X-ray shielding element comprising a lead substitute

Abstract

A shielding element (5, 6) for shielding X-rays (3) has a base body (7). The base body (7) consists of a composite material containing a plastic (8) in which a metal powder (9) is contained, by means of which the X-rays (3) can be absorbed. The base body (7) is coated by a continuous layer (10) of a conductive material, such that the base body (7) is completely encased by the layer (10) of the conductive material.

Description

[0001] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0002] The present invention relates to a shielding element for shielding X-ray radiation, wherein the shielding element has a base body, wherein the base body consists of a composite material containing a plastic in which a powder of a metal is contained, by means of which the X-ray radiation can be absorbed.

[0003] Such shielding elements are generally known. Examples include WO 2005 / 024 846 A1, US 2007 / 0 145 294 A1 and WO 2021 / 165 988 A1.

[0004] X-rays are used in many fields. For example, they are used in industrial applications such as rolling mills to determine the thickness of rolled materials. However, they are most commonly used in the medical field, for example in C-arm and CT scanners.

[0005] To protect people – for example, medical personnel, and where possible also the person being examined – X-rays are shielded as much as possible so that people are only exposed to ionizing X-rays to the extent absolutely necessary.

[0006] For many years, materials containing significant amounts of lead have been used to shield against X-rays. Lead possesses several advantageous properties in this regard. It is resistant to X-rays and also exhibits high absorption capacity for them. Furthermore, it is oil-resistant, which is advantageous and sometimes even essential for use in certain environments. It also has high electrical conductivity and is easily electrically conductive. In addition, lead is relatively soft and easily machinable. However, lead has the crucial disadvantage of being hazardous to health. Therefore, the use of lead as a shielding material is no longer permitted in many industrial applications. It is still permitted for radiation protection in medical technology. However, efforts are underway to ban lead even for medical applications.

[0007] Other substances, particularly metals, that are resistant to X-rays like lead, absorb X-rays well, and are oil-resistant are known. These other substances are referred to below as lead substitutes. Tungsten, for example, is a suitable alternative. However, some of these lead substitutes are just as harmful to health as lead itself. If a lead substitute is harmful to health, replacing lead with such a substitute is not advisable. Other lead substitutes, while not toxic, have the disadvantage of being difficult or impossible to process mechanically.

[0008] From the prior art – see the patent publications mentioned above – it is known to embed lead substitutes in powder form in a radiation-resistant polymer matrix to create a composite material. With a sufficiently high fill level of the lead substitute, a high absorption capacity for X-rays can be achieved. Due to its powder form and embedding in the polymer matrix, the composite material is easy to process and machine.

[0009] The resulting composite material and the shielding element produced from it are thus resistant to X-rays and exhibit high absorption capacity for X-rays. Furthermore, they are easy to process and machine. However, most such composite materials are not oil-resistant. They are also electrically insulating or have only low electrical conductivity. In some cases, electrical contact is also impossible. Therefore, it is difficult or impossible to bring the shielding element to a defined potential. This can lead to problems, especially if the shielding element is located near the high-voltage field. In this case, the shielding element can also influence the electron trajectory in the X-ray tube through static charge.Finally, it must also be possible to safely divert any potential high-voltage flashovers into the composite material.

[0010] The object of the present invention is to create possibilities by means of which the disadvantages of the prior art can be overcome.

[0011] The problem is solved by a screen element having the features of claim 1. Advantageous embodiments of the screen element are the subject of dependent claims 2 to 13.

[0012] According to the invention, a shielding element of the type mentioned above is designed in such a way that the base body is coated by means of a closed layer of a conductive material, so that the base body is completely enclosed by the layer of conductive material.

[0013] The encapsulation serves two purposes: firstly, it prevents the base material itself (i.e., the composite material) from coming into contact with oil. While the base material itself is not oil-resistant, this is irrelevant because the oil only comes into contact with the conductive layer. Furthermore, the conductive layer surrounds the base material, forming a Faraday cage. While the base material itself is not electrically conductive, or only poorly so, this is irrelevant because it is enclosed within the Faraday cage. Finally, electrical contact with the conductive layer is readily possible, allowing the shielding element to be easily set to a defined potential.Finally, the high currents that occur during a discharge (arcing) in the oil can be easily dissipated via the Faraday cage.

[0014] Preferably, the base body is designed as an injection-molded part. This eliminates the need for subsequent machining of the base body or at least reduces it to a minimum.

[0015] Preferably, the composite material consists of at least 90% by mass, preferably at least 95% by mass, and / or at least 30% by volume, preferably at least 40% by volume, and particularly at least 50% by volume, of the metal powder. This allows the composite material to exhibit a high absorption capacity for ionizing radiation.

