Radiation imaging apparatus and radiation imaging system

Abstract

To provide a radiation imaging apparatus and a radiation imaging system capable of accurately synchronizing an irradiation period by a radiation source and a charge accumulation period by detection of radiation when generating a moving image.SOLUTION: A radiation imaging apparatus that generates a moving image including a plurality of frames by repeatedly executing a storage period for storing electric charges based on radiation emitted from a radiation source and a readout period for reading out the stored electric charges, the radiation imaging apparatus including an output unit that outputs information for radiation emission control by the radiation source based on dose information of the emitted radiation, and an image control unit that directly or indirectly determines at least one of a start timing and an end timing of the readout period in at least one of a current frame based on the acquired dose information and a next frame after the current frame based on the radiation based on the acquired dose information.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a radiographic apparatus and a radiographic system. [Background technology]

[0002] 2. Description of the Related Art Radiography systems that generate radiographic images by detecting radiation that has passed through a subject using a radiation detection element are becoming widespread.

[0003] An example of a radiation imaging device used in such a radiation imaging system is an FPD (Flat Panel Detector). An FPD has a structure in which multiple radiation detection elements are arranged in a matrix. Each radiation detection element is provided with a switch that controls signal readout. When radiation is irradiated from a radiation source onto a subject, charges corresponding to the amount of detected radiation are accumulated in the radiation detection elements. In this state, each switch is individually controlled to sequentially read out charges from each radiation detection element, generating a radiation image.

[0004] Some of these radiation imaging systems are capable of generating moving images. Radiation moving images are generated, for example, by the following process. The radiation source repeatedly irradiates radiation pulses at a predetermined cycle number per unit time over a predetermined period. In parallel with this, the FPD accumulates, for a predetermined period (accumulation period), charges generated in the radiation detection elements of the FPD according to the dose of radiation received through the subject, and then reads out the amount of accumulated charge as a signal value at a predetermined cycle number per unit time, thereby generating frame images (still images) for each unit time based on the amount of accumulated charge. In other words, a radiation moving image is generated by sequentially arranging frame images whose imaging times differ from each other by a pulse cycle.

[0005] In order to generate a radiological video image appropriately, it is necessary to synchronize the irradiation period during which the radiation source irradiates radiation with the charge accumulation period in each radiation detection element of the FPD. As an example of a technique for synchronizing the irradiation period and the accumulation period, Patent Document 1 discloses a technique in which a clock in an X-ray generator and a clock in an image acquisition device are synchronized while radiation is not being irradiated, and the clocks are constantly monitored for any discrepancy between the clocks, and if a discrepancy is detected, the discrepancy is corrected. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-94174 Summary of the Invention [Problem to be solved by the invention]

[0007] When generating a moving image in such a radiation imaging system, a series of radiation irradiations from the radiation generating device to the subject and a process of reading out charges from each radiation detection element are alternately performed. The radiation imaging device can generate a moving image by repeating the operation of performing a readout process after the series of radiation irradiations are completed.

[0008] When generating moving images, it is desirable that the radiation irradiation cycle and radiation irradiation time from the radiation source be constant throughout the series of images. However, there are cases where the irradiation cycle and irradiation time are not constant. In such cases, synchronization between the irradiation period and the accumulation period cannot be achieved, which can result in a deterioration in the quality of the generated moving images.

[0009] The present disclosure aims to provide a radiographic imaging device and a radiographic imaging system that can precisely synchronize the irradiation period of a radiation source and the accumulation period of charge due to radiation detection when generating moving images. [Means for solving the problem]

[0010] A radiographic imaging device according to one aspect of the present disclosure generates a moving image including a plurality of frames by repeatedly executing an accumulation period for accumulating charges based on radiation irradiated from a radiation source and a readout period for reading out the accumulated charges, and includes an output unit that outputs information for controlling irradiation of radiation by the radiation source based on dose information of the irradiated radiation, and an image control unit that directly or indirectly determines, based on the dose information, at least one of the start timing and the end timing of the readout period for at least one of a current frame and a frame following the current frame based on the radiation related to the acquired dose information.

[0011] A radiation imaging system according to one aspect of the present disclosure includes a radiation imaging device having a plurality of radiation detection elements, the radiation imaging device, and a radiation source that starts or ends irradiation of the radiation based on the automatic exposure control. [Effects of the Invention]

[0012] According to the present disclosure, when generating a moving image, the irradiation period by the radiation source and the period of charge accumulation due to radiation detection can be synchronized with high precision. [Brief explanation of the drawings]

[0013] [Figure 1] Block diagram showing the overall configuration of a radiological diagnostic system [Figure 2] Block diagram showing the equivalent circuit of an FPD cassette [Figure 3] A block diagram showing an example of the configuration of a control unit. [Figure 4] FIG. 10 is a diagram for explaining a method for determining the readout start timing by the image control unit; [Figure 5] Block diagram showing the functional configuration of a radiation control device [Figure 6] Figure showing an example of a setting screen for inputting the frame rate or dose per time (tube voltage (kV value), tube current (mA), irradiation time (sec), mAs value, etc.) before imaging. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, each embodiment of the present disclosure will be described with reference to the drawings.

