X-ray tube and medical imaging device having the same

Abstract

The present invention provides an X-ray tube, comprising an electron emitter; the X-ray tube further comprises a switching assembly, the switching assembly comprising a first power supply and an electron transmission layer relative to the electron emitter, two opposite sides of the electron transmission layer being electrically connected to the positive electrode and the negative electrode of the first power supply respectively, and the voltage of the first power supply can be changed and the transmittance of the electron transmission layer to the electrons emitted by the electron emitter can be adjusted. The X-ray tube provided by the present invention realizes the control and adjustment of the electron emission amount by setting the electron transmission layer and utilizing the adjustable penetration of the electron transmission layer to the electrons emitted by the electron emitter under the first power supply, which has a good improvement in the timeliness, precision and accuracy of the control.

Description

Technical Field

[0001] The present invention relates to the technical field of medical imaging, and in particular to an X-ray tube and a medical imaging device having the X-ray tube. Background Art

[0002] Dual-energy computed tomography (CT) can analyze the composition of a material by utilizing the different absorption characteristics of X-rays at different energy levels, thereby improving its ability to develop soft tissues and having a very high clinical application value. As a type of dual-energy CT, the rapid kilovolt switching of single-source CT has the advantages of being simultaneous, homologous, and homodirectional compared to traditional dual-source CT, and is an excellent dual-energy imaging method.

[0003] X-ray sources mainly generate thermal electrons by electrically heating the cathode filament to 1900-2600℃ through the current of the electron emitter. In order to achieve consistent radiation dose of the X-ray source in dual-energy CT and increase the clarity of dual-energy imaging, the electron emitter needs to emit different numbers of electrons to the anode while switching between high energy (such as 140kV) and low energy (such as 80kV). However, as people's requirements for the accuracy of X-rays become higher and higher, high-voltage generators can quickly switch kilovolts at a speed of microseconds. Although the current switching speed of the electron emitter can reach the same microsecond level, due to the hysteresis of the temperature rise and fall of the cathode filament, it is impossible to quickly heat up or cool down with the current change of the electron emitter, and it is still difficult to synchronously control the number of electrons escaping to the anode. Summary of the invention

[0004] In view of this, it is necessary to provide an improved X-ray tube and medical imaging equipment.

[0005] The present invention provides an X-ray tube, comprising an electron emitter; the X-ray tube also comprises a switching component, the switching component comprises a first power supply and an electron transmission layer relative to the electron emitter, two opposite sides of the electron transmission layer are respectively electrically connected to the positive electrode and the negative electrode of the first power supply, the voltage of the first power supply can be changed and the transmittance of the electron transmission layer to the electrons emitted by the electron emitter can be adjusted.

[0006] Furthermore, the electron transmission layer is a secondary electron amplification film.

[0007] Furthermore, the secondary electron amplifying film is a diamond film.

[0008] Furthermore, the first side of the diamond film is coated with a conductive layer.

[0009] Furthermore, the conductive layer is one of a zinc-plated layer, a gold-plated layer or a copper-plated layer.

[0010] Furthermore, a potential reducing layer is provided on the second side of the diamond film.

[0011] Furthermore, the potential-reducing layer is a hydrogenated layer or a cesiumated layer.

[0012] Furthermore, two opposite side surfaces of the electron transmission layer are electrically connected to the positive electrode and the negative electrode of the first power source through the conductive layer and the potential reduction layer respectively.

[0013] Furthermore, the electron emission direction of the electron emitter is perpendicular to the electron transmission layer.

[0014] The present invention provides a medical imaging device, comprising an X-ray tube, wherein the X-ray tube is any one of the X-ray tubes described above.

[0015] The X-ray tube provided by the present invention realizes control and regulation of the electron emission amount by setting an electron transmission layer, utilizing the adjustable penetration of the electron transmission layer into the electrons emitted by the electron emitter under the first power supply, thereby greatly improving the control timeliness, precision and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. 1 is a schematic diagram of the structure of an X-ray tube in one embodiment of the present invention.

[0017] Main component symbols

[0018] X-ray tube 100 Electron Emitter 10 Second power supply 11 Target 20 Switching components 30 Electron Transmitting Layer 31 Diamond film 32 Conductive layer 321 Downward layer 322

[0019] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly mounted on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time. When a component is considered to be "fixed to" another component, it may be directly fixed on the other component or there may be a central component at the same time.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0023] See also Figure 1 , Figure 1 FIG. 1 is a schematic structural diagram of an X-ray tube 100 according to an embodiment of the present invention.

