JPS58115738A - X-ray generator unit for ultrahigh speed ct scanner - Google Patents

Abstract

PURPOSE:To revolve a stable X-ray focal point with a high speed and facilitate high speed photographing by providing a rotary target and an electron beam generation means by means of a magnetic bearing mechanism in a donut-shaped vacuum container that coaxially encloses a subject. CONSTITUTION:A vacuum container 116 is provided on a floor 100 through support stands 114 and 115. This container is of a donut-shaped from that coaxially surrounds a subject 117 and is always kept in high vacuum by means of a vacuum pump 18 and encloses a target 101 and a cathode 106 arranged opposedly at regular intervals. The target 101 is used to generate an X ray by the collision of an electron beam emitted from the cathode 106 and is fixed to a target rotor 102 through a support body 123. This rotor 102 is non-contact- supported by means of a magnetic bearing 103 and rotates around an axis (a) by the rotary torque applied by means of a rotary magnetic field generator.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an X1m generator for an ultra-high-speed CT scanner that enables high-speed imaging in an X-ray scanner.

TECHNICAL BACKGROUND OF THE INVENTION A conventional X-ray generator cover for an X@CT scanner is constructed as shown in FIG. 1.

In the figure, 1 is an X-ray tube device that generates X-rays, and 2 is an X-ray tube device that generates X-rays.
3 is a wedge filter for making the intensity distribution of X-rays uniform; 4 is a slot for limiting the intensity distribution of X-rays;
are the sources of X-rays emitted through these. Further, 5 is a subject whose tomographic image is obtained by this apparatus, and 6 is a detector for receiving the X-rays 4 that have passed through the subject 5 and converting them into electrical signals. Further, 7 is a data acquisition circuit for amplifying the output of the detector 6, AD converting it and sending it to a combinator (not shown); 8 is the X-ray tube device 1, the wedge filter 2, the slot 3, and the detector 6; , a rotating pedestal for rotating all or a part of the data acquisition circuit around the subject 5; 9 is a fixed pedestal for supporting the rotating pedestal 8;・10 is a bearing for fixing the rotary pedestal 8 concentrically to the fixed pedestal 9 and rotating it; 11 is a drive device for rotating the rotary pedestal 8; 12 is a high voltage for the X-ray tube device IK; Represents a high voltage cable for supply.

Such an X-ray generator for an X-ray CT scanner has the X-ray tube f1 and the detector 6 facing each other, rotates around the subject 5, and detects all points at every point in the inspection cross section of the subject 5. Projection data covering the angle is obtained, and a tomographic image is obtained from this data using a pre-programmed reconstruction program. Although it has been described here that the detectors 6 are rotated while facing the X-ray tube device 1, the detectors 6 can also be fixed if arranged around the entire circumference.

Problems with the Background Art In the above-mentioned X@CT scanner, large parts such as the X-ray tube device 1, the wedge filter 2, and the
, the detector 6, the data acquisition circuit 2, the rotating frame 8, the high voltage cable 12, or a part thereof must be rotated, and there is a limit to the rotation speed. If the time for one rotation is 0.58, then (b) the centrifugal force at the time of rotation becomes IOC, and an unrealistic force is applied to the X-ray tube device 1 and other rotating parts.

On the other hand, there is a need for high-speed imaging of several milliseconds, such as when photographing the heart of a human body, and for this purpose, by running an electron beam through a fishing platform-shaped vacuum container and rotating only the electron beam, A so-called electronic scan type CT scanner in which an X-ray source is rotated around the subject 5 has been considered. However, in this CT scanner, the traveling distance of the electron beam is 2 to 2
．． 5 lightning, the electrons are repelled and sufficient focusing cannot be obtained. Furthermore, with this method, if the acceleration energy of the electron beam changes even slightly, the deflection angle will shift significantly, making it extremely difficult to ensure beam stability.

Purpose of the Invention The purpose of the present invention is to provide an X-ray generator for an ultra-high-speed CT scanner that can eliminate the above-mentioned conventional drawbacks, rotate a stable Xls focal point at high speed, and easily realize high-speed imaging. It is.

SUMMARY OF THE INVENTION In the present invention, a rotating target and electron beam generating means are provided by a magnetic bearing mechanism in a donut-shaped vacuum container that coaxially surrounds an object.