[0015] First Embodiment First, the first embodiment will be described.

[0016] (Configuration of Radiography System 100) 1 is a diagram showing an example of the overall configuration of a radiation imaging system 100 according to an embodiment of the present disclosure. The radiation imaging system 100 is a system for irradiating a subject with radiation to capture a radiation image, and includes a radiation control device 1, a radiation source 2, and an FPD (Flat Panel Detector) cassette 3. The FPD cassette 3 is an example of a radiation imaging device according to the present disclosure.

[0017] In the example shown in FIG. 1, the radiation control device 1 has wheels and is a mobile medical cart. In the example shown in FIG. 1, the radiation imaging system 100 is used by being brought into an operating room, an intensive care unit, a hospital room Rc, or the like. The FPD cassette 3 is placed, for example, between a subject H lying on a bed B and the bed B. The radiation source 2 irradiates radiation under the control of the radiation control device 1. The FPD cassette 3 outputs a detection signal based on the radiation that has passed through the subject. The radiation control device 1 generates a radiation image based on the detection signal.

[0018] The present disclosure is not limited to the embodiment shown in FIG. 1, and each component may be installed in an examination room or the like for use.

[0019] In the present disclosure, the radiation imaging system 100 can generate moving images of the subject H. The radiation imaging system 100 repeatedly irradiates the subject H with pulsed radiation such as X-rays at predetermined time intervals (pulse irradiation) in response to an imaging operation. Here, a moving image is generated by irradiating the FPD cassette 3 with radiation from the radiation source 2 and repeatedly executing an accumulation period in which charge is accumulated in the radiation detection elements of the FPD cassette 3 and a readout period in which the charge accumulated in the radiation detection elements is read out. Each of the multiple images constituting the moving image is referred to as a frame image. One frame image is generated through one accumulation period and one readout period. In this specification, a period including one accumulation period and one readout period may be referred to as a frame (one frame). In other words, one frame is a period corresponding to one frame image.

[0020] Each device constituting the radiation imaging system 100 will be described below.

[0021] (FPD Cassette 3) The FPD cassette 3 is a radiographic imaging device compatible with video imaging. In this embodiment, the FPD cassette 3 is an indirect type imaging device that converts irradiated radiation into light of another wavelength, such as visible light, using a scintillator and obtains image data using a radiation detection element. The present disclosure is not limited to this, and the radiographic imaging device of the present disclosure may also be a direct type imaging device that detects radiation directly using a radiation detection element without using a scintillator.

[0022] Fig. 2 is a block diagram showing an equivalent circuit of the FPD cassette 3. As shown in Fig. 2, the FPD cassette 3 has a plurality of radiation detection elements 7, a scan driver 15, a readout IC 16, a controller 22, a memory 23, a built-in power supply 24, a timer 25, and a wireless communication unit 30.

[0023] A plurality of radiation detection elements 7 are arranged in a matrix on a substrate. Each radiation detection element 7 accumulates an electric charge according to the dose of radiation irradiated thereto. A bias line 9 is connected to each radiation detection element 7. The bias line 9 is connected to a bias power supply 14 via a connection 10. With this structure, a reverse bias voltage is applied to each radiation detection element 7 from the bias power supply 14.

[0024] A thin film transistor (TFT) 8 is connected as a switching element to each radiation detection element 7. The TFT 8 is connected to a signal line 6. Of the radiation detection elements 7 arranged as each radiation detection element 7, some radiation detection elements operate individually as detection elements that detect the amount of incident radiation during the period when exposure control is performed, that is, during radiation irradiation. In this specification, these elements are referred to as dose detection elements. The dose detection values ​​described below are values ​​obtained from the dose detection elements.

[0025] The scan driver 15 has a power supply circuit 15a, a gate driver 15b, and wiring 15c. In the scan driver 15, an on voltage and an off voltage supplied from the power supply circuit 15a via wiring 15c are switched by the gate driver 15b and applied to each of the lines L0 to Lx of the scan lines 5. When an on voltage is applied via the scan line 5, each TFT 8 turns on, and releases the charge accumulated in the radiation detection element 7 to the signal line 6. When an off voltage is applied via the scan line 5, each TFT 8 turns off, and cuts off the electrical connection between the radiation detection element 7 and the signal line 6, causing the charge generated in the radiation detection element 7 to accumulate in the radiation detection element 7. Each radiation detection element 7 (each TFT 8) constitutes a pixel.