[0024] The X-ray tube 100 is used to emit X-rays, which can use accelerated electrons to impact a metal target, and release part of the energy of the electrons (about 1%) in the form of photons through the kinetic energy loss of the electrons during the impact (braking radiation), thereby emitting X-rays with a continuous X-ray spectrum. Alternatively, electrons can knock out inner-shell electrons of metal atoms so that the outer-shell electrons of the atoms can transition to the inner-shell (characteristic radiation), thereby emitting X-rays with a characteristic X-ray spectrum (characteristic radiation).

[0025] In this embodiment, the X-ray tube 100 is applied to medical imaging equipment, which can be used for X-ray emission of single-modality medical imaging equipment, such as CT machines, CR machines, and DR machines, etc.; it can also be used for X-ray emission of multi-modality medical imaging equipment, such as PET / CT machines, etc.

[0026] It is understandable that the present invention does not limit the application of the X-ray tube 100 to medical imaging equipment; in other embodiments, the X-ray tube 100 can also be used in industrial flaw detection, safety testing, biomacromolecule analysis, X-ray satellite navigation and other fields.

[0027] Specifically, the X-ray tube 100 includes a tube shell (not shown), a cathode assembly (not shown) and an anode assembly (not shown). The interior of the tube shell forms a closed vacuum space. The anode assembly and the cathode assembly are both accommodated in the vacuum space inside the tube shell, and the anode assembly and the cathode assembly are arranged relative to each other.

[0028] The tube shell is used to accommodate and carry the cathode assembly and the anode assembly. The cathode assembly is used to emit electron beams, and the anode assembly is used to withstand the electron beams emitted by the cathode assembly. The electron beam emitted by the cathode assembly is transmitted in a low-loss state in the vacuum space provided by the tube shell, and is accelerated and bombarded to the surface of the anode assembly under the action of an external electric field, and emits X-rays using the principle of characteristic radiation or braking radiation.

[0029] As for the structure of the tube shell itself, it can adopt a conventional structure, and can be made of glass, or other materials other than glass, such as ceramics or metal, as long as the tube shell itself can form a closed vacuum environment.

[0030] The cathode assembly includes an electron emitter 10 and a second power source 11 electrically connected to the electron emitter 10. The second power source 11 supplies power to the electron emitter 10 through a driving circuit (not shown), thereby driving the electron emitter to emit an electron beam. The structure of the electron emitter can be a spiral coil, a D-shape, a planar emitter, etc., as long as it can emit an electron beam after being powered on. The material of the electron emitter can be tungsten or other materials that can emit electron beams after being powered on.

[0031] The electron emitter generates high temperature (generally greater than 2000K) when driven by the electron emitter driving circuit. At this time, the surface electrons of the electron emitter have sufficient escape energy due to the high temperature and escape from the surface of the electron emitter in the form of thermal motion. From a macroscopic perspective, this manifests itself as the electron emitter emitting an electron beam.

[0032] The anode assembly includes a target plate 20 and a rotating shaft (not shown) for driving the target plate 20 to rotate. The target plate 20 is arranged opposite to the electron emitter and connected to the rotating shaft. The target plate 20 is used to receive and withstand the electron beam emitted by the electron emitter. The surface of the target plate 20 that directly withstands the bombardment of the electron beam (often referred to as the focus) generates and emits X-rays; the rotating shaft is used to drive the target plate 20 to rotate.

[0033] The X-ray tube 100 provided by the present invention is a rotating anode X-ray tube, in which the electron beam emitted by the electron emitter bombards the surface of the target disk 20, and most of its kinetic energy (more than 99%) is dissipated as heat energy after encountering the obstruction of the surface of the target disk 20; due to the high-speed rotation of the target disk 20, the focus position directly carrying the electron beam on the target disk 20 is continuously changed, thereby improving the heat dissipation effect and extending the life of the target disk 20, which is also the direct reason why the rotating anode X-ray tube can gradually replace the fixed anode X-ray tube.

[0034] The shape of the target plate 20 itself can be a disk or other shapes such as a column. In order to increase the thermal conductivity of the target plate 20, the interior of the target plate 20 can be set to be hollow, and correspondingly filled with materials for increasing the heat dissipation effect. Since the target plate 20 will accumulate a large amount of heat when it is bombarded by the electron beam, the operating temperature of the target plate 20 is generally above 1200°C, and may even reach 1800°C. Therefore, the material of the target plate 20 is preferably an alloy material with good thermal conductivity and a high melting point, such as copper, cobalt, nickel, iron, and aluminum.

