JP2001333897A - Imaging equipment, imaging system, method of imaging, and storing medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide imaging equipment with which an X-ray of high-quality is always produced by controlling moving velocity of a grid accurately and by preventing insufficient moving amount of the grid and occurrence of artifacts such as plaids and spurious resolutions of the grid caused when the grid stops or turns back even in a case when appropriate exposure time can not be estimated before imaging. SOLUTION: A controlling means 110 makes an estimate of an entire period of time to emit X-ray depending on the amount of X-ray at the beginning of the period of emitting X-ray, computes moving velocity of a grid 102 according to the estimated period of time, and changes the speed of the grid 102 during emitting X-ray to the computed moving velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, an image processing system, an image processing method and an image processing method for use in an apparatus or a system for performing radiography of X-rays or the like. The present invention relates to a storage medium readable by a computer.

[0002]

2. Description of the Related Art Conventionally, for example, in an X-ray imaging apparatus,
A subject is irradiated with X-rays generated by an X-ray tube of the X-ray generating unit, and an intensity distribution of the X-rays transmitted through the subject is imaged by an imaging unit, so that a captured image (X-ray image) of the subject is obtained. Have been made to get. However, at the time of imaging the X-ray intensity distribution, in addition to the originally required straight transmission component,
Since the image is formed including X-rays scattered in the subject or the like, the contrast of the X-ray image may be reduced.
Such a problem of lowering the contrast of an X-ray image particularly affects image diagnosis in the medical field.

In order to solve the above problem, a grid called a grid for removing scattered rays is used. As the grid, for example, a substance having a high X-ray absorptance (X-ray transmittance) such as lead and a substance having a low X-ray absorptivity such as aluminum are alternately arranged in a thin film (plate shape) (in one direction). (Arrayed in the form of a lattice), and only those components that are directed straight to the irradiated X-rays are guided to an imaging unit (or a fluorescent screen) that images the X-ray intensity distribution.

However, since the grid has a structure in which two kinds of plate-like substances having different X-ray transmittances are arranged in a one-way lattice, the lattice fringes appear on the X-ray image obtained by the imaging unit. There was a case. This plaid is
When an X-ray image is output on a film or the like, the image tends to be noticeable.

In recent years, instead of directly outputting an X-ray image obtained by an image pickup unit to a film, the data of the X-ray image obtained by the image pickup unit is sampled and converted into a digital image. In such a case, the grid image is modulated by the sampling carrier, and stripes having a frequency different from the grid frequency tend to be conspicuous on the output image. . This can be regarded as aliasing of the spatial spectrum of the grid by sampling.

Therefore, in order to solve the above-described problem of the grid pattern caused by the grid, for example, the grid itself is moved in a direction perpendicular to the fringe during the generation (irradiation) of the X-rays, so that the grid contrast is reduced. Many methods are used to reduce the occurrence of lattice fringes. Such a grid mechanism is called a moving grid.

In the above-described grid moving method, the amount of grid movement is, as described in Japanese Patent Application Laid-Open No. 10-305030, such that the number of grid stripes moved during X-ray irradiation is 11 or more. It is preferable that the moving speed of the grid is equal to or higher than the speed satisfying the condition.

However, when the moving distance of the grid increases (when the number of moving stripes increases), a large speed fluctuation such as stopping or turning of the grid occurs due to the limitation of the driving mechanism of the grid, the outer shape of the device or the system. Would. As described above, even if the number of grid stripe movements during X-ray irradiation is 11 or more, the grid contrast reduction effect is reduced if a large speed fluctuation such as grid stop or turnover occurs. In particular, when the imaging of the X-ray intensity distribution is directly performed by the imaging unit, and the data of the X-ray image obtained by the imaging is sampled and converted into a digital image, the stripes due to aliasing of the grid image (grid frequency) Fringe of another frequency).

Therefore, in order to solve the above problem, the irradiation time of X-rays is acquired in advance, and the movement of the stripes of the grid during the irradiation of X-rays is acquired based on the acquired irradiation time. The number of lines is 11 or more, and the speed at which the stop or the turn of the grid does not occur is calculated, and the grid is driven at the calculated speed.

