Radiographic imaging system, imaging control device, radiographic imaging device, radiographic imaging method, and computer-readable storage medium

Abstract

A radiographic imaging system includes a radiographic imaging apparatus including dose detection pixels that detect a dose of radiations irradiated from a radiation source, and an imaging control apparatus that controls the radiographic imaging apparatus. Before radiographic imaging, the imaging control apparatus specifies positions of the dose detection pixels in a region of interest for calculating a dose index value of a radiographic image, determines a threshold value according to the positions of the dose detection pixels, and transmits the positions of the dose detection pixels and the threshold value to the radiographic imaging apparatus. The radiographic imaging apparatus performs setting of the positions of the dose detection pixels in the region of interest and the threshold value transmitted from the imaging control apparatus, and performs imaging based on the setting.

Description

Technical Field

[0001] This invention relates to a radiation imaging system, an imaging control device, a radiation imaging apparatus, a radiation imaging method, and a computer-readable storage medium. Background Technology

[0002] Radiographic imaging devices that use radiation, such as X-rays, for medical image diagnosis, non-destructive examinations, etc., have matrix substrates that combine switches, such as thin-film transistors (TFTs), with conversion elements, such as photoelectric conversion elements.

[0003] This type of radiation imaging device has an extremely wide dynamic range for radiation dose and, through automatic concentration correction performed via image processing, offers the advantage of providing output at a more stable concentration than conventional analog radiation imaging, even under conditions of insufficient or excessive dose. However, a problem exists: technicians may find it difficult to notice when they capture images at an insufficient dose, which increases the amount of radiation exposed to the patient, especially at excessive doses.

[0004] Therefore, to address this issue, the common practice is to display the value used as a guide for the imaging dose in digital radiography (hereinafter referred to as the "dose index value") along with the captured image. Various methods have been proposed for calculating the dose index value. The International Electrotechnical Commission (IEC) recently published the international standard IEC 62494-1, which defines the "exposure index (EI)" as a standardized dose index value. In this international standard, EIt (target exposure index) is specified as the value of the dose used as the target (hereinafter referred to as the "dose target value"), and operational methods for managing dose using the deviation DI (deviation index), which represents the amount of deviation between the dose index value EI and the dose target value EIt, are also given.

[0005] PTL 1 describes a device with AEC functionality that stops X-ray irradiation at a target dose, wherein the receptor field, which is the region of the detection pixel that detects the dose, is automatically set during X-ray irradiation based on the pixel value of the detection pixel, and the dose index value EI is calculated based on a representative value V extracted from the pixel value in the receptor field.

[0006] PTL 2 describes the process of dividing a radiographic image into multiple anatomical regions, extracting at least one of the multiple anatomical regions, and calculating the dose index value EI for the radiographic imaging of the extracted region based on the pixel values ​​in the extracted region.

[0007] Citation List

[0008] Patent documents

[0009] PTL 1: Japanese Patent Application Publication No. 2014-158580

[0010] PTL 2: Japanese Patent Application Publication No. 2020-25730 Summary of the Invention

[0011] Technical issues

[0012] In managing dose in radiographic imaging, there is a need to minimize the deviation between the dose index value EI and the dose target value EIt.

[0013] Therefore, the object of the present invention is to provide a radiation imaging technique that enables appropriate dose management by reducing the deviation between a target dose value set as a radiation exposure threshold and the dose index value at the time of actual image capture.

[0014] Solution to the problem

[0015] According to one aspect of the present invention, a radiation imaging system includes a radiation imaging apparatus and an imaging control apparatus. The radiation imaging apparatus includes dose detection pixels for detecting the dose of radiation irradiated from a radiation source, and the imaging control apparatus controls the radiation imaging apparatus. Before radiation imaging, the imaging control apparatus specifies the position of the dose detection pixels in a region of interest for calculating dose index values ​​of a radiation image, determines a threshold based on the position of the dose detection pixels, and transmits the position of the dose detection pixels and the threshold to the radiation imaging apparatus. The radiation imaging apparatus sets the position of the dose detection pixels in the region of interest and the threshold transmitted from the imaging control apparatus, and performs imaging based on the settings.

[0016] According to another aspect of the invention, an imaging control device includes a dose detection pixel for detecting the dose of radiation irradiated from a radiation source. The imaging control device sets the position and threshold of the dose detection pixel in a region of interest to be transmitted, and controls a radiation imaging device to capture an image based on the settings.

[0017] Prior to radiation imaging, the imaging control device:

[0018] The location of the dose detection pixel in the region of interest used to calculate the dose index value of the radiation image is specified, a threshold is determined based on the location of the dose detection pixel, and the location of the dose detection pixel and the threshold are transmitted to the radiation imaging device.

[0019] According to another aspect of the present invention, a radiation imaging apparatus includes a dose detection pixel for detecting the dose of radiation irradiated from a radiation source, the radiation imaging apparatus comprising:

[0020] A controller that sets up the radiographic imaging device prior to radiographic imaging based on information transmitted from the imaging control device.

[0021] Prior to radiation imaging, the imaging control device specifies the position of the dose detection pixel in the region of interest for calculating dose index values ​​of the radiation image, determines a threshold based on the position of the dose detection pixel, and transmits the position of the dose detection pixel and the threshold to the radiation imaging device.

[0022] The controller sets the position of the dose detection pixel in the region of interest and the threshold value, which are transmitted from the imaging control device, and performs imaging based on the settings.

[0023] According to yet another aspect of the present invention, a radiation imaging method is a radiation imaging method using a radiation imaging apparatus, the radiation imaging apparatus including a dose detection pixel for detecting the dose of radiation irradiated from a radiation source, the radiation imaging method comprising:

[0024] The control steps of the radiographic imaging device are set up before radiographic imaging based on information transmitted from the imaging control device.

[0025] Prior to radiation imaging, the imaging control device specifies the position of the dose detection pixel in the region of interest for calculating dose index values ​​of the radiation image, determines a threshold based on the position of the dose detection pixel, and transmits the position of the dose detection pixel and the threshold to the radiation imaging device.

[0026] In the control step, the position of the dose detection pixel in the region of interest and the threshold are set from the imaging control device, and imaging is performed based on the settings.

[0027] Advantages of the invention

[0028] According to the present invention, the dose can be appropriately managed by reducing the deviation between the target dose value set as the radiation irradiation threshold and the dose index value when the actual image is captured. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0030] Figure 1This is a diagram illustrating an example configuration of a radiation imaging system including a radiation imaging device.

[0031] Figure 2 This is a diagram illustrating an example of data communication in a radiographic imaging system.

[0032] Figure 3 This is a diagram illustrating an example of the external configuration of a radiation imaging device.

[0033] Figure 4 This is a diagram illustrating the functional configuration of the radiation imaging system in the illustrated embodiment.

[0034] Figure 5 This is a diagram illustrating an example of the operation of a digital signal-based radiographic imaging system.

[0035] Figure 6A This is a diagram illustrating an example of the internal configuration of a radiation imaging apparatus according to an embodiment.

[0036] Figure 6B This is a diagram illustrating an example of the internal configuration of a radiation imaging apparatus according to an embodiment.

[0037] Figure 6C This is a diagram illustrating an example of the internal configuration of a radiation imaging apparatus according to an embodiment.

[0038] Figure 7 This is a timing diagram of the internal operation of the radiation imaging apparatus of the illustrated embodiment.

[0039] Figure 8 This is a diagram illustrating the process used to calculate dose index values.

[0040] Figure 9 This is a diagram illustrating the pre-irradiation adjustments used in the method for calculating dose index values.

[0041] Figure 10 This is a diagram illustrating the adjustments made during irradiation in a method used to calculate dose index values.

[0042] Figure 11 This diagram illustrates the procedure performed when the predetermined receptor field and the area of ​​actual radiation exposure are misaligned. Detailed Implementation

[0043] In the following, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention. Several features are described in the embodiments, but the invention is not limited to requiring all such features, and multiple such features can be suitably combined. Furthermore, in the drawings, the same reference numerals are given to the same or similar configurations, and repeated descriptions thereof are omitted. In the embodiments described below and within the scope of the patent claims, "radiation" includes not only X-rays but also alpha rays, beta rays, gamma rays, various particle rays, etc.

[0044] Configuration of a radiation imaging system

[0045] The following will refer to Figure 1 The configuration and processing of the radiation imaging system 1000 according to this embodiment are described. Figure 1 This is a block diagram illustrating an example configuration of a radiographic imaging system including a radiographic imaging apparatus according to this embodiment. The radiographic imaging system 1000 is used, for example, in a hospital to capture radiographic images, and as a system configuration includes a radiographic imaging apparatus 1001, an imaging control device 1002, a radiation source 1003, a high-voltage generation device 1004, a LAN 1005 (hospital LAN), and a display unit 1006.

[0046] The radiation imaging device 1001 detects radiation passing through a subject (not shown) and forms an image in response to an operator's operation of the operation switch 46. The imaging control device 1002 performs settings such as imaging conditions and operation control settings within the radiation imaging device 1001, and the radiation imaging device 1001 communicates with the imaging control device 1002, such as transmitting images, transmitting the arriving dose, and transmitting automatic exposure control signals for controlling irradiation from the radiation source 1003.

[0047] The imaging control device 1002 includes, for example, an input device such as a mouse and keyboard enabling input of information such as setting shooting conditions, operation settings, and image information, and an output device such as a display enabling output. The imaging control device 1002 also controls the irradiation of radiation by the high-voltage generating device 1004. The imaging control device 1002 is functionally configured with a communication control unit 1021 that performs communication and acts as a communication intermediary, and a control unit 1022 that performs operation settings, dose information notifications, etc., and monitors the status of the radiation imaging device 1001 and the high-voltage generating device 1004 to control radiation irradiation and image capture. The communication control unit 1021 can also be provided as a separate unit of the imaging control device 1002 and operate as a circuit for acting as a communication intermediary for the imaging control device 1002.

[0048] The radiation source 1003 includes, for example, an X-ray tube and a rotor, which uses a high voltage to accelerate electrons to generate radiation and cause electrodes to strike an anode. The subject is irradiated with radiation emitted from the radiation source 1003, and the radiation imaging apparatus 1001 detects the radiation passing through the subject and forms an image. For convenience, Figure 1 The imaging control device 1002 and the high-voltage generation device 1004 are illustrated as being deployed in separate locations, but they can be deployed in the same unit. Functions other than image acquisition can be provided in any part other than the radiation imaging device 1001.

[0049] Figure 2 This is a diagram illustrating an example of data communication in a radiographic imaging system. Figure 2 An example of data communication between the imaging control device 1002, the radiation imaging device 1001, and the high-voltage generating device 1004 is illustrated. In the communication between the imaging control device 1002 and the radiation imaging device 1001, information such as imaging condition settings, operation control settings, image transmission, AEC threshold, arriving dose, automatic exposure control signals, and information during automatic exposure is transmitted and received. The radiation imaging device 1001 has two communication units: a wireless communication unit and a wired communication unit, and the radiation imaging device 1001 can use these two communication units to connect to the communication control unit 1021 of the imaging control device 1002.

