JP4174544B2 - Imaging apparatus and imaging method - Google Patents

Description

  The present invention relates to an imaging apparatus and an imaging method used in an apparatus or system that performs radiography of an object using a grid, for example.

  Conventionally, radiation methods for irradiating an object with radiation such as X-rays, detecting the intensity distribution of the radiation transmitted through the object, and obtaining a radiation image of the object are industrial nondestructive inspection and medical treatment. Widely used in the field of diagnosis and the like.

  As a radiographic method, the most commonly used method is a method using a so-called “fluorescent screen” (or “sensitizing screen”) that emits fluorescence by radiation and a silver salt film in combination.

In the above radiographic method, first, radiation is irradiated onto an object, the radiation transmitted through the object is converted into visible light by a fluorescent plate, and a latent image is formed on the silver salt film. A visible image is obtained by chemically treating the film.
The film image (radiation image) obtained in this way is a so-called analog photograph and is used for medical diagnosis, examination, and the like.

  In addition, a computed radiography apparatus (hereinafter referred to as “CR apparatus”) that acquires a radiographic image using an imaging plate (hereinafter referred to as “IP”) coated with a stimulable phosphor as a fluorescent substance. It is starting to be used.

  In the CR apparatus, when secondary excitation is performed by visible light such as a red laser on IP that is primarily excited by radiation irradiation, light emission called stimulable fluorescence is generated. In this case, a radiation image is acquired by detecting the light sensor, and a visible image is output to a photographic material or a CRT based on the data of the radiation image.

The CR device is a digital photographing device, but it is an indirect digital photographing device because it requires an image forming process of reading by secondary excitation.
Here, the reason why it is called “indirect” is to display the radiation image immediately, as in the case of the device for acquiring an analog radiation image such as an analog photo as described above (hereinafter referred to as “analog imaging device”). This is because it cannot be done.

  On the other hand, in recent years, as an image receiving means for acquiring a radiation image from radiation through an object, a photoelectric conversion device in which pixels composed of minute photoelectric conversion elements, switching elements, etc. are arranged in a grid pattern is used. Technology to acquire images has been developed.

  For example, as a radiation imaging apparatus having a configuration in which a phosphor is stacked on a sensor such as a CCD or an amorphous silicon two-dimensional image sensor employing the above technique, “USP 5,418,377”, “USP 5,396,072”. , “USP 5,381,014”, “USP 5,132,539”, “USP 4,810,881”, and the like. Such a radiation imaging apparatus is capable of displaying the acquired radiation image data immediately, and thus is a direct digital imaging apparatus.

Advantages of the indirect or direct digital photographing device over the analog photographing device include that it can be made filmless, the acquired information can be expanded by image processing, and can be made into a database.
An advantage of the direct digital photographing device over the indirect digital photographing device is immediacy. For example, since a radiographic image obtained by imaging can be displayed instantaneously on the spot, it is effective in an emergency medical site.

  By the way, when the radiation imaging apparatus as described above is used as a medical apparatus and the radiation transmission density of the subject as an object is detected, the influence of scattered radiation generated when the radiation passes through the subject. In order to reduce this, a scattered radiation removing member, usually called a “grid”, is installed between the subject and a radiation transmission density detector (hereinafter also simply referred to as “detector”).

The grid, for example, a material that does not easily transmit radiation, such as lead, and a material that easily transmits radiation, such as aluminum, are each made into a thin foil and arranged alternately perpendicular to the radiation direction. It is configured.
With such a configuration, radiation with an angle from the irradiation axis, such as scattered radiation in the subject generated by radiation irradiation on the subject, is absorbed by the lead foil in the grid before reaching the detector. Therefore, a radiographic image with high contrast can be obtained.

  Here, if the grid is stopped during imaging, the radiation that reaches the lead in the grid is absorbed not only by the scattered radiation but also by the primary line of radiation. As a result, the striped radiation image is obtained. This is inconvenient for interpretation at the time of diagnosis or the like.

