JP2014068857A - Radiation image photographing control device, radiation moving image photographing system, defect determination method for radiation image photographing apparatus, and radiation image photographing control program - Google Patents

Abstract

An object of the present invention is to make it possible to easily detect a defect of a pixel for detecting a radiation dose.
The output value of the radiation dose detection pixel with respect to the dose has a linear characteristic when it is normal, but a predetermined high dose region or a predetermined low dose with respect to the dose due to the influence of defects. In this region, the linearity may not be maintained, and the linearity is used to determine the defect of the radiation dose detection pixel. That is, the defect of the radiation dose detection pixel is detected based on the pixel value of the radiation dose detection pixel at at least one of the predetermined high dose and low dose and the predetermined normal value.
[Selection] Figure 9

Description

  The present invention relates to a radiographic imaging control device, a radiographic imaging system, a defect determination method for a radiographic video imaging device, and a radiographic imaging control program.

  In recent years, radiation detectors such as FPD (Flat Panel Detector) that can arrange radiation sensitive layers on TFT (Thin Film Transistor) active matrix substrates and convert radiation dose into digital data (electrical signals) In some cases, a radiation image capturing apparatus that captures a radiation image represented by the amount of irradiated radiation using this radiation detector has been put into practical use.

  Some of such radiographic imaging apparatuses are provided with a radiation irradiation amount detection pixel for monitoring radiation in order to control the start and stop of radiation irradiation.

  By the way, defective pixels can be cited as one cause of the deterioration of the image quality of a radiation image in a radiation detector such as an FPD. In other words, it is impossible to obtain an appropriate image in the portion where the defective pixel is generated, and when the defective pixel is generated in the irradiation dose detection pixel, radiation irradiation is started and stopped accurately. Will not be able to.

  As such a defective pixel detection method, for example, techniques described in Patent Document 1 and Patent Document 2 have been proposed.

  In the technique described in Patent Document 1, when detecting a defect in a radiographic image capturing pixel, a reference value of a detection image is determined in advance, and a difference from the reference value has a predetermined threshold value in the detection image. It has been proposed to detect more pixels as defective pixels.

  In the technique described in Patent Document 2, a radiation source that irradiates radiation, a solid detector that detects radiation irradiated from the radiation source and generates a radiation image, and a radiation dose irradiated from the radiation source are detected. A radiation source control unit that controls the amount of radiation emitted from the radiation source based on the output of the AEC sensor, and a reference output storage unit that stores a reference output range that defines a range of output serving as a reference for the solid state detector and the AEC sensor And an abnormality detector capable of detecting any abnormality of the solid detector, the AEC sensor, or the radiation source by comparing the output of the solid detector and the AEC sensor with the reference output range. .

JP 2010-226634 A JP 2008-228750 A

  However, although the defect of a radiographic imaging pixel or an AEC sensor can be detected by the techniques of Patent Literature 1 and Patent Literature 2, the radiation dose detection pixel has a plurality of radiation doses without using a switching element. Some of the detection pixels detect signals that flow through the same signal wiring. In the radiation dose detection pixel having such a configuration, the values of a plurality of pixels are added. When a defect occurs in the detection pixel, it may be difficult to detect the defective pixel.

  In addition, the radiation irradiation amount detection pixel is not different from the pixel value of a normal pixel depending on the irradiation dose, and it may be difficult to determine a defect.

  The present invention has been made in consideration of the above-described facts, and an object of the present invention is to make it possible to easily detect a defect in a radiation dose detection pixel.

  In order to achieve the above object, the radiographic imaging device of the present invention is experimentally designed to detect the radiation dose for detecting the radiation dose, and the output when the defect occurs is nonlinear. Defects in the radiation dose detection pixel based on the pixel value of the radiation dose detection pixel obtained at the time of photographing with at least one of a predetermined high dose and low dose determined and a predetermined normal value Detecting means for detecting.

  According to the radiographic imaging device of the present invention, the radiation dose detection pixel is used to detect the radiation dose.

  By the way, the radiation dose detection pixel has a linear characteristic when it is normal, but the linearity cannot be maintained in a predetermined high-dose region or a low-dose region with respect to the dose due to a defect. There is. Therefore, the detection means uses this linearity to determine the defect of the radiation dose detection pixel. That is, in the detection means, the output when the defect occurs is non-linear, and the radiation dose detection pixel when the image is taken with at least one of a predetermined high dose and low dose determined experimentally. Based on the pixel value and a predetermined normal value, a defect in the radiation dose detection pixel is detected. As a result, it is possible to easily detect a defect in the radiation dose detection pixel.

  For example, the detection means may change a pixel value with respect to a change in dose from each pixel value of the radiation dose detection pixel when imaging is performed with two different doses including at least one of a predetermined high dose and low dose. The radiation dose detection is performed by comparing the obtained change rate and the reference change rate obtained from the normal value for each dose and representing the change in pixel value with respect to the dose change. It is also possible to detect defective pixels.

  In addition, the normal value is a predetermined value, a pixel value of a radiation image capturing pixel for capturing a radiation image around the radiation exposure detection pixel, or a pixel value of another radiation irradiation detection pixel. May be applied.

  Further, the detection means detects a defect by comparing a pixel value of the radiation dose detection pixel when photographing with at least one of the high dose and the low dose and a predetermined normal value. When a defect in the radiation dose detection pixel is detected by one detection means and the first detection means, the image is taken at two different doses including at least one of the high dose and the low dose. The pixel value for the change in dose obtained from the pixel value of each radiation dose detection pixel that represents the change rate indicating the change in the pixel value with respect to the change in the dose, and the obtained change rate and the normal value for each dose. A second detection unit that detects a defect in the radiation dose detection pixel by comparing a reference change rate that represents a change in the radiation dose. That is, defect detection can be performed more accurately by performing two-stage detection.

  Further, the detection means detects a defect by comparing a pixel value of the radiation dose detection pixel when photographing with at least one of the high dose and the low dose and a predetermined normal value. 1 represents a change in the pixel value with respect to a change in dose from each pixel value of the radiation dose detection pixel when the image is taken with two different doses including at least one of the high dose and the low dose. By determining the rate of change and comparing the calculated rate of change with a reference rate of change that represents a change in pixel value with respect to a change in dose, obtained from the normal value for each dose, the radiation dose detection pixel And detecting a defect of the radiation dose detection pixel based on the detection results of the first detection unit and the second detection unit. Moyo . Even if it does in this way, since a defect is detected by two types of methods, a defect can be detected more accurately.

  The radiation dose detection pixel may include a sensor unit that generates a charge corresponding to the irradiated radiation and directly outputs the generated charge to the signal line.

  In addition, this invention is good also as a radiographic imaging system provided with the above-mentioned radiographic imaging apparatus and the radiation irradiation means to irradiate the said radiographic imaging apparatus through a subject.

  On the other hand, the defect determination method of the radiographic imaging device of the present invention uses a radiographic imaging device that includes a radiation dose detection pixel for detecting the radiation dose when a defect has occurred. An acquisition step of acquiring a pixel value of the radiation dose detection pixel when imaged with at least one of a predetermined high dose and low dose determined experimentally; A detecting step of detecting a defect of the radiation dose detection pixel by a detecting means based on the acquired pixel value and a predetermined normal value.

  According to the defect determination method of the radiographic image capturing apparatus of the present invention, in the obtaining step, a defect occurs using the radiographic image capturing apparatus including the radiation dose detection pixel for detecting the radiation dose. The pixel value of the radiation dose detection pixel is acquired when imaging is performed with at least one of a predetermined high dose and low dose determined experimentally.

  As described above, the radiation dose detection pixel has a linear characteristic in a normal state, but maintains linearity in a predetermined high-dose region or a low-dose region with respect to the dose due to the defect. In some cases, the detection step determines a defect in the radiation dose detection pixel using this linearity. That is, in the detection step, a defect in the radiation dose detection pixel is detected by a detection means based on the pixel value acquired in the acquisition step and a predetermined normal value. As a result, it is possible to easily detect a defect in the radiation dose detection pixel.

