Patent Application
20070291903
In order that the manner in which the above-recited and other advantages and features of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Reference will now be made to the figures wherein like structures will be provided with like reference designations. It is understood that the drawings are diagrammatic and schematic representations of exemplary embodiments of the invention, and are not limiting of the present invention nor are they necessarily drawn to scale.
Reference is first made to
As is typical, a high-voltage potential is provided between anode 106 and cathode 108. In the illustrated embodiment, cathode 108 is biased by a power source (not shown) to have a large negative voltage, while anode 106 is maintained at ground potential. In other embodiments, the cathode is biased with a negative voltage while the anode is biased with a positive voltage. X-ray tubes featuring either of these biasing configurations can utilize cable connector assembly 200. Also, while x-ray tube 100 features a rotating anode, it is appreciated that stationary anode x-ray tubes can also benefit from cable connector assembly 200 described herein.
Cathode 108 includes at least one filament 114 that is electrically connected to high-voltage cable connector assembly 200 through one or more conductive elements, illustrated in this embodiment as electrical leads 116. Electrical leads 116 are configured to connect with one or more conductive elements of cable connector assembly 200, illustrated in this embodiment as electrically conductive pins 214. Each of pins 214, in turn, connects to a conductor of a high-voltage cable, as shown in later figures. The high-voltage cable is, in turn, connected to a high-voltage power source (not shown). Cable connector assembly 200, via the high-voltage cable, the conductors within the cable, pins 214, and electrical lead 116, facilitates the provision of an electrical voltage bias to cathode 108, as well as an electric current to the filament 114 during x-ray tube operation. As such, cable connector assembly 200 couples electrical components of cathode 108 with the high-voltage cable. During operation, electrical current is passed through the filament 114 to cause electrons, designated at 118, to be emitted from cathode 108 by thermionic emission. Application of the high-voltage differential between anode 106 and cathode 108 then causes electrons 118 to accelerate from cathode filament 114 toward a focal track 120 that is positioned on a target surface of rotating anode 106. Focal track 120 is typically composed of tungsten or a similar material having a high atomic (“high Z”) number.
As electrons 118 accelerate, they gain a substantial amount of kinetic energy, and upon striking the target material on focal track 120, some of this kinetic energy is converted into electromagnetic waves of very high frequency, i.e., x-rays. At least some of the emitted x-rays, designated at 122, are directed through x-ray transmissive window 124 disposed in outer housing 102. Window 124 is comprised of an x-ray transmissive material so as to enable the x-rays to pass through window 124 and exit x-ray tube 100. The x-rays exiting the tube 100 can then be directed for penetration into an object, such as a patient's body during a medical evaluation, or a sample for purposes of materials analysis.
Other x-rays, however, emanate in undesired directions and, accordingly, are of no practical use. Some of these unusable x-rays emanate into focal track 120 or other portions of anode 106. These x-rays are absorbed and generally are not problematic insofar as x-ray device operators and other personnel and equipment in the surrounding area are concerned. As indicated in
Where, as discussed further below, terminal 204 is made from a material that is substantially non-transmissive to x-rays, terminal 204 functions as an x-ray shield for the x-rays in pattern 128 when operably connected to x-ray tube 100. Likewise, where, as also discussed further below, connector housing 202 is filled with a material that is substantially non-transmissive to x-rays, connector housing 202 functions as an x-ray shield for the x-rays in pattern 126. Absent making connector housing 202 and/or terminal 204 out of a material that is substantially non-transmissive to x-rays, it is necessary to provide x-ray shielding in order to shield the x-rays in patterns 128 and 126. This shielding can be provided by detachable shielding 130. However, constructing detachable shielding 130 out of a material substantially non-transmissive to x-rays is problematic. As can be seen from the expanding patterns 126 and 128, since detachable shielding 130 is further from anode 106 than terminal 204 is from anode 106, a larger area 132 of shielding material is required for detachable shielding 130 than the area 134 of shielding required when terminal 204 is made from shielding material. Likewise, since detachable shielding 130 is further from anode 106 than connector housing 202 is from anode 106, a larger area 136 of shielding material is required for detachable shielding 130 than the area 138 of shielding required when connector housing 202 is made from shielding material.
Where terminal 204 is formed out of a conductive x-ray shielding material, such as brass, terminal 204 can be configured to function as a Faraday Cage with respect to the electrical connection between pins 214 and the corresponding electrical leads 116. A Faraday Cage is an equi-potential region in a high voltage field, created in this case to allow feeding electricity into the x-ray tube and prevent ionization of any air captured in the interface volume between cable connector assembly 200 and the x-ray tube 100. This interface volume is defined by an evacuated enclosure seal 140, an inner cathode housing 142, and terminal 204. The Faraday Cage removes the need to fill the interface volume with oil or create a vacuum in the interface volume in order to avoid the ionization of air trapped in the interface volume.
Reference is now made to
As illustrated in
Cable connector assembly 200 also includes cable ground lead 212, which is used to provide a ground for the components of cable connector assembly 200. Cable connector assembly 200 also includes one or more conductive elements, which are illustrated as electrically conductive pins 214. Each of pins 214 is electrically connected within connector housing 202 to a corresponding conductor within high-voltage cable 210, as discussed and illustrated below in connection with
As illustrated in
Connector housing 202, as discussed above, is formed from an insulating epoxy, such as a thermosetting plastic material. In order to maintain dialectic properties as well as provide x-ray shielding, this plastic can be filled with at least one x-ray attenuating material, or in other words, a material that is substantially non-transmissive to x-rays. This material can be any type of x-ray shielding material, such as, for example, a high Z material. Some suitable exemplary materials which can fill connector housing 202 include at least one of bismuth oxide, barium sulfate, or lead oxide. Since connector housing 202 is filled with a material that is substantially non-transmissive to x-rays, connector housing 202 functions as an x-ray shield with respect to a projected area defined by connector housing 202, illustrated in
At least one advantage of the x-ray shielding properties of terminal 204 is that terminal 204 is integral to cable connection assembly 200. In order for x-ray tube 100 to function and produce x-rays, cable connection assembly 200 must be operably connected to x-ray tube 100. Since x-ray shielding is integrated into terminal 204 of cable connection assembly 200, x-ray tube 100 will not function unless the x-ray shielding integrated into terminal 204 is in place. Likewise, where x-ray shielding is integrated into connector housing 202 of cable connection assembly 200, x-ray tube 100 will not function unless the x-ray shielding integrated into connector housing 202 is in place. Unlike detachable shielding configured to surround cable connector assembly 200, the shielding integrated into terminal 204 or connector housing 202 can not be inadvertently missing during the operation of x-ray tube 100.
The disclosed embodiments are to be considered in all respects only as exemplary and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing disclosure. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
