Radiography apparatus, radiation imaging 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 Art

[0002] Currently, as a radiation imaging apparatus used for medical image diagnosis or non-destructive inspection using radiation such as X-rays, a radiation imaging apparatus equipped with a flat panel detector (FPD) formed of a semiconductor material has become widespread. Such a radiation imaging apparatus is used, for example, in medical image diagnosis as a digital radiation imaging apparatus that performs still image imaging such as general imaging or moving image imaging such as fluoroscopic imaging.

[0003] Some radiation imaging apparatuses monitor the dose (cumulative dose) of the irradiated radiation and stop the radiation irradiation when the cumulative dose reaches a threshold value (for example, transmit an irradiation stop signal for stopping the radiation irradiation to the radiation generator). This operation is called automatic exposure control (AEC), and by this, for example, over-irradiation of radiation can be prevented.

[0004] As such a radiation imaging apparatus, for example, Patent Document 1 discloses a radiation imaging apparatus provided with a dose detection unit that detects the dose of radiation reaching the imaging region within the imaging region of the FPD. In this Patent Document 1, based on the dose detected by the dose detection unit and a preset dose target value, the stop timing at which the radiation irradiation should be stopped in the radiation generator is predicted. Then, an irradiation stop timing notification for notifying the radiation generator of the radiation irradiation stop timing is transmitted before the irradiation stop timing arrives.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, the technology described in Patent Document 1 has issues with the accuracy of controlling the stopping of radiation irradiation from the radiation generator. Specifically, in the technology described in Patent Document 1, when the transmission dose rate of radiation passing through the subject is high, the time until the cumulative radiation dose reaches the threshold becomes short, about a few milliseconds. As a result, a problem may arise in which the cumulative radiation dose exceeds the threshold before the radiation generator stops irradiating radiation because the notification of the irradiation stop timing is not given in time. [Means for solving the problem]

[0007] The above problem is solved by using a sensor unit that detects radiation incident from a radiation generator, the cumulative dose received by the radiation detected by the sensor unit, the radiation irradiation time, and an irradiation stop threshold to generate a signal related to stopping radiation irradiation. Send Faith vinegar In a radiography apparatus comprising a control unit, the control unit controls the cumulative dose received However, after reaching a predetermined amount which is changed by the operator's actions, the irradiation time and the predetermined amount and Based on, A signal is transmitted regarding the cessation of the aforementioned radiation irradiation. This is solved by a radiographic imaging device characterized by the following: [Effects of the Invention]

[0008] At least one embodiment of this disclosure enables highly accurate control over stopping radiation irradiation from a radiation generator. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of a schematic configuration of a radiography system according to the first embodiment. [Figure 2] This flowchart shows 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 radiography system according to the first embodiment. [Figure 3] This figure shows an example of a processing procedure in a series of control methods for measuring communication delay time in a radiography system according to the first embodiment. [Figure 4] This is a table showing the relationship between communication delay times for each communication mode in the radiography system according to the first embodiment. [Figure 5] This figure shows an example of the relationship between the time change of the threshold set by the threshold change control unit according to the first embodiment and the dose. [Modes for carrying out the invention]

[0010] The embodiments for implementing this disclosure will be described below with reference to the drawings. In this specification, X-rays are preferred as the radiation, but the radiation is not limited to X-rays and includes alpha rays, beta rays, gamma rays, etc.

[0011] (First Embodiment) Figure 1 shows an example of a schematic configuration of a radiography system 100 according to an embodiment of the present disclosure. In this embodiment, the radiography system 100 is particularly suitable for medical use. As shown in Figure 1, the radiography system 100 comprises a radiation generator 110, a radiography device 120, and an irradiation control device 130.

[0012] The radiation generator 110 irradiates a subject (not shown) with radiation based on the control of the irradiation control device 130 (more specifically, the imaging control device 131). This radiation generator 110 includes a radiation tube, which is a radiation generation unit that generates radiation, and a collimator that defines the beam divergence angle of the radiation generated by the radiation tube.

[0013] The radiography apparatus 120 is configured, for example, with an FPD (Flat Panel Detector) and has a sensor unit 121 that includes two-dimensionally distributed image sensors. This sensor unit 121 detects the incident radiation irradiated from the radiation generator 110.

