JPH0412439A - X-ray generator - Google Patents

Abstract

PURPOSE:To form an X-ray generator into a compact and short shape in the vertical direction to the plane of a target by providing three deflecting coils arranged between a circular arc-shaped target and an electron gun section and a current feeding device interrelatedly changing the currents flowing in the deflecting coils respectively. CONSTITUTION:An electron beam proceeding to a circular arc-shaped target 3 nearly at a right angle is bent in the circular arc direction of the target 3 and curved along a circular arc by three deflecting coils 5, 6, 7, it can be again returned to the nearly vertical. direction to the target 3 and fed to the target 3. When the currents flowing in three deflecting coils 5, 6, 7 are interrelatedly changed respectively, the electron beam can collide at an optional position on the target 3, and the collision position can be scanned at a high speed in the circular arc direction of the target 3. The X-ray emission position can be scanned at a high speed on the circular arc, and an X-ray generator can be made compact in shape.

Description

[Detailed description of the invention] [Industrial application field] This invention is suitable for an X-ray generating device such as an X-ray CT device, and can emit X-rays from various positions along an arc, and can scan the emitting position on the arc at high speed. This invention relates to an X-ray generator. [Conventional technology]

For example, in an X-ray CT apparatus, the X-ray emission position may be scanned in a circumferential direction. In other words, when explaining an X-ray CT device, this device irradiates X-rays from various directions within 360° (or 180°) around the subject and performs image reconstruction processing on multidirectional X-ray transmission data collected. X in the cross section across the subject
It obtains a linear absorption rate distribution image, and its multidirectional X
In order to collect radiographic data, it is necessary to move the X-ray emitting position on the circumference around the subject. Conventionally, in this X-ray CT apparatus, the X-ray tube itself is usually rotated by a rotation mechanism to scan the X-ray generation position on the circumference around the subject. By the way, when the X-ray tube itself is rotated in this way, it takes about 1 second to make one rotation (360° or 180°), making it impossible to collect data at high speed. On the other hand, we know from X-ray fluoroscopy that there are organs in the human body, such as the heart, whose movements can only be captured with high-speed images of about 30 frames per second. Therefore, in recent years, an X-ray generator (high-speed scanning type X-ray generator W manufactured by Imatron, Inc., USA) that can scan the X-ray generation position on the circumference at a very high speed has come into use. This method creates an elongated ring-shaped target within a single vacuum chamber, generates an electron beam from a direction perpendicular to the plane formed by this ring-shaped target, and deflects the electron beam on its way to the ring-shaped target. By controlling the deflection means (deflection coil, deflection electrode), the electron beam impinges on the ring target at a desired position. The X-ray generation position is scanned circumferentially at high speed along the ring-shaped target, and the imaging time for one frame is approximately 50 m5ec. This is what I did.

[Problem to be solved by the invention]

However, with conventional high-speed scanning X-ray generators, the ring-shaped target has a very long, large horn-like shape of about 4 m in the direction perpendicular to the plane, and the subject is forced to enter the horn. There is a problem in that the subject is forced into the body from the head, and the subject is forced to feel as though he or she is surrounded by a large horn, giving him or her an unnecessary sense of anxiety. This invention can have a compact shape that is short in the direction perpendicular to the plane formed by the target, and
When applied to the XI
It is an object of the present invention to provide a high-speed scanning type X-ray generation device that enables high-speed imaging such that a still image of the heart can be obtained at about 30 frames per second when applied to an ICT device.

