JP2000340149A - X-ray tube device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray tube device capable of emitting a plurality of parallel X-ray beams. SOLUTION: A rotary anode 1 of an X-ray tube is equipped with a target 2 having two focal track surfaces, namely, a large-radius focal track surface 3A and a small-radius focal track surface 3B. The two focal track surfaces 3A, 3B are disposed leaving a space of tens of mm between them in the anode axis direction. Two focal points 4A, 4B are formed over the two focal track surfaces 3A, 3B supported by a cathode 5 against respective two focal track surfaces 3A, 3B. This construction causes two parallel X-ray beams 9, 10 spaced tens of mm apart to be emitted from the two focal points 4A, 4B to the exterior by way of a vessel emission window 12 and a tube-container emission window 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an X-ray tube apparatus suitable for an X-ray CT apparatus, and more particularly to an X-ray tube apparatus suitable for an X-ray CT apparatus capable of simultaneously photographing a plurality of slices.

[0002]

2. Description of the Related Art In an X-ray CT apparatus, an X-ray tube apparatus and an X-ray detector are usually mounted on a gantry, facing each other, and rotating around a subject while maintaining a mutual positional relationship. By doing so, image diagnosis is performed. In this case, one tomographic image is obtained by one rotation. At present, many tomographic images are obtained by continuously rotating the combination of the X-ray tube apparatus and the X-ray detector around the subject. In this technique, X-rays are continuously irradiated for 20 to 60 seconds while rotating a gantry of an X-ray CT apparatus equipped with an X-ray tube apparatus and an X-ray detector, and the object table is moved during the irradiation. And a plurality of slice images of the subject. However, in the current image reconstruction method in which one slice of image data is acquired in one rotation, an artefact caused by a rapid change in the X-ray dose is obtained particularly in imaging at a high gradient portion such as the top of the subject. Is liable to occur.

[0003] In order to solve the above problem, for example,
A method is adopted in which two detectors are arranged side by side on the X-ray detector side. An example of this method is disclosed in Japanese Patent Application Laid-Open No. 5-184563. According to this method, image information of two slices can be obtained simultaneously by two detectors in one rotation. When this method is applied to imaging of the crown, artifacts can be suppressed by recognizing the gradient of the crown from the image information of two slices and correcting the X-ray dose.

[0004] As one of the above solutions, when X-ray irradiation is performed using a combination of one X-ray tube device and two X-ray detectors, the X-ray dose distribution in the slice axis direction is as follows. X
The X-rays radiated from the X-ray tube device enter the two X-ray detectors in a fan-shaped distribution as if the slice thickness were widened.
For this reason, the X-rays in the slice axis direction often enter obliquely with respect to the longitudinal direction of the detector elements constituting the X-ray detector, and when a highly sensitive detector such as a solid-state detector is used, the X-rays are re-emitted. There is a problem that artifacts occur in the constituent images.

[0005] For this reason, it is necessary for two X-ray detectors arranged in parallel so that the X-rays are vertically incident on the respective X-ray detectors. An X-ray source may correspond to each of two X-ray detectors. In order to prepare two X-ray sources, two X-ray tube devices are required. However, mounting two X-ray tube devices on an X-ray CT device restricts mounting space and increases costs. Problematic and inefficient. In some cases, two or more X-ray detectors are arranged in parallel to improve the imaging efficiency. In such a case, mounting two or more X-ray tube apparatuses on an X-ray CT apparatus is more difficult. This is a difficult problem.

[0006]

As described above, 2
Arranging two or more X-ray tube apparatuses in order to combine them with more than one X-ray detector arranged in parallel poses a problem in terms of mounting space on an X-ray CT apparatus and cost. For this reason,
An object of the present invention is to realize an X-ray tube device including two or more X-ray sources corresponding to two or more X-ray detectors arranged in parallel.

