JP7626178B2 - Radiography system and radiation photography method - Google Patents

Description

The present invention relates to a radiography system and a radiography method.

To capture images using an imaging device, it is necessary to match the exposure timing of the radiation control device with the readout timing of the imaging device. In continuous imaging (hereinafter referred to as serial imaging) that generates multiple frames of images in accordance with pulse irradiation, the shorter the interval between frames, the shorter the accumulation period of the imaging device becomes, so high-precision control of the irradiation timing and readout timing (on the order of several ms to several hundred μs in some cases) is required.
Timing synchronization is generally achieved by exchanging timing information related to exposure and readout between the imaging device and the radiation control device. When the communication between the radiation control device and the imaging device is wired communication using a dedicated line, it has the advantage of enabling highly accurate timing control, but it has the disadvantage that it is difficult to handle the imaging device when it is placed directly under the patient to take images.
Therefore, there is a demand for wireless imaging devices. However, when the communication method between the radiation control device and the imaging device uses a wireless communication standard that employs best-effort arbitration using the CSMA/CA method, such as IEEE802.11, the adjustment time for packet transmission is variable, resulting in variations in communication delays and making it difficult to achieve high-precision timing control.
In order to address these issues, the following technologies have been proposed:

Patent Document 1 describes an imaging system that includes an imaging device that starts reading when a first counter, which is reset in response to a beacon signal of a wireless communication standard and restarts counting, reaches a specified time, and a radiation control device that instructs the start of exposure when a second counter, which is reset in response to the beacon signal and restarts counting, reaches a specified time.
Furthermore, Patent Document 1 also describes that in wireless communication standards that use best-effort arbitration using the CSMA/CA method, such as IEEE802.11, there can be a discrepancy in the timing of beacon transmission, which can cause a problem of not being able to emit and read out at the desired timing. It also describes how this discrepancy in the timing of beacon transmission can be prevented by stopping wireless communication of the system itself when a beacon signal is transmitted.

Patent Document 2 describes an imaging system that includes a radiation control device that instructs the start of exposure when a first timing means reaches a predetermined time, and an imaging device that starts readout when a second timing means reaches a predetermined time, where the timing of exposure and readout is matched by synchronizing the time of the first timing means with the time of the second timing means.
In still image capture, a method in which the readout timing is determined based on the timing of irradiation detection by a radiation sensor is widely used.

JP 2009-186439 A JP 2010-081960 A

The technology described in Patent Document 1 claims that the variation in communication delay of the beacon signal can be prevented by stopping the wireless communication of the system when the beacon signal is transmitted. However, the communication standard IEEE802.11 adopted in the technology described in Patent Document 1 is adopted in a large number of devices. In addition, the number of devices that function as parent devices is increasing due to the spread of tethering. For this reason, wireless communication that the system cannot control occurs at various times around the imaging system described in Patent Document 1, and the variation in communication delay of the beacon signal cannot be prevented by simply stopping the wireless communication of the system, making it difficult to control exposure at a stable timing.
In other words, the synchronization control by the imaging system described in Patent Document 1 cannot withstand a typical wireless communication environment.

Furthermore, the technology described in Patent Document 2 synchronizes the time of a first timing means of the imaging device and a second timing means of the radiation control device, and starts exposure and readout using the time of each timing means. Therefore, as long as the accuracy of time synchronization is maintained sufficiently high, it is possible to coordinate the timing of exposure and readout.
However, if an abnormality occurs in the time synchronization function while a series of exposures and readouts are being repeated (for example, in a configuration in which the first and second timing means are synchronized with the time held by a third device other than the radiation control device and the imaging device, the third device is turned off or restarted, causing a sudden change in time), the accuracy of the time synchronization will decrease, the timing of the exposures and readouts will not match, and imaging will not be successful.

In still image capture, a method is widely used in which the readout timing is determined from the timing of irradiation detection by a radiation sensor, but if the radiation dose reaching the radiation sensor is low, it may not be detected or may take a long time to detect (for example, about 10 ms from the start of irradiation to detection).Since many images are captured in serial imaging, the dose per frame is often kept lower than the dose for one still image, and it is difficult to achieve the required timing accuracy with a method using a radiation sensor.
On the other hand, it is possible to adopt a highly sensitive radiation sensor, but the higher the sensitivity of the radiation sensor, the more expensive it becomes, which increases the manufacturing cost of the imaging system.

The present invention was made in consideration of the above problems, and aims to enable stable serial imaging in a radiation imaging system that uses multiple timing means to synchronize a radiation irradiation device and a radiation imaging device.

In order to solve the above problems, the radiation imaging system according to the present invention comprises:
a radiation control device for controlling radiation irradiation by the radiation irradiation device;
a radiation imaging apparatus capable of synchronizing with the radiation irradiation by a plurality of synchronization methods;
An imaging method selection means for selecting an imaging method;
a synchronization method selection means for selecting the synchronization method based on the photographing method selected by the photographing method selection means,
the radiation imaging apparatus includes a detection unit that detects a connection state of a wired cable;
the imaging method selection means selects wired serial imaging for generating one or more radiation images through wired communication between the radiation irradiation device and the radiation imaging device when the wired cable is connected, and selects wireless serial imaging for generating one or more radiation images through wireless communication between the radiation irradiation device and the radiation imaging device when the wired cable is not connected ;
The synchronization method includes a first synchronization method for synchronizing based on at least clock information from a first clock unit included in the radiation control apparatus and clock information from a second clock unit included in the radiation imaging apparatus.
The radiation imaging method according to the present invention further comprises:
a radiation control device for controlling radiation irradiation by the radiation irradiation device;
a radiation imaging apparatus capable of synchronizing with the radiation irradiation by a plurality of synchronization methods,
selecting a shooting method;
selecting a plurality of synchronization methods for synchronizing radiation irradiation by a radiation irradiation device and a radiation imaging device based on the selected imaging method,
the radiation imaging apparatus includes a detection unit that detects a connection state of a wired cable;
the step of selecting the imaging method selects wired serial imaging in which one or more radiation images are generated by wired communication between the radiation irradiation device and the radiation imaging device when the wired cable is connected, and selects wireless serial imaging in which one or more radiation images are generated by wireless communication between the radiation irradiation device and the radiation imaging device when the wired cable is not connected;
The synchronization method includes a first synchronization method for synchronizing based on at least clock information from a first clock unit included in the radiation control apparatus and clock information from a second clock unit included in the radiation imaging apparatus .

According to the present invention, wireless serial photography can be performed stably.

1 is a block diagram showing a configuration of a radiation imaging system according to an embodiment of the present invention. 2 is a block diagram showing a specific configuration of a radiation control device provided in the radiation imaging system of FIG. 1 . 2 is a block diagram showing a specific configuration of a radiation imaging apparatus included in the radiation imaging system of FIG. 1 . 2 is a block diagram illustrating an example of a configuration of an access point included in the radiation imaging system of FIG. 1 . FIG. 11 is a block diagram illustrating another configuration of the radiation imaging system according to the embodiment. 2 is a timing chart illustrating an example of the operation of the radiation imaging system of FIG. 1 . 10 is a timing chart showing another example of the operation of the radiation imaging system of FIG. 1 . 2 is a block diagram showing the configuration of a radiation imaging system according to an associated technology. 9 is a block diagram showing a specific configuration of a radiation control device provided in the radiation imaging system of FIG. 8 . 9 is a block diagram showing a specific configuration of a radiation imaging apparatus included in the radiation imaging system of FIG. 8 . 9 is a timing chart showing a basic operation of the radiation imaging system of FIG. 8 . 9A to 9C are diagrams showing time information of each timer when the photographing system of FIG. 8 is operating. FIG. 11 is a block diagram showing a functional configuration of the radiation imaging apparatus of FIG. 10 . FIG. 10 is a block diagram showing a functional configuration of the radiation control device of FIG. 9 . 11 is a timing chart showing the operation of the radiation control device in FIG. 9 or the radiation imaging apparatus in FIG. 10 . 11 is a timing chart showing the operation of the radiation control device in FIG. 9 or the radiation imaging apparatus in FIG. 10 . 11 is a timing chart showing the operation of the radiation control device in FIG. 9 or the radiation imaging apparatus in FIG. 10 . 9 is a block diagram showing another configuration of the radiation imaging apparatus included in the radiation imaging system of FIG. 8 . 20 is a timing chart showing the operation of a radiation imaging system including the radiation imaging apparatus of FIG. 18. 9 is a block diagram showing another configuration of the radiation imaging apparatus included in the radiation imaging system of FIG. 8 . 21 is a timing chart showing the operation of a radiation imaging system including the radiation imaging apparatus of FIG. 20. FIG. 1 is a block diagram illustrating a configuration of a radiation imaging system according to an embodiment 1-1. FIG. 1 is a block diagram illustrating a configuration of a radiation imaging system according to an embodiment 1-2. FIG. 1 is a block diagram illustrating a configuration of a radiation imaging system according to an embodiment 1-3. FIG. 1 is a block diagram illustrating a configuration of a radiation imaging system according to an embodiment 1-4. FIG. 11 is a block diagram illustrating a configuration of a radiation imaging system according to an embodiment 1-5. FIG. 11 is a block diagram showing a configuration of a radiation imaging system according to an embodiment 1-6. FIG. 11 is a block diagram illustrating a configuration of a radiation imaging system according to an embodiment 1-7. 1 is a block diagram showing a specific configuration of a radiation imaging device included in a radiation imaging system according to an embodiment 1-8. 24 is a timing chart showing the operation of a radiation imaging system including the radiation imaging apparatus of FIG. 23 . 11 is a timing chart showing the operation of a radiation imaging system according to Example 1-9. 11 is a timing chart showing the operation of a radiation imaging system according to Example 1-11. 11 is a flowchart showing the operation of a radiation imaging system according to Example 2-1. 13 is a flowchart showing the operation of a radiation imaging system according to Example 2-2. 13 is a flowchart showing the operation of a radiation imaging system according to Example 2-3. 13 is a flowchart showing the operation of a radiation imaging system according to Example 2-4. FIG. 13 is a perspective view of a radiation imaging device provided in a radiation imaging system according to Example 2-5. 13 is a graph showing the operation of the radiation imaging system according to Example 3-1. 13 is a graph showing the operation of a radiation imaging system according to Example 3-2. 13 is a graph showing the operation of a radiation imaging system according to Example 3-3. 13 is a graph showing the operation of the radiation imaging system according to Example 4-1. 13 is a graph showing the operation of a radiation imaging system according to Example 4-2. 13 is a flowchart showing the operation of a radiation imaging system according to Example 4-3. 13 is a graph showing the operation of the radiation imaging system according to Example 5-1. 5A is a graph showing the relationship between temperature and clocking speed, and FIG. 5B is a graph showing the operation of the radiation imaging system according to the embodiment 5-3 of the first and second aspects of the present invention. 13 is a flowchart showing the operation of a radiation imaging system according to Example 6-2. 13 is a flowchart showing the operation of a radiation imaging system according to Example 6-3. 13 is a flowchart showing the operation of a radiation imaging system according to Example 6-4. 13 is a flowchart showing the operation of a radiation imaging system according to Example 6-5. 13 is a flowchart showing the operation of a radiation imaging system according to Example 6-6. 11 is a flowchart showing the operation of a radiation imaging system according to Example 7-1. 13 is a flowchart showing the operation of a radiation imaging system according to Example 7-2. 13 is a flowchart showing the operation of a radiation imaging system according to Example 7-3. 11 is a flowchart showing the operation of a radiation imaging system according to Example 9-1. 13 is a flowchart showing the operation of a radiation imaging system according to Example 9-2. FIG. 11 is a block diagram showing a configuration of a radiation imaging system according to an embodiment 11-1. FIG. 11 is a block diagram showing a configuration of a radiation imaging system according to an embodiment 11-2. FIG. 11 is a block diagram showing a configuration of a radiation imaging system according to an embodiment 11-3.

The following describes an embodiment of the present invention with reference to the drawings. However, the technical scope of the present invention is not limited to the examples shown in the drawings.

[Configuration of Radiation Imaging System]
First, an outline of a radiation imaging system according to the present embodiment (hereinafter, referred to as an imaging system 100) will be described.

As shown in FIG. 1, the imaging system 100 of this embodiment is configured to include a radiation irradiation device (hereinafter referred to as irradiation device 1), an access point (hereinafter referred to as AP2), one or more radiation imaging devices (hereinafter referred to as imaging device 3), and a console 14.
The irradiation device 1 and the AP 2, and the AP 2 and the photographing device 3 are capable of communicating with each other. That is, the irradiation device 1 and the photographing device 3 are capable of communicating with each other via the AP 2.
In addition, the imaging system 100 is capable of communicating with a Radiology Information System (RIS) and a Picture Archiving and Communication System (PACS), neither of which are shown.

The irradiation device 1 generates radiation (such as X-rays) and irradiates the radiation R to the subject S and the imaging device 3 arranged behind it, and is composed of a radiation control device (hereinafter referred to as control device 12), a radiation tube (hereinafter referred to as tube 13), etc.

The control device 12 applies a voltage to the tube 13 according to preset radiation irradiation conditions, based on an exposure start operation by a user.
The specific configuration of the control device 12 will be described later.

When a voltage is applied to the tube 13 by the control device 12, the tube 13 generates radiation R of a dose corresponding to the voltage for the duration that the voltage is applied.
That is, the tube 13 is configured to irradiate radiation R continuously when a voltage is applied continuously from the control device 12, and to irradiate radiation R in a pulsed manner when a pulsed voltage is applied.

The console 14 is configured by a PC, a mobile terminal, or a dedicated device.
Furthermore, the console 14 is capable of performing various types of image processing on the received image data as necessary.
The console 14 also has a display unit (not shown) that is capable of displaying a radiation image based on image data.

The console 14 is also capable of setting a photography mode.
In this embodiment, there are two types of shooting modes, a still image shooting mode and a serial shooting mode, and it is possible to select either one of them.
The still image capture mode is an capture mode in which radiation R is irradiated only once for a time duration set in the irradiation conditions in response to a single exposure start operation, thereby generating one radiation image.
The serial imaging mode is an imaging mode in which, in response to a single exposure start operation, pulsed radiation R having a time width set in the irradiation conditions is irradiated one or more times to generate one or more radiation images.
Furthermore, when serial photography is set as the photography mode, the console 14 is capable of setting a frame rate. The frame rate may be any value input by the user, or may be selected from a number of options (e.g., 15 frames/s (hereinafter referred to as fps), 7.5 fps, 30 fps, etc.).

The AP 2 includes a communication unit and relays communication between the irradiation device 1 and the imaging device 3 .
The communication unit includes an antenna and a connector, and is capable of performing both wired and wireless communication.
The communication unit is also configured to repeatedly transmit a beacon to the irradiation device 1 and the imaging device 3 at a predetermined cycle.
The AP 2 may be built into the irradiation device 1 or the imaging device 3, rather than being provided separately from the irradiation device 1 or the imaging device 3.

The imaging device 3 receives radiation R from the irradiation device 1 and generates image data.
The photographing device 3 will be described in detail later.

The imaging system 100 of this embodiment configured as described above is capable of performing radiography of a subject S placed in front of the imaging device 3 by irradiating radiation R from the irradiation device 1 to the subject S.
If the imaging mode on the console 14 is set to a still image imaging mode, a single still image is obtained, whereas if the imaging mode is set to a serial imaging mode, a dynamic image consisting of a series of multiple images is obtained.
Hereinafter, a series of a plurality of images obtained by serial photography will be referred to as a dynamic image, and each image constituting the dynamic image will be referred to as a frame image.

In addition, FIG. 1 illustrates the photographing system 100 in which the AP 2 and the irradiation device 1, and the AP 2 and the photographing device 3 both perform wireless communication. However, the photographing system 100 according to this embodiment may be configured so that at least one of the timing information source devices 2, 4 and the irradiation device 1, and the timing information source devices 2, 4 and the photographing device 3 communicate wirelessly. For example, as shown in FIG. 8, the AP 2 and the irradiation device 1 may be connected by wire.
In this way, the synchronization accuracy between the control device 12 and AP2 can be maintained at a sufficiently high level, so there is no need to give the control device 12 the function of switching operating modes, and the control device 12 can be manufactured at low cost.
It is also possible to change the IF of the photographing device 3 from wireless communication to wired communication, and further to connect the AP 2 and the photographing device 3 with a dedicated line.
In this way, it becomes unnecessary to provide the photographing device 3 with a function for switching between operation modes.

The imaging system 100 of this embodiment configured in this way can be installed and used in, for example, an imaging room in a hospital, or can be used as a mobile system by configuring the irradiation device 1 as a wheeled medical cart. If it is mobile, it can be moved to the location of a subject S (subject S) who has difficulty moving around and can capture a radiation image.

For example, when performing imaging using an imaging stand installed in an imaging room in a hospital, a wired cable can be connected to the imaging device 3 installed on the imaging stand to transmit and receive information between the irradiation device 1 and the imaging device 3, and to supply power to the imaging device 3, etc.
For example, when a wired cable is used to connect to the imaging device 3, a pulse signal or a timing signal can be included in the signal of the wired cable, so that the timing of the irradiation device 1 and the imaging device 3 can be synchronized to capture images.
However, even when taking pictures in a radiography room, there are cases where the patient must be in a wheelchair or bed. In such cases, if the radiography device 3 is connected to a wired cable,
- The cables get in the way - There is a risk that the cables will come loose and cause communication to become impossible - There are hygiene issues as the cables come into contact with the subject, so there was a demand for imaging that does not use wired cables.

When imaging is performed using a mobile cart, imaging is performed in the ward where the subject is recuperating. In this case, imaging is performed in the bed where the subject is lying down, and it is necessary to place a radiography device between the subject and the bed to perform imaging. Therefore, there are problems such as the cable being in the way, the risk of the cable coming loose and causing communication failure, and hygiene issues as the cable comes into contact with the subject, more than in the case of the imaging room described above, and there has been a demand for imaging without using wired cables.
In particular, in radiography using CR prior to the advent of radiation imaging devices using FPDs, no wired cables were required during imaging, and there was a demand for imaging without using wired cables in order to obtain the same ease of operation as with a CR.
However, by using the imaging system 100 according to this embodiment, a medical examination cart that meets such needs can be constructed.

[Configuration of Radiation Control Device]
Next, a specific configuration of the control device 12 provided in the irradiation device 1 will be described.

As shown in FIG. 2, the control device 12 according to this embodiment includes a radiation control unit 121, a high voltage generating unit 122, a memory unit 123, a communication unit 124, an irradiation side timing unit 125, a second irradiation side timing unit 126, a display unit 127, an operation unit 15, etc.

The radiation control unit 121 is capable of setting various imaging conditions (conditions related to the subject S, such as the part to be imaged and physique, and conditions related to radiation irradiation, such as tube voltage, tube current, irradiation time, and current-time product) based on control signals from the console 14 or the operation panel 15. Then, based on receiving an imaging start signal from the exposure switch 15a, it is configured to transmit control information to the high-voltage generating unit 122 to instruct it to start applying voltage (irradiating radiation).

The memory unit 123 is composed of a static RAM (SRAM), a synchronous DRAM (SDRAM), a NAND type flash memory, a hard disk drive (HDD), etc.

The communication unit 124 is a communication means in the present invention, and includes an antenna and a connector for communicating with the outside.
The communication unit 36 can select whether to perform wireless communication or wired communication based on a control signal from the outside. That is, when wireless communication is selected, wireless communication using an antenna is performed, and when wired communication is selected, information can be sent and received using a wired LAN or the like. When synchronization is to be performed using wired communication, synchronization can be performed using a protocol such as NTP (Network Time Protocol) or a method as specified in the international standard IEEE Std. 1558-2008 (hereinafter abbreviated as IEEE1588).

The irradiation side timing unit 125 is a second timing means in the present invention, and is configured to start timing and generate timing information when the power is turned on or when a specified control signal is received from the outside.
The output from the irradiation-side timing unit 125 may be timing information such as pulses at regular intervals, or time information such as the year, month, day, hour, minute, and second, or a count number counted up at regular intervals from a certain point in time.
The irradiation-side timer unit 125 may be provided outside the control device 12 instead of being built into the control device 12 .
In recent years, there are wireless LAN chips that are equipped with a timing synchronization function (hereinafter referred to as TSF) defined in the IEEE 802.11 communication standard as standard and have the timer function described above. Therefore, it is possible to use such wireless LAN chips as the irradiation-side clock unit 125.

The second irradiation side timing unit 126 has the same timing operation as the irradiation side timing unit 125, and is configured to start timing and generate timing information when the power is turned on or when a specified control signal is received from the outside.
The output from the second irradiation side timing unit 126 may be timing information such as pulses at regular intervals, or time information such as the year, month, day, hour, minute, and second, or a count number counted up at regular intervals from a certain point in time.
In recent years, there are wireless LAN chips that are equipped with a timing synchronization function (TSF) defined in the IEEE 802.11 communication standard as standard and have the timer function described above. Therefore, such wireless LAN chips can be used as the second irradiation side clock unit 126.

