X-ray rotating anode analysis system

Abstract

The invention relates to an X-ray rotating anode analysis system (54) for analyzing a used X-ray rotating anode (33) having a circumferential focus path (40) on a surface. An X-ray rotating anode analysis system (54) includes a positioning device (56) for an X-ray rotating anode (33), an image recording unit (58), and a data processing unit (64) coupled to the image recording unit (58). The positioning device (56) and the image recording unit (58) are designed such that the X-ray rotating anode (33) is positioned as a single part in a predetermined position relative to the image recording unit (58). The image recording unit (58) and the data processing unit (64) are arranged such that the image recording unit (58) and the data processing unit (64) can detect a 3-dimensional height profile of a surface section of the X-ray rotating anode (33) in the region of its focal path (40), and enabling a data processing unit (64) to determine an expected radiation power or characteristic value of the X-ray rotating anode (33) as a function of the detected 3-dimensional height profile or part thereof.

Description

Technical Field

[0001] The invention relates to an X-ray rotating anode analysis system for analyzing a used X-ray rotating anode having a circumferential focal path on its surface. In addition, the invention relates to a method for analyzing such a used X-ray rotating anode. Background Art

[0002] The X-ray rotating anode is built into an X-ray tube, which in turn is integrated into the corresponding X-ray device. The X-ray rotating anode is used to generate X-rays as follows: During use, electrons are emitted from the cathode of the X-ray tube and accelerated in the form of a focused electron beam onto the rotating X-ray anode. Due to the rotational motion of the X-ray rotating anode, the electron beam scans a circular path - the focal path. Most of the energy from the electron beam is converted into heat in the rotating X-ray anode, while a small part is emitted as X-rays. The locally released heat causes the X-ray rotating anode to heat up significantly. The rotation of the X-ray rotating anode counteracts the overheating of the anode material.

[0003] Especially in the high performance range, in particular for medical imaging applications such as computed tomography, a high radiation output of the emitted X-rays is required. Each time the focal path material moves under the electron beam due to rotation, the surface of the focal path in the region of the focal spot initially experiences a high temperature increase and thermally induced stresses and subsequently a temperature drop. This leads to focal path aging, which can be seen in roughening of its surface, formation of cracks, grain collapse and / or local melting.

[0004] Ageing of the focal path leads to a reduction in the emitted radiation power and a deterioration in the operational stability of the X-ray tube. However, other influences, such as ageing of the cathode (emitter), wear in the area of ​​the bearing components and / or deformations of the X-ray rotating anode also lead to this reduction and / or degradation. It is therefore a challenge to assess the cause. If the X-ray rotating anode is suspected or determined to be the (co-)cause, the question of its further use arises. If the X-ray rotating anode is still functional, the choice is to reuse it immediately, as long as the functionality can be restored, readjust it (also called "repair"; for example, repair the focal path, process and reapply the focal path, mechanical repair in the area of ​​the bearing components, etc.) or recycle the X-ray rotating anode in another way. This decision is usually made subjectively by an individual after visually inspecting the X-ray rotating anode. From the point of view of ecology, sustainability and cost, it is desirable to recycle the X-ray rotating anode that can be reused or reprocessed. The condition of the focal path is a key factor affecting the further use of the X-ray rotating anode.

[0005] From the publication CN114428099A, an X-ray rotating anode test bench for evaluating X-ray rotating anodes is known, wherein the X-ray rotating anode to be inspected is placed in a vacuum chamber of the test bench, arranged to rotate and brought to operating temperature by the electron beam in the region of its focal path. The test bench also has a temperature sensor for detecting the X-ray rotating anode and a control device, which in particular evaluates the condition of the X-ray rotating anode based on the heat provided and the detected temperature.

[0006] Furthermore, the publication "Geometrical model for calculating the effect of surface morphology on total x-ray output of medical x-ray tubes" by Siller, Maximilian et al., Medical Physics 48.4 (2021): 1546-1556 describes a geometrical calculation model that can be used to determine the effect of surface morphology on the emitted radiation output of medical x-ray tubes. In this publication, X-ray upright anodes are exposed to a pulsed electron beam so that their surface morphology in the focal spot region corresponds to the surface morphology of aged X-ray upright anodes, and a 3-dimensional height profile of the surface is recorded using a laser scanning confocal microscope (LSCM). The geometrical calculation model is used to determine the reduction in the emitted radiation power due to the surface structure contained in the 3-dimensional height profile compared to a smooth surface. Furthermore, the geometrical calculation model is validated with experimental comparison values. Summary of the invention

[0007] The object of the present invention is therefore to provide an analysis system for used X-ray rotating anodes removed from corresponding X-ray tubes, by means of which the condition of the corresponding X-ray rotating anode in the region of its focal path can be reliably and objectively evaluated.

[0008] This problem is solved by an X-ray rotating anode analysis system according to claim 1 and a method for analyzing a used X-ray rotating anode according to claim 14. Advantageous further embodiments of the invention can be seen from the dependent claims, which can be freely combined with each other.

[0009] According to the present invention, an X-ray rotating anode analysis system is provided for analyzing a used X-ray rotating anode having a circumferential focal path on its surface. The X-ray rotating anode analysis system has a positioning device for the X-ray rotating anode, an image recording unit and a data processing unit connected to the image recording unit. The positioning device and the image recording unit are designed so that the X-ray rotating anode can be positioned at a predetermined position relative to the image recording unit as a single component (i.e., in a state removed from the X-ray tube). The image recording unit and the data processing unit are arranged so that a 3-dimensional height profile of a surface segment of the X-ray rotating anode in the region of its focal path can be acquired by the image recording unit and the data processing unit, and so that the desired radiation power of the X-ray rotating anode or a characteristic value of the desired radiation power can be determined by the data processing unit from the acquired 3-dimensional height profile or a part thereof.

[0010] The expected radiation power determined by the 3-dimensional height profile is generally a key criterion regarding the expected performance of the X-ray rotating anode, in particular regarding the condition of the focal path. The surface morphology of the focal path is a significant influencing factor on the emitted radiation power, since inhomogeneities lead to local absorption effects of the emitted X-rays. Therefore, the determined expected radiation output is essential for deciding on the further use of the X-ray rotating anode in question. Based on the 3-dimensional height profile, further advantageous analyses are also possible, as explained with reference to further embodiments. The automatic determination of the expected radiation output of the X-ray rotating anode analysis system represents a significant advantage, in particular compared to an individual visual assessment of the X-ray rotating anode, because it is objective and enables significantly more data and details to be included. Compared to assessment methods performed on the X-ray rotating anode in its state installed in the X-ray tube (e.g. direct measurement of the emitted radiation power and / or assessment of backscattered electrons), the X-ray rotating anode analysis system according to the invention has the advantage that the condition of the focal path is directly recorded and the analysis result is not distorted by other influencing factors (e.g. aging of the cathode, the filters used, etc.). The X-ray rotating anode analysis system is a system different from an X-ray device or an X-ray tube; in particular, it has no vacuum bottle or unit for accelerating the electron beam onto the X-ray rotating anode. Finally, by using a suitably equipped data processing unit, the invention advantageously exploits the option of automatic calculation, which enables the processing of large amounts of data. At the same time, the use of an image recording unit and a positioning device eliminates the need for expensive components, such as those used in other evaluation methods (e.g., for spectral correlation detection of backscattered electrons when generating an electron beam, etc.).

[0011] The "X-ray rotating anode used" does not form part of the claimed X-ray rotating anode analysis system; the function and design of the X-ray rotating anode analysis system are described only with reference to the former. The term "focal path" refers at least to the (annular) surface area of ​​the X-ray rotating anode which is scanned by the electron beam when the X-ray rotating anode is in use. In many cases, the X-ray rotating anode has an annular coating (formed on a carrier underneath) in this surface area and in any area directly adjacent thereto, which is specially designed for generating X-rays. Suitable materials for the coating are in particular materials with a high atomic number, such as tungsten, tungsten-based alloys, in particular tungsten-rhenium alloys (e.g. with a rhenium content of up to 26 wt %, preferably in the range of 5-15 wt %, in practice typically in the range of 5-10 wt %). In the latter case, the term "focal path" refers to the annular coating of the X-ray rotating anode. The design of the X-ray rotating anode defines an axial direction (along or parallel to the axis of rotation, with which the X-ray rotating anode is essentially rotationally symmetrical; also referred to as the z-direction), a circumferential direction (rotating about the axis of rotation in a plane perpendicular to the axis of rotation) and a radial direction, each of which extends away from the axis of rotation in a plane perpendicular to the axis of rotation (and ultimately spans the main extension plane of the X-ray rotating anode). The x and y directions also extend in this plane, the y direction corresponding to the X-ray emission direction. The surface segment whose 3-dimensional height profile is recorded may extend over or cover the entire circumferential focal path. However, it may also comprise only one or more partial regions thereof, in particular the region actually scanned by the electron beam in the radial direction (in particular with a radially wider focal path coating), and / or at least one sector or other cross-section (e.g. rectangular) in the circumferential direction. Preferably, the at least one partial region covered is therefore a region representative of the surface morphology of the focal path, or the most severely damaged region, which can be evaluated, for example, using a simple (e.g. only 2-dimensional) overview image of the focal path created at the beginning. Since the focus path surface is usually curved and inclined to the main extension plane (which usually corresponds to the course of a truncated cone surface), suitable corrections must be performed in a known manner so that the height of the individual image points is accurately reproduced relative to the (theoretically assumed) ideal course of a smooth focus path (i.e., the truncated cone surface) in the 3D height profile.

