Radiographic device, radiographic system, and control method

Abstract

To provide a mechanism which can perform irradiation stop control of radiation from a radiation generation device with high accuracy.SOLUTION: A radiographic device includes: a control part 200 including a dose calculation part 126 for calculating an accumulation reached dose of radiation detected by a sensor part 121 from the start of imaging, a timer part 125 for timing irradiation time of radiation from predetermined timing, a threshold determination part 124 for determining an irradiation stop threshold based on the irradiation time, and a threshold determination part 122 for transmitting an irradiation stop signal so as to stop irradiation of radiation with respect to a radiation generating device 110 when the accumulation reached dose becomes the irradiation stop threshold; and the sensor part 121 for detecting the radiation which has entered from the radiation generating device 110. The threshold determination part 122 allows the timer part 125 to start timing of the irradiation time when the dose calculation part 126 performs the calculation and finds out that the accumulation reached dose from the start of imaging has reached a predetermined amount.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a radiation imaging apparatus, a radiation imaging system, and a control method. [Background technology]

[0002] Currently, radiation imaging devices equipped with flat panel detectors (FPDs) made of semiconductor materials are widely used as radiation imaging devices for medical image diagnosis and non-destructive testing using radiation such as X-rays. In medical image diagnosis, for example, such radiation imaging devices are used as digital radiation imaging devices for taking still images such as general radiography and moving images such as fluoroscopy.

[0003] Some radiography devices monitor the dose of irradiated radiation (accumulated dose) and stop irradiating radiation when the accumulated dose reaches a threshold (for example, send an irradiation stop signal to the radiation generating device to stop irradiating radiation). This operation is called Automatic Exposure Control (AEC), and it can prevent, for example, overirradiation of radiation.

[0004] As such a radiation imaging apparatus, for example, Patent Document 1 discloses a radiation imaging apparatus having a dose detection unit that detects the dose of radiation reaching the imaging area of ​​an FPD. In Patent Document 1, the timing at which radiation irradiation should be stopped in the radiation generating apparatus is predicted based on the dose detected by the dose detection unit and a preset dose target value. Then, an irradiation stop timing notification for notifying the radiation generating apparatus of the timing to stop irradiation of radiation is transmitted before the irradiation stop timing arrives. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-138829 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology described in Patent Document 1 has an issue with the accuracy of control to stop irradiation of radiation from the radiation generating device. That is, in the technology described in Patent Document 1, when the transmitted dose rate of radiation passing through the subject is high, the time until the accumulated dose of radiation reaches the threshold is short, about several ms. As a result, a problem may occur in which the notification of the irradiation stop timing is not sent in time, and the accumulated dose of radiation becomes greater than the threshold before the radiation generating device stops irradiating radiation. [Means for solving the problem]

[0007] The above problem is solved by a radiation imaging device including a sensor unit that detects radiation incident from a radiation generating device, and a control unit that causes the radiation generating device to send a signal regarding the stop of radiation irradiation using a cumulative reached dose of radiation detected by the sensor unit, a radiation irradiation time, and an irradiation stop threshold, wherein the control unit measures the irradiation time based on the cumulative reached dose. Effect of the Invention

[0008] According to at least one embodiment of the present disclosure, it is possible to perform highly accurate control of stopping irradiation of radiation from a radiation generating device. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a radiation imaging system according to a first embodiment. [Diagram 2] 5 is a flowchart showing an example of a processing procedure in a series of control methods from the start to the end of imaging of a subject in the radiation imaging system according to the first embodiment. [Diagram 3]5 is a diagram showing an example of a processing procedure in a series of control methods for measuring a communication delay time in the radiation imaging system according to the first embodiment. FIG. [Figure 4] 4 is a table showing the relationship of communication delay time for each communication mode in the radiation imaging system according to the first embodiment. [Diagram 5] 5 is a diagram showing an example of the relationship between the dose and the change over time of the threshold set by the threshold change control unit according to the first embodiment; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a mode (embodiment) for carrying out the present disclosure will be described with reference to the drawings. In this specification, it is preferable to use X-rays as radiation, but radiation is not limited to X-rays and also includes α-rays, β-rays, γ-rays, etc.

[0011] (First embodiment) Fig. 1 is a diagram showing an example of a schematic configuration of a radiation imaging system 100 according to an embodiment of the present disclosure. In this embodiment, the radiation imaging system 100 is particularly suitable for use in medical applications. As shown in Fig. 1, the radiation imaging system 100 includes a radiation generating device 110, a radiation imaging device 120, and an irradiation control device 130.

[0012] The radiation generating device 110 irradiates radiation toward a subject (not shown) under the control of the irradiation control device 130 (more specifically, the imaging control unit 131). The radiation generating device 110 includes a radiation tube, which is a radiation generating unit that generates radiation, and a collimator that defines the beam spread angle of the radiation generated by the radiation tube.