[0016] Preferably, the plastic contained in the composite material is a thermoplastic, an elastomer, or a thermoset. Suitable plastics include, for example, PEEK and polyimides.

[0017] As far as functionality is concerned, the metal simply needs to be resistant to X-rays and exhibit high absorption capacity for them. Theoretically, the metal could even be lead. However, since the composite material is intended to replace lead, this is not practical. Preferably, the metal is a refractory metal. Refractory metals are the high-melting-point, base metals of groups 4, 5, and 6 of the periodic table, namely titanium, zirconium, and hafnium (group 4); vanadium, niobium, and tantalum (group 5); and chromium, molybdenum, and tungsten (group 6).

[0018] The conductive material can be a metal, for example aluminum, copper, silver, chromium, nickel-chromium, silver-palladium, or nickel-gold, with aluminum being particularly preferred. A metal typically has a conductivity of 10⁴ < S / cm. However, it can also be another metal or other materials whose electrical conductivity is comparable to that of a semiconductor. Their conductivity is typically below 10⁻⁸ < S / cm. An example of such a semiconducting material is zinc oxide (ZnO).

[0019] Preferably, the layer of conductive material has a thickness between 1 µm and 500 µm, particularly between 80 µm and 200 µm. A layer of conductive material with such a thickness can be easily produced.

[0020] Provided a suitable application method is used, the coating can be applied to the substrate in a single pass at its full thickness. Alternatively, it is also possible to apply the coating in several passes, with each pass applying only one layer of the coating, each layer being relatively thin, so that the total thickness of the coating is the sum of the individual layer thicknesses. If necessary, the layers can even consist of different materials, for example, a copper-gold base coat and a zinc layer on top.

[0021] Preferably, the shielding element comprises a contact by means of which the conductive material layer can be connected to a defined potential, in particular to ground or earth. Alternatively, the defined potential can also be a high-voltage potential, for example, the potential of the anode. It can also be another high-voltage potential, in particular a potential between ground and earth potential and the potential of the anode or cathode. The contact can, in particular, be a soldered contact or a screw contact. In the case of a screw contact, the base body can contain an insert, which in turn provides either a simple recess or a thread. A clamping contact is also possible. The base body itself can also include a recess.For example, an element (such as a threaded bolt) can be passed through the recess so that the bolt head of the threaded bolt is pressed against the layer applied to the base body on one side, and a nut screwed onto the threaded bolt is pressed against the layer applied to the base body on the other side. Finally, the contact can also be designed differently, for example as a plug contact or a welded contact. In the latter case, the contact can be applied or attached by spot welding.

[0022] Preferably, the conductive material layer is applied to the substrate by electroplating, vapor deposition, dipping, brushing, spraying, or plating. These techniques are relatively simple, reliable, and cost-effective.

[0023] Preferably, an oil-resistant sealant is applied locally, over a surface, or across the entire surface of the conductive material. This can further improve the oil resistance.

[0024] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings. These show, in schematic representation: FIG 1 an X-ray arrangement, FIG 2 a section through a screen element, FIG 3 a top view of a screen element and FIG 4 a section along a line IV-IV through the screen element of FIG 3 .

[0025] According to FIG 1 An X-ray device 1 has an X-ray source 2. X-ray radiation 3 is emitted by means of the X-ray source 2 and is detected by means of an X-ray detector 4.

[0026] To ensure that the X-ray radiation 3 reaches only the desired areas, the X-ray device 1 has shielding elements 5, 6 by which the X-ray radiation 3 is shielded. The shielding elements 5, 6 can, for example, comprise an outer casing 5 that surrounds the X-ray source 2 as a whole. The shielding elements 5, 6 can also include movable aperture elements 6 by means of which a window is adjusted through which the X-ray radiation 3 is to exit.

[0027] FIG 2 shows an example of a screen element 5, 6. According to FIG 2 The shielding element 5, 6 has a base body 7. The base body 7 consists of a composite material containing a plastic 8 in which a metal powder 9 is contained, by means of which the X-ray radiation 3 is absorbable. The composite material can consist of at least 90% by mass, preferably at least 95% by mass, and / or at least 30% by volume, preferably at least 40% by volume, and particularly at least 50% by volume, of the metal powder 9.

[0028] The plastic 8 can be a thermoplastic, an elastomer, or a thermoset, for example, PEEK or a polyimide. The metal can be, for example, a refractory metal. The base body 7 can, in particular, be designed as an injection-molded part.