[0012] When determining the "expected radiation power", the entire relevant (wavelength) spectrum of the X-ray radiation is included, as is the case in the actual use of X-ray rotating anodes. In addition, depending on the operating conditions, filtering typical in X-ray devices is preferably also applied, which in particular reduces the long-wave radiation component. The kinetic energy released in the air (KERMA: kinetic energy released in the substance) is preferably used as the decisive physical quantity for the radiation power. It is measured in the physical unit Gray (Joule / kilogram) and indicates how much energy (Joule) is released per kilogram of substance (in this case air), whereby the entire relevant radiation spectrum (i.e. across all wavelengths) is added up. However, deviating physical quantity characteristics of the radiation power can also be determined, which are correspondingly meaningful, such as a reduction in the expected radiation power due to the surface morphology of the focal path, a ratio of the expected radiation power to the comparative radiation power of a smooth focal path surface, or a deviating definition / representation of the radiation power and / or the application of no filtering or deviating filtering.

[0013] The positioning device is designed for positioning the X-ray rotating anode as a "single component", i.e. in a state removed from the X-ray tube. In particular, the positioning device can engage or abut for positioning in a central opening / hole, on a centrally mounted rod, on a circumferential cross section and / or on the underside of the X-ray rotating anode, opposite the focal path in the axial direction. In addition to contacting and / or engaging, it can also be designed for fixing and, if necessary, additionally for rotating the X-ray rotating anode around its rotation axis.

[0014] The positioning device, the image recording unit and the data processing unit can all be integrated into one and the same integral device. Alternatively, however, they can also be designed as separate units: the positioning device thus enables an exact positioning of the X-ray rotating anode to be examined relative to the image recording unit (this is also possible, for example, by a corresponding mounting of the image recording unit relative to the positioning device). Furthermore, a coupling of the data processing unit to the image recording unit is necessary so that at least data (image data) can be transferred from the image recording unit to the data processing unit. In particular, they communicate and exchange data with each other. The data processing unit itself can be completely integrated into the image recording unit, but it can also be completely or partially outsourced to at least one other device.

[0015] The use of a data processing unit means that this is a computer-aided method. The recording of the 3D height profile and the determination of the expected radiation power are performed in particular according to (at least) an algorithm that can be performed by one or more appropriately configured software modules. In other words, both steps are software-supported. The 3D height profile contains the relevant height information of each image point (pixel) along the total area of ​​the recorded surface segment. In particular, it is a high-resolution 3D height profile that has been recorded and created. In particular, a resolution of ≤5μm is used in all three spatial directions, preferably a resolution of ≤4μm. Special methods can be used to improve the resolution, in particular by recording a larger number of individual images by the image recording unit and processing the obtained image data accordingly. Due to the shielding effect of the surface structure, achieving high resolution is particularly advantageous in the vertical direction (in fact, a resolution of up to ≤1μm can be achieved in all three spatial directions). The desired radiation power can be determined from the entire recorded 3D height profile or only from partial information. As will be explained below with reference to other embodiments of the present invention, for example, a regional profile covering only a partial area of ​​the recorded surface segment, or only one or more line profiles can be used as a basis.

[0016] According to another embodiment, the image recording unit and the data processing unit are arranged so that, using electromagnetic radiation (in particular in the wavelength range of 10-3000 nm; nm: nanometer), several individual images can be created, each image having different depth information of the surface segment of the X-ray rotating anode to be analyzed, and the 3-dimensional height profile of the surface segment to be analyzed can be reconstructed by the data processing unit from the individual images. This is an efficient method for creating a 3-dimensional height profile, which can be implemented cost-effectively, in particular due to the low cost of computer performance and equipment available today. The electromagnetic radiation used can consist of a spectrum of several wavelengths, or can be monochromatic. In addition, the electromagnetic radiation used can also have a large coherence length of the wave (laser), in which case it is usually monochromatic radiation. In principle, there are various known possibilities in the prior art for creating a plurality of individual images and then creating a 3-dimensional height profile from them. Preferably, the image recording unit works according to an optical method. For example, individual images can be captured from different angles and then combined to create a 3-dimensional height profile (photogrammetry). Alternatively, for example, an inspection method using laser scanning confocal microscopy (LSCM) can be used to gradually (preferably in steps of ≤0.5 μm, for example in steps of 100 nm; in modern devices significantly smaller step sizes can be set) adjust the focus of the optical device (for example using a corresponding aperture) to different heights (for example perpendicular to the plane of the surface section to be analyzed), and the sharply imaged partial areas can be recorded as individual images in order to then combine these individual images to form a 3D height profile.

[0017] According to another embodiment, the image recording unit and the data processing unit are arranged in such a way that, in particular using electromagnetic radiation in the wavelength range of 380 nm-780 nm (which corresponds to the visible range of the human eye), several individual images of the surface segment to be analyzed can be created from different angles. By changing the recording direction, corresponding depth information (in the axial or z-direction) can be obtained. In addition, the illumination angle of the surface segment is also preferably varied together with the exposure direction or independently of the corresponding exposure direction, and the shadows cast by the surface structure of the surface segment to be analyzed are also evaluated. In particular, "white" light covering the spectrum in this wavelength range can be used. In this way, the image recording unit (camera) can work with (light) optical methods and record high-resolution individual images in an efficient and cost-effective manner. In particular, the image recording unit records the individual images at a corresponding magnification (e.g. in the range of 5-20X, in particular 10X). Then, a 3-dimensional height profile can be generated from the individual images taken from different angles (number ≥ 2). The principle here is that the resolution of the 3-dimensional height profile generated from the surface segment to be analyzed can increase with the number of individual images taken from different angles. The number of individual images of the surface section to be analyzed, taken from different angles, is therefore preferably ≥ 20, even more preferably in the range of 50-100. Therefore, if the alternative variant also applies to this principle, in which the focus is set stepwise (preferably in steps of ≤ 0.5 μm, for example in steps of 100 nm) to different heights and the sharply imaged partial areas are taken as individual images, in this case, ≥ 200, in particular ≥ 500 individual images are preferred. If a step size of 100 nm is set and a height range of, for example, 100 μm is to be covered, this corresponds to, for example, 1000 individual images.

[0018] According to another embodiment, the data processing unit is arranged in such a way that the expected radiation power or characteristic value of the X-ray rotating anode can be determined based on the automatically calculated absorption of the X-rays in the direction of the X-ray emission, taking into account local absorption effects due to local surface denaturation or surface structure according to the recorded 3D height profile. This further embodiment has the advantage that not only one or several individual physical quantity characteristics or the description of the surface morphology as a whole, such as the average roughness value R a Or square roughness R q, and the absorption of each (local) surface change (bump, crack, grain break, local melting, etc.) located in the analyzed surface section is determined and its influence on the expected radiation output is thus taken into account. This also enables additional analysis options, such as the determination of severe local damage (e.g. large cracks or grain avalanches) and / or fluctuations in the expected radiation output occurring in the circumferential direction, which can lead to a deviating assessment of the X-ray anode even in the case of an otherwise acceptable surface morphology of the surrounding surface area of ​​the focal path. This determination is carried out in particular with computer support (i.e. in particular with the aid of a data processing unit) using corresponding algorithms, which can be executed by one or more correspondingly equipped software modules. With currently available computer performance, it is possible to take into account all local absorption effects (i.e., for example, for each image point or pixel, or for each coordinate of the included surface section or line profile). The so-called "X-ray emission direction" is determined by the geometry of the corresponding X-ray rotating anode. Typically, the portion of the X-ray rotating anode on which the focal path is formed corresponds to the side surface of a truncated cone, whereby the side surface is inclined at an inclination angle (e.g., 10°) relative to the radial direction (relative to the rotation axis). In the corresponding X-ray device, the X-ray radiation emission direction usually extends precisely in the radial direction, so that it is inclined at an inclination angle (e.g., 10°) relative to the side surface and thus relative to the surface of the focal path (locally approximately a plane).