[0013] The radiation imaging device 120 is configured to include, for example, an FPD, and includes a sensor unit 121 including imaging elements distributed two-dimensionally. The sensor unit 121 detects radiation irradiated from the radiation generating device 110 and incident thereon.

[0014] Specifically, the radiation imaging apparatus 120 detects information on a two-dimensional distribution of the amount of radiation that has reached the imaging element (dose information) in the sensor unit 121, and generates radiation image data. Thereafter, the radiation imaging apparatus 120 transmits the generated radiation image data to an image processing unit 134 of the irradiation control device 130 via the communication unit 123. The irradiation control device 130 controls the operations of the radiation generation device 110 and the radiation imaging apparatus 120, and also acquires and processes radiation image data captured by the radiation imaging apparatus 120.

[0015] Further, the radiation imaging apparatus 120 includes a control unit 200. The control unit 200 includes a threshold determination unit 122, a threshold determination unit 124, a timer unit 125, and a dose calculation unit 126. The threshold determination unit 122 has a function of determining whether the dose detected by the sensor unit 121 has reached a threshold. When the threshold determination unit 122 determines that the dose of radiation (accumulated achieved dose) detected by the sensor unit 121 and calculated by the dose calculation unit 126 has reached a predetermined irradiation stop threshold, the threshold determination unit 122 transmits an irradiation stop signal 127 to the irradiation control device 130 via the communication unit 123. When the irradiation control device 130 receives an irradiation stop notification from the radiation imaging apparatus 120 via the communication unit 133, the imaging control unit 131 performs irradiation stop control 136 to stop the radiation irradiation from the radiation generation device 110.

[0016] At the same time, the communication unit 133 returns a response to the radiation imaging apparatus 120 that the irradiation stop signal 127 has been received. If no response is received within a certain period of time after transmitting the irradiation stop signal 127, the radiation imaging apparatus 120 transmits the irradiation stop signal 127 to the irradiation control device 130 again.

[0017] When the dose calculation unit 126 calculates that the cumulative dose since the start of imaging has reached a predetermined amount, the threshold determination unit 122 determines that irradiation has started and causes the timer unit 125 to start measuring the irradiation time. The dose threshold at this time is called the irradiation start threshold. When the dose detected by the sensor unit 121 reaches the irradiation start threshold, the threshold determination unit 122 transmits that information to the threshold determination unit 124. When the threshold determination unit 122 transmits the information that the irradiation start threshold has been reached, the threshold determination unit 124 determines that time as a threshold change reference point. The predetermined amount that is the irradiation start threshold is a dose value that serves as a reference for determining that irradiation by the radiation generation device 110 has started to stabilize, and an appropriate value is set in the threshold determination unit 122 according to the characteristics of the radiation generation device 110.

[0018] The timer unit 125 is a timer that measures the radiation irradiation time from a predetermined timing. In this embodiment, the irradiation time is measured from a threshold change reference point determined by the threshold determination unit 124. The threshold determination unit 124 refers to the irradiation time of the timer unit 125 and the irradiation start threshold of the threshold judgment unit 122, and continuously corrects the timing of transmitting an irradiation stop signal based on the time change from the threshold change reference point, the irradiation start threshold, and a communication delay time Tdc described later.

[0019] The communication unit 123 is capable of wired and wireless communication with the irradiation control device 130. Prior to imaging, communication is performed with the communication unit 133 of the irradiation control device 130, and a communication response time between the two devices is counted by the timer unit 125 to calculate a communication delay time Tdc, and the threshold determination unit 124 holds the communication delay time Tdc. The threshold determination unit 124 reflects the calculated communication delay time Tdc in the setting of the irradiation stop threshold.

[0020] The communication delay time Tdc stored here is stored in the threshold determination unit 124 in a table or the like so that it is possible to store as many as the number of combinations of the communication modes between the communication unit 123 and the communication unit 133. The Tdc reflected by the threshold determination unit 124 in the setting of the irradiation stop threshold is switched according to the communication mode between the communication unit 123 and the communication unit 133. Note that the method is not limited to storing the Tdc in a table, and it may be calculated based on a formula or by measurement.

[0021] Next, the functions of the components 131 to 135 included in the irradiation controller 130 will be described.

[0022] The imaging condition setting unit 132 sets imaging condition data including imaging condition information such as the imaging part of the subject, the tube voltage and tube current in the radiation generation device 110, and a target value Dref of the dose (accumulated reached dose) at which radiation passes through the subject and reaches the radiation imaging device 120. Here, the dose generally means the accumulated reached dose during irradiation of radiation, but a similar dose value or a linked dose value may also be used, and will be referred to as "accumulated reached dose" below as necessary.

[0023] The communication unit 133 is capable of communicating with the radiation imaging apparatus 120 in a wired and wireless manner.

[0024] The image processing unit 134 performs image processing such as gradation processing and noise reduction processing on the radiation image data transmitted from the radiation imaging apparatus 120. Then, the image processing unit 134 transmits the radiation image data after the image processing to the display unit 135.

