JPH02238448A - Radiographic device - Google Patents

Abstract

PURPOSE:To evade the useless irradiation with radiant rays to the object to be irradiated even when the photographing distance becomes longer by variably controlling the aperture area of a collimator corresponding to the change in the distances between a radiation source and the collimator, and a projected image recording means. CONSTITUTION:The radiation source 2 for irradiating the object to be irradiated 7 with radiant rays and the collimator 3 are integrally constituted so as to contact with and separate from the projected image recording means 16. Corresponding to the distance which is changed by their contact and separation, the aperture area of the collimator 3 is variably controlled. That, means, by variably controlling the aperture area of the collimator 3 corresponding to the change in the distance, the solid angle of radiant rays which is restricted by the aperture area of the collimator 3 is automatically set to the value suitable to the distance. Thus, even when the photographing distance becomes longer, the useless irradiation with radiant rays to the object to be irradiated 7 can be avoided.

Description

[Detailed description of the invention] Industrial application field> The present invention relates to a radiographic apparatus, and in particular, to regulation and control of radiation irradiation in a radiographic apparatus in which the distance between a radiation source and a projection image recording device (imaging distance) changes. Regarding.

<Prior art> Conventionally, as a radiographic apparatus, for example, Japanese Patent Laid-Open No. 62-1
There is a method that scans an object to be irradiated with a fan beam of radiation, such as disclosed in Japanese Patent No. 29034.

This includes a radiation source, generally an X-ray tube, a radiation sensitive film, a fluorescent display screen, etc., which detects the amount of radiation from the radiation source that has passed through the irradiated object and records a radiation projection image. A projection image recording device such as an electron image intensifier tube and a collimator located between the radiation source and the object to be irradiated are provided, and a fan beam is formed by a slit aperture opened in the collimator, and the object is irradiated by the fan beam. It records the projected image of radiation by scanning the irradiated object. <<Problems to be Solved by the Invention>> By the way, in the radiographic apparatus as described above, due to differences in the required radiation dose depending on the thickness of the irradiated object and requirements of the usage environment, there are A device for irradiating radiation (radiation irradiation device),
Since the structure is configured so that the distance from the recording device that detects and records the radiation that has passed through the irradiated object (hereinafter referred to as the imaging distance) can be changed, the longer the imaging distance becomes, the more the radiation dose of the irradiated object is wasted. The problem was that there were too many.

That is, in the case of an apparatus configured to scan using a fan beam, as shown in FIG. , a second collimator 55 is provided in front of the recording device 54 and moves in synchronization with the scanning by the fan beam, and even if the photographing distance changes, the radiation exposed to the recording device 54 is transferred to the second collimator 55.
Since the fan beam is controlled by the aperture 56 of No. 5, it does not interfere with the scanning operation by the fan beam. However, as the photographing distance becomes longer, the fan beam obtained through the slit diaphragm 5l provided in the first collimator 52 spreads significantly before reaching the recording device 54, and the fan beam is expanded beyond the aperture of the second collimator 55. Radiation is applied to unnecessary parts of the body. Here, when the irradiated object 57 is a human body, the radiation that is wasted on the second collimator 55 as described above is also wasted radiation for the human body, and the amount of exposure to harmful radiation is wasted. It was becoming more common.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a radiographic apparatus configured to avoid unnecessary radiation being irradiated onto an irradiated object even if the imaging distance becomes long. do.

<Means for Solving the Problems> Therefore, the present invention provides a radiation source, a projection image recording means for detecting the radiation dose from the radiation source that has passed through an irradiated object and recording a radiation projection image, and the radiation source. and a collimator having an aperture located between the object and the irradiated object and allowing the radiation to pass therethrough, and the radiation source and the collimator are configured to be integrally separable from and to the projection image recording means. The apparatus is provided with aperture area variable control means for variably controlling the aperture area of the collimator in accordance with changes in the distance between the radiation source and collimator and the projection image recording means. According to this configuration, in the radiographic apparatus, the radiation generated by the radiation source is irradiated onto the object to be irradiated through the aperture of the collimator, and the radiation that has passed through the object to be irradiated is projected onto the object behind the object to be irradiated. It is detected by an image recording means and a radiation projection image is recorded. Here, a radiation source and a collimator for irradiating the irradiated object with radiation are integrally configured to be able to move toward and away from the projection image recording means, and the distance at which this distance changes (imaging distance) The opening area of the collimator is variably controlled accordingly. That is, by variably controlling the aperture area of the collimator in accordance with the change in distance, the solid angle of the radiation, which is limited by the aperture area of the collimator, can be automatically set to a value commensurate with the distance. .