  Therefore, in order not to cause the above phenomenon, a radiation imaging apparatus having a mechanism for moving the grid during imaging has already been commercialized.

  However, in the conventional radiographic apparatus provided with the grid as described above, signal readout in the two-dimensional solid-state image sensor is real-time electrical processing regardless of the light receiving method using a sensor such as a CCD or amorphous silicon two-dimensional image sensor. For this reason, the vibration effect of the photographing unit and the electromagnetic effect of the drive motor caused by the grid movement have become problems, which were not a problem in the indirect digital photographing device such as the analog photographing device or the CR device.

Specifically, a capacitor, a signal line, and the like are shaken due to the influence of the vibration of the imaging unit due to the movement of the grid, the weak electric capacity is fluctuated, and noise is superimposed on the radiation image.
In addition, when a signal is read out by a sensor and a motor is driven to move the grid in the vicinity, the signal potential and the control power supply potential fluctuate due to the influence of electromagnetic noise, and noise is detected in the radiation image. Will be superimposed.
Therefore, in the radiographic image on which noise is superimposed, for example, there is a possibility that the medical diagnostic ability may be reduced.

  On the other hand, in a sensor such as a two-dimensional solid-state imaging device, the electric charge accumulated in the sensor increases in proportion to the signal accumulation time due to the influence of dark current even in an unexposed state. As the electric charge that does not contribute to such an image signal increases, a larger noise is added to the output image signal.

  Accordingly, it is desired to optimize the imaging control so as to reduce the accumulation time in the sensor as much as possible while eliminating the influence of grid vibration, but there has been no apparatus or system that realizes this conventionally.

The present invention has been made to eliminate the above drawbacks, and an object thereof is to provide a photographic image of optimum quality.

Under such an object, the present invention provides a grid moving means for moving a grid that reduces the influence of scattered radiation based on the radiation emitted from the radiation generator , and a plurality of imaging elements, and the radiation transmitted through the grid. A sensor that converts a signal into an electrical signal, a first time that is taken from the time when a radiographing request is made to the radiation generator until the radiation is actually irradiated, and a time that the grid reaches a target moving speed and position. The grid moving means and a control means for controlling the sensor based on the second time and a third time taken until the sensor is initialized , and the control means includes the first time The longest time among the time, the second time, and the third time is acquired as the irradiation delay time, and the initialization of the sensor is started based on the irradiation delay time. Time and that, and determines the time and for starting the movement of the grid.

The present invention is also an imaging method for converting radiation that has passed through a grid to reduce the influence of scattered radiation based on radiation emitted from the radiation generation apparatus into an electrical signal, and the radiation generation apparatus is requested to perform imaging. The first time it takes for the radiation to be irradiated from the first time, the second time it takes for the grid to reach the target moving speed and position, and the third time it takes to initialize the sensor The longest time is acquired as the irradiation delay time, and the time for starting the initialization of the sensor and the time for starting the movement of the grid are determined based on the irradiation delay time .

According to the present invention, it is possible to obtain a high quality photographed image.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The present invention is applied to, for example, a radiation imaging system 100 as shown in FIG.

<Configuration of Radiation Imaging System 100>
As shown in FIG. 1, the radiation imaging system 100 includes an imaging device 110 that acquires a captured image signal of a subject (subject) 102, a control device 111 that controls operation of the entire system 100, and a control device 111. A storage device 112 for storing various data such as a processing program for the control processing and a photographed image, a display device 113 for displaying the photographed image, and the like, and a photographed image signal of the subject 102 obtained by the photographing device 110. An image processing device 114 for performing arbitrary image processing on the image, a shooting condition instruction device 115 for instructing various shooting conditions in the shooting device 110, and a shooting button for instructing the system 100 to start a shooting operation. 116 and a radiation generator 117 that generates radiation (such as X-rays) from the radiation tube 101 to the subject 102 via the system bus 120. And a data exchange can be connected to each other mutually Te.