[0026] The readout IC 16 reads out the charges emitted from each radiation detection element 7 to the signal line 6. The readout IC 16 has a plurality of readout circuits 17, an amplifier circuit 18, a CDS (Correlated Double Sampling) circuit 19, an A / D converter 20, and a multiplexer 21.

[0027] In the readout process, when electric charges are emitted from the radiation detection elements 7, the amplifier circuit 18 outputs a voltage value corresponding to the amount of electric charges that have flowed into the readout circuit 17 via the signal line 6. The CDS 19 reads out the voltage value output from the amplifier circuit 18 as an analog detection signal and outputs it downstream. The analog detection signals are sequentially sent to the A / D converter 20 via the multiplexer 21. The A / D converter 20 sequentially converts the analog detection signals into digital values. The digital detection signals are sequentially stored in the memory unit 23.

[0028] The control unit 22 is configured by a computer having a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and an input / output interface connected to a bus, or a field programmable gate array (FPGA). The control unit 22 may be configured by a dedicated control circuit. The control unit 22 is connected to a storage unit 23 configured by static RAM (SRAM), synchronous dynamic RAM (SDRAM), NAND flash memory, or the like.

[0029] The control unit 22 controls the operations of the scan driver 15 and the readout circuit 17. This allows the control unit 22 to accumulate charges corresponding to the radiation dose in each radiation detection element 7 and read out the accumulated charges using the readout circuit 17. The control unit 22 determines the start timing of reading out the charges from each radiation detection element 7 based on the dose detection value obtained from a dose detection element that is part of the radiation detection elements 7.

[0030] The configuration of the control section 22 for controlling the operations of the scan driver 15 and the readout circuit 17 will be described later.

[0031] The wireless communication unit 30 performs wireless communication with the radiation control device 1 via the antenna 29 under the control of the control unit 22. Because communication between the radiation control device 1 and the FPD cassette 3 is performed wirelessly, there is no need to connect the radiation control device 1 and the FPD cassette 3 with a cable or the like when capturing a radiation image, which is convenient.

[0032] The wireless communication unit 30 transmits, for example, a detection signal read out by the readout circuit 17 to the radiation control device 1, and transmits a control signal for controlling the radiation source 2 via the radiation control device 1. The wireless communication unit 30 also receives a control signal for operating the FPD cassette 3 from the radiation control device 1.

[0033] The built-in power supply 24 supplies the necessary power to the scan driver 15, the readout circuit 17, the control unit 22, the storage unit 23, the bias power supply 14, and the like.

[0034] The timing device 25 is, for example, a crystal oscillator that oscillates due to the piezoelectric effect. The control unit 22 can measure time with high accuracy based on the number of oscillations of the crystal oscillator. The timing device 25 is an example of a timing device of the present disclosure. Note that in the present disclosure, the timing device is not limited to a crystal oscillator, and may be any device that can measure time with high accuracy.

[0035] Here, the configuration of the control section 22 for controlling the operations of the scan driving section 15 and the readout circuit 17 will be described.

[0036] 3 is a block diagram showing an example of the configuration of the control unit 22. As shown in FIG. 3, the control unit 22 includes a radiation amount detection unit 221, an output unit 222, and an image control unit 223.

[0037] The dose detection unit 221 detects the detected dose value of radiation irradiated from the radiation source 2 toward the FPD cassette 3 during the accumulation period by using detection values ​​read out from some of the multiple radiation detection elements 7. The detected dose value is an example of dose information in the present disclosure. The dose detection unit 221 detects the detected dose value by sampling detection values ​​at two or more different times within one accumulation period, for example. The accumulation period is a period during which radiation is irradiated from the radiation source 2 to the FPD cassette 3 via the subject, and charge is accumulated in the radiation detection elements 7 of the FPD cassette 3.

[0038] The output unit 222 performs automatic exposure control on the radiation source 2 based on the detected dose value. Automatic exposure control refers to controlling the radiation source 2 to irradiate an appropriate amount of radiation for each frame to produce a high-quality radiographic image. Automatic exposure control is an example of irradiation control in the present disclosure. For example, when the detected dose value exceeds a predetermined first threshold, the output unit 222 notifies the radiation control device 1 that the detected dose value has exceeded the first threshold. Automatic exposure control is performed by the radiation control device 1 controlling the radiation source 2 to stop irradiation. Note that the method of automatic exposure control is not limited to the above example. For example, the output unit 222 may periodically transmit the detected dose value to the radiation control device 1, and the radiation control device 1 may compare the detected dose value with a threshold each time and control the radiation source 2 to stop irradiation. Alternatively, the output unit 222 may directly control the radiation source 2 to stop subsequent radiation irradiation without going through the radiation control device 1.

