Imaging device, radiation imaging device, control method thereof, and program

Abstract

To accurately and efficiently specify a luminous field used for monitoring an irradiation dose.SOLUTION: A radiation imaging device comprises: a radiation detector having a plurality of imaging pixels for imaging a radiographic image based on incident radiation and a plurality of detection pixels for monitoring an irradiation dose of the radiation; an acquisition unit configured to acquire, after a plurality of luminous fields each including one or more of the plurality of detection pixels are defined in the radiation detector, the irradiation dose in each of the plurality of luminous fields based on the irradiation dose detected from the detection pixels contained therein; and a specification unit configured to specify, based on the irradiation dose acquired from each of the plurality of luminous fields, a luminous field among the plurality of luminous fields used for monitoring the irradiation dose.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Radiation imaging devices equipped with radiation detectors (e.g., X-ray flat panel detectors) that perform automatic exposure control (hereinafter, AEC) have been put into practical use. This type of radiation imaging device is used as medical diagnostic equipment, non-destructive testing equipment, etc. Generally, the detection region targeted by AEC in a radiation detector is set by a user according to the region of interest (e.g., lung field) of the subject, which is the target part of radiation imaging. However, due to the size of the region of interest of the subject and the positional relationship between the subject and the radiation detector, the position of the set detection region may deviate from the actual position of the region of interest. Positional deviations between the detection region and the region of interest result in a decrease in the accuracy of AEC. The radiation detector described in Patent Document 1 generates multiple images for each level based on the radiation dose being monitored, and identifies the detection region based on the similarity between these multiple images and a reference image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-036467 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the technology described in Patent Document 1, multiple images are generated and compared with a reference image, which means that it takes time to identify the detection area used for AEC. If it takes time to identify the detection area, it may be difficult to stop the radiation irradiation at the appropriate time. For example, in cases where the radiation irradiation time is short, such as in chest imaging, on the order of 10 ms, it may not be possible to identify the detection area in time.

[0005] One aspect of the present invention provides a technique that enables accurate and efficient identification of an irradiation field that is to be monitored for an exposure dose. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a radiation imaging device comprising: a radiation detector having a plurality of imaging pixels for capturing a radiation image based on incident radiation and a plurality of detection pixels for monitoring the exposure dose of the radiation; a plurality of irradiation fields defined in the radiation detector, each including one or more of the plurality of detection pixels; an acquisition means for acquiring the exposure dose in each of the plurality of irradiation fields based on the exposure dose detected from the detection pixels included in the plurality of irradiation fields; and an identification means for identifying a irradiation field from the plurality of irradiation fields to be used for monitoring the exposure dose based on the exposure dose acquired from each of the plurality of irradiation fields. [Effects of the Invention]

[0007] According to the present invention, it is possible to accurately and efficiently identify the irradiation field to be monitored for the exposure dose. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of the schematic configuration of a radiation imaging system according to a first embodiment. [Figure 2] FIG. 1 is a diagram showing an example of the arrangement of a radiation imaging apparatus according to a first embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device according to the first embodiment. [Figure 4] 1A is a diagram for explaining the measurement field, FIG. 1B is a diagram for explaining the arrangement of detection pixels in the measurement field, and FIG. 1C is a diagram for explaining the arrangement of the measurement field according to the first embodiment. [Figure 5] FIG. 10 is a diagram for explaining selection of a first radiation measurement field used for monitoring an irradiation dose. [Figure 6] 10A and 10B are diagrams for explaining the process of specifying a second irradiation field used for monitoring the irradiation dose. [Figure 7] 5 is a flowchart showing control of the radiation imaging apparatus according to the first embodiment. [Figure 8] 10 is a flowchart showing a process of excluding second measurement fields containing a blank area or a skin line from a target area to be used for AEC, from a plurality of second measurement fields used for monitoring accumulated dose values, in a radiation imaging apparatus according to a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating a second measurement field included in a first measurement field and the respective cumulative dose values ​​in the processing according to the second embodiment. [Figure 10] FIG. 10 is a diagram for explaining a second measurement field used in subtraction processing according to the second embodiment. [Figure 11] FIG. 10 is a diagram showing an example of selection of a second measurement field adjacent to a first measurement field used in calculation according to the second embodiment. [Figure 12] 10A and 10B are diagrams illustrating a calculation process for identifying a second measurement field that is either completely exposed or includes a boundary with a subject, using a second measurement field adjacent to a first measurement field selected in the process according to the second embodiment. [Figure 13] 10A and 10B are diagrams illustrating a calculation process for identifying a second measurement field that is either completely exposed or includes a boundary with a subject, using a second measurement field adjacent to a first measurement field selected in the process according to the second embodiment. [Figure 14] 10A and 10B are diagrams for explaining the deviation of the imaging region from the first measurement field. [Figure 15] 10A and 10B are diagrams for explaining a process of specifying a second irradiation field used in monitoring an irradiation dose according to the third embodiment. [Figure 16] 10 is a flowchart showing control of a radiation imaging apparatus according to the third embodiment. [Figure 17] 10A and 10B are diagrams for explaining the deviation of the imaging region from the first measurement field. [Figure 18] 10A to 10C are diagrams for explaining a process for setting a first measurement field according to the fourth embodiment. [Figure 19] 10 is a flowchart showing control of a radiation imaging apparatus according to the fourth embodiment. [Figure 20] FIG. 13 is a diagram showing an example of a measurement field according to the fifth embodiment. [Figure 21]10 is a flowchart showing control of a radiation imaging apparatus according to the fifth embodiment. [Figure 22] 10 is a flowchart showing control of a radiation imaging apparatus according to the fifth embodiment. [Figure 23] FIG. 13 is a diagram showing an example of a monitoring candidate area according to the fifth embodiment. [Figure 24] FIG. 13 is a diagram showing an example of aligned cumulative doses according to the fifth embodiment. [Figure 25] FIG. 13 is a diagram showing an example of a difference in cumulative dose according to the fifth embodiment. [Figure 26] FIG. 13 is a diagram showing an example of a monitoring candidate area according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0010] [First embodiment] <About the Radiation Imaging System> 1 is a diagram showing an example of the schematic configuration of a radiation imaging system 1 according to the first embodiment. The radiation imaging system 1 includes a radiation imaging apparatus 10, a radiation generating apparatus 20, a control apparatus 300, a RIS 450, a PACS 460, and an HIS 470. RIS is an abbreviation for Radiology Information Systems. PACS is an abbreviation for Picture Archiving and Communication Systems (image server). HIS is an abbreviation for Hospital Information Systems.

[0011] The radiation generating device 20 includes a radiation tube that generates radiation, and irradiates a subject 30, such as a patient, with the radiation. The radiation imaging device 10 generates a radiation image based on the radiation irradiated from the radiation generating device 20. The radiation imaging device 10 includes, for example, a flat panel detector (FPD). The radiation imaging device 10 also has a function for performing automatic exposure control (hereinafter, referred to as AEC). Details of the radiation imaging device 10 will be described later.

[0012] The control device 300 is connectable to the radiation imaging device 10 and the radiation generation device 20. The control device 300 is also connectable to the RIS 450, PACS 460, and HIS 470 via the network 400. The control device 300 can exchange radiation images, patient information, and the like with the RIS 450, PACS 460, and HIS 470. Although FIG. 1 illustrates the radiation imaging system 1 as including the RIS 450, PACS 460, and HIS 470, the radiation imaging system 1 may be a system that does not include at least some of these.

[0013] The control device 300 includes an imaging control unit 310, an irradiation control unit 320, and a user interface (UI) control unit 330. The imaging control unit 310 communicates with the radiation imaging apparatus 10 to perform various controls for radiation imaging. For example, the imaging control unit 310 executes various communication processes associated with radiation imaging with the radiation imaging apparatus 10. In this communication process, for example, setting information for imaging conditions is transmitted from the imaging control unit 310 to the radiation imaging apparatus 10, and image information and dose information are transmitted from the radiation imaging apparatus 10 to the imaging control unit 310. The imaging conditions include a stop determination threshold Dth corresponding to a target dose to be achieved in AEC, time information (hereinafter referred to as determination timing) Ctim indicating the timing for determining a candidate radiation field, and a set irradiation time (hereinafter referred to as backup time) Bt. The imaging conditions also include radiation field information (ROI) that specifies the radiation field used for AEC. The image information includes a radiation image acquired by the radiation imaging apparatus 10 (S712 in FIG. 7). The dose information includes, for example, a normal stop request (S711 in FIG. 7) generated based on the dose information acquired by the radiation imaging apparatus 10.

[0014] The irradiation control unit 320 sets radiation irradiation conditions (tube current (mA), tube voltage (kV), backup time Bt, etc.) in the radiation generation device 20 through communication with the radiation generation device 20. The irradiation control unit 320 also transmits an irradiation control signal to the radiation generation device 20 based on an exposure permission signal and dose information (normal stop request) acquired from the radiation imaging device 10. The irradiation control unit 320 starts irradiation by the radiation generation device 20 in response to the exposure permission signal, and stops radiation irradiation by the radiation generation device 20 in response to the normal stop request.

[0015] The UI control unit 330 controls the input of information via the operation unit 331 and the output of information via the display unit 332. For example, imaging conditions and irradiation conditions are input via the operation unit 331, and the results of radiation imaging (radiation images) are output via the display unit 332. The operation unit 331 includes input devices such as a keyboard, a pointing device (e.g., a mouse), and a touch panel. The display unit 332 includes a monitor such as a liquid crystal display. The UI control unit 330 accepts imaging conditions and irradiation conditions input by a user such as a radiologist using the operation unit 331. The accepted imaging conditions are transmitted to the radiation imaging apparatus 10 via the imaging control unit 310, and the accepted irradiation conditions are transmitted to the radiation generation apparatus 20.

[0016] The imaging control unit 310, the illumination control unit 320, and the UI control unit 330 can cooperate by communicating with each other. Note that, for simplicity of explanation, the control device 300 is shown as a single device in Fig. 1, but the control device 300 may be composed of multiple devices. For example, the imaging control unit 310, the illumination control unit 320, and the UI control unit 330 may each be an independent device.

[0017] The control device 300 is connected to the radiation generation device 20 via wired communication and to the radiation imaging device 10 via wired or wireless communication, and controls the operations of the radiation generation device 20 and the radiation imaging device 10. For wired communication, a LAN (Local Area Network) such as Ethernet (registered trademark) can be used, but other wired communication methods may also be used. The wireless communication configuration includes, for example, an antenna and a communication IC. The circuit board equipped with the communication IC performs communication processing using a protocol based on a wireless LAN via the antenna. The frequency band, standard, and method of wireless communication are not particularly limited. For example, methods such as near-field communication (NFC) and proximity wireless communication, and ultra-wide band (UWB) can be used for the above-mentioned wireless communication. The control device 300 may be configured to be able to use multiple wireless communication methods and appropriately select a method to use for communication with the radiation imaging device 10.

[0018] <Configuration of the control device 300> 3 is a diagram showing an example of the configuration of the control device 300. The control device 300 has a CPU (central processing unit) 301, a RAM (writable memory) 302, a ROM (read-only memory) 303, an external memory 304, a communication interface (I / F) unit 305, and a bus 306. The CPU 301, RAM 302, ROM 303, external memory 304, and communication I / F unit 305 are connected via the bus 306 so as to be able to communicate with each other.

[0019] The CPU 301 comprehensively controls the operation of the control device 300. The CPU 301 controls, for example, each component shown in FIG. 3 via a bus 306. The RAM 302 functions as the main memory, work area, etc. of the CPU 301. When executing processing, the CPU 301 loads the necessary computer program 3031, data, etc. from the ROM 303 into the RAM 302 and executes the computer program 3031, etc. to realize various functional operations. The ROM 303 stores the computer program 3031, data, etc. required for the CPU 301 to execute processing. The computer program 3031, data, etc. may be stored in an external memory 304.

[0020] The external memory 304 is a large-capacity storage device, and is realized by, for example, a hard disk drive, an IC memory, or the like. The external memory 304 stores, for example, various types of data and information required when the CPU 301 executes the computer program 3031 and the like to perform processing. The external memory 304 also stores, for example, various types of data and information obtained when the CPU 301 executes the computer program 3031 and the like to perform processing. The communication I / F unit 305 controls communication between the control device 300 and the outside. The bus 306 communicatively connects the CPU 301 with the RAM 302, the ROM 303, the external memory 304, and the communication I / F unit 305.

[0021] The control device 300 is provided as, for example, a dedicated embedded device, but is not limited to this and may be realized by a general-purpose information processing device such as a PC (personal computer), a tablet terminal, etc. Also, as described above, the control device 300 may be configured by multiple devices, in which case each of the multiple devices has the above-mentioned configuration.

[0022] <Configuration of Radiation Imaging Apparatus 10> FIG. 2 is a diagram showing an example of the configuration of a radiation imaging device 10. The radiation imaging device 10 has a radiation detector 100 (sensor panel) in which a plurality of pixels are arranged to form a plurality of rows and a plurality of columns. The plurality of pixels arranged in the radiation detector 100 form an imaging region of the radiation detector 100. These plurality of pixels include a plurality of imaging pixels 101 for acquiring a radiographic image based on detected radiation, and a plurality of detection pixels 121 that function as detection elements for detecting doses of radiation to monitor the amount of radiation exposure. The imaging pixels 101 include a conversion element 102 that converts radiation into an electrical signal, and a switch element 103 arranged between a column signal line 106 and the conversion element 102. The detection pixel 121 has a configuration similar to that of the imaging pixel 101, and includes a conversion element 122 that converts radiation into an electrical signal, and a switch element 123 arranged between a detection signal line 125 and the conversion element 122.

[0023] The conversion elements 102, 122 include a scintillator that converts radiation into light and a photoelectric conversion element that converts light into an electrical signal. The scintillator is formed, for example, in a sheet shape so as to cover an imaging area formed by the multiple imaging pixels 101. The conversion elements 102, 122 may also be replaced with a conversion element that directly converts radiation into an electrical signal. The switch elements 103, 123 are, for example, thin film transistors (TFTs) whose active regions are made of a semiconductor such as amorphous silicon or polycrystalline silicon. In this embodiment, TFTs using polycrystalline silicon are used as the switch elements 103, 123.

[0024] The radiation imaging device 10 includes a plurality of column signal lines 106, a plurality of detection signal lines 125, a plurality of drive lines 104, and a plurality of detection drive lines 124. Each of the plurality of column signal lines 106 and each of the plurality of detection signal lines 125 corresponds to one of the columns of pixels in the imaging region of the radiation detector 100. Each of the plurality of drive lines 104 and each of the plurality of detection drive lines 124 corresponds to one of the rows of pixels in the imaging region of the radiation detector 100. Here, the "columns" correspond to the vertical direction in FIG. 2, and the "rows" correspond to the horizontal direction in FIG. 2. A drive signal is supplied to the drive lines 104 by a first drive unit 221, and a drive signal is supplied to the detection drive lines 124 by a second drive unit 241.

