a detection unit that detects whether or not application of the radiation has been started based on electrical signals indicating detection results of sensors that detect the application of the radiation and that are disposed in correspondence to the radiation detector; a determination unit that determines whether or not noise is superimposed on the electrical signals after the detection unit has detected whether or not the application of the radiation has been started; and a communication unit that is connected to another radiographic imaging device and transmits to and receives from the other connected radiographic imaging device a detection result signal indicating the detection result of the detection unit and a determination result signal indicating the determination result of the determination unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC 119 from Japanese Patent Applications No. 2014-041013 filed on Mar. 3, 2014, and No. 2014-257920 filed on Dec. 19, 2014, the disclosures of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a radiographic imaging system, a radiographic imaging device, a radiographic imaging device control method, and a program storage medium.

Related Art

Conventionally, as radiographic imaging devices that image a subject, those that perform radiographic imaging for the purpose of medical diagnosis, for example, have been known. The radiographic imaging device detects radiation that has been applied from a radiation application device and passed through the subject to thereby capture a radiographic image. The radiographic imaging device performs radiographic imaging by collecting and reading out electric charges (charges) generated in accordance with the applied radiation.

Technologies that perform imaging using plural radiographic imaging devices for the purpose of imaging a large subject such as a long subject, for example, have been known.

For example, Japanese Patent Application Laid-open (JP-A) No. 2012-85794 describes a radiographic imaging system equipped with plural radiation detectors. JP-A No. 2011-72775 describes a radiographic imaging system in which the imaging plane is elongated by disposing plural electronic cassettes adjacent to one another.

A radiographic imaging device equipped with an application detection unit has been known, in which the application detection unit is equipped with sensor portions, which are configured by photoelectric conversion elements or the like that generate charges when radiation or light into which radiation has been converted is applied thereto, and switch elements, which read out the charges generated by the sensor portions. The application detection unit also detects that application of the radiation has been started (radiographic imaging has been started) based on the charges that have been read out from the switch elements.

In a case in which the radiographic imaging system is equipped with plural radiographic imaging devices, the entire imaging plane for imaging the subject becomes long, so there are cases in which the amount of radiation applied differs among the radiographic imaging devices. In such a case, there is a concern that even though the start of the application of the radiation has been detected in some of the radiographic imaging devices, the start of the application of the radiation is not detected in the other radiographic imaging devices.

For example, in a case of applying radiation near the center of an elongated imaging plane, the radiographic imaging device disposed near the center may detect the starts of the application of the radiation. However, the radiographic imaging devices arranged on the end sides may not detect the start of the application of the radiation, or that the timing when they detect the start of the application of the radiation may be later, because the amount of radiation applied thereto is smaller than the amount of radiation applied to the radiographic imaging device disposed near the center.

In such a case, the radiographic imaging device that has detected the start of the application of the radiation starts accumulating the charges. However, the radiographic imaging devices that have not yet detected the start of the application do not start accumulating the charges. For that reason, the imaging operations end up differing for each radiographic imaging device, and in terms of the radiographic imaging devices for imaging an elongated radiographic image overall, the imaging operations may no longer be uniform. In the technology described in JP-A No. 2012-85794, there is a concern that such a problem may arise in the case of detecting the start of the application of the radiation in each of the radiation detectors.

In the technology described in JP-A No. 2011-72775, since the start of the application of the radiation is not detected by the individual electronic cassettes, and control for accumulating the charges is performed by a separately disposed device, time is required until the charge accumulation operation is started.

SUMMARY

The present invention has been made in light of the above and provides a radiographic imaging system, a radiographic imaging device, a radiographic imaging device control method, and a program storage medium that may improve the trackability of incident radiation in a radiographic imaging system equipped with plural radiographic imaging devices that independently detect the start of application of radiation and perform imaging operations.

A first aspect of the present invention is a radiographic imaging system including plural radiographic imaging devices that image a same subject with same applied radiation, each of the plural radiographic imaging devices including: a radiation detector including plural pixels, each of the plural pixels including a sensor portion that generates a charge corresponding to an amount of applied radiation and accumulates the generated charge, and a switch element for reading out the charge from the sensor portion; a detection unit configured to detect whether or not application of the radiation has been started with respect to the radiation detector based on electrical signals indicating detection results of sensors that detect the application of the radiation and that are disposed in correspondence to the radiation detector; a determination unit configured to determine whether or not noise is superimposed on the electrical signals after the detection unit has detected whether or not the application of the radiation has been started with respect to the radiation detector; and a communication unit that is connected to another radiographic imaging device and transmits to and receives from the other connected radiographic imaging device a detection result signal indicating the detection result of the detection unit and a determination result signal indicating the determination result of the determination unit.

In the first aspect, the detection result signal and the determination result signal may be binary signals.

In the first aspect, each of the plural radiographic imaging devices may further include a control unit configured to effect control of starting accumulation of the charges generated by the sensor portions in a case in which it is determined, based on the detection result signal received via the communication unit, that the detection unit included in a first number or more of the radiographic imaging devices among the plural radiographic imaging devices has detected the start of the application of the radiation, the first number being a predetermined positive integer.

In the above-described configuration, the control unit may be further configured to effect control of continuing accumulation of the charges generated by the sensor portions in at least one case of: (a) a case in which the determination unit included in a second number or more of the plural radiographic imaging devices has determined that noise is not superimposed, the second number being a predetermined positive integer, or (b) a case in which the determination unit included in a third number or more of the radiographic imaging devices, in which the start of the application of the radiation has been detected by the detection unit, has determined that noise is not superimposed, the third number being a predetermined positive integer.

In the above-described configuration, the control unit may be further configured to effect control of discontinuing accumulation of the charges generated by the sensor portions in at least one case of: (c) a case in which the determination units included in all of the plural radiographic imaging devices, connected to the communication unit, have determined that noise is superimposed, or (d) a case in which the determination units included in all of the radiographic imaging devices, in which the start of the application of the radiation has been detected by the detection units, have determined that noise is superimposed.

In the above-described configuration, the control unit may be further configured to release the charges accumulated in the sensor portions after discontinuing accumulation of the charges generated by the sensor portions, and the detection unit may be further configured to detect whether or not the application of the radiation has been started again with respect to the radiation detector.

In the first aspect, the plural radiographic imaging devices may be housed in a single casing. In the first aspect, the sensors that detect the radiation may also be housed in the casing.

In the first aspect, the detection unit may be further configured to detect whether or not the application of the radiation has been started based on whether or not the electrical signals satisfy a preset condition.

A second aspect of the present invention is a radiation detector including plural pixels, each of the pixels including a sensor portion that generates a charge corresponding to an amount of applied radiation and accumulates the generated charge, and a switch element for reading out the charge from the sensor portion; a detection unit configured to detect whether or not application of the radiation has been started with respect to the radiation detector based on electrical signals indicating detection results of sensors that detect application of the radiation and that are disposed in correspondence to the radiation detector; a determination unit configured to determine whether or not noise is superimposed on the electrical signal after the detection unit has detected whether or not the application of the radiation has been started with respect to the radiation detector; and a communication unit that is connected to another radiographic imaging device, which images a same subject with same applied radiation, and transmits to and receives from the other connected radiographic imaging device a detection result signal indicating the detection result of the detection unit and a determination result signal indicating the determination result of the determination unit.

A third aspect of the present invention is a method of controlling radiographic imaging devices in a radiographic imaging system including plural radiographic imaging devices that image a same subject with same applied radiation and are connected to one another via communication units, each of the plural radiographic imaging devices including a radiation detector in which plural pixels are disposed, and each of the pixels including a sensor portion that generates a charge corresponding to an amount of the applied radiation and accumulates the generated charge, and a switch element for reading out the charge from the sensor portion, the method including: detecting whether or not the application of the radiation has been started with respect to the radiation detector based on electrical signals indicating detection results of sensors that detect application of the radiation and that are disposed in correspondence to the radiation detector; determining whether or not noise is superimposed on the electrical signals after detecting whether or not the application of the radiation has been started with respect to the radiation detector; and transmitting to and receiving from another connected radiographic imaging device a detection result signal indicating the detection result and a determination result signal indicating the determination result.

In the third aspect, the detection result signal and the determination result signal may be binary signals.

A fourth aspect of the present invention is a non-transitory storage medium storing a program that causes a computer to execute processing for controlling each of radiographic imaging devices in a radiographic imaging system in which plural radiographic imaging devices are connected to one another, the processing including: detecting whether or not application of radiation has been started with respect to a radiation detector of the radiographic imaging device on the basis of electrical signals indicating detection results of sensors that detect the application of the radiation and that are disposed in correspondence to the radiation detector; determining whether or not noise is superimposed on the electrical signals after detecting whether or not the application of the radiation has been started with respect to the radiation detector; and transmitting to and receiving from another connected radiographic imaging device a detection result signal indicating the detection result and a determination result signal indicating a the determination result.

According to the above aspects, the trackability of incident radiation may be improved in a radiographic imaging system equipped with plural radiographic imaging devices that independently detect the start of application of radiation and perform imaging operations.

DETAILED DESCRIPTION

First Embodiment

An example of the present embodiment will be described below with reference to the drawings.

First, the overall schematic configuration of a radiographic imaging system equipped with radiographic imaging devices of the present embodiment will be described.FIG. 1is a schematic configuration diagram illustrating the overall configuration of an example of a radiographic imaging system10of the present embodiment. The radiographic imaging system10includes an electronic cassette12equipped with plural radiographic imaging devices14(e.g.,141,142, and143). Each of the radiographic imaging devices14has a function of detecting the start of application of radiation (i.e., the start of imaging).

The radiographic imaging system10performs radiographic imaging when it is operated by a doctor or a radiologic technologist based on instructions (an imaging menu) that have been input from an external system such as a radiology information system (RIS), for example, via a console20.

The radiographic imaging system10also allows a doctor or a radiologic technologist to read a radiographic image by displaying the radiographic image that has been captured by the electronic cassette12on a display (not illustrated in the drawings) of the console20or a radiographic image reading device (not illustrated in the drawings). The non-illustrated radiographic image reading device is not particularly limited, and may be any device having a function of allowing a reader to read captured radiographic images. Examples thereof include image viewers, displays, portable terminals, and tablet computers.

The radiographic imaging system10is equipped with the electronic cassette12, a radiation application device16, and the console20.

The radiation application device16applies radiation from a radiation application source (not illustrated in the drawings) to an imaging target region of a subject18under control by the console20.

The radiation that has passed through the subject18is applied to the electronic cassette12. The radiographic imaging devices14of the electronic cassette12generates charges corresponding to the amount of radiation that has passed through the subject18, creates image information (data) representing a radiographic image based on the generated charge amount, and outputs the image data. The electronic cassette12has plural radiographic imaging devices14inside a casing13(details described later).

