Patent Application
20130322602
The disclosure relates generally to an x-ray tube and more specifically to methods and structures for shielding x-rays within the x-ray tube.
Traditional x-ray imaging system includes an x-ray source and a detector array. The x-ray source generates x-rays that pass through an object under scan. These x-rays are attenuated while passing through the object and are received by the detector array. The detector array includes detector elements that produce a separate electrical signal indicative of the attenuated x-rays received by each detector element. Further, the produced electrical signals are transmitted to a data processing system for analysis, which ultimately produces an image.
Typically, the x-ray source includes an x-ray tube that generates x-rays in all directions around a focal spot. A portion of these x-rays may be utilized as intended x-rays for imaging the object that is under scan. However, a large portion of the x-rays are unintended or undesired x-rays that penetrate into other areas of the x-ray tube. Also, these unintended x-rays may escape from the x-ray source causing undesirable health effects to a user in an x-ray environment. In addition, these x-rays may interfere with the intended x-rays causing reduced image quality results. Thus, there is a need to shield these unintended x-rays to safeguard the user from undesirable health hazards and also to improve the quality of the reproduced image.
In a conventional x-ray imaging system, a lead lining is provided on a housing that contains the x-ray tube. The lead lining is used to absorb the unintended x-rays that penetrate through an evacuated enclosure of the x-ray tube. Although the lead lining provides radiation leakage resistance, the housing requires a large surface area to accommodate the lead lining of sufficient thickness. Also, the lead is relatively heavy and substantially adds to the weight of the x-ray tube.
In addition, a large amount of lead is used to cover relatively large portions of the enclosure surface to account for the radially expanding pattern of x-ray emission from the target surface. Indeed, nearly the entire surface area of the housing or the evacuated enclosure is covered by the lead lining to prevent x-ray emission from the tube. This addition of lead lining may in turn increase the cost of the x-ray tube. Also, since the lead lining is provided on the entire surface area of the housing, the time and labor for manufacturing each x-ray tube is substantially increased.
Hence, there is a need for an improved method and structure for shielding the x-rays within the x-ray tube. Also, there is need to substantially reduce the weight of the x-ray tube.
Briefly in accordance with one aspect of the present disclosure, an x-ray tube is presented. The x-ray tube includes a cathode unit configured to emit electrons. The x-ray tube further includes an anode unit positioned to receive the emitted electrons, wherein the anode unit includes a base having a target surface configured to generate x-rays when the emitted electrons impinge on the target surface. Also, the anode unit includes a first shielding unit enclosing the base to attenuate at least a first portion of the generated x-rays within the anode unit.
In accordance with a further aspect of the present disclosure, a method for shielding the x-rays within the x-ray tube is presented. The method includes emitting, by a cathode unit, electrons toward an anode unit. The method further includes generating x-rays when the emitted electrons impinge on a target surface of the anode unit. Also, the method includes attenuating at least a first portion of the generated x-rays within the anode unit by enclosing at least the target surface of the anode unit with a first shielding unit.
In accordance with another aspect of the present disclosure, an x-ray tube is presented. The x-ray tube includes a cathode unit comprising an electron source configured to emit electrons. Further, the x-ray tube includes an anode unit positioned to receive the emitted electrons, and configured to generate x-rays when the emitted electrons impinge on the anode unit. Also, the x-ray tube includes a first shielding unit enclosing the anode unit to attenuate at least a first portion of the generated x-rays within the anode unit. In addition, the x-ray tube includes a second shielding unit disposed at the cathode unit, and configured to attenuate at least the first portion of the generated x-rays exited through a first window of the first shielding unit.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
As will be described in detail hereinafter, various embodiments of an exemplary structures and methods for shielding x-rays within the x-ray tube are presented. By employing the methods and the various embodiments of the x-ray shielding structures described hereinafter, the weight of the x-ray tube is substantially reduced. Also, the cost and time for manufacturing the x-ray tube is substantially reduced.
