X-ray device and method for determining the state of an X-ray device

Abstract

The invention relates to an object X-ray device (10) comprising a radiation source (12) configured to generate and emit electromagnetic radiation for irradiating an object, and a detector device (16) arranged such that the emitted electromagnetic radiation, which at least partially passes through the object, is at least partially reflected by the detector device, and configured to generate an X-ray image of the object. In addition to the detector device (16), a sensor arrangement (20) is provided, which is configured to determine a radiation characteristic associated with the radiation source (12).An evaluation unit (26) is designed to determine or receive a quality parameter of the acquired radiographic image, to evaluate the radiation characteristic and to make a statement about the condition of the detector device and / or the radiation source based on the quality parameter and the radiation characteristic.

Description

[0001] The invention relates to an object radiography device and a method for radiating an object. In particular, the invention relates to a solution for determining the functionality of a detector used to acquire object radiography images and / or a radiation source for generating the radiation.

[0002] X-ray devices and methods are used to examine objects, particularly for inspecting industrially or manually manufactured workpieces. This allows, for example, the dimensional accuracy of a workpiece or the presence of internal defects to be checked and / or detected. Solutions from the field of computed tomography (CT) are particularly used for this purpose. These are based on invasive electromagnetic radiation, particularly in the form of X-rays. X-rays can be generated by accelerating (decelerating) particles (e.g., electrons) in a target of an X-ray source. The spectral range of the invasive radiation is not limited by specific wavelengths.

[0003] In CT devices and processes, a workpiece is irradiated with X-rays from different angles of incidence to acquire a plurality of transmission images, or more specifically, X-ray images. These are therefore projection images. These are then combined by a computer to create a three-dimensional (3D) representation of the irradiated workpiece.

[0004] To generate the results of the transmission, i.e. the transmission images, detectors are used which comprise, for example, a scintillator and / or photodiodes. In particular, the detectors can be designed as so-called flat panel detectors, i.e. detectors with a shallow depth. The detectors are particularly configured to generate a two-dimensional transmission image from the electromagnetic radiation which at least partially penetrates the object or workpiece and then falls onto the detector. For this purpose, the detectors can comprise a plurality of individual detector elements, each generating a pixel, which are often designed in a matrix form with detector elements arranged in rows and columns and each detects a radiation value individual for the element, i.e. a value of the amount of radiation incident on the element in the detection time interval.

[0005] In particular, a gradual radiation value can be recorded pixel by pixel, which can be displayed in a corresponding image as the so-called gray value of the pixel.

[0006] It has been shown that the quality of the images captured by a detector device can deteriorate over time due to aging effects. In particular, the detector device may produce erroneous or inaccurate image captures over time. This can make meaningful workpiece inspection difficult or even impossible. However, since the detector device is a comparatively expensive component, unnecessarily early replacement should be avoided.

[0007] The quality of the source of invasive radiation can also deteriorate over time. In particular, the target can wear out, and the transmittance of a window through which the invasive radiation leaves the source and is radiated onto the measurement object can decrease. With target wear, the radiant flux density of the radiation radiated onto the target within the source can decrease over time.

[0008] The source and its components are also parts that should not be replaced too early for economic reasons.

[0009] US Pat. No. 6,505,966 B1 discloses a method and apparatus for evaluating the performance of an X-ray imaging system, in which radiation incident on a detector device is detected and compared with target performance data. Malfunctions of a detector device are detected by the occurrence of uneven attenuation in a captured reference specimen radiograph.

[0010] DE 10 2012 210 638 A1 further discloses a method for determining the condition of a radiation source and an X-ray device in which measured values ​​relating to a radiation dose are determined.

[0011] US 2010 / 0 316 183 A1 discloses an X-ray computer tomograph for examining an object by means of X-ray computer tomography with an X-ray source for generating X-rays, an X-ray detector for detecting the X-rays, a specimen slide for positioning an object to be examined between the X-ray source and the X-ray detector and an evaluation unit for evaluating the detected X-rays.

[0012] US 2005 / 0 100 133 A1 discloses a microfocus X-ray device and a method for controlling the intensity of the X-ray radiation generated by a microfocus X-ray device.

[0013] US 2014 / 0 086 390 A1 discloses a method and apparatus for determining the radiation exposure dose and a radiation image acquisition system that determines a radiation exposure dose of the human body based on a radiation image signal obtained by radiological imaging of a human body containing an artificial object.

[0014] US 2017 / 0 184 737 A1 discloses an imaging system comprising, among other things: a high-energy X-ray source for irradiating at least a portion of an object with an X-ray beam and a detector arrangement for acquiring object measurement data indicating an interaction of X-rays with at least a portion of the object.

[0015] KR 10 2017 082 525 A discloses a radiation dose meter for computer tomography.

[0016] There is therefore a need to reliably detect degradations of the detector device and the radiation source.

[0017] The invention generally relates to the approach of detecting additional variables in addition to detecting any defect variables in the detector device in order to rule out other sources of error for poor image quality. For example, in one aspect, a radiation dose of the electromagnetic radiation is additionally determined to rule out the possibility that the image quality is deteriorating due to a faulty radiation source rather than a faulty detector device, or to determine the extent to which the performance of the radiation source has decreased. Thus, it can be determined with greater reliability whether and / or to what extent the detector device and / or the radiation source is actually faulty and / or needs to be replaced.

[0018] In detail, the invention proposes an object radiography device and a method according to the appended independent claims. Advantageous further developments are specified in the dependent claims. According to the invention, the condition of the detector device is determined based on the quality parameter and the radiation characteristic, although reference is made below to the theoretically equally possible condition determination of the radiation source.

