JPS6114816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray apparatus, and more specifically to an apparatus capable of obtaining an X-ray tomographic image of a subject in an extremely short time.

Conventionally, an X-ray tube and an X-ray detector are rotated with the subject in between, and the intensity of transmitted X-rays at different irradiation angles is measured multiple times, and the obtained measurement data is processed to obtain a tomographic image of the subject. things are being done. In order to shorten the measurement time in such conventional methods, it is necessary to increase the rotation speed of the X-ray tube and X-ray detector, but it is necessary to increase the rotation speed of the X-ray tube and X-ray detector, which have a large mass. In particular, it has its own mechanical limitations, and it has been difficult to sufficiently shorten the measurement time.

The present invention has been made in view of the above-mentioned points, and consists of irradiating an electron beam along an arbitrary circle on an annular X-ray generation target, emitting electrons from the target,
To provide an X-ray apparatus configured to detect X-rays transmitted through an object by a detector group consisting of a large number of X-ray detection elements, and capable of obtaining a tomographic image of the object in an extremely short time. The purpose is to

An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, 1 is a column body having a shape similar to a hanging bell, and the inside thereof is kept in a vacuum. An electron gun 2 is installed at one end of the column 1, and an electron beam 3 emitted from the electron gun 2 is focused by a focusing lens 4.
a pair of X direction coils, Y
It is deflected by deflection coils 5 and 6 consisting of directional coils and projected onto an annular target 7. X-rays generated from the electron beam projection point on the target 7 are sent to the column via a cylindrical X-ray extraction window 8 provided in the column wall and an annular beam guide 9 having n X-ray passage ports of a desired shape. The beam is taken out into the imaging room 10 inside the camera, and is irradiated onto a subject 12 on a movable bed 11 made of a material with low X-ray absorption. The X-rays transmitted through the object 12 are detected by an X-ray detector group 13 consisting of a large number of X-ray detection elements arranged in a ring inside the beam guide 9. This X-ray detector group 13 is arranged on a virtual plane including a circular electron beam irradiation point (X-ray generation point) on the target 7 so as not to prevent the object from being irradiated with the X-rays from the annular beam guide 9. X-rays taken out by the beam guide 9 in a direction tilted at a slight angle with respect to the plane are directed to the X-ray detector group 1.
Detected by 3. Detection signals from the detector group 13 are sent to a central processing unit 14 for arithmetic processing. The subject 12 is placed along the axis of the apparatus, that is, the central axis of the annular target 14. The beam guide 9 is held on a rotating body 15,
The object 12 is rotated by the rotation of the rotating body. The rotating body is connected to a motor 17 via a gear mechanism 16. 18 is a control device which controls the deflection coils 5 and 5 based on command signals issued by the central processing unit according to a predetermined program.
The electron beam projection point on the target 7 is moved by controlling the current flowing through the electron beam guide 6, and the motor 17 is controlled so as to intermittently rotate the beam guide 9 in conjunction with the movement of the electron beam projection point.

In the above-described configuration, the electron beam generated by the electron gun 2 is largely deflected by the deflection coil 5, and then reversely deflected by the deflection coil 6 and returned to its original state, ultimately parallel to the axis of the device. The electron beam is projected onto the target 7 as an electron beam. The X-rays generated from the electron beam projection point on the target 7 are turned into a thin fan-shaped beam with a certain opening angle by the beam guide 9 and are taken out into the imaging chamber 10 and directed to the object 12.
is irradiated. These relationships can be more clearly understood from FIG. 2, which is a sectional view taken along line E--E in the embodiment shown in FIG. That is, the X-rays generated from the electron beam projection point _P1 on the target 7 pass through the X-ray passage hole _H1 provided in the beam guide 9, which is in a stationary state, and become a thin fan-shaped beam with a constant opening angle to the object 12. is irradiated. The X-rays that have passed through each part of the object 12 are detected by the detector group 13, and all the obtained detection values are sent to the processing device 14 and stored. That is, the processing device 14 stores information regarding the X-ray absorption of the subject tissue along each X-ray path connecting the X-ray generation point _P1 and each detector and having slightly different incident angles to the subject.

Next, the processing device 14 sends a command signal to the control device 18 according to the program, and in order to change the current flowing through the deflection coils 5 and 6, the electron beam projection point changes from P ₁ to P ₂ on the target 7, and then from P 2 to P ₂ . From there, it repeats sequential movement and stopping from P ₃ to the position corresponding to the X-ray passage hole provided in the beam guide. When the electron beam irradiation point moves to Pn and completes one round on the target 7, the processing device 14 receives the detection data from a series of detectors obtained by irradiating the X-ray beam from n different angles. All values are memorized. The steps up to this point constitute one cycle, and this cycle is simply repeated thereafter. In other words, the processing device is 1
When one unit stroke is completed, a command signal is sent to the control device 18 according to the program, and the motor 17 is driven to rotate the beam guide 9 by a minute angle.
After the beam guide 9 comes to rest, the previous unit stroke is repeated, and the electron beam projection point moves over the target 7 and makes one revolution. At this time, the electron beam
Needless to say, the electron beam is projected at a point shifted from each of the electron beam projection points P ₁ to Pn in the previous stroke by a small rotation angle θ degree. Thereafter, the unit stroke is repeated in exactly the same way, and each time the beam guide repeats rotation by θ degrees, correspondingly, the electron beam projection point also changes to θ.
Shifts by degrees. In this way, the beam guide becomes mθ
When the object is rotated by a degree (mθ゜=360゜/n), the object is irradiated with a fan beam m×n times with different irradiation angles by θ degrees, and the detector group for those m×n irradiations is All information from is stored in the processing unit. The processing device then performs arithmetic processing based on this information to determine the X-ray absorption coefficient of each point in the virtual matrix on the E-E cross section of the subject.
By displaying this on a display device, a tomographic image of the subject E-E section can be obtained.