<Example> An example of the present invention will be described below. The radiographic apparatus shown in FIG.
This is a radiography device 1, which is assumed to be mainly used for chest photography of patients.

FIG. 1 is a top view of the X-ray photographic apparatus 1, and the direction passing through the diagram is the actual top and bottom. Here, x as a radiation source
A cylindrical first collimator 3 is provided on the front surface of the X-ray tube 2 around the vertical axis of the X-ray tube 2.
A slit diaphragm 4 for forming a fan beam is opened along the vertical (vertical) direction.

The first collimator 3 is rotatably supported in a predetermined angular range around an axis relative to the main body, and when the feed remoter 5 is driven and rotated by the swing controller 6,
According to the rotation, the first collimator 3 rotates around the X-ray tube 2, and due to this rotation, the fan beam formed by the slit diaphragm 4 scans in the left and right direction of the patient (up and down direction in FIG. 1). It is designed to perform actions. The fan beam formed by the slit diaphragm 4 is irradiated onto the patient's chest 7 as the object to be irradiated, and behind the patient's standing position is a second collimator having a rectangular opening 8 corresponding to the slit diaphragm 4. 9 is provided, and this second collimator 9 moves in parallel in the left and right (up and down in the figure) direction in synchronization with the swinging operation (scanning operation) of the first collimator 3, and the slit aperture of the first collimator 3 4 and passes through the chest 7, the fan beam passes through the opening 8 of the second collimator 9.

The parallel movement of the second collimator 9 is caused by the parallel movement of the second collimator 9
As in the case of , the feed motor 10 is connected to the movement controller 1
1, the second collimator 9 is configured to move in parallel according to the rotation.

An X-ray transparent detector l2 is fixed behind the opening 8 of the second collimator 9 so as to receive all the X-rays passing through the opening 8. The detector 12 is an assembly including a plurality of detectors in the transverse direction of the opening 8, and detects the dose of X-rays passing through the opening 8.
(fan beam) is detected at multiple locations in the transverse direction. Further, behind the detector l2, a shielding plate 13 that is not transparent to X&51 is supported so as to be freely movable in parallel with the second collimator 9. 15 and the opening 8 of the second collimator 9. It selectively moves in parallel between a position where it blocks the X-rays that have passed through the detector 12 and a position where it retreats from the position and allows the X-rays to pass through.

A film cassette 16 is provided behind the shielding plate 13 as a projection image recording means. This film cassette 16 is attached to the front screen. It consists of an X-ray film and a back screen, and when the shielding plate 13 is removed from the X-ray passing position, it passes through the chest 7 and passes through the opening 8.
The X-rays passing through the detector 12
6, and a projection image corresponding to the dose is recorded, that is, an X-ray photograph of the chest 7 is taken. Each said controller 6.11.14 comprises a control unit 1
7, and this control unit 17 also includes a modulator 1 that variably controls the opening area of the slit diaphragm 4 that forms the fan beam at multiple locations in the transverse direction (longitudinal direction).
8 and the X-ray tube controller 19.

