Method for operating an X-ray device, X-ray device, computer program and electronically readable data carrier

Abstract

The invention relates to a method for operating an X-ray device (1), comprising an X-ray emitter arrangement (2) with an X-ray emitter (5) for emitting an X-ray field (26) for examining an object under investigation and an X-ray detector (7) for receiving X-ray radiation from the X-ray field (26), wherein the X-ray emitter arrangement (2) comprises: - a tank (4) for the X-ray source (5) with a housing (10) in which a radiation exit window (15) for the X-ray radiation generated by the X-ray source (5) is arranged, and - a beam shaping device (6) for adjusting the desired extent and position of the X-ray field (26), wherein the X-ray device (1) is controlled by means of a control device (9) - a deviation information that describes a deviation (22) of the current extent and position of the X-ray field (26) from the desired position and extent of the X-ray field (26) caused by the temperature conditions in the X-ray source arrangement (2), is determined, and - the beam shaping device (6) is controlled to at least partially compensate the deviation (22) depending on the deviation information.

Description

[0001] The invention relates to a method for operating an X-ray device, comprising an X-ray emitter arrangement with an X-ray emitter for emitting an X-ray field for examining an object to be examined and an X-ray detector for receiving X-ray radiation from the X-ray field, wherein the X-ray emitter arrangement comprises: - a single tank for the X-ray source with a housing in which a radiation exit window for the X-ray radiation generated by the X-ray source is arranged, and - a beam shaping device for setting a desired extent and position of the X-ray field.

[0002] The invention also relates to an X-ray device, a computer program and an electronically readable data carrier.

[0003] X-ray devices for imaging a patient typically include an X-ray tube for generating X-rays. In order to provide an X-ray field of a desired position and extent, the X-ray tube is typically assigned a beam-shaping device, which can be implemented together with the X-ray tube as part of an X-ray tube arrangement. Such a beam-shaping device can be, for example, a collimator and / or a diaphragm device. If the X-ray tube is accommodated, for example, in a single tank, which typically has a housing filled with a, for example, circulating, cooling medium, in which the X-ray tube is also arranged and emits the X-rays through a beam exit window of the housing, the beam-shaping device can be attached, in particular flange-mounted, to the single tank, in particular in a separate additional housing.The arrangement is then such that apertures (often also referred to as slats) of the beam shaping device act on the X-rays as desired and, depending on the setting of the beam shaping device, an X-ray field of a desired extent and position is created.

[0004] In X-ray systems for mammography (mammography systems), the breast to be examined is placed directly or indirectly on the X-ray detector and compressed using a so-called "paddle", i.e. a compression plate, while the patient stands directly against the support arrangement comprising the compression plate and the X-ray detector. In this case, the beam-shaping device can comprise a front aperture (front blade) and a rear aperture (rear blade), with the front aperture being the aperture directed towards the patient and the rear aperture being the aperture directed away from the patient. The X-ray field can be adjusted by appropriate control of the beam-shaping device, i.e. positioning the apertures, so that the entire breast is imaged if possible, but ideally as little radiation directed towards the patient as possible misses the X-ray detector.For example, limit values ​​may be provided in this regard.

[0005] When the X-ray tube is operated using appropriate electrical power, it heats up. If, for example, it is designed as an X-ray tube with a rotating anode mounted in a vacuum by means of a support assembly, power is also required for a drive device for the rotating anode, which can lead to further heating. This in turn can cause the rotating anode and its focal path to shift relative to the X-ray device as a whole, so that a shift of the focal spot, i.e., the focus point, can also occur relative to the beam shaping device and / or the X-ray detector. Secondary effects, such as heating of the housing of the single-tank, can also play a role. This effect is particularly pronounced with vacuum-mounted rotating anodes that are not directly connected to the coolant, since the rotating anode and the support assembly can only be cooled with difficulty into the cooling medium in the single-tank.

[0006] Generally speaking, thermal effects cause a shift in the X-ray field and thus in the irradiated area. This means that the field of view can change during the examination, so that in order to fully capture the object being examined, such as a breast, its extent and position would have to be adjusted with certain safety buffers. However, in cases where X-ray radiation outside the actual imaging area is undesirable, for example, where there are required maximum overexposure lengths, this is disadvantageous, especially if such required maximum overexposure lengths are reached or even exceeded, for example, in mammography towards the patient.

