Patent Publication Number: US-2022225956-A1

Title: Radiation imaging apparatus, its control method, and medium

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a radiation imaging apparatus for imaging a radiation image based on incident radiation, a control method thereof, and a non-transitory tangible medium having recorded thereon a program for causing a computer to execute the control method. 
     Description of the Related Art 
     Radiation imaging apparatuses using radiation detectors that detect radiation such as X-rays are widely used in industries and medical fields. In recent years, multi-functional radiation imaging apparatuses have been investigated, and as one of the functions thereof, a function for monitoring the irradiation of radiation has been considered to be incorporated. This function enables, for example, the detection of the timing at which the irradiation of the radiation from the radiation source is started, the detection of the timing at which the irradiation of the radiation is to be stopped, and the detection of the irradiation amount or the integrated irradiation amount of the radiation. Automatic exposure control (AEC) is also possible by detecting the integrated irradiation amount of radiation transmitted through the subject and stopping the irradiation of radiation by the radiation source when the detected integrated irradiation amount reaches an appropriate amount. In order to realize this automatic exposure control (AEC), for example, a radiation imaging apparatus has been proposed in which pixels for detecting the dose of irradiated radiation are embedded in addition to pixels for photographing a radiation image. 
     Here, as described in Japanese Patent Application Laid-Open No. 2019-146039, a part of pixels for generating a radiation image may be used for an AEC, and a row in which pixels for use in an AEC are arranged may not be used for generating the radiation image because signals are read out during the AEC. For this reason, in the arrangement shown in Japanese Patent Application Laid-Open No. 2019-146039, a group of linear pixels of rows (lines) which cannot be used for generating a radiation image as a defective line. Further, Japanese Patent Application Laid-Open No. 2009-11566 proposes a method for synthesizing the defect lines described above. 
     However, in the prior art such as Japanese Patent Application Laid-Open No. 2019-146039, there are points to be improved with respect to correction of missing pixels in a radiation image. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a mechanism for appropriately correcting defective pixels in a radiation image in a radiation imaging apparatus having an automatic exposure control (AEC) function, both in the case of performing AEC and in the case of not performing AEC. 
     A disclosed aspect of a radiation imaging apparatus for acquiring a radiation image based on incident radiation, comprises a radiation detecting unit including a pixel region provided with a plurality of pixels for detecting the radiation, configured to output an electric signal related to the radiation image; storage unit configured to store (1) a first defect map in which information on the pixel position of a defective pixel among the pixels provided in the pixel region is registered and the defective linear pixel group is not included in a region of interest for detecting the radiation dose in the pixel region in order to perform automatic exposure control for stopping the irradiation of the radiation, and (2) a second defect map in which the defective linear pixel group is included in the region of interest; and a correction unit configured to correct the radiation image by using one of the first defect map and the second defect map selected in accordance with whether or not the automatic exposure control is performed. Other aspect of a radiation imaging apparatus for imaging a radiation image based on incident radiation, comprises: a radiation detecting unit including a pixel region provided with a plurality of pixels for detecting the radiation, configured to output an electric signal related to the radiation image; a storage unit configured to store a defect map in which information relating to the pixel position of a defective pixel among the pixels provided in the pixel region is registered, and in which the defective linear pixel group is not included in a region of interest for detecting the radiation dose in the pixel region in order to perform automatic exposure control for stopping the irradiation of the radiation; a setting unit configured to set the defective linear pixel group in the region of interest; and a correction unit configured to select the validity or invalidity of the setting by the setting unit in accordance with whether or not the automatic exposure control is performed, and correct the radiation image by using the information relating to the selected validity or invalidity and the defect map. In addition, an aspect of the disclosure includes a control method for the radiation imaging apparatus, and a non-transitory tangible medium having recorded thereon a program for causing a computer to execute the control method. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  illustrates an example of a schematic configuration of a radiation imaging system according to a first embodiment of the present disclosure. 
         FIG. 2  shows an example of the internal configuration of the radiation imaging device shown in  FIG. 1 . 
         FIG. 3  shows an exemplary arrangement of a plurality of regions of interest (ROI) set within the pixel region of the radiation detector shown in  FIG. 2 . 
         FIG. 4  shows an example of the internal configuration of a control unit of the imaging device shown in  FIG. 2 . 
         FIG. 5  is a flowchart showing an example of a processing procedure in a control method of a radiation imaging device according to a first embodiment of the present disclosure. 
         FIGS. 6A and 6B  show a first embodiment of the present disclosure and shows specific examples of a first image defect map and a second image defect map stored in the memory shown in  FIG. 4 . 
         FIG. 7  is a flowchart showing an example of a processing procedure in a control method of a radiation imaging device according to a second embodiment of the present disclosure. 
         FIGS. 8A, 8B, 8C and 8D  show a second embodiment of the present disclosure, showing specific examples of a first image defect map and a missing pixel register stored in the memory shown in  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments are disclosed below with reference to the drawings. 
     First Embodiment 
     At the first, a first embodiment is disclosed. 
       FIG. 1  is a diagram showing an example of the schematic configuration of the radiation imaging system  10  according to the first embodiment. As shown in  FIG. 1 , the radiation imaging system  10  includes a photographing mechanism  11  and a control mechanism  12 . A photographing mechanism  11  irradiates the subject H with radiation R and performs radiography of the subject H. In addition to X-rays, the radiation R includes α-rays, β-rays, γ-rays, and various kinds of particle rays. 
