JPH0582059A - X-ray tube with rotary anode - Google Patents

Abstract

PURPOSE:To lessen change in the side of a focal point depending upon the slicing position by furnishing a rotary shaft at each end of a rotary anode whose target is embodied in a specific form. CONSTITUTION:A rotary anode 3 rotated by rotary shafts 5 on the ends has a target to receive an electron beam from a cathode 2, and the peripheral surface 3a of this target is formed with recessed section. According to the constitution to generate a focal point on this peripheral surface 3a, the shape and size of the focal point do not vary whichever direction about the sensor side it is viewed from, and change in the size of the focal point due to the slicing position lessens to accomplish an enhanced space resolution of X-ray image. The actual focal point size become large because the peripheral surface of the anode 3 has recessed section. Further, the anode 3 is held while shafts are provided at the two ends so as to enlarge the heat capacity of the anode side, and the service life of X-ray tube including bearing etc., can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary anode type X-ray tube used in, for example, an X-ray CT apparatus, and more particularly to improvement of a rotary anode.

[0002]

2. Description of the Related Art Generally, an X-ray tube of an X-ray CT apparatus is shown in FIG.
The rotary anode type X-ray tube 100 as shown in FIG.
This conventional rotating anode type X-ray tube 100 has a cathode 101 for generating an electron beam and a taper surface for generating an X-ray by being irradiated with this electron beam, and also has a rotating shaft 10.
3 has a structure in which a disk-shaped rotating anode 102 driven by 3 is arranged to face each other, and a geometrical position where an incident position of an electron beam on a tapered surface of the rotating anode 102 becomes a focal position of an X-ray fan beam. Is arranged so as to face the detector 104.

Such a conventional rotary anode type X-ray tube is constructed in consideration of the fact that the detector 104 is a one-dimensional detector that collects two-dimensional data. X-rays are radiated toward the detector 104 in the form of a fan beam so that the detector 104 can detect the X-rays transmitted through the subject P. In this case, the focus size viewed from the detector 104 side has a fixed relationship with each channel.

[0004]

However, when the detector 104 is a two-dimensional detector and collects three-dimensional data, if the conventional rotary anode type X-ray tube 100 described above is adopted, the detector will have a cone-beam shape. When the X-ray is irradiated in the direction of 104, since the rotating anode 102 has the above-described shape, the apparent focus size varies depending on the angle formed from each point on the two-dimensional surface with respect to the focus. Therefore, the spatial resolution of the image obtained based on the projection data collected by the detector differs depending on the slice position. If the real focus size is made small, the spatial resolution will be improved, but if it is too small, the X-ray output will be greatly limited, so that the real focus size is limited. Therefore, the conventional rotary anode X-ray tube 100 is
When applied to an X-ray CT apparatus using a two-dimensional detector, the phenomenon that the spatial resolution of the obtained image becomes non-uniform is inevitable.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to suppress the change amount of the focus size depending on the slice position without significantly impairing the actual focus size. It is to provide an X-ray tube that can be used.

[0006]

To achieve the above object, the present invention comprises a rotating anode in which a target for receiving an electron beam emitted from a cathode is an outer peripheral surface having a concave sectional shape. To do. Further, the invention is characterized in that rotating shafts are provided at both ends of the rotating anode.

[0007]

In the rotating anode type X-ray tube of the present invention having the above structure, the focus is formed on the outer peripheral surface of the rotating anode, so that the shape and size of the focus do not change much from any position on the detector side. That is, since the amount of change in the apparent focus size due to the relative position in the slice direction can be suppressed, the spatial resolution of the obtained image is improved. However, the actual focal spot size becomes small by this alone, and the X-ray output is greatly limited. However, the actual focal spot size can be increased by making the outer peripheral surface of the rotating anode into a concave sectional shape. it can.