[0029] The base body 7 is coated with a continuous layer 10 of a conductive material, such that the base body 7 is completely encased by the layer 10 of the conductive material. The conductive material can be a metal, in particular aluminum, copper, silver, chromium, nickel-chromium, silver-palladium, or nickel-gold. It can also be a semiconducting material. The layer 10 preferably has a thickness d between 1 µm and 500 µm, in particular between 80 µm and 200 µm. The layer 10 can be applied to the base body 7, for example, by electroplating, vapor deposition, dipping, brushing, spraying, or plating.

[0030] According to FIG 2 The shielding element 5, 6 includes a contact 11. The layer 10 can be brought to a defined potential by means of the contact 11. The defined potential can be, in particular, ground or earth. However, a high-voltage potential is also possible. The contact 11 is designed according to FIG 2 a solder contact.

[0031] FIG 3 shows a top view of an alternative design of the screen element 5, 6. FIG 4 shows a section along a line IV-IV in FIG 3 .

[0032] The design of the screen element 5, 6 of the FIG 3, 4 largely corresponds to the design of the screen element 5, 6 of FIG 2 The essential difference lies in the design of contact 11. Specifically, the shielding element 5, 6 has a recess 12 through which a screw 13 can be inserted and screwed into a nut 14 on the opposite side of the shielding element 5, 6. This makes it possible, for example, to press a cable lug 15 onto layer 10. The contact 11 of the design of FIG 3, 4 It can be viewed as a screw contact or a clamp contact, depending on requirements.

[0033] FIG 4 This also shows a further modification of the screen element 5, 6. This modification is also present in the screen element 5, 6 of FIG 2 feasible. Specifically, an oil-resistant sealant 16 is applied to layer 10. The sealant 16 is according to FIG 4 The sealant 16 is applied over the entire surface of layer 10. However, it is also possible to apply the sealant 16 only locally (specifically at critical points) to layer 10.

[0034] The present invention offers many advantages. The shielding element 5, 6 is compact. Its X-ray properties are comparable to those of lead. The shielding element 5, 6 is inexpensive and easy to manufacture and can be used directly as a replacement for existing lead shielding elements without any further design modifications. The current-carrying capacity of layer 10 is high. This allows the shielding element 5, 6 to even withstand arcing. If necessary, it is even possible to connect several shielding elements 5, 6 according to the invention, for example by soldering. Small unmetallized areas, for example at butt joints, can be disregarded or separately provided with a protective layer of sealant 16.

[0035] Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived by the person skilled in the art without leaving the scope of protection of the invention.

Claims

1. Shielding element for shielding X-rays (3), - wherein the shielding element has a base body (7), - wherein the base body (7) consists of a composite material containing a plastic (8) in which a powder (9) of a metal is contained, by means of which the X-rays (3) can be absorbed, characterized by that the base body (7) is coated by means of a closed layer (10) of a conductive material, so that the base body (7) is completely enclosed by the layer (10) of the conductive material.

2. Shield element according to claim 1, characterized by that the base body (7) is designed as an injection molded part.

3. Shield element according to claim 1 or 2, characterized by thatthe composite material consists of at least 90% by mass, preferably at least 95% by mass, and / or at least 30% by volume, preferably at least 40% by volume and in particular at least 50% by volume, of the powder (9) of the metal.

4. Shield element according to claim 1, 2 or 3, characterized by that the plastic (8) contained in the composite material is a thermoplastic, an elastomer or a thermoset.

5. Shield element according to one of the above claims, characterized by that the metal is a refractory metal.

6. Shielding element according to one of claims 1 to 5, characterized by that the conductive material is a metal.

7. Shield element according to claim 6, characterized by that the conductive material is aluminum, copper, silver, chromium, nickel-chromium, silver-palladium or nickel-gold.

8. Shielding element according to one of claims 1 to 5, characterized by that the conductive material is a semiconducting material.

9. Shield element according to one of the above claims, characterized by that the layer (10) of the conductive material has a layer thickness (d) between 1 µm and 500 µm, in particular between 80 µm and 200 µm.

10. Shielding element according to one of the above claims, characterized by that the shielding element includes a contact (11) by means of which the layer (10) of the conductive material can be placed at a defined potential, in particular at ground or earth.

11. Shield element according to one of the above claims, characterized by that the contact (11) is a solder contact or a screw contact.

12. Shield element according to one of the above claims, characterized by that the layer (10) of conductive material is applied to the base body (7) by electroplating, vapor deposition, dipping, brushing, spraying or plating.

13. Shield element according to one of the above claims, characterized by that an oil-resistant sealant (16) is applied locally, over a surface or over the entire surface to the layer (10) of the conductive material.

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