[0019] The object irradiation device comprises a radiation source configured to generate and emit electromagnetic radiation for irradiating an object. It further comprises a detector device configured such that the emitted electromagnetic radiation, which at least partially passes through the object, impinges on it, and configured to generate a irradiation image of the object (also called a projection image). A sensor arrangement of the object irradiation device, present in addition to the detector device, is further configured to determine a radiation parameter associated with the radiation source, namely a radiation dose (e.g., in a solid angle range detected by the sensor arrangement) or an instantaneous radiation power, in particular a radiation flux density.An evaluation unit is configured to determine or receive a quality parameter of the acquired radiographic image and to evaluate the radiation characteristic. According to the invention, the evaluation unit is configured to determine or receive the quality parameter of the acquired radiographic image and, if the quality parameter satisfies a predetermined degradation criterion, to check whether the radiation characteristic lies within a predetermined range that indicates a desired mode of operation of the radiation source. This is an example of an evaluation of the radiation characteristic. Furthermore, the evaluation unit is configured to determine a degradation of the detector device if the degradation criterion is met and if a radiation dose is present within the predetermined dose range.Alternatively or additionally, the radiation parameter can be used to determine the quality degradation experienced by the radiation source and / or the detector device. According to the invention, the evaluation unit can therefore be configured to use the quality parameter and the radiation parameter to make a statement about the condition of the detector device and, as an alternative example not covered by the invention, also about the condition of the radiation source.

[0020] The radiation source can be configured to emit electromagnetic radiation in the form of X-rays. For this purpose, the radiation source can comprise an X-ray tube and / or a particle beam source, in particular for emitting electrons. The emitted electrons or other emitted particles can strike a target configured to generate the invasive radiation in the form of bremsstrahlung. The invasive radiation ultimately emitted by the radiation source can be radiated through an object receiving area (also referred to as a measurement volume) onto the detector device. The object receiving area can comprise a suitable structure for positioning, supporting, and / or holding the object, for example, a turntable or a holder.The object to be irradiated may be an industrial or handcrafted product and / or a workpiece that is to be checked for dimensional accuracy, quality and / or freedom from defects.

[0021] The detector device can comprise a flat-panel detector as mentioned above or can be designed as such. In particular, it can comprise a scintillator and / or a preferably matrix-like arrangement of sensor elements (e.g., photodiodes). The detector device can generally be designed to capture two-dimensional radiographic images of the object.

[0022] In particular, the object radiography device can be designed in the manner of an industrial CT device and can acquire a plurality of, in particular, two-dimensional radiographic images from different irradiation directions. These can then be reconstructed into three-dimensional views of the irradiated object.

[0023] The sensor array can, for example, determine a current radiation dose (recorded by the sensor array within a current measurement period) and / or a cumulative radiation dose (over a period since the object irradiation device was put into operation or a dose counter was reset). The cumulative radiation dose can indicate the measured radiation dose accumulated over a previous service life or a defined operating time of the detector device. The current radiation dose, on the other hand, can refer to the radiation dose emitted for a current image acquisition and / or incident on the detector device for a current image acquisition. In the case of X-rays, the radiation dose can be measured in the form of an energy dose (for example, in the unit gray) or in the form of an ion dose.

[0024] The radiation dose measured by the sensor arrangement can, in principle, be measured at any point in the beam path of the radiation generated by the radiation source and / or relate to any radiation dose along this path. In one embodiment, the measured radiation dose is converted into a radiation dose incident on the detector device. The incident radiation dose provides information about the radiation dose actually available to the detector device for image capture. Additionally or alternatively, the radiation dose measured by the sensor arrangement can be converted into a radiation dose directly emitted by the radiation source (hereinafter referred to as the source dose). The source dose can provide information about the performance of the radiation source and / or whether it reaches a predetermined target value.The relationships required for the conversion can be determined experimentally and / or calculated.

[0025] The emitted radiation dose measured by the sensor arrangement can also be approximately assumed to be identical to the incident radiation dose and / or the source dose. In particular, the incident radiation dose can be approximately assumed to be identical to the source dose. Instead of a respective identity, a predetermined constant ratio of the above values ​​can also be assumed. Furthermore, all of the above radiation dose values ​​can again be considered as current and / or cumulative values.

[0026] A predetermined range of values ​​of the radiation parameter (e.g. a dose range), which indicates a desired and, in particular, error-free functioning of the radiation source, can be determined in advance (e.g. experimentally or by calculations).

[0027] As mentioned, another radiation parameter, such as a radiation flux density within the spatial detection range of the sensor array, can be measured alternatively or in addition to the dose. Conversions to the corresponding value at the radiation source and / or detector can be performed in the same way as for the dose.

[0028] The evaluation unit can be part of a computer or control device of the object radiography device or form such a device. In particular, the evaluation unit can comprise a processor (or a CPU) and / or be connected to the sensor arrangement for transmitting data or signals. The evaluation unit can, for example, determine a predetermined quality parameter of the radiography image using image evaluation algorithms. The quality parameter is preferably a signal-to-noise ratio of the image signals generated by the detector device. Alternatively or additionally, a spectral error, a contrast error, a degree of blur, an exposure error, or another suitable parameter can be determined, which allows a conclusion to be drawn about the quality and / or the accuracy (or an error) of the image acquisition.In any case, additional information, such as information about image values ​​from at least one dark frame of the detector device, can optionally be used to determine the quality parameter of the radiographic image. When a dark frame is acquired, the detector device is not irradiated by the radiation source.

[0029] Noise is defined as a deviation from measured values ​​due to random processes (e.g., due to thermal, electrical, or photonic interference). The signal-to-noise ratio is, in particular, the quotient of a mean signal intensity and a standard deviation of that signal intensity. The standard deviation can be calculated from the temporal change of the signal (e.g., a pixel) or from the spatial deviation and / or variation of the signal (e.g., from a defined number of pixels that share the same mean signal intensity).

