Reflection type microfocus X-ray tube and imaging system

Abstract

The utility model provides a reflective microfocus X-ray tube and an imaging system, an exit port of the X-ray tube is provided with two layers of exit windows, a first exit window cover is provided with a filter, and the thickness of the filter is gradually increased and then gradually reduced along the movement direction of electron beams. A traditional flat plate type structure with the uniform thickness is replaced with the asymmetric wedge block type structure with the non-uniform thickness, and the positions with the high light intensity and the positions with the low light intensity are filtered through the thick area and the thin area of the filter respectively, so that the light intensity distribution of X rays emitted by the X-ray tube can be more uniform, and the light intensity uniformity is improved. The second emergent window is arranged at the end part of the metal cover, and the metal cover is arranged near an anode target material and is used for capturing electrons scattered by the target material, reducing the generation of stray rays and improving the quality of an X-ray beam; the second emergent window is used for reducing the attenuation of the metal cover to the emergent X-rays; and meanwhile, the mounted transmission sheet can play a role in improving the field intensity distribution of the anode and filtering the low-energy X-rays.

Description

Technical Field

[0001] The utility model relates to the technical field of X-ray tubes, in particular to a reflective micro-focus X-ray tube and an imaging system. Background Art

[0002] X-ray tubes can be divided into reflection and transmission types based on their anode structure. In reflection X-ray tubes, the anode target surface is tilted at a certain angle to the incident electron beam, which increases the heat dissipation area. The substrate is typically made of oxygen-free copper, a material with a high thermal conductivity, further improving the heat dissipation efficiency of the entire tube core. However, a disadvantage is the heel effect, which causes uneven light intensity distribution within the X-ray tube's radiation range. The X-ray intensity near the anode target is significantly lower than that near the cathode.

[0003] To mitigate the heel effect, existing technologies typically increase the focus-to-object distance, the target angle of the anode target, and external flat-plate filters. However, for some imaging systems with high resolution requirements and strict system volume requirements, the focus-to-object distance needs to be kept within a small range, making this method unsuitable. While increasing the target angle can effectively improve the heel effect, it has a significant impact on the focal spot size. For X-ray tubes with high resolution requirements, the target angle needs to be kept within a small range, making it unsuitable. Compared to the first two methods, the external flat-plate filter method has the advantage of not changing the original imaging system geometry and X-ray tube configuration. Currently, this method mostly involves users adding external flat-plate filters themselves. However, the thickness design and position of the filters are highly dependent on each other, resulting in poor versatility. In addition, the flat-plate filters have essentially the same attenuation level at each location in the radiation space, making it difficult to adapt the filtering to the uneven intensity distribution at each location in the radiation space. Utility Model Content

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a reflective microfocus X-ray tube, comprising:

[0005] A cathode outer cylinder, wherein the vacuum inner cavity of the cathode outer cylinder is provided with a cathode for emitting an electron beam;

[0006] A conductive shell is cylindrical and vertically connected to the cathode outer cylinder. A target material is provided in the inner cavity of the conductive shell, and the target material generates X-rays when bombarded by an electron beam. A first exit window is provided on the first end face of the conductive shell perpendicular to the axis. The first exit window cover is provided with a filter. Along the movement direction of the electron beam, the thickness of the filter first gradually increases and then gradually decreases.

[0007] Optionally, it further includes a glass shell, which is coaxially connected to the second end face of the conductive shell opposite to the first end face. An anode rod is provided at the axis of the glass shell. The anode rod extends to the first end of the conductive shell and is an inclined surface facing the cathode. The target material is located on the inclined surface.

[0008] Optionally, it also includes an anode cover sleeved on the first end of the anode rod, the end face of the anode cover close to the first exit window and perpendicular to the axis is the second exit window, the second exit window cover is provided with a transmissive sheet, and the side wall area of the anode cover close to the cathode is provided with an opening for the electron beam to pass through.

[0009] Optionally, the transmission plate is a beryllium plate.

[0010] Optionally, the filter sheet is an aluminum sheet.

[0011] Optionally, the filter sheet is an asymmetric wedge-shaped structure with non-uniform thickness.

[0012] Optionally, the axis of the electron beam passes through a center point of the target.

[0013] Optionally, the filter sheet is a wedge-shaped sheet, with a thicker side of the wedge-shaped sheet facing the cathode end.

