Shielding mask for ionizing scattered radiation and methods for its manufacture

Abstract

Shielding grid (1) against ionizing scattered radiation, in particular for an imaging X-ray device, comprising - a disk (3) with a first side (5) and a second side (7) opposite the first side (5), wherein the disk (3) - has an arrangement of depressions (15) which are open towards the second side (7) of the disk (3), and wherein - the disc (3) has a grid (9) of trenches (11) open towards the first side (5), wherein - the trenches (11) are filled with an X-ray absorbing material (13), and wherein - the trenches (11) viewed from one of the sides (5, 7) run between the depressions (15) and at a distance from the depressions (15) such that walls (19) remain between the depressions and the trenches (11).

Description

[0001] The invention relates generally to imaging methods using ionizing radiation, such as X-ray imaging methods in particular. In particular, the invention relates to masks for shielding a radiation detector from scattered ionizing radiation.

[0002] A well-known imaging technique using ionizing radiation is computed tomography, as it is used in diagnostic radiology. In this procedure, the object being examined is scanned from different planes and directions using a fan-shaped X-ray beam. A computer can then reconstruct a three-dimensional model of the object from the spatially resolved signals recorded.

[0003] One form of computed tomography is digital volume tomography (DVT). In this procedure, the object is illuminated with radiation from a point-like X-ray source and recorded with a matrix detector.

[0004] For the signal-to-noise ratio, and thus the resolution and contrast of the tomograms, it is advantageous to block scattered radiation before it reaches the detector. For this purpose, it is known to use gratings that absorb radiation arriving at the detector at an angle to the direct, straight path to the X-ray source. One currently used embodiment of such a grating consists of a stack of lead strips with paper strips as spacers between them. The disadvantage here is, among other things, that such a structure only suppresses scattered radiation in one plane, namely perpendicular to the surfaces of the lead strips. Furthermore, such a structure is not very mechanically stable and can easily become permanently deformed. The design also generally does not allow for very fine structuring, which in turn can affect the spatial resolution of the tomograph.

[0005] From WO 2007 / 034352 A2, an X-ray absorption grating is known in which lamellae made of X-ray absorbing material, such as tungsten or molybdenum, are embedded in a rigid foam material in a similar manner and are mechanically stabilized by the rigid foam material.

[0006] US Patent 2016 / 0163408A1 describes the fabrication of an X-ray absorption grating using a silicon substrate. For this purpose, cavities are created in the silicon substrate by etching, which are then electroplated with X-ray-absorbing metal.

[0007] The X-ray absorption grating known from US 5581592 A is produced by sawing channels into a substrate, preferably made of plastic. Saw blades such as those used for cutting silicon wafers in chip manufacturing can be used for this purpose. An X-ray-absorbing alloy is then melted into the channels. For this to work, the substrate must be able to withstand the melting temperature without softening.

[0008] The invention is based on the objective of providing an improved grating for shielding against ionizing scattered radiation, in particular X-rays. This objective is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are specified in the respective dependent claims.

[0009] Accordingly, the invention provides a shielding grid against X-ray scattering radiation, in particular for an imaging X-ray device, for example an X-ray computed tomography scanner, comprising - a disk with a first side and a second side opposite the first side, wherein the disk - has an arrangement of depressions which are open towards the second side of the disk, and wherein - the disc has a grid of trenches open towards the first side, wherein - the trenches are filled with an X-ray-absorbing material, and wherein - viewed from one side, the trenches run between the depressions and at a distance from the depressions, so that walls remain between the depressions and the trenches.

[0010] Viewed from one side of the disc, the depressions are thus arranged between the grooves. Direct X-rays can easily pass through the disc at the locations of the depressions. Since the walls around the depressions are made of the same material as the disc, the disc is given sufficient mechanical stability, even though the X-ray-absorbing material in the grooves itself is not mechanically robust. Because the depressions and grooves open to opposite sides of the disc, and the depressions are therefore closed on the side toward which the grooves open, it is easily avoided that the depressions will be filled simultaneously with the X-ray-absorbing material when the grooves are filled.For the purposes of this disclosure, an X-ray-absorbing material is defined as a material whose X-ray absorption coefficient is at least three times greater than the X-ray absorption coefficient of the disk material for X-rays with an energy of 69.5 keV. According to an alternative or additional preferred embodiment, the X-ray-absorbing material is a material with a density at least four times greater than the density of the disk material. The content of elements with a high atomic number is also particularly important for its effectiveness as an X-ray-absorbing material.According to yet another alternative or additional embodiment, an X-ray-absorbing material is a material which comprises at least 10% by weight of elements with an atomic number of at least Z = 56, preferably at least 25% by weight, and particularly preferably at least 50% by weight of such elements with Z ≥ 56. For the purposes of this disclosure, X-ray-absorbing materials also generally include materials which absorb ionizing radiation, in particular electromagnetic radiation. Such materials also typically have a high absorption capacity against particulate ionizing radiation. Therefore, this disclosure generally relates to the aforementioned shielding grid against ionizing scattered radiation. In this sense, the term X-ray-absorbing material is a simplification for all materials that are suitable for absorbing high-energy radiation.X-ray absorbing materials also include radiopaque materials.

[0011] The invention is explained in more detail below with reference to the figures. In this context, identical reference numerals in the figures refer to identical or corresponding elements. Brief description of the characters: Fig. Figure 1 schematically shows a computed tomography scanner with a shielding grid. Fig. Figure 2 shows a cross-section of a shielding grid. Fig. Figure 3 shows a shielding grid in top view. Fig. Figure 4 shows a variant of the shielding grid. Fig. Figure 5 shows a cross-section of a variant of the shielding grid with recesses aligned towards a point source. Fig. Figure 6 shows a laser processing device for inserting filament-shaped defects into the disc. Fig.Figure 7 shows a cross-section of a disc with inserted filament-shaped defects. Fig. Figure 8 shows the disc after etching. Fig. Figure 9 shows the disc after the trenches were filled with an X-ray absorbing material. Fig. Figure 10 shows a variant of the embodiment according to Fig. 9 with a thinned disc. Fig. Figure 11 schematically shows a cross-section through an X-ray-absorbing material. Fig. Figure 12 shows a particle size distribution for a ground glass solder. Fig. Figure 13 shows particle size distributions for ground glass, two metal dusts and their mixture. Fig. 14 represents further training in Fig. 2 shown embodiment. Fig. 15 is a further training course in Fig. 2 embodiment shown.

[0012] The invention relates not only to the shielding grid but also to an imaging X-ray device, such as a computed tomography scanner. The imaging X-ray device generally comprises an X-ray source, an X-ray detector, and a shielding grid 1 arranged in front of the X-ray detector for detecting the X-rays emitted by the X-ray source. The function of a shielding grid 1, as provided for in the invention, is described by reference to Fig. 1 explained. Fig. Figure 1 shows a schematic diagram of an imaging X-ray device 2. In the illustrated embodiment, this device comprises an X-ray source, in particular an X-ray tube 30 with a vacuum bulb 33, and an anode 31 and a cathode 32 arranged therein. During operation, X-rays are emitted from the anode. An object to be examined, for example a patient or a body part, is positioned between the X-ray tube 30 and an X-ray detector 39.