[0019] According to another embodiment, the data processing unit is configured so that it can be used to automatically calculate the absorption of X-rays using at least one line profile, which extends over a predetermined minimum length along the detected surface segment of the X-ray rotating anode in the direction of X-ray emission and has a local surface degeneration or surface structure according to a 3-dimensional height profile. By selectively using one or more line profiles according to this other embodiment, the required computer performance can be reduced. Each line profile represents an elevation profile along a specified route direction according to a 3-dimensional elevation profile. The corresponding line profile should extend along the detected surface segment of the X-ray rotating anode in this direction at least over the extended length of the focal spot in the direction of X-ray emission. This minimum length must be used because it is well known that the electron beam is not precisely focused on a point on the X-ray rotating anode, but has a limited extension (i.e., focal spot) on the focal path surface with a specific electron intensity distribution (see Rolf Behling "Modern Diagnostic X-Ray Sources", Second Edition, 2021, pp. 226-231). For the focal spot, a focal spot size specific to the respective X-ray tube in which the X-ray rotating anode is used (if known) or a generally common focal spot size and electron intensity distribution on the focal path surface may be assumed (e.g. in the range of 4-12 mm, in particular for example 10 mm, with a maximum extension in at least one direction; however, if necessary, only the partial area with the highest electron intensity may be used). Furthermore, it should be explained that due to the generally provided inclination angle of the focal path (formed on the side of the truncated cone) with respect to the X-ray emission direction (usually exactly corresponding to the radial direction), the line profile results from the projection of the X-ray emission direction onto the detected surface segment (along the axial direction), which is represented above by the formula "over a predetermined minimum length along the detected surface segment in the X-ray emission direction". As explained below with respect to simplification / method number 2, the use of such a line profile and the approximation of the focal spot as a linear, appropriately adjusted intensity profile is particularly advantageous for an X-ray rotating anode due to the high speed of rotation occurring during use.

[0020] According to another embodiment, the data processing unit is arranged so that it can be used to automatically calculate the absorption of X-rays using at least one surface profile, which extends along the detected surface segment in the direction of X-ray emission over a predetermined minimum length and extends substantially perpendicularly to the predetermined minimum length over a predetermined minimum width, and has a local surface degeneration according to a 3-dimensional height profile. The advantage of including at least one surface profile is that all surface degenerations located on the included surface are included in the calculation. Each surface profile shows a height profile according to a 3-dimensional height profile of each pixel within the included surface. The above explanations about the length and route of the line profile apply accordingly to the minimum length and its route. With regard to width, the included surface can be particularly fan-shaped (i.e., the inner and outer sides each extend in the circumferential direction, wherein the inner side has a smaller extension than the outer side). However, other shapes of the surface profile are also possible.

[0021] In another embodiment involving line profiles and in another embodiment involving surface profiles, only a single (e.g., representative) line or surface profile of only one line or one surface section of the focal path is selected for determination. In particular, several line or area profiles are used, which are preferably evenly distributed in the circumferential direction on the circumferential focal path. They may also cover or contain the entire circumferential focal path.

[0022] According to a further embodiment, the data processing unit is arranged such that at least one of the following input variables is included in the automatic calculation of the X-ray absorption:

[0023] - the generation depth of the X-rays (in the focal path), which is related to the penetration depth of the electrons into the focal path to be analyzed;

[0024] - X-ray emission angle;

[0025] - Materials in the X-ray anode focal path;

[0026] - the size of the focal spot;

[0027] - the electron intensity distribution of the focal spot; and

[0028] -filter.

[0029] By taking these input variables into account, the accuracy and reliability of determining the expected radiation power is increased. The penetration depth of electrons into the focal path to be analyzed is essentially an intensity distribution over depth, which depends on the accelerating voltage of the electrons. Therefore, the relevant generation depth of X-rays is also an intensity distribution (which does not correspond exactly to the intensity distribution of the penetration depth of the electrons due to absorption effects, etc.). However, for simplicity, an average value of, for example, 1.6 μm (μm: micrometer) can be used for the generation depth of X-rays at an assumed acceleration voltage of, for example, 100 kV (kV: kilovolt) (literature values ​​are in the range of 1.0-1.6 μm). The X-ray emission angle corresponds to the tilt angle explained above (usually 10° or even 7°), and based on the assumed generation depth of the X-rays, this tilt angle must be taken into account when determining the path length of the generated X-rays through the material of the focal path and the associated (material-dependent) absorption of the X-rays. Depending on the material of the focal path of the X-ray rotating anode and depending on an assumed acceleration voltage of, for example, 100 kV (kV: kilovolt), the generated X-ray radiation spectrum (which can be obtained from publicly available sources) can be determined. Furthermore, the absorption of the generated X-rays until they are emitted from the surface of the focal path depends on the material of the focal path (and on the corresponding wavelength of the X-ray spectrum), which is why the material of the focal path is preferably taken into account when determining the radiation power. With regard to the size of the focal spot and the electron intensity distribution, the above explanations apply (depending on the calculation method, they can be specified in each case as an intensity distribution on the surface or as a linear intensity distribution with the corresponding size). Furthermore, filtering is used in X-ray devices (e.g. by borosilicate glass, which is used as a component in the radiation path, and / or aluminum or copper, as a specific wavelength-dependent filter; both are collectively referred to as "filters" or "filtering"). In particular, wavelength-dependent filters (e.g. made of aluminum or copper) are used to reduce the proportion of long-wave radiation (also called "soft" radiation), since this makes little or no contribution to imaging and leads to unnecessary radiation exposure. Therefore, wavelength-dependent filtering by such filters (e.g. 2.5 mm borosilicate glass and 2 mm aluminum filters) that are commonly used in X-ray devices is preferably included when determining the expected radiation output.

[0030] According to another embodiment, the data processing unit is arranged such that it can be used to identify and classify damages to the focal path of the X-ray rotating anode in the region of the surface segment according to the recorded 3-dimensional height profile or according to otherwise recorded image information of the surface segment of the focal path. In addition to determining the expected radiation output, the detection and classification of damages according to their type, such as roughening, local melting, cracks, grain collapse, and / or according to their severity, such as height / depth, lateral expansion, etc., is another important criterion for assessing the condition of the focal path and thus helps to issue further recommendations on the use of the X-ray rotating anode in question. According to another embodiment, individual images taken from different angles of the surface segment to be analyzed form the basis for creating the image information captured elsewhere. In particular, each image point can be assigned coordinates (in all three spatial directions), RGB values ​​(R: red component, G: green component, B: blue component in additive color space), B / W values ​​(B: black component, W: white component with respect to grayscale representation), and if necessary, also other information. Based on this, different 2-dimensional contrast representations of the analyzed surface segment can be created, from which damages to the focal path of the X-ray rotating anode in the region of the surface segment can be particularly well identified and classified individually and in combination with several such contrast representations. Furthermore, image information captured in other ways can also be derived from the 3-dimensional height profile (e.g., representation of minimum and maximum heights, etc.), or formed by images captured separately with special camera settings, or derived therefrom. For example, cracks extending deeply into the material of the focal path or even extending through the entire focal path coating and / or local melting resulting in a noticeably raised melt bead on the focal path surface can be an indication that the focal path needs to be reworked to a considerable extent (e.g., by removing a considerable proportion of the focal path or even the entire focal path coating and by reapplying the focal path material) and that not only surface grinding is sufficient.

[0031] This automatic recognition and classification is in particular software-supported. In particular, the software can be designed and arranged in such a way that it learns this recognition and classification by machine learning or has previously learned it. As part of this machine learning, the software is in particular trained by a technician to recognize and classify ("mark") lesions in corresponding example images (e.g. 3-dimensional height profiles or other image information of surface segments of the focal path), whereby the software is given access to the example images and their recognition and classification. The software is set up in such a way that it recognizes and learns patterns from sample images using a learning strategy. The quality of the recognition and classification of the software increases with the number and quality of the provided and thus "marked" example images. In addition, a suitable representation of the relevant surface segments can also facilitate the recognition and classification, which is why this recognition and classification can also be performed based on image information acquired elsewhere.

[0032] According to a further embodiment, the image recording unit and the data processing unit are arranged such that the image recording unit and the data processing unit are able to record at least one image of a further surface section of the X-ray rotating anode in the region near its focal path. This allows to draw additional conclusions about the quality of further regions of the X-ray rotating anode, which may be located, for example, on the same side of the focal path (top side) or on the opposite side of the focal path seen in the axial direction (rear side). As described above, it is also possible to generate a 3-dimensional height profile or other recorded image information from the at least one image recording in order to perform further analysis.