The imaging device 110 is installed at a position where the radiation generated from the radiation tube 101 of the radiation generation device 117 can be received via the subject 102, and the breast pad 103, the grid 104, the phosphor 105, A sensor (two-dimensional solid-state imaging device or the like) 106, a signal reading unit 107, and a grid moving unit 108 are provided.
The breast pad 103, the grid 104, the phosphor 105, and the sensor 106 are arranged in this order from the side closer to the radiation tube 101 of the radiation generator 117.

<A series of operations of the radiation imaging system 100>
Here, the outline | summary about the imaging | photography procedure in the radiography system 100 and the production | generation process of a radiographic image is demonstrated.

First, a user (radiologist, etc.) positions the subject 102 with respect to the breast pad 103, and uses the imaging condition instruction device 115 to set appropriate imaging conditions (for example, tube voltage, tube current, irradiation time, sensor 106). Type, type of radiation tube 101, etc.).
In the present embodiment, the input of the shooting condition is a manual input from the user by the shooting condition instruction device 115. However, the present invention is not limited to this, and the shooting condition is connected to the shooting device 110, for example. You may make it input via a native work (not shown).

Next, the user presses the shooting button 116 to request the control device 111 to start a shooting operation.
After accepting the imaging operation start request from the user, the control device 111 performs necessary initialization in the system 100 and prompts the radiation generation device 117 to irradiate the radiation.

The radiation generation device 117 generates radiation from the radiation tube 101 in accordance with an irradiation instruction from the control device 111.
The radiation generated from the radiation tube 101 passes through the subject 102 and reaches the breast pad 103.

The breast pad 103 is exposed to the subject 102 with a transmitted radiation distribution corresponding to the structure by the radiation transmitted through the subject 102.
Further, since the breast pad 103 is sufficiently transmissive to the radiation, the radiation transmitted through the breast pad 103 reaches the grid 104.

The grid 104 removes scattered radiation components in the radiation that has passed through the breastplate 103 and allows only effective radiation to reach the phosphor 105.
The phosphor 105 makes visible light so that the radiation (effective radiation) from the grid 104 matches the spectral sensitivity of the sensor 106.

The sensor 106 receives radiation from the phosphor 105 and accumulates the radiation light as an electrical signal (image signal) by two-dimensional photoelectric conversion according to the two-dimensional distribution light intensity.
The signal reading unit 107 reads the accumulated image signal from the sensor 106 and stores it in the storage device 112 as a radiation image signal.

The image processing device 114 performs appropriate image processing on the radiation image signal stored in the storage device 112.
The display device 113 displays the radiation image signal processed by the image processing device 114.

<The most characteristic operation and configuration of the radiation imaging system 100>
FIG. 2 shows the operation control processing of the system 100 executed by the control device 111, and FIG. 3 shows the timing of the operation control.
Note that the process shown in FIG. 2 is a process from the input of the imaging condition by the user described above to the reading of the image signal by the sensor 106.

Step S201:
The control device 111 recognizes the irradiation time Texp, the type of the sensor 106 used for imaging, and the type of the radiation tube 101 based on the imaging conditions selected and input from the user by the imaging condition instruction device 115.
And the control apparatus 111 determines the control to radiation irradiation and the control after radiation irradiation from the said recognition information by the process from following step S202.

Step S202:
The control device 111 determines the sensor initialization time Tss according to the type of the sensor 106.
Although the sensor initialization time Tss differs depending on the type of the sensor 106, for example, when the sensor 106 is a sensor that requires prior discharge of dark current, the idle reading time becomes the sensor initialization time Tss. From this time, Signal accumulation at the sensor 106 begins.

Step S203:
The control device 111 determines a grid initialization time Tgs and a grid vibration convergence time Tge from the irradiation time Texp.

Specifically, first, in order to reduce the fringe reflection of the grid 104, for example, it is necessary to pass radiation through the fringes of 10 cycles or more. On the other hand, the moving distance of the grid 104 is limited. Therefore, it is necessary to optimize the moving speed of the grid 104 according to the irradiation time Texp. In addition, since the grid 104 generally has a focus, it is necessary to align the radiation irradiation center position with the center position of the grid 104 in order to obtain a good image quality of the captured image.
Therefore, the grid initialization time Tgs is the optimum moving speed of the grid 104 (target moving speed) and the time for the position of the grid 104 to reach the radiation irradiation center position (target position).