In the present embodiment, the image data representing the radiographic image that has been output by the electronic cassette12is input to the console20. The console20controls the electronic cassette12and the radiation application device16using the imaging menu and various types of information (data) acquired from the external system via a wireless local area network (LAN) or the like. The console20also transmits various types of information (data) to, and receives various types of information from, the electronic cassette12. The console20outputs the radiographic image acquired from the electronic cassette12to a picture archiving and communication system (PACS)22. The radiographic image imaged by the electronic cassette12is managed by the PACS22.

The console20is configured as a server computer and is equipped with a control unit, a display driver, a display, an operation panel, an input/output (I/O) unit, and an interface (I/F) unit (none of which are illustrated in the drawings).

The control unit of the console20controls the operations of the entire console20and is equipped with a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). The CPU controls the operations of the entire console20, and various programs including a control program used by the CPU are stored in advance in the ROM. The RAM temporarily stores various data, and the HDD stores and retains various data.

The display of the console20displays, under control of the display driver, imaging menus and captured radiographic images. The operation panel of the console20is provided for allowing a doctor or a radiologic technologist to input operation instructions relating to radiographic imaging and includes, for example, a touch panel, a touch pen, plural keys, and a mouse.

The I/O unit and the I/F unit of the console20transmits various types of information (data) to, and receives various types of information from, the electronic cassette12, the radiation application device16, and the PACS22by at least one of wireless communication or wired communication.

Next, the schematic configuration of the electronic cassette12of the present embodiment will be described. The electronic cassette12is equipped with the plural radiographic imaging devices14. In the present embodiment, as a specific example, a case will be described in which, the electronic cassette12is equipped with three radiographic imaging devices14(141,142, and143) as illustrated inFIG. 1. However, the number of radiographic imaging devices14is not limited to this. Since the radiographic imaging devices141to143have the same configuration, they will be called “the radiographic imaging device(s)14” when they are generically referred to, and when they are individually referred to, subscript numbers 1, 2, and 3 indicating each will be added after “14”.

The three radiographic imaging devices14are housed inside the casing13. As illustrated inFIG. 1, in the present embodiment, the radiographic imaging devices14are disposed adjacent to one another with the imaging plane facing the subject18. In the electronic cassette12, as illustrated inFIG. 1, the radiographic imaging devices14are disposed with their end portions overlying those of the adjacent radiographic imaging devices14, but the configuration of the electronic cassette12is not limited to this. In the present embodiment, the radiographic imaging devices14are disposed with their end portions overlying one another as illustrated inFIG. 1so that no spaces form in the imaging plane in order to suppress imaging omissions of the imaging region of the subject18, but in a case in which no spaces will form in the imaging plane, the end portions of the radiographic imaging devices14do not have to overlie one another.

By disposing the plural (three) radiographic imaging devices14in this way, the electronic cassette12overall provides an elongated imaging plane.

FIG. 2is a configuration diagram illustrating an example of a configuration of the radiographic imaging device14pertaining to the present embodiment. In the present embodiment, a case will be described in which an indirect conversion type radiographic imaging device14, which first converts radiation such as X-rays into light and then converts the light into charges, is adopted. InFIG. 2, a scintillator that converts the radiation into light is not illustrated.

A radiation detector26of the radiographic imaging device14includes pixels100. Each of the pixels100includes a sensor portion103, which receives the light, generates a charge, and accumulates the generated charge, and a thin-film transistor (TFT) switch74, which is a switch element for reading out the charge accumulated in the sensor portion103. In the present embodiment, the charges are generated in the sensor portions103as a result of the light into which the radiation has been converted by the scintillator being applied thereto.

The pixels100are plurally arranged in a matrix form in one direction (a gate line direction inFIG. 2) and an intersecting direction (a signal line direction inFIG. 2) intersecting the gate line direction.FIG. 2illustrates a simplified array of the pixels100, but, for example, the pixels100are arranged in an array of 1024×1024 pixels in the gate line direction and the signal line direction.

In the present embodiment, radiographic imaging pixels100A and radiation detection pixels100B functioning as an example of sensors that detect the radiation are determined in advance among the plural pixels100. InFIG. 2, the radiation detection pixels100B are encircled by dashed lines. The radiographic imaging pixels100A are used to detect the radiation and create an image expressed by the radiation. The radiation detection pixels100B are used in radiation detection for detecting the start of the application of the radiation and output charges even during the charge accumulation period (details described later).

FIG. 3is a plan view illustrating an example of the structure of the indirect conversion type radiation detector26pertaining to the present embodiment.FIG. 4is a sectional view, taken along line A-A ofFIG. 3, of one of the radiographic imaging pixels100A.FIG. 5is a sectional view, taken along line B-B ofFIG. 3, of one of the radiation detection pixels100B.

As illustrated inFIG. 4, in each of the pixels100A of the radiation detector26, a gate line101(seeFIG. 3) and a gate electrode72are formed on an insulating substrate71formed by alkali-free glass, for example. The gate line101and the gate electrode72are connected to one another (seeFIG. 3). The wiring layer in which the gate line101and the gate electrode72are formed (hereinafter this wiring layer will also be called a “first signal line layer”) is formed using Al or Cu or a laminate film whose main constituent is Al or Cu, but the configuration of the wiring layer is not particularly limited to this.

An insulating film85is formed on the entire surface of the first signal line layer. The region of the insulating film85positioned over the gate electrode72acts as a gate insulating film in the TFT switch74. The insulating film85contains SiNx, for example, and is formed by chemical vapor deposition (CVD).

A semiconductor active layer78is formed in an island form over the gate electrode72on the insulating film85. The semiconductor active layer78is the channel portion of the TFT switch74and is formed by an amorphous silicon film, for example.

A source electrode79and a drain electrode83are formed above the insulating film85. In the wiring layer in which the source electrode79and the drain electrode83are formed, a signal line73is formed together with the source electrode79and the drain electrode83. The source electrode79is connected to the signal line73(seeFIG. 3). The wiring layer in which the source electrode79, the drain electrode83, and the signal line73are formed (hereinafter this wiring layer will also be called a “second signal line layer”) is formed using Al or Cu laminate film, or a laminate film whose main constituent is Al or Cu, but the configuration of the wiring layer is not particularly limited to this. An impurity-doped semiconductor layer (not illustrated in the drawings) configured by impurity-doped amorphous silicon, for example, is formed between the source electrode79and drain electrode83and the semiconductor active layer78. The TFT switch74for switching is configured by these layers and components. The source electrode79and the drain electrode83of the TFT switch74may be reversed due to the polarity of the charge collected and accumulated by a later-described lower electrode81.

Covering the second signal line layer, on substantially the entire surface of the region (substantially the entire region) on the substrate71where the pixel100is disposed, a TFT protective film layer98is formed in order to protect the TFT switch74and the signal line73. The TFT protective film layer98contains SiNx, for example, and is formed by CVD, for example.

A coated interlayer insulating film82is formed on the TFT protective film layer98. The interlayer insulating film82is formed having a film thickness of 1 to 4 μm by a low-permittivity (having a relative permittivity εr=2 to 4) photosensitive organic material (e.g., a positive-acting photosensitive acrylic resin, a material in which a positive-acting naphthoquinone diazide photosensitizer is mixed together with a base polymer formed by a copolymer of methacrylic acid and glycidyl methacrylate).

In the radiation detector26pertaining to the present embodiment, the capacitance between metals disposed above and below the interlayer insulating film82is kept low due to the interlayer insulating film82. Usually the material used as the interlayer insulating film82also has a function as a planarizing film and also has an effect of smoothing out differences in the height of the underlying layer. In the radiation detector26, a contact hole87is formed in the interlayer insulating film82and the TFT protective film layer98in a position opposing the drain electrode83.

On the interlayer insulating film82, a lower electrode81of the sensor portion103is formed in a manner so as to fill the contact hole87and cover the pixel region. The lower electrode81is connected to the drain electrode83of the TFT switch74. There are virtually no restrictions on the material used for the lower electrode81provided that the material is conductive in a case in which a later-described semiconductor layer91has a thickness of around 1 μm. For this reason, there is no problem if the lower electrode81is formed using a conductive metal such as an Al material or indium tin oxide (ITO).

However, in a case in which the film thickness of the semiconductor layer91is thin (around 0.2 to 0.5 μm), since light absorption by the semiconductor layer91is insufficient, in order to prevent an increase in leak current caused by the application of light to the TFT switch74, it is preferable for the lower electrode81to contain an alloy or a laminate film whose main constituent is a light-blocking metal.

On the lower electrode81, a semiconductor layer91that functions as a photodiode is formed. In the present embodiment, a photodiode having a PIN structure formed by laminating an n+ layer, an i layer, and a p+ layer (n+ amorphous silicon, amorphous silicon, and p+ amorphous silicon) is used as the semiconductor layer91. The semiconductor layer91is formed by successively laminating an n+ layer91, an i layer91B, and a p+ layer91C from the lower layer. The i layer91B generates a charge (a free electron and a free hole pair) when light is applied thereto. The n+ layer91A and the p+ layer91C function as contact layers and electrically connect the i layer91B to the lower electrode81and a later-described upper electrode92, respectively.

On each of the semiconductor layers91, an upper electrode92is individually formed. A highly light-transmitting material such as ITO or indium zinc oxide (IZO), for example, is used for the upper electrode92. In the radiation detector26pertaining to the present embodiment, the sensor portion103are configured to include the upper electrode92, the semiconductor layer91, and the lower electrode81.

On the interlayer insulating film82, the semiconductor layers91, and the upper electrodes92, a coated interlayer insulating film93is formed in a manner so as to cover each of the semiconductor layers91and have openings97A in the parts corresponding to the upper electrodes92.

On the interlayer insulating film93, common electrode lines95are formed by Al or Cu or an alloy or laminate film whose main constituent is Al or Cu. The common electrode lines95have contact pads97formed thereon near the openings97A and are electrically connected to the upper electrodes92via the openings97A in the interlayer insulating film93.

Turning now to the radiation detection pixels100B of the radiation detector26, as illustrated inFIG. 5, the TFT switch74is formed with the source electrode79and the drain electrode83in contact with one another. That is, in the pixels100B, the source and drain of the TFT switch74are shorted. Consequently, in the pixels100B, the charges collected in the lower electrodes81flow out to the signal lines73regardless of the switching state of the TFT switches74.