As shown in FIG. 2, the modulator 18 is made up of a plurality of shutter members 20 that move in and out from one end of the slit diaphragm 4 in the scanning direction toward the opening and are adjacent to each other throughout the lateral direction (longitudinal direction) of the slit diaphragm 4. Each shutter member 20 is individually driven by an actuator (not shown), and the opening area of the slit diaphragm 4 in the transverse direction can be varied by the amount of protrusion toward the opening. Therefore, the dose of the fan beam formed by the slit diaphragm 4 is variably adjusted at multiple points in the transverse direction by the modulator 18. Here, the recording side A consisting of the second collimator 9, film cassette 16, etc., and the XvA irradiation side B consisting of the X-ray tube 2, first collimator 3, etc. are each integrated and can be moved into and out of contact with each other. For example, while the second collimator 9 and film cassette 16 are fixed to the main body (not shown),
The wire tube 2 and the first collimator 3 are integrally configured to be movable relative to the main body at least in the direction toward and away from the recording side A. As a configuration according to the present invention, the recording side A and the recording side
A distance sensor 2l is provided to detect the distance l (shadow distance) to the radiation side B using, for example, a potentiometer. A shutter 22 for variable control of the slit width of the diaphragm 4, a feed remoter 23 for moving the shutter 22 in the slit width direction, and a slit width controller 24 for controlling the drive of the feed motor 23 are provided. In the shutter 22, the first collimator 3 provided with the slit diaphragm 4 has a double structure, and the shutter 22, which is provided on the inner side of the outer side where the scanning operation is performed by the feed motor 5, is supported so as to be movable in the circumferential direction. It is something. Next, the photographic shadows produced by the X-ray photographic apparatus I having the above configuration will be explained. First, in the initial state, the control unit 17 sends a signal to the controllers 5 and 1l so that the first collimator 3 and move the second collimator 9 to the initial position. Further, the shielding plate 13
is moved into the X-ray passing space, and the X-rays are transferred to the film cassette
6, and modulator 1.
The shutter members 20 of 8 are all moved to the same initial position so that the aperture area of the slit diaphragm 4 is made the same in the transverse direction without controlling the aperture area by the modulator 18. From this state, a signal is sent to the controller 19 to generate X-rays from the X-ray tube 2, and at the same time, the controller 6.11
The first collimator 3 is rotated to start the scanning operation by the fan beam. At this time, the movement of the second collimator 9 is controlled by the controller l1 so as to follow the scanning of the fan beam, and the X-rays that have passed through the patient's chest 7 are detected by the detector 12 through the opening 8 of the second collimator 9. Make sure that it is done. In this first scanning, as described above, the shielding plate 13 prevents the X-rays from reaching the film cassette 16, so the film is not exposed, and predictive data of the transmitted dose reaching the film light-transmitting surface is collected. The shape of the modulator 18 that variably adjusts the radiation dose in the transverse direction of the fan beam is determined based on the data so that the degree of exposure in the film exposure in the second scan is averaged and a photograph with a large amount of information can be taken. Ru. In the second scan, in order to expose the film cassette 16 and record the X-ray projected image as a photograph, the control unit 17 sends a signal to the controller 14 to rotationally drive the feed motor 15 to remove the block 13 from the X-rays. Remove from transit space. Then, scanning is performed again from the initial scanning position, but at this time, the shutter member 20 is
The amount of protrusion from the opening of the slit diaphragm 4 is controlled, and the exposure to the film cassette 16 is performed while adjusting the radiation dose irradiated to the chest 7 depending on the region.

Further, in the X-ray photographic apparatus l in this embodiment, as described above, the recording side A and the X-ray irradiation side B are configured to be able to come into contact with and separate from each other, and the distance between the recording side A and the X-ray irradiation side B is When l is changed from the initial state, the slit width of the slit diaphragm 4 is variably controlled as follows. The distance 2 between the recording side A and the X-ray irradiation side B is detected by the distance sensor 2l, and this detection result is sent to the control unit 1.
7 is input. The control unit that received the detection signal at distance l}1? For example, calculates the deviation between the reference distance and the detected distance jilf, determines the required value of the slit width of the slit diaphragm 4 according to this deviation amount, and sends a signal corresponding to this required slit width value to the slit width controller. Output to 24. The slit width controller 24 sets the amount of movement of the shutter 22 based on the input slit width request value, and drives the feed remoter 23 by an amount equivalent to this amount of movement.
The slit width of the slit diaphragm 4 is variably adjusted by moving the shutter 22 in the circumferential direction (scanning direction). If the slit width of the slit diaphragm 4 is constant and the solid angle of the radiation determined by this slit width is constant, for example, from the state shown in FIG. 1, the distance between the recording side A and the X-ray irradiation side B! By increasing the distance P, the spread of the fan beam when it reaches the second collimator 9 increases in accordance with the extension of the distance P, so in reality, radiation other than the radiation passing through the opening 8 of the second collimator 9 is irrelevant to imaging. Even though there is a large amount of radiation that does not pass through the opening 8, the amount of radiation that the human body is exposed to increases. Therefore, as the distance 2 becomes longer, it is necessary to reduce the slit width of the slit diaphragm 4 to suppress the spread of the fan beam in the width direction. The slit width can be variably controlled by moving 22, and when the distance l becomes long, the slit width is narrowed to prevent expansion.
distance! When the slit becomes shorter, the inside of the slit is widened so that the radiation to be imaged can be regulated by the opening 8 on the second collimator 9 side. In this way, according to this embodiment, the distance between the recording side A and the X-ray irradiation side B! When the slit aperture 4 is changed, the slit aperture 4
The width of the slit is variably adjusted, and the solid angle of the X-ray determined by the width of the slit is changed to control the spread of the fan beam in the width direction when it reaches the second collimator 9 on the recording side A to be approximately constant. Distance between recording side A and X-ray irradiation side B.
Even if the %Il (imaging distance) becomes longer, the amount of radiation to the human body, which is the irradiated object, does not increase unnecessarily. Note that the opening area variable control means in this embodiment is the shutter 22. Slit width controller 24. Feed motor 23, distance sensor 21. It is composed of a control unit 17 and the like.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4.