[0013] The invention is particularly suitable for so-called cone-beam computed tomography. In this method, a sequential scan with a rotating fan beam is not performed, but rather a beam cone emanating from the X-ray tube 30 is detected by a matrix detector. Data suitable for the tomogram can be obtained from X-rays 35 passing straight through the object under investigation. Scattered X-rays, on the other hand, contain no spatial information and merely increase noise. As demonstrated by the Fig.As can be seen in Figure 1, scattered X-rays strike the X-ray detector 39 at an angle to the straight path between the X-ray tube and the detector. The shielding grid 1 is designed to allow the X-rays 35 coming straight from the X-ray tube 30 to pass through with as little attenuation as possible, while absorbing scattered X-rays 34. This is achieved by openings defined by the spaces in the grid made of X-ray-absorbing material, which allow only rays passing through at a small angle to a straight path.

[0014] A shielding grid 1 has a cross-section in Fig.Figure 2 illustrates the shielding grid 1, which comprises a disk 3 as a support or base element. According to a particularly preferred embodiment of the invention, and without limiting itself to the illustrated example, the disk 3 is a glass disk. Glass is a particularly preferred material, among other reasons, because it is not ductile and therefore cannot be permanently deformed by mechanical stress. This prevents changes in the collimating properties or the selectivity for direct versus scattered X-rays. Another reason is that glass can now be structured very finely, which also facilitates the production of a shielding grid with high selectivity. A further advantage is that the thermal expansion of the glass can be adjusted by selecting a suitable type of glass.This allows, for example, temperature-induced shifts of the grating relative to the pixels of an X-ray detector 39 to be minimized. This also applies to comparatively large dimensions. Therefore, according to a further development, without restriction to specific materials of the shielding grating, it is provided that the shielding grating 1 has an area of ​​at least 0.25 m². 2 exhibits. In particular, the area can even be at least 1 / 3 m 2 The dimensions may vary. For example, according to one embodiment, a shielding grid with dimensions of 600 mm × 600 mm is provided.

[0015] The disk 3 has two opposite sides 5, 7. Preferably, the disk 3 is plane-parallel, so that the opposite sides 5, 7 are also parallel. As shown by Fig.As can be seen, recesses are inserted into both sides 5 and 7. The recesses inserted into the first side 5 are designed as trenches 11. In the opposite second side 7, recesses 15 are inserted, located between the trenches 11. The recesses 15 are open towards the second side 7. Correspondingly, the trenches 11 are open towards the opposite first side 5. The opening of the trenches 11 towards the first side 5 allows them to be filled with an X-ray-absorbing material 13. Since the trenches 11 extend essentially perpendicularly into the disk 3, the X-ray-absorbing material contained therein can effectively absorb X-rays entering the disk 3 at an oblique angle. For illustration, an X-ray beam 35, arriving essentially perpendicularly, is shown, which can pass through the disk 3 via a recess 15.An obliquely arriving X-ray beam 36, such as that produced by scattering at an object under investigation, is absorbed in the X-ray-absorbing material 13. The depressions 15 thus serve to minimize the interaction of the X-ray radiation with the material of the disk 3, preferably glass, even with a thicker disk 3. The X-ray radiation only needs to pass through the bottom wall 16, which is considerably thinner than the disk 3.

[0016] Generally, a disk 3 with a thickness of at least 2 millimeters, preferably at least 3 millimeters, is preferred. This allows for the insertion of correspondingly deep grooves 11 and thus good shielding of obliquely incident scattered radiation. Preferably, however, the thickness is less than 10 mm so that the grooves 11 can still be easily filled with X-ray-absorbing material.

[0017] Between the depressions 15 and the trenches 11, walls 19 are present. While the disk 3 retains its full thickness in the area of ​​these walls, the walls 19 can be kept narrow. Furthermore, these walls provide the arrangement with its mechanical stability.

[0018] To further increase mechanical stability, according to a further development of the invention, an edge region 27 of the disk 3 can also be provided which has no depressions 15 or grooves 11. This edge region thus acts as a stabilizing border. Without limiting itself to the illustrated example, the edge region can have a width that is at least twice as wide as the period length of the sequence of grooves and depressions.

[0019] The arrangement of trenches 11 and depressions 15 can be specifically tailored to the pixel spacing of a detector. With such pixel matching, even small changes to the shielding grid 1, for example due to mechanical deformation, can result in significant transmission losses. This is another reason why glass is a particularly preferred material for the disk 3. Borosilicate glasses are generally especially suitable, both in terms of stability and structuring capabilities. However, other materials are also conceivable, such as glass ceramics, ceramics, or certain plastics. Besides borosilicate glass, soda-lime glass and aluminosilicate glass are also generally well-suited as disk materials. A criterion for selecting the disk 3 material can generally be its linear coefficient of thermal expansion.This can be approximated to the coefficient of thermal expansion of the X-ray-absorbing material in order to keep temperature-induced mechanical stresses low. For example, a soda-lime glass may be well suited if the X-ray-absorbing material 13 has a high coefficient of thermal expansion.

[0020] Fig. Figure 3 shows the shielding grid 1 in a top view of the first side 5. According to a preferred embodiment of the invention, the grid 9 is configured as a cross grid with grooves 11, as in the illustrated example. The intersecting grooves 11 form cells within which the recesses 15 are arranged. However, other arrangements are also possible. For example, high transmission for direct X-rays can be achieved with a hexagonal grid. Such a variant with a hexagonal grid is shown in Figure 3. Fig. 4.

[0021] In general, the shape of the grid 9 can be adapted to the shape of pixels of the detector 39. In addition to the ones based on the Fig. 3 and Fig. As shown in the four examples, other shapes are also conceivable. For example, grid 9 can also define rectangular, round, triangular, or even octagonal channels.

[0022] The representations of Fig. 3 and Fig. Figure 4 is to be understood schematically only. In the illustration, the trenches 11 are drawn significantly narrower than the depressions 15. In practice, however, it is generally advantageous to provide trenches 11 and depressions 15 with similar widths, or conversely, a smaller distance between trenches relative to the width of the trenches 11, in order to achieve good shielding of scattered radiation. The illustration of the Fig.In this respect, embodiment 2 is closer to the preferred embodiments. According to a further development of the invention, the width of the trenches 11 differs from the width of the depressions 15 by a maximum factor of 2.

[0023] A large depth-to-width ratio of the trenches is particularly advantageous for the transmission of direct X-rays and the shielding of scattered radiation. It is especially possible, using a method described later, to fill trenches 11 with an X-ray-absorbing material if the depth-to-width ratio is 40:1 or greater. However, with an excessively high aspect ratio, sufficiently homogeneous or complete filling may no longer be guaranteed. Therefore, it is preferable to limit the width-to-depth ratio to 150:1 or less. It is also evident here that the drawings are merely schematic. The aspect ratio of the trenches 11 in Fig. 2 is significantly smaller than 40:1.

