X-ray rotating anode analysis system.

Abstract

The present invention relates to an X-ray rotating anode analysis system for analyzing a used X-ray rotating anode having a revolving focal track on a surface section. The X-ray rotating anode analysis system includes a positioning device for the X-ray rotating anode, an image acquisition unit, and a data processing unit coupled to the image acquisition unit. The positioning device and the image acquisition unit are configured to position the X-ray rotating anode as an individual component at a predetermined position relative to the image acquisition unit. The image acquisition unit and the data processing unit are configured such that the image acquisition unit and the data processing unit can detect a three-dimensional height profile of the surface section of the X-ray rotating anode in the region of the focal track, and the data processing unit can determine a predicted radiation output or characteristic value of the X-ray rotating anode from the detected three-dimensional height profile or a portion thereof.

Description

[Technical Field]

[0001] The present invention relates to an X-ray rotating anode analysis system for analyzing a used X-ray rotating anode having a revolving focal orbit on a surface portion, and further to a method for analyzing such a used X-ray rotating anode.

[0002] The rotating X-ray anode is incorporated into an X-ray tube, which is integrated into the corresponding X-ray device. The rotating X-ray 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 that reaches the rotating X-ray anode. The rotational movement of the rotating X-ray anode causes the electron beam to scan a circular orbit, or focal track. Most of the energy of the electron beam is converted into heat at the rotating X-ray anode, while a small portion is emitted as X-rays. The locally released heat strongly heats the rotating X-ray anode. The rotation of the rotating X-ray anode prevents the anode material from overheating.

[0003] Particularly in the high-power field, a high radiation power of the emitted X-rays is required, which is especially true for medical imaging applications such as computed tomography. Each time the material of the focal track moves under the electron beam by rotation, the focal spot area on the surface of the focal track is first subjected to a high temperature increase and thermally induced stress, followed by a temperature decrease. This causes the focal track to age, which is manifested in particular by surface roughening, crack formation, particle generation, and / or localized melting.

[0004] Deterioration of the focal track over time leads to a decrease in the emitted radiation output and a decrease in the operational stability of the X-ray tube. However, other influences, such as aging of the cathode (emitter), wear in the area of ​​the bearing components, and / or distortion of the X-ray rotating anode, can also lead to such a reduction and / or deterioration. Therefore, assessing the cause of this is a challenge. If the X-ray rotating anode is suspected or identified as the (common) cause, its continued use is problematic. The options are to continue using the X-ray rotating anode if it is still functional, to recondition it (also called "rework"; e.g., reworking the focal track, removing and installing a new focal track, mechanical reworking in the area of ​​the bearing components, etc.) if functionality can be restored, or to recycle the X-ray rotating anode. This decision is often made subjectively by personal inspection of the X-ray rotating anode. From ecological, sustainability, and cost perspectives, it is preferable to continue using or recondition X-ray rotating anodes. In this case, the state of the focal track is an essential influencing factor regarding the continued use of the X-ray rotating anode.

[0005] An X-ray rotating anode test stand for evaluating a plurality of X-ray rotating anodes is known from US Pat. No. 5,623,999, in which the X-ray rotating anode to be inspected is brought into a vacuum chamber of the test stand, rotated, and its focal track region is brought to the operating temperature by an electron beam. The test stand also has a temperature sensor for detecting the temperature of the X-ray rotating anode, and a control device for evaluating the state of the X-ray rotating anode, particularly depending on the supplied heat and the detected temperature.

[0006] Furthermore, Non-Patent Document 1 describes a geometric computational model that can determine the effect of surface morphology on the radiation output emitted from a medical X-ray tube. In this publication, multiple X-ray stationary anodes were exposed to a pulsed electron beam so that the surface morphology of the focal spot was similar to that of an aged X-ray stationary anode, and the three-dimensional height profile of this surface was detected using laser scanning confocal microscopy (LSCM). Using the geometric computational model, the reduction in radiation output due to surface structures contained in the three-dimensional height profile was determined compared to a smooth surface. Furthermore, the geometric computational model was validated with experimental comparisons. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Chinese Patent Application Publication CN114428099A [Non-patent literature]

[0008] [Non-Patent Document 1] Siller, Maximilian, et al. "Geometrical model for calculating the effect of surface morphology on to total X-ray output of medical x-ray tubes." Medical Physics 48.4(2021):1546-1556 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is therefore to provide an analysis system for used X-ray rotating anodes removed from their respective X-ray tubes, which system makes it possible to reliably and objectively assess the condition of each X-ray rotating anode in the region of its focal track. [Means for solving the problem]

[0010] This problem is solved by an X-ray rotating anode analysis system according to claim 1 and by a method for analyzing a used X-ray rotating anode according to claim 14. Further advantageous embodiments of the invention can be seen from the dependent claims, which can be freely combined with one another.

[0011] According to the present invention, there is provided an X-ray rotating anode analysis system for analyzing a used X-ray rotating anode having a revolving focal track on a surface section. The X-ray rotating anode analysis system includes a positioning device for the X-ray rotating anode, an image acquisition unit, and a data processing unit coupled to the image acquisition unit. The positioning device and the image acquisition unit are configured to position the X-ray rotating anode as a separate component (i.e., removed from the X-ray tube) at a predetermined position relative to the image acquisition unit. The image acquisition unit and the data processing unit are configured to detect a three-dimensional height profile of the surface section of the X-ray rotating anode in the region of the focal track by the image acquisition unit and to determine a predicted radiation output or characteristic value of the X-ray rotating anode from the detected three-dimensional height profile or a portion thereof by the data processing unit.

[0012] The predicted radiation output determined via the three-dimensional height profile is an important criterion for the predicted output performance of the X-ray rotating anode in general and the condition of the focal track in particular. The surface morphology of the focal track is an important influencing factor for the emitted radiation output, since unevenness results in local absorption of the emitted X-rays. Therefore, this determined predicted radiation output is important for decisions regarding the continued use of the X-ray rotating anode in question. Further advantageous analyses are possible based on this three-dimensional height profile, which will be described with reference to further embodiments. The automated determination of the predicted radiation output by this X-ray rotating anode analysis system is inherently advantageous because it is particularly objective and allows for the inclusion of significantly more data and details compared to visual evaluation of the X-ray rotating anode by an individual. Compared to evaluation methods performed on the X-ray rotating anode while it is installed in the X-ray tube, such as direct measurement of the emitted radiation output and / or evaluation of backscattered electrons, the X-ray rotating anode analysis system according to the present invention has the advantage that the condition of the focal track is directly detected and the analysis results are not adversely affected by other influencing factors (e.g., aging of the cathode, filter, etc. used). This X-ray rotating anode analysis system is a separate system from the X-ray device or X-ray tube, and in particular does not include a vacuum valve or a unit for accelerating the electron beam towards the X-ray rotating anode. Finally, the invention advantageously uses multiple automatic calculation options that allow the processing of large amounts of data by using an appropriately configured data processing unit. At the same time, the use of an image acquisition unit and a positioning device eliminates the need for expensive components that are used in other evaluation methods (e.g., when generating an electron beam, when detecting the spectrum of backscattered electrons, etc.).

[0013] Here, the term "used X-ray rotating anode" does not constitute part of the claimed X-ray rotating anode analysis system, but is mentioned only to describe the function and design of the X-ray rotating anode analysis system. The term "focal track" refers to at least the (annular) surface area of ​​the X-ray rotating anode that is scanned by the electron beam when the X-ray rotating anode is in use. X-ray rotating anodes often have an annular layer (on an underlying carrier body) on this surface area, and possibly on an area directly adjacent to it, that is specifically designed to generate X-rays. Suitable materials for this layer are particularly those with a high atomic number, such as tungsten, tungsten-based alloys, and especially tungsten-rhenium alloys (e.g., with a rhenium content of up to 26% by weight, preferably in the range of 5-15% by weight, and in practice typically in the range of 5-10% by weight). In the latter case, the term "focal track" refers to the annular layer of the X-ray rotating anode. In this case, the design of the rotating X-ray anode defines an axial direction (along or parallel to the axis of rotation about which the anode is substantially rotationally symmetric; also called the z-direction), a circumferential direction (circling around the axis of rotation in a plane perpendicular to the axis of rotation), and several radial directions extending away from the axis of rotation in a plane perpendicular to the axis of rotation (where the main extension surface of the anode ultimately extends). The x- and y-directions also run in this plane, with the y-direction corresponding to the X-ray emission direction. The surface section from which the three-dimensional height profile is detected can extend over or cover the entire rotating focal track. However, it can also include only one or more subregions thereof, in particular the area actually scanned by the electron beam in the radial direction (especially in the case of a focal track layer formed wider in the radial direction) and / or at least one sector or another (e.g., rectangular) portion in the circumferential direction. In this case, preferably, this at least one partial region contained therein is a region representative of the surface morphology of the focal track, or alternatively, it can be, for example, the most heavily damaged region, which can be assessed using a simple (for example, only two-dimensional) overview image of the initially created focal track.Since the surface of the focal track is generally curved and inclined relative to the main extension plane (which generally corresponds to the shape of the side of a truncated cone), appropriate corrections must be made in known manner so that the heights of the individual image points in the three-dimensional height profile are accurately reproduced relative to the ideal shape of a (theoretically assumed) smooth focal track (i.e., of the side of a truncated cone).

