JPH0584302U - X-ray tube - Google Patents

Abstract

(57) [Summary] [Purpose] X without changing the distance between the X-ray focal point and the collimator.
To realize an X-ray tube in which the position of the tube can be set close to the center of rotation. [Arrangement] The anode 41 is installed at a slight inclination with respect to the tube axis of the X-ray tube 1, and the front surface thereof is a plane perpendicular to the rotation axis 42. A target 24 is provided on the whole or a part of the flat surface of the front surface of the anode 41, a filament 23 that emits an electron beam 26 is installed on the upper part of the tube, and the electron beam 26 is made to collide with the target 24 on the upper part of the anode 41. Irradiate with X-rays.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of an X-ray tube used for X-ray CT.

[0002]

[Prior Art]

 In order to know lesions and the like inside the human body, a method of irradiating X-rays, detecting the transmitted X-rays, and detecting structures and lesions inside the human body from differences in transmittance is used. X-ray CT is used as an apparatus for obtaining a tomographic image of a human body.

FIG. 2 shows an example of the configuration of the X-ray CT. In the figure, reference numeral 1 denotes an X-ray tube that generates X-rays, and the X-rays emitted from the X-ray tube 1 pass through a subject 3 through a collimator 2 and are detected by a detector 4. The data acquired by the detector 4 is subjected to processing such as amplification and integration by the data collection device 5, AD-converted, and then processed by the data processing device 6 to reconstruct an image. Reference numeral 7 denotes a gantry that mounts the X-ray tube 1, the collimator 2, and the detector 4, and accommodates the subject 3 in the central opening.

Reference numeral 8 denotes a display device for displaying a tomographic image or the like based on the image-reconstructed data. Reference numeral 9 is a table / gantry controller for controlling the position of a table (not shown) on which the subject 3 is placed, and for controlling the posture and movement of the gantry 7, and 10 is an X-ray controller for controlling the high voltage generator 11. It is an X-ray controller for supplying high pressure to the tube 1.

Reference numeral 12 relates to tomography, such as communicating with an operator through an operating device 13, controlling the operation of the data processing device 6 and controlling the operation of the table / gantry controller 9 and the X-ray controller 10. It is a system controller that performs unified control.

[0006]

[Problems to be solved by the device]

 In this X-ray CT, the gantry 7 has the largest external dimensions and weight, so there is a market demand to make the gantry 7 lightweight and compact. However, the central opening of the gantry 7 is required to accommodate the subject 3 having a large body, which is contrary to the miniaturization that is desired to be large.

If the central opening is fixed, the outer dimensions of the gantry 7 are almost always determined by the position of the X-ray tube 1 rotating around the object 3 in the gantry 7. Therefore, it is necessary to install the X-ray tube 1 close to the rotation axis to meet the demand for miniaturization of the gantry 7.

FIG. 3 is a structural diagram of an example of the X-ray tube 1. Only the main part will be described below. In the figure, 21 is an anode to which a high voltage is applied and which attracts thermoelectrons from the filament 23 attached to the cathode 22. Reference numeral 24 is a target that emits X-rays by collision of electrons from the filament 23, and the anode 21 is a rotating anode in order to prevent overheating of the target 24 due to collision of electrons. Reference numeral 25 is a glass tube for accommodating the above-mentioned respective parts and maintaining airtightness.

An electron beam 26 generated by thermoelectrons emitted from the filament 23 collides with the target 24, and the target 24 irradiates X-rays toward the center of rotation of the X-ray tube 1 in the lower part of the figure.

FIG. 4 is a diagram showing the relationship between the electron beam 26 emitted from the filament 23 and the X-ray 27 emitted from the target 24. In the figure, the same parts as those in FIG. 3 are designated by the same reference numerals. In the figure, 31 is a focal point on the target 24 on which the focused electrons collide. If the focal point 31 is not made as small as possible, geometric blurring occurs in the X-ray image. At the same time, since the temperature of the focal point rises sharply, the cooling efficiency determines the load per unit area. Therefore, in order to increase the area of the focal point 31 and reduce the area of the irradiated X-ray, the target 24 is inclined with respect to the direction perpendicular to the tube axis to reduce the effective focal point. When the tilt angle is θ, the actual focal area is S ₁ , and the effective focal area is S ₂ , the following equation is established.

S ₂ = S ₁ sin θ (1) That is, the smaller the θ, the thinner the irradiated X-ray. Actually, a collimator 2 having a slit is provided between the subject 3 and the X-ray tube 1 to limit the width of the irradiation X-ray. FIG. 5 is a diagram showing the influence of the position of the collimator 2 on the width of the effective focus and the width of the irradiation X-ray. In the figure, it is assumed that the slit of the collimator 2 is a pinhole, the effective focus width is F ₁ , the irradiation X-ray width is F ₂ , the distance from the X-ray focal point 31 to the collimator 2 is d ₁ , and the collimator 2 is Assuming that the distance to the rotation center 32 is d ₂ , F ₂ = F ₁ × (d ₂ / d ₁ ) ... (2) From the formula (2), the distance d ₁ between the X-ray tube 1 and the rotation center is It can be seen that the larger the size, the smaller the width of X-ray obtained.