[0050] In the communication between the imaging control device 1002 and the high-voltage generating device 1004, information such as dose information, irradiation control signals, and optical image information using visible light, infrared light, etc., related to the planned irradiation area are transmitted and received. This optical image information is information about the focal point, aperture, etc., which are optically similar to radiation and can be shared between the imaging control device 1002 and the high-voltage generating device 1004.

[0051] The transmission path for transmitting information does not necessarily need to be mediated by the imaging control device 1002, and data can be directly transmitted and received through communication between the radiation imaging device 1001 and the high voltage generating device 1004, or information can be shared between the imaging control device 1002, the radiation imaging device 1001 and the high voltage generating device 1004 through communication based on data transmission standards such as Controller Area Network (CAN).

[0052] "Dose information" refers to the dose of radiation irradiated from radiation source 1003, and "the dose that reaches" refers to the dose of radiation irradiated from radiation source 1003 that reaches radiation imaging device 1001.

[0053] The “AEC threshold” is a threshold information that is set as a dose target value and used as a reference for comparison with the arrived dose. This “AEC threshold” corresponds to dose information per unit area. The “AEC threshold” is set to reflect a pre-set dose target value EIt. The imaging control device 1002 compares the “AEC threshold” with the arrived dose calculated within the radiation imaging device 1001, and notifies the high-voltage generation device 1004 when the AEC threshold exceeds the arrived dose. The imaging control device 1002 appropriately converts this into dose information per unit area and performs processing for comparing the AEC threshold with the arrived dose.

[0054] "Automatic exposure control signal" is a signal that includes two signals, such as a stop signal (irradiation stop signal) for stopping radiation exposure and an irradiation start signal (non-irradiation stop signal) for starting radiation exposure.

[0055] "Information during automatic exposure (ROI / calculation method)" refers to instruction information transmitted from the imaging control device 1002 to the radiographic imaging device 1001, indicating the region of interest (ROI) (receptor field) and calculation method used for automatic exposure control. Information such as the ROI (receptor field 1012) and corresponding calculation method during actual automatic exposure are transmitted from the radiographic imaging device 1001 to the imaging control device 1002.

[0056] In addition, the imaging control device 1002 controls the display unit 1006 to display “dose information (dose index value EI / deviation DI)” during image capture, to display input for setting “dose target value EIt”, or to display control for displaying information set during radiation imaging.

[0057] The wired communication unit included in the radiographic imaging apparatus 1001 as a communication medium serves as a path for transmitting information, enabling the transmission and reception of information via cable connections using communication standards with predetermined arrangements, such as RS232C, USB, Ethernet (registered trademark). Similarly, the wireless communication unit included in the radiographic imaging apparatus 1001 as a communication medium also serves as a path for transmitting information and includes a circuit board, for example, with a communication IC. The wireless communication unit is electrically connected to an antenna (not shown) and wirelessly transmits and receives radio waves. The circuit board with the communication IC, etc., can perform communication processing via the antenna according to a wireless LAN-based protocol. The frequency band, standard, method, etc., of the wireless communication are not particularly limited, and short-range wireless communication such as Near Field Communication (NFC) and Bluetooth (registered trademark), ultra-wideband (UWB), etc., can be used. Furthermore, the wireless communication unit can have multiple wireless communication methods, which can be appropriately selected for communication.

[0058] The radiation imaging device 1001 can be configured, for example, as a portable box-type flat panel detector (FPD). Figure 3 This is a diagram illustrating an example of the external configuration of a portable radiography imaging device 1001. The radiography imaging device 1001 includes a power button 1007 for turning the power on and off, a battery unit 1008 for power supply, and a connector connection unit 1009. The battery unit 1008 is configured to be removable, and the battery body of the battery unit 1008 is configured to be rechargeable via a battery charger.

[0059] The radiation imaging device 1001 can be connected to the imaging control device 1002 using a sensor cable 1010, and the radiation imaging device 1001 is connected to the sensor cable 1010 via a connector connection unit 1009. When the radiation imaging device 1001 and the imaging control device 1002 are connected via the sensor cable 1010, the connection between the two switches to communication using a wired communication unit, and Figure 2 The information communication between the radiation imaging device 1001 and the imaging control device 1002 shown is performed via wired communication. Regardless of the connection format, the communication unit can be switched by the imaging control device 1002 in response to user operation.

[0060] Reference Figure 4 The functional configuration of the radiation imaging system 1000 of this embodiment is described. Signals from the radiation source 1003 and the operation signal generation unit 1041 are input to the radiation generation control unit 1042 of the high-voltage generation device 1004. Signals expressing the stable state of anode rotation, signals expressing the temperature state, etc., are input from the radiation source 1003 to the radiation generation control unit 1042. The operation switch 46 is connected to the operation signal generation unit 1041, and the input signal from the switch operation performed by the operator is input to the radiation generation control unit 1042.

[0061] Furthermore, various signals are input from the radiation imaging device 1001 and the imaging control device 1002 to the radiation generation control unit 1042 via the signal selection unit 1043, the signal integration determination unit 1044, and the signal processing unit 1045. Signals indicating the shooting preparation state are input from the radiation imaging device 1001 to the radiation generation control unit 1042. Signals concerning exposure control (described later) are input to the radiation generation control unit 1042 via the signal selection unit 1043. Stop signals for radiation 1103 in the analog signal path from the signal integration determination unit 1044 and in the digital communication path from the signal processing unit 1045 are input to the signal selection unit 1043, and the first input signal is transmitted to the radiation generation control unit 1042.

[0062] The radiation imaging apparatus 1001 of this embodiment includes a digital processing unit 401 that outputs a stop signal when the dose information obtained by a first processing (digital signal processing) based on the result of detection of a dose detection pixel (detection unit) exceeds a threshold, and an analog processing unit 402 (conversion processing unit) that outputs a signal obtained by performing a second processing (analog conversion processing) on ​​the signal that has undergone the first processing (digital signal processing) by the digital processing unit 401.

[0063] The digital processing unit 401 (first processing unit) generates a signal obtained by performing digital signal processing on the detection result from the dose detection pixel as a first processing step. The digital processing unit 401 (first processing unit) can output the generated signal as a synchronization control signal with the radiation source 1003. The digital processing unit 401 (first processing unit) is configured to, for example, detect radiation exposure to the radiation imaging device 1001 based on the generated signal, calculate the radiation dose and the accumulated exposure amount (integrated dose), etc. The digital processing unit 401 (first processing unit) outputs a stop signal (first stop signal) when the dose information obtained from the first processing (digital signal processing) based on the detection result of the dose detection pixel 121 (detection unit) exceeds a threshold.

[0064] The analog processing unit 402 (conversion processing unit) and the signal integration determination unit 1044 (integration determination unit) constitute the second processing unit in the radiation imaging system 1000 of this embodiment. The second processing unit outputs a stop signal (second stop signal) when the dose information obtained based on the second processing (analog conversion processing) of the signal that has undergone the first processing (digital signal processing) by the digital processing unit 401 (first processing unit) exceeds a threshold.

[0065] Here, the analog processing unit 402 (conversion processing unit) outputs a signal obtained by performing a second processing (analog conversion processing) on ​​the signal that has undergone first processing (digital signal processing) by the digital processing unit 401 (first processing unit), and the signal integration determination unit 1044 determines whether the dose information obtained by performing integration processing on the signal output from the analog processing unit 402 (conversion processing unit) exceeds a threshold. When the signal integration determination unit 1044 (integration determination unit) determines that the dose information exceeds the threshold, the second processing unit outputs a stop signal (second stop signal).

[0066] The radiation generation control unit 1042 controls the radiation source 1003 based on a first stop signal output from the digital processing unit 401 (first processing unit) or a second stop signal output from the analog processing unit 402 and the signal integration determination unit 1044 (second processing unit). In other words, the radiation generation control unit 1042 controls the radiation source 1003 to stop radiation irradiation based on the first stop signal or the second stop signal.

[0067] The stop signal (second stop signal) of radiation 1103 input from signal integration determination unit 1044 (integration determination unit) via analog signal path (second signal path) and the stop signal (first stop signal) of radiation 1103 input from signal processing unit 1045 via digital signal path (first signal path) are input to signal selection unit 1043 (selection unit). The first input stop signal is selected by signal selection unit 1043 (selection unit), and the selected stop signal is transmitted to radiation generation control unit 1042. In other words, signal selection unit 1043 (selection unit) selects either the first stop signal or the second stop signal. At this time, signal selection unit 1043 (selection unit) selects the signal that was input first among the first and second stop signals.

[0068] The radiation generation control unit 1042 controls radiation generation while confirming the status of each input. The radiation generation control unit 1042 controls the irradiation of radiation from the radiation source 1003 based on the input signals regarding the exposure status. In other words, the radiation generation control unit 1042 controls the radiation source 1003 to stop irradiation based on the signal selected by the signal selection unit 1043 (selection unit).

[0069] Furthermore, the radiation imaging apparatus 1001 can communicate with the signal processing unit 1045 of the high-voltage generation apparatus 1004 via the relay unit 1023 and signal generation unit 1024 of the imaging control apparatus 1002. A signal expressing the image capture readiness state is input from the radiation imaging apparatus 1001 to the signal processing unit 1045 via the relay unit 1023 and signal generation unit 1024 of the imaging control apparatus 1002. The signal processing unit 1045 inputs an input signal expressing the image capture readiness state to the radiation generation control unit 1042. Here, when the communication between the radiation imaging apparatus 1001 and the imaging control apparatus 1002 is wireless, the relay unit 1023 acts as an access point; when the communication is wired, the relay unit 1023 acts as a switching hub. The communication control unit 1021 is also connected to the relay unit 1023, and the functions of the communication control unit 1021 are implemented through application software running on a platform such as a PC (information processing device).

[0070] In this embodiment, there are two types of signal paths for dose control, using analog and digital signals. One of the signal paths is an analog signal path for dose control (the second signal path), which is connected from the communication unit 227 of the radiation imaging apparatus 1001 to the signal integration and determination unit 1044 in the high-voltage generation apparatus 1004. This analog signal is the output signal of the simulated dose control sensor 1011 (the analog output signal for dose control). This connection format allows the processing circuitry of the high-voltage generation apparatus 1004 to process the analog output signal from the dose control sensor 1011, and therefore does not require any changes to the processing circuitry of the high-voltage generation apparatus 1004. Note that the dose control sensor 1011 is an ion chamber type, a type that applies a phosphor to an optical fiber and detects the phosphor using an image intensifier, a type that uses a thin-film semiconductor sensor, etc. As will be described later, this signal path is configured to provide a circuit configuration for dose control in the high-voltage generation apparatus 1004. Note that dose control can be redundantly configured using dose control sensor 1011 and its output as an analog signal, instead of using radiation imaging device 1001.

