JP2890666B2 - High-speed scanning X-ray generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention provides a high-speed scanning X-ray generation device capable of emitting X-rays from various annular positions suitable as an X-ray generation device of an X-ray CT device and scanning the emission position at high speed. Related to the device.

[Prior art]

With an X-ray CT system, 360 ° (or 180 °) around the subject
It is necessary to irradiate X-rays from various directions and collect X-ray transmission data. Therefore, conventionally, the X-ray tube itself is usually rotated by a rotating mechanism to irradiate X-rays from various directions around the subject. However, when the X-ray tube itself is rotated in this manner, it takes a certain amount of time to make one rotation (360 ° or 180 °), so that data cannot be collected at high speed and the heart or the like moves rapidly. No image of the organ could be obtained. Therefore, in recent years, the target has been made ring-shaped, and deflecting means (deflection coils and deflecting electrodes) have been provided so that electrons can collide with arbitrary positions on the ring-shaped target. A high-speed scanning X-ray generator (U.S.A.) that scans the collision position of the X-ray at high speed along the ring, thereby moving the X-ray generation position at high speed along the ring and changing the irradiation direction at high speed. A high-speed scanning X-ray generator manufactured by Imatron Corporation has been used.

[Problems to be solved by the invention]

However, in the conventional high-speed scanning X-ray generator,
Electrons are generated from a direction perpendicular to the plane formed by the ring-shaped target, and are deflected in the course of traveling toward the ring-shaped target to collide with a desired position of the ring-shaped target. There is a problem that it becomes. The subject is placed in a ring-shaped target and placed parallel to its central axis, so if the height of the subject is included, the subject is extremely long in the body axis (height) direction of the subject. Will be. The present invention allows a compact shape,
An object of the present invention is to provide a high-speed scanning X-ray generator that can be shorter in the body axis direction of a subject.

[Means for Solving the Problems]

In order to achieve the above object, in a high-speed scanning X-ray generator according to the present invention, a donut-shaped vacuum tube, a ring-shaped target arranged in the vacuum tube along the vacuum tube, and a tangent to the donut-shaped vacuum tube are provided. An electron beam incident tube having an electron generating filament and an electron accelerating electrode connected in a direction, and forming a magnetic field in a direction perpendicular to a plane formed by the donut-shaped vacuum tube so that the electron beam is applied to the donut-shaped vacuum tube. Along the doughnut-shaped vacuum tube, for deflecting the electron beam so as to make a circular motion inside the ring-shaped target, a number of electromagnet devices, and a current flowing through these many electromagnet devices are provided. The electron beam is controlled independently of each other only in the forward section in the electron beam traveling direction from the electron beam incident position to an arbitrary position. By forming a deflecting magnetic field that makes circular motion of the electron beam, and by not forming the deflecting magnetic field in any other section, the electron beam is removed from the circular motion in the section where there is no deflecting magnetic field, and the electron beam is applied to the target at a desired position. And a current control device for generating X-rays by colliding the X-rays.

[Action]

The electron beam injection tube has a filament for generating electrons,
An electrode for electron acceleration is provided, and electrons generated in the filament are accelerated by the electrode. This electron beam injection tube, donut-shaped vacuum tube,
It is tangentially connected, so that accelerated electrons are incident on this donut-shaped vacuum tube from the tangential direction. A number of electromagnet devices are arranged along the donut-shaped vacuum tube, and a magnetic field in a direction perpendicular to a plane formed by the donut-shaped vacuum tube is formed from each of the electromagnet devices. Therefore, the magnetic field applies a force toward the center of the donut-shaped vacuum tube to the incident electron beam, and the electron beam travels on a circular orbit along the donut-shaped vacuum tube. Therefore, if the above-mentioned magnetic field is generated from a large number of electromagnet devices, the electron beam circularly moves along the donut-shaped vacuum tube in the donut-shaped vacuum tube and does not collide with the ring-shaped target. The current flowing through each of the many electromagnet devices is independently controlled by a current control device. Then, a current is applied only to the electromagnet device disposed in the section on the front side in the electron beam traveling direction from the electron beam incident position to an arbitrary position, and a deflection magnetic field for circularly moving the electron beam only in that section is formed. Let it. No current is supplied to the electromagnet devices arranged in sections other than the section, or a current in the opposite direction is supplied. As a result, in the electromagnet device in this section, at least the current for generating the magnetic field for circularly moving the electron beam does not flow, and in this section, the force toward the center of the circular motion disappears. As a result, the electron beam deviates from the circular orbit along the above-described donut-shaped vacuum tube, collides with the outer ring-shaped target, and generates X-rays from the collision position. Therefore, the X-ray can be generated from an arbitrary position by controlling which electromagnet device does not allow the current for the magnetic field for the circular motion of the electron beam to flow by the current control device. The X-ray generation position can be switched without any mechanical operation by controlling the current flowing through the electromagnet device, and the X-ray generation device can be moved at high speed. In addition, since the electron beam incident tube is connected to the donut-shaped vacuum tube in a tangential direction, it is planar as a whole, and does not become so thick in a direction perpendicular to the plane formed by the donut-shaped vacuum tube. It is compact. The subject is placed in the center of the donut-shaped vacuum tube, and the length in the body axis direction is short including the height of the subject.