  In the present embodiment, for example, the grid initialization time Tgs for reaching the target moving speed and position of the grid 104 and the grid vibration convergence time Tge required for the apparatus vibration generated during the movement to converge are varied. Corresponding to the irradiation time Texp of a simple pattern and the moving speed of the grid 104, it is experimentally obtained and tabulated and stored in the storage device 112. Thereby, the grid initialization time Tgs and the grid vibration convergence time Tge corresponding to the actually obtained irradiation time Texp may be determined from the tabulated information in the storage device 112.

Step S204:
The control device 111 determines a pre-irradiation delay time Txs and a post-irradiation delay time Txe according to the type of the radiation tube 101.

The pre-irradiation delay time Txs is the time from when the radiation generation apparatus 117 is instructed to permit radiation irradiation to when radiation irradiation actually starts in the radiation generation apparatus 117. The pre-irradiation delay time Txs is a radiation generation apparatus 117 or a radiation tube. It is determined by the type of the sphere 101.
In the present embodiment, for example, pre-irradiation delay times Txs corresponding to various types of the radiation generator 117 and the radiation tube 101 are prepared in advance as a table, and the corresponding pre-irradiation is obtained from this tabulated information. The delay time Txs is determined.

  The post-irradiation delay time Txe is a delay time until the radiation generator 117 actually ends irradiation after the irradiation time Texp has elapsed. The post irradiation delay time Txe is also determined in the same manner as the pre-irradiation delay time Txs.

Step S205:
The control device 111 determines the irradiation delay time T1.
The irradiation delay time T1 is a delay time from when the user makes a shooting request with the shooting button 116 to when the radiation generator 117 actually irradiates the radiation, and the sensor initialization time determined in step S202. The longest time of Tss, grid initialization time Tgs determined in step S203, and pre-irradiation delay time Txs determined in step S204 is determined as the irradiation delay time T1.

Step S206:
The control device 111 determines a time table until irradiation.
This time table is determined from the sensor initialization time Tss determined in step S202, the grid initialization time Tgs determined in step S203, and the pre-irradiation delay time Txs determined in step S204.

Specifically, the control sequence of initialization of the sensor 106, start of driving of the grid 104, and radiation irradiation instruction (irradiation permission) to the radiation generator 117 after recognizing that a photographing request has been made by the photographing button 116 from the user. And the time (timing) are determined by subtracting the delay time from the irradiation delay time T1 determined in step S205.
That is, the initialization timing of the sensor 106 is determined as “T1−Tss”, the driving start timing of the grid 104 is determined as “T1−Tgs”, and a radiation irradiation instruction (irradiation permission) to the radiation generator 117 is determined. The timing is determined as “T1-Txs”.

Step S207:
After determining the control before radiation irradiation as described above, the control device 111 determines whether or not an imaging request has been made by the user with the imaging button 116 and remains in a standby state until the imaging request is made.

Step S208:
When the control device 111 recognizes that the user has requested the shooting by the shooting button 116, the control device 111 executes the operation control according to the time table determined in step S206.
Thereby, the initialization start of the sensor 106 is executed after "T1-Tss" has elapsed, the drive start of the grid 104 is executed after "T1-Tgs" has elapsed, and the irradiation permission is executed after "T1-Txs" has elapsed.

Step S209:
The control device 111 adds the irradiation time (actual exposure time) Texp determined in step S201, the post-irradiation delay time Txe determined in step S204, and the irradiation delay time T1 determined in step S205 ( It will be in a standby state until (T1 + Texp + Txe) elapses.

Step S210:
When the control device 111 recognizes that the time “T1 + Texp + Txe” has elapsed, the control device 111 stops driving the grid 104 via the grid moving unit 108.