[0014] Optionally, the inner cavity of the cathode outer cylinder is further provided with a hot wire for heating the cathode and a focusing electrode for controlling the shape of the electron beam.

[0015] An imaging system includes the X-ray tube and an X-ray detector.

[0016] As described above, the present invention provides a reflective microfocus X-ray tube and imaging system, wherein the X-ray tube has a two-layer exit window at its exit port. The first exit window is covered with a filter, and the thickness of the filter gradually decreases along the direction of motion of the electron beam. Here, an asymmetric, non-uniform wedge-shaped structure is used to replace the traditional uniform-thickness flat plate structure. For locations with higher light intensity, the thicker area of the filter is used for filtering, and for locations with lower light intensity, the thinner area of the filter is used for filtering. This can make the intensity distribution of the X-rays emitted by the X-ray tube more uniform, thereby improving the intensity uniformity and imaging quality. The second exit window is opened at the end of the metal cover, which is installed near the anode target material to capture electrons scattered by the target material, reduce the generation of stray rays, and improve the quality of the X-ray beam. The second exit window is used to reduce the attenuation of the metal cover on the emitted X-rays, and the installed transmission film can improve the anode field intensity distribution and filter low-energy X-rays. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a schematic diagram of the overall structure of the X-ray tube in Example 1 of the present utility model.

[0018] Figure 2 Shown is a schematic structural diagram of a wedge-shaped filter disc in Example 1 of the present invention.

[0019] Figure 3 It shows a schematic structural diagram of a flat-plate transmissive sheet in the first embodiment of the present invention.

[0020] Component number description

[0021] 1 hot wire

[0022] 2 cathode

[0023] 3 bunching pole

[0024] 4 Cathode outer cylinder

[0025] 5 filter

[0026] 6 Conductive shell

[0027] 7 Transmission film

[0028] 8 Target

[0029] 9 Anode cover

[0030] 10 Anode rod

[0031] 11 Glass Bulb

[0032] 91 Opening DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different perspectives and applications without departing from the spirit of the present invention.

[0034] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0035] Example 1

[0036] like Figures 1 to 3 As shown, this embodiment provides a reflective microfocus X-ray tube, comprising:

[0037] A cathode outer cylinder 4, wherein a cathode 2 is provided in a vacuum inner cavity of the cathode outer cylinder 4 for emitting an electron beam;

[0038] A conductive shell 6 is cylindrical and vertically connected to the cathode outer cylinder 4. A target material 8 is provided in the inner cavity of the conductive shell 6, and the target material 8 generates X-rays when bombarded by electrons. A first exit window is provided on the first end face of the conductive shell 6 perpendicular to the axis. The first exit window cover is provided with a filter 5. Along the movement direction of the electron beam, the thickness of the filter 5 first gradually increases and then gradually decreases.

[0039] Specifically, the conductive shell 6 is grounded during operation, which can reduce the charge accumulation around the anode assembly, improve the voltage resistance of the X-ray tube, and improve the stability of electron emission and electric field focusing; the conductive shell 6 can be made of stainless steel, oxygen-free copper and / or monel alloy, which is firm, reliable and economical.

[0040] The wedge-shaped filter 5 with varying thickness is specifically designed to correct for the heel effect. By using an asymmetric, non-uniformly thick wedge-shaped structure instead of the traditional uniformly thick flat plate structure, the thicker areas of the filter 5 are used to filter locations with higher light intensity, while the thinner areas of the filter 5 are used to filter locations with lower light intensity. This allows for a more uniform intensity distribution of the X-rays emitted by the X-ray tube. Because the X-ray intensity near the anode target is significantly lower than that near the cathode target, the thickness of the wedge-shaped filter 5 near the cathode end is designed to be greater than that near the anode end. This further attenuates the X-rays near the cathode 2 end, improving X-ray intensity uniformity and imaging quality. As a preferred embodiment, the filter 5 is a wedge-shaped piece, with the thicker side of the wedge facing the cathode 2 end.