[0033] According to a further embodiment, the data processing unit is arranged in such a way that further utilization options of the X-ray rotating anode can be evaluated by it based on the determined expected radiation output or on characteristic values ​​for this radiation output and corresponding utilization recommendations can be issued (e.g. via a display or a display unit of the data processing unit). In this way, the proposed utilization recommendation is based on an objective evaluation of the X-ray rotating anode, taking into account the condition of the focal path, so that in particular those X-ray rotating anodes which can be directly reused or restored by reprocessing (also called "repair") can also be put to such resource-saving further use. In addition to the expected radiation output, other criteria, such as damage to the focal path or the condition of other areas of the X-ray anode, can also be included in the evaluation. In particular, the further utilization recommendation can include one or more of the following options:

[0034] - Direct further use of the X-ray anode,

[0035] - Surface sanding of the focal path surface,

[0036] - Localized repair focal pathways within areas of severe damage (e.g., localized removal and reapplication of focal pathway material),

[0037] - large-scale mechanical removal of the entire focal path material (in particular the entire focal path coating) or a corresponding surface area, followed by application of the focal path coating and optionally subsequent smoothing of the applied focal path material (e.g. by grinding),

[0038] - mechanical reworking of the X-ray rotating anode outside the focal path area (e.g. in the area of ​​the axial mounting to eliminate imbalances etc.),

[0039] In case of direct reuse or after reprocessing, further usage recommendations may also include recommendations for specific operating conditions (eg operation with certain parameters or in certain X-ray tubes or X-ray devices).

[0040] According to a further embodiment, the data processing unit is coupled to a memory unit, which can in particular be distributed over a single device / memory or alternatively also over several devices / memories (in particular, they are in a communication connection and in data exchange with each other), and the data processing unit and the memory unit are set up for at least one of the following interactions:

[0041] - information determined individually for the respective analyzed X-ray rotating anode can be stored in the memory unit by the data processing unit and read out from the memory unit (individualized, for example by automatic recognition of the serial number of the X-ray rotating anode), for example recorded 3D height profiles, line profiles, surface profiles, individual images, additionally recorded image information, damage in each case from the area of ​​the focal path and / or the area close to the focal path, determined expected radiation power, issued recommendations for further use, etc.;

[0042] - type-specific information for different types of X-ray rotating anodes can be stored in the memory unit by the data processing unit and can be read out from the memory unit, such as drawings, structures (including used connection techniques, coatings, etc.), manufacturing data (e.g. also a unique identification number assigned to each X-ray rotating anode during manufacturing), transport data, dimensions of the X-ray rotating anode, materials of the X-ray rotating anode (in particular the focal path, the anode disk formed underneath, etc.), etc.;

[0043] - the data processing unit is capable of storing and reading out from the memory unit individually recorded operating data of the X-ray rotating anode for the respective analysis, such as, for example, duty cycle, operating time, rotation speed, accelerating voltage applied between cathode and X-ray rotating anode, cathode type, size of the focal spot and electron intensity distribution, etc.; and

[0044] - The individual history of each analyzed X-ray rotating anode regarding its use in the field (i.e. in the X-ray device) and regarding modifications and modifications made to it (such as those carried out after the analysis in the X-ray rotating anode analysis system during its life cycle) can be stored in the memory unit and read out from the memory unit.

[0045] In this way, the entire "life history" of an X-ray rotating anode can be tracked and recorded by the X-ray rotating anode analysis system. In particular, the data is stored together with the relevant date ("date stamp"). Based on this data, better predictions / recommendations can then be made regarding further utilization options when analyzing a specific X-ray rotating anode. This is sometimes summarized as the keyword of life cycle management.

[0046] According to a further embodiment, the data processing unit is arranged to include at least one of the following further information in the evaluation of further utilization options for the X-ray rotating anode:

[0047] - Uniformity of the 3D height profile along the circumference of the X-ray rotating anode;

[0048] - damage to the focal path of the X-ray rotating anode in the region of the surface segment;

[0049] - an image of another surface section of the X-ray rotating anode in the region near its focal path;

[0050] - geometrical changes of the X-ray rotating anode (eg, which can be determined by 3-dimensional measurements of the X-ray rotating anode, for example, tactilely using, in particular, sensors scanning the outer dimensions of the X-ray rotating anode);

[0051] - information determined individually for the respective X-ray rotating anode analyzed;

[0052] - Type-specific information of the respective X-ray rotating anode analyzed;

[0053] - Individual operational data collected for each X-ray rotating anode analyzed; and

[0054] - Individual history of the X-ray rotating anode analyzed.

[0055] Including at least one of these additional information improves the quality of the evaluation of further utilization options. For example, the need for local repairs can be derived from strong inhomogeneities of the 3-dimensional height profile in the circumferential direction. In the case of changes in geometry, the imbalance that occurs, the increase in the outer diameter and / or the enlargement of the central mounting hole (in the case of X-ray rotating anodes without integrally formed rods) are particularly critical. In particular, the need for mechanical reworking can be derived from this, or, if the extent is too great, measures for recycling of the X-ray rotating anode. In addition, on this basis, the remaining service life of the X-ray rotating anode can also be estimated. This leads to an improvement in the overall life cycle management of the X-ray rotating anode. Furthermore, measures for improving future X-ray rotating anodes can be derived from the collected data, such as design adjustments, optimization of the connection technology (e.g. by brazing, welding, etc.) and / or the application of coatings.

[0056] In principle, the present invention relates to an X-ray rotating anode analysis system which does not have a corresponding X-ray rotating anode to be analyzed. According to a further embodiment, the X-ray rotating anode (to be analyzed) is accommodated in the positioning device as a separate component. This corresponds to the operating state of the X-ray rotating anode analysis system. In particular, the positioning device is designed such that the X-ray rotating anode can be positioned accurately relative to the image recording unit. This can be achieved in the simplest way by corresponding (preferably adjustable) stops. Preferably, the positioning device enables the X-ray rotating anode to be positioned in at least two spatial directions (e.g. perpendicular to the rotation axis), in particular in all three spatial directions (in particular by appropriately provided fixing elements) at least by positive locking, even more preferably additionally by friction locking. Furthermore, it is preferred that the positioning device allows the X-ray rotating anode to be rotated about the rotation axis by a (preferably adjustable) rotation angle after the first fixing, in order to, for example, examine different sections of the focal path.

[0057] The invention also relates to a method for analyzing a used X-ray rotating anode having a circumferential focal path on its surface. The method comprises the following steps:

[0058] - positioning the X-ray rotating anode as a single component relative to the image recording unit by means of a positioning device;

[0059] - the acquisition of a 3-dimensional height profile of a surface section of the X-ray rotating anode in the region of its focal path by an image recording unit and a data processing unit connected to the image recording unit; and

[0060] - the expected radiation power or a characteristic value of the X-ray rotating anode is automatically determined by a data processing unit based on the recorded 3D height profile or on a part thereof.

[0061] The steps of acquiring a 3D height profile and automatically determining the expected radiation power are specifically performed according to (at least) an algorithm, which can be executed by one or more appropriately configured software modules. This means that both steps are software-supported. In particular, at least one software module is stored in a data processing unit or on a separate memory, so that it can be loaded into a data processing unit and executed on the data processing unit. The method according to the invention achieves substantially the same advantages as the X-ray rotating anode analysis system according to the invention. In addition, the above-mentioned further improvements and modifications can be implemented in a corresponding manner, wherein in particular the features described on the device side can also be implemented by the units / components by corresponding method steps. In particular, the method according to the invention is performed using the X-ray rotating anode analysis system according to the invention, whereby one or more of the above-mentioned further developments / variations can also be achieved.