[0030] A degradation criterion, with respect to which the quality parameter can be evaluated, can include reaching a predetermined threshold value (or falling below or exceeding it). However, alternatively or additionally, the quality of the radiographic image and, in particular, the value of the quality parameter can be repeatedly determined. If the quality of the detector device decreases (e.g., due to decreasing effectiveness of a scintillation layer) and / or the quality of the radiation source (due to decreasing radiation output), a decreasing quality can be determined accordingly. The quality corresponds to a state of the object radiographic device. Optionally, based on the quality, it is possible to predict when (e.g.,This determines the time (i.e., after how many further irradiation processes and / or after what further operating time, optionally taking into account the radiation power incident on the detector) before maintenance, replacement, or repair will be required. Since the sensor arrangement also determines the radiation parameter, the evaluation unit can also determine the proportion of the radiation source and the detector device contributing to the loss of quality. It can therefore also be predicted whether and when maintenance, replacement, or repair of the radiation source and the detector device will be necessary. Further details will be discussed below.

[0031] If degradation, a loss of quality, and / or a predefined state of the radiation source and / or the detector device is detected, an alarm signal and / or a warning message can be issued (e.g., via the evaluation unit). The warning message and / or alarm signal can be displayed to a user via a display device of the object radiography device and / or transmitted to other units or components of this device.

[0032] The object radiography device disclosed herein can, overall, enable the reliable determination of a state of the detector device and / or the radiation source. In particular, it is provided to determine a radiation dose from the radiation source as a radiation parameter. Only if this dose lies within a predetermined dose range, which indicates a desired and, in particular, error-free functioning of the radiation source, is it concluded that any quality defects in the acquired radiographic image are attributable to quality defects in the detector device. The same applies to other radiation parameters. In other words, it is ensured that defects in the acquired radiographic image are not caused solely by defects in the radiation source, but that the detector device is actually the cause or a contributing factor.This prevents unnecessary and, above all, premature replacement of the comparatively expensive detector unit. It also allows for greater certainty in determining which unit is actually responsible for a decline in image quality.

[0033] In principle, it is also possible to determine degradation and / or poor quality of the radiation source when a radiation parameter is determined outside a predetermined value range. This can also be determined by the evaluation unit and displayed, for example, in the form of a warning or alarm signal. In addition, a condition can be provided according to which a corresponding poor quality of the radiation source is only determined if both the determined radiation parameter lies outside the predetermined value range and the determined quality parameter meets a predetermined criterion that indicates poor image generation by the detector device. In other words, the poor quality of the radiation source can be redundantly checked and determined using the radiation parameter and the quality parameter.

[0034] Furthermore, it can be provided to record the information in the form of the radiation characteristic and / or the quality parameter repeatedly over a longer operating period and / or a larger number of image acquisitions. This can be used to determine emerging trends regarding a declining quality of the detector device and / or the radiation source. For example, a progressive decrease in the quality parameter with a substantially constant radiation characteristic indicates increasing aging of the detector device. Within the scope of the method and device disclosed here, a user can be informed of such a development, e.g., through suitable warning messages.

[0035] Further developments of the method and device are explained below. However, particularly in developments concerning the structure of the object radiography device, it is not mandatory to provide an evaluation unit of the above type and / or a test performed by it.

[0036] A further development of the method and device provides that the sensor arrangement comprises at least one ionization chamber to determine the radiation flux density and / or the radiation dose as the radiation parameter. By using an ionization chamber, reliable monitoring of the radiation parameter can be ensured over a long operating period (for example, over several weeks or months). The ionization chamber can be based on the principle of a plate capacitor with air as the dielectric, whereby unwanted damage to the sensor arrangement caused by invasive radiation, in particular X-rays, can be minimized. Furthermore, the ionization chamber is characterized by comparatively low manufacturing costs and offers extensive degrees of freedom with regard to its positioning and / or extension within the object radiography device.

[0037] Although not preferred, instead of using a sensor arrangement to determine the radiation parameter, at least one known object can be permanently or temporarily introduced into the beam path between the radiation source and the detector device. In particular, the effect on the radiation passing through the respective object can be known (e.g., determined in advance). The radiation changed by interaction with the object can be detected by the detector device, and by comparing it with the known effects, it can be determined whether and to what extent the detector device has qualitative defects or what its condition is. However, this method is less accurate than measuring the radiation parameter. If the object is only temporarily introduced into the beam path, the method is also more complex.

[0038] The ionization chamber can further provide a return signal that corresponds to the radiation flux density and can be converted, for example, into a measured radiation dose, for example by time integration. If the ionization chamber has a capacitor, the capacitor can be regulated, for example, to a constant electrical voltage, and the electrical current required for this can be used as the return signal. In one specific embodiment, the electrical current can be measured as the voltage drop across an electrical load. Alternatively, the discharge of the capacitor, i.e., the time derivative of the electrical voltage, can be determined as the return signal by integrating it over a time interval of predetermined length.

[0039] The return signal can be evaluated by software, for example, adding up a counter to obtain a dose value. Adding up can occur at or after predetermined time intervals. The software can supplement the added counter or dose value with time information and / or information about a specific image acquisition process. For example, the value can be saved as a time-stamped data value and / or as a data value associated with a specific image acquisition process.

[0040] Alternatively or in addition to determining a dose value, the evaluation unit can be configured to record further operating parameters of the object radiography device and to store them (for example, as a single data set within a database) preferably with the assignment of a respective time stamp and / or a specific image acquisition process. This can also be provided as a corresponding method step within the scope of the method disclosed here. The operating parameters can include current parameters of the radiation source such as electron beam density, the quality parameter of the acquired radiography image, or other detector parameters. Thus, information can be collected in order to, for example, understand at what point in time and under what conditions quality losses on the part of the detector device are occurring or have occurred.

[0041] In general, the sensor arrangement can also comprise a plurality of individual sensor units in order to achieve a certain spatial resolution of the detected radiation dose. Each sensor unit can determine its own, preferably location-specific, value of the radiation parameter. In particular, separate measurements can be taken in several predetermined areas or at several predetermined positions, so that a spatial assignment of the respectively measured radiation parameter is possible and / or a spatial distribution of the total emitted radiation (e.g., the radiation flux density) can be determined. For example, by using ionization chambers, such individual sensor units, which can each comprise at least one of their own ionization chambers, can be provided with little effort and cost.