[0010] Particularly, in the X-ray imaging in the medical field, depending on the site (imaging site) of the object (examined subject) to be imaged and the conditions such as the thickness of the subject (hereinafter also referred to as "imaging conditions"). Since the X-ray irradiation time varies, the grid moving speed is determined based on the X-ray irradiation time preset for each parameter of the imaging condition.

[0011]

By the way, in the conventional X-ray imaging apparatus or system having the above-described grid configuration, the required X-ray dose varies with the subject such as the human body (for example, the body thickness or the body thickness). The X-rays transmitted through the subject are monitored while integrating the X-rays transmitted through the subject by using a device called a phototimer that measures the X-rays after the subject transmits the X-rays. In some cases, a method of acquiring an optimal X-ray dose (irradiation time) by cutting off the X-ray exposure when the dose is reached, and acquiring a high-quality X-ray image may be adopted. This method is called "AE
C ".

However, in the above method, since the X-ray irradiation time is unknown, that is, it is difficult to predict the irradiation time before imaging, it is possible to determine (calculate) the optimal grid moving speed. As a result, depending on the photographing conditions, the number of moving grids may be insufficient, lattice fringes due to folding, pseudo resolution of grid images, and the like may occur.

Therefore, the present invention has been made to eliminate the above-mentioned disadvantages, and it is desirable to reduce the grid moving speed even in the case of an imaging in which it is difficult to predict an appropriate radiation exposure time before the imaging. Radiation of high quality is always achieved by using a configuration that can accurately control and prevent the occurrence of artifacts such as grid stripes and pseudo resolution of grid images due to lack of movement of the grid, stopping or turning back of the grid. It is an object of the present invention to provide a recording medium capable of acquiring an image, in which a computer stores a photographing apparatus, a photographing system, a photographing method, and processing steps for implementing the method.

[0014]

For such a purpose,
A first invention is an imaging device for irradiating a subject with radiation to obtain a radiographic image of the subject, wherein the movable grid for removing scattering of radiation at the subject, and the grid A driving unit for driving the grid, a detection unit for detecting the radiation dose, and a control unit for controlling a moving speed of the grid by the driving unit based on a detection result of the detection unit for a predetermined period. And

According to a second aspect, in the first aspect,
The control means predicts a radiation irradiation time based on the radiation dose during the predetermined period, and changes a moving speed of the grid based on the predicted irradiation time.

According to a third aspect, in the first aspect,
The control means controls a moving speed of the grid within a radiation irradiation time to the subject.

According to a fourth aspect, in the first aspect,
The predetermined period includes at least one of a period until the radiation amount detected by the detection unit reaches an arbitrary threshold value and a period from the start of irradiation of the radiation to the elapse of an arbitrary time. It is characterized by.

According to a fifth aspect of the present invention, there is provided an imaging system in which a plurality of devices are communicably connected to each other, wherein at least one of the plurality of devices is the one according to any one of claims 1 to 4. It has a function of a photographing device.

According to a sixth aspect of the present invention, there is provided an imaging method for irradiating a subject with radiation to obtain a radiographic image of the subject, wherein a movable grid for removing the scattering of radiation at the subject is provided. A driving step of driving, a monitoring step of monitoring the radiation dose, and a control step of controlling a moving speed of the grid by the driving step based on a monitoring result of the monitoring step at an initial stage of irradiation start of the radiation. It is characterized by including.

According to a seventh aspect, in the sixth aspect,
The control step includes a step of predicting a total irradiation time of the radiation based on the radiation dose at the beginning of the irradiation, and reducing or accelerating the moving speed of the grid based on the predicted time.

According to an eighth aspect based on the sixth aspect,
The control step includes a step of controlling a moving speed of the grid within a radiation irradiation time to the subject.

According to a ninth aspect, in the sixth aspect,
The initial period of the irradiation start is at least one of a period until the radiation dose monitored by the monitoring step reaches an arbitrary threshold and a period until an arbitrary time elapses after the irradiation of the radiation is started. It is characterized by including.

