JP2772663B2 - Radiographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a radiographic apparatus, and more particularly to a radiographic apparatus configured to scan an irradiation target with a radiation beam and record a radiation projection image. The present invention relates to a radiation dose adjusting device for averaging exposure.

<Prior Art> A radiographic apparatus generally detects a radiation source using an X-ray tube and a radiation dose from the radiation source that has passed through an object to be irradiated, and records a radiation projection image. It is composed of a projection image recording device such as a film, a fluorescent display surface, and an electronic image intensifier tube.

By the way, in such a radiation imaging apparatus, a certain part is properly exposed due to a difference in thickness and radiation absorbability in an imaging part, and another part is underexposed. In order to obtain desired information, the contrast of the image is insufficient. For this reason, for example, in chest imaging with an X-ray examination apparatus used for medical use, there is a small difference between a soft part such as a lung and an abdomen and a hard part such as a rib and a spine. In contrast, it is not easy to see in a visible form.

In order to solve such a problem, conventionally, in order to equalize the degree of exposure in different imaging parts, the irradiation radiation dose is variably adjusted according to the imaging part (Japanese Patent Laid-Open No. 62-12 / 1987).
No. 9034).

That is, a radiation shielding member having a plurality of slit apertures for forming a fan beam is located between a radiation source and an irradiation target, and the fan beam (radiation beam) formed by the plurality of slit apertures is scanned at a constant speed. It is configured to perform an operation. Then, for example, a slit for forming a fan beam on the rear side in the scanning direction while detecting the amount of radiation passing through the object to be irradiated by the fan beam on the front side in the scanning direction at a plurality of locations in the transverse direction of the fan beam (direction intersecting the scanning operation direction). The aperture is provided with a shutter that varies the opening area at each of a plurality of locations in the transverse direction of the fan beam, and the shutter is driven to average the amount of transmitted radiation in the transverse direction of the fan beam based on the detected amount of transmitted radiation. Thus, the radiation dose to the irradiation target is variably controlled in accordance with the imaging region.

<Problems to be Solved by the Invention> Incidentally, in the case of a configuration in which the opening area of the slit aperture for forming the fan beam is variably controlled in the transverse direction to make the exposure constant as described above, for example, When scanning in the direction, the shutter is opened to increase the radiation dose when the radiation dose is small such as the spine, but the radiation dose is increased when the radiation dose is large such as the lungs off the spine. The shutter is closed to reduce it so that the spine and lungs are each photographed with proper exposure.

However, in the conventional apparatus, for example, the spine that requires a large amount of radiation and the lung that does not require a large amount of radiation are scanned at the same speed. There is a problem in that even an object with a small number of scans requires the same time for scanning, and in imaging an object with a small required radiation dose, the scanning time becomes unnecessarily long, and the radiation dose increases accordingly. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made to reduce the scanning time while averaging the exposure degree in a radiographic apparatus, so that a large amount of information can be captured in a short time. Aim.

<Means for Solving the Problems> Therefore, according to the present invention, a radiation source, projection image recording means for recording a radiation projection image by detecting a radiation dose from a radiation source that has passed through an object to be irradiated, and a radiation source and a radiation source. A radiation shielding member having an opening that forms a radiation beam between the radiation object and a radiation beam obtained through the radiation shielding member to perform a scanning operation. A passing radiation dose detecting means for detecting a radiation dose passing through the irradiation object at a plurality of locations in a direction intersecting the scanning operation direction, and a radiation beam positioned between the radiation source and the irradiation target and exposed to the projection image recording means Irradiating radiation dose adjusting means for variably adjusting the radiation dose in the direction intersecting with the scanning operation direction, and the passing radiation dose detected by the passing radiation dose detecting means. Together controls the radiation amount adjusting means morphism is a variable control to irradiated dose in the middle scan the scanning speed of the radiation beam that is provided with an exposure control means for variably controlling, the.

<Operation> According to this configuration, the irradiation radiation dose adjusting means is a radiation dose of a radiation beam that is located between the radiation source and the irradiation target and is exposed to the projection image recording means, that is, for exposure to the irradiation target. The radiation dose to be applied is variably adjusted in a direction intersecting the scanning operation direction of the radiation beam so that different radiation doses can be applied in a direction intersecting the scanning operation direction.