     As shown in  FIG. 1 , the photographing mechanism  11  includes a radiation imaging apparatus  100 , a standing stand  200 , a communication cable  211 - 214 , a communication control device  220 , an access point (AP)  230 , a radiation generating device  240 , and a radiation source  250 . 
     As shown in  FIG. 1 , the control mechanism  12  includes a control device  310 , a radiation irradiation switch  320 , an input device  330 , a display device  340 , a local area network (LAN)  350 , and a communication cable  360 . 
     Firstly, the respective components inside the photographing mechanism  11  will be described. The radiation imaging apparatus  100  acquires or images a radiation image based on the incident radiation R. In the present embodiment, it is assumed that the radiation imaging apparatus  100  has the above-described automatic exposure control (AEC) function. As shown in  FIG. 1 , the radiation imaging apparatus  100  includes a power supply control unit  101 , a wired communication unit  102 , a wireless communication unit  103 , and a mounting detection unit  104 . The radiation imaging apparatus  100  detects radiation R transmitted through the subject H and generates image data of a radiation image. 
     The power supply control unit  101  is a component composed of a battery or the like. The wired communication unit  102  communicates information by, for example, a cable connection using a communication standard having a predetermined agreement or a standard such as Ethernet (registered trademark). The wireless communication unit  103  has a circuit board including, for example, an antenna and a communication IC, and the circuit board performs wireless communication processing of a protocol based on a wireless LAN via the antenna. Note that the frequency band, standard and system of the radio communication in the wireless communication unit  103  are not limited, and a system such as proximity radio such as NFC or Bluetooth (registered trademark) or UWB may be used. The wireless communication unit  103  has a plurality of wireless communication systems, and may perform communication by appropriately selecting them. The mounting detection unit  104  is a component for detecting that the radiation imaging apparatus  100  is mounted on the standing stand  200 . The mounting detection unit  104  can be realized by providing, for example, a contact type detection element using a limit switch or the like, a detection element such as an inductive type, a capacitive type, or a magnetic proximity sensor, or a signal for electrically detecting when the sensor is mounted on the standing stand  200 . 
     The standing stand  200  is a frame on which the radiation imaging apparatus  100  is mounted and which allows radiation imaging in the standing position. The radiation imaging apparatus  100  can be attached to and detached from the standing stand  200 , and can be imaged in either the attached state or the detached state. 
     The communication cable  211  is a cable for communicably connecting the radiation imaging apparatus  100  and the communication control device  220 . The communication cable  212  is a cable for communicably connecting the access point (AP)  230  and the communication control device  220 . The communication cable  213  is a cable for communicably connecting the radiation generating device  240  and the communication control device  220 . The communication cable  214  is a cable for communicably connecting the radiation source  250  and the radiation generating device  240 . 
     The communication control device  220  is a component for controlling communication in each component of the radiation imaging system  10 . Specifically, the communication control device  220  controls, for example, the access point (AP)  230 , the radiation generating device  240 , and the control device  310  so that they can communicate with each other. 
     An access point (AP)  230  performs wireless communication with a radiation imaging apparatus  100 . For example, the access point (AP)  230  is used to relay communication between the radiation imaging apparatus  100 , the control device  310 , and the radiation generating device  240  when the radiation imaging apparatus  100  is removed from the standing stand  200  and used. The radiation imaging apparatus  100  or the communication control device  220  may have an access point (AP). In this case, the radiation imaging apparatus  100 , the control device  310 , and the radiation generating device  240  may communicate with each other via the access point (AP) of the radiation imaging apparatus  100  or the communication control device  220  without via the access point (AP)  230 . 
     The radiation generating device  240  controls the radiation source  250  to irradiate the radiation R based on a predetermined irradiation condition through the communication cable  214 . The radiation source  250  is a component for irradiating the subject H with radiation R under the control of the radiation generating device  240 . 
     Next, the components inside the control mechanism  12  will be described. The control device  310  communicates with the radiation generating device  240  and the radiation imaging apparatus  100  via the communication cable  360  and the communication control device  220  to integrally control the radiation imaging system  10 . 
     The radiation irradiation switch  320  is a switch for inputting the irradiation timing of the radiation R from the radiation source  250  by the operation of the operator S. 
     The input device  330  is a device for inputting an instruction from the operator S, and includes various input devices such as a keyboard and a touch panel. 
     The display device  340  is a device for displaying an image-processed radiation image or GUI, and includes a display or the like. 
     The LAN  350  is, for example, a core network in the hospital. The communication cable  360  is a cable for communicably connecting the control device  310  and the communication control device  220 . 
     Next, the internal configuration of the radiation imaging apparatus  100  shown in  FIG. 1  will be described.  FIG. 2  is a diagram showing an example of the internal configuration of the radiation imaging apparatus  100  shown in  FIG. 1 . In  FIG. 2 , components similar to those shown in  FIG. 1  are denoted by the same reference numerals, and a detailed description thereof will be omitted. 