In this rotary anode, since the focal point is located on the outer peripheral surface of the rotary anode, the rotary shaft can be provided at both ends of the rotary anode so that the rotary shaft can be held from both ends. Therefore, the force applied to each bearing is reduced, the service life of the bearing is extended, and the mass of the rotating shaft is increased, so that the heat capacity on the anode side can be increased.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a structural view of the inside of an insert tube in a rotary anode type X-ray tube of a first embodiment of the present invention, and FIG. 2 is a schematic view showing an X-ray CT to which the rotary anode type X-ray tube of the present invention is applied. ..

1 and 2, the rotary anode type X-ray tube 1
The insert tube 4 includes a cathode 2 for generating an electron beam and a rotating anode 3 as a target for receiving the electron beam.
It is enclosed inside. The rotating anode 3 has an outer peripheral surface 3a having a concave cross-sectional shape for generating X-rays by being irradiated with an electron beam, and is driven by a rotating shaft 5 to rotate the rotating anode 3
The position of incidence of the electron beam on the outer peripheral surface 3a is located facing the detector 9 at a geometric position where the position of focus of the X-ray cone beam is obtained. In FIG. 1, 6 is a bearing, 7 is a rotor part, and 8 is a stator part.

When X-rays are generated, the rotating anode 3, which is rotating at high speed, irradiates the target with an electron beam from the cathode 2 to generate X-rays. The X-rays are made into a cone beam shape and exposed to the subject P, and the data of the X-rays transmitted through the subject P are collected by the detector 9, and a plurality of tomographic images are simultaneously reconstructed based on this data. To be done.

In this rotating anode type X-ray tube 1, since the focus is focused on the outer peripheral surface 3a of the rotating anode 3, the detector 9
The shape and size of the focal point do not change much from any position on the side. That is, the amount of change in the apparent focus size due to the relative position in the slice direction can be suppressed, so that the spatial resolution of the image obtained based on the projection data collected by the detector 9 is improved. However, with this alone, the size of the actual focal point becomes small and the X-ray output is greatly limited. Therefore, the actual focus size can be increased by making the cross-sectional shape of the outer peripheral surface 3a concave.

The cross-sectional shape of the outer peripheral surface 3a is such that the shape and size of the focus do not change much from any position on the detector side, for example, a semicircular shape as shown in FIG. 3 and a triangular shape as shown in FIG. Etc. are formed in a concave shape.

In this rotating anode, the focal point is the rotating anode 3
Since it is tied on the outer peripheral surface 3a, it is possible to provide rotary shafts at both ends of the rotary anode and hold the rotary shafts from both ends as shown in FIGS. Therefore, the force applied to each bearing is reduced, and the service life of the bearing can be extended. Also, the heat capacity on the anode side can be increased by increasing the mass of the rotating shaft. In addition, an X-ray tube using cone-beam-shaped X-rays can be used for X-ray CT.
When applied to, the amount of X-ray exposure can be reduced and the throughput of patients can be improved.

[0015]

As described above, according to the present invention, it is possible to reduce the change in the focus size depending on the slice position. Further, by holding both ends of the rotating anode by the rotating shaft, the heat capacity on the anode side can be increased, and the service life of the bearing and thus the X-ray tube can be extended.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inside of an insert tube in a rotary anode type X-ray tube according to a first embodiment of the present invention.

FIG. 2 is an X-ray CT to which the rotating anode X-ray tube of the present invention is applied.
FIG.

FIG. 3 is a configuration diagram inside an insert tube in a rotary anode type X-ray tube according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram inside an insert tube in a rotary anode type X-ray tube according to a third embodiment of the present invention.

FIG. 5: X applying a rotating anode type X-ray tube in a conventional example
It is a schematic diagram of line CT.

[Explanation of symbols]

 1 rotating anode type X-ray tube 2 cathode 3 rotating anode 3a outer peripheral surface 5 rotating shaft 6 bearing

Claims (2)

[Claims] 1. A rotary anode type X-ray tube comprising a rotary anode whose target for receiving an electron beam emitted from a cathode is an outer peripheral surface having a concave sectional shape. 2. The rotating anode type X-ray tube according to claim 1, further comprising a rotating shaft capable of holding the rotating anode from both ends.