  For example, the detection step includes a change in pixel value with respect to a change in dose from each pixel value of the radiation dose detection pixel when imaging is performed with two different doses including at least one of a predetermined high dose and low dose. The radiation dose detection is performed by comparing the obtained change rate and the reference change rate obtained from the normal value for each dose and representing the change in pixel value with respect to the dose change. It is also possible to detect defective pixels.

  In addition, the normal value is a predetermined value, a pixel value of a radiation image capturing pixel for capturing a radiation image around the radiation exposure detection pixel, or a pixel value of another radiation irradiation detection pixel. May be applied.

  Further, the detection step detects a defect by comparing a pixel value of the radiation dose detection pixel when the radiographing is performed with at least one of the high dose and the low dose, and a predetermined normal value. When a defect in the radiation dose detection pixel is detected in one detection step and in the first detection step, the image is taken at two different doses including at least one of the high dose and the low dose. A change rate indicating a change in pixel value with respect to a change in dose is obtained from each pixel value obtained by obtaining each pixel value of the radiation dose detection pixel, and the obtained change rate and the normal value for each dose A second detection step of detecting a defect of the radiation dose detection pixel by comparing a reference change rate representing a change in pixel value with respect to a change in dose obtained from . That is, defect detection can be performed more accurately by performing two-stage detection.

  Further, the detection step detects a defect by comparing a pixel value of the radiation dose detection pixel when the radiographing is performed with at least one of the high dose and the low dose, and a predetermined normal value. From each pixel value acquired by acquiring each pixel value of the radiation irradiation amount detection pixel when the image is taken with two different doses including one detection step and at least one of the high dose and the low dose The rate of change representing the change in pixel value relative to the change in dose is obtained, and the obtained rate of change is compared with the reference rate of change representing the change in pixel value relative to the change in dose obtained from the normal value for each dose. A second detection step of detecting a defect of the radiation dose detection pixel, and based on the detection results of the first detection step and the second detection step, It may be detected defects linear dose detection pixels. Even if it does in this way, since a defect is detected by two types of methods, a defect can be detected more accurately.

  In addition, this invention is good also as a radiographic imaging program for functioning a computer as the said detection means in the above-mentioned radiographic imaging apparatus.

  As described above, the present invention has an excellent effect that the defect of the radiation dose detection pixel can be easily detected.

It is a schematic block diagram which shows schematic structure of an example of the radiographic imaging system which concerns on this Embodiment. It is a block diagram which shows an example of the whole structure of the electronic cassette concerning this Embodiment. It is a top view which shows an example of a structure of the radiation detector concerning this Embodiment. It is line sectional drawing of an example of the radiation detector which concerns on this Embodiment. It is line sectional drawing of an example of the radiation detector which concerns on this Embodiment. It is a schematic block diagram which shows an example of schematic structure of the signal detection circuit of the radiographic imaging apparatus which concerns on this Embodiment. It is a functional block diagram which shows the structural example of the control part in the electronic cassette of this Embodiment. It is a figure which shows the figure where the pixel for a some radiation irradiation amount detection exists on 1 line. (A) is a figure for demonstrating the defect of the radiation dose detection pixel in a high dose area | region, (B) is a figure for demonstrating the defect of the radiation dose detection pixel in a low dose area | region. is there. It is a flowchart which shows an example of the defect detection process of the radiation irradiation amount detection pixel performed in a control part. It is a flowchart which shows the modification of the defect detection process of the radiation irradiation amount detection pixel performed in a control part. (A) is a figure which shows the other pixel structural example, (B) is a figure which shows the circuit structure in another pixel structural example, (C) is a figure which shows the modification of a pixel structure.

  Hereinafter, an example of the present embodiment will be described with reference to the drawings.

  First, a schematic configuration of the entire radiographic image capturing system including the radiographic image processing apparatus of the present embodiment will be described. FIG. 1 shows a schematic configuration diagram of an overall configuration of an example of a radiographic imaging system according to the present exemplary embodiment. The radiographic image capturing system 10 of the present embodiment can capture still images in addition to radiographic images as moving images. Note that in this embodiment, a moving image refers to displaying still images one after another at a high speed and recognizing them as moving images. The still images are captured, converted into electric signals, transmitted, and transmitted. The process of replaying a still image is repeated at high speed. Therefore, so-called “frame advance”, in which the same area (part or all) is photographed a plurality of times within a predetermined time and continuously reproduced depending on the degree of “high speed”, is also included in the moving image. Shall. Moreover, the radiographic imaging system 10 of this Embodiment has the function in which the electronic cassette 20 itself detects a radiation irradiation start (imaging start) and a radiation irradiation stop (imaging end). .

  The radiographic imaging system 10 of the present exemplary embodiment is based on an instruction (imaging menu) input from an external system (for example, RIS: Radiology Information System) via the console 16 and a doctor or radiographer. It has a function of taking a radiographic image by an operation such as the above.

  The radiographic image capturing system 10 of the present embodiment has a function of causing a doctor, a radiographer, or the like to interpret a radiographic image by displaying the captured radiographic image on the display 50 of the console 16 or the radiographic image interpretation device 18. It is what you have.

  The radiographic imaging system 10 according to the present exemplary embodiment includes a radiation generation device 12, a radiographic image processing device 14, a console 16, a storage unit 17, a radiographic image interpretation device 18, and an electronic cassette 20.

  The radiation generator 12 includes a power supply 22, a radiation irradiation controller 23, and a high voltage generator 24. The radiation irradiation control unit 23 has a function of irradiating the imaging target region of the subject 30 on the imaging table 32 from the radiation irradiation source 25 based on the control of the radiation control unit 62 of the radiation image processing apparatus 14. ing. The radiation irradiation control unit 23 according to the present embodiment supplies the current supplied from the power supply 22 to the high voltage generator 24, supplies the high voltage generated by the high voltage generator 24 to the radiation irradiation source 25, and generates radiation. X is generated. The power source 22 may be either an AC power source or a DC power source. Moreover, the high voltage generator 24 may be any of a single-phase transformer system, a three-phase transformer system, an inverter system, and a capacitor system. In addition, FIG. 1 shows a stationary radiation generator 12, but the invention is not limited to this, and the radiation generator 12 may be of a mobile type.

  The radiation X transmitted through the subject 30 is applied to the electronic cassette 20 held by the holding unit 34 inside the imaging table 32. The electronic cassette 20 has a function of generating a charge corresponding to the dose of the radiation X transmitted through the subject 30, generating image information indicating a radiation image based on the generated charge amount, and outputting the image information. The electronic cassette 20 according to the present embodiment includes a radiation detector 26. In the present embodiment, “dose” refers to radiation intensity, for example, radiation applied at a predetermined tube voltage and a predetermined tube current per unit time.

  In the present embodiment, image information indicating a radiographic image output from the electronic cassette 20 is input to the console 16 via the radiographic image processing device 14. The console 16 according to the present embodiment uses the radiographing device 12 and the electronic cassette 20 using an imaging menu and various information acquired from an external system (RIS) or the like via wireless communication (LAN: Local Area Network) or the like. It has a function to perform control. In addition, the console 16 according to the present embodiment has a function of transmitting / receiving various information including image information of a radiographic image to / from the radiographic image processing apparatus 14 and a function of transmitting / receiving various information to / from the electronic cassette 20. have.

  The console 16 of the present embodiment is configured as a server computer, and includes a control unit 49, a display driver 48, a display 50, an operation input detection unit 52, an operation panel 54, an I / O unit 56, and an I / F unit 57. , And an I / F unit 58.

  The control unit 49 has a function of controlling the operation of the entire console 16 and includes a CPU, a ROM, a RAM, and an HDD. The CPU has a function of controlling the operation of the entire console 16, and various programs including a control program used by the CPU are stored in advance in the ROM. The RAM has a function of temporarily storing various data, and the HDD (hard disk drive) has a function of storing and holding various data.