The display unit 127 is composed of a monitor such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays the input contents from the operation unit 15, radiation irradiation result information (e.g., tube voltage, tube current, irradiation time, tube current irradiation time product, number of shots, incident dose, area dose, etc.), and radiation images based on image data, in accordance with the instructions of a display signal input from the radiation control unit 121.

The operation unit 15 includes a two-stage exposure switch 15a.
The exposure switch 15a is connected by wire to the main body of the operation unit 15. The exposure switch 15a may be connected to the operation unit 15 wirelessly.
Then, based on the operation of the exposure switch 15a, an imaging start signal is transmitted to the control device 12 and the imaging device 3. That is, in this embodiment, pressing the exposure switch 15a is one of the exposure start operations.
As will be described later (as shown in FIG. 8), the operation unit 15 may be provided as an operation panel 15 outside the control device 12.

In this embodiment, the control device 12 has an equipment configuration including the high voltage generating unit 122. This allows the user to handle radiation without being aware of the high voltage generating unit 122. Therefore, it becomes possible to handle radiation with an equipment configuration that reduces the occurrence of unintended malfunctions due to, for example, matching between devices.
On the other hand, it is also possible that the control device 12 does not include the high voltage generating unit 122, and the high voltage generating unit 122 is configured to be independent from the main body of the control device 12. In this way, the user can select any high voltage generating unit 122 independent of the control device 12 to configure the device, thereby increasing the freedom of device selection.

[Configuration of the Radiation Imaging Apparatus]
Next, a description will be given of a specific configuration of the photographing device 3 included in the photographing system 100. FIG.
Note that, here, an example will be described of a so-called indirect type imaging device in which the radiated radiation R is converted into electromagnetic waves of another wavelength, such as visible light, to obtain an electrical signal; however, the present invention may also be a so-called direct type imaging device in which the radiation R is directly converted into an electrical signal by a detection element.
Further, other configurations of the imaging device 3 are not necessarily limited to those illustrated in FIG. 3 as long as they are capable of generating image data of a radiation image.

The imaging device 3 according to this embodiment includes an imaging control unit 31, a radiation detection unit 32, a scan drive unit 33, a readout unit 34, a memory unit 35, a communication unit 36, an imaging side clock unit 37, a second imaging side clock unit 39, and the like, as shown in FIG. 3, in addition to a housing and a scintillator (not shown). Each unit 31 to 39 is supplied with power from a battery 38.

The housing is provided with a power switch, a changeover switch, an indicator, a connector 36b of a communication unit 36 (described later), and the like, all of which are not shown.
When exposed to radiation R, the scintillator emits electromagnetic waves having a longer wavelength than radiation such as visible light.

The imaging control unit 31 is composed of a computer with a central processing unit (CPU), read only memory (ROM), random access memory (RAM), input/output interface, etc. connected to a bus (not shown), a field programmable gate array (FPGA), etc. It may also be composed of a dedicated control circuit.

The radiation detection unit 32 is configured to generate electric charges by receiving radiation R, and is composed of a substrate 32a, a plurality of scanning lines 32b, a plurality of signal lines 32c, a plurality of radiation detection elements 32d, a plurality of switching elements 32e, a plurality of bias lines 32f, a power supply circuit 32g, etc.
The substrate 32a is formed in a plate shape and is disposed so as to face the scintillator in parallel.
The multiple scanning lines 32b are provided to extend parallel to one another at predetermined intervals.
The signal lines 32c are provided so as to extend parallel to one another at a predetermined interval, so as to extend perpendicular to the scanning lines 32b, and so as not to be electrically connected to the scanning lines.
That is, the plurality of scanning lines 32b and signal lines 32c are provided to form a lattice.

The radiation detection elements 32d generate an electrical signal (current, charge) corresponding to the dose of radiation irradiated to the radiation detection element (or the amount of electromagnetic wave light converted by the scintillator), and are composed of, for example, a photodiode or a phototransistor.
The radiation detection elements 32d are provided in a plurality of regions on the surface of the substrate 32a, which are partitioned by the scanning lines 32b and the signal lines 32c. That is, the radiation detection elements 32d are arranged in a matrix. Therefore, each radiation detection element 32d faces a scintillator.
One terminal of each radiation detection element 32d is connected to a drain terminal of a switch element 32e, which is a switch element, and the other terminal is connected to a bias line.

Similar to the radiation detection elements 32d, the multiple switch elements 32e are provided in multiple regions defined by the multiple scanning lines 32b and the multiple signal lines 32c.
Each switch element 32e has a gate electrode connected to the adjacent scanning line 32b, a source electrode connected to the adjacent signal line 32c, and a drain electrode connected to one terminal of the radiation detection element 32d in the same region.

The multiple bias lines 32f are connected to the other terminals of each of the radiation detection elements 32d.
The power supply circuit 32g generates a reverse bias voltage and applies the reverse bias voltage to each radiation detection element via a bias line 32f.

The scan driver 33 includes a power supply circuit 33a and a gate driver 33b.
The power supply circuit 33a generates an on-voltage and an off-voltage, which are different from each other, and supplies them to the gate driver 33b.
The gate driver 33b switches the voltage applied to each scanning line 32b between an ON voltage and an OFF voltage.

The readout section 34 includes a plurality of readout circuits 34a, an analog multiplexer 34b, an A/D converter 34c, and the like.
The plurality of readout circuits 34a are connected to the signal lines 32c of the radiation detection unit 32, respectively, and are adapted to apply a reference voltage to each of the signal lines 32c.
Each read circuit 34a is made up of an integrating circuit 34d and a correlated double sampling circuit (hereinafter referred to as a CDS circuit) 34e.

The integration circuit 34d integrates the charge discharged to the signal line 32c, and outputs a voltage value according to the amount of the integrated charge to the CDS circuit 34e.
The CDS circuit 34e samples and holds the output voltage of the integration circuit 34d before applying an on-voltage to the scanning line 32b to which the radiation detection element 32d from which the signal is to be read out is connected (while an off-voltage is being applied), applies an on-voltage to the corresponding scanning line 32b to read out the signal charge of the radiation detection element, and outputs the difference in the output voltage of the integration circuit 34d after applying an off-voltage to the corresponding scanning line 32b.

The analog multiplexer 34b outputs the plurality of differential signals output from the CDS circuit 34e one by one to the A/D converter 34c.
The A/D converter 34c sequentially converts the input image data of analog voltage values into image data of digital values.

The memory unit 35 is composed of SRAM (Static RAM), SDRAM (Synchronous DRAM), NAND type flash memory, HDD (Hard Disk Drive), etc.

The communication unit 36 is a communication means in the present invention, and includes an antenna 36a and a connector 36b for communicating with the outside.
The communication unit 36 can select whether to perform wireless communication or wired communication based on a control signal from the outside. That is, when wireless communication is selected, wireless communication is performed using the antenna 36a, and when wired communication is selected, information can be transmitted and received using a wired LAN or the like. When synchronization is to be performed using wired communication, synchronization can be performed using a protocol such as NTP (Network Time Protocol) or a method defined in the international standard IEEE 1588.

The photographing side timing unit 37 is the third timing means in the present invention, and is configured to start timing and generate timing information when the power is turned on or when a specified control signal is received from the outside.
The output from the photographing side timing unit 37 may be timing information such as pulses at regular intervals, or time information such as the year, month, day, hour, minute, second, or the number counted up at regular intervals from a certain point in time.
The photographing side clock unit 37 may be provided outside the photographing device 3 instead of being built into the photographing device 3 .
In recent years, there are wireless LAN chips that are equipped with a timing synchronization function (TSF) defined in the IEEE 802.11 communication standard (described later) as standard and have the timer function described above. Therefore, such wireless LAN chips can also be used as the imaging-side clock unit 37.

The second photographing side timing unit 39 has a timing operation similar to that of the photographing side timing unit 37, and is configured to start timing and generate timing information when the power is turned on or when a specified control signal is received from the outside.
The output from the second photographing side timing unit 39 may be timing information such as pulses at regular intervals, or time information such as the year, month, day, hour, minute, second, or the like, or the number counted up at regular intervals from a certain point in time.
In recent years, there are wireless LAN chips that are equipped with a timing synchronization function (TSF) defined in the IEEE 802.11 communication standard as standard and have the timer function described above. Therefore, such wireless LAN chips can be used as the second imaging side clock unit 39.

When the imaging device 3 configured in this way is turned on, it takes one of the following states: "initialization state,""storagestate," and "reading and transfer state." The timing for switching states will be described later.
The "initialized state" is a state in which an on voltage is applied to each switch element 32e and the charge generated by the radiation detection element 32d is not accumulated in each pixel (the charge is discharged to the signal line 32c).
The "accumulation state" is a state in which an off voltage is applied to each switch element 32e, and charges generated by the radiation detection element 32d can be accumulated in the pixel (charges are not released to the signal line 32c).
The “read and transfer state” is a state in which an on voltage is applied to each switch element 32e and the readout unit 34 is driven to read out image data based on the incoming electric charges and transmit the image data to another device.
Depending on the configuration of the element and device, the accumulated charge may be cleared by reading, so "reading" and "initialization" may not be distinguished as separate operations, and may be performed simultaneously as the same operation.

[Timing deviation]
Although details will be described later, in the photographing system 100 according to this embodiment, the control device 12 determines the operation timing based on the timing information of the second irradiation side clock unit 126 included in the control device 12, and the photographing device 3 determines the operation timing based on the second imaging side clock unit 39 included in the control device 12. Therefore, if the clock speed of the second irradiation side clock unit 126 and the clock speed of the second imaging side clock unit 39 are the same, the irradiation device 1 and the photographing device 3 are synchronized.
However, for example, due to the influence of an error in the frequency of an oscillator included in the control device 12 or the photographing device 3, a slight difference may occur between the clocking speed of the second irradiation side clock unit 126 linked to the control device 12 and the clocking speed of the second photographing side clock unit 39 linked to the photographing device 3. In such a case, when photographing for a relatively long time such as serial photographing is performed, the difference between the clocking information of the second irradiation side clock unit 126 and the clocking information of the second photographing side clock unit 39 gradually increases, causing a difference between the operation timing of the irradiation device 1 and the operation timing of the photographing device 3.

Therefore, the photographing system 100 of this embodiment is capable of periodically aligning the timing information of the second irradiation side timing unit 126 and the timing information of the second photographing side timing unit 39 based on reference timing information (hereinafter referred to as first timing information).
The first timing information may be generated, for example, by the following method.

[Method 1 for generating first timing information]
The first generation method is to use, as the first timekeeping information, time information used in a Timing Synchronization Function (TSF) included in the IEEE 802.11 communication standard.

"TSF" is a function for synchronizing the time between an access point and a device when the devices communicate wirelessly with each other.
Specifically, the access point is provided with a free-running timing means (TSF timer) that counts up periodically (every 1 μs), and the beacon transmitted periodically (every 100 ms by default) includes time information at the time of transmission and transmits it to the terminal.
On the other hand, the terminal also has a timing means that counts up periodically (every 1 μs), and when it receives a beacon, it updates the time information of its own timing unit 125, 37 to the time information included in the beacon and continues counting up.

When using this TSF time information as the first timing information, for example as shown in Figure 4, a TSF timer 22 is provided in AP 2, and the time information is included in a beacon output by a communication unit 21 of AP 2 and output to the control device 12 and the photographing device 3.
The clocking method, for example, starts counting from 0, and when the time information reaches a predetermined maximum value, resets to 0 and repeats the counting.
In addition, the TSF timer 22 may be configured to output timing information based on timing independent of the control device 12 or the photographing device 3, or may be configured to output timing information linked to the timing information of the control device 12 or the photographing device 3.
The TSF timer 22 included in this beacon is the first time measuring means in the present invention, and the time information of the TSF timer 22 at the time of transmitting the beacon is the first time measuring information.
Hereinafter, the AP 2 in the case where the TSF is used as the first timing information will be referred to as a timing information source device 2 .

[Method 2 for generating first timing information]
A second generation method is to use a dedicated device that outputs the first timing information.

Specifically, for example, as shown in FIG. 5, a timing means (not shown) is provided, and a timing information source device 4 capable of communicating timing information with the control device 12 and the photographing device 3 is provided.
The timing information source device 4 has built-in timing means (not shown).
In addition, the timing means of the timing information source device 4 may be configured to output timing information based on timing independent of the control device 12 or the photographing device 3, or may be configured to output timing information linked to the timing information of the control device 12 or the photographing device 3.
The output from the timing information source device 4 may be timing information such as pulses at regular intervals, or time information such as the year, month, day, hour, minute, second, or a count number counted up at regular intervals from a certain point in time.
The measured time information is then periodically transmitted as first time information.
Hereinafter, the TSF timer 22 of the AP 2 and the timing means (not shown) of the timing information source device 4 may be collectively referred to as a reference timing unit.

[Correction of deviations]
In this embodiment, of the radiation control unit 121 of the control device 12 and the imaging control unit 31 of the imaging device 3, the control unit of the device that receives the first timing means (hereinafter, control units 121, 31) updates the timing information of the timing unit of the device that receives the first timing information, of the irradiation side timing unit 125 of the control device 12 and the imaging side timing unit 37 of the imaging device 3 (hereinafter, timing units 37, 125), to the value of the first timing information each time it receives first timing information from the timing information source devices 2, 4.

Furthermore, the timer units 126 and 39 of this embodiment are capable of setting their own operation mode to a synchronous mode, and are adapted to switch to a self-operating mode as the case may be.
The switching between these operation modes will be described later.

Furthermore, the control units 121, 31 update the timing information of the timing unit of the device that receives the first timing information, either the second irradiation side timing unit 126 of the control device 12 or the second imaging side timing unit 39 of the imaging device 3 (hereinafter referred to as the second timing units 126, 39), to the timing information of the timing units 125, 37 at a predetermined timing, and then continue counting. As described above, the timing units 125, 37 synchronize with the timing information source devices 2, 4 every time they receive the first timing information from the timing information source devices 2, 4. Therefore, the second timing units 126, 39 also repeatedly synchronize with the timing information source devices 2, 4 at a predetermined cycle while operating in the synchronization mode.
When the second timers 126, 39 operate in the free running mode, the control units 121, 31 allow the second timers 126, 39 to continue counting without updating the timing information of the timers 125, 37.

[Mode switching]
Next, details of the switching of the operation modes of the second irradiation side clock unit 126 and the second imaging side clock unit 39 performed by the radiation control unit 121 and the imaging control unit 31 will be described.

For example, if an abnormality occurs in the timing information source devices 2, 4, the first timing information of the timing information source devices 2, 4 may be reset midway, and the timing information of the imaging side timing unit 37 and the irradiation side timing unit 125 (hereinafter, timing units 37, 125), which are synchronized with the timing information source devices 2, 4, and the second imaging side timing unit 39 and the second irradiation side timing unit 126 (hereinafter, second timing units 39, 126), which correct their own timing information based on the timing information of these timing units 37, 125, may also be updated midway. In such a case, if serial imaging is performed in which irradiation of radiation and accumulation of electric charge are repeated multiple times, the timing will be shifted only for the imaging immediately after the timing information is updated.
Therefore, in this embodiment, the control units 121 and 31 are configured to switch the operating mode of the second irradiation side timing unit 126 and the second shooting side timing unit 39 as necessary so as not to disrupt the shooting cycle of the serial shooting even in such a case.

The control units 121 and 31 are adapted to determine whether or not a predetermined condition is met.
In this embodiment, the specified condition is satisfied when an abnormality that may adversely affect the timing of shooting is detected. Specifically, the specified condition is determined to be satisfied when, for example, a specified event is detected during the shooting period, the time from the last synchronization to the current synchronization during the shooting period (first timing information reception interval) exceeds a specified threshold, the amount of change in the timing information when the second shooting side timing unit 39 and the second irradiation side timing unit 126 are synchronized exceeds a specified threshold during the shooting period, the timing information changes suddenly due to a restart of the timing information source devices 2, 4, etc. during the shooting period, or reception of the first timing information fails for a long period of time during the shooting period.
That is, the control units 121 and 31 function as the determination means of the present invention.

In addition, the occurrence of the events listed in (1) to (3) below can be regarded as the occurrence of the predetermined condition. These may be used alone or in combination.
(1) The number of times the first timing information is received during the shooting period is counted, and the number falls below a predetermined threshold.
(2) During the shooting period, the reception interval of the first timing information is repeatedly measured, and at least any reception interval of the first timing information exceeds a predetermined threshold value.
(3) During the photographing period, the amount of change in the timing information of the second photographing side timing unit 39 and the second irradiation side timing unit 126 when synchronized is repeatedly measured, and at least either amount of change exceeds a predetermined threshold.
In particular, by using (2) or (3), a synchronization failure can be detected immediately.

Furthermore, when it is determined that a predetermined condition is satisfied, the control units 121 and 31 switch the operation mode of the second irradiation side clock unit 126 and the second imaging side clock unit 39 to the self-running mode.
The control units 121 and 31 are configured to set the operation mode to the synchronous mode from when the power is turned on until it is determined that a predetermined condition is satisfied (default state).
Furthermore, when shooting is performed in the free-running mode, the control units 121 and 31 are configured to switch (return) to the synchronous mode when a predetermined condition is no longer satisfied.
That is, the control units 121 and 31 function as a switching means in the present invention.

Note that the self-running mode may not be switched to only when the predetermined condition is satisfied, but may be switched to the self-running mode throughout the entire period during which the predetermined condition may be satisfied.
An example of such a period is the period from the start to the end of imaging, as shown in FIG.

Examples of the shooting start trigger for determining the start of shooting include the following actions (Open-1) to (Open-8). A combination of a plurality of these actions is also possible.
(Open-1) A user instruction is received via a user interface (hereinafter referred to as UI) such as the console 14, the imaging device 3, the control device 12, the operation unit 15, or the exposure switch 15a. (Open-2) An imaging order is selected via the console 14. (Open-3) The imaging device 3 has completed preparation for radiation irradiation. (Open-4) The first stage of the exposure switch 15a has been pressed. (Open-5) The control device 12 has received a signal from the tube 13 indicating that preparation for irradiation has been completed, or the control unit 121 has received a signal from the high-voltage generation unit 122 indicating that preparation for irradiation has been completed. (Open-6) The second stage of the exposure switch 15a has been pressed. (Open-7) The control device 12 has received a signal from the tube 13 indicating that radiation irradiation for the first frame has started, or the control unit 121 has received a signal from the high-voltage generation unit 122 indicating that radiation irradiation for the first frame has started. (Open-8) A predetermined time has elapsed since the generation of the imaging start triggers described above in (Open-1) to (Open-7).

As a trigger for judging the end of shooting, the following actions (END-1) to (END-9) can be mentioned. A combination of these actions is also possible.
(END-1) A user instruction has been received via a UI such as the console 14, the imaging device 3, the control device 12, the operation unit 15, or the exposure switch 15a. (END-2) The control device 12 has received a signal from the tube 13 indicating that radiation irradiation for capturing the final frame has ended, or the control unit 121 has received a signal from the high-voltage generator 122 indicating that radiation irradiation for capturing the final frame has ended. (END-3) Processing of the final frame has been completed by the imaging device 3 or the control device 12. (END-4) Readout of the final frame has been completed by the imaging device 3. (END-5) The second step of the exposure switch 15a has been released. (END-6) The first step of the exposure switch 15a has been released. (END-7) An error has occurred that prevents imaging from continuing. (END-8) The next imaging order has been selected on the console 14. (END-9) A predetermined time has elapsed since the imaging end triggers (END-1) to (END-8) above were generated.

When performing serial imaging or still image imaging, which have a short imaging time, the deviation in exposure and accumulation timing due to an error in the oscillator frequency of the imaging device 3 and the control device 12 may be within the required accuracy even if the mode is switched to free-running mode before a specified condition is met during the imaging period. Therefore, by doing this, it is possible to simplify the processing in the control units 121, 31 in the imaging system 100, which only performs serial imaging or still image imaging, which have a short imaging time, and the imaging system 100 can be developed at low cost and in a short period of time.

However, the shorter the period of operation in the self-propelled mode, the less likely it is that there will be a mismatch between the operation of the imaging device 3 and the control device 12. For this reason, it is preferable to switch to the self-propelled mode at a timing closer to the start of radiation irradiation. For example, if the first press of the exposure switch listed above in (Open-4) is used as the imaging start trigger to determine that imaging has started, if the period from pressing the first press to pressing the second press is long, the period of operation in the self-propelled mode will be long, so it is preferable to use (Open-5) to (Open-7) etc. rather than (Open-4) above as the trigger.