On the radiation detector26, a protective film is formed as needed using a low light-absorbing insulating material, and the scintillator that is a radiation conversion layer is adhered to the surface using a low light-absorbing adhesive resin. Or, the scintillator may be formed by vacuum deposition. As the scintillator, a scintillator that generates fluorescent light having a relatively wide wavelength range, and which is able to generate light with an absorbable wavelength range, is preferred. Examples of scintillators include CsI:Na, CaWO4, YTaO4:Nb, BaFX:Eu (X is Br or Cl), or LaOBr:Tm and GOS. Specifically, in a case of performing imaging using X-rays as the radiation, a scintillator including cesium iodide (CsI) is preferable, and it is particularly preferable to use CsI:Ti (cesium iodide doped with thallium) or CsI:Na whose emission spectrum when X-rays are applied is 400 nm to 700 nm. The emission peak wavelength in the visible light range of CsI:Ti is 565 nm. In a case of using a scintillator including CsI as the scintillator, it is preferable to use a scintillator formed as a rectangular columnar crystal structure by vacuum deposition.

As illustrated inFIG. 4, in a case in which a penetration side sampling (PSS) method is adopted to the radiation detector26, i.e., the radiation is applied from the side on which the semiconductor layer91is formed and the radiographic image is read by the TFT substrate disposed on the back side of the surface on which the radiation is made incident, light is more strongly emitted by the upper side inFIG. 4of the scintillator that is disposed on the semiconductor layer91. In contrast, in a case in which an irradiation side sampling (ISS) method is adopted to the radiation detector26, i.e., the radiation is applied from the TFT substrate side and the radiographic image is read by the TFT substrate disposed on the front side of the surface on which the radiation is made incident, the radiation that has passed through the TFT substrate is made incident on the scintillator and the TFT substrate side of the scintillator emits light more strongly. Charges are generated at the sensor portion103of each of the pixels100disposed on the TFT substrate, due to the light generated by the scintillator. Since the light emission position of the scintillator relative to the TFT substrate is closer in the radiation detector26adapted to the irradiation side sampling method than in the radiation detector26adapted to the penetration side sampling method, the resolution of the radiographic image obtained by the imaging is higher in the radiation detector26adapted to the irradiation side sampling method.

The radiation detector26is not limited to the configuration illustrated inFIG. 3toFIG. 5and may be modified in a variety of ways. For example, in the case of adopting the penetration side sampling method, the potential for the radiation to arrive is low, instead of the above described configuration, other imaging elements such as complementary metal-oxide semiconductor (CMOS) image sensors, whose tolerance to radiation is low, and TFTs may also be combined. Or, charge-coupled device (CCD) image sensors that shift and transfer charges using shift pulses corresponding to gate signals of TFTs may also be employed as the imaging elements.

Furthermore, for example, a flexible substrate may be used for the radiation detector26. As the flexible substrate, it is preferable in terms of improving the transmittance of the radiation to apply a substrate that uses, as its base material, ultrathin glass made by the float process that has been developed in recent years. Ultrathin glass that can be applied in this case is disclosed online, for example, in “AGC Develops World's Thinnest Sheet Float Glass at Just 0.1 MM” (URL: https://www.agc.com/english/news/2011/0516e.pdf) (searched Aug. 20, 2011).

In the radiation detector26, the plural gate lines101for switching on and off the TFT switches74and the plural signal lines73for reading out the charges accumulated in the sensor portions103are disposed intersecting one another on the substrate71(seeFIG. 4). In the present embodiment, the signal lines73are disposed one for each pixel row in the one direction and the gate lines101are disposed one for each pixel row in the intersecting direction. For example, in a case in which the pixels100are arranged in an array of 1024×1024 pixels in the gate line direction and the signal line direction, there are 1024 lines of the signal lines73and 1024 lines of the gate lines101.

The common electrode lines95are disposed in parallel with the signal lines73in the radiation detector26. One end and the other end of each of the common electrode lines95are connected in parallel, with the one end of each of the common electrode lines95being connected to a power supply110that supplies a predetermined bias voltage. The sensor portions103are connected to the common electrode lines95, and the bias voltage is applied to the sensor portions103via the common electrode lines95.

Control signals for switching the TFT switches74through the gate lines101. The TFT switches74are switched as a result of the control signals flowing through the gate lines101.

Electrical signals corresponding to the charges accumulated in the pixels100flow through the signal lines73in accordance with the switching state of the TFT switches74of the pixels100. More specifically, electrical signals corresponding to the amount of charge accumulated as a result of any of the TFT switches74of the pixels100connected to the signal lines73being switched on flow through the signal lines73.

A signal detection circuit105that detects the electrical signals flowing through the signal lines73is connected to the signal lines73. Furthermore, a scan signal control circuit104that outputs to the gate lines101the control signals for switching on and off the TFT switches74is connected to the gate lines101.FIG. 2simplistically illustrates one signal detection circuit105and one scan signal control circuit104. However, for example, plural signal detection circuit105and plural scan signal control circuit104may be provided and a predetermined number (e.g., 256 lines) of the signal lines73or the gate lines101may be connected to each of them. For example, in a case in which 1024 lines of the signal lines73and 1024 lines of the gate lines101are provided, four scan signal control circuits104may be provided and 256 gate lines101may be connected to each of the four scan signal control circuits104, and four signal detection circuits105may also be provided and 256 signal lines73may be connected to each of the four signal detection circuits105.

The signal detection circuit105includes, for each of the signal lines73, amplifier circuits (not illustrated in the drawings) that amplify the input electrical signals. In the signal detection circuit105, the electrical signals input from the signal lines73are amplified by the amplifier circuits and are converted into digital signals by analog-to-digital converters (ADC).

A control unit106is connected to the signal detection circuit105and the scan signal control circuit104. The control unit106performs predetermined processing such as denoising on the digital signals into which the electrical signals have been converted in the signal detection circuit105, outputs control signals indicating signal detection timings to the signal detection circuit105, and outputs control signals indicating scan signal output timings to the scan signal control circuit104.

The control unit106of the present embodiment is a microcomputer and is equipped with a CPU, a ROM, a RAM, and a HDD (seeFIG. 9). The control unit106performs control for radiographic imaging by executing in the CPU a program stored in the ROM. The control unit106also performs, on the image data on which the aforementioned predetermined processing has been performed, processing (interpolation processing) that interpolates the image data of the radiation detection pixels100B to thereby generate an image represented by the applied radiation. That is, the control unit106generates an image represented by the applied radiation by interpolating, on the basis of the image data on which the aforementioned predetermined processing has been performed, the image data of the radiation detection pixels100B.

Furthermore, the control unit106functions as a detection unit that detects the start of the application of the radiation by the radiation application device16with respect to the radiation detector26, and as a determination unit that determines whether or not noise is superimposed (occurring).

First, a case will be described where the control unit106functions as a detection unit that detects the start of the application of the radiation. The electrical signal (charge information) of a signal line73(in the case ofFIG. 2, at least one of D2and D3; for example, D2) to which a radiation detection pixel100B is connected is detected by an amplifier circuit of the signal detection circuit105. The control unit106compares the value of the digital signal into which the electrical signal has been converted by the signal detection circuit105with a detection threshold value determined beforehand, and performs a detection as to whether or not the radiation has been applied based on whether or not the value of the digital signal is equal to or greater than the threshold value, i.e., performs the detection relating to the application of the radiation without requiring a control signal from an external system such as the console20. The detection by the control unit106as to whether or not the radiation has been applied is not limited to a comparison with a detection threshold value and may also, for example, be performed on the basis of a preset condition such as the number of detections.

The “detection” of the electrical signal in the present embodiment means sampling the electrical signal.

Next, a case will be described where the control unit106functions as a determination unit that determines whether or not noise is occurring. Specifically, the control unit106determines whether or not electrical signals generated by noise are superimposed on the electrical signals output from the radiation detection pixels100B by determining whether or not noise is occurring.

When imaging the subject18as an imaging subject, there are cases in which noise (charges) occurs in the sensor portions103due to a disturbance such as an impact, electromagnetic waves, and particularly vibration. An electrical signal (charge information) corresponding to noise (charges) that has occurred due to a disturbance has characteristics that differ from those of an electrical signal (charge information) corresponding to charges generated as a result of radiation application during normal radiographic imaging, and in particular its temporal change is different. For example, in a case in which the electrical signal is noise, there are cases in which the polarity of the electrical signal is the opposite to normal as a result of the charges reversely flowing. Furthermore, in a case in which the electrical signal is noise, the waveform representing the temporal change in the electrical signal has an amplitude.

The difference between an electrical signal resulting from the application of the radiation in the radiation detector26and an electrical signal resulting from noise will be described in greater detail.FIG. 6illustrates graphs of a temporal change in an electrical signal in a case in which radiation has been applied to the radiation detector26pertaining to the present embodiment. Graph (1) ofFIG. 6show a temporal change in an electrical signal Di, graph (2) shows a temporal change in a first-order differential value Di1of the electrical signal Di, and graph (3) shows a temporal change in a second-order differential value Di2of the electrical signal Di.FIG. 7illustrates graphs of a temporal change in an electrical signal in a case in which noise has occurred in the radiation detector26pertaining to the present embodiment. Graph (1) ofFIG. 7shows a temporal change in an electrical signal Di, graph (2) shows a temporal change in a first-order differential value Di1of the electrical signal Di, and graph (3) shows a temporal change in a second-order differential value Di2of the electrical signal Di.

As shown in graph (1) of FIG., when the radiation is applied, since the electrical signal Di increases and changes over time, the temporal change can be expressed as a function f(t) of time t. In the radiation detector26of the present embodiment, the control unit106detects the start of the application of the radiation based on whether or not the electrical signal Di has exceeded a detection threshold value. In graph (1) ofFIG. 7, the electrical signal Di generated by noise changes over time in the same way as the electrical signal Di in the case in which the radiation has been applied, and the temporal change can also be expressed as a function g(t) of time t. However, in this case the electrical signal is a sine wave whose period is constant and whose amplitude gradually decreases, which is to say the electrical signal has a damped oscillatory waveform. When the electrical signal is subjected to first-order differentiation, as shown in graph (2) ofFIG. 7, a waveform g1(t) whose phase is 90° different is obtained.

As shown in graph (2) ofFIG. 6, the first-order differential f1(t) of the function f(t) in the case in which the radiation has been applied rises abruptly because of the application of the radiation and soon becomes constant. In contrast, in the first-order differential g1(t) of the function g(t) of the waveform resulting from noise of graph (2) ofFIG. 7, only the phase is shifted and the waveform of the damping signal does not change. In a case in which the radiation has truly been applied, the first-order differential f1(t) always exhibits a positive polarity, but in the case resulting from noise, the first-order differential g1(t) reverses polarity and has an amplitude that alternates between a positive polarity and a negative polarity.