[0024] Another alternative or additional factor for good shielding of scattered radiation and transmission of direct radiation is the depth of the trenches 11. Preferably, the depth of the trenches 11 is at least 1.5 millimeters, preferably at least 2 millimeters.

[0025] It is also advantageous for the property of high shielding of scattered radiation if the passages or channels defined by the trenches 11 of the grating 9 are as long as possible. The longer these channels are in relation to their width, the more selective the grating is for the transmission of direct radiation and the shielding of obliquely incident scattered radiation. Thus, according to a further embodiment of the invention, the center-to-center distance of two adjacent trenches is smaller than their depth. Preferably, the center-to-center distance is even at least three times smaller than the depth of the trenches 11.

[0026] Finally, for good shielding, the walls of the trenches 11 should be as perpendicular as possible to the planes of sides 5 and 7. In this regard, it is preferred if the angle of the wall 25 of a trench 11 to the first side 5 deviates from a right angle by less than 5°. Even small taper angles of less than 5° can be achieved with the manufacturing process described later, particularly in a glass pane. This applies to the special case of trenches 11 and depressions 15 that cut perpendicularly into the pane.

[0027] Trench 11 runs near the in Fig.In the example shown in Figure 2, the grooves are parallel to each other in a direction perpendicular to sides 5 and 7. Such an arrangement is particularly advantageous when the X-rays to be detected arrive as a parallel beam, for example, when the X-ray source is located far away. Typically, however, an X-ray imaging device, such as a computed tomography scanner, uses a more closely positioned X-ray source, so that a conical beam of rays falls onto the shielding grid. Therefore, in one embodiment of the invention, the grooves 11 are generally provided to have varying inclinations, such that the walls of the grooves 11 run along directions that point towards a common virtual point source. In other words, the grooves 11 are inserted into the disk 3 at such an inclination that the central axes of channels defined by adjacent grooves 11 point towards a common virtual point source.This also applies accordingly to the central axes of the recesses 15. Accordingly, in one embodiment of the invention, the central axes 17 of the recesses 15 are directed towards a common virtual point source. Such an arrangement is shown schematically in the figure. Fig.5. The center axes 17 of the depressions 15 generally coincide with the center axes of the channels 12 defined by the adjacent trenches 11. In addition to the depressions 15, the channels 12 also contain the material of the disk 3, which forms the walls 16, 19. As can be seen from the diagram, the trenches 11 are also directed towards the virtual point source 18, so that the walls of the trenches 11 run in the direction of the point source 18. Due to the conical beam path, the widths of the depressions 15 and trenches 11 would change along their course within the disk 3, as shown in the diagram. The widths on the side facing the point source 18 (here the second side 7) would be smaller than on the opposite side. In practice, however, this is usually unnecessary, since the point source is generally much farther away relative to the thickness of the disk 3 than shown in the diagram. Fig.5. It is therefore preferred that the trenches 11 and depressions 15 have a constant width in the direction of the beam, or in the direction perpendicular to the sides 5, 7. This progression of widths corresponds accordingly to the representation of the Fig. 2.

[0028] The following describes a method for manufacturing a shielding grid 1 according to the invention. The method for manufacturing a shielding grid 1 against X-ray scattering radiation comprises the following steps: - Providing a disc 3 with a first side 5 and a second side 7 opposite the first side 5, and - Irradiating disk 3 with a laser beam, wherein the material of disk 3 is transparent to the laser beam, so that the laser beam penetrates disk 3, wherein - the laser beam leaves 3 filament-shaped damages along its path through the disk, wherein the filament-shaped damages are inserted such that a first group of filament-shaped damages ends on the first side and a second group of filament-shaped damages ends on the second side 7, - Removal of the material of disk 3 in the area of ​​the first and second groups of filamentous damage by etching disk 3 with an etching medium, so that - by removing the material in the area of ​​the second group, an arrangement of depressions 15 is formed, which are open towards the second side 7 of the disk 3, and - by removing the material in the area of ​​the first group, a grid 9 is created from trenches 11 open towards the first side 5, and wherein then - an X-ray absorbing material 13 is filled into the trenches 11.

[0029] An ultrashort pulse laser is particularly suitable for creating the filament-shaped defects. Fig.Figure 6 shows a laser processing device for inserting filament-shaped defects 41 into the disk 3 in order to subsequently create grooves 11 and depressions 15 in an etching process. The device 50 comprises an ultrashort pulse laser 51 with upstream focusing optics 52 and a positioning device 53. The positioning device 53 allows the point of impact 54 of the laser beam 40 of the ultrashort pulse laser 51 to be laterally positioned on one of the sides 5, 7 of a disk 3 to be processed. In the example shown, the positioning device 53 comprises an xy-table on which the disk 3 rests on one of its sides 5, 7. Alternatively or additionally, the optics can be made movable to move the laser beam 40, so that the point of impact 54 of the laser beam 40 can be moved across the disk 3.The focusing optics 52 now focuses the laser beam 40 into a focus elongated in the beam direction, i.e., perpendicular to the irradiated side of the disk 3. Such a focus can be generated, for example, with a conical lens (a so-called axicon) or a lens with high spherical aberration. The positioning device 53 and the ultrashort pulse laser 51 are preferably controlled by a computer 55 programmed with software. In the illustration of the... Fig.6. The laser beam 40 strikes the disk 3 perpendicularly. However, according to a preferred embodiment, the positioning device 53 and / or the focusing optics 52 can also be designed to allow oblique illumination in order to generate filament-shaped defects 41, which are each parallel in the longitudinal direction to the provided central axes 17, or more generally parallel to the direction towards the virtual point source 18. In general, without being limited to the specific embodiments shown here, a further development of the method provides that the filament-shaped defects 41 are inserted at least partially obliquely to one of the sides 5, 7 of the disk 3.By successively inserting impact points or positions of filament-shaped damage 41 distributed on the disk 3 according to a predetermined pattern using the positioning device 53, predetermined patterns can be created which are then elaborated in a subsequent etching step.

[0030] According to one embodiment, the following parameters can be used for the laser beam: The wavelength of the laser beam is 1064 nm, typical for a YAG laser. A laser beam with a raw beam diameter of 12 mm is generated and then focused using a biconvex lens with a focal length of 16 mm. The pulse duration of the ultrashort pulse laser is less than 20 ps, ​​in one embodiment approximately 10 ps. The pulses are emitted in bursts of 2 or more, preferably 4 or more pulses. The burst frequency is 12–48 ns, in one example approximately 20 ns, the pulse energy at least 200 microjoules, and the corresponding burst energy at least 400 microjoules. According to one embodiment, the ultrashort pulse laser can be operated with a repetition rate for the bursts or pulse packets which is between 1 kHz and 1000 kHz, preferably between 2 kHz and 100 kHz, and particularly preferably between 3 kHz and 200 kHz.This repetition rate and / or scan speed can be selected to achieve a desired spacing between adjacent defects / channels. Other variants of the Nd:YAG laser, such as wavelengths of 532 nm and 355 nm generated by frequency doubling (SHG) or frequency tripling (THG), or a Yb:YAG laser operating at an emission wavelength of 1030 nm, can be used as suitable beam sources.