[0007] DE 10 2011 083 416 A1 discloses an X-ray device comprising an X-ray source and a detector interacting with the X-ray source, as well as a correction object arranged between the X-ray source and the detector with a defined geometry and known radiation absorption behavior.

[0008] DE 10 2017 203 932 A1 discloses a control unit which, depending on at least one operating parameter of an electronic drive for a rotational movement of a rotatably mounted anode in an X-ray tube, controls a deflection unit deflecting an electron beam in such a way that a movement of the focal spot of the electron beam on the anode caused by electromagnetic fields of the electric drive can be at least partially compensated.

[0009] WO 2008 / 132635 A2 discloses a medical imaging system comprising an X-ray source with a focal point that emits radiation that penetrates an examination region. The position of the focal point in the longitudinal direction depends on the temperature of one or more components of the X-ray source. A focal point estimator estimates the position of the focal point along the longitudinal direction depending on the temperature of the one or more components of the X-ray source. A collimator positioner positions a collimator along the longitudinal direction depending on the estimated position of the focal point.

[0010] WO 2009 / 110399 A1 discloses a position correction of a tube depending on a current temperature of the tube and the knowledge of whether the tube is in a heating process or a cooling process.

[0011] The invention is therefore based on the object of achieving a more reliable application of X-ray radiation in the actually desired field of view.

[0012] This object is achieved according to the invention by a method, in particular a computer-implemented method, an X-ray device, a computer program, and an electronically readable data carrier according to the independent patent claims. Advantageous further developments are set out in the subclaims.

[0013] In a method of the type mentioned at the outset, the invention provides that by means of a control device of the X-ray device - a deviation information describing a deviation of the current extent and position of the X-ray field from the desired position and extent of the X-ray field caused by the temperature conditions in the X-ray tube arrangement is determined, and - the beam-forming device is controlled to at least partially compensate for the deviation depending on the deviation information.

[0014] It is therefore proposed to directly or indirectly determine temperature effects that lead to deviations, in particular by measuring, estimating, and / or directly detecting deviations. The corresponding deviation information is then used to readjust the beam-shaping device accordingly and to maintain the desired extent and position of the X-ray field as accurately as possible, in particular by limiting the X-ray field to the detector surface of the X-ray detector.

[0015] In particular and preferably, the deviation information relates to the relevant temperature conditions, in particular relevant temperatures, within the X-ray tube, which can be measured and / or estimated based on the known use of the X-ray tube. This temperature information, in particular at least one temperature value, then available as deviation information can be used, for example, to calculate the position of the focal point, in particular the focal spot, relative to the X-ray detector and the beam-shaping device and to readjust the beam-shaping device accordingly. As will be explained in more detail below, an explicit calculation of the position of the focal point does not have to be carried out directly; rather, it is also possible to use a deviation model that directly outputs deviations or necessary corrective measures.

[0016] This makes it possible to largely or entirely eliminate potentially excessive safety buffers due to thermal effects in the X-ray tube arrangement, thus ensuring, in particular, that the actual desired area is imaged and, in particular, that no unwanted X-ray radiation is generated, particularly if it does not reach the X-ray detector. The radiation exposure for patients and / or other persons present can thus be reduced. No additional X-ray dose is applied due to an incorrectly adjusted X-ray field.

[0017] The application of the inventive procedure is particularly advantageous when an X-ray tube with a rotating anode arranged in a vacuum via a support arrangement is used as the X-ray source. Such rotating anodes are not directly connected to a coolant, such as oil, and can therefore heat up along with their support arrangement, which can lead to relevant position changes, in particular displacements, of the rotating anode, and thus of the focal path and the actual focal point. In this case, relevant temperatures can be considered, for example, the temperature of the rotating anode and / or its support arrangement, although these can also be determined indirectly, for example, via a temperature in the tank.