[0042] The determined radiation characteristic can also be taken into account when regulating the radiation emitted by the radiation source. In a variant of the method and device according to the invention, the control can, for example, keep the radiation output of the radiation source constant, at least within certain limits, despite the decreasing quality of the radiation source.

[0043] In particular, the determined value of the radiation parameter is compared with an expected target value, and the resulting target-actual deviation is used to control the radiation source. For example, this can be used to regulate a voltage source by means of which the radiation source generates a particle beam (in particular an electron beam) that is directed at a target to generate bremsstrahlung or X-ray radiation emitted into the environment. In other words, the radiation parameter can be used to control the ultimately emitted electromagnetic radiation, or, in other words, to spot control this radiation. Furthermore, the status of the detector device can be determined, as described.In a variant of the method and device, if the target-actual deviation with respect to the radiation characteristic meets a predetermined criterion (for example, exceeding a threshold value), it is concluded that the radiation source has reached a state of inferior quality and, for example, a predetermined value of the radiation characteristic is no longer achieved.

[0044] Using the radiation parameter as a parameter for radiation source control can supplement or partially replace parameters commonly used for radiation source control. The usual parameters can be a measured electron current generated by electrons flowing toward a target. Additionally or alternatively, it can be a measured target current generated by electrons reaching a target. With a known voltage and a known target material, the measured radiation parameter can also be converted into the target current. In particular, a proportional relationship can exist between the target current and the measured radiation parameter.

[0045] The detection of the radiation parameter for radiation source control can also offer the advantage of increased fault tolerance and, in particular, be insensitive to erroneous target current signals due to potential changes caused by contact with conductive objects within the object irradiation device and electrical charges within the radiation source. Furthermore, electrical or thermal insulation within the radiation source, which is known to be used for detecting the usual control variables, can be eliminated or used only to a reduced extent. Furthermore, the detected radiation parameter can also be used to more directly and reliably detect malfunctions such as incipient target wear (e.g., in the form of burn-off).

[0046] In a further development of the method and the device, a portion of electromagnetic radiation that is not used to capture the transmission image can be detected to determine the radiation parameter (e.g. by means of the aforementioned sensor arrangement). This portion can be an outcoupled radiation portion (e.g. outcoupled from a transmission cone) and / or a radiation portion that does not interact with the detector device. In one variant, this is a region of an expanded beam cone and in particular its outer edge region that does not interact with the detector device for image capture. Generally speaking, the radiation portion detected by the sensor arrangement can be spatially remote from and / or interaction-free with respect to the detector device.

[0047] In one variant of the method and device, the sensor arrangement is arranged such that it detects a radiation component of the radiation generated by the radiation source that lies or extends outside a solid angle containing the detector device. The solid angle containing the detector device extends from the radiation source and, for example, from an output window or a radiation emission region of the radiation source to the detector device. The solid angle can contain or define a transmission cone (or also called a useful beam cone) of the emitted radiation, wherein this transmission cone is used to generate the transmission image. In other words, the sensor arrangement can thus be designed to detect a radiation component outside the useful beam cone.

[0048] In general, in the context of the present application, instead of a beam cone, it may be a deformed, non-rotationally symmetric beam cone or a differently shaped irradiation area within which the invasive radiation propagates from the radiation source to the detector.

[0049] A further development provides that the device comprises a separation arrangement in order to separate (or, in other words, to couple out) the radiation component detected by the sensor arrangement from the radiation generated by the radiation source. The separation arrangement can, as explained below, have a diaphragm or a collimator. In particular, such a separation or division of the emitted radiation can be carried out so that the above-explained detection of the radiation dose outside of a solid angle containing the detector device is enabled. In one variant of the method and device, the emitted radiation is divided into a transmission cone for irradiating the object and into a separate radiation component for dose detection.

[0050] The separation arrangement therefore allows for a reliable split of the radiation into a portion for determining the radiation characteristic and a portion for image acquisition. This defined split allows for reliable and precise capture of the radiation characteristic and the radiographic image.

[0051] As mentioned, the separation arrangement can in particular comprise a collimator and / or a diaphragm or be formed by such a diaphragm. In the case of a diaphragm, the separation arrangement can be impermeable to the electromagnetic radiation, with the exception of openings for the passage of the radiation, and thus only allow radiation incident on the diaphragm to pass through the openings. Preferably, the separation arrangement has at least a first and a second opening for splitting the radiation into individual radiation components. The openings can separate or define the above-described components for determining the radiation characteristic and for image capture. The use of a diaphragm with openings can enable reliable definition of the desired radiation components with a comparatively simple design.

[0052] According to one embodiment of the device and the method, the sensor arrangement and the detector device extend, at least in sections, in a common plane or in mutually parallel or substantially parallel planes. The plane containing the sensor arrangement can be a radiation incidence plane of the sensor arrangement, e.g., an ionization chamber. The plane containing the detector device can be a detection plane of the detector device, e.g., in the form of the detector surface of a possible flat-panel detector.

[0053] In one variant, the sensor array is arranged parallel to the detector device but further away from the radiation source than the detector device. In this case, an arrangement along a common spatial axis and / or a preferably contactless but at least partially overlapping arrangement of the detector device and sensor array (e.g., overlapping from the radiation source's perspective) is also conceivable.

[0054] In a further embodiment, the sensor arrangement is arranged in the same plane as the detector device or, from the perspective of the radiation source, parallel to the detector device but less distant than the detector device. In this case, an overlapping arrangement of the detector device and the sensor arrangement is preferably not provided, so that the sensor arrangement does not hinder image capture by the detector device. In other words, the sensor arrangement is preferably positioned such that it does not prevent or block any radiation component intended for object irradiation and / or image capture from reaching the detector device. This can be achieved by the arrangement options of the sensor arrangement explained herein outside a solid angle containing the detector device.

[0055] Additionally or alternatively, the sensor arrangement can extend at least partially along the detector device and / or enclose it in a frame-like manner. In both cases, the sensor arrangement and the detector device can extend in a common plane. Extension in parallel and preferably only slightly offset planes can also be provided, whereby the sensor arrangement can be arranged, for example, in a plane positioned in front of or behind the detector device from the perspective of the radiation source.