[0039] In the present disclosure, known techniques can be appropriately adopted for the automatic exposure control performed by the output unit 222.

[0040] The image control unit 223 generates control signals for the scan driver 15 and the readout circuit 17 based on the imaging conditions and the detected dose value. More specifically, the control signal that determines the start timing of the readout period for the current frame and subsequent frames includes at least information such as the length of the accumulation period for each frame, the start timing of the readout period, and the length of the readout period. The readout period is a period during which radiation irradiation by the radiation source 2 is stopped and electric charges are read out from each radiation detection element 7 of the FPD cassette 3. In the following description, the start timing of the readout period may be referred to as the readout start timing.

[0041] The present disclosure has a feature in which the image control unit 223 controls the readout start timing in the readout circuit 17 using the dose detection value during the accumulation period that is generated by the dose detection unit 221 for the output unit 222 to automatically control exposure of the radiation source 2. This feature allows the radiation irradiation end timing in the radiation source 2 to be precisely synchronized with the readout start timing in the readout circuit 17. This allows the radiation imaging system 100 to generate high-quality moving radiation images.

[0042] In this way, the image control unit 223 controls the readout circuit 17 and therefore the readout start timing in the FPD cassette 3 using the dose detection value for automatic exposure control, thereby achieving the following effects.

[0043] As a first effect, the period during which accurate synchronization can be maintained—in other words, the available imaging time for generating high-quality moving images—can be extended compared to when the irradiation end timing and the readout start timing are synchronized using a timing device provided in each of the FPD cassette 3 and the radiation source 2. When the irradiation end timing and the readout start timing are synchronized using a timing device provided in each of the FPD cassette 3 and the radiation source 2, the timing devices do not synchronize with each other, resulting in a discrepancy between the timing devices over time. For example, time correction via wireless communication could be considered as a means of correcting the discrepancy between the timing devices of the FPD cassette 3 and the radiation source 2, but because wireless communication itself is affected by the surrounding wireless environment, the wireless communication time becomes an uncertain factor, making it difficult to accurately correct the time. The present disclosure eliminates the need for discrepancy correction, enabling stable synchronization control.

[0044] A second effect is that not only can the image control unit 223 determine the timing to start reading, but also the output unit 222 can automatically control the exposure of the radiation source 2, thereby improving image quality.

[0045] 4 is a diagram illustrating a method for determining the readout start timing by the image control unit 223. FIG. 4A shows the readout start timing T1 for the current frame and the readout start timing T2 for the next frame. FIG. 4B shows an enlarged view of the portion of FIG. 4A related to the current frame. As a result, FIG. 4B shows the relationship between the reference timing at which the dose detection value for the current frame transitions from below the first threshold to above the first threshold, and the readout start timing T1. In this specification, the current frame refers to a frame based on radiation related to the dose detection value detected by the dose detection unit 221.

[0046] The image control unit 223 determines the timing at which the dose detection value transitions from below the first threshold to above the first threshold during the accumulation period of each frame as the reference timing. The image control unit 223 then determines the timing at which the first time has elapsed since the reference timing for the current frame as the readout start timing T1 for the current frame. The first time may be set to an appropriate value based on, for example, the frame rate of the moving image set in advance as an imaging condition. Note that in the example shown in FIG. 4 , the image control unit 223 determines the readout start timing T1 for the current frame, but the present disclosure is not limited to this. For example, the image control unit 223 may use a different determination method to determine only the readout start timing for the first frame immediately after the start of irradiation, and determine the readout start timing T2 for the next frame based on the reference timing for the current frame.

[0047] By appropriately determining at least one of the readout start timings for the current frame and the next frame in this manner, the timing of irradiation by the radiation source 2 and the timing of accumulation in the FPD cassette 3 can be synchronized with high precision.

[0048] Furthermore, if the readout start timing determined by the above-described method is earlier than the start timing based on the frame rate included in the imaging conditions, the image control unit 223 may determine the start timing based on the frame rate as the readout start timing. The start timing based on the frame rate included in the imaging conditions refers to, for example, the timing obtained by adding a period calculated backward from the frame rate, starting from the readout start timing of the previous frame. In this way, the frame rate can be accurately maintained while the timing of irradiation by the radiation source 2 and the timing of accumulation in the FPD cassette 3 are synchronized.