Referring to
Further, the anode unit 104 includes a support platform 110 and a base 112 having a target surface 114. The base 112 is coupled to the support platform 110 and the target surface 114 is disposed atop of the base 112. Also, the target surface 114 is positioned in the direction of emitted electrons to receive the electrons from the cathode unit 102. Particularly, in the embodiment of
During operation, the cathode unit 102 generates electrons that are accelerated towards the target surface 114 of the anode unit 104 by applying a high voltage potential between the cathode unit 102 and the anode unit 104. These electrons impinge upon the target surface 114 at a focal spot and release kinetic energy as electromagnetic radiation of very high frequency, i.e., x-rays. Particularly, the electrons are rapidly decelerated upon striking the target surface 114, and in the process, the x-rays are generated therefrom. These x-rays emanate in all directions from the target surface 114. A portion of these x-rays does indeed pass through an outlet 116 of the evacuated enclosure 106 to exit the x-ray tube and be utilized to interact in or on a material sample, patient, or other object. In one embodiment, the target surface 114 may angled towards the outlet 116 of the evacuated enclosure 106 to maximize the number of x-rays produced at the target surface 114 that can exit the x-ray tube 100.
However, the remaining portions of the x-rays that do not pass through the outlet 116 of the evacuated enclosure 106 may penetrate through other areas of the evacuated enclosure 106 and may escape from the x-ray tube 100. It is to be noted that the portion of the x-rays that do not pass through the outlet of the evacuated enclosure is referred to as a first portion 118 of the x-rays or the unintended x-rays 118. Similarly, the portion of the x-rays that pass through the outlet of the evacuated enclosure is referred to as a second portion 120 of the x-rays or the intended x-rays 120. Further, the first portion 118 of the x-rays may scatter at a plurality of angles from the target surface 114. Also, the first portion 118 of the x-rays that penetrate through the evacuated enclosure 106 may represent a significant source of x-ray contamination to the x-ray tube 100 or device surroundings. For instance, users of the x-ray tube 100 may receive relatively high doses of x-ray radiation, which may result in adverse health effects.
To address these shortcomings or problems, a shielding unit 122 is employed within the evacuated enclosure 106 to resist leakage of x-rays from the x-ray tube 100. Particularly, a first shielding unit 122 is disposed at the anode unit 104 to shield the first portion 118 of the x-rays within the anode unit 104. More specifically, the first shielding unit 122 is used to enclose the anode unit 104 so that the first portion 118 of the x-rays is attenuated within the anode unit 104. In one embodiment, the first shielding unit 122 may include a tungsten layer that is placed around the base 112 of the anode unit 104. Since the first portion 118 of the x-rays is shielded within the evacuated enclosure 106, specifically at the focal spot, the surface area for disposing the shielding unit 122 is substantially reduced. Also, as the surface area for disposing the shielding unit 122 is reduced, the size of the shielding unit 122 is reduced, which in turn reduces the weight and cost of the x-ray tube 100. In one example, the first shielding unit 122 may have a thickness in a range from about 1 mm to about 10 mm and a diameter in a range from about 20 mm to about 40 mm. It is to be noted that the thickness and the diameter of the shielding unit may vary depending upon the voltage (HV) and current (mAs) provided to the x-ray tube 100. Also, the first shielding unit 122 may have a length in a range from about 10 mm to about 30 mm. Further, the first shielding unit 122 includes a tungsten copper alloy material for attenuating the first portion 118 of the x-rays. The tungsten copper alloy may be easily molded to a desired shape. Also, the tungsten copper alloy may be easily brazed to the copper base 112 of the anode unit 104.