[Means to solve the problem]

In order to achieve the above object, the X-ray generator according to the present invention includes a cylindrical vacuum container having a curved shape forming a part of the cylindrical side surface, and a cylindrical periphery inside the cylindrical vacuum container. An arc-shaped target arranged along the direction,
an electron gun section disposed in the cylindrical vacuum container to face the target in the central axis direction of the cylindrical shape;
A first magnetic field that generates a magnetic field in the radial direction of the cylindrical vacuum container, which is disposed on the electron gun section side between the target and the electron gun section.
and a deflection coil disposed on the target side between the target and the electron gun section, which generates a magnetic field in the radial direction of the cylindrical vacuum container in the opposite direction to the magnetic field generated by the first deflection coil. a second deflection coil; a third deflection coil disposed between the target and the electron gun section and generating a magnetic field in the central axis direction of the cylindrical vacuum container;
The present invention is characterized by being equipped with a current supply device that changes the currents flowing through the two deflection coils in relation to each other.

[For production]

The electron beam generated from the electron gun section is directed toward the arc-shaped target. The electron gun section and the arcuate target are housed in a cylindrical vacuum container that is curved to form a part of the cylindrical side surface. The arc-shaped target is arranged along the circumferential direction of the cylindrical shape, and the electron gun section is arranged so as to face the target in the direction of the central axis of the cylindrical shape. Therefore, the electron beam from the electron gun section is directed toward the arcuate target so as to be substantially perpendicular to the target. Between the electron gun section and the arc-shaped target, first, second,
A third deflection coil is arranged. The first deflection coil is provided on the electron gun side, and generates a magnetic field in the radial direction of the cylindrical vacuum container. The second deflection coil is provided on the target side and generates a magnetic field in the radial direction of the cylindrical vacuum vessel and in the opposite direction to the magnetic field generated from the first deflection coil. A magnetic field in the direction of the central axis of the cylindrical vacuum container is generated from the third deflection coil. Due to the magnetic field from the first deflection coil, the electron beam is subjected to a bending force in the circumferential direction of the cylindrical vacuum vessel. Therefore, the electron beam is directed in the arc direction of the arc-shaped target. On the other hand, since the magnetic field from the second deflection coil is in the opposite direction to the magnetic field from the first deflection coil, it is subjected to a bending force in the opposite direction in the circumferential direction. As a result, the electron beam that was once bent in the circumferential direction by the first deflection coil is bent in the opposite direction, and these two
By adjusting the magnitude of the two magnetic fields, the magnetic field can be made to collide with the targeter 1- in a direction substantially perpendicular to the target. Due to the magnetic field in the direction of the central axis of the cylindrical vacuum vessel from the third deflection coil, the electron beam is subjected to a force directed toward the radial center of the cylindrical vacuum vessel, and is bent by the first deflection coil as described above. The electronic beano can be curved in the circumferential direction of the cylindrical vacuum container. These three deflection coils bend the electron beam, which is directed almost perpendicularly to the arc-shaped target, in the direction of the arc of the arc-shaped target, curve it along the arc, and return it in a direction almost perpendicular to the arc-shaped target to form an arc-shaped beam. You can direct it to the target. By changing the currents flowing through these three deflection coils in relation to each other, it is possible to make the electron beam collide with an arbitrary position on the arc-shaped target, and the collision position can be changed to the arc of the arc-shaped target. It is possible to scan at high speed in the direction. When the electron beam collides with this arc-shaped target laser 1~, X-rays are generated from that position, so the X-ray generation position is scanned at high speed in the arc direction of the arc-shaped target within the range where the target exists. It turns out.