[0025] The first drive unit 221 supplies drive signals to the imaging pixels 101 to be driven via the drive lines 104 in accordance with control signals from the control unit 225. In this embodiment, the drive signals are signals for turning on the switch elements 103 included in the imaging pixels 101 to be driven. The switch elements 103 are turned on by a high-level signal and turned off by a low-level signal. Therefore, this high-level signal is referred to as a drive signal. When the drive signal is supplied to the imaging pixel 101, the signal accumulated in the conversion element 102 of the pixel becomes readable by the first readout unit 222. The first electrode of the conversion element 102 is connected to the first main electrode of the switch element 103, and the second electrode of the conversion element 102 is connected to a bias line 108. The bias line 108 extends in the column direction and is commonly connected to the second electrodes of the multiple conversion elements 102 arranged in the column direction. A bias voltage Vs is supplied to the bias line 108 from the power supply unit 226. In a plurality of imaging pixels 101 constituting one column, the second main electrode of the switch element 103 is connected to a corresponding one column signal line 106. In a plurality of imaging pixels 101 constituting one row, the control electrode of the switch element 103 is connected to a corresponding one drive line 104.

[0026] The multiple column signal lines 106 are connected to a first readout unit 222. The first readout unit 222 includes a detection unit 132, a multiplexer 134, and an analog-to-digital (AD) converter 136. Each of the multiple column signal lines 106 is connected to a corresponding one of the multiple detection units 132 of the first readout unit 222. One column signal line 106 corresponds to one detection unit 132. The detection unit 132 includes, for example, a differential amplifier and amplifies a signal input from the column signal line 106. The multiplexer 134 selects the multiple detection units 132 in a predetermined order and supplies a signal output from the selected detection unit 132 to the AD converter 136. The AD converter 136 converts the supplied analog signal into a digital signal and outputs it.

[0027] The detection pixels 121 have the same configuration as the imaging pixels 101. That is, a first electrode of the conversion element 122 is connected to a first main electrode of the switch element 123, and a second electrode of the conversion element 122 is connected to a bias line 108. A second main electrode of the switch element 123 is connected to a detection signal line 125. A control electrode of the switch element 123 is connected to a detection drive line 124. One or more detection pixels 121 (second main electrodes of the switch elements 123) arranged in the same column are connected to one detection signal line 125. The detection drive line 124 is driven by a second drive unit 241. One or more detection pixels 121 (control electrodes of the switch elements 123) arranged in the same row are connected to one detection drive line 124.

[0028] The second drive unit 241 supplies drive signals to the detection pixels 121 to be driven through the plurality of detection drive lines 124 in accordance with control signals from the control unit 225. When the drive signals are supplied to the detection pixels 121, the signals accumulated in the conversion elements of the detection pixels 121 become available for reading by the second readout unit 242.

[0029] The plurality of detection signal lines 125 are connected to a second readout unit 242. The second readout unit 242 includes a plurality of detection units 142, a multiplexer 144, and an AD converter 146. Each of the plurality of detection signal lines 125 is connected to a corresponding one of the plurality of detection units 142 of the second readout unit 242. One detection signal line 125 corresponds to one detection unit 142. The detection unit 142 includes, for example, a differential amplifier and amplifies the signal input from the detection signal line 125. The multiplexer 144 selects the plurality of detection units 142 in a predetermined order and supplies the signal output from the selected detection unit 142 to the AD converter 146. The AD converter 146 converts the supplied signal into a digital signal and outputs it.

[0030] The output of the AD converter 146 of the second readout unit 242 is supplied to the signal processing unit 224 and processed by the signal processing unit 224. Based on the output of the AD converter 146 of the second readout unit 242, the signal processing unit 224 generates and outputs information related to the radiation irradiated to the radiation imaging device 10. Based on the electrical signals generated by the detection pixels 121 in response to the radiation irradiated, the signal processing unit 224 acquires information about the dose of radiation incident on the detection pixels 121. The signal processing unit 224 may perform digital signal processing on signals (output of the AD converter 146) obtained by digitally converting the signals from the detection pixels 121. Based on the generated information, the signal processing unit 224 detects the start of irradiation of the radiation to the radiation imaging device 10. Alternatively, based on the generated information, the signal processing unit 224 calculates the radiation exposure dose and the cumulative exposure dose (reached dose) of radiation.

[0031] The control unit 225 controls the operations of the first driving unit 221, the second driving unit 241, the first reading unit 222, and the second reading unit 242. The control unit 225 has, for example, a CPU and memory (ROM, RAM), and can perform various processes by executing programs stored in the memory with the CPU.

[0032] The control unit 225 controls the first driving unit 221 and the first readout unit 222 based on information from the signal processing unit 224. The control unit 225 also controls the start and end of exposure (accumulation of charge in the imaging pixels 101) based on information from the signal processing unit 224. The control unit 225 also acquires, for example, dose information of radiation incident on the detection pixels 121 via the signal processing unit 224 and determines whether or not radiation irradiation needs to be stopped. The control unit 225 can also control the second driving unit 241 independently of the first driving unit 221. This allows the control unit 225 to acquire dose information from the output of the detection pixels 121 even while charge is being accumulated in the imaging pixels 101.

[0033] The radiation imaging device 10 includes a communication unit 227 for communicating with the control device 300 (imaging control unit 310). The communication unit 227 has either a wired communication unit or a wireless communication unit, or both. The communication unit 227 transmits information output from the control unit 225 to the control device 300 using the wired communication unit or the wireless communication unit. For example, the communication unit 227 outputs information on the necessity of stopping radiation irradiation, determined by the control unit 225, to the control device 300.

[0034] <Explanation of the light field> The imaging region of the radiation detector 100 defines one or more measurement fields, each including a plurality of detection pixels 121. The measurement field is a region for detecting the radiation exposure dose during radiation imaging. The exposure dose detected from the measurement field is determined based on the exposure dose detected by the detection pixels 121 included in the measurement field. The measurement field will be described using FIG. 4A as an example. As described above, the measurement field 150 is a region for detecting the exposure dose during imaging based on the exposure dose detected by the plurality of detection pixels 121 included in the measurement field. While FIG. 4A shows an example in which 5 × 5 = 25 measurement fields 150 are arranged in the imaging region of the radiation detector 100, the plurality of measurement fields may be arranged in any manner. However, by arranging the measurement fields 150 symmetrically with respect to the center of the radiation imaging device 10, AEC control can be achieved regardless of the orientation of the radiation imaging device 10. Furthermore, the shape of the measurement field 150 is not limited to a quadrilateral, such as a square or a rectangle, and may be any shape. For example, the shape of the measurement field 150 may be circular or elliptical, or may be a shape that conforms to the shape of the subject. In AEC, the generation of radiation from the radiation generating device 20 is controlled based on the exposure dose obtained from the measurement field 150 selected according to the region to be imaged, etc. The user can arbitrarily select the measurement field to be used for dose detection depending on conditions such as the region to be imaged. For example, the measurement field to be used may be selected according to the region to be imaged, or the user may be able to select the measurement field to be used during radiation imaging.

[0035] <Explanation of the light collection area according to this embodiment> Next, the configuration of the measurement field in this embodiment will be described using FIGS. 4(B) and 4(C) as examples.

[0036] As shown in FIGS. 4B and 4C, in this embodiment, in the radiation detector 100, a plurality of first measurement fields 151 are defined as a plurality of measurement fields (second measurement fields 152) each including one or more detection pixels 121. In FIG. 4B, one second measurement field 152 includes five rows and nine columns of detection pixels 121, but this is not necessarily limited to this. Also, as shown in FIGS. 4B and 4C, the plurality of first measurement fields 151 are defined as each including two or more second measurement fields 152. The first measurement field 151 is an area defined to include a plurality of second measurement fields 152. The first measurement field 151 shown in FIGS. 4B and 4C corresponds to the measurement field 150 in FIG. 4A, and the measurement field used in AEC is selected in units of the first measurement field 151. In the example of FIG. 4(B), the first measurement field 151 is composed of 2 × 2 second measurement fields 152. The second measurement fields 152 are composed of detection pixels 121 arranged in a one-dimensional or two-dimensional matrix in the imaging region of the radiation detector 100. The irradiation dose is detected for each second measurement field 152. In this embodiment, the number of detection pixels 121 included in each of the multiple second measurement fields 152 is the same, and the total value of the irradiation dose (accumulated dose value) obtained from the detection pixels 121 in the second measurement field 152 can be used as the irradiation dose for the second measurement field 152. If the number of detection pixels 121 included in each of the multiple second measurement fields 152 is different, the average value obtained by dividing the total value of the irradiation dose (accumulated dose value) obtained from each detection pixel 121 in the second measurement field 152 by the number of detection pixels 121 in the second measurement field 152 may be used. The multiple first measurement fields 151 are arranged one-dimensionally or two-dimensionally in the radiation imaging device 10. The measurement field to be used for detecting the dose among the multiple first measurement fields 151 can be arbitrarily selected depending on conditions such as the imaging region, as described in Fig. 4(A). Fig. 4(C) shows an example in which 5 x 5 = 25 first measurement fields 151, each consisting of four (2 x 2) second measurement fields 152, are arranged in the imaging region of the radiation detector 100.

[0037] Although FIG. 4C shows adjacent first illumination fields 151 as being spaced apart, this does not limit the present disclosure. A detection pixel 121 that does not belong to any second illumination field (independent detection pixel 121) may or may not exist between adjacent first illumination fields 151. Independent detection pixels 121 are not used for AEC. Similarly, in FIGS. 4B and 4C, adjacent second illumination fields 152 are not spaced apart (there are no independent detection pixels 121 between adjacent second illumination fields 152), but this is not a limitation. An independent detection pixel 121 may exist between adjacent second illumination fields 152. Furthermore, although multiple first illumination fields 151 are defined in the above example, this is not a limitation, and only one first illumination field 151 may be defined. Furthermore, one first illumination field 151 may be defined to include all of the detection pixels 121 provided in the radiation detector 100, or may be defined to include a portion of all of the detection pixels 121 provided in the radiation detector 100. Furthermore, the number of second illumination fields included in a first illumination field may be the same in all first illumination fields as shown in Fig. 4(C), or may be different.

[0038] <Specifying the light collection area> Next, we will explain the effect of treating the first measurement field 151 as an area including multiple second measurement fields, as shown in Figures 4(B) and 4(C). Figure 5 shows an example in which a measurement field selected externally for a lung field is outside the target region. In Figure 5, the first measurement fields 151a and 151b indicated by thick lines are selected based on the target region (lung field). Figure 5(A) shows an example in which radiation dose detection is performed in the selected first measurement fields 151a and 151b, and the first measurement field 151a includes an area outside the target region. Such radiation dose detection in an area outside the target region can hinder the realization of appropriate AEC. On the other hand, by configuring the first measurement field 151 with multiple smaller second measurement fields 152 as shown in Figure 5(B), it is possible to exclude the second measurement field 152a, which corresponds to a position outside the target region, from the target region used for AEC. In this way, by configuring the first measurement field 151 with the finer second measurement field 152, it is possible to select a more appropriate measurement field for the region to be imaged. Furthermore, when selecting the measurement field to use, the first measurement field 151 can be selected as a unit, allowing the user to easily select the measurement field. Furthermore, since the measurement field using the second measurement field 152 as a unit is specified, AEC using a more appropriate measurement field becomes possible, and the timing to stop radiation irradiation can be correctly determined. In other words, the detection accuracy of AEC is improved, and overexposure and underexposure can be prevented.

[0039] The second measurement field 152 for AEC is identified for each first measurement field 151 based on the cumulative irradiation dose obtained from the second measurement field 152. For example, the second measurement field to be used for AEC can be identified using easily calculated statistics such as the average, median, maximum, and minimum of the irradiation dose obtained from the multiple second measurement fields 152 included in one first measurement field 151. The second measurement field is identified by the signal processing unit 224. For example, a determination threshold can be determined based on the statistics of the cumulative irradiation dose obtained from the multiple second measurement fields 152, and the cumulative irradiation dose of each of the multiple second measurement fields 152 can be compared with the determination threshold to identify the second measurement field to be used for AEC.

[0040] More specifically, when the average or median value obtained as a statistical quantity is used, a value obtained by multiplying or adding a predetermined value α to the average or median value can be used as the judgment threshold. The judgment threshold or the predetermined value α may be set by taking into account the maximum or minimum value obtained as a statistical quantity, or the difference between them. Furthermore, if the value of the irradiation dose (or cumulative irradiation dose) obtained from the second measurement field 152 exceeds a predetermined value, the second measurement field 152 may be excluded as a non-exposed region. Furthermore, if the value of the irradiation dose (or cumulative irradiation dose) obtained from the second measurement field 152 is below a predetermined value, the second measurement field 152 may be excluded as a diaphragm region. In this way, various algorithms can be applied to the method for identifying the second measurement field used in AEC and / or the method for setting the reference value such as the judgment threshold. Furthermore, the method for identifying the second measurement field used in AEC and / or the method for setting the reference value such as the judgment threshold may be changed depending on the imaging region. Furthermore, the method for identifying the second measurement field used in AEC and / or the method for setting a reference value such as a judgment threshold may be varied depending on the position of the first measurement field (for example, the relative positional relationship of the selected first measurement field). Furthermore, in a configuration in which the number of second measurement fields included in the first measurement field is different, the method for identifying the second measurement field used in AEC and / or the method for setting a reference value such as a judgment threshold may be varied depending on the number of second measurement fields included in the first measurement field.

[0041] An example of a procedure for identifying the second measurement field 152 used for AEC based on the average value will be described using FIG. 6. For simplicity, an example will be described in which the average value itself is used as the determination value. In this embodiment, all second measurement fields 152 include the same number of detection pixels 121. In FIG. 6(A), for each of the multiple second measurement fields included in one first measurement field 151a, the numerical values ​​in parentheses represent the detected irradiation dose value (dose value). In this case, the signal processing unit 224 calculates the average of the four dose values ​​as follows: Average value: (726+1151+1264+1315) / 4=1114 The calculated average value (1114) is used as a judgment threshold, and the second measurement fields 152 having a dose value equal to or greater than the average value (judgment threshold) are selected from the plurality of second measurement fields 152. Fig. 6(B) shows the result of threshold judgment, in which the dose value of the second measurement field 152a, which has a dose value of 726, is smaller than the average value (judgment threshold), and therefore the second measurement field 152a is excluded from the measurement fields to be used for AEC. Of the plurality of second measurement fields included in the first measurement field 151A, the second measurement fields excluding the second measurement field 152a are selected as the measurement fields to be used for AEC.

[0042] Furthermore, the determination process for identifying the second measurement field to be used for AEC may be changed depending on the imaging region. For example, a large amount of radiation is transmitted through lung fields, resulting in a large detected radiation dose, while a smaller amount of radiation is transmitted around the lung fields, resulting in a smaller detected radiation dose. Therefore, in the case of lung fields, the second measurement field 152 whose dose value is equal to or greater than the determination threshold is identified as the measurement field to be used for AEC, as described above. Conversely, in the case of imaging regions with a small amount of radiation transmitted through them, the second measurement field 152 whose dose value is equal to or less than the determination threshold is identified as the measurement field to be used for AEC.