[0018] In a first, advantageous embodiment of the present invention, it can be provided that at least part of the deviation information is measured by means of at least one temperature sensor of the X-ray tube arrangement. In this case, for example, from a measured temperature distribution in the single-tank, further temperatures at locations where they cannot be measured directly can be derived as part of the deviation information. However, it is particularly expedient and for determining precise compensation measures if relevant temperatures can be measured directly. In the case of an X-ray tube with a rotating anode arranged so as to rotate in a vacuum, for example, it can be provided in a specific embodiment of the invention that the at least one temperature sensor, designed in particular as an infrared sensor, measures a temperature of the rotating anode and / or the support arrangement.If the temperature sensor is designed as an infrared sensor, it does not have to be arranged directly on the rotating anode and / or the carrier arrangement, but can be aligned with them in order to detect the corresponding temperature.

[0019] In advantageous embodiments, it can further be provided that at least part of the deviation information describes a power of the X-ray tube that leads to heating and / or a cooling period and / or is determined from these variables. Since the control device, for example a corresponding recording unit for controlling the recording operation, knows when the X-ray tube is operated, thus X-ray radiation is generated and / or the drive device of the rotating anode is in operation, the correspondingly applied powers and the power periods in which they are applied are also known and can be used as deviation information and / or to determine them.Particularly advantageously, a power curve is determined that indicates both when (and ideally where) electrical power is applied to operate the X-ray tube, and when cooling periods occur between these phases in which electrical power is applied. The applied power and the cooling periods in between primarily determine the temperature behavior of the X-ray tube. Therefore, a useful further development in this context provides that, using a temperature model describing the heating and cooling behavior of the X-ray tube, a current temperature of the X-ray tube, in particular of the rotating anode and / or its support arrangement, is determined as deviation information from the power and the cooling period.Temperature models that also describe cooling during cooling periods are already known in the prior art from other applications for X-ray tubes, especially X-ray tubes, for example, when estimating the potential throughput of X-ray devices. Such temperature models, which describe both the heating during power input and the cooling without power input and thus allow for the actual temperature estimation, can be used effectively to continuously update the temperature conditions in the X-ray tube as deviation information.

[0020] In a specific embodiment of the present invention, it can be provided that the deviation information is used as input data for a deviation model that provides at least one corrective measure according to which the beam-forming device is controlled, as output data. Such a deviation model can fundamentally be an analytical model, which, for example, allows a shift of the focal point relative to a desired position of the focal point to be determined as an internal intermediate result and to generate corresponding corrective measures in order to derive deviations of the current extent and position of the X-ray field from the desired extent and position of the X-ray field resulting from this shift. However, the deviation model can also be at least partially empirical, whether with regard to the shift of the focal point or directly to the corrective measures.

[0021] Generally speaking, the deviation model provides a link between the deviation information and the corrective measures to be carried out, i.e., readjustment. For example, the deviation model can therefore contain a relationship between at least one relevant temperature and a readjustment path of at least one aperture. In this case, particularly in empirical relationships where, for example, a function can be adapted to calibration data recorded in a calibration process yet to be discussed, temperature values ​​do not necessarily have to form the direct input data; rather, power outputs, in particular power curves with cooling periods, and comparable variables from which the temperature conditions are indirectly derived can also be used. In particular, it is fundamentally also conceivable for the deviation model to include at least one trained function that was trained using machine learning.Such a trained function may, for example, comprise a neural network, in particular a CNN, and be trained using calibration data as training data.

[0022] In a calibration process, values ​​for the deviation information and associated values ​​for the deviations, thus corrective measures, can be recorded and used to suitably adapt the deviation model. It can therefore be provided that at least one parameter of the deviation model is determined in a calibration process in which deviations for various thermal states, described by respective deviation information, of the X-ray tube arrangement are measured. The calibration can be determined either across X-ray devices, for example for one type or model of X-ray device, in particular with measurements on several different X-ray devices; however, it is also possible to perform a calibration specific to a particular X-ray device. In concrete terms, there are a variety of ways to perform measurements that indicate the deviation.