【Example】

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to an X-ray CT apparatus. In this diagram,
The X-ray tube 1 has a cylindrical vacuum vessel 11 that forms part of the side surface of the cylinder. Inside the vacuum vessel 11, an arc-shaped target 3 is arranged along the vacuum vessel 11. Further, the electron gun section 2 is arranged in the cylindrical vacuum vessel 11 so as to face the arcuate target 3 in the vertical direction. The cylindrical vacuum container 11 is thin on the electron gun section 2 side, but expands in a fan shape toward the arcuate target 3, and as it expands, it curves along the cylindrical side surface. When applied to a CT device, the arc-shaped target 3 is divided into three or four parts of a 360° circumference, and is approximately 120° and 90° (or may be divided into smaller pieces). Three (or four, or more) X-ray tubes 1 having such arcuate targets 3 are placed around the subject. Alternatively, in the case of so-called half-scan, a plurality of X-ray tubes 1 are arranged, which are divided into a plurality of angles somewhat larger than 180°. As shown in FIG. 2, the electron gun section 2 includes an electron generation filament 21 and an electron acceleration electrode 2 applied with high voltage to accelerate the electrons generated from the filament 21.
2 occurs in the electron gun section 2, which is equipped with
The accelerated electron beam heads in the axial direction of the cylindrical vacuum vessel 11, that is, perpendicularly to the arcuate target 3. On the other hand, outside the cylindrical vacuum vessel 11, as shown in FIG. It is provided. The converging coil 4 is for converging the electron beam generated from the electron gun section 2, and the deflection coil 5.6.7
is for deflecting the electron beam. As shown in FIGS. 2 and 4, the deflection coil 5 is provided on the side closer to the electron gun section 2, receives current supply from a power source 51, and has a cylindrical shape as shown by a dotted line 52 in FIG. A magnetic field is generated in the radial direction of the shaped vacuum vessel 11. As shown in FIGS. 2, 3, and 4, the deflection coil 7 is provided on the side closer to the arcuate target 3, and receives current from a power source 71, as shown by the dotted line 72 in FIG. The above-mentioned magnetic field 5 in the radial direction of the cylindrical vacuum vessel 11, such as
2 generates a magnetic field in the opposite direction. As shown in FIGS. 2, 3, and 4, the deflection coil 6 is common to the three X-ray tubes 1, receives current from a power source 61, and is connected to the dotted line 62 in FIG. As shown in
A magnetic field is generated in a direction parallel to the central axis of the cylindrical vacuum vessel 11. Therefore, due to the magnetic field 52, the electron beam moves in the left and right directions of movement, that is, toward the cylindrical vacuum container 1, as shown by the dotted line in FIG.
It is bent in the circumferential direction of 1 (moves in a circular motion). The magnetic field 72 is
Since the magnetic field is in the opposite direction to this magnetic field 52, the electron beam is bent (circularly moved) in the opposite direction. In other words, if the electron beam is bent to the left (upper side in FIG. 2) by the magnetic field 52, it will be bent to the right by the magnetic field 72. The curvature of these bends (circular motion) is the magnetic field 52.7
2 is inversely proportional to the axial length of the cylindrical vacuum vessel 11. Therefore, the ampere turns of the deflection coil 5.7 due to the current supplied from the power source 51.71 are in the opposite direction and maintain the above-mentioned inversely proportional relationship. As a result, the electron beam bent by a certain angle in one direction is returned by the same angle in the opposite direction, so it can be moved to any position (as shown by a, b, c, and d in Figures 2 and 3). Even if the electron beam is incident on the arcuate target 3 at the position ), the angle of incidence is kept approximately at right angles, and the shape of the incident electron beam is kept constant. From the deflection coil 6, the cylindrical vacuum vessel 11 is connected as described above.
direction parallel to the axial direction (dotted line 62 in Figure 4, that is, the second
Since a magnetic field is generated in the horizontal direction (in the figure), this magnetic field 62
However, when the traveling direction of the electron beam includes a component in the vertical direction in FIG. 2, the electron beam is bent (circularly moved) in a direction perpendicular to the plane of the paper in FIG. As a result, a centripetal force directed toward the central axis of the cylindrical vacuum vessel 11 is applied to the electron beam, and the arc-shaped target 3 is curved in the arc direction. Then, the current supplied from the power supply 51, 61, 71 is controlled so that the ampere turns of the deflection coils 5, 6, 7 correspond to the curves 53, 63, 73 in FIG. 5, respectively. Under the ampere turn condition at time a in FIG. 5, the electron beam is largely bent downward in FIG. Under the ampere turn condition at time C, the electron beam is bent to the lower side of FIG. Under the turn condition, the electron beam is bent upward in FIG. 2 and enters the arc-shaped target 3 at position ffc (see FIGS. 2 and 3). Under the ampere turn condition at time d, the electron beam is bent upward in FIG. It is largely bent upward in FIG. 2 and enters the arc-shaped tarkerat 3 at position d (see FIGS. 2 and 3). By repeating the waveform shown in FIG. 5, the incident position of the electron beam moves back and forth along the arc of the arc-shaped target 3 from one end to the other. The convergence coil 4 converges the electron beam at the point when it reaches the target 3j, even if the electron beam trajectory length until it reaches the arcuate target 3j changes in this way, and the convergence coil 4 converges the electron beam when it reaches the target 3j\. It is connected to a power source whose current is controlled according to the incident position of the arcuate target laser 1-31\. In this way, when the electron beam is incident on the arcuate target 3, X-rays are generated toward the center of the arc of the arcuate target 3. By scanning the electron beam incident position as described above, the X-ray emission position is scanned along the arcuate target array 1-3. No matter where the X-rays are generated, since the incident direction and shape of the electron beam are constant, it is possible to always generate XR of the same quality. This scanning of the X-ray emission position can be performed simply by controlling the current flowing through the deflection coils 5, 6, 7, and since there is no mechanical movement at all, very high-speed scanning is possible. In this embodiment, X-rays are emitted from three X-ray tubes 1 at the same time toward the subject, and the emitting positions are set within each angular range (120° range in the example shown in Fig. 1). It is designed to simultaneously move back and forth in the circumferential direction surrounding the subject. In this case, the subject is surrounded by three X-ray tubes 1, but each of the X-ray tubes 1 is not very long in the body axis direction of the subject; Since it is thin, it can give the subject a sense of openness. Although the case where the present invention is applied to an X-ray CT apparatus has been described, this X-ray tube can also be applied to an X-ray rotating tomography apparatus.