[0043] The radiation doses detected by the detection pixels 121 included in one second measurement field 152 are simultaneously read out via the second drive unit 241 in response to an instruction from the control unit 225, and a value (binned value) is obtained by combining (adding) the radiation doses (pixel value). The column-direction binning process combines (adds) the radiation doses detected by the detection pixels 121 in each column by simultaneously driving the corresponding drive lines from the control unit 225. As a result, the column-direction binned radiation doses from the detection pixels 121 included in one second measurement field 152 are output from the second readout unit 242. For example, in the case of FIG. 4B, five rows of detection drive lines 124 are simultaneously driven, and the sum of the radiation doses from the five detection pixels 121 arranged in the column direction is read out to the detection unit 142. The signal processing unit 224 then combines (adds) the radiation doses AD-converted by the AD converter 146 for each second measurement field. For example, in the case of FIG. 4B, values ​​for nine columns are added together. In this way, binning processing is performed in the column direction within one second measurement field.

[0044] By performing column-direction (vertical direction) binning, radiation doses (pixel values) detected by multiple vertically arranged detection pixels 121 are combined (added), thereby reducing the number of readouts by the second readout unit 242. This reduces noise that occurs and is added each time a radiation dose is read. This improves the signal-to-noise ratio of the exposure dose (pixel values) used in the calculation to identify the second measurement field 152, enabling accurate identification of the second measurement field to be used. Furthermore, in row-direction (horizontal direction) binning, the signal processing unit 224 acquires column-direction binning values ​​as digital signals and combines (adds) exposure doses (pixel values) from multiple rows. This compresses the amount of information, thereby shortening processing time. As described above, treating radiation doses in units of second measurement fields 152 improves the signal quality of the radiation dose, thereby improving the accuracy of measurement field selection.

[0045] Of the multiple second measurement fields 152 included in the first measurement field 151 set based on conditions such as the imaging region, one or more second measurement fields 152 selected as described above are used as the final measurement field for AEC detection. The second measurement field 152 may be composed of multiple smaller third measurement fields each including a detection pixel 121. In this case, the irradiation dose of the third measurement field is obtained by performing a binning process on the irradiation doses from the multiple detection pixels 121 included in the third measurement field. The irradiation dose of the second measurement field is determined by summing the irradiation doses obtained from the third measurement fields included in the second measurement field. First, the second measurement field to be used for AEC is identified from the multiple second measurement fields included in the first measurement field as described above. Then, the process described above is applied to the multiple third measurement fields included in the identified second measurement field to identify the third measurement field to be used for AEC.

[0046] <Image capture control> 7 is a flowchart showing imaging processing by the radiation imaging apparatus 10 according to the first embodiment. In S701, the control unit 225 of the radiation imaging apparatus 10 communicates with the control device 300 and sets various information. The set information includes imaging condition information (irradiation condition information), such as the tube voltage and tube current of the radiation tube, a stop determination threshold Dth, a set irradiation time (backup time) Bt, time information Ctim for determining the candidate irradiation field, and irradiation field information (ROI information). A first irradiation field used for AEC is selected based on the irradiation field information. The control unit 225 may receive a target dose Dref indicated by a dose index from the control device 300, convert the target dose Dref into a stop determination threshold Dth (a signal value corresponding to the target dose), and set the target dose Dref. This configuration allows the user to specify the target dose using the dose index.

[0047] In S702, the control unit 225 starts preparations to receive radiation irradiation in response to the start request signal received from the control device 300. Then, when preparations to receive irradiation are complete, the exposure permission signal is switched from Lo level to Hi level. This exposure permission signal is transmitted to the radiation generation device 20 via the irradiation control unit 320, and the radiation generation device 20 starts generating radiation. Furthermore, at the timing when the exposure permission signal is switched to Hi level, the control unit 225 controls the first drive unit 221 to start accumulating charges in the imaging pixels 101 and starts timing by an internal timer. In this way, radiation imaging is started. Processing after the start of radiation imaging will be described below.

[0048] In S703, the control unit 225 drives the second drive unit 241 to acquire dose values ​​from the multiple second irradiation fields 152 that constitute each of the selected one or more first irradiation fields 151 corresponding to the irradiation field information. As described above, the dose value obtained from each second irradiation field 152 is the binned dose value of the multiple detection pixels 121 in the second irradiation field 152. In S704, the signal processing unit 224 performs horizontal (row) binning processing and dose value accumulation processing in response to an instruction from the control unit 225, and updates the accumulated dose value.

[0049] In S705, the control unit 225 determines whether or not the second measurement field 152 used for AEC has been specified. If it is determined that the second measurement field 152 has been specified (YES in S705), the processes for specifying the second measurement field to be used for AEC (S706, S707) are skipped, and the process proceeds to S708. On the other hand, if it is determined that the second measurement field 152 has not been specified (NO in S705), the process proceeds to S706.

[0050] In S706, the control unit 225 determines whether the timing indicated by the internal timer has reached the timing indicating the execution of measurement field determination (the determination timing indicated by Ctim). If the measurement field determination timing (Ctim) has been reached (YES in S706), the control unit 225 proceeds to S707. If the measurement field determination timing (Ctim) has not been reached (NO in S706), the control unit 225 returns the process to S703. In this manner, S703 to S706 are repeated until the measurement field determination timing (Ctim) is reached. Note that the determination timing Ctim is set to, for example, A% of the backup time Bt. Here, there is no particular limitation on the value of A, and A is set so as to obtain an arriving dose that can identify the second measurement field 152 used for AEC with sufficient accuracy. Also, the value of A may be set to a different value depending on the imaging region. Also, the determination timing Ctim may be a value independent of the backup time Bt or may be a fixed value. However, it goes without saying that in either case, Bt>Ctim must be satisfied.

[0051] If it is determined that the timing indicated by the internal timer has reached the measurement field determination timing (Ctim) (YES in S706), the process proceeds to S707. In S707, the signal processing unit 224, in response to an instruction from the control unit 225, identifies a second measurement field 152 to be used for monitoring the irradiation dose for AEC for each of the one or more selected first measurement fields 151. For example, the signal processing unit 224 acquires statistics (e.g., average, median, maximum, minimum, etc.) of the cumulative dose values ​​of the multiple second measurement fields 152 included in the first measurement field 151. The signal processing unit 224 identifies the second measurement field 152 to be used based on the acquired statistics.

[0052] In S708, the control unit 225 determines whether the timing indicated by the internal timer has reached the backup time Bt, i.e., whether the backup time Bt has elapsed. If it is determined that the timing indicated by the internal timer has reached the backup time Bt (YES in S708), the process proceeds to S709, where the control unit 225 stops imaging. At this time, the radiation generation device 20 stops irradiating radiation in accordance with the backup time Bt included in the irradiation conditions. The control unit 225 controls the first drive unit 221 to read out signals from the imaging pixels 101. Then, in S712, the control unit 225 transfers the signals read out from the imaging pixels 101 to the control device 300 as a radiographic image. Note that information indicating that irradiation has stopped at the set irradiation time may be added to this radiographic image.

[0053] On the other hand, if the timing indicated by the internal timer has not yet elapsed the backup time Bt (NO in S708), the control unit 225 proceeds to S710. In S710, the control unit 225 compares the accumulated dose value from the identified second measurement field with the stop determination threshold Dth. If it is determined that the accumulated dose value is not equal to or greater than the stop determination threshold Dth (NO in S710), the control unit 225 returns to S703. On the other hand, if it is determined that the accumulated dose value is equal to or greater than the stop determination threshold Dth (YES in S710), the control unit 225 proceeds to S711. For example, if the accumulated dose values ​​of all the second measurement fields 152 identified in S707 exceed the stop determination threshold Dth, the control unit 225 determines YES in S710. Alternatively, the control unit 225 may determine YES in S710 if at least one of the accumulated dose values ​​of the second measurement fields 152 identified in S707 exceeds the stop determination threshold Dth. In S711, the control unit 225 transmits a normal stop request (AEC stop request) to the control device 300. Then, the first drive unit 221 is controlled to read signals from the imaging pixels 101, and imaging is terminated. In S712, the signals read from the imaging pixels 101 are transferred to the control device 300 as a radiographic image. Information indicating normal stop may be added to this radiographic image. The radiographic image transferred to the control device 300 is used for display on the display unit 332 for diagnosis and for dose management.

[0054] As described above, according to the above embodiment, a measurement field to be used for AEC is identified from among a plurality of second measurement fields included in a first measurement field based on the irradiation dose obtained from each of the plurality of second measurement fields. As a result, for example, in radiographic imaging, if a portion of a first measurement field is outside the region of interest (ROI), the second measurement field corresponding to the outside portion can be prevented from being used for AEC, thereby improving the accuracy of AEC. Furthermore, by changing the method and / or criteria for determining whether or not to use a second measurement field depending on the region of interest, it is possible to select a second measurement field appropriate for the region of interest. Furthermore, a common measurement field selection method (e.g., user specification of a measurement field, selection of a measurement field appropriate for the region of interest, etc.) can be used to select a first measurement field, thereby enabling an appropriate measurement field to be used for AEC without imposing any special burden on the user in specifying and selecting a measurement field.

[0055] [Second embodiment] When the first and second measurement fields 151 and 152 include a spot where radiation directly strikes the detection pixel 121 or a boundary between the spot and the subject (hereinafter referred to as a "skin line"), the accuracy of AEC may be reduced due to overexposure or underexposure, which may require re-imaging. To address this issue, the present embodiment describes a configuration in which, for a second measurement field 152 of interest among a plurality of second measurement fields 152 included in the first measurement field 151 selected as a target region to be used for AEC, the second measurement field 152 that includes the spot or the skin line is identified based on the difference between the cumulative dose value of the second measurement field 152 of interest and the sum of the cumulative dose values ​​of the adjacent second measurement fields 152, and the second measurement field 152 is excluded from the target region to be used for AEC. According to the present embodiment described below, it is possible to improve the accuracy of AEC by identifying and excluding second light collection fields 152 that include bare areas or skin lines from the second light collection fields 152 included in the first light collection field 151 selected as the target area to be used for AEC.

[0056] The configurations of the radiation imaging system 1, radiation imaging device 10, and control device 300 of the second embodiment are the same as those of the first embodiment, and in the accompanying drawings, the same or similar configurations are given the same reference numerals, and duplicated explanations will be omitted. In this embodiment, as shown in Figures 4(B) and 4(C), in the radiation detector 100, a plurality of first irradiation fields 151 are defined as a plurality of second irradiation fields 152, each of which includes one or more detection pixels 121.

[0057] In this embodiment, the control unit 225 of the radiation imaging apparatus 10 communicates with the control device 300 and selects a first measurement field to be used for AEC using a control signal based on the acquired measurement field information. Then, the signal processing unit 224 performs processing to identify a target to be used for AEC from the second measurement field 152 included in the first measurement field 151 selected as the region of the target to be used for AEC.

[0058] The second illumination field 152 used to identify the target to be used in AEC is composed of multiple detection pixels 121, as shown in FIG. 4B. If the second illumination field 152 does not include multiple detection pixels 121 but is independent of each other, the number of output pixels increases, which requires a long calculation process to identify the illumination field to be used in AEC. In addition, an appropriate signal-to-noise ratio for the exposure dose (pixel value) per detection pixel 121 cannot be ensured, which may reduce the accuracy of identifying the second illumination field 152 to be used in AEC. On the other hand, if too many detection pixels 121 are included in the second illumination field 152, many areas other than the target area will be included, which may reduce the accuracy of identifying the second illumination field 152 to be used in AEC. As an example of the number of pixels, assuming that the second illumination field 152 includes 15 rows and 15 columns of detection pixels 121, the sum of the irradiation doses obtained from each of the detection pixels 121 in the second illumination field 152 may be divided by the number of detection pixels 121 to calculate an average value, which may be used as a representative value for the second illumination field 152. This reduces the amount of calculation required to identify the second illumination field 152 used for AEC, shortens the time required for calculation processing, and ensures an appropriate signal-to-noise ratio of the irradiation dose (pixel value). Note that the configuration of 15 rows and 15 columns of detection pixels 121 shown for explaining the calculation of the average value is merely an example, and the average value may be calculated using various settings.

[0059] 8 is a flowchart showing a process for excluding second measurement fields 152 containing a non-exposed area or a skin line from the area to be used for AEC, among the multiple second measurement fields 152 used for monitoring the cumulative dose value, in the radiation imaging apparatus 10 according to the second embodiment. Steps S801 and S802 are similar to steps S701 and S702 in the flowchart of FIG. 7. In step S801, the control unit 225 of the radiation imaging apparatus 10 communicates with the control device 300 and sets various information. In step S802, the control unit 225 starts preparations for radiation irradiation in response to a start request signal received from the control device 300. Once preparations for irradiation are complete, the control unit 225 switches the exposure permission signal from Low level to High level. This exposure permission signal is transmitted to the radiation generation device 20 via the irradiation control unit 320, and the radiation generation device 20 starts generating radiation. The control unit 225 controls the first drive unit 221 to start accumulating charges in the imaging pixels 101 and starts timing using an internal timer.

[0060] In S803, similarly to S703, the control unit 225 drives the second drive unit 241 to acquire dose values ​​(dose information) from the plurality of second measurement fields 152 that respectively constitute the one or more selected first measurement fields 151 corresponding to the measurement field information. In this step, in addition to acquiring dose values ​​(dose information), the control unit 225 also acquires dose information for the second measurement fields 152 adjacent to the one or more selected first measurement fields 151. Specific examples of the processing in this step will be described later with reference to FIGS. 9 to 13.

[0061] S804 to S806 are the same as S704 to S706, and in S804, the signal processing unit 224 performs binning processing and dose value accumulation processing to update the accumulated dose value in response to an instruction from the control unit 225. In S805, the control unit 225 determines whether or not the identification of the second measurement field 152 to be used for AEC has been completed. In S806, the control unit 225 determines whether or not the timing indicated by the internal timer has reached the timing indicating the execution of measurement field determination (the determination timing indicated by Ctim).

[0062] In S807, the signal processing unit 224 performs a convolution operation using a differential filter to obtain difference information between a sum of the results of multiplying the irradiation doses (cumulative dose values) of the second measurement fields adjacent to a second measurement field of interest among the second measurement fields included in each of the first measurement fields 151 by the coefficient of the differential filter and a product of the irradiation dose (cumulative dose value) of the second measurement field of interest by the coefficient of the differential filter. The obtained difference information can be a feature value indicating a change in irradiation dose (cumulative dose value) between the second measurement field of interest and each of the adjacent second measurement fields. The signal processing unit 224 identifies the second measurement field to be used for monitoring the radiation exposure dose based on the difference information (feature value) indicating the change in irradiation dose. The signal processing unit 224 identifies a second measurement field to be excluded from monitoring the irradiation dose from among the multiple second measurement fields included in the first measurement field 151 based on a comparison between the difference information (feature) indicating the change in irradiation dose and a threshold value, and identifies the second measurement field obtained by excluding the identified second measurement field from the multiple second measurement fields as the second measurement field to be used for monitoring the irradiation dose.