[0056] Arranging the sensor array along the detector device or enclosing it in a frame-like manner allows the sensor array to be positioned close to the detector device and thus detect radiation that essentially corresponds to the radiation used for image acquisition. This can increase the significance of the radiation dose determined by the sensor array.

[0057] In this context (i.e., extending along the detector device or enclosing it in a frame-like manner), the sensor arrangement can further be dimensioned such that it can compensate for centering errors between an impingement surface of the radiation and the detector device (in particular centering errors in the plane of the detector device). For example, the radiation can be expanded in the form of a transmission cone, in particular by a predetermined amount, so that it does not only impinge on the surface of the detector device for the sensor arrangement to detect the radiation parameter. By expanding, an external radiation component (e.g., in a lateral surface of the transmission cone) in addition to the actual transmission cone is provided for measuring the radiation parameter.In particular, the widening can be performed in such a way that the detector device and a sensor array extending along or surrounding it can be irradiated simultaneously. A centering error could, in principle, result in the transmission cone being shifted relative to, and in particular parallel to, the detector device and the sensor array, and at least no longer covering the latter as expected. Despite the same radiation dose on the detector, the radiation characteristic measured by the sensor array may decrease due to this changed coverage.

[0058] According to further developments of the invention, a width and / or an edge region of the sensor arrangement is therefore dimensioned such that, with optimal centering of the emitted radiation and the detector device, the sensor arrangement comprises regions that are not completely covered by the incident surface of the radiation. These regions can provide reserves to compensate for any centering errors. For example, these regions can only be irradiated when there is a relative shift of the transmission cone and the detector device relative to the optimal centering, thus enabling detection of the radiation parameter despite the centering error. The relative shift can occur, in particular, in the plane of the detector device.

[0059] In one variant, the sensor arrangement comprises corresponding (reserve) areas on at least two sides of the detector device and, in particular, a correspondingly wide, frame-like edge area. In this case, the detected radiation characteristic can remain essentially constant despite centering errors. For example, it may therefore be irrelevant that a first area of ​​the sensor arrangement, which would be irradiated with optimal centering, is no longer irradiated due to the centering error if, instead, a reserve area explained above is irradiated (e.g., on an opposite side and, in particular, an opposite edge area of ​​a possible frame structure). Since the total irradiated sensor area thus remains essentially constant despite centering errors, the measured radiation characteristic can also remain constant.

[0060] Alternatively or additionally, at least a portion of the sensor array can be located to the side of a radiography region of the object radiography device, in which objects can be placed for radiography and within which the invasive radiation propagates from the radiation source to the detector. Particularly if the separation arrangement for separating the radiation generated by the radiation source is present, the portion of the sensor array or the sensor array can be arranged significantly closer to the radiation source than the detector device. A compact object radiography device can therefore be realized. The space required for the object radiography device can be reduced in the region of the detector device.

[0061] In summary, the above embodiments can prevent a centering error between the emitted radiation and the detector device from inevitably resulting in a measurement error of the radiation parameter.

[0062] The invention further relates to a method for determining a state of a detector device, comprising the steps: - Emitting electromagnetic radiation by means of a radiation source of the object irradiation device, so that the radiation is directed at an object to be irradiated and radiation passing through the object falls at least partially on a detector device of the object irradiation device, - capturing a radiographic image of the object using the detector device, - Determination of a radiation parameter assigned to the radiation source, - Determining a quality parameter of the acquired radiographic image, - Evaluation of the radiation parameter taking into account the quality parameter and - Determining a state of the detector device from a result of the evaluation.

[0063] Unless otherwise stated or apparent, the above list is not intended to be a strict chronological order. The method may further include any further steps and any further features to provide any of the interactions, operating states, or effects discussed above or below.

[0064] In particular, the method may include a step of regulating the radiation emitted by the radiation source based on the determined radiation characteristic. A step of separating a radiation component for detecting the radiation characteristic may also be provided.

[0065] In the following, embodiments of object radiography devices according to the invention, each of which carries out a method according to the invention, are explained with reference to the attached schematic figures. Comparable features may be provided with the same reference numerals across all embodiments. They schematically depict: Fig. 1 an object radiography device according to a first embodiment; Fig. 2a,b an object radiography device according to a second embodiment; Fig. 3a,b are views for explaining centering error compensation by means of an object irradiation device according to a third embodiment; and Fig. 4 an object radiography device according to a fourth embodiment.

[0066] Various embodiments are described below. It should be noted again that the invention provides for the condition of the detector device to be determined based on a quality parameter and a radiation characteristic, although the condition of a radiation source is discussed below as a theoretically equally possible alternative.

[0067] In Fig. 1 shows an object irradiation device 10 according to a first embodiment. The object irradiation device 10 comprises an X-ray tube as the radiation source 12. This is configured to emit electromagnetic radiation in the form of X-rays from a radiation generation region 14 and direct them onto a detector device 16. The illustration shows a rear side of the detector device 16. On its front side facing the radiation source 12, the detector device 16 has a detector surface for detecting the incident radiation. The detector device 16 is designed as a flat-panel detector for X-rays and comprises components such as a scintillator layer on a matrix of photodiodes.

[0068] As in Fig. 1, the radiation emitted by the radiation source 12 expands within a transmission area 18, whereby in Fig. 1 limiting beams 181, 182, and 184 of the irradiation region 18 are shown. The irradiation region 18 defines a solid angle in which the radiation propagates from the radiation source 12. The irradiation region 18 extends between the radiation generation region 14 and the detector device 16, wherein the detector device contains at least the detector surface. Fig. 1 and other figures, the arrangement of the boundary beams of the irradiation region 18 can be interpreted to represent a pyramid-shaped irradiation region 18. Radiation emanating from the radiation source and passing through the irradiation region 18 strikes the particularly rectangular detector surface of the detector device 16.