[0014] When determining the "predicted radiation output," the entire relevant (wavelength) spectrum of X-ray radiation is included, as in the case of actual use of an X-ray rotating anode. Furthermore, preferably, typical filtering in X-ray devices is also applied, particularly to reduce long-wavelength radiation components, depending on the conditions of use. The physical quantity used as a measure of radiation output is preferably the kinetic energy emitted in air (KERMA: kinetic energy emitted in matter). This is measured in the physical unit Gray (Joules / kilogram) and indicates how much energy (Joules) is emitted per kilogram of matter (air in this case), summed over the entire relevant radiation spectrum (i.e., across all wavelengths). However, other physical quantities specific to the radiation output can also be used, such as the reduction in the predicted radiation output due to the surface morphology of the focal track, the ratio of the predicted radiation output to the reference radiation output for a smooth focal track surface, or a different definition / expression of radiation output and / or no filtering or application of different filtering.

[0015] The positioning device is designed to position the X-ray rotating anode as a "separate component," i.e., removed from the X-ray tube. In particular, the positioning device can engage or abut a centrally mounted handle, a circumferential portion, and / or an underside of the X-ray rotating anode opposite the axial focal track for positioning in the central opening / bore. In addition to abutting and / or engaging, the positioning device can also be designed for fixation and, if necessary, for rotation of the X-ray rotating anode about its axis of rotation.

[0016] In this case, the positioning device, the image acquisition unit, and the data processing unit can all be integrated into the same overall device. However, alternatively, they can be formed as separate units; what is important in this case is that the positioning device can accurately position the X-ray rotating anode to be inspected relative to the image acquisition unit (this can be done, for example, by properly holding the image acquisition unit relative to the positioning device). Furthermore, the data processing unit must be coupled to the image acquisition unit so that at least a plurality of data (a plurality of image data sets) can be transferred from the image acquisition unit to the data processing unit. In particular, they are in communication with each other and are able to exchange data. The data processing unit itself can be completely integrated into the image acquisition unit, or it can be separated in whole or in part into at least one other device.

[0017] The use of the data processing unit is a computer-supported method. The detection of the three-dimensional height profile and the determination of the predicted radiation power are performed, in particular, according to (at least) one algorithm, which can be implemented by one or more appropriately configured software modules. That is, both steps are software-supported. The three-dimensional height profile contains height information for each image point (pixel) along the total area of ​​the detected surface section. This is particularly a three-dimensional height profile created by high-resolution imaging. Work is performed in all three spatial directions, in particular with a resolution of ≦5 μm, preferably ≦4 μm. This resolution can be increased in special ways, in particular by capturing more individual images with the image capture unit and processing the resulting multiple image data accordingly. Achieving a high resolution, especially in the height direction, is advantageous, considering the shielding effect of raised surface structures (in practice, a resolution of ≦1 μm can be achieved in all three spatial directions). In this case, the predicted radiation power can be determined from the entire detected three-dimensional height profile or only from its partial information. As will be explained below with reference to further embodiments of the invention, for example, a surface profile covering only a partial area of ​​the detected surface section can be used as a basis, or only one or more line profiles can be used as a basis.

[0018] According to a further embodiment, the image acquisition unit and the data processing unit are configured to use electromagnetic radiation (especially in the wavelength range of 10 to 3,000 nm; nm: nanometer) to generate a plurality of individual images, each carrying different depth information of the analyzed surface section of the X-ray rotating anode, and to reconstruct a three-dimensional height profile of the analyzed surface section from these individual images by the data processing unit. This is an efficient method for generating a three-dimensional height profile, which can be realized at advantageous cost, especially due to the low cost of currently available computer power and equipment. In this case, the electromagnetic radiation used may be spectral, including multiple wavelengths, or may be monochromatic. Furthermore, the electromagnetic radiation used may have a large wave coherence length (laser), in which case it is typically monochromatic radiation. Basically, there are various possibilities known in the prior art for generating a plurality of individual images and then generating a three-dimensional height profile from them. In this case, the image acquisition unit preferably operates according to optical techniques. For example, these individual images can be taken from multiple different angles and then combined to create a three-dimensional height profile (photogrammetry). Alternatively, for example, using a laser scanning confocal microscope (LSCM) inspection method, the focus of the optical system can be adjusted (e.g., using a corresponding aperture) to multiple heights (e.g., perpendicular to the plane of the surface section to be analyzed) in steps (preferably in steps of ≦0.5 μm, e.g., 100 nm; modern devices can adjust even smaller step widths), and multiple sharply imaged subregions can be taken as multiple individual images, which can then be combined to create a three-dimensional height profile.

[0019] According to a further embodiment, the image capture unit and data processing unit are configured to generate multiple individual images of the analyzed surface section from multiple different angles, particularly using electromagnetic radiation in the wavelength range of 380 nm to 780 nm (which corresponds to the visible range of the human eye). By varying the capture direction, corresponding depth information (in the axial or z-direction) can be obtained. Furthermore, the illumination angle of the surface section is preferably varied together with or independently of the capture direction, and shadows cast by multiple surface structures on the analyzed surface section are also evaluated. In particular, "white" light, whose spectrum covers this wavelength range, can be used. In this way, the image capture unit (camera) can operate in a (photo)optical manner, efficiently and cost-effectively capturing multiple high-resolution individual images. In particular, the image capture unit can capture multiple individual images at a suitable magnification (e.g., in the range of 5 to 20 times, in particular 10 times). A three-dimensional height profile can then be generated from the multiple individual images (number ≥ 2) captured from the multiple different angles. The principle here is that increasing the number of individual images taken from different angles of the analyzed surface section increases the resolution of the resulting three-dimensional height profile. Therefore, the number of individual images obtained from different angles of the analyzed surface section is preferably 20 or more, more preferably in the range of 50-100. This principle also applies to alternative variants in which the focus is adjusted stepwise (preferably in steps of ≦0.5 μm, e.g., in steps of 100 nm) to different heights, and sharply imaged partial areas are captured as individual images, in which case a number of individual images of ≧200, particularly ≧500, is preferred. If a step width of 100 nm is set and a height range of, e.g., 100 μm is covered, this corresponds to, e.g., 1000 individual images.

[0020] According to a further embodiment, the data processing unit is configured to be able to determine a predicted radiation output or characteristic value of the X-ray rotating anode according to the detected three-dimensional height profile on the basis of an automatically calculated absorption of X-rays along the X-ray emission direction, taking into account local absorption effects due to local surface variations or surface structures. An advantage of this further embodiment is that the average roughness R a or root mean square roughness R q Not only are one or a few individual physical quantities characteristic of or describing the overall surface morphology, such as the surface morphology, used, but the absorption at each (local) surface variation (such as bumps, cracks, particle initiation, local melting, etc.) present in the analyzed surface section is determined, thereby taking into account its impact on the predicted radiation output. This also allows for additional analysis options. For example, the identification of significant local damage (e.g., large cracks or particle initiation) and / or the identification of predicted radiation output variations in the circumferential direction, which may lead to a separate evaluation of the X-ray rotating anode, even if the surface area around the focal track as a whole has an acceptable surface morphology. This determination is performed, in particular, with computer support (i.e., in particular with a data processing unit) using algorithms executable by one or more appropriately equipped software modules. In this case, the currently available computer capabilities allow for the consideration of 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 respective X-ray rotating anode. Typically, the section of the rotating X-ray anode on which the focal track is formed corresponds to the side of a truncated cone, which is inclined at an angle (e.g., 10°) to the radial direction (relative to the axis of rotation). The X-ray emission direction in each X-ray device generally extends exactly along the radial direction, and is therefore inclined at an angle (e.g., 10°) to the side and thus to the (locally approximated flat) surface of the focal track.

