JP2003135444A - X-ray ct device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT device suppressing focus movement by changing a position of a rotary anode of a rotary anode X-ray tube. SOLUTION: On a cylindrical rotating body 2 whose one end side is freely rotatably supported on a supporting rack 1, the rotary anode X-ray tube 4 is loaded so as to position the rotary anode 4a on a supporting part side of the rotating body 2. Also, an X-ray detector 7 is loaded on the rotating body 2 so as to face the rotary anode X-ray tube 4. By centrifugal loads generated when the rotating body 2 is rotated at a high speed, even when the rotating body 2 is deformed so as to spread open a supporting part and an end part on the opposite side, since the rotary anode X-ray tube 4 is loaded on the rotating body 2 so as to turn the rotary anode 4a to the supporting part side, a moving amount of a focus of an X-ray beam 9 with which the X-ray detector 7 is irradiated is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus mainly used in fields such as industry and medical care.

[0002]

2. Description of the Related Art Some conventional X-ray CT apparatuses that have been widely used in the fields of industry and medical care are equipped with an ionization chamber type X-ray detector. This ionization chamber type X-ray detector has a halogen gas sealed in a gas chamber, makes X-rays incident in the gas chamber, and causes a difference in the amount of current generated by the ionization action of the gas according to the incident X-ray dose. Is detected to obtain image data, and since the gas concentration in the gas chamber is uniform, the sensitivity distribution in the rotation direction of the rotating plate provided in the X-ray CT apparatus is uniform, but Since the level is not sufficient, a highly sensitive detector is necessary to improve the image quality of the X-ray CT apparatus.

Therefore, as a highly sensitive detector, a solid-state detector using a fluorescent semiconductor element has been developed and has been spreading in recent years. However, while the solid-state detector has high sensitivity, it uses a semiconductor. Therefore, when it is used for an X-ray detector of an X-ray CT apparatus due to partial characteristic variation of the substance, the solid-state detector has The sensitivity distribution is not uniform.

Therefore, conventionally, when performing image processing,
The calibration work is performed to capture the image data and create the correction data without placing the subject in advance, but when the subject is actually photographed, X
The focus position of the line may move and the amount of movement may exceed the allowable range of the correction data obtained by the calibration work.

FIG. 6 shows a cross section of a conventional X-ray CT apparatus, which has a cylindrical rotating body c rotatably supported by a support base a via a bearing b. A rotary anode X-ray tube d is mounted on the outer periphery of the rotary anode c, and an X-ray detector e is mounted at a position facing the rotary anode X-ray tube d with the center of the rotor c interposed therebetween. The rotating anode X-ray tube d has a rotating anode f inside.
And the cathode g are installed so as to face each other, and the rotating anode f
The generated X-rays are configured to reach the X-ray detector e as an X-ray beam i by being focused by a collimator h, as shown in FIG.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the T-apparatus, the rotating body c is rotated at a high speed in order to reduce the X-ray exposure amount of the subject and shorten the output time of the image data. Therefore, a centrifugal force proportional to the square of the rotation speed acts on the rotating anode X-ray tube d and the X-ray detector e mounted on the rotating body c. When the bracket j supporting the rotary anode f is bent by this centrifugal force, the focal point f ′ of the rotary anode f and the pinhole h ′ of the collimator h are displaced as shown in FIG. The line beam i is an X-ray detector e
A deviation occurs with respect to the center e ′ of the.

In the rotating body c, the end opposite to the end supported by the bearing b is shown in FIG. 7 by the centrifugal load acting on the mounted rotary anode X-ray tube d and the X-ray detector e. C)
As shown in Fig. 3, the beam spreads and deforms into a cone shape. As a result, the X-ray beam i is further displaced from the center e'of the X-ray detector e and exceeds the allowable range of the correction data obtained by the calibration work. Therefore, there is a problem in that ring artifacts occur in the CT image, the image deteriorates, and a high-quality tomographic image cannot be obtained.

The present invention has been made to solve the above conventional problems, and provides an X-ray CT apparatus in which the movement of the focus is suppressed by changing the position of the rotary anode, and a high-quality tomographic image is obtained. It is intended to be obtained.

[0009]

In order to achieve the above-mentioned object, an X-ray CT apparatus of the present invention comprises a cylindrical rotating body whose one end is rotatably supported by a supporting base, and an outer peripheral portion of the rotating body which faces each other. A rotary anode X-ray tube and an X-ray detector, and a collimator that focuses X-rays generated from the rotary anode of the rotary anode X-ray tube into an X-ray beam and irradiates the X-ray detector. An X-ray CT apparatus equipped with a rotating anode X-ray tube mounted on a rotating body such that the rotating anode is located on the bearing side of the rotating body.