[0007]

In order to achieve the above object, an X-ray tube apparatus according to the present invention comprises a rotating anode having a target having a focal orbital surface for emitting X-rays, and a rotating anode disposed opposite to the target. X on the focal orbit plane of the target
A cathode having a focusing electrode for emitting an electron beam for forming a radiation source, an envelope enclosing the rotating anode and the cathode in a vacuum-tight manner, and having a tube radiation window on a side surface around the target; An X-ray tube apparatus for supporting a rotating anode X-ray tube composed of the following in the interior of a tube container, and radiating X-rays generated by the X-ray source to the outside from a tube container radiation window provided in the tube container. In the above, the target has at least two orbital orbital planes, and an X-ray source is formed on each of the focal orbital planes by arranging focusing electrodes opposite to each of the focal orbital planes. The radiation sources are arranged at predetermined intervals in the tube axis direction of the rotating anode X-ray tube when viewed from the tube container radiation window side (claim 1).

In this configuration, since the X-ray sources (focal points) formed on the two or more focal track surfaces of the target are arranged at predetermined intervals when viewed from the direction of the tube radiation window, the X-ray source of the present invention is used. When a tube device is used, two or more parallel X-ray beams can be emitted. The X-ray tube apparatus of the present invention
When applied to the X-ray CT apparatus, the predetermined interval is adjusted to the length of the detection element of the multi-channel type X-ray detector, for example, 10 mm to 45 mm, so that multi-slices in which the X-ray detectors are arranged in parallel It can be used in combination with a type X-ray detector, and image data of a plurality of slices can be collected by one rotation scan.

[0009] In the X-ray tube apparatus according to the present invention, the target has focal track surfaces having different diameters. This configuration has a multi-stage structure in which the outer diameter of the target is changed for each focal track surface having a different diameter, but the focusing electrode of the cathode faces the target in one direction (the cathode side).
, The cathode structure is simplified.

In the X-ray tube apparatus according to the present invention, at least one of the focal track surfaces faces the anode end of the rotating anode X-ray tube. This configuration can be realized by forming a focal track surface on the back surface of the conventional target or arranging a target of the same structure behind the conventional target on the back side, so that the anode structure is simple. The method described in claim 2 and the method described in claim 3
Are also possible, and the number of parallel X-ray beams can be further increased by this combination.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the X-ray tube apparatus of the present invention.
It is sectional drawing which shows the outline of the whole structure of Example of 1st. FIG. 1 shows an X-ray beam generator which is a main part of the first embodiment. In FIG. 1, the X-ray tube includes a rotating anode 1, a cathode 5, and an envelope 11. As shown in FIG. 2, the rotating anode 1 and the cathode 5 are enclosed and supported in a vacuum-tight manner in an envelope 11.

The rotating anode 1 has a substantially disk-shaped target 2.
And a rotating shaft, a bearing, a rotor, and the like (all not shown) are included as a mechanism for rotating the target 2. This target 2 has two focal points (X-ray source) 4,
That is, it has a first focus 4A and a second focus 4B. This 2
When used in combination with an X-ray CT device, the focal points 4A and 4B generate two parallel fan-shaped X-ray beams,
The two X-ray beams are configured to be incident on two parallel X-ray detectors arranged to face the X-ray tube device. Therefore, the two focal points 4A and 4B are arranged at a distance D, corresponding to the distance between the two X-ray detectors arranged in parallel.

As shown in FIG.
It has a large-diameter portion 26 having a large-diameter first focal-orbit surface 3A and a small-diameter portion 27 having a small-diameter second focal-orbit surface 3B. A first focal point 4A is formed on the first focal track surface 3A, and a second focal point 4B is formed on the second focal track surface 3B. Each of the focal track surfaces 3A and 3B is made of a material having high heat resistance such as tungsten or a tungsten alloy and having a high X-ray generation efficiency, and the other part of the target 2 is made of a material having good heat resistance such as molybdenum or its alloy. Be composed.
When it is desired to make the target 2 light, a lightweight graphite or the like is used instead of molybdenum or the like.