[0049] Furthermore, if the read start timing determined by the above-mentioned method is later than the start timing based on the frame rate included in the shooting conditions, the image control unit 223 may determine the start timing based on the frame rate included in the shooting conditions as the read start timing.

[0050] These determination methods can prevent the generated video from not satisfying the frame rate condition set as the shooting condition.

[0051] As shown in FIG. 2, in the FPD cassette 3, a plurality of radiation detection elements 7 are arranged in a matrix. The image control unit 223 preferably determines the timing at which readout starts for each radiation detection element 7 so that readout starts in order, starting from the radiation detection elements 7 arranged at the ends of the matrix. The reason for this is as follows: Irradiation continues until an appropriate dose is achieved by automatic exposure control, but if a low dose is irradiated, the irradiation time will be longer. In this case, it is expected that the readout period and the irradiation period will overlap. Even in this case, if readout starts in order from the ends of the matrix, image interference will occur at the edges of the image, reducing the influence on the central portion, which is the diagnostic area.

[0052] In the above description, it has been explained that the image control unit 223 determines at least one of the readout start timings of the current frame and the next frame. The present disclosure is not limited to this, and the image control unit 223 may determine the readout end timings of the current frame and the next frame in addition to or instead of the readout start timings. The readout end timings may be determined using a method similar to the method for determining the readout start timings.

[0053] Also, in the above description, the image control unit 223 determines the read start timing for each frame based on the reference timing. For example, instead of acquiring the reference timing for each frame, the image control unit 223 may acquire the reference timing once every few frames, and determine the read start timing for each of those few frames based on the acquired reference timing. Specifically, if the frame for which the reference timing is acquired is the first frame, the image control unit 223 may determine the read start timing Tn for the nth frame using the following formula (1) (n is an integer greater than or equal to 2): Tn=P1+P frame *(n-1) (1) P1 is the first time, P frame is the frame period (the reciprocal of the frame rate, a fixed value).

[0054] The reference timing is obtained by comparing the dose detection value that rises immediately after the start of irradiation with the first threshold, and is therefore susceptible to the influence of noise. By obtaining the reference timing only once every few frames, the influence of noise can be minimized.

[0055] Furthermore, the image control unit 223 may acquire candidate timings that are candidates for the reference timing for each frame by comparing the detected dose value with the first threshold, and then determine whether or not to use the candidate timings as the reference timing. Specifically, if the elapsed time from the reference timing of the previous frame to the candidate timing of the current frame is a value that is significantly different from the frame period, the image control unit 223 may not use the candidate timing as the reference timing of the current frame. In this case, the image control unit 223 may set the timing at which a frame period has elapsed since the reference timing of the previous frame as the reference timing of the current frame. In this case, the influence of noise can also be minimized.

[0056] Here, the image control unit 223 may determine the reference timing of the current frame based on the reference timing and frame period of two or more previous frames. For example, data regarding the reference timing of multiple past frames may be stored, and statistical information based on the data may be used to determine whether to use the candidate timing of the current frame as the reference timing. Alternatively, the image control unit 223 may use the reference timing of multiple past frames to derive the time difference between the reference timings of adjacent frames as the frame period, calculate the average and variation (variance, standard deviation, etc.) of the derived multiple frame periods, and determine whether to use the candidate timing as the reference timing based on whether the absolute value of the difference between the newly acquired frame period and the average frame period exceeds a predetermined value. In this case, the image control unit 223 may not use the candidate timing as the reference timing if the difference exceeds the predetermined value. The predetermined value may be a fixed value, or a variation value of the frame period, such as the standard deviation σ × 0.5.

[0057] Also, in the above description, the image control unit 223 directly determines the readout start timing based on the reference timing and the first time. In the present disclosure, instead of directly determining the readout timing in this manner, the image control unit 223 may indirectly determine the readout start timing. The method of indirectly determining the readout start timing is useful, for example, when other processing (such as processing for acquiring some kind of correction value) is performed between the start of accumulation and readout of each frame. This is because there are cases in which it is necessary to shift the readout start timing to match the time required for that processing.

[0058] An example of a method in which the image control unit 223 indirectly determines the readout start timing is to first determine the end timing of the readout period of the previous frame, the start timing of correction value acquisition, or the start or end timing of the accumulation period before or after the readout period, and then indirectly determine the readout start timing based on this. Specifically, for example, the reference timing may be a time period after the determined timing. Because the end timing of the readout period of the previous frame, the start timing of correction value acquisition, or the start or end timing of the accumulation period before or after the readout period are known at the time of imaging, such a determination method can also accurately determine the readout start timing, and essentially enable radiation irradiation and the accumulation period to be synchronized with high precision.