[0062] Further advantages and conveniences of the present invention appear from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The accompanying drawings show:

[0064] Figure 1 : Schematic representation of a longitudinal section of an X-ray tube;

[0065] Figure 2 : A stereogram of the X-ray rotating anode;

[0066] Figure 3 : A cross-sectional perspective view of another X-ray rotating anode;

[0067] Figure 4 : A schematic representation of an X-ray rotating anode analysis system according to the present invention;

[0068] Figure 5 : An exemplary 3-dimensional height profile of the focal path surface;

[0069] Figure 6 : shows the calculation of the path length of the generated X-rays through the focal path material for a completely smooth focal path surface;

[0070] Figure 7 : For a focal path surface with surface structure, calculate the path length of the generated X-rays through the focal path material;

[0071] Figure 8 : The three figures show at the top (first figure) an exemplary line profile of the focal path surface used, below (second figure) the resulting additional path length distribution, and below again (third figure) the resulting emission distribution. DETAILED DESCRIPTION

[0072] Figure 1A schematic longitudinal cross section of an X-ray tube 2 is shown. It has a glass bulb 4 with a vacuum interior 6, in which there is a cathode 8 with a heating coil 10, which emits electrons 12 when in use (i.e. when current flows). An X-ray rotating anode 14 is arranged opposite the cathode 8. The X-ray rotating anode 14 has a central mounting hole, to which a rod (shaft) 16 is connected by a fixing 17. The shaft 16 connects the X-ray rotating anode 14 to a rotor 18 of an electric motor 20. The electric motor 20 has a stator 22 outside the glass bulb. When in use, the electric motor 20 rotates the X-ray rotating anode 14 about a rotation axis 24 in a known manner. The electrons 12 emitted by the cathode 8 are accelerated onto a rotating focal path 26 of the X-ray rotating anode 14. When they hit the focal path 26, their kinetic energy is converted into heat and, to a lesser extent, into X-rays 28. Through an exit window 30, which may be formed, for example, of borosilicate glass and is used to extract X-rays from the X-ray tube, a portion of the generated X-rays 28 is extracted in an X-ray emission direction 32 perpendicular to the rotation axis 24. In addition, further filters, such as filters made of aluminum or copper, are also typically used in the beam path of the X-rays in order to reduce the proportion of long-wave (soft) X-rays. The extracted X-rays are then used in an X-ray machine to radiate through an object, for example for diagnostic imaging in a medical X-ray machine.

[0073] Below, Figure 2 As an example, the structure of the X-ray rotating anode 33 is explained. In its basic form, it has an anode disk 38 with a central mounting hole 39, which is rotationally symmetrical about the rotation axis 36 (axial direction or also z direction). In particular, the anode disk 38 is made of a molybdenum-based material (molybdenum ≥ 50wt%, in particular molybdenum ≥ 90wt%) or pure molybdenum. On one side of the anode disk 38, i.e. the cover side, there is a circumferential focal path 40 with a focal path coating made of a tungsten-rhenium alloy (tungsten: 95wt%; Re: 5wt%). Figure 2The circular area on the focal path 40 shown by the dashed line shows the focal spot path 41, i.e. the annular area scanned by the electron beam (focal spot) during the rotation of the X-ray rotary anode 33. In the area of ​​the focal path 40, the anode disk 38 has a circumferentially inclined focal path surface 42. It is inclined at an inclination angle α (in the present case: α=10°) relative to a main extension plane 44 extending perpendicularly to the rotation axis 36, which is spanned by the radial direction and is also referred to as the xy plane in the present case. The course of the focal path surface 42 corresponds to the side surface of a truncated cone. In each case, the circumferential direction extends locally perpendicularly to the radial direction around the rotation axis 36. The X-ray emission direction 46 usually extends exactly along one of the radial directions, so that it is inclined at an inclination angle α (e.g. 10°) relative to the focal path surface 42. In the rectangular coordinate system used for the description, it is spanned by the x-axis, the y-axis and the z-axis, the y-axis extending along the X-ray radiation exit direction 46 (thereby this is only in the case of the X-ray radiation exit direction 46). Figure 2 The x-axis extends perpendicularly to this direction in the main extension plane 44 and the z-axis extends in the axial direction (shown as an example in FIG. 4 and defined in the X-ray tube by the position of the exit window). Figure 2 On the back side (ie opposite the cover side), a graphite body 43 is attached (in particular welded) to the anode disk 38 .

[0074] Figure 3 Another embodiment of an X-ray rotating anode 34 is shown, wherein the same reference numerals are used as in the embodiment of the X-ray rotating anode 34. Figure 2 The same or corresponding parts / portions of the X-ray rotating anode 33, and only the differences are discussed below, while also referring to Figure 2 Description of the accompanying drawings. Figure 3 No graphite body is provided in the X-ray rotating anode 34. In addition, it has an integrally formed rod 48 on the rear side, which, in the schematic diagram shown, consists of a socket 50 integrally formed with the anode disk 38 and a tubular part 52 connected thereto (for example by welding). The tubular part 52 may also have further mechanical connection elements at its distal end for attachment to other components (for example a rotor).

[0075] Figure 4 A schematic diagram of an X-ray rotating anode analysis system 54 according to the invention is shown. It has a positioning device 56, an image recording unit 58, additional image recording units 60, 62 and a data processing unit 64, which are described in more detail below. The positioning device 56 is designed to receive and precisely position X-ray anodes of different designs, in particular with or without integrally provided rods. In this case, a substantially similar Figure 2The illustrated X-ray rotary anode corresponds to the exemplary X-ray rotary anode 33, whose components / parts are correspondingly designated with the same reference numerals, which is securely mounted on the shaft 66 of the positioning device 56 via its fastening hole 39. The shaft 66 can be rotated by means of a rotation device 68, which is motorized in this case and can be controlled by means of a data processing unit 64, so that the rotational position of the X-ray rotary anode 33 relative to the image recording unit 58 (and the additional image recording units 60, 62) can be adjusted. Furthermore, the shaft 66 is mounted on a carrier part 70 via the rotation device 68. The carrier part 70 is in turn connected to a (schematically shown) frame structure 72 of the X-ray rotary anode analysis system 54, so that the X-ray rotary anode 33 can be precisely positioned relative to the frame structure 72 (and therefore relative to the image recording units 58, 60, 62).

[0076] Therefore, the image recording units 58, 60, 62 are also connected to the frame structure 72 via supports 74, so that their position and inclination (see joints 76) can be adjusted precisely relative to the frame structure 72 (and therefore relative to the X-ray rotating anode 33). The image recording unit 58 (and the additional image recording units 60, 62) also communicate with the data processing unit 64. The image recording unit 58 can be controlled via the data processing unit 64 in order to record individual images of a surface section of the X-ray rotating anode 33 to be analyzed, in particular of a surface section in the region of the focal path 40 of the X-ray rotating anode 33. The image recording unit 58 is formed by a high-resolution camera (which preferably operates in the optically visible range) having a magnification in the range of 5-20x and a lateral resolution of less than 4 μm (in the xy plane, with respect to the X-ray rotating anode 33). Figure 2 Defined in and also in Figure 4). In particular, the camera has a lateral resolution of 3.355 μm in the xy plane of the surface segment and a vertical resolution of 3.565 μm in the z direction, and a magnification of 10x is provided, whereby the resolution can be increased by a large number of individual images. Preferably, a separate illumination unit is provided, in particular an illumination unit with variably adjustable positioning (e.g. an LED with “white” light, i.e. which preferably covers the spectrum essentially in the visible wavelength range). Additionally or alternatively, the camera has an internally designed illumination unit (e.g. an LED with “white” light, i.e. which preferably covers the spectrum essentially in the visible wavelength range). The same preferably applies to the further image recording units 60, 62, wherein these image recording units can, for example, be designed and positioned such that the image recording unit 60 can record images of a larger cross section of the cover side (or also the entire cover side) of the X-ray rotating anode 33, and / or such that the image recording unit 62 can also record images of a larger part of the rear side (or also the entire rear side) of the X-ray rotating anode 33.

[0077] The data processing unit 64 is connected to the interface 78 (in Figure 4 The data processing unit 64 (schematically shown in FIG. 1 ) controls and communicates with the image recording unit 58 and other system components of the X-ray rotating anode analysis system 54 (in particular with the additional image recording units 60, 62, the rotation device 68, the tactile measurement device 84, etc. described below). In addition, the data processing unit 64 has an input and display unit 80, through which a user can make inputs (information input, action triggering, etc.) and display corresponding information (results, suggestions, prompts, etc.), and a memory unit 82, in which data can be stored by the data processing unit and can be read out from the unit.

[0078] Preferably, the individual images are recorded such that the rotating device 68 further rotates the X-ray rotating anode 33 about the rotation axis 36 by a predetermined feed angle (e.g., by an angle in the range of 1-2°) so that at each of these different angular positions, the image recording unit 58 generates individual images of the surface segments of the focal path 40 to be analyzed (i.e., individual images of the surface segments respectively located below the recording area of ​​the image recording unit 58, so that the individual surface segments are overlapped multiple times). At the same time, separate images can also be generated by additional image recording units 60, 62 (individually or optionally only at selected angular positions). In addition, in Figure 4, a tactile measuring device 84 is shown, which has a sensor 86 which is mounted on a support 90 in an angular position which can be variably adjusted via a joint 88 and via which is in turn connected to the frame structure 72. The X-ray rotating anode 33 can be tactilely measured by the tactile measuring device 84 (also possibly during its rotation) in order to determine any geometric changes of the X-ray rotating anode 33 which may have occurred.