However, depending on the specifications of the tube 13 and the high voltage generating unit 122 and the system configuration, it may be necessary to modify the device or wiring in order to use a preferred imaging start trigger. For this reason, from the viewpoint of reducing development costs, it is desirable to determine the imaging start trigger to be adopted in accordance with the device and system configuration.
In addition, if the period of operation in the self-propelled mode becomes long due to the limited number of imaging start triggers to be used, the timing of switching to the self-propelled mode can be brought closer to the start of irradiation of radiation by using the above (Open-8) as the imaging start trigger.

Furthermore, as mentioned above in (Open-1) and (End-1), if the operating mode can be switched at the user's will, if the user is aware that the accuracy of synchronization with the reference time may decrease due to deterioration of the wireless radio wave conditions due to the placement of the photographing device 3 or radio wave interference with other devices being used simultaneously, the decrease in synchronization accuracy can be avoided by manually switching the operating mode on the spot.
In addition, if the current operating mode can be displayed on the display unit 127, the console 14, the operation unit 15, or a display unit (not shown) of the imaging device 3, the usability of the system 100 can be improved and the user can be prevented from performing unnecessary switching operations.

In addition, if the imaging system 100 is configured to include multiple timing information source devices 2, 4, and the imaging device 3 and control device 12 are moved so that when the radio wave conditions with the other timing information source device 2, 4(n+1) improve from the currently connected timing information source device 2, 4(n), the connection destination is switched to the timing information source device 2, 4(n+1) (performing wireless LAN roaming), if the connection destination is switched during imaging, the reference time will change, and the exposure and readout timing will not be consistent, resulting in imaging failure. To avoid this, it is recommended to switch to self-running mode even when the connected timing information source device 2, 4 is changed during imaging, and to switch back to synchronous mode after imaging is completed.

Hereinbefore, an example of the imaging system 100 has been described in which both the control device 12 and the imaging device 3 have the operation mode switching function, but these functions may be provided in at least one of the control device 12 and the imaging device 3.

[Serial photography process]
Next, a flow of serial photography using the photography system 100 of this embodiment capable of switching between the above-mentioned operation modes will be described. FIG 7 is a timing chart showing the operation of the photography system 100 of this embodiment.
Note that, here, the photographing conditions are described as an example in which the connection type of the photographing device 3 is wireless, the photographing mode is serial photographing, and the frame rate is 15 fps, but the flow is similar for other photographing conditions.

When the user selects the imaging conditions on the console 14, the console 14 transmits the imaging conditions to the imaging device 3 via the wired communication network, the timing information source devices 2 and 4, and wirelessly, and also transmits the imaging conditions and radiation irradiation conditions (tube current, tube voltage, irradiation time) to the control device 12. Note that the irradiation time here is the irradiation time per pulse in pulse irradiation.
When the photographing device 3 and the control device 12 receive the photographing conditions and the irradiation conditions, they store the photographing conditions and the irradiation conditions in their respective storage units 35, 123 and start processing for performing wireless serial photographing.

(Step 1)
Then, the control device 12 sets the received irradiation conditions in the high voltage generating unit 122 via the control unit 121. Note that a system configuration in which the user can input the irradiation conditions from the operation unit 15 may be used. In this configuration, the control device 12 sets the irradiation conditions input from the operation unit 15 in the high voltage generating unit 122 via the control unit 121.
Before the first step of the exposure switch 15a is pressed or before the second step is pressed, the control device 12 sets the irradiation conditions in the high voltage generating unit 122 via the control unit 121 each time new irradiation conditions are received from the console 14. The same applies to a system configuration in which the user can input the irradiation conditions from the operation unit 15. Normally, the irradiation conditions are finely adjusted according to the physique of the patient, but by doing so, the degree of freedom of the operation sequence is increased, improving usability.

(Step 2)
Then, the imaging control unit 31 and the radiation control unit 121 set the operation modes of the second timers 39 and 126, respectively, to the synchronous mode.

(Step 3)
Furthermore, the timing information source devices 2 and 4 periodically (every 100 ms as a standard) transmit the first timing information to the photographing device 3 and the control device 12. At that time, the timing information source devices 2 and 4 transmit the first timing information at that time to the photographing device 3 and the control device 12.
At this time, if wireless communication is established between the timing information source device 2, 4 and the photographing device 3 and the control device 12, the photographing device 3 and the control device 12 receive the first timing information from the timing information source device 2, 4, update their own timing units 37, 125, and continue counting.

(Step 4)
Furthermore, the imaging device 3 and the control device 12 continuously determine whether or not a predetermined condition is satisfied, i.e., whether or not their own timing units 37, 125 are synchronized with the timing information source devices 2, 4 with the required accuracy. The reason for determining whether or not synchronization is achieved in advance in this manner is that if the synchronization accuracy decreases during imaging, the timing of radiation irradiation and the timing of image data readout will differ, causing imaging failure.

(Step 5)
Furthermore, the image capture device 3 and the control device 12 share their respective judgment results by periodically transmitting them to each other. In this way, if the first timing information cannot be received from the timing information source devices 2, 4 for a long period of time, or if the first timing information of the timing information source devices 2, 4 changes significantly due to a restart of the timing information source devices 2, 4, etc., this can be immediately detected.

(Step 6)
When the control unit 121 of the control device 12 detects that the exposure switch 15a has been pressed to the second level (receives the shooting start signal), it sends a signal to that effect to the high voltage generating unit 122 and transitions to a standby state in which it waits for a completion notification signal to be returned from the high voltage generating unit 122 indicating that preparations for irradiation have been completed.
Upon receiving the imaging start signal, the high voltage generation unit 122 starts preparation for irradiation. Specifically, the high voltage generation unit 122 prepares the voltage and current to be output to the tube 13, instructs the tube 13 to start rotating the rotating anode, and so on.
When the rotating anode reaches a predetermined rotation speed, the bulb 13 transmits a preparation completion notification signal to the high voltage generating unit 122. When the high voltage generating unit 122 completes preparation for irradiation, it transmits a completion notification signal to the control unit 121 to notify the control unit 121 that preparation for irradiation has been completed.
When the control unit 121 receives the irradiation preparation completion notification signal, it transmits a command to the imaging device 3 via the communication unit 124 to notify that preparation for irradiation of radiation has been completed.

(Step 7)
When the image capturing device 3 receives the command, it transitions to a state in which it is ready to capture images.
Thereafter, the photographing device 3 and the control device 12 wait for the second clock units 39 and 126 to update their respective clock information to the clock information of the clock units 37 and 125 .
If the update of the timing information is not completed within a predetermined time, the console 14 or the like may be notified that synchronization has failed, and a display unit (not shown) of the console 14 may display a message indicating that synchronization has failed, a message encouraging troubleshooting such as restarting the timing information source devices 2 and 4 or checking the network settings, or a message encouraging wired shooting, etc. This allows for an early recovery from the abnormality.

When the updating of the timing information of both the second timing units 39 and 126 has been completed, the photographing device 3 calculates the start time of the photographing sequence by adding the waiting time for the start of the photographing sequence stored in the memory unit 35 to the timing information of the second timing unit 39 at the time of completion, and stores this in the memory unit 35 and transmits it to the control device 12.
The waiting time for starting the shooting sequence is determined in advance based on the expected communication delay time, and by setting it to be equal to or greater than the expected maximum delay time, it is possible to avoid a situation in which, if there is a delay in transmitting the shooting sequence start time, the shooting sequence start time has already passed by the time the control device 12 receives the shooting sequence start time, resulting in failure to shoot.
In the above, the photographing device 3 is configured to transmit the photographing sequence start time to the control device 12. However, the control device 12 may also be configured to calculate the photographing sequence start time by adding the photographing sequence start waiting time stored in the memory unit 123 to the timing information of the second timing unit 126 at the time when both updates are completed, and store this in the memory unit 126 and transmit it to the photographing device 3.

(Step 8)
Even after the image capturing device 3 and the control device 12 have completed synchronization with each other, they continue to determine whether or not they are synchronized.
Furthermore, when the photographing device 3 and the control device 12 detect that synchronization has failed during the period from the time when synchronization between the photographing device 3 and the control device 12 is completed to the start of readout of the last frame of serial photographing after an irradiation preparation completion notification signal is transmitted from the high voltage generating unit 122 to the control unit 121, the photographing device 3 and the control device 12 operate the second clock units 39, 126 in a self-running mode for at least the period from that time to the start of readout of the last frame of serial photographing, and thereafter return to the synchronous mode. Note that, when synchronization failure is detected, by switching to the self-running mode before updating the timing information of the second clock units 39, 126 to the timing information of the clock units 37, 125, it is possible to prevent an abnormal value from being set in the second clock units 39, 126.

(Step 9)
Furthermore, when the control device 12 receives the imaging sequence start time from the imaging device 3, it stores it in the storage unit 123. Then, based on the stored imaging sequence start time and the frame rate (15 fps, etc.), it generates an exposure start time for each frame.
A specific method of generating the exposure start time is, for example, to set the imaging sequence start time as the exposure start time of the first frame, and from the second frame onwards, to cumulatively add the imaging cycle (=1/frame rate) to it. In this case, the exposure start time of the Nth frame = imaging sequence start time + (frame number N-1) x imaging cycle.
Note that the exposure start time may be generated in advance in multiple times and stored in the storage unit 123 so that it can be referred to later each time an exposure start instruction for each frame is received, or may be generated each time an exposure start instruction for each frame is received by adding the imaging period to the exposure start time of the previous frame. In the latter case, the capacity of the storage unit 123 can be reduced and it becomes easier to deal with cases where the number of frames per imaging varies.

(Step 10)
Furthermore, the control unit 121 transmits a signal to the high voltage generating unit 122 to instruct the start of exposure for each frame every time the timing information of the second irradiation side timing unit 126 coincides with the exposure start time for each frame.
Each time the high voltage generating unit 122 receives a signal instructing the start of exposure, it controls the tube 13 to irradiate radiation R for a preset irradiation time. That is, the control device 12 causes the tube 13 to irradiate radiation R when the timing information of the second irradiation side timing unit 126 reaches a first predetermined value.

(Step 11)
Furthermore, when the control unit 121 detects an image capture end event, such as when the second stage of the exposure switch 15a is released, the number of image capture frames reaches the maximum number of frames stored in the storage unit 123, a stop notification is received from the high voltage generating unit 122, or a stop notification is received from the image capture device 3, the control unit 121 transmits a command notifying the end of image capture via the communication unit 124 to the image capture device 3, and does not transmit a new exposure start instruction for the image capture to the high voltage generating unit 122. In other words, the image capture is terminated.
The maximum number of frames may be a fixed value stored in the storage unit 123 , or a value entered on the console 14 may be sent to the control device 12 and stored in the storage unit 123 .

(Step 12)
Furthermore, the image capturing device 3 generates a readout start time for each frame based on the image capturing sequence start time, the frame rate, and the accumulation time per frame stored in the storage unit 123 .
The accumulation time is set to be longer than the irradiation time per frame in order to avoid exposure during readout.
A specific method of generating the readout start time is, for example, to set the readout start time of the first frame as the imaging sequence start time + accumulation time per frame, and from the second frame onwards, to cumulatively add the imaging cycle (=1/frame rate) to it. In this case, the exposure start time of the Nth frame = imaging sequence start time + accumulation time per frame + (frame number N-1) x imaging cycle.
Note that the read start time may be generated in advance in multiple times and stored in the storage unit 123 so that it can be referred to later each time a read process for each frame is performed, or the read start time may be generated each time a read process for each frame is performed by adding the shooting period to the read start time of the previous frame. In the latter case, the capacity of the storage unit 123 can be reduced and it becomes easier to deal with cases where the number of frames per shooting varies.

In this way, by using a method in which the imaging device 3 independently generates the readout start time from the imaging sequence start time and frame rate, and the control device 12 similarly independently generates the exposure start time, the minimum information that needs to be shared between the imaging device 3 and the control device 12 is the imaging sequence start time and frame rate, and this reduces the risk of imaging failure caused by communication delays due to packet loss between the imaging device 3 and the control device 12, such as the readout start time arriving after the timing when readout should be started, or the exposure start time arriving after the timing when exposure should be started.

(Step 13)
Furthermore, the imaging device 3 starts reading out the charges accumulated in the radiation detection unit 32 and generates image data of the frame image every time the second imaging side clock unit 39 coincides with the readout start time of each frame. That is, the imaging device 3 reads out image data of the radiation image based on the charges generated in the radiation detection unit 32 when the clock information of the second imaging side clock unit 39 reaches a second predetermined value.

(Step 14)
Then, when the photographing device 3 detects a photographing end event, such as receiving a command from the control device 12 notifying the end of photographing, or the number of photographed frames reaching the maximum number of frames stored in the memory unit 35, the photographing device 3 ends the photographing.
If an end of image capture event is detected during readout, it is preferable to end the image capture after the readout is completed, which can avoid an abnormality such as only a partial frame image being displayed for the final frame.

So far, the imaging system 100 according to this embodiment has been described, but the connection configuration of the timing information source devices 2, 4, the radiation control device 12, the console 14, the operation unit 15, and the exposure switch 15a is not limited to the configuration shown in FIG. 1 and can take various configurations.
For example, the device can be configured so that the operation unit 15 is connected only to the console 14, and signals in response to operations on the operation unit 15 enter the control device 12 via the console 14. Also, for example, the timing information source devices 2, 4 do not necessarily need to be connected to both the control device 12 and the console 14, and can be configured so that they are connected only to the console 14, information and time correction is performed between the console 14, and the control device 12 performs information and time control via the console 14.
Further, for example, the exposure switch 15 a may be directly connected to the control device 12 instead of to the operation unit 15 .
In this manner, in the following figures as well, device connection configurations other than those described above can be used that do not impede the objects, actions, and effects described in the present invention.

<Additional Technology>
Next, another embodiment of a radiation imaging system to which the present invention can be applied will be described.
In addition, here, the same components as those in the above embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[Configuration of Radiation Imaging System]
First, an outline of a radiation imaging system according to this embodiment (hereinafter, referred to as imaging system 100A) will be described. Fig. 8 is a block diagram showing a schematic configuration of imaging system 100A.

As shown in FIG. 8, the imaging system 100A of this embodiment is configured to include a tube 13, a console 14, and timing information source devices 2 and 4 similar to those of the above embodiment, as well as a radiation control device (hereinafter, referred to as the control device 12A), a radiation imaging device (hereinafter, referred to as the imaging device 3A), and an operation panel 15.
The control device 12A and the photographing device 3A are capable of communicating with each other via the timing information source devices 2 and 4.
The control device 12A and the photographing device 3A will be described in detail later.

The operation panel 15 has the same structure as the operation unit 15 of the above embodiment.
Therefore, similarly to the embodiment described above (as shown in FIG. 1), the operation panel 15 may be provided as the operation unit 15 within the control device 12A.

[Configuration of Radiation Control Device]
Next, a specific configuration of the control device 12A provided in the image capture system 100A will be described below. Fig. 9 is a block diagram showing a specific configuration of the control device 12A.

As shown in FIG. 9, the control device 12A of this embodiment is configured to include a radiation control unit 121, a memory unit 123, a communication unit 124, and an irradiation side timing unit 125 similar to those of the above embodiment, as well as a high voltage generating unit 122, etc.
However, the control device 12A of the present embodiment does not have a configuration corresponding to the second irradiation side timer unit 126 of the above embodiment.

The high voltage generating unit 122 is configured to apply a voltage to the tube 13 according to the preset radiation irradiation conditions based on receiving a control signal from the tube control unit.

[Configuration of the Radiation Imaging Apparatus]
Next, a specific configuration of the image capturing device 3A included in the image capturing system 100A will be described below. Fig. 10 is a block diagram showing a specific configuration of the image capturing device 3B.

The imaging device 3A has a configuration similar to that of the imaging device 3 of the above embodiment, that is, as shown in Fig. 10, it includes an imaging control unit 31A, a radiation detection unit 32 similar to that of the above embodiment, a scan drive unit 33, a readout unit 34, a storage unit 35, a communication unit 36, a battery 38, and an imaging side timer unit 37A.
However, the photographing device 3A of this embodiment does not have a configuration equivalent to the second photographing side clock unit 39 of the above embodiment.

[Radiation imaging system imaging operation]
Next, a basic photographing operation performed by the photographing system 100A will be described below. Fig. 11 is a timing chart showing the operation of the photographing system 100A, and Fig. 12 is a diagram showing the time information of each timer when the photographing system 100A is operating.

First, when an operation is performed that triggers the start of timing by the irradiation side timing unit 125 of the control device 12A and the photographing side timing unit 37 of the photographing device 3A (for example, each device of the photographing system 100A is turned on), the irradiation side timing unit 125 and the photographing side timing unit 37 each start timing.
At this time, the timing start timing of the irradiation side timing unit 125 and the timing start timing of the photography side timing unit 37 will be different, and the timing information of one timing unit or the timing information of a timing means linked to one timing unit will cause the timing information of the other timing unit to be synchronized with the timing information of the other timing unit.
Thereafter, when the user presses the exposure switch 15a of the irradiation device 1, the irradiation device 1 transmits an imaging start signal to the control device 12A and the imaging device 3A.
Then, when the timing information (time information) of the photographing side timing unit 37 reaches a first predetermined value (t1) or (when a first predetermined time (t1) has elapsed since the start of timing), the photographing device 3A applies an on voltage to each switch element 32e, thereby performing initialization to release the dark charge accumulated in each pixel to the signal line 32c.

After that, when the timing information of the imaging side clock unit 37 reaches a second predetermined value (t2) that is greater than the first predetermined value (when the second predetermined time (t2) has elapsed since the start of timing), the imaging device 3A applies an off voltage to each scanning line 32b, thereby enabling the charge generated by the radiation detection element 32d to be stored in the pixel. This state in which charge can be stored continues until the timing information of the imaging side clock unit 37 reaches a fourth predetermined value (t4) that is greater than the second predetermined value (until the fourth predetermined time has elapsed since the start of timing).

Furthermore, when the timing information of the irradiation-side timing unit 125 of the control device 12A reaches a third predetermined value (t3) that is greater than the second predetermined value and less than the fourth predetermined value (when a third predetermined time has elapsed since the start of timing), the irradiation device 1 irradiates the subject S and the imaging device 3A behind it with radiation R. That is, the irradiation device 1 irradiates radiation while the imaging device 3A is in a state capable of accumulating electric charge (t2 to t3).
When the imaging device 3A receives radiation R, each radiation detection element 32d of the radiation detection section 32 generates an electric charge, which is accumulated in each pixel.

When the timing information of the photographing side timer 37 reaches a fourth predetermined value (t4) that is greater than the third predetermined value (when the fourth predetermined time (t4) has elapsed since the start of timing), the photographing device 3A first applies an on-voltage to each TFT 35 connected to each scanning line 32b in the same manner as in the initialization, and releases the electric charge accumulated in each pixel to each signal line 32c. Then, the readout unit 34 reads out image data based on the electric charge that has flowed in.
Depending on the configuration of the radiation detection elements of the imaging device 3A, the accumulated charges may be released and an initialization operation may be performed when the charges are read out.

When the shooting mode is set to serial shooting mode, the irradiation device 1 and the shooting device 3A repeat the above-mentioned series of operations for the number of frame images to be shot, based on the timing information of the TSF timer 22 and the shooting side timing unit 37.

[Timing deviation]
While the photographing system 100A is operating as described above, for example, due to the influence of an error in the frequency of an oscillator provided in the control device 12A or the photographing device 3A, a slight difference may occur between the clocking speed of the irradiation side clock unit linked to the control device 12A and the clocking speed of the photographing side clock unit 37 linked to the photographing device 3A. In such a case, when photographing for a relatively long time such as serial photographing is performed, for example, as shown in Fig. 12, the difference between the clocking information of the irradiation side clock unit 125 and the clocking information of the photographing side clock unit 37 gradually increases, so that the operation timing of the irradiation device 1 and the operation timing of the photographing device 3A are shifted.
Therefore, the imaging system 100A of the present embodiment is configured to take appropriate measures before the difference in operation timing between the irradiation device 1 and the imaging device 3A becomes so large that it affects diagnosis.

In order to confirm the degree of deviation, first timing information that serves as a reference for comparison and second timing information with which to compare are required.
The method of generating the first timing information may be, as in the above embodiment, a method in which the time information used in the TSF of the IEEE 802.11 communication standard is used as the first timing information, or a method in which time information or timing information from a timing information source device 4 other than AP 2 is used as the first timing information.

[Acquisition of second timing information]
Of the control device 12A and the photographing device 3A, the control unit of the device that receives the first timing information from the timing information source device 2, 4 acquires the timing information of the irradiation side timing unit 125 or the photographing side timing unit 37 at the time when the first timing information is received (acquired) from the timing information source device 2, 4 as second timing information.
In particular, in this embodiment, a plurality of pieces of first time information and a plurality of pieces of second time information are acquired at a plurality of predetermined points in time during at least a portion of the shooting period.
The specific period may be set to a desired length based on a user operation.