  The display driver 48 has a function of controlling display of various information on the display 50. The display 50 according to the present embodiment has a function of displaying an imaging menu, a captured radiographic image, and the like. The operation input detection unit 52 has a function of detecting an operation state with respect to the operation panel 54. The operation panel 54 is used by a doctor, a radiographer, or the like to input operation instructions related to radiographic image capturing. In the present embodiment, the operation panel 54 includes, for example, a touch panel, a touch pen, a plurality of keys, a mouse, and the like. When configured as a touch panel, it may be configured the same as the display 50.

  The I / O unit 56 and the I / F unit 58 transmit and receive various types of information to and from the radiographic image processing apparatus 14 and the radiation generation apparatus 24 through wireless communication, and also perform image information with the electronic cassette 20. And the like. The I / F unit 57 has a function of transmitting / receiving various types of information to / from the RIS.

  The control unit 49, the display driver 48, the operation input detection unit 52, the I / F unit 58, and the I / O unit 56 are connected so that information can be exchanged with each other via a bus 59 such as a system bus or a control bus. Has been. Therefore, the control unit 49 controls the display of various information on the display 50 via the display driver 48 and controls the transmission / reception of various information with the radiation generator 12 and the electronic cassette 20 via the I / F unit 58. Can be performed respectively.

  The radiographic image processing apparatus 14 according to the present embodiment has a function of controlling the radiation generating apparatus 12 and the electronic cassette 20 based on an instruction from the console 16 and also stores the radiographic image received from the electronic cassette 20 into the storage unit 17. And the function of controlling the display on the display 50 of the console 16 and the display on the radiographic image interpretation device 18.

  The radiographic image processing apparatus 14 according to the present embodiment includes a system control unit 60, a radiation control unit 62, a panel control unit 64, an image processing control unit 66, and an I / F unit 68.

  The system control unit 60 has a function of controlling the entire radiographic image processing apparatus 14 and a function of controlling the radiographic image capturing system 10. The system control unit 60 includes a CPU, ROM, RAM, and HDD. The CPU has a function of controlling operations of the entire radiographic image processing apparatus 14 and the radiographic imaging system 10, and various programs including a control program used by the CPU are stored in advance in the ROM. The RAM has a function of temporarily storing various data, and the HDD has a function of storing and holding various data. The radiation control unit 62 has a function of controlling the radiation irradiation control unit 23 of the radiation generator 12 based on an instruction from the console 16 or the like. The panel control unit 64 has a function of controlling the electronic cassette 20 based on an instruction from the console 16 or the like. The image processing control unit 66 has a function of performing various image processing on the radiation image.

  The system control unit 60, the radiation control unit 62, the panel control unit 64, and the image processing control unit 66 are connected to each other via a bus 69 such as a system bus or a control bus so that information can be exchanged.

  The storage unit 17 of the present embodiment has a function of storing a captured radiographic image and information related to the radiographic image. An example of the storage unit 17 is an HDD.

  The radiographic image interpretation device 18 according to the present embodiment is a device having a function for a radiographer to interpret a captured radiographic image, and is not particularly limited, and examples thereof include a so-called radiogram interpretation viewer and console. The radiographic image interpretation apparatus 18 of this embodiment is configured as a personal computer, and, like the console 16 and the radiographic image processing apparatus 14, a CPU, ROM, RAM, HDD, display driver, display 40, and operation input detection. Unit, operation panel 42, I / O unit, and I / F unit. In FIG. 1, only the display 40 and the operation panel 42 are shown, and other descriptions are omitted in order to avoid complicated description.

  Next, a schematic configuration of the electronic cassette 20 according to the present embodiment will be described. In FIG. 2, the schematic block diagram of an example of the electronic cassette 20 of this Embodiment is shown. In the present embodiment, a case will be described in which the present invention is applied to an indirect conversion radiation detector 26 that once converts radiation such as X-rays into light and converts the converted light into electric charges. In the present embodiment, the electronic cassette 20 includes an indirect conversion type radiation detector 26. In FIG. 2, description of a scintillator that converts radiation into light is omitted.

  The electronic cassette 20 according to the present embodiment detects synchronization of radiographic image capturing operations, such as detecting the start of radiation and starting radiographic imaging when radiation X irradiation to the radiation detector 26 is started. Perform control processing. In addition, the electronic cassette 20 detects an irradiation amount of the radiation X to the radiation detector 26 and terminates the capturing of the radiation image based on the accumulated irradiation amount, for example, AEC (Automatic Exposure Control) for controlling the capturing operation of the radiation image. Perform control processing.

  The radiation detector 26 includes a sensor unit 103 that receives light to generate electric charge, accumulates the generated electric charge, and a TFT switch 74 that is a switching element for reading out the electric charge accumulated in the sensor unit 103. A plurality of pixels 100 constituted by the above are arranged in a matrix. In the present embodiment, the sensor unit 103 generates electric charges when irradiated with light converted by the scintillator.

  A plurality of pixels 100 are arranged in a matrix in one direction (gate wiring direction in FIG. 2) and in a direction intersecting with the gate wiring direction (signal wiring direction in FIG. 2). In FIG. 2, the arrangement of the pixels 100 is shown in a simplified manner. For example, 1024 × 1024 pixels 100 are arranged in the gate wiring direction and the signal wiring direction.

  In the present embodiment, among the plurality of pixels 100, a radiation image capturing pixel 100A and a radiation irradiation amount detection pixel 100B are determined in advance. In FIG. 2, the radiation dose detection pixel 100B is surrounded by a broken line. The radiation image capturing pixel 100A is used to detect the radiation X and generate an image indicated by the radiation X. The radiation irradiation amount detection pixel 100B is a pixel used for detection of the radiation X for detecting the start or stop of irradiation of the radiation X, and is a charge accumulation period regardless of whether the TFT switch 74 is on or off. However, it is a pixel that outputs electric charge, and in this embodiment, the source and drain of the TFT switch 74 are short-circuited.

  The radiation detector 26 has a plurality of gate wirings 101 for turning on / off the TFT switch 74 and a plurality for reading out the charges accumulated in the sensor unit 103 on the substrate 71 (see FIG. 4). The signal wiring 73 is provided so as to cross each other. In this embodiment, one signal wiring 73 is provided for each pixel column in one direction, and one gate wiring 101 is provided for each pixel column in the cross direction. For example, the pixel 100 is arranged in the gate wiring direction. When 1024 × 1024 are arranged in the signal wiring direction, 1024 signal wirings 73 and 1024 gate wirings 101 are provided.

  Further, the radiation detector 26 is provided with a common electrode wiring 95 in parallel with each signal wiring 73. The common electrode wiring 95 has one end and the other end connected in parallel, and one end connected to a bias power supply 110 that supplies a predetermined bias voltage. The sensor unit 103 is connected to the common electrode wiring 95, and a bias voltage is applied via the common electrode wiring 95.

  A scan signal for switching each TFT switch 74 flows through the gate wiring 101. In this way, each TFT switch 74 is switched by the scan signal flowing through each gate wiring 101.

  An electric signal corresponding to the electric charge accumulated in each pixel 100 flows through the signal wiring 73 in accordance with the switching state of the TFT switch 74 of each pixel 100. More specifically, an electric signal corresponding to the amount of charge accumulated by turning on any TFT switch 74 of the pixel 100 connected to the signal wiring 73 flows through each signal wiring 73.

  Each signal wiring 73 is connected to a signal detection circuit 105 that detects an electrical signal flowing out to each signal wiring 73. Each gate line 101 is connected to a scan signal control circuit 104 that outputs a scan signal for turning on / off the TFT switch 74 to each gate line 101. In FIG. 2, the signal detection circuit 105 and the scan signal control circuit 104 are shown in a simplified form. However, for example, a plurality of signal detection circuits 105 and a plurality of scan signal control circuits 104 are provided (for example, 256). The signal wiring 73 or the gate wiring 101 is connected every time. For example, when 1024 signal wirings 73 and 1024 gate wirings 101 are provided, four scan signal control circuits 104 are provided, 256 gate wirings 101 are connected, and four signal detection circuits 105 are provided 256. The signal wiring 73 is connected one by one.