In a tenth aspect based on the sixth aspect, the control step is such that a speed at which at least one of the stop and the return of the grid does not occur within the irradiation time of the radiation to the subject. , And controlling the moving speed of the grid.

According to an eleventh aspect of the present invention, a processing program for implementing the function of the photographing apparatus according to any one of claims 1 to 4 or the function of the photographing system according to claim 5 is stored in a computer readable manner. It is characterized by being a storage medium.

According to a twelfth aspect of the present invention, there is provided a storage medium in which the processing steps of the photographing method according to any one of claims 6 to 10 are readable by a computer.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) The present invention provides, for example,
The present invention is applied to an X-ray imaging apparatus 100 as shown in FIG. The X-ray imaging apparatus 100 particularly predicts the irradiation time from the initial X-ray irradiation amount, and based on the predicted irradiation time,
The moving speed at the time of moving the grid 102 is controlled.

<Structure of X-ray imaging apparatus 100> The X-ray imaging apparatus 100 is, as shown in FIG.
A line generator 101, a movable grid 102, a servo motor 103 for driving the grid 102, an encoder 104 for detecting the number of rotations of the servo motor 103, and a servo for controlling the rotation speed of the servo motor 103 A motor control circuit 105, a fluorescent plate 106 for converting X-rays into visible light that can be sensed by the imaging medium 107, an imaging medium 107 such as an imaging device for imaging the visible light distribution by the fluorescent plate 106, and a subject (subject) ) 130, an X-ray monitor 108 for measuring the amount of X-rays transmitted through the grid 102, and the like, and the output of the X-ray monitor 108 is integrated. When the integrated value reaches a specified value, the X-ray generation unit 101 The output of the X-ray output cutoff control unit 109 for cutting off the X-ray output and the output of the X-ray monitor 108 are integrated, and the grid 102 is moved based on the integrated value. The grid speed controller 110 for controlling the degree, and the imaging device read control unit 112 for performing A / D conversion and the like of the signal reading and the signal from the imaging medium 107,
The control unit 121 controls the operation of the entire device 100.

The grid 102, the fluorescent plate 106, and the imaging medium 107 are positioned at a position where the X-rays generated by the X-ray generation unit 101 are incident via the subject 130.
01 are arranged in this order.

The control unit 121 reads out and executes a processing program stored in the memory 122 in advance, thereby performing the operation of the most characteristic configuration of the apparatus 100.

<A series of operations of the X-ray imaging apparatus 100> First, the grid speed control unit 110 starts driving the grid 102. The control unit 121 controls the driving of the X-ray generation unit 101 when the grid 102 reaches the fixed speed. Thus, the X-ray generation unit 101 generates (irradiates) X-rays.

The X-rays emitted from the X-ray generator 101 are:
After passing through the subject (subject) 130 and removing the scattered rays on the subject 130 by the grid 102,
The light is converted into visible light by the fluorescent plate 106, and
Reach 7

The image pickup medium 107 photoelectrically converts light from the fluorescent plate 106 and accumulates the charges as electric charges. X-ray generator 10
After the X-ray exposure in step 1 is completed, the image sensor readout control unit 112
Reads out the stored charge signal from the imaging medium 107 sequentially.
The read signal is digitized and subjected to various processes, and then displayed on a diagnostic monitor or the like.

On the other hand, the X-ray monitor 108
And X-rays transmitted through the grid 102 and the like, and outputs the detection result (a signal proportional to the X-ray intensity).

The grid speed controller 110 measures the time from when the output of the X-ray monitor 108 is integrated to reach a predetermined threshold value after the start of exposure, and based on the measured time, the moving speed of the grid 102 Is changed (deceleration or acceleration). The predetermined threshold here is information given in advance from the control unit 121 via the control line 111.

The X-ray output cutoff control unit 109 determines that the integrated value of the output of the X-ray monitor 108 has reached a specified value.
The X-ray output of the X-ray generation unit 101 is cut off. The specified value is information given in advance from the control unit 121 via the control line 111.