[0023] In this case, the measurement of the deviation particularly advantageously relates to the position of at least one aperture of the beam-shaping device, as imaged by the X-ray radiation. Such a position of an aperture represents a boundary of the X-ray field. Once the position of the aperture and thus the boundary of the X-ray field should actually be located is known, an actual position of the aperture or boundary of the X-ray field can be determined for several different thermal states, i.e. temperature conditions, in the X-ray source arrangement, in particular the X-ray source, in order to determine suitable calibration data. It is generally conceivable to use an external measuring device for this purpose; however, the X-ray detector and / or a measuring device that forms part of the X-ray device are preferably used.

[0024] In summary, it can be provided that at least one measured position of an aperture of the beam-shaping device (and thus of a boundary of the X-ray field) is compared with a target position according to the control of the beam-shaping device to determine the deviation. The X-ray detector and / or a measuring device permanently installed in the X-ray device are preferably used as the measuring means for the calibration process.

[0025] Specifically, for example, it can be provided that, without a patient being present, the aperture is adjusted so that its shadow falls on the X-ray detector, thus detecting the boundary of the X-ray field by the X-ray detector. The target position and the actually measured position can then be measured for different thermal conditions in order to determine the deviation by comparison. It is also possible to provide a measuring device laterally adjacent to the X-ray detector with which a deviation can be measured and determined outwards beyond the X-ray detector when the aperture is adjusted to the edge of the X-ray detector. Such an additional measuring device can preferably have several measuring chambers in order to obtain spatial resolution.

[0026] In some situations, a deviation can actually be measured during examination operation of the X-ray system and used to update the deviation model. For example, it is conceivable that at least one measuring device connected to one side of the X-ray detector can be used to update the deviation model during examination operation and / or that, if the examination object does not cover the entire X-ray detector, the X-ray detector can be used to determine the position of a boundary of the X-ray field (and thus the measured position of an aperture). If the entire X-ray detector is not required, for example in mammography with a small breast, the unused portion of the X-ray detector can be shaded using an aperture of the beam shaping device.If it is determined that this shadowing is not occurring as desired, i.e., the measured position of the boundary of the X-ray field does not correspond to the target position, a deviation is detected that can be attributed to a current thermal state of the X-ray tube arrangement, described by the deviation information. Since the X-ray detector is fully utilized in most cases, the X-ray field is usually also deployed in such a way that the X-ray detector is fully utilized. Therefore, it may be expedient to use a permanently installed, additional measuring device connected to the X-ray detector on at least one side to measure the current position of a boundary of the X-ray field beyond the extent of the X-ray detector.To provide spatial resolution, such a measuring device can, for example, have several consecutive measuring chambers of the same, predetermined size in the extension direction. This allows the measuring device to be kept simple while still providing spatial resolution.

[0027] In other embodiments of the present invention, however, it is also possible to measure at least part of the deviation directly and use it to derive a corrective measure. In this case, it can be provided that at least part of the deviation information is measured as a deviation of the position of a boundary of the X-ray field from a target position according to the desired position and extent of the X-ray field by means of the X-ray detector or a measuring device connected to the X-ray detector on one side. For example, if the X-ray field is set such that it should completely cover the X-ray detector, or more precisely its detection area, in the desired extent and position, but shadowing is detected on one side in the recorded X-ray image, this constitutes a (measured) deviation that can be taken into account for further, subsequent X-ray images.If the deviation shifts to the other side, a measuring device connected to the X-ray detector, as already described, can be useful for measuring it, in particular a design with multiple measuring chambers in the direction in which the measuring device connects to the X-ray detector. This is particularly useful with regard to mammographic applications, as it can then be measured, for example, on the "back" side, i.e. away from the patient, and from this a corrective measure for the "front" side, i.e. towards the patient, can be derived. If there is no symmetry, the theorem of rays can be used, for example, to determine deviations for other sides of the X-ray detector and thus also corrective measures in this regard. However, since this type of "on the fly" calibration requires an initial, uncompensated image acquisition, it is less preferred.

