X-ray or gamma ray systems or devices – Source – Electron tube
Reexamination Certificate
1999-05-06
2001-04-03
Porta, David P. (Department: 2876)
X-ray or gamma ray systems or devices
Source
Electron tube
C378S125000, C378S144000
Reexamination Certificate
active
06212257
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention is directed to a modular system for use in assembling an x-ray radiator, the assembled x-ray radiator being of the type having a radiator housing, containing an x-ray tube, and a drive attachable to the x-ray tube for rotating the x-ray tube.
2. Description of the Prior Art X-ray radiators are used for a wide variety of purposes today, the foremost being various medical examinations in the framework of X-ray analysis or material examinations. For practically each individual application—for example, in the framework of medical technology—there is a particular type of X-ray tube which differs from other types for other applications with respect to the requirements. This results in a number of different X-ray radiator types for different performance classes, with which different focal spots are generated on the anode plate. The different focal spots are adapted to different detector formats or are produced on different anode materials. The wide variety of types necessarily results in low piece numbers for each X-ray radiator type, which has a disadvantageous effect on the material and manufacturing costs of each X-ray radiator and on the automation level in the manufacturing procedure.
SUMMARY OF THE INVENTION
An object of the present invention is to reduce the wide variety of X-ray radiator types without limiting the applications, so that a cost reduction is possible.
The object is achieved in an X-ray radiator system having at least one type of base X-ray radiator, with a rotating bulb tube with a cathode that emits an electron beam, an anode, and an arrangement for adjusting the size of the focal spot of the electron beam on the anode, and a number of drives of varying drive power for rotationally driving the rotating bulb tube, being selectively attachable to the base X-ray radiator.
The inventive X-ray radiator system preferably provides for the use of only one or a few types of base X-ray radiator(s), which are quasi-standardized types which, in contrast to known X-ray radiators, are not designed for a specific purpose, e.g. with respect to X-ray power and focal spot size. Rather, these types of base X-ray radiators each have a rotating bulb tube with an arrangement for adjusting the size of the focal spot. It is thus possible to adjust the size of the focal spot to account for application-specific requirements. Given the use of a specific type of base X-ray radiator, a wide range of different focal spots can be generated which are suitable for a variety of applications. An advantage of the rotating bulb tube used in the invention is that the heat loss arising during the operation (only about 1% of the electrical power which is fed to the rotary piston tube is converted into X-rays), which limits the X-ray power and the application range of the X-ray radiator, is conveyed, via the anode dish that acts as cooling block, to a cooling medium which is situated inside a radiator housing that surrounds the rotating bulb tube and which serves for cooling the tube. The maximum power loss to be dissipated in the form of heat is essentially determined by the product of the average radius of the anode dish and the angular velocity of the anode dish, the latter being determined by the type of drive mechanism of the rotating bulb tube. This means that, given a low power loss to be dissipated, a correspondingly low-power type of drive mechanism is sufficient, while for applications in which higher X-ray powers are demanded, and thus a greater power loss occurs, a higher-power type of drive mechanism is used to achieve a higher angular velocity. The weaker the type of drive mechanism is, the fewer its costs, so that an appreciable reduction of types and of costs can be achieved by a suitable selection, in connection with the suitable type of base X-ray radiator, of a drive mechanism type which fits the particular application and the required X-ray power. A modular X-ray radiator system is thus described herein from which a number of different X-ray radiators can be constructed, the type of base X-ray radiator and of drive mechanism to be respectively utilized being selected specifically for the application and the X-ray power.
Different designs for rotating bulb tubes are described in U.S. Pat. Nos. 5,883,936; 5,703,926; U.S Pat. No. 5,086,442 and U.S Pat. No. 4,788,705. The disclosure of these documents and the disclosure of co-pending United States Application filed simultaneously herewith having U.S. Ser. No. 09/306,099 are hereby incorporated herein by reference.
In an embodiment of the invention, the X-ray radiator system can include a number of types of base X-ray radiators of different X-ray powers (preferably two), to which any one of a number of drive mechanism types can be attached in order to cover the total requirement range from low-end X-ray examination apparatuses to high-end X-ray examination apparatuses. It has proven advantageous if at least one drive mechanism type of a specific drive power can be attached to different types of base X-ray radiators; i.e., one type of drive mechanism, of a specific drive power, which permits high angular velocities given a type of base X-ray radiator of low X-ray power, can likewise be coupled to a type of base X-ray radiator of high X-ray power in order to cover the range of low angular velocities.
To further increase the variety of possibilities within the X-ray radiator system, in another embodiment of the invention a cooling arrangement can be selectively attached to at least one type of base X-ray radiator. Whether to use such a cooling arrangement at all, and the design and/or cooling power thereof (if used), are dependent on the particular application and on the required X-ray power. A cooling arrangement such as a heat exchanger can be used alternatively to the utilization of a stronger drive mechanism type; i.e., it is possible to likewise achieve high X-ray powers with a weakly dimensioned type of drive mechanism in combination with a cooling arrangement. Given a number of types of base X-ray radiators, for at least one X-base radiator type of low or average X-ray power, a gaseous cooling medium can be employed in the cooling arrangement instead of a liquid cooling medium. In types of base X-ray radiators of low or average X-ray power, the use of a gaseous cooling medium suffices to dissipate the heat. This has the advantage that the rotating bulb tube can be rotated with appreciably less friction; i.e., a weaker drive mechanism type can be utilized, which in turn lowers the costs.
For adjustment of the size of the focal spot, a focusing electrode which is allocated to the cathode can be provided, in conventional fashion, this electrode being supplied with a focusing voltage which determines the size of the focal spot. In a variation of the invention, the arrangement for adjusting the size of the focal spot can be a magnet system. It is then possible to adjust the size of the focal spot in the manner described in the aforementioned co-pending U.S. application Ser. No. 9/306,099, for example.
In order to be able to move the focal spot to a position on the anode as is needed for the particular application of the X-ray radiator, in an embodiment of the invention at least one type of base X-ray radiator has an arrangement for deflecting the electron beam, which is preferably a magnet system. If an arrangement for deflecting the electron beam is used, then according to another variant of the invention at least one type of base X-ray radiator can have an anode into which at least two radially spaced, different target materials are deposited onto which the electron beam can be selectively guided by the beam deflecting arrangement, so that different X-ray spectra can be produced as needed.
To be able to adjust the anode angle, i.e. the angle between the primary direction of propagation of the X-rays and the region of the anode which contains the focal spot, the rotating bulb tube is mounted so that it can be tilted inside the radiator housing. This tilting ena
Hell Erich
Mattern Detlef
Schardt Peter
Ho Allen C.
Porta David P.
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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