Furthermore, as shown in graph (3) ofFIG. 6, the second-order differential f2(t) of the function f(t) in the case in which the radiation has been applied behaves like a Gaussian function. In contrast, in the second-order differential g2(t) of the function g(t) of the waveform resulting from noise of graph (3) ofFIG. 7, only the phase is shifted similarly to the case of the first-order differential and the waveform of the damping signal does not change. In this way, in the case of the second-order differential also, similarly to the first-order differential, in a case in which the radiation has truly been applied, the second-order differential f21(t) always exhibits a positive polarity, but in the case resulting from noise, the second-order differential g2(t) reverses polarity, exhibits a negative polarity, and has an amplitude that alternates between a positive polarity and a negative polarity.

As will be understood by comparingFIG. 6andFIG. 7, the first-order differential f1(t) in the case in which the radiation has been truly applied is smaller than the first-order differential g1(t) in the case of noise. Similarly, the second-order differential f2(t) in the case in which the radiation has been truly applied is smaller than the second-order differential g2(t) in the case of noise. Therefore, noise judgment threshold values (th1, th2) for discriminating between the first-order differential f1(t) and the first-order differential g1(t) may be determined in advance, and the control unit106may judge that noise has occurred in a case in which the temporal change in the electrical signal has exceeded the noise judgment threshold values. Similarly, noise judgment threshold values (th3, th4) for discriminating between the second-order differential f2(t) and the second-order differential g2(t) may be determined beforehand, and the control unit106may judge that noise has occurred in a case in which the temporal change in the electrical signal has exceeded the noise judgment threshold values.

In the present embodiment, the control unit106continues detecting the electrical signals output from the radiation detection pixels100B even after detecting the start of the application of the radiation and judges whether or not noise has occurred based on whether or not the temporal change in the electrical signals in a predetermined detection period have the noise characteristic described above. Specifically, as described above, examples for such determination include determining based on whether or not the polarity of the electrical signals has become the opposite to the normal; determining based on whether or not the slope is decreasing, such as differentiating (e.g., first-order differentiation or second-order differentiation) the electrical signals that have been output in a predetermined detection period and judging that noise is not occurring in a case in which the slope can be regarded as being substantially constant or gradually increasing; and determining using noise judgment threshold values. In order to enhance the precision with which the control unit106detects the occurrence of noise, it is preferable to perform several types of judgments in combination.

Since the aforementioned predetermined detection period differs depending on the imaging conditions and the radiographic imaging devices14, it is preferable to obtain the predetermined detection period by an experiment or the like in advance, for example, as a certain percentage of the accumulation period in which the charges corresponding to the applied radiation are accumulated by the pixels100.

The noise that occurs may differ depending on the signal lines73, such as charges being generated in a particular signal line73in a case in which the radiation detector26has received a strong impact as a disturbance. Or, the noise that occurs may differ depending on the region where the pixels100are disposed. In such cases, the noise that occurs in each of the signal lines73may be obtained in advance by an experiment or the like, and the judgment criteria may be varied in accordance with each of the signal lines73. Alternatively, the region where the pixels100are disposed (the region where the radiation is applied) may be divided into plural regions, the noise that occurs may be obtained in advance by an experiment or the like for each divided region, and the judgment criteria may be varied in accordance with each of the regions. For example, the aforementioned noise judgment threshold values (th1to th4) may be determined in advance in accordance with each of the signal lines73and each of the regions. In a case in which the judgment criteria are varied in accordance with the signal lines73or each of the regions, the control unit106may judge whether or not noise is occurring in each of the signal lines73or each of the regions. In a case in which the number of judgment results indicating that noise has occurred is equal to or greater than one, or equal to or greater than a predetermined number, the control unit106may determine that noise has occurred.

In the present embodiment, three radiographic imaging devices14are connected to one another, and the control unit106of each of the radiographic imaging devices14communicates to the other radiographic imaging devices14the detection result of the start of the application of the radiation and the determination result of whether or not noise has occurred.

FIG. 8is an explanatory drawing for describing an example of a connection relationship between the radiographic imaging devices141to143.

As illustrated inFIG. 8, the three radiographic imaging devices14(141to143) are electrically connected in parallel to one another by wires. Because the radiographic imaging devices14are connected in parallel, each of the radiographic imaging devices14is equipped with one transmission terminal33and a number of reception terminals35(35aand35b) equal to the number of radiographic imaging devices14included in the electronic cassette12minus one (in the present case, 3−1=2).

In the present embodiment, the transmission terminal33of the radiographic imaging device141is connected by signal wires36to the reception terminal35aof the radiographic imaging device142and the reception terminal35bof the radiographic imaging device143. A transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device141is received as a reception signal Fa by the reception terminal35aof the radiographic imaging device142. The transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device141is received as a reception signal Fb by the reception terminal35bof the radiographic imaging device143.

In the present embodiment, flags Fx and Ft are internal signals of each device and are flags. The transmission signal Fg and the reception signals Fa and Fb are each signals defined by the flags Fx and Ft and have two types of states: a high level and a low level. In the present embodiment, the high level is assigned to “TRUE” and the low level is assigned to “FALSE”.

Similarly, the transmission terminal33of the radiographic imaging device142is connected by signal wires36to the reception terminal35bof the radiographic imaging device141and the reception terminal35aof the radiographic imaging device143. A transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device142is received as a reception signal Fb by the reception terminal35bof the radiographic imaging device141. The transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device142is received as a reception signal Fa by the reception terminal35aof the radiographic imaging device143.

The transmission terminal33of the radiographic imaging device143is connected by signal wires36to the reception terminal35aof the radiographic imaging device141and the reception terminal35bof the radiographic imaging device142. A transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device143is received as a reception signal Fa by the reception terminal35aof the radiographic imaging device141. The transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device143is received as a reception signal Fb by the reception terminal35bof the radiographic imaging device142.

In the present embodiment, the signals (Fg, Fa, and Fb) communicated via communication units30between the radiographic imaging devices14are analog signals. For that reason, the signal wires36are preferably wires suited to communicating analog signals at a high speed. In the present embodiment, hard wires are used as a specific example.

FIG. 9is a schematic configuration drawing illustrating an example of a configuration for describing the function of communicating the detection result and the determination result to the radiographic imaging devices142and143to which the radiographic imaging device141pertaining to the present embodiment is connected.

As illustrated inFIG. 9, the radiographic imaging device14(141) is equipped with a communication unit30. The communication unit30has both transmitting and receiving functions. The exemplary communication unit30includes a transmission unit32and a reception unit34.

The transmission unit32transmits, to the other radiographic imaging devices14(142and143) via the transmission terminal33, a detection result signal indicating the detection result obtained by the control unit106and a determination result signal indicating the determination result of whether or not noise has occurred.

The reception unit34receives, via the reception terminals35aand35b, detection result signals and determination result signals transmitted from the transmission units32of the other radiographic imaging devices14(142and143).

FIG. 10is a schematic configuration drawing for describing an example of the transmission unit32and the reception unit34of the present embodiment.

The transmission unit32is equipped with a buffer amp40A, a resistor element40B, and a switching element41. A power supply such as a power supply line or a power supply unit disposed inside the radiographic imaging device14is connected to the input of the buffer amp40A, and the switching element41is connected to the output of the buffer amp40A. One end of the resistor element40B is connected to a signal wire or the like (a ground as a specific example), to which a voltage corresponding to a low level that is a lower voltage than a voltage signal Vcc is applied, and the other end is connected to the switching element41.

The control unit106outputs a control signal to the switching element41of the transmission unit32based on the detection result and the determination result. In the transmission unit32, the switching on and off of the switching element41is controlled by the control signal input from the control unit106. When the switching element41is switched on, the reception units34(reception signal detection units44) of the other radiographic imaging devices14are connected by the signal wires36to the power supply via the buffer amp40A. Because of this, a high-level (e.g., “1”) transmission signal Fg corresponding to the potential of the voltage signal Vcc is transmitted from the transmission unit32of the radiographic imaging device14. In a case in which the switching element41is off, the reception units34(the reception signal detection units44) of the other radiographic imaging devices14are connected by the signal wires36to the ground via the resistor element40B, and a low-level (e.g., “0”) transmission signal Fg is transmitted.

The reception unit34of the present embodiment is equipped with the reception signal detection unit44. The reception signal detection unit44interprets the received reception signals Fa and Fb. The reception signal detection unit44may be configured by a hardware resource such as an analog or digital circuit or may be configured by embedded software. The reception signal detection unit44may be provided for each reception signal, or one reception signal detection unit44may be provided with respect to plural reception signals.

In the present embodiment, as an example, the switching element41is off in an initial state, such as when the electronic cassette12is turned on. In a case in which the control unit106has detected the start of the application of the radiation, the switching element41switches on in accordance with the control signal, and the high-level transmission signal Fg is transmitted. In contrast, in a case in which the control unit106has not detected the start of the application of the radiation, the switching element41switches off in accordance with the control signal, and the low-level transmission signal Fg is transmitted.

In a case in which the control unit106has determined that noise is not occurring, the switching element41switches on in accordance with the control signal, and the high-level transmission signal Fg is transmitted. In a case in which the control unit106has determined that noise is occurring, the switching element41switches off in accordance with the control signal, and the low-level transmission signal Fg is transmitted.

In this way, in the present embodiment, the signals communicated between the radiographic imaging devices14are binary signals, and 1-bit signals are communicated at a time.

Next, details of a flow of imaging operations of a radiographic image with the electronic cassette12of the present embodiment will be described.FIG. 11is a flowchart of an exemplary flow of imaging operations of a radiographic image.

Each of the radiographic imaging devices14of the electronic cassette12images a radiographic image by detecting the start of the application of the radiation, accumulating charges in the pixels100of the radiation detector26, and outputting a radiographic image based on image data corresponding to the accumulated charges.

In the present embodiment, when radiographic imaging is performed, the radiographic imaging devices14are notified of a transition to an imaging mode. When the radiographic imaging devices14transitions to the imaging mode, the imaging operations illustrated inFIG. 11start.

Below, the case of the specific example illustrated inFIG. 12will be described. As illustrated inFIG. 12, the radiographic imaging device141detects the start of the application of the radiation and determines that noise is occurring. The radiographic imaging device142detects the start of the application of the radiation and determines that noise is not occurring. The radiographic imaging device143does not detect the start of the application of the radiation and determines that noise is occurring.

In step S100, the radiographic imaging device14transitions to a standby state for detecting the radiation. In the next step S102, the control unit106judges whether or not the start of the application of the radiation has been detected. In the present embodiment, the flag Fx becomes a high level (TRUE) in a case in which the control unit106has detected the start of the application of the radiation, and the flag Fx remains at a low level (FALSE) in a case in which the control unit106has not detected the start of the application of the radiation. In the radiographic imaging device14, at the time when the control unit106has detected the start of the application of the radiation, the control unit106cannot distinguish between charges generated by noise and charges generated by the application of the radiation and, therefore, cannot determine whether or not noise is occurring. For that reason, the control unit106considers that the start of the application of the radiation has been detected even if the detection is a misdetection caused by noise.