[0063] 10(c), the signal processor 224 acquires difference information between a sum of the cumulative dose values ​​of adjacent second measurement fields 152 (e.g., 152(o, m, p, k, l, q, n, r)) multiplied by a coefficient of a differential filter for a second measurement field 152 of interest (e.g., 152j) among the plurality of second measurement fields 152 included in the selected first measurement field 151, and a product of the cumulative dose value of the second measurement field 152 of interest multiplied by the coefficient of the differential filter. The signal processor 224 performs threshold-based judgment on the acquired difference information to identify second measurement fields 152 that include a bare area or a skin line and exclude them from the target area used for AEC. In this step, the signal processor 224 performs similar processing on each of the plurality of second measurement fields 152 included in the selected first measurement field 151 as the second measurement field of interest. A specific example of the process in S807 will be described later with reference to FIGS.

[0064] S808 to S812 are the same as S708 to S712. In S808, the control unit 225 determines whether the timing indicated by the internal timer has reached the backup time Bt, that is, whether the backup time Bt has elapsed. If it is determined that the timing indicated by the internal timer has reached the backup time Bt (YES in S808), the process proceeds to S809, and the control unit 225 stops image capture.

[0065] On the other hand, if the timing indicated by the internal timer has not yet passed the backup time Bt (NO in S808), the control unit 225 proceeds to S810. In S810, the control unit 225 compares the cumulative dose value from the identified second measurement field with the stop determination threshold Dth.

[0066] If it is determined that the accumulated dose value is not equal to or greater than the stop determination threshold Dth (NO in S810), the control unit 225 returns the process to S803. On the other hand, if it is determined that the accumulated dose value is equal to or greater than the stop determination threshold Dth (YES in S810), the control unit 225 proceeds to S811. In S811, the control unit 225 transmits a normal stop request (AEC stop request) to the control device 300. Then, the control unit 225 controls the first drive unit 221 to read signals from the imaging pixels 101 and terminates imaging. In S812, the signals read from the imaging pixels 101 are transferred to the control device 300 as a radiographic image. Note that information indicating normal stop may be added to this radiographic image. The radiographic image transferred to the control device 300 is used for display on the display unit 332 for diagnosis and for dose management.

[0067] <Non-visible skin line removal treatment> 9 is a diagram illustrating the second measurement fields 152 (152b-152e, 152f-152i) included in the first measurement field 151 (151c, 151d) selected when imaging the elbow using the processing according to the second embodiment, and the cumulative dose values ​​for each. Here, the first measurement field 151 collectively refers to the first measurement fields 151c and 151d, and the second measurement field 152 collectively refers to the second measurement fields 152b-152e and 152f-152i.

[0068] 9(a) shows an example in which two first illumination fields 151c and 151d are selected. The selected first illumination field 151c includes four second illumination fields 152, and the selected first illumination field 151d includes four second illumination fields 152. Note that the number of second illumination fields 152 included in the first illumination field 151 and the number of selected first illumination fields 151 are not limited to the example shown in FIG. 9(a), and it is sufficient that one or more first illumination fields 151 are selected.

[0069] 9(b) is a diagram showing details of the second measurement field 152 included in the selected first measurement fields 151c and 151d. The first measurement field 151c includes the second measurement fields 152b to 152e, and the first measurement field 151d includes the second measurement fields 152f to 152i. The numerical values ​​in the second measurement fields 152b to 152i indicate the cumulative dose values ​​at the timing of identifying the candidate measurement field (for example, YES in S806 in FIG. 8).

[0070] <Definition of adjacent skin lines> 10 is a diagram illustrating a second illumination field 152 used in a subtraction process for identifying a second illumination field that includes a clear area or a boundary (skin line) with a subject in a process according to the second embodiment. Among the second illumination fields included in the first illumination field 151 selected as a target area for AEC, a second illumination field adjacent to a second illumination field 152j of interest in at least one of the row direction (horizontal direction), column direction (vertical direction), and diagonal direction is used in the subtraction process. Specifically, the second illumination field 152 used in the subtraction process is a second illumination field adjacent to the second illumination field 152j of interest in the positional relationship shown in FIGS. 10(a), 10(b), and 10(c).

[0071] 10(a) shows an example of second illumination fields 152k, 152l and second illumination fields 152m, 152n adjacent to a second illumination field 152j of interest in two neighborhoods. When performing differential processing based on a two-neighbor adjacency relationship, the second illumination fields 152k, 152l adjacent to the second illumination field 152j of interest in two neighborhoods in the horizontal direction (row direction) or the second illumination fields 152m, 152n adjacent to the second illumination field 152j of interest in two neighborhoods in the vertical direction (column direction) are used for differential processing.

[0072] 10(b) shows an example of second measurement fields adjacent to a second measurement field 152j of interest in four neighborhoods. When performing differential processing based on a four-neighborhood relationship, second measurement fields 152k and 152l adjacent to the second measurement field 152j of interest in two neighborhoods in the horizontal direction and second measurement fields 152m and 152n adjacent to the second measurement field 152j in two neighborhoods in the vertical direction are used for differential processing.

[0073] 10(c) shows an example of second measurement fields that are eight-neighbors adjacent to a second measurement field 152j of interest. When performing differential processing based on an eight-neighbor relationship, second measurement fields 152k, 152l, 152m, 152n, 152o, 152p, 152q, and 152r that are eight neighbors horizontally, vertically, and diagonally adjacent to the second measurement field 152j of interest are used for differential processing. Note that the differential processing calculation can use either two neighbors, four neighbors, or eight neighbors as neighbor information, and a configuration may be adopted in which the neighbor information can be selected from two neighbors, four neighbors, or eight neighbors via external input.

[0074] <Selection outside the frame when selecting nearby> In the process of identifying the second measurement field 152 that includes a bare area or a skin line and excluding it from the region to be used for AEC, the accumulated dose values ​​of the second measurement fields 152s adjacent to the first measurement field 151 selected as the region to be used for AEC are also used for calculation. The multiple first measurement fields 151 are defined in a matrix in the imaging region of the radiation detector 100, and the adjacent second measurement fields 152s are adjacent to the second measurement field 152j of interest in one of two neighbors in the row direction or column direction, four neighbors in the row direction and column direction, or eight neighbors in the row direction, column direction, and diagonal directions of the imaging region.

[0075] Fig. 11 is a diagram showing an example of selecting a second measurement field 152s adjacent to a first measurement field 151 used in the calculation. Fig. 11(a) shows an example of two neighboring fields in the horizontal direction (row direction), and the accumulated dose value of the second measurement field 152s adjacent to the first measurement field 151 in the horizontal direction (row direction) is used for the calculation. Fig. 11(b) shows an example of two neighboring fields in the vertical direction (column direction), and the accumulated dose value of the second measurement field 152s adjacent to the first measurement field 151 in the vertical direction (column direction) is used for the calculation.

[0076] Fig. 11(c) shows an example of four neighborhoods, in which the calculation uses the accumulated dose values ​​of the second measurement fields 152s that are adjacent in the vertical direction (column direction) and horizontal direction (row direction) to the first measurement field 151. Fig. 11(d) shows an example of eight neighborhoods, in which the calculation uses the accumulated dose values ​​of the second measurement fields 152s that are adjacent in the vertical direction (column direction), horizontal direction (row direction) and diagonal direction to the first measurement field 151.

[0077] In response to instructions from the control unit 225, a process (neighborhood selection process) is performed to select a second measurement field adjacent to the first measurement field, and the cumulative dose values ​​of the second measurement field included in the first measurement field 151 and the cumulative dose values ​​of the second measurement field adjacent to the first measurement field, which are necessary for the calculation process, are read out, and the calculation process is performed in the signal processing unit 224.

[0078] If there is no second measurement field 152 adjacent to the first measurement field 151, or if the irradiation dose of the adjacent second measurement field cannot be obtained, difference information can be obtained by performing a calculation in which the accumulated dose value of the second measurement field located on the outer periphery of the first measurement field 151 is used as the accumulated dose value of the adjacent second measurement field 152. The signal processing unit 224 can obtain difference information by using the irradiation dose of the second measurement field 152 of interest as the irradiation dose of the adjacent second measurement field. For example, as shown in Figure 11(e), when selecting four adjacent second measurement fields, if there are no horizontally adjacent second measurement fields 152t, 152u, or if information on the cumulative dose values ​​of the second measurement fields 152t, 152u cannot be obtained, the cumulative dose values ​​of the second measurement fields 152v, 152w located on the outer periphery of the first measurement field 151 can be used as the cumulative dose values ​​of the adjacent second measurement fields 152t, 152u to obtain difference information.

[0079] <Specifying the light collection area> 12 and 13 are diagrams illustrating a calculation process for identifying a second measurement field 152 containing a bare area and a skin line using a second measurement field adjacent to a first measurement field 151 selected as a target area for AEC. FIG. 12(a) shows first measurement fields 151c and 151d selected as a target area for AEC when imaging an elbow, and a second measurement field 152s adjacent to the first measurement fields 151c and 151d (hereinafter also referred to as an adjacent second measurement field 152s). The adjacent second measurement field 152s is adjacent to eight neighbors, and the following description will be given using an example of eight neighbors. Note that the adjacent second measurement field 152s is not limited to eight neighbors, and the same applies to two-neighbor or four-neighbor measurement fields.

[0080] 12(b) shows an example of a 3×3 differential filter used in a calculation to obtain difference information between the sum of the cumulative dose values ​​in adjacent second measurement fields and the multiplied value of the cumulative dose value in the second measurement field of interest. Note that the coefficients of the differential filter are merely illustrative, and the processing of this embodiment is not limited to this example.

[0081] Figure 12(c) is a diagram illustrating the cumulative dose values ​​of the irradiation dose detected in the second irradiation fields included in the first irradiation fields 151c, 151d selected as the target area to be used for AEC, and the cumulative dose values ​​of the irradiation dose values ​​detected in each of the adjacent second irradiation fields 152s.

[0082] The first measurement field 151c includes the second measurement fields 152b-152e, and the first measurement field 151d includes the second measurement fields 152f-152i. The signal processing unit 224 performs a convolution operation using the differential filter shown in Fig. 12(b) on the accumulated dose values ​​of the second measurement fields shown in Fig. 12(c).

[0083] Fig. 13(a) is a diagram illustrating the results of a convolution operation performed using the differential filter of Fig. 12(b) with the second measurement fields 152b-152i included in the first measurement fields 151c and 151d as the second measurement fields of interest. As a specific example of the convolution operation using the differential filter shown in Fig. 12(b), a convolution operation example for the second measurement field 152b as the second measurement field of interest will be described here. In this case, the signal processing unit 224 performs the convolution operation using the differential filter of Fig. 12(b) as follows.

[0084] The signal processing unit 224 multiplies the accumulated dose values ​​of each of the eight neighboring second measurement fields of the second measurement field 152b of interest by a coefficient of a differential filter (for example, 1 in FIG. 12(b)), and sums up the eight neighboring multiplication results. Next, the signal processing unit 224 multiplies the accumulated dose value of the second measurement field 152b of interest by a coefficient of a differential filter (for example, −8 in FIG. 12(b)). Then, the signal processing unit 224 obtains difference information between the sum of the multiplication results of the accumulated dose values ​​of the eight neighboring second measurement fields and the multiplied value of the accumulated dose value of the second measurement field 152b of interest. The specific calculation result of the difference information for the second measurement field 152b of interest is as follows:

[0085] (Calculation result of difference information) 2844×1+2867×1+2956×1+2853×1+2986×1 +1623×1+1552×1+1520×1+2878×(-8)=-3823 The signal processing unit 224 performs similar calculations on the adjacent second measurement fields 152c-152i included in the first measurement fields 151c, 151d, regarding each of the other second measurement fields 152c-152i as a second measurement field of interest. The numerical values ​​of the second measurement fields 152c-152i included in the first measurement fields 151c, 151d shown in Fig. 13(a) indicate the calculation results of difference information obtained by performing similar calculations.

[0086] Next, the signal processing unit 224 performs a threshold determination on the calculation result of the difference information of the second measurement field after the calculation process. If the calculation value (difference information) of the second measurement field is equal to or less than the threshold (thr), the signal processing unit 224 determines that the second measurement field for which the calculation result of the difference information is equal to or less than the threshold is a second measurement field that includes a bare area or a skin line, and excludes the second measurement field from the region to be used for AEC. Then, the signal processing unit 224 determines, from among the second measurement fields included in the first measurement field 151, the second measurement field that has not been excluded by the threshold determination as the second measurement field to be used for AEC.

[0087] FIG. 13B illustrates the results of threshold determination according to the second embodiment. Based on the results of the threshold determination, second measurement fields identified as second measurement fields containing a non-transparent area or a skin line are excluded from the multiple second measurement fields 152b-152i included in the first measurement fields 151c and 151d. For example, when the threshold (thr) is set to 2000, the second measurement fields 152b-152e, 152h, and 152i (hatched second measurement fields in FIG. 13B) that yield calculation results below the threshold are identified as second measurement fields containing a non-transparent area or a skin line and are excluded from the target region to be used for AEC. As a result, the signal processor 224 selects the second measurement fields 152f and 152g (non-hatched second measurement fields in FIG. 13B) that are not excluded by the threshold determination as the second measurement fields to be used for AEC. Here, the threshold value may be a parameter that can be set externally, or may be arbitrarily set by the user based on the shooting conditions. As an example of the calculation process, an example using an 8-neighbor differential filter is shown, but the present invention is not limited to this coefficient, and any filter that can calculate a difference value (differential value) may be used.

[0088] According to this embodiment, the second measurement field including the bare area or the skin line can be identified and excluded from the area to be used for AEC. Furthermore, according to this embodiment, the measurement field to be monitored for the exposure dose can be identified accurately and efficiently, preventing overexposure and underexposure and improving the accuracy of AEC.

[0089] [Third embodiment] According to the first embodiment, even if a portion of the first measurement field 151 is outside the imaging region, the second measurement field 152 corresponding to the outside portion can be prevented from being used in AEC, thereby improving the accuracy of AEC. However, if the imaging region is significantly displaced from the first measurement field 151, the accuracy of AEC may decrease. This situation will be described with reference to FIG. 14. FIG. 14 shows a state in which the lung field, which is the imaging region, is displaced to the right from the first measurement fields 151a and 151b selected according to the imaging region, etc. The amount of displacement of the lung field from the first measurement fields 151a and 151b is greater in the example of FIG. 14 than in the example of FIG. 5(B). As a result, of the multiple second measurement fields 152 included in the first measurement fields 151a and 151b, only the second measurement fields 152b and 152c entirely overlap the lung field, while the other second measurement fields 152 partially or completely overlap the lung field. In particular, none of the second measurement fields 152 included in the first measurement field 151a entirely overlaps with the lung field. Therefore, if the second measurement field 152 included in the first measurement field 151a is used to monitor the exposure dose, the accuracy of AEC may be reduced. Therefore, the radiation imaging device 10 according to the third embodiment specifies the first measurement field 151 and the second measurement field 152 used to monitor the exposure dose so as not to include areas outside the imaging region.