[0021] According to a further embodiment, the data processing unit is configured such that at least one line profile can be used by the data processing unit for automatically calculating the absorption of X-rays, the at least one line profile extending in the X-ray emission direction over a predetermined minimum length along the detected surface section of the X-ray rotating anode and having local surface variations or surface structures according to a three-dimensional height profile. This further embodiment makes it possible to reduce the required computer performance by selectively using one or more line profiles. Each line profile represents the height differences (height distribution) along a specified extension direction according to the three-dimensional height profile, in this case extending in the X-ray emission direction along the detected surface section of the X-ray rotating anode at least over the extension distance of the focal spot in this direction. This minimum distance must be determined because, as is known, the electron beam is not focused precisely on the X-ray rotating anode, but has a finite extent (i.e., a focal spot) on the focal track surface with a specific electron intensity distribution (see Rolf Behling, "Modern Diagnostic X-Ray Sources", 2nd edition, 2021, pp. 226-231). In this case, the focal spot can be a focal spot size (if known) specific to the X-ray tube in which the X-ray rotating anode is installed, or a commonly used focal spot size and electron intensity distribution on the focal track surface (for example, a maximum distance in the range of 4 to 12 mm, in particular, for example, 10 mm, in at least one direction. However, in some cases, only the partial area with the highest electron intensity can be used). It should be further explained that due to the tilt angle typically formed in the focal orbit (on the side of the truncated cone) with respect to the X-ray emission direction (which typically corresponds exactly to the radial direction), this line profile is obtained from the projection of the X-ray emission direction (along the axial direction) onto the detected surface section, which is expressed above by the summary "in the X-ray emission direction over a predetermined minimum length along the detected surface section."As explained below with respect to simplification / approach 2, the use of such multiple line profiles and the approximation of the focal spot as a linearly running, appropriately adjusted intensity profile is particularly advantageous for X-ray rotating anodes, which are rotated at high speeds during use.

[0022] According to a further embodiment, the data processing unit is configured to use at least one surface profile for the automatic calculation of X-ray absorption, the at least one surface profile extending in the X-ray emission direction over a predetermined minimum length along the detected surface section and over a predetermined minimum width approximately perpendicular thereto, and having local surface variations according to a three-dimensional height profile. The inclusion of at least one surface profile has the advantage that all surface variations on the included surface are included in the calculation. In this case, each surface profile reproduces the height distribution of each pixel in the included surface according to the three-dimensional height profile. With regard to its minimum length and its distribution, the above explanations regarding the length and distribution of the line profile apply as well. With regard to its width, the included plane can in particular be sector-shaped (i.e., the inner and outer sides each extend in the circumferential direction, the inner side having a smaller extension than the outer side). However, the surface profile can also have other shapes.

[0023] In both the line profile related developments and the surface profile related embodiments, only a single (e.g., representative) line or surface profile that extracts only a line or surface section of the focal track can be used for the determination. In particular, multiple line or surface profiles, preferably evenly distributed circumferentially over the circumferential focal track, can be used. Furthermore, they can cover or include the entire circumferential focal track.

[0024] According to a further embodiment, the data processing unit receives the following input variables: The depth of X-ray generation (within the focal track), which correlates with the penetration depth of the electrons into the focal track being analyzed; the angle of emission of X-ray radiation, Materials for the focal track of rotating X-ray anodes, The size of the focal spot, the electron intensity distribution in the focal spot, and filter, At least one of these is set to be included in the automatic calculation of X-ray absorption.

[0025] Considering these input variables increases the accuracy and reliability of the predicted radiation output. The electron penetration depth of the focal track to be analyzed is essentially an intensity distribution over depth, which depends on the electron acceleration voltage. Correlated with this, the X-ray emission depth is also an intensity distribution (although it does not exactly correspond to the intensity distribution of the electron penetration depth, due to absorption effects, among other things). However, for simplicity, we can use an average value of, for example, 1.6 μm (μm: micrometer) as the X-ray emission depth for an assumed acceleration voltage of, for example, 100 kV (kV: kilovolts) (literature values ​​are in the range of 1.0–1.6 μm). The X-ray emission angle corresponds to the tilt angle described above (usually 10° or 7°), which must be taken into account when determining the path length of the generated X-rays through the material of the focal track and the associated (material-dependent) absorption of X-rays based on the assumed X-ray emission depth. Depending on the material of the focal track of the X-ray rotating anode and the assumed acceleration voltage, e.g., 100 kV (kV: kilovolt), the generated X-ray radiation spectrum can be determined (available from publicly accessible sources). Furthermore, since the absorption of the generated X-rays before they leave the surface of the focal track depends on the material of the focal track (as well as on the respective wavelengths of the X-ray spectrum), the material of the focal track is preferably taken into account when determining the radiation output. The above explanations apply regarding the size and electron intensity distribution of the focal spot (which can be specified as an intensity distribution over a surface or as a linear intensity distribution, with the corresponding size in each case, depending on the calculation method). Furthermore, filtering is used in the X-ray device (e.g., by borosilicate glass used as a component of the radiation path and / or aluminum or copper as specific wavelength-dependent filters, both of which are collectively referred to as "filters" or "filtering"). Special wavelength-dependent filters (e.g., made of aluminum or copper) are used to reduce the proportion of long-wavelength radiation (also called "soft" radiation), which contributes little or nothing to imaging and causes unnecessary radiation exposure.Therefore, wavelength dependent filtering with such filters as are typically used in X-ray equipment (eg, 2.5 mm borosilicate glass filtering and 2 mm aluminum filtering) is preferably included in the determination of the predicted radiation output.

[0026] According to a further embodiment, the data processing unit is configured to identify and classify damage in the region of the surface section of the focal track of the X-ray rotating anode from the detected three-dimensional height profile of the surface section of the focal track or from multiple image information detected in other ways. In addition to determining the expected radiation output, identifying and classifying damage according to type (e.g., roughening, local melting, cracks, particle generation, etc.) and / or according to its severity (e.g., height / depth, lateral expansion, etc.) is another important criterion for assessing the condition of the focal track and thus serving to issue a recommendation for the continued use of the X-ray rotating anode in question. According to a further embodiment, individual images taken from different angles of the surface section to be analyzed form the basis for generating the image information obtained in other ways. In this case, 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 in grayscale representation), and, if necessary, other information. Based on this, various two-dimensional contrast representations of the analyzed surface section can be created, which, either individually or by combining several such contrast representations, allow particularly good identification and classification of defects in the focal track of the X-ray rotating anode within the area of ​​the surface section. Additionally, other image information can also be derived from three-dimensional height profiles (e.g., representations of minimum and maximum heights) or can be formed or derived from several images taken separately with special camera settings. For example, cracks that extend deep into the focal track material or through the entire focal track layer, and / or localized melting that results in a significantly raised molten bead on the surface of the focal track, can be indicators that the focal track needs to be significantly reworked (e.g., by removing a significant portion of the focal track or even the entire focal track layer and then reapplying the focal track material) and that surface grinding alone is insufficient.

[0027] Such automated identification and classification is particularly software-supported. The software can be specifically configured and set up to learn this identification and classification through machine learning, or to have previously learned it. As part of this machine learning, the software is specifically trained by a person skilled in the art to identify and classify ("label") defects in corresponding example images (e.g., three-dimensional height profiles of surface sections in a focal track or multiple image information obtained by other methods), to which the software is given access and their identification and classification. The software is configured to identify and learn patterns from sample images using the applied learning strategy. The quality of the software's identification and classification improves with the number and quality of the provided, i.e., "labeled," example images. Furthermore, an appropriate representation of the surface section in question facilitates identification and classification, so that the software can also operate based on image information obtained by other methods.

[0028] According to a further embodiment, the image acquisition unit and the data processing unit are configured to acquire at least one image of another surface section in a region adjacent to the focal track of the X-ray rotating anode, which allows additional conclusions to be drawn about the quality of other regions of the X-ray rotating anode, which may be located, for example, on the same side of the focal track (front side) or on the opposite axial side of the focal track (back side). As mentioned above, this at least one image acquisition may also generate a three-dimensional height profile or multiple images acquired in other ways, on the basis of which further analyses can be performed.