The cathode 5 is arranged so as to face the focal track surface 3 of the target 2. The cathode 5 includes two focusing electrodes 6, that is, a first focusing electrode 6A arranged opposite to the first focal point 4A and a second focusing electrode 6B arranged opposite to the second focal point 4B. The first electron beam 7 emitted from the first focusing electrode 6A collides with the first focal point 4A and emits a first X-ray beam 9, and the second electron beam 8 emitted from the second focusing electrode 6B is a second focal point. 4B and the second X-ray beam 1
Emit 0. The first X-ray beam 9 and the second X-ray beam 10 pass through a tube radiation window 12 provided on a side surface of an envelope 11 of the X-ray tube, and are further provided on a side surface of a tube container 19 of the X-ray tube device. After passing through the tube container radiation window 20, the radiation is emitted in the X-ray radiation direction 18 indicated by the arrow outside the X-ray tube device. When the X-ray tube device is mounted on the X-ray CT device,
An X-ray detector is provided in the X-ray emission direction 18.

Electron beams 7, 8 are applied to focusing electrodes 6A, 6B.
An electron source such as a filament that emits electrons is included. The first focusing electrode 6A corresponds to the position of the focal point 4A,
It is arranged on the side near the inner surface of the envelope 11. In FIG. 1, the first focusing electrode 6A and the second focusing electrode 6B are arranged on the same surface of the cathode 5, but in consideration of the electron beam emission efficiency, the first focusing electrode 6A is It is better to be closer to the target 2 than to the two focusing electrodes 6B.

As the tube radiation window 12 provided in the envelope 11, a beryllium window having good X-ray transmission is used. The beryllium window 12 may be circular, but in the present invention, the distance between the first focal point 4A and the second focal point 4B is large.
An elliptical shape that extends along the central axis (tube axis) 17 of the X-ray tube may be used. In some cases, two beryllium windows 12 may be provided such that a separate beryllium window 12 corresponds to each focal point. As the tube container radiation window 20 on the side surface of the tube container 19, a window made of plastic or thin aluminum having good X-ray transparency is used. Also in the case of this window, if an elliptical window is used, the X-ray beams 9 and 10 from the two focal points 4A and 4B can be efficiently emitted to the outside.

The two X-ray beams 9 and 10 emitted from the X-ray tube device are shaped by a collimator 14 arranged on the front surface of the X-ray tube device. The collimator 14 has two holes arranged in parallel, that is, a first collimator hole 15.
And a second collimator hole 16 are provided. Two holes 1
Numerals 5 and 16 denote elongated rectangular holes which limit the slice width of the X-ray beams 9 and 10 at the narrow short sides and form a fan beam at the elongated long sides.

The distance between the two focal points 4A and 4B of the X-ray tube apparatus, that is, the distance D between the two X-ray beams 9 and 10 is X
It is determined in association with the X-ray detector combined on the X-ray CT apparatus. In the case of the present embodiment, it is considered that a two-slice X-ray detector in which two conventional one-slice X-ray detectors are arranged in parallel is used as the X-ray detector to be combined. The interval D between the X-ray beams 9 and 10 may correspond to the center interval between the two X-ray detectors when two X-ray detectors are arranged in close contact in parallel. This 2
Since the distance between the centers of the X-ray detectors is substantially equal to the length of the detector elements constituting the X-ray detector, it is appropriate that the D dimension is 10 mm to 45 mm.

Although the embodiment of FIG. 1 has been described for the case of two focal points, the present invention can be extended to a case of three or more focal points. The embodiment of FIG. 1 is an example of a combination of a target having two focal track surfaces and a cathode having two focusing electrodes. However, it is possible to provide a target with three or more focal track surfaces. Yes, it is possible for the cathode to have three or more focusing electrodes, so that an X-ray CT capable of emitting three or more parallel X-ray beams
It is also possible to configure an X-ray tube for the device.

FIG. 2 schematically shows the entire structure of the first embodiment of the X-ray tube apparatus according to the present invention. In FIG.
The X-ray tube 13 in the X-ray tube device 25 is configured as shown in FIG. 1, and includes an anode 1 having a target 2 having two focal track surfaces 3A and 3B, and two focusing electrodes 6A and 6B. And a cathode 5 having a vacuum sealed inside the envelope 11. The X-ray tube 13 has the anode side as the anode side support 2.
At 1, the cathode side is insulated and supported on the inner wall of the tube container 19 by a cathode side support 22. An anode-side cable receptacle and a cathode-side cable receptacle (both not shown) are attached to the anode side and the cathode side of the tube container 19, and a high voltage is supplied to the anode 1 and the cathode 5 of the X-ray tube 13 through these. You. Around the anode 1 of the X-ray tube 13, a stator 24 for rotating and driving the anode 1 is provided. The tube container 19 is filled with insulating oil 23 and plays a role of high-voltage insulation and cooling of the X-ray tube 13.