[0069] In Fig. 1, it is not separately shown that the radiography region 18 extends through an object recording region. An object to be radiated (e.g., an industrially manufactured workpiece) can be positioned in the object recording region. If the X-ray radiation from the radiation source 12 is directed onto such an object, a two-dimensional radiographic image of this object can be created and evaluated in a conventional manner by means of the detector device 16. The object radiography device 10 of the present and also the subsequent embodiments can be operated in the manner of a computer tomography scanner in order to reconstruct a three-dimensional image of the object.

[0070] At the viewer in Fig. A sensor arrangement 20 is arranged on the rear side of the detector device 16 facing the front side of the detector device 16. This comprises four individual sensor units 22, which are positioned in a plane parallel to the detector device 16 and, from the perspective of the radiation source 12, at least partially overlap with the detector device 16. The sensor units 22 are each configured to determine a radiation parameter (e.g., a radiation dose) of the X-ray radiation emitted by the radiation source 12 and at least partially passing through the detector device 16. For example, the sensor units 22 are each configured as ionization chambers.

[0071] By using a plurality of individual sensor units 22, which are further assigned to different positions and regions of the detector device 16, the radiation parameter can be determined, not only in this exemplary embodiment, resolved into spatial regions (or regions of a detection plane of the sensor arrangement) or spatially resolved with respect to the detector device 16. In particular, the multi-part structure of the sensor arrangement 20 shown enables spatial resolution when detecting a radiation dose.

[0072] The sensor arrangement 20 further comprises an optional and only schematically indicated measuring unit 24 for evaluating and / or processing the measurement signals acquired by the sensor units 22 and making them available to an evaluation unit 26 of the object radiography device 10. In Fig. In this context, signal paths between the sensor units 22 and the measuring unit 24, as well as between the measuring unit 24 and the evaluation unit 26, are schematically indicated in Figure 1. The signal transmitted by the sensor units 22 and / or the measuring unit 24 can be continuous, but is preferably time-discrete.

[0073] For example, the measuring unit 24 can detect a voltage signal generated by the sensor units 22 at predetermined time intervals (e.g., according to a measuring cycle) and, for example, add up a dose count accordingly. From this, a dose value can be determined over a predetermined total period, e.g., a dose value for a single object irradiation process (or a single image acquisition) and / or for the total operating time of the detector device 16. When determining a current dose value for a single image acquisition, the aforementioned time intervals for adding up a dose count are correspondingly short. The determined dose value can be provided with a time stamp and compared with a quality parameter of a simultaneously acquired irradiation image in the following manner.

[0074] The evaluation unit 26 is connected to a Fig. 1 is also connected to the detector device 16. Image signals and / or fully acquired radiographic images determined by the detector device 16 are thus also transmitted to the evaluation unit 26 in addition to the measured radiation dose. The evaluation unit 26 can comprise a processor and suitable software to further process and / or prepare the information obtained in the manner explained below.

[0075] In particular, the evaluation unit 26 determines a signal-to-noise ratio from the acquired radiographic image, which constitutes a quality parameter of the radiographic image. By forming a quotient of the signal component and the noise component, a scalar signal-to-noise ratio or a signal-to-noise map is subsequently determined with respect to the pixel matrix.

[0076] The signal-to-noise ratio determined by the evaluation unit is stored as a quality parameter of the acquired radiographic image and checked against a quality criterion. In the case shown, the quality criterion defines a threshold value for the signal-to-noise ratio that should not be exceeded. If this is the case, the noise component in the acquired image is too high, and the detector device 16 is classified as potentially faulty and / or in a state of inferior quality.

[0077] In summary, after an image capture, the evaluation unit 26 thus has information about a quality parameter of the captured radiographic image and a radiation characteristic of the emitted radiation impinging on the sensor array 20. In the embodiment shown, the current value of the radiation characteristic is considered for each image capture and used as the basis for further evaluation.

[0078] The evaluation unit 26 is further configured to determine a state of the detector device 16 based on this information. In particular, it is configured to check the quality parameter with regard to fulfillment of the quality criterion explained above. Fulfillment of the quality criterion means a possible inferior quality of the image generation by the detector device 16. If it is determined that this quality criterion is fulfilled and the detector device 16 is potentially in a state of inferior quality, the determined radiation parameter is additionally considered. In particular, it is checked whether the value or values ​​of the radiation parameter lie / lie within a predetermined value range that indicates a desired functioning of the radiation source. If this is the case, it can be concluded that the inferior quality of the acquired radiographic image (orThe lower value of the quality parameter is primarily due to a correspondingly poor condition of the detector device 16. The detector device 16 should therefore be serviced or replaced, which can be communicated to a user by a corresponding warning message.

[0079] However, if the value or values ​​of the radiation parameter are not within the predetermined value range (e.g., the radiation dose is below a predetermined minimum limit of the dose range), it can be concluded that the radiation source 12 is in a state of inferior quality and, for example, has emitted too low a radiation dose or radiation with too low a radiation flux density. In this case, the radiation source 12 would have to be serviced or replaced, but not necessarily the detector device 16. This can also be determined by the evaluation unit 26 and communicated to a user via a corresponding warning message.

[0080] Of course, the evaluation unit 26 can also determine that, if at least one radiographic image is of poor quality, both the radiation source and the detector device are in a state of poor quality, e.g., if the radiation output of the source is too low, this alone cannot lead to the poor image quality. In particular, this can be determined by determining a relationship between the image quality and the radiation output of the source in advance when the detector device is of good quality, and this information is subsequently used during operation of the device.

[0081] In summary, the design of Fig. 1 thus enables a reliable determination of the cause of quality defects in a captured object radiograph. In particular, it is possible to reliably determine whether the detector device 16 is in a poor quality state and represents the cause of any quality defects. Alternatively or additionally, it can be determined whether the radiation source 12 is the cause by emitting too little radiation.

