JP3177993B2 - Rotating cathode X-ray tube device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Cathode for X-ray CT configured to be able to irradiate X-rays
The present invention relates to a tube device.

[0002]

2. Description of the Related Art As a conventional rotary cathode X-ray tube apparatus, for example, as shown in Japanese Patent Application Laid-Open No. 55-129043, a hollow vacuum vessel having a concave portion for inserting a subject at the center thereof is provided.
Equipped with a cylinder that can rotate around the axis of the recess,
An electron beam emitted from an electron gun attached to three places in the circumferential direction of this cylinder is irradiated on a ring-shaped anode target fixed in a vacuum vessel, and X-rays generated from the anode target are irradiated on a subject in the concave portion in a circumferential direction. There is a configuration in which irradiation is performed from three places and the cylinder is rotated by 120 ° to capture a tomographic image of the entire circumference of the subject.

As another conventional example, Japanese Patent Publication No. 59-23206
As shown in the publication, a ring-shaped anode target is provided inside a hollow vacuum vessel also provided with a concave portion for inserting an object at the center, and electrons from an electron gun provided at the inner center of the vacuum vessel are provided. There is also a configuration in which a line is irradiated on the entire circumference of the anode target by a deflection coil and a deflection plate, and an entire circumference tomographic image of the subject is photographed by the generated X-ray.

[0004]

However, in the above-described conventional apparatus, since the subject is inserted into the concave portion formed in the vacuum container, a concave portion that is too deep is formed due to the strength of the vacuum container. However, there is a limit to the length of the subject that can be imaged with the subject once inserted, and if the length is exceeded, it is necessary to change the direction in which the subject is inserted, and it may take time to shoot.

[0005] Further, since the volume of this kind of vacuum vessel becomes considerably large, once the degree of vacuum is reduced at the time of maintenance or at the end of operation, it is necessary to obtain a degree of vacuum that can be used for starting and restarting operation. It takes a long time, and has the disadvantage of taking time to shoot.

Further, since the subject is inserted into the concave portion of the vacuum container from the head, the subject is susceptible to mental pressure, which may adversely affect the physical condition.

The present invention has been made in view of such circumstances, and the invention according to claim 1 improves the vacuum vessel, does not limit the length of the subject, and ,
It is an object of the present invention to obtain a usable degree of vacuum at an early stage so that imaging can be performed quickly and with less trouble. Further, the invention according to claim 2 is directed to an image quality caused by secondary X-rays caused by bounced electrons. It is an object of the present invention to improve the accuracy of an all-round tomographic image of a subject taken by equalizing the amount of X-rays incident on a detector. The purpose is to be able to.

[0008]

According to a first aspect of the present invention, there is provided a hollow ring-shaped vacuum vessel having a subject insertion hole formed at a center thereof, and a vacuum chamber having the same. A ring-shaped anode target installed and fixed in the container, opposed to the anode target in the vacuum container,
And a ring-shaped rotating body rotatably mounted around the axis of the subject insertion hole, at least attached to the target facing surface of the rotating body and irradiating a part of the anode target in the circumferential direction with an electron beam. It comprises one electron gun and driving means for rotating the rotating body about the axis of the subject insertion hole.

According to a second aspect of the present invention, in order to achieve the above-mentioned object, the rotating body of the first aspect is provided such that the rotating body is positioned closer to the axis of the subject insertion hole than the anode target. Then, a shielding member that shields secondary X-rays due to rebound electrons is provided so as to rotate integrally, and the shielding member is provided with an opening for passing X-rays from the focal point of the anode target toward the axis of the subject insertion hole. Constitute.

According to a third aspect of the present invention, in order to achieve the above-mentioned object, the opening of the shielding member of the second aspect is covered, and the circumferential direction of the rotating body is set from the center of the opening. X with different thicknesses so that the transmission length becomes larger on both sides
It is configured by providing a line irradiation amount adjusting member.

[0011]

According to the structure of the rotary cathode X-ray tube device of the invention according to the first aspect, the rotating body is rotated in the ring-shaped vacuum vessel, so that the electron beam from the electron gun provided in the rotating body is removed. The entire periphery of the ring-shaped anode target is irradiated, and the X-rays generated thereby can be applied to the entire periphery of the subject located at the center of the vacuum container.