[0079] In the following, reference Figures 5 to 8 , describes an exemplary embodiment for calculating the absorption of X-rays along the direction of X-ray emission, taking into account local absorption effects due to local surface morphology according to the recorded 3-dimensional height profile, in order to then determine characteristic values ​​of the expected radiation power. Further information and literature on the simplifications performed and the calculation method can be found in Siller, Maximilian et al. "Geometrical model for calculating the effect of surfacemorphology on total x-ray output of medical x-ray tubes", Medical Physics 48.4 (2021): 1546-1556. In order to be able to perform this calculation automatically, software is in particular provided, by which the calculation can be performed according to a corresponding algorithm and can be loaded into a data processing unit (for example, loaded into Figure 4 ) and executed thereon.

[0080] Figure 5 An example of a 3D height profile Mheight(x,y) of the analyzed surface segment is shown, for example, for an aged focal path of an X-ray rotating anode after the X-ray rotating anode has been used in an X-ray device, which is typical (ref. Figure 2 and 4 ). Each image point or pixel in the xy plane of the 3-dimensional height profile is assigned a corresponding height value or z value, whereby this is represented by a grayscale representation. The z range shown is -30 μm in the negative range (shown in black) to 0 μm (shown in gray) to +30 μm (μm: micrometer) in the positive range (shown in white). Figure 5Also shown are typical damages to the focal path surface that occur after prolonged use. Two pit-shaped indentations marked "A" can be seen in the lower left portion of the profile. These are particle collapses in the focal path material. In the right-hand half, a narrow depression can be seen, which extends essentially vertically across the center portion of the image and is marked "B". This is a crack in the focal path material. In addition, a bead-like protrusion marked "C" can be seen in the upper right portion, which is a localized melt. This 3-dimensional height profile - regardless of its specific shape and specific height profile - forms the starting point for calculating the X-ray absorption along the direction of X-ray emission.

[0081] The calculation according to the present embodiment is based on the concept that for each generation point of the X-ray (corresponding to the generation depth of the X-ray in the z direction below the focal path surface), the absorption of the generated X-ray by the focal path material is determined taking into account the local surface modification according to the 3-dimensional height profile and then summed or integrated over all relevant generation points (in this case, the line profile) when the X-ray is directed along the X-ray emission direction. The X-ray radiation emitted at each generation point in the X-ray emission direction ("initial spectrum") is based on the characteristic X-ray spectrum (braking radiation distribution with characteristic lines) of the corresponding focal path material as a function of the accelerating voltage (in this case 100 kV). Data and calculation methods for typical accelerating voltages and focal path materials are available in the literature (for simplification, pure tungsten can be used for the tungsten-rhenium alloy with a major proportion of tungsten due to their similar atomic number and density). Furthermore, it has to be taken into account that only those individual image points or pixels of the 3-dimensional height profile (or in the present case the line profile derived therefrom) will be included in the focal spot region of the X-ray rotating anode and these will then be weighted according to the electron intensity distribution, whereby this only takes place as one of the last steps in the present calculation model. In this example, the calculation is performed for the line profile of the surface section of the focal path to be analyzed, assuming that the electrons are accelerated with an accelerating voltage of 100 kV to this section with a typical size and intensity distribution of a focal spot.

[0082] According to this embodiment, the following simplifications / methods are used:

[0083] 1. For simplification purposes, the average generation depth of X-rays d is used. e-, rather than the actual distribution of the generation depths along the z-axis (the latter would mean several generation points along the z-coordinate for each xy-coordinate according to the distribution function, and these generation points would need to be summed or integrated). In other words, according to this simplification, for each image point or pixel with an associated xy-coordinate in the z-direction, exactly one generation point with a z-coordinate falling below the focal path surface is assumed. In the literature one can find average generation depths as a function of the surface tension applied between the cathode and the X-ray anode in, for example, tungsten-based focal path materials. For example, for an accelerating voltage of 100 kV, the average generation depth d of X-rays in a tungsten-based material of 1.6 μm is e- Given in Poludniowski, Gavin G., and Philip M. Evans. "Calculation of x-ray spectra emerging from an x-ray tube. Part I. Electron penetration characteristics in x-ray targets" Medical Physics 34.6, Part I (2007): 2164-2174 (another related source: Behling, Rolf. "Modern diagnostic x-ray sources: technology, manufacturing, reliability". CRC Press 2021, page 71).

[0084] 2. Regarding the size of the focal spot and the electron intensity distribution: Compared to a static arrangement of the focal spot on the focal path surface (see, for example, a vertical anode), where the electron intensity distribution over the affected area of ​​the focal spot (x, y coordinates) must be taken as a basis, an X-ray rotating anode can be based on a linear (along the X-ray emission direction or y direction) and a correspondingly adapted intensity distribution due to the rotation in use. For example, this can be determined using an X-ray rotating anode and in many cases (depending on the type of cathode) can be approximated by two superimposed sine functions (in many cases, the intensity distribution is formed by having two superimposed "humps" in the height in the y direction). Alternatively, it can also be simulated by including electromagnetic interactions of different cathode types as required. Regarding the 3-dimensional height profile: Therefore, the comparison of the radiation power emitted by an aged focal path with surface structure with the radiation power emitted by a completely smooth focal path does not require a two-dimensional view of the recorded 3-dimensional height profile and a corresponding application of the surface function (with x and y coordinates) (see, for example, the method in the above-mentioned publication of Maximilian Siller et al. for upright anodes), but it is sufficient if corresponding line profiles of the 3-dimensional height profile extending in the radial direction are used and compared with each other (which point to the X-ray emission direction or y direction once per revolution during the rotation of the X-ray rotating anode). This is described in the following calculations using line profiles extending in the radial direction along the focal path surface, which can be obtained as described in Figure 3 below. For the following calculations, it is assumed that the radial direction is simultaneously aligned with the X-ray emission direction or y direction.

[0085] 3. Regarding the line profile to be created in the radial direction: Due to the rotational symmetry of the X-ray rotating anode, the image points / pixels of the captured 3-dimensional height profile are usually not exactly along the corresponding radial direction, so that in order to generate a line profile extending in this direction, a corresponding approximation of the captured surface structure has to be performed (e.g. by means of a fitted height profile extending along the captured image points / pixels) in order to create a line profile for all y coordinates. This means that in order to generate a line profile extending in this direction, a corresponding approximation of the recorded surface structure has to be performed (e.g. by means of a fitted height profile extending along the recorded image points / pixels) in order to obtain corresponding z values ​​(i.e. heights) for all y coordinates (or radial coordinates) along the line profile. The determination of the line profile extending in the radial direction is preferably performed with software support, e.g. using a fitting function.

[0086] 4. For simplicity, the radiation power of each generation point of the line profile used as an example is strictly determined only in the radial direction, assuming in the present case that it is aligned in the X-ray emission direction or y-direction, and not for each generation point initially emitting a cone of radiation in a region around the X-ray emission direction in order to then sum or integrate the radiation emitted exactly in the X-ray emission direction across the generation point. This enables calculations using the line profile, as explained in detail below.

[0087] 5. Furthermore, regardless of the generation point and the surface structures locally present at the generation point along the X-ray emission direction, it is assumed that the emitted X-rays travel a minimum path length in the focal path material. Depending on the tilt angle (in this case: α=10°), this minimum path length will be chosen as a fraction of the path length of the locally emitted radiation through the focal path material that is expected for a smooth surface, e.g. 5 μm for an expected path length of 9.07 μm (this is an example for a tilt angle of the focal path of α=10°). Due to the special features of the 3-dimensional height profile and its resolution, this avoids theoretically possible peaks in the radiation power locally emitted from individual generation points, which would lead to local distortions (e.g. on the sides of surface structures of the focal path surface that are very steeply inclined along the X-ray emission direction).

[0088] refer to Figure 6 , 7 and 8, the following explains how to determine the absorption of the focal track material for each generation point of the X-rays, taking into account the local surface variability according to the 3D height profile: Figure 8 , the top figure shows an exemplary line profile of the focal path surface used, which is plotted as height (in millimeters) (see "height [mm]" in the figure) in the y direction (in millimeters) (see "y [mm]" in the figure). It can be obtained, for example, from Figure 5 The 3D height profile shown is generated along the cross section of the X-ray emission direction y, Figure 6 and 7 Each shows a schematic cross section of such a line profile of the focal path surface. Figure 6 In the example, the case of a completely smooth focus path surface 92 is first shown, which is inclined at an inclination angle α=10° relative to the y direction (for illustration purposes, in FIG. Figure 6 and 7 Using two exemplary electrons 94, 96, which impinge on the focal path surface 92 at two different y-coordinates, and (simplified) according to the average production depth d of the X-rays e- Penetration to the corresponding generation point 98 shows the path length d that the generated X-rays travel through the focal path material in the X-ray emission direction (y direction). x-rayRegardless of where the electron appears within the focal spot, the path length it travels can be determined using the following formula:

[0089]

[0090] In d e- = 1.6 μm and α = 10°, which results in a constant “theoretical path length d x-ray =9.07 μm. This means that for a completely smooth focal path surface 92, the generated X-rays first travel along a path length d of constant 9.07 μm before they emerge from the focal path surface. x-ray The radiation is then filtered through the focal path material before it hits the detector 104 (if there are no other obstacles or objects to be transmitted in the radiation path). For example, a filter made of borosilicate glass with a thickness of 2.5 mm (e.g. as an exit window) and an aluminum filter with a thickness of 2 mm can be used in the calculation model. With regard to the filtering through the focal path material, filtering through pure tungsten (W) can be used to simplify the filtering associated with a tungsten-rhenium focal path (with a predominant proportion of tungsten), since tungsten (W) and rhenium (Re) differ only slightly in their atomic number and density. The absorption by the focal path material (in each case over a path length of 9.07 μm) and the filtering by the filter 102 that occurs on a completely smooth focal path surface are referred to as basic filtering.