[0014] Furthermore, the radiography apparatus 120 specifically detects information (dose information) of the two-dimensional distribution of the radiation dose that has reached the image sensor in the sensor unit 121 and generates radiographic image data. Subsequently, the radiography apparatus 120 transmits the generated radiographic image data to the image processing unit 134 of the irradiation control device 130 via the communication unit 123. The irradiation control device 130 controls the operation of the radiation generator 110 and the radiography apparatus 120, and also acquires and processes the radiographic image data captured by the radiography apparatus 120.

[0015] Furthermore, the radiography device 120 has a control unit 200. The control unit 200 has 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 the 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 radiation dose (cumulative dose received) detected by the sensor unit 121 and calculated by the dose calculation unit 126 has reached a predetermined irradiation stop threshold, it 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 radiography device 120 via the communication unit 133, the imaging control unit 131 performs irradiation stop control 136 to stop the radiation irradiation from the radiation generator 110.

[0016] At the same time, the communication unit 133 sends a response to the radiation imaging device 120 acknowledging receipt of the irradiation stop signal 127. If the radiation imaging device 120 does not receive a response after a certain period of time following the transmission of the irradiation stop signal 127, it retransmits the irradiation stop signal 127 to the irradiation control device 130.

[0017] When the threshold determination unit 122 calculates that the cumulative dose reached since the start of imaging by the dose calculation unit 126 has reached a predetermined amount, it determines that the irradiation has started and causes the timer unit 125 to start timing the irradiation time. The dose threshold at this time is referred to as 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 fact to the threshold determination unit 124. When the threshold determination unit 124 receives the transmission from the threshold determination unit 122 that the irradiation start threshold has been reached, it designates that point as the threshold change reference point. The predetermined amount that becomes the irradiation start threshold is a dose value that serves as a reference for determining that the irradiation of the radiation generator 110 has started to stabilize, and an appropriate value is set in the threshold determination unit 122 according to the characteristics of the radiation generator 110.

[0018] The timer unit 125 is a timer that times the irradiation time of radiation from a predetermined timing. In the present embodiment, the irradiation time is timed from the threshold change reference point determined by the threshold determination unit 124. While referring to the irradiation time of the timer unit 125 and the irradiation start threshold of the threshold determination unit 122, the threshold determination unit 124 continuously corrects the timing for transmitting the irradiation stop signal based on the time change from the threshold change reference point, the irradiation start threshold, and the communication delay time Tdc described later.

[0019] The communication unit 123 can communicate with the irradiation control device 130 both wired and wirelessly. Prior to imaging, it communicates with the communication unit 133 of the irradiation control device 130, calculates the delay time due to communication by counting the communication response time between the two devices with the timer unit 125, 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] Note that the communication delay time Tdc to be held here is to be held in the threshold determination unit 124 in a table or the like so that it can be held for the number of combinations of communication forms between the communication unit 123 and the communication unit 133. The Tdc that the threshold determination unit 124 reflects in the setting of the irradiation stop threshold shall be switched according to the communication form between the communication unit 123 and the communication unit 133. Note that it is not limited to holding in a table, and it may be calculated based on a calculation formula or calculated by measurement.

[0021] Subsequently, the functions of each component 131 to 135 included in the irradiation control device 130 will be described.

[0022] The imaging condition setting unit 132 sets imaging condition data including imaging condition information such as, for example, the imaging site of the subject, the tube voltage and tube current in the radiation generator 110, and the target value Dref of the dose (cumulative arrival dose) of radiation that passes through the subject and reaches the radiation imaging device 120. Here, the dose generally means the cumulative arrival dose during radiation irradiation, but a dose value similar thereto or a linked dose value may be used, and hereinafter, it will be described as the "cumulative arrival dose" as necessary.

[0023] The communication unit 133 can communicate with the radiation imaging device 120 both wired and wirelessly.

[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 device 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 radiography system 100 described in this embodiment, the timing for transmitting the irradiation stop signal 127 from the radiography device 120 to the irradiation control device 130 is based on the transmission time of the irradiation stop signal 127 from the radiography device 120 to the irradiation control device 130. Furthermore, it is desirable that the timing take into account the delay time from when the irradiation control device 130 performs the irradiation stop control 136 to stop the irradiation of radiation to the radiation generator 110 until the radiation irradiation is stopped in the radiation generator 110.