Step S211:
The control device 111 is in a standby state until the grid vibration convergence time Tge determined in step S203 elapses.

Step S212:
When recognizing that the grid vibration convergence time Tge has elapsed, the control device 111 starts reading the accumulated signal of the sensor 106 via the signal reading unit 107.

In the operation control of the radiation imaging system 100 shown in the flowchart of FIG. 2 above, since the configuration is such that the post-irradiation delay time Txe is in a standby state after the irradiation time Texp has elapsed, the fringes of the grid 104 are reflected. Can be prevented.
In addition, since the driving of the grid 104 is stopped, the influence of electromagnetic noise generated from the grid moving unit 108 can be prevented.
In addition, since the grid vibration convergence time Tge is set in the standby state after the grid 104 is stopped, the influence of the apparatus vibration can be prevented.
Therefore, after recognizing the photographing request from the user, the control device 111 performs operation control of the system 100 according to the flowchart of FIG.

The operation of the radiation imaging system 100 as described above will be described more specifically with reference to the timing chart of FIG. 3 as follows.
Note that the timing chart in FIG. 3 describes the timing from when the shooting button 116 is pressed.

First, depending on the shooting conditions input by the user, for example,
Irradiation time Texp = 100ms
Sensor initialization time Tss = 200 ms
Grid initialization time Tgs = 300ms
Pre-irradiation delay time Txs = 100ms
Grid vibration convergence time Tge = 300ms
Post irradiation delay time Txe = 100 ms
To decide.
In this case, the irradiation delay time T1 is the longest time among the sensor initialization time Tss, the grid initialization time Tgs, and the pre-irradiation delay time Txs.
T1 = max (Tss, Tgs, Txs) = Tgs = 300 ms
And decide.
The operation control until radiation irradiation is determined from these initial conditions.

Next, the control timing after the imaging request recognition for the sensor initialization, grid movement start, and irradiation permission instruction is obtained by subtracting the time required for the operation from the irradiation delay time T1. Therefore,
Sensor initialization timing: T1-Tss = 100 ms
Grid movement start timing: T1-Tgs = 0 ms
Irradiation permission signal transmission timing: T1-Txs = 200 ms
It becomes.

Then, the movement control of the grid 104 is stopped after the real sunshine time obtained by adding the irradiation time Texp and the post-irradiation delay time Txe to the irradiation delay T1, and the grid vibration convergence time. It is determined at the timing of starting signal readout by the sensor 106 after Tge has elapsed.
That is, the grid control stop timing and the signal readout start timing are
Grid control stop timing: T1 + Texp + Txe = 500 ms
Signal read start timing: T1 + Texp + Txe + Tge = 800 ms
And decide.

After the determination of the control timing is completed, the user waits for a shooting request (see (a) of FIG. 3) by pressing the shooting button 115 from the user.
When the imaging request is recognized, the operation control of the radiation imaging system 100 is started based on the determined control timings.

That is, first, as shown in FIG. 3B, the movement (movement) of the grid 104 is started.
As shown in FIG. 3C, the moving speed of the grid 104 increases in an accelerated manner, and reaches the irradiation enabled state after 300 ms (grid initialization time Tgs = 300 ms).

  Next, as shown in FIG. 3 (f), the initialization of the sensor 106 is started after 100 ms (sensor initialization timing: T1-Tss = 100 ms) from the recognition of the photographing request, and 200 ms (sensor initialization time). After Tss = 200 ms), the initialization of the sensor 106 is completed.

Next, as shown in FIG. 3D, 200 ms (irradiation permission signal transmission timing: T1−Txs = 200 ms) after the imaging request recognition, the radiation generation apparatus 117 is instructed to perform irradiation.
As a result, the radiation generator 117 starts actual irradiation after 100 ms (pre-irradiation delay time Txs = 100 ms) as shown in FIG.

And after 500 ms (grid control stop timing: T1 + Texp + Txe = 500 ms) from the recognition of the imaging request, the actual irradiation with the radiation generator 117 ends.
At this time, the movement control of the grid 104 is stopped as shown in FIG. Thereby, the moving speed of the grid 104 is gradually decelerated. Along with this, the vibration of the photographing apparatus 110 generated by moving the grid 104 starts to converge.

