JP7567082B2 - Radiation imaging device, radiation imaging system, control device, and irradiation termination method - Google Patents

Description

The present invention relates to a radiation imaging device, a radiation imaging system, a control device, and an irradiation stopping method.

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. For example, in medical image diagnosis, such radiation imaging devices are used as digital radiation imaging devices that take still images such as general radiography and video images such as fluoroscopy.

Some radiography devices monitor the amount of radiation irradiated (accumulated dose) and stop irradiating radiation when the accumulated dose reaches a threshold (for example, outputting 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, over-irradiation.

For example, Patent Document 1 discloses such a radiation imaging device that includes 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 device is predicted based on the dose detected by the dose detection unit and a preset dose target value, and an irradiation stop timing notification is sent to inform the radiation generating device of the timing to stop irradiation before the irradiation stop timing arrives.

JP 2013-138829 A

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

The present invention was made in consideration of these problems, and aims to provide a mechanism that can control the termination of radiation irradiation from a radiation generating device with high accuracy.

The radiation imaging apparatus of the present invention includes a sensor unit that detects radiation irradiated from a radiation irradiation device, a means for acquiring a cumulative dose of the radiation, and a means for outputting a predetermined signal for stopping the irradiation of the radiation by the radiation irradiation device based on the cumulative dose becoming equal to or greater than a threshold of a predetermined threshold condition, the predetermined threshold condition being a threshold condition having different thresholds at a plurality of timings including at least a first timing and a second timing at which elapsed times from a start of the irradiation of the radiation are different, the threshold at the first timing being a threshold for stopping irradiation of radiation at a first dose rate near a target cumulative dose in an environment in which a predetermined delay time occurs in communication with the radiation irradiation device, and the threshold at the second timing being a threshold for stopping irradiation of radiation at a second dose rate lower than the first dose rate near the target cumulative dose in an environment in which the predetermined delay time occurs .
A radiation imaging system of the present invention is a radiation imaging system in which radiation irradiated from a radiation irradiation device is detected by the radiation imaging device, and includes a sensor unit that detects radiation, a means for acquiring a cumulative dose of the radiation detected by the sensor unit, a means for outputting a predetermined signal for stopping the irradiation of the radiation by the radiation irradiation device based on the cumulative dose becoming equal to or greater than a threshold of a predetermined threshold condition, and a means for stopping the irradiation of the radiation based on the predetermined signal, wherein the predetermined threshold condition is a threshold condition in which the threshold differs at a plurality of timings including at least a first timing and a second timing at which elapsed times from a start of the irradiation of the radiation are different, and the threshold at the first timing is a threshold for stopping irradiation of radiation at a first dose rate near a target cumulative dose in an environment in which a predetermined delay time occurs in communication with the radiation irradiation device, and the threshold at the second timing is a threshold for stopping irradiation of radiation at a second dose rate lower than the first dose rate near the target cumulative dose in an environment in which the predetermined delay time occurs .
The control device of the present invention is a control device capable of communicating with a radiation imaging device that detects radiation irradiated from a radiation irradiation device using a sensor unit, and includes a means for acquiring a cumulative dose of the radiation, and a means for outputting a predetermined signal for stopping the irradiation of the radiation by the radiation irradiation device based on the cumulative dose becoming equal to or greater than a threshold of a predetermined threshold condition, wherein the predetermined threshold condition is a threshold condition having different thresholds at a plurality of timings including at least a first timing and a second timing at which elapsed times from a start of the irradiation of the radiation are different, and the threshold at the first timing is a threshold for stopping irradiation of radiation at a first dose rate near a target cumulative dose in an environment in which a predetermined delay time occurs in communication with the radiation irradiation device, and the threshold at the second timing is a threshold for stopping irradiation of radiation at a second dose rate lower than the first dose rate near the target cumulative dose in an environment in which the predetermined delay time occurs .
An irradiation stopping method of the present invention is an irradiation stopping method for stopping irradiation of radiation by a radiation irradiation device in a radiation imaging system in which radiation irradiated from a radiation irradiation device is detected by a sensor unit of a radiation imaging device, the irradiation stopping method comprising the steps of: acquiring a cumulative dose of the radiation; outputting a predetermined signal for stopping the irradiation of radiation by the radiation irradiation device based on the cumulative dose becoming equal to or greater than a threshold of a predetermined threshold condition; and stopping the irradiation of radiation based on the predetermined signal, wherein the predetermined threshold condition is a threshold condition having different thresholds at a plurality of timings including at least a first timing and a second timing at which elapsed times from a start of the irradiation of the radiation are different, the threshold at the first timing is a threshold for stopping irradiation of radiation at a first dose rate near a target cumulative dose in an environment in which a predetermined delay time occurs in communication with the radiation irradiation device, and the threshold at the second timing is a threshold for stopping irradiation of radiation at a second dose rate lower than the first dose rate near the target cumulative dose in an environment in which the predetermined delay time occurs.