In a case in which the control unit106has not detected the start of the application of the radiation, the processing proceeds to step S104where the control unit106judges whether or not a predetermined amount of time has elapsed or whether or not it has received a detection result from another radiographic imaging device14.

In the radiographic imaging system10, two cases may be given as cases in which the control unit106of the radiographic imaging device14does not detect that the application of the radiation has been started. The first is a case in which the radiation is actually not applied from the radiographic application device16, and in this case the control units106of all the radiographic imaging devices14do not detect that the application of the radiation has been started. The second is a case in which, in the local radiographic imaging device14, the amount of radiation applied is small and the control unit106does not detect that the application of the radiation has been started, while in the other radiographic imaging devices14, the control units106have detected that the application of the radiation has been started. In the second case, the reception unit34receives the detection result signals that have been transmitted by the processing of later-described step S106executed by the other radiographic imaging devices14.

Thus, because there are above two cases, in step S104the control unit106judges whether or not the reception unit34has received a detection result signal. In a case in which the reception unit34has not received a detection result signal, the control unit106returns to step S100and repeats the processing. In a case in which the reception unit34has received a detection result signal, the processing proceeds to step S110.

When the radiation is applied from the radiation application device16, the applied radiation is absorbed by the scintillator of the radiation detector26and is converted into visible light. The radiation may be applied from either the front side or the back side of the radiation detector26. The visible light into which the radiation has been converted by the scintillator is applied to the sensor portions103of the pixels100.

When the light is applied to the sensor portions103, charges are generated inside the sensor portions103. The generated charges are collected by the lower electrodes81.

In the radiographic imaging pixels100A, the drain electrode83and the source electrode79are not shorted, and the charges collected by the lower electrodes81are accumulated. However, in the radiation detection pixels100B, the drain electrode83and the source electrode79are shorted, and the charges collected by the lower electrodes81flow out to the signal lines73.

In the electronic cassette12, as described above, the electrical signals that have been output from the radiation detection pixels100B are detected by the amplifier circuits of the signal detection circuit105. The control unit106compares the detected electrical signals with a detection threshold value determined in advance and detects the start of the application of the radiation based on whether or not the electrical signals are equal to or greater than the threshold value. When the control unit106detects the start of the application of the radiation, the control unit106proceeds to step S106where, on the basis of the flag Fx, a transmission signal Fg (Fx=Fg), which is a detection result signal indicating that the control unit106has detected the start of the application, is transmitted to the other radiographic imaging devices14.

In the specific example illustrated inFIG. 12, the radiographic imaging device141transmits a high-level (TRUE) transmission signal Fg, the radiographic imaging device142receives a high-level reception signal Fa, and the radiographic imaging device143receives a high-level reception signal Fb. The radiographic imaging device142transmits a high-level (TRUE) transmission signal Fg, the radiographic imaging device141receives a high-level reception signal Fb, and the radiographic imaging device143receives a high-level reception signal Fa.

Although the radiographic imaging devices141and142both detect the start of the application of the radiation and output a high-level transmission signal Fg, the timings when they output the signals may not be simultaneous. In a case in which the amount of radiation applied to the radiation detectors26of the radiographic imaging devices141and142are different, there are cases in which the timings when the control units106detect the start of the application are different.

Since the radiographic imaging device143does not detect the start of the application of the radiation, a low-level (FALSE) signal that is an initial state is transmitted. The radiographic imaging device141receives a low-level reception signal Fa, and the radiographic imaging device142receives a low-level reception signal Fb.

In the next step S108, the control unit106judges whether or not a predetermined amount of time has elapsed or whether or not a detection result signal (in the present embodiment, a high-level signal) has been received. For example, there are cases in which, while the start of the application of the radiation is detected in the local device, the start of the application of the radiation has not been detected in any of the other radiographic imaging devices14. In this case, the local device does not receive a detection result signal (a high-level signal) and, therefore, in the present embodiment, the control unit106judges whether or not a predetermined amount of time has elapsed, such as, for example, whether or not a predetermined amount of time has elapsed since the start of the application of the radiation is detected in the local device.

The predetermined amount of time may be determined in advance in accordance with the type of imaging and the characteristics of the radiographic imaging device14. From the standpoint of ensuring real time imaging, it is preferable that the predetermined amount of time is short. The predetermined amount of time may be determined in consideration of a synchronous tolerable time difference (details described later). For example, about 1 msec is preferable and 1 msec or less is more preferable.

In step S108, in a case in which the predetermined amount of time has not elapsed or the reception unit34has not received a high-level signal as a detection result signal, the processing returns to step S108and the radiographic imaging device14stands by. In a case in which the predetermined amount of time has elapsed or the reception unit34has received a high-level signal as a detection result signal, the processing proceeds to step S110.

In step S110, the control unit106judges whether or not a predetermined number or more of the radiographic imaging devices14, including the local device, have detected the start of the application. In the present embodiment, as a specific example, the control unit106judges whether or not one or more of the radiographic imaging devices14have detected the start of the application. Consequently, the control unit106judges that the predetermined number or more of the radiographic imaging devices14have detected the start of the application of the radiation if one or more of the flag Fx and the reception signals Fa and Fb is a high level. The predetermined number is not limited to one as in the present embodiment. The predetermined number may also be determined in accordance with the type of imaging and the size of the radiation detector26(the size of the imaging plane).

In a case in which the predetermined number or more of the radiographic imaging devices14have not detected the start of the application of the radiation, the processing returns to step S100and repeats the processing. In a case in which the predetermined number or more of the radiographic imaging devices14have detected the start of the application of the radiation, the processing proceeds to step S112.

In step S112, each of the radiographic imaging devices14starts accumulating the charges generated in the pixels100in accordance with the applied radiation. In the present embodiment, in a case in which the radiographic imaging device14is accumulating charges, the flag Ft becomes a high level (TRUE), and in a case in which the radiographic imaging device14is not accumulating charges, the flag Ft becomes a low level (FALSE).

In this way, since each of the radiographic imaging devices14starts accumulating the charges, the times when the radiographic imaging devices14start accumulating the charges are synchronous, and time differences between when the devices start the accumulation (synchronous tolerable time difference) are kept within about 1 msec. In a case in which the times when all the radiographic imaging devices14start accumulating the charges are not synchronous, there are cases in which radiation loss occurs and the percentage of the amount of radiation that does not contribute to the radiographic image increases, which may no longer be ignored or may cause artifacts in the radiographic image. However, in the electronic cassette12of the present embodiment, the times when the radiographic imaging devices14start accumulating the charges are synchronized, and radiation loss can be reduced. The synchronous tolerable time difference is not limited to 1 msec. The synchronous tolerable time difference is determined by tolerable artifacts, the imaging region of the subject18, radiation application conditions or the like.

In the radiographic imaging pixels100A of the radiation detector26, the TFT switches74remain off, so the charges remain accumulated. However, in the radiation detection pixels100B, since the TFT switches74are shorted, even during the charge accumulation period (when the TFT switches74are off), the charges are output to the signal detection circuit105. At a predetermined timing the control unit106reads out, as electrical signals from the signal detection circuit105, the information of the charges that have been output from the radiation detection pixels100B.

In the next step S114, the control unit106of each of the radiographic imaging devices14judges whether or not noise has occurred. In a case in which noise is occurring, that is, in a case in which the detection of the start of the application of the radiation was a misdetection, it is necessary for the radiographic imaging device14to return as quickly as possible to the standby state to detect the start of the application of the radiation. In the case of a misdetection, during the period from the start of the accumulation of the charges to until the radiographic imaging device14returns again to the radiation application start detection standby state after detecting the start of the application of the radiation, the radiographic imaging device14becomes insensitive (cannot detect) the radiation. Therefore, in order to appropriately judge the start of the application, it is preferable for the amount of time until the radiographic imaging device14returns to the detection standby state to be as short as possible, such as, for example, 300 msec or less.

As described above, the control unit106continues detecting the electrical signals output from the radiation detection pixels100B and judges whether or not noise has occurred based on whether or not the temporal changes in the electrical signals in the predetermined detection period have the noise characteristic.

In the present embodiment, in a case in which the control unit106has determined that noise is not occurring, the flag Fx becomes a high level (TRUE), and in a case in which the control unit106has determined that noise is occurring, the flag Fx becomes a low level (FALSE).

In the next step S116, on the basis of the flag Fx, a transmission signal Fg (Fx=Fg) that is a noise determination result signal is transmitted to the other radiographic imaging devices14.

In the next step S118, the control unit106judges whether or not a predetermined amount of time has elapsed or whether or not a determination result signal (in the present embodiment, a high-level signal) has been received. In this step, similarly to step S108described above, the control unit106judges whether or not a predetermined amount of time has elapsed after making the noise occurrence determination in the local device, for example.

In step S118, in a case in which the predetermined amount of time has not elapsed or the reception unit34has not received a high-level signal as a determination result signal, the local device stands by. In a case in which the predetermined amount of time has elapsed or the reception unit34has received a high-level signal as a determination result signal, the processing proceeds to step S120.

In step S120, the control unit106judges whether or not a predetermined number or more of the radiographic imaging devices14, including the local device, have determined that noise is not occurring. In the present embodiment, as a specific example, the control unit106judges whether or not one or more of the radiographic imaging devices14have determined that noise is not occurring. That is, the control unit106judges that the predetermined number or more of the radiographic imaging devices106have determined that noise is not occurring if one or more of the flag Fx and the reception signals Fa and Fb is a high level. The predetermined number is not limited to one as in the present embodiment. The predetermined number may be determined in accordance with the type of imaging and the desired image quality of the radiographic image.

In a case in which less than the predetermined number of the radiographic imaging devices14have determined that noise is not occurring (or in a case in which the predetermined number or more of the radiographic imaging devices14have determined that noise is occurring), the processing proceeds to step S122. In the present embodiment, as a specific example, the processing proceeds to step S122in a case in which all of the radiographic imaging devices14have determined that noise is occurring.FIG. 13illustrates a specific example of the signals and flags in a case in which all of the radiographic imaging devices14have determined that noise is occurring.

In step S122, the control unit106of each of the radiographic imaging devices14discontinues accumulating the charges in the pixels100of the radiation detector26. In this case, the flag Ft becomes a low level (FALSE).

The user, such as a doctor, may be notified that noise has occurred. The method of notification is not particularly limited. For example, the notification may be displayed on the display of the console20, or an audio notification or the like may be given.