[0035] In this embodiment, the target disk 20 and the electron emitter are eccentrically arranged, that is, the electron emitter is not arranged relative to the axis of the target disk 20 (that is, the axis of the rotating shaft), but is eccentrically arranged with respect to the axis of the target disk 20. At this time, the bombardment receiving area of ​​the target disk 20 has a larger rotation linear speed, and the heat dissipation effect is better.

[0036] Existing X-ray tubes heat the electron emitter through a second power source, and use the electron overflow of the electron emitter at high temperature (mostly 1900°C to 2600°C) to generate hot electrons. In medical imaging equipment such as dual-energy CT that requires rapid changes in X-ray characteristic parameters, the X-ray tube needs to quickly switch between high energy (such as 140kV) and low energy (such as 80kV) so that the target disk can emit different numbers of electrons. Although the current second power source can use a high-voltage generator and can achieve microsecond-level kilovolt switching, there is still a lag between the temperature rise and fall of the electron emitter and the voltage change between the high-voltage generators. It is impossible to quickly heat up or cool down with the current change of the electron emitter, and it is still difficult to synchronously control the number of electrons escaping to the target disk.

[0037] The X-ray tube 100 provided by the present invention is also provided with a switching component 30. The X-ray tube 100 provided by the present invention realizes rapid switching of the electron emission amount by providing the switching component 30 and utilizing the adjustable permeability of the electrons emitted by the electron emitter 10 by the switching component 30.

[0038] Specifically, the switching component 30 includes a first power supply (not shown) and an electron transmission layer 31 relative to the electron emitter 10. The first power supply is used to apply an electric field to the electron transmission layer 31. The electron transmission layer 31 is used to absorb the primary electrons emitted by the electron emitter 10 and release secondary electrons. Under the loading of the first power supply, the secondary electrons released by the electron transmission layer 31 can be more than the primary electrons released by the electron emitter 10, so that the emission amount of the electron beam (that is, the emission amount of secondary electrons) can be adjusted by adjusting the voltage of the first power supply.

[0039] It is necessary to explain that the "transmittance" of the electron transmission layer 31 to the electrons emitted by the electron emitter 10 referred to in this article refers to the ratio between the amount of electrons emitted by the electron transmission layer 31 and the initial amount of electrons emitted by the electron emitter 10; in essence, the electrons derived from the electron transmission layer 31 are not generated by the transmission of the initial electrons emitted by the electron emitter 10; this only indicates the quantitative relationship between the amount of electrons emitted by the electron transmission layer 31 and the initial amount of electrons emitted by the electron emitter 10, and does not represent the derivation mechanism between the two.

[0040] The excitation mechanism of electrons by the electron transmission layer 31 is briefly described below:

[0041] After the primary electrons are injected into the electron transmission layer 31, the electrons in the electron transmission layer 31 are excited by the primary electrons, transition from a low energy state to a high energy state, and move toward the surface from the location where the excitation occurs. In the process of moving toward the surface, the secondary electrons collide with free electrons, lattice atoms, and lattice defects, and recombine with ions to lose energy. The internal secondary electrons that reach the surface overcome the surface potential barrier and escape.

[0042] Therefore, the amount of electrons can be controlled by controlling the voltage of the first power supply. Since the voltage regulation of the first power supply can directly affect the amount of electron emission without hysteresis, the control precision and accuracy of the amount of electron emission are improved.

[0043] The X-ray tube 100 provided by the present invention is provided with an electron transmission layer 31, and uses the electron transmission layer 31 to control and adjust the electron emission amount by adjustable penetration of electrons emitted by the electron emitter 10 under the first power supply, thereby greatly improving the control timeliness, precision and accuracy.

[0044] In this embodiment, the electron transmission layer 31 is a secondary electron amplifying film; in this case, the emission amount of secondary electrons can be greater than the emission amount of primary electrons, which is beneficial to reduce the amount of primary electrons required to be emitted by the electron emitter 10 and reduce the operating temperature of the electron emitter 10. According to actual detection, the equivalent emission amount of electrons generated by the secondary electron amplifying film can reduce the operating temperature of the electron emitter 10 by an order of magnitude.

[0045] It can be understood that in other embodiments, the electron transmission layer 31 may also be a transmission layer other than the secondary electron amplification film, as long as the electron transmission layer can adjust its own excitation amount of electrons under voltage.

[0046] At the same time, due to the amplification effect of secondary electrons, the first power supply does not need to switch at the kilovolt level, but can switch at the hundred-volt level or even tens of volts, thereby improving the reliability of switching.