According to the present invention, it is possible to control the termination of radiation irradiation from a radiation generating device with high precision.

1 is a diagram showing an example of a schematic configuration of a radiation imaging system according to an embodiment of the present invention. 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 a radiation imaging system according to an embodiment of the present invention. 10 is a diagram illustrating an embodiment of the present invention, showing an example of a threshold value of a dose (accumulated achieved dose) set in an imaging control unit and a relationship between a time change of the threshold value and the dose (accumulated achieved dose). FIG.

Below, a mode (embodiment) for carrying out the present invention will be described with reference to the drawings. In this specification, it is preferable to use X-rays as the radiation according to the present invention, but this is not limited to X-rays, and alpha rays, beta rays, gamma rays, etc. are also included.

Fig. 1 is a diagram showing an example of the schematic configuration of a radiation imaging system 100 according to an embodiment of the present invention. 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 is configured to have a radiation generating device 110, a radiation imaging device 120, and a control device 130. The control device 130 is configured to be able to communicate with the radiation generating device 110 and the radiation imaging device 120, and includes an imaging condition setting unit 131, a calculation unit 132, an imaging control unit 133, an image processing unit 134, and a display unit 135.

The radiation generating device 110 irradiates radiation R toward the subject P based on the control of the control device 130 (more specifically, the imaging control unit 133). This radiation generating device 110 includes a radiation tube 111, which is a radiation generating unit that generates radiation R, and a collimator 112 that determines the beam spread angle of the radiation R generated by the radiation tube 111.

The radiation imaging device 120 is configured with, for example, an FPD, and is configured with a sensor unit including imaging elements distributed two-dimensionally. This sensor unit detects the radiation R irradiated from the radiation generating device 110 and incident thereon. Specifically, the radiation imaging device 120 detects information (dose information) of the two-dimensional distribution of the radiation dose that has reached the imaging element in the sensor unit, and generates radiation image data. Thereafter, the radiation imaging device 120 transmits the generated radiation image data to the image processing unit 134 of the control device 130. The radiation imaging device 120 also transmits information (dose information) of the two-dimensional distribution of the radiation dose detected in the sensor unit to the calculation unit 132 of the control device 130.

The control device 130 controls the operation of the radiation generating device 110 and the radiation imaging device 120, and also acquires and processes dose information detected by the sensor unit of the radiation imaging device 120 and radiation image data captured by the radiation imaging device 120.

Next, the functions of the components 131 to 135 of the control device 130 will be described.
The imaging condition setting unit 131 sets imaging condition data including imaging condition information such as the imaging part of the subject P input by the operator, the tube voltage and tube current in the radiation tube 111, delay time, a reference value Dref of the dose (accumulated reached dose) of radiation R passing through the subject P and reaching the radiation imaging device 120, and a threshold value Dth for controlling the output of an irradiation stop signal to the radiation generation device 110. Then, the imaging condition setting unit 131 transmits necessary imaging condition information from the set imaging condition data to the imaging control unit 133. Here, the dose generally means the accumulated reached dose during radiation irradiation, but a dose value similar thereto or a dose value linked thereto may be used, and will be referred to as "accumulated reached dose" below as necessary.

The calculation unit 132 calculates the dose (accumulated reaching dose) of radiation R detected by the sensor unit of the radiation imaging device 120 based on the dose information transmitted from the radiation imaging device 120, and transmits this to the imaging control unit 133.