[0031] The process for producing blind holes / channels can be specifically adapted by modifying the laser beam. In particular, an extremely short focal length, especially one less than 20 mm, can be used. According to an alternative or additional embodiment, a significantly expanded raw beam is employed. Preferably, the laser beam has a beam radius of at least 4 mm when it strikes the objective lens or focusing optics.

[0032] Another measure is a modification of the intensity distribution. This can involve shifting the maximum intensity from the optical axis to the edges of the focusing optics or, more generally, distributing it over a larger area. Beam profiles with this feature include, among others, a flat-top profile and a donut profile.

[0033] Since aligning the depressions and trenches with a point source also results in oblique illumination, it is advantageous to couple the light, especially near Brewster's angle, with the polarization oriented parallel to the substrate surface. Furthermore, asymmetric illumination of the focusing optics can be used, if necessary, to achieve larger incidence angles.

[0034] Embodiments for the method of inserting filamentous defects and the suitable laser parameters, as well as parameters for the subsequent etching, can also be found in DE 10 2017 101 673.2, DE 10 2018 110 211.9 and PCT / EP2021 / 077030. These applications, with respect to the embodiments for inserting the filamentous defects 41 and the parameters for laser irradiation and etching, are also fully incorporated into this disclosure.

[0035] Fig.Figure 7 shows a disk 3 with inserted filament-shaped defects. The filament-shaped defects 41 are subdivided into two groups 43 and 44. The filament-shaped defects 41 of the first group 43 terminate at the first side 5, and the filament-shaped defects 41 of the second group 44 terminate at the second side 7. Without limiting itself to the illustrated example, it is generally particularly preferred if at least a portion, preferably all, of the filament-shaped defects 41, or the filament-shaped defects of both groups 43 and 44, terminate within the disk 3 as shown. In this way, depressions 15 in the form of blind holes, or grooves 11 terminating in the disk, are easily produced during subsequent etching, even if the disk is exposed to the etching medium on all sides.The filaments preferably penetrate 50% to 90% of the thickness of the glass, so that after the etching process the channels or blind holes / cavities which form the depressions 15 and grooves 11 preferably reach 55% to 95% of the glass thickness.

[0036] The filamentous damage 41 thus terminates on the one hand within the disk, and on the other hand at one of the sides 5, 7. As also shown by the Fig.As can be seen in Figure 6, the filament-shaped defects 41 are also inserted obliquely, depending on the angle of the direction subsequently intended to the virtual point source. According to one embodiment of the method, it is not necessary to rotate the disk 3 for inserting the filament-shaped defects 41. Rather, it is sufficient to adjust or change the position of the elongated focus of the laser beam 40. For this purpose, the position of the lens and / or the position of the disk 3 can be changed. For example, if the disk 3 is rotated according to Figure 6, the position of the elongated focus of the laser beam 40 can be adjusted or changed. Fig. 7 If the laser beam 40 is directed onto the first side 5, the beginning of the elongated focus for the filaments of group 43 can be on or even in front of the disk 3.

[0037] To insert the filaments of group 44, the focus can then be shifted in the beam direction so that the beginning of the elongated focus of the laser beam 40 lies within the disk 3. Without being limited to specific embodiments, one embodiment of the method provides that at least a portion of the filament-shaped damage 41 of both groups 43, 44 is generated by irradiating the same side 5, 7 of the disk 3 with the laser beam 40 and changing the position of the focus of the laser beam 40 relative to the disk and in the direction along the laser beam 40.

[0038] If glass is used as the material of the disk 3 and an alkali as the etching medium, a characteristic surface topography can be achieved on the walls of the grooves 11 and depressions 15, particularly during slow etching. Specifically, the surface of the grooves 11 and depressions can exhibit a multitude of adjacent small, dome-shaped depressions. Preferably, the dome-shaped depressions have a depth of less than 10 µm, more preferably less than 5 µm, and more preferably less than 2 µm, the depth being defined by the difference between the center of a depression and the mean peak of the ridge surrounding the depression. The dome-shaped depressions are also described in more detail in DE 10 2017 101 673.2, DE 10 2018 110 211.9 and PCT / EP2021 / 077030, the content of which is also fully incorporated into this disclosure.The surface topography with its dome-shaped depressions ensures a good bond between disk 3 and the X-ray-absorbing material. A particularly strong bond can be achieved when the X-ray-absorbing material includes molten glass, such as glass solder. The depressions increase the surface area for material bonding, resulting in a true interlocking of the two materials.

[0039] In Fig.Figure 8 shows the disk 3 after etching. The material of disk 3 etchs significantly faster along the filamentous defects 41 than in areas without such defects. Therefore, the material, preferably glass, is removed during etching by widening the filamentous defects 41. The channels thus formed eventually merge and create the desired structures in the form of grooves 11 extending from the first side 5 and depressions 15 extending from the second side 7 into the disk 3. Corresponding to the inclination of the filamentous defects 41, the grooves 11 and depressions 15 are also oriented towards a virtual point source, as shown in Fig. 5 shown.

[0040] Finally, on page 5, the X-ray absorbing material 13, for example in the form of a paste, can be filled into the grooves 11, so that the in Fig.The shielding grid 1 shown in Figure 9 is obtained. According to a further development of the method, it is generally provided, without limitation to the specific embodiment shown, that the disk 3 can also be thinned after being filled with the X-ray-absorbing material 13, for example to reduce the X-ray absorption. Fig. 9 shows a dashed line running parallel to and near the second side 7. If the disc 3 is now ground down on side 7 up to this line, a disc 3 will be obtained as shown. Fig. Figure 10 shows. According to yet another alternative or additional development, which also applies to the embodiment of the Fig.When the disk is thinned, the grooves 11 and thus the X-ray-absorbing material 13 on the second side 7 are exposed. This generally results in an embodiment in which the grooves 11 are at least partially open on both sides 5, 7 of the disk 3. This embodiment is not limited to thinning; for example, it is also possible to insert the filament-shaped defects 41 at least partially through the disk 3, so that the filament-shaped defects 41 terminate on both sides 5, 7. Another possibility is to insert closely spaced filament-shaped defects 41 that alternately terminate on one side 5, 7 and then the other. During etching, the channels forming along the filament-shaped defects 41 then connect, creating a groove 11 with a continuous connection between both sides 5, 7.However, in some cases, there may no longer be a direct connection between the sections of disk 3 adjacent to a trench 11. To maintain mechanical stability, however, webs can be left in place, for example, which are maintained by sections of the trenches 11 with reduced depth. An alternative or additional possibility is to provide an X-ray-absorbing material that forms a material bond with the wall of the trench 11. This applies generally, not only to the variant of... Fig.10, it is preferred to provide a glass, in particular a glass solder, as a component of the X-ray-absorbing material 13, wherein the glass is melted and thus forms a metallurgical bond with the material of the disk 3, preferably also a glass. Optionally, partial melting of the glass is sufficient. A lead- and / or bismuth-containing glass, such as lead glass, is particularly suitable as a component of the X-ray-absorbing material 13, regardless of whether it is in molten form or not. Lead- and / or bismuth-containing glass has good shielding properties against ionizing radiation, especially X-rays, due to its lead or bismuth content. The glass can also crystallize completely or partially. Specifically crystallizing glasses and glass solders are known.In this case too, for the purposes of this disclosure, the X-ray-absorbing material refers to a fused or partially fused glass. Accordingly, in one embodiment, it is generally provided that the X-ray-absorbing material 13 comprises a fused or partially fused glass.