  The signal detection circuit 105 incorporates an amplification circuit 120 (see FIG. 6) for amplifying an input electric signal for each signal wiring 73. In the signal detection circuit 105, an electric signal input from each signal wiring 73 is amplified by an amplifier circuit and converted into a digital signal by an ADC (analog / digital converter) (details will be described later).

  The signal detection circuit 105 and the scan signal control circuit 104 are subjected to predetermined processing such as noise removal on the digital signal converted by the signal detection circuit 105, and the signal detection circuit 105 is provided with a signal detection timing. A control unit 106 that outputs a control signal indicating the timing of outputting the scan signal is connected to the scan signal control circuit 104.

  The control unit 106 according to the present embodiment is configured by a microcomputer, and includes a nonvolatile storage unit including a CPU (Central Processing Unit), a ROM and a RAM, a flash memory, and the like. The control unit 106 performs control for radiographic imaging by executing a program stored in the ROM by the CPU. Further, the control unit 106 performs a process (interpolation process) for interpolating the image data of each radiation irradiation amount detection pixel 100B on the image data on which the predetermined process has been performed, so that the irradiated radiation X is obtained. Generate the image shown. That is, the control unit 106 generates an image indicated by the irradiated radiation X by interpolating the image data of each radiation irradiation amount detection pixel 100B based on the image data subjected to the predetermined processing.

  3 is a plan view showing the structure of the radiation detector 26 of the indirect conversion type according to the present embodiment, and FIG. 4 is a cross-sectional view taken along line AA of the radiographic image capturing pixel 100A of FIG. FIG. 5 is a sectional view taken along line BB of the radiation dose detection pixel 100B of FIG. As shown in FIG. 4, the pixel 100A of the radiation detector 26 includes a gate wiring 101 (see FIG. 3) and a gate electrode 72 formed on an insulating substrate 71 made of non-alkali glass or the like. 101 and the gate electrode 72 are connected (see FIG. 3). The wiring layer in which the gate wiring 101 and the gate electrode 72 are formed (hereinafter, this wiring layer is also referred to as “first signal wiring layer”) uses Al or Cu, or a laminated film mainly composed of Al or Cu. Although formed, it is not limited to these.

An insulating film 85 is formed on one surface of the first signal wiring layer, and a portion located on the gate electrode 72 functions as a gate insulating film in the TFT switch 74. The insulating film 85 is made of, for example, SiN _X or the like, and is formed by, for example, CVD (Chemical Vapor Deposition) film formation.

  A semiconductor active layer 78 is formed in an island shape on the gate electrode 72 on the insulating film 85. The semiconductor active layer 78 is a channel portion of the TFT switch 74 and is made of, for example, an amorphous silicon film.

  On these upper layers, a source electrode 79 and a drain electrode 83 are formed. In the wiring layer in which the source electrode 79 and the drain electrode 83 are formed, a signal wiring 73 is formed together with the source electrode 79 and the drain electrode 83. The source electrode 79 is connected to the signal wiring 73 (see FIG. 3). The wiring layer in which the source electrode 79, the drain electrode 83, and the signal wiring 73 are formed (hereinafter, this wiring layer is also referred to as a “second signal wiring layer”) is a laminated layer mainly composed of Al or Cu or Al or Cu. The film is formed using, but is not limited to these. Between the source electrode 79 and the drain electrode 83 and the semiconductor active layer 78, an impurity doped semiconductor layer (not shown) made of impurity doped amorphous silicon or the like is formed. These constitute a switching TFT switch 74. In the TFT switch 74, the source electrode 79 and the drain electrode 83 are reversed depending on the polarity of charges collected and accumulated by the lower electrode 81 described later.

In order to protect the TFT switch 74 and the signal wiring 73, a TFT protective film layer 98 is provided on almost the entire area (substantially the entire area) where the pixels 100 are provided on the substrate 71 so as to cover these second signal wiring layers. Is formed. The TFT protective film layer 98 is made of, for example, SiN _X or the like, and is formed by, for example, CVD film formation.

  A coating type interlayer insulating film 82 is formed on the TFT protective film layer 98. This interlayer insulating film 82 is a photosensitive organic material having a low dielectric constant (relative dielectric constant εr = 2 to 4) (for example, a positive photosensitive acrylic resin: a base made of a copolymer of methacrylic acid and glycidyl methacrylate). It is formed with a film thickness of 1 to 4 μm by a material obtained by mixing a polymer with a naphthoquinonediazide positive photosensitive agent.

  In the radiation detector 26 of the present embodiment, the capacitance between the metals arranged in the upper layer and the lower layer of the interlayer insulating film 82 is suppressed by the interlayer insulating film 82. In general, such a material also has a function as a flattening film, and has an effect of flattening a lower step. In the radiation detector 26 of the present embodiment, a contact hole 87 is formed at a position facing the drain electrode 83 of the interlayer insulating film 82 and the TFT protective film layer 98.

  A lower electrode 81 of the sensor unit 103 is formed on the interlayer insulating film 82 so as to cover the pixel region while filling the contact hole 87, and the lower electrode 81 is connected to the drain electrode 83 of the TFT switch 74. ing. If the semiconductor layer 91 described later is as thick as about 1 μm, the material of the lower electrode 81 is not limited as long as it has conductivity. For this reason, there is no problem if it is formed using an Al-based material, a conductive metal such as ITO.

  On the other hand, when the thickness of the semiconductor layer 91 is thin (around 0.2 to 0.5 μm), light is not sufficiently absorbed by the semiconductor layer 91, so that an increase in leakage current due to light irradiation to the TFT switch 74 is prevented. An alloy mainly composed of a light-shielding metal or a laminated film is preferable.

  A semiconductor layer 91 that functions as a photodiode is formed on the lower electrode 81. In the present embodiment, a PIN structure photodiode in which an n + layer, an i layer, and a p + layer (n + amorphous silicon, amorphous silicon, p + amorphous silicon) are stacked is employed as the semiconductor layer 91, and the n + layer 21A is formed from the lower layer. , I layer 21B and p + layer 21C are sequentially stacked. The i layer 21 </ b> B generates charges (a pair of free electrons and free holes) when irradiated with light. The n + layer 21A and the p + layer 21C function as contact layers, and electrically connect the lower electrode 81 and an upper electrode 92 described later to the i layer 21B.

  An upper electrode 92 is individually formed on each semiconductor layer 91. For the upper electrode 92, for example, a material having high light transmittance such as ITO or IZO (zinc oxide indium) is used. In the radiation detector 26 according to the present exemplary embodiment, the sensor unit 103 includes the upper electrode 92, the semiconductor layer 91, and the lower electrode 81.

  On the interlayer insulating film 82, the semiconductor layer 91, and the upper electrode 92, a coating type interlayer insulating film 93 is formed so as to have a part of the opening 97 </ b> A corresponding to the upper electrode 92 and cover each semiconductor layer 91. Yes.

  On the interlayer insulating film 93, the common electrode wiring 95 is formed of Al or Cu, or an alloy or laminated film mainly composed of Al or Cu. The common electrode wiring 95 has a contact pad 97 formed in the vicinity of the opening 97 </ b> A and is electrically connected to the upper electrode 92 through the opening 97 </ b> A of the interlayer insulating film 93.

  On the other hand, as shown in FIG. 5, in the radiation dose detection pixel 100B of the radiation detector 26, the TFT switch 74 is formed so that the source electrode 79 and the drain electrode 83 are in contact with each other. That is, in the pixel 100B, the source and drain of the TFT switch 74 are short-circuited. As a result, in the pixel 100 </ b> B, the charges collected by the lower electrode 81 flow out to the signal wiring 73 regardless of the switching state of the TFT switch 74.