The tube radiation window 13 attached to the envelope 11 of the X-ray tube 13 and the tube container radiation window 20 attached to the tube container 19 are composed of two focal points 4A of the X-ray tube 13,
Positioning is performed so that two X-ray beams 9 and 10 from 4B can be emitted as X-ray beams parallel to the X-ray emission direction (the direction of arrow 18 in FIG. 1).

FIG. 3 is a sectional view of a main part when the X-ray tube apparatus of the present invention is mounted on an X-ray CT apparatus. Fig. 3 shows X-ray CT
In the cross-sectional view of the gantry portion of the apparatus, the X-ray tube device 25 of the present invention is disposed on the upper side, and the X-ray detector 55 is disposed on the lower side. The gantry 52 of the X-ray CT apparatus 51 has two focuses 4A, 4A,
X-ray tube device 25 having B and two X-ray detectors 56, 5
7, when the gantry 52 rotates around the rotation axis 53, the X-ray tube device 25 and the two X-ray detectors 56 and 57 rotate around the rotation axis 53 while maintaining the relative positions. I do. At the time of examination by the X-ray CT apparatus 51, the subject 54 is inserted into the gantry 52, and the X-ray tube apparatus 25 and the two X-ray detectors 56 and 57 rotate around the subject 54 by rotation of the gantry 52. Then, the image data is collected.

The two focal points of the X-ray tube device 25, the first focal point 4
A and the two X-ray beams radiated from the second focal point 4B, the first X-ray beam 9 and the second X-ray beam 10 become two parallel fan-shaped X-ray beams at the holes 15 and 16 of the collimator 14, After passing through the subject 54, it is incident on two X-ray detectors, a first X-ray detector 56 and a second X-ray detector 57. Although the width of the two parallel X-ray beams is reduced to an arbitrary slice thickness by the collimator 14, the X-ray tube device 2
5 is a parallel X-ray beam emitted from the two focal points 4A and 4B, and is incident almost perpendicularly on the incidence surfaces of the two X-ray detectors 56 and 57.

As a result, when the X-ray tube apparatus according to the present invention is used, it is obliquely incident on the incident surface of the X-ray detector 55 as in the case where an X-ray beam emitted from one focal point is used. Since the amount of X-rays to be remarkably reduced, even if a high-sensitivity solid-state detector is used as the X-ray detector, it is possible to eliminate the problem that artifacts occur in the reconstructed image.

When the X-ray tube apparatus according to the present invention is used for imaging a portion having a particularly high gradient such as the crown, image data for two slices can be collected at the same time. Since the image data can be corrected with high accuracy using the image data of (1), artifacts based on the steep gradient of the dose distribution of transmitted X-rays such as the top of the head can be reduced.

FIG. 4 is a sectional view showing a main part of a second embodiment of the X-ray tube apparatus according to the present invention. FIG. 4 shows only the structure of the X-ray tube. About the tube container part, it is almost the same as FIG. 2 of the first embodiment. In FIG. 4, an X-ray tube 30 of this embodiment is opposed to an anode (rotating anode) 1A having a target 31 having focal orbital surfaces 32A and 32B on both upper and lower surfaces, and two focal orbital surfaces 32A and 32B. And cathodes 34A and 34B having focusing electrodes 33A and 33B arranged in a vertical direction, and an envelope 11A that supports the anode 1A and the cathodes 34A and 34B and encloses them in a vacuum.