The X-ray photographic apparatus of the second embodiment shown in FIGS. 3 and 4 is as follows:
The chest of the human body is scanned by a fan beam, and the X of the chest is
In the first embodiment shown in Figs. 1 and 2, the scanning direction was in the left-right direction of the human body, whereas in the second embodiment shown in Figs. 3 and 4, line photographs were taken. The difference is that the scanning direction in the example is the vertical direction (vertical direction) of the human body, but the basic configuration of each equipment related to other X-ray photography is the first one.
This is the same as the example. Therefore, in FIGS. 3 and 4, the same elements as those in the first embodiment are given the same reference numerals and their explanations will be omitted.

In the X-ray photographic apparatus 1 shown in FIGS. 3 and 4, a second collimator 9 integrally equipped with a detector 12 is guided and supported so as to be movable in parallel along the scanning direction, and is driven by a feed motor (not shown). One end of the belt 31 is engaged with the belt 31, which is fed forward in the scanning direction, so that it moves in parallel in the vertical direction as the belt 3l rotates. Further, one end of a scanning synchronizing plate 38 is rotatably supported through a rotary shaft 9a which is formed protruding from the end of the second collimator 9 opposite to the belt 31. One end of a scanning shaft 32 that rotatably supports the X-ray tube 2 is fitted into the elongated hole 38a.
One end of the scanning shaft 32 fitted into the elongated hole 38a is formed into a prismatic shape with a square cross section having a side slightly shorter than the width of the elongated hole 38a. When the scanning axis 32 swings around the scanning axis 32, a moment about the axis is applied to the scanning axis 32, and the scanning axis 32 is moved around the scanning synchronizing plate 38.
It will rotate with the oscillation of. Therefore, when the second collimator 9 moves up and down along the scanning direction and one end of the scan synchronization plate 38 moves up and down accordingly, the scan synchronization temporary 38 swings about the scanning axis 32, and this scan synchronization plate 38 is transmitted to the scanning shaft 32, and in accordance with the movement of the second collimator 9, the X-ray tube 2 performs vertical swinging motion (scanning). Incidentally, as described above, the second IJ. The X-ray tube 2, which swings in synchronization with the vertical movement of the meter 9, is provided with a first collimator 3 integrally having a slit diaphragm 4 and a modulator 18. Performs the swinging motion in conjunction with 2. Further, the scanning shaft 32 that supports the X-ray tube 2 rotatably around the axis has its bearing portion 32a on the recording side A.
The X-ray tube 2, together with other devices constituting the XvA irradiation side B, such as the first collimator 3 and the modulator 18, is installed horizontally with respect to the recording side A. It is possible to separate and separate. When the distance l between the recording side A and the XLIA irradiation side B is changed, the scanning axis 32 becomes
The fitting position within the elongated hole 38a is changed in the longitudinal direction of the elongated hole 38a. The slit diaphragm 4 of the first collimator 3 is configured such that its width can be variably controlled by varying the relative distance of a shutter 33.34 divided into two in the width direction. Slit width control bin 35.36
One end of each of the slit width control pins 35, 36 is fixed, and when the relative distance of the slit width control pins 35, 36 is increased, the shutters 33, .
34 increases, and the slit width of the slit diaphragm 4 increases. The other ends of the slit width control pins 35 and 36 extend to a position sandwiching the upper and lower ends of the scanning synchronization plate 38, and the slit width control pins 35. A tension coil spring 37 is stretched between the two in the middle part of the slit width control pin 35.36 to urge them toward each other.
36 are pressed against the upper and lower ends of the scan synchronization plate 38 by the tension coil springs 37, and the relative distances are controlled according to the width of the scan synchronization plate 38. It is controlled by width.