In the radiation detector 26 formed in this way, a protective film is formed of an insulating material having a low light absorption as required, and radiation conversion is performed using an adhesive resin having a low light absorption on the surface. A layer scintillator is affixed. Alternatively, the scintillator is formed by a vacuum deposition method. As the scintillator, a scintillator that generates fluorescence having a relatively wide wavelength region that can generate light in an absorbable wavelength region is desirable. Examples of such a scintillator include CsI: Na, CaWO ₄ , YTaO ₄ : Nb, BaFX: Eu (X is Br or Cl), LaOBr: Tm, and GOS. Specifically, when imaging using X-rays as the radiation X, those containing cesium iodide (CsI) are preferable, and CsI: Tl (thallium is added) having an emission spectrum at 420 nm to 700 nm at the time of X-ray irradiation. It is particularly preferable to use cesium iodide) or CsI: Na. Note that the emission peak wavelength in the visible light region of CsI: Tl is 565 nm. Moreover, when using the scintillator containing CsI as a scintillator, it is preferable to use what was formed as a strip-like columnar crystal structure by the vacuum evaporation method.

  As shown in FIG. 4, the radiation detector 26 is irradiated with radiation X from the side on which the semiconductor layer 91 is formed, and reads a radiation image with a TFT substrate provided on the back side of the incident surface of the radiation X. In the case of a so-called back side scanning method (PSS (Pentation Side Sampling) method), light is emitted more strongly on the upper surface side of the scintillator provided on the semiconductor layer 91 in the figure. On the other hand, radiation X is irradiated from the TFT substrate side, and a radiation image is read by a TFT substrate provided on the surface side of the incident surface of the radiation X, which is a so-called surface reading method (ISS (Irradiation Side Sampling) method). In this case, the radiation X transmitted through the TFT substrate enters the scintillator, and the TFT substrate side of the scintillator emits light more strongly. Electric charges are generated in the sensor portion 103 of each pixel 100 provided on the TFT substrate by light generated by the scintillator. For this reason, the radiation detector 26 has a higher resolution of the radiographic image obtained by photographing because the light emission position of the scintillator with respect to the TFT substrate is closer when the front surface reading method is used than when the rear surface reading method is used.

  The radiation detector 26 is not limited to those shown in FIGS. 3 to 5 and can be variously modified. For example, in the case of the back side scanning method, since there is a low possibility that the radiation X will reach, in place of the above, other imaging elements such as a CMOS (Complementary Metal-Oxide Semiconductor) image sensor having low resistance to the radiation X You may combine with TFT. Further, it may be replaced with a charge-coupled device (CCD) image sensor that transfers charges while shifting them with a shift pulse corresponding to a TFT scan signal.

  For example, a flexible substrate may be used. In order to improve the transmittance | permeability of the radiation X, it is preferable to apply what uses the ultra-thin glass by the float method developed recently as a base material as a flexible substrate. As for the ultra-thin glass that can be applied at this time, for example, “Asahi Glass Co., Ltd.,“ Successfully developed the world's thinnest 0.1 mm-thick ultra-thin glass by the float process ”, Aug. 20 search], Internet <URL: http://www.agc.com/news/2011/0516.pdf> ”.

  Next, a schematic configuration of the signal detection circuit 105 of the present embodiment will be described. FIG. 6 is a schematic configuration diagram of an example of the signal detection circuit 105 according to the present embodiment. The signal detection circuit 105 according to the present embodiment includes an amplification circuit 120 and an ADC (analog / digital converter) 124. Although not shown in FIG. 6, the amplifier circuit 120 is provided for each signal wiring 73. In other words, the signal detection circuit 105 includes a plurality of amplifier circuits 120 that are the same number as the number of signal wirings 73 of the radiation detector 26.

  The amplifier circuit 120 includes a charge amplifier circuit, and includes an amplifier 122 such as an operational amplifier, a capacitor C connected in parallel to the amplifier 122, and a charge reset switch SW1 connected in parallel to the amplifier 122. It is prepared for.

  In the amplifying circuit 120, the charge (electric signal) is read by the TFT switch 74 of the pixel 100 with the charge reset switch SW1 turned off, and the charge read by the TFT switch 74 is accumulated in the capacitor C. The voltage value output from the amplifier 122 increases in accordance with the amount of stored charge.

  The control unit 106 applies a charge reset signal to the charge reset switch SW1 to control on / off of the charge reset switch SW1. When the charge reset switch SW1 is turned on, the input side and output side of the amplifier 122 are short-circuited, and the capacitor C is discharged.

  The ADC 124 has a function of converting an electrical signal that is an analog signal input from the amplifier circuit 120 into a digital signal when the S / H (sample hold) switch SW is in an ON state. The ADC 124 sequentially outputs electrical signals (charge information) converted into digital signals to the control unit 106.

  Note that the ADC 124 of this embodiment receives the electrical signals output from all the amplifier circuits 120 provided in the signal detection circuit 105. That is, the signal detection circuit 105 of this embodiment includes one ADC 124 regardless of the number of amplifier circuits 120 (signal wiring 73).

  In the present embodiment, it is configured to perform detection related to irradiation of the radiation X without requiring a control signal from the outside (for example, the radiation image processing apparatus 14). In the present embodiment, an electrical signal (charge information) of the signal wiring 73 (in the case of FIG. 2, at least one of D2 and D3, for example, D2) connected to the radiation dose detection pixel 100B is supplied to the signal detection circuit 105. The signal is detected by the amplifier circuit 120 and converted into a digital signal. In the present embodiment, the control unit 106 is configured to acquire the digital signal converted by the signal detection circuit 105 and detect the start and stop of irradiation of the radiation X based on the set parameters. ing. In this embodiment, “detection” of an electric signal indicates sampling of the electric signal.

  FIG. 7 is a functional block diagram showing a configuration example of the control unit 106 in the electronic cassette 20 of the present embodiment.

  The control unit 106 includes a CPU 160, a ROM 161, a RAM 162, and an input / output unit 163, and each is connected to a bus such as a system bus or a data bus.

  The CPU 160 has a function of controlling the operation of the entire electronic cassette 20, and various programs used by the CPU 160 are stored in the ROM 161 in advance. The RAM 162 has a function of temporarily storing various data, and has a function of developing and storing programs and the like stored in the ROM 161.

  A hard disk (HDD) 165, an I / F unit 166, a scan signal control circuit 104, and a signal detection circuit 105 are connected to the input / output unit 163.

  The HDD has a function of storing and holding various data, and the I / F unit 166 has a radiography or wired communication with the radiographic image processing device 14, the console 16, or the like to obtain an imaging menu or radiographic image. It has a function of transmitting and receiving various information including image information.

  The control unit 106 according to the present embodiment activates various programs, controls the scan control circuit 104 and the signal detection circuit 105, and performs imaging by the radiation detector 26. Further, the control unit 106 has a function of acquiring the electrical signal (charge information) output from the radiation dose detection pixel 100B and detecting the start and stop of radiation irradiation.

  Incidentally, in the electronic cassette 20 configured as described above, it may be difficult to detect a defect in the radiation dose detection pixel 100B.

  For example, in the radiation dose detection pixel 100B in which the source and drain of the TFT switch 74 are short-circuited as in the present embodiment, as shown in FIG. 8, a plurality of (on one signal wiring 73) are provided on one line (one signal wiring 73). In FIG. 8, there are two radiation dose detection pixels 100B, and the values of the radiation dose detection pixels 100B of all the lines are added and output, so it is not possible to specify which pixel is defective. Further, when the output of the radiation dose detection pixel 100B is smaller than the output of the radiation image capturing pixel 100A, it is difficult to determine the defect from the viewpoint of the S / N ratio.

  In addition, even when another sensor is used, even if a sensor unit defect can be detected from the sensor offset output, a defect caused by another factor (for example, a foreign object on the sensor vertically) is detected. Can not do it.

  Furthermore, even if a pixel has a defect depending on the dose of irradiation, it may be difficult to determine the defect because there is no difference from the pixel value of a normal pixel.

  Therefore, in the present embodiment, the control unit 106 performs radiation based on the pixel value of the radiation irradiation amount detection pixel 100B at a predetermined high dose and / or low dose and the predetermined normal value. A defect in the dose detection pixel is detected.