[0082] The evaluation unit 26 can optionally also be configured to record the acquired information, and in particular its temporal progression over multiple image acquisitions and / or longer operating periods of the object radiography device 10. This information can be evaluated to determine any decreasing quality of the detector device 16 and / or the radiation source 12. This occurs, for example, when the quality parameter of the radiography image(s) progressively decreases over an extended period with a constant value of the radiation parameter. Such a development can indicate that the detector device 16 is undergoing aging and that maintenance or replacement may be necessary in the near future. The evaluation unit 26 can inform a user of the object radiography device 10 of this by means of appropriate warning messages or a forecast.

[0083] In Fig. 2a and Fig. 2b shows an object irradiation device 10 according to a further embodiment. In Fig. 2a shows a radiation source 12 which radiates a radiation area 18, of which four boundary beams 181, 182, 183 and 184 are shown. The representation of Fig. 2a deviates from that Fig. 1, but now the front side of a detector device 16 is considered. It can be seen that the emitted radiation, which is again in the form of X-rays, irradiates the detector device 16. More precisely, the transmission area 18 covers the entire front surface of the detector device 16, which can be used to capture a transmission image. Not explicitly shown is again an object to be irradiated in the object recording area. Analogous to Fig. 1, however, this recording area is again located between the radiation source 12 and the detector device 16, so that the emitted X-rays pass through it.

[0084] In Fig. 2a further shows that the transmission area 18 is widened beyond the front surface of the detector device 16 upon impingement in the area of ​​the detector device 16. For reasons of simplified representation of distances between edges of the detector surface and edges of the transmission area, adjacent intersection points of the four limiting beams 181, 182, 183 and 184 with the plane of the detector device 16 are connected to one another by straight lines. This corresponds to a pyramid shape of the transmission area 18. The widening can be effected via a suitable collimator device, e.g., near the radiation generation area 14 of the radiation source 12. The extent of the widening is indicated by corresponding distance dimensions x1 and x2. With optimal centering of the transmission area 18 and the detector device 16 (ieIn a concentric arrangement, this distance is constant along the entire detector device 16. In this case, the detector device 16 is positioned centrally within the irradiation area 18.

[0085] A corresponding widening of the radiation area 18 laterally beyond the front side of the detector device 16 cannot generally be avoided anyway for tolerance reasons, but is intentionally set in the present embodiment in order to detect the radiation parameter by means of a frame-like sensor arrangement 20 which, from the perspective of the radiation source 12, extends around the detector device 16.

[0086] This is illustrated by the representation of Fig. 2b, which shows a detailed view of the Fig. 2a irradiated components. More precisely, the detector device 16 is shown, which, from the perspective of the radiation source, is enclosed or, in other words, framed by a frame-like sensor arrangement 20. The width of the frame regions or edge regions 21 outside the detector surface, which are to be assigned to the sensor arrangement 20, is again adapted to the widening of the radiation area 18 according to Fig. 2a (see corresponding dimensions x1 and x2). The sensor arrangement 20 is therefore positioned outside a solid angle (cf. Fig. 1), which only contains the detector device 16, but can reliably detect radiation in an outer part of the irradiation area 18 in order to determine the radiation characteristic.

[0087] The sensor arrangement 20 is again connected to a measuring unit 24. Both the detector device 16 and the measuring unit 24 are further connected to an evaluation unit 26. The evaluation unit 26 can again be analogous to the procedure from Fig. 1 determine a quality parameter of the acquired radiographic image, detect a poor quality of the radiographic image and evaluate the determined radiation parameter. From this, a condition of poor quality of the detector device 16 and / or the radiation source can be determined, e.g. in an identical manner to that determined by means of Fig. 1 explained procedure.

[0088] Based on the Fig. 3a, Fig. 3b, an embodiment for compensating for any centering errors in the plane of the detector device 16 is explained below. This embodiment is based on the frame-like sensor arrangement 20 according to Fig. 2b and is identical to the previous embodiment with the exception of the following deviations.

[0089] In case of inaccurate centering of the Fig. 3a, Fig. 3b, the distance dimensions x1 and x2 may differ from each other. In particular, edge regions of the incident electromagnetic radiation may vary in width around the detector device 16. The impact region of the penetration region 18 is then not centered in relation to the detector device 16 (in Fig. 3a to the left, in Fig. 3b shifted to the right). However, the sum of the corresponding distance measurements x1 and x2 remains essentially constant, since any centering deficiencies result primarily in a shift of the relevant impact area parallel to the plane of the detector device 16. This becomes clear from a summary of the Fig. 3a and Fig. 3b.

[0090] If the frame-like sensor arrangement 20 is designed to be sufficiently wide, preferably with a width that exceeds the corresponding distance dimensions x1 and x2 with optimal centering by a factor of 2 or 3, reliable detection of the radiation dose is possible even with inaccurate centering and with differing distance dimensions x1 and x2. A correspondingly dimensioned sensor arrangement 20 is shown in the Fig. 3a and Fig. 3b. In this case, edge regions 21 are available as reserves, which are only partially irradiated as a result of a centering error. The total irradiated area of ​​the sensor arrangement 20 is thus constant. For the sake of completeness, it is noted that preferably also for the sum of the only in Fig. 3a referenced upper and lower distance dimensions x3 and x4 and the width of the sensor arrangement 20 in this direction applies accordingly.

[0091] In detail, Fig. 3a, more radiation enters a left edge region 21 compared to the case of optimal centering, whereas less radiation enters an opposite right edge region 21. For Fig. 3b, the opposite applies. However, the total irradiated area of ​​the sensor array 20 remains essentially constant.

[0092] As a result, the total radiation quantity detected by the sensor array 20 also remains essentially constant and is therefore largely independent of any centering errors. By making the edges of the frame-like sensor array 20 sufficiently wide, the radiation characteristic can be reliably determined. A high tolerance to any centering errors is ensured.