<Operation Timing of X-Ray Imaging Apparatus 100>
2A to 2D show the X-ray imaging apparatus 1 as described above.
The operation timing at 00 is shown.

FIG. 2A shows the X-ray cutoff control unit 109.
X-ray output and cut-off at the X-ray generation unit 101 (ON
(B) shows the time characteristic of the X-ray output from the X-ray generation unit 101, and FIG.
Shows the result obtained by integrating the output of the X-ray monitor 108 obtained by the X-ray output by the arithmetic means and the like, and FIG. 4D shows the moving speed of the grid 102. In FIG. 2D, the dotted line indicates the moving speed of the grid in the conventional configuration when the grid is driven, the solid line indicates the moving speed of the grid 102 in the configuration of the present embodiment when the grid is driven, and the hatched portion. Indicates the total moving distance of the grid.

Here, the configuration of the X-ray generator 101 is, for example, a configuration using an inverter system.

Therefore, first, when radiography by the X-ray radiography apparatus 100 is started (at the start of radiography), at that time (indicated by "" in FIG. 2D), the grid speed control unit 110
Starts driving the grid 102. Then, when the acceleration of the grid 102 ends and the grid 102 reaches the constant speed v0 (indicated by “” in FIG. 2D), the X-ray generation unit 101 starts to emit X-rays. (See FIG. 2 above.
(See (a) and (b)).

When the X-ray irradiation is started, the grid speed control unit 110 determines that the value obtained by integrating the outputs of the X-ray monitor 108 is a predetermined threshold value (the value indicated by “B” in FIG. 2C). ) Is reached (indicated by “” in FIG. 2C), the time t0 from the start of the irradiation is acquired (measured), and the speed v1 of the grid 102 is calculated based on the value of the time t0. Then, the moving speed of the grid is changed from the speed v0 to the speed v1.

Thereafter, the X-ray cutoff control unit 109 sets the integrated value of the output of the X-ray monitor 108 to a specified value (see FIG.
At the time when the value reaches the value indicated by “A” in FIG.
By outputting a cutoff signal to the X-ray generation unit 101 (shown by “” in (c)), the X-ray output is cut off (OFF).

<Moving speed of grid 102> Grid 1
The speed v0 of 02 is determined based on the highest speed at which the grid 102 can be moved, the speed set for each subject (photographing site) of the subject 130, the tube voltage, the tube current, the photographing distance, and the like. The speed is the speed v1 of the grid 102
Is a speed at which the grid 102 does not stop or turn back until the X-ray irradiation ends.

The speed v1 of the grid 102 is calculated by the grid speed control unit 110 based on the irradiation time obtained from the initial output (initial X-ray irradiation amount) of the X-ray monitor 108. An example of the calculation method will be described below.

First, in an X-ray generation unit having a small temporal change in the output of X-rays, such as the X-ray generation unit 101 using the inverter method, the value obtained by integrating the outputs of the X-ray monitor 108 is a linear function. Becomes For this reason, the entire X-ray irradiation time (exposure prediction time) texp is a specified value A that is a reference for the X-ray cutoff control unit 109 to output a cutoff signal, and is used to predict the entire X-ray irradiation time. Using the threshold B and the time t0 from the start of the exposure until the value obtained by integrating the output of the X-ray monitor 108 to reach the threshold B, it is obtained from the following equation (1): text = (A · t0) / B (1) Can be

For example, when the integrated value of the output of the X-ray monitor 108 is expressed as a voltage value, the specified value A is "10".
V ", the threshold B is" 2 V ", and the time t0 is" 10 ms ", the total X-ray irradiation time texp is given by the following equation (1): texp = (10 V.10 ms) / 2V = 50 ms .

For simplicity of explanation, the grid 102
Is assumed to be negligibly small, the grid 102 moves at the speed vo during the time t0, and then moves at the speed v1 until the X-ray irradiation ends. Thereby, the grid 102 during X-ray exposure is
Is calculated from the following equation (2): L = v0 · t0 + v1 · (exp−t0) (2)

Therefore, in order to take into account that the movable distance of the grid 102 is limited by a mechanism or the like,
Assuming that the maximum movable distance is “Lmax”, according to the above equation (2), the speed v1 at which the stop or the turning back of the grid 102 does not occur is: v1 = (Lmax−v0 · t0) / (exp−t0) (3) It is determined by the following equation (3), and the moving speed of the grid 102 may be set to be equal to or lower than the speed v1.