[0041] Furthermore, for a material bond between the X-ray-absorbing material 13 and the disk 3 and / or a permanent, stable fixation of the X-ray-absorbing material 13 in the grooves 11, it is advantageous if the X-ray-absorbing material 13 comprises a molten glass solder. The availability of lead-containing glass solders is particularly advantageous in this regard. Lead oxide, as a glass component, is especially suitable for achieving a low softening point and simultaneously providing a high shielding effect. To enable the glass to be melted in the grooves 11 without deforming the disk 3, it is generally preferred if at least one of the following characteristics applies to both the glass of the X-ray-absorbing material 13 and the glass of the disk 3: - the glass of the X-ray absorbing material 13 has a glass transition temperature T g, which is at least 100 °C, preferably at least 160 °C or even at least 220 °C lower than the glass transition temperature T g of the glass of pane 3, - the glass of the X-ray absorbing material 13 has a processing temperature at which its viscosity is 10 4 dPa·s is, which is at least 100 °C, in particular at least 200 °C, particularly preferably at least 250 °C lower than the processing temperature of the glass of the pane 3, - the glass of the X-ray absorbing material 13 has a processing temperature at which its viscosity is 10 4 dPa·s is lower than the temperature of the softening point of the glass of disk 3, where the softening point is defined by a viscosity of 10 7,6 dPa·s is defined.

[0042] In one example, a glass solder of type G017-52 from Schott AG is used for the X-ray-absorbing material 13. For a disk 3 made of the glass Borofloat 33 from Schott AG, a difference in the glass transition temperatures Tg of 263 °C is observed. The viscosity of the glass solder G017-52 is 10 7,6 dPas at 347 °C. This temperature is 218 °C lower than the softening point of Borofloat 33 glass.

[0043] Glass as a component of the X-ray-absorbing material, regardless of whether the glass contains lead or not, offers a further advantage in conjunction with the arrangement described here. As a brittle material, glass can be ground very finely. The resulting glass dust is then ideally suited, for example as a component of a paste-like preparation, to be filled into the narrow, deep grooves 11. Filling can then be carried out simply, for example by using a doctor blade. In one embodiment, the paste-like preparation is filled into the grooves 11 and then preferably dried at 100 °C to 200 °C. The filling and drying process can be repeated, particularly with a large aspect ratio of the grooves 11, to completely fill them.Once the trenches 11 are sufficiently filled, annealing at 350 °C to 450 °C can be carried out, during which the glass of the preparation is melted to obtain an X-ray-absorbing material 13 firmly bonded to the walls of the trenches 11. According to one embodiment, a powdered glass, preferably a glass solder 21 as a component of the X-ray-absorbing material 13, or more preferably a mixture of a powdered glass with particles, is filled into the trenches 11, and the glass solder 21 is melted or partially melted so that a solid X-ray-absorbing material 13 is produced which adheres to the walls of the trenches 11.

[0044] Fig.Figure 11 schematically shows a preferred embodiment of the X-ray-absorbing material. According to this embodiment, the X-ray-absorbing material 13 generally contains particles, preferably metal particles 23. In a particularly preferred further development, the X-ray-absorbing material 13 comprises particles embedded in a molten material, in particular metal particles 23 and / or mineral particles and / or ceramic particles. For the purposes of this disclosure, a component in particle form or as particles includes not only metallic grains or particles, but also ceramic or glass-ceramic or semi-crystalline glasses, as well as crystallites (monocrystalline or polycrystalline) as grains or particles, or a combination thereof. The molten material can preferably be, as in the illustrated example, a molten glass or glass solder 21.The glass ensures a firm and generally also mechanically resilient bond between the X-ray-absorbing material 13 and the disk 3. Without limiting itself to specific embodiments, a further development of the manufacturing process provides that a paste is supplied which contains glass particles and particles, preferably metal particles 23, wherein the paste is preferably filled into the grooves 11 by means of a doctor blade, and wherein the disk 3 with the glass particles and particles in the grooves 11 is heated so that the glass particles soften and an X-ray-absorbing material 13 with particles, preferably metal particles 23, embedded in glass is obtained.

[0045] Without being limited to specific embodiments, a preferred embodiment provides that the paste contains, in addition to the respective solids, preferably at least glass dust and metal dust, or metal particles, 23 organic solvents or suspending agents. In general, the paste in a preferred embodiment is thus a mixture of ground glass with metal dust and one or more organic solvents. Optionally, further additives, for example crystalline inorganic materials, are included. Preferably, liquid organic substances with low viscosity and a high boiling point are used as organic solvents or suspending agents. Preferably, the boiling point is at least 120 °C, particularly preferably at least 180 °C. The viscosity at 20 °C is preferably less than 5 mPa·s. Various glycol ethers are particularly suitable.

[0046] For the metal particles 23, it is advantageous to use a particularly heavy metal or an alloy containing at least one heavy metal. Generally, it is preferred that the metal particles 23 contain metals with an atomic number greater than 55 in a proportion of at least 66 at%. According to an alternative or additional embodiment, the metal particles 23 have a density of at least 9 g / cm³. 3 to achieve good X-ray absorption. In particular, the density of the X-ray-absorbing material 13 is preferably significantly higher than the density of the disk 3. This results in very different X-ray absorption in the different materials and, accordingly, high contrast. Therefore, it is preferred if the density of the X-ray-absorbing material 13 is at least four times greater than the density of the disk 3.

[0047] The X-ray-absorbing material most preferably comprises 13 particles of a tungsten-containing material, preferably in the form of metallic tungsten or a tungsten alloy. Tungsten has a particularly high density. In its pure metallic form, tungsten has a density of 19.25 g / cm³. 3 Alternatively or additionally, particles of a tungsten-containing mineral and / or a tungsten-containing ceramic can also be included. With heavy metals, such as tungsten, a high density of the X-ray-absorbing material 13 can also be achieved. Thus, in a preferred embodiment, the X-ray-absorbing material 13 is provided to have a density of at least 9 g / cm³. 3 , preferably at least 11 g / cm² 3exhibits such high densities. Particularly with a combination of metal particles of heavy metals and glass, especially lead glass or glass solder, these high densities can be achieved. These densities are not a given even for X-ray-absorbing materials. For example, tungsten-containing plastics or polymer pastes typically only achieve densities slightly above 8 g / cm³. 3 .