[0025] The display unit 135 outputs and displays a radiation image based on the radiation image data transmitted from the image processing unit 134 on a monitor or the like.

[0026] In the radiation imaging system 100 described in this embodiment, the timing of transmitting the irradiation stop signal 127 from the radiation imaging apparatus 120 to the irradiation control device 130 is based on the transmission time of the irradiation stop signal 127 from the radiation imaging apparatus 120 to the irradiation control device 130 described above. Furthermore, it is preferable that the timing takes into consideration a delay time from when the irradiation control device 130 performs irradiation stop control 136 for causing the radiation generation apparatus 110 to stop irradiation of radiation until the radiation generation apparatus 110 stops irradiating radiation.

[0027] The time at which radiation irradiation is stopped in the radiation generating device 110 is the time at which the tube voltage in the radiation tube of the radiation generating device 110 starts to drop or the time at which the tube voltage has dropped to its lowest point. When setting the delay time based on the time at which the tube voltage has dropped to its lowest point, it is desirable to set the delay time by taking into consideration the time of the unsteady period from when the tube voltage in the radiation tube starts to drop to when it has dropped to its highest point multiplied by a coefficient that takes into account changes in dose and radiation quality.

[0028] More specifically, the delay time Td is divided into a stationary period Ta from the signal transmission until the tube voltage starts to drop, and an unsteady period Tb from when the tube voltage starts to drop until it has completely dropped. At this time, the unsteady period Tb is multiplied by a coefficient k (wherein the coefficient k is 1 or less) because the tube voltage in the radiation tube drops. That is, the delay time Td when the unsteady period Tb is taken into account can be determined based on the following formula.

[0029] Td = Ta + kTb In this embodiment, the delay time Td needs to be acquired for each generator before irradiation of radiation for radiography of the subject (before imaging). In addition, a value actually measured when the radiography apparatus 120 is installed can be used as the delay time Td. Furthermore, the imaging environment and the radiation generation apparatus 110 to be used may be registered in a database in advance, and the delay time Td may be calculated by referring to the database. It is desirable that the delay time Td is notified in advance to the threshold determination unit 124, and the irradiation stop threshold is set taking the delay time Td into consideration.

[0030] Next, the process of photographing a subject will be described with reference to FIG.

[0031] FIG. 2 is a flowchart showing an example of a processing procedure in a series of control methods from the start to the end of imaging of a subject in the radiation imaging system 100 according to this embodiment.

[0032] In this imaging process, the irradiation stop threshold Dth of the dose (cumulative achieved dose) and the change in Dth over time are set based on the delay time Td stored in advance, the communication delay time Tdc acquired in advance, the irradiation start threshold Dobs, and the target value Dref of the dose (cumulative achieved dose), and radiation imaging of the subject is performed.

[0033] First, in step S201, the imaging condition setting unit 132 receives an instruction to start imaging input by an operator via an input unit (not shown), and sets, for example, imaging condition information (irradiation condition information) input by the operator. Here, the imaging condition setting unit 132 sets, as the imaging condition information (irradiation condition information), the tube voltage and tube current of the radiation tube, the target value Dref of the dose (accumulated achieved dose), the irradiation start threshold Dobs, the delay time Td, and the like.

[0034] Thereafter, the imaging condition setting unit 132 transmits the acquired imaging start instruction and the set imaging condition information (irradiation condition information) to the radiation imaging device 120. In addition, the value of the delay time Td may be stored in any of the devices constituting the radiation imaging system 100 and the value may be referred to.

[0035] Next, in step S202, the threshold determination unit 124 sets the irradiation stop threshold Dth of the dose (accumulated reaching dose) and its time change based on the target value Dref of the dose (accumulated reaching dose), the irradiation start threshold Dobs, the delay time Td, and the communication delay time Tdc set in step S201. The setting of the irradiation stop threshold Dth of the dose (accumulated reaching dose) and its time change will be described later with reference to FIG.

[0036] Next, in step S203, the imaging control unit 131 transmits an irradiation execution signal for irradiating radiation to the radiation generating device 110 together with the imaging condition information (irradiation condition information) received from the imaging condition setting unit 132 in step S201. In response to this, the radiation generating device 110 irradiates radiation to the subject under irradiation conditions based on the imaging condition information (irradiation condition information) received from the imaging condition setting unit 132.

[0037] Next, in step S204, first, the dose calculation unit 126 calculates a value D representative of the radiation dose (cumulative reaching dose) detected by the sensor unit 121. Note that the maximum value, average value, median value, etc. of the dose (cumulative reaching dose) may be used as the value D representative of the radiation dose (cumulative reaching dose) here. In the following description, the value D representative of the radiation dose (cumulative reaching dose) will be referred to as the "radiation dose (cumulative reaching dose) D."

[0038] Then, the threshold determination unit 122 compares the radiation dose (cumulative reaching dose) D with the irradiation stop threshold Dth set in step S202, and determines whether the dose (cumulative reaching dose) D is smaller than the irradiation stop threshold Dth. If the result of this determination is that the dose (cumulative reaching dose) D is smaller than the irradiation stop threshold Dth (S204 / YES), the unit waits in step S204.