In this case, the subject is located only in the subject insertion hole of the vacuum container only in the vicinity of the part to be subjected to X-ray imaging, and the other parts are exposed to the outside.

According to the configuration of the rotary cathode X-ray tube apparatus according to the second aspect of the present invention, along with the irradiation of the anode target, some of the electrons bounce off the anode target and then irradiate around the focal point of the anode target. Then, the shielding member can prevent the secondary X-rays generated from around the focus by the rebounded electrons from being incident on the X-ray detector.

According to the configuration of the rotary cathode X-ray tube apparatus according to the third aspect of the present invention, when the X-ray generated from the focal point of the anode target is incident on the X-ray detector, the axis of the object insertion hole is adjusted. Because the distance between the X-ray detector and the X-ray detector that is circumferentially adjacent to the X-ray detector at the center of the incident range is shorter than the distance between the X-ray detector and the focal point connected by a virtual straight line passing through the heart, As the X-ray detector is closer to the center of the incident area, the amount of X-rays incident thereon decreases, but the X-rays generated from the focal point of the anode target are converted to X-rays.
By attenuating through the X-ray dose adjusting member, the X-ray dose incident on each X-ray detector can be made uniform.

[0015]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 7 is an overall schematic perspective view of a high-speed X-ray CT using a rotating cathode X-ray tube apparatus according to the present invention. In this figure, reference numeral 1 denotes a gantry.
In addition, the subject insertion hole 2 is formed to penetrate back and forth,
A rotating cathode X-ray tube device A described later is incorporated so as to surround the subject insertion hole 2. Reference numeral 3 denotes a vertically movable bed on which the subject M is placed. The top plate 4 slides back and forth horizontally to advance into the subject insertion hole 2.

Next, a first embodiment of the rotary cathode X-ray tube apparatus A will be described with reference to a longitudinal sectional side view of FIG. 1, an enlarged sectional view of a main part of FIG. 2, and a sectional view of FIG.

In these figures, reference numeral 5 denotes a hollow ring-shaped vacuum vessel having the subject insertion hole 2 formed at the center thereof, and the pressure is reduced by a vacuum pump 6. The vacuum container 5 is formed by joining a front container portion 5a and a rear container portion 5b made of a non-magnetic material such as glass in an airtight manner through two O-rings 7 inside and outside. A rear wall 5c of the portion 5b and a filament terminal
Only the periphery of 15 is made of an insulating material.

Reference numeral 8 denotes a ring-shaped anode target fixedly mounted on the inner surface of the rear wall 5c of the rear container portion 5b.
Its surface is slightly inclined toward the axis X of the subject insertion hole 2.

Reference numeral 9 denotes a ring-shaped rotating body rotatably incorporated in the front container portion 5a, which is formed in a ring shape by connecting a number of ferrite magnet pieces in a circumferential direction, and has a front end ( N poles and S poles of each magnet piece are arranged alternately at the left end in the figure).

Reference numeral 10 denotes a ring-shaped stator provided as a driving means disposed near the front surface of the front container portion 5a.
Driven at ~ 100Hz.

Numeral 11 denotes a magnetic bearing coil for rotatably supporting the rotating body 9 in a rotatable manner. The coil is provided at a plurality of positions in the circumferential direction on the outer peripheral surface of the front container portion 5a and the front and rear outer surfaces of the step formed near the outer periphery. ing. The radial position and the axial direction position of the rotating body 9 are detected by bearing sensors 12 and 13 each comprising a proximity switch or the like, and each magnetic bearing coil is supported so that the rotating body 9 is levitated and supported concentrically with the center of the container. 11 is controlled to be energized.

Reference numeral 14 denotes a cathode filament as an electron gun mounted on the rear surface of the rotating body 9 so as to face the anode target 8, and is connected to a pair of filament terminals 15 provided on the inner peripheral surface of the front container portion 5a. Conductive connection is made via a slip ring 16, and power is supplied from an AC power supply 17. The three cathode filaments 14 are provided at a pitch of 120 ° in the circumferential direction.

Reference numeral 18 denotes a DC high-voltage power supply, the plus side of which is connected to the anode target 8 and the minus side thereof is connected to the cathode filament 14, respectively, and the electron beam (a) emitted from the cathode filament 14 is provided on the front surface of the anode target 8. By being irradiated, the X-ray (b) is irradiated from three directions to the subject M in the subject insertion hole 2 from the front surface of the target.