A first focal track surface 32A and a second focal track surface 32B are formed above and below the target 31 supported by the anode 1A. The second focal path surface 32B on the upper surface side of the target 31 is the same as the conventional focal path surface, but the first focal path surface 32A on the lower surface is formed in the opposite direction to the conventional one, that is, on the rear surface side. The inclination angle is the same as the conventional one. The materials of the target 31 and the focal track surfaces 32A and 32B are the same as in the first embodiment.

A second focusing electrode 33B arranged opposite to the second focal track surface 32B is supported by a second cathode 34B.
Through the second cathode envelope 35B, the envelope 11 is placed on the cathode side.
A is connected. The first focusing electrode 33A arranged opposite to the first focal track surface 32A is supported by the first cathode 34A, and is connected to the envelope 11A on the anode side via the first cathode envelope 35A. You. Most of the envelope portions of the cathode envelopes 35A and 35B are made of an insulating material such as ceramic or glass, and insulate and support leads for supplying power to the filaments attached to the focusing electrodes 33A and 33B.

First focusing electrode 33A and second focusing electrode 3
The electron beam emitted from 3B is the first focal track surface 32A.
Then, it collides with the second focal point orbit plane 32B, and emits X-rays from the first focal point 4A and the second focal point 4B. The X-rays from the first focal point 4A are extracted as a first X-ray beam 9 and the X-rays from the second focal point 4B are extracted as a second X-ray beam 10 from the tube radiation window 12 to the outside of the X-ray tube. It is shaped into two parallel X-ray beams.

In the above description, the distance between the first focal path plane 32A and the second focal path plane 32B on the target 31 needs to be determined in correspondence with the distance between the two X-ray detectors. It is set to 10 mm to 45 mm as in the first embodiment. In an X-ray tube apparatus, the cathode of the X-ray tube is 2
It is necessary to attach two cathode-side cable receptacles in order to obtain a single unit.

FIG. 5 is a sectional view of a main part of an X-ray tube apparatus according to a third embodiment of the present invention. FIG. 5 shows only the structure of the X-ray tube. In the case of this embodiment, the portion of the tube container is almost the same as that of FIG. 2 of the first embodiment. This embodiment is characterized in the anode structure, and differs from the second embodiment in that point. In FIG. 5, the X-ray tube 40 of the present embodiment includes two targets 41A and 41B, and the two targets 41A and 41B are surrounded by a lower anode 1B and an upper auxiliary anode 43 so as to surround the envelope 11B. It is supported by. The first target 41A on the lower side and the second target 41B on the upper side have their respective focal track surfaces 42A and 42B facing outward and their respective rear faces facing inward, and the lower first target 41A has a focal point. The orbit 2A is supported by the anode 1B on the side of the orbital surface 42A, and the upper second target 41B is
On the 2B side, it is supported by an auxiliary anode 43 via a column A44. First target 41A and second target 41B
Are connected by a support B45. The anode 1B is a conventional rotating anode. The auxiliary anode 43 includes a rotating shaft, a bearing, and a fixed portion, but does not include a rotor.
It only serves to rotatably support the target. The auxiliary anode 43 is connected to the envelope 1 via the auxiliary anode envelope 46.
1B is insulated and supported. Most of the auxiliary anode envelope 46 is made of an insulating material such as glass or ceramic.

The focal track surface 42A of the first target 41A
The first focusing electrode 33A is arranged to face the second target 41B, and the second focusing electrode 33B is arranged to face the focal orbit surface 42B of the second target 41B.
A first X-ray beam 9 and a second X-ray beam 10 are emitted from a first focal point 4A and a second focal point 4B formed on B.

As a fourth embodiment of the X-ray tube apparatus of the present invention, a combination of the first embodiment and the second or third embodiment can be considered. That is, whether the third focal path surface is provided on the back surface of the target 2 having the large-diameter first focal path surface 3A and the small-diameter second focal path surface 3B of the first embodiment as in the second embodiment, Another target having a third focal point orbit plane is arranged on the back surface of the target 2 as in the third embodiment. By configuring the target in this way and arranging the focusing electrode opposite to the focal track surface, 3
Since three X-ray sources (focal points) are obtained, three parallel X-ray beams can be emitted. Therefore, in this embodiment, X
When the X-ray CT apparatus is applied to the X-ray CT apparatus, it can be used in combination with a multi-slice X-ray detector in which three X-ray detectors are arranged in parallel.