[0039] On the other hand, if the result of the determination in step S204 is that the dose (cumulative achieved dose) D is equal to or greater than the irradiation stop threshold Dth (the dose (cumulative achieved dose) D is equal to or greater than the threshold) (S204 / NO), the process proceeds to step S205.

[0040] In step S205, since the dose (accumulated achieved dose) D has reached the irradiation stop threshold Dth, the radiation imaging apparatus 120 transmits an irradiation stop signal 127 to the irradiation control device 130 to stop the irradiation of radiation from the radiation generation apparatus 110. Upon receiving the irradiation stop signal, the irradiation control device 130 causes the imaging control unit 131 to perform irradiation stop control 136 on the generation apparatus 110.

[0041] At this time, radiation continues to be irradiated for a communication delay time Tdc required for transmitting the irradiation stop signal 127 and a delay time Td from the irradiation stop control 136 to the actual stopping of radiation irradiation in the radiation generation device 110. Therefore, it is possible to make the actually irradiated dose (accumulated achieved dose) D approach the target value Dref of the dose (accumulated achieved dose).

[0042] Next, in step S206, the radiation imaging apparatus 120 controls the imaging element in the sensor unit 121 to stop conversion into dose information, and transmits the generated radiation image data to the image processing unit .

[0043] Next, in step S207, the image processing unit 134 performs image processing such as gradation processing and noise reduction processing on the radiation image data received from the radiation imaging apparatus 120. Thereafter, the image processing unit 134 transmits the radiation image data after the image processing to the display unit 135.

[0044] Next, in step S208, the display unit 135 outputs and displays a radiographic image based on the radiographic image data received from the image processing unit 134 on a monitor or the like, and presents the radiographic image to the operator.

[0045] When the process of step S208 ends, the process of the flowchart relating to radiography of the subject shown in FIG. 2 ends.

[0046] Next, a method for acquiring the communication delay time Tdc before shooting will be described with reference to FIG.

[0047] When the radiation imaging apparatus 120 and the irradiation control device 130 are started up and wired and wireless communication are possible, the radiation imaging apparatus 120 sends an inquiry via the communication unit 123 to the communication unit 133 of the irradiation control device 130 to obtain the communication delay time.

[0048] At that time, the radiation imaging apparatus 120 refers to the counter of the timer unit 125. When the irradiation control device 130 receives the communication delay time inquiry, it immediately responds. When the radiation imaging apparatus 120 receives the response from the irradiation control device 130, it refers to the counter of the timer unit 125 and holds the time obtained by dividing the round-trip communication time (t1) by 2 as the tentative communication delay time (T1).

[0049] The radiation imaging device 120 continues to repeat this operation until imaging starts, and acquires multiple provisional communication delay times (T2, T3, T4, ...). When the maximum number of acquired provisional communication delay times is exceeded, the oldest information is overwritten as necessary. When imaging starts, one communication delay time is calculated from the multiple acquired provisional communication delay times, and is set as the communication delay time Tdc. Here, the single communication delay time may be determined by using the average value of some or all of the multiple communication delay times, or the minimum value of some or all of the multiple communication delay times.

[0050] Using the communication delay time Tdc, the threshold determination unit 124 sets the irradiation stop threshold Dth of the dose (accumulated reaching dose) and its change over time for the target value Dref of the dose (accumulated reaching dose). Setting of the irradiation stop threshold Dth of the dose (accumulated reaching dose) and its change over time will be described later with reference to FIG.

[0051] In addition, when the following formula is satisfied in the relationship between the calculated Tdc, the delay time Td of the generator, and the nominal shortest irradiation time, it can be determined before the imaging that the communication delay time is very large and irradiation cannot be stopped at the desired timing. In this situation, for example, imaging is prohibited. Alternatively, an action such as issuing a warning to the user may be performed.

[0052] Tdc>nominal minimum exposure time - Td In addition, since the communication delay time Tdc is the delay time of communication from the radiation imaging device 120 to the irradiation control device 130, the components of the delay time include the internal processing time of units such as the access point, HUB, wireless repeater, etc. In addition, it includes application layer delay, transmission delay, propagation delay, wireless management server processing (encryption processing, etc.), and when multiple HUBs are used, the communication delay time Tdc includes the times of all of these components.

[0053] The communication delay time Tdc varies depending on the type of communication between the radiation imaging device 120 and the irradiation control device 130. Specifically, it will vary depending on whether the communication is wired or wireless, and even in the case of wireless communication, in a system equipped with a technology for improving communication quality by using multiple antennas, the communication time will also vary depending on which of the multiple antennas is used. The communication delay times that vary depending on the type of communication are stored in the threshold value determination unit 124 as a table as shown in FIG. 4.