In the embodiment of
In a similar manner, the second window 126 is aligned along the outlet 116 of the evacuated enclosure 106 to exit the intended or second portion 120 of the x-rays from the anode unit 104. The length 138 of the second window 126 may be in a range from about 5mm to about 25 mm. Further, the exited second portion of x-rays may be utilized to scan the object. Also, the c-shaped structure may provide a vacuum passage/gap 134 at the target surface 114 of the anode unit 104 to allow the electrons to impinge on the target surface 114 and generate the x-rays. Particularly, the vacuum passage/gap 134 is provided between the windows 124, 126 of the first shielding unit 122 and the target surface 114 of the anode unit 104.
In addition, open ends 127, 128 of the c-shaped structure 122 are rigidly coupled to the support platform 110 of the anode unit 104. Also, the walls 130, 132 of the c-shaped structure may be integrated with the base 112 of the anode unit 104, as depicted in
Thus, by employing the shielding unit 122 within the evacuated enclosure 106, the radiation of unintended x-rays surrounding the x-ray tube 100 is substantially reduced. Also, as the shielding unit 122 is provided within the evacuated enclosure 106, the surface area utilized to shield the x-rays is substantially minimized, which in turn reduces the weight of the x-ray tube or device 100.
Further, the second shielding unit 204 is disposed outside the evacuated enclosure 106, as depicted in
Moreover, the second shielding unit 204 is positioned outside the evacuated enclosure 106 facing the second end 208 of the cathode unit 102. Particularly, the second shielding unit 204 may be positioned to face the first window 124 to collect the unintended x-rays generated at the anode unit 104. In one embodiment, the second shielding unit 204 may be a disc like structure that is rigidly coupled to an outer surface of the evacuated enclosure 106 at the second end 208 of the cathode unit 102, as depicted in
Referring to
Additionally, at step 304, x-rays are generated at the anode unit 104 when the emitted electrons impinge on a target surface 114 of the anode unit 104. Particularly, the electrons are accelerated towards the target surface 114 of the anode unit 104 by applying a high voltage potential between the cathode unit 102 and the anode unit 104. These electrons impinge upon the target surface 114 at a focal spot and release kinetic energy as electromagnetic radiation of very high frequency, i.e., x-rays. These x-rays may include a first portion 118 of the x-rays and a second portion 120 of the x-rays. The first portion 118 of the x-rays emanate in all directions from the target surface 114. Particularly, the first portion 118 of the x-rays may penetrate through other areas of the evacuated enclosure 106 and may escape from the x-ray tube 100. On the other hand, the second portion 120 of the x-rays may pass through an outlet 116 of the evacuated enclosure 106 to exit the x-ray tube 100 and may be utilized to scan the object.
Further, at step 306, the first portion of the generated x-rays may be attenuated within the anode unit 104 by enclosing at least the target surface 114 of the anode unit 104. To that end, the first shielding unit 122 is enclosed within the evacuated enclosure 106, particularly over the target surface 114 of the anode unit 104, to absorb or attenuate the first portion 118 of the x-rays that scatter at one or more angles from the target surface 114. In addition to the first shielding unit, the second shielding unit 204 may be disposed at the cathode unit 102 to absorb or attenuate the first portion 118 of the x-rays that passes through the first window 124 of the first shielding unit 122. Thus, by employing the shielding units 122 and 204 within the evacuated enclosure 106, the radiation of unintended x-rays surrounding the x-ray tube 100 is substantially reduced. Also, as the shielding units 122 and 204 are provided within the evacuated enclosure 106, the surface area utilized to shield the x-rays is substantially minimized, which in turn reduces the weight of the x-ray tube 100 and also cost and time for manufacturing the x-ray tube 100.
The various embodiments of the method and the structures of the x-ray tube aid in shielding the unintended x-rays within the x-ray tube. Also, as the shielding unit is disposed within the evacuated enclosure, the weight of the x-ray tube is substantially reduced. Also, by disposing the shielding unit within the evacuated enclosure, the surface area that is used for shielding the x-rays is reduced, which in turn reduces the cost and time for manufacturing the x-ray tube.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