  Here, the predetermined high dose and low dose are doses obtained experimentally in which the defect does not maintain linearity. Although the characteristics vary depending on the type of radiation detector 26, even in the case of a defective pixel, there is a case where linearity is maintained between the high dose and the low dose, and thus a defect has occurred in the present embodiment. The defective pixel is determined by determining the linearity of the dose at a predetermined high dose or low dose determined experimentally in which the output at that time becomes nonlinear.

  In this embodiment, as shown in FIGS. 9A and 9B, the output value of the radiation irradiation amount detection pixel 100B with respect to the dose has a linear characteristic when normal, but the dose is affected by the defect. On the other hand, since the linearity may not be maintained in the above-described high dose region (FIG. 9A) or the low dose region (FIG. 9B), the linearity is used to reduce radiation. The defect of the irradiation amount detection pixel 100B is determined.

  The above-mentioned high dose and low dose may be obtained experimentally, but assuming actual use, for example, under the condition that the pixel value of the region of interest in the normal image is saturated with the subject being placed. Alternatively, if the output value of the radiation dose detection pixel 100B does not become a strange value (for example, a value far from a predetermined value by a predetermined value or more) under a low dose condition where the pixel value is low and an image is not formed, You may judge that it is not a defect.

  Note that the doses at the high dose and the low dose are defined by the drive current (mA) of the radiation source 25 in the present embodiment. For example, even when the drive current (mAs) expressed by the time and the drive current of the radiation irradiation source 25 is the same value, the dose per unit time of the radiation irradiation source 25 is higher and the irradiation time is lower. Since the output becomes unstable as compared with the case where it is long, the dose is defined by the drive current (mA) of the radiation irradiation source 25 in this embodiment.

  Here, a specific method for detecting a defect in the radiation dose detection pixel 100B of the present embodiment will be described.

  In the present embodiment, the radiation irradiation source 25 is driven with at least one of the above-described high dose and low dose to irradiate the electronic cassette 20 with radiation, and the pixel value of the radiation dose detection pixel 100B is acquired. In the present embodiment, there are a plurality of radiation dose detection pixels 100B on one line (one signal wiring 73), and the values of the radiation dose detection pixels 100B of all the lines are added. In order to obtain a pixel value added for one line, the added pixel value may be handled as it is or may be a pixel value calculated as one pixel.

  Next, a value predetermined by experiment or the like, a pixel value of another radiation dose detection pixel 100B, or a pixel value of the radiation image capturing pixel 100A is acquired as a normal value and compared. The pixel values of the other radiation dose detection pixels 100B are pixel values obtained by adding one line as the pixel value of the radiation dose detection pixel 100B. The pixel value of the detection pixel 100B is acquired, and as the pixel value of the radiographic image capturing pixel 100A, the number of pixels of the radiographic image capturing pixel 100A corresponding to the added number of the radiation irradiation amount detection pixels 100B to be compared is obtained. Get the value and compare. Further, when the pixel value of the radiation dose detection pixel 100B is calculated as one pixel, the pixel value of another radiation dose detection pixel 100B or the radiographic image capturing pixel 100A corresponding to one pixel. Obtain and compare pixel values. Furthermore, when performing the comparison, only one dose of high dose or low dose may be compared with the normal value, or each of the two doses of high dose and low dose may be compared with the normal value. Good.

  Based on the comparison result, the defect of the radiation dose detection pixel 100B is determined. For example, the defect is determined to be a defect when the pixel value of the target radiation irradiation amount detection pixel 100B cannot obtain the accuracy of the radiation irradiation stop control from the comparison result. As an example, if the comparison result has a difference greater than or equal to a predetermined threshold with respect to the normal value, the defect is determined. In addition, when comparing with the normal value of each of the two doses, if any one is determined to be defective, the radiation dose detection pixel 100B is determined to be defective.

  In the present embodiment, the radiation dose detection pixel is based on the pixel value of the radiation dose detection pixel 100B at a predetermined high dose and / or low dose and the predetermined normal value. However, the present invention is not limited to this. For example, the pixel values of the radiation dose detection pixels 100B at two different doses including at least one of the high dose and the low dose are tilted (pixel values corresponding to changes in dose). The rate of change of the output value is such that the accuracy of radiation irradiation stop control cannot be obtained compared to the slope (reference rate of change) obtained from the normal value determined in advance for each dose. When the value is an absolute value, the radiation dose detection pixel 100B may be determined to be defective.

  Further, when it is determined that the defect is a defect at the above-described high dose or low dose, the pixel value (output value) of the radiation dose detection pixel 100B is within a predetermined usable range. Alternatively, the radiation dose detection pixel 100B determined to be defective may be used by performing offset correction or gain correction.

  Next, an example of processing performed by the control unit 106 of the electronic cassette 20 according to the present embodiment will be described. FIG. 10 is a flowchart showing an example of the defect detection processing of the radiation dose detection pixel performed by the control unit 106.

  In step S100, the value of the radiation dose detection pixel at at least one of the high dose and the low dose is acquired, and the process proceeds to step S102. That is, the radiation irradiation amount detection pixel value is acquired by performing imaging by driving the radiation irradiation source 25 so as to irradiate at least one of a high dose and a low dose. In the present embodiment, a value obtained by adding the values of the radiation irradiation amount detection pixels 100B for one line is acquired.

  In step S102, the normal value is acquired and compared with the acquired value, and the process proceeds to step S104. Note that the normal value is a value determined in advance by an experiment or the like (a value determined from a normal pixel value), the pixel value of the radiation irradiation amount detection pixel 100B of another line, or the surrounding radiation image capturing pixel 100A. Pixel values can be applied. Then, by comparing the normal value with the value of the radiation dose detection pixel 100B at at least one of the high dose and the low dose, as shown in FIG. 9A and FIG. It becomes possible to detect a defect having no linearity in a dose region or a low dose region. Further, since the radiation dose detection pixel 100B is a value obtained by adding a plurality of pixels, when comparing, the normal value is compared as a value obtained by adding the corresponding number of pixels. Alternatively, the pixel value of the radiation dose detection pixel may be converted into one pixel for comparison.

  In step S104, it is determined whether the pixel is a defective pixel based on the comparison result in step S102. The determination is made, for example, when the comparison result has a difference equal to or greater than a predetermined threshold with respect to the normal value, and when the determination is affirmed, the process proceeds to step S106, and when the determination is negative, the step is performed. The process proceeds to S112. That is, when there is a defect in the radiation dose detection pixel 100B, linearity may not be maintained in a high dose or low dose region as shown in FIGS. 9A and 9B. It detects and determines the defect of the radiation dose detection pixel 100B.

  In step S106, it is determined whether or not the defect is at a usable level. The determination is made, for example, by determining whether or not the pixel value (output value) of the radiation dose detection pixel 100B is within a predetermined usable range. If the determination is negative, the process proceeds to step S108. If the result is affirmative, the process proceeds to step S110.

  In step S108, one line of radiation irradiation amount detection pixels 100B is set to be prohibited from use, and the process proceeds to step S112.

  In step S110, the radiation irradiation amount detection pixel 100B of the target line is set to be usable by offset correction or gain correction, and the process proceeds to step S112.

  In step S112, it is determined whether or not the defect determination has been performed for all the lines. If the determination is negative, the process proceeds to step S114, and the target radiation irradiation amount detection pixel 100B is changed (line change). Then, returning to step S100, the above-described processing is repeated, and when the determination in step S112 is affirmed, the series of processing ends.

  As described above, in the present embodiment, the radiation dose is based on the value of the radiation dose detection pixel 100B and the normal value at at least one of the high dose and the low dose that do not maintain the linearity due to the defect. By determining the defect of the detection pixel 100B, it becomes possible to detect the defect of the radiation dose detection pixel 100B accurately and easily, rather than performing defect detection with a dose other than a high dose or a low dose. Even when there is a foreign object on the top or when the values of a plurality of radiation dose detection pixels 100B are added to one line, it is possible to easily detect a defect in the radiation dose detection pixels 100B.

