Patent Application
20130083899
X-ray tubes are extremely valuable tools that are used in a wide variety of applications, both industrial and medical. An x-ray tube typically includes a cathode and an anode positioned within an evacuated enclosure. The cathode includes an electron emitter and the anode includes a target surface that is oriented to receive electrons emitted by the electron emitter. During operation of the x-ray tube, an electric current is applied to the electron emitter, which causes electrons to be produced by thermionic emission. The electrons are then accelerated toward the target surface of the anode by applying a high-voltage potential between the cathode assembly and the anode. When the electrons strike the anode target surface, the kinetic energy of the electrons causes the production of x-rays. The x-rays are produced in an omnidirectional fashion where the useful portion ultimately exits the x-ray tube through a window in the x-ray tube, and interacts with a material sample, patient, or other object with the remainder being absorbed by other structures including those whose specific purpose is absorption of x-rays with non-useful trajectories or energies.
During the operation of a typical x-ray tube, electrons are produced at a single energy resulting in x-rays having a distribution of energies with a mean value, herein referred to as x-ray energy. While having one x-ray energy is useful, in some situations it would be desirable to examine a material sample, patient, or other object with x-rays having different x-ray energies. For example, x-rays having multiple energies would be useful in baggage scanning applications where attempts are made to detect materials of different densities.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.
In general, example embodiments relate to dual-energy x-ray tubes. The example dual-energy x-ray tubes disclosed herein include two cathodes configured to emit electrons at different energies resulting in the generation of x-rays at different energies. Among other things, the generation of x-rays having different energies from a single x-ray tube can be useful in applications where attempts are made to detect materials of different densities.
In one example embodiment, a dual-energy x-ray tube includes an evacuated enclosure, an anode positioned within the evacuated enclosure, a first cathode positioned within the evacuated enclosure, and a second cathode positioned within the evacuated enclosure. The first cathode and the second cathode are configured to operate simultaneously at different voltages.
In another example embodiment, a dual-energy x-ray tube includes an evacuated enclosure, an anode positioned within the evacuated enclosure, a first cathode positioned within the evacuated enclosure, and a second cathode positioned within the evacuated enclosure. The anode is configured to operate at a positive high voltage. The first cathode is configured to operate at a negative high voltage. The second cathode is configured to operate at about zero voltage. The first cathode and the second cathode are configured to continuously operate simultaneously.
In yet another example embodiment, a dual-energy x-ray system includes a high-voltage generator configured to continuously generate a single positive high voltage and a single negative high voltage and an x-ray tube. The x-ray tube includes an evacuated enclosure, an anode positioned within the evacuated enclosure, a first cathode positioned within the evacuated enclosure, and a second cathode positioned within the evacuated enclosure. The anode is configured to operate at the single positive high voltage. The first cathode is configured to operate at the single negative high voltage. The second cathode is configured to operate at about zero voltage. The first cathode and the second cathode are configured to continuously operate simultaneously.
These and other aspects of example embodiments of the invention will become more fully apparent from the following description and appended claims.
To further clarify certain aspects of the present invention, a more particular description of the invention will be rendered by reference to example embodiments thereof which are disclosed in the appended drawings. It is appreciated that these drawings depict only example embodiments of the invention and are therefore not to be considered limiting of its scope. Aspects of example embodiments of the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Example embodiments of the present invention relate to dual-energy x-ray tubes. Reference will now be made to the drawings to describe various aspects of example embodiments of the invention. It is to be understood that the drawings are diagrammatic and schematic representations of such example embodiments, and are not limiting of the present invention, nor are they necessarily drawn to scale.
With reference first to
As disclosed in
The anode 108 and the first cathode 110 are connected in a first electrical circuit that allows for the application of a first high voltage potential between the anode 108 and the first cathode 110. Similarly, the anode 108 and the second cathode 112 are connected in a second electrical circuit that allows for the application of a second high voltage potential between the anode 108 and the second cathode 112. In order to create x-rays at dual energies, the anode 108 is configured to operate at a positive high voltage, the first cathode 110 is configured to operate at a negative high voltage, and the second cathode 112 is configured to operate at about zero voltage. Thus, the anode 108 and the first cathode 110 are both electrically insulated from about ground, while the second cathode 112 is not electrically insulated from about ground and thus requires no high-voltage stand-off.