[0027] Furthermore, the time when radiation irradiation stops in the radiation generator 110 is the time when the tube voltage in the radiation tube of the radiation generator 110 begins to decrease or the time when the tube voltage has completely decreased. When setting the delay time based on the time when the tube voltage has completely decreased, it is desirable to set the delay time by adding a time that is calculated by multiplying the non-steady period from when the tube voltage in the radiation tube begins to decrease until it has completely decreased by a coefficient that takes into account the changes in dose and radiation quality.

[0028] More specifically, the delay time Td can be divided into a steady-state period Ta from signal transmission until the tube voltage begins to decrease, and a transient period Tb from when the tube voltage begins to decrease until it has completely decreased. In this case, the transient period Tb is added by multiplying it by a coefficient k (where the coefficient k is 1 or less) because the tube voltage in the radiation tube decreases. That is, the delay time Td when the transient 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 must be obtained for each generating device before the radiation related to the radiography of the subject is irradiated (before imaging). Furthermore, the delay time Td can be the value actually measured when the radiography apparatus 120 is installed. Alternatively, the imaging environment and the radiation generating device 110 to be used may be registered in a database beforehand, and the delay time Td may be calculated by referring to the database. It is desirable that the delay time Td be notified to the threshold determination unit 124 in advance, and that the irradiation stop threshold be set taking the delay time Td into consideration.

[0030] Next, we will explain the processing of the subject's image using Figure 2.

[0031] 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 in the radiography system 100 according to this embodiment.

[0032] In this imaging process, the radiation stop threshold Dth and the time variation of Dth are set based on a pre-held delay time Td, a previously acquired communication delay time Tdc, an irradiation start threshold Dobs, and a target value Dref for the dose (cumulative dose received), and then radiographic imaging of the subject is performed.

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

[0034] Subsequently, the imaging condition setting unit 132 transmits the acquired instruction to start imaging and the set imaging condition information (irradiation condition information) to the radiation imaging device 120. Alternatively, the value of the delay time Td may be stored in one of the devices constituting the radiation imaging system 100 and referenced from that value.

[0035] Next, in step S202, the threshold determination unit 124 sets the irradiation stop threshold Dth for the dose (cumulative dose) and its time variation based on the target value Dref for the dose (cumulative dose) set in step S201, the irradiation start threshold Dobs, the delay time Td, and the communication delay time Tdc. The setting of this irradiation stop threshold Dth for the dose (cumulative dose) and its time variation will be described later with reference to Figure 5.

[0036] Next, in step S203, the imaging control unit 131 transmits an irradiation execution signal to the radiation generator 110 to initiate radiation irradiation, along with the imaging condition information (irradiation condition information) received from the imaging condition setting unit 132 in step S201. Accordingly, the radiation generator 110 irradiates the subject with radiation under the irradiation conditions based on the imaging condition information (irradiation condition information) received from the imaging condition setting unit 132.

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

[0038] The threshold determination unit 122 then compares the radiation dose (cumulative dose received) D with the irradiation stop threshold Dth set in step S202 and determines whether the dose (cumulative dose received) D is less than the irradiation stop threshold Dth. If, as a result of this determination, the dose (cumulative dose received) D is less than the irradiation stop threshold Dth (S204 / YES), the unit waits in step S204.

[0039] On the other hand, if, as a result of the judgment in step S204, the dose (cumulative dose received) D is equal to or greater than the irradiation stop threshold Dth (i.e., the dose (cumulative dose received) D is equal to or greater than the threshold), then the process proceeds to step S205 (S204 / NO).

[0040] When the process proceeds to step S205, the radiation imaging device 120 transmits an irradiation stop signal 127 to the irradiation control device 130 to stop the irradiation of radiation from the radiation generator 110, because the dose (cumulative dose received) D has reached the irradiation stop threshold Dth. Upon receiving the irradiation stop signal, the irradiation control device 130 performs an irradiation stop control 136 to the generator 110 via the imaging control unit 131.