  Subsequently, a modified example of processing performed by the control unit 106 of the electronic cassette 20 according to the present exemplary embodiment will be described. FIG. 11 is a flowchart illustrating a modification of the defect detection process for the radiation dose detection pixel performed by the control unit 106. The same processes as those in the above embodiment are denoted by the same reference numerals and the description thereof is omitted.

  In the above embodiment, the defect of the radiation dose detection pixel is detected based on the pixel value of the radiation dose detection pixel of at least one of the high dose and the low dose and the predetermined normal value. However, in the modification, a defect in the radiation dose detection pixel is detected based on the pixel value of the radiation dose detection pixel at at least one of the high dose and the low dose and a predetermined normal value. When a defect is detected, in order to increase detection accuracy, a change rate (gradient) that serves as an index of linearity is calculated using the pixel value of the radiation dose detection pixel at a different dose, A defect is detected by comparison with a slope (predetermined reference change rate) obtained from a normal value. In the modification, since the defect detection is performed in two stages, the processing speed is higher when the first defect detection uses the pixel value of the radiation dose detection pixel of one kind of high dose or low dose. From the viewpoint of

  That is, in step S200 of the modified example, the value of the radiation irradiation amount detection pixel at at least one of the high dose and the low dose is acquired, and the process proceeds to step S202. That is, the radiation irradiation amount detection pixel value is acquired by driving the radiation irradiation source 25 so as to irradiate at least one of a high dose and a low dose. In the case of the same pixel configuration as that in the above embodiment as shown in FIG. 2, a value obtained by adding the values of the radiation irradiation amount detection pixels 100B for one line is acquired.

  In step S202, the normal value is acquired and compared with the acquired value, and the process proceeds to step S204. Note that the normal value is a value determined in advance by an experiment or the like (a value determined from a normal pixel value), the pixel value of the radiation irradiation amount detection pixel 100B of another line, or the surrounding radiation image capturing pixel 100A. Pixel values can be applied. Then, by comparing the normal value with the value of the radiation dose detection pixel 100B at a high dose or a low dose, as shown in FIG. 9A or FIG. It becomes possible to detect a defect having no linearity in a region. Further, since the radiation dose detection pixel 100B is a value obtained by adding a plurality of pixels, when comparing, the normal value is compared as a value obtained by adding the corresponding number of pixels. Alternatively, the pixel value of the radiation dose detection pixel may be converted into one pixel for comparison.

  In step S204, it is determined whether the pixel is a defective pixel based on the comparison result in step S202. The determination is made, for example, when the comparison result has a difference greater than or equal to a predetermined threshold value with respect to the normal value, and when the determination is affirmed, the process proceeds to step S206. The process proceeds to S218. That is, when there is a defect in the radiation dose detection pixel 100B, linearity may not be maintained in a high dose or low dose region as shown in FIGS. 9A and 9B. It detects and determines the defect of the radiation dose detection pixel 100B.

  In step S206, the value of the radiation dose detection pixel 100B at another dose is acquired, and the process proceeds to step S208. That is, the radiation irradiation amount detection pixel value is acquired by driving the radiation irradiation source 25 so as to irradiate the radiation with another dose. In the case of the configuration of FIG. 2 as in the above-described embodiment, a value obtained by adding the values of the radiation irradiation amount detection pixels 100B for the other one line is acquired as in step A200. In addition, when the value of the high dose radiation exposure detection pixel is acquired in step S200, the value of the radiation dose detection pixel 100B is acquired by photographing at a low dose, and the low dose value is acquired. If it is, it is preferable to acquire the value of the radiation dose detection pixel 100B by photographing at a high dose.

  In step S208, the inclination at two doses is calculated and compared with a normal value (reference inclination), and the process proceeds to step S210. Since the radiation dose detection pixel 100B is a value obtained by adding a plurality of pixels, when calculating and comparing the inclination, the inclination is calculated as a value obtained by adding the normal value for the corresponding number of pixels. Compare. Alternatively, the pixel value of the radiation dose detection pixel may be converted into one pixel, and the inclination may be calculated and compared.

  In step S210, it is determined whether the pixel is a defective pixel based on the comparison result in step S208. In the determination, for example, when the comparison result has a difference of a predetermined threshold value or more with respect to the normal value (reference inclination), it is determined as a defect. If not, the process proceeds to step S214 described above. That is, in order to increase the defect detection accuracy, the radiation dose detection pixel is compared with the above embodiment by calculating the slope that is an index of linearity using the pixel value at two doses and comparing it with the normal value. The detection accuracy of 100B defects can be improved.

  In step S212, it is determined whether the defect is at a usable level. The determination is made, for example, by determining whether or not the pixel value (output value) of the radiation dose detection pixel 100B is within a predetermined usable range. If the determination is negative, the process proceeds to step S214. If the determination is affirmative, the process proceeds to step S216.

  In step S214, one line of radiation dose detection pixels 100B is set to be prohibited from use, and the process proceeds to step S218.

  In step S216, the radiation irradiation amount detection pixel 100B of the target line is set to be usable by offset correction or gain correction, and the process proceeds to step S218.

  In step S218, it is determined whether or not defect determination has been performed on all lines. If the determination is negative, the process proceeds to step S220, and the target radiation irradiation amount detection pixel 100B is changed (line change). Then, returning to step S200, the above-described processing is repeated, and when the determination in step S218 is affirmed, the series of processing ends.

  In the modified example, one of the two types of defect detection methods is used to detect a defect, and when a defect is detected, the other defect detection method is further used to detect the defect. However, the present invention is not limited to this, and two types of defect detection methods may be performed, and defects may be determined based on the detection results of the methods. For example, the defect of the radiation dose detection pixel is detected based on the pixel value of the radiation dose detection pixel at at least one of the high dose and the low dose and a predetermined normal value, and two different doses are detected. An inclination that serves as an index of linearity may be calculated using the pixel value of the radiation irradiation amount detection pixel in, and a defect may be detected by comparison with the inclination obtained from the normal value of each dose.

  Note that the configuration and method for detecting the start and stop of radiation X by the electronic cassette 20 itself are not limited to the present embodiment. For example, in the above description, the pixel including the TFT switch 74 in which the source and the drain are short-circuited has been described as the radiation dose detection pixel 100B, but is not limited thereto. For example, a connection wiring may be formed in the middle of the drain electrode 83 and connected to the signal wiring 73. Also in this case, the source and drain of the TFT switch 74 are substantially short-circuited. Further, when the source and drain of the TFT switch 74 are short-circuited, the gate electrode 72 may be formed away from the gate wiring 101. Further, for example, in the radiation dose detection pixel 100 </ b> B, by connecting the sensor unit 103 and the signal wiring 73 via the connection wiring 82 and the contact hole 87, the drain electrode 83 and the contact hole 87 are electrically connected. It may be cut.

  In the present embodiment and the modification, the case where a pixel in which the TFT switch 74 is short-circuited is used as the radiation dose detection pixel 100B. However, the radiation dose detection pixel 100B is not particularly limited. For example, as a radiation image capturing pixel 100A, a pixel in which the TFT switch 74 is not short-circuited may be used as the radiation dose detection pixel 100B. In this case, the control of the TFT switch 74 of the pixel 100B is controlled independently of the control of the TFT switch 74 of the pixel 100A. In this case, as the pixel 100B, the predetermined pixel 100 of the radiation detector 26 may be used, or a pixel different from the pixel 100 in the radiation detector 26 may be provided.

  In the above-described embodiment and modification, the radiation image capturing pixel 100A and the radiation irradiation amount detection pixel 100B exist as one pixel, but the pixel configuration is not limited to this. For example, FIG. 12 (A) and 12 (B), a configuration in which the radiographic image capturing pixel 100A and the radiation dose detection pixel 100B exist as sub-pixels in one pixel may be applied. As shown in FIG. 12C, a configuration may be adopted in which one radiation irradiation amount detection pixel 100B is provided as a sub-pixel for a plurality of radiation image capturing pixels 100A. 12A and 12B, the radiation dose detection pixel 100B is configured such that the sensor unit 103 is directly connected to the signal wiring 73 without providing the TFT switch 74, and each sensor unit is directly connected. Since the electric charge 103 can be read, the radiation dose detection (AEC) can be quickly performed as compared with the case where the sensor unit 106 and the signal wiring 73 are connected via the TFT switch 74.