【Effect of the invention】

According to the X-ray generator of the present invention, the X-ray emission position can be scanned on an arc at high speed, and since there is no mechanical movement at all, the X-ray generator has high durability. Moreover, it is compact in shape, and when applied to an X-ray CT apparatus, it gives a sense of openness to the subject and does not cause unnecessary anxiety.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view of an embodiment of the present invention, Fig. 2 is a schematic diagram of the X-ray tube of Fig. 1 developed in a plan view, and Fig. 3 is a schematic diagram seen from the right side of Fig. 1. FIG. 4 is a sectional view taken along the line IV--IV in FIGS. 2 and 3, and FIG. 5 is a waveform diagram showing temporal changes in ampere turns of each deflection coil. 1... X-ray tube, 11... Cylindrical vacuum container, 2...
Electron gun section, 21...Filament for electron generation, 22.
... Electrode for electron acceleration, 3 ... Arc-shaped target, 4
... Convergence coil, 5.6.7 ... Deflection coil, 51
．． 61.71...Power supply, 52.62.72...Magnetic field.

Claims (1)

[Claims] (1) A cylindrical vacuum container having a curved shape forming a part of the cylindrical side surface, an arcuate target disposed within the cylindrical vacuum container along the circumferential direction of the cylindrical shape, and a cylindrical an electron gun section disposed in a vacuum container to face the target in the central axis direction of the cylindrical shape; and the cylindrical vacuum disposed on the electron gun section side between the target and the electron gun section. a first deflection coil that generates a magnetic field in the radial direction of the container; and the first deflection coil in the radial direction of the cylindrical vacuum container, which is disposed on the target side between the target and the electron gun section. a second deflection coil that generates a magnetic field in the opposite direction to the generated magnetic field; and a third deflection coil that generates a magnetic field in the direction of the central axis of the cylindrical vacuum container, which is disposed between the target and the electron gun section. , and a current supply device that correlates and changes the currents flowing through the three deflection coils, respectively.