After that, as shown in FIG. 3 (f), after the imaging request is recognized, after 800 ms (signal readout start timing: T1 + Texp + Txe + Tge = 800 ms), signal accumulation in the sensor 106 is terminated with respect to the signal readout unit 107. An instruction to start signal readout is given.
At this time, the vibration of the photographing apparatus 110 is reduced so as not to affect the image quality, and as a result, a good photographed image can be acquired.

(Second Embodiment)
The present invention is applied to, for example, a radiation imaging system 300 as shown in FIG.
The radiation imaging system 300 has the same configuration as the radiation imaging system 100 in FIG. 1, but measures the vibration state of the radiation detector 302 and the grid 104 for detecting the radiation irradiation state in the imaging apparatus 110. The vibration measuring instrument 301 is further provided.

  In the radiation imaging system 300 of FIG. 4, the same reference numerals are given to portions that operate in the same manner as the radiation imaging system 100 of FIG. 1, and detailed description thereof is omitted. Here, only the configuration different from the radiation imaging system 100 of FIG. 1 will be specifically described.

  FIG. 5 shows the operation control processing of the system 100 executed by the control device 111 in the present embodiment, and FIG. 6 shows the timing of the operation control.

  In the flowchart of FIG. 5 described above, the same reference numerals are assigned to the steps for performing the same processing steps as those in the flowchart of FIG. 2, and the details thereof are omitted.

Step S201:
The control device 111 recognizes the irradiation time Texp, the type of the sensor 106 used for imaging, and the type of the radiation tube 101 based on the imaging conditions selected and input from the user by the imaging condition instruction device 115.
And the control apparatus 111 determines the control to radiation irradiation and the control after radiation irradiation from the said recognition information by the process from following step S202.

Step S202:
The control device 111 determines the sensor initialization time Tss according to the type of the sensor 106.

Step S203 ′:
The control device 111 determines the grid initialization time Tgs (time to reach the target moving speed and position of the grid 104) from the irradiation time Texp.

Step S204 ′:
The control device 111 determines the pre-irradiation delay time Txs (from instructing the radiation generator 117 to allow radiation irradiation until the radiation generator 117 actually starts radiation irradiation, depending on the type of the radiation tube 101. Time).

Step S205:
The control device 111 determines the irradiation delay time T1 (the longest time among the sensor initialization time Tss, the grid initialization time Tgs, and the pre-irradiation delay time Txs).

Step S206:
As a time table until irradiation, the control device 111 sets the initialization timing of the sensor 106 as “T1-Tss”, the driving start timing of the grid 104 as “T1-Tgs”, and a radiation irradiation instruction to the radiation generator 117 ( “T1-Txs” is determined as the timing of irradiation permission.

Step S207:
After determining the control before radiation irradiation as described above, the control device 111 determines whether or not an imaging request has been made by the user with the imaging button 116 and remains in a standby state until the imaging request is made.

Step S208:
When the control device 111 recognizes that the user has requested the shooting by the shooting button 116, the control device 111 executes the operation control according to the time table determined in step S206.
Thereby, the initialization start of the sensor 106 is executed after "T1-Tss" has elapsed, the drive start of the grid 104 is executed after "T1-Tgs" has elapsed, and the irradiation permission is executed after "T1-Txs" has elapsed.

Step S209 ′:
Based on the detection signal output from the radiation detector 302, the control device 111 determines whether or not the radiation irradiation by the radiation generator 117 has ended.

Step S210:
When the control device 111 recognizes that the radiation irradiation by the radiation generator 117 is completed, the control device 111 stops the driving of the grid 104 via the grid moving unit 108.

Step S211 ':
The control device 111 determines whether the vibration of the grid 104 has converged based on the measurement result of the vibration measuring device 301.