With the above construction, even if the rotor is deformed so that the end opposite to the bearing expands due to the centrifugal load generated when the rotor rotates at a high speed, the rotary anode becomes the bearing side. As described above, since the rotating anode X-ray tube is mounted on the rotating body, the movement amount of the focal point of the X-ray beam irradiated on the X-ray detector is suppressed, which allows the allowable range of the correction data obtained by the calibration work. Since the focal position does not exceed the point of, it is possible to easily obtain a high-quality tomographic image without deterioration of the image due to the occurrence of ring artifacts. Further, since the movement of the X-ray beam focus can be suppressed only by mounting the rotating anode X-ray tube on the rotating body so that the rotating anode is on the bearing side, it is possible to easily carry out the operation.
It is economical because the conventional rotary anode X-ray tube can be used as it is.

In order to achieve the above object, the X-ray CT of the present invention
The device has a rotating anode supported by a bracket formed in a substantially inverted L shape.

With the above construction, the amount of deformation of the bracket deformed by centrifugal force and the amount of deformation of the rotating body cancel each other out, so that the amount of movement of the focal point can be greatly reduced.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the drawings. 1 is a perspective view of an X-ray CT apparatus, FIG. 2 is a sectional view, FIG. 3 is a schematic view, and FIGS. The X-ray CT apparatus shown in FIGS. 1 and 2 has a support base 1 installed in a case (not shown).
In addition, a rotating body 2 formed in a cylindrical shape is rotatably supported via a bearing 3. A rotary anode X-ray tube 4, a high-voltage power supply 5 for supplying electric power to the rotary anode X-ray tube 4, a cooler 6 for cooling the rotary anode X-ray tube 4, and the like are mounted on the outer periphery of the rotating body 2. Rotating anode X-ray tube 4 with the center of the rotor 2 in between
An X-ray detector 7 composed of a solid-state detector is mounted at a position opposed to. As shown in FIG. 2, the rotating anode X-ray tube 4 includes a rotating anode 4a and a cathode 4b which is left inside so as to face the rotating anode 4a in a horizontal direction. The rotating anode 4a supports the rotating body 2. The rotating anode X-ray tube 4 is mounted on the rotating body 2 so that the cathode 4b is located on the side of the bearing 3 and the cathode 4b is on the side opposite to the bearing 3.

The rotary anode 4a in the rotary anode X-ray tube 4 is adapted to generate X-rays at a focal position 4d by being rotated by a rotary drive source 4c such as a motor.
The X-ray generated by the rotating anode 4a is configured to be a fan-shaped X-ray beam 9 from the focal position 4d by the slit 8a of the collimator 8 and enter the center 7a of the X-ray detector 7. The rotary anode 4a is fixed in the rotary anode X-ray tube 4 by a bracket 4e formed in a substantially inverted L shape.

Next, the operation of the X-ray CT apparatus configured as described above will be described with reference to FIGS. 4 and 5. Subject (not shown)
In order to reduce the X-ray exposure amount of the subject and to shorten the output time of the image data, the rotating body 2 is rotated at a high speed by a rotation drive source (not shown). In consideration of the deformation of the rotator 1, a calibration operation is performed in which the image data is captured and correction data is created without placing the subject in advance before performing the image processing.

When the calibration work is completed, the subject is carried into the opening 2a of the rotating body 2 to start the photographing of the subject, which is generated by the rotating anode 4a of the rotating anode X-ray tube 4 and collimator. When the rotator 2 is not rotating, the X-ray beam condensed by
Although it is set to irradiate the center of the X-ray detector 7 as shown in FIG. 1, when the rotating body 2 starts rotating, the centrifugal force generated by the rotation causes the rotating anode X-rays mounted around the rotating body 2. Acts on the tube 4.

In the rotating anode X-ray tube 4, there is provided a rotating anode 4a which is cantilevered by a substantially L-shaped bracket, and the bracket is shown in FIG. Although it is deformed to the outside as shown in (b), since the bracket that supports the rotating anode 4a is installed on the bearing side (the bearing 3 side) of the rotating body 2, the X-ray beam reaching the X-ray detector 7 In contrast to the conventional X-ray CT apparatus shown in FIG. 7B, the focal point is the center 7a of the X-ray detector 7.
It moves to the bearing 3 side by the same amount as the conventional X-ray CT apparatus.