[0028] Overall, the procedure described here can also be applied particularly advantageously to mammography. A mammography system can therefore be used as the X-ray system in which the beam shaping device has a front aperture arranged towards the patient and a rear aperture arranged away from the patient, with at least the position of the front aperture being adjusted to compensate for deviations by controlling the beam shaping device. The front aperture is often also referred to as the front lamella or front blade, and the rear aperture is referred to as the rear lamella. Especially in mammography, even small deviations on the front side, i.e. towards the patient, can be extremely relevant, so compensation is particularly advantageous here. If the X-ray field deviates towards the patient, radiation that is not used for imaging can be introduced into the patient, which is undesirable.In this regard, for example, a maximum overexposure length, as already mentioned, can also be specified as a default. On the other hand, if the front edge of the X-ray field moves away from the patient, the breast may no longer be completely captured, which is equally undesirable. Since deviations of several millimeters due to thermal effects have been observed, these are certainly relevant, and the inventive procedure can be used particularly advantageously in mammography.

[0029] In addition to the method, the invention also relates to an X-ray device comprising an X-ray emitter arrangement with an X-ray emitter for emitting an X-ray field for examining an object to be examined and an X-ray detector for receiving X-ray radiation from the X-ray field, wherein the X-ray emitter arrangement comprises: - a single tank for the X-ray source with a housing in which a radiation exit window for the X-ray radiation generated by the X-ray source is arranged, and - a beam shaping device for setting a desired extent and position of the X-ray field, wherein the X-ray device further comprises a control device which comprises: - a determination unit for determining deviation information describing a deviation of the current extent and position of the X-ray field from the desired position and extent of the X-ray field caused by the temperature conditions in the X-ray tube arrangement, and - a compensation unit for controlling the beam-forming device for at least partially compensating the deviation depending on the deviation information.

[0030] In other words, the control device is designed to implement the method according to the invention. All statements regarding the method according to the invention can be applied analogously to the X-ray device according to the invention and vice versa, so that the aforementioned advantages can also be achieved with the latter.

[0031] In particular, the X-ray device can, for example, have at least one temperature sensor and / or at least one measuring device that is connected to the X-ray detector in one direction. The control device can comprise at least one processor and at least one storage means and has functional units formed by hardware and / or software, comprising the determination unit and the compensation unit. The control device can also have further functional units, be they basically known functional units such as an acquisition unit for controlling the acquisition operation or functional units for implementing advantageous embodiments of the method according to the invention. The latter functional units can, for example, comprise a temperature model unit for applying the temperature model and / or a deviation model unit for applying the deviation model.

[0032] A computer program according to the invention can be loaded directly into a storage means of a control device of an X-ray device and has program means which, when the computer program is executed on the control device, cause the control device to carry out the steps of a method according to the invention. The computer program can be stored on an electronically readable data carrier according to the present invention, which thus comprises control information stored thereon, which comprises at least one computer program according to the invention and is designed such that, when the data carrier is used in a control device of an X-ray device, the data carrier is designed to carry out a method according to the invention. The data carrier can in particular be a non-transient data carrier, for example a CD-ROM.

[0033] Further advantages and details of the present invention will become apparent from the exemplary embodiments described below and from the drawings. In the drawings: Fig. 1 a schematic diagram of an X-ray device according to the invention, Fig. 2 a schematic representation of the problem underlying the invention, Fig. 3 an arrangement of an object under examination for image recording, Fig. 4 a sketch to explain the use of a measuring device, Fig. 5 a flow chart of an embodiment of the method according to the invention, and Fig. 6 the functional structure of a control device of the X-ray device.

[0034] Fig. Figure 1 schematically shows an X-ray device 1 according to the invention, which is embodied as a mammography device. In the following exemplary embodiments, the present invention is discussed with regard to an application in the mammography field.

[0035] The X-ray device 1 comprises an X-ray tube arrangement 2, which is mounted on a stand 3 and, in addition to a single-tank 4 in which an X-ray tube 5 is arranged, also includes a beam-shaping device 6, in this case a collimator. By means of a beam exit window (not shown in detail here) in the housing of the single-tank 4, which faces the, for example, flange-mounted beam-shaping device 6, and the beam-shaping device 6, an X-ray field of the desired extent and position relative to an X-ray detector 7 can be generated. A compression plate 8 (“paddle”) is provided above the X-ray detector 7, which also serves as a support for a breast to be examined. The operation of the X-ray device 1 is controlled by a control device 9.