     As shown in  FIG. 1 , the radiation imaging apparatus  100  includes a power supply control unit  101 , a wired communication unit  102 , a wireless communication unit  103 , a mounting detection unit  104 , a radiation detector  110 , a driving circuit  120 , a readout circuit  130 , a power supply circuit  140 , a signal processing unit  150 , and an imaging apparatus control unit  160 . 
     The radiation detector  110  includes a pixel region (which may be referred to as an “imaging region”)  110   a  having a plurality of pixels for detecting incident radiation R, and is a component for outputting an electric signal related to a radiation image. Specifically, the pixel region  110   a  is provided with a plurality of pixels arranged in a matrix. The plurality of pixels provided in the pixel region  110   a  have a plurality of detection pixels  111  and a plurality of correction pixels  112 , and convert incident radiation R into electric signals. Here, the detection pixel  111  is a pixel for generating the radiation image or outputting an electric signal for detecting the dose of the radiation R (the irradiation amount of the radiation R) generated, and the correction pixel  112  is a pixel for outputting an electric signal for removing the dark current component and the crosstalk component. 
     Each of the plurality of detection pixels  111  includes a conversion element  1111  and a switching element  1112 . The conversion element  1111  converts the incident radiation R into an electric signal. The conversion element  1111  includes, for example, a scintillator for converting incident radiation R into light, and a photoelectric conversion element for converting light generated by the scintillator into an electric signal, so as to convert the incident radiation R into an electric signal. In this case, the scintillator is formed in a sheet shape so as to cover the pixel region  110   a , and is shared by a plurality of pixels. Note that the conversion element  1111  may be provided with a conversion element for directly converting the incident radiation R into an electric signal without constituting the scintillator described above, so that the incident radiation R is converted into an electric signal. The switching element  1112  is an element for electrically connecting the column signal line  114  and the conversion element  1111 , and outputs an electric signal obtained by the conversion element  1111  to the column signal line  114 . The switching element  1112  includes, for example, a thin film transistor (TFT) formed of a semiconductor such as amorphous silicon or polycrystalline silicon (preferably polycrystalline silicon) and having an active region. 
     Each of the plurality of correction pixels  112  includes a conversion element  1121  and a switching element  1122 . The conversion element  1121  has the same structure as that of the conversion element  1111 , and converts the incident radiation R into an electric signal. The switching element  1122  is formed in the same structure as that of the switching element  1112 , and is a switch for electrically connecting the column signal line  114  and the conversion element  1121 , and outputs an electric signal obtained by the conversion element  1121  to the column signal line  114 . 
     The correction pixel  112  has the same structure as that of the detection pixel  111 . However, the detection pixel  111  has a larger area for detecting the incident radiation R than the correction pixel  112 . For example, when the correction pixel  112  has a direct conversion element  1121  for directly converting incident radiation R into an electric signal, the correction pixel  112  adopts a configuration in which a shielding member using heavy metals such as lead is provided on the conversion element  1121  as a shielding member for shielding radiation R. Further, when the correction pixel  112  has, for example, an indirect conversion element  1121  that converts incident radiation R into light by using a scintillator and converts this light into an electric signal, a shielding member that uses, for example, an aluminum shielding film as a shielding member for shielding the light is provided between the conversion element of the correction pixel  112  and the scintillator. The correction pixel  112 , whether the conversion element  1121  is a direct type or an indirect type, is arranged in a region where the shielding member overlaps at least a part of the conversion element  1121  of the correction pixel  112  in a plan view with respect to the pixel region  110   a.    
     The correction pixel  112  is shielded from radiation R, detects a dark current component or a crosstalk component, and outputs an electric signal related to the detected dark current component or the crosstalk component. The detection pixel  111  outputs an electric signal related to the radiation image based on the incident radiation R. The signal processing unit  150  generates a more appropriate radiation image by subtracting the electric signal relating to the dark current component or the crosstalk component outputted from the correction pixel  112  from the electric signal relating to the radiation image outputted from the detection pixel  111  via the readout circuit  130 . 
       FIG. 3  is a diagram showing an arrangement example of a plurality of regions of interest (ROI)  301 - 305  set in the pixel region  110   a  of the radiation detector  110  shown in  FIG. 2 . In the present embodiment, the region of interest (ROI)  301 - 305  is an area for detecting the dose of the radiation R incident on the pixel region  110   a  in order to perform the automatic exposure control (AEC) for stopping the irradiation of the radiation R from the radiation source  250 . In the present embodiment, in the pixel region  110   a  of the radiation detector  110 , the region of interest  301 - 305  has a detection pixel  111  and a correction pixel  112 , and regions other than the region of interest  301 - 305  have a detection pixel  111 . 
     Here, the description of  FIG. 2  is returned again. The radiation detector  110  further includes a plurality of column signal lines  114 , a plurality of driving lines  113 , and a plurality of bias lines  115  in the pixel region  110   a . The plurality of column signal lines  114  are connected in common to the pixels of each column in the pixel region  110   a . The plurality of driving lines  113  are connected in common to the pixels of each row in the pixel region  110   a . The plurality of bias lines  115  are connected in common to the pixels of each column in the pixel region  110   a.    