With continued reference to
The target 118 is oriented so that many of the emitted x-rays are visible to the x-ray tube window 104. As the x-ray tube window 104 is comprised of an x-ray transmissive material, the x-rays emitted from the focal spot on the target 118 pass through the x-ray tube window 104 in order to image an intended target (not shown) to produce an x-ray image (not shown). The window 104 therefore hermetically seals the vacuum of the evacuated enclosure of the x-ray tube 100 from the atmospheric air pressure outside the x-ray tube 100 and yet enables the x-rays generated by the anode 108 to exit the x-ray tube 100.
As noted above, the cathodes 110 and 112 include emitters 114 and 116, respectively. The emitter 114 of the cathode 110 and the anode 108 are both configured to be electrically connected to an appropriate high-voltage generator (not shown). For example, a bi-polar high-voltage generator (not shown) may be configured to continuously generate a single positive high voltage and a single negative high voltage. The single positive high voltage can define the voltage potential of the anode 108 and the single negative high voltage can define the voltage potential of the cathode 110. An about ground voltage can define the voltage potential of the cathode 112. For example, the high-voltage generator (not shown) can be configured to produce a voltage potential on the anode 108 at a voltage between about 50 kV and about 320 kV and the first cathode 110 at a voltage between about −320 kV and about −50 kV.
In some example embodiments, the high-voltage generator (not shown) may be balanced such that the single positive high voltage is about opposite the single negative high voltage. For example, the anode 108 may be configured to operate at about 75 kV, the first cathode 110 may be configured to operate at about −75 kV, and the second cathode 112 may be configured to operate at 0 kV. This example results in the generation of x-rays at about 150 keV from the first cathode 110 and x-rays at about 75 keV from the second cathode 112. Thus, the operation of the second cathode 112 results in x-rays that are about half the energy of the x-rays that result from the operation of the first cathode 110.
In other example embodiments, the high-voltage generator (not shown) may be unbalanced such that the single positive high voltage is not opposite the single negative high voltage. For example, the anode 108 may be configured to operate at about 50 kV, the first cathode 110 may be configured to operate at about −100 kV, and the second cathode 112 may be configured to operate at 0 kV. This example results in the generation of x-rays at about 150 keV from the first cathode 110 and x-rays at about 50 keV from the second cathode 112. Thus, the operation of the second cathode 112 results in x-rays that are less than half the energy of the x-rays that result from the operation of the first cathode 110. It is understood that an unbalanced high-voltage generator (not shown) could alternatively be configured such that the operation of the second cathode 112 result in x-rays that are greater than half the energy of the x-rays that result from the operation of the first cathode 110. It is also noted that in this example the total voltage potential difference between the cathode 110 and the anode 108 is equal to the previous example at 150 keV, while the voltage potential difference between cathode 112 and the anode 108 is reduced to 50 keV.
Since both the cathodes 110 and 112 can operate simultaneously, the x-ray tube 100 is configured to generate x-rays at dual energies simultaneously or intermittently, with the energy of the x-rays produced by the cathode 110 being higher than the energy of the x-rays produced by the cathode 112. The x-ray tube 100 can therefore be employed in connection with an x-ray detector, such as a flat-panel detector, that is specifically designed to simultaneously detect x-rays at each of the dual energies.
With reference now to
The operation of the second example x-ray tube 200 of
The x-ray tube 200 is therefore configured to consecutively generate x-rays at dual energies, with the energy of the x-rays produced by the cathode 210 being higher than the energy of the x-rays produced by the cathode 212. The x-ray tube 200 can be employed in connection with an x-ray detector, such as a flat-panel detector, that is specifically designed to consecutively detect x-rays at each of the dual energies.
Although the example x-ray tubes 100 and 200 are depicted as stationary anode x-ray tubes, the example dual-energy x-ray configurations disclosed herein may alternatively be employed, for example, in rotatable anode x-ray tubes. Also, while the example x-ray tubes 100 and 200 are configured for use in baggage scanning applications, but it is understood that the dual-energy x-ray configurations disclosed herein can be employed in x-ray tubes configured for use in other applications including, but not limited to, other industrial or medical applications.
Further, while the example x-ray tube 100 is disclosed in connection with
The example embodiments disclosed herein may be embodied in other specific forms. The example embodiments disclosed herein are therefore to be considered in all respects only as illustrative and not restrictive.