After that, when the rotating body 2 is further rotated at a high speed, the open end of the rotating body 2 on the side opposite to the bearing portion expands,
The rotor 2 is deformed into a substantially cone shape as shown in FIG. 4C, but the deformation of the rotor 2 cancels the deformation of the bracket that supports the rotating anode 4a. Bearing 3 from the center 7a of the X-ray detector 7
The focus of the X-ray beam, which has been deviated to the side, moves to the center 7a side of the X-ray detector 7 as shown in FIG. As a result, even if the rotating body 2 is deformed into a cone shape due to the centrifugal load generated when the rotating body 2 is rotated at a high speed, the movement of the focus of the X-ray beam is suppressed and the shift of the focus is obtained by the calibration work. Since the allowable range of the correction data thus obtained is not exceeded, deterioration of the image due to the occurrence of ring artifacts is reduced, and a high-quality tomographic image can be obtained in a short time.

FIG. 5 shows an X-ray CT according to an embodiment of the present invention.
FIG. 6 is a diagram comparing the deviation of the focal position of the X-ray beam due to the bending of the bracket that supports the rotating anode of the X-ray CT apparatus and the bending of the rotating body 2 of the conventional X-ray CT apparatus, where curve A is the present invention, And the curve B shows the conventional one. As is clear from this figure, when the bracket supporting the rotating anode 4a is deformed by centrifugal force, the focus of the X-ray beam moves from the center 7a of the X-ray detector 7 to the (-) side, and the rotating body 2 Is deformed by the centrifugal force, the deformation of the rotating body 2 is absorbed by the deformation of the bracket, so that the substantial shift amount is significantly reduced as compared with the conventional X-ray CT apparatus.

[0020]

As described above in detail, the present invention provides a rotary anode X-ray so that the rotary anode is located on the support side of the rotary body on a cylindrical rotary body whose one end side is rotatably supported by a support frame. The tube is mounted and the X-ray detector is mounted on the rotating body so as to face the rotating anode X-ray tube. The movement amount of the focal point of the X-ray beam irradiated to the X-ray detector is suppressed, and the ring is It is possible to easily obtain a high-quality tomographic image without image deterioration due to the occurrence of artifacts.

Further, the movement of the focal point of the X-ray beam can be suppressed only by mounting the rotary anode X-ray tube on the rotating body so that the rotary anode is on the bearing side. Since the rotating anode X-ray tube can be used as it is, it is economical, and since the rotating anode X-ray tube is supported by the bracket formed in an almost inverted L shape, the amount of deformation of the bracket deformed by centrifugal force and the deformation of the rotating body. Since the amounts cancel each other, the amount of movement of the focal point can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of an X-ray CT apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of an X-ray CT apparatus according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of an X-ray CT apparatus according to an embodiment of the present invention.

4 (a) to (c) are operation explanatory views of the X-ray CT apparatus according to the embodiment of the present invention.

FIG. 5 is a diagram comparing the amount of movement of the focal point due to bending of the X-ray CT apparatus according to the embodiment of the present invention and the conventional X-ray CT apparatus.

FIG. 6 is a configuration diagram of a conventional X-ray CT apparatus.

7 (a) to 7 (c) are diagrams for explaining the operation of the conventional X-ray CT apparatus.

[Explanation of symbols]

1 Support stand 2 rotating bodies 4 rotating anode X-ray tube 4a rotating anode 4e bracket 7 X-ray detector 8 Collimator 9 X-ray beam

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koichi Hirokawa             1-chome 1-14-1 Kanda, Chiyoda-ku, Tokyo             Inside the Hitachi Medical Co. (72) Inventor Masahiro Nakano             1-chome 1-14-1 Kanda, Chiyoda-ku, Tokyo             Inside the Hitachi Medical Co. F term (reference) 4C093 AA22 CA13 EA02 EC17 EC41                       EC43

Claims (2)

[Claims] 1. A cylindrical rotating body, one end of which is rotatably supported by a support base, a rotating anode X-ray tube and an X-ray detector mounted on the outer peripheral portion of the rotating body so as to face each other,
X-rays generated from the rotating anode of the rotating anode X-ray tube,
An X-ray CT apparatus comprising: a collimator that focuses an X-ray beam and irradiates the X-ray detector toward the X-ray detector, wherein the rotating anode X-ray tube is positioned so that the rotating anode is located on the bearing side of the rotating body. X-ray C, characterized in that
T device. 2. The X according to claim 1, wherein the rotating anode is supported by a bracket formed in a substantially inverted L shape.
X-ray CT equipment.