The imaging control unit 133 controls the radiation generating device 110 and the radiation imaging device 120 based on the imaging condition information received from the imaging condition setting unit 131 and the dose (accumulated achieved dose) information received from the calculation unit 132.

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 device 120. The image processing unit 134 then transmits the radiation image data after the image processing to the display unit 135.

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

The delay time set by the imaging condition setting unit 131 is the time from when an irradiation stop signal for stopping irradiation of radiation R is output from the imaging control unit 133 to the radiation generating device 110 based on the dose (accumulated reached dose) of radiation R calculated by the calculation unit 132 to when irradiation of radiation R is stopped in the radiation generating device 110. The time when irradiation of radiation R is stopped in the radiation generating device 110 is the time when the tube voltage in the radiation tube 111 of the radiation generating device 110 starts to drop or the time when the tube voltage has dropped to its final drop. Here, when the delay time is set based on the time when the tube voltage in the radiation tube 111 of the radiation generating device 110 has dropped to its final drop, it is desirable to set the delay time by taking into consideration the time multiplied by a coefficient considering changes in dose and radiation quality for the non-steady period from when the tube voltage in the radiation tube 111 starts to drop to when it has dropped to its final drop. More specifically, the delay time Td is divided into a stationary period Ta from 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) to add, since the tube voltage in the radiation tube 111 drops. That is, the delay time Td when the unsteady period Tb is taken into consideration can be determined based on the following formula.
Td = Ta + kTb

In this embodiment, this delay time Td needs to be obtained for each imaging environment before irradiation with radiation R for radiography of the subject P (before imaging). In addition, a value actually measured when the radiography device 120 is installed can be used as this delay time Td. Furthermore, the imaging environment and the radiation generating device 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.

Next, the process of photographing subject P will be explained using Figure 2.

Figure 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 P in a radiation imaging system 100 according to an embodiment of the present invention.

In this imaging process, a dose (cumulative dose) threshold Dth and its change over time are set based on the previously acquired delay time Td and dose (cumulative dose) reference value Dref, and then radiography of the subject P is performed.

First, in step S201, the imaging condition setting unit 131 receives an instruction to start imaging input by the 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 131 sets the tube voltage and tube current of the radiation tube 111, the reference value Dref of the dose (accumulated reaching dose), the delay time Td, and the like as the imaging condition information (irradiation condition information). Thereafter, the imaging condition setting unit 131 transmits the acquired instruction to start imaging and the set imaging condition information (irradiation condition information) to the imaging control unit 133. In addition, the value of the delay time Td may be stored in any of the devices constituting the radiation imaging system 100 and referenced.

Next, in step S202, the imaging control unit 133 sets a dose (cumulative dose) threshold Dth and its change over time based on the dose (cumulative dose) reference value Dref and delay time Td set in step S201. Setting of the dose (cumulative dose) threshold Dth and its change over time will be described later with reference to FIG. 3.

Next, in step S203, the imaging control unit 133 transmits to the radiation generating device 110 an irradiation execution signal for irradiating radiation R together with the imaging condition information (irradiation condition information) received from the imaging condition setting unit 131 in step S201. In response to this, the radiation generating device 110 irradiates radiation R toward the subject P under irradiation conditions based on the imaging condition information (irradiation condition information) received from the imaging condition setting unit 131 and the threshold value Dth set in step S202.

Next, in step S204, the calculation unit 132 first calculates a value D representing the dose (accumulated reaching dose) of radiation R detected by the sensor unit based on the dose information (e.g., dose information for each image pickup element in the sensor unit) transmitted from the radiation imaging device 120. Note that the value D representing the dose (accumulated reaching dose) of radiation R may be the maximum value, average value, median value, etc. of the dose (accumulated reaching dose). In the following description, the value D representing the dose (accumulated reaching dose) of radiation R is described as the "dose (accumulated reaching dose) D of radiation R." Then, the imaging control unit 133 compares the dose (accumulated reaching dose) D of radiation R received from the calculation unit 132 with the threshold value Dth set in step S202, and determines whether the dose (accumulated reaching dose) D is smaller than the threshold value Dth. If the result of this determination is that the dose (cumulative achieved dose) D is less than the threshold Dth (S204/YES), the system waits in step S204.