[0054] The threshold determination unit 124 determines the communication mode between the communication unit 123 and the communication unit 133 at the imaging timing, and reflects the value of the communication delay time Tdc corresponding to the communication mode in the setting of the irradiation stop threshold from a table of the communication delay time Tdc.

[0055] For example, if wired communication is disconnected and switched to wireless communication immediately before imaging, and the delay time Tdc during wired communication acquired immediately before is reflected in the setting of the irradiation stop threshold, it will be impossible to perform AEC with high accuracy. Therefore, if the delay time Tdc according to the communication type is stored as in the table of Figure 4, the correct communication delay time Tdc according to the communication type at the imaging timing can be reflected in the setting of the irradiation stop threshold, and AEC can be performed with high accuracy.

[0056] In FIG. 4, Table 4(A) holds the delay time for each communication mode as a table, but as shown in Table 4(B), the difference from the base delay time may also be held.

[0057] Although FIG. 4 shows two antennas for wireless communication, the number is not limited and may be more than one or may be one.

[0058] Next, the process of setting the irradiation stop threshold Dth of the dose (accumulated achieved dose) and its change over time in step S202 in Fig. 2 will be described with reference to Fig. 5. When setting the change over time of the irradiation stop threshold Dth of the dose (accumulated achieved dose), if a positive determination is made in step S204 (S204 / YES), the process in step S202 is also performed.

[0059] Fig. 5 is a diagram showing an example of the irradiation stop threshold Dth of the dose (cumulative achieved dose) in this embodiment, and its change over time, and the relationship between the dose (cumulative achieved dose) D. In Fig. 5, the relationship between the dose (cumulative achieved dose) D shown on the vertical axis and the time (elapsed time) shown on the horizontal axis is shown.

[0060] As shown in Fig. 5, the threshold determination unit 124 performs control to change the irradiation stop threshold Dth of the dose (accumulated ultimate dose) according to the elapsed time from the start of radiation irradiation. Specifically, in Fig. 5, the threshold determination unit 124 performs control to increase the irradiation stop threshold Dth of the dose (accumulated ultimate dose) with the elapsed time.

[0061] Here, the starting point for measuring the elapsed time is the threshold change reference point shown in Fig. 5. As described above, when the threshold determination unit 122 determines that the dose (accumulated reached dose) D detected by the sensor unit 121 has reached the irradiation start threshold held by the threshold determination unit 122, that point in time is notified to the threshold determination unit 124 as the threshold change reference point.

[0062] The threshold determination unit 124 counts the elapsed time from the reference point, and performs control to change the irradiation stop threshold Dth of the dose (accumulated achieved dose) in accordance with the elapsed time.

[0063] When imaging is performed, even if the imaging control 131 instructs the generator 110 to start irradiation, some tubes of the generator 110 require time to start up, and the start-up may be unstable. If the elapsed time is counted from the point where the irradiation start instruction is issued, the actual dose (cumulative achieved dose) D and the irradiation dose estimated from the dose rate will not be consistent, and it will be impossible to change the irradiation stop threshold Dth of the dose (cumulative achieved dose) with high accuracy. In order to avoid this, the timing when the irradiation starts to stabilize is set as the threshold change reference point, thereby making it possible to improve the accuracy of the irradiation stop control.

[0064] In determining the dose (accumulated reached dose) D detected by the sensor unit 121 and whether the irradiation start threshold has been reached when determining the threshold change reference point, it is preferable to use the dose (accumulated reached dose) D detected by the sensor unit 121. In this case, if the S / N ratio of the dose detected by the sensor unit 121 is sufficiently high, the dose of one sample may be used to determine whether the irradiation start threshold has been reached.

[0065] Then, when the dose (accumulated reached dose) D detected by the sensor unit 121 becomes equal to or greater than the irradiation stop threshold Dth of the dose (accumulated reached dose) that changes with time shown in Fig. 5 (S204 / NO), the threshold determination unit 122 proceeds to step S205 in Fig. 2. Then, in step S205, an irradiation stop signal 127 is transmitted to the irradiation control device 130, and the imaging control unit 131 performs irradiation stop control 136 to stop the irradiation of radiation from the radiation generation device 110.

[0066] At this time, radiation continues to be irradiated for a communication delay time Tdc required for transmitting the irradiation stop signal 127 and a delay time Td from when the irradiation stop control 136 is performed until the radiation generation device 110 actually stops irradiating radiation.

[0067] 5, when the dose rate of radiation incident on the radiation imaging apparatus 120 is a high dose rate 501, the dose (accumulated achieved dose) D obtained by the dose calculation unit 126 becomes equal to or greater than the irradiation stop value Dth of the dose (accumulated achieved dose) at the irradiation time Thigh. As a result, at the point of time of the irradiation time Thigh, the radiation imaging apparatus 120 transmits an irradiation stop signal 127 to the irradiation control device 130, and then the irradiation of radiation in the radiation generation device 110 is stopped.