[0036] Fig. Figure 2 shows the structure of the X-ray tube assembly 2 in more detail, including relevant components, and explains the problem underlying the invention. The X-ray tube 5, arranged in the housing 10 of the single-tank 4, is designed as an X-ray tube having a rotating anode 11, which in the present case is held in a vacuum by a support arrangement 12 and is rotatable by a drive device 13. An electron beam emanating from an electron source 14, indicated only schematically, strikes a focal path of the rotating anode 11 and is converted there into X-ray radiation, which exits through the beam exit window 15, for example, a local thinning of the material of the housing 10. The beam shaping device 6 comprises a front, directed towards the patient, thus in Fig. 1 from the image plane, arranged movable aperture 16 and a rear aperture 17, which can also be referred to as front slat and rear slat, for example.

[0037] If the beam-shaping device 6 is adjusted to a desired extent and position of the X-ray field, the rotating anode 11 is in a thermal reference state relative to the beam-shaping device 6 and to the X-ray detector 7, indicated here by the detector surface 18, in the position shown in solid lines, at which an X-ray beam forming the front boundary of the X-ray field, which can just pass the front aperture 16, is shown as arrow 19. Due to thermal effects, depending on the temperature conditions, i.e. the thermal state, the rotating anode 11 can be shifted into a shifted position 20, shown in dashed lines, so that the relative position to the beam-shaping device 6 and the X-ray detector 7 is changed.

[0038] This leads to the boundary of the X-ray field, here again indicated by a peripheral beam as arrow 21, also changing, thus resulting in a deviation 22 from the desired position of the boundary of the X-ray field according to the desired extent and position, which is undesirable. Therefore, the procedure described here aims to analyze the thermal state of the X-ray source 5 and to determine at least one corrective measure to at least partially compensate for this. A corrective measure for the front aperture 16 is described in Fig. 2 is indicated by the arrow 23; a corresponding corrective measure can also be determined for the rear panel 17 if necessary.

[0039] Fig. Figure 3 explains the situation during mammography in more detail. A patient 24 with a breast 25 to be examined is indicated; for the sake of clarity, the compression plate 8 is not shown. An optimal X-ray field 26 for this situation is shown and in this case encompasses exactly the breast 25 and the X-ray detector 7, specifically its detector surface 18. If thermal effects cause a displacement of the rotating anode 11, the front boundary 27 of the X-ray field 26 is particularly relevant, since displacements in both directions are undesirable. Displacements of the boundary 27 forward, i.e., toward the patient 24, miss the detector 7 and represent an unnecessary radiation exposure. Displacements of the boundary 27 backward, i.e., away from the patient 24, result in the breast 25 no longer being fully imaged.Therefore, corrective measures in the present case include at least the corresponding adjustment of the position of the front panel 16.

[0040] Fig. 3 also shows a possibility of obtaining further information regarding the rear boundary 28 of the X-ray field 26 in the context of a measurement, particularly in the case of small breasts, or for calibrating a deviation model, which will be discussed in more detail below. This corresponds, like the front boundary 27 with respect to the front aperture 16, to the shadow cast by the rear aperture 17. If a measuring device 29 is now connected to the rear of the X-ray detector 7 in continuation of the detector surface 18 of the detector 7, which measuring device can, for example, comprise several measuring chambers 30 to produce spatial resolution, a displacement of the rear boundary 28 in the rearward direction can also be traced after the measuring chambers 30 have been exposed to X-ray radiation accordingly.

[0041] An example of a measurement at the rear edge of the X-ray detector 7 shows Fig. 4, where in the event of a deviation from the desired boundary 28 to the front, the shadow cast, deviating boundary 28', is recognizable on the X-ray detector 7, and in the event of a displacement to the rear, deviating boundary 28'', measuring chambers 30 are exposed to X-ray radiation and thus indicate this displacement. In particular, in mammography, it is conceivable to implement the correction method according to the invention in such a way that, by means of the X-ray detector 7 and optionally the measuring device 29, a deviation of the position of the rear boundary 28 from the desired position caused by thermal effects is measured by means of the X-ray detector 7 and / or the further measuring device 29, and from this, a necessary corrective measure with regard to the front aperture 16 is determined accordingly, in the case of asymmetry using the theorem of rays.