[0090] In the third embodiment, imaging regions are classified into three types. The first type of imaging region is a region where the transmission amount of the imaging region is greater than the transmission amount of its surroundings. This type of imaging region is referred to as a high transmission region. For example, a lung field is a high transmission region. The second type of imaging region is a region where the transmission amount of the imaging region is less than the transmission amount of its surroundings. This type of imaging region is referred to as a low transmission region. For example, the spine and bones are low transmission regions. The third type of imaging region is a region where the transmission amount of the imaging region is approximately the same as the transmission amount of its surroundings. This type of imaging region is referred to as an equivalent region. The radiation imaging device 10 may determine the type of imaging region in accordance with a user specification. Alternatively, the radiation imaging device 10 may determine the type of imaging region based on the type of imaging region.

[0091] The radiation imaging apparatus 10 identifies a first measurement field 151 to be used for monitoring the exposure dose from among the plurality of first measurement fields 151 based on the exposure doses acquired from each of the plurality of second measurement fields 152 included in the first measurement field 151. Specifically, the radiation imaging apparatus 10 identifies a representative exposure dose for each of the plurality of first measurement fields 151 based on the exposure doses acquired from each of the plurality of second measurement fields 152 included in the first measurement field 151. The representative exposure dose for the first measurement field 151 is referred to as the representative exposure dose for the first measurement field 151. Then, the radiation imaging apparatus 10 identifies a first measurement field 151 to be used for monitoring the exposure dose from among the plurality of first measurement fields 151 based on the representative exposure dose for each of the plurality of first measurement fields 151. The radiation imaging device 10 identifies the exposure dose used to determine whether to stop the radiation irradiation based on the representative exposure dose of the first radiation measurement field 151 identified in this manner. The exposure dose used to determine whether to stop the radiation irradiation is referred to as the determination target amount. The radiation imaging device 10 determines whether to stop the radiation irradiation by monitoring the determination target amount.

[0092] A method for determining a representative irradiation dose for each of the multiple first irradiation fields 151 will be described below. The method for determining the representative irradiation dose for the first irradiation field 151 varies depending on the type of imaging region. When the imaging region is a highly transparent region, the second irradiation field 152 with a relatively small irradiation dose is likely not overlapping the imaging region. Therefore, the radiation imaging device 10 determines the representative irradiation dose for the first irradiation field 151 using the irradiation dose of the second irradiation field 152 with a relatively large irradiation dose among the multiple second irradiation fields 152 included in the first irradiation field 151. For example, the radiation imaging device 10 may determine the maximum irradiation dose of the multiple second irradiation fields 152 as the representative irradiation dose. The maximum irradiation dose of the multiple second irradiation fields 152 may be an outlier. Therefore, in order to reduce the influence of outliers, the radiation imaging device 10 may set the representative exposure dose to the average value of the n largest exposure doses of the multiple second measurement fields 152, or may set the nth largest exposure dose of the multiple second measurement fields 152 to the representative exposure dose. n is a natural number equal to or greater than 2, and may be a value equal to or less than 1 / 2, or even 1 / 4, of the number of second measurement fields 152 included in the first measurement field 151. In this way, one or more second measurement fields 152 are identified to identify the representative exposure dose.

[0093] When the imaging region is a low-transmittance region, the second irradiation field 152 with a relatively high irradiation dose is likely not overlapping the imaging region. Therefore, the radiation imaging apparatus 10 determines the representative irradiation dose of the first irradiation field 151 using the irradiation dose of a second irradiation field 152 with a relatively low irradiation dose among the multiple second irradiation fields 152 included in the first irradiation field 151. For example, the radiation imaging apparatus 10 may determine the minimum irradiation dose of the multiple second irradiation fields 152 as the representative irradiation dose. The minimum irradiation dose of the multiple second irradiation fields 152 may be an outlier. Therefore, to reduce the influence of the outlier, the radiation imaging apparatus 10 may determine the average value of the n smallest irradiation doses of the multiple second irradiation fields 152 as the representative irradiation dose, or may determine the n smallest irradiation dose of the multiple second irradiation fields 152 as the representative irradiation dose.

[0094] When the imaging regions are equivalent regions, the second measurement fields 152 that do not overlap the imaging region also have the same exposure dose as the second measurement fields 152 that overlap the imaging region. Therefore, the radiation imaging device 10 determines the representative exposure dose of the first measurement field 151 using the exposure dose of the second measurement field 152 with the intermediate exposure dose among the multiple second measurement fields 152 included in the first measurement field 151. For example, the radiation imaging device 10 may determine the representative exposure dose as the median value of the exposure doses of the multiple second measurement fields 152. Alternatively, the radiation imaging device 10 may determine the representative exposure dose as the average value of the interquartile range of the exposure doses of the multiple second measurement fields 152.

[0095] Next, a method for identifying the determination target quantity will be described below. The method for identifying the determination target quantity varies depending on the type of region to be imaged. When the region to be imaged is a highly transmissive region, the first measurement field 151 with a relatively small representative exposure dose is likely not overlapping the region to be imaged. Therefore, the radiation imaging apparatus 10 identifies the determination target quantity using the exposure dose of a first measurement field 151 with a relatively large representative exposure dose among the multiple first measurement fields 151. For example, the radiation imaging apparatus 10 may determine the determination target quantity as the maximum representative exposure dose of the multiple first measurement fields 151. The maximum exposure dose of the multiple first measurement fields 151 may be an outlier. Therefore, to reduce the influence of the outlier, the radiation imaging apparatus 10 may determine the determination target quantity as the average value of the n largest representative exposure doses of the multiple first measurement fields 151, or may determine the n largest representative exposure dose of the multiple first measurement fields 151 as the determination target quantity. n is a natural number of 2 or more, and may be a value equal to or less than 1 / 2, or even equal to or less than 1 / 4, of the number of first measurement fields 151 selected according to the imaging region, etc. In this way, one or more first measurement fields 151 are specified to identify the determination target quantity.

[0096] When the imaging region is a low-transmittance region, the first measurement field 151 with a relatively large representative exposure dose is likely not overlapping with the imaging region. Therefore, the radiation imaging apparatus 10 determines the determination target amount using the exposure dose of a first measurement field 151 with a relatively small representative exposure dose among the multiple first measurement fields 151. For example, the radiation imaging apparatus 10 may determine the determination target amount as the minimum value of the representative exposure doses of the multiple first measurement fields 151. The minimum value of the exposure doses of the multiple first measurement fields 151 may be an outlier. Therefore, to reduce the influence of the outlier, the radiation imaging apparatus 10 may determine the determination target amount as the average value of the n smallest representative exposure doses of the multiple first measurement fields 151, or may determine the n smallest exposure dose of the multiple first measurement fields 151 as the determination target amount.

[0097] When the imaging regions are equivalent regions, the first measurement fields 151 that do not overlap the imaging regions also have a representative exposure dose that is approximately the same as that of the first measurement fields 151 that overlap the imaging regions. Therefore, the radiation imaging device 10 specifies the determination target amount using the exposure dose of the first measurement field 151 that has the intermediate representative exposure dose among the multiple first measurement fields 151 selected according to the imaging region, etc. For example, the radiation imaging device 10 may use the median value of the representative exposure doses of the multiple first measurement fields 151 as the determination target amount. Alternatively, the radiation imaging device 10 may use the average value of the interquartile range of the representative exposure doses of the multiple first measurement fields 151 as the determination target amount.

[0098] A specific example of a method for identifying a representative irradiation dose and a determination target amount will be described with reference to Fig. 15. In the example of Fig. 15, first measurement fields 151c and 152d are selected according to the imaging region, etc., and the imaging region is assumed to be a highly transmittance region. The first measurement field 151c is composed of four second measurement fields 152d to 152g, and the first measurement field 151d is composed of four second measurement fields 152h to 152k. The numerical values ​​indicated by the second measurement fields 152d to 152k each represent an irradiation dose at a certain point in time.

[0099] The radiation imaging apparatus 10 determines the maximum exposure dose ("821") for the first measurement field 151c as the representative exposure dose. In this example, the second measurement field 152g is identified. Alternatively, the radiation imaging apparatus 10 may determine the second largest exposure dose ("790") as the representative exposure dose for the first measurement field 151c. In this example, the second measurement field 152e is identified. Furthermore, the radiation imaging apparatus 10 may determine the average value ("805.5") of the two largest exposure doses as the representative exposure dose for the first measurement field 151c. In this example, the second measurement fields 152e and 152g are identified. The radiation imaging apparatus 10 determines the maximum exposure dose ("1315") for the first measurement field 151d as the representative exposure dose.

[0100] Next, the radiation imaging device 10 identifies the maximum value ("1315") between the representative exposure dose ("821") of the first measurement field 151c and the representative exposure dose ("1315") of the first measurement field 151d as the amount to be determined. In this example, the first measurement field 151d is identified. The radiation imaging device 10 stops irradiating radiation when the amount to be determined exceeds the threshold.

[0101] 16 is a flowchart showing imaging processing by the radiation imaging apparatus 10 according to the third embodiment. First, S701 to S704 are executed in the same manner as in FIG. 7. In S1601, the control unit 225 determines whether the timing indicated by the internal timer has reached the timing indicating the execution of measurement field determination (determination timing indicated by Ctim). If the measurement field determination timing (Ctim) has been reached (YES in S1601), the control unit 225 proceeds to S1602. If the measurement field determination timing (Ctim) has not been reached (NO in S1601), the control unit 225 returns the process to S703. The determination timing Ctim is the same as that described in FIG. 7.

[0102] If it is determined that the timing indicated by the internal timer has reached the measurement field determination timing (Ctim) (YES in S1601), the process proceeds to S1602. In S1602, the signal processing unit 224, in response to an instruction from the control unit 225, identifies a representative irradiation dose for each of the selected first measurement fields 151 using the method described above. In S1602, the cumulative dose value updated in S704 is used as the irradiation dose for the second measurement field 152. Subsequently, in S1603, in response to an instruction from the control unit 225, the signal processing unit 224 identifies a determination target amount using the method described above based on the representative irradiation dose for the selected first measurement fields 151. Thereafter, S708 to S712 are executed as in FIG. 7. However, in S710, the determination target amount identified in S1603 is used instead of the cumulative dose value.

[0103] In the above-described method, the truth or falsity of the proposition that the maximum value of the irradiation doses of the second irradiation fields 152 is greater than a threshold value (e.g., stop determination threshold Dth) coincides with the truth or falsity of the logical sum of the propositions for each of the second irradiation fields 152 that the irradiation doses of the second irradiation fields 152 are greater than the threshold value. The truth or falsity of the proposition that the minimum value of the irradiation doses of the second irradiation fields 152 is greater than a threshold value (e.g., stop determination threshold Dth) coincides with the truth or falsity of the logical product of the propositions for each of the second irradiation fields 152 that the irradiation doses of the second irradiation fields 152 are greater than the threshold value. The truth or falsity of the proposition that the maximum value of the representative irradiation doses of the first irradiation fields 151 is greater than a threshold value (e.g., stop determination threshold Dth) coincides with the truth or falsity of the logical sum of the propositions for each of the first irradiation fields 151 that the representative irradiation doses of the first irradiation fields 151 are greater than the threshold value. The truth or falsity of the proposition that the minimum value of the representative exposure dose of the multiple first light-gathering fields 151 is greater than a threshold value (e.g., the stop determination threshold Dth) coincides with the truth or falsity of the logical product of the propositions for each of the multiple first light-gathering fields 151 that the representative exposure dose of the first light-gathering fields 151 is greater than the threshold value.

[0104] As described above, according to the embodiment, the first and second measurement fields 151 and 152 used for monitoring the irradiation dose are specified so as not to include any part outside the imaging region. This makes it possible to suppress a decrease in the accuracy of AEC even when the imaging region is significantly displaced from the first measurement field.

[0105] [Fourth embodiment] According to the first embodiment, even if a portion of the first measurement field 151 is outside the imaging region, the second measurement field 152 corresponding to the portion outside the imaging region can be prevented from being used in AEC, thereby improving the accuracy of AEC. However, if only one first measurement field 151 is selected and the imaging region is significantly displaced from the first measurement field 151, the accuracy of AEC may be reduced. This situation will be described with reference to FIG. 17. FIG. 17(A) shows a state in which the hand, which is the imaging region, is positioned so as to overlap the first measurement field 151e selected according to the imaging region, etc. FIG. 17(B) shows a state in which the hand, which is the imaging region, is positioned so as to be displaced downward from the first measurement field 151e selected according to the imaging region, etc. In the state of FIG. 17(B), the first measurement field 151e includes only the finger and the non-existent portion, so the second measurement field 152 overlapping the imaging region (hand) cannot be identified, which may result in a reduction in the accuracy of AEC. Therefore, the radiation imaging device 10 according to the fourth embodiment sets a third measurement field 1800 (FIG. 18) larger than the first measurement field 151, and sets a plurality of first measurement fields 151 from the third measurement field 1800.

[0106] A specific example of the third illumination field 1800 will be described with reference to FIG. 18 . The third illumination field 1800 includes a plurality of second illumination fields 152. The radiation imaging apparatus 10 may determine the position of the third illumination field 1800 in response to a user instruction. Alternatively, the radiation imaging apparatus 10 may determine the position of the third illumination field 1800 based on the type of region to be imaged. The size of the third illumination field 1800 is determined taking into account the positional deviation of the region to be imaged. In the example of FIG. 18 , the third illumination field 1800 includes 6×6=36 second illumination fields 152, but the layout of the second illumination field 152 is not limited to this. In the example of FIG. 18 , one third illumination field 1800 is set in the imaging region of the radiation detector 100, but multiple third illumination fields 1800 may be set.

[0107] The radiation imaging apparatus 10 sets a plurality of first measurement fields 151 within the third measurement field 1800. The radiation imaging apparatus 10 may set a plurality of first measurement fields 151 so that they share at least one second measurement field 152. In the example of FIG. 18, a plurality of (e.g., 25) first measurement fields 151 including first measurement fields 151f and 151g are set. Each first measurement field 151 is made up of four second measurement fields 152. The first measurement field 151f and the first measurement field 151g share two second measurement fields 152. Alternatively, the radiation imaging apparatus 10 may set a plurality of first measurement fields 151 so that they do not share any second measurement field 152.

[0108] The number of first measurement fields 151 set within the third measurement field 1800 may be the maximum number that can be set within the third measurement field 1800, or a number less than that. For example, the radiation imaging device 10 may determine the number of first measurement fields 151 in terms of calculation speed and signal-to-noise ratio. If the first measurement field 151 includes a large number of output pixels, calculation processing takes time. On the other hand, if the first measurement field 151 includes a small number of output pixels, an appropriate signal-to-noise ratio per first measurement field 151 cannot be ensured, resulting in poor accuracy of the irradiation dose. Furthermore, if the first measurement field 151 is too large, it may include a large area other than the imaging region, which may reduce the accuracy of identifying the second measurement field 152 used for AEC. For example, by setting the number of pixels included in the second measurement field 152 to 15 × 15, the amount of calculation can be reduced while ensuring an appropriate signal-to-noise ratio.