[0048] The coefficient of thermal expansion of the X-ray-absorbing material 13 can also be adjusted by selecting its constituents. According to a further development of the shielding grid 1, by choosing the constituents and a suitable material for the disk 3, in particular a suitable glass, the difference between the linear coefficients of thermal expansion of the X-ray-absorbing material 13 and the material of the disk 3 can be limited to less than 3 ppm / K.To match the coefficients of thermal expansion or at least reduce the difference between the coefficients of expansion of the disk and the X-ray-absorbing material, one embodiment provides for at least one component in the X-ray-absorbing material, preferably in particle form, or as a particulate additive for its preparation, which has a linear coefficient of thermal expansion of less than 1 ppm / K or even negative in at least part of the temperature range between 0 °C and 200 °C. The particles can, for example, be present at least partially in the form of crystallites. A particular advantage here is that there are also high-density materials that meet these conditions and therefore also exhibit good shielding properties. Lead or tungsten compounds are known, in particular, to have such coefficients of thermal expansion.In a further development of this embodiment, the X-ray absorbing material 13 contains at least one of the compounds lead titanate and / or zirconium tungstate.

[0049] According to yet another embodiment, the linear coefficients of thermal expansion of the glass of the X-ray-absorbing material 13 and the metal particles 23 are also matched to each other. Preferably, the glass and the metal particles 23 are selected such that the absolute difference in the linear coefficients of thermal expansion is at most 5 ppm / K. An exemplary embodiment of the X-ray-absorbing material 13, or rather of the ingredients of a paste for producing the X-ray-absorbing material 13, is described below. A lead oxide-containing glass solder of type G017-52 is used as the glass. The glass has a high lead content, with a PbO content of 86% by weight. Tungsten metal particles are added as a further component. The properties and composition of the X-ray-absorbing material produced therefrom are given in the following table: Tabel: Linear coefficient of thermal expansion of tungsten 4,5·10 -6 K -1 Density tungsten 19,25 g / cm 3 Linear coefficient of thermal expansion of glass 11,4·10 -6 K -1 Dense glass 6,65 g / cm 3 Material combination: volume fraction tungsten 60,85% mass fraction tungsten 81,82% Volume fraction of glass 39,15% Mass fraction of glass 18,18% Expansion coefficient of the combination 7,2·10 -6 K -1 Density of the combination: 14,34 g / cm 3

[0050] As can be seen from this example, the combination of materials can achieve a very high density of well over 9 g / cm³. 3 , even significantly above 11 g / cm² 3 can be achieved.

[0051] Another glass that can be used for the X-ray-absorbing material is the bismuth glass solder G018-423 from Schott AG. This glass solder contains up to 84% Bi2O3 by weight.

[0052] One challenge in filling the trenches 11 by squeegeeing, as described above, is that the trenches 11 are very narrow and deep due to the high aspect ratio. Nevertheless, the trenches 11 should be filled as completely as possible. Furthermore, no pores, or as few and as small as possible, should form after the glass melts. These properties can be surprisingly effectively influenced by the grain size of the materials.

[0053] Fig.Figure 12 shows a particle size distribution for a glass solder ground with an attritor. One suitable glass type is the applicant's solder glass G017-052. The dashed curve is the histogram of the glass particle diameters. The solid line indicates the cumulative distribution of the particle sizes. The glass particles are not spherical; therefore, the diameter shown on the abscissa of the diagram represents the mean of the lateral dimensions. The glass powder has a 90% diameter of 1.39 µm. This is the maximum diameter of 90% of the glass particles. The 50% diameter is 0.67 µm, and the 10% diameter is 0.24 µm. According to a further development of the process, the components used, in particular the glass powder and the metal particles, are selected to maximize the fill factor. Typically, this is done under the constraint that the metal particle content is as high as possible.Even under this constraint and with potentially predetermined particle size distributions, the fill level can be adjusted by adding two metal powders with different particle size distributions to the paste, or more generally, to the mixture of glass and metal particles. The fill level can then be optimized by using different weights of the two powders and taking into account the particle size distribution of the glass powder. According to a preferred embodiment, the fill level of the material 13, which is optionally solidified, preferably as described above, by fusing or melting a glass, in the grooves 11, is at least 40 vol%, preferably at least 60 vol%. A fill level of at least 70 vol% is both desirable and achievable.

[0054] The degree of fill can be calculated, for example, using an Andreasen model. An Andreasen model assumes a particle size distribution which determines the shape F(d)=100∗(ddmax)n

[0055] The function values ​​F(d), which depend on the particle diameter, are the cumulative percentages of particles with a diameter less than or equal to d. The function values ​​F(d) therefore correspond to the cumulative values ​​Q3, or the solid line of the diagram. Fig. 12. The shape of the distribution is determined in particular by the constant n. The parameter d max specifies the maximum diameter of the existing particles.

[0056] Optimization can also be performed using other models known to experts. Alternative models include, for example, the ψ-model or the Dinger-Funk model.

[0057] Fig. Figure 13 shows particle size distributions according to an exemplary embodiment. In particular, in addition to the particle size distribution of the ground glass, the following are shown: Fig.Figure 12 shows two particle size distributions for tungsten metal powders B10 and B20, as well as for the mixture of all three components, i.e., the ground glass with the two metal powders. The particle size distributions can be characterized, among other things, by their d50 value. This is the value at which the number of larger and smaller particles is equal. In other words, half of all particles in the respective dust or ground material have a diameter smaller than the d50 value. The d50 value of metal powder B10 is 3 µm, the d50 value of metal powder B20 is 5 µm, and the d50 value of the ground glass is only 0.67 µm. Metal powders B10 and B20 are offered by ALMT Corp. (JP).

[0058] As demonstrated by Fig.As can be seen in Figure 13, the glass has the smallest particle sizes and the metal powder B20 the largest. According to one embodiment, the at least three components, namely the ground glass and the two metal powders, are mixed in such a way as to achieve the highest possible packing density. According to a further development, the method generally includes the steps of measuring or calculating the packing density of a mixture of ground glass (or glass dust) with at least one other powder, calculating and / or measuring the packing density of the mixture, calculating or measuring the packing density of a mixture with a varied mixing ratio at least once, selecting or determining a mixing ratio for a preparation for filling the trenches 11 from the at least two results of the calculation or measurement, and producing a preparation with the mixing ratio.The selected mixing ratio for preparation may, but does not have to, correspond to one of the measured or calculated mixing ratios. An ideal mixing ratio can also be interpolated or extrapolated from the results.

[0059] The particle size distribution of a mixture of glass powder and the two metal powders B10 and B20, optimized with respect to packing density, lies between that of the metal powders on the one hand and the glass powder on the other. According to the exemplary embodiment, the preparation has the following mixture: component weight percent Volume percent d50 value Wolfram B10 21,82 16,19 3 µm Wolfram B20 60 44,65 5 µm Glass G017-052 18,18 39,16 0,67 µm

[0060] The tungsten metal particles therefore have a weight fraction of slightly over 80 percent and a volume fraction of about 30 percent.