[0029] According to a further embodiment, the data processing unit is configured to evaluate a number of further use options for the X-ray rotating anode based on the determined predicted radiation output or based on the characteristic values, and to issue a corresponding use recommendation (e.g., via a display or a display unit of the data processing unit). In this way, the issued use recommendation is based on an objective evaluation of the X-ray rotating anode taking into account the state of the focal track, so that in particular either an X-ray rotating anode that can be directly used again or an X-ray rotating anode that can be repaired by reprocessing (also called "reworking") can be provided for its next use, which saves such resources. In this case, in addition to the predicted radiation output, other criteria such as damage to the focal track or the condition of other areas of the X-ray rotating anode can also be included in the evaluation. In particular, the further use recommendation is based on the following number of options: Direct and continuous use of the X-ray rotating anode, Surface polishing of the focal track surface, Localized repair of the focal track in highly damaged areas (e.g., localized removal of focal track material and reapplication of focal track material), large-area mechanical removal of the entire focal track material (in particular the entire focal track layer) or removal of the corresponding surface area, followed by application of focal track material and, optionally, subsequent smoothing (e.g., by grinding) of the applied focal track material; Mechanical reworking of the X-ray rotating anode outside the focal track area (e.g., in the fixed area of ​​the axis to remove rotational imbalances), Recycling of X-ray rotating anodes (in case of irreparable damage), In the case of direct continued use or use after reprocessing, this further recommendation for use may additionally include recommendations for specific conditions of use (e.g. operation at specific parameters or with a specific X-ray tube or X-ray device), may include one or more of:

[0030] According to a further embodiment, the data processing unit is coupled to a memory unit, which may in particular be arranged on a single device / memory or alternatively distributed on several devices / memories (in particular they are in communication with each other and exchange data), and the data processing unit and the memory unit are configured for at least one of the following interactions: The individual information determined for each analyzed X-ray rotating anode, such as detected three-dimensional height profiles, line profiles, surface profiles, individual images, image information detected by other methods, damage, determined predicted radiation output, issued recommendations for its next use, etc., each obtained from the area of ​​its focal track and / or from areas adjacent to its focal track, can be stored in a memory unit by this data processing unit and read out from the memory unit (e.g., individualization by automated identification of the serial number of the X-ray rotating anode). Type-specific information for a number of different types of X-ray rotating anodes, such as drawings, structure (including the connection techniques used, coatings, etc.), manufacturing data (including, for example, a unique identification number assigned to each X-ray rotating anode during manufacture), transportation data, dimensions of the X-ray rotating anode, materials of the X-ray rotating anode (in particular the focal track, the anode disk formed thereunder, etc.), etc., can be stored in and read out from the memory unit by this data processing unit. The usage data obtained for each analyzed X-ray rotating anode, such as duty cycle, duration of use, rotation speed, acceleration voltage applied between the cathode and the X-ray rotating anode, type of cathode, focal spot size and electron intensity distribution, can be individually stored in a memory unit by the data processing unit and can be read out from the memory unit. An individual history of each analyzed X-ray rotating anode's use in situ (i.e., in an X-ray device) and of any subsequent processing and repairs (e.g., as performed after each analysis by an X-ray rotating anode analysis system throughout its life cycle) can be stored in and read out from a memory unit. In this way, the X-ray rotating anode analysis system allows tracking and documenting the entire "life cycle history" of an X-ray rotating anode, in particular with the associated date reference date ("date stamp"). Based on this database, it is also possible to make better predictions / recommendations regarding the next use options when analyzing a specific X-ray rotating anode. This can also be partially summarized under the keyword life cycle management.

[0031] According to a further embodiment, the data processing unit takes into account the following further information in the evaluation of the next use option of the X-ray rotating anode: Uniformity of the three-dimensional height profile along the circumferential direction of the rotating X-ray anode, Damage to the focal track of the X-ray rotating anode in the surface section area, an image of another surface section in a region adjacent to the focal track of the X-ray rotating anode; Geometric changes of the X-ray rotating anode (which can be determined, for example, by three-dimensional measurements of the X-ray rotating anode, in particular tactilely, for example, using a scanner that scans the external dimensions of the X-ray rotating anode), Individual information determined for each analyzed X-ray rotating anode, Type-specific information about each X-ray rotating anode analyzed; The individual usage data found for each analyzed X-ray rotating anode, and The individual history of each X-ray rotating anode analyzed; is set to include at least one of the following: The inclusion of at least one of these additional pieces of information improves the quality of the evaluation of subsequent use options. For example, a strong nonuniformity in the three-dimensional height profile along the circumferential direction can indicate the need for local repairs. In the case of geometric changes, the resulting rotational imbalance, the increase in the outer diameter, and / or the enlargement of the central mounting hole (in the case of X-ray rotating anodes without an integrally formed stem) are particularly significant. This can indicate, in particular, the need for mechanical reworking or, if the extent of the damage is too advanced, measures to recycle the X-ray rotating anode. Based on this, the remaining useful life of the X-ray rotating anode can also be estimated. This leads to an improvement of the overall life cycle management of the X-ray rotating anode. From these detected data, further measures for improving future manufactured X-ray rotating anodes can be derived, such as design adjustments, optimization of the connection technique (e.g., soldering, welding, etc.), and / or the application of a coating.

[0032] Basically, the present invention relates to an X-ray rotating anode analysis system that does not include a respective X-ray rotating anode to be analyzed. According to a further embodiment, the X-ray rotating anode (to be analyzed) is accommodated as a separate component in a positioning device. This corresponds to the use state of the X-ray rotating anode analysis system. In particular, the positioning device is configured to enable precise positioning of the X-ray rotating anode relative to the imaging unit. This can be most easily achieved by means of corresponding (preferably adjustable) stops. Preferably, the positioning device allows for positioning of the X-ray rotating anode in at least two spatial directions (e.g., two spatial directions perpendicular to the rotation axis) and in particular in all three spatial directions (e.g., by means of correspondingly provided fixing elements) by at least a mating connection, and more preferably by an additional frictional connection. Furthermore, it is preferred that the positioning device allows for rotation of the X-ray rotating anode around the rotation axis by a (preferably adjustable) rotation angle after the initial fixation, for example, to examine different sections of the focal track.

[0033] The invention further relates to a method for analyzing a used X-ray rotating anode having a circumferential focal track on its surface section, said method comprising the following steps: positioning the X-ray rotating anode as a separate component relative to the imaging unit using a positioning device; - acquiring a three-dimensional height profile of a surface section of the X-ray rotating anode in the region of the focal track by means of an image acquisition unit and a data processing unit coupled to said image acquisition unit; - automatically determining, by a data processing unit, from the acquired three-dimensional height profile or a portion thereof, a predicted radiation output or characteristic value of the X-ray rotating anode; Includes: The steps of acquiring the three-dimensional height profile and automatically determining the predicted radiation power are performed, in particular, according to (at least) one algorithm, which can be implemented by one or more appropriately configured software modules. That is, both steps are software-supported. In this case, the at least one software module is particularly stored in the data processing unit or in a separate memory so that it can be loaded into and executed on the data processing unit. The method according to the invention achieves essentially the same advantages as those achieved by the X-ray rotating anode analysis system according to the invention. Furthermore, further developments and variations of the above-described are possible in appropriate ways, in which the features described on the device side can be performed or are performed by the respective mentioned units / components, in particular as 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, in which case one or more of the above-described further developments / variations can also be realized.