[0042] Fig. 5 shows a flow chart of another exemplary embodiment of the method according to the invention. In step S1, deviation information is determined, which in the present case, in the form of at least one estimated and / or measured temperature, describes the temperature conditions in the X-ray tube assembly 2, specifically for the rotating anode 11 and its support assembly 12, i.e., the thermal state of relevant components of the X-ray tube 5. Here, it is possible, on the one hand, to measure the temperature of the rotating anode 11 and / or the support assembly 12, as well as possibly other temperatures, via corresponding temperature sensors 31, see Fig. 2, ideally using infrared temperature sensors 31 within the X-ray source 5. However, it is also possible to derive the temperature from other temperature measurements; alternatively, or preferably additionally, a temperature can also be derived from the use of the X-ray source 5 known in the control device 9. For this purpose, a power curve is provided that describes the power output during power periods for operating the electron source 14 and the drive device 13, as well as the cooling periods in between. Using a temperature model, an estimated current temperature of the rotating anode 11 and / or the carrier arrangement 12 can be determined from this and used as deviation information.

[0043] In step S2, the deviation information, specifically the temperatures, is transferred as input data to a deviation model, which provides the deviations as output data, which can be directly translated into corrective measures, and / or the corrective measures themselves. This can be an empirical, previously calibrated deviation model, but also an analytical deviation model, which, for example, can first calculate the shifted position of the focal point and derive the deviations and necessary corrective measures from this.

[0044] As already mentioned, the corrective measures do not necessarily have to refer to all deviations from limits 27, 28, but in mammography, for example, may refer only to the front aperture 16.

[0045] To calibrate such a deviation model, i.e., to determine at least one parameter of the deviation model, a calibration process can be performed. In this case, it is possible, for example, using the X-ray detector 7 alone, without an object under examination, but also with additional use of the measuring device 29, to measure actually occurring deviations for various thermal states described by deviation information, for example, as a deviation of the position of boundaries 27, 28 from the target position. The resulting calibration data, in which deviation information of actual deviations is assigned, can be used to correctly parameterize the deviation model, for example, to fit a function of the deviation model and / or to machine learn a trained function of the deviation model.If it is possible to measure deviations during the investigation, these can be used to further optimize / verify the results of the deviation model.

[0046] In a step S3, the corrective measures resulting from the output data of the deviation model are then implemented accordingly by the control device controlling the beam forming device 6 accordingly.

[0047] Fig. Finally, Figure 6 shows the functional structure of the control device 9. In addition to conventional functional units not shown here, such as a recording unit, this device initially comprises a determination unit 32, in which the deviation information is determined according to step S1. For this purpose, the determination unit 32 can interact with an optional temperature model unit 33, which evaluates the power curve and provides estimated current temperatures.

[0048] In a deviation model unit 34, the deviation model can be applied according to step S2. Finally, in a compensation unit 35, the corresponding corrective measures are implemented according to step S3.

[0049] The control device 9 additionally has a storage means 36 in which, for example, the temperature model and the deviation model can be stored.

[0050] It should be noted at this point that the control device can preferably implement the corrective measures immediately and automatically. However, embodiments are also conceivable in which these are first presented to the user for confirmation as a correction option.

[0051] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0052] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