For example, the maximum movable distance Lmax of the grid 102 is “5 cm”, the initial speed v0 of the grid 102 is “15 cm / s”, the time t0 until reaching the threshold B is “100 ms”, and the predicted exposure time texp is “ 500m
s ", the above equation (3) gives: v1 = (5 cm−15 cm / s · 100 ms) / (500 ms−100 ms) = 8.75 cm / s, and the initial velocity v0 is reduced to the velocity v1 = 8.75 cm / s or less. In this case, the grid 102 does not stop or turn back during X-ray irradiation.

<Driving of Grid 102> The servo motor control unit 105 controls the grid 102 so that the speed of the grid 102 becomes the speed (v0, v1) specified by the grid speed control unit 110 during X-ray irradiation. Are driven by the servo motor 103. Thus, grid 1
2 is driven so as to move up and down in the paper plane in FIG.

More specifically, first, the rotation speed of the servo motor 103 is controlled by an encoder 104 provided on the motor shaft.
Is detected by The servo motor control unit 105 recognizes the rotation speed of the servo motor 103 based on the detection result of the encoder 104, and controls the rotation speed of the servo motor 103 according to an instruction from the grid speed control unit 110. For example, the servo motor control unit 105 controls the speed of the grid 102 via the servo motor 103 so that the speed becomes proportional to the input voltage from the grid speed control unit 110.

FIG. 3 specifically shows a mechanism for driving the grid 102 by the servo motor 103. As shown in FIG. 3 described above, by rotating the pulley 103a mounted on the motor shaft of the servo motor 103, the grid 102 moves in the direction of the arrow in FIG.

In the mechanism shown in FIG. 3, the moving speed of the grid 102 is proportional to the rotation speed of the servomotor 103.
Therefore, the speed of the grid 102 is controlled by the servo motor 1
03 is multiplied by the reduction ratio of the pulley 103a, and the rotation speed of the graph shown in FIG. 2D is multiplied by the reduction ratio of the pulley 103a.
The speed of the servo motor 103 may be controlled.

As described above, in the present embodiment, the entire X-ray irradiation time (exposure prediction time) texp is predicted from the initial (time t0) X-ray irradiation amount, and the X-ray Since the speed of the grid 102 is controlled (the speed is changed from the initial speed v0 to the speed v1) based on the exposure time texp, the grid 102 is not sufficiently moved, and the grid pattern and the grid image are misunderstood due to a stop or a turn. An optimal grid 102 that can prevent the occurrence of artifacts such as images
Speed control. Further, even in the case of imaging by AEC or the like, the entire X-ray exposure time (exposure predicted time) text can be predicted, so that the optimal speed control of the grid 102 can be performed so as to prevent the occurrence of the artifact.

In this embodiment, the X-ray monitor 108
The time t0 until the integrated value of the outputs reaches the threshold value B is measured. For example, a certain time t0 is determined in advance, and the X-ray monitor 1 after the elapse of the time t0 from the start of the X-ray exposure.
08, the total exposure time texp
May be predicted.

In this embodiment, the grid 102
In order to eliminate the influence of the acceleration of the servo motor 103 that drives the X-ray, when the grid 102 reaches a constant speed (the rotational speed of the servo motor 103 is constant) v0, the X-ray irradiation is started. If the rise of the servomotor 103 is fast and the influence of acceleration is negligibly small, the driving of the grid 102 and the X-ray irradiation may be performed simultaneously.

In this embodiment, the servo motor 1
The driving of the grid 102 was performed by 03, but the invention is not limited to this, and any means for driving the grid 102 may be used, such as a pulse motor or any other motor capable of speed control.

(Second Embodiment) In this embodiment,
In the X-ray imaging apparatus 100 shown in FIG. 1, the configuration for driving the grid 102 is configured as shown in FIG.