[0091] The potential basic radiation power of the line profile or y-coordinate expected on such a completely smooth focal path surface is used as a reference value. In particular, based on the above initial spectrum, the potential basic radiation power expected for a single y-coordinate in the X-ray emission direction due to absorption by the focal path material over a path length of 9.07 μm and filtering by the filter 102 is first determined. This is achieved in particular by software support (e.g. SpekCalc pro 1.1, which was developed by Gavin Poludniowski and Phil Evans at the "Institute of Cancer Research" in London, UK for theoretical methods and by Francois deBlois, Guillaume Landry and Frank Verhaegen at McGill University in Montreal, Canada for a graphical user interface; currently available at www.spekcalc.weebly.com). The software is preferably arranged in such a way that it first determines a reduction / filtering (wavelength-dependent) of the initial spectrum for a single y-coordinate of the line profile (because the strength of the reduction / filtering depends on the wavelength or energy of the photons) in order to obtain a "potential base spectrum" ("potential" because the electron intensity distribution and the size of the focal spot have not yet been taken into account) whose intensity distribution is reduced (wavelength-dependent) compared to the initial spectrum. Then, a "potential base radiant power" is preferably determined for a single y-coordinate, which results from the sum or integration of the radiant powers over the individual wavelengths of the potential base spectrum obtained after base filtering. Since a completely smooth focus path surface is assumed here and only the "potential" base spectrum and the "potential" base radiant power are taken into account (i.e. the electron intensity distribution and the focal spot size have not yet been taken into account), these are constant at different y-coordinates of the line profile and correspondingly also in the circumferential direction for different line profiles.

[0092] on the contrary, Figure 7 The focal path surface has surface structures or surface modifications 100, for example, as they occur in the X-ray rotating anode used (in addition, Figure 7 With Figure 6 According to the calculation model, for each generation point 98 of the X-ray, i.e. for each y coordinate along the y direction (X-ray emission direction) of the line profile, the actual path length d' travelled by the focal path material is now determined taking into account the surface deformation according to the 3-dimensional height profile. x-ray (in the y direction), such as Figure 7 In order to determine the "actual path length" d' x-ray, if the X-ray initially leaves the focal path surface from the generation point in the y direction, but then re-enters the focal path material (e.g. due to localized elevation) (once or several times) before finally reaching a free area outside the focal path material, then a partial path length may also have to be added. Preferably, this determination and the other calculation steps are performed with software support using appropriately configured software (e.g. Matlab R2017b 64-bit; currently available at www.mathworks.com) (unless otherwise stated). For this purpose, the corresponding line profile (e.g. in Figure 8 ) are imported into the software. Alternatively, one or more 3D height profiles are input into the software and then a line profile extending in the radial direction is generated according to the above simplification / method no. 3. In addition, the tilt angle (here: α=10°) and the average generation depth of the X-rays (here: d e- = 1.6 μm) must be taken as a basis so that then Figure 7 The determination shown starts from the corresponding associated generation point (displaced downward in the z direction by d e- into the focal path material) and travels in the y direction through the actual path length d' for each y coordinate of the corresponding line profile of the focal path material x-ray This can be achieved, for example, by software, i.e. by comparing the original line profile (determining the focal path surface) with an otherwise identical line profile (determining the generation point) offset downwards in the z direction into the focal track material, so that the actual track length traversed in the y direction can then be determined from the respective y coordinates of the respective line profiles. Then, by calculating the actual path length d' from the actual path length d' x-ray (y) minus the theoretical path length d x-ray , the additional path length distribution f is determined as follows add (y):

[0093] (2)f add (y) = d′ x-ray (y)-d x-ray

[0094] If d' x-ray (y)≤5μm:

[0095] Then f add (y):=5μm-9,07μm=-4,07μm

[0096] If the actual path length of the y coordinate is d' x-ray (y) Deviation from the theoretical path length d x-ray , this results in an actual filtering different from the basic filtering described above. The surface changes that occur result in an actual path length d' for most y coordinates x-ray(y) and the theoretical path length d x-ray (i.e. f add However, for a certain proportion of y coordinates, the actual path length d' x-ray (y) decreases (i.e., f add <0), in which case, according to the above simplification / method number 5 (see line 2 of equation (2)), a minimum path length of at least 5 μm must be used. Figure 8 The second diagram shows the additional path length distribution, which is plotted as the additional path length f in the y direction (in millimeters). add (y) (unit: micrometer or μm) (the “f add (y) [μm]”) (see "y [mm]" in the figure), which specifically leads to the above Figure 8 The line profile shown in .

[0097] Then, much like a fully smoothed focus path (preferably software supported, e.g. using SpekCalc pro 1.1; see above), the (wavelength-dependent) reduction / filtering of the initial spectrum is first determined as f add function (not yet specialized for different y coordinates) in order to obtain as f add The “potential actual spectrum” of the function of , whose intensity distribution is reduced compared to the initial spectrum. Then, as f add The "potential actual radiated power" is determined as a function of the potential actual radiated power, which is generated by the sum or integration of the radiated powers at the various wavelengths of the potential actual spectrum. As a further step, the ratio of this potential actual radiated power to the potential basic radiated power (determined as described above) is red As f add The ratio f is thus determined by forming a function of (preferably again with software support, for example using SpekCalc pro 1.1; see above). red (f add ) represents the degree to which the potential actual radiation power of the X-ray starting point varies relative to the potential basic radiation power of a completely smooth focal path surface, which is the additional path length f that the X-ray must travel from the starting point. add The determined ratio f red (f add ) can in particular be fitted with a function, preferably with a double exponential function (ie by means of the sum of two exponential functions). Starting from the minimum value (in this case -4.07 μm), for the additional path length f add negative value, which is greater than 1, and then decreases continuously, and for f add = 0, which reaches the value 1 exactly. For a positive additional path length fadd value, which is less than 1, and for increasing additional path length f add This function is now preferably applied specifically to the additional path length distribution f again using software support (e.g. using Matlab R2017b 64-bit; see above). add (y), as determined for the line profile using equation (2) in order to obtain the emission distribution f at each y coordinate of the line profile emi (y), as shown in equation (3):

[0098] (3)f emi (y) = f red (f add (y))

[0099] Emission distribution f emi (y) represents the ratio of the potential actual radiated power to the potential base radiated power for each y coordinate of the line profile, where for lines with f add The y-coordinate of the associated negative value (i.e., d' x-ray (y)<d x-ray ), the ratio is greater than 1, while for f add Positive value (i.e., d' x-ray (y)>d x-ray ), the ratio is less than 1. This means that for the corresponding generated point, the actual path length d' x-ray Relative to the theoretical path length d x-ray The larger is the potential actual radiated power relative to the potential base radiated power, the lower the ratio (i.e., the more emitted radiation is absorbed), and vice versa. Figure 8 This ratio or this emission distribution is shown in the third figure, plotted as the emission distribution f in the y direction (in millimeters) emi (y)(“f emi (y)[-]”) (see “y[mm]” in the figure), which specifically leads to Figure 8 The additional path length f shown in add (y).