Reference numeral 19 denotes a ring-shaped X-ray detector arranged close to the rear side of the vacuum vessel 5, which detects the amount of X-ray that has passed through the subject M and transmits it to an analyzer (not shown).

The rotating cathode X-ray tube apparatus A is configured as described above. By rotating the rotating body 9 by 120 °, it is possible to take a tomographic image of the subject M all around. By the way, the rotating body 9 having three cathode filaments 14 is set to 20 Hz.
When it is driven and rotated, the entire circumference can be taken in 17 ms.

FIG. 4 is a longitudinal sectional side view showing a second embodiment of the rotary cathode X-ray tube apparatus, FIG. 5 is an enlarged sectional view of a main part, and
FIG. 6 is a sectional view taken along line ZZ of FIG. According to the second embodiment, the rotating body 9 incorporated in the front container part 5a
An outer ring 9a rotatably supported by a fixed outer ring 20 via a ball 21 and an inner ring 9b rotatably supported by a fixed inner ring 22 via a ball 23 are connected to a ring plate 9c.
The cathode filament 14 and the filament terminal 15 provided on the rear surface of the rotating body 9 are configured as follows.
The fixed outer ring 20 and the ball 21 are connected to each other, and the fixed inner ring 22 and the ball 23 are connected to each other. And this rotating body 9 is also a stator
Rotated by 10

FIG. 8 is a sectional view of a main part of a rotary cathode X-ray tube apparatus according to a third embodiment, in which a rotating body 9 is positioned closer to the axis X of the subject insertion hole 2 than the anode target 8. Then, a shielding member 24 that shields secondary X-rays caused by the rebounded electrons is connected to the shielding member 24 so as to be integrally rotatable. The shielding member 24 extends from the focal point 25 of the anode target 8 toward the axis X of the subject insertion hole 2.
An opening 26 for passing a line is formed. In the figure, reference numeral 27 denotes a collimator that adjusts the width of the X-ray radiated to the subject M, that is, the slice width for capturing a full-sectional tomographic image of the subject M.

Next, the operation of the shielding member 24 will be described with reference to the schematic front view of FIG. The width of the opening 26 in the circumferential direction of the rotating body 9 is set so that the X-rays generated at the focal point 25 are incident on the X-ray detector 19 within a predetermined range. Along with the irradiation of the anode target 8, some of the electrons bounce off the anode target 8 and then are irradiated around the focal point 25 of the anode target 8, and the bounced electrons generate secondary X-rays from around the focal point 25. At this time, the secondary X-rays from the portion exceeding the region S1 are shielded by the shielding member 24, and the amount of the secondary X-rays incident on the X-ray detector 19 is reduced, so that the deterioration of the image quality can be avoided.

As the position where the above-mentioned shielding member 24 is provided, the range of incidence on the X-ray detector 19 is set as shown by a two-dot chain line 24a in FIG. Must be large, and accordingly,
Since the area S2 that cannot be shielded by the shielding member 24 increases,
A position closer to the focal point 25 is more desirable.

As shown in the schematic front views of FIGS. 8 and 10, the shielding member 24 covers the opening 26 thereof,
An X-ray irradiation amount adjusting member 28 made of aluminum or the like is provided, the thickness of which is different so that the transmission length becomes larger toward both sides in the circumferential direction of the rotating body 9 from the center of the opening 26.
It is configured so as to make the X-ray dose incident on 19 uniform.

That is, when the X-rays generated from the focal point 25 of the anode target 8 are incident on the X-ray detector 19, the focal point 25 formed by the virtual straight line L 1 passing through the axis X of the subject insertion hole 2.
X at the center of the incident range, rather than the distance between
The distance between the X-ray detector 19 adjacent to the X-ray detector 19 in the circumferential direction and the focal point 25 (a virtual straight line connecting the X-ray detectors 19 and the focal point 25 at both ends of the incident range is indicated by L2) is shortened (L1). > L2), the X-ray detector 19 located closer to the center of the incident area decreases the X-ray dose incident thereon, but the X-rays generated from the focal point 25 of the anode target 8 are transmitted to the X-ray irradiation amount adjusting member 28. The X-ray attenuation increases as the distance from the center of the aperture 26 increases.
The X-ray dose at the time of reaching 19 is made equal to each other.