[0109] 19 is a flowchart showing the imaging process by the radiation imaging apparatus 10 according to the fourth embodiment. The imaging process of the fourth embodiment differs from that of the first embodiment in that S1901 is executed between S706 and S707. In S1901, the signal processing unit 224 sets a plurality of first measurement fields 151 from the third measurement field 1800 by the above-described method in response to an instruction from the control unit 225. The process of S1901 may be executed at any timing before S707.

[0110] In the example of Fig. 19, S1901 is added to the imaging process of the first embodiment. Alternatively, S1901 may be added to the imaging process of the third embodiment. For example, S1901 may be executed between S1601 and S1602 in the method of Fig. 16.

[0111] As described above, according to the embodiment, a plurality of first measurement fields 151 are set from the third measurement field 1800, and the second measurement field 152 is identified from these first measurement fields 151. This makes it possible to suppress a decrease in the accuracy of AEC even when the imaging region is significantly displaced from the first measurement field.

[0112] [Fifth embodiment] If the radiation measurement field for monitoring radiation dose includes a non-exposed area or a skin line (the boundary between the non-exposed area and the subject), this may result in a decrease in AEC accuracy due to overexposure or underexposure. The decrease in AEC accuracy caused by an inappropriate selection of the radiation measurement field also applies to imaging devices other than radiation imaging devices. In this embodiment, the radiation measurement field to be monitored is identified accurately and efficiently.

[0113] <Explanation of the light collection area according to this embodiment> In this embodiment, in the radiation detector 100, the detection field 150 is defined to include a plurality of detection pixels 121, as shown in Fig. 20. Fig. 20 shows an example in which 14 × 14 = 196 detection fields 150 are arranged in the imaging region of the radiation detector 100, and one of the detection fields 150 is shown in detail. Fig. 20 shows an example in which one detection field 150 includes 5 rows and 9 columns of detection pixels 121, but this is not limiting. One detection field 150 may include only one detection pixel 121, or one detection field 150 may include two or more detection pixels 121.

[0114] In the radiation detector 100, a monitoring candidate area 151 is set to include one or more measurement areas 150. The monitoring candidate area 151 may be set to include multiple measurement areas 150. The measurement areas 150 included in the monitoring candidate area 151 are candidates for the measurement areas 150 used in AEC (i.e., monitoring of radiation exposure dose). Therefore, the measurement areas 150 not included in the monitoring candidate area 151 are not used for AEC. Furthermore, as will be described later, even among the measurement areas 150 included in the monitoring candidate area 151, measurement areas 150 that satisfy certain conditions are not used for AEC. In the example of FIG. 20, the monitoring candidate area 151 includes 6×6 measurement areas 150. The measurement area 150 is composed of detection pixels 121 arranged one-dimensionally or two-dimensionally in the imaging area of ​​the radiation detector 100. In the example of FIG. 20, the monitoring candidate area 151 is a single area. Alternatively, the monitoring candidate area 151 may be divided into multiple areas.

[0115] The control unit 225 acquires an accumulated dose for each of the multiple measurement fields 150 included in the candidate monitoring area 151 based on the radiation dose detected at the detection pixels 121 included in the measurement field 150. The accumulated dose for one measurement field 150 may be a representative value (e.g., an average value) of the radiation dose from the start of radiation irradiation for one or more detection pixels 121 included in the measurement field 150. When the multiple measurement fields 150 each include the same number of detection pixels 121, the total value of the radiation doses for the one or more detection pixels 121 included in each measurement field 150 may be used as the accumulated dose for the measurement field 150. In this way, by having each measurement field 150 include multiple detection pixels 121 and using a representative value of the radiation doses for the multiple detection pixels 121 as the accumulated dose for the measurement field 150, the amount of calculation required to identify the measurement field 150 to be monitored can be reduced, shortening the processing speed and ensuring an appropriate signal-to-noise (SN) ratio.

[0116] The control unit 225 may be able to change the position of the candidate monitoring region 151. Changing the position of the candidate monitoring region 151 may mean changing the measurement field 150 included in the candidate monitoring region 151 among the multiple measurement fields 150 included in the radiation detector 100. For example, the control unit 225 may determine the position of the candidate monitoring region 151 according to a designation from the user of the radiation imaging system 1. Specifically, the UI control unit 330 of the control device 300 may acquire a designation of the position of the candidate monitoring region 151 from the user of the radiation imaging system 1. Alternatively or in addition to this, the control unit 225 may determine the position of the candidate monitoring region 151 based on a region of the imaging target. Specifically, the position of the candidate monitoring region 151 for each region may be stored in the memory of the control unit 225, and the control unit 225 may read out from the memory and use the position of the candidate monitoring region 151 associated with the region of the imaging target designated by the user.

[0117] <Image capture control method> 21 is a flowchart showing imaging processing by the radiation imaging apparatus 10 according to an embodiment. In S2101, the control unit 225 of the radiation imaging apparatus 10 communicates with the control device 300 and sets various information. The set information includes imaging condition information (irradiation condition information), such as the tube voltage and tube current of the radiation tube, a stop determination threshold Dth, a set irradiation time (backup time) Bt, time information Ctim for determining the candidate irradiation field, and irradiation field information (ROI information). A monitoring candidate region 151 used for AEC is selected based on the irradiation field information. The control unit 225 may receive a target dose Dref indicated by a dose index from the control device 300, convert the target dose Dref into a stop determination threshold Dth (a signal value corresponding to the target dose), and set the target dose. This configuration allows the user to specify a target dose using a dose index.

[0118] In S2102, the control unit 225 starts preparations to receive radiation irradiation in response to the start request signal received from the control device 300. Then, when preparations to receive irradiation are complete, the exposure permission signal is switched from Lo level to Hi level. This exposure permission signal is transmitted to the radiation generation device 20 via the irradiation control unit 320, and the radiation generation device 20 starts generating radiation. Furthermore, at the timing when the exposure permission signal is switched to Hi level, the control unit 225 controls the first drive unit 221 to start accumulating charges in the imaging pixels 101 and starts timing by an internal timer. In this way, radiation imaging is started. Processing after the start of radiation imaging will be described below.

[0119] In S2103, the control unit 225 drives the second drive unit 241 to read out the irradiation dose of one or more detection pixels 121 in the multiple irradiation fields 150 included in the candidate monitoring area 151. In S2104, the control unit 225 updates the cumulative dose of the multiple irradiation fields 150 included in the candidate monitoring area 151 using the irradiation dose of the detection pixel 121 read out in S2103. As described above, the cumulative dose of each irradiation field 150 is a representative value of the irradiation dose of one or more detection pixels 121 included in each irradiation field 150.

[0120] In S2105, the control unit 225 determines whether or not the identification of the measurement field 150 to be used for AEC has been completed. If it is determined that the identification of the measurement field 150 has been completed (YES in S2105), the processes for identifying the measurement field 150 to be used for AEC (S2106, S2107) are skipped, and the process proceeds to S2108. On the other hand, if it is determined that the identification of the measurement field 150 has not been completed (NO in S2105), the process proceeds to S2106.

[0121] In S2106, the control unit 225 determines whether the timing indicated by the internal timer has reached the timing indicating the execution of determination of the measurement field 150 (determination timing indicated by Ctim). If the determination timing (Ctim) of the measurement field 150 has been reached (YES in S2106), the control unit 225 proceeds to S2107. If the determination timing (Ctim) of the measurement field 150 has not been reached (NO in S2106), the control unit 225 returns the process to S2103. In this manner, S2103 to S2106 are repeated until the determination timing (Ctim) of the measurement field 150 is reached. Note that the determination timing Ctim is set to, for example, A% of the backup time Bt. Here, there is no particular limitation on the value of A, and A is set so as to obtain a dose that can identify the measurement field 150 used for AEC with sufficient accuracy. Furthermore, the value of A may be set to a different value depending on the imaging region. Furthermore, the determination timing Ctim may be a value that does not depend on the backup time Bt, or may be a fixed value, but in either case, it goes without saying that Bt>Ctim must be satisfied.

[0122] If it is determined that the timing indicated by the internal timer has reached the measurement field determination timing (Ctim) (YES in S2106), the process proceeds to S2107. In S2107, the control unit 225 identifies the measurement field 150 to be used for monitoring the irradiation dose for AEC from among the multiple measurement fields 150 included in the monitoring candidate area 151. Details of S2107 will be described later.

[0123] In S2108, the control unit 225 determines whether the timing indicated by the internal timer has reached the backup time Bt, i.e., whether the backup time Bt has elapsed. If it is determined that the timing indicated by the internal timer has reached the backup time Bt (YES in S2108), the process proceeds to S2109, where the control unit 225 stops imaging. At this time, the radiation generation device 20 stops radiation in accordance with the backup time Bt included in the irradiation conditions. The control unit 225 controls the first drive unit 221 to read out signals from the imaging pixels 101. Then, in S2112, the control unit 225 transfers the signals read out from the imaging pixels 101 to the control device 300 as a radiographic image. Note that information indicating that irradiation has stopped at the set irradiation time may be added to this radiographic image.

[0124] On the other hand, if the timing indicated by the internal timer has not yet elapsed the backup time Bt (NO in S2108), the control unit 225 proceeds to S2110. In S2110, the control unit 225 compares the accumulated dose from the measurement field 150 identified in S2107 with the stop determination threshold Dth. If it is determined that the accumulated dose is not equal to or greater than the stop determination threshold Dth (NO in S2110), the control unit 225 returns to S2103. On the other hand, if it is determined that the accumulated dose is equal to or greater than the stop determination threshold Dth (YES in S2109), the control unit 225 proceeds to S2111. For example, if the accumulated doses of all the measurement fields 150 identified in S2107 exceed the stop determination threshold Dth, the control unit 225 determines YES in S2109. Alternatively, the control unit 225 may determine YES in S2109 if even one of the accumulated doses of the measurement fields 150 identified in S2107 exceeds the stop determination threshold Dth. In S2111, the control unit 225 transmits a normal stop request (AEC stop request) to the control device 300. Then, the first drive unit 221 is controlled to read signals from the imaging pixels 101, and imaging is terminated. In S2112, the signals read from the imaging pixels 101 are transferred to the control device 300 as a radiographic image. Information indicating normal stop may be added to this radiographic image. The radiographic image transferred to the control device 300 is used for display on the display unit 332 for diagnosis and for dose management.

[0125] <How to identify the lighting field> Details of S2107 will be described with reference to FIG. 22. As described above, in S2107, the control unit 225 identifies the measurement fields 150 to be used for monitoring the irradiation dose for AEC from among the plurality of measurement fields 150 included in the monitoring candidate area 151. Specifically, the control unit 225 identifies the measurement fields 150 that are considered to be non-transmitted areas or skin line areas from among the plurality of measurement fields 150 as measurement fields 150 not to be used for AEC. The measurement fields 150 not to be used for AEC are referred to as excluded measurement fields. The non-transmitted areas are areas to which radiation that has not passed through the subject 30 is irradiated. The skin line area is an area including the boundary between the non-transmitted areas and the subject 30. Of the plurality of measurement fields 150, the measurement fields 150 not identified as excluded measurement fields are used for AEC. That is, as described above, in S2110, the control unit 225 determines whether to stop the irradiation of radiation by monitoring the cumulative dose of the measurement field 150 that has not been identified as an excluded measurement field (i.e., the measurement field 150 other than the excluded measurement field).

[0126] In S2201, the control unit 225 divides the multiple measurement fields 150 into one or more groups based on the cumulative dose of each of the multiple measurement fields 150. Before executing the method of Fig. 22, the cumulative dose of each of the multiple measurement fields 150 included in the candidate monitoring area 151 is acquired in S2104. Specifically, the control unit 225 divides the multiple measurement fields 150 so that one or more measurement fields 150 with similar cumulative doses are included in the same group. As a result of S2201, all of the measurement fields 150 may be included in one group, or the multiple measurement fields 150 may be divided into multiple groups.

[0127] In S2202, the control unit 225 identifies the measurement fields 150 included in one or more groups that satisfy a predetermined condition as an excluded measurement field not to be used for AEC. The predetermined condition used in S2202 is hereinafter referred to as the "exclusion condition." As described above, the measurement fields 150 not identified as the excluded measurement field are used for AEC. The exclusion condition is set to identify the bare area and the skin line area as the excluded measurement field.

[0128] <Specific examples of light collection areas> A specific example of the method of FIG. 22 will be described with reference to FIGS. 23 to 26. As shown in FIG. 23(A), the region to be imaged is the neck, and a monitoring candidate region 151 is set to overlap the neck. The monitoring candidate region 151 includes 6×6=36 measurement fields 150. Some of these measurement fields 150 are non-transparent regions, and others overlap the skin line. By executing the method of FIG. 22, these non-transparent regions and regions overlapping the skin line are identified as exclusion measurement fields. FIG. 23(B) shows, for the sake of explanation, numbers 1 to 36 assigned to the multiple measurement fields 150 in the monitoring candidate region 151. FIG. 23(C) shows the integrated doses of the multiple measurement fields 150 at the time of executing the method of FIG. 22.

[0129] First, the control unit 225 sorts the multiple measurement fields 150 in order of cumulative dose. Sorting may be performed using any sorting algorithm, such as quick sort or bubble sort. The order of cumulative dose may be descending or ascending. FIG. 24 shows the cumulative doses sorted in descending order for the example of FIG. 23. The horizontal axis of FIG. 24 indicates the number of the measurement field 150, and the vertical axis of FIG. 24 indicates the cumulative dose of each measurement field 150.

[0130] Next, the control unit 225 calculates the difference in cumulative dose between two adjacent measurement fields 150 in the array of aligned measurement fields 150. FIG. 25 shows the difference in cumulative dose between two adjacent measurement fields 150 for the example of FIG. 23. The horizontal axis of FIG. 25 indicates the number of the measurement field 150 with the larger cumulative dose between the two measurement fields 150 for which the difference in cumulative dose was calculated. The numbers of the measurement fields 150 are shown, and the vertical axis of FIG. 25 indicates the cumulative dose of each measurement field 150. For example, the difference in cumulative dose for measurement field No. 6 is the difference ("142") between the cumulative dose of measurement field No. 6 ("7618") and the cumulative dose of measurement field No. 12 ("7476"), which has the next largest cumulative dose. For the 36th measurement field 150 with the smallest cumulative dose, there is no measurement field 150 with the next largest cumulative dose, so the difference in cumulative dose for the previous 35th measurement field 150 may be used as the difference in cumulative dose for the 36th measurement field 150. Alternatively, the processing described below may be performed assuming that there is no difference in cumulative dose for the 36th measurement field 150.