[0041] In this case, radiation continues to be emitted for the duration of the communication delay Tdc required for transmitting the irradiation stop signal 127, and the delay Td from the irradiation stop control 136 until the radiation emission in the radiation generator 110 actually stops. Therefore, it becomes possible to bring the actual irradiated dose (cumulative dose) D closer to the target value Dref of the dose (cumulative dose received).

[0042] Next, in step S206, the radiography apparatus 120 controls the image sensor in the sensor unit 121 to stop the conversion to dose information and transmits the generated radiographic image data to the image processing unit 134.

[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 radiography apparatus 120. After that, the image processing unit 134 transmits the processed radiation image data to the display unit 135.

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

[0045] Then, once the process in step S208 is completed, the flowchart related to the radiographic imaging of the subject shown in Figure 2 is terminated.

[0046] Next, we will explain how to obtain the communication delay time Tdc before shooting using Figure 3.

[0047] Once the radiography device 120 and the irradiation control device 130 are activated and wired and wireless communication are operational, the radiography device 120 sends an inquiry from its 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 radiography apparatus 120 refers to the counter in the timer unit 125. When the irradiation control device 130 receives a communication delay time inquiry, it responds immediately. When the radiography apparatus 120 receives a response from the irradiation control device 130, it refers to the counter in the timer unit 125 and holds a time equal to the round-trip communication time (t1) ÷ 2 as the provisional communication delay time (T1).

[0049] The radiography apparatus 120 continuously repeats this operation until the start of imaging, acquiring multiple provisional communication delay times (T2, T3, T4, ...). If the maximum number of acquired provisional communication delay times is exceeded, the oldest information is overwritten as needed. When the timing transitions to the start of imaging, one communication delay time is calculated from the multiple acquired provisional communication delay times and set as the communication delay time Tdc. Here, the method for determining one communication delay time may be to use the average value of some or all of the multiple communication delay times, or to use the minimum value of some or all of them.

[0050] Using the communication delay time Tdc, the threshold determination unit 124 sets the dose (cumulative dose received) irradiation stop threshold Dth and its time variation for the target value Dref of the dose (cumulative dose received). The setting of this dose (cumulative dose received) irradiation stop threshold Dth and its time variation will be described later with reference to Figure 5.

[0051] Furthermore, if the following equation holds true regarding the relationship between the calculated Tdc, the delay time Td of the generator, and the nominal minimum irradiation time, it can be determined before shooting that the communication delay time is very large and that irradiation cannot be stopped at the desired timing. In this situation, for example, control to prohibit shooting may be implemented, or an action such as issuing a warning to the user may be taken.

[0052] Tdc > Nominal minimum irradiation time - Td Furthermore, since the communication delay time Tdc is the delay time for communication from the radiation imaging device 120 to the irradiation control device 130, the components of the delay time include the time for internal processing in units such as access points, hubs, and wireless repeaters. In addition, application layer delay, transmission delay, propagation delay, and processing by the wireless management server (encryption processing, etc.) are also included, and even when multiple hubs are used, the communication delay time Tdc includes the time for all of these components.

[0053] The communication delay time Tdc varies depending on the communication method between the radiation imaging device 120 and the irradiation control device 130. Specifically, it will differ depending on whether it is wired or wireless communication, and even within wireless communication, in systems that use multiple antennas to improve communication quality, the communication time will differ depending on which of the multiple antennas is used. Due to these differences in communication methods, the threshold determination unit 124 stores the different communication delay times in a table as shown in Figure 4.

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

[0055] For example, if wired communication is interrupted and switched to wireless communication immediately before imaging, and the delay time Tdc acquired during the wired communication immediately beforehand is used to set the irradiation stop threshold, it will become impossible to perform AEC accurately. Therefore, by maintaining the delay time Tdc for each communication type as shown in the table in Figure 4, it becomes possible to use the correct communication delay time Tdc depending on the communication type at the time of imaging and reflect it in the setting of the irradiation stop threshold, thereby enabling accurate AEC.

[0056] In Figure 4, Table 4(A) stores the delay time for each communication method as a table, but as shown in Table 4(B), it is also acceptable to store the difference relative to the base delay time.

[0057] Note that while Figure 4 shows two antennas for wireless communication, the number is not limited and can be more than one, or even just one.