[0034] Further advantages and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. [Brief explanation of the drawings]

[0035] [Figure 1] Schematic diagram of the longitudinal cross section of an X-ray tube [Figure 2] Perspective view of a rotating X-ray anode [Figure 3] Perspective view of a cross section of another rotating X-ray anode [Figure 4] Schematic diagram of an X-ray rotating anode analysis system according to the present invention. [Figure 5] Exemplary three-dimensional height profiles for the focal track surface [Figure 6] Illustration of the calculation of the path length of generated x-rays through the focal track material for a perfectly smooth focal track surface. [Figure 7] Illustrated calculation of the path length of generated x-rays through the focal track material for a focal track surface having a surface structure. [Figure 8] Three diagrams are shown: the top (first diagram) shows an example line profile of the used focal track surface, the bottom (second diagram) shows the distribution of additional path lengths obtained from the first diagram, and the bottom (third diagram) shows the resulting radiation distribution. DETAILED DESCRIPTION OF THE INVENTION

[0036] FIG. 1 shows a schematic diagram of a longitudinal cross section of an X-ray tube 2. It has a glass bulb 4 with an evacuated interior 6, within which is a cathode 8 with a heating coil 10, which, in use (i.e., when current is passed through it), emits electrons 12. Opposite the cathode 8 is an X-ray rotating anode 14. The X-ray rotating anode 14 has a central mounting hole to which a handle (shaft) 16 is attached using a fastener 17. The handle 16 connects the X-ray rotating anode 14 to a rotor 18 of an electric motor 20, which has a stator 22 outside the glass bulb. In use, the electric motor 20 rotates the X-ray rotating anode 14 about an axis of rotation 24 in a known manner. Electrons 12 emitted by the cathode 8 are accelerated toward the rotating focal track 26 of the X-ray rotating anode 14. When the electrons strike the focal track 26, their kinetic energy is converted into heat and, to a lesser extent, into X-rays 28. A portion of the generated X-rays 28 are extracted in an X-ray emission direction 32 perpendicular to the rotation axis 24 through an exit window 30, which may be made of, for example, borosilicate glass and serves to extract the X-rays from the X-ray tube. In addition to this, a further filter made of aluminum or copper is typically also used in the X-ray beam path to reduce the proportion of long-wave (soft) X-rays. The extracted X-rays are then used in the X-ray device to penetrate an object, for example for diagnostic imaging in a medical X-ray device.

[0037] An example of the structure of the X-ray rotating anode 33 is described below with reference to FIG. 2. In its basic form, it has an anode disk 38 that is rotationally symmetric about a rotation axis 36 (also called the axial or z-direction) and has a central mounting hole 39. The anode disk 38 is typically made of a molybdenum-based material (≥50 wt. %, particularly ≥90 wt. % molybdenum) or pure molybdenum. On one side of the anode disk 38, the front side, is an orbiting focal track 40 with a focal track layer made of a tungsten-rhenium alloy (95 wt. % tungsten; 5 wt. % resonant iron). The orbiting region on the focal track 40, depicted by multiple dots in FIG. 2, visualizes the focal track 41, i.e., the annular region (focal spot) scanned by the electron beam during rotation of the X-ray rotating anode 33. The anode disk 38 has an orbiting, tilted focal track surface 42 in the region of the focal track 40. It is inclined at an inclination angle α (in this case α=10°) with respect to a radially extending main extension plane 44, which extends perpendicular to the rotation axis 36 and is also referred to herein as the xy-plane. The shape of the focal track plane 42 corresponds to the side of a truncated cone. Circumferential directions rotate around the rotation axis 36, each perpendicular to the radial direction. The X-ray emission direction 46 generally extends exactly along one of the radial directions, and is therefore inclined with respect to the focal track plane 42 by an inclination angle α (for example, 10°). In the Cartesian coordinate system used herein, spanning the x-, y-, and z-axes, the y-axis extends along the X-ray emission direction 46 (which is shown only by way of example in FIG. 2 and is fixed in the X-ray tube by the position of the exit window), the x-axis extends perpendicularly thereto within the main extension plane 44, and the z-axis extends axially (as shown schematically in FIG. 2). On the rear side (ie opposite the front side), a graphite body 43 is attached (in particular soldered) to the anode disk 38 .

[0038] Figure 3 shows a further embodiment of an X-ray rotating anode 34, in which the same reference numerals are used for components / sections that are the same or correspond to those of the X-ray rotating anode 33 of Figure 2; only the differences are explained below, while for the rest, please refer to the description of Figure 2. The X-ray rotating anode 34 of Figure 3 does not have a graphite body. Furthermore, a handle 48 is integrally formed on the back of this X-ray rotating anode, which in the illustrated schematic view consists of a sleeve 50 monolithically formed on the anode disk 38 and a tubular part 52 connected thereto (e.g., by welding). This tubular part 52 can also have an additional mechanical connection element at its distal end for attachment to another component (such as a rotor).

[0039] FIG. 4 shows a schematic diagram of an X-ray rotating anode analysis system 54 according to the present invention. It includes a positioning device 56, an image acquisition unit 58, additional image acquisition units 60 and 62, and a data processing unit 64, which will be described in more detail below. In this case, the positioning device 56 can be configured in various ways, particularly with an integral handle or without an integral handle, to receive and accurately position the X-ray rotating anode. Here, an exemplary X-ray rotating anode 33, which essentially corresponds to the X-ray rotating anode of FIG. 2 and therefore uses the same reference numerals, is fixedly mounted on a shaft 66 of the positioning device 56 by means of its mounting hole 39. The shaft 66 can be rotated via a rotation device 68, which in this example is motorized and can be controlled via the data processing unit 64, thereby adjusting the rotational position of the X-ray rotating anode 33 relative to the image acquisition unit 58 (and the additional image acquisition units 60 and 62). Furthermore, the shaft 66 is attached to a support part 70 via the rotation device 68. This support part 70 is then coupled to a (schematically shown) frame structure 72 of the X-ray rotating anode analysis system 54, thereby enabling accurate positioning of the X-ray rotating anode 33 relative to the frame structure 72 (and therefore relative to the image acquisition units 58, 60, 62).

[0040] The image acquisition units 58, 60, 62 are therefore also connected to the frame structure 72 via beams 74 so that their position and inclination (see joints 76) can be precisely adjusted relative to the frame structure 72 (and therefore relative to the X-ray rotating anode 33). The image acquisition unit 58 (and the additional image acquisition units 60, 62) are also connected in communication with the data processing unit 64. The image acquisition unit 58 can be controlled via the data processing unit 64 to acquire a number of individual images of the surface section of the X-ray rotating anode 33 to be analyzed, in particular of the surface section in the region of the focal track 40 of the X-ray rotating anode 33. This image acquisition unit 58 is formed by a high-resolution camera (preferably operating in the optically visible range) with a magnification of 5 to 20 times and a lateral resolution (in the x-y plane with reference to the spatial direction defined in FIG. 2 and also depicted in FIG. 4) of 4 μm or less. In particular, the camera has a lateral resolution of 3.355 μm along the xy plane of the surface section and a vertical resolution of 3.565 μm in the z direction, with a magnification of 10x, which can be increased by increasing the number of individual images. A separate, particularly a variably positionable, illumination unit is preferably provided (e.g., an LED with "white" light, i.e., preferably covering a spectrum spanning essentially the visible wavelength range). Additionally or alternatively, the camera has an internally formed illumination unit (e.g., an LED with "white" light, i.e., preferably covering a spectrum spanning essentially the visible wavelength range). The same applies to the additional image capture units 60, 62, which can be designed and positioned such that, for example, the image capture unit 60 can capture images of a larger section of the front side (or the entire front side) of the X-ray rotating anode 33 and / or the image capture unit 62 can capture images of a larger section of the back side (or the entire back side) of the X-ray rotating anode 33.

[0041] Control of the image acquisition unit 58 and communication with other system components of the X-ray rotating anode analysis system 54, in particular with the additional image acquisition units 60, 62, the rotation device 68 and the tactile sensor 84 described below, is performed by the data processing unit 64 via an interface 78 (schematically shown in Figure 4). Furthermore, the data processing unit 64 has an input and display unit 80 to which a user can make inputs (enter information, trigger actions, etc.) and to which corresponding information (results, recommendations, command prompts, etc.) can be displayed, as well as a memory unit 82 from which data can be stored and from which data can be retrieved via the data processing unit.

[0042] The acquisition of the multiple individual images is preferably carried out by the rotation device 68 further rotating the X-ray rotating anode 33 around the rotation axis 36 by a predetermined feed angle (e.g., in each case an angle in the range of 1 to 2°), so that at each of these different angular positions, the image acquisition unit 58 can generate multiple individual images of the surface section of the focal track 40 to be analyzed (i.e., the individual images of the multiple surface sections, each of which falls within the image acquisition range of the image acquisition unit 58, overlap multiple times). In parallel, the additional image acquisition units 60, 62 can also generate individual images (at each angular position or only at selected angular positions). Furthermore, FIG. 4 shows a tactile measuring device 84 with a tactile sensor 86, which is attached to a support 90 with a variably adjustable angular position via a joint 88 and is connected to the frame structure 72 via this. The tactile sensor 84 can tactilely measure the X-ray rotating anode 33 (even during its rotation, if necessary) to determine any geometric changes that may have occurred in the X-ray rotating anode 33.