[0131] If the difference in cumulative dose between two measurement fields 150 is greater than a predetermined threshold, the control unit 225 divides the multiple measurement fields 150 into one or more groups so that the two measurement fields 150 are included in a different group. For example, in the example of FIG. 25 , the threshold Th is set to 850. In this case, the difference in cumulative dose between the measurement fields 150 Nos. 32, 33, and 4 exceeds the threshold Th. Therefore, the control unit 225 places the measurement fields 150 Nos. 32 and 33 in a different group, the measurement fields 150 Nos. 33 and 11 in a different group, and the measurement fields 150 Nos. 4 and 9 in a different group. Furthermore, when the difference in cumulative dose between two measurement fields 150 is equal to or less than the predetermined threshold, the control unit 225 divides the plurality of measurement fields 150 into one or more groups so that the two measurement fields 150 are included in the same group. As a result, the plurality of measurement fields 150 are divided into four groups 2301 to 2304.

[0132] The control unit 225 may determine a predetermined threshold to be compared with the difference in cumulative dose, in accordance with a specification from the user of the radiation imaging system 1. Specifically, the UI control unit 330 of the control device 300 may acquire a specification of the predetermined threshold from the user of the radiation imaging system 1.

[0133] Finally, the control unit 225 identifies groups that satisfy the exclusion criteria. The multiple measurement fields 150 that are non-transparent regions are considered to all have high cumulative doses and to have cumulative doses that are close to each other. Therefore, among the multiple groups, the measurement fields 150 in group 2301, which includes the measurement field 150 with the highest cumulative dose, are considered to all be non-transparent regions. The multiple measurement fields 150 that are skin line regions are considered to have the next highest cumulative dose after the non-transparent regions and to have some degree of variation. On the other hand, the multiple measurement fields 150 that are neither non-transparent regions nor skin line regions (i.e., overlap only with the subject 30) are considered to have cumulative doses that are lower than the skin line regions and to have cumulative doses that are close to each other. Therefore, among the multiple groups, the measurement field 150 in sub-group 2304, which includes the measurement field 150 with the smallest cumulative dose, is considered to be neither a non-transparent region nor a skin line region. Therefore, in the fifth embodiment, the exclusion condition may include not including the measurement field 150 with the smallest integrated amount among the plurality of measurement fields 150 (the measurement field 150 No. 36 in the example of FIG. 24 ). In other words, a group that satisfies the exclusion condition is a group that does not include the measurement field 150 with the smallest integrated amount among the plurality of measurement fields 150. Under this condition, all of the measurement fields 150 included in the groups 2301 to 2303 (the ten measurement fields Nos. 6, 12, 31, 5, 32, 33, 11, 18, 10, and 4) are identified as excluded measurement fields. All of the remaining measurement fields 150 included in the group 2304 are used for AEC. In FIG. 26 , the ten measurement fields 150 identified as excluded measurement fields are hatched. In this way, both the bare area and the skin line area are identified as excluded measurement fields.

[0134] If the candidate monitoring area 151 does not include a bare area or a skin line area, there are no two adjacent measurement fields 150 whose difference in cumulative dose exceeds the threshold Th. Therefore, as a result of the above process, all of the measurement fields 150 included in the candidate monitoring area 151 are included in one group. In this case, none of the measurement fields 150 are identified as excluded measurement fields. Thus, to efficiently detect cases in which all of the measurement fields 150 are included in one group, the control unit 225 may determine whether the difference between the minimum and maximum cumulative doses among the multiple measurement fields 150 is less than a predetermined threshold before grouping the multiple measurement fields 150. If the difference between the minimum and maximum cumulative doses is less than the predetermined threshold, the control unit 225 may include all of the multiple measurement fields 150 in one group.

[0135] In the above example, all of the measurement fields 150 other than the non-transparent region and the skin line region are included in one group 2304. However, depending on the region of the imaging target, multiple measurement fields 150 other than the non-transparent region and the skin line region may be divided into multiple groups. Therefore, the exclusion condition may be different from the condition in the above example. For example, if the imaging target is a region where multiple measurement fields 150 other than the non-transparent region and the skin line region are likely to be divided into two groups, the group that satisfies the exclusion condition may be a group other than the group with the smallest integrated dose and the group with the second smallest integrated dose. The group with the smallest integrated dose is the group with the smallest average integrated dose among the multiple groups. The group with the second smallest integrated dose is the group with the second smallest average integrated dose among the multiple groups.

[0136] In the above example, the control unit 225 calculates the difference in cumulative dose between two adjacent irradiation fields 150 in a row of aligned irradiation fields 150. Alternatively, the control unit 225 may calculate the difference in cumulative dose between two irradiation fields 150 that are separated by a predetermined number of fields (e.g., two or three) in the row of aligned irradiation fields 150, and divide the irradiation fields 150 into one or more groups based on this difference, as described above.

[0137] In the above example, the plurality of aligned measurement fields 150 are divided into one or more groups based on the difference in cumulative dose between two adjacent measurement fields 150 in the row of the plurality of aligned measurement fields 150. Alternatively, the control unit 225 may divide the plurality of measurement fields 150 into one or more groups using an existing clustering method.

[0138] According to the above embodiment, the measurement field 150 to be used for AEC is identified from among the plurality of measurement fields 150 included in the candidate monitoring region 151 based on the cumulative dose of the plurality of measurement fields 150. As a result, for example, in radiation imaging, if a portion of the candidate monitoring region is outside the region of interest (ROI), the measurement field corresponding to the outside portion can be prevented from being used for AEC, thereby improving the accuracy of AEC. Furthermore, by changing the method or criteria for identifying the measurement field 150 to be used for AEC depending on the region of interest, it is possible to select a measurement field 150 appropriate for the region of interest. Furthermore, a general method for selecting a measurement field (such as user specification of the measurement field 150 or selection of the measurement field 150 according to the region of interest) can be used to select the candidate monitoring region 151. Therefore, an appropriate measurement field 150 can be used for AEC without imposing any special burden on specifying the measurement field 150.

[0139] In the above-described embodiment, the method for identifying the illumination field 150 has been described in the context of the radiation imaging device 10. The above-described method for identifying the illumination field 150 may also be applied to imaging devices other than the radiation imaging device 10 (e.g., imaging devices that detect visible light). Such imaging devices include a photodetector having a plurality of imaging pixels for capturing an image based on incident light and a plurality of photoelectric conversion elements for monitoring the amount of light. The amount of light detected by the plurality of photoelectric conversion elements is used as the exposure dose detected by the detection pixel 121. The imaging device divides the illumination fields into one or more groups based on the integrated light amount of each of the illumination fields, and identifies illumination fields included in one or more groups that satisfy an exclusion condition as excluded illumination fields that will not be used for monitoring the amount of light.

[0140] For example, when an imaging device is used outdoors on a clear day, the brightness of the light-collecting field capturing the sky is high. Therefore, if AEC is performed using such a high-brightness area, the accuracy of the AEC may be reduced. Therefore, the exclusion condition may include including the light-collecting field with the largest integrated light intensity. In this case, all light-collecting fields in the group including the light-collecting field with the largest integrated light intensity are identified as excluded light-collecting fields.

[0141] [Other embodiments] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0142] [Summary of the embodiment] (Item 1) a radiation detector having a plurality of imaging pixels for capturing a radiographic image based on incident radiation and a plurality of detection pixels for monitoring an exposure dose of the radiation; and a plurality of radiation collection fields defined in the radiation detector, each including one or more of the plurality of detection pixels; an acquiring means for acquiring an exposure dose in each of the plurality of irradiation fields based on an exposure dose detected from a detection pixel included in the plurality of irradiation fields; a specifying means for specifying a measurement field to be used for monitoring the irradiation dose from the plurality of measurement fields based on the irradiation doses acquired from the plurality of measurement fields; A radiation imaging apparatus comprising: (Item 2) a first measurement field including two or more of the plurality of measurement fields as a plurality of second measurement fields is defined in the radiation detector; The radiation imaging device described in item 1 is characterized in that the identification means identifies a second light-collection field to be used for monitoring the exposure dose from among the plurality of second light-collection fields based on the exposure dose obtained from each of the plurality of second light-collection fields included in the first light-collection field. (Item 3) In the radiation detector, a plurality of first measurement fields are defined, each of which includes two or more of the plurality of measurement fields as a second measurement field; The radiation imaging device described in item 1 or 2 is characterized in that the identification means identifies, for each of the plurality of first measurement fields, a second measurement field to be used for monitoring the exposure dose from among the plurality of second measurement fields based on the exposure dose obtained from each of the plurality of second measurement fields included in the first measurement field. (Item 4) Further, a selection means for selecting one or more of the plurality of first light-collecting areas is provided, The radiation imaging device described in item 3, characterized in that the identification means identifies the second light-gathering field to be used for monitoring the exposure dose from the plurality of second light-gathering fields included in the selected first light-gathering field. (Item 5) 5. The radiation imaging apparatus according to item 4, wherein the selection means selects one or more of the plurality of first measurement fields in response to an instruction from a user. (Item 6) 6. The radiation imaging device according to item 4 or 5, wherein the selection means selects one or more of the plurality of first radiation measurement fields according to an imaging region to be radiographically imaged. (Item 7) The radiation imaging device described in any one of items 2 to 6, characterized in that the acquisition means acquires the exposure dose of the second irradiation field by adding up signals from all detection pixels included in the second irradiation field using a binning process. (Item 8) The radiation imaging device described in any one of items 3 to 7, characterized in that the identification means identifies a second light-gathering field to be used for the monitoring from the plurality of second light-gathering fields based on statistics of irradiation doses obtained from the plurality of second light-gathering fields included in the first light-gathering field. (Item 9) 9. The radiation imaging device according to any one of items 2 to 8, wherein the plurality of first radiation measurement fields are arranged one-dimensionally or two-dimensionally on the radiation detector. (Item 10) 10. The radiation imaging device according to item 9, wherein the plurality of second measurement fields are arranged one-dimensionally or two-dimensionally in the first measurement field. (Item 11) The radiation imaging device described in any one of items 2 to 10, characterized in that the identification means varies the process for identifying the second light-collection field to be used for monitoring the exposure dose from the plurality of second light-collection fields depending on the imaging area. (Item 12) The radiation imaging device described in any one of items 2 to 11, characterized in that the identification means changes the process for identifying a second light-gathering field to be used for monitoring the exposure dose from the plurality of second light-gathering fields depending on the first light-gathering field. (Item 13) The radiation imaging device described in any one of items 2 to 12, characterized in that the identification means varies the process for identifying the second light-collecting field to be used for monitoring the irradiation dose from the plurality of second light-collecting fields depending on the number of second light-collecting fields included in the first light-collecting field. (Item 14) 14. The radiation imaging device according to any one of items 1 to 13, further comprising a determination means for determining whether to stop the irradiation of radiation by monitoring the irradiation dose obtained from the specified irradiation field. (Item 15) The radiation imaging device described in any one of items 1 to 14, characterized in that the acquisition means acquires the cumulative irradiation dose in each of the multiple irradiation fields at a timing before the set irradiation time set for radiation imaging is reached. (Item 16) In the radiation detector, a plurality of first measurement fields are defined, each of which includes two or more of the plurality of measurement fields as a second measurement field; The radiation imaging device described in any one of items 1 to 15, characterized in that the identification means identifies, for each of the plurality of first measurement fields, a second measurement field to be used for the monitoring from among the plurality of second measurement fields included in the plurality of first measurement fields, based on the irradiation dose obtained from each of the plurality of second measurement fields included in the first measurement field and each of the plurality of second measurement fields adjacent to the periphery of each of the plurality of first measurement fields. (Item 17) the specifying means acquires, by a convolution operation using a differential filter, difference information between a sum of results obtained by multiplying the irradiation doses of the second measurement fields adjacent to a second measurement field of interest among the second measurement fields included in each of the first measurement fields by a coefficient of the differential filter and a multiplication value obtained by multiplying the irradiation dose of the second measurement field of interest by the coefficient of the differential filter, as a feature amount indicating a change in irradiation dose between the second measurement field of interest and each of the adjacent second measurement fields; 17. The radiation imaging device according to any one of items 3 to 16, wherein a second measurement field to be used for the monitoring is identified based on the difference information. (Item 18) The radiation imaging device described in item 17, characterized in that the identification means identifies a second measurement field to be excluded from monitoring of the exposure dose from among the plurality of second measurement fields included in the first measurement field based on a comparison between the difference information and a threshold value, and identifies the second measurement field obtained by excluding the identified second measurement field from the plurality of second measurement fields as the second measurement field to be used for the monitoring. (Item 19) In the radiation detector, a plurality of first measurement fields are defined, each of which includes two or more of the plurality of measurement fields as second measurement fields; The radiation imaging device described in any one of items 1 to 18, characterized in that the identification means identifies a first light-gathering field to be used for monitoring the exposure dose from among the plurality of first light-gathering fields based on the exposure dose obtained from each of the plurality of second light-gathering fields included in the first light-gathering field. (Item 20) The identification means For each of the plurality of first measurement fields, a representative irradiation dose of the first measurement field is determined based on the irradiation doses acquired from each of the plurality of second measurement fields included in the first measurement field; Item 19. The radiation imaging device according to item 19, characterized in that a first measurement field to be used for monitoring the exposure dose is identified from among the plurality of first measurement fields based on the representative exposure dose of each of the plurality of first measurement fields. (Item 21) The specifying means specifies a determination target amount based on the representative exposure dose of the specified first irradiation field, 21. The radiation imaging apparatus according to item 20, further comprising a determination unit that determines whether to stop irradiation of radiation by monitoring the determination target amount. (Item 22) In the radiation detector, third measurement fields are defined, each of which includes two or more of the plurality of measurement fields as second measurement fields; The identification means A plurality of first measurement areas are set from the third measurement area, each of which includes a plurality of the second measurement areas; The radiation imaging device of any one of items 1 to 21, characterized in that for each of the plurality of first light-gathering fields, a second light-gathering field to be used for monitoring the exposure dose is identified from among the plurality of second light-gathering fields based on the exposure dose obtained from each of the plurality of second light-gathering fields included in the first light-gathering field. (Item 23) 23. The radiation imaging apparatus according to item 22, wherein the specifying means sets a plurality of first measurement fields so as to share at least one of the second measurement fields. (Item 24) 1. A method for controlling a radiation imaging apparatus including a radiation detector having a plurality of imaging pixels for capturing a radiation image based on incident radiation and a plurality of detection pixels for monitoring an exposure dose of the radiation, the method comprising: defining a plurality of radiation detection fields in the radiation detector, each of the radiation detection fields including one or more of the plurality of detection pixels; acquiring an irradiation dose in each of the plurality of irradiation fields based on an irradiation dose detected from a detection pixel included in the plurality of irradiation fields; identifying a measurement field to be used for monitoring the irradiation dose from the plurality of measurement fields based on the irradiation doses acquired from the respective measurement fields; 2. A method for controlling a radiation imaging apparatus comprising: (Item 25) 25. A program for causing a computer to execute the method for controlling a radiation imaging apparatus according to Item 24. (Item 26) a radiation detector having a plurality of imaging pixels for capturing a radiographic image based on incident radiation and a plurality of detection elements for monitoring the radiation exposure dose; an acquisition means for acquiring an integrated dose of each of a plurality of measurement fields, each of which includes one or more of the plurality of detection elements, based on the irradiation dose detected by the detection element included in each measurement field; a dividing means for dividing the plurality of measurement areas into one or more groups based on the cumulative doses of the plurality of measurement areas; and specifying means for specifying, as an excluded irradiation field that is not to be used for monitoring the radiation exposure dose, an irradiation field included in a group that satisfies a predetermined condition among the one or more groups. (Item 27) Item 27. The radiation imaging apparatus according to item 26, further comprising a determination unit that determines whether to stop irradiation of radiation by monitoring an integrated dose in the plurality of measurement fields other than the excluded measurement field. (Item 28) 28. The radiation imaging apparatus according to item 26 or 27, wherein the predetermined condition includes excluding the measurement field with the smallest cumulative dose from among the plurality of measurement fields. (Item 29) Item 29. The radiation imaging device according to item 28, wherein the dividing means includes all of the plurality of irradiation fields in one group when the difference between the minimum and maximum cumulative doses among the plurality of irradiation fields is less than a first threshold value. (Item 30) Item 30. The radiation imaging device described in Item 29, wherein the dividing means divides the plurality of measurement fields into the one or more groups based on the difference in cumulative dose between two adjacent measurement fields or two measurement fields separated by a predetermined number in a row of the plurality of measurement fields obtained by arranging the plurality of measurement fields in order of cumulative dose. (Item 31) Item 31. The radiation imaging device according to item 30, wherein the dividing means divides the plurality of measurement fields into one or more groups so that the two measurement fields are included in another group when the difference in cumulative dose between the two measurement fields is greater than a second threshold value. (Item 32) Item 32. The radiation imaging apparatus according to item 31, wherein the dividing means determines the second threshold value according to a specification from a user of the radiation imaging apparatus. (Item 33) Item 33. The radiation imaging device according to item 32, wherein the plurality of measurement fields are included in a monitoring candidate area. (Item 34) Item 34. The radiation imaging apparatus according to item 33, further comprising a determining means for determining the position of the monitoring candidate region in accordance with a user's designation. (Item 35) Item 35. The radiation imaging apparatus according to item 33 or 34, further comprising a determination unit that determines a position of the monitoring candidate region based on a part of an imaging target. (Item 36) 1. A method for controlling a radiation imaging apparatus including a radiation detector having a plurality of imaging pixels for capturing a radiation image based on incident radiation and a plurality of detection elements for monitoring an exposure dose of the radiation, the method comprising: a step of acquiring an integrated dose of each of a plurality of measurement fields, each of which includes one or more of the plurality of detection elements, based on the irradiation dose detected by the detection element included in each measurement field; dividing the plurality of measurement areas into one or more groups based on the cumulative doses of the plurality of measurement areas; and identifying a measurement field included in one or more groups that satisfies a predetermined condition as an excluded measurement field that will not be used for monitoring the radiation exposure dose. (Item 37) A program for causing a computer to execute each step of the control method described in Item 36. (Item 38) a photodetector having a plurality of imaging pixels for capturing an image based on incident light and a plurality of photoelectric conversion elements for monitoring the amount of the light; an acquisition means for acquiring an integrated light amount of each of a plurality of light measurement areas, each of which includes one or more of the plurality of photoelectric conversion elements, based on the light amount detected by the photoelectric conversion element included in each of the light measurement areas; a dividing means for dividing the plurality of measurement areas into one or more groups based on the integrated light amount of each of the plurality of measurement areas; and an identification means for identifying a light measurement field included in a group among the one or more groups that satisfies a predetermined condition as an excluded light measurement field that will not be used for monitoring the amount of light.