On the other hand, if the result of the determination in step S204 is that the dose (cumulative reaching dose) D is not smaller than the threshold Dth (the dose (cumulative reaching dose) D is equal to or greater than the threshold) (S204/NO), the process proceeds to step S205.
When the process proceeds to step S205, since the dose (accumulated reaching dose) D has exceeded (reached) the threshold value Dth, the imaging control unit 133 outputs an irradiation stop signal to the radiation generating device 110 to stop the irradiation of radiation R. At this time, the radiation R continues to be irradiated for a delay time Td from the output of the irradiation stop signal from the imaging control unit 133 to the radiation generating device 110 to the actual stop of the irradiation of radiation R in the radiation generating device 110, so that it is possible to bring the actually irradiated dose (accumulated reaching dose) D closer to the reference value Dref of the dose (accumulated reaching dose).

Next, in step S206, the imaging control unit 133 first transmits an imaging control signal to the radiation imaging device 120. Then, the radiation imaging device 120 controls the image sensor in the sensor unit based on the imaging control signal received from the imaging control unit 133, stops conversion to dose information after a predetermined time has elapsed since receiving the imaging control signal, and transmits the generated radiation image data to the image processing unit 134.

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 device 120. After that, the image processing unit 134 transmits the radiation image data after the image processing to the display unit 135.

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.

When the process of step S208 is completed, the process of the flowchart relating to radiography of subject P shown in FIG. 2 is completed.

Next, the process of setting the dose (cumulative dose) threshold Dth and the change over time of the threshold Dth in step S202 in FIG. 2 will be described with reference to FIG. 3. When setting the change over time of the dose (cumulative dose) threshold Dth, if a positive determination (S204/YES) is made in step S204, the process of step S202 will also be performed.

Figure 3 illustrates an embodiment of the present invention, and shows an example of a dose (cumulative dose) threshold Dth set in the imaging control unit 133, and a relationship between the change in the threshold Dth over time and the dose (cumulative dose) D. In Figure 3, the relationship between the dose (cumulative dose) D shown on the vertical axis and the time (elapsed time) shown on the horizontal axis is shown.

As shown in FIG. 3, the imaging control unit 133 performs control to change the dose (cumulative achieved dose) threshold Dth according to the elapsed time from the start of irradiation of radiation R. Specifically, in FIG. 3, the imaging control unit 133 performs control to increase the dose (cumulative achieved dose) threshold Dth with the elapsed time.

Then, when the dose (cumulative achieved dose) D obtained from the calculation unit 132 becomes equal to or greater than the threshold value Dth of the dose (cumulative achieved dose) that changes over time as shown in FIG. 3 (S204/NO), the imaging control unit 133 outputs an irradiation stop signal to the radiation generating device 110 in step S205 of FIG. 2. At this time, radiation R continues to be irradiated for the delay time Td from when the imaging control unit 133 outputs the irradiation stop signal to the radiation generating device 110 to when the irradiation of radiation R is actually stopped in the radiation generating device 110.

In the example shown in FIG. 3, when the dose rate of radiation R entering the radiation imaging device 120 is a high dose rate 301, the dose (cumulative achieved dose) D obtained from the calculation unit 132 at the irradiation time Thigh is equal to or greater than the dose (cumulative achieved dose) threshold Dth. As a result, at the point in time of irradiation Thigh, the imaging control unit 133 outputs an irradiation stop signal to the radiation generating device 110, and then the irradiation of radiation R in the radiation generating device 110 is stopped. In this case, radiation R with a dose (cumulative achieved dose) Dhigh reaches the radiation imaging device 120.

Similarly, when the dose rate of radiation R entering the radiography device 120 is a low dose rate 302, the dose (cumulative achieved dose) D obtained from the calculation unit 132 at the irradiation time Tlow becomes equal to or greater than the dose (cumulative achieved dose) threshold Dth. As a result, at the point in time Tlow, the radiography control unit 133 outputs an irradiation stop signal to the radiation generation device 110, and then the irradiation of radiation R in the radiation generation device 110 stops. In this case, radiation R with a dose (cumulative achieved dose) Dlow reaches the radiography device 120.