[0068] The irradiation stop threshold Dth at this time is an irradiation stop threshold Dth that is detected by the dose calculation unit 126 and takes into consideration the communication delay time Tdc and the delay time Td on the generator side. Therefore, when the irradiation from the generator 110 actually stops, radiation of the target value Dref reaches the radiation imaging device 120.

[0069] Similarly, when the dose rate of the radiation R incident on the radiation imaging device 120 is a low dose rate 502, the dose (cumulative achieved dose) D obtained by the dose calculation unit 126 at the irradiation time Tlow becomes equal to or greater than the irradiation stop threshold Dth for the dose (cumulative achieved dose).

[0070] As a result, at the point of the irradiation time Tlow, the radiation imaging apparatus 120 transmits an irradiation stop signal 127 to the irradiation control device 130, and then the irradiation of radiation is stopped in the radiation generation apparatus 110. The irradiation stop threshold Dth is determined by detecting that the dose calculation unit 126 has exceeded the irradiation stop threshold Dth, and taking into account the communication delay time Tdc and the delay time Td on the generation apparatus side. Therefore, when the irradiation from the generation apparatus 110 actually stops, radiation of the target value Dref reaches the radiation imaging apparatus 120.

[0071] Here, as shown in Fig. 5, the radiation dose rate 501 and the dose rate 502 are determined based on the relationship between the dose (accumulated reached dose) D and time. In Fig. 5, for example, if the irradiation stop threshold Dth of the dose (accumulated reached dose) is constant, the actual dose (accumulated reached dose) D changes according to the change in the dose rate. As a result, irradiation continues longer than the timing at which it is actually desired to stop, and the value becomes far from the target value Dref of the dose (accumulated reached dose), resulting in over-irradiation.

[0072] 5, in this embodiment, control is performed to change the irradiation stop threshold Dth of the dose (accumulated ultimate dose) according to the elapsed time from the start of irradiation of radiation (specifically, the irradiation stop threshold Dth of the dose (accumulated ultimate dose) is increased with the elapsed time). Therefore, the target value Dref of the dose (accumulated ultimate dose) can be set in both the case of a high dose rate 501 and the case of a low dose rate 502. This allows the irradiation stop control of radiation to be performed with high accuracy regardless of the magnitude of the dose rate.

[0073] In this embodiment, as shown in FIG. 5, the time change of the irradiation stop threshold Dth of the dose (accumulated achieved dose) is changed continuously with respect to the elapsed time, but it may be expressed by a step function that changes stepwise with respect to the elapsed time, for example, taking into account memory capacity.

[0074] In this case, the length of the time segment of the step function related to the irradiation stop threshold Dth of the dose (accumulated achieved dose) may be different for each time segment.

[0075] In this embodiment, the irradiation stop threshold Dth of the dose (cumulative achieved dose) relative to the elapsed time t can be set to satisfy the following formula 1 using the elapsed time t, the delay time Td, the communication delay time Tdc, the irradiation start threshold Dobs, and the target value Dref of the dose (cumulative achieved dose).

[0076]

number

[0077] That is, as shown in Equation 1, the threshold determination unit 124 changes the irradiation stop threshold Dth of the dose (accumulated ultimate dose) according to the elapsed time t. In addition, the threshold determination unit 124 sets the time change of the irradiation stop threshold Dth of the dose (accumulated ultimate dose) based on the target value Dref of the dose (accumulated ultimate dose), the irradiation start threshold Dobs, the delay time Td, and the communication delay time Tdc.

[0078] When a step function is used as the irradiation stop threshold Dth of the dose (accumulated achieved dose), it is desirable to set a function such that each step of the step intersects with the formula (1).

[0079] According to this configuration, it is possible to perform highly accurate control of stopping irradiation of radiation from the radiation generation device 110. In other words, it is possible to perform AEC with high accuracy.

[0080] In this embodiment, irradiation is stopped when the cumulative reached dose reaches the irradiation stop threshold Dth, but the time at which the irradiation stop threshold Dth is reached may be predicted from the dose rate, and irradiation may be stopped at the predicted time. Furthermore, the time until the cumulative reached dose reaches the irradiation stop threshold Dth may be predicted from multiple dose rates, and the time at which the irradiation stop threshold Dth is reached may be updated according to changes in the dose rate. In this case, too, if the irradiation time is measured from the time when it is detected that the cumulative reached dose has reached the irradiation start threshold, the stop of irradiation can be predicted with high accuracy.

[0081] (Other embodiments) The present disclosure can also be realized by supplying a program that achieves the above-mentioned functions to a system or device via a network or storage medium, and having one or more processors in a computer of the system or device read and execute the program.

[0082] In addition, various recording media can be used, such as a flexible disk, an optical disk (e.g., CD-ROM, DVD-ROM), a magneto-optical disk, a magnetic tape, a non-volatile memory (e.g., USB memory), a ROM, etc. In addition, a program for implementing the above-mentioned functions may be downloaded via a network and executed by a computer.

[0083] In addition, the functions of the above-mentioned embodiments are not limited to being realized only by a computer executing the read program code, but also include cases where an operating system (OS) running on a computer performs part or all of the actual processing based on instructions from the program code, thereby realizing the functions of the above-mentioned embodiments.