Figure 13 shows a configuration in which the imaging device 3 corrects the timing information generated by its own timing unit 37 and outputs the timing information to the imaging control unit 31, and Figure 14 shows a configuration in which the control device 12A corrects the timing information generated by its own timing unit 125 and outputs the timing information to the radiation control unit 125.

Of the photographing device 3A and the control device 12A, the device that acquires the first timing information has a timing control means 3a, 12a. The timing control means 3a, 12a is connected to its own timing unit 125, 37 and is adapted to acquire the second timing information (time information or timing information) from its own timing unit 125, 37.
Furthermore, the timing control means 3 a, 12 a is connected to its own communication section 124, 36 and is capable of acquiring first timing information (time information or timing information) from the timing information source device 2, 4.
Such timing control means 3a, 12a may be configured as individual semiconductors, boards, or devices, or may be incorporated as part of the functions of a general-purpose processing unit such as a CPU or FPGA (including the radiation control unit 121 and the imaging control unit 31).

Furthermore, it is possible to preset the timing information of the timing information source devices 2 and 4 or setting information relating to the transmission of time information in the timing control means 3a and 12a.
If the first timing information output by the timing information source device 2, 4 is timing information, for example, if the interval at which timing information (pulses, etc.) is output from the timing information source device 2, 4 is set to x seconds, it is possible to set the interval at which the first timing information can be obtained from outside to x seconds.
On the other hand, when the first timing information output by the timing information source device 2, 4 is time information, for example, if the interval at which the time information (such as the time or the number of counts counted up by the timing information source device 4 from a certain point in time) is output from the timing information source device 2, 4 is set to x seconds, it is possible to set the interval at which the timing information can be obtained from outside to x seconds.
In particular, when the time information is a count-up value in the timing information source device 4, the timing control means 3a, 12a can acquire and set the count interval of the timing information source device 4. For example, when the count frequency of the timing information source device 2, 4 is y Hz, it is possible to acquire and set the count interval to be 1/y seconds.

[Combination of methods for checking deviation]
In this embodiment, as described above, the first timing means generated by the timing information source devices 2 and 4 may be time information or timing information, and the second timing information acquired by the irradiation side timing unit 125 or the imaging side control unit 37 may be time information or timing information.
Therefore, the comparison to check the discrepancy between the first and second timekeeping information is performed in one of the following four ways, depending on the configuration of each device.
1. Comparison of timing information with timing information 2. Comparison of timing information with time information 3. Comparison of time information with timing information 4. Comparison of time information with time information Below, the methods for checking the amount of discrepancy between the first and second timing information will be described in detail.

[How to check the amount of timing information discrepancy by comparing timing information]
15 and 16 show the operation of the device that receives the first timing information, out of the control device 12A and the photographing device 3A.
When the timing information source device 2, 4 is configured to generate timing information as a first timing means, and the timing control means 3a, 12a is configured to acquire timing information as a second timing means, for example in the example shown in Figures 15 and 16, the timing control means 3a, 12a counts the number of pulses of its own timing unit 125, 37 during the period from when timing information is input from the timing information source device 2, 4 to when the next timing information is input (the period from when the (N-1)th pulse is received to when the Nth pulse is received), and determines the timing speed of its own timing unit 125, 37 relative to the timing speed of the timing information source device 2, 4.

For example, if the output period of the first timing information from the timing information source device 2, 4 is set to 1 second and the clock of its own timing unit 125, 37 is set to 10 MHz, the settings will be such that 10,000,000 pulses are counted per second.
In reality, however, the pulse generation speed varies due to fluctuations in the timing means of the timing information source devices 2 and 4, the accuracy of the photographing side timing unit 37 or the irradiation side timing unit 125 itself, and changes in temperature, and therefore the pulse generation speed does not reach exactly 10,000,000 times.
This difference is the time difference between the timing means of the timing information source device 4 and the timing means of the photographing device 3A or the control device 12A.

For example, in the case shown in Figure 15, if the number of pulses during the period from when the (N-1)th pulse is received to when the Nth pulse is received is 10,000,010, which is 10 more than the set value, it is possible for the timing information source device 4 to recognize that its own timing unit 125, 37 is 10/10,000,000 faster than the timing information source device 4.
On the other hand, for example, in the case shown in Figure 16, if the number of pulses during the period from when the (N-1)th pulse is received to when the Nth pulse is received is 9,999,990, which is 10 pulses less than the set value, it becomes possible to recognize that its own timing unit 125, 37 is 10/10,000,000 slower than the timing information source device 4.

[How to check the amount of timing information discrepancy by comparing timing information and time information]
When the timing information source device 2, 4 is configured to generate timing information as a first timing means, and the timing control means 3a, 12a is configured to acquire time information as a second timing means, for example in the example shown in Figures 15 and 16, the timing control means 3a, 12a generates time information from timing information such as pulses of its own timing unit 125, 37 during the period from when timing information is input from the timing information source device 2, 4 to when the next timing information is input (the period from when the (N-1)th pulse is received to when the Nth pulse is received), and determines the timing speed of its own timing unit 125, 37 relative to the timing speed of the timing information source device 4 from the generated time information.

For example, if the output period of the first timing information from the timing information source device 2, 4 is set to 1 second and the clock of its own timing unit 125, 37 is set to 10 MHz, 10,000,000 pulses are generated per second, which means that a pulse is generated every 0.0000001 seconds. Therefore, by correcting the time information by 0.0000001 seconds for each pulse, it is possible to obtain time information at each timing.
The time information may be adjusted for each pulse, or may be adjusted after collecting multiple pulses. Also, the time information may be adjusted collectively when an inquiry about the time information is made.
If the time information is repeatedly corrected for one second with the above settings, the time information will be one second.
However, in reality, the pulse generation speed varies due to fluctuations in the timing means of the timing information source devices 2 and 4, the accuracy of the photographing side timing unit 37 or the irradiation side timing unit 125 itself, and changes in temperature, so that the interval is not exactly one second, and a difference occurs.
This difference is the time difference between the timing means of the timing information source device 4 and the photographing side timing unit 37 or the irradiation side timing unit 125 .

For example, in the case shown in Figure 15, if the number of pulses during the period from when the (N-1)th pulse is received to when the Nth pulse is received is 10,000,010, which is 10 more than the set value, the period from when the (N-1)th pulse is received to when the Nth pulse is received is 1.000001 seconds, and it becomes possible to recognize that the timing speed of its own timing unit 125, 37 is faster than the timing speed of the timing information source device 4 by 0.000001 seconds per second.
On the other hand, for example, in the case of Figure 16, if the number of pulses in the period from when the (N-1)th pulse is received to when the Nth pulse is received is 9,999,990, which is 10 less than the set value, the period from when the (N-1)th pulse is received to when the Nth pulse is received is 0.999999 seconds, and it becomes possible to recognize that the timing speed of its own timing unit 125, 37 is slower than the timing speed of the timing information source device 4 by 0.000001 seconds per second.

[How to check the amount of timing information discrepancy by comparing time information and timing information]
FIG. 17 shows the operation of the device that receives the first timing information, out of the control device 12A and the photographing device 3A.
When the timing information source device 2, 4 is configured to generate time information as a first timing means, and the timing control means 3a, 12a is configured to acquire timing information as a second timing means, for example in the example shown in Figure 17, the timing control means 3a, 12a counts the number of pulses of its own timing unit 125, 37 during the period from when time information is input from the timing information source device 2, 4 to when the next time information is input (the period from when the (N-1)th piece of time information is received to when the Nth piece of time information is received), and determines the timing speed of its own timing unit 125, 37 relative to the timing speed of the timing information source device 2, 4.

For example, by obtaining the time at point (N-1) and the time at point N as time information from the timing information source devices 2 and 4, and calculating the difference between these, the timing control means 3a and 12a can obtain the length (time) of the period from (N-1) to N.
On the other hand, when acquiring timing information at time point (N-1) and timing information at time point N as time information from its own timing unit 125, 37, the timing control means 3a, 12a can acquire the period from time point (N-1) to time point N by multiplying the difference between the timing information at time point (N-1) and the timing information at time point N by the count interval of the timing information source device 4.
The timing control means 3a, 12a can determine the timing speed of its own timing unit 125, 37 relative to the timing speed of the timing information source device 4 by comparing the period from time (N-1) to time N with the value obtained by multiplying the timing information of the pulses of its own timing unit 125, 37 during this period by its own pulse interval.

[How to check the amount of time information discrepancy by comparing time information]
When the timing information source device 2, 4 is configured to generate time information as a first timing means, and the timing control means 3a, 12a is configured to acquire time information as a second timing means, for example in the example shown in Figure 17, the timing control means 3a, 12a can acquire the length of the period (time) from time (N-1) to time N by acquiring the time at time (N-1) and the time at time N as time information from the timing information source device 2, 4 and calculating the difference between these.
On the other hand, the timing control means 3a, 12a can obtain the period from time (N-1) to time N by obtaining the time at time (N-1) and the time at time N as time information from its own timing unit 125, 37 and calculating the difference between these.
The timing control means 3a, 12a can determine the timing speed of its own timing unit 125, 37 relative to the timing speed of the timing information source device 4 by comparing the period from time (N-1) to time N based on the first timing information with the period from time (N-1) to time N based on the second timing information.

By comparing the first timing information with the second timing information using any of the above four methods, it is possible to determine the timing speed of the own timing unit 125, 37 relative to the timing speed of the timing information source device 2, 4.

[Determination of whether specific conditions are met]
Furthermore, the photography control unit 31 is configured to determine whether or not a specific condition is established based on the acquired first timing information and second timing information.
In this embodiment, for example, a determination is made as to whether or not the timekeeping accuracy is sufficient using at least one of the determination methods 1 to 3 listed below, and if the timekeeping accuracy is insufficient, it is determined that a specific condition is met.

[Method 1 for determining timing accuracy (difference)]
When the deviation (difference) between the first and second timing information is used to judge timing accuracy, for example, the difference between the acquired first and second timing information is calculated and it is judged whether it exceeds a specific value, and if the difference exceeds the specific value, it is judged that the timing accuracy is insufficient, i.e., a specific condition is met.

[Method 2 for determining timing accuracy (amount of change)]
Furthermore, when using the change in the deviation (difference) for the judgment, for example, each time the first timing information and the second timing information are acquired, the difference between the first timing information and the second timing information is calculated and stored in the memory unit 35. Then, the amount of change between the stored difference and the previously calculated difference is calculated, and it is judged whether the calculated amount of change exceeds the previously calculated amount of change. If the calculated amount of change exceeds the previous amount of change, it is judged that the timing accuracy is insufficient, that is, that the specific condition is met.

When using a predicted difference for judgment, for example, the difference between the acquired first and second timing information and the amount of change therein are calculated and stored in the memory unit 35. Then, from the stored difference and amount of change, it may be determined whether a specific value will be exceeded if a similar change continues for a predetermined period (for example, the shooting period).

In determining whether a specific condition is met, the difference between the first timing information and the second timing information, or the amount of change may be used as is, or an average value may be calculated for these values, or a method such as linear interpolation or spline interpolation may be used to calculate the change state or future predicted values.
When calculating the average value, for example, the difference between the acquired first timing information and second timing information is calculated and stored in the memory unit 35. The average value is then calculated from the stored differences. Since the amount of change in the difference may change suddenly, calculating the average value makes it possible to deal with such changes.
The parameters required for linear interpolation and spline interpolation can be obtained, for example, by using the least squares method, etc. This method for making judgments can make more advanced judgments by incorporating the techniques of interpolation and extrapolation used in other fields.

[Specific Output]
Furthermore, the timing control means 3a, 12a are adapted to perform a specific output when it is determined that a specific condition is met.
The specific outputs in this embodiment include, for example, the following:

[Specific output 1 (correction of timing information)]
In this case, when the timing control means 3a, 12a determines that a specific condition is met, it modifies the operation of the timing unit 125, 37 so that the difference between the first timing information of the timing information source device 2, 4 and the timing information of its own timing unit 125, 37 is reduced.
The method of correction includes, for example, correction of timing information and correction of time information, as described below.

[Timing information correction]
For example, in the examples shown in Figures 15 and 16, the timing control means 3a, 12a can be configured to check the speed of its own timing unit 125, 37 using the above method during the period from when the (N-1)th piece of timing information is received to when the Nth piece of timing information is received, and if it determines that a specific condition is met, then correct the timing information of its own timing unit 125, 37 during the period from when the Nth piece of timing information is received to when the (N+1)th piece of timing information is received.
The correction can be achieved by, for example, thinning out or adding pulses for a certain period of time in accordance with the detected speed difference, as shown in FIG.

15, if the number of pulses during the period from when the (N-1)th pulse is received to when the Nth pulse is received is 10,000,010, which is 10 more than the set value, a process may be performed to thin out one pulse out of every 1,000,000 during the period from when the Nth pulse is received to when the (N+1)th pulse is received. Alternatively, a pulse generation may be delayed so that one pulse is generated less.
16, if the number of pulses in the period from when the (N-1)th pulse is received to when the Nth pulse is received is 9,999,990, which is 10 less than the set value, the pulses can be counted twice so that there is one extra pulse per 1,000,000 in the period from when the Nth pulse is received to when the (N+1)th pulse is received. Alternatively, the pulse generation can be made faster so that there is one extra pulse.

The timing control means 3a, 12a may also be configured to correct the pulse interval.
For example, when a CR oscillator circuit or an LC oscillator circuit is used as a pulse source, the pulse interval can be easily adjusted by changing the values of C (capacitor), R (resistance), and L (coil).

[Time correction]
The timing control means 3a, 12a can be configured to check the timing speed of its own timing unit 125, 37 using the above-mentioned method during the period from the (N-1)th piece of timing information to the reception of the Nth piece of timing information, and if it determines that a specific condition is met, correct the time information of its own timing unit 125, 37 during the period from the Nth piece of time information to the reception of the (N+1)th piece of time information.

As described above, whether the timing information transmitted from the timing information source device 2, 4 is timing information or time information, or whether the target of correction by the timing control means 3a, 12a is timing information or time information, by using the method described above, it is possible to appropriately correct the timing speed of the timing unit 125, 37 according to the difference with the timing speed of the timing information source device 2, 4.

[Specific output 2 (warning about deviation in timing accuracy and permission to take pictures)]
In this case, when the control unit 31, 121 determines that the specific condition is met, it performs the following operations, for example.
- Notify the user that the timing information has not been corrected for a specified period of time - Notify the user that photography is not permitted - Do not permit photography - Ask the user to choose whether to stop photography - Stop photography

The notification can be given by displaying on a display unit, emitting light, making a sound, vibrating, or the like.
When imaging is not permitted or is to be stopped, control is performed such that the radiation control unit 121 does not transmit a control signal to the high voltage generating unit 122 or transmits a signal instructing the stop.
When the user is to make a selection, for example, options are displayed on the display unit, and the operation is performed based on the operation of the operation unit.
In addition, at least one of the above operations such as canceling the notification shooting may be performed at the same time.
Also, after stopping the shooting, the timing information of the shooting side timing unit 37 may be corrected based on the timing information of the timing information source devices 2 and 4.

In some general radiography systems, the timing information of the second clock means is corrected each time timing information is periodically transmitted from a first clock means linked to a radiation irradiation device to a second clock means, thereby enabling synchronization between the radiation irradiation device and the radiography device.

When performing serial imaging, a radiation imaging device repeatedly performs the following operations: accumulating electric charges generated mainly by irradiation with radiation in an image receiving section, reading out and transferring the accumulated electric charges, and initializing the image receiving section.
For example, the length of the accumulation period for accumulating charge in pixels in capturing a particular frame image may be different from the accumulation period in capturing other consecutive frame images due to the timing information of the timing means being corrected, and the image receiving section will then differ in the amount of charge accumulated by the difference in the length of the periods.
For example, if the timing information of the timing means is corrected so that the accumulation period in shooting a specific frame image becomes longer than the accumulation period in shooting other consecutive frame images, the image receiving section will receive an image for a longer period in shooting the specific frame image than the accumulation period in shooting other consecutive frame images, i.e., the image receiving section will accumulate charges for a longer period than the accumulation period in shooting other consecutive frame images.

To address this problem, by controlling the operation of the radiation irradiation device so that it irradiates, for example, pulsed radiation only during a portion of the accumulation period, it is possible to keep the amount of radiation irradiated from the radiation irradiation device constant during each accumulation period, even if the length of the accumulation period differs.
However, the image receiving section generates and accumulates electric charges not only due to radiation irradiated from the radiation irradiator, but also due to scattered radiation radiated from the outside or from the subject S. In order to eliminate this, a grid for eliminating scattered radiation may be placed between the subject S and the image receiving section when performing imaging, but even this method does not completely eliminate scattered radiation. In other words, even if the operation of the radiation irradiator is controlled so that radiation is irradiated only for a part of the accumulation period, it is not possible to stop image reception due to scattered radiation, i.e., accumulation of electric charges. For this reason, if the length of the accumulation period in capturing a specific frame image differs from the accumulation period in capturing other consecutive frame images due to a change in the time of the clocking means, only the capture of the specific frame image for which the time of the clocking means has been changed will result in image reception that is affected by scattered radiation to a degree different from that in capturing other consecutive frame images.

However, in the imaging system 100A according to this embodiment, when first timing information is transmitted from the timing information source devices 2, 4, the imaging device 3A (judgment means) judges whether or not a specific condition is met, and corrects the timing information of the imaging side timing unit 37 (second timing means) only if the specific condition is met. Therefore, appropriate measures can be taken only at the appropriate time, such as when the difference in the timing information of each timing unit is so great that it affects the content (diagnosis) of the image.

[Method 4 for determining timing accuracy]
In order for the photography system 100A according to the embodiment to perform the various operations described above, it is assumed that communication between the timing information source devices 2 and 4 and the device that receives the first timing information (at least one of the control device 12A and the photography device 3A) is established. For this reason, depending on the usage environment of the photography system 100A, communication may not be established (the various operations described above may not be performed), and the operations of the irradiation device 1 and the photography device 3A may become out of sync.
Therefore, the imaging system 100A of the above embodiment may be provided with a function for detecting a deviation in movement in the following manner.

Specifically, the control device 12A or the photographing device 3B which receives the first timing information is provided with a second photographing side timing unit 39A which counts in conjunction with the photographing device 3B, separate from the photographing side timing unit 37, as shown in FIG. 18.
The timing control means 3a, 12a is provided with a function of resetting the timing information of the second photographing side timing unit 39A when the first timing information is received from the timing information source device 2, 4.
The reset second photographing side clock unit 39A starts counting again from the initial value.
The timing control means 3a, 12a is provided with a function of determining whether or not the timing information of the second photographing side timing unit 39A has exceeded a predetermined threshold value.

As shown in FIG. 19, when there is no abnormality in the communication between the timing information source devices 2, 4 and the photographing device 3B (t0-t1), the second photographing side clock unit 39A repeatedly resets the timing information every time the photographing device 3B receives the first timing information, so that the timing information does not exceed the threshold. However, when an abnormality occurs in the communication between the timing information source devices 2, 4 and the photographing device 3B and the first timing information cannot be received from the timing information source device (t1-t2), the photographing side clock unit 37 does not correct the timing information, and the second photographing side clock unit 39A continues counting without resetting the timing information. When the timing information of the second photographing side clock unit 39A eventually exceeds the threshold (t3), the photographing device 3B detects that the timing information of the photographing side clock unit could not be corrected by the first timing information of the timing information source devices 2, 4 for a predetermined period of time, and outputs a signal to that effect.

At the time of output, at least one of the following operations may be performed in conjunction with the above embodiment when it is determined that a specific condition is met.
- Notify the user that the timing information has not been corrected for a specified period of time - Notify the user that photography is not permitted - Do not permit photography - Ask the user to choose whether to stop photography - Stop photography

After that, when communication is restored and the first timing information is received, the second image capture side timing unit 39A resets the timing information (t4), and the image capture system 100A resumes its original operation.

By configuring the shooting system 100A of the above embodiment in this manner, if the second shooting side timing unit 39A is unable to correct the timing information of the timing units 37, 125 with the first timing information during a specified period of time, it becomes possible to grasp this fact and measure the length of the specified period.
In addition, by comparing the timing information of the second shooting side timing unit with a threshold value, it is possible to determine whether the deviation between the timing information of the first timing unit and the timing information of the shooting side timing unit is within an acceptable range, and if it is outside the acceptable range, appropriate measures can be taken.

[Method 5 for determining timing accuracy]
In addition, in consideration of the problem that communication may not be established depending on the usage environment of the above-mentioned photographing system 100A, and the operations of the irradiation device 1 and the photographing device 3A may become out of sync, the photographing system 100A of the above embodiment may be provided with a function to detect the operation out of sync in the following manner.