In the above-described embodiment, the rotating body 9 is driven to rotate by the stator 10 from the outside, but it can be driven by a brushless motor.

[0034]

As described above, according to the rotary cathode X-ray tube apparatus of the first aspect, the following effects can be obtained. Since the vacuum vessel as an X-ray tube has a ring shape with the subject insertion hole formed through the center, there is no restriction on the length of the subject, and any part of the subject can be efficiently photographed by a single insertion. Now you can. The ring-shaped vacuum container has a small volume, so that even if the degree of vacuum is reduced, the time required to obtain a usable degree of vacuum is short, and shooting can be quickly started at the start of operation or after restarting operation after maintenance. Became. Since the subject insertion hole is a through hole that is short in the axial direction, even if inserted from the head, there is no feeling of oppression, and imaging can be performed with confidence.

According to the rotary cathode X-ray tube apparatus of the second aspect of the present invention, it is possible to prevent the secondary X-rays generated from around the focal point by the rebounding electrons from being incident on the X-ray detector by the shielding member. Accordingly, it is possible to prevent the image quality of the captured all-around tomographic image of the subject from being deteriorated due to the secondary X-ray due to the rebounding electrons.

According to the rotary cathode X-ray tube apparatus of the third aspect of the present invention, since the X-ray dose incident on each X-ray detector from the focal point of the anode target is made uniform, the distance between adjacent X-ray detectors can be reduced. In this case, the difference in density can be eliminated, and the accuracy of the captured tomographic image of the entire circumference of the subject can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a first embodiment of a rotary cathode X-ray tube device.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a sectional view taken along line YY in FIG. 1;

FIG. 4 is a vertical sectional side view showing a second embodiment of the rotary cathode X-ray tube device.

FIG. 5 is an enlarged sectional view of a main part of FIG. 4;

FIG. 6 is a sectional view taken along the line ZZ in FIG. 4;

FIG. 7 is an external perspective view of an X-ray CT using the rotating cathode X-ray tube device of the present invention.

FIG. 8 is a vertical sectional side view showing a third embodiment of the rotary cathode X-ray tube device.

FIG. 9 is a schematic front view illustrating the operation of the shielding member.

FIG. 10 is a schematic front view illustrating the operation of an X-ray irradiation amount adjusting member.

[Explanation of symbols]

 2. Subject insertion hole 5 ... Vacuum container 8 ... Anode target 9 ... Rotating body 10 ... Stator as driving means 14 ... Cathode filament as electron gun 24 ... Shielding member 25 ... Focus 26 ... Opening 28 ... X-ray irradiation amount adjustment Member b: electron beam X: axis of subject insertion hole

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-129043 (JP, A) JP-A-62-47346 (JP, A) JP-A-4-263839 (JP, A) 24050 (JP, U) Japanese Utility Model 2-35100 (JP, U) Japanese Utility Model Application Sho 58-165657 (JP, U) Tokuyo Sho 59-501429 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) A61B 6/03

Claims (3)

(57) [Claims] 1. A hollow ring-shaped vacuum vessel having a subject insertion hole formed therethrough at a center, a ring-shaped anode target installed and fixed in the vacuum vessel, and opposed to the anode target in the vacuum vessel. And, a ring-shaped rotator equipped rotatably around the axis of the subject insertion hole, attached to the target facing surface of the rotator,
A rotating device comprising: at least one electron gun for irradiating a part of the anode target in a circumferential direction with an electron beam; and driving means for rotating the rotating body about an axis of a subject insertion hole. Cathode X-ray tube device. 2. A rotator according to claim 1, further comprising: a shielding member that is located closer to the axis of the subject insertion hole than the anode target and shields secondary X-rays due to rebound electrons so as to rotate integrally. A rotary cathode X-ray tube device, wherein an opening for passing X-rays from the focal point of the anode target toward the axis of the subject insertion hole is provided in the shielding member. 3. An X-ray irradiation amount adjusting member which covers an opening of the shielding member according to claim 2 and has a different thickness so that the transmission length becomes larger from the center of the opening toward both sides in the circumferential direction of the rotating body. The rotating cathode X-ray tube device provided.