[0059] (Radiation control device) The radiation control device 1 is a device that controls the radiation source 2 and the FPD cassette 3. Figure 5 is a block diagram showing the functional configuration of the radiation control device 1. The radiation control device 1 includes a control unit 101, an operation unit 102, a display unit 103, a storage unit 104, a drive unit 105, and a wireless communication unit 106.

[0060] The control unit 101 is composed of a CPU, a ROM, a RAM, etc. In response to an operation by an operator via the operation unit 102, the CPU of the control unit 101 reads out a system program and various processing programs stored in the ROM, loads them into the RAM, and controls the operation of each unit of the radiation control device 1 in accordance with the loaded programs. The operator is a person who intends to generate a radiographic image of a subject using the radiation imaging system 100, such as a radiographer or a doctor.

[0061] The operation unit 102 includes various buttons, a keyboard, a mouse, a trackball, a touchpad, etc. The operation unit 102 accepts an operation by an operator and outputs operation information.

[0062] The display unit 103 is a display such as an LCD (Liquid Crystal Display), a CRT (Cathode Ray Tube), or an organic EL display. The display unit 103 is an example of the notification unit of the present disclosure. Note that the notification unit of the present disclosure may include not only a display unit but also an audio sound device such as a speaker or earphones.

[0063] The storage unit 104 is configured by a non-volatile semiconductor memory, a hard disk, etc. The storage unit 104 stores programs and parameters required for the operation of each component of the radiation control device 1, or data related to various processes executed in the radiation imaging system 100, etc.

[0064] The driving unit 105 is a circuit that drives the tube of the radiation source 2. The driving unit 105 and the radiation source 2 are connected by wire, for example, via a cable. The wireless communication unit 106 communicates with the FPD cassette 3 by wireless communication.

[0065] The control unit 101 controls the radiation source 2 and the FPD cassette 3 based on imaging conditions set in response to operations by an operator.

[0066] The imaging conditions are conditions set by the operator based on the tissue of the subject to be imaged, etc. The imaging conditions are, for example, the radiation dose per time and the frame rate of the moving image. The radiation dose per time is, for example, the tube voltage (kV value), tube current (mA), irradiation time (sec), mAs value, etc. The frame rate of the moving image is a value indicating how many frame images the moving image generated by the radiation imaging system 100 contains per unit time (for example, 1 second).

[0067] <Second embodiment> A second embodiment of the present disclosure will now be described. In the second embodiment, the dose detection unit 221 of the FPD cassette 3 can change the cycle at which the detection values ​​detected by each radiation detection element 7 during the accumulation period are sampled. Except for this, the configuration and operation of each device of the radiation imaging system 100 in the second embodiment are the same as those described in the first embodiment.

[0068] When detecting the dose of radiation irradiated from a radiation source, if the irradiated radiation is relatively weak, shortening the sampling period for the detected value increases the proportion of noise contained in the detected value detected by the dose detection element. This is because the number of samplings required to reach the first threshold for determining the dose detection value increases as the detected value per sampling decreases, thereby increasing the number of times noise components are superimposed on the detected value. In this case, errors occur in the detected value detected by the dose detection element, and the reference timing for determining the readout start timing also becomes inaccurate, which can reduce the accuracy of synchronization between the radiation irradiation and the accumulation period.

[0069] On the other hand, if the irradiated radiation is relatively strong, extending the sampling period for the detection value increases the amount of change in the detection value per sampling, and the detection value may instantaneously exceed the first threshold for determining the dose detection value. In this case, an error occurs in the reference timing for determining the readout start timing by the time interval of the sampling period, which may reduce synchronization accuracy.

[0070] In the second embodiment, the dose detection unit 221 determines whether the radiation emitted by the radiation source 2 is weaker or stronger than a predetermined second threshold based on the mAs value included in the imaging conditions. The second threshold used by the dose detection unit 221 for this determination is different from the first threshold used to determine the dose detection value for determining the readout start timing. If the dose detection unit 221 determines that the radiation emitted by the radiation source 2 is weaker than the second threshold, it sets the cycle for sampling the detection values ​​to a relatively long first cycle. On the other hand, if the dose detection unit 221 determines that the radiation emitted by the radiation source 2 is stronger than the second threshold, it sets the cycle for sampling the detection values ​​to a relatively short second cycle. This enables appropriate sampling to be performed based on the mAs value set in the imaging conditions, reduces errors in the reference timing for determining the readout start timing, and prevents a decrease in synchronization accuracy.

[0071] <Third embodiment> A third embodiment of the present disclosure will now be described. In the third embodiment, the image control unit 223 can determine the readout start timing of the FPD cassette 3 using one of two different determination methods. Except for this, the configuration and operation of each device of the radiation imaging system 100 in the third embodiment are the same as those described in the first or second embodiment.