[0143] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0144] 1: Radiation imaging system, 10: Radiation imaging device, 20: Radiation generating device, 300: Control device, 310: Imaging control unit, 320: Irradiation control unit, 330: UI control unit, 331: Operation unit, 332: Display unit

Claims

1. a radiation detector having a plurality of imaging pixels for capturing a radiographic image based on incident radiation and a plurality of detection pixels for monitoring an exposure dose of the radiation; and a plurality of radiation collection fields defined in the radiation detector, each including one or more of the plurality of detection pixels; an acquiring means for acquiring an exposure dose in each of the plurality of irradiation fields based on an exposure dose detected from a detection pixel included in the plurality of irradiation fields; a specifying means for specifying a measurement field to be used for monitoring the irradiation dose from the plurality of measurement fields based on the irradiation doses acquired from the plurality of measurement fields; A radiation imaging apparatus comprising:

2. a first measurement field including two or more of the plurality of measurement fields as a plurality of second measurement fields is defined in the radiation detector; The radiation imaging device of claim 1, characterized in that the identification means identifies a second radiation field to be used for monitoring the exposure dose from among the plurality of second radiation fields based on the exposure dose obtained from each of the plurality of second radiation fields included in the first radiation field.

3. In the radiation detector, a plurality of first irradiation fields are defined, each of which includes two or more of the plurality of irradiation fields as a second irradiation field; The radiation imaging device of claim 1, characterized in that the identification means identifies, for each of the plurality of first irradiation fields, a second irradiation field to be used for monitoring the irradiation dose from among the plurality of second irradiation fields based on the irradiation dose obtained from each of the plurality of second irradiation fields included in the first irradiation field.

4. Further, a selection means for selecting one or more of the plurality of first light-collecting areas is provided, 4. The radiation imaging device according to claim 3, wherein the identifying means identifies the second radiation field to be used for monitoring the exposure dose from the plurality of second radiation fields included in the selected first radiation field.

5. 5. The radiation imaging apparatus according to claim 4, wherein the selection means selects one or more of the plurality of first measurement fields in response to an instruction from a user.

6. 5. The radiation imaging apparatus according to claim 4, wherein the selection means selects one or more of the plurality of first radiation measurement fields in accordance with an imaging region to be radiographically imaged.

7. The radiation imaging device according to claim 2, wherein the acquisition means acquires the exposure dose of the second irradiation field by adding signals from all detection pixels included in the second irradiation field using a binning process.

8. The radiation imaging device of claim 3, wherein the identification means identifies a second measurement field to be used for the monitoring from the plurality of second measurement fields based on statistics of the exposure dose obtained from the plurality of second measurement fields included in the first measurement field.

9. 3. The radiation imaging apparatus according to claim 2, wherein the plurality of first radiation measurement fields are arranged one-dimensionally or two-dimensionally on the radiation detector.

10. 10. The radiation imaging apparatus according to claim 9, wherein the plurality of second measurement fields are arranged one-dimensionally or two-dimensionally in the first measurement field.

11. 3. The radiation imaging apparatus according to claim 2, wherein the specifying unit varies the process for specifying the second measurement field to be used for monitoring the exposure dose from the plurality of second measurement fields depending on the imaging region.

12. The radiation imaging device according to claim 2, wherein the identification means changes the process for identifying the second radiation measurement field to be used for monitoring the exposure dose from the plurality of second radiation measurement fields depending on the first radiation measurement field.

13. The radiation imaging device of claim 2, characterized in that the identification means varies the process for identifying a second light-gathering field to be used for monitoring the exposure dose from the plurality of second light-gathering fields depending on the number of second light-gathering fields included in the first light-gathering field.

14. 2. The radiation imaging apparatus according to claim 1, further comprising a determination unit that determines whether to stop the irradiation of radiation by monitoring the irradiation dose obtained from the specified irradiation field.

15. 2. The radiation imaging device according to claim 1, wherein the acquisition means acquires the cumulative irradiation dose in each of the plurality of radiation collection fields at a timing before a set irradiation time set for radiation imaging is reached.

16. In the radiation detector, a plurality of first irradiation fields are defined, each of which includes two or more of the plurality of irradiation fields as a second irradiation field; The radiation imaging device of claim 1, characterized in that the identification means identifies, for each of the plurality of first measurement fields, a second measurement field to be used for the monitoring from among the plurality of second measurement fields included in the plurality of first measurement fields based on the exposure dose obtained from each of the plurality of second measurement fields included in the first measurement field and each of the plurality of second measurement fields adjacent to the periphery of each of the plurality of first measurement fields.

17. the specifying means acquires, by a convolution operation using a differential filter, difference information between a sum of results obtained by multiplying the irradiation doses of the second measurement fields adjacent to a second measurement field of interest among the second measurement fields included in each of the first measurement fields by a coefficient of the differential filter and a multiplication value obtained by multiplying the irradiation dose of the second measurement field of interest by the coefficient of the differential filter, as a feature amount indicating a change in irradiation dose between the second measurement field of interest and each of the adjacent second measurement fields; 4. The radiation imaging apparatus according to claim 3, wherein a second radiation field used for the monitoring is identified based on the difference information.

18. The radiation imaging device described in claim 17, characterized in that the identification means identifies a second irradiation field to be excluded from monitoring of the exposure dose from among the plurality of second irradiation fields included in the first irradiation field based on a comparison between the difference information and a threshold value, and identifies the second irradiation field obtained by excluding the identified second irradiation field from the plurality of second irradiation fields as the second irradiation field to be used for the monitoring.

19. In the radiation detector, a plurality of first measurement fields are defined, each of which includes two or more of the plurality of measurement fields as second measurement fields; The radiation imaging device of claim 1, wherein the identification means identifies a first light-gathering field to be used for monitoring the exposure dose from among the plurality of first light-gathering fields based on the exposure dose obtained from each of the plurality of second light-gathering fields included in the first light-gathering field.

20. The identification means For each of the plurality of first measurement fields, a representative irradiation dose of the first measurement field is determined based on irradiation doses acquired from each of the plurality of second measurement fields included in the first measurement field; 20. The radiation imaging device according to claim 19, wherein a first measurement field to be used for monitoring the exposure dose is identified from among the plurality of first measurement fields based on the representative exposure dose of each of the plurality of first measurement fields.

21. The specifying means specifies a determination target amount based on the representative exposure dose of the specified first irradiation field; 21. The radiation imaging apparatus according to claim 20, further comprising a determination unit that determines whether to stop irradiation of radiation by monitoring the determination target amount.

22. In the radiation detector, third measurement fields are defined, each of which includes two or more of the plurality of measurement fields as second measurement fields; The identification means A plurality of first measurement areas are set from the third measurement area, each of which includes a plurality of the second measurement areas; 2. The radiation imaging device of claim 1, wherein for each of the plurality of first measurement fields, a second measurement field to be used for monitoring the exposure dose is identified from among the plurality of second measurement fields based on the exposure dose obtained from each of the plurality of second measurement fields included in the first measurement field.

23. 23. The radiation imaging apparatus according to claim 22, wherein the specifying unit sets a plurality of first measurement fields so as to share at least one of the second measurement fields.

24. 1. A method for controlling a radiation imaging apparatus including a radiation detector having a plurality of imaging pixels for capturing a radiation image based on incident radiation and a plurality of detection pixels for monitoring an exposure dose of the radiation, the method comprising: defining a plurality of radiation detection fields in the radiation detector, each of the radiation detection fields including one or more of the plurality of detection pixels; acquiring an irradiation dose in each of the plurality of irradiation fields based on an irradiation dose detected from a detection pixel included in the plurality of irradiation fields; identifying a measurement field to be used for monitoring the irradiation dose from the plurality of measurement fields based on the irradiation doses acquired from the respective measurement fields; 2. A method for controlling a radiation imaging apparatus comprising:

25. A program for causing a computer to execute the method for controlling a radiation imaging apparatus according to claim 24.

26. a radiation detector having a plurality of imaging pixels for capturing a radiographic image based on incident radiation and a plurality of detection elements for monitoring the radiation exposure dose; an acquisition means for acquiring an integrated dose of each of a plurality of measurement fields, each of which includes one or more of the plurality of detection elements, based on the irradiation dose detected by the detection element included in each measurement field; a dividing means for dividing the plurality of measurement areas into one or more groups based on the cumulative doses of the plurality of measurement areas; and specifying means for specifying, as an excluded irradiation field that is not to be used for monitoring the radiation exposure dose, an irradiation field included in a group that satisfies a predetermined condition among the one or more groups.

27. 27. The radiation imaging apparatus according to claim 26, further comprising a determination unit that determines whether to stop irradiation of radiation by monitoring an integrated dose in the plurality of measurement fields other than the excluded measurement field.

28. 27. The radiation imaging apparatus according to claim 26, wherein the predetermined condition includes excluding the measurement field with the smallest cumulative dose from among the plurality of measurement fields.

29. 29. The radiation imaging apparatus according to claim 28, wherein the dividing means includes all of the plurality of measurement fields in one group when a difference between a minimum cumulative dose and a maximum cumulative dose among the plurality of measurement fields is less than a first threshold value.

30. 30. The radiation imaging device of claim 29, wherein the dividing means divides the plurality of irradiation fields into the one or more groups based on the difference in cumulative dose between two irradiation fields that are adjacent or separated by a predetermined number in a row of the plurality of irradiation fields obtained by arranging the plurality of irradiation fields in order of cumulative dose.

31. 31. The radiation imaging device according to claim 30, wherein the dividing means divides the plurality of irradiation fields into the one or more groups such that the two irradiation fields are included in another group when a difference in cumulative dose between the two irradiation fields is greater than a second threshold value.

32. 32. The radiation imaging apparatus according to claim 31, wherein the dividing means determines the second threshold value in accordance with a specification from a user of the radiation imaging apparatus.

33. The radiation imaging apparatus according to claim 32 , wherein the plurality of irradiation fields are included in a candidate monitoring area.

34. 34. The radiation imaging apparatus according to claim 33, further comprising a determining unit for determining a position of the monitoring candidate region in accordance with a user's designation.

35. The radiation imaging apparatus according to claim 33, further comprising a determining means for determining a position of the monitoring candidate region based on a part of an imaging target.

36. 1. A method for controlling a radiation imaging apparatus including a radiation detector having a plurality of imaging pixels for capturing a radiation image based on incident radiation and a plurality of detection elements for monitoring an exposure dose of the radiation, the method comprising: a step of acquiring an integrated dose of each of a plurality of measurement fields, each of which includes one or more of the plurality of detection elements, based on the irradiation dose detected by the detection element included in each measurement field; Dividing the plurality of measurement fields into one or more groups based on the cumulative doses of the plurality of measurement fields; and identifying a measurement field included in a group among the one or more groups that satisfies a predetermined condition as an excluded measurement field that will not be used for monitoring the radiation exposure dose.

37. A program for causing a computer to execute each step of the control method according to claim 36.

38. a photodetector having a plurality of imaging pixels for capturing an image based on incident light and a plurality of photoelectric conversion elements for monitoring the amount of the light; an acquisition means for acquiring an integrated light amount of each of a plurality of light measurement areas, each of which includes one or more of the plurality of photoelectric conversion elements, based on the light amount detected by the photoelectric conversion element included in each of the light measurement areas; a dividing means for dividing the plurality of measurement areas into one or more groups based on the integrated light amount of each of the plurality of measurement areas; and an identification means for identifying a light measurement field included in a group among the one or more groups that satisfies a predetermined condition as an excluded light measurement field that will not be used for monitoring the amount of light.

Images