That is, in the present embodiment, the pulley 1 shown in FIG.
A cam 201 is attached instead of 03a.
Further, a detector 202 for detecting the rotational position of the cam 201 is provided. In such a configuration, the servo motor 103
Is converted into a parallel movement, so that the grid 102 moves. Accordingly, it is not necessary to detect the movable range of the grid 102, and the movement of the grid 102 can be easily controlled.

Here, only the configuration different from that of the first embodiment will be specifically described.

More specifically, first, as shown in FIG. 4, the cam 201 is connected by an arm 203 movable together with the grid 102, and converts the rotational movement of the servo motor 103 into a parallel movement. The detector 202 detects that the rotational position of the cam 201 is a relatively stable position of the parallel movement speed (for example, ± 25 of the maximum angular velocity position if 10%).
°), a pulse is output.

Therefore, the control unit 121 controls the driving of the X-ray generator 101 when the grid speed control circuit 110 starts driving the grid 102 and a pulse is emitted from the detector 202. Thereby, X-rays are emitted from the X-ray generation unit 101.

After the X-ray exposure, the servo motor controller 105
Drives the servomotor 103 at a fixed speed according to an instruction from the grid speed control unit 110. The grid speed control unit 110 measures the time from when the output of the X-ray monitor 108 is integrated to reach a predetermined threshold value from the start of irradiation, and changes the moving speed of the grid 102 based on the measured time. Is issued to the servo motor control unit 105.

FIGS. 5A to 5D show operation timings of the X-ray imaging apparatus 100 according to the present embodiment.

FIG. 5A shows the X-ray cutoff control unit 109.
X-ray output and cut-off at the X-ray generation unit 101 (ON
(B) shows the time characteristic of the X-ray output from the X-ray generation unit 101, and FIG.
Shows the result obtained by integrating the output of the X-ray monitor 108 obtained by the X-ray output by the arithmetic means and the like, and FIG. 4D shows the moving speed of the grid 102. In FIG. 5D, the dotted line indicates the moving speed of the conventional configuration when driving the grid, the solid line indicates the moving speed of the grid 102 according to the configuration of the present embodiment when driving, and the hatched portion. Indicates the total moving distance of the grid.

Therefore, first, when the radiography by the X-ray radiographing apparatus 100 is started (at the start of radiography), at that time (indicated by "" in FIG. 5D), the grid speed control unit 110 is started.
Starts driving the grid 102. When the acceleration of the grid 102 is completed and the grid 102 reaches the constant speed v0 (indicated by "" in FIG. 5D), that is, the cam 201 becomes the constant speed (angular speed) ω0, and the detector 2
When a pulse is emitted from the X-ray generation unit 101, the X-ray generation unit 101
Starts the X-ray irradiation (see FIGS. 5A and 5B).

When the X-ray irradiation is started, the grid speed control unit 110 determines that the integrated value of the output of the X-ray monitor 108 is a predetermined threshold value (the value indicated by “B” in FIG. 5C). ) Is reached (indicated by “” in FIG. 5C), the time t0 from the start of the exposure is acquired (measured), and the speed ω1 of the cam 201 is calculated based on the value of the time t0. And then cam 2
An instruction to change the speed of No. 01 from the speed ω0 to the speed ω1 is issued to the servo motor control unit 105. Thereby, the moving speed of the grid 102 is changed from the speed v0 to the speed v1.

Thereafter, the X-ray cutoff control unit 109 sets the integrated value of the output of the X-ray monitor 108 to a specified value (see FIG.
At the time when the value reaches the value indicated by “A” in FIG.
By outputting a cutoff signal to the X-ray generation unit 101 (shown by “” in (c)), the X-ray output is cut off (OFF).

Here, the angular velocity ω0 of the cam 201 is the highest speed at which the cam 201 can move, or the speed set for each subject (photographing part) of the subject 130, or the tube voltage, tube current, and photographing distance. The angular speed ω1 of the cam 201 is a speed at which the grid 102 does not stop or turn back until the X-ray irradiation ends. That is, the angular velocities ω0 and ω1 of the cam 201 are the speeds for implementing the velocities v0 and v1 of the grid 102 in the first embodiment.