[0041] There are three methods for structural design of the filter. The first is to design through pure experimental measurement. Filters 5 of different thicknesses are placed at the first exit window position in turn, and their light intensity distribution is measured. Then, the attenuation values of filters 5 of different thicknesses at various positions in the radiation space are analyzed. Through an asymmetric, non-uniform wedge-shaped structure, the light intensity at various positions in the radiation space is attenuated to the same value, and finally the light intensity distribution is evened out (advantage: high accuracy; disadvantage: low efficiency). The second is to design through pure simulation. Monte Carlo simulation software is used to model the X-ray tube. The light intensity distribution of filters 5 of different thicknesses placed at the first exit window position is simulated in turn. Then, the attenuation values of filters 5 of different thicknesses at various positions in the radiation space are analyzed. Through an asymmetric, non-uniform wedge-shaped structure, the light intensity at various positions in the radiation space is attenuated to the same value, and finally the light intensity distribution is evened out (advantage: high efficiency; disadvantage: low accuracy). The third method is to design by combining experiments and theories. First, the light intensity distribution of the first exit window is measured through experiments, and then the Monte Carlo simulation program is calibrated to match the simulation results with the experimental results. Then, the light intensity distribution of filters 5 of different thicknesses placed at the first exit window is simulated in turn, and the attenuation values of filters 5 of different thicknesses at various positions in the radiation space are analyzed. Through the wedge-shaped structure with asymmetric and non-uniform thickness, the light intensity at various positions in the radiation space is attenuated to the same value, and finally the light intensity distribution is smoothed. That is, the simulation calculation is combined with the actual test, taking into account the advantages of the first and second methods mentioned above (advantages: high efficiency and high accuracy).

[0042] Since the filter 5 is used to correct the heel effect, a portion of the X-ray tube's light intensity will be sacrificed. In order to reduce the attenuation of the X-rays and ensure that the filtered X-rays still have a certain intensity, the atomic number and density of the filter 5 material should not be too large. At the same time, considering the imaging magnification, the focus-to-object distance (Focus-to-object) should not be too large. Therefore, the thickness of the filter 5 should not be designed to be too thick, and the atomic number and density of the filter material should not be too small. Comprehensive analysis shows that aluminum Al is usually the most suitable material for the heel effect filter.

[0043] Furthermore, the inner cavity of the cathode outer cylinder 4 is further provided with: a hot wire 1 for heating the cathode 2; a bunching electrode 3 for controlling the shape of the electron beam;

[0044] Furthermore, the device includes a glass shell 11 coaxially connected to the second end face of the conductive housing 6, opposite the first end face. The glass shell 11 is an insulating medium, ensuring good insulation between the electrodes. An anode rod 10 is positioned at the axis of the glass shell 11. The first end of the anode rod 10, extending from the conductive housing 6, is inclined toward the cathode 2. The target 8 is positioned on the inclined surface. The anode rod 10 serves as a target carrier, possessing high-voltage resistance and thermal conductivity. The axis of the electron beam passes through the center point of the target 8, causing the electron beam to strike the target 8, thereby generating X-rays that are emitted through the first exit window.

[0045] Furthermore, it also includes an anode cover 9 that is sleeved on the first end of the anode rod 10, and the end face of the anode cover 9 close to the first exit window and perpendicular to the axis is the second exit window. The second exit window cover is provided with a transmission plate 7, and the side wall area of the anode cover 9 close to the cathode 2 is provided with an opening 91 for the electron beam to pass through.

[0046] Specifically, an anode shield 9, or metal shield, is installed near the anode target 8, at the same potential as the anode. This shield captures electrons scattered by the target 8, reducing stray radiation and improving X-ray beam quality. A flat second exit window is located along the X-ray emission direction of the shield to reduce the shield's attenuation of the outgoing X-rays. A transmissive sheet 7, typically made of low-atomic-number, low-density beryllium (Be), also serves to improve the anode field strength distribution and filter low-energy X-rays.

[0047] The entire X-ray tube operates as follows: a barium tungsten cathode 2 is selected, and the heat radiation from the hot filament 1 indirectly heats the cathode 2, generating electrons. The advantages of a barium tungsten cathode are its long lifespan and stable emission. Electrons emitted by the cathode 2 are accelerated by the anode voltage and focused by the buncher 3, striking the target 8 with high energy and small size, generating X-rays. Approximately 99% of this energy is converted into heat and deposited on the target 8, which is then conducted to the outside world through the anode rod 10 for dissipation. Only 1% is converted into X-rays. Passing through the second exit window filters out low-energy X-rays, while passing through the first exit window improves the uniformity of the spatial intensity of the radiation.