[0058] Next, using Figure 5, we will explain the process for setting the dose (cumulative dose received) irradiation stop threshold Dth and its time variation in step S202 of Figure 2. Note that when setting the time variation of the dose (cumulative dose received) irradiation stop threshold Dth, the processing in step S202 will also be performed if an affirmative judgment (S204 / YES) is made in step S204.

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

[0060] As shown in Figure 5, the threshold determination unit 124 controls the irradiation stop threshold Dth of the dose (cumulative dose achieved) according to the elapsed time since the start of radiation irradiation. Specifically, in Figure 5, the threshold determination unit 124 controls the irradiation stop threshold Dth of the dose (cumulative dose achieved) to increase with elapsed time.

[0061] Here, the starting point for measuring elapsed time is the threshold change reference point shown in Figure 5. As mentioned above, when the threshold determination unit 122 determines that the dose (cumulative dose received) D detected by the sensor unit 121 has reached the irradiation start threshold held by the threshold determination unit 122, it notifies the threshold determination unit 124 of that point in time as the threshold change reference point.

[0062] The threshold determination unit 124 counts the elapsed time from the reference point and controls the irradiation stop threshold Dth of the dose (cumulative dose received) according to the elapsed time.

[0063] When taking images, even if the imaging control unit 131 instructs the generator 110 to start irradiation, some of the tubes in the generator 110 may take time to start up, and some may have an unstable start-up. If the elapsed time is counted from the point when the irradiation start instruction is given, the actual dose (cumulative dose received) D and the irradiation dose expected from the dose rate will not match, making it impossible to accurately change the irradiation stop threshold Dth for the dose (cumulative dose received). To avoid this, the timing when irradiation begins to stabilize is set as the threshold change reference point, thereby improving the accuracy of irradiation stop control.

[0064] Furthermore, when determining the threshold change reference point, it is preferable to use the dose (cumulative dose received) D detected by the sensor unit 121 and the dose (cumulative dose received) D detected by the sensor unit 121 for determining whether the irradiation start threshold has been reached. In this case, if the signal-to-noise ratio of the dose detected by the sensor unit 121 is sufficiently high, the dose of a single sample may be used instead of the total dose received to determine whether the irradiation start threshold has been reached.

[0065] Then, the threshold determination unit 122 proceeds to step S205 in Figure 2 when the dose (cumulative dose) D detected by the sensor unit 121 becomes greater than or equal to the irradiation stop threshold Dth of the dose (cumulative dose) that changes with the elapsed time shown in Figure 5 (S204 / NO). 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 generator 110.

[0066] In this case, radiation continues to be emitted for a duration equal to the communication delay time Tdc required for transmitting the irradiation stop signal 127, and the delay time Td from the time the irradiation stop control 136 is performed until the radiation emission in the radiation generator 110 actually stops.

[0067] In the example shown in Figure 5, when the dose rate of radiation incident on the radiography device 120 is a high dose rate 501, at irradiation time Thigh, the dose (cumulative dose) D obtained by the dose calculation unit 126 becomes equal to or greater than the irradiation stop dose (cumulative dose) Dth. As a result, at irradiation time Thigh, the radiography device 120 transmits an irradiation stop signal 127 to the irradiation control device 130, and thereafter, radiation irradiation is stopped in the radiation generator 110.

[0068] The irradiation stop threshold Dth in this case is determined by the dose calculation unit 126 detecting that the irradiation stop threshold Dth has been exceeded, and taking into account the communication delay time Tdc and the delay time Td on the generator side. Therefore, when irradiation from the generator 110 actually stops, the radiation at the target value Dref will reach the radiography device 120.

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

[0070] As a result, at irradiation time Tlow, the radiography device 120 transmits an irradiation stop signal 127 to the irradiation control device 130, and thereafter, radiation irradiation stops in the radiation generator 110. The dose calculation unit 126 detects that the irradiation stop threshold Dth has been exceeded, and the irradiation stop threshold Dth is calculated taking into account the communication delay time Tdc and the delay time Td on the generator side. Therefore, when irradiation from the generator 110 actually stops, the radiation at the target value Dref will reach the radiography device 120.