Specifically, the control device 12A or the photographing device 3C that receives the first timing information is provided with a memory 39B instead of the second photographing side timing unit 39A as shown in FIG.
This memory 39B is configured so that, upon receiving the first timing information from the timing information source device 2, 4, the memory 39B stores the first timing information (=the timing information of the photographing side timing unit 37 after correction).
It is also possible to provide the storage unit 35 with the function of the memory 39B without providing the memory 39B.
The timing control means 3a, 12a is provided with a function of determining whether or not the difference between the timing information of the photographing side timing section 37 and the stored value of the memory 39B exceeds a predetermined threshold value.

As shown in FIG. 21, when there is no abnormality in the communication between the timing information source devices 2, 4 and the photographing device 3C (between t0 and t1), the photographing system 100A of this embodiment does not allow the difference between the timing information of the photographing side clock unit 37 and the first timing information of the memory 39B to exceed the threshold value because the memory 39B stores the first timing information every time the photographing device 3C receives the first timing information. However, when an abnormality occurs in the communication between the timing information source devices 2, 4 and the photographing device 3C and the first timing information cannot be received from the timing information source devices 2, 4 (between t1 and t2), the photographing side clock unit 37 does not correct the timing information and the memory 39B does not update the first timing information. When the difference between the timing information and the old first timing information of the memory 39B eventually exceeds the threshold value, the photographing device 3C detects that the timing information of the photographing side clock unit could not be corrected with the first timing information of the timing information source devices 2, 4 for a certain period of time, as with the photographing device 3B, and outputs that fact.

When outputting, at least one of the following operations may be performed in conjunction with the operation described above in "Method 4 for determining timing accuracy" when it is determined that a specific condition is met.
Thereafter, when communication is restored and the first time information is received, the memory 39B updates the first time information, and the image capture system 100A resumes its original operation.

If the imaging system 100A according to the above embodiment is configured in this way, it is possible to grasp, without using the second imaging side timing unit 39A, i.e., with a smaller number of timing units than in the first embodiment, when the timing information of the timing units 37, 125 cannot be corrected with the first timing information for a specified period of time.

Next, we will explain various problems that may arise in the imaging systems 100, 100A, 100B, and 100A according to the above embodiments, and provide specific examples for solving these problems.

[Example 1-1]
The console 14 controls the entire photography system 100, that is, monitors the operating status (operating status includes whether the operating status is normal or abnormal, or whether the operating status is starting or ending, etc.) of each device in the photography system 100 and devices that transmit and receive information with systems other than the photography system 100, and synchronizes each device in the photography system 100 and devices that transmit and receive information with systems other than the photography system. However, in the above embodiment, the timing information source devices 2 and 4 are connected to the control device 12 instead of the console 14, so the console 14 has to perform processes such as synchronization confirmation via the control device 12, which reduces the efficiency of the process.
In view of this problem, for example, as shown in Fig. 22, the timing information source devices 2, 4 may be connected to the console 14. In this way, the timing information source devices 2, 4 and the console 14 are directly connected, so that the console 14 can efficiently carry out processes such as synchronization confirmation.

It is also possible to connect the timing information source devices 2, 4 to the console 14 and to connect the timing information source devices 2, 4 to the control device 12. In this way, not only the console 14 but also the control device 12 can be synchronized with the timing information source devices 2, 4, so that the control device 12 and the console 14 can each be synchronized with the image capture device 3.
In this case, a process may be performed to check whether there is a mismatch in operation timing between the control device 12 and the console 14. In this way, if synchronization between the timing information source devices 2, 4 and the control device 12 or between the timing information source devices 2, 4 and the console 14 is lost due to a communication failure or the like, the operation timing of the control device 12 and the operation timing of the console 14 will be mismatched, and by detecting this, it becomes possible to stop shooting or display a warning.

[Example 1-2]
In the above embodiment, when the timing information source devices 2, 4 and the control device 12 or console 14 are connected by wire, it is necessary to synchronize them, so that they must be connected by a dedicated line.

In view of these problems, in the above embodiment, as shown in FIG. 23, the timing information source devices 2, 4 and the photographing device 3 may be wirelessly connected, and the timing information source devices 2, 4 and the control device 12 may also be wirelessly connected.
In this case, for example, by utilizing the TSF defined in the IEEE802.11 communication standard, that is, by updating the timing information of the photographing side timing unit 37 of the photographing device 3 with the first timing information transmitted from the timing information source devices 2 and 4, the timing information of both timing units can be synchronized.

In this way, the same timing information can be used to synchronize between the timing information source devices 2, 4 and the imaging device 3, and between the timing information source devices 2, 4 and the control device 12. This allows time synchronization without running cables around the subject S. Furthermore, because the timing information is updated based on the same first timing information, the operational lag between the control device 12 and the imaging device 3 can be reduced, and additional configuration to compensate for synchronization lag with other devices is not required. Furthermore, because the timing information is updated using the same radio waves, the lag can be reduced.

Incidentally, instead of wirelessly connecting the timing information source devices 2, 4 and the control device 12, the timing information source devices 2, 4 and the console 14 may be wirelessly connected and synchronized.
Furthermore, the timing information source devices 2, 4 and the control device 12 may be wirelessly connected, and the timing information source devices 2, 4 and the console 14 may be wirelessly connected to achieve synchronization.

[Examples 1-3]
In the above embodiment, when the timing information source devices 2, 4 and the control device 12 are directly connected, there is a problem that there may be restrictions on the arrangement of the timing information source devices 2, 4, the control device 12, and the cables connecting them.
Furthermore, if the timing information source devices 2, 4 and the control device 12 are directly connected, the connection distance becomes longer, which increases the possibility of communication failure occurring between the timing information source devices 2, 4 and the control device 12.

In view of such problems, in the above embodiment, as shown in Fig. 24, the timing information source devices 2 and 4 and the radiation control device may be connected via a network device 5. An example of the network device 5 is a HUB.
In this case, it is preferable to use dedicated lines with little time delay to connect the timing information source devices 2, 4 to the network device 5, and to connect the network device 5 to the control device 12, and to use time synchronization for wired communication defined in IEEE 1588.

This reduces restrictions on the layout of the timing information source devices 2, 4, the control device 12, and the cables.
In addition, by making a connection via the network device 5, it is possible to prevent degradation of the communication signal caused by wiring over long distances without any devices being inserted along the way, thereby making it possible to increase the reliability of communication.

[Examples 1 to 4]
In the above embodiment, when synchronization is performed by an external signal using timing information, there is a problem in that it is not possible to determine whether synchronization is achieved on the imaging device 3 side. Specifically, when wireless communication is not possible due to radio wave interference or the like, even if the imaging device 3 side is aware that synchronization may be lost, it is not possible to convey this to the control device 12, and therefore it is not possible to stop radiation irradiation.

In view of these problems, in the above embodiment, as shown in FIG. 25, the timing information source devices 2, 4 may be built into the photographing device 3, and synchronization may be achieved by transmitting first timing information from the photographing device 3 to the control device 12.
In this case, it is preferable to provide a timer unit in the control device 12 so that the control device 12 is synchronized.
In this way, if synchronization has not been achieved for a certain period of time and there is a possibility of operation being out of sync, the control device 12 can recognize this fact, making it possible to stop radiation irradiation even if wireless communication with the imaging device 3 is not possible.
In addition, since there is no need to go through the timing information source devices 2 and 4 along the way, the risk of communication delays due to an abnormality occurring in the timing information source devices 2 and 4 can be reduced.

[Examples 1 to 5]
In the above embodiment, there is a problem that the radiation device 12 that does not support wireless communication cannot perform time synchronization using wireless communication.
In view of these problems, in the above embodiment, as shown in FIG. 26 , a communication module 16 capable of receiving radio waves from the timing information source devices 2, 4 may be connected to the control device 12, and the reference time from the timing information source devices 2, 4 may be received via the communication module 16.
It is preferable that the communication module 16 and the control device 12 are connected using a dedicated line with little time delay, and that time synchronization for wired communication defined by IEEE1588 be used.

In this way, even a radiation control device that does not support wireless communication can achieve time synchronization using wireless communication.
In addition, since the communication module 16 only receives signals, no wireless signals are emitted from the communication module 16 or the irradiation device 1. This reduces the risk of malfunctions caused by the emission of wireless signals.
In addition, when there is no need to consider the problem of radio signal emission from the communication module 16 or the irradiation device 1, there is no obstacle to providing the communication module with a transmission function.

[Examples 1 to 6]
In the above embodiment, when it is desired to compare the captured still image or dynamic image with the measurement results or captured image by another device, it is necessary to synchronize the imaging system 100 with the other device in order to ensure that the images are captured at the same timing. For example, when capturing images synchronized with a heartbeat, it is necessary to capture images at the same timing as the heartbeat, extract images at the timing of the heartbeat from the captured continuous images, or associate the captured continuous images with heartbeat data, and therefore it is necessary to synchronize the time.

In view of these problems, in the above embodiment, as shown in FIG. 27 , the photographing system 100 and other equipment 6 may be connected by a communication means similar to that of the timing information source devices 2, 4 and the control device 12 or the photographing device 3, and synchronization may be achieved based on the first timing information from the timing information source devices 2, 4.
In this way, it becomes possible to capture images in synchronization with the other device 5. For example, by connecting a heart rate monitor as the other device 5 and controlling the timing appropriately and storing and displaying the timing, it becomes possible to capture images in synchronization with the heart rate and to confirm at which heart rate a captured dynamic image was captured, thereby making a diagnosis.
In addition, examples of other devices 5 are not limited to the heart rate sensor mentioned above, but include various other devices depending on the subject to be photographed, such as a respiratory condition measuring device such as a spirometer, a displacement sensor or acceleration sensor that measures movement, etc.
It should be noted that any or all of the other device 5, the control device 12 and the photographing device 3 may be provided with a means for storing time information.
Furthermore, by storing the timing information, information measured or photographed at the same time can be organized or extracted from the timing information and output.

[Examples 1 to 7]
In the above embodiment, the communication unit that sends and receives timing information for synchronization also sends and receives data, which causes problems such as limitations on the amount of data that can be sent and received and the speed at which it can be sent and received, delays in sending and receiving data, and data being lost midway through sending and receiving.

In view of this problem, in the above embodiment, the timing information source devices 2 and 4 and the control device 12 may be connected by a plurality of different communication means, as shown in FIG.
For example, the timing information source devices 2, 4 and the control device 12 are connected wirelessly, and timing information for synchronizing the time of both timing means is transmitted and received wirelessly, while the timing information source devices 2, 4 and the control device 12 are also connected via a wire (Ethernet, etc.), and information other than time synchronization (e.g. radiation exposure conditions, radiation exposure period, etc.) is transmitted and received via a wire.

In this way, the communication means for time synchronization and the communication means for information transmission and reception can be separated, and information transmission and reception and time synchronization can be achieved simultaneously without causing delays in the transmission and reception of information or loss of information.
In addition, it is possible to select a communication means suitable for time synchronization and for transmitting and receiving information.

[Examples 1 to 8]
In the above embodiment, for example, as shown in Fig. 29, the photographing device 3D may be provided with a second photographing side clock unit 39D different from the above embodiment. This second photographing side clock unit 39D may be configured using, for example, a radio clock, a GPS, an NTP, etc. When a radio clock, a GPS, etc. is used, an antenna for receiving radio waves may be provided.
Then, at an appropriate timing, the timing information of the photographing side timing unit 37 is compared with the timing information of the second photographing side timing unit 39D, thereby detecting any discrepancy between the timing information of the photographing side timing unit 37 and the second photographing side timing unit 39D.

In this way, even if communication between the timing information source devices 2, 4 and the photographing device 3 is interrupted and the deviation between the first timing information of the timing information source devices 2, 4 and the second timing information of the photographing side timing unit 37 gradually increases, as shown in Figure 30, the occurrence of the deviation can be detected by comparing the timing information of the photographing side timing unit 37 with the timing information of the second photographing side timing unit 39D.
In addition, by calculating the difference (deviation) between the timekeeping information of both clocking units, comparing it with a predetermined value, and judging whether the predetermined value has been exceeded, it is possible to grasp whether the accuracy of time synchronization is sufficient. If the deviation exceeds the predetermined value, similarly to the above embodiment, output may be given to notify that the deviation exceeds the predetermined value, to notify that shooting is not permitted, or to stop shooting.

Note that FIG. 30 illustrates an example in which the second photographing side timing unit 39D detects deviations only during a synchronization failure period in which synchronization between the timing information source devices 2, 4 and the photographing device 3 has been lost. However, the second photographing side timing unit 39D may be configured to detect deviations not only during a synchronization failure period, but also during a synchronization period in which synchronization with the timing information source devices 2, 4 is achieved.

[Examples 1 to 9]
In the above-mentioned Examples 1-8, the shooting control unit 31 may be configured to control updating of the timing information of the shooting side timing unit 37 to the timing information of the second shooting side timing unit 39D, or updating of the timing information of the second shooting side timing unit 39D to the timing information of the shooting side timing unit 37.
In this manner, as shown in Figure 31, during the period when communication is taking place between the timing information source devices 2, 4 and the photographing device 3, the photographing device 3 periodically updates the timing information of the photographing side timing unit 37 using the first timing information of the timing information source devices 2, 4, and even after synchronization between the timing information source devices 2, 4 and the photographing device 3 is lost midway, the photographing device 3 periodically updates the timing information of the photographing side timing unit 37 using the timing information of the second photographing side timing unit 39D.
Therefore, even if communication between the timing information source devices 2, 4 and the photographing device 3 is interrupted, it is possible to continue time synchronization with the timing information source devices 2, 4, and photographing can be continued.

Note that FIG. 31 illustrates an example in which the second photographing side timing unit 39D updates the timing information of the photographing side timing unit 37 only during periods when communication between the timing information source devices 2, 4 and the photographing device 3 is interrupted, but the second photographing side timing unit 39D may update the timing information of the photographing side timing unit 37 even during periods when synchronization with the timing information source devices 2, 4 is maintained.

[Examples 1-10]
In the above-mentioned embodiments 1-8 and 1-9, a measuring means may be provided for measuring the reliability of communication between the second photographing side clock unit 39D and the outside.
For example, if the second photographing side clock unit 39D is a type that uses radio waves, such as a radio clock or GPS, a device for measuring the strength of radio waves is provided as the measuring means.
The shooting control unit 31 is then configured to periodically compare the measurement value by the device with a predetermined value, and if the measurement value falls below the predetermined value, it is determined that the reliability of communication cannot be ensured, and output such as notifying the user that the reliability of the third timing means has decreased, notifying that shooting is not permitted, or canceling shooting.
In this way, it is possible to prevent the subject S from being unnecessarily exposed to radiation due to erroneous imaging being performed in a state where the reliability of communication with the second imaging side clock unit 39D is reduced.

[Examples 1-11]
In the above embodiment, for example, as shown in FIG. 32, the timing information may be updated only before entering the shooting period (shifting from standby state to execution), and during the shooting period, the timing information may not be updated, and only the difference (deviation) between the first timing information of the timing information source device 2, 4 and the timing information of the shooting side timing unit 37 may be monitored.
The monitoring may be performed at the time synchronization timing between the timing information source devices 2, 4 and the photographing device 3 (the timing at which the timing information source devices 2, 4 transmit the first timing information), at a predetermined timing in the photographing side timing unit 37, or the like.

It is also possible to start monitoring at both the time synchronization timing of the timing information source devices 2, 4 and a predetermined timing of the photographing device 3. In this way, even if a malfunction occurs in either the timing information source devices 2, 4 or the photographing side timing unit 37, it is possible to monitor the amount of deviation.
In addition, when the second photographing side clock unit 39D as described in the above Examples 1-9 to 1-11 is provided, the difference between the clock information of the photographing side clock unit 37 and the clock information of the second photographing side clock unit 39D may be monitored. In this case, the amount of deviation may be monitored at a predetermined timing in the second photographing side clock unit 39D.

[Examples 1-12]
In the above embodiment, the communication unit 36 of the image capture device 3 or the image capture control unit 31 may have a monitoring function for monitoring whether or not the communication is maintained in a normally established state.
When the shooting control unit 31 or the communication unit 36 having such a monitoring function detects that communication has been disconnected, it determines that communication is not maintained in a normally established state, and outputs an output such as notifying the user that the communication connection has been disconnected, notifying that shooting is not permitted, or canceling shooting.
In this way, it is possible to prevent the subject S from being unnecessarily exposed to radiation due to erroneous imaging being performed without maintaining a normally established communication state.

[Example 2-1]
In the above embodiment, there is a problem that imaging is started without checking whether synchronization has been achieved before imaging, which results in the imaging failing without obtaining the desired imaging results, and the subject S being unnecessarily exposed to radiation if imaging is to be performed again.

In view of such a problem, in the above embodiment, as shown in Fig. 33, time synchronization may be checked when starting imaging, such as when pressing the exposure switch (step S1). If the time is synchronized with a desired accuracy or higher as a result of the check (step S1: Yes), imaging is permitted (step S2) and imaging operation is started (step S3). On the other hand, if the time synchronization accuracy is insufficient (step S1: No), a response is taken such as notifying the user that synchronization is not possible, notifying that imaging is not permitted, or canceling imaging (step S4).
It is preferable that the decision as to whether to notify the user or to notify the user that photography is not permitted be changed depending on the amount of deviation in time synchronization.
In this way, it is possible to prevent the subject S from being unnecessarily exposed to radiation due to erroneous imaging performed in an out-of-synchronization state.

[Example 2-2]
In the above embodiment 2-1, as shown in FIG. 34, after the operation of step S4, the synchronization process may be performed again (step S11), and then the operations of steps S1 to S4 may be repeated.
When performing the synchronization process again, a notification may be given or shooting may be stopped.
Furthermore, it is preferable that the decision as to whether to notify the user or whether to notify the user that photography is not permitted be changed depending on the amount of deviation in time synchronization.
In this way, it is possible to more reliably prevent imaging from being performed in an asynchronous state, resulting in unnecessary exposure of the subject S to radiation.

[Example 2-3]
In the above-mentioned Example 2-2, as shown in FIG. 35, after the second step S4, the timing information source devices 2, 4 and the control device 12, and the timing information source devices 2, 4 and the photographing device 3 may be reconnected (step S21), and then the operations of steps S1 to S4 may be repeated.
If the time synchronization accuracy is still insufficient even after communication is disconnected and then reconnected, it is preferable to take measures such as notifying the user that synchronization is not possible, notifying the user that shooting is not permitted, or canceling shooting.
Furthermore, it is preferable that the decision as to whether to notify the user or whether to notify the user that photography is not permitted be changed depending on the amount of deviation in time synchronization.
In this way, it is possible to more reliably prevent imaging from being performed in an out-of-synchronization state, resulting in unnecessary exposure of the subject S to radiation.

[Example 2-4]
In the above embodiment 2-3, as shown in FIG. 36, after step S4 is performed for the third time, the timing information source devices 2 and 4 may be restarted (step S31), and the operations of steps S1 to S4 may then be repeated.
If the time synchronization accuracy is not sufficient even after the power supply of the timing information source devices 2, 4 is turned off once and then reconnected after restarting the timing information source devices 2, 4, it is preferable to take measures such as notifying the user that synchronization is not possible, notifying that photography is not permitted, or canceling photography.
Furthermore, it is preferable that the decision as to whether to notify the user or whether to notify the user that photography is not permitted be changed depending on the amount of deviation in time synchronization.
In this way, it is possible to more reliably prevent imaging from being performed in an asynchronous state, resulting in unnecessary exposure of the subject S to radiation.

[Example 2-5]
In the above embodiment, there is a problem in that even if the user wants to perform synchronization processing at a desired timing, there is no way for the user to instruct synchronization processing.
In view of this problem, in the above embodiment, as shown in FIG. 37, a specific operation button 3b may be provided on the photographing device 3, and synchronization processing may be performed when this operation button 3b is pressed.
In this way, the times of the photographing device 3 and the timing information source devices 2 and 4 can be synchronized at a timing desired by the user.

The synchronization process may be performed when a special operation is performed, such as when the operation button 3b is pressed for a long time or pressed multiple times.
In this way, other buttons that are already provided can be used as the operation buttons 3b, so that the number of buttons on the photographing device 3 can be reduced without increasing the number of buttons too much.

[Example 3-1]
In the above embodiment, there was a problem that imaging was continued despite a large difference between the operation of the irradiation device 1 and the operation of the imaging device 3, resulting in imaging failure and subject S being unnecessarily exposed to radiation.
In consideration of these problems, in the above embodiment, the user may be notified or shooting may be stopped depending on the difference (amount of deviation) between the first timing information of the timing information source device 2, 4 and the second timing information of the shooting side timing unit 37 of the shooting device 3.