[0100] Finally, the electron intensity distribution in the y-direction (i.e. in the radial direction) must also be taken into account in order to compare quantities that are not only designated as "potential", since the radiation power generated at the respective y-coordinate depends on whether an electron impinges on this y-coordinate and with what intensity. For this purpose, for example, damage to the focus path surface in the radial direction outside the focal spot region is less critical, since no X-rays are generated at these locations, whereas damage in regions of high electron intensity may be particularly critical, especially if it leads to strong shadowing. As explained above in simplification / method no. 2, the electron intensity distribution in an X-ray rotating anode can be given by a linear (in the y-direction or radial direction) intensity profile f e- (y) is used to describe the emission distribution f emi (y) Correspondingly, the intensity distribution f e- (y) weighted to obtain the ratio O(y) of the "actual radiated power" to the "basic radiated power" for the corresponding y coordinate, as shown in the following equation:

[0101] (4) O(y) = f e- (y)*f emi (y)

[0102] In order to obtain the ratio of the actual radiant power emitted over the entire line profile of the damaged focal path surface with the surface structure to the corresponding basic radiant power which would be emitted over the entire line profile in the case of a completely smooth focal path surface, Linie , we must integrate O(y) over the y coordinate, as shown in the following equation:

[0103] (5)O Linie =∫f e- (y)*f emi (y)dy

[0104] In this way, the influence of the surface structures occurring in the region of a specifically analyzed line profile of the focal path surface of the damage on the emitted radiation power can be evaluated. Linie = represents a characteristic value of the radiation power attenuation due to damage to the focal path surface. Furthermore, of course, a large number of line profiles (each extending radially and preferably distributed in the circumferential direction around the X-ray anode) can be analyzed in a corresponding manner. On the one hand, possible changes in the circumferential direction of the X-ray rotating anode can be determined. In addition, the total radiation power can also be obtained by analyzing the O obtained for each line profile. Linie The values ​​are determined by summing / integrating.

[0105] The invention is not limited to the described embodiments. For example, as an alternative to simplification / method No. 2 (see above), it is also possible to use the electron intensity distribution over the affected area with respect to the focal spot and the line profile, i.e. the function f e-(x,y). Then, depending on the size of the focal spot, multiple adjacent line profiles of the 3D height profile must be included and, finally, the electron intensity distribution f e- The resulting emissivity distribution f is obtained by scalar multiplication of (x,y) emi Several such surface sections in the circumferential direction of the focus path are then preferably analyzed in the same way.

Claims

1. An X-ray rotating anode analysis system for analyzing a used X-ray rotating anode (14; 33; 34) having a circumferential focal path (26; 40) on the surface, the X-ray rotating anode analysis system being provided with: - a positioning device (56) for the X-ray rotating anode (14; 33; 34), - an image recording unit (58), and - a data processing unit (64) which is connected to the image recording unit (58), wherein: The positioning device (56) and the image recording unit (58) are designed so that the X-ray rotating anode (14; 33; 34) can be positioned at a predetermined position relative to the image recording unit (58) as a separate component. The image recording unit (58) and the data processing unit (64) are arranged such that a 3-dimensional height profile of a surface section of the X-ray rotating anode (14; 33; 34) in the region of its focal path (26; 40) can be detected by the image recording unit (58) and the data processing unit (64), and Therein, the data processing unit (64) is capable of determining the expected radiation power or a characteristic value thereof of the X-ray rotating anode (14; 33; 34) based on the recorded 3D height profile or based on a part thereof.

2. The X-ray rotating anode analysis system according to claim 1, characterized in that: The image recording unit (58) and the data processing unit (64) are configured so that, using electromagnetic radiation, a plurality of individual images having respectively different depth information of the surface segment to be analyzed of the X-ray rotating anode (14; 33; 34) can be generated, and a three-dimensional height profile of the surface segment to be analyzed can be reconstructed based on the individual images by the data processing unit (64).

3. The X-ray rotating anode analysis system according to claim 2, characterized in that: The image recording unit (58) and the data processing unit (64) are configured such that, using electromagnetic radiation in the wavelength range of 380 nm-780 nm, a plurality of individual images of the surface section to be analyzed can be generated from different angles.

4. X-ray rotating anode analysis system according to at least one of the preceding claims, characterized in that The data processing unit (64) is arranged to determine the expected radiation power of the X-ray rotating anode (14; 33; 34) or a characteristic value for the expected radiation power based on the automatically calculated absorption of X-rays along the X-ray emission direction (32; 46), taking into account local absorption effects due to local surface deformations (100) according to the recorded 3D height profile.

5. The X-ray rotating anode analysis system according to claim 4, characterized in that: The data processing unit (64) is arranged so that at least one line profile can be used by it for the automatic calculation of X-ray absorption, the line profile extending over a predetermined minimum length along a detected surface segment of the X-ray rotating anode (14; 33; 34) in the X-ray emission direction (32; 46) and having a local surface modification according to the 3D height profile.

6. The X-ray rotating anode analysis system according to claim 4, characterized in that: The data processing unit (64) is configured to enable at least one surface profile to be used for automatic calculation of X-ray absorption, the at least one surface profile extending along the detected surface segment over a predetermined minimum length in the X-ray emission direction (32; 46) and extending over a predetermined minimum width substantially perpendicularly to the predetermined minimum length, and having a local surface degeneration according to the 3D height profile.

7. The X-ray rotating anode analysis system according to at least one of claims 4 to 6, characterized in that: The data processing unit (64) is arranged to include at least one of the following input values ​​in the automatic calculation of the absorption of X-rays: The depth at which the X-rays are produced; X-ray emission angle (α); The material of the focal path (26; 40) of the X-ray rotating anode (14; 33; 34); The size of the focal spot; the electron intensity distribution of the focal spot; and Filter (102).

8. X-ray rotating anode analysis system according to at least one of the preceding claims, characterized in that The data processing unit (64) is arranged to enable identification and classification of damages (A, B, C) to the focal path (26; 40) of the X-ray rotating anode (14; 33; 34) in the region of the surface segment based on the recorded 3-dimensional height profile or based on image information of the surface segment recorded in another way.

9. X-ray rotating anode analysis system according to at least one of the preceding claims, characterized in that The image recording unit (58, 60, 62) and the data processing unit (64) are arranged such that they can record at least one image recording of another surface section of the X-ray rotating anode (14; 33; 34) in an area adjacent to its focal path (26; 40).

10. The X-ray rotating anode analysis system according to at least one of the preceding claims, characterized in that The data processing unit (64) is configured such that it can evaluate further usage options of the X-ray rotating anode (14; 33; 34) based on the determined expected radiation power or based on a characteristic value for the expected radiation power and can issue a corresponding usage recommendation.

11. X-ray rotating anode analysis system according to at least one of the preceding claims, characterized in that The data processing unit (64) is coupled to a memory unit (82), and the data processing unit (64) and the memory unit (82) are configured for at least one of the following interactions: The information determined individually for the respective analyzed X-ray rotating anode (14; 33; 34) can be stored in the memory unit (82) by the data processing unit (64) and can be read out from the memory unit (82); Type-specific information of different types of X-ray rotating anodes (14; 33; 34) can be stored in the memory unit (82) by the data processing unit (64) and can be read out from the memory unit (82); The operating data recorded individually for the respective analyzed X-ray rotating anode (14; 33; 34) can be stored in the memory unit (82) and can be read out from the memory unit (82) by the data processing unit (64); and The individual history of the individual analyzed X-ray rotating anodes (14; 33; 34) regarding their use on site and regarding their changes and degeneration can be stored in a memory unit (82) and read out from said memory unit (82).

12. The X-ray rotating anode analysis system according to claim 10 or 11, characterized in that: The data processing unit (64) is configured to include at least one of the following further information in the evaluation of further use options of the X-ray rotating anode (14; 33; 34): uniformity of the three-dimensional height profile along the circumferential direction of the X-ray rotating anode (14; 33; 34); damage (A, B, C) to the focal path (26; 40) of the X-ray rotating anode (14; 33; 34) in the region of the surface section; an image of another surface section of the X-ray rotating anode (14; 33; 34) in a region near its focal path (26; 40); geometrical variation of the X-ray rotating anode (14; 33; 34); Information individually determined for the respective analyzed X-ray rotating anode (14; 33; 34); type-specific information for the respective analyzed X-ray rotating anode (14; 33; 34); recording operating data individually for each X-ray rotating anode (14; 33; 34) analyzed; and Individual histories of the analyzed X-ray anodes (14; 33; 34).

13. X-ray rotation analysis system according to at least one of the preceding claims, characterized in that The X-ray rotating anode (14; 33; 34) is accommodated in the positioning device (56) as a separate component.

14. A method for analyzing a used X-ray rotating anode (14; 33; 34) having a circumferential focal path (26; 40) on its surface, the method comprising the following steps: Positioning the X-ray rotating anode (14; 33; 34) as a separate component relative to an image recording unit (58) by means of a positioning device (56); The image recording unit (58) and a data processing unit (64) connected to the image recording unit (58) acquire a 3D height profile of a surface section of the X-ray rotating anode (14; 33; 34) in the region of its focal path (26; 40); and The expected radiation power or a characteristic value of the X-ray rotating anode (14; 33; 34) is automatically determined by the data processing unit (64) based on the recorded 3D height profile or based on a part thereof.

15. The method according to claim 14, characterized in that The method is performed using an X-ray rotating anode analysis system (54) according to any one of claims 1 to 13.

Images