[0071] As shown in Figure 5, the radiation dose rates 501 and 502 are determined based on the relationship between the dose (cumulative dose received) D and time. In Figure 5, for example, if the irradiation stop threshold Dth for the dose (cumulative dose received) is kept constant, the actual dose (cumulative dose received) D changes in accordance with the change in the dose rate. As a result, irradiation may continue for longer than the desired stopping time, resulting in a value that deviates from the target value Dref for the dose (cumulative dose received), leading to over-irradiation.

[0072] In this embodiment, as shown in Figure 5, the radiation dose (cumulative dose achieved) irradiation stop threshold Dth is changed according to the elapsed time since the start of radiation irradiation (specifically, the radiation dose (cumulative dose achieved) irradiation stop threshold Dth is increased with elapsed time). Therefore, the target value Dref for the dose (cumulative dose achieved) can be set to the value of Dref in both the case of a high dose rate 501 and a low dose rate 502. This makes it possible to control the stopping of radiation irradiation with high precision regardless of the magnitude of the dose rate.

[0073] In this embodiment, as shown in Figure 5, the time change of the irradiation stop threshold Dth of the dose (cumulative dose received) is made to change continuously with respect to the elapsed time. However, for example, considering the memory capacity, it may also be expressed as a step function that changes stepwise with respect to the elapsed time.

[0074] In this case, the length of the time segment of the step function related to the radiation stopping threshold Dth of the dose (cumulative dose received) may differ for each time segment.

[0075] In this embodiment, the irradiation stop threshold Dth for dose (cumulative dose) relative to elapsed time t can be set to satisfy the following equation 1, using elapsed time t, delay time Td, communication delay time Tdc, irradiation start threshold Dobs, and target value Dref for dose (cumulative 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 (cumulative dose received) according to the elapsed time t. Furthermore, the threshold determination unit 124 sets the time change of the irradiation stop threshold Dth of the dose (cumulative dose received) based on the target value Dref of the dose (cumulative dose received), the irradiation start threshold Dobs, the delay time Td, and the communication delay time Tdc.

[0078] Furthermore, when using a step function as the radiation stop threshold Dth for dose (cumulative dose received), it is desirable to set a function such that the equation in Equation 1 intersects with each step of the step.

[0079] With this configuration, the irradiation stop control from the radiation generator 110 can be performed with high precision. In other words, AEC can be performed with high precision.

[0080] In this embodiment, irradiation is stopped when the cumulative dose reaches the irradiation stop threshold Dth. However, the time at which the irradiation stop threshold Dth is reached may be predicted from the dose rate, and irradiation may be stopped at that predicted time. Furthermore, the time until the cumulative 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 in accordance with the change in dose rate. In this case as well, if the irradiation time is measured from the time it is detected that the cumulative dose has reached the irradiation start threshold, the stopping of irradiation can be predicted with high accuracy.

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

[0082] Furthermore, various recording media can be used, such as flexible disks, optical disks (e.g., CD-ROMs, DVD-ROMs), magneto-optical disks, magnetic tapes, non-volatile memory (e.g., USB memory), and ROMs. Additionally, a program that performs the above-mentioned functions may be downloaded via a network and executed by a computer.

[0083] Furthermore, the functionality of the above-described embodiment is not limited to being realized solely by the execution of program code read by a computer. It also includes cases where the OS (operating system) running on the computer performs some or all of the actual processing based on the instructions of the program code, and the functionality of the above-described embodiment is realized through that processing.

[0084] Furthermore, program code read from a recording medium may be written to the memory of a function expansion board inserted into a computer or a function expansion unit connected to a computer. This also includes cases where the CPU or other components of the function expansion board or function expansion unit perform some or all of the actual processing based on the instructions of the program code, and the above-mentioned functions are realized through that processing.

[0085] With respect to the above embodiments, the following additional notes are disclosed as aspects of the invention and selective features.

[0086] (Note 1) A sensor unit that detects radiation incident from a radiation generator, A radiation imaging device comprising: a control unit that causes the radiation generator to transmit a signal regarding the cessation of radiation irradiation using the cumulative radiation dose received by the sensor unit, the radiation irradiation time, and the irradiation cessation threshold; The control unit is characterized by timing the irradiation time based on the cumulative dose received.