[0071] like Figure 4 As shown, five receptor fields 1012 are provided in the dose control sensor 1011. Note that the arrangement of the receptor fields 1012 is merely an example, and the spirit of this embodiment is not intended to be limited to this example. Figure 4In the example shown, the receptor field 1012 based on five regions corresponds to a corresponding dose detection pixel among the multiple dose detection pixels 121 of the radiation imaging device 1001. The operator can select the receptor field 1012 from the set irradiation area mode using the user interface (setting unit; not shown) in the high-voltage generation device 1004. Based on the operator's input, the user interface (setting unit) sets the irradiation area of ​​the radiation source. Once the irradiation area of ​​the radiation source is set, the control circuit 225 of the radiation imaging device 1001 (… Figures 6A to 6C The control circuit 225 of the radiation imaging apparatus 1001 can specify the dose detection pixel 121 (detection unit) arranged at the position corresponding to the set irradiation area from among the multiple dose detection pixels 121 (detection units) arranged in the image capture area 100. Furthermore, the control unit 1022 (acquisition unit) of the imaging control device 1002 can obtain information about the image capture location of the subject from information from an image capture order system (such as a Hospital Information System (HIS) or Radiology Information System (RIS)) via LAN 1005. When the information about the image capture location of the subject is obtained by the control unit 1022 (acquisition unit), the control circuit 225 (designation unit) of the radiation imaging apparatus 1001 can specify the dose detection pixel 121 (detection unit) arranged at the position corresponding to the image capture location of the subject from among the multiple dose detection pixels 121 (detection units) arranged in the image capture area 100.

[0072] The digital processing unit 401 (first processing unit) of the radiation imaging apparatus 1001 obtains dose information based on the detection results from the designated dose detection pixel 121 (detection unit). In addition, the analog processing unit 402 (conversion processing unit) of the radiation imaging apparatus 1001 generates and outputs an analog output signal that simulates the output of the dose control sensor at the position corresponding to each receptor field (i.e., an analog output signal for dose control (a signal corresponding to the received dose)).

[0073] The digital signal path (first signal path) used for dose control will be described next. This signal transmission path uses a dedicated digital communication path or equivalent path to transmit a handshake signal for imaging preparation between the high voltage generating device 1004 and the radiation imaging device 1001.

[0074] Reference Figure 4 and 5 Describes the handshake operation performed during radiographic imaging. Utilizing... Figure 5The sequence indicated by 5a in the diagram is used to determine the irradiation time on the high-voltage generating device 1004. The radiation generation control unit 1042 prepares to generate radiation in response to the operator's operation of the operating switch 46. Once the anode rotation speed of the radiation source 1003 is stable and other internal circuits are ready, the signal processing unit 1045 of the high-voltage generating device 1004 outputs a shooting preparation request signal 501 based on the signal input from the radiation generation control unit 1042, representing a request level signal. Figure 5 5a).

[0075] The image capture preparation request signal 501 (request level) output from the signal processing unit 1045 of the high voltage generation device 1004 is transmitted to the radiation imaging device 1001 via the signal generation unit 1024 of the imaging control device 1002. Then, once image capture preparation is complete, the radiation imaging device 1001 outputs a signal indicating that image capture preparation is complete. Then, based on the signal input from the radiation imaging device 1001, the signal generation unit 1024 of the imaging control device 1002 outputs an image capture preparation completion signal 502 (request level signal) as a preparation completion level signal. Figure 5 (5a) The image capture preparation completion signal 502 (preparation completion level) is input to the radiation generation control unit 1042 via the signal processing unit 1045 of the high voltage generation device 1004. Here, the signal indicating image capture preparation completion output from the radiation imaging device 1001 corresponds to the irradiation start signal for starting radiation irradiation. The radiation generation control unit 1042 monitors the status of other signals, confirms preparation completion, and then irradiates the radiation 1103. Here, the radiation generation control unit 1042 can control the irradiation stop based on the radiation irradiation time set by the operator. Under the control of the radiation generation control unit 1042, the radiation 1103 changes from the irradiation state to the non-irradiation state (irradiation stop control). Figure 5 5a).

[0076] Then, based on the signal input from the radiation generation control unit 1042, the signal processing unit 1045 of the high-voltage generation device 1004 changes the image capture preparation request signal 501 to a non-request level and outputs a signal (non-request output). In other words, based on the signal input from the radiation generation control unit 1042, the signal processing unit 1045 outputs the image capture preparation request signal 501 as a non-request level signal (image capture preparation request signal 501 (non-request level)). The image capture preparation request signal 501 (non-request level) output from the signal processing unit 1045 of the high-voltage generation device 1004 is transmitted to the radiation imaging device 1001 via the signal generation unit 1024 of the imaging control device 1002. In response to the image capture preparation request signal 501 (non-request level), the radiation imaging device 1001 changes its state from the image capture preparation completed state to the preparation not completed state.

[0077] Next, we will refer to Figure 5 Section 5b describes the sequence of operations to be performed when a sufficient dose is detected before the set radiation exposure time has elapsed. This sequence of operations is related to... Figure 5 The same applies to 5a in the above description, until actual irradiation of radiation 1103 occurs. Thereafter, when a sufficient dose is detected within the radiation imaging apparatus 1001 by the method described later, based on the signal output from the radiation imaging apparatus 1001, the signal generation unit 1024 outputs a signal that transitions the image capture preparation completion signal 502 from a preparation completion level to a preparation incomplete level (incomplete level), even if the image capture preparation request signal 501 is at a request level. Here, when a sufficient dose is detected within the radiation imaging apparatus 1001, the signal output from the radiation imaging apparatus 1001 corresponds to the stop signal (first stop signal) output from the digital processing unit 401 (first processing unit) when the dose information obtained based on the first processing (digital signal processing) exceeds a threshold. Figure 5In the case indicated by 5b, when a sufficient dose is detected within the radiation imaging device 1001, the state transitions from the preparation-complete level to the preparation-incomplete level (incomplete state) after the set radiation irradiation time has elapsed. The image capture preparation-complete signal 502 (incomplete level) is input from the signal generation unit 1024 to the signal processing unit 1045 of the high-voltage generation device 1004. When the image capture preparation request signal 501 is at the request level and the image capture preparation-complete signal 502 is at the incomplete level, the signal processing unit 1045 outputs the image capture preparation-complete signal 502 (incomplete state) input from the signal generation unit 1024 to the signal selection unit 1043 as a stop signal for the radiation 1103 on the digital signal path. In other words, the stop signal (first stop signal) output from the digital processing unit 401 (first processing unit) is input to the signal selection unit 1043 via the relay unit 1023 of the imaging control device 1002, the signal generation unit 1024, and the signal processing unit 1045 of the high voltage generation device 1004.

[0078] exist Figure 5 In case 5b, when a stop signal (first stop signal) output from, for example, the digital processing unit 401 (first processing unit) is input to the signal selection unit 1043 before a stop signal (second stop signal) traveling on the analog signal path (second signal path), the radiation generation control unit 1042 detects, based on the stop signal (first stop signal) first input to the signal selection unit 1043, that the image capture preparation completion signal 502 has changed from a preparation completion state to a preparation incomplete state. In other words, the radiation generation control unit 1042 detects that the dose information (integrated dose) has reached the predetermined dose and controls the radiation source 1003 to stop irradiating the radiation 1103.

[0079] Despite Figure 5 The signals are represented in circuit signal format. However, it should be noted that communication between the high-voltage generation device 1004 and the radiation imaging device 1001 can also be achieved via command communication for the image capture preparation request signal 501 and the image capture preparation completion signal 502. In this embodiment, the signal path is used for radiation dose control and handshake operations during irradiation, and is therefore configured to transmit a signal for controlling the stop of radiation irradiation within, for example, less than 1 ms. From this perspective, the device used as the signal generation unit 1024 can be, for example, an optocoupler, an opto-MOS relay, etc. For command communication, communication methods that can guarantee communication time and delay time can be used, such as, for example, 100BaseTX / 1000BaseT via wired communication. By ensuring reliability and responsiveness, the signal path can also be configured using wireless communication.

[0080] On the other hand, if the specification stipulates that the stop function only needs to be triggered during long irradiation periods (such as approximately 1 second), for example, when dose suppression is only intended for excessive irradiation that does not contribute to image quality improvement, then even a delay of approximately 100 ms can achieve the purpose. Therefore, this function can be implemented using an interface that performs a normal shooting handshake that is not intended for dose suppression, etc.

[0081] The following describes the operation of radiation dose detection for the purpose of automatic exposure or dose suppression. Figures 6A to 6C This is a diagram illustrating an example of the internal configuration of a radiation imaging apparatus according to an embodiment.

[0082] The radiation imaging apparatus 1001 has a plurality of pixels arranged in an image capture area 100 to form a plurality of rows and a plurality of columns. This embodiment will describe an example in which each pixel is amorphous silicon or polycrystalline silicon. The plurality of pixels includes a plurality of image capture pixels 101 for detecting radiation and obtaining a radiation image based on the detected radiation, and a dose detection pixel 121 (detection unit) for detecting the dose of radiation irradiated from a radiation source.

[0083] In order to accurately control the dose used to form an image through automatic exposure control, it is extremely important to clearly understand the input / output relationship for radiation between the image capture pixel 101 and the dose detection pixel 121. It is impossible to accurately determine the spectrum of radiation quality that has passed through the subject and varies at every location within the body. Therefore, when the outputs of the image capture pixel 101 used to form the image and the dose detection pixel 121 used for automatic exposure control are skewed due to radiation quality, the skew between their outputs cannot be corrected. Consequently, accurate automatic exposure control cannot be performed.

[0084] Thus, for accurate automatic exposure control, it is necessary to clearly know the input / output relationship for radiation, and the simplest way to achieve this is to make the image capture pixel 101 and the dose detection pixel 121 identical. In the case of an image sensor capable of performing non-destructive readout (such as an image sensor made of CMOS), the image capture pixel 101 and the dose detection pixel 121 can be made identical. In other words, the functions of image capture and dose detection can be performed by a single image sensor. In the case of amorphous silicon or polycrystalline silicon, as in this embodiment, the destructive readout pixel structure means that non-destructive readout is impossible. A suboptimal option is to make the image capture pixel 101 and the dose detection pixel 121 separate pixels, where their structures are similar. This allows for identical output characteristics, such as radiation quality dependence, where the only difference between the image capture pixel 101 and the dose detection pixel 121 is a slight difference in spatial location.

[0085] Image capture pixel 101 includes a first conversion element 102 that converts radiation into an electrical signal, and a first switch 103 disposed between column signal line 105 and the first conversion element 102. Dose detection pixel 121 includes a second conversion element 122 that converts radiation into an electrical signal, and a second switch 123 disposed between detection signal line 125 and the second conversion element 122.