Step S212:
When recognizing that the vibration of the grid 104 has converged, the control device 111 starts reading of the accumulated signal of the sensor 106 via the signal reading unit 107.

In the operation control of the radiation imaging system 100 shown in the flowchart of FIG. 5, the driving of the grid 104 is stopped particularly when it is recognized that the radiation irradiation has been completed based on the detection result of the radiation detector 302. Therefore, the influence of electromagnetic noise generated from the grid moving unit 108 can be prevented.
In addition, after the driving of the grid 104 is stopped, the standby state is set until the vibration of the grid 104 converges based on the measurement result of the vibration measuring device 301, so that the influence of the apparatus vibration can be prevented.
Therefore, after recognizing the photographing request from the user, the control device 111 performs operation control of the system 100 according to the flowchart of FIG.

The operation of the radiation imaging system 100 as described above will be described more specifically with reference to the timing chart of FIG. 6 as follows.
The timing chart of FIG. 6 describes the timing from when the shooting button 116 is pressed.

First, depending on the shooting conditions input by the user, for example,
Irradiation time Texp = 100ms
Sensor initialization time Tss = 200 ms
Grid initialization time Tgs = 300ms
Pre-irradiation delay time Txs = 100ms
To decide.
In this case, the irradiation delay time T1 is the longest time among the sensor initialization time Tss, the grid initialization time Tgs, and the pre-irradiation delay time Txs.
T1 = max (Tss, Tgs, Txs) = Tgs = 300 ms
And decide.
The operation control until radiation irradiation is determined from these initial conditions.

Next, the control timing after the imaging request recognition for the sensor initialization, grid movement start, and irradiation permission instruction is obtained by subtracting the time required for the operation from the irradiation delay time T1. Therefore,
Sensor initialization timing: T1-Tss = 100 ms
Grid movement start timing: T1-Tgs = 0 ms
Irradiation permission signal transmission timing: T1-Txs = 200 ms
It becomes.

After the determination of the above control timing is completed, the user waits for a shooting request (see FIG. 6A) by pressing the shooting button 115 from the user.
When the imaging request is recognized, the operation control of the radiation imaging system 100 is started based on the determined control timings.

That is, first, as shown in FIG. 6B, the movement (movement) of the grid 104 is started. At the same time, as shown in FIG. 6G, the vibration detection signal indicating that the grid 104 is in the moving state is set to the high level.
As shown in FIG. 6C, the moving speed of the grid 104 increases in an accelerated manner, and reaches the irradiation enabled state after 300 ms (grid initialization time Tgs = 300 ms).

  Next, as shown in FIG. 6H, the initialization of the sensor 106 is started after 100 ms (sensor initialization timing: T1−Tss = 100 ms) from the recognition of the photographing request, and 200 ms (sensor initialization time). After Tss = 200 ms), the initialization of the sensor 106 is completed.

Next, as shown in FIG. 6D, 200 ms (irradiation permission signal transmission timing: T1−Txs = 200 ms) after the imaging request is recognized, the irradiation is instructed to the radiation generator 117.
As a result, the radiation generator 117 starts actual irradiation after 100 ms (pre-irradiation delay time Txs = 100 ms) as shown in FIG. At the same time, as shown in FIG. 6F, the radiation detection signal indicating the radiation irradiation is set to the high level.

  When the radiation irradiation is completed and the output of the radiation detector 302 falls below a predetermined threshold value, it is determined that the irradiation is completed, and the radiation detection signal is set to the low level as shown in FIG. Accordingly, the movement control of the grid 104 is stopped as shown in FIG. Thereby, the moving speed of the grid 104 is gradually decelerated. The vibration state of the grid 104 at this time is observed by the vibration measuring instrument 301.

When it is recognized that the vibration of the imaging device 110 generated by moving the grid 104 starts to converge and the output of the vibration measuring device 301 is lower than a predetermined vibration amount, as shown in FIG. The signal is set to the low level.
Then, as shown in FIG. 6 (h), the signal reading unit 107 is instructed to end the signal accumulation in the sensor 106 and start the signal reading.
At this time, the vibration of the photographing apparatus 110 is reduced so as not to affect the image quality, and as a result, a good photographed image can be acquired.