In the next step S124, the control unit106performs a reset operation, which resets the charges accumulated in the pixels100, and discards the electrical signals in order to eliminate misjudgment of the detection of the start of the application of the radiation resulting from the charges accumulated in the pixels100. After the reset operation, the processing returns to step S100, again transitions to the radiation application start detection standby state, and repeats the processing. When the reset operation is performed, the period performing the reset operation becomes a radiation insensitive period (a non-detection period). In order to shorten this period, it is preferable that an operation for resetting the plural gate lines101be performed at the same time.

In step120, in a case in which the predetermined number or more of the radiographic imaging devices14have determined that noise is not occurring, the processing proceeds to step S126and the radiographic imaging devices14continue accumulating the charges in the pixels100. In this case, the flag Ft remains at a high level (TRUE).

In the next step S128, the control unit106judges, on the basis of a timer not illustrated in the drawings, whether or not a predetermined amount of time has elapsed since the start of the application of the radiation has been detected. In a case in which the predetermined amount of time has not elapsed, the determination is negative, the processing returns to step S126and repeats the subsequent processing.

In a case in which the predetermined amount of time has elapsed, the processing proceeds to S130where the control unit106reads out the charges accumulated by the pixels100and then the processing ends. Specifically, the control unit106sequentially applies on-signals via the gate lines101to the gate electrodes72of the TFT switches74. Due to the application of the on-signals, the TFT switches74of the pixels100A are sequentially switched on, and electrical signals corresponding to the charge quantities accumulated in the pixels100A are output to the signal lines73.

Second Embodiment

In the first embodiment, a case has described in which if the predetermined number or more of the radiographic imaging devices14among all of the radiographic imaging devices14included in the electronic cassette12have detected the start of the application of the radiation, the control unit106starts accumulating the charges, and if the predetermined number or more of the radiographic imaging devices14among all of the radiographic imaging devices14have determined that noise is not occurring, the control unit106continues accumulating the charges. In the present embodiment, a case will be described in which, if a predetermined number or more of the radiographic imaging devices14, among the radiographic imaging devices14that have detected the start of the application of the radiation, have determined that noise is not occurring, the control unit106continues accumulating the charges.

The configurations of the radiographic imaging system10, the electronic cassette12, and the radiographic imaging devices14are similar to those in the first embodiment, so description thereof will be omitted.

In each of the radiographic imaging devices14of the present embodiment, since the imaging operations of a radiographic image are partially different from those of the first embodiment, only the operations that are different will be described in detail.

FIG. 14is a flowchart of an exemplary flow of imaging operations of a radiographic image. InFIG. 14, some of the operations that are similar to the imaging operations of the first embodiment (seeFIG. 11) are not illustrated.

In the imaging operations executed by the control unit106of each of the radiographic imaging devices14, as illustrated inFIG. 14, step S111is added between step S110and step S112.

In step S110, as described above, the control unit106judges whether or not the predetermined number or more of the radiographic imaging devices14, including the local device, have detected the start of the application of the radiation. In a case in which the predetermined number or more of the radiographic imaging devices14have detected the start of the application of the radiation, the processing proceeds to step S111.

In step S111, the control unit106stores information identifying which radiographic imaging devices14, including the local device, have detected the start of the application of the radiation, and thereafter proceeds to step S112. For example, the information may be stored in a storage unit located in the control unit106. The information identifying the radiographic imaging devices14is not particularly limited and, for example, may be numbers (IDs or the like) associated with the radiographic imaging devices14or may be information corresponding to the transmission terminals33and the reception terminals35(35aor35b).

Moreover, in the imaging operations in the radiographic imaging devices14of the present embodiment, as illustrated inFIG. 14, step S120A is provided instead of step S120between step S118and step S126.

In step S118, as described above, the control unit106judges whether or not a predetermined amount of time has elapsed or whether or not the reception unit34has received a high-level signal as a determination result signal. In a case in which the predetermined amount of time has elapsed or the reception unit34has received a high-level signal as a determination result signal, the processing proceeds to step S120A.

In step S120A, the control unit106judges whether or not a predetermined number or more of the radiographic imaging devices14, among the radiographic imaging devices14that have detected the start of the application of the radiation, have determined that noise is not occurring, the processing proceeds to step S126or step S122depending on the judgment. In the present embodiment, as a specific example, the control unit106judges whether or not one or more of the radiographic imaging devices14among the radiographic imaging devices14stored by step S111as having detected the start of the application of the radiation have determined that noise is not occurring.

That is, in the present embodiment, the control unit106judges whether or not the number of radiographic imaging devices14in which the start of the application of the radiation in step S102has been appropriately performed (not a misdetection) is equal to or greater than the predetermined number (one). If the number is equal to or greater than one, the processing proceeds to step S126where the radiographic imaging devices14continue accumulation of the charges in the pixels100.

Third Embodiment

In the first embodiment and the second embodiment, cases have been described in which the radiographic imaging devices14are connected in parallel to one another. In the present embodiment, a case will be described in which the radiographic imaging devices14are connected in series to one another.

The configurations of the radiographic imaging system10and the electronic cassette12are similar to those in the first embodiment, so description thereof will be omitted. In the present embodiment, since the connection of the radiographic imaging devices14is different, the configuration relating to the connection will be specifically described.

FIG. 15is an explanatory drawing for describing an example of a connection relationship between radiographic imaging devices141to143.

As illustrated inFIG. 15, in the present embodiment, three radiographic imaging devices14(141to143) are electrically connected in series to one another by wires. Because the radiographic imaging devices14are connected to another one in series, they are each equipped with one reception terminal35aregardless of the number of the radiographic imaging devices14included in the electronic cassette12.

In the present embodiment, the transmission terminal33of the radiographic imaging device141is connected by a signal wire36to the reception terminal35aof the radiographic imaging device142. A transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device141is received as a reception signal Fa by the reception terminal35aof the radiographic imaging device142.

Similarly, the transmission terminal33of the radiographic imaging device142is connected by a signal wire36to the reception terminal35aof the radiographic imaging device143. A transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device142is received as a reception signal Fa by the reception terminal35aof the radiographic imaging device143. Further similarly, the transmission terminal33of the radiographic imaging device143is connected by a signal wire36to the reception terminal35aof the radiographic imaging device141. A transmission signal Fg transmitted from the transmission terminal33of the radiographic imaging device143is received as a reception signal Fa by the reception terminal35aof the radiographic imaging device141.

Next, imaging operations of a radiographic image in the radiographic imaging devices14of the present embodiment will be described.

In the present embodiment, the detection result signal and the determination result signal are binary (1-bit) signals as in the above embodiments. However, in contrast to the above embodiments, since the radiographic imaging devices14are connected in series to one another, the detection result and the determination result are circularly referenced. Therefore, the imaging operations are partially different from those of the above embodiments.

FIG. 16andFIG. 17are flowcharts of an exemplary flow of imaging operations of a radiographic image. In the radiographic imaging devices14of the present embodiment, as in the first embodiment, the control unit106starts accumulating the charges in a case in which a predetermined number (=1) or more of the radiographic imaging devices14have detected the start of the application of the radiation. Furthermore, in the radiographic imaging devices14of the present embodiment, as in the first embodiment, the control unit106continues accumulating the charges in a case in which the predetermined number (=1) or more of the radiographic imaging devices14have determined that noise is not occurring.

Since the imaging operations in the radiographic imaging devices14of the present embodiment include operations similar to the imaging operations of the first embodiment (seeFIG. 11), similar operations are indicated as such and detailed description thereof will be omitted.

The operations of steps S200to S208correspond to the operations of steps S100to S108of the first embodiment, respectively.

In step S200, the radiographic imaging device14transitions to a standby state for detecting the radiation. In the next step S202, the control unit106judges whether or not the start of the application of the radiation has been detected. In a case in which the control unit106has not detected the start of the application of the radiation, the processing proceeds to step S204where the control unit106judges whether or not a predetermined amount of time has elapsed or whether or not a detection result has been received from another radiographic imaging device14. In a case in which a detection result signal has not been received, the processing returns to step S200and repeats the subsequent processing. In a case in which a detection result signal has been received, the processing proceeds to step S216.

In a case in which the control unit106detects the start of the application of the radiation, the processing proceeds to step S206where, on the basis of the flag Fx, a transmission signal Fg (Fx=Fg), which is a detection result signal indicating that the start of the application has been detected, is transmitted to the other radiographic imaging devices14.

In the specific example illustrated inFIG. 18, the radiographic imaging device141transmits a high-level (TRUE) transmission signal Fg and the radiographic imaging device142receives a high-level reception signal Fa. The radiographic imaging device142transmits a high-level (TRUE) transmission signal Fg and the radiographic imaging device143receives a high-level reception signal Fa. The radiographic imaging device143transmits a low-level (FALSE) transmission signal Fg and the radiographic imaging device141receives a low-level reception signal Fa. Since the radiographic imaging device143does not detect the start of the application of the radiation, the radiographic imaging device143transmits the low-level (FALSE) signal, which is an initial state and the radiographic imaging device141receives the low-level reception signal Fa.

In the next step S208, the control unit106judges whether or not a predetermined amount of time has elapsed or whether or not a detection result signal has been received. In step S208, in a case in which the predetermined amount of time has not elapsed or the reception unit34has not received a detection result signal, the processing returns to step S208and the local device stands by. In a case in which the predetermined amount of time has elapsed or the reception unit34has received a detection result signal, the processing proceeds to step S210.

In step S210, the control unit106updates the detection result (the flag Fx) based on the reception signal Fa and the flag Fx. In the present embodiment, the control unit106updates the detection result (the flag Fx) by performing an OR logic operation on the reception signal Fa and the flag Fx.

In the next step S212, similarly to step S206, the updated detection result is transmitted.

In the next step S214, the control unit106judges whether or not the detection results of all of the radiographic imaging devices14have been received. For example, the control unit106makes this judgment based on the number of receptions or whether or not a predetermined amount of time has elapsed. In the present embodiment, it may be judged that the detection results of all of the radiographic imaging devices14have been received in a case in which detection result signals have been received two times. The processing returns to step S208and repeats the subsequent processing until the detection results of all of the radiographic imaging devices14have been received. In a case in which the detection results of all of the radiographic imaging devices14have been received, the processing proceeds to step S216.

Step S216corresponds to step S110of the first embodiment. In step S216, the control unit106judges whether or not a predetermined number or more of the radiographic imaging devices14, including the local device, have detected the start of the application of the radiation. In the present embodiment, the detection result of the local device is also included in the last received reception signal Fa, and since the predetermined number is 1, the processing proceeds to step S218if the reception signal Fa is a high level (TRUE). If the reception signal Fa is a low level (FALSE), the processing returns to step S208and repeats the subsequent processing.

The operations of steps S218to S224correspond to the operations of steps S112to S118of the first embodiment, respectively.