Further, the radiation dose passing through the irradiation object is detected at a plurality of positions in a direction intersecting with the scanning operation direction of the radiation beam by the passing radiation dose detection means, and based on the detection result, the exposure control means In addition to controlling the driving of the dose adjusting means, the irradiation speed is variably controlled by variably controlling the scanning speed of the radiation beam during scanning.

That is, the irradiation dose in the direction intersecting with the scanning operation direction is variably controlled based on the radiation dose in the direction intersecting with the scanning operation direction of the radiation beam, and the scanning speed of the radiation beam (the irradiation dose in the scanning direction). For example, when the average irradiation dose is reduced by the irradiation dose adjusting means at the reference scanning speed, the irradiation dose is made equal by increasing the scanning speed instead of reducing the aperture amount, The scanning time can be shortened together with the adjustment of the irradiation dose for averaging the degree of exposure.

<Examples> Examples of the present invention will be described below.

The radiographic apparatus shown in FIG. 1 is an X-ray apparatus used for medical treatment, and is assumed to be used mainly for imaging a chest of a patient.

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

The first collimator 3 is rotatably supported within a predetermined angle range around the axis with respect to the main body. When the feed motor 5 is driven and controlled by the swing controller 6 to rotate, the first collimator 3 is rotated in accordance with the rotation. First collimator 3 is X-ray tube 2
, The fan beam formed by the slit diaphragm 4 performs a scanning operation in the left-right direction (up-down direction in FIG. 1) of the patient.

The fan beam formed by the slit diaphragm 4 is irradiated to a patient's chest 7 as an object to be irradiated, and a second collimator 9 having a slit diaphragm 8 corresponding to the slit diaphragm 4 is provided behind the standing position of the patient. The second collimator 9 moves in parallel in the left and right (up and down directions in the figure) in synchronization with the swinging operation (scanning operation) of the first collimator 3 and is formed by the slit diaphragm 4 of the first collimator 3. The fan beam that has passed through the chest 7 passes through the slit diaphragm 8 of the second collimator 9.

The parallel movement of the second collimator 9 is performed in the same manner as in the case of the first collimator 3 by the feed motor 10
And the second collimator 9 is configured to move in parallel according to the rotation.

Behind the slit stop 8 of the second collimator 9, an X-ray transmissive detector 12 as a passing radiation dose detecting means is fixed so as to receive all the X-rays passing through the slit stop 8. The detector 12 is an assembly including a plurality of detectors in the transverse direction of the slit diaphragm 8, and scans the dose of X-rays passing through the slit diaphragm 8 in the transverse direction of the slit diaphragm 8 (fan beam), that is, in the scanning direction. The detection is performed at a plurality of locations in the direction intersecting with the operation direction.

Behind the detector 12, an X-ray opaque shielding plate 13 is supported so as to be able to move in parallel to the second collimator 9, and the shielding plate 13 is driven by a movement controller 14 to be controlled. It is translated by the motor 15 and selectively translates into a position where X-rays that have passed through the slit diaphragm 8 and the detector 12 of the second collimator 9 are blocked, and a position where X-rays are retreated from this position and pass through.

Behind the shielding plate 13, a film cassette 16 is provided as projection image recording means. The film cassette 16 is composed of a front screen, an X-ray film, and a back screen. When the shielding plate 13 is retreated from the X-ray passing position, the X-ray passes through the chest 7 and passes through the slit diaphragm 8 and the detector 12. Is exposed to the film cassette 16 to record a projection image in accordance with the dose, that is, to take an X-ray photograph of the chest 7.

The controllers 6, 11, and 14 are controlled by a control unit 17 as exposure control means.
Reference numeral 17 denotes a modulator 18 and an X-ray tube controller as irradiation radiation dose adjusting means for variably controlling the opening area of the slit diaphragm 4 for forming the fan beam at a plurality of transverse positions.
19 control is also performed.