[0061] Alternatively or additionally to metal particles, minerals or ceramics containing heavy elements, particularly heavy metals, can also be used. A heavy element, as defined above, is any element with an atomic number of 55 or higher. Here too, it is preferred that the X-ray-absorbing material contains at least 10% by weight of elements with an atomic number of at least Z = 56, preferably at least 25% by weight, and most preferably at least 50% by weight of such elements with Z ≥ 56, even if no additional metal particles are present. Suitable minerals include, among others, scheelite, calcium tungstate (CaWO4), lead oxide, and lead sulfide.

[0062] If, as is preferred, the mixture filled into the grooves 11 is heated so that the glass melts or softens and thus forms a solid matrix for the metal particles 23, the glass particles are generally no longer visible on the finished shielding grid. However, a characteristic of a preferred mixture with high packing density, and thus also of an X-ray absorbing material 13 with high absorption capacity, is that the metal particles 23 exhibit a broad size distribution due to the mixture of two metal dusts of different fineness. In general, without limiting oneself to the example described above, an X-ray absorbing material 13 is therefore provided in which the particles, preferably fixed in glass, are in the form of a mixture of at least two powders, in particular metal powders, and / or mineral powders and / or ceramic powders with different d50 values.In particular, these d50 values ​​can also differ by at least 1.5 µm, as in the exemplary embodiment. This mixture also results in a comparatively broad particle size distribution, at least significantly broader than the particle size distributions of the two metal dusts individually. If an Andreasen distribution is fitted to such a real distribution according to the equation above, a comparatively small exponent n results. According to a further embodiment, an X-ray-absorbing material 13 is therefore provided, which contains particles, preferably metal particles 23, exhibiting a particle size distribution for which the exponent (or modulus) n of an Andreasen distribution adapted to the particle size distribution of the metal particles 23 corresponds to the particle diameter d. F(d)=100∗(ddmax)n smaller than n=0.33, preferably smaller than n=0.28, where d maxThe maximum particle diameter of the fitted Andreasen distribution is given by... Since the Andreasen distribution is idealized and fitted to the actual distribution of the metal particles 23, the... max The value does not correspond to the actual maximum particle diameter of the metal particles 23. In the double-logarithmic representation of the Fig. 13 Andreasen distributions are not curves, like the actual particle size distributions shown, but straight lines.

[0063] By using two metal powders of different fineness, the particle size distribution can not only be broadened. According to an alternative or additional embodiment, the particle size distribution of the particles, in particular metal particles 23 in the X-ray-absorbing material 13, can also be bi- or multimodal. In the representation of the particle size distribution as it appears for the ground glass in Fig.As shown in 12, this means that the histogram has two or more distinguishable maxima.

[0064] In addition to tungsten dust, other components may also be present in particle form. These could include, for example, additives that allow the coefficient of thermal expansion of the X-ray-absorbing material to be adjusted, such as low-expansion materials or even components with negative thermal expansion, like lead titanate or zirconium tungstate. By inserting the grooves 11 and depressions, large portions of the material from the disk 3 are removed. In particular, the continuous material bonds in the disk 3 can be removed, as shown in the embodiments of the Fig. 2, Fig. 8 and Fig.As can be seen in Figure 9, this structuring does not follow a straight line, but rather a meandering pattern. This reduces the stability of the disk 3. The strength can be increased again by bonding it with a solid X-ray-absorbing material 13, such as the molten glass or glass solder 2. Nevertheless, it may be desirable to give the structured disk 3 more strength. One possibility for this is to bond the disk 3 to another disk. Preferably, the disk 3 can be bonded to a glass disk. In particular, a thin glass disk can be used for this purpose. Fig.Figure 14 shows an example of this embodiment. According to one variant, the thin glass disc 8 is attached to the second side 7 of the disc 3, as shown. An advantage of this arrangement is that the recesses 15 are additionally sealed, thus preventing contamination or soiling of the recesses 15. For the purposes of this disclosure, a thin glass disc 8 is understood to be a glass disc with a thickness of at most 250 µm, preferably at most 150 µm. Thin glass is particularly suitable in this case because the X-ray absorption is low due to the small material thickness. It is also particularly advantageous that even the thin glass significantly increases the mechanical stability of the arrangement. This is because the recesses 15 typically have only a small width, or lateral width.This prevents the thin glass from bending much over the recesses 15, resulting in a significant increase in stiffness. The same applies accordingly to a thin glass disc 8 that is attached to the first side 5 of the disc 3. In general, without limiting it to the illustrated example, one embodiment provides that a thin glass disc 8 is attached to at least one side 5, 7 of the disc 3. Several methods are suitable for attaching it. A simple option is bonding, for example with an epoxy resin or a silicone. The use of a glass solder is also conceivable, for example the same glass solder used for the X-ray-absorbing material 13. Using a glass solder makes it possible to attach the thin glass disc 8 to the disc 3 and to melt the glass solder onto the X-ray-absorbing material 13 in a single step.It is also possible to weld the two discs 3 and 8 together using a laser. Anodic bonding is also conceivable.

[0065] An alternative or additional processing method for the shielding grid 1 is the application of an organic layer or encapsulation, for example by dipping. An example of this is shown. Fig.15. In this example, the disk 3 of the shielding grid 1 is completely surrounded by an organic encapsulation 10. The encapsulation 10 can also completely or at least partially fill the recesses 15, as shown. Provided the organic material does not have high X-ray absorption, this does not lead to significant absorption losses within the recesses 15. Polymers, lacquers, synthetic resins, and silicones are particularly suitable as organic encapsulations. Unlike shown, the organic encapsulation 10 can also be applied only to a portion of the disk 3, for example, to the first side 5. In general, this embodiment provides that an organic encapsulation 10 is applied to the disk 3 at least partially, or to at least a portion of the disk 3's surface. This embodiment can, of course, also be combined with the embodiment using the thin-glass disk 8.The organic encapsulation 10 can, for example, serve as mechanical protection for the disk 3 and, in particular, the thin glass disk 8. Reference symbol list 1 Shielding grid 2 imaging X-ray machine 3 discs 5 first page of 3 7 second page of 3 8 thin glass panes 9 grids 10 organic encapsulation 11 trench 12-channel 13 X-ray absorbing material .... 15 In-depth study 16 floor wall of 15 17 center axis of 15 18 Point Source 19 Wall between 11, 15 21 Glass solder 23 metal grain 25 wall of 11 27 Edge area of ​​1 30 X-ray tubes 31 Anode 32 Cathode 33 vacuum pistons 34 objects 35 X-rays 36 scattered X-ray beam 39 Detector 40 laser beam 41 filamentous damage 43 first group of filamentous damage 41 44 second group of filamentous damage 41 45 Etching medium 50 laser processing devices 51 ultrashort pulse lasers 52 Focusing optics 53 Positioning device 54 Point of impact of 40 55 computer equipment