Embodiment of the Invention The X-ray generator of the present invention is constructed as shown in FIGS. 2 and 3, and a vacuum container 116 is provided on a floor 100 via support stands 114 and 115. This vacuum container 116 has a donut shape that coaxially surrounds the subject 117, and is constantly maintained at a high vacuum by a vacuum pump 118. In this vacuum vessel 116, a target 101 and a cathode 106 are arranged facing each other at a predetermined interval. Reference numeral 107 is a focusing electrode.
is connected to the brush, 119.120, and the brush 11
Between the cathode 106 and the brush 119.9.120, there is a brush 119.
A shielding plate 121 is provided to prevent debris from going toward the cathode 106 when the material 120 is worn away.

The target 101 is for colliding with the electron beam emitted from the cathode 106 to generate X-rays, and is formed in a ring shape and is rotatable about an axis a. That is, tarr.

The turbine rotor 101 is fixed to the rotor 102 via a support 123.
02 is supported in a non-contact manner by a magnetic bearing 103, and rotational torque is applied by a rotating magnetic field generator (not shown).
It is designed to rotate around the axle load. During operation, a high voltage of about +70 kV is supplied to the target rotor 102 from the outside through the brush 104. Further, a touchdown mechanism 105 is provided near the rotor 102, and this touchdown mechanism 105 operates when the power of the magnetic bearing 103 is turned off (
OFF), the target rotor 102
is mechanically supported, and when the tar r9 rotor 102 rotates normally and sails, the targ rotor 102
Do not come into contact with.

On the other hand, the cathode 106 is a ring-shaped charged particle generating mechanism that emits electrons, and the focusing electrode 107
is for restricting the electron beam emitted from the cathode 106 to an appropriate distribution and controlling the amount of electrons over time. Furthermore, inside the above-mentioned Tada,) 101, there is a Tada! -/) A concave wedge filter 124 is provided to shape the intensity distribution of the X-rays emitted from the X-ray focal point 108 on J ox .

This wedge filter 124, together with the cathode 106 and the focusing electrode 107, is connected to the cathode rotor 1.
It is fixed to 09. This cathode rotor 109 is supported in a non-contact manner by a magnetic bearing 110 located inside the cathode rotor 109, and a rotational torque is applied by a rotating magnetic field generator (not shown) to rotate the cathode rotor 109 in a direction opposite to that of the targut 101 around an axis a. It is designed to rotate in the direction of. Therefore, cathode 1
06, the focusing electrode 107, sea urchin, and shift filter 124 will also rotate in the opposite direction to the direction of rotation (2171). Further, an X-ray emission port 113 is provided inside the shift filter 124, and a collimator 111 is provided inside this X-ray emission port 113.

A detector 1 is located near this collimator 111.
25 are arranged. Further, a tilt-down mechanism 139 is provided near the cathode rotor 109, and this tilt-down mechanism 139 operates when the power to the magnetic bearing 110 is turned off (
OFF), the cathode rotor 109 is mechanically supported, and does not come into contact with the cathode rotor 109 when the cathode rotor 109 is rotating normally.

Incidentally, when the brush 104 is worn out, there is debris between the brush 104 and the tar 1",) 101.
A shielding plate 126 is provided to prevent the light from moving toward the target 101. Further, 122 is a brush for bringing the can rotor 135 to ground potential, and 128 is a brush for bringing the anode rotor 129 to ground potential.

Furthermore, 130.131, 132, 1.33, and 134 are all insulators. Also, between the anode rotor 129 and the rotor 1'',) 1010 and the cathode rotor 135
and cathode 106 are insulators 136 and 1, respectively.
37 is the provision.

Now, during operation, the X-rays 138 generated from the focal point 108 pass through the wedge filter 124 and then enter the vacuum vessel 11.
The X-ray radiation passes through the X-ray emission port 113 of No. 6, and its distribution range is restricted by the pickpocket and the gate 111. After passing through the object 117, a ring-shaped detector 12 is installed coaxially with the axis a.
5. The output of this detector 125 is sent to a computer for image reconstruction (data collection/throughout) and converted into a tomographic image of the subject 117 by a predetermined reconstruction program.

Effects of the Invention By using the x11 generator of this invention, ultra-high-speed photography, which was extremely difficult to achieve in the past, can be easily performed.
An ICT scanner can be realized. The imaging time can be set arbitrarily, and sufficient X-ray intensity can be obtained in any case. Also, the rotating shaft a is a magnetic bearing 103.110
The focal point 108 is automatically and accurately controlled by
The position of can be precisely controlled. Furthermore, since the focal point 108 and the wedge filter 124 rotate together, the X-ray intensity distribution can be constantly shaped, which could not be achieved with a so-called beam scan type CT scanner, so that good images can be obtained. In addition, since power is supplied by Pravshe 119 and 120 in a vacuum, it not only has good voltage resistance characteristics, but also can continue to rotate in the same direction, making it possible to take pictures at any speed at any time. can.

Next, we specifically explain the various effects using mathematical formulas.
In the present invention, as described above, at least the electron incident surface of the tar 101 is made of a heavy metal such as tungsten. The density of this heavy metal is ρ, the specific heat is 01, and the thermal conductivity is λ
, the length of one side of the square X-ray focus is ω, tada, t10
1.01 and cathode 10G
If the temperature of the focal orbital surface of 101 is To, then the relative rotational speed with respect to f1 is f1.

The vector arm P that can be input to the port 101 is represented by . Here, Tmax is the maximum temperature.

When tungsten is used as the surface material of Terdoubt 101, Tmax = 2800°C, IC = 3.64
J/, jdeg, λ = 0.8 J 7cm, se
e, dog. Also, T) = 1000°C, R = 5
When 0crlI and e=8°, the above equation (1) becomes P=346ω2mef (kw) ・・−
・−・−・・(2), and ω=0. +18aRSf
= 100 Hz, P = 78 kW can be input. This corresponds to approximately twice the maximum peaks of a conventional rotating anode x-ray tube of the same focal spot size.

Further, in the present invention, the weight of the target can be reduced to about 15 yen, and it is easy to accurately rotate the rotating shaft a while automatically controlling the magnetic bearing 103.

Furthermore, the cathode rule rotor 135 is
It rotates in the opposite direction to the rotation direction of the subject 117, and if its rotational speed is fl, the time (photographing time) T required to obtain projection data of the entire circumference of the subject 117 is given by the following equation.

Here N is the number of cathodes. and N=10, fl
= 50 Hz, T = 2 ms, and dynamic imaging of the human heart can be carried out sufficiently effectively.

In addition, in this invention, the weight of the rotating part on the cathode side can be reduced to 9 to 10 or less, and if the rotational balance is maintained sufficiently,
As described above, it is fully possible to rotate around the axis 1 at 50 Hz while automatically controlling the magnetic bearings 103 and 110 with high precision. The rotating portion on the cathode side can be kept at a sufficiently low temperature (below 500° C.), and thermal imbalance can be reduced.

In the above embodiment, the rotational speed of the rotor 101 is f −f 1 = 50 Hz, but if the number of input sheaths may be smaller,
It is also possible to fix the tarps, and it is also possible to perform forced cooling such as water cooling. Also, the number of cathodes may be one,
It doesn't matter if there are more than one.

Furthermore, conventional mechanical bearings may be used in place of the magnetic bearings 103, 110. Further, the bra and sea 128 may be a non-contact energization mechanism using an emissive element. Furthermore, a bearing may be used in place of the pickpocket or the pull, or a mechanism for directly twisting the conducting wire may be used.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the conventional X-ray generator cover for the X@C scanner. Figure 2 shows the ultra high-speed CT scanner X of this invention.
It is a sectional view showing a line generation device. 101...tergtuto, 102...tar'r'
-t) Rotor, 103, 110... Magnetic bearing, 1
04゜119.120.127.128...Brush,
105.139...Touchdown mechanism, 106...
Curled, 107... Focusing electrode, 108... Focal point, 1♂"r... Cathode rotor, 111... Collimator, 113... X-ray emission port, 116... Vacuum vessel, 117・-Subject, 118...Vacuum windde, 1
21° 126... Shielding plate, 124... Sea urchin, shift filter, 125... Detector, 129... Anode side rotor, 130.131, 132, 133, 134.
...Gile, 135...Cathode side rotor, 138
...X-ray.

Claims (3)

[Claims] (1) Inside a doughnut-shaped vacuum container coaxially surrounding the subject,
An X-ray generator for an ultra-high-speed CT scanner, characterized in that an electron beam generating means and a tar that emits X-rays by the electron beam generated from the means are rotatably arranged to face each other. (2) The X-ray generator for an ultra-high-speed CT scanner according to claim 1, wherein the rotations of the electron beam generating means and the target are each controlled by magnetic bearings. (3) A concave lens-shaped wedge filter is provided in the radiation direction of the X-rays emitted from the target. X-ray generator for ultra-high speed CT scanner as described in item 1.