In step S218, each of the radiographic imaging devices14starts accumulating the charges generated in the pixels100in accordance with the applied radiation. In the next step S220, the control unit106of each of the radiographic imaging devices14judges whether or not noise has occurred. In the next step S222, on the basis of the flag Fx, a transmission signal Fg (Fx=Fg) that is a noise determination result signal is transmitted to the other radiographic imaging devices14.

In the next step S224, the control unit106judges whether or not a predetermined amount of time has elapsed or whether or not a detection result signal has been received.

In step S224, in a case in which the predetermined amount of time has not elapsed or the reception unit34has not received a determination result signal, the local device stands by. In a case in which the predetermined amount of time has elapsed or the reception unit34has received a determination result signal, the processing proceeds to step S226.

In step S226, similarly to step S210, the control unit106updates the determination result (the flag Fx) on the basis of the reception signal Fa and the flag Fx. In the present embodiment, the control unit106updates the detection result (the flag Fx) by performing an OR logic operation on the reception signal Fa and the flag Fx.

In the next step S228, similarly to step S212, the updated detection result is transmitted.

In the next step S230, similarly to step S214, the control unit106judges whether or not the determination results of all of the radiographic imaging devices14have been received. For example, the control unit106makes this judgment based on the number of receptions or whether or not a predetermined amount of time has elapsed. In the present embodiment, it may be judged that the determination results of all of the radiographic imaging devices14have been received in a case in which determination result signals have been received two times. The processing returns to step S224and repeats the subsequent processing until the determination results of all of the radiographic imaging devices14have been received. In a case in which the determination results of all of the radiographic imaging devices14have been received, the processing proceeds to step S232.

Step S232corresponds to step S120of the first embodiment. In step S232, the control unit106judges whether or not a predetermined number or more of the radiographic imaging devices14, including the local device, have detected that noise is occurring. In the present embodiment, the determination result of the local device is also included in the last received reception signal Fa, and since the predetermined number is 1, the processing proceeds to step S238if the reception signal Fa is a high level (TRUE). If the reception signal Fa is a low level (FALSE), the processing proceeds to S234.

The subsequent steps S234to S242until ending the processing correspond to steps S122to S130of the first embodiment, respectively, so description thereof will be omitted.

Fourth Embodiment

In the above embodiments, cases have been described in which one radiographic imaging device14is directly connected to all of the other radiographic imaging devices14and directly transmits a transmission signal Fg to all of the other radiographic imaging devices14. In contrast, in the present embodiment, a case will be described in which the radiographic imaging devices14disposed with a predetermined separation therebetween are not directly connected with each other, but are connected via another radiographic imaging device14disposed therebetween, and transmission signals (Fga, Fgb) corresponding to the transmission signal Fg are transmitted via the intervening radiographic imaging device14.

Since the configurations of the radiographic imaging system10and the electronic cassette12are similar to those in the first embodiment, description thereof will be omitted.

In the present embodiment, since the configuration of the radiographic imaging devices14is different, the configuration of the radiographic imaging devices14will be specifically described.

FIG. 19is an explanatory drawing describing an example of a connection relationship between the radiographic imaging devices141to143pertaining to the present embodiment.

As illustrated inFIG. 19, the radiographic imaging device141is connected only to the radiographic imaging device142. Therefore, the transmission signal Fg transmitted by the radiographic imaging device141is transmitted to the radiographic imaging device143via the radiographic imaging device142.

The radiographic imaging device142is connected to the radiographic imaging devices141and143.

The radiographic imaging device143is connected only to the radiographic imaging device142. Therefore, the transmission signal Fg transmitted by the radiographic imaging device143is transmitted to the radiographic imaging device141via the radiographic imaging device142.

FIG. 20is a schematic configuration diagram describing an exemplary configuration of a function of the radiographic imaging device142for communicating a detection result and a determination result to the radiographic imaging devices141and143connected thereto.

As illustrated inFIG. 20, in the communication unit30of the radiographic imaging device142, the function of the reception unit34is different from that of the reception unit34(seeFIG. 9) in the communication unit30of the radiographic imaging device14according to the first embodiment.

The transmission unit32and the reception unit34of the radiographic imaging device142of the present embodiment have functions equivalent to those of the radiographic imaging device142of the first embodiment. Therefore, the radiographic imaging device142of the present embodiment is able to perform imaging operations (seeFIG. 11) as well as the radiographic imaging device142of the first embodiment.

In addition to the above function, the reception unit34of the radiographic imaging device142of the present embodiment has a function of directly transmitting received reception signals Fa and Fb to another radiographic imaging device14.

A reception signal Fa received by the reception unit34of the radiographic imaging device142via the reception terminal35afrom the radiographic imaging device141is transmitted to the radiographic imaging device143as a transmission signal Fga via the transmission terminal33a. The transmission signal Fga is received by the reception terminal35bof the radiographic imaging device143as a reception signal Fb.

In the radiographic imaging device141, a transmission signal Fgb corresponding to a transmission signal Fg transmitted by the radiographic imaging device143is received by the reception terminal35a, and a transmission signal Fg transmitted by the radiographic imaging device142is received by the reception terminal35b. Therefore, the radiographic imaging device141may perform imaging operations similar to the radiographic imaging device141of the first embodiment.

A reception signal Fb received by the reception unit34of the radiographic imaging device142via the reception terminal35bfrom the radiographic imaging device143is transmitted to the radiographic imaging device141as a transmission signal Fgb via the transmission terminal33b. The transmission signal Fgb is received by the reception terminal35aof the radiographic imaging device141as a reception signal Fa.

In the radiographic imaging device143, a transmission signal Fg transmitted by the radiographic imaging device142is received by the reception terminal35a, and a transmission signal Fga corresponding to the transmission signal Fg transmitted by the radiographic imaging device141is received by the reception terminal35b. Therefore, the radiographic imaging device143may perform imaging operations similar to the radiographic imaging device143of the first embodiment.

The configurations of the radiographic imaging device141and the radiographic imaging device143of the present embodiment may be made similar to that of the radiographic imaging device142. A specific example of such a case will be described using the radiographic imaging device141.FIG. 21is a schematic configuration diagram describing an exemplary configuration of a communication function of the radiographic imaging device141in this case, for communicating detection results and determination results with the radiographic imaging devices142and143connected thereto.

As illustrated inFIG. 21, since only the radiographic imaging device142is connected to the transmission terminal33of the radiographic imaging device141, the transmission unit32transmits a transmission signal Fg only to the radiographic imaging device142via the transmission terminal33.

Via the reception unit34, the reception terminal35ais connected to the transmission terminal33a, and the reception terminal35bis connected to the transmission terminal33b. However, since no transmission destination is connected to either of the transmission terminal33aor33b, transmission signals Fga and Fgb, corresponding to reception signals Fa and Fb, are not transmitted from the radiographic imaging device141.

Thus, the radiographic imaging device141and143of the present embodiment may perform imaging operations similar to the radiographic imaging device14of the first embodiment.

In this way, by configuring all of the radiographic imaging devices14(141to143) in the same configuration, the type of the radiographic imaging device14to be manufactured may be unified, making the manufacturing easy. Further, since the radiographic imaging devices14only need to be connected as described above, there is no need to consider the arranging positions of the radiographic imaging devices14.

Alternatively, the configurations of the radiographic imaging devices141and143of the present embodiment may be made similar to that of the radiographic imaging device14(seeFIG. 9) of the first embodiment.FIG. 22is a schematic configuration diagram describing an exemplary configuration of a communication function of the radiographic imaging device141in this case, for communicating detection results and determination results with the radiographic imaging devices142and143connected thereto.

As illustrated inFIG. 22, in the communication unit30of the radiographic imaging device141of the present embodiment, only the radiographic imaging device142is connected to the transmission terminal33, and the configuration is similar to the communication unit30of the first embodiment except that the transmission unit32transmits a transmission signal Fg only to the radiographic imaging device142via the transmission terminal33.

Thus, the radiographic imaging device141and143of the present embodiment may perform imaging operations similar to the radiographic imaging device14of the first embodiment.

In this way, by configuring the radiographic imaging devices141and143in the same configuration as the radiographic imaging device14of the first embodiment, more simple configuration may be adopted than that of the radiographic imaging devices142of the present embodiment, in respect that the transmission terminal33aand33bare omitted.

While the present embodiment has been described related to a case in which three radiographic imaging devices14are used, in cases in which there are three or more radiographic imaging devices14, two radiographic imaging devices14disposed with a predetermined separation (e.g., a separation corresponding to a length of a predetermined number of radiographic imaging devices14) may not be directly connected with each other, and may be connected via other radiographic imaging devices14disposed between the two radiographic imaging devices14. In this case, when transmitting a transmission signal Fg to a radiographic imaging device14that is not directly connected, for example, a signal corresponding to the transmission signal Fg may be sequentially transmitted to the adjacent radiographic imaging devices14.

The imaging operations of the radiographic imaging devices14of the present embodiment may be different from the imaging operations (seeFIG. 11) of the radiographic imaging devices14of the first embodiment. While in the imaging operations of the radiographic imaging devices14of the first embodiment each of the radiographic imaging devices14determines whether or not to continue accumulation of charges, in the following, a case in which only the radiographic imaging device142determines whether or not to continue accumulation of charges will be described as the imaging operations of the radiographic imaging devices14of the present embodiment.

FIG. 23illustrates a flowchart of an exemplary flow of imaging operations of the radiographic imaging devices14of the present embodiment. The processes similar to those in the imaging operations (seeFIG. 11) of the radiographic imaging devices14of the first embodiment are appended with similar reference numerals and detailed descriptions thereof are omitted

Herebelow, a case of a specific example illustrated inFIG. 24will be described. In the specific example ofFIG. 24, the flow until receiving determination result signals are similar to that in the specific example related to the first embodiment illustrated inFIG. 13.

In the imaging operations illustrated inFIG. 23, steps S100to S116are similar to those of the imaging operations (seeFIG. 11) of the first embodiment.

The imaging operations of the present embodiment proceed to step S117after step S116. At step S117, the control unit106determines whether or not to continue accumulation of charges. Here, information related to whether or not to continue accumulation of charges is stored in advance in a HDD or the like of the control unit106, and the control unit106determines whether or not a determination to continue accumulation of charges should be performed at the local device itself based on this information. As described above, since the radiographic imaging device142determines whether or not to continue accumulation of charges by itself, the determination is affirmative at the radiographic imaging device142and the processing proceeds to step S118.

In steps S118and S120, whether or not noise has been occurred is determined as in the first embodiment, and if the determination at step S120is affirmative, the processing proceeds to step S126where accumulation of charges is continued. Steps S126to S130are similar to those of the first embodiment.

In a case in which the determination at step S120is negative, the processing proceeds to step S121. In step S121, the control unit106transmits a discontinuation signal respectively to the radiographic imaging devices141and143and then proceeds to step S122. Here, a low level (FALSE) transmission signal Fg is transmitted to the radiographic imaging devices141and143as the discontinuation signal.