[0047] In this embodiment, the secondary electron amplifying film is a diamond film 32. Since the diamond film 32 has better advantages in permeability adjustment range and cost than other films, the cost performance of the X-ray tube 100 can be improved.

[0048] In this embodiment, the two sides of the diamond film 32 are also coated with a conductive layer 321 and a potential reduction layer 322, respectively. The conductive layer 321 and the potential reduction layer 322 are respectively electrically connected to the positive electrode and the negative electrode of the first power supply. The conductive layer 321 is used to realize the application of the electric field of the first power supply to the diamond film 32, and the potential reduction layer 322 is used to reduce the negative electron affinity on the surface of the diamond film.

[0049] Further, the conductive layer 321 is one of a zinc-plated layer, a gold-plated layer or a copper-plated layer. At this time, the conductive layer 321 has better conductivity. It can be understood that in other embodiments, the conductive layer 321 can also use other plating layers besides the zinc-plated layer, the gold-plated layer or the copper-plated layer, as long as the conductive layer 321 can achieve the guidance of the first power supply power.

[0050] Further, the potential reducing layer 322 is a hydrogenated layer or a cesiumated layer. In this case, the potential reducing layer 322 has a better effect of reducing the negative electron affinity on the surface of the diamond film. It can be understood that in other embodiments, the potential reducing layer 322 can also use a functional coating other than a hydrogenated layer or a cesiumated layer, as long as the potential reducing layer 322 can reduce the negative electron affinity on the surface of the diamond film.

[0051] Furthermore, in order to improve the electron absorption rate of the electron transmission layer 31 to the electron emitter 10, the electron emission direction of the electron emitter 10 is perpendicular to the extension direction of the electron transmission layer 31. At this time, the electron transmission layer 31 has the best absorption rate to the electron emitter 10.

[0052] Of course, if the electron absorption rate of the electron transmission layer 31 to the electron emitter 10 is not considered, the extension direction of the electron transmission layer 31 and the electron emission direction of the electron emitter 10 may be at an angle other than 90°.

[0053] Since the first power supply can adjust the transmittance of the electron transmission layer 31 to the electrons emitted by the electron emitter 10 by changing its own voltage, the second power supply 11 does not need to adopt a periodic switching power supply and does not need to switch between 80KV or 110KV, which further reduces the performance requirements for the first power supply and reduces costs.

[0054] The present invention also provides a medical imaging system (not shown) using the above-mentioned X-ray tube 100. The medical imaging system emits X-rays by utilizing the above-mentioned X-ray tube 100, and irradiates the human body with the X-rays to form medical images.

[0055] In this embodiment, the medical imaging system is a CT machine. It is understood that in other embodiments, the medical imaging system can also be a dual-modality medical imaging device such as PET / CT.

[0056] The medical imaging system provided by the present invention can achieve accurate adjustment of the electron emission amount by adopting the above-mentioned X-ray tube 100.

[0057] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, appropriate changes and modifications to the above embodiments are within the scope of protection claimed by the present invention.

Claims

1. An X-ray tube comprising an electron emitter; characterized in that: The X-ray tube further comprises a switching assembly, the switching assembly comprising a first power supply and an electron transmission layer relative to the electron emitter, two opposite sides of the electron transmission layer are electrically connected to the positive electrode and the negative electrode of the first power supply respectively, the voltage of the first power supply can be changed and the transmittance of the electron transmission layer to the electrons emitted by the electron emitter can be adjusted; The two opposite sides of the electron transmission layer are respectively provided with a conductive layer and a potential reduction layer, and are electrically connected to the positive and negative electrodes of the first power source through the conductive layer and the potential reduction layer. The potential reduction layer is used to reduce the negative electron affinity on the surface of the electron transmission layer.

2. The X-ray tube according to claim 1, wherein The electron transmission layer is a secondary electron amplification film.

3. The X-ray tube according to claim 2, characterized in that The secondary electron amplifying film is a diamond film.

4. The X-ray tube according to claim 3, characterized in that The first side of the diamond film is coated with a conductive layer.

5. The X-ray tube according to claim 4, characterized in that The conductive layer is one of a zinc-plated layer, a gold-plated layer or a copper-plated layer.

6. The X-ray tube according to claim 1, wherein: The potential-reducing layer is a hydrogenation layer or a cesiumation layer.

7. The X-ray tube according to claim 1, wherein The electron emission direction of the electron emitter is perpendicular to the electron transmission layer.

8. A medical imaging device comprising an X-ray tube, characterized in that: The X-ray tube is the X-ray tube according to any one of claims 1 to 7.

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