[0084] Furthermore, the program code read from the recording medium may be written to a memory provided in a function expansion board inserted into a computer or a function expansion unit connected to a computer. This also includes cases where a CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing based on the instructions of the program code, thereby realizing the above-mentioned functions.

[0085] Regarding the above embodiment, the following supplementary notes are disclosed as one aspect and optional features of the invention.

[0086] (Appendix 1) a sensor unit for detecting radiation incident from a radiation generating device; a control unit that causes the radiation generating device to transmit a signal regarding a stop of radiation irradiation, using a cumulative reaching dose of radiation detected by the sensor unit, an irradiation time of the radiation, and an irradiation stop threshold, The control unit measures the irradiation time based on the accumulated radiation dose.

[0087] (Appendix 2) The control unit may time the irradiation time when the accumulated radiation dose reaches a predetermined amount.

[0088] (Appendix 3) The control unit may perform control to set the irradiation stop threshold based on a target value of the cumulative achieved dose in radiation imaging, the irradiation time, and a delay time from the transmission of a signal regarding the stop of the irradiation to the stop of the radiation irradiation in the radiation generating device.

[0089] (Appendix 4) a communication unit that transmits a signal related to the stop of the irradiation to the radiation generating device; The control unit may derive the delay time based on a communication delay time in communication between the communication unit and the radiation generation device.

[0090] (Appendix 5) The communication unit has a plurality of communication modes, The control unit may derive the delay time based on the communication delay time in a communication form when performing the radiation imaging, among the plurality of communication forms.

[0091] (Appendix 6) The control unit may obtain a plurality of the communication delay times before performing the radiation imaging.

[0092] (Appendix 7) The control unit may derive the delay time based on one of the plurality of communication delay times.

[0093] (Appendix 8) The control unit may derive the delay time based on an average value of some or all of the plurality of communication delay times.

[0094] (Appendix 9) The control unit may derive the delay time based on a minimum value of the plurality of communication delay times.

[0095] (Appendix 10) When there is no response from the radiation generation device to the transmitted signal regarding the stop of irradiation within a predetermined time, the control unit may transmit the signal regarding the stop of irradiation again to the radiation generation device.

[0096] (Appendix 11) The control unit determines a time point when the cumulative reached dose reaches a predetermined amount as an irradiation start threshold, and The control unit may determine a timing for transmitting a signal regarding stopping the irradiation based on the irradiation time and the irradiation start threshold.

[0097] (Appendix 12) a sensor unit for detecting radiation incident from a radiation generating device; a control unit that causes the radiation generating device to transmit a signal regarding a stop of radiation irradiation, using a cumulative reaching dose of radiation detected by the sensor unit, an irradiation time of the radiation, and an irradiation stop threshold, The control unit determines the start of irradiation by setting a time when the cumulative reached dose reaches a predetermined amount as an irradiation start threshold, and determines a timing for transmitting a signal regarding the stop of the irradiation based on the irradiation time and the irradiation start threshold. A radiation imaging device comprising:

[0098] (Appendix 13) A radiographic imaging apparatus according to any one of claims 1 to 12, The radiation generating device. A radiation imaging system comprising:

[0099] (Appendix 14) a sensor unit for detecting radiation incident from a radiation generating device; a control unit that causes the radiation generation device to transmit a signal regarding stop of radiation irradiation, using a cumulative reaching dose of radiation detected by the sensor unit, an irradiation time of the radiation, and an irradiation stop threshold, the control method comprising: A timing step is performed to measure the irradiation time based on the cumulative dose. A control method comprising:

[0100] (Appendix 15) In the timing step, the irradiation time may be timed when the cumulative radiation dose reaches a predetermined amount.

[0101] (Appendix 16) After the timing step, a setting step is performed to set the irradiation stop threshold value in accordance with the irradiation time. The setting process may set the irradiation stop threshold based on a target value of the cumulative achieved dose in radiation imaging and a delay time from when a signal regarding the stop of radiation irradiation is sent to the radiation generating device to when the radiation irradiation is stopped in the radiation generating device.

[0102] (Appendix 17) a measurement step of measuring a communication delay time in communication with the radiation generating device by a communication unit having a plurality of communication forms and transmitting a signal related to the stop of the irradiation to the radiation generating device, prior to the setting step; The setting step may derive the delay time based on a communication delay time in a communication form when performing the radiation imaging, among the plurality of communication forms.

[0103] (Appendix 18) In the setting step, a timing for transmitting a signal regarding stopping the irradiation to the radiation generation device may be set based on the irradiation time and the irradiation start threshold.

