X-ray or gamma ray systems or devices – Accessory
Reexamination Certificate
2000-08-15
2002-12-17
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Accessory
C378S203000, C378S194000
Reexamination Certificate
active
06494618
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates generally to x-ray tubes. More particularly, the present invention relates to a high voltage connector receptacle having combined radiation attenuating and dielectric properties, and to an x-ray tube housing incorporating the high voltage connector receptacle.
2. The Relevant Technology
X-ray generating devices are used in a variety of medical and industrial applications. A typical x-ray device consists of an x-ray tube disposed within an outer housing, sometimes referred to as the “can.” The x-ray tube itself is usually comprised of an evacuated housing that encloses an anode and a cathode. The outer housing/can is typically filled with a dielectric oil, or similar coolant, to remove heat from the x-ray tube during operation. Electrical leads are provided through the outer housing and connected to the x-ray tube so that in operation, power can be supplied to a filament portion of the cathode, thereby causing the release of electrons by thermionic emission. Electrical leads are also connected to the x-ray tube in a manner so as to provide a voltage potential between the cathode and the anode. The voltage potential causes the released electrons to accelerate towards the anode at high speeds. Upon striking the target surface of the anode, which is comprised of a material having a high atomic number, a portion of the resulting kinetic energy is converted to electromagnetic waves of very high frequency, i.e., x-rays.
The resulting x-rays emanate from the target surface, and are then collimated through windows formed through the evacuated housing and the outer housing for penetration into an object, such as a patient's body. As is well-known, the x-rays that pass through the object can be detected and analyzed so as to be used in any one of a number of applications, such as x-ray medical diagnostic examinations or material analysis procedures.
Although a majority of the generated x-rays are emitted from the target surface so as to be directed towards the x-ray transmission windows, some of the x-rays may be directed in other directions. These “off focus” x-rays can potentially present health hazards to nearby personnel, including equipment operators and patients, and are thus preferably attenuated so that they are not released from the x-ray device. For example, the outer housing/can may be provided with a shielding or liner made from an x-ray absorbing material, such as lead or a similar dense material. However, the use of such materials (e.g., lead) can be problematic. For instance, care must be taken in the manufacturing and assembly processes to protect workers and the environment from excessive lead exposure. Further, care must be taken in the disposal of such potentially hazardous materials. Moreover, it is difficult in practice to effectively shield all parts of the x-ray device to completely prevent x-rays from exiting in unwanted locations. In particular, the electrical leads or conductors used to provide the filament power and the high voltage potentials to the x-ray tube must be supplied via connectors through a openings formed through the x-ray tube housing. Because of the high voltages involved, to avoid arcing and/or related electrical problems, such connectors are usually provided in the form of a receptacle that is made of a dielectric material. Unfortunately, and depending upon the specific geometry of the x-ray device, a fraction of the off-focus x-rays produced can travel along paths that can allow them to escape the x-ray tube housing through the openings provided to accommodate the high voltage receptacle/connector. Consequently, further shielding of the high voltage receptacle is required. However, this adds additional cost and complexity to the manufacturing and assembly process, and often entails more extensive handling of, and consequent exposure to, lead materials by assembly personnel.
Thus, it would be an improvement in the art to provide a high voltage receptacle that effectively prevents x-rays from exiting the x-ray device. Moreover, it would be desirable if the connector would be implemented in a manner such that the additional costs, complexities, and health risks associated with conventional x-ray shielding materials—such as lead—were minimized.
OBJECTIVES AND SUMMARY OF EMBODIMENTS OF THE INVENTION
It is therefore a general objective of the present invention to provide a high voltage receptacle for use with an x-ray device that is capable of attenuating x-ray radiation.
Another objective is to provide a high voltage receptacle that does not require the use of lead lining or separate shielding structures to provide x-ray attenuation.
Still another objective is to provide a receptacle that is comprised of a dielectric material that permits use in the high voltage environment of an x-ray tube.
A related objective is to provide an x-ray tube housing assembly formed integrally with the high voltage receptacle so as to provide improved attenuation of off-focus radiation.
In accordance with these and other objects, embodiments of the present invention are directed to high voltage receptacles and x-ray tube housing assemblies wherein at least a portion of the receptacle or housing assembly is formed of a material having both dielectric and radiation attenuating properties. In one embodiment, the present invention provides a high voltage receptacle formed of a dielectric material, such as a dielectric thermoset plastic, which is doped or filled with an x-ray attenuating material, such as a metal-containing compound. In a preferred embodiment, the high voltage receptacle is molded from a mixture of a dielectric plastic and a heavy metal sulfate or oxide, thereby providing both dielectric and radiation attenuating properties within a single structure. This eliminates the need for additional radiation shielding components, such as lead liners or shields, and thus minimizes related health and/or environmental risks. Moreover, the elimination of traditional shielding components reduces the manufacturing complexity and costs.
In another preferred embodiment, an x-ray tube housing assembly having an x-ray tube housing and a high voltage receptacle is provided. In this embodiment, the high voltage receptacle and at least a portion of the x-ray tube housing are formed as a single integral structure from the dielectric material and an x-ray attenuating material. Again, this provides for an improved and less complex assembly that exhibits superior shielding of off-focus x-rays.
Preferred embodiments of the present invention use conventional dielectric materials such as thermoset plastics in combination with metal-containing compounds having good radiation attenuation properties, such as heavy metal sulfates and heavy metal oxides. Preferred metals include lead, bismuth, barium, tellurium and strontium, and preferred x-ray attenuating compounds include lead oxide, bismuth oxide, barium sulfate, tellurium oxide and strontium sulfate. hi practice, the combination of a dielectric material and an x-ray attenuating material in the high voltage receptacle and optionally in a portion of the x-ray tube housing essentially prevents x-rays from exiting the x-ray device through the receptacle opening.
These and other objects, features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
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Kiknadze Irakli
Kim Robert H.
Varian Medical Systems Inc.
Workman & Nydegger & Seeley
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