  In the embodiment and the modification described above, when a defect of the radiation dose detection pixel 100B is detected, if the output is within a predetermined allowable range, offset correction or gain correction is performed. However, the present invention is not limited to this. For example, when a defective pixel of the radiation dose detection pixel 100B is detected, the number of defective pixels and the number of defective pixels are detected. Depending on the amount of deviation of the output value of the pixel, the electronic cassette 20 may not be used, or may be interpolated using the output value of the adjacent or nearby radiation dose detection pixel. It may be used only when calculating the region, or the dose (radiation dose) may be calculated excluding the detected defective line or block. Further, in the case of the radiation dose detection pixel 100B having the same configuration as the radiation image capturing pixel 100A, the pixel arrangement of the radiation dose detection pixel 100B may be changed and used.

  In the embodiment and the modification described above, the case where the present invention is applied to the radiation detector 26 of the indirect conversion type that converts the converted light into electric charge has been described, but the present invention is not limited to this. For example, the present invention may be applied to a direct-conversion radiation detector that uses a material that directly converts radiation X into charge, such as amorphous selenium, as a photoelectric conversion layer that absorbs radiation and converts it into charges.

  In addition, the configurations, operations, and the like of the radiographic imaging system 10, the radiation generator 12, the electronic cassette 20, and the radiation detector 26 described in the present embodiment are examples, and the scope of the present invention is not deviated. Needless to say, it can be changed according to the situation.

  Moreover, the radiation X in this Embodiment is not specifically limited, X-ray, a gamma ray, etc. can be applied.

  The processing shown in the flowcharts in the above embodiments may be stored and distributed as various programs in various storage media.

  Furthermore, in the above description, the defective pixel detection process of the radiation dose detection pixel has been described as a process performed by the control unit 106. However, the present invention is not limited to this, and may be a process performed by the radiation image processing device 14, for example. The processing performed by the console 16 may be performed.

DESCRIPTION OF SYMBOLS 10 Radiation imaging system 12 Radiation generator 14 Radiation image processing apparatus 16 Console 20 Electronic cassette 25 Radiation irradiation source 26 Radiation detector 100 Pixel 100A Radiation image photographing pixel 100B Radiation irradiation amount detection pixel 106 Control part

Claims (13)

A radiation dose detection pixel for detecting the radiation dose,
The output when the defect is generated becomes nonlinear, and the pixel value of the radiation dose detection pixel when photographing with at least one of a predetermined high dose and low dose determined experimentally is determined in advance. Detection means for detecting a defect of the radiation dose detection pixel based on the normal value
A radiographic imaging apparatus comprising:   The detection means detects a change in pixel value with respect to a change in dose from each pixel value of the radiation dose detection pixel when imaging is performed with two different doses including at least one of a predetermined high dose and low dose. By calculating the rate of change to be expressed and comparing the obtained rate of change with a reference rate of change representing a change in pixel value with respect to a change in dose, obtained from the normal value for each dose, the radiation dose detection The radiation image capturing apparatus according to claim 1, wherein a defect of a pixel is detected.   The normal value is a predetermined value, a pixel value of a radiation image capturing pixel for capturing a radiation image around the radiation exposure detection pixel, or a pixel value of another radiation irradiation detection pixel. The radiographic imaging device according to claim 1 or 2. The detection means is
A first detection means for detecting a defect by comparing a pixel value of the radiation dose detection pixel when imaged with at least one of the high dose and the low dose, and a predetermined normal value;
When the first detection means detects a defect in the radiation dose detection pixel, the radiation dose detection is performed when imaging is performed with two different doses including at least one of the high dose and the low dose. A change rate that represents a change in pixel value with respect to a change in dose is determined from each pixel value of the pixel, and a reference that represents a change in pixel value with respect to a change in dose obtained from the obtained change rate and the normal value for each dose. A second detection means for detecting a defect of the radiation dose detection pixel by comparing the rate of change;
The radiographic imaging apparatus of Claim 1 or Claim 3 which has these. The detection means is
A first detection means for detecting a defect by comparing a pixel value of the radiation dose detection pixel when imaged with at least one of the high dose and the low dose, and a predetermined normal value;
Obtaining a change rate representing a change in pixel value with respect to a change in dose from each pixel value of the radiation dose detection pixel when imaged at two different doses including at least one of the high dose and the low dose, By comparing the obtained change rate with a reference change rate representing a change in pixel value with respect to a change in dose obtained from the normal value for each dose, a defect in the radiation dose detection pixel is detected. A second detection means;
The radiographic imaging device according to claim 1, wherein a defect of the radiation dose detection pixel is detected based on a detection result of each of the first detection unit and the second detection unit. .   6. The pixel according to claim 1, wherein the radiation dose detection pixel includes a sensor unit that generates a charge corresponding to the irradiated radiation and directly outputs the generated charge to the signal line. Radiation imaging device. The radiographic imaging device according to any one of claims 1 to 6,
Radiation irradiating means for irradiating the radiation imaging apparatus with radiation through a subject;
Radiographic imaging system equipped with. Using a radiographic imaging device equipped with a radiation dose detection pixel for detecting the radiation dose, an output obtained when a defect occurs becomes non-linear, and a predetermined high value obtained experimentally An acquisition step of acquiring a pixel value of the radiation irradiation amount detection pixel when imaged with at least one of a dose and a low dose; and
A detection step of detecting a defect in the radiation dose detection pixel by a detection means based on the pixel value acquired in the acquisition step and a predetermined normal value;
A defect determination method for a radiographic imaging apparatus comprising:   In the detection step, a change in the pixel value with respect to a change in the dose is determined from each pixel value of the radiation dose detection pixel when imaging is performed with two different doses including at least one of a predetermined high dose and low dose. By calculating the rate of change to be expressed and comparing the obtained rate of change with a reference rate of change representing a change in pixel value with respect to a change in dose, obtained from the normal value for each dose, the radiation dose detection The defect determination method of the radiographic imaging apparatus according to claim 8, wherein a defect of a pixel is detected.   The normal value is a predetermined value, a pixel value of a radiation image capturing pixel for capturing a radiation image around the radiation exposure detection pixel, or a pixel value of another radiation irradiation detection pixel. The radiographic imaging device according to claim 8 or 9. The detecting step comprises:
A first detection step of detecting a defect by comparing a pixel value of the radiation dose detection pixel when imaged with at least one of the high dose and the low dose and a predetermined normal value;
For detecting the radiation dose when photographing with two different doses including at least one of the high dose and the low dose when a defect of the radiation dose detection pixel is detected in the first detection step. Dose obtained from each pixel value obtained by obtaining each pixel value of the pixel to obtain a change rate representing a change in pixel value with respect to a change in dose, and obtained from the obtained change rate and the normal value for each dose A second detection step of detecting a defect in the radiation dose detection pixel by comparing a reference change rate representing a change in pixel value with respect to a change in
The defect determination method of the radiographic imaging apparatus of Claim 8 or Claim 10 which has these. The detecting step comprises:
A first detection step of detecting a defect by comparing a pixel value of the radiation dose detection pixel when imaged with at least one of the high dose and the low dose and a predetermined normal value;
Pixels corresponding to a change in dose from each pixel value acquired by acquiring each pixel value of the radiation dose detection pixel when imaging is performed with two different doses including at least one of the high dose and the low dose By determining a change rate representing a change in value and comparing the obtained change rate with a reference change rate representing a change in pixel value with respect to a change in dose, obtained from the normal value for each dose, the radiation A second detection step of detecting a defect in the dose detection pixel;
The radiographic imaging device according to claim 8 or 10, wherein a defect of the radiation dose detection pixel is detected based on a detection result of each of the first detection step and the second detection step. Defect determination method.   The radiographic imaging program for functioning a computer as the said detection means in the radiographic imaging apparatus of any one of Claims 1-6.

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