As described above, according to the present invention, the X-ray generation point can be moved only by electrical scanning of the electron beam by the deflection coil, so it is extremely easy to increase the speed, and the beam guide can also be moved by only 360°/n. Therefore, it can be performed in an extremely short time, and as a result, one tomographic image can be obtained in an extremely short time. Further, in the present invention, since the electron beam is moved at high speed over the target, the load resistance of the target is relatively improved. Therefore, it is possible to narrowly focus a large current electron beam and project it onto a target, and as a result, more powerful and minutely focused X-rays can be obtained, making it possible to obtain accurate tomographic images.

In order to move the electron beam in a circle along the target, an alternating current having a sine and cosine relationship corresponding to a specified angle must be passed through the X-direction coils and Y-direction coils of the deflection coils 5 and 6. Good luck,
It is possible to move the electron beam extremely quickly and accurately.

In the above embodiment, the beam guide was rotated by θ degrees to perform fan beam irradiation m×n times, but this is not always necessary, and if precision is not required, the beam guide may be fixed at a certain position and the electron It goes without saying that a tomographic image can be obtained only by irradiating the fan beam n times by making the line go around the annular target once.

Incidentally, the main purpose of the annular beam guide in the above-described embodiment is to irradiate a thin layer of X-rays onto a desired part of the subject for which a tomographic image is to be obtained, to prevent X-rays from being irradiated to unnecessary parts of the subject, and to This is to prevent scattered X-rays from entering the detector when X-rays are irradiated to unnecessary parts of the target. X expanding in the direction
It is formed to block the line. Furthermore, another purpose of the beam guide is to limit the X-rays that spread in the direction perpendicular to the subject's axis in order to irradiate the subject with a fan-shaped X-ray beam, thereby preventing them from penetrating the subject. The number of X-ray detection elements on which X-rays are incident can be reduced, and as a result, the life of the detection elements can be extended. However, if there is no need to consider the lifetime of the detection element so much, the spread angle of the fan-shaped X-ray beam may be increased, and in extreme cases, it is not necessary to limit the spread of X-rays in the direction perpendicular to the subject axis. good. If the X-rays are not restricted in the direction perpendicular to the subject axis,
This simply increases the number of detection elements on which X-rays are directly incident without passing through the object, and does not have any adverse effect on the arithmetic processing for obtaining a tomographic image of the object based on the detection signal of each detection element.

As described in detail above, according to the present invention, in order to project an electron beam onto an annular target and move it along the target at high speed, it is possible to
Compared to the method using a rotating line generator, accurate tomographic images can be obtained in an extremely short time, and its significance is extremely significant.

Note that the present invention is not limited to the embodiments described above, and can be modified. For example, although the shape of the target was a complete ring in the above-described embodiment, it is not necessary to do so, and if a slight decrease in accuracy is taken into account, the tomographic image can be obtained even if the target is shaped like a semi-ring or a part of a ring. can be obtained. In that case,
It goes without saying that the beam guide and the detector group may also have a semicircular shape or a partial circular shape depending on the shape of the target. That is, the term cyclic as used herein includes shapes of a complete ring, a semi-ring, and a portion of a ring.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line EE in FIG. 1: Column, 2: Electron gun, 3: Electron beam, 4: Focusing lens, 5, 6: Deflection coil, 7: Annular target, 8: X-ray extraction window, 9: Beam guide, 1
0: Imaging room, 11: Moving bed, 12: Subject, 1
3: Detector group, 14: Processing device, 15: Rotating body,
16: Gear mechanism, 17: Motor, 18: Control device.

Claims (1)

[Claims] 1. An electron beam source, means for focusing the electron beam from the electron beam source,
an annular target that generates a beam; means for deflecting the electron beam so that the projection point of the electron beam moves intermittently along an arbitrary circle on the target;
an annular beam that is placed between the target and the object placed at its axial center and restricts the X-rays generated from the target and irradiated to the object in order to thin them in the axial direction of the object; The beam guide consists of a guide and a group of detectors arranged in a ring to detect the X-rays that have passed through the subject. The beam guide and the detector group are positioned so that the beam is taken out in a direction inclined at a slight angle with respect to the virtual plane containing the circular electron beam irradiation point on the target and detected by the detector group. An X-ray device characterized by: