JPH0352174B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to microfocusing x-ray tubes such as those used for extracting medical x-rays.

This type of x-ray tube has the medical advantage of focusing the electron beam onto a very small point on the target and producing a very sharp x-ray hemifield image. However, in such x-ray tubes, the high density of small electron spots quickly melts the target no matter what type of cooling device is used, and thus the x-ray target is consumed in a single use. Either the electron beam must be stored away or fewer beam electrons than desired must be used. Also, in medical x-ray operations, it is particularly desirable to use extremely short exposure times so that movement of the patient or his internal organs does not blur the image. However, with conventional microfocusing x-ray tubes, the x-ray production rate is so low that exposure times must be relatively long to obtain enough x-rays to form an image.

The above-mentioned problems do not tend to be eliminated, and even tend to reduce the effectiveness of conventional microfocusing x-ray tubes. Although there are other problems worth noting, the above-mentioned problems should suffice to prove that prior art microfocusing x-ray tubes are completely inadequate.

In addition, somewhat elaborate equipment is used to move the target anode during which the electrons are colliding, thereby spreading the heat generated by the electron beam on a portion of the target anode surface far beyond the cross-sectional area of the electron beam. Many x-ray tubes for extracting medical x-rays that are distributed over a wide range are known. Typical of the inconvenient arrangements that have been relied upon by others skilled in the art to remove or disperse the heat generated on the target material by the action of the electron beam are:
The device is disclosed in U.S. Pat. No. 3,825,786, issued July 23, 1974.

Furthermore, a number of medical x-ray extraction tubes are known which use similarly sophisticated equipment to bring a coolant into thermal contact with a target anode with which the electron beam is impinging. This coolant may be water or air, for example.

Other x-ray tubes that can move the target anode between electron beam collisions are suitable for x-ray crystallography, but are not suitable for medical x-ray extraction. Are known. A typical example of such an x-ray tube is
U.S. Patent No. 2,298,335 issued on August 4, 1973
This is the device shown in US Pat. No. 3,753,020, issued in Japan. These devices have multiple separate target anodes made from different materials and allow the operator to change from one target anode to another, thereby obtaining different readings from different types of anodes. It's something you get. However, these devices do not allow automatic replacement of each target anode after each use, requiring the operator (as is often the case) to replace the target anode with a different one. It is possible to use the same segment of the same target anode many times before Moreover, the above U.S. patent no.
Devices such as those disclosed in US Pat. No. 2,298,335 and US Pat. No. 3,753,020 do not allow the user to use a different portion of each target anode each time a particular target anode is used again. If the next time a particular target anode is used, a new part of the target anode is directed toward the electron beam, it happened by chance, and it was not done consciously and consistently. do not have.

Finally, US Pat. No. 3,290,540, issued December 6, 1966, discloses an electron emitting tube with a movable cathode tape. This cathode tape acts as a radiating element and can be incremented after it has been used to create a depression. However, the depression created in the emitting cathode used is physically and conceptually quite different from the partial dissolution of the target anode due to electron beam impingement.

It is therefore a general object of the present invention to provide a microfocusing x-ray tube that obviates or minimizes the problems described above.

A particular object of the present invention is to provide a device that is reusable and that generates a relatively large number of x-rays in a relatively short period of time using a narrowly focused electron beam.

Another object of the invention is to keep the target anode stationary during x-ray generation, but to move the target anode so that each time the x-ray tube is used a new portion of the target anode surface faces the electron beam. An object of the present invention is to provide a micro-focusing x-ray tube equipped with a device.

Yet another object of the present invention is to provide a microfocusing x-ray tube in which the target anode is in the form of a ribbon.

Other objects and advantages of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.

A preferred embodiment of the invention includes a conventional exhaust glass tube 10, a high voltage line 12, a filament current line 14,
Heater cathode 16 and electron beam collimator 18
These integrally constitute a device that generates a fine electron beam 20. However, instead of the conventional conical target anode, the x-ray tube according to the present embodiment has a target anode preferably in the form of a ribbon 22 wound around two spools 24 mounted on a bracket 26 within the x-ray tube. has. This ribbon 22 is preferably made from tungsten. However, in any case, the working surface of ribbon 22 is made from a single anode material.

A stepping motor 28 is also attached to the x-ray tube, and this motor 28 is connected to a drive belt 30.
is operatively connected to spool 24 via. Power for motor 28 is provided by motor wires 32. Further, the motor 28 and the target anode 22 are grounded by a grounding wire 34.

It goes without saying that the uneven portion of the ribbon 22 caused by the collision of the electron beam 20 is greatly exaggerated in size, and this is done to make it more obvious. In fact, the diameter of the bumps is approximately 50 microns, and their center-to-center distance (i.e., the amount that stepping motor 28 advances ribbon 22 each time it is activated) is approximately 100 microns. .

In use, the heater cathode 16 and the motor 2
8 keeps the ribbon 22 stationary during the generation of x-rays 36, but moves the ribbon 22 each time the x-ray tube is used.
2 to face the electron beam 20. Therefore, with each use of the x-ray tube, at least that portion of the surface of the ribbon 22 where the electron beam 20 is focused will melt;
Ribbon 22 is then moved a short distance, often in the manner of a typewriter ribbon, before the x-ray tube is used again.

FIG. 2 schematically shows an example of a system for aligning such an electron generating device with a ribbon feeding device. This device consists of three coupling switches 38,
40, 42, and three circuits respectively controlled by these switches. These link switches may be operated simultaneously by a single pushbutton (not shown). One of these three circuits includes a power supply 44, a switch 42 and a filament current line 1.
Consists of 4. The second circuit includes a high voltage generator 46 grounded at line 48, a switch 40 and high voltage line 1.
Consists of 2. These two circuits are conventional and require no further explanation. but,
The third circuit is not conventional. That is,
This circuit is a circuit that matches the first two circuits and the stepping motor 28. This circuit is
It consists of a switch 38, a battery 50 (which may be the same as battery 44), a timer 52 (which may be, for example, a two second timer), a pulse generator 54, a driver card 56, and a motor line 32.

When the coupling switches 40, 42 are turned on, an electron beam with a duration of less than 0.1 seconds is generated in the usual manner. If you operate switch 38 at the same time, 2
Second timer 52 is activated. After two seconds, pulse generator 54 generates a pulse which activates driver card 56. driver·
Card 56 causes stepping motor 28 to step. The step of the stepping motor 28 is, for example,
It may be 1.8°. In addition, the stepping motor 2
The spools 24 and the starting spools are sized such that a 1.8 degree step of the stepping motor 28 moves the ribbon 22 approximately 100 microns. Since the time lapse between each x-ray is much greater than 2 seconds, in the illustrated apparatus,
Ensure that the ribbon 22 is
A new beam of electrons is directed at the surface.

Although not shown in the figures, it is within the scope of the present invention that the target anode take on shapes other than the ribbon shape shown. For example, the target anode may be wheel- or cone-shaped. But whatever its shape, the general feature of the invention is that the target moves intermittently so that each electron emission faces a new target area, and that the target remains stationary during each emission. That's true.

From the above description of a microfocusing x-ray tube according to a preferred embodiment of the present invention, those skilled in the art will appreciate various advantages that individually distinguish the present invention over the prior art. Next, some of these advantages will be discussed. Although the following advantages are considered to be accurate and representative, they are not exhaustive.

One particular advantage of the present invention is that it is reusable and generates a relatively large number of x-rays in a relatively short period of time from a narrowly focused electron beam.

Another advantage of the present invention is that very sharp and sharp x-ray hemiplane images are produced. In particular, x
Because the linear hemiplane image is created in a short exposure time, the image is not blurred by movement of the patient's organs.

Although the present invention has been described above in detail with reference to preferred embodiments, it will be obvious to those skilled in the art that various modifications can be made within the scope of the technical idea of the present invention.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an x-ray tube according to a preferred embodiment of the invention, and FIG. 2 is a control device for the x-ray tube shown in FIG. 16... Heater cathode, 18... Electron beam cosometer, 20... Electron beam, 22...
Target anode, 24...Spool, 28...Stepping motor, 52...Timer, 54...Pulse generator, 56...Driver card.

Claims (1)

[Scope of Claims] 1. A minute focusing X-ray tube, which includes (a) electron beam generators 16 and 18 that generate a fine electron beam, and (b) that can generate X-rays when hit by the electron beam. a ribbon-shaped target anode 22; and (c) target anode moving devices 24, 28 for moving the ribbon-shaped target anode 22; A plurality of spools 24 for winding, the positional relationship of the plurality of spools with respect to the electron beam generating device is such that the ribbon-shaped target anode is wound around the plurality of spools.
a plurality of spools 24 having flat portions extending between the plurality of spools and impinged by the electron beam; and () a plurality of spools mounted within the x-ray tube. a motor arrangement 28, 30 operatively connected to at least one of the ribbon target anodes, which keeps the ribbon target anode stationary during the generation of the electron beams, and which moves the ribbon target anode each time the electron beam is generated; said motor device 28, 30 driving said spool to drive said ribbon-shaped target anode such that a new portion of the surface of said ribbon-shaped target anode is located at a point of said flat portion that is hit by said electron beam; , a target anode moving device 24, 28 including
A micro-focusing X-ray tube equipped with and. 2. The microfocusing X-ray tube of claim 1, wherein the ribbon target anode is made of tungsten. 3. The target anode moving device is an alignment device 52, 54, 56 that aligns the electron beam generation device and the motor device,
During the generation of the electron beam, the ribbon-shaped target anode is kept stationary, and after a predetermined period of time after the generation of the electron beam, the ribbon-shaped target anode is moved a predetermined distance so that the ribbon-shaped target anode is Microfocusing X-ray tube according to claim 1, characterized in that it comprises the above-mentioned alignment device 52, 54, 56 for positioning the new part of the surface at the point where the electron beam hits. . 4. The microfocusing X-ray tube of claim 3, wherein the ribbon target anode is made of tungsten. 5 Devices 16, 18 for generating fine electron beams
A method for generating X-rays using a minute focusing X-ray tube comprising A method characterized in that the target anode is moved relative to the electron beam so that each time a new portion of the surface of the target anode faces the electron beam. 6. The target anode is moved a short distance between each use of the x-ray tube so that each used portion of the target anode is slightly spaced apart. The method described in paragraph 5.