Steps S122and S124are similar to those of the first embodiment.

In this way, similarly to the first embodiment, the radiographic imaging device142determines whether or not to continue accumulation of charges and when discontinuing accumulation, transmits a discontinuation signal to the radiographic imaging devices141and143.

At the radiographic imaging devices141and143, respectively, the determination of step S114is negative and the processing proceeds to step S119. In step S119, the control unit106determines whether or not a discontinuation signal has been input. In a case in which a discontinuation signal has not been input, the determination is negative and the processing proceeds to step S126.

In a case in which a discontinuation signal has been input, the determination of step S119is affirmative and the processing proceeds to step S122. In the radiographic imaging devices141and143, respectively, in a case in which a discontinuation signal (FALSE) has been received after transmission of a determination result, accumulation of charges at the pixels100of the radiation detector26is discontinued based on the received discontinuation signal. It is preferable that the processing proceeds to step S122in a case in which a discontinuation signal is received within a predetermined amount of time at step S119.

In this way, the radiographic imaging devices141and143discontinue accumulation of charges based on the discontinuation signal received from the radiographic imaging device142.

As described in the above embodiments, the electronic cassette12of the radiographic imaging system10includes the plural (three) radiographic imaging devices14(141to143). The communication units30of the radiographic imaging devices141to143are connected to one another by the signal wires36. In the first embodiment and the second embodiment, the radiographic imaging devices14are connected in parallel to one another. In the third embodiment, the radiographic imaging devices14are connected in series to one another.

The control unit106of each of the radiographic imaging devices14detects the start of the application of the radiation and transmits a detection result signal from the transmission unit32to all of the other radiographic imaging devices14that are connected. After detecting the start of the application of the radiation, the control unit106determines whether or not noise is occurring and transmits a determination result signal from the transmission unit32to all of the other radiographic imaging devices14that are connected.

In particular, in the radiographic imaging devices14of the above embodiments, the detection result signal and the determination result signal are binary (1-bit) signals and are communicated by the signal wires36that are hard wires. Thus, the necessary information can be communicated at a high speed.

The control unit106of each of the radiographic imaging devices14starts accumulating the charges in the pixels100in a case in which one or more of the radiographic imaging devices14have detected the start of the application of the radiation, based on the detection results of all of the radiographic imaging devices14. Furthermore, the control unit106of each of the radiographic imaging devices14continues accumulating the charges in the pixels100in a case in which one or more of the radiographic imaging devices14have determined that noise is not occurring, based on the determination results of all of the radiographic imaging devices14.

Each of the radiographic imaging devices14may share the detection results and the determination results of all of the radiographic imaging devices14included in the electronic cassette12. Each of the radiographic imaging devices14may start and continue accumulating the charges based on the detection results and the determination results of all of the radiographic imaging devices14. Therefore, operations may be carried out at a high speed and delays in operations can be suppressed compared to a case in which a control unit is separately disposed outside the radiographic imaging devices14, all of the radiographic imaging devices14transmit the detection results and the determination results to the control unit, and the control unit controls the accumulation of the charges in each of the radiographic imaging devices14based on the detection results and the determination results.

Consequently, the trackability of incident radiation X is improved, radiation loss is reduced and the percentage of the amount of radiation that does not contribute to the radiographic image decreases, thereby preventing the occurrence of artifacts in the radiographic image.

Furthermore, in a case in which the start of the application of the radiation is a misdetection, the period in which the radiographic imaging devices14become insensitive to the radiation until they return again to the radiation application start detection standby state may be shortened.

Furthermore, in the first embodiment and the second embodiment, since the radiographic imaging devices14are connected in parallel to one another, the detection result signals and the determination result signals may be communicated at a higher speed.

In the third embodiment, since the number of reception terminals35can be reduced to one regardless of the number of radiographic imaging devices14, the configuration of the radiographic imaging devices14may be simplified.

In the above embodiments, the control unit106has the function of a detection unit that detects the start of the application of the radiation and the function of a determination unit that determines whether or not noise is occurring. However, it suffices for each of the radiographic imaging devices14to have the functions of a detection unit and a determination unit, and the configuration or implementation method are not particularly limited. For example, the control unit106may have either one function, and the other function may be implemented by another functional unit (a sensor, a circuit, or a microcomputer). Or, for example, both functions of the detection unit and the determination unit may be realized by another functional unit. The same functional unit may have the functions of the detection unit and the determination unit, or separate functional units may have the functions of the detection unit and the determination unit.

The method of detecting the start of the application and the method of determining whether or not noise is occurring are not limited to the above embodiments. Examples of other methods include methods (1) to (7) described below.

(1) Pixels arbitrarily selected from the radiographic imaging pixels (two-dimensional array) are used as dedicated pixels for radiation detection. In this case, the radiographic imaging pixels and the radiation detection pixels have the same configuration.

(2) Pixels arbitrarily selected from the radiographic imaging pixels (two-dimensional array) are given a configuration in which they are also capable of detecting start of radiation application. That is, some of the pixels are used as pixels for both radiographic imaging and radiation detection. One method for implementing this may be, for example, to divide the sensor portions of the selected pixels into two and use the sensor portions selectively in the case of radiographic imaging and the case of radiation detection. Or, for example, additional TFT switches may be provided in the selected pixels and the start of radiation application may be detected on the basis of leak current in the additionally disposed TFT switches.

(3) Dedicated sensors for radiation detection are arbitrarily disposed between (e.g., in interstices between) the radiographic imaging pixels (two-dimensional array).

In methods (2) and (3), with respect to the configuration of the radiation detector used in these methods, only the selected pixels (the selected interstices) may have this kind of configuration, or the sensor portions and the TFT switches may be repeatedly patterned (i.e., having the same configuration) and the connection thereof may be configured to retrieve the charges only from the selected pixels.

(4) A detection unit is separately disposed without changing the configuration of the radiographic imaging pixels (two-dimensional array) and the interstices between them. Examples of detection methods include detecting the bias current, detecting the gate current, and detecting the leak current of the radiation detector.

(5) A radiographic imaging control unit may also be used without separately disposing a detection unit and without changing the configuration of the radiographic imaging pixels (two-dimensional array) and the interstices between them. Examples of detection methods include detecting the leak current.

Methods (1) to (5) all correspond to a case in which sensors that generate charges (electrical signals) in response to an amount of applied radiation are disposed inside the radiation detector. The methods are not limited to these, and a sensor may be disposed outside the radiation detector as in methods (6) and (7) described below.

(6) A radiation detection sensor is disposed outside the radiation detector. For example, a radiation detection sensor may be disposed at the bottom surface of the radiation detector to which the radiation is not applied.

(7) A vibration sensor is disposed outside the radiation detector. The vibration sensor cannot detect the start of the application of the radiation but may be used to determine whether or not noise is occurring.

In any of the methods (1) to (7), the radiation may be detected in a case in which the gates of the TFT switches are on, or the radiation may be detected in a case in which the gates are off.

The method of communicating the detection result signals and the determination result signals is not limited to the above embodiments provided that both signals are binary (1-bit) signals and can be communicated at a high speed. For example, optical fibers may be used as the signal wires36. Or, for example, a photocoupler in which a transmission end is a light source such as a light emitting diode (LED) and a reception end is a sensor such as a phototransistor may be provided, and communication may be performed by switching on and off the light source. The signals may also be transmitted as radio waves. Alternatively, a digital circuit may be configured, unique communication protocol in which unnecessary communication headers are deleted from Ethernet (registered trademark) or Bluetooth (registered trademark) may be created, and wire or wireless communication may be performed using these configurations.

In the above embodiments, the determination of whether or not noise is occurring is performed only once. However, embodiments are not limited thereto, and the determination of whether or not noise is occurring may be repeatedly performed. For example, even during the charge accumulation period, the determination of whether or not noise is occurring may be continued in the same way as described above, with all of the radiographic imaging devices14sharing the determination results. By continuing the determination, imaging may be quickly cancelled and restart of imaging may be quickly performed in a case in which noise has occurred during imaging (during the accumulation period).

In a case in which the radiographic imaging devices14are connected in series to one another as in the third embodiment, the control unit106may decide to continue accumulating the charges on the basis of the determination results of the radiographic imaging devices14that have detected the start of the application of the radiation as in the second embodiment. Or, in a case in which the radiographic imaging devices14are connected in series to one another as in the third embodiment, rather than performing circular referencing as described above, the control unit106may store the received detection result signals and determination result signals, and after receiving all of the detection result signals and determination result signals, determine whether or not to start and continue accumulating the charges based on the stored signals.

In the above embodiments, a case has been described in which, as illustrated inFIG. 1, the plural radiographic imaging devices14are arranged adjacent to one another in one direction parallel to the subject18, but the arranged positions and arranging method are not particularly limited thereto. For example, four radiographic imaging devices14may be arranged in a manner in which two in one direction parallel to the subject18and two in a direction intersecting the one direction (2×2=4 radiographic imaging devices).

In the above embodiments, a case has been described in which the plural radiographic imaging devices14are disposed in the casing13of the one electronic cassette12, but the present disclosure may also be applied to a radiographic imaging system including plural electronic cassettes. For example, a configuration may be made in which a long imaging plane is provided by arranging plural electronic cassettes, each having one radiographic imaging device, adjacent to one another. Specific example configurations of cases in which plural electronic cassettes are arranged adjacent to one another are illustrated inFIG. 25andFIG. 26.FIG. 25andFIG. 26illustrates cases in which three electronic cassettes62(621to623) are arranged adjacent to one another.

In both of the cases illustrated inFIG. 25andFIG. 26, the signal wires (which correspond to the signal wires36of the above embodiments), transmission terminals, and reception terminals connecting each of the electronic cassettes62are preferably disposed inside the electronic cassettes62, and the electronic cassettes62are preferably connected to one another via connection portions64. For example, signal wires for interconnecting the electronic cassettes62may be disposed in inner walls of the electronic cassettes62, and the signal wires may be connected to the transmission terminals and reception terminals.

The above embodiments have been described as cases in which the present disclosure is applied to the indirect conversion type radiation detector26that converts the radiation into light and then converts the light into charges. However, embodiments are not limited to this and, for example, the present disclosure may be applied to a direct conversion type radiation detector that uses, as a photoelectric conversion layer that absorbs and converts radiation into charges, a material such as amorphous selenium that directly converts radiation.

In addition, the configurations and operations of the radiographic imaging system10, the electronic cassette12, and the radiographic imaging devices14described in the embodiments are examples and, obviously, may be modified depending on the situation without departing from the spirit of the present disclosure.

Furthermore, in the embodiments, the radiation is not particularly limited, and X-rays or gamma rays may be applied.