[0086] The first conversion element 102 and the second conversion element 122 are composed of a scintillator that converts radiation into light and a photoelectric conversion element that converts light into an electrical signal. The scintillator is generally formed in a sheet shape to cover the image capture area 100 and can be shared among multiple pixels. Alternatively, the first conversion element 102 and the second conversion element 122 can be composed of a conversion element that directly converts radiation into light.

[0087] The first switch 103 and the second switch 123 may include, for example, thin-film transistors (TFTs), wherein the active region is made of semiconductors such as amorphous silicon or polycrystalline silicon (preferably polycrystalline silicon).

[0088] The radiation imaging apparatus 1001 has a plurality of column signal lines 105 and a plurality of drive lines 104. Each column signal line 105 corresponds to one of the plurality of columns in the image capture area 100. Each drive line 104 corresponds to one of the plurality of rows in the image capture area 100. Each drive line 104 is driven by a drive circuit 221 (row selection unit).

[0089] The first electrode of the first switching element 102 is connected to the first main electrode of the first switch 103, and the second electrode of the first switching element 102 is connected to the bias line 108. Here, a single bias line 108 extends in the column direction and is collectively connected to the second electrodes of the plurality of first switching elements 102 arranged in the column direction. The bias line 108 receives a bias voltage from the power supply circuit 226. The second main electrode of each first switch 103 in the plurality of image capture pixels 101 constituting a single column is connected to a single column signal line 105. The control electrode of each first switch 103 in the plurality of image capture pixels 101 constituting a single row is connected to a single drive line 104.

[0090] Multiple column signal lines 105 are connected to a readout circuit 222. Here, the readout circuit 222 may include multiple detection units 132, a multiplexer 134, and an analog-to-digital converter (hereinafter "AD converter") 136. Each of the multiple column signal lines 105 is connected to a corresponding detection unit 132 among the multiple detection units 132 in the readout circuit 222. Here, a single column signal line 105 corresponds to a single detection unit 132. The detection unit 132 includes, for example, a differential amplifier. The multiplexer 134 selects the multiple detection units 132 in a predetermined order and supplies signals from the selected detection units 132 to the AD converter 136. The AD converter 136 converts the supplied signals into digital signals and outputs the digital signals.

[0091] The first electrode of the second conversion element 122 is connected to the first main electrode of the second switch 123, and the second electrode of the second conversion element 122 is connected to the bias line 108. The second main electrode of the second switch 123 is electrically connected to the detection signal line 125. The control electrode of the second switch 123 is electrically connected to the drive line 124. The radiation imaging apparatus 1001 may include a plurality of detection signal lines 125. One or more dose detection pixels 121 may be connected to a single detection signal line 125. The drive line 124 is driven by the drive circuit 241. One or more dose detection pixels 121 may be connected to a single drive line 124.

[0092] The detection signal line 125 is connected to the readout circuit 242 (AEC sensor readout circuit). Here, the readout circuit 242 may include 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 detection unit 142 among the plurality of detection units 142 in the readout circuit 242. Here, a single detection signal line 125 corresponds to a single detection unit 142. The detection unit 142 includes, for example, a differential amplifier. The multiplexer 144 selects the plurality of detection units 142 in a predetermined order and supplies the signal 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 the digital signal.

[0093] The output of the AD converter 146 of the readout circuit 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 readout circuit 242, the signal processing unit 224 outputs information indicating radiation exposure to the radiation imaging device 1001.

[0094] The signal processing unit 224 of the radiation imaging apparatus 1001 in this embodiment includes: a digital processing unit 401, which outputs a stop signal when the dose information obtained by a first processing (digital signal processing) performed based on the result of detection of the dose detection pixel 121 (detection unit) exceeds a threshold; and an analog processing unit 402 (conversion processing unit), which outputs a signal obtained by performing a second processing (analog conversion processing) on ​​the signal that has undergone the first processing (digital signal processing) by the digital processing unit 401.

[0095] Specifically, for example, the digital processing unit 401 detects radiation exposure on the radiation imaging device 1001, calculates the radiation exposure amount and / or the integrated exposure amount, etc. For use in such applications, the earlier second conversion element 122 is configured to have a pixel count ratio not greater than 1% of that of the first conversion element 102 corresponding to the original image sensor. This is to suppress the amount of radiation that does not contribute to image formation to less than the amount absorbed by existing AEC sensors. To handle various measurements, it is useful to distribute the second conversion element 122 uniformly or centrally within the region of interest to increase the density in the peripheral portion used for applications such as radiation area detection.

[0096] The analog processing unit 402 converts the irradiation dose, which has been digitally processed by the digital processing unit 401, into an analog quantity and generates an analog output signal that simulates the output of the dose control sensor (ionization chamber / exposure meter, etc.). The control circuit 225 controls the drive circuits 221 and 241 and the readout circuits 222 and 242 based on information from the signal processing unit 224. Based on information from the signal processing unit 224, the control circuit 225 generates signals that can express, for example, the start and end of exposure (the accumulation of charge corresponding to the irradiated radiation by the image capture pixel 101). The radiation imaging apparatus 1001 also includes a communication unit 227, which handles communication with the imaging control apparatus 1002. The communication unit 227 includes two communication units (i.e., a wired communication unit and a wireless communication unit) for outputting signals via a digital signal signal path (first signal path), and an analog output unit for outputting an analog output signal (analog output signal for dose control) that simulates the output of the dose control sensor via an analog signal signal path (second signal path). In other words, the communication unit 227 outputs the signal from the digital processing unit 401 (first processing unit) through the digital signal path (first signal path), and outputs the signal from the analog processing unit 402 (conversion processing unit) through the analog signal path (second signal path).

[0097] Figure 6A The illustration shows an example of dose detection pixels 121 deployed in a 1×1 pixel unit, while Figure 6B and 6C The illustration shows an example of dose detection pixels 121 arranged in a single row (such as m×1). When dose detection pixels 121 are deployed in a single row (such as m×1), a line distribution map can be generated in real time, and the detection information of dose detection pixels 121 can be used for real-time irradiation dose determination through more advanced image processing, as well as for processing for the purpose of such determination.

[0098] also, Figure 6A and 6B The illustration shows an example of image capture pixel 101 and dose detection pixel 121 being read out via separate and independent circuit configurations (readout circuit 222 and readout circuit 242), while Figure 6C The diagram illustrates the configuration read out by the image capture pixel 101 and the dose detection pixel 121 through a shared circuit configuration.

[0099] exist Figure 6C In the text, the read circuits used for both read circuits 222 and 242 are indicated by "222C", and the drive circuits used for both drive circuits 221 and 241 are indicated by "221C".

[0100] In addition, Figure 6CIn the diagram, the detection unit used as both detection unit 132 and detection unit 142 is indicated by "132C", the multiplexer used as both multiplexer 134 and multiplexer 144 is indicated by "134C", and the AD converter used as both AD converter 136 and AD converter 146 is indicated by "136C".

[0101] use Figure 6C The circuit configuration in the image capture pixel 101 is slightly more complex to control than the shared drive circuit 221C and readout circuit 222C. However, the drive circuit 241, readout circuit 242, etc. of each dose detection pixel 121 are shared with the drive circuit 221 and readout circuit 222 of each image capture pixel 101. This is advantageous in terms of quality and cost because it simplifies the circuit configuration and reduces the number of components.

[0102] In addition, utilizing Figure 6C The circuit configuration shown allows the dose detection pixel 121 to be used as the image capture pixel 101 when not using the dose detection pixel 121 for imaging. Furthermore, as... Figure 6C As indicated by the shaded lines, a correction pixel 151 is provided. The correction pixel 151 comprises at least one pixel for correcting the amount of radiation exposure, and its sensitivity to radiation is set to be lower than that of the image capture pixel 101. Although the correction pixel 151 has substantially the same structure as the dose detection pixel 121 and the image capture pixel 101, the difference lies in that the second conversion element 122 is covered with a film that blocks visible light from the outside. For example, the shielding of light from the correction pixel 151 is achieved by covering the second conversion element 122 with a metal layer such as aluminum.

[0103] The radiation imaging system 1000 of this embodiment includes a radiation imaging device 1001 and an imaging control device 1002. The radiation imaging device 1001 includes dose detection pixels 121 for detecting the dose of radiation irradiated from a radiation source 1003. The imaging control device 1002 controls the radiation imaging device 1001. Here, before radiation imaging, the imaging control device 1002 specifies the position of the dose detection pixels in the region of interest (receptor field 1012) for calculating the dose index value of the radiation image, determines a threshold based on the position of the dose detection pixels, and transmits the position of the dose detection pixels and the threshold to the radiation imaging device 1001. The control circuit 225 of the radiation imaging device 1001 sets the position and threshold of the dose detection pixels in the region of interest (receptor field 1012) transmitted from the imaging control device 1002, and captures an image based on this setting.

[0104] This will be referenced Figure 7 Timing diagram description Figure 6C An example of the operation of the dose detection pixel 121 is shown. These operations are performed by a control circuit 225 that controls the drive circuit 221C and the readout circuit 222C, and a signal processing unit 224 operating in series. Therefore, the combination of the signal processing unit 224 and the control circuit 225 can be referred to as an exposure determination unit.

[0105] exist Figure 7 In the text, "radiation" indicates whether the radiation imaging device 1001 is exposed to radiation. In a low (signal OFF) state, no radiation is emitted, while in a high (signal ON) state, radiation is emitted.

[0106] “Vg1” through “Vgn” indicate drive signals supplied from drive circuit 221C to multiple drive lines 104. “Vgk” indicates drive signals supplied to drive line 104 in the k-th row (where k = 1, ..., the number of drive lines n). Some of the multiple drive lines supplied by drive circuit 221C are used as drive lines 124 to supply drive signals for driving dose detection pixels 121 or correction pixels 151. “Vgk / Vdj” corresponds to drive line 124 in the k-th row and the j-th detection drive line (where k = 1, ..., the number of drive lines n, and j = 1, ..., the number of detection drive lines). For example, “Vg2 / Vd1” indicates drive signals supplied to drive line 124 (which indicates drive lines in the second row and the first detection drive line).

[0107] "Dose detection pixel signal" indicates the value of the signal read from dose detection pixel 121. "Correction pixel signal" indicates the value of the signal read from correction pixel 151. "Integrated exposure" indicates the integrated value of the radiation irradiated onto the radiation imaging device 1001. The method for determining this integrated value will be described later.

[0108] The period from time t0 to t4 is the "reset operation period". At time t0, control circuit 225 initiates a reset operation for multiple pixels. The reset operation is used to remove the charge accumulated in the switching elements of each pixel, and specifically, it is used to put the switching elements (first switch 103 and second switch 123) of each pixel into the conducting state by supplying drive signals from drive circuit 221C to drive lines 104 and 124. Control circuit 225 resets each pixel connected to drive line 104 in the first row by controlling drive circuit 221C. Control circuit 225 then resets each pixel connected to drive line 124 in the second row. Control circuit 225 repeats these operations until the drive line 104 in the last row. At time t1, control circuit 225 completes the reset operation for the drive line 104 in the last row, and then repeats the reset operation again starting from the drive line 104 in the first row.