Here, as shown in FIG. 3, the dose rate 301 and dose rate 302 of radiation R are determined based on the relationship between the dose (cumulative dose) D and time. In FIG. 3, for example, if the dose (cumulative dose) threshold Dth is constant, the actual dose (cumulative dose) D changes according to the change in dose rate, and becomes a value far from the dose (cumulative dose) reference value Dref. In contrast, in this embodiment, as shown in FIG. 3, the dose (cumulative dose) threshold Dth is changed according to the elapsed time from the start of irradiation of radiation R (specifically, the dose (cumulative dose) threshold Dth is increased with the elapsed time), so that both the dose (cumulative dose) Dhigh in the case of a high dose rate 301 and the dose (cumulative dose) Dlow in the case of a low dose rate 302 can be set to a value close to the dose (cumulative dose) reference value Dref. This allows for highly accurate control of radiation R irradiation termination regardless of the dose rate.

In this embodiment, as shown in FIG. 3, the time change of the dose (accumulated dose) threshold Dth can be expressed by a step function that changes stepwise with respect to the elapsed time. In this case, the length of the time segments T1 to T4 of the step function related to the dose (accumulated dose) threshold Dth may be different for each time segment, as shown in FIG. 3. In this case, as shown in FIG. 3, if the length of the time segments T1 to T4 of the step function is gradually increased with the elapsed time (T2 is made longer than T1, T3 is made longer than T2, and T4 is made longer than T3), the number of time segments can be reduced. That is, in this case, the imaging control unit 133 decreases the increase in the dose (accumulated dose) threshold Dth per hour with the elapsed time. And, if the number of time segments can be reduced in this way, the memory used can be reduced, and the load on the control device 130 caused by changing the dose (accumulated dose) threshold Dth can be reduced.

In addition, in this embodiment, the time change of the dose (cumulative achieved dose) threshold Dth may be changed continuously with respect to the elapsed time.

In addition, in this embodiment, the threshold value Dth of the dose (cumulative reaching dose) with respect to the elapsed time t can be set to satisfy the following equation (1) using the elapsed time t, the delay time Td, and the reference value Dref of the dose (cumulative reaching dose).

That is, as shown in equation (1), the imaging control unit 133 changes the dose (cumulative dose) threshold Dth according to the elapsed time t, and sets the time change of the dose (cumulative dose) threshold Dth based on the dose (cumulative dose) reference value Dref and the delay time Td.

When using a step function as the dose (cumulative dose) threshold Dth, it is desirable to set a function such that each step of the step intersects with equation (1).

As described above, the shooting control unit 133 changes the dose (cumulative reaching dose) threshold Dth according to the elapsed time t, and sets the change over time of the dose (cumulative reaching dose) threshold Dth based on the dose (cumulative reaching dose) reference value Dref and the delay time Td.
According to this configuration, it is possible to perform highly accurate control of stopping irradiation of radiation from the radiation generating device 110. In other words, it is possible to perform AEC with high accuracy.

Other Embodiments
The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.
This program and a computer-readable storage medium storing the program are included in the present invention.

The above-mentioned embodiments of the present invention are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted in a limiting manner based on these. In other words, the scope of the present invention includes any modifications or improvements to the above-mentioned embodiments of the present invention that are made based on the ordinary knowledge of a person skilled in the art without departing from the technical concept or main features of the present invention.

100: Radiation imaging system, 110: Radiation generator, 111: Radiation tube, 112: Collimator, 120: Radiation imaging device, 130: Control device, 131: Imaging condition setting unit, 132: Calculation unit, 133: Imaging control unit, 134: Image processing unit, 135: Display unit, P: Subject, R: Radiation