[0087] (Note 2) The control unit may measure the irradiation time when the cumulative dose received reaches a predetermined amount.

[0088] (Note 3) The control unit may perform control to set the irradiation stop threshold based on the target value of the cumulative dose received in radiography, the irradiation time, and the delay time from the transmission of a signal regarding the cessation of irradiation until the irradiation of the radiation is stopped in the radiation generator.

[0089] (Note 4) It has a communication unit that transmits a signal regarding the cessation of the irradiation to the radiation generating device, The control unit may derive the delay time based on the communication delay time in the communication between the communication unit and the radiation generator.

[0090] (Note 5) The aforementioned communication unit has multiple communication modes, The control unit may derive the delay time based on the communication delay time in the communication mode used when performing the radiography, among the plurality of communication modes.

[0091] (Note 6) The control unit may acquire a plurality of communication delay times before performing the radiography.

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

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

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

[0095] (Note 10) If the control unit does not receive a response from the radiation generator within a predetermined time in response to the transmission of the signal regarding the cessation of irradiation, it may resend the signal regarding the cessation of irradiation to the radiation generator.

[0096] (Note 11) The control unit determines the start of irradiation using the point in time when the cumulative dose received reaches a predetermined amount as the irradiation start threshold. The control unit may determine the timing for transmitting a signal regarding the cessation of irradiation based on the irradiation time and the irradiation start threshold.

[0097] (Note 12) A sensor unit that detects radiation incident from a radiation generator, A radiation imaging device comprising: a control unit that causes the radiation generator to transmit a signal regarding the cessation of radiation irradiation using the cumulative radiation dose received by the sensor unit, the radiation irradiation time, and the irradiation cessation threshold; The control unit determines the start of irradiation using the point at which the cumulative dose received reaches a predetermined amount as the irradiation start threshold, and determines the timing for transmitting a signal to stop the irradiation based on the irradiation time and the irradiation start threshold. A radiography device characterized by the following features.

[0098] (Note 13) A radiography apparatus described in any one of the items 1 to 12 of the appendix, The radiation generating device has A radiography system characterized by the following features.

[0099] (Note 14) A sensor unit that detects radiation incident from a radiation generator, A control method for a radiation imaging device, comprising: a control unit that causes the radiation generator to transmit a signal regarding the cessation of radiation irradiation using the cumulative radiation dose received by the sensor unit, the radiation irradiation time, and the irradiation cessation threshold; A timing step is performed to measure the irradiation time based on the cumulative dose received. A control method characterized by the following:

[0100] (Note 15) In the timing step, the irradiation time may be measured when the cumulative dose reached reaches a predetermined amount.

[0101] (Note 16) After the timing step, a setting step is performed to set the irradiation stop threshold according to the irradiation time. The setting step may involve setting the irradiation stop threshold based on the target value of the cumulative dose received in radiography and the delay time from the time a signal regarding the cessation of radiation irradiation is transmitted to the radiation generator until the radiation irradiation is stopped in the radiation generator.

[0102] (Note 17) Prior to the setting step, a measurement step is performed to measure the communication delay time in communication with the radiation generator by a communication unit that has multiple communication modes and transmits a signal regarding the cessation of irradiation to the radiation generator. The setting step may also involve deriving the delay time based on the communication delay time in the communication mode used when performing the radiographic imaging, among the multiple communication modes.

[0103] (Note 18) In the setting step described above, the timing for transmitting a signal regarding the cessation of irradiation to the radiation generator may be set based on the irradiation time and the irradiation start threshold.

[0104] (Note 19) A sensor unit that detects radiation incident from a radiation generator, A control method for a radiation imaging device, comprising: a control unit that causes the radiation generator to transmit a signal regarding the cessation of radiation irradiation using the cumulative radiation dose received by the sensor unit, the radiation irradiation time, and the irradiation cessation threshold; A setting step is performed to set the irradiation stop threshold according to the irradiation time, In the setting step, the timing for transmitting a signal regarding the cessation of irradiation to the radiation generator is set based on the irradiation time and the irradiation start threshold. A control method characterized by the following:

[0105] (Note 20) A program for causing a computer to execute the control method described in any one of the appendices 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 Unit

Claims

1. A sensor unit that detects radiation incident from a radiation generator, A radiography apparatus comprising a control unit that transmits a signal regarding the cessation of radiation irradiation using the cumulative radiation dose received by the sensor unit, the radiation irradiation time, and the irradiation cessation threshold, The radiography apparatus is characterized in that, after the cumulative dose received reaches a predetermined amount which is changed by the operator's operation, the control unit transmits a signal regarding the cessation of radiation irradiation based on the irradiation cessation threshold obtained using the irradiation time and the predetermined amount.