[0109] At time t3, the "irradiation start request signal" is activated by transmitting an irradiation start request signal from the imaging control device 1002 to the control circuit 225. At this time, the imaging condition settings are finally determined by the information transmitted from the imaging control device 1002. The maximum radiation exposure time, and in some cases, information about the irradiation area, direct radiation dose, automatic exposure control signals, and information during automatic exposure (ROI / calculation method) are transmitted from the imaging control device 1002 to the control circuit 225 of the radiation imaging device 1001. The control circuit 225 can use the information transmitted from the imaging control device 1002 as correction information for AEC operation.

[0110] Upon receiving an irradiation start request signal, control circuit 225 performs a reset operation up to the last row and then completes the reset operation. Control circuit 225 can terminate the reset operation before performing a reset operation on the last row and move to the next process. For example, if an irradiation start request signal is received during the reset operation of drive line 104 (124) in row k, control circuit 225 can execute control to move to the next process without performing the reset operation on drive line 104 (124) in row k+1 and subsequent rows. In this case, a staircase-like image artifact will appear near row k+1, but the staircase-like image artifact can be reduced by adjusting the drive performed when obtaining the corrected image for correcting the radiation image, such as by terminating the drive of row k+1 in a similar manner, and by performing image processing on the radiation image.

[0111] The period from time t4 to t8 is the "readout operation period". At time t4, control circuit 225 begins a measurement operation to measure the amount of radiation irradiated onto the radiation imaging device 1001. During the measurement operation, control circuit 225 repeatedly performs readout operations from dose detection pixel 121 and correction pixel 151. In the multiple readout operations, at least one readout operation in the first half is performed to determine a correction value, and the repeated readout operations in the second half are performed to continuously measure the amount of radiation at each time.

[0112] At time t5, control circuit 225 activates the "illuminable and readable signal". Readout operations are performed only on drive line 124 (AEC drive line) and not on other drive lines 104 during the effective period of the "illuminable and readable signal". Specifically, control circuit 225 supplies drive signals to drive line 124 (AEC drive line) among the plurality of drive lines 104 and 124 that are connected to at least one of the dose detection pixel 121 and correction pixel 151. Control circuit 225 does not supply drive signals to drive lines 104 among the plurality of drive lines 104 and 124 that are not connected to either the dose detection pixel 121 or the correction pixel 151.

[0113] Furthermore, the control circuit 225 can perform a drive to simultaneously supply drive signals to drive lines 124 among the plurality of drive lines 104 and 124 that are connected to at least one of the dose detection pixel 121 and the correction pixel 151. As a result, signals from the plurality of pixels connected to the same drive line are simultaneously read out by the readout circuit 222C. Because the image capture pixel 101 (including the dose detection pixel 121 and the correction pixel 151) is connected to column signal lines 105C (105 and 125) but is selectively read out by the control circuit 225, the readout circuit 222C can read out the signal for AEC detection separately from the signal for image detection.

[0114] The control circuit 225 performs a predetermined number of readout operations, i.e., at least once, to determine the correction value. The signal processing unit 224 determines the correction value Od based on the signal read from the dose detection pixel 121 through the predetermined number of readout operations, and the correction value Oc based on the signal read from the correction pixel 151 through the predetermined number of readout operations.

[0115] The determination of the correction values ​​Od and Oc will be described next. The parameters used to determine the correction values ​​are actually composed of outputs from multiple pixels, and which pixels are used, how these pixels are used, etc., will be described later.

[0116] If the predetermined number of readout operations is one, then only one signal is read from each pixel of dose detection pixel 121, and the signal processing unit 224 uses the value of that signal as the correction value Od. If the predetermined number of readout operations is multiple, then the signal processing unit 224 uses the average of the multiple readout signals as the correction value Od. Other statistical values ​​can be used instead of the average value, and the value of the correction value (offset signal) is represented as Od. Based on the signal read from correction pixel 151, the correction value Oc can also be determined in a similar manner, that is, Oc is determined as the value of the correction value (offset signal). The signal processing unit 224 stores the correction values ​​Od and Oc determined in this way in the storage unit 172, and these values ​​can be used in subsequent processing.

[0117] Because the value of the offset signal changes depending on factors such as the sensor's temperature environment, as in this embodiment, obtaining the offset signal immediately before radiation detection reduces the difference between the offset signal obtained and the offset component during radiation detection, and allows for accurate correction of the offset component during radiation detection.

[0118] Conversely, there are cases where the error due to random noise components is higher than the fluctuation component due to temperature changes, etc., during the "readout operation period" (times t4 to t8), because the number of samples used to generate the correction values ​​Od and Oc is small. In such cases, for example, when a sufficient number of samples can be ensured and the error due to random noise components such as thermal noise can be suppressed, the correction values ​​Od and Oc can be generated at a timing when there is extra time (such as during the reset operation period).

[0119] The time from when the imaging control device 1002 transmits an "irradiation start request signal" to the control circuit 225 until the control circuit 225 transmits an "irradiation and readability signal" to the high-voltage generation device 1004 via the imaging control device 1002 is called the "exposure delay". In this case, it is no longer necessary to obtain data during the time period from t4 to t5 (the "exposure delay" time period), and the time period corresponding to the exposure delay can be shortened.

[0120] After completing the readout operation of correction values ​​Od and Oc at least once, control circuit 225 transmits an "irradiable and readable signal" to high-voltage generating device 1004 via imaging control device 1002 at time t5. Control circuit 225 repeats the above readout operation after the effective transmission of the irradiable and readable signal. Signal processing unit 224 measures the "integrated DOSE" as an integrated value of the radiation dose (described later) for each readout operation and determines whether the integrated value exceeds a preset "AEC threshold". At time t5, control circuit 225 sends the "irradiable and readable signal" to high-voltage generating device 1004, and then radiation irradiation begins at time t6.

[0121] The method for determining the radiation dose DOSE is described below. The value of the signal read from the dose detection pixel 121 by the most recent readout operation is indicated by Sd. The value of the signal read from the correction pixel 151 by the most recent readout operation is indicated by Sc. The signal processing unit 224 calculates the radiation dose DOSE by applying Sd, Sc, Od, and Oc to the formulas (1) and (2) below. Since the “AEC threshold” corresponds to the dose per unit area, formula (2) indicating the integrated radiation dose DOSE is similarly normalized to the dose per unit area for comparison. Based on the signal read from the correction pixel 151 that blocks visible light, the control circuit 225 of the radiation imaging device 1001 reads the signal from the dose detection pixel 121 in the region of interest (receptor field 1012) specified by the imaging control device 1002, and calculates the integrated dose of radiation based on the corrected signal.

[0122] DOSE per unit sample = (Sd - Od) - (Sc - Oc)...(1)

[0123] The integral DOSE = Σ{(Sd-Od)-(Sc-Oc)}...(2)

[0124] Figure 7 The DOSE per unit sample indicated in the text is an example of the calculation result of the above formula (1). In practice, this is a discrete value updated each time the irradiated radiation is read out by supplying a drive signal to each of the drive lines 124 (AEC drive lines) and causing the dose detection pixel 121 to operate. Figure 7 The diagram in the middle shows a continuous pattern. Figure 7 The DOSE indicated in the middle is an example of the calculation result of the DOSE of the integral in the above formula (2). Figure 7 The diagram illustrates the trend of the accumulated DOSE being updated and increased with each read.

[0125] Signal processing unit 224 obtains (i) the value Sd of the signal read from dose detection pixel 121 after the control circuit 225 has transmitted the irradiable and readable signals, and (ii) the difference (Sd-Od) between the signal value Sd read from dose detection pixel 121 after the control circuit 225 has transmitted the irradiable and readable signals. Signal processing unit 224 also obtains (i) the value Sc of the signal read from correction pixel 151, and (ii) the difference (Sc-Oc) between the signal value Sc read from correction pixel 151 after the control circuit 225 has transmitted the irradiable and readable signals. Then, signal processing unit 224 calculates the radiation dose DOSE (DOSE per unit sample) and the integrated DOSE based on the obtained difference (Sd-Od) and difference (Sc-Oc).

[0126] like Figure 7As shown, the “dose detection pixel 121 signal (Sd-Od),” which is the signal read from the unmasked dose detection pixel 121, changes significantly immediately after the reset operation ends (immediately after time t4) and stabilizes over time (e.g., at approximately 100 ms). Thus, even if only the value of the signal Sd obtained from the dose detection pixel 121 and the correction value Od are used to calculate the radiation dose DOSE, the offset will not be sufficiently removed. If the start of the readout operation to obtain the correction value Od is delayed until the signal read from the dose detection pixel 121 stabilizes, then the time from the transmission of the irradiation start request signal to the actual start of radiation exposure (the time from time t3 to t5, i.e., the exposure delay) becomes longer.

[0127] exist Figure 6C In the circuit configuration shown, the signal value Sc read from the correction pixel 151 and the correction value Oc are further used to measure the radiation dose DOSE. Because the correction pixel 151 is less sensitive to radiation than the dose detection pixel 121 and the image capture pixel 101, the signal value Sc read from the correction pixel 151 after radiation irradiation begins can be considered to represent an offset component of the signal value Sd read from the dose detection pixel 121. Furthermore, in this embodiment, the radiation dose DOSE is determined using the correction values ​​Od and Oc based on the signals read from the dose detection pixel 121 and the correction pixel 151 before radiation irradiation begins. This allows for the correction of inherent characteristic differences in each pixel (e.g., differences in detection circuit channels, differences in parasitic resistance and capacitance in each pixel, etc.).

[0128] exist Figure 7 At time t7, the accumulated DOSE has reached the AEC threshold preset by the control circuit 225. In response, the control circuit 225 transmits information indicating that the AEC threshold has been reached by transmitting a "threshold reached signal" to the high-voltage generation device 1004 via the imaging control device 1002 and by deactivating the "irradiable and readable signal". The imaging control device 1002 controls the irradiation from the radiation source so that the dose target value set as the threshold becomes equal to the dose index value in the radiation image. Instead of transmitting the threshold reached signal to the imaging control device 1002 at the time when the accumulated DOSE reaches the AEC threshold, the control circuit 225 can estimate the time when the accumulated irradiation dose will reach the threshold and transmit the threshold reached signal at the estimated time. After receiving the threshold reached signal from the imaging control device 1002 to report that the AEC threshold has been reached, the high-voltage generation device 1004 ends the radiation irradiation at time t8.