     In the pixel region  110   a , the first electrode of the conversion element  1111  of the detection pixel  111  is connected to the first main electrode of the switching element  1112  of the detection pixel  111 . The second electrode of the conversion element  1111  of the detection pixel  111  is connected to the bias line  115 . Here, one bias line  115  extends in the column direction of the pixel region  110   a  and is commonly connected to the second electrodes of the plurality of conversion elements  1111  arranged in the column direction. The second main electrode of the switching element  1112  of the detection pixel  111  is connected to the column signal line  114 . 
     In the pixel region  110   a , the first electrode of the conversion element  1121  of the correction pixel  112  is connected to the first main electrode of the switching element  1122  of the correction pixel  112 . The second electrode of the conversion element  1121  of the correction pixel  112  is connected to the bias line  115 . Here, one bias line  115  is commonly connected to the second electrodes of the plurality of conversion elements  1121  arranged in the column direction of the pixel region  110   a . The second main electrode of the switching element  1122  of the correction pixel  112  is connected to the column signal line  114 . 
     In this manner, the second main electrodes of both the switching elements  1112  and the switching elements  1122  in each column are respectively connected to the column signal lines  114  in each column. The control electrodes of the switching elements  1112  and the switching elements  1122  in each row are connected to the driving lines  113  in each row. The plurality of column signal lines  114  are connected to the readout circuit  130 . 
     The driving circuit  120  supplies voltages Vg 1 -Vgn to a plurality of pixels in a row unit through a plurality of driving lines  113 . 
     The power supply circuit  140  supplies a bias voltage Vs to the bias line  115 . The power supply control unit  101  includes a battery, a DC-DC converter, and the like. The power supply control unit  101  controls the power supply circuit  140  to generate a power supply voltage for an analog circuit and a power supply voltage for a digital circuit for performing drive control, communication, and the like. 
     The readout circuit  130  includes a plurality of detection units  131 , a multiplexer  132 , and an analog-to-digital converter (Hereinafter referred to as “AD converter”)  133 . As shown in  FIG. 2 , the plurality of column signal lines  114  are respectively connected to the plurality of detection units  131 . At this time, one column signal line  114  is connected to one detection unit  131 . The detection unit  131  has, for example, a differential amplifier and amplifies the electric signal of the column signal line  114 . The multiplexer  132  selects one of the plurality of detection units  131  in a predetermined order and supplies an electric signal from the selected detection unit  131  to the AD converter  133 . The AD converter  133  converts the supplied electric signal from an analog signal to a digital signal and outputs the digital signal. 
     The signal processing unit  150  processes the electric signal output from the AD converter  133  to output a radiation image based on the radiation R applied to the radiation detector  110  (pixel region  110   a ) of the radiation imaging apparatus  100 . Specifically, the signal processing unit  150  performs signal processing for subtracting the electric signal relating to the dark current component or the crosstalk component generated by the correction pixel  112  from the electric signal relating to the radiation image generated by the detection pixel  111 . 
     The imaging apparatus control unit  160  performs detection of irradiation of the radiation R, calculation of the irradiation amount of the radiation R, calculation of the integrated irradiation amount, and the like on the basis of information from the signal processing unit  150 . The imaging apparatus control unit  160  controls the driving circuit  120 , the readout circuit  130 , and the like on the basis of information from the signal processing unit  150  and a control command from the control device  310  shown in  FIG. 1 . Further, the imaging apparatus control unit  160  transmits information from the signal processing unit  150  to the control device  310  via the wired communication unit  102  or the wireless communication unit  103 . 
       FIG. 4  is a diagram showing an example of the internal configuration of the imaging apparatus control unit  160  shown in  FIG. 2 . As shown in  FIG. 4 , the imaging apparatus control unit  160  includes a driving control unit  161 , a CPU  162 , a memory  163 , a radiation generating apparatus control unit  164 , an image data control unit  165 , a communication switching unit  166 , and a defect determination/correction unit  167 . 
     The driving control unit  161  controls the drive of the driving circuit  120  and the readout circuit  130  shown in  FIG. 2  based on the information from the signal processing unit  150  shown in  FIG. 2  and the command from the control device  310  shown in  FIG. 1 . 
     The CPU  162  controls the entire radiation imaging apparatus  100  using programs and various data stored in the memory  163 . 
     The memory  163  stores, for example, programs to be executed by the CPU  162 , and various data. In this case, the various data include various data obtained by the processing of the CPU  162  and image data of the radiation image. 
     The radiation generating apparatus control unit  164  controls the operation of the radiation generating device  240  shown in  FIG. 1  based on the information from the signal processing unit  150  and the information from the driving control unit  161  shown in  FIG. 2 . The radiation generating apparatus control unit  164  and the radiation generating device  240  communicate information relating to the control of the radiation generating device  240  (for example, notification of the start or stop of irradiation of the radiation R, the amount of irradiation of the radiation R and the integrated amount of irradiation, etc.). 
     The image data control unit  165  controls the memory  163  to store the image data of the radiation image from the signal processing unit  150  shown in  FIG. 2 . The image data control unit  165  controls communication with the control device  310  shown in  FIG. 1  to communicate image data of the radiation image and information relating to the control (For example, a control command or the like). 
     The communication switching unit  166  enables communication by the wired communication unit  102  when the communication cable  211  is connected to the radiation imaging apparatus  100 , and enables communication by the wireless communication unit  103  when the communication cable  211  is disconnected from the radiation imaging apparatus  100 . 