Claims

[1] Method for operating an X-ray device (1), comprising an X-ray emitter arrangement (2) with an X-ray emitter (5) for emitting an X-ray field (26) for examining an object to be examined and an X-ray detector (7) for receiving X-ray radiation from the X-ray field (26), wherein the X-ray emitter arrangement (2) comprises: - a single tank (4) for the X-ray source (5) with a housing (10) in which a radiation exit window (15) for the X-ray radiation generated by the X-ray source (5) is arranged, and - a beam shaping device (6) for setting a desired extent and position of the X-ray field (26), characterized by that by means of a control device (9) of the X-ray device (1) - a deviation information describing a deviation (22) of the current extent and position of the X-ray field (26) from the desired position and extent of the X-ray field (26) caused by the temperature conditions in the X-ray source arrangement (2) is determined, and - the beam-forming device (6) is controlled to at least partially compensate for the deviation (22) in dependence on the deviation information. [2] Method according to claim 1, characterized by that an X-ray tube with a rotating anode (11) arranged rotatably in a vacuum via a support arrangement (12) is used as the X-ray emitter (5). [3] Method according to claim 1 or 2, characterized by that at least part of the deviation information is measured by means of at least one temperature sensor (31) of the X-ray emitter arrangement (2). [4] Method according to claim 2 and 3, characterized bythat the at least one temperature sensor (31), designed in particular as an infrared sensor, measures a temperature of the rotating anode (11) and / or the carrier arrangement (12). [5] Method according to one of the preceding claims, characterized by that at least part of the deviation information describes a power of the X-ray source (5) which leads to heating and / or a cooling period and / or is determined from these variables. [6] Method according to claim 5, characterized by that by means of a temperature model describing the heating and cooling behavior of the X-ray source (5) from the power and the cooling period, a current temperature of the X-ray source (5), in particular of the rotating anode (11) and / or its carrier arrangement (12), is determined as deviation information. [7] Method according to one of the preceding claims, characterized bythat the deviation information is used as input data for a deviation model providing output data for at least one corrective measure according to which the beam-forming device (6) is controlled. [8] Method according to claim 7, characterized by that at least one parameter of the deviation model is determined in a calibration process in which deviations for different thermal states, described by respective deviation information, of the X-ray source arrangement (2) are measured. [9] Method according to claim 8, characterized by that the X-ray detector (7) is used as measuring means for the calibration process and / or that at least one measured position of an aperture (16, 17) of the beam-shaping device (6) is compared with a desired position according to the control of the beam-shaping device (6) in order to determine the deviation. [10] Method according to one of claims 7 to 9, characterized bythat in order to update the deviation model during the examination operation, at least one measuring device (29) connected to the X-ray detector (7) on one side thereof and / or in the case of an examination object which does not cover the entire X-ray detector (7), the X-ray detector (7) is used to determine the position of a boundary (27, 28) of the X-ray field (26). [11] Method according to one of the preceding claims, characterized by that at least part of the deviation information is measured as a deviation of the position of a boundary (27, 28) of the X-ray field (26) from a desired position according to the desired extent and position of the X-ray field (26) by means of the X-ray detector (7) or a measuring device (29) connected to the X-ray detector (7) on one side thereof. [12] Method according to one of the preceding claims, characterized bythat a mammography device is used as the X-ray device (1), in which the beam-shaping device (6) has a front diaphragm (16, 17) arranged towards a patient (24) and a rear diaphragm (16, 17) arranged away from the patient (24), wherein at least the position of the front diaphragm (16) is adapted to compensate for the deviation by controlling the beam-shaping device (6). [13] X-ray device (1), comprising an X-ray emitter arrangement (2) with an X-ray emitter (5) for emitting an X-ray field (26) for examining an object to be examined and an X-ray detector (7) for receiving X-ray radiation from the X-ray field (26), wherein the X-ray emitter arrangement (2) comprises: - a single tank (4) for the X-ray source (5) with a housing (10) in which a radiation exit window (15) for the X-ray radiation generated by the X-ray source (5) is arranged, and - a beam shaping device (6) for setting a desired extent and position of the X-ray field (26), characterized by that the X-ray device (1) further comprises a control device (9) which comprises: - a determination unit (32) for determining deviation information which describes a deviation of the current extent and position of the X-ray field (26) from the desired position and extent of the X-ray field (26) caused by the temperature conditions in the X-ray source arrangement (2), and - a compensation unit (35) for controlling the beam-forming device (6) for at least partially compensating the deviation as a function of the deviation information. [14] Computer program which, when executed on a control device (9) of an X-ray device (1), causes the device (1) to carry out the steps of a method according to one of claims 1 to 12. [15] An electronically readable data carrier on which a computer program according to claim 14 is stored.

Images