[0129] Note that, in order to accurately calculate the irradiation dose and stop radiation irradiation at the appropriate response time, the readout period of the drive line 124 (AEC drive line) Vgk / Vdj can be sufficiently short compared to the actual irradiation time, for example, no more than 1 / 10 at most. Typically, when using an amorphous silicon sensor, reading out the signal of a single line takes 10 μs to 50 μs. Therefore, in order to read out a wide area, it is necessary to set the overall operation of the dose detection pixel 121 to be in line with the optimal timing by simultaneously enabling multiple drive lines 124 (AEC drive lines) Vgk / Vdj and reading out their outputs. Similarly, especially when the actual irradiation time is no more than a few ms, the delay time from detecting the accumulated radiation irradiation to outputting a "threshold reached signal" after comparing the reached threshold with the AEC threshold can be set to, for example, 1 ms or less. The delay time can also be pre-considered based on the slope of the accumulated dose, and control can be performed by setting the AEC threshold to a small delay time.

[0130] At this time, the control circuit 225 also transmits the actual "information during automatic exposure (ROI / calculation method)" and the received dose information to the imaging control device 1002.

[0131] From time t7 to time t9 to t10 (which is a predetermined time until the radiation stops after at least an assumed delay), the drive circuit 221C again supplies drive signals Vg1 to Vgn to the plurality of drive lines 104, the readout circuit 222C reads signals from the plurality of image capture pixels 101, and the signals processed by the readout circuit 222C are transmitted from the communication unit 227 to the imaging control device 1002 via the signal processing unit 224. The imaging control device generates a radiation image based on the signals transmitted from the communication unit 227 of the radiation imaging device 1001, and performs image processing on the generated radiation image. The radiation image generated and processed by the imaging control device 1002 is transmitted to the display unit 1006 via the imaging control device 1002.

[0132] In the example above, control circuit 225 initiates a predetermined number of readout operations immediately after the reset operation to determine the correction values ​​Od and Oc. Alternatively, control circuit 225 may initiate a predetermined number of readout operations after a predetermined time (e.g., several ms to tens of ms) has elapsed since the reset operation was completed. This allows signal readouts to be suppressed during periods of particularly large time fluctuations.

[0133] For the calculation of a typical dose index value (EI), there are two typical examples: the calculation area for the dose index value EI does not change based on differences in the image based on the shooting method, the subject's shooting posture, the image capture location, etc., and the calculation area for the dose index value EI changes. When the calculation area for the dose index value EI does not change, this method calculates the dose index value EI in a fixed ROI and in a predetermined area (fixed ROI) of the image capture device. This provides the advantage that the operator can clearly identify the area in the image where the calculation is performed. On the other hand, due to the large variations between methods caused by differences in the subject, a fixed ROI has the disadvantages of making it difficult to set the target dose value EIt and manage deviations (DI).

[0134] In contrast, when the calculation area of ​​the dose index value EI is changed, the control circuit 225 first specifies the EI value calculation area for each shot, sets the specified EI value calculation area as the ROI for calculating the EI value, and calculates the dose index value EI by obtaining the representative value in the set ROI.

[0135] Although it may be difficult for the operator to know in which area the dose index value EI will be calculated during the shooting process, the set ROI can be confirmed by sharing the calculation algorithm with the operator in advance and by displaying the ROI to be used after calculation when necessary. Furthermore, because the dose index value EI is calculated after the designated irradiation area, the variation caused by differences in the protocol, subject image, etc., is smaller compared to a fixed ROI, and medical facilities can accurately control the dose during shooting by setting the dose target value EIt and managing the deviation DI.

[0136] From the perspective of properly managing the irradiation dose for the purpose of introducing the dose index value EI, it is better to calculate the dose index value EI by changing the region (setting the ROI) when the effective area of ​​the actual image is known than to calculate the dose index value EI in a fixed ROI where the area of ​​the image capture device does not change regardless of the conditions of the subject (e.g., the subject's shooting posture, the image capture location, etc.).

[0137] Figure 8 This is a flowchart illustrating the process for calculating the dose index value EI. Figure 8The diagram illustrates the sequence for calculating the dose index value EI from images captured after acquisition. First, in step S801 (removing the exterior of the irradiated area), regions in the diagnostic image that are not irradiated by the irradiated area and are clearly located outside the region of interest are excluded from the regions used to calculate the dose index value EI of the captured image. As processing methods, methods such as calculation based on collimator information and tube-FPD distance (FDD) information, extraction of irradiation and region from the image using previously captured site information, and AI-based determination using machine learning can be used.

[0138] Next, in step S802 (removal of the equivalent region of direct rays), a direct ray region including only the grid region is specified, and regions outside the region of interest are excluded from the region used to calculate the dose index value EI. As processing methods, empirical fixed thresholding, modal analysis, differential histogram analysis, p-block analysis, discriminant analysis, etc., can be used.

[0139] Furthermore, in step S803 (removal of unnecessary regions such as metals), low-dose regions within the region of interest but not intended to be used as dose indicators in typical diagnostic images are excluded from the regions used to calculate the dose indicator value EI. As a processing method, region growing, snake methods, etc., can be used. The processing up to this point (S801 to S803) can determine the regions in the captured image used to calculate the dose indicator value EI as the extraction regions.

[0140] Next, in step S804 (calculation of representative values ​​for the extracted region), a representative value (such as the average or median of pixel values) is calculated in the region (extraction region; region of interest) used to calculate the dose index value EI. Finally, in step S805 (conversion of representative values ​​to EI values), the representative values ​​calculated in step S804 are converted such that, for example, 100 = 1 μGy, and the dose index value EI is calculated. The deviation DI between the calculated dose index value EI and the dose target value EIt is also calculated. Based on the calculated deviation DI, the operator can confirm whether the radiographic image was taken with the expected radiation dose. Currently, even if the deviation DI can be confirmed, it is often necessary to determine which modifications should be made to reduce the deviation DI through trial and error in the hospital facility (including the operator).

[0141] Figure 9 This is a diagram illustrating the pre-irradiation adjustment process for calculating dose index values, and... Figure 10 This is a diagram illustrating the adjustment during irradiation for calculating dose index values. The following will describe... Figure 9 and 10 Adjustment processing and Figure 8The specific processing in the flow of this embodiment is shown below. Although the dose index value EI is used as the dose index in this embodiment, similar techniques can be applied to general dose indexes.

[0142] Prior to radiographic imaging, the imaging control device 1002 may use at least one of the following to designate the region of interest: (i) a radiographic projection area calculated based on position measurement information between the radiographic source 1003 and the radiographic imaging device 1001, (ii) an optical image of the subject in the radiographic projection area obtained by the camera, or (iii) a previously captured radiographic image of the subject.

[0143] Figure 9 and 10 The illustration shows an operator obtaining radiographic images of the subject's knees. The operator positions the subject on a table (not shown) placed between the radiation source 1003 and the radiation imaging device 1001. Figure 9 As indicated by 9a, image 5310 (optical image) is displayed in display unit 1006 as a real-time camera image of visible or infrared light corresponding to the area (radiation projection area) where the radiation image of the subject is to be captured. Image 5310 shows the two-dimensional outline 5301 of the radiation imaging device 1001, the radiation projection area 5302, and the direct ray area 5303.

[0144] The simplest way to achieve this display is to perform a real-time display with the indicator light for the radiation irradiation area lit (a common function of the collimator (not shown) in the radiation source 1003). In this case, the outline 5301 is either a two-dimensional outline shape of the desktop radiation imaging device 1001 or a two-dimensional outline shape of the radiation imaging device 1001 under the top of a table made of a material that transmits visible light (such as acrylic material).

[0145] exist Figure 9 In 9b, besides Figure 9 In addition to 9a, five default receptor fields 1012 (AEC receptor fields) are displayed in an overlay manner. When photographing the knee, the default five receptor fields 1012 are not focused on the knee joint to be photographed, and are therefore unsuitable. Therefore, for example, the operator may change the position of the receptor fields 1012 (AEC receptor fields) to match the position of the knee joint (e.g., Figure 9 The instruction (9c) is given. Furthermore, if the operator knows in advance that the metal has been inserted into the facing... Figure 9 If the left knee joint is in the photo, then they can make an instruction to exclude the left knee joint area from the receptor field 1012 (AEC receptor field) during the photoshoot.

[0146] Alternatively, such as Figure 9 As indicated by 9d, overlays of past images taken in the past can be displayed in a semi-transparent manner. Figure 9 Above the 9c and other indicated images, the state of previously treated areas is clearly shown. Figure 9 In 9c, the display control can also show the status of the treatment area (such as metal inserted into the knee joint) in an easy-to-understand way, such as by using shading or coloring of the treatment area, like the metal treatment area. Figure 9 The metal region 5304 in 9d is indicated. Similar to the previously recognized situation, the operator, if necessary, issues an instruction to exclude the left knee joint region from the receptor field 1012 (AEC receptor field) at the time of the image capture, and issues an instruction to change the position of the receptor field 1012 to match the position of the knee joint.

[0147] Figure 9 The image capture of the knee joint shown is an example, and after the processes of "removing the exterior of the irradiation area" (S801), "removing the equivalent area of ​​direct radiation" (S802), and "removing unnecessary areas such as metal" (S803), the receptor field 1012 serves as the operating area of ​​the dose detection pixel 121. By using the image capture pixel 101 near the dose detection pixel 121 shown in FIG. 6 as the dose index value EI and the area information of the set receptor field 1012 to calculate the dose index value EI of the captured image, the dose can be managed more accurately than in the past.

[0148] As described above, when referencing past images to observe progress, the operator can more proactively use past images to determine the receptor field 1012 (AEC receptor field) rather than simply displaying the image as a reference image for determining the receptor field 1012 (AEC receptor field). For example, if the receptor field 1012 (AEC receptor field) of the referenced past image was initially determined using the same sequence as described in this embodiment, then the receptor field 1012 (AEC receptor field) used when capturing past images of the target can be read out using information recorded by the manufacturer in a given area of ​​the DICOM head at the time of capture, and displayed as the default recommended receptor field 1012 (AEC receptor field) used in the current capture. Alternatively, the appropriate receptor field 1012 can also be derived by excluding the direct radiation region 5303 and the metal region 5304 in a manner similar to the method used herein, and by calculating the dose index value EI. In this process, for example, a recommended shape for the appropriate receptor field 1012 for the current capture can be derived. When the recommended receptor field is shown to the operator, the receptor field 1012, which is considered to be in the appropriate position for image 5310, can be displayed after the pre-identification of image 5310 and contour.

[0149] This section will describe according to Figure 8 Another method for determining the receptor field is illustrated in the flowchart. For example, when the radiation imaging device 1001 is deployed on a table or similar surface, the distance (FDD) between the focal point of the radiation source 1003 and the center of the radiation imaging device 1001, as well as their positional relationship, is automatically measured. The collimator aperture is measured by the function of the collimator (not shown) of the radiation source 1003. These measurements can be performed, for example, based on the table and tube holding mechanism, or by providing automatic positioning functions that enable general imaging, as position measurement information in the tube of the radiation source 1003 and the holding mechanism of the radiation imaging device 1001. The imaging control device 1002 can obtain this measurement information via the aforementioned high-voltage generating device 1004 or similar means, and can calculate the profile 5301 and the radiation projection area 5302 based on this information.