Claims

[1] Shielding grid (1) against ionizing scattered radiation, in particular for an X-ray imaging device, comprising - a disk (3) with a first side (5) and a second side (7) opposite the first side (5), wherein the disk (3) - has an arrangement of depressions (15) which are open towards the second side (7) of the disk (3), and wherein - the disc (3) has a grid (9) of trenches (11) open towards the first side (5), wherein - the trenches (11) are filled with an X-ray absorbing material (13), and wherein - the trenches (11) viewed from one of the sides (5, 7) run between the depressions (15) and at a distance from the depressions (15) such that walls (19) remain between the depressions and the trenches (11). [2] Shielding grid (1) according to the preceding claim, characterized bythat the pane is designed as a glass pane. [3] Shielding grid (1) according to one of the preceding claims, characterized by at least one of the following characteristics: - the trenches (11) have a depth-to-width ratio of at least 40:1, - the depth of the trenches is at least 1.5 millimeters, - the angle of the wall (25) of a trench (11) or a depression deviates by less than 5° from the nominal angle, in particular from the direction of the central axis (17), - the center-to-center distance of two adjacent trenches is smaller than their depth, preferably smaller by at least a factor of three. - the width of the trenches (11) differs from the width of the depressions (15) by a maximum factor of 2. [4] Shielding grid (1) according to any one of the preceding claims, characterized by, that the central axes (17) of the depressions (15) and / or the trenches (11) are directed towards a common virtual point source (18) [5] Shielding grid (1) according to any one of the preceding claims, characterized by at least one of the following characteristics: - the X-ray absorbing material (13) comprises a fused or melted glass, - the X-ray absorbing material (13) comprises a lead- and / or bismuth-containing glass - the X-ray absorbing material (13) contains particles embedded in a partially or fully molten material, preferably a glass, in particular metal particles (23) and / or mineral particles and / or ceramic particles, - the X-ray absorbing material (13) has a density of at least 9 g / cm³ 3 , preferably at least 11 g / cm² 3 on, - the density of the X-ray absorbing material (13) is at least four times greater than the density of the material of the disk (3), - the X-ray absorbing material (13) comprises at least 10% by weight of elements with an atomic number of at least Z = 56, preferably at least 25% by weight, - the X-ray absorbing material (13) comprises particles of a tungsten-containing material, preferably in the form of metallic tungsten, a tungsten alloy and / or a tungsten-containing mineral and / or a tungsten-containing ceramic, - the difference in the linear coefficients of thermal expansion of the x-ray-absorbing material (13) and the material of the disk (3) is less than 3 ppm / K, - the fill level of the X-ray absorbing material (13) in the trenches (11) is at least 40 vol%, preferably at least 60 vol%, - the glass of the X-ray absorbing material (13) has a glass transition temperature T g , which is at least 160 °C, preferably at least 220 °C lower than the glass transition temperature T g of the glass of pane 3, - the glass of the X-ray absorbing material (13) has a processing temperature at which its viscosity is 10 4 dPa·s is, which is at least 100 °C lower than the processing temperature of the glass of the pane (3), - the glass of the X-ray absorbing material (13) has a processing temperature that is lower than the softening point temperature of the glass of the disc (3), the softening point being determined by a viscosity of 10 7,6 dPa·s is defined. - the X-ray absorbing material (13) contains at least one component in particle form which has a linear coefficient of thermal expansion that is less than 1 ppm / K or negative in at least part of the temperature range between 0 °C and 200 °C. [6] Shielding grid (1) according to one of the preceding claims, wherein the trenches (11) are at least partially open on both sides (5, 7) of the disk (3). [7] Shielding grid (1) according to any one of the preceding claims, characterized by at least one of the following characteristics: - the X-ray absorbing material (13) comprises particles in the form of a mixture of at least two powders, in particular metal powders, and / or mineral powders and / or ceramic powders with different d50 values, - the X-ray absorbing material (13) contains particles having a particle size distribution for which the exponent n of an Andreasen distribution adapted to the particle size distribution of the metal particles (23) is the particle diameter d, F(d)=100∗(ddmax)n smaller than n = 0.33, preferably smaller than n = 0.28, where d max the maximum particle diameter of the fitted Andreasen distribution is, - the particle size distribution of the particles in the X-ray absorbing material (13) is bimodal or multimodal. [8] Shielding grid (1) according to any one of the preceding claims, characterized by at least one of the following characteristics: - a thin glass pane (8) is attached to at least one side (5, 7) of the pane (3), - an organic encapsulation (10) is applied to at least part of the surface of the disk (3). [9] Imaging X-ray device, in particular computed tomography (2), comprising an X-ray source and a shielding grid (1) arranged in front of an X-ray detector (39) for detecting the X-ray radiation emitted by the X-ray source according to one of the preceding claims. [10] Method for manufacturing a shielding grid (1) against X-ray scattering radiation according to one of the preceding claims, comprising the steps: - Providing a disk (3) with a first side (5) and a second side (7) opposite the first side (5), and - Irradiating the disk (3) with a laser beam (40), wherein the material of the disk (3) is transparent to the laser beam (40) so that the laser beam (40) penetrates the disk (3), and wherein - the laser beam (40) leaves filament-shaped damage (41) along its path through the disk (3), wherein the filament-shaped damage (41) is inserted such that a first group (43) of the filament-shaped damage (41) terminates at the first side (5) and a second group (44) of the filament-shaped damage (41) terminates at the second side (7), - Removal of the material of the disk (3) in the area of ​​the first and second groups (43, 44) of filamentous damage (41) by etching the disk (3) with an etching medium (45), so that - by removing the material in the area of ​​the second group (44) an arrangement of depressions (15) which are open towards the second side (7) of the disk (3), and - by removing the material in the area of ​​the first group (43) a grid (9) of trenches (11) open towards the first side (5) is created, and wherein then - an X-ray absorbing material (13) is filled into the trenches (11). [11] Method according to the preceding claim, characterized by , that a powdered glass, preferably a glass solder (21) as a component of the X-ray absorbing material (13), preferably a mixture of a powdered glass with particles, is filled into the trenches (11), and wherein the glass solder (21) is melted or fused so that a solid X-ray absorbing material (13) is produced which adheres to the walls of the trenches (11). [12] Method according to one of the two preceding claims, characterized by , that the filament-shaped defects (41) are inserted at least partially obliquely to one of the sides (5, 7) of the disk (3). [13] Method according to any one of the three preceding claims, characterized by, that at least a part, preferably the filament-shaped damage of both groups (43, 44) ends within the disk (3). [14] Method according to any one of the four preceding claims, characterized by , that at least some of the filamentous damage (41) of both groups (43, 44) is produced by irradiating the laser beam (40) on the same side (5, 7) of the disk (3) and changing the position of the focus of the laser beam (40) relative to the disk and in the direction along the laser beam (40). [15] Method according to one of the five preceding claims, wherein a paste is provided which contains glass particles and metal particles (23), wherein the paste is filled into the grooves (11), and wherein the disk (3) is heated so that the glass particles soften and an X-ray absorbing material (13) with particles embedded in glass is obtained. [16] Method according to any one of claims 10-15, comprising the steps: - Measuring or calculating the packing density of a mixture of ground glass with at least one other powder, - Calculating or measuring the packing density of the mixture, - at least a one-time calculation or measurement of the packing density of a mixture with varying mixing ratios, - from at least two results of the calculation or measurement, select or determine a mixing ratio for a preparation for filling the trenches (11) and - Preparation of a mixture with the specified ratio.

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