The angular speed ω 1 of the cam 201 is calculated by the grid speed control unit 110 based on the irradiation time obtained from the initial output (initial X-ray irradiation amount) of the X-ray monitor 108. An example of the calculation method will be described below.

First, regarding the entire X-ray irradiation time (expected irradiation time) texp, the above equation (1) (texp =
(A · t0) / B).

Further, in order to prevent the grid 102 from stopping or turning back, it is desirable that the rotation angle of the cam 201 be within the maximum angular velocity position ± 90 °. Here, for the sake of simplicity, assuming that the acceleration / deceleration time of the cam 201 is so small that it can be ignored, the cam 201 takes the time t
During the period of 0, the cam 201 rotates at the angular velocity ωo, and thereafter rotates at the angular velocity ω1 until the end of the X-ray exposure. Therefore, the rotational angle of the cam 201 during the X-ray exposure is ω0 · t0 + ω1 · (tex− t0)... (2 ′) It is obtained from equation (2 ′).

Therefore, for example, when the rotational position of the cam 201 is limited to a position where the parallel movement speed is relatively stable, that is, ± θ of the maximum angular velocity position, the above equation (2)
′), The angular velocity ω1 of the cam 201 at which the grid 102 does not stop or turn back is determined by the following equation (3 ′): ω1 = (2θ−ω0 · t0) / (expp−t0) (3 ′) That is, the angular velocity of the cam 201 may be set to be equal to or less than the velocity ω1. As a result, the amount of movement of the grid 102 falls within ± θ of the maximum angular velocity position of the cam 201.

As for the moving speed of the grid 102 due to the rotation of the cam 201 as described above, the rotation speed of the cam 201 is “ω”, the radius of the cam 201 is “R”,
Assuming that the speed of No. 2 is “v”, it is expressed by the following equation: v = Rωsin (ωt).

The rotation speed of the cam 201 is obtained by multiplying the rotation speed of the servo motor 103 by the gear reduction ratio, and controls the rotation speed of the servo motor 103 according to the graph shown in FIG. By doing so, the moving speed of the grid 102 can be controlled as shown in FIG.

As described above, in the present embodiment, the cam 2
01, the rotary motion of the servomotor 102 is converted into a parallel motion.
02 moves in a sinusoidal manner. As a result, in the related art, as shown by the dotted line in FIG. 5D, the grid is turned back during the X-ray irradiation, and the speed fluctuation at this time reduces the effect of reducing the grid pattern.
According to the above configuration in the present embodiment, it is possible to prevent the grid 102 from being turned back during X-ray irradiation, and thus it is possible to sufficiently expect the effect of reducing the lattice fringes.

An object of the present invention is to supply a storage medium storing program codes of software for realizing the functions of the host and the terminal according to the first and second embodiments to a system or an apparatus, and to provide the system or the apparatus. By reading and executing the program code stored in the storage medium by the computer (or CPU or MPU) of the device,
Needless to say, this is achieved. In this case, the program code itself read from the storage medium is the first and second program codes.
The functions of the embodiment are realized, and the storage medium storing the program code constitutes the present invention. ROM, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-R
An OM, a CD-R, a magnetic tape, a nonvolatile memory card, or the like can be used. The functions of the first and second embodiments are realized by executing the program code read by the computer, and the OS running on the computer based on the instruction of the program code. Do some or all of the actual processing,
It goes without saying that the processing may realize the functions of the first and second embodiments. Further, after the program code read from the storage medium is written to a memory provided in an extension function board inserted into the computer or a 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 included in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the first and second embodiments.