As shown in FIGS. 2 and 3, the modulator 18 is arranged so that the shutter member 20 which enters and exits from one end of the slit diaphragm 4 in the scanning direction toward the opening is located in the transverse direction of the slit diaphragm 4 (in the scanning direction of the fan beam). The shutter members 20 are individually driven by actuators (not shown), and are traversed in the transverse direction of the slit diaphragm 4 by the amount of projection toward the opening, that is, scanning. The opening area can be varied in a direction intersecting with the operation direction. Accordingly, the dose of the fan beam formed by the slit diaphragm 4 is variably adjusted in the transverse direction by the modulator 18.

Next, photographing in the X-ray apparatus 1 having the above configuration will be described.

First, in the initial state, the control unit 17 sends a signal to the controllers 5 and 11 to send a signal to the first collimator 3 so that the fan beam can be emitted from a predetermined scanning start position (for example, the right end of the patient viewed from the X-ray tube 2). And move the ninth collimator to the initial position. In addition, the shielding plate 13 is moved to the X-ray passage space so that the X-rays are not exposed to the film cassette 16, and the shutter members 20 of the modulator 18 are all moved to the same initial position.
The aperture area control by 18 is not performed, and the aperture area of the slit diaphragm 4 is made the same in the transverse direction.

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 first collimator 3 is rotated by the controllers 6, 11 to start the scanning operation by the fan beam. At this time, the movement of the second collimator 9 is controlled by the controller 11 so as to follow the scanning of the fan beam, and the X-rays passing through the chest 7 of the patient are detected by the detector 12 via the slit diaphragm 8 of the second collimator 9. To be done.

In the first scan, since the X-rays are prevented from reaching the film cassette 16 by the shielding plate 13 as described above,
No film exposure is performed and transmitted dose data is collected as shown in FIG.

For example, as shown in FIG. 4, the cross-section A including the lung has a larger transmitted dose than the mid-thoracic cross-section B with the backbone, and the data of such a transmitted dose is obtained in the scanning direction and the transverse direction of the fan beam, respectively. The shape of the modulator 18 at the time of film exposure in the second scan is determined based on the data of the transmitted dose. That is, in the case of the cross-section A, the lungs allow a large amount of X-rays to pass, while the other abdomen and the like receive a small amount of X-rays.
For a lung with a large transmitted dose (transmitted dose), the shutter member 20 is made to protrude into the opening to reduce the opening area. The dose obtained with the abdomen should be close. Such determination of the shape of the modulator 18 is performed along the scanning direction based on the detection result of the detector 12 in the first scan.

In the first scan performed to detect the transmitted dose of the patient as described above, since the film exposure is not performed, the scanning speed is set higher than the general speed in order to minimize the X-ray exposure of the patient. Alternatively, it is preferable that the modulator 18 narrows the opening area of the slit diaphragm 4 to perform scanning.

Also, from the data of the passing dose collected in the first scan,
As shown in FIG. 4, the average value or the minimum value of the passing dose in the direction traversing the fan beam is obtained. The average dose or the minimum dose indicates the degree of transmission of X-rays in the direction traversing the fan beam. For example, in the section A including the lung, where the average pass dose is large (the place where the minimum dose is high), the average pass Even if the scanning speed is higher than that of the section B, for example, where the dose is small (the minimum dose is low), an equivalent average transmitted dose (minimum dose) can be obtained. The scanning speed for the scanning position in the second scanning (film exposure) is set as shown in FIG.

As described above, when the shape and the scanning speed of the modulator 18 are determined from the data of the passing dose in the first scan, the second scan is performed.

In the second scanning, the control unit 17 sends a signal to the controller 14 to rotate the feed motor 15 so that the shielding plate 13 is moved to the X-ray passing space in order to expose the film cassette 16 and record an X-ray projection image in a photograph. Dismiss Then, the scanning is performed again from the initial scanning position. At this time, the modulator determined from the detection result of the transmitted dose in the first scanning is used.
The protruding amount of the shutter member 20 with respect to the opening of the slit diaphragm 4 is sequentially controlled in accordance with the shape of the shutter 18, and for example, scanning is performed by A in FIG.
When moving to the point, the shape of the modulator 18 is changed as shown in FIG. The exposure to the film cassette 16 is performed while adjusting the radiation dose to be performed according to the site.

The exposure of the film cassette 16 is performed by the chest 7 because the detector 12 is fixed to the second collimator 9.
And the radiation that has passed through the detector 12 is exposed.