     Based on the image data of the radiation image stored in the memory  163 , the defect determination/correction unit  167  determines whether or not each of the plurality of detection pixels  111  is defective, and generates an image defect map and a dose detection defect map both related to the pixel defect provided in the pixel region  110   a . In this case, the defect maps such as the image defect map and the dose detection defect map are those in which information on the pixel position of a defective pixel detected by performing an inspection at the time of shipment inspection after manufacturing or periodic calibration accompanied by irradiation is registered. In the present embodiment, at least two kinds of defect maps are used as the defect maps for images. Specifically, the first image defect map out of the two types of image defect maps is a first image defect map in which a defective linear pixel group is not included in the region of interest  301 - 305  for detecting the dose of radiation R (the irradiation amount of radiation R) in the pixel region  110   a  (the linear pixel group for detecting the dose of radiation R is not included as a defective pixel) in order to perform automatic exposure control (AEC) for stopping the irradiation of radiation R from the radiation source  250 . The second image defect map out of the two types of image defect maps is a second image defect map in which a defective linear pixel group is included in the region of interest  301 - 305  (the linear pixel group for detecting the dose of radiation R is included as a defective pixel). The defect determination/correction unit  167  stores the generated image defect map (including the first image defect map and the second image defect map described above) and the dose detection defect map in the memory  163 . 
     Then, the defect determination/correction unit  167  performs defect determination on the dose of the detected radiation R using the dose detection defect map stored in the memory  163 . The defect determination/correction unit  167  performs defect correction on the image data of the radiation image by using the image defect map (including the first image defect map and the second image defect map described above) stored in the memory  163 . In this case, in the defect correction, in the case of correcting a point defect (isolated defective pixel), the defect correction is performed by replacing it with the average value of surrounding pixels. In the case of correcting a line defect (defective line) which is a group of defective linear pixels, correction is performed by replacing it with the average value of pixels of the preceding and following orthogonal lines, that is, the average value of the upper and lower pixels. In addition, the line defect, which is a group of defective linear pixels described here, is a group of defective pixels in a row direction, which is a horizontal direction, and the column direction is similarly corrected by substituting the average of the right and left pixels. However, the defect correction is not limited to that described here. 
     Next, the operation of the radiation imaging system  10  at the time of photographing with the automatic exposure control (AEC) will be described. 
     The operator S uses the input device  330  to set subject information such as the ID, name, and date of birth of the subject H and photographing information such as the photographing position of the subject H to the control device  310 . Subsequently, the operator S uses the input device  330  to input the dose of the radiation R, the maximum irradiation time of the radiation R, the tube current and tube voltage of the radiation source  250 , the region of interest for detecting the dose of the radiation R in order to perform the automatic exposure control (AEC), and the site information to the control device  310 . 
     Then, the control device  310  transmits the irradiation conditions of the radiation R inputted from the input device  330 , the region of interest for detecting the dose of the radiation R in order to perform the automatic exposure control (AEC), the site information, and the like to the radiation imaging apparatus  100  and the radiation generating device  240 . 
     When the photographing preparation is completed, the operator S depresses the radiation irradiation switch  320 . When the radiation irradiation switch  320  is depressed, the radiation source  250  irradiates the subject H with the radiation R under the control of the radiation generating device  240 . At this time, the radiation imaging apparatus  100  communicates with the radiation generating device  240  to perform irradiation start control of the radiation R. The radiation R irradiated to the subject H passes through the subject H and enters the radiation imaging apparatus  100  (specifically, radiation detector  110 ). The radiation imaging apparatus  100  drives a driving line  113  designated for each designated region of interest by a driving circuit  120 . The plurality of detection pixels  111  connected to the designated driving line  113  detect the dose of the radiation R (the irradiation amount of the radiation R) and output the detected dose as dose information. 
     Then, the imaging apparatus control unit  160  calculates an integrated irradiation amount that is an integrated value of the dose of the radiation R detected by the detection pixel  111  during a predetermined period. Further, the imaging apparatus control unit  160  calculates a target value of an appropriate dose from the site information and photographing conditions inputted by the operator S, and determines the irradiation stop timing of the radiation R. When the integrated irradiation amount of the radiation R calculated by the imaging apparatus control unit  160  reaches the target value, the radiation imaging apparatus  100  transmits a radiation irradiation stop signal to the radiation generating device  240  via the communication cable  211 , the communication control device  220  and the communication cable  213 . In this case, the radiation generating device  240  stops irradiation of the radiation source  250  with the radiation R based on the radiation irradiation stop signal received from the radiation imaging apparatus  100 . 
     After the irradiation of the radiation R is stopped, the detection pixel  111  converts the incident radiation R into an electric signal and generates an electric signal (radiation image signal) relating to the radiation image. An AD converter  133  converts an analog radiation image signal into a digital radiation image signal. Then, the signal processing unit  150  subtracts the electric signal related to the dark current component or the crosstalk component from the radiation image signal output from the AD converter  133  to generate image data of an appropriate radiation image. The imaging apparatus control unit  160  transmits image data of the generated digital radiation image to the control device  310  via the communication cable  211 , the communication control device  220 , and the communication cable  360 . 