[0078]

As described above, according to the present invention, the moving speed of the grid is controlled based on the radiation dose during a predetermined period. For example, the total time of irradiating radiation is predicted based on the radiation dose at the beginning of radiation (e.g., X-ray) irradiation (at the time of radiation exposure), and the moving speed of the grid is calculated based on the predicted time. The speed of the grid (speed during irradiation) is changed (deceleration or acceleration, etc.) to the moving speed. With such a configuration, the speed of the grid can be optimally controlled, so that it is possible to prevent shortage of the movement amount of the grid, and occurrence of artifacts such as a grid pattern and a pseudo-resolution of the grid image due to a stop or a turn, thereby achieving high quality. Can be provided. In addition, even in the case of an AEC or the like in which it is difficult to predict an appropriate radiation exposure time before imaging, it is possible to reliably predict the radiation exposure time. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an X-ray imaging apparatus to which the present invention is applied in a first embodiment.

FIG. 2 is a diagram for explaining operation timing of the X-ray imaging apparatus.

FIG. 3 is a diagram illustrating a grid driving mechanism of the X-ray imaging apparatus.

FIG. 4 is a diagram illustrating a grid driving mechanism of the X-ray imaging apparatus according to the second embodiment.

FIG. 5 is a diagram for explaining operation timing of the X-ray imaging apparatus according to the second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 X-ray imaging apparatus 101 X-ray generation unit 102 Moving grid 103 Servo motor 103 a Pulley 104 Encoder 105 Servo motor control unit 106 Fluorescent screen 107 Imaging medium 108 X-ray monitor 109 X-ray output cutoff control unit 110 Grid speed control unit 111 Control line 112 Image sensor read control unit 121 Control unit 122 Memory 130 Subject 201 Cam 202 Detector 203 Arm

Claims (12)

[Claims] An imaging apparatus for irradiating a subject with radiation to acquire a radiographic image of the subject, comprising: a movable grid for removing scattering of radiation at the subject; A driving unit for driving; a detection unit for detecting the radiation dose; and a control unit for controlling a moving speed of the grid by the driving unit based on a detection result of the detection unit for a predetermined period. Shooting device. 2. The apparatus according to claim 1, wherein the control unit predicts a radiation irradiation time based on the radiation dose during the predetermined period, and changes a moving speed of the grid based on the predicted irradiation time. The imaging device according to the above. 3. The photographing apparatus according to claim 1, wherein said control means controls a moving speed of said grid within a radiation irradiation time to said subject. 4. The predetermined period is at least one of a period until the radiation dose detected by the detection means reaches an arbitrary threshold value and a period from the start of irradiation of the radiation to the elapse of an arbitrary time. The photographing apparatus according to claim 1, wherein the photographing apparatus includes any one of the above. 5. An imaging system in which a plurality of devices are communicably connected to each other, wherein at least one of the plurality of devices is a function of the imaging device according to any one of claims 1 to 4. An imaging system comprising: 6. An imaging method for irradiating a subject with radiation to obtain a radiographic image of the subject, wherein a driving step of driving a movable grid for removing scattering of the radiation at the subject. A monitoring step of monitoring the radiation dose; and a control step of controlling a moving speed of the grid by the driving step based on a monitoring result of the monitoring step at an initial stage of irradiation start of the radiation. And the shooting method. 7. The control step includes a step of predicting a total irradiation time of the radiation based on the radiation dose at the beginning of the irradiation, and reducing or accelerating a moving speed of the grid based on the predicted time. The photographing method according to claim 6, wherein: 8. The imaging method according to claim 6, wherein the control step includes a step of controlling a moving speed of the grid within a radiation irradiation time to the subject. 9. The irradiation initial period includes a period until the radiation dose monitored by the monitoring step reaches an arbitrary threshold value and a period until an arbitrary time elapses after the irradiation is started. The photographing method according to claim 6, wherein at least one of the periods is included. 10. The controlling step includes controlling a moving speed of the grid so that the moving speed of the grid is set to a speed at which at least one of the stop and the turning of the grid does not occur within the irradiation time of the radiation to the subject. 7. The photographing method according to claim 6, further comprising: 11. A processing program for implementing the function of the photographing apparatus according to claim 1 or the function of the photographing system according to claim 5, readable by a computer. Storage medium. 12. A storage medium, wherein the processing steps of the photographing method according to claim 6 are stored in a computer readable manner.