As described above, according to the present embodiment, the influence of electromagnetic noise due to the grid movement can be eliminated by the configuration in which the grid is stopped before the reading of the signal accumulated in the image sensor is started. Thereby, noise is not superimposed on a captured image (radiation image or the like) obtained from a readout signal from the image sensor, and a high-quality captured image can be obtained.
In addition, when a certain waiting time is provided after the grid is stopped, signal readout from the image sensor is started after the influence of the vibration of the image sensor due to the movement of the grid is reduced. Can be obtained.
Therefore, it is possible to prevent deterioration of the image quality of the captured image due to the influence of electromagnetic noise due to the grid movement, and it is possible to prevent deterioration of the image quality of the captured image due to the influence of the vibration of the image sensor due to the grid movement.
  For example, if the present invention is applied to radiography, a good radiographic image without noise can be provided, so that erroneous diagnosis in image diagnosis can be reliably prevented.

It is to be noted that an object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the host and terminal according to the first and second embodiments to a system or apparatus, and the computer of the system or apparatus Needless to say, this can also be achieved by (or CPU or MPU) reading and executing the program code stored in the storage medium.
In this case, the program code itself read from the storage medium realizes the functions of the first and second embodiments, and the storage medium storing the program code constitutes the present invention.
As a storage medium for supplying the program code, ROM, flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, and the like can be used.

  Further, by executing the program code read by the computer, not only the functions of the first and second embodiments are realized, but also an OS running on the computer based on the instruction of the program code. Needless to say, the present invention includes a case where the functions of the first and second embodiments are realized by performing part or all of the actual processing.

  Further, after the program code read from the storage medium is written to the memory provided in the extension function board inserted in the computer or the function extension unit connected to the computer, the function extension is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the first and second embodiments are realized by the processing.

In 1st Embodiment, it is a block diagram which shows the structure of the radiography system to which this invention is applied. It is a flowchart for demonstrating operation | movement of the said radiography system. It is a figure for demonstrating the operation control timing of the said radiography system. In 2nd Embodiment, it is a block diagram which shows the structure of the radiography system to which this invention is applied. It is a flowchart for demonstrating operation | movement of the said radiography system. It is a figure for demonstrating the operation control timing of the said radiography system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Radiography system 101 Radiation tube 102 Examinee 103 Chest rest part 104 Grid 105 Phosphor 106 Sensor (two-dimensional image sensor)
107 Signal Reading Unit 108 Grid Moving Unit 110 Imaging Device 111 Control Device 112 Storage Device 113 Display Device 114 Image Processing Device 115 Imaging Condition Instruction Device 116 Imaging Button 117 Radiation Generation Device 120 System Bus

Claims (2)

Grid moving means for moving the grid to reduce the influence of scattered radiation based on radiation emitted from the radiation generator;
A sensor configured by a plurality of image sensors, and converting radiation transmitted through the grid into an electrical signal;
A first time required from when a radiographing request is made to the radiation generating apparatus until actual radiation is irradiated; a second time required for the grid to reach a target moving speed and position; and the sensor. The grid moving means based on a third time taken until the initialization , and a control means for controlling the sensor,
The control means acquires the longest time among the first time, the second time, and the third time as an irradiation delay time, and initializes the sensor based on the irradiation delay time. An imaging apparatus characterized by determining a start time and a time for starting the movement of the grid . An imaging method for converting radiation transmitted through a grid to reduce an influence of scattered radiation based on radiation radiated from a radiation generator into an electrical signal,
A first time required from when a radiographing request is made to the radiation generation apparatus to actual radiation irradiation, a second time required for the grid to reach a target moving speed and position, and a sensor are initialized. The longest time in the third time taken until the acquisition is acquired as the irradiation delay time, and the time for starting the initialization of the sensor based on the irradiation delay time and the time for starting the movement of the grid An imaging method characterized by deciding.

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