[0104] (Appendix 19) a sensor unit for detecting radiation incident from a radiation generating device; a control unit that causes the radiation generation device to transmit a signal regarding stop of radiation irradiation, using a cumulative reaching dose of radiation detected by the sensor unit, an irradiation time of the radiation, and an irradiation stop threshold, the control method comprising: A setting step of setting the irradiation stop threshold value according to the irradiation time is performed; In the setting step, a timing for transmitting a signal regarding the stop of the irradiation to the radiation generating device is set based on the irradiation time and the irradiation start threshold. A control method comprising:

[0105] (Appendix 20) A program for causing a computer to execute the control method according to any one of appendixes 14 to 19. [Explanation of symbols]

[0106] 110 Radiation Generator 120 Radiography Equipment 121 Sensor section 127 Irradiation stop signal 130 Irradiation control device 200 Control section

Claims

1. a sensor unit that detects radiation incident from a radiation generating device; a control unit that transmits a signal regarding the stop of radiation irradiation using a cumulative dose of radiation detected by the sensor unit, a radiation irradiation time, and an irradiation stop threshold, the control unit transmits a signal regarding the termination of the irradiation of the radiation based on the irradiation termination threshold obtained using the irradiation time and the predetermined amount after the cumulative achieved dose reaches a predetermined amount that changes depending on an operation by an operator.

2. The radiographic imaging apparatus according to claim 1 , wherein the control unit measures the irradiation time when the cumulative radiation dose reaches a predetermined amount.

3. 3. The radiation imaging device according to claim 2, wherein the control unit performs control to set the irradiation stop threshold based on a target value of the cumulative reached dose in radiation imaging, the irradiation time, and a delay time from transmission of a signal regarding the stop of irradiation to the stop of radiation irradiation in the radiation generation device.

4. a communication unit that transmits a signal related to the stop of the irradiation; the control unit derives the delay time based on a communication delay time in communication between the communication unit and the radiation generation device.

4. The radiographic imaging apparatus according to claim 3, wherein:

5. the communication unit has a plurality of communication modes, the control unit derives the delay time based on the communication delay time in a communication mode when performing the radiation imaging among the plurality of communication modes.

5. The radiographic imaging apparatus according to claim 4, wherein:

6. The radiation imaging apparatus according to claim 4 , wherein the control unit acquires a plurality of the communication delay times before performing the radiation imaging.

7. 7. The radiographic imaging apparatus according to claim 6, wherein the control unit derives the delay time based on one of the plurality of communication delay times.

8. The radiographic imaging apparatus according to claim 6 , wherein the control unit derives the delay time based on an average value of some or all of the plurality of communication delay times.

9. The radiographic imaging apparatus according to claim 6 , wherein the control unit derives the delay time based on a minimum value among the plurality of communication delay times.

10. 2. The radiation imaging apparatus according to claim 1, wherein if there is no response from the radiation generation device within a predetermined time in response to the transmitted signal regarding the stop of irradiation, the control unit transmits the signal regarding the stop of irradiation again.

11. the control unit determines the start of irradiation when the cumulative reached dose reaches a predetermined amount as an irradiation start threshold; 2. The radiographic imaging apparatus according to claim 1, wherein the control unit determines the timing of transmitting the signal regarding the stop of irradiation based on the irradiation time and the irradiation start threshold.

12. a sensor unit that detects radiation incident from a radiation generating device; a control unit that transmits a signal regarding the stop of radiation irradiation using a cumulative dose of radiation detected by the sensor unit, a radiation irradiation time, and an irradiation stop threshold, The control unit determines the start of irradiation by setting a time when the cumulative reached dose reaches a predetermined amount that changes depending on an operation by an operator as an irradiation start threshold, and determines a timing to send a signal regarding the stop of the irradiation based on the irradiation time and the irradiation start threshold. A radiographic imaging device characterized by:

13. The radiographic imaging apparatus according to any one of claims 1 to 12, The radiation generating device A radiography system comprising:

14. a sensor unit that detects radiation incident from a radiation generating device; a control unit that transmits a signal related to stopping radiation irradiation using a cumulative radiation dose detected by the sensor unit, a radiation irradiation time, and an irradiation stop threshold, a transmission step of transmitting a signal regarding the termination of the irradiation of radiation based on the irradiation termination threshold obtained using the irradiation time and the predetermined amount after the cumulative reached dose reaches a predetermined amount that changes depending on an operation by an operator.

15. a sensor unit that detects radiation incident from a radiation generating device; a control unit that transmits a signal related to stopping radiation irradiation using a cumulative radiation dose detected by the sensor unit, a radiation irradiation time, and an irradiation stop threshold, a determining step of determining whether to start irradiation when the cumulative reached dose reaches a predetermined amount that changes depending on an operator's operation, using the irradiation start threshold as the time when the cumulative reached dose reaches a predetermined amount; and a determining step of determining the timing of transmitting a signal regarding the end of irradiation based on the irradiation time and the irradiation start threshold. A method for controlling a radiation imaging apparatus comprising:

16. A program for causing a computer to execute the control method according to claim 14 or 15.

17. The radiation imaging device according to claim 1, wherein the predetermined amount is the cumulative dose achieved when irradiation from the radiation generating device is in a stable state.

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