[0072] The first determination method is a method of determining the readout start timing for the current frame and subsequent frames based on a reference timing determined by a detected dose value, as described in the first embodiment.

[0073] The second determination method is a method of determining the readout start timing based on the timing device 25 mounted on the FPD cassette 3. In the second determination method, the image control unit 223 determines the timing regardless of the dose detection value detected by the dose detection unit 221.

[0074] When capturing moving images, the radiation irradiated each time is much lower than when capturing still images. Therefore, when capturing extremely low doses, it may be difficult for the dose detection unit 221 to accurately detect the dose detection value during the accumulation period. If the dose detection value cannot be accurately detected, even if the FPD cassette 3 is controlled at the readout start timing using the first determination method, the desired accuracy in synchronization of radiation irradiation and the accumulation period may not be achieved, and moving images with good image quality may not be generated.

[0075] For this reason, in the third embodiment, when the mAs value included in the imaging conditions is smaller than a predetermined third threshold (different from the first and second thresholds), the image control unit 223 determines the timing to start readout and accumulation using a highly accurate timing device 25 (see FIG. 2) mounted on the FPD cassette 3. This makes it possible to select an appropriate method to synchronize the radiation irradiation and accumulation period, even when imaging is performed with an extremely low dose of radiation irradiated by the radiation source 2.

[0076] In the third embodiment, the display unit 103 may notify the operator which determination method is used to determine the readout start timing. In the second determination method, it is assumed that, over time, a difference will occur between the timing device 25 of the FPD cassette 3 and the timing device provided in the radiation source 2. If the difference exceeds an allowable range, synchronization between the irradiation of radiation and the accumulation period will be lost, and imaging will not be achieved (no diagnostic image will be obtained). For this reason, the operator may be notified of the available imaging time, which is calculated in advance before imaging starts based on the accuracy of the timing device, along with the selected determination method.

[0077] In the third embodiment, at least one of the frame rate and the mAs value may be changeable before imaging in response to an operator's operation via the operation unit 102 (see FIG. 5) of the radiation control device 1. In this case, the method for determining whether at least one of the frame rate and the mAs value has been changed and the imaging available time may be notified before imaging.

[0078] 6A and 6B are diagrams showing examples of the display screen of the display unit 103 when a change to the frame rate or mAs value is accepted before shooting. As shown in Fig. 6A, the change acceptance screen 400 has an mAs value change field 401 and a frame rate change field 402.

[0079] Fig. 6B shows an example of a screen that appears when the operator attempts to change the mAs value. When the operator selects mAs value change field 401, in the example shown in Fig. 6B, mAs value change candidate field 403 is displayed adjacent to mAs value change field 401. Acceptable change value candidates are displayed side by side in mAs value change candidate field 403.

[0080] 6B, a determination method suggestion field 404 is displayed adjacent to the mAs value change candidate field 403. The determination method suggestion field 404 displays the determination method when each of the change candidate values ​​listed in the mAs value change candidate field 403 is selected. In the example shown in FIG. 6B, the determination method suggestion field 404 also displays, in addition to the determination method, the available shooting time when each of the change candidate values ​​listed in the mAs value change candidate field 403 is selected. This allows the operator to easily obtain the information necessary to select a mAs value.

[0081] The example shown in Fig. 6C shows an example of a screen when an operator attempts to change the frame rate. When the operator selects frame rate change field 402, in the example shown in Fig. 6C, a frame rate change candidate field 405 is displayed adjacent to frame rate change field 402. Candidates for acceptable change values ​​are displayed side by side in frame rate change candidate field 405.

[0082] 6C, a determination method suggestion field 406 is displayed adjacent to the frame rate change candidate field 405. The determination method suggestion field 406 displays the determination method when each of the change candidate values ​​listed in the frame rate change candidate field 405 is selected. In the example shown in FIG. 6C, the determination method suggestion field 406 also displays the available shooting time when each of the change candidate values ​​listed in the frame rate change candidate field 405 is selected, along with the determination method. This allows the operator to easily obtain the information necessary to select a frame rate.

[0083] In the present disclosure, the notification of the determination method and the available imaging time may be made by other methods than displaying them on the display unit 103 as shown in FIG. 6. For example, a display having a plurality of LEDs arranged in a row may be used, and the display may become shorter as time passes from the start of imaging and the available imaging time becomes shorter. Alternatively, the available imaging time may be notified by the interval at which the LED display blinks. Alternatively, the available imaging time may be notified by audio. Such an embodiment is useful, for example, when the radiation control device 1 is configured as a medical cart and there is no space available to install a display device.