[0048] When the electron beam strikes the target 8, it generates a large number of scattered electrons. Without the anode shield 9, these scattered electrons would strike the conductive housing 6, generating stray X-rays that could affect imaging quality. Therefore, the anode shield 9 captures scattered electrons, reduces the generation of stray radiation, and improves X-ray beam quality. The anode shield 9 and the second exit window are at the same potential as the anode, improving the field strength distribution near the anode and preventing the emission of field-induced electrons.

[0049] The welding of the transmission sheet 7 of the second exit window and the anode cover 9 does not need to ensure airtightness, but only needs to be secure. The welding of the filter sheet 5 of the first exit window and the conductive housing 6 needs to ensure both airtightness and security.

[0050] Example 2

[0051] Based on the X-ray tube in the above-mentioned embodiment 1, this embodiment provides an imaging system, which includes the X-ray tube and an X-ray detector. The object to be detected is located between the X-ray tube and the X-ray detector. The object to be detected can be a body part, an industrial part, etc.

[0052] In summary, the present invention provides a reflective microfocus X-ray tube and imaging system, wherein the exit port of the X-ray tube is provided with two layers of exit windows, the first exit window cover is provided with a filter, and the thickness of the filter gradually decreases along the direction of movement of the electron beam. Here, an asymmetric, non-uniform thickness wedge-type structure is used to replace the traditional uniform thickness flat plate structure. For locations with stronger light intensity, the thicker area of the filter is used for filtering, and for locations with weaker light intensity, the thinner area of the filter is used for filtering. This can make the intensity distribution of the X-rays emitted by the X-ray tube more uniform, improve the intensity uniformity and imaging quality. The second exit window is opened at the end of the metal cover, and the metal cover is installed near the anode target material to capture electrons scattered by the target material, reduce the generation of stray rays, and improve the quality of the X-ray beam; the second exit window is used to reduce the attenuation of the metal cover on the outgoing X-rays, and the installed transmission film can improve the anode field intensity distribution and filter low-energy X-rays.

[0053] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed in the present invention are intended to be covered by the claims of the present invention.

Claims

1. A reflective microfocus X-ray tube, characterized in that: include: A cathode outer cylinder, wherein the vacuum inner cavity of the cathode outer cylinder is provided with a cathode for emitting an electron beam; A conductive shell is cylindrical and vertically connected to the cathode outer cylinder. A target material is provided in the inner cavity of the conductive shell, and the target material generates X-rays when bombarded by an electron beam. A first exit window is provided on the first end face of the conductive shell perpendicular to the axis. The first exit window cover is provided with a filter. Along the movement direction of the electron beam, the thickness of the filter first gradually increases and then gradually decreases.

2. The reflective microfocus X-ray tube according to claim 1, wherein: It also includes a glass shell, which is coaxially connected to the second end face of the conductive shell opposite to the first end face. An anode rod is provided at the axis of the glass shell. The anode rod extends to the first end of the conductive shell and is an inclined surface facing the cathode. The target material is located on the inclined surface.

3. The reflective microfocus X-ray tube according to claim 2, wherein: It also includes an anode cover sleeved on the first end of the anode rod, the end surface of the anode cover close to the first exit window and perpendicular to the axis is the second exit window, the second exit window cover is provided with a transmission plate, and the side wall area of the anode cover close to the cathode is provided with an opening for the electron beam to pass through.

4. The reflective microfocus X-ray tube according to claim 3, wherein: The transmission plate is a beryllium plate.

5. The reflective microfocus X-ray tube according to claim 1, wherein: The filter sheet is an aluminum sheet.

6. The reflective microfocus X-ray tube according to claim 1, wherein: The filter sheet is an asymmetric wedge-shaped structure with non-uniform thickness.

7. The reflective microfocus X-ray tube according to claim 1, wherein: The axis of the electron beam passes through the center point of the target.

8. The reflective microfocus X-ray tube according to claim 1, wherein: The filter sheet is a wedge-shaped sheet, with the thicker side of the wedge-shaped sheet facing the cathode end.

9. The reflective microfocus X-ray tube according to claim 1, wherein: The inner cavity of the cathode outer cylinder is also provided with a hot wire for heating the cathode and a focusing electrode for controlling the shape of the electron beam.

10. An imaging system, characterized in that: The imaging system comprises the X-ray tube according to any one of claims 1 to 9, and further comprises an X-ray detector.

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