Specifically, the imaging control unit 31, etc. is provided with a function to compare the amount of deviation with a predetermined threshold, and if the amount of deviation exceeds the threshold, a warning is displayed to the user, or radiation irradiation is stopped and imaging is discontinued.
In this way, it is possible to prevent imaging from being performed in an asynchronous state, thereby preventing the subject S from being unnecessarily exposed to radiation.

As shown in FIG. 38, two thresholds, one large and one small, may be set, and a warning may be issued when the amount of deviation exceeds threshold 1 (the lower one), and shooting may be stopped when the amount of deviation exceeds threshold 2 (the higher one).
Furthermore, even if the deviation exceeds the threshold 1 for issuing a warning, if the deviation is showing a decreasing tendency, such as in the time period in range (2), a warning display may not be issued.

[Example 3-2]
In the embodiment described in Example 3-1 above, in order to address the problem of continuing shooting despite a large misalignment between the operation of the irradiation device 1 and the operation of the shooting device 3, Example 3-1 notifies the user or stops shooting depending on the actual amount of misalignment, but it is also possible to predict future misalignment and notify the user or stop shooting depending on the predicted misalignment.

Specifically, the memory unit 31 stores the relationship between the shooting time (number of shots) in past shooting and the difference (amount of deviation) between the first timing information of the timing information source devices 2, 4 and the second timing information of the shooting side timing unit 37.
The shooting control unit 31 is provided with a function as a prediction means for predicting the amount of deviation when the set number of shots are taken in a new shooting based on the relationship between the stored past shooting time and the amount of deviation, a function as a comparison means for comparing the predicted amount of deviation with a predetermined threshold, and a function as an output means for outputting, when it is determined that the predicted amount of deviation exceeds the threshold, a notification that synchronization may be lost and shooting may fail if shooting is continued to the end, a notification that shooting is not permitted, or an output to cancel shooting.
In this way, it is possible to reduce the risk that imaging may be performed in an asynchronous state, resulting in unnecessary exposure of the subject S to radiation.

As shown in FIG. 39, two thresholds, a large one and a small one, are provided, and a warning is issued when it is predicted that the deviation will exceed threshold 1 (the lower one) but not threshold 2 (the higher one), as in case 1, i.e., when it is determined that the deviation will not significantly affect the shooting, and when it is predicted that threshold 2 will clearly be exceeded, as in case 2, i.e., when shooting would definitely fail if shooting were continued until the end, the photographer may be notified that synchronization may become out of sync during the shooting period to the extent that it will affect the image, or shooting may be stopped.

[Example 3-3]
Even if the difference (deviation) between the first timing information of the timing information source device 2, 4 and the second timing information of the imaging side timing unit 37 exceeds a certain threshold, there are cases where an image usable for diagnosis can be obtained. In the above embodiment, when the deviation exceeds the threshold, the imaging is stopped or a notification is given to prompt the user to stop imaging, so that when the deviation exceeds the threshold, the images captured up to that point become useless, and there is a possibility that the subject S may be unnecessarily exposed to radiation.

In consideration of such a problem, in the above embodiment, even if the amount of deviation exceeds the threshold, shooting may be continued up to a predetermined number of images, and a notification to that effect may be given later.
Specifically, the shooting control unit 31 functions as a comparison means for comparing the difference (deviation amount) between the first timing information of the timing information source devices 2 and 4 and the second timing information of the shooting side timing unit 37 with a predetermined threshold value.
Furthermore, the imaging control unit 31 is provided with a function as a notification unit that, when it is determined that the amount of deviation exceeds the threshold, stores that fact and notifies the user during or after the imaging period.
In this way, even if the amount of deviation becomes relatively large, an image that can be used for diagnosis can be obtained, thereby reducing the risk of unnecessarily exposing the subject S to radiation.

When the amount of deviation exceeds the threshold, the period during which the threshold was exceeded may be stored, or specific information (such as a flag) may be linked to the image data of the images taken during the period during which the threshold was exceeded. In this way, when checking the images later, it is possible to identify which images were taken during the period during which the threshold was exceeded.
Also, as shown in FIG. 40, two thresholds, a large one and a small one, may be provided, and the period during which the deviation amount exceeded threshold 1 (the lower one) (a deviation occurred to the extent that a warning was issued), as in case 1, and the period during which the deviation amount exceeded threshold 2 (the higher one) (a deviation occurred to the extent that shooting had to be stopped), as in case 2, may be stored.

[Example 4-1]
In the above embodiment, if the first timing information of the timing information source device 2, 4 and the timing information of the shooting side timing unit 37 were matched all at once, there was a problem that the timing information of the updating timing unit would fluctuate significantly, resulting in malfunctions.
For example, the timing information fluctuates so much that it spans the occurrence of multiple events at once, causing problems such as radiation irradiation, charge accumulation, readout, and transfer to occur simultaneously, making it difficult to take pictures properly.

In view of this problem, in the above embodiment, when it becomes necessary to update the timing information during the shooting period, the timing information may be gradually brought closer to each other rather than being made to match and synchronize.
Specifically, each time the first timing information is transmitted or received, the difference (deviation) between the first timing information of the timing information source devices 2, 4 and the second timing information of the photographing side timing unit 37 is updated so as to gradually decrease.
"Little by little" may be, for example, a predetermined percentage (such as ○%) of the amount of deviation as shown in FIG. 41, or a predetermined amount (such as one-tenth of ○) of the amount of deviation.
In this way, problems caused by large changes in the timekeeping information can be prevented.
On the other hand, if the amount of deviation is large, gradually narrowing the time difference without synchronizing as described above may result in having to wait a long time before the amount of deviation becomes small enough that it does not affect the captured image.
Therefore, depending on the magnitude of the deviation, control may be performed so that the amount of time change for correction is increased so as to reduce the deviation.

[Example 4-2]
In the above embodiment, when the first timing information of the timing information source device 2, 4 and the timing information of the photographing side timing unit 37 are made to coincide at once, the timing information of the updating timing unit becomes smaller than the previous timing information (the time goes back), which causes a problem.
42(a), after the time when the timing information exceeds the time when a certain event is generated, the timing information is updated to return to the time before the time when the event is generated, and the same event is repeated twice. If the event is radiation irradiation, the subject S may be unnecessarily exposed to radiation due to repeated radiation irradiation, or only the frames captured when the radiation irradiation is repeated may be irradiated with radiation R twice, resulting in an image of different image quality from the others.

In view of this problem, in the above embodiment, when it is detected that the timekeeping information of both the timekeeping units is out of sync, the timekeeping speed of at least one of the timekeeping units may be adjusted.
Specifically, as shown in FIG. 42(b), when the first timing information is transmitted and received, the timing information is not updated, but the timing speed of the faster timing unit is slowed down or the timing speed of the slower timing unit is increased, so that the amount of deviation when the first timing information is subsequently transmitted and received is kept to a level that makes it unnecessary to update the timing information.
In this way, problems caused by the timing information becoming small can be prevented.

[Example 4-3]
In response to the problem mentioned in the above embodiment 4-2 that the timing information becomes smaller due to updates, which may result in the same event being repeated, the above embodiment 4-2 changes the timing speed of the timing unit, but as shown in Figure 43, it is also possible to set an event occurrence prohibition period Td immediately after the occurrence of an event, which restricts the occurrence of the same type of event.
In this way, it is possible to prevent the occurrence of a problem in which the same event is repeated without changing the counting speed of the clock section.

[Example 5-1]
In the above embodiment, if communication between the timing information source device 2, 4 (illumination device 1) and the photographing device 3 is interrupted, even if photographing is possible to continue, it is unclear how much photographing is possible, so photographing must be stopped.

In consideration of these problems, in the above embodiment, the number of shots that can be taken is calculated based on the timing speed and accuracy of the timing information source device 2, 4 or the shooting side timing unit 37, and shooting may be continued until the calculated number of shots that can be taken is reached.
Specifically, the relationship between the factors that affect the accuracy of the oscillation period of the oscillators of the irradiation device 1 and the image capture device 3 and the oscillation period is stored in advance in the storage unit 35 .
The photographing control unit 31 is also provided with a function for predicting a change in the amount of deviation based on the difference (deviation) between the first timing information of the timing information source devices 2, 4 and the second timing information of the photographing side timing unit 37 immediately after the connection is lost, the timing speeds of the first and photographing side timing units 37 immediately after the connection is lost, and the relationship between the factors and accuracy stored in the photographing control unit 31. As shown in Fig. 44, this change in the amount of deviation may increase or decrease depending on the accuracy at that time.
In addition, the imaging control unit 31 is provided with a function to calculate the imaging time required until the amount of deviation exceeds a predetermined threshold (the upper limit of the amount of deviation for radiation to be irradiated during the accumulation period) based on the predicted change in the amount of deviation.
The photographing control unit 31 is also provided with a function for calculating the number of photographs that can be taken thereafter from the calculated photographing time and frame rate.
In this way, even if communication between the timing information source devices 2, 4 and the photographing device 3 is interrupted, it is possible to continue photographing up to the maximum number of photographs that can be taken.

[Example 5-2]
In response to the problem mentioned in the above-mentioned Example 5-1 that shooting had to be stopped when communication was interrupted, the above-mentioned Example 5-1 calculates the number of shots that can be taken and continues shooting until the calculable number is reached. However, it may be possible to determine whether or not to continue shooting based on the required number of shots (remaining number) and the accuracy of the oscillators of the irradiation device 1 and the shooting device 3.
Specifically, the same parameters as those in Example 5-1 are stored in the storage unit 35 .
Moreover, the shooting control unit 31 (having a function of calculating the number of shots that can be taken) in the embodiment 5-1 is further provided with a function of comparing the calculated number of shots that can be taken with the remaining number of shots that need to be taken thereafter.
The photographing control section 31 is further provided with a function of continuing photographing when the number of photographable frames is equal to or greater than the remaining number, and outputting a message to the effect that photographing cannot be completed to the end, a message to the effect that photographing is not permitted, or a message to stop photographing when the number of photographable frames is less than the remaining number.
In this way, even if communication between the timing information source devices 2, 4 and the photographing device 3 is interrupted, photographing can be continued as long as the preset number of shots can be taken.

When continuing shooting, the user may be notified that although the connection has been lost, shooting can be continued until the end.
Furthermore, if image capture is continued after communication is interrupted, specific information (such as a flag) may be linked to the image data of the images captured during the period when communication was interrupted.

[Example 5-3]
In the above embodiment 5-1, the number of shots that can be taken may be calculated taking temperature into consideration, that is, the temperature may be used as a factor that affects the accuracy of the oscillation period of the oscillator.
Specifically, the relationship between the temperature and the oscillation period of the oscillators of the irradiation device 1 and the imaging device 3, for example as shown in Fig. 45(a), is stored in advance in the storage unit 35. The solid line in the figure indicates a theoretical value, and the upper and lower dashed lines indicate an upper limit value and a lower limit value taking into account accuracy.
In addition, the shooting control unit 31 is given a function to predict changes in the amount of deviation based on the difference (amount of deviation) between the first timing information of the timing information source devices 2, 4 and the second timing information of the shooting side timing unit 37 immediately after the connection is lost, the timing speeds of the first and shooting side timing units 37 immediately after the connection is lost, and the relationship between factors and accuracy stored in the shooting control unit 31.
Other functions of the imaging control unit 31 are the same as those in the above-mentioned embodiment 5-1.

The temperature of the oscillator has a greater effect on the accuracy of the oscillator's oscillation period than any other factor, so
In this way, as shown in FIG. 45B, it is possible to predict the change in the amount of deviation with higher accuracy, and in turn, it is possible to calculate the number of shots that can be taken with higher accuracy.
As in the above-mentioned embodiment 5-2, it is also possible to judge whether or not the image capturing can be completed to the end, and if it can be completed, to continue the image capturing, and if it cannot be completed, to interrupt the image capturing.

[Example 6-1]
In the above embodiment, it is also possible to not establish synchronization once synchronization has been established.
Specifically, the imaging control unit 31 is provided with a function of performing time synchronization when the first timing information is transmitted immediately after the exposure switch is pressed.
In addition, the imaging control unit 31 has a function of not updating the timing information of the imaging side clock unit 37 while the exposure switch is being pressed after the synchronization confirmation has been performed.
In this way, there is no fluctuation in the operation timing of the image capturing device 3 during the image capturing period, so that image capturing can be performed stably.

In addition, after time synchronization, the shooting control unit 31 may measure the difference between the first timing information and the second timing information when the next first timing information is transmitted, to check whether time synchronization has been performed normally, whether the amount of deviation after time synchronization is within a predetermined value, etc.
In this way, it is possible to prevent the subject S from being unnecessarily exposed to radiation due to erroneous imaging being performed in an actually out-of-synchronization state.

[Example 6-2]
In the above embodiment, when synchronization is performed irregularly, there is a problem that the fluctuation in the operation timing of the irradiation device 1 or the imaging device 3 affects the captured image, which may cause a misdiagnosis.
In view of such a problem, in the above embodiment, as shown in FIG. 46, synchronization may be achieved in accordance with the shooting cycle (for each frame) during the shooting period.
In this way, synchronization is achieved at the same timing in shooting each frame, so that it is possible to prevent influences caused by synchronizing the operation timing only for a specific frame image.
The effects of such fluctuations in operation timing on images are likely to be particularly evident when using differences in features between adjacent frame images for analysis, but by following the steps described above, it is possible to prevent such effects from being felt in analysis that uses differences in features.

The first timing information transmission period of the timing information source devices 2 and 4 may be set to the same as the photographing period or to an integer division of the photographing period.
In this case, the timing of transmitting the first timing information and the timing of synchronization may be shifted by a predetermined phase.

[Example 6-3]
In response to the problem mentioned in the above embodiment 5-1 that irregular synchronization may affect the captured image, the above embodiment 5-1 is configured to synchronize for each frame captured, but it is also possible to synchronize every few tens of frames, for example, as shown in Figure 47.
In this way, even when serial imaging is performed for a long period of time, the influence on the frame images can be reduced.

In this case, it is preferable to synchronize at a timing during the shooting period that is unlikely to affect the image.
For example, when performing serial imaging of the lung field, synchronization is achieved not with the timing of inhalation or exhalation (when lung movement is large) which is of interest in diagnosis, but with the timing when air has been completely inhaled or exhaled (when lung movement is small).
In this way, it is possible to prevent the influence of fluctuations in the timing of operations on images captured at timings of interest in diagnosis.

[Example 6-4]
In response to the problem mentioned in the above embodiment 5-1 that irregular synchronization may affect the captured image, the above embodiment 5-1 is configured to synchronize each time each frame is captured, but it is also possible to synchronize every few frames, as shown in FIG. 48, for example.
As in the above-mentioned Example 6-1, if synchronization is performed for each frame, the processing may take a long time and may not be completed within the shooting time of the frame, which may affect the next frame. On the other hand, as in the above-mentioned Example 6-2, if synchronization is performed for every several tens of frames, the deviation in the operation timing may become too large. However, by doing this, it is possible to synchronize at appropriate intervals, so that the effect of the synchronization process on the next frame can be eliminated, and the amount of change in the timing when synchronizing can be reduced, thereby reducing the effect on the captured image.

It should be noted that after a process for changing the time information of the clock unit is performed in a certain frame, a process related to this may be performed in the next frame or later.
In this way, the updating of the timing information and other processing can be distributed across multiple frames, and the updating of the timing information can be reliably performed at the specified timing even when the device is under a load from other processing.

[Example 6-5]
In response to the problem mentioned in the above embodiment 5-1 that irregular synchronization would affect the captured image, the above embodiment 5-1 is configured to synchronize for each frame captured, but it is also possible to synchronize at a period shorter than the capture period (synchronization multiple times during the capture of one frame), as shown in FIG. 49, for example.
In this way, the amount of change in timing when synchronizing can be reduced, and the effect on the captured image can be reduced.

Although not shown in the drawings, the timing of a specific sequence in shooting one frame may not be synchronized.
The specific sequence refers to, for example, the accumulation of electric charge by the imaging device 3, the reading and transfer of image data, and initialization.
Since such a specific sequence is susceptible to the effects of synchronization processing, this can reduce the effects on the captured image. Specifically, by not synchronizing the accumulation timing, the effects on the image contrast of each captured frame can be reduced, and by not synchronizing the readout/transfer timing, the effects of noise can be reduced.

[Example 6-6]
In the above embodiment, synchronization may affect the captured image, so depending on the imaging technique or image analysis method, there may be a demand to not perform synchronization processing as long as the operational delay is within an acceptable range.
In consideration of these problems, in the above embodiment, as shown in Figure 50, the difference (deviation) between the first timing information of the timing information source device 2, 4 and the second timing information of the shooting side timing unit 37 may be measured periodically, and synchronization may be achieved only when the deviation exceeds a threshold value.
In this way, it is possible to minimize the need for synchronization operations and reduce the risk of the captured image being affected.

Even if the deviation exceeds the threshold value, synchronization may not be achieved immediately while the specific sequence is being performed, but may be achieved after the specific sequence is completed.
The specific sequence refers to, for example, the accumulation of electric charge by the image capturing device 3, the reading and transfer of image data, and initialization.
Since there is a possibility that an image may be affected if synchronization is performed during execution of a specific sequence, this makes it possible to minimize the effect on the captured image.

Furthermore, information indicating that synchronization processing has been performed may be associated with the frame image captured at the synchronized timing and saved.
In this way, it is possible to later check which frame the synchronization process was performed on. If the synchronization process affects the image, by identifying the frame later, it is possible to determine whether the effect on the image was caused by the synchronization process or by the diagnosis target.

[Example 7-1]
In the above embodiment, when the operations of the irradiation device 1 and the imaging device 3 are out of sync, the image quality may be affected depending on which device's operation is used as the reference for synchronization.
In view of this problem, in the above embodiment, the operation of the irradiation device 1 may be synchronized with the image capturing device 3 when a misalignment in operation is detected.
Specifically, as shown in FIG. 51, the radiation irradiation timing that has become earlier is delayed, and conversely, the radiation irradiation timing that has become later is advanced.
When the operation of the photographing device 3 is modified, the contrast between frame images is likely to be affected, but by doing so, it is possible to prevent the contrast from being affected.

As in the above-described Example 6-6, the frame images captured at the synchronized timing may be associated with information indicating that the synchronization process has been performed and saved.
In this way, it is possible to later check which frame the synchronization process was performed on. If the synchronization process affects the image, by identifying the frame later, it is possible to determine whether the effect on the image was caused by the synchronization process or by the diagnosis target.

[Example 7-2]
In response to the problem mentioned in the above Example 7-1 that the image quality is affected depending on which of the irradiation device 1 and the imaging device 3 is used as the reference for synchronization, the operation of the irradiation device 1 is corrected based on the imaging device 3 in the above Example 7-1, but it is also possible to adjust the operation of the imaging device 3 to match that of the irradiation device 1 when an operational misalignment is detected.
Specifically, as shown in FIG. 52, the delayed accumulation timing is advanced by shortening the initialization timing, or conversely, the advanced accumulation timing is delayed by lengthening the initialization timing.

Even if the need for synchronization arises, synchronization may not be achieved immediately while the specific sequence is being performed, but may be achieved after the specific sequence is completed.
The specific sequence refers to, for example, the accumulation of electric charge by the image capturing device 3, the reading and transfer of image data, and initialization.
Since there is a possibility that an image may be affected if synchronization is performed during execution of a specific sequence, this makes it possible to minimize the effect on the captured image.

Also, similarly to the above-mentioned embodiment 7-1, the frame images captured at the synchronized timing may be associated with information indicating that the synchronization process has been performed and saved.
In this way, it is possible to later check which frame the synchronization process was performed on. If the synchronization process affects the image, by identifying the frame later, it is possible to determine whether the effect on the image was caused by the synchronization process or by the diagnosis target.

[Example 7-3]
In the above-mentioned Example 7-1, there was a problem that the image quality is affected depending on which of the irradiation device 1 and the photographing device 3 is used as the reference for synchronization. In the above-mentioned Example 7-1, the operation of the irradiation device 1 is corrected based on the photographing device 3. However, as shown in FIG. 53, if a misalignment in operation is detected, the operation of both the irradiation device 1 and the photographing device 3 may be corrected.
When correcting the operation of the irradiation device 1 and correcting the operation of the photographing device 3 have different effects on an image, it is difficult to eliminate the effect on the image by correcting only one of them. However, in this way, the operation of the irradiation device and the operation of the photographing device can be corrected little by little, so that the effect on each image can be reduced.

The operations of both the irradiation device 1 and the radiation detector may be corrected based on the first timing information from the timing information source devices 2 and 4.
In this way, the timing information source devices 2 and 4 connected to the irradiation device 1 and the imaging device 3, respectively, are used as a reference, and synchronization can be stably achieved.
In addition, the timing information source devices 2, 4 can communicate with external networks using communication standards such as IEEE 1588, thereby enabling them to cooperate with other external timing units to perform time synchronization, thereby enabling more accurate timing information to be used as a reference.
In addition, the irradiation device 1 and the photographing device 3 generate heat during their operation, which may affect the oscillator that serves as the reference for the built-in timing unit. However, by doing this, the timing information source devices 2 and 4 can be installed away from the irradiation device 1 and the photographing device 3, and are less susceptible to the effects of heat from these devices, making it possible to provide a stable count.