[0043] 5-8, an exemplary embodiment for calculating the absorption of X-rays along the X-ray emission direction according to a detected three-dimensional height profile, taking into account local absorption effects due to local surface variations, is described below. Based on this, a characteristic value of the predicted radiation output can then be determined. Additional information and literature on the relevant simplifications and approaches for this calculation can be found in Siller, Maximilian, et al. "Geometrical model for calculating the effect of surface morphology on the total x-ray output of medical x-ray tubes." Medical Physics 48.4 (2021): 1546-1556. To enable this calculation to be performed automatically, software is provided that can perform the calculation according to a corresponding algorithm and can be loaded and executed on a data processing unit (e.g., data processing unit 64 shown in FIG. 4).

[0044] Figure 5 shows, for example, the three-dimensional height profile M of the analyzed surface section, which is typical for the aged focal track of an X-ray rotating anode after use in an X-ray machine. heightAn example of an (x,y) height profile is shown (based on the coordinate system defined in Figures 2 and 4). Each image point or pixel in the xy plane of this 3D height profile is assigned a corresponding height or z-value, represented by a grayscale representation. The z-range shown here spans from a negative range of -30 μm (shown in black) through 0 μm (shown in gray) to a positive range of +30 μm (shown in white) (μm: micrometers). Figure 5 also illustrates typical damage to the focal track surface after extended use. In the lower left portion of this profile, two crater-shaped depressions labeled "A" are visible. These are the occurrence of particles in the focal track material. In the right half, a narrow depression extending approximately vertically across the central portion of the image is visible, labeled "B." This is a crack in the focal track material. Additionally, in the upper right portion, a bead-like protrusion labeled "C" is visible, representing localized melting. Such a three-dimensional height profile, independent of its specific shape and specific height distribution, forms the starting point for calculating the absorption of X-rays along the X-ray emission direction.

[0045] The concept underlying this calculation is that for each X-ray generation point (corresponding to the X-ray generation depth below the focal track in the z-direction), the absorption of the generated X-rays by the focal track material is determined according to a three-dimensional height profile, taking into account local surface variations, and then summed or integrated over all relevant generation points (in this example, line profiles) as long as the X-rays are directed along the X-ray emission direction. The X-ray radiation emitted at each generation point in the X-ray emission direction (the "power spectrum") is based on the X-ray spectrum (a bremsstrahlung distribution with multiple characteristic lines) specific to each focal track material as a function of the accelerating voltage (100 kV in this case). Data and calculation methods for typical accelerating voltages and focal track materials are available in the literature. (To simplify matters, pure tungsten can be used, due to its similar atomic number and density, as opposed to a tungsten-rhenium alloy with a high tungsten content.) Furthermore, it should be taken into account that only the individual image points or pixels of the three-dimensional height profile (or in this case the line profile derived therefrom) that lie within the focal spot area of ​​the X-ray rotating anode are taken into account, and these are then weighted according to the electron intensity distribution, which in this case is only done in the last step of the calculation model. Here, the calculation of the line profile of the surface section of the focal trajectory to be analyzed is carried out assuming that the electrons are accelerated with an accelerating voltage of 100 kV to this section having a size and intensity distribution typical of the focal spot.

[0046] According to this embodiment, the following simplifications / approaches are used: For simplicity, the average depth of X-ray generation d e- is used, rather than the actual distribution of the depth of occurrence along the z axis (the latter implies multiple occurrence points along the z coordinate that follow a distribution function for each x and y coordinate, requiring summation or integration over these occurrence points). That is, with this simplification, for each image point or pixel with x and y coordinates, a depth d below the focal track plane at the z coordinate is used. e-The exact point of origin is assumed to have a value of . For example, the average origin depth in tungsten-based focal track materials can be found in the literature as a function of the surface voltage applied between the cathode and the X-ray anode. For example, the average origin depth of X-rays in tungsten-based materials at 1.6 μm for an accelerating voltage of 100 kV is published in "Calculation of x-ray spectra emerging from an x-ray tube. Part 1. Electron penetration characteristics in x-ray target" by Poludniowski, Gavin G., and Philip M. Evans. Medical physics 34.6 Part 1 (2007): 2164-2174. (Further related source: Behling, Rolf. "Modern diagnostic x-ray sources: technology, manufacturing, reliability". CRC Press, 2021, p. 71). Regarding the focal spot size and electron intensity distribution, in the case of a fixed location of the focal spot on the focal track surface (e.g., a fixed anode), reference must be made to the electron intensity distribution across the impacted surface (x,y coordinates) of the focal spot, whereas in the case of a rotating X-ray anode, reference can be made to the linear intensity profile (along the X-ray emission direction, i.e., the y-direction) that results from the rotation during use. For example, this can be determined when using a rotating X-ray anode, and in many cases (depending on the cathode type), can be well approximated by two overlapping sinusoidal functions (often this intensity distribution is formed by two overlapping "bumps" in the y-direction). Alternatively, different cathode types can be simulated, taking electromagnetic interactions into account, if necessary. With regard to the three-dimensional height profile, and therefore also for the comparison of the radiation power emitted from an aged focal track having surface structures with the radiation power emitted from a perfectly smooth focal track surface, it is not necessary to observe the detected three-dimensional height profile as a surface and apply an area function (with x and y coordinates) to it (see, for example, the approach taken in the above-mentioned publication by Maximilian Siller et al. for a fixed anode), but it is sufficient if the radially running line profiles of the corresponding three-dimensional height profile are considered and compared with each other (these point in the X-ray emission direction, i.e., the y direction, once per revolution during the rotation of the X-ray rotating anode). In the following calculations, this is described using a line profile running radially along the focal track plane, which is given by the third term below: Note that in the following calculations, it is assumed that this radial direction also points in the X-ray emission direction, i.e., the y-direction. For line profiles generated in the radial direction, due to the rotational symmetry of the X-ray rotating anode, the image points / pixels of the detected three-dimensional height profile generally do not lie exactly along each radial direction, so that to generate the line profiles running in this direction, it is necessary to perform a corresponding approximation to the detected surface structure (e.g., by a fitted height profile running along the detected image points / pixels), so that for every y coordinate (i.e., radial coordinate) along the line profile, a corresponding z value (i.e., height) can be obtained. This determination of the line profiles running in the radial direction is preferably performed with software support, for example by using a fitting function. For simplicity, from each source point of the line profile used as an example, only the radiation power strictly directed in the radial direction, which in this case is considered to be directed in the X-ray radiation output direction, i.e., the y-direction, is extracted and determined, and the cone of radiation emitted in the area around the X-ray radiation direction for each source point is not determined first, so that the radiation emitted exactly in the X-ray radiation direction for multiple source points can then be summed or integrated, which allows calculations based on multiple line profiles, as will be explained in detail below. Furthermore, it is assumed that the emitted X-rays travel a minimum path length within the focal track material, regardless of the origin point along the X-ray emission direction and the surface structure locally present at that origin point. This minimum path length is selected as a fraction of the path length of the locally emitted radiation through the focal track material expected for a smooth surface, depending on the tilt angle (in this case, α = 10°), e.g., 5 μm for an expected path length of 9.07 μm (this is the example for a focal track tilt angle α = 10°). This avoids theoretically possible peaks in the radiation power locally emitted from individual origin points based on the special features of the three-dimensional height profile and its resolution, which could result in local false information (e.g., on the side of a surface structure of the focal track surface that is very steeply tilted in the X-ray emission direction).

[0047] With reference to Figures 6, 7, and 8, we now explain how the absorption by the focal track material at each point of X-ray emission is determined according to a three-dimensional height profile, taking into account local surface variations. The top diagram in Figure 8 shows an exemplary line profile of a used focal track surface, plotted as height (in millimeters) (see "height [mm]" in the figure) over the y-direction (in millimeters). This can be obtained, for example, from a section of the three-dimensional height profile shown in Figure 5 along the X-ray emission direction y. Figures 6 and 7 each show a schematic cross-section of such a line profile of the focal track surface. Figure 6 first shows the situation of a perfectly smooth focal track surface 92 inclined with respect to the y-direction at an inclination angle α = 10° (shown larger in Figures 6 and 7 for clarity). The average emission depth d of X-rays impinging on the focal track surface 92 at two different y-coordinates (simplified representation) is shown. e- Using two exemplary electrons 94, 96 penetrating into their respective generation points 98 according to x-ray Regardless of where the electron appears within the focal spot, the path length traveled can be determined using the following equation: d x-ray =d e- / tan(α) Equation (1) d e- = 1.6 μm and α = 10°, the constant advanced "theoretical path length" d x-ray In other words, in the case of a perfectly smooth focal track surface 92, the generated X-rays first travel a constant path length d x-ray10.5 μm) and then exit the focal track surface. The X-rays are then filtered by filter 102 before striking detector 104 (assuming there are no obstructions or other transmitted objects in the radiation path). For example, a 2.5 mm thick borosilicate glass filter (e.g., as an exit window) and a 2 mm thick aluminum filter can be used in this computational model. Regarding the filtering by focal track material, filtering by pure tungsten (W) can be used for simplicity with a tungsten-rhenium focal track (with a predominant proportion of tungsten) because tungsten (W) and rhenium (Re) differ only slightly in their atomic numbers and densities. The absorption by the focal track material (each over a path length of 9.07 μm) and filtering by filter 102, which would occur in the case of a perfectly smooth focal track surface, are referred to as basic filtering.