Simultaneously with such a change in the shape of the modulator 18, the control unit 17 controls the controllers 6 and 11 to control the moving speeds of the first collimator 3 and the second collimator 9 in accordance with the scanning speed determined in the first scanning. To change. Therefore, if the reference scanning speed is adjusted to a place where the average passing dose is small (for example, point B in FIG. 4), the scanning speed is set to a place where the passing dose is large on average (for example, point A in FIG. 4). Even if the scanning speed is faster than the reference scanning speed, the same passing dose can be obtained, and only parts where the passing dose is small are scanned slowly, and the scanning time can be shortened when there are many parts with high average passing dose. Becomes

Further, if the irradiation dose is adjusted based on the shape and the scanning speed of the modulator 18 as described above, the adjustment amount by the modulator 18 can be reduced and the adjustment can be performed by the scanning speed correspondingly. The controllability can be improved by minimizing the shape change.

In this embodiment, an X-ray film is used as the projection image recording means. However, the present invention is not limited to this, and a fluorescent display surface or an electronic image intensifier may be used, and the recording means is limited. There is no. The modulator 18 may be configured to variably control the opening area of the slit diaphragm 4 as in this embodiment, or may be configured to adjust the irradiation radiation dose by a filter device capable of changing the absorbance of radiation such as X-rays. ,
Further, a combination of a radiation absorbing material and aperture area control may be used.

Further, the irradiation radiation dose in the first scan is reduced,
At this time, the film cassette 16 is weakly exposed and the amount of light passing through the object to be illuminated (the chest 7 in this embodiment) is detected. In the second scan, the exposure of only the portion that is insufficiently exposed in the first scan is modulated. Alternatively, the control may be performed by variable control of the scanning speed 18 and the scanning speed.

Furthermore, in this embodiment, the chest X-ray apparatus 1 used for medical purposes has been described. However, it is apparent that the present invention can be applied to a radiographic apparatus used for industrial purposes such as inspection of internal defects of parts. Is not limited to X-rays but may be γ-rays or the like.

<Effects of the Invention> As described above, according to the present invention, a dose that has passed through an irradiation target is detected at a plurality of locations in a direction that intersects a scanning operation direction of a radiation beam, and irradiation is performed based on the detection result. The radiation dose is adjusted in the direction that intersects the scanning operation direction, and the scanning speed of the radiation beam is changed during scanning, so that the exposure in each part of the projected image is averaged to obtain a photograph with a large amount of information. In addition, the scanning speed can be increased in a place where the required radiation dose is small, and the scanning time (imaging time) can be shortened.

[Brief description of the drawings]

FIG. 1 is a top view showing an embodiment of the radiographic apparatus according to the present invention, FIG. 2 is a partially enlarged perspective view showing the slit stop shown in FIG. 1, and FIG. 3 is dose adjustment in the slit stop shown in FIG. FIG. 4 is a partial top view for explaining the mechanism, FIG. 4 is a diagram for explaining a mode of radiation dose adjustment in the embodiment, and FIG. 5 is a front view showing an example of a modulator shape in the embodiment. DESCRIPTION OF SYMBOLS 1 ... X-ray apparatus, 2 ... X-ray tube, 3 ... 1st collimator, 4 ... Slit stop, 9 ... 2nd collimator, 12
...... Detector, 16 ... Film cassette, 17 ... Control unit, 18 ... Modulator

Claims (1)

(57) [Claims] 1. A radiation source, projection image recording means for recording a radiation projection image by detecting a radiation dose from the radiation source passing through an irradiation object, and a position between the radiation source and the irradiation object. A radiation shielding member having an opening for forming a radiation beam, wherein the radiation beam obtained through the radiation shielding member is configured to perform a scanning operation, A passing radiation dose detecting means for detecting a radiation dose at a plurality of locations in a direction intersecting with a scanning operation direction of the radiation beam, and a radiation beam which is located between the radiation source and the irradiation target and is exposed to the projection image recording means. Irradiating radiation dose adjusting means for variably adjusting the radiation dose in a direction intersecting the scanning operation direction; and To drive control the irradiation dose adjusting means, radiographic apparatus for an exposure control means for variably controlling, characterized in that the provided radiation dose the scanning speed of the radiation beam variably controlled to the way scanning.