In addition, the configuration may be such that it is possible to switch between correcting the operation of the irradiation device 1, correcting the operation of the imaging device 3, or correcting both, depending on the imaging content and imaging technique. In this way, by selecting a synchronization method according to the imaging method and imaging technique, it is possible to keep the influence on the image within a tolerance range that differs for each imaging method and imaging technique.
In addition, when correcting both, the ratio of the corrections of both may be changed. For example, in blood flow analysis, it is important to suppress contrast fluctuations between adjacent frame images. In this way, it is possible to make the ratio of the correction amount on the irradiation device 1 side larger than the correction amount on the imaging device 3 side so as to suppress contrast fluctuations.

[Example 7-4]
In response to the problem mentioned in the above Example 7-1 that the image quality is affected depending on which of the irradiation device 1 and the imaging device 3 is used as the basis for synchronization, in the above Examples 7-1 to 7-3, the operation of at least one of the irradiation device 1 and the imaging device 3 is modified. However, even so, when synchronization is achieved while a specific sequence is being performed, the image may still be affected.
In view of this problem, in the above embodiment, synchronization may not be achieved at the timing of a specific sequence in shooting one frame.
The specific sequence refers to, for example, the accumulation of electric charge by the imaging device 3, the reading and transfer of image data, and initialization.
Since there is a possibility that an image may be affected if synchronization is performed during execution of a specific sequence, this makes it possible to minimize the effect on the captured image.

[Example 8-1]
In the above embodiment, if the imaging device 3C independently generates the readout start time from the imaging sequence start time and the frame rate, and the control device 12 similarly independently generates the exposure start time, imaging will fail if the frame rate switching timing differs between the imaging device 3C and the control device 12. For example, when frame rate information is transmitted from the control device 12 to the imaging device 3C, it is considered that the frame rate switching timing on the imaging device 3C side will be delayed due to a communication delay caused by packet loss or the like.

In view of these problems, in the above embodiment, a common frame number may be counted by the control device 12 and the photographing device 3C, and when the control device 12 (which may be the photographing device 3C) receives an instruction to change the frame rate, it may transmit the rate switching frame number and frame rate to the photographing device 3C.
The rate switching frame number can be set to the current frame number plus a number greater than "expected communication delay/frame period+1", thereby making it possible to avoid the influence of communication delay.
The control device 12A and the image capturing device 3C switch the frame rate when the rate switching frame number is reached.
In this way, the frame rate switching timing can be prevented from being delayed.

In addition, the rate switching time may be notified instead of the rate switching frame number. However, if the rate switching time is close to a frame change, the switching timing may not match depending on the synchronization accuracy of the timing unit, so the rate switching time should not be set to a frame change ±α. Also, α should be a value greater than the expected synchronization accuracy during shooting.

[Example 8-2]
In the above-mentioned Example 8-1, when the reading start time is generated independently by the imaging device 3C and the exposure start time is generated by the control device 12, there is a problem that the timing for switching the frame rate on the imaging device 3C side is delayed due to communication delays. In the above-mentioned Example 8-1, a frame number common to the control device 12 and the imaging device 3C is counted, and when the control device 12 receives an instruction to change the frame rate, the rate switching frame number and frame rate are transmitted to the imaging device 3C. However, imaging at a desired frame rate may be realized by having the imaging device 3C read out at the fastest frame rate and having the control device 12 perform exposure every time the imaging device 3C reads out a predetermined number of times.
For example, when shooting at 7.5 fps in a system with a fastest frame rate of 15 fps, the imaging device 3C is made to read out images at 15 fps, and the control device 12 is made to perform exposure once every time the imaging device 3C reads out two frames.

In this manner, a method can be used in which the imaging device generates the readout start time independently and the radiation control device generates the exposure start time independently. Therefore, the minimum information that needs to be shared between the imaging device 3C and the control device 12A is the imaging sequence start time and the frame rate only. This reduces the risk of imaging failure caused by communication delays or packet loss between the imaging device 3C and the control device 12A, such as reading out start time information arriving after the timing when reading should actually be started, or exposure start time information arriving after the timing when exposure should actually be started.
In addition, this eliminates the need for frame rate switching information to be exchanged between the control device 12 and the image capturing device 12A as in Example 8-1 above, making it possible to switch frame rates instantaneously. This allows the user to select the frame rate they need at the timing they need, improving usability.

[Example 8-3]
In the above-mentioned Example 8-2, the imaging device 3C has the fastest frame rate, and the exposure is performed every time the imaging device 3C reads out several frames, so that unexposed images (hereinafter, white images) are mixed in with the frame images generated by the imaging device 3C. Then, there is a problem that the visibility of the dynamic image mixed with the white images is poor.
In view of this problem, in the above-mentioned Example 8-2, the white image may be excluded.
Specifically, for each frame, the average or maximum signal value of pixels in a predetermined area (including the entire area) in the frame is compared with a predetermined threshold, and if it is equal to or less than the threshold, it is determined to be a white image. If it is determined to be a white image, the frame is deleted, or white image attribute information is assigned to the frame, and the frame image with the attribute is not displayed when it is displayed.
These processes may be performed by the photographing device 3C or by the console 14. However, performing these processes by the photographing device 3C can reduce the amount of data transmitted from the photographing device 3C to the console 14, thereby making it less likely that a delay will occur between photographing and displaying the frame image on the console 14.

[Example 8-4]
In regard to the problem of white images being mixed into the frame images generated in Example 8-2, mentioned in Example 8-3 above, in Example 8-3, frames determined to be white images based on the signal values of the pixels of the frame image are excluded, but frames determined to be white images based on the frame number may also be excluded.

Specifically, in accordance with a common rule between the control device 12 and the photographing device 3C, a unique frame number (for example, a consecutive number) is assigned to each of all frames in a series of photographs.
The control device 12 also has a function of linking information indicating the presence or absence of exposure to a frame number, storing the information as exposure frame information, and transmitting the exposure frame number to the imaging device 3C or the console 14.
The imaging device 3C or the console 14 is then provided with a function to save the timer time for each frame (e.g., the start and end times of exposure, or any time within one frame, etc.) and, by referring to the received exposure frame number, delete a frame image that has been read out without exposure or not display that frame image.

The control device 12 may have a function of saving the timer time for exposed or unexposed frames as information indicating whether or not each frame has been exposed, and transmitting this information to the imaging device 3C or console 14, and the imaging device 3C or console 14 may have a function of saving the timer time for each frame, comparing it with the received information, and deleting frame images that have been read out without exposure, or not displaying the frame images.
In this way, since there is no need to determine whether an image is white or not, the processing load in the imaging device and console can be reduced, thereby shortening the delay between imaging and displaying the frame image on the console.

[Example 8-5]
In the above embodiment, there is a demand to be able to perform exposure and associated readout at any timing after starting imaging by pressing the exposure switch.
An arbitrary timing may be, for example, the timing when the tube 13 reaches a predetermined position (or multiple positions) when imaging is performed while changing the position of the tube 13, the timing when a predetermined announcement is made (or multiple times) when an announcement is made to encourage the subject S to breathe, or the timing when the subject S reaches a predetermined position when imaging is performed while changing the position of the subject S.

In consideration of such problems, in the above embodiment, after an arbitrary timing is reached, the control device 12 determines the exposure start time and the readout start time, and the irradiation control device 12A notifies the imaging device 3C of the readout start time.The control device 12 then starts exposure when the timing information of the timing unit reaches the exposure start time, and the imaging device starts readout when the timing information of the timing unit reaches the readout start time.
The exposure start time and the readout start time are determined based on an expected wireless communication delay.
The readout start time is set to the synchronized timing information at the time the arbitrary timing is reached plus the greater of either "the time from the current time until the imaging device receives the readout start time and starts reading (determined taking into account expected wireless notification delays)" or "the time required for the control device 12 to prepare to start exposure + the exposure time of one frame."
In addition, the exposure start time is set to a time at least "one frame's exposure time" before the readout start time.

In this way, it is possible to avoid a situation in which the reading start time has already passed when the photographing device 3C receives the reading start time, and therefore it is possible to prevent photographing failure.
Note that the imaging apparatus 3C may determine the exposure start time and the readout start time instead of the control apparatus 12A.

[Example 8-6]
In the above embodiment 8-5, in order to address the issue of being able to perform exposure and associated readout at any timing after starting imaging by pressing the exposure switch, the control device 12 determines the exposure start time and readout start time after the arbitrary timing is reached in the above embodiment 8-5, but the imaging device 3C and the control device 12 may independently generate the readout start time from the imaging sequence start time and frame rate so that imaging can always be performed at the fastest frame rate, and the control device 12 may independently generate the exposure start time. In addition, the imaging device always performs readout at the fastest frame rate, and the control device 12 instructs the tube 13 to start exposure when the nearest exposure timing is reached after the arbitrary timing is reached.

In the above Examples 1-5, if the expected wireless notification delay is large, the time from when the arbitrary timing is reached to when exposure starts becomes long, and exposure cannot be performed at the desired timing, which may result in failed imaging. However, by doing this, the maximum delay from when the arbitrary timing is reached to when exposure starts can be limited to the period of the fastest frame rate (for example, approximately 66.6 ms for 15 fps), thereby preventing imaging failures due to delays.
In this case, a white image is generated, but this problem can be avoided by applying the above-mentioned Example 8-3 or the like.

[Example 9-1]
The above embodiment is an imaging method in which exposure and readout are performed according to the timing information of multiple synchronized timing units. Therefore, when capturing multiple frames continuously, if the synchronization accuracy of the timing units decreases during a series of exposures, the timing of exposure and readout may not match.

In view of this problem, in the above embodiment, synchronization may be achieved using the timing information only when the imaging sequence is started.
Specifically, the radiation control unit 121 has a function of starting operation when the timing information of the second irradiation side timing unit 126 reaches the imaging start trigger time, and performing exposure at a predetermined timing.
The photographing control unit 31 also has a function of starting operation when the timing information of the second photographing side clock unit 39 reaches the photographing start time, and reading out at a predetermined timing.
The timing at which the imaging device 3 executes the readout sequence is determined in advance to be after the timing at which the control device 12 executes the exposure sequence.

In this way, as shown in FIG. 54, the imaging device 3 starts read sequence control based on the timing information, and after the control device 12 starts exposure sequence control based on the timing information, exposure and readout are performed without using the timing information. Therefore, as shown in FIG. 55, even if an abnormality occurs in the timing information source devices 2 and 4 during the imaging period and the timing information of the second timing units 39 and 126 respectively fluctuates, the control device 12 and imaging device 3 can continue to operate without being affected.

[Example 9-2]
In the above embodiment, the photographing device 3 is provided with the photographing side clock unit 37 and the second photographing side clock unit 39, and the photographing side clock unit 37 is synchronized with the timing information source devices 2 and 4 regardless of the operation mode of the second photographing side clock unit 39. This is the configuration when a general WLAN module is used.
However, by customizing the WLAN module, it is possible to eliminate the need for the photographing side timing unit 37 and synchronize the timing information source device 2, 4 with the second photographing side timing unit 39 when the second photographing side timing unit 39 is in synchronization mode.
If the photographing side clock unit 37 is not provided, the number of clock units used will be reduced accordingly, making it possible to reduce and simplify the scale of the circuits and software.
Note that, although the case where the photographing device 3 is not provided with the photographing side timing unit 37 has been described here, it is also possible to not provide the illumination side timing unit 125 in the control device 12 and to synchronize the second illumination side timing unit 126 with the timing information source devices 2 and 4.

[Example 9-3]
In the above embodiment, the shooting sequence start time is determined based on a notification signal indicating completion of irradiation preparation from the high voltage generating unit 122. However, depending on the specifications of the high voltage generating unit 122 and the system configuration, modification of the device or wiring may be required to transmit the notification signal indicating completion of irradiation preparation, which may result in increased development costs.
In view of such a problem, in the above embodiment, an alternative trigger other than the notification of completion of preparation for irradiation may be used to determine the start time of the imaging sequence.
Possible alternative triggers are as follows: (1) to (3).
(1) The first step of the exposure switch is pressed. (2) The second step of the exposure switch is pressed. (3) A user instruction is received via the UI of the console 14, the imaging device 3, the control device 12, or the exposure switch 15a.

However, the time from when the exposure switch is pressed down to when it is pressed down to the second level varies depending on the user's operation. Also, after the exposure switch is pressed down to the first level, in order for the high voltage generating unit 122 to complete preparation for irradiation, it is necessary to complete the rotor up of the rotating anode in the tube 13, but the rotor up time also varies depending on the conditions. For this reason, when the above (1) is used as an alternative trigger, it is not possible to predict the time from when the exposure switch is pressed down to when preparation for irradiation is completed, and a new problem arises in that the exposure start time and the readout start time cannot be determined.
To deal with this problem, it is effective to carry out steps 6 to 11 of the above-mentioned serial photography procedure as follows. Note that the procedures up to step 5 and from step 12 onwards are the same as those described above. Also, supplementary notes and the like that were given in the above explanation will be omitted.

(Step 6)
When the control device 12 detects that the exposure switch has been pressed to the first position (receives the imaging start signal), it transmits a command to that effect to the imaging device 3 .
(Step 7)
When the image capturing device 3 receives the command, it transitions to a state in which it is ready to capture images.
Thereafter, the image capture device 3 and the control device 12 wait for the second timing units 39 and 126 to update their respective second timing information to the first timing information of the timing information source devices 2 and 4 .
When the updating of the timing information of the second timing unit 39, 126 is completed, the photographing device 3 calculates the start time of the photographing sequence by adding the waiting time for the start of the photographing sequence stored in the memory unit 35 to the timing information of the second timing unit 39 at the time of completion, and stores this in the memory unit 35 and transmits it to the control device 12.
In the above, the photographing device 3 is configured to transmit the photographing sequence start time to the control device 12. However, the control device 12 may also be configured to calculate the photographing sequence start time by adding the photographing sequence start waiting time stored in the memory unit 123 to the timing information of the second timing unit 126 at the time when both updates are completed, and store this in the memory unit 126 and transmit it to the photographing device 3.

(Step 8)
Even after the image capturing device 3 and the control device 12 have completed synchronization with each other, they continue to determine whether or not they are synchronized.
Furthermore, when the imaging device 3 and the control device 12 detect that synchronization has failed during the period from the time when synchronization between the imaging device 3 and the control device 12 is completed to the start of readout of the last frame of serial imaging after an irradiation preparation completion notification signal is transmitted from the high voltage generating unit 122 to the control unit 121, the imaging device 3 and the control device 12 operate the second clock units 39, 126 in a self-running mode for at least the period from that time to the start of readout of the last frame of serial imaging, and thereafter return to the synchronous mode. Note that, when synchronization failure is detected, by switching to the self-running mode before updating the timing information of the second clock units 39, 126 to the timing information of the clock units 37, 125, it is possible to prevent an abnormal value from being set in the second clock units 39, 126.

(Step 9)
Furthermore, when the control device 12 receives the imaging sequence start time from the imaging device 3, it stores it in the storage unit 123. Then, based on the stored imaging sequence start time and the frame rate (15 fps, etc.), it generates an exposure start time for each frame.
A specific method of generating the exposure start time is, for example, to set the imaging sequence start time as the exposure start time of the first frame, and from the second frame onwards, to cumulatively add the imaging cycle (=1/frame rate) to it. In this case, the exposure start time of the Nth frame = imaging sequence start time + (frame number N-1) x imaging cycle.

(Step 10)
Furthermore, the control unit 121 transmits a signal to the high voltage generating unit 122 to instruct the start of exposure for each frame every time the timing information of the second irradiation side timing unit 126 coincides with the exposure start time for each frame.
Each time high-voltage generating unit 122 receives a signal instructing to start exposure, if exposure is possible, high-voltage generating unit 122 controls tube 13 to irradiate radiation R for a preset irradiation time. That is, control device 12 causes tube 13 to irradiate radiation R when the timing information of second irradiation side timing unit 126 reaches a first predetermined value.

(Step 11)
Furthermore, when the control unit 121 detects an image capture end event, such as when the first stage of the exposure switch 15a is released, the number of image capture frames reaches the maximum number of frames stored in the storage unit 123, a stop notification is received from the high voltage generating unit 122, or a stop notification is received from the image capture device 3, the control unit 121 transmits a command notifying the end of image capture via the communication unit 124 to the image capture device 3, and does not transmit a new exposure start instruction for the image capture to the high voltage generating unit 122. In other words, the image capture is terminated.

In addition, after the second stage of the exposure switch is pressed, in order for the high voltage generating unit 122 to be ready for irradiation, it is necessary to complete the rotor up of the rotating anode in the tube 13, but the rotor up time also varies depending on the conditions. Therefore, when the above (2) is used as the alternative trigger, it is necessary to set the maximum time required for rotor up as the time from when the second stage of the exposure switch is pressed to when irradiation preparation is complete, and since the user has to wait a relatively long time from when the second stage of the exposure switch is pressed to when imaging starts, a new problem occurs in that imaging cannot be started at the intended timing (for example, at maximum inspiration, etc.).
To address this problem, serial photography can be performed by replacing "first step of the exposure switch" with "second step of the exposure switch" in the description of the flow of serial photography when (1) above is used as the alternative trigger.

Furthermore, when the above (3) is used as an alternative trigger, if neither the first nor second stage of the exposure switch goes through the control device 12 (if the exposure switch is directly connected to the tube 13), the user will instruct the start of imaging via a UI such as the console 14, the imaging device 3, the control device 12, or the exposure switch. However, just as in the case where the above (1) is used as an alternative trigger, there is a problem in that the time from the user operation to the completion of irradiation preparation cannot be predicted, and the exposure start time and readout start time cannot be determined.
To address this problem, serial photography can be performed by replacing "first press of the exposure switch" in the description of the flow of serial photography when the above (1) is used as the trigger with "user instructions via the UI of the console 14, the photography device 3, the control device 12, or the exposure switch 15a, etc."

[Example 9-4]
In the above-mentioned Example 9-3, there is a problem that a white image is generated until the high voltage generating unit 122 and the lamp 13 are ready for exposure, but this problem can be avoided by applying the above-mentioned Example 8-3, etc.

[Example 9-5]
In regard to the problem mentioned in the above Example 9-3 that a white image is generated until the high voltage generating unit 122 and the tube 13 are ready for exposure, in the above Example 9-3, the presence or absence of a white image was determined from the pixels of the frame image, but if the control unit 121 obtains information indicating that exposure is in progress from the high voltage generating unit 122, the control unit 121 may determine the presence or absence of a white image based on that information.
Specifically, the radiation control unit 121 is provided with the function of storing in the memory unit 126 the timing information of the second timing unit 126 at the time when the exposure is first indicated as being in progress after the shooting sequence start time is reached, and transmitting the information to the console 14 or the shooting device 3.
The shooting control unit 31 is also provided with a function of comparing the readout start time of each frame stored in the memory unit 35 with the received timing information at the time when irradiation was first indicated, and deleting images of frames that have not been exposed or not displaying them when displaying frame images.
In this way, since it is not necessary to determine whether an image is a white image from the pixels of the image, it is possible to reduce the processing load in the image capturing device 3 and the console 14. This also makes it possible to reduce the occurrence of a delay between when an image is captured and when a frame image is displayed on the console 14.

[Example 9-6]
In response to the problem raised in Example 9-3 above of a white image being generated until the high voltage generating unit 122 and the tube 13 are ready for exposure, in Example 9-3 above, the presence or absence of a white image was determined from the pixels of the frame image, but the imaging device 3 may be equipped with a radiation sensor capable of measuring the amount of radiation, and when the measurement value of the radiation sensor exceeds a predetermined threshold value after the imaging sequence start time is reached, it may be assumed that imaging of the first frame has begun, and previous frames may be deleted or not displayed when displayed.
In this way, since it is not necessary to determine whether an image is a white image from the pixels of the image, it is possible to reduce the processing load in the image capturing device 3 and the console 14. This also makes it possible to reduce the occurrence of a delay between when an image is captured and when a frame image is displayed on the console 14.

[Example 9-7]
In the above Example 9-6, if the radiation detection accuracy of the radiation sensor satisfies the minimum accumulated dose per frame, the measurement value of the radiation sensor may be read out for each frame and compared with a threshold value, and the sensor value may be initialized in preparation for the next frame.
If the radiation detection accuracy of the radiation sensor is below the minimum cumulative dose per frame, the measurement value is not initialized for each frame, but the cumulative value of the dose over multiple frames is compared with a threshold, and if the cumulative value exceeds the threshold, exposure is deemed to have started. In this way, it is possible to use inexpensive radiation sensors with low radiation detection performance.