[0048] In this case, the potential base radiation power of the line profile or y-coordinate predicted for such a perfectly smooth focal track surface is used as a reference value. In particular, based on the above-mentioned power spectrum, absorption by the focal track material over a path length of 9.07 μm, and filtering by filter 102, the potential base radiation power predicted for a single y-coordinate in the X-ray emission direction is first determined. This is done, in particular, with software support (e.g., using SpekCalc pro 1.1, a software developed by Gavin Poludniowski and Phil Evans of the Institute of Cancer Research, London, UK, for the theoretical approach, and by Francois deBlois, Guillaume Landry, and Frank Verhaegen of McGill University, Montreal, Canada, for the graphical user interface, currently available at www.Spekcalc.weebly.com). In this case, the software is preferably configured to first determine the reduction / filtering of the output spectrum for a single y-coordinate of the line profile (wavelength-dependent) (since the intensity of the reduction / filtering depends on the wavelength or energy of the photons). Based on this, a "potential base spectrum" is obtained ("potential" because the electron intensity distribution and size of the focal spot are not yet taken into account), the intensity distribution of which is reduced for the output spectrum (wavelength-dependent). Then, preferably, a "potential base radiant power" is determined for a single y-coordinate. This is obtained by summing or integrating the radiant power over various wavelengths of the potential base spectrum obtained after base filtering. Here, since we start from a completely smooth focal track surface and only the "potential" base spectrum and "potential" base radiant power are considered (i.e., the electron intensity distribution and size of the focal spot are not yet taken into account), they are constant across multiple y-coordinates of the line profile and, accordingly, are also constant in the circumferential direction for different line profiles.

[0049] In contrast, the focal track surface of Figure 7 has a surface structure or surface variations 100, such as occurs in, for example, a used x-ray rotating anode (Figure 7 is otherwise constructed the same as Figure 6, and like components / parts are labeled with the same reference numerals). According to the present computational model, the actual path length d' (in the y-direction) traveled through the focal track material is x-ray is determined for each X-ray generation point 98, i.e., for each y-coordinate along the y-direction (X-ray emission direction) of the line profile, taking into account surface variations according to the three-dimensional height profile, as shown in Figure 7. In this case, this "actual path length" d' x-ray In some cases, partial path lengths must be added to determine . This is the case when the X-rays initially exit the focal track plane in the y direction from the point of origin, but then re-enter the focal track material (one or more times) (e.g., due to local bumps) before finally reaching a free region outside the focal track material. This determination and other calculation steps are preferably performed with software support (unless otherwise specified) using appropriately configured software (e.g., Matlab R2017b 64bit; currently available at www.Mathworks.com). For this purpose, the respective line profile (e.g., as shown in the top diagram of Figure 8) is preferably imported into this software. Alternatively, one or more three-dimensional height profiles are imported into this software, and then multiple radially running line profiles are generated according to the simplification / approach 3 above. Furthermore, the tilt angle (here, α = 10°) and the average origin depth of the X-rays (here, d e- = 1.6 μm), as shown in FIG. 7, for each y-coordinate of each line profile, the distance d e- the actual path length d' in the y direction through the focal track material, starting from the focal point (offset by x-rayThis can be done using the software, for example, by determining the original line profile (which is important for the focal track plane) and the line profile d downwards in the z direction into the focal track material. e- This can be done by comparing the line profile (of interest for the point of origin) with an otherwise identical line profile shifted by a factor of 1, thereby determining the actual path length in the y direction according to the respective y coordinates of each line profile. An additional path length distribution f add (y) is the actual path length d' as follows: x-ray (y) to the theoretical path length d x-ray is determined by subtracting f add (y)=d' x-ray (y)-d x-ray Formula (2) If d'(y)<=5μm, then f(y)=5μm-9.07μm=-4.07μm

[0050] Actual path length d' relative to the y coordinate x-ray (y) is the theoretical path length d x-ray This results in actual filtering that differs from the basic filtering described above. The surface changes cause the theoretical path length d x-ray Compared to the actual path length d' x-ray (y) becomes larger (i.e., f add (where d' is greater than 0). However, unlike this, for some of the y coordinates, the actual path length d' x-ray (y) becomes smaller (i.e., f add is less than 0), in which case a minimum path length of at least 5 μm applies according to simplification / approach item 5 above (see the second line of equation (2)). The second diagram in Figure 8 shows the additional path length f add (y) (unit: micrometer or μm) ("f" in the figure) add(y) [μm]”), which occurs specifically for the line profile shown in the top panel of FIG. 8.

[0051] Then, as for a perfectly smooth focal trajectory (preferably software-supported, e.g., SpekCalc pro 1.1; see above), first a general (wavelength-dependent) reduction / filtering of the output spectrum is performed at f add is determined as a function of (the specifics for different y coordinates have not yet been determined), from which f add A "potential actual spectrum" is obtained as a function of f, whose intensity distribution is reduced compared to the output spectrum. The "potential actual radiant power" resulting from the sum or integral of the radiant power over the various wavelengths of the potential actual spectrum is then given by f add As a further step (preferably again with software support, e.g. SpekCalc pro 1.1; see above), the ratio f of this potential actual radiated power to the potential base radiated power (determined as above) is calculated. red is f add Therefore, this determined ratio f red (f add ) is the additional path length f that the X-rays must travel from the point of origin add This ratio f indicates how much the potential actual radiation power of the X-ray generation point varies relative to the potential base radiation power of a perfectly smooth focal orbital plane. red (f add ) can be adjusted in particular by a function, preferably a double exponential function (i.e., by the sum of two exponential functions), which, starting from a minimum value (in this example -4.07 μm), increases with the additional path length f add is greater than 1 when f is negative, then falls continuously, add = 0 reaches exactly 1. Additional path length add If is positive, it is less than 1 and the additional path length f addapproaches 0 as the value of increases. This function is again preferably supported by software (e.g., Matlab R2017b 64bit, see above) and specifically provides an additional path length distribution f as determined for the line profile using equation (2). add (y) and gives the radiation distribution f over the various y coordinates of the line profile, as shown in equation (3) below: emi (y) is obtained. f emi (y)=f red (f add (y)) Equation (3)

[0052] In this case, the radiation distribution f emi (y) denotes the ratio of the potential actual radiant power to the potential base radiant power for different y coordinates of the line profile, and this ratio is the negative of the associated f add (i.e., d' x-ray (y) <d x-ray ) for y coordinates with a positive value f add (i.e., d' x-ray (y)>d x-ray ) is less than 1. This means that the actual path length d' x-ray is the theoretical path length d of each generation point x-ray The larger the ratio of the potential actual radiant power to the potential base radiant power, the lower the ratio (i.e., more emitted radiation is absorbed), and vice versa. The third diagram in Figure 8 shows how this ratio, or radiation distribution, varies with the radiation distribution f over the y direction (units: millimeters) (see "y [mm]" in the diagram). emi (y) ("f" in the figure) emi (y)[-]"), which specifically refers to the additional path length f shown in the second diagram of Figure 8. add It results from (y).