[0084] Although the above describes each embodiment of the present disclosure, these embodiments are merely examples of the present disclosure and do not limit the scope of the present disclosure. The present disclosure can be embodied in various forms other than the above-described embodiments, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents set forth in the claims. [Explanation of symbols]

[0085] 100 Radiography System 1. Radiation control equipment 101 Control section 102 Operation section 103 Display section 104 Storage section 105 Drive unit 106 Radio Communication Department 109 Dose detection unit 110 Exposure control unit 111 Image control unit 2 Radiation source 3 FPD cassette 5 scan lines 6 Signal Line 7 Radiation detection elements 9 Bias wire 10 Wiring 14 Bias power supply 15 Scanning driver 15a power circuit 15b Gate Driver 15c wiring 17 Readout circuit 18 Amplification circuit 20 A / D converter 21 Multiplexer 22 Control Unit 23 Memory section 24 Built-in power supply 25 Timing device 29 Antenna 30 Wireless Communication Department

Claims

1. A radiographic imaging apparatus that generates a moving image including a plurality of frames by repeatedly executing an accumulation period in which charges based on radiation irradiated from a radiation source are accumulated and a readout period in which the accumulated charges are read out, an output unit that outputs information for controlling irradiation of radiation by the radiation source based on dose information of the irradiated radiation; an image control unit that directly or indirectly determines, based on the dose information, at least one of a start timing and an end timing of the readout period in at least one of a current frame based on radiation related to the acquired dose information and a frame subsequent to the current frame; A radiographic imaging device comprising:

2. When the start timing of the determined readout period is later than a start timing based on a preset frame rate, the image control unit controls to immediately start readout at the start timing based on the frame rate, or to start readout when the start timing of the determined readout period does not occur within a certain time. The radiographic apparatus according to claim 1 .

3. When the determined start timing of the readout period is earlier than a start timing based on a preset frame rate, the image control unit controls the readout to start at the start timing based on the frame rate. The radiographic apparatus according to claim 1 .

4. the plurality of radiation detection elements are arranged in a matrix, the image control unit determines at least one of the start timing and the end timing of the readout for each of the radiation detection elements so that the readout is started in order from the radiation detection elements arranged at an end of the matrix. The radiographic apparatus according to claim 1 .

5. the image control unit determines at least one of the start timing and the end timing of the readout period based on the dose information. The radiographic apparatus according to claim 1 .

6. a dose detection unit that detects the radiation irradiated to the radiation imaging apparatus based on detection values ​​of at least a portion of the radiation detection elements during the accumulation period and outputs a dose detection value as the dose information; The radiographic imaging apparatus according to claim 5 .

7. the image control unit determines at least one of the start timing and the end timing of the readout period based on a reference timing at which the radiation amount detection value transitions from a predetermined first threshold value or less to a predetermined first threshold value or more. The radiographic imaging apparatus according to claim 6 .

8. the dose detection unit generates the dose detection value by sampling the radiation detection value at two or more different times within the accumulation period; The radiographic imaging apparatus according to claim 7 .

9. the dose detection unit changes a period for sampling the detection value based on a predetermined second threshold value that is set in advance; The radiographic imaging apparatus according to claim 8 .

10. The first threshold value and the second threshold value are different values. The radiographic apparatus according to claim 9 .

11. the image control unit determines at least one of the start timing and the end timing of the readout period based on an end timing of a readout period of a frame immediately before the current frame, a start timing of acquisition of a correction value in the current frame, or a start timing or an end timing of an accumulation period before or after the readout period in the current frame. The radiographic imaging apparatus according to claim 6 .

12. The image control unit a first determination method for determining at least one of the start timing and the end timing of the readout period in at least one of the current frame and the next frame based on the dose detection value; or a second determination method for determining a start timing or an end timing of at least one of the readout period and the accumulation time based on a timing device installed in the radiation imaging apparatus; which of the above is to be used is set based on the preset photographing conditions. The radiographic apparatus according to claim 1 .

13. The imaging condition is a dose per time set in the radiation source. The radiographic imaging apparatus according to claim 12.

14. a notification unit configured to notify a time during which the moving image can be captured using the second determination method when the image control unit determines to use the second determination method; The radiographic imaging apparatus according to claim 13.

15. further comprising an operation unit that accepts a change of at least one of a frame rate or the dose per time, the notification unit notifies the available imaging time according to at least one of the frame rate or the dose per hour changed in the operation unit. The radiographic apparatus according to claim 14.

16. a radiation imaging device having a plurality of radiation detection elements; The radiographic imaging apparatus according to claim 1 ; a radiation source that starts or stops irradiating the radiation based on the automatic exposure control; A radiography system comprising:

Images