[Examples 9-8]
In the configuration described in Example 9-7 above in which the cumulative dose value of multiple frames is compared with a threshold value, if there is a long period of time between when the first stage of the exposure switch is pressed and when the second stage is pressed, the radiation sensor may not be initialized for a long period of time, causing noise to accumulate, which may result in an erroneous determination that the threshold value has been exceeded.
To address this problem, initialization may be performed every time a predetermined time or number of frames elapses.

[Example 9-9]
In the above embodiment, serial imaging was performed in which the number of exposure frames and the number of readout frames were equal, but some imaging systems require a frame without exposure (only readout) before the first exposure frame. For example, in order to stabilize the temperature inside the imaging device or to obtain a frame image without exposure for the purpose of using it for image processing, a predetermined number of frames (or more) are readout only without exposure, and then exposure and readout are performed.
When the above embodiment is applied to an imaging system that requires such non-exposed frames, if the switching between non-exposed frames and exposed frames is not appropriately controlled, exposure may be performed when acquiring a non-exposed frame, which may result in the desired image not being obtained and the imaging failing.

To deal with this problem, it is effective to change steps 6 to 16 of the above-mentioned serial photography flow to steps 6 to 15 below. Note that the flow up to step 5 is the same as above. Also, the supplementary notes provided in the above explanation will be omitted.

(Step 6)
When synchronization between the timing unit 37 and the timing information source devices 2 and 4 is completed, the photographing device 3 transitions to a state in which photographing is possible.
Thereafter, the image capture device 3 and the control device 12 wait for the second timing units 39 and 126 to update their respective second timing information to the first timing information of the timing information source devices 2 and 4 .
Here, if the update of the timing information is not completed within a predetermined time, the console 14 or the like may be notified that synchronization has failed, and a display unit (not shown) of the console 14 may display a message indicating that synchronization has failed, a message encouraging troubleshooting such as restarting the timing information source devices 2 and 4 or checking the network settings, or a message encouraging wired shooting, etc. This allows for early recovery from the abnormality.
When the updating of the timing information of both second timing units 39, 126 is completed, the photographing device 3 calculates the start time of the photographing sequence by adding the waiting time for the start of the photographing sequence stored in the memory unit 35 to the timing information of the second timing unit 39 at the time of completion, and stores this in the memory unit 35 and transmits it to the control device 12.
In the above, the photographing device 3 is configured to transmit the photographing sequence start time to the control device 12. However, the control device 12 may also be configured to calculate the photographing sequence start time by adding the photographing sequence start waiting time stored in the memory unit 123 to the timing information of the second timing unit 126 at the time when both updates are completed, and store this in the memory unit 126 and transmit it to the photographing device 3.

(Step 7)
Even after the image capturing device 3 and the control device 12 have completed synchronization with each other, they continue to determine whether or not they are synchronized.
In addition, when the photographing device 3 and the control device 12 detect that synchronization has failed during the period from the time when synchronization between the photographing device 3 and the control device 12 that have transitioned to a photographing-enabled state is completed to the time when the readout of the last frame of serial photographing begins, the photographing device 3 and the control device 12 operate the second timing units 39, 126 in a self-running mode for at least the period from that time to the time when the readout of the last frame of serial photographing begins, and thereafter return to the synchronous mode.

(Step 8)
Furthermore, the image capturing device 3 generates a readout start time for each frame based on the image capturing sequence start time, the frame rate, and the accumulation time per frame stored in the storage unit 123 .
The accumulation time is set to be longer than the irradiation time per frame in order to avoid exposure during readout.
(Step 9)
Furthermore, when the control device 12 receives the imaging sequence start time from the imaging device 3, it stores it in the storage unit 123. Then, based on the stored imaging sequence start time and the frame rate (15 fps, etc.), it generates an exposure start time for each frame.

(Step 10)
Furthermore, the imaging device 3 starts reading out the charges accumulated in the radiation detection unit 32 each time the second imaging side clock unit 39 coincides with the readout start time of each frame, and generates image data of a frame image. Then, when the imaging device 3 completes reading out the number of frames required for warm-up (or when it finishes acquiring non-exposed frame images required for image processing), it notifies the control device 12 of permission for imaging. Even after the notification of permission for exposure, the imaging device 3 starts reading out the charges from the radiation detection unit 32 each time the second imaging side clock unit 39 coincides with the readout start time of each frame, and generates a frame image.

(Step 11)
When the control unit 121 of the control device 12 detects that the exposure switch 15a has been pressed to the second level (receives the shooting start signal), it sends a signal to that effect to the high voltage generating unit 122 and transitions to a standby state in which it waits for a completion notification signal to be returned from the high voltage generating unit 122 indicating that preparations for irradiation have been completed.
Upon receiving the imaging start signal, the high voltage generation unit 122 starts preparation for irradiation. Specifically, the high voltage generation unit 122 prepares the voltage and current to be output to the tube 13, instructs the tube 13 to start rotating the rotating anode, and so on.

(Step 12)
Furthermore, the control unit 121 does not instruct the high voltage generation unit 122 to start exposure until it receives both an irradiation preparation completion notification signal from the high voltage generation unit 122 and an exposure permission notification from the imaging device. Upon receiving both, the control unit 121 notifies the imaging device of the completion of irradiation preparation by a communication command, and then transmits a signal to the high voltage generation unit 122 to instruct the high voltage generation unit 122 to start exposure of each frame every time the timing information of the second irradiation side timing unit 126 matches the exposure start time of each frame.
Each time the high voltage generating unit 122 receives a signal instructing the start of exposure, it controls the tube 13 to irradiate radiation R for a preset irradiation time. That is, the control device 12 causes the tube 13 to irradiate radiation R when the timing information of the second irradiation side timing unit 126 reaches a first predetermined value.

(Step 13)
Furthermore, when the control unit 121 detects an image capture end event, such as when the second stage of the exposure switch 15a is released, the number of image capture frames reaches the maximum number of frames stored in the storage unit 123, a stop notification is received from the high voltage generating unit 122, or a stop notification is received from the image capture device 3, the control unit 121 transmits a command notifying the end of image capture via the communication unit 124 to the image capture device 3, and does not transmit a new exposure start instruction for the image capture to the high voltage generating unit 122. In other words, the image capture is terminated.
The maximum number of frames may be a fixed value stored in the storage unit 123 , or a value entered on the console 14 may be sent to the control device 12 and stored in the storage unit 123 .

(Step 14)
In addition, after receiving an irradiation preparation completion notification signal from the control device 12, the imaging device 3 starts reading out the charges accumulated in the radiation detection unit 32 each time the second imaging side timing unit 39 coincides with the readout start time of each frame, and generates image data of the frame image.

(Step 15)
Then, when the photographing device 3 detects a photographing end event, such as receiving a command from the control device 12 notifying the end of photographing, or the number of photographed frames reaching the maximum number of frames stored in the memory unit 35, the photographing device 3 ends the photographing.

[Example 10-1]
In the above embodiment, serial photography is performed by wirelessly connecting the control device 12A and the photographing device 3, but if the photographing device 3 is connected via a wired connection, it is preferable to switch to a method that is less susceptible to the effects of reduced accuracy of the second photographing side timing unit 39 and errors in the frequencies of the oscillators of the photographing device 3 and the control device 12.
Specifically, the irradiation control device 12 generates the exposure start timing and readout start timing for each frame, notifies the imaging device 3 of the readout start timing via a dedicated line, and instructs the tube 13 to start exposure at the exposure start timing for each frame.
Then, the image capturing device 3 starts reading out at the timing for starting reading out each frame.

In addition, the photographing device 3 may be given a function for detecting the connection type, so that when a connection via a wired cable is detected, the wired serial photographing described here is selected, and when a non-connection with a wired cable is detected, the serial photographing method described above is selected.
This reduces the number of operations required by the user and improves usability.

[Example 10-2]
Although the above embodiment is directed to wireless serial photography, the number of frames may be 1. In this way, wireless still image photography can also be handled with common control, and development costs can be reduced by standardizing the control.
On the other hand, when performing wireless still image shooting, more stable wireless still image shooting can be performed by switching to a method that is less susceptible to the effects of reduced accuracy of the timing unit and errors in the oscillator frequencies of the shooting device 3 and the control device 12 (for example, SRM shooting with AeroDR or AeroSync shooting).
Furthermore, if the console 14 is provided with a function for switching the photographing method to be instructed to the photographing device 3 and the control device 12 depending on whether the selected order is a wireless still image or a wireless serial, the user's operations can be reduced and usability can be improved.

[Example 11-1]
By displaying both the dynamic changes in the radiation image and the dynamic changes in the biological information and analyzing the relationship between the two, the condition of the subject S can be grasped in more detail.
For example, by taking dynamic images of the chest of the subject S while wearing a pulse oximeter, the pulse oximeter can provide information on arterial blood oxygen saturation (SpO2) and pulse rate, and the dynamic images can provide information on pulmonary ventilation function. By integrating and analyzing both pieces of information, it is possible to evaluate changes in respiratory function over time.
However, normally, a device for measuring biological information such as a pulse oximeter and a radiation system are separate devices, and each operates with its own oscillator, so there is a discrepancy in the timekeeping information. If each is equipped with an oscillator with a frequency tolerance of ±100 ppm, there will be a difference of up to 720 ms per hour (60 seconds x 60 minutes x ±0.01% = ±360 ms, when one device is +360 ms and the other is -360 ms). In this case, if the timekeeping information of both clocks is accurately aligned and then a dynamic image is taken at 30 fps one hour later, the discrepancy between the dynamic image and the biological information will be up to about 22 frames, which is a problem in that it is not suitable for displaying or analyzing biological functions on a frame-by-frame basis.

Nowadays, various devices are compatible with a wireless LAN communication function. Therefore, in the above embodiment, as shown in Fig. 56, the bio-measuring device 6 may be connected to the timing information source devices 2 and 4, and the imaging system 100 and the bio-measuring device 6 may be synchronized based on the first timing information included in the first timing information from the timing information source devices 2 and 4.
Specifically, the imaging system 100 is provided with a function for linking and storing a timer time corresponding to each frame image. For example, the exposure start time, exposure end time, and readout start time (time stamp) of each frame are linked.
The bio-measuring device 6 also has a function of storing time information at the time when the bio-information is sampled, in association with each sampled value.

In this way, image data of the radiographic image and the biometric information can be sent to an apparatus that integrates the radiographic image and the biometric information for analysis and display, and the frame image and the sampling values of the biometric information can be simultaneously played back according to the timing information linked to each, thereby making it possible to display the changes in both pieces of information over time while minimizing time lag.
In addition to displaying the data, it is also possible to use the timing information from both devices to analyze what biological changes were occurring at the same time.

It should be noted that it is possible to connect not only two devices, the timing information source devices 2, 4 and the bio-measuring device 6, but also three or more devices.
Furthermore, synchronization may be achieved not only via wireless LAN but also via IEEE1588, NTP, radio clocks, or the like.
The frequency band of the wireless LAN may be selectable. In this way, for example, if the bio-measuring device 6 (e.g., a pulse oximeter) to be linked only supports a 2.4 GHz WLAN, the imaging system 100 can support the same by adjusting the frequency band of the wireless LAN to 2.4 GHz.
Also, a list of other devices that may be connected to the photography system 100 and the frequency bands they use may be stored in advance in the console 14, etc., so that when another device is connected to the console 14 via the timing information source devices 2 and 4, the stored list may be referred to and the frequency bands used by the photography device 3 and the control device 12 may be changed. In this way, the user does not need to be aware of the frequency bands used or perform operations to switch between them, improving usability.

Furthermore, by using TSF, it is possible to synchronize devices with an accuracy of the order of tens to hundreds of μs. For example, when capturing dynamic images at 30 fps, the capture cycle is 33.3 ms, and the time lag can be suppressed to less than one frame. This makes it possible to link the radiation frame images and biological information sampling values on the time axis on a frame-by-frame basis, enabling more accurate display and analysis.

[Example 11-2]
In the above embodiment 11-1, the bio-measuring device and the radiation system are usually separate devices, each of which operates using its own oscillator, resulting in a discrepancy in the timing information. In order to address this issue, the bio-measuring device is connected to the timing information source devices 2 and 4, and synchronization can be achieved using the TSF at that time. However, some wireless LAN modules cannot read out the timing information using the TSF from outside the module.
If such a wireless LAN module is used in a bio-measuring device, it will be necessary to modify or replace the wireless LAN module or to correct the hardware, which will require a lot of development time and cost.

In such cases, it may be possible to select a synchronization method that can be implemented in more general software, such as IEEE 1588 or NTP, but if NTP is used to control the exposure and readout timing of serial radiation imaging, the timing precision may be insufficient, resulting in imaging failure.
On the other hand, if different synchronization methods are used, such as one device using NTP and the other using WLAN TSF, the definitions of the timestamp values are different, and there is a problem that the times of the results of both devices cannot be displayed or analyzed together.

In view of this problem, in the above embodiment, two synchronization methods may be used in combination, as shown in FIG.
Specifically, since the shooting system 100 requires highly accurate time management for its own control, synchronization is achieved using a highly accurate time synchronization method (such as TSF for WLAN), and when timestamps are added to results such as frame images, the time of a general time synchronization method is used.
On the other hand, a bio-measuring device 6 (such as a pulse oximeter) that does not require highly accurate time management for its own control uses a general time synchronization method when attaching a time stamp to the results such as heart rate.

In this way, the frame images of the imaging system 100 and the sampling values of the bio-measuring device 6 can be linked on the time axis without modifying the hardware of external devices such as the bio-measuring device 6.

[Example 11-3]
In the above embodiment 11-1, the bio-measuring device and the radiation system are usually separate devices, and each operates using its own oscillator, which causes a discrepancy in the timing information. In the above embodiment 11-1, the bio-measuring device is connected to the timing information source devices 2 and 4.
If the bio-measuring device to be synchronized is not determined in advance, the synchronization method that can be used with the bio-measuring device cannot be determined, which poses a problem that the imaging system cannot determine the reference time to be used for the time stamp.

In view of this problem, in the above embodiment, as shown in FIG. 58, a bridge device 7 that associates a plurality of reference times may be connected in advance.
Each device (biometric measuring device 6 and imaging system) attaches a time stamp to the test results using the reference time that each device can use.
The bridge device 7 synchronizes with, for example, TSF, NTP, and IEEE1588, and saves a list of combinations of the respective reference times (for example, adding combinations of three reference times to the list at 10 msec intervals).
Each modality transmits examination results with a time stamp to the bridge device, and the bridge device rewrites the time stamp to an arbitrary reference time and sends it to the console.
Alternatively, each modality may send examination results to the console, and the console 14 may inquire of the bridge device.

In this way, even if the bio-measuring device 6 to be linked has not been determined in advance, it is possible to construct an imaging system that can link the results of multiple devices on a time axis.

[Example 12]
In the above embodiment, if the frame rate is configured to be changeable, the amount of dark charge in one frame image changes when the frame rate is changed, and therefore it is necessary to perform correction processing by switching the correction table used for image processing according to the frame rate.
Incidentally, it is desirable that the frame images read out by the imaging device 3 be displayed on the console 14 with as little delay as possible. In this way, the user can determine abnormalities in the body position of the subject S during imaging at an early stage, interrupt and restart imaging, and reduce the radiation exposure.
However, when the frame rate is variable, a configuration is conceivable in which the photographing device 3 reads out a correction table corresponding to the frame rate from the memory unit 35 and performs correction processing. However, with such a configuration, there is a problem that the processing in the photographing device 3 takes too long, increasing the delay in the time until the image is displayed on the console 14.

In view of such problems, in the above embodiment, the image capturing device 3 may store information indicating the time between temporally adjacent frame images in association with each frame image.
For example, the read start time (synchronized timing information) of each frame image and the read end time (synchronized timing information) of each frame image are stored in association with each frame image.
The image capturing device 3 does not perform correction processing according to the frame rate, but attaches only a time stamp to each frame image and transmits it to the console 14.
The console 14 calculates the time interval between each frame image based on the received time stamp, and displays the images in the order of the frame images at the calculated time interval. The images displayed at this time have not been subjected to image processing, but are sufficient for determining whether re-shooting is necessary.
After displaying the images (or simultaneously if the CPU has sufficient processing capacity), a correction table is selected in accordance with the time interval between the derived frame images, and correction processing is performed.

In this way, the processing in the imaging device 3 is minimized, and the frame images read by the imaging device 3 can be displayed on the console 14 without delay. This allows the user to discover abnormalities in the subject S's position during imaging at an early stage and interrupt or restart the imaging, thereby reducing the amount of radiation exposure to the subject S.

In addition, in the above embodiments and examples, an example has been described in which the timing information source devices 2, 4 are connected to both the control devices 12, 2A and the console 14, but the present invention is not limited to this connection, and it is also possible to connect only the timing information source devices 2, 4 to the radiation control devices 12, 12A, or to connect only the timing information source devices 2, 4 to the console 14.
Since the irradiation device 1 is a device that irradiates radiation, if the timing information source devices 2, 4 and the control devices 12, 12A are directly connected, the timing of radiation irradiation can be controlled more accurately.
On the other hand, since the console 14 is a device that controls the entire image capturing system 100, if the timing information source devices 2, 4 and the console 14 are directly connected, the console 14 can efficiently perform processes such as synchronization confirmation.

100, 100A Radiation imaging system 1 Radiation irradiation device 12, 12A Radiation control device 12a Timekeeping control means 121 Radiation control unit 122 High voltage generation unit 123 Memory unit 124 Communication unit 125 Irradiation side timekeeping unit 126 Second irradiation side timekeeping unit 127 Display unit 13 Radiation tube 14 Console 15 Operation unit, operation panel 15a Exposure switch 16 Communication module 2 Access point (timekeeping information source device)
21 Communication section 22 Timer 3, 3A, 3B, 3C, 3D Imaging device 3a Timing control means 3b Operation button 31, 31A Imaging control section 32 Radiation detection section 33 Scanning drive section 34 Readout section 35 Memory section 35 Memory section 36 Communication section 36a Antenna 36b Connector 37, 37A Imaging side timing section 38 Battery 39, 39A Second imaging side timing section 39B Memory 39D Second imaging side timing section 4 Timing information source device 5 Network device 5 Other device 6 Biometric measuring device 7 Bridge device R Radiation S Subject

Claims (8)

a radiation control device for controlling radiation irradiation by the radiation irradiation device;
a radiation imaging apparatus capable of synchronizing with the radiation irradiation by a plurality of synchronization methods;
An imaging method selection means for selecting an imaging method;
a synchronization method selection means for selecting the synchronization method based on the photographing method selected by the photographing method selection means,
the radiation imaging apparatus includes a detection unit that detects a connection state of a wired cable;
the imaging method selection means selects wired serial imaging for generating one or more radiation images through wired communication between the radiation irradiation device and the radiation imaging device when the wired cable is connected, and selects wireless serial imaging for generating one or more radiation images through wireless communication between the radiation irradiation device and the radiation imaging device when the wired cable is not connected ;
A radiation imaging system, wherein the synchronization method includes a first synchronization method for synchronizing based on at least timing information of a first timing unit provided in the radiation control device and timing information of a second timing unit provided in the radiation imaging device . The radiography system according to claim 1, wherein the radiation irradiation device is a mobile cart. 2. The radiation imaging system according to claim 1 , wherein the synchronization method selection means selects the first synchronization method when the wireless serial imaging is selected. 4. The radiation imaging system according to claim 3 , wherein the synchronization method selection means selects a synchronization method different from the first synchronization method when the wired serial imaging is selected. a radiation control device for controlling radiation irradiation by the radiation irradiation device;
a radiation imaging apparatus capable of synchronizing with the radiation irradiation by a plurality of synchronization methods,
selecting a shooting method;
selecting a plurality of synchronization methods for synchronizing radiation irradiation by a radiation irradiation device and a radiation imaging device based on the selected imaging method,
the radiation imaging apparatus includes a detection unit that detects a connection state of a wired cable;
the step of selecting the imaging method selects wired serial imaging in which one or more radiation images are generated by wired communication between the radiation irradiation device and the radiation imaging device when the wired cable is connected, and selects wireless serial imaging in which one or more radiation images are generated by wireless communication between the radiation irradiation device and the radiation imaging device when the wired cable is not connected;
The radiation imaging method includes a first synchronization method for synchronizing based on at least timing information of a first timing unit provided in the radiation control device and timing information of a second timing unit provided in the radiation imaging device . The radiographic imaging method according to claim 5 , wherein the radiation irradiation device is a medical cart. The radiation imaging method according to claim 5 , wherein the step of selecting the synchronization method selects the first synchronization method when the wireless serial imaging is selected. The radiation imaging method according to claim 7 , wherein the step of selecting a synchronization method selects a synchronization method different from the first synchronization method when the wired serial imaging is selected.

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