[0053] And finally, to compare quantities other than those designated "potential", the electron intensity distribution in the y direction (i.e., along the radial direction) must also be taken into account, since the radiation power generated at each y coordinate depends on whether electrons impinge on this y coordinate and with what intensity. For this reason, for example, damage to the focal track surface in the radial direction outside the focal spot area is less significant since no x-rays are generated at these locations, but damage in areas of high electron intensity can be particularly significant, especially if it causes strong shadowing. As explained in Simplification / Approach 2 above, the electron intensity distribution in an x-ray rotating anode is characterized by a linear (running in the y or radial direction) intensity profile f e- (y) can be described by the radial distribution f emi (y) is the intensity profile f e- (y) should be weighted accordingly as shown in the following equation, resulting in the ratio O(y) of the "actual radiant power" to the "base radiant power" at each y coordinate: O(y)=f e- (y)*f emi (y) Equation (4)

[0054] Next, the ratio O of the actual radiation power emitted across the line profile of the damaged focal track surface with the surface structure to the corresponding base radiation power that would be emitted across the line profile in the case of a perfectly smooth focal track surface is calculated. Linie To obtain O(y), O(y) must be integrated over the y coordinate, as shown by the following equation: O Linie =∫f e- (y)*f emi (y)dy Equation (5)

[0055] In this way, the effect of surface structures occurring in the specifically analyzed line profile region of the damaged focal track surface on the emitted radiation power can be evaluated. Linieis an indicator of the attenuation of the radiation power due to damage to the focal track surface. Furthermore, it is of course possible to evaluate a large number of line profiles (each running radially and preferably distributed circumferentially around the X-ray rotating anode) in a similar way. In this case, on the one hand, possible variations in the circumferential direction of the X-ray rotating anode can be determined. Furthermore, the total radiation power can be calculated by multiplying the O obtained for the individual line profiles. Linie It can also be determined by summing / integrating the values.

[0056] The invention is not limited to the described embodiments. For example, as an alternative to the simplification / approach 2 (see above) for the focal spot and line profile, the electron intensity distribution over the region of interest, i.e., the function f e- (x,y) can also be used. Then, depending on the size of the focal spot, many adjacent line profiles of the three-dimensional height profile can be incorporated, and finally, the resulting emissivity distribution f emi (x,y) is the electron intensity distribution f e- The surface sections are weighted by a scalar multiplication with (x,y). Then several such surface sections around the periphery of the focal track are analyzed in the same way.

Claims

1. 1. An X-ray rotating anode analysis system for analyzing a used X-ray rotating anode (14; 33; 34) having a focal track (26; 40) orbiting over a surface section, comprising: a positioning device (56) for said X-ray rotating anode (14; 33; 34); an image capture unit (58); a data processing unit (64) coupled to the image capturing unit (58); In an X-ray rotating anode analysis system comprising: the positioning device (56) and the image capturing unit (58) are configured such that the X-ray rotating anode (14; 33; 34) is positioned as a separate component in a predetermined position relative to the image capturing unit (58), the image capturing unit (58) and the data processing unit (64) are configured so that a three-dimensional height profile of a surface section of the X-ray rotating anode (14; 33; 34) in the region of its focal track (26; 40) can be detected by the image capturing unit (58) and the data processing unit (64); And, the data processing unit (64) is configured to determine a predicted radiation output or characteristic value of the X-ray rotating anode (14; 33; 34) from the detected three-dimensional height profile or a portion thereof. X-ray rotating anode analysis system.

2. The image capturing unit (58) and the data processing unit (64) configured to use electromagnetic radiation to create a plurality of individual images, each having different depth information of the surface section of the X-ray rotating anode (14; 33; 34) to be analyzed, the data processing unit (64) is configured to reconstruct from the individual images a three-dimensional height profile of the surface section being analyzed.

10. The X-ray rotating anode analysis system of claim 1.

3. 3. The X-ray rotating anode analysis system of claim 2, wherein the image capturing unit (58) and the data processing unit (64) are configured to be able to create a plurality of individual images of the surface section being analyzed from different angles using electromagnetic radiation in the wavelength range of 380 nm to 780 nm.

4. 4. The X-ray rotating anode analysis system of claim 1, wherein the data processing unit (64) is configured to be able to determine the predicted radiation output or characteristic value of the X-ray rotating anode (14; 33; 34) based on automatically calculated absorption of X-rays along the X-ray emission direction (32; 46) according to a detected three-dimensional height profile, taking into account local absorption effects due to local surface variations (100).

5. 5. The X-ray rotating anode analysis system of claim 4, wherein the data processing unit (64) is configured to generate at least one line profile extending in the X-ray emission direction (32, 46) over a predetermined minimum length along the detected surface portion of the X-ray rotating anode (14, 33, 34) and having local surface variations according to the three-dimensional height profile, so that the line profile can be used for automatic calculation of X-ray absorption.

6. The data processing unit (64) at least one surface profile for automatically calculating the absorption of the X-rays, the surface profile extending in the X-ray emission direction over a predetermined minimum length along the detected surface section and over a predetermined minimum width substantially perpendicular thereto; having local surface variations according to the three-dimensional height profile; 5. An X-ray rotating anode analysis system according to claim 4, configured for use with said data processing unit.

7. The data processing unit (64) receives the following input values: Depth of X-ray generation, the emission angle of the X-ray radiation (α), the material of the focal track (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 a filter (102), 7. The X-ray rotating anode analysis system according to claim 4, wherein at least one of the above is set to be included in automatic calculation of X-ray absorption.

8. 8. The X-ray rotating anode analysis system of claim 1, wherein the data processing unit (64) is configured such that, from a detected three-dimensional height profile of the surface section of the focal track (26; 40) or from multiple image information detected in other ways, the data processing unit (64) can identify and classify damages (A, B, C) in the region of that surface section of the focal track (26; 40) of the X-ray rotating anode (14; 33; 34).

9. 9. The X-ray rotating anode analysis system of claim 1, wherein the image capturing unit (58, 60, 62) and the data processing unit (64) are configured such that at least one image of another surface section in an area adjacent to the focal track (26; 40) of the X-ray rotating anode (14; 33; 34) can be detected by the image capturing unit (58, 60, 62) and the data processing unit (64).

10. 10. The X-ray rotating anode analysis system of claim 1, wherein the data processing unit (64) is configured to evaluate a plurality of subsequent use options for the X-ray rotating anode (14; 33; 34) based on the determined predicted radiation output or based on characteristic values, and to issue corresponding use recommendations.

11. The data processing unit (64) is coupled to a memory unit (82), and the data processing unit (64) and the memory unit (82) have the following interactions: the individual information determined for each of the analyzed X-ray rotating anodes (14; 33; 34) can be stored in and read out from the memory unit (82) by the data processing unit (64); type-specific information for a plurality of different types of X-ray rotating anodes (14; 33; 34) can be stored in and read from the memory unit (82) by the data processing unit (64); the usage data ascertained for each of the analyzed X-ray rotating anodes (14; 33; 34) can be stored in and read from the memory unit (82) by the data processing unit (64); an individual history of the analyzed X-ray rotating anode (14; 33; 34) with respect to its use in the field and with respect to subsequent processing and repairs can be stored in and read out from the memory unit (82); 11. The X-ray rotating anode analysis system according to claim 1, configured for at least one of the following:

12. The data processing unit (64) takes into account the following further information in its evaluation of the next 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) of the focal track (26; 40) of the X-ray rotating anode (14; 33; 34) in the area of ​​the surface section, - further detailed surface section images in the area adjacent to the focal track (26; 40) of said X-ray rotating anode (14; 33; 34); Geometrical changes of the X-ray rotating anode (14; 33; 34), information determined individually for each of the analyzed X-ray rotating anodes (14; 33; 34), type-specific information for each of the analyzed X-ray rotating anodes (14; 33; 34), individual usage data of each of the analyzed X-ray rotating anodes (14; 33; 34), and the individual history of the analyzed X-ray rotating anode (14; 33; 34), 12. The X-ray rotating anode analysis system according to claim 10, wherein the system is configured to include at least one of the following:

13. 13. An X-ray rotating anode analysis system according to any one of claims 1 to 12, wherein the X-ray rotating anode (14; 33; 34) is housed in the positioning device (56) as a separate component.

14. 1. A method for analyzing a used X-ray rotating anode (14; 33; 34) having a focal track (26; 40) revolving over a surface section, comprising the following steps: positioning the X-ray rotating anode (14; 33; 34) as an individual component relative to an image acquisition unit (58) using the positioning device (56); acquiring, by means of the image acquisition unit (58) and a data processing unit (64) coupled to the image acquisition unit (58), a three-dimensional height profile of a surface section in the region of a focal track (26; 40) of the X-ray rotating anode (14; 33; 34); - the data processing unit (64) automatically determining a predicted radiation output or characteristic value of the X-ray rotating anode (14; 33; 34) from the acquired three-dimensional height profile or part thereof; A method comprising:

15. 15. The method of claim 14, carried out using an X-ray rotating anode analysis system (54) according to any one of claims 1 to 13.

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