As described above, the conditions required for the gantry 7 are as follows. The size of the X-ray at the irradiation point is reduced. The diameter of the central opening of the gantry 7 is increased. In order to satisfy the above condition, the distance between the focal point 31 and the collimator 2 is increased.

The present invention has been made in view of the above points, and an object thereof is to install the X-ray tube close to the center of rotation without changing the distance between the X-ray focal point 31 and the collimator 2. It is to realize an X-ray tube for X-ray CT that makes it possible.

[0014]

[Means for Solving the Problems]

 The present invention, which solves the above-mentioned problems, provides an X-ray tube including an filament that emits an electron beam of thermoelectrons, and an anode that has a target that receives the electron beam and irradiates the X-ray toward a rotation center. In order to obtain an X-ray narrower than the width of the wire, an anode is installed which is slightly inclined with respect to the tube axis, and the surface on the side of the filament is a plane perpendicular to the rotation axis, and a rectangular cross section of the anode. A target provided on all or part of the surface for the filament, the anode is rotated while keeping the inclined surface with the rotation of the rotating shaft, and the filament is provided above the tube and the electron beam It is characterized by a long length.

[0015]

[Action]

 The anode, which is tilted with respect to the electron beam emitted from the filament, is rotated by a rotary shaft that is attached to the back surface of the anode perpendicularly to the anode surface. The electron beam emitted from the filament mounted above collides with the target on the upper surface of the anode to irradiate X-rays. The position of the X-ray tube can be lowered by setting the target surface on which the electron beam collides to an upper part apart from the tube axis.

[0016]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram of a rotating anode of an X-ray tube according to an embodiment of the present invention. In the figure, the same reference numerals are used for the same parts as in FIG. (A) is a diagram showing the relationship between the rotating anode and the filament of one embodiment of the present invention, and (b) is a diagram using a conventional rotating anode. In the figure, 41 is an anode according to the present invention.

The conventional anode 21 shown in (b) has a shape obtained by cutting the peripheral portion of a thin cylindrical anode at an angle of θ, but the anode 41 shown in (a) is a thin cylindrical anode. The entire structure is provided by inclining it by an angle θ with respect to a plane perpendicular to the pipe axis without cutting the periphery as it is. Rotating the tilted anode 41 around the tube axis, and thus around the rotation center 32 while maintaining the angle θ, is achieved by connecting the bevel gear to the rotation shaft 42 that is vertically attached to the anode 41. It is performed by rotating it.

Since the surface of the anode 41 is a uniform plane, no matter which point on the plane is used as a focal point and the thermoelectrons are applied from the filament 23, the X-ray is irradiated downward as shown in the figure. In the case of the conventional example shown in (b), X-rays can be irradiated only on the surface appearing below the target 24.

In the figure (a), the focal point 31 can be selected to be the distance L ₁ from the upper side shown in the figure, and for the distance L ₂ from the upper side of the focal point 31 of the conventional X-ray tube 1 in the figure (b). Since the X-ray tube 1 can be brought closer to the center by (L ₂ −L ₁ ), the outer dimensions of the gantry 6 can be reduced.

As described above, according to this embodiment, the X-ray tubes installed on the outermost side of the gantry have the same geometrical arrangement, but the X-ray tubes can be arranged on the inner side by the above dimensions. As a result, a more compact gantry can be realized. Therefore, the counterweight for maintaining the moment balance during rotation can be lightened, and the gantry can be rotated with less electric power.

Further, there is no need for a step of providing a target angle of 6 to 10 ° on the anode for precision processing, and since it is only a flat surface, the cost can be reduced.

[0022]

[Effect of the device]

 As described in detail above, according to the present invention, even if the X-ray tube is installed close to the center of rotation, it is not necessary to change the distance between the X-ray focal point and the collimator, and it is possible to take a large distance. Therefore, the practical effect is great.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of an anode of an X-ray tube according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an X-ray CT.

FIG. 3 is a schematic structural diagram of a conventional X-ray tube.

FIG. 4 is a diagram showing a relationship between an electron beam and an irradiation X-ray.

FIG. 5 is an explanatory diagram showing a relationship between a position of a collimator and a width of an irradiation X-ray.

[Explanation of symbols]

 23 filament 24 target 26 electron beam 27 X-ray 41 anode 42 rotating shaft

Claims (1)

[Scope of utility model registration request] 1. An X-ray tube comprising a filament that emits an electron beam of thermoelectrons and an anode having a target that receives the electron beam and irradiates the X-ray toward the center of rotation. In order to obtain an X-ray (27) narrower than the width, the anode (41) is installed at a slight inclination with respect to the tube axis, and the surface on the side with respect to the filament (23) is a plane perpendicular to the rotation axis (42). ) And the filament (23) of rectangular cross section of the anode (41)
The target (2
4), the anode (41) is rotated with the inclined surface according to the rotation of the rotating shaft (42), and the filament (23) is provided above the tube to pass the electron beam (26). X-ray tube characterized by having a long length.