Claims (11)

a sensor unit for detecting radiation irradiated from a radiation irradiation device;
A means for acquiring a cumulative dose of said radiation;
and a means for outputting a predetermined signal for stopping the irradiation of the radiation by the radiation irradiation device based on the fact that the accumulated dose has become equal to or greater than a threshold of a predetermined threshold condition,
the predetermined threshold condition is a threshold condition in which the threshold is different at a plurality of timings including at least a first timing and a second timing at which the elapsed time from the start of the irradiation of the radiation is different ,
the threshold value at the first timing is a threshold value for stopping irradiation of radiation at a first dose rate near a target cumulative dose in an environment in which a predetermined delay time occurs in communication with the radiation irradiating device,
a threshold value at the second timing for stopping irradiation of radiation at a second dose rate lower than the first dose rate near the target cumulative dose in an environment in which the specified delay time occurs. The radiographic imaging device according to claim 1, characterized in that the predetermined threshold condition is a threshold condition in which the threshold increases as the elapsed time increases. 2. The radiation imaging apparatus according to claim 1 , wherein the predetermined threshold condition is expressed by a step function that changes stepwise with respect to the elapsed time. 4. The radiation imaging apparatus according to claim 3 , wherein the length of each time segment in the step function is different for each time segment. 4. The radiation imaging apparatus according to claim 3 , wherein the length of the time division in the step function gradually increases with the elapsed time. 2. The radiation imaging apparatus according to claim 1 , wherein the predetermined threshold condition is a threshold condition in which the threshold changes continuously with respect to the elapsed time. 7. The radiation imaging apparatus according to claim 6 , wherein the predetermined threshold condition is a threshold condition in which an increase in the threshold per unit time decreases as the elapsed time increases. The radiation imaging apparatus according to claim 1 , wherein a radiation image is acquired based on the radiation. A radiation imaging system in which radiation irradiated from a radiation irradiation device is detected by a radiation imaging device,
A sensor unit for detecting radiation;
a means for acquiring a cumulative dose of the radiation detected by the sensor unit;
a means for outputting a predetermined signal for stopping the irradiation of the radiation by the radiation irradiation device based on the fact that the accumulated dose has become equal to or greater than a threshold of a predetermined threshold condition;
and a means for stopping the irradiation of the radiation based on the predetermined signal,
the predetermined threshold condition is a threshold condition in which the threshold is different at a plurality of timings including at least a first timing and a second timing at which the elapsed time from the start of the irradiation of the radiation is different ,
the threshold value at the first timing is a threshold value for stopping irradiation of radiation at a first dose rate near a target cumulative dose in an environment in which a predetermined delay time occurs in communication with the radiation irradiating device,
a threshold value at the second timing for stopping irradiation of radiation at a second dose rate lower than the first dose rate near the target cumulative dose in an environment in which the specified delay time occurs. A control device capable of communicating with a radiation imaging device that detects radiation irradiated from a radiation irradiation device using a sensor unit,
A means for acquiring a cumulative dose of said radiation;
and a means for outputting a predetermined signal for stopping the irradiation of the radiation by the radiation irradiation device based on the fact that the accumulated dose has become equal to or greater than a threshold of a predetermined threshold condition,
the predetermined threshold condition is a threshold condition in which the threshold is different at a plurality of timings including at least a first timing and a second timing at which the elapsed time from the start of the irradiation of the radiation is different ,
the threshold value at the first timing is a threshold value for stopping irradiation of radiation at a first dose rate near a target cumulative dose in an environment in which a predetermined delay time occurs in communication with the radiation irradiating device,
a threshold value at the second timing for stopping irradiation of radiation at a second dose rate lower than the first dose rate near the target cumulative dose in an environment in which the specified delay time occurs. 1. An irradiation stopping method for stopping irradiation of radiation by a radiation irradiation device in a radiation imaging system in which radiation irradiated from a radiation irradiation device is detected by a sensor unit of the radiation imaging device, the method comprising:
obtaining a cumulative dose of said radiation;
outputting a predetermined signal for stopping the irradiation of the radiation by the radiation irradiation device based on the fact that the accumulated dose has become equal to or greater than a threshold of a predetermined threshold condition;
and stopping the irradiation of the radiation based on the predetermined signal,
the predetermined threshold condition is a threshold condition in which the threshold is different at a plurality of timings including at least a first timing and a second timing at which the elapsed time from the start of the irradiation of the radiation is different ,
the threshold value at the first timing is a threshold value for stopping irradiation of radiation at a first dose rate near a target cumulative dose in an environment in which a predetermined delay time occurs in communication with the radiation irradiating device,
the threshold at the second timing is a threshold for stopping irradiation of radiation at a second dose rate lower than the first dose rate near the target cumulative dose in an environment in which the specified delay time occurs.

Images