[0150] Alternatively, the imaging control device 1002 can maintain the contour 5301 and the radiation projection area 5302 as information by performing image recognition from the real-time video image. Here, the optical axis, focal point, and image forming point are optically substantially the same as the projection system of the display lamp from the collimator, the actual radiation illumination system, and the real-time camera image capture optical system, which makes it possible to obtain an accurate contour 5301 and radiation projection area 5302.

[0151] Despite such as Figure 9 The knee joint shown in the example is unlikely to be a problem, but when photographing areas such as the head, the burden on the subject due to the continuous projection of visible light increases. Therefore, in addition to a visible light optical system, it is preferable to also provide a real-time image capture system projection system and receiver system using near-infrared light, as well as an infrared light receiver system used only as a thermal distribution image capture system.

[0152] Based on this information, the imaging control device 1002 can also perform display control for overlaying the contour 5301 and the radial projection area 5302 onto the real-time camera image. This allows the process to be performed before image capture. Figure 8 The process of removing the outside of the irradiated area in step S801.

[0153] The method for deriving the direct ray region 5303 will be described next. Calculations can be performed by extracting an image from a real-time video image. To improve accuracy, easily distinguishable colors, especially those highly sensitive to the camera, can be used for the top plate (not shown) or the radiation imaging device 1001, or the temperature difference between the top plate or radiation imaging device 1001 and the subject can be distinguished using an infrared real-time camera. The direct ray region 5303 can also be extracted from image 5310 (optical image) by pre-determining the region of a sample image of the direct ray using information such as previously used capture location information and information about past images, or by using threshold information from a fixed threshold method or p-pattern method for region differentiation. The imaging control device 1002 is capable of handling the descriptions to be made later and... Figure 10 It is useful to show the overall information of the dose detection pixel 121 area shown, as well as the percentage information of direct rays calculated in units of detection lines, to send the calculated information to the radiation imaging device 1001 immediately before radiation imaging, and to accurately exclude the direct ray area 5303 based on the integrator value used for comparison with the AEC threshold calculation.

[0154] The imaging control device 1002 can perform display control to display an optical image in the display unit 1006 corresponding to the radiation projection area of ​​the captured radiation image, and the imaging control device 1002 can also perform display control to display an image in the display unit 1006 in which a radiation image of a previously captured subject is superimposed on an optical image.

[0155] Based on this information, the imaging control device 1002 can also perform display control for overlaying the direct ray region 5303 onto the real-time camera image. This allows the process to be performed before image capture. Figure 8 The process of removing the direct ray equivalent region in step S802. As a result, the region within the irradiation area but outside the direct ray equivalent region can be automatically exported as the equivalent of the remaining receptor field 1012. Furthermore, the receptor field 1012 can be identified as the region of interest based on a receptor field template based on the capture site information of the subject. For example, in Figure 9 In this case, since the subject has been identified as "both knees", the region (extraction region) for calculating the dose index value EI can be automatically selected from the region outside the irradiation area and outside the direct ray equivalent region, with the part that can be identified as the knee as the center.

[0156] Here, after the information based on the subject is transmitted to the radiation imaging device 1001, the main functions performed are as follows: Figure 9The process shown involves removing unwanted regions, such as metal, prior to performing radiographic imaging of the knee joint. However, the removal of unwanted regions, such as metal, can be performed based on past images of the same subject. The imaging control device 1002 can overlay past images onto the aforementioned image 5310 (optical image) and can notify the radiographic imaging device 1001 that the region extracted from image 5310 (optical image) that is equivalent to the receptor field 1012, excluding the metal region, is used as the receptor field 1012 in the region (extraction region) for calculating the dose index value EI.

[0157] For reference Figure 9 The described sequence, changes in the imaging site, and changes related to the relative position of the image are completed before time t3, before the operation switch 46 is operated. After the operator indicates radiation irradiation by operating the operation switch 46, the imaging control device 1002 and the high-voltage generation device 1004 do not accept any changes in the imaging site, the relative position of the image, etc. After time t3, the receptor field 1012 in the region (extraction region) used to calculate the dose index value EI is finally determined, and the imaging control device 1002 notifies the radiation imaging device 1001 of the finally determined receptor field 1012.

[0158] Although an embodiment in which the receptor field 1012 (AEC receptor field) is disposed in a limited area within the irradiation area and the subject area has been described above, as shown in Figure 6 and Figure 4 Alternatively, the entire area within the irradiated region and the subject region can be set as the receptor field 1012 (AEC receptor field). In this case, the period used to determine when the AEC threshold is reached increases with the number of rows of dose detection pixels 121 to be read in the receptor field 1012 (AEC receptor field). Therefore, this is not suitable for cases where the expected irradiation time is within milliseconds.

[0159] Next, the following will refer to Figure 10 The description is mainly in Figure 7 The operation is performed during the time period from time t3 to t7. Based on the information of the receptor field 1012 (AEC receptor field) notified to the radiation imaging device 1001 after time t3, the control circuit 225 determines the dose detection pixel 121 for this AEC dose calculation from the dose detection pixels 121 distributed in the image capture area 100.

[0160] like Figure 10 As indicated by 10a, five driving lines 1241 to 1245 are selected corresponding to the receptor field 1012. For example... Figure 10As indicated by 10b, the receptor field 1012 (AEC receptor field) and five selected drive lines 1241 to 1245 within the receptor field 1012 are superimposed on the radiation image to be captured. Other dose detection pixels 121 that are not selected are not driven at all during the radiation irradiation period to shorten the AEC response time and these pixels are used as normal pixels in the image.

[0161] Before time t5, the driving for the correction of the corresponding five dose detection pixels 121 is completed, and the control circuit 225 outputs an irradiable and readable signal at time t5, while simultaneously starting the driving for AEC dose measurement. In this case, the driving signal can be sequentially output to the five driving lines 124 (AEC driving lines) as a five-line drive, or the five driving lines can be selected simultaneously as a one-line drive. The readout time required when driving in five lines is five times longer than that required when driving in one line, but because the spatial resolution is increased, the determination of each line region can be performed in detail, as described later. On the other hand, when driving in one line, the time is as fast as 1 / 5, and the signal components can be ensured five times faster, which provides excellent short-time response; however, the spatial resolution is inferior to that of driving in five lines, so the accuracy is reduced when performing integration while processing fine line regions. The control circuit 225 can control the driving to change the number of lines to be driven during imaging, such as driving five driving lines together at the start of radiation irradiation, and then driving several lines together after a predetermined time has elapsed.

[0162] When the radiation begins at time t6, the output corresponding to each of the drive lines 124 (AEC drive lines) is output from the readout circuit 222C (AEC readout circuit).

[0163] Figure 10 10c and 10e in the figure indicate the line graph and histogram of the final image before post-processing in the section corresponding to drive line 1243 (AEC drive line). Figure 10 The 10d and 10f values ​​indicate the output waveform and histogram of a single sample from drive line 1243 (AEC drive line). Here, in... Figure 10 In 10c and 10e, reference symbol 5411 indicates the maximum pixel value; reference symbol 5412 indicates the maximum pixel value PV used in calculating the integrated DOSE; and reference symbol 5413 indicates the level corresponding to the pixel value corresponding to the minimum value. Figure 10In 10d and 10f, reference symbol 5420 indicates the maximum pixel value of dose detection pixel 121 in a row; reference symbol 5421 indicates the pixel value corresponding to reference symbol 5411, which is the maximum value in the final image; reference symbol 5422 indicates the maximum pixel value PV used when calculating the integrated DOSE; and reference symbol 5423 indicates the pixel value level corresponding to the minimum value.

[0164] In this embodiment, several methods exist for determining the target pixel when calculating the integrated DOSE. The simplest method is to determine the target pixel by the imaging control device 1002 (e.g., through a previous reference). Figure 9 The given description determines that all outputs of the pixels corresponding to dose detection pixel 121 in the region are integrated. For example, this method will... Figure 10 The outputs of all pixels corresponding to the calibrated dose detection pixel 121 are integrated between reference symbols 5401 and 5402 and between reference symbols 5403 and 5404 in 10a. (See previous reference...) Figure 9 As described, the area between reference symbols 5401 and 5402 is embedded with metal and can therefore be excluded from the integration.

[0165] In addition, such as Figure 10 As indicated by 10c, the maximum value 5412 and minimum value 5413 of pixel value PV can be predetermined by referring to past images, and the integration process can be performed by excluding these from the integration targets in the previously indicated area. In this case, when direct rays in the direct ray area 5303 are unintentionally mixed due to positional misalignment between the subject and the radiation imaging device 1001 (contrary to the instructions from the imaging control device 1002), the maximum value 5412 can prevent the radiation dose in the region of interest from reaching the AEC threshold due to insufficient dose. The minimum value 5413 can similarly suppress the effects of irradiation outside the irradiation area or in the metallic area, and suppress the situation where the AEC threshold is reached due to excessive radiation dose in the region of interest. The excluded dose detection pixels 121 are treated as if they were originally excluded, and the integrated DOSE is calculated by normalizing only the dose detection pixels 121 used for integration to appropriately correspond to the dose per unit area.

[0166] In fact, by means of Figure 10 The 10c value is difficult to determine with each sampling. Figure 10 The pixel values ​​in 10d are used. This is because no dose is set for each sampling time. Therefore, the maximum value 5412, minimum value 5413, etc., are determined by the ratio to the area of ​​direct radiation. Furthermore, because the radiation dose received is... Figure 10 10c in Figure 10The values ​​of 10d in the output waveform of a single sample are of course different, so the pixel value of 5420 (the maximum pixel value) in the direct ray dose region of the output waveform of a single sample is 5420. Figure 10 The pixel value 5411 (the maximum pixel value) in the direct ray region of the final image is 10d) and the pixel value 5411 (the maximum pixel value) in the direct ray region of the final image. Figure 10 The values ​​in 10c) are different. Therefore, in order to determine the maximum value 5422 and the pixel value level 5423 corresponding to the minimum value of the pixel value PV in the output waveform of the first sample before irradiation, the pixel value 5420 of the direct ray region is calculated by the imaging control device 1002 from the setting information of the radiation generating device immediately before the start of irradiation and is transmitted to the radiation imaging device 1001.

[0167] Another method to obtain the maximum value 5422 of pixel value PV and the pixel value level 5423 corresponding to the minimum value is to prepare to maintain Figure 10 The 10d indicates the memory of the integration result for each line graph pixel, and the integration calculation is performed based on the summed or averaged line graph updated after each sampling. This is in the process of calculating the histogram of the line graph ( Figure 10 The calculation is performed at time 10f). If the arithmetic processing can be completed in time, the calculation results can be obtained for each sampling period, or, since the line graph-like integration results are preserved, the histogram can be calculated every few line periods.