A scanning synchronization plate 38 and the slit width control bin 35. 36
Since the alignment position is related to the distance (imaging distance) 2 between the recording side A and the X-ray irradiation side B, the width of the slit diaphragm 4 required by the distance Ml is determined in advance by the opening 8 of the second collimator 9. The vertical width of the scan synchronizing plate 38 is determined from the width of the fan beam in the X-ray tube 2 so that the required width of the slit diaphragm 4 can be obtained by changing the distance l. It changes in stages so that it becomes tapered towards the sides. That is, as the distance 2 between the recording side A and the X-ray irradiation side B increases, the slit width control pin 35. The position of the scanning synchronizing plate 38 sandwiched between the fan beams 36 is further away from the rotating shaft 9a, and as the distance 2 becomes longer, it is necessary to narrow the width of the slit diaphragm 4 to suppress the spread of the fan beam (solid angle of radiation). Therefore, if the elongated hole 38a side of the scanning synchronization plate 38 is made narrower, the width of the slit diaphragm 4 can be controlled to be narrower as the distance 2 increases, thereby avoiding unnecessary spread of the fan beam. . Therefore, in the second embodiment, as in the first embodiment, even if the distance 2 between the recording side A and the X-ray irradiation side B is increased, unnecessary radiation will not be irradiated to the human body. can be avoided.

In this way, while the first embodiment changes the slit width of the slit diaphragm 4 by electrical control, the second embodiment mechanically changes the width of the slit diaphragm 4 according to the distance C. The scanning synchronization plate 38
The component not only has the function of synchronizing the movements of the recording side A and the X-ray irradiation side B, but also has an aperture area variable control means,
The aperture area variable control means is constituted by the scanning synchronizing plate 38, shutters 33, 34, slit width control pins 35, 36, and the like.

In the above embodiment, an X-ray film is used as the projection image recording means, but the present invention is not limited to this, and a fluorescent display screen, an electronic image intensifier tube, etc. may also be used, and the recording means is limited. There isn't.

Furthermore, although this embodiment has described the chest X-ray apparatus 1 used for medical purposes, it is clear that it can also be applied to radiographic apparatuses used for industrial purposes such as internal defect inspection of parts. is not limited to XIIA but γ
It may also be possible to use wires, infrared rays, or the like.

Furthermore, in this embodiment, the aperture of the first collimator 3 is the slit diaphragm 4, but the shape of the aperture is not limited, and it does not have to be configured to perform the scanning operation. The modulator 18 is not an essential requirement. Effects of the Invention> As explained above, according to the present invention, the front side of the radiation source is adjusted according to the change in the distance (imaging distance) between the radiation irradiation side, which includes the radiation source and the collimator, and the projection image recording side. Since the aperture area of the provided collimator is configured to be variably controlled, it is possible to avoid unnecessary radiation being irradiated to the irradiated object even if the distance is long, and especially when the irradiated object is a human body. In some cases, it has the effect of minimizing the amount of exposure to harmful radiation such as X-rays.

[Brief explanation of drawings]

FIG. 1 is a top view showing a first embodiment of the radiographic apparatus according to the present invention, FIG. 2 is a partially enlarged perspective view showing the slit diaphragm shown in FIG. FIG. 4 is a sectional view of the projection image recording device in the apparatus shown in FIG. 3, and FIG. 5 is a state diagram for explaining the conventional problems. 1...X-ray photography device 2...XvA tube 3...
・First collimator 4...Slit aperture 16・
...Film cassette l7...Control unit
21...Distance sensor 22...Shutter 23
...Feed motor 24...Slit width controller
33.34...Shutter 35.36...Slit width control pin 38...Scan synchronization plate

Claims (1)

[Claims] a radiation source, a projection image recording means for detecting the radiation dose from the radiation source that has passed through the irradiated object and recording a radiation projection image, and a projection image recording means that is located between the radiation source and the irradiated object and allows the radiation to pass therethrough. a collimator having an opening, and the radiation source and the collimator are configured to be integrally separable with respect to the projection image recording means, wherein the radiation source, the collimator, and the projection image recording means are 1. A radiographic apparatus comprising: an aperture area variable control means for variably controlling an aperture area of the collimator in accordance with a change in distance of the collimator.