     The control device  310  processes the image data of the radiation image received from the imaging apparatus control unit  160 . Then, the control device  310  displays the radiation image based on the image data of the image-processed radiation image on the display device  340 . In this embodiment, the control device  310  also functions as an image processing apparatus and a display control apparatus. 
       FIG. 5  is a flowchart showing an example of a processing procedure in the control method of the radiation imaging apparatus  100  according to the first embodiment of the present invention. In the processing of the flowchart shown in  FIG. 5 , processing up to the defective pixel correction of the radiation image is shown. 
     Before the start of photographing, first, in step S 101 , the defect determination/correction unit  167  stores and registers the generated first image defect map in the memory  163 . 
     Subsequently, in step S 102 , the defect determination/correction unit  167  stores and registers the generated second image defect map in the memory  163 . 
     Here, specific examples of the first image defect map registered in step S 101  and the second image defect map registered in step S 102  will be described.  FIGS. 6A and 6B  show a first embodiment of the present invention, and shows specific examples of the first image defect map  610  and the second image defect map  620  stored in the memory  163  shown in  FIG. 4 . Here, the first image defect map  610  shown in  FIG. 6A  and the second image defect map  620  shown in  FIG. 6B  are, for example, defect maps related to pixel defects provided in the pixel region  110   a  of the radiation detector  110  shown in  FIG. 3 . 
     The first image defect map  610  shown in  FIG. 6A  is an image defect map effective when the above-described automatic exposure control (AEC) operation is not performed (That is, in the case where the detection of the dose of the radiation R (the irradiation amount of the radiation R) is not performed in the region of interest  301 - 305  shown in  FIG. 3 ). The first image defect map  610  shown in  FIG. 6A  is an image defect map including isolated defective pixels  611  that are point defects. 
     The second image defect map  620  shown in  FIG. 6B  is an image defect map effective when the above-described automatic exposure control (AEC) operation is performed (that is, in the case where the detection of the dose of the radiation R (the irradiation amount of the radiation R) is performed in the region of interest  301 - 305  shown in  FIG. 3 ). The second image defect map  620  shown in  FIG. 6B  is an image defect map including, in addition to isolated defective pixels  621  that are point defects, defective pixels (lines)  622 - 0  to  622 - 2  that are a group of defective linear pixels included in the region of interest  301 - 305 . The pixels included in the region of interest  301 - 305  may use some of the pixels for generating the radiation image in the AEC operation, and the rows in which the pixels used in the AEC operation are located cannot be used to generate the radiation image because the electrical signals are read out during the AEC operation. Therefore, in this embodiment, in the second image defect map  620  shown in  FIG. 6B , the pixel groups of the rows (lines) that cannot be used for generating the radiation image are the defective pixels (lines)  622 - 0  to  622 - 2 . Here, the second image defect map  620  shown in  FIG. 6B  is an image defect map in the case where all the region of interest  301 - 305  are applied as a region of interest for detecting the dose of radiation R in order to perform automatic exposure control (AEC). In the present embodiment, the second image defect map  620  is not limited to the one shown in  FIG. 6B , and for example, a second image defect map may be generated for each region of interest used when performing automatic exposure control (AEC), stored in the memory  163 , and registered. 
     On the other hand, since the first image defect map  610  shown in  FIG. 6A  is an image defect map effective when the automatic exposure control (AEC) operation is not performed, the image defect map does not include the defective pixels (lines)  622 - 0  to  622 - 2  shown in  FIG. 6B , but only includes the isolated defective pixels  621  that are point defects. 
     Here, the description of  FIG. 5  is returned again. After the processing in step S 102  is completed, in step S 103 , the radiation imaging apparatus  100  starts photographing to acquire a radiation image. 
     When the photographing is started, in step S 104 , the imaging apparatus control unit  160  determines whether or not to execute the above-described automatic exposure control (AEC) operation. 
     As a result of the determination in step S 104 , when the above-described operation of automatic exposure control (AEC) is performed (S 104 /YES), the process proceeds to step S 105 . In step S 105 , the defect determination/correction unit  167  validates the second image defect map  620  as the image defect map used when the defect image correction of the radiation image obtained by photographing is performed. 
     On the other hand, as a result of the determination in step S 104 , if the above-described automatic exposure control (AEC) operation is not performed (step  104 /NO), the process proceeds to step S 106 . In step S 106 , the defect determination/correction unit  167  validates the first image defect map  610  as the image defect map used when the defect image correction of the radiation image obtained by photographing is performed. 
     When the process of step S 105  is completed or when the process of step S 106  is completed, the process proceeds to step S 107 . In step S 107 , the defect determination/correction unit  167  corrects the defect image of the radiographic image obtained by photographing by using the valid image defect map (the second image defect map  620  when the AEC operation is performed, and the first image defect map  610  when the AEC operation is not performed). 
     When the process of step S 107  is completed, the process of the flowchart shown in  FIG. 5  is completed. 