[0034]

As described above, according to the present invention, 1
X-ray CT apparatus comprising a multi-slice type X-ray detector in which a plurality of X-ray detectors can emit a plurality of parallel X-ray beams in one X-ray tube apparatus. When combined, image data of a plurality of slices can be acquired by one rotation scan. As a result, X
This can contribute to a reduction in the space for mounting the X-ray tube device on the X-ray CT device and a reduction in the cost of the X-ray CT device.
Further, since a plurality of X-ray beams from the X-ray tube device are perpendicularly incident on the corresponding X-ray detectors, an effect of preventing the occurrence of artifacts due to the non-uniformity of the X-ray intensity distribution can be obtained. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a principal part showing a basic configuration of a first embodiment of an X-ray tube device according to the present invention.

FIG. 2 is a cross-sectional view schematically showing the overall configuration of the first embodiment of the X-ray tube apparatus according to the present invention.

FIG. 3 is a sectional view of a main part when the X-ray tube device of the present invention is attached to an X-ray CT device.

FIG. 4 is a sectional view of a main part of a second embodiment of the X-ray tube apparatus according to the present invention.

FIG. 5 is a sectional view of a main part of a third embodiment of the X-ray tube apparatus according to the present invention.

[Explanation of symbols]

 1, 1A, 1B Anode (rotating anode) 2, 31 Target 3 Focal track surface 3A, 32A, 42A First focal track surface 3B, 32B, 42B Second Focus orbit plane 4 Focus 4A First focus 4B Second focus 5 Cathode 5A, 34A First cathode 5B, 34B Second cathode 6 Focusing Electrodes 6A, 33A First focusing electrode 6B, 33B Second focusing electrode 7 First electron beam 8 Second electron beam 9 First X-ray beam 10 First electrode 2 X-ray beam 11, 11A, 11B Envelope 12 Beryllium window (tube radiation window) 13, 30, 40 X-ray tube 14 Collimator 15 First collimator hole 16 Second collimator hole 17 Central axis (tube axis) of X-ray tube 18 X-ray Radiation direction 19 Tube vessel 20 Tube vessel radiation window 21 Cathode-side support 22 Anode-side support 23 Insulating oil 24 Stator 25 X-ray tube Device 26 Large Diameter Part 27 Small Diameter Part 35A First Cathode Enclosure 35B Second Cathode Enclosure 41A First Target 41B Second Target 43 ... Auxiliary anode 44... Post A 45... Post B 46... Auxiliary anode envelope 51... X-ray CT device 52. Specimen 55 X-ray detector 56 First X-ray detector 57 Second X-ray detector

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Koji Akita, Inventor Hitachi Medical Corporation, 1-1-1 Uchikanda, Chiyoda-ku, Tokyo F-term (reference) 4C092 AA01 AB04 AB22 AB27 AC17 BD06 BD12 BD16

Claims (3)

[Claims] 1. A rotating anode having a target having a focal orbit plane for emitting X-rays, and an electron beam arranged to face the target and forming an X-ray source on the focal orbit plane of the target. A cathode comprising a focusing electrode that emits
The rotating anode and the cathode are enclosed in a vacuum-tight manner, and a rotating anode X-ray tube including an envelope having a tube radiation window on a side surface around the target is supported inside a tube container.
An X-ray tube device that emits X-rays generated by the X-ray source to the outside from a tube container emission window provided in the tube container,
The target has at least two orbital orbital planes, and an X-ray source is formed on each of the focal orbital planes by arranging focusing electrodes opposite each of the focal orbital planes. Are arranged at predetermined intervals in the tube axis direction of the rotary anode X-ray tube when viewed from the tube container radiation window side. 2. The X-ray tube apparatus according to claim 1, wherein
An X-ray tube apparatus, wherein the target has focal track surfaces having different diameters. 3. The X-ray tube apparatus according to claim 1, wherein at least one of the focal track surfaces faces the anode end of the rotary anode X-ray tube.