[0168] Because the imaging control device 1002 knows in advance the percentage of the direct ray region calculated from camera images, etc., the direct ray region information can be used as threshold information in the p-pattern method. Figure 10 The histogram in 10f calculates a maximum value of 5422. Similarly, the imaging control device 1002 can obtain the percentage of metallic parts by referring to unilluminated areas, past images, etc. Figure 10 The minimum value 5423 is calculated from the histogram in 10f. From these, the range of pixel values ​​of dose detection pixels 121 that should be converted during irradiation for comparison with the AEC threshold can be determined. The advantage of using a histogram is that it is not necessary to know the absolute values ​​of pixel values ​​in the direct ray portion, and even if the direct ray portion is saturated, the previous maximum value 5422 can be derived if the ratio of the direct ray area to other areas is known.

[0169] Next, we will refer to Figure 11 This describes the positional information of the subject before imaging irradiation (i.e., the pre-determined receptor field 1012) and the procedures performed when the area to be irradiated by radiation is misaligned. Consider the assumption that the right foot is in... Figure 11 11a and Figure 11 The 11b indicates the state, but in reality, the right foot moves to the right, as shown in the image. Figure 1111c and Figure 11 The 11d designation indicates this. Possible causes of such misalignment include a moving subject or misalignment between the camera's optical axis and the radial optical axis.

[0170] If the entire region of the receptor field 1012 is as follows Figure 11 If simply integrated as indicated by 11d in the diagram, the direct ray region 5303 will exist within the region of the receptor field 1012, thus reaching the AEC threshold due to insufficient dose in the region of interest. Insufficient irradiation can result in a decrease in fine-grained quality, and in some cases, re-image capture may be necessary.

[0171] refer to Figure 10 The described method prevents insufficient illumination from reaching the AEC threshold. In other words, if the maximum value 5422 can be obtained by pre-determining the area of ​​the direct ray using a camera image or similar means, then even if the direct ray accidentally enters the receptor field 1012, it can be excluded from the area to be integrated, making it possible to compare with the AEC threshold with almost no loss of accuracy. Similarly, by pre-determining the ratio of the area outside the irradiated area from a camera image or collimator information, a minimum value equivalent to the minimum value 5423 can be obtained. This ensures that information outside the irradiated area does not affect the comparison operation between the AEC threshold and the integrated value, even without pre-setting the receptor field 1012. In other words, the integrated value can be obtained solely from the result of dose detection pixels 121 between the maximum value 5422 and the minimum value 5423, and compared with the AEC threshold. This method is particularly effective for shooting conditions where the ratio of the direct ray to the subject does not change significantly even if the position of the subject moves slightly (such as when the subject is smaller relative to the irradiated area).

[0172] As previously described, a threshold-reached signal is output from the radiation imaging device 1001, and radiation irradiation stops at an appropriate timing. The radiation image is then transmitted to the imaging control device 1002, and the equivalent value of the integrated DOSE value compared to the actual AEC threshold is also transmitted to the imaging control device 1002. The imaging control device 1002 recalculates the dose index value EI from the acquired radiation image using a dose index value EI calculation algorithm, comparing the dose target value EIt set as the AEC threshold, the dose index value EI calculated from the image, and the integrated DOSE value corresponding to when the AEC threshold is exceeded, and calculates the corresponding differences, specifically the dose target value EIt, the dose index value EI, and the deviation DI. A conversion factor for setting the AEC threshold from the dose target value EIt can also be derived through machine learning of those deviations, etc., so that the deviation DI between the dose target value EIt and the dose index value EI is minimized, and feedback is provided for setting the AEC threshold.

[0173] The deviation DI can be reduced by having the imaging control device 1002 associate the portion of the radiation image corresponding to the dose target value EIt in the receptor field 1012 of the radiation image with the dose detection pixel 121. Furthermore, the imaging control device 1002 can perform display control to display the position in the region of interest corresponding to the dose target value set to a threshold in the display unit 1006 in a recognizable manner. Then, the imaging control device 1002 performs display control such as adding shading or coloring to make the portion corresponding to the dose target value EIt in the receptor field 1012 and the position of the dose detection pixel 121 recognizable, and displays it in the display unit 1006, which also improves operator usability.

[0174] Other embodiments

[0175] The present invention can also be implemented as a process in which a program implementing one or more functions of the above embodiments is supplied to a system or device via a network or storage medium, and then one or more processors of a computer of the system or device reads and executes the program. The present invention can also be implemented by circuitry (e.g., an ASIC) for implementing one or more functions.

[0176] This invention is not limited to the above embodiments, and various changes and modifications can be made within the spirit and scope of this invention. Therefore, claims have been appended to inform the public of the scope of this invention.

[0177] This application claims priority to Japanese Patent Application No. 2020-086046, filed on May 15, 2020, which is hereby incorporated herein by reference.

[0178] Symbol Explanation

[0179] 1001: Radiation imaging device; 1002: Imaging control device; 1021: Communication control unit; 1022: Control unit; 1003: Radiation source; 1103: Radiation; 1004: High voltage generation device; 1042: Radiation generation control unit; 1043: Signal selection unit; 100: Image capture area; 101: Image capture pixel; 102: First conversion element; 103: First switch; 104: Drive line; 105: Signal line (column signal line); 121: Dose detection pixel ; 122: Second conversion element; 123: Second switch; 124: Drive line; 125: Detection signal line; 132: Detection unit; 142: Detection unit; 151: Correction pixel; 221, 221C: Drive circuit; 222, 222C: Readout circuit; 224: Signal processing unit; 225: Control circuit; 226: Power supply circuit; 227: Communication unit; 241: Drive circuit; 242: Readout circuit; 401: Digital processing unit; 402: Analog processing unit; 1012: Receiving field.

Claims

1. A radiation imaging system, comprising a radiation imaging device and an imaging control device, wherein the radiation imaging device includes a dose detection pixel for detecting the dose of radiation irradiated from a radiation source, and the imaging control device controls the radiation imaging device, wherein... Prior to radiation imaging, the imaging control device: The location of the dose detection pixel within the region of interest used to calculate dose index values ​​for a radiation image is specified; a threshold is determined based on the location of the dose detection pixel; and the location of the dose detection pixel and the threshold are transmitted to the radiation imaging device. The radiation imaging device: The position of the dose detection pixel and the threshold in the region of interest are set according to the imaging control device, and imaging is performed based on the settings. The imaging control device: Setting the threshold reduces the deviation between the dose index value calculated using pixel values ​​from the radiation image and the target dose value determined as the threshold.

2. The radiation imaging system according to claim 1, wherein, Prior to radiation imaging, the imaging control device designates the region of interest using at least one of the following: (i) a radiation projection region calculated based on positional measurement information between the radiation source and the radiation imaging device; (ii) an optical image of the subject in the radiation projection region obtained by the camera; or (iii) a previously captured radiation image of the subject.

3. The radiation imaging system according to claim 2, wherein, The imaging control device also specifies the region of interest based on a template, which is based on the capture location information of the subject.

4. The radiation imaging system according to claim 2, wherein, The imaging control device performs display control to display the optical image on a display corresponding to the radiation projection area of ​​the captured radiation image.

5. The radiation imaging system according to claim 4, wherein, The imaging control device also performs display control for displaying an image on the display of a previously captured radiation image of the subject superimposed on the optical image.

6. The radiation imaging system according to claim 2, wherein, The imaging control device performs display control to display, in a recognizable manner, the position in the region of interest corresponding to the dose target value set to the threshold on the display.

7. The radiation imaging system according to any one of claims 1 to 6, wherein, The imaging control device controls the irradiation from the radiation source such that the target dose value set as the threshold and the dose index value in the radiation image become equal.

8. The radiation imaging system according to any one of claims 1 to 6, wherein, Based on the signal read from the correction pixel where visible light is blocked, the radiation imaging device corrects the signal read from the dose detection pixel in the region of interest specified by the imaging control device, and calculates the integrated dose of radiation based on the corrected signal.

9. The radiation imaging system according to claim 8 further includes a radiation generation controller, which controls the radiation source to stop irradiating radiation when the cumulative dose of radiation reaching the radiation imaging device exceeds a threshold.

10. The radiation imaging system according to any one of claims 1 to 6, wherein, The radiation imaging apparatus includes image capture pixels for generating radiation images.

11. An imaging control device comprising a dose detection pixel for detecting a dose of radiation irradiated from a radiation source, the imaging control device setting a position and a threshold of the dose detection pixel in a region of interest for transmission, and controlling a radiation imaging device to capture an image based on the settings, wherein, Prior to radiation imaging, the imaging control device: The location of the dose detection pixel in the region of interest used to calculate the dose index value of the radiation image is specified, a threshold is determined based on the location of the dose detection pixel, and the location of the dose detection pixel and the threshold are transmitted to the radiation imaging device. The imaging control device: Setting the threshold reduces the deviation between the dose index value calculated using pixel values ​​from the radiation image and the target dose value determined as the threshold.

12. The imaging control device according to claim 11, wherein, Prior to radiation imaging, the imaging control device designates the region of interest using at least one of the following: (i) a radiation projection region calculated based on positional measurement information between the radiation source and the radiation imaging device; (ii) an optical image of the subject in the radiation projection region obtained by the camera; or (iii) a previously captured radiation image of the subject.

13. The imaging control device according to claim 12, wherein, The imaging control device also specifies the region of interest based on a template, which is based on the capture location information of the subject.

14. The imaging control device according to claim 12, wherein, The imaging control device performs display control to display the optical image on a display corresponding to the radiation projection area of ​​the captured radiation image.

15. The imaging control device according to claim 14, wherein, The imaging control device also performs display control for displaying an image on the display of a previously captured radiation image of the subject superimposed on the optical image.

16. The imaging control device according to claim 12, wherein, The imaging control device performs display control to display, in a recognizable manner, the position in the region of interest corresponding to the dose target value set to the threshold on the display.

17. The imaging control apparatus according to any one of claims 11 to 16, wherein, The imaging control device controls the irradiation from the radiation source such that the target dose value set as the threshold and the dose index value in the radiation image become equal.

18. A radiation imaging method using a radiation imaging apparatus, the radiation imaging apparatus including a dose detection pixel for detecting the dose of radiation irradiated from a radiation source, the radiation imaging method comprising: The control steps of the radiographic imaging device are set up before radiographic imaging based on information transmitted from the imaging control device. Prior to radiation imaging, the imaging control device specifies the position of the dose detection pixel in the region of interest for calculating the dose index value of the radiation image, determines a threshold based on the position of the dose detection pixel, and transmits the position of the dose detection pixel and the threshold to the radiation imaging device. In the control step, the position of the dose detection pixel in the region of interest and the threshold are set, as transmitted from the imaging control device, and imaging is performed based on the settings. In the control step, the threshold is set such that the deviation between the dose index value calculated using the pixel values ​​of the radiation image and the dose target value determined as the threshold is reduced.

19. A computer-readable storage medium storing a program that causes a computer to perform control steps of the radiographic imaging method according to claim 18.

Images