     In the radiation imaging apparatus  100  according to the first embodiment described above, the defect determination/correction unit  167  selects either of the first image defect map  610  and the second image defect map  620  according to whether or not automatic exposure control (AEC) is performed, and corrects the radiation image using the selected image defect map. Specifically, the defect determination/correction unit  167  selects the first image defect map  610  to correct the radiation image when not performing AEC, and selects the second image defect map  620  to correct the radiation image when performing AEC. According to this configuration, in the radiation imaging apparatus  100  having the function of automatic exposure control (AEC), the defective pixel correction of the radiation image can be performed appropriately and with high accuracy both in the case of performing AEC and in the case of not performing AEC. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. In the description of the second embodiment described below, matters common to the first embodiment will be omitted, and matters different from the first embodiment will be described. 
     The schematic configuration of the radiation imaging system according to the second embodiment is the same as that of the radiation imaging system  10  according to the first embodiment shown in  FIG. 1 . The internal configuration of the radiation imaging apparatus  100  according to the second embodiment is the same as that of the radiation imaging apparatus  100  according to the first embodiment shown in  FIG. 2 . The internal configuration of the imaging apparatus control unit  160  according to the second embodiment is the same as that of the imaging apparatus control unit  160  according to the first embodiment shown in  FIG. 4 . 
       FIG. 7  is a flowchart showing an example of a processing procedure in the control method of the radiation imaging apparatus  100  according to the second embodiment of the present invention. In the processing of the flowchart shown in  FIG. 7 , processing up to the defective pixel correction of the radiation image is shown. 
     Before the start of photographing, first, in step S 201 , the defect determination/correction unit  167  stores and registers the generated first image defect map in the memory  163 . 
     Subsequently, in step S 202 , in order to perform automatic exposure control (AEC), the defect determination/correction unit  167  sets a defective pixel register related to the defective linear pixel group in a region of interest for detecting the dose of the radiation R in the pixel region  110   a , and stores and registers it in the memory  163 . At this time, as the defective pixel register, information including position information such as coordinates in the defective linear pixel group is set. 
     Here, specific examples of the first image defect map registered in step S 201  and the defect pixel register registered in step S 202  will be described.  FIGS. 8A to 8D  show a second embodiment of the present invention, and shows specific examples of the first image defect map  810  and the defect pixel register stored in the memory  163  shown in  FIG. 4 . 
     The image defect maps shown in  FIGS. 8A to 8D  are common in that they include isolated defective pixels (defective pixel  811  in  FIG. 8A , defective pixel  821  in  FIG. 8B , defective pixel  831  in  FIG. 8C , and defective pixel  841  in  FIG. 8D  that are point defects). In the image defect map shown in  FIGS. 8B to 8D , a defective pixel register for a defective pixel (line), which is a group of defective linear pixels, is registered in accordance with a region of interest for detecting the dose of radiation R related to automatic exposure control (AEC). In the AEC defect line information  815 - 845  corresponding to the image defect maps shown in  FIGS. 8A to 8D , the positions line_pos [ 0 ] to line_pos [ 2 ] of the defect lines are common, but the defect line enable lines line_en [ 0 ] to line_en [ 2 ] indicating whether or not each defect line is effective are different. 
     The image defect map  810  shown in  FIG. 8A  is a first image defect map that is set when the automatic exposure control (AEC) operation is not performed (that is, in the case where the detection of the dose of the radiation R (the irradiation amount of the radiation R) is not performed in the region of interest  301 - 305  shown in  FIG. 3 ). The image defect map (first image defect map)  810  shown in  FIG. 8A  is an image defect map including only isolated defect pixels  811  that are point defects. In the image defect map (first image defect map)  810  shown in  FIG. 8A , as shown in the AEC defect line information  815 , all of the defect line enable lines_en [ 0 ] to line_en [ 2 ] are OFF. 
     The image defect map  820  shown in  FIG. 8B  shows a state set when the automatic exposure control (AEC) operation is performed. Specifically, the image defect map  820  shown in  FIG. 8B  is an image defect map in which a defect pixel register related to a defective pixel (line)  822 - 1 , which is a group of defective linear pixels, is registered at a position of a central region of interest  303  in an image defect map (first image defect map)  810  shown in  FIG. 8A , for detecting a dose of radiation R related to automatic exposure control (AEC). In the image defect map  820  shown in  FIG. 8B , as shown in the AEC defect line information  825 , only the defect line enable line_en [ 1 ] is turned on. 
     The image defect map  830  shown in  FIG. 8C  shows a state set when the automatic exposure control (AEC) operation is performed. Specifically, the image defect map  830  shown in  FIG. 8C  is an image defect map in which a defect pixel register related to the defective pixels (lines)  832 - 0  to  832 - 1 , which are a group of defective linear pixels, is registered at the position of the region of interest  301 - 303  in an image defect map (first image defect map)  810  shown in  FIG. 8A , in the lung field for detecting the dose of the radiation R related to the automatic exposure control (AEC). In the image defect map  830  shown in  FIG. 8C , as shown in the AEC defect line information  835 , only the defect line enable line_en [ 2 ] is OFF. 
     The image defect map  840  shown in  FIG. 8D  shows a state set when the automatic exposure control (AEC) operation is performed. Specifically, the image defect map  840  shown in  FIG. 8D  is an image defect map in which the defect pixel register related to the defective pixels (lines)  842 - 0  to  842 - 2 , which are a group of defective linear pixels, is registered at the positions of all the regions of interest  301 - 305  in an image defect map (first image defect map)  810  shown in  FIG. 8A , for detecting the dose of the radiation R related to the automatic exposure control (AEC). In the image defect map  840  shown in  FIG. 8D , as shown in the AEC defect line information  845 , the defect line enable line_en [ 0 ] to line_en [ 2 ] are all turned ON. 