【Example】

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the embodiment shown in FIG. 1, a ring-shaped target 2 is arranged in a donut-shaped vacuum tube 1 along the same. In addition, a donut-shaped vacuum tube 1
Is connected to the electron beam incident tube 3 in the tangential direction. The electron beam incident tube 3 is provided with an electron generating filament 4 and an electron accelerating electrode 5 to which a high pressure is applied for accelerating electrons generated from the filament 4. Generated in the electron beam incident tube 3,
The accelerated electron beam 10 enters the donut-shaped vacuum tube 1 from its tangential direction. On the other hand, in the donut-shaped vacuum tube 1, a large number of electromagnet devices 6, 6,... Are arranged along the donut-shaped vacuum tube 1 in a ring shape over the entire circumference excluding the electron beam incident portion. As shown in FIG. 2, each of the electromagnet devices 6 includes a U-shaped core 7 made of a ferromagnetic material and a coil 8 wound therearound. When a current flows through the coil 8, a magnetic field is formed on the open end side of the U-shaped core 7. As shown by the dotted line in FIG. 2, the electromagnet device 6 is used in this doughnut-shaped vacuum tube so that the direction of the magnetic field is perpendicular to the plane formed by the donut-shaped vacuum tube (the direction perpendicular to the plane of FIG. 1). Attached to The current flowing through the coil 8 is independently controlled by the current controller 9 for each electromagnet device 6. Here, assuming that all the current is passed through the coil 8 of each electromagnet device 6 and the above-described magnetic field is formed in the entire region in the circumferential direction of the donut-shaped vacuum tube 1, the donut from the electron beam injection tube 3 is used. The electron beam 10 entering the vacuum tube 1 travels in the magnetic field at right angles to the direction of the magnetic field as shown in FIG. 2, and receives a force in the left direction in FIG. Proceed in orbit. Therefore,
If the intensity of this magnetic field is made appropriate by adjusting the current flowing through the coil 8, the electron beam 10 can draw a trajectory concentric with the donut-shaped vacuum tube 1. In this case, the electron beam 10 makes a circular motion inside the donut-shaped vacuum tube 1 without colliding with the ring-shaped target 2. Therefore, for example, as shown in FIG.
A current flows through the coil 8 of the electromagnet device 6 disposed in a section A on the near side in the traveling direction from the incident position to a certain position, and this current does not flow in a subsequent section B on the traveling direction. I do. Then, in the section A, the electron beam 10 draws a circular orbit due to the magnetic field, but in the section B, since no magnetic field is generated, the electron beam 10 moves linearly and deviates from the circular orbit in the tangential direction. Become. A ring-shaped target 2 is placed outside the circular orbit of the electron beam 10.
(See FIGS. 2 and 3), the electron beam 10 collides with the ring-shaped target 2, and X-rays are emitted from the collision position toward the center of the donut-shaped vacuum tube 1. The collision position of the electron beam 10 is
Since 10 moves straight in the tangential direction, it can be easily calculated according to which section the current flows and from where the current did not flow. Therefore, the current control device 9 controls how many sections the current flows in the large number of electromagnet devices 6, so that X-rays can be generated from an arbitrary position in the circumferential direction of the ring-shaped target. This movement of the X-ray generation position can be performed by current switching control, and does not require any mechanical movement, so that it can be performed at extremely high speed. In the X-ray CT apparatus, the subject is inserted into the central hollow portion of the donut-shaped vacuum tube 1 such that the body axis is perpendicular to a plane (a surface parallel to the paper surface) formed by the donut-shaped vacuum tube 1. The fact that the X-ray generation position moves at high speed in the circumferential direction of the donut-shaped vacuum tube 1 as described above means that the projection direction in the X-ray CT apparatus is switched at high speed, and 360 ° around the subject ( Or, the acquisition of projection data in the 180 ° direction is completed in a very short time. In the above description, the current flowing through the coils 8 of the large number of electromagnet devices 6 is controlled to be turned on in a certain section and turned off in a section earlier than the section. You can also. This not only does not generate a magnetic field that gives a force to cause the electron beam 10 to draw a circular orbit, but also generates a magnetic field that exerts a force in the direction opposite to the center direction, as shown in FIG. It can be made to collide with the ring-shaped target 2 at a position on the near side than in FIG.

【The invention's effect】

According to the high-speed scanning X-ray generator of the present invention, X-rays can be emitted from various annular positions,
The firing position can be scanned at high speed, and since there is no mechanical movement, the durability is high. Further, this high-speed scanning X-ray generator has a relatively flat, flat planar shape including a donut-shaped vacuum tube, and is very compact.

[Brief description of the drawings]

FIG. 1 is a schematic view of a high-speed scanning type X-ray generator according to one embodiment of the present invention as viewed from the front, and FIG. 2 is a II-II of FIG.
3 and 4 are schematic views for explaining the electron beam trajectory. 1. Donut-shaped vacuum tube, 2. Ring target, 3.
Electron beam injection tube, 4 ... filament for electron generation, 5 ...
Electrode for electron acceleration, 6: electromagnet device, 7: core, 8: coil, 9: current control device, 10: electron beam.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-81381 (JP, A) JP-A-2-181636 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 35/24 H01J 35/30 A61B 6/03

Claims (1)

(57) [Claims] 1. A donut-shaped vacuum tube, a ring-shaped target disposed in the vacuum tube along the vacuum tube, and an electron generating filament and an electron accelerating electrode connected tangentially to the donut-shaped vacuum tube. An electron beam incident tube having a donut-shaped vacuum tube and a magnetic field in a direction perpendicular to a plane formed by the donut-shaped vacuum tube so that the electron beam moves circularly inside the ring-shaped target along the donut-shaped vacuum tube. A number of electromagnet devices arranged along the donut vacuum tube for deflecting the electron beam;
A deflection magnetic field that circularly moves the electron beam only in a section on the front side of the electron beam traveling direction from the incident position of the electron beam to an arbitrary position by independently controlling the currents flowing through these many electromagnet devices is formed, By not forming the deflecting magnetic field in other than that section,
A high-speed scanning X-ray, comprising: a current control device for generating an X-ray by removing the electron beam from the circular motion in a section where there is no deflection magnetic field and causing the electron beam to collide with the target at a desired position. Generator.