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

3. The radiography apparatus according to claim 2, characterized in that the control unit performs control to set the irradiation stop threshold based on the target value of the cumulative dose received in radiography, the irradiation time, and the delay time from the transmission of a signal regarding the cessation of irradiation until the irradiation of the radiation is stopped in the radiation generator.

4. It has a communication unit that transmits a signal regarding the cessation of the irradiation, The control unit derives the delay time based on the communication delay time in the communication between the communication unit and the radiation generator. The radiography apparatus according to claim 3, characterized by the following:

5. The aforementioned communication unit has multiple communication modes, The control unit derives the delay time based on the communication delay time in the communication mode used when performing radiography, among the plurality of communication modes. The radiography apparatus according to claim 4, characterized by the following:

6. The radiography apparatus according to claim 4, characterized in that the control unit acquires a plurality of communication delay times before performing the radiography.

7. The radiography apparatus according to claim 6, characterized in that the control unit derives the delay time based on one of the plurality of communication delay times.

8. The radiography apparatus according to claim 6, characterized in that the control unit derives the delay time based on the average value of some or all of the plurality of communication delay times.

9. The radiography apparatus according to claim 6, characterized in that the control unit derives the delay time based on the minimum value among the plurality of communication delay times.

10. The radiation imaging apparatus according to claim 1, characterized in that the control unit resends the signal to stop irradiation if there is no response from the radiation generator within a predetermined time to the transmission of the signal to stop irradiation.

11. The control unit determines the start of irradiation using the point in time when the cumulative dose received reaches a predetermined amount as the irradiation start threshold. The radiation imaging apparatus according to claim 1, characterized in that the control unit determines the timing for transmitting a signal regarding the cessation of irradiation based on the irradiation time and the irradiation start threshold.

12. A sensor unit that detects radiation incident from a radiation generator, A radiography apparatus comprising a control unit that transmits a signal regarding the cessation of radiation irradiation using the cumulative radiation dose received by the sensor unit, the radiation irradiation time, and the irradiation cessation threshold, The control unit determines the start of irradiation using the point at which the cumulative dose received reaches a predetermined amount that changes due to the operator's actions as the irradiation start threshold, and determines the timing for transmitting a signal to stop the irradiation based on the irradiation time and the irradiation start threshold. A radiography device characterized by the following features.

13. A radiography apparatus according to any one of claims 1 to 12, The radiation generating device has A radiography system characterized by the following features.

14. A sensor unit that detects radiation incident from a radiation generator, A control method for a radiography apparatus comprising: a control unit that transmits a signal regarding the cessation of radiation irradiation using the cumulative radiation dose received by the sensor unit, the radiation irradiation time, and the irradiation cessation threshold; A control method for a radiography apparatus, characterized in that, after the cumulative dose reached reaches a predetermined amount that changes according to the operator's actions, a transmission step is performed to transmit a signal regarding the cessation of radiation irradiation based on the irradiation cessation threshold obtained using the irradiation time and the predetermined amount.

15. A sensor unit that detects radiation incident from a radiation generator, A control method for a radiography apparatus comprising: a control unit that transmits a signal regarding the cessation of radiation irradiation using the cumulative radiation dose received by the sensor unit, the radiation irradiation time, and the irradiation cessation threshold; The following steps are performed: a determination step to determine the start of irradiation, using the point at which the cumulative dose received reaches a predetermined amount that changes due to the operator's actions as the irradiation start threshold; and a determination step to determine the timing for transmitting a signal regarding the cessation of irradiation, based on the irradiation time and the irradiation start threshold. A method for controlling a radiography apparatus, characterized by the following features.

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

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

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