     Here, the description of  FIG. 7  is returned again. After the processing in step S 202  is completed, in step S 203 , the radiation imaging apparatus  100  starts photographing to acquire a radiation image. 
     When the photographing is started, in step S 204 , the imaging apparatus control unit  160  determines whether or not to execute the above-described automatic exposure control (AEC) operation. 
     As a result of the determination in step S 204 , when the above-described operation of the automatic exposure control (AEC) is performed (S 204 /YES), the process proceeds to step S 205 . In step S 205 , the defect determination/correction unit  167  makes the defective pixel register registered in step S 202  valid (turns on the defective pixel register). 
     On the other hand, as a result of the determination in step S 204 , if the above-described operation of the automatic exposure control (AEC) is not performed (step  204 /NO), the process proceeds to step S 206 . In step S 206 , the defect determination/correction unit  167  invalidates the defective pixel register registered in step S 202  (turns off the defective pixel register). 
     When the process of step S 205  is completed or when the process of step S 206  is completed, the process proceeds to step S 207 . In step S 207 , the defect determination/correction unit  167  validates the first image defect map registered in step S 201 . Here, if the above-described automatic exposure control (AEC) operation is not performed, the state of the defect map for image used in a case where the defect pixel correction of the radiation image is performed is the state of the image defect map  810  shown in  FIG. 8A . In addition, when the above-described automatic exposure control (AEC) operation is performed, the state of the defect map for image used in a case where the defect pixel correction of the radiation image is performed is one of the states of the image defect maps  820 - 840  shown in  FIGS. 8B to 8D , depending on the region of interest for detecting the dose of the radiation R related to the AEC. 
     Subsequently, in step S 208 , the defect determination/correction unit  167  corrects the defect image of the radiographic image obtained by the photographing by using the first image defect map valid in step S 207  and the information of the defect pixel register (information on the defective pixel register that became valid in step S 205  or information on the defective pixel register that became invalid in step S 206 ). 
     When the process of step S 208  is completed, the process of the flowchart shown in  FIG. 7  is completed. 
     In the radiation imaging apparatus  100  according to the second embodiment described above, the defect determination/correction unit  167  sets a group of defective linear pixels in the region of interest of the pixel region  110   a , selects whether the setting is valid or invalid according to whether or not automatic exposure control (AEC) is performed, and corrects the radiation image by using the selected valid or invalid information and the first image defect map  810 . Specifically, the defect determination/correction unit  167  selects invalidity of the setting when not performing AEC, corrects the radiation image by using the information related to the selected invalidity and the first image defect map  810 , selects the validity of the setting when performing AEC, and corrects the radiation image by using the selected information related to the validity and the first image defect map  810 . According to this configuration, in the radiation imaging apparatus  100  having the function of automatic exposure control (AEC), the defective pixel correction of the radiation image can be performed appropriately and with high accuracy both in the case of performing AEC and in the case of not performing AEC. 
     Other Embodiments 
     In the first and second embodiments described above, defect determination is performed from a radiation image obtained by irradiating radiation R, but defect determination may be performed using an image obtained without irradiating radiation R. In the first and second embodiments described above, defect determination/correction is performed from one type of image, but defect determination/correction may be performed for images in a plurality of photographing modes (for example, a size difference due to binning processing, a sensor gain difference, a fluoroscopic mode, a continuous photographing mode, etc.). In the first and second embodiments described above, in the operation of automatic exposure control (AEC), defective pixels as a linear pixel group have been described as an example, but the present invention is applicable not only to the case where the defective pixels are linearly located, but also to various defective pixel shapes. For example, by specifying a pixel to be used for the operation of automatic exposure control (AEC) among the detection pixels  111  and connecting the pixel to a separately provided AEC dedicated driving line, it is possible to discretely position defective pixels accompanying the AEC operation. In this case, the defect map corresponding to the layout of the pixels connected to the AEC exclusive driving line is generated, and the defect pixel correction is performed by using the defect map. In the first and second embodiments described above, the pixels used for the automatic exposure control (AEC) are arranged in the region of interest (ROI)  301 - 305  shown in  FIG. 3 , but the pixels used for the AEC need not be limited to the pixels located in the ROI. In this manner, the present invention provides a mechanism for properly correcting defective pixels in a radiation image in accordance with whether or not an AEC operation using pixels located in various locations in various layouts is performed. 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     It should be noted that the foregoing embodiments are merely illustrative examples of the embodiments of the present invention, and the technical scope of the present invention should not be interpreted in a limited manner. That is, the present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the present invention. Accordingly, in order to make the scope of the present invention public, the following claims are attached. 
     According to the present invention, in the radiation imaging apparatus having the function of automatic exposure control (AEC), the defective pixel correction of the radiation image can be appropriately performed both in the case of performing AEC and in the case of not performing AEC. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-005077, filed Jan. 15, 2021, and Japanese Patent Application No. 2021-195715, filed Dec. 1, 2021, which are hereby incorporated by reference herein in their entirety.