[0093] In Fig. Figure 4 shows a fourth embodiment of an object radiography device 10. In this case, the radiation emitted by an X-ray source 12 is divided into different components for determining the radiation characteristic and for image acquisition. In detail, Fig. 4 shows the radiation source 12, which is configured to emit electromagnetic radiation in the form of X-rays. A detector device 16 for image capture and a sensor arrangement 20 for determining the radiation characteristic are arranged with respect to a separation arrangement 30 opposite a radiation generation region 14 of the radiation source 12. The detector device 16 can again be designed as a flat-panel detector, analogous to the previous examples. The sensor arrangement 20 comprises, for example, an ionization chamber, as is also the case in the previous exemplary embodiments. Furthermore, the sensor arrangement 20 is connected to a measuring unit 24, which in turn is coupled to an evaluation unit 26 for signal transmission. In this embodiment, the sensor arrangement is arranged laterally of the irradiation region 18 of the object irradiation device.

[0094] Positioned near the radiation generation region 14 of the radiation source 12 is a separation arrangement 30, e.g., in the form of a diaphragm plate. This comprises a first, comparatively smaller opening 32 and a second, comparatively larger opening 34. The diaphragm plate (e.g., made of lead) is essentially impermeable to the incident X-ray radiation except in the region of its openings 32, 34. In other words, unhindered passage of X-ray radiation is only possible in the region of the openings 32, 34, so that the radiation generated by the radiation source 12 is divided into corresponding portions passing through the openings 32, 34.

[0095] In detail, a first radiation component S is separated or coupled out from the total available radiation by means of the first opening 32. The resulting radiation component S is directed onto the sensor arrangement 20 and can be evaluated analogously to the preceding embodiments to determine the radiation characteristic. In general, the sensor arrangement 20 should be positioned as close as possible to the radiation source 12 in order to ensure a compact design. Furthermore, for example, using previously determined relationships, the radiation characteristic determined by the sensor arrangement 20 can be converted into a radiation characteristic of the radiation impinging on the detector device 16 (e.g. into a radiation dose). The radiation component passing through the second opening 34, on the other hand, defines a transmission region 18, which is directed onto the detector device 16 and is used for image acquisition.

[0096] Defining different radiation components ensures that image capture is not compromised by the simultaneous determination of the radiation characteristic. Furthermore, the radiation components can be optimized with regard to positioning and / or the properties of the sensor arrangement 20 and the detector device 16, so that all detection processes are carried out as precisely as possible. The evaluation of the determined radiation characteristic and the acquired radiographic image is again performed by the evaluation unit 26, for example, in an identical manner to the above embodiments.

[0097] An advantage of the arrangement of Fig. 1 is a compact design and that the individual sensor units 22 enable a spatially resolved detection of the X-ray dose, taking into account the additional attenuation by a test object. The embodiment according to Fig. 2a and Fig. 2b allows the radiation characteristic to be determined independently of the state of the detector device 16. More precisely, the radiation detected by the sensor arrangement 20 does not have to first pass the detector device 16, as is the case with the solution according to Fig. 1 is the case. Thus, the radiation characteristic is determined independently of the object positioning in front of the detector device 16.

[0098] Even in the embodiment according to Fig. 4, a radiation component is detected for determining the radiation characteristic, which does not interact with the detector device 16 and thus cannot be falsified by it. Furthermore, in this case, it is possible to reliably spatially separate the image acquisition and determination of the radiation characteristic and to avoid impairments or interactions between these processes. Finally, the embodiment of the Fig. 3a, Fig.3b provides a high error tolerance regarding possible centering errors.

[0099] Finally, all embodiments have in common that the corresponding sensor arrangements 20, including measuring and / or evaluation units 24, 26, can also be retrofitted with little effort. Furthermore, the determined values ​​of the radiation parameter can also be used to control the radiation source 12, as explained in detail in the general description section of this disclosure.

Claims

[1] Object radiography device (10), comprising: - a radiation source (12) which is arranged to generate and emit electromagnetic radiation for penetrating an object; - a detector device (16) which is arranged in such a way that the electromagnetic radiation emitted and at least partially passing through the object impinges at least partially on it, and which is designed to generate a radiographic image of the object; - a sensor arrangement (20) which is provided in addition to the detector device (16) and is designed to determine a radiation characteristic associated with the radiation source (12), the radiation characteristic being a radiation power or a radiation flux density or a radiation dose, and - an evaluation unit (26) which is designed to determine or receive a quality parameter of the acquired radiographic image, to evaluate the radiation characteristic and to make a statement about a state of the detector device (16) on the basis of the quality parameter and the radiation characteristic, wherein, if the quality parameter fulfills a predetermined degradation criterion, it is checked whether the radiation characteristic lies in a predetermined range which indicates a desired mode of operation of the radiation source (12), wherein, if the degradation criterion is fulfilled and if the radiation characteristic is present in the predetermined range, a degradation of the detector device (16) is determined. [2] Object irradiation device (10) according to claim 1, wherein the sensor arrangement (20) comprises at least one ionization chamber to determine the radiation flux density and / or the radiation dose as the radiation characteristic. [3] Object radiography device (10) according to claim 1 or 2, wherein the object radiography device (10) is configured to take the determined radiation characteristic into account when regulating the radiation emitted by the radiation source (12). [4] Object radiography device (10) according to one of the preceding claims, wherein the sensor arrangement (20) is arranged such that it detects a radiation component (S) of the radiation generated by the radiation source (12) which lies outside a solid angle containing the detector device (16). [5] Object radiography device (10) according to claim 4, further comprising a separation arrangement (30) which is designed to separate the radiation component (S) detected by the sensor arrangement (20) from the radiation generated by the radiation source (12). [6] Object radiography device (10) according to claim 5, wherein the separation arrangement (30) comprises a diaphragm, at least with a first opening (32) and a second opening (34) for dividing radiation incident on the diaphragm into individual radiation components, to which the radiation component (S) detected by the sensor arrangement (20) belongs. [7] Object radiography device (10) according to one of the preceding claims, wherein the sensor arrangement (20) and the detector device (16) extend at least in sections in a common plane or in planes parallel to one another. [8] Object radiography device (10) according to one of the preceding claims, wherein the sensor arrangement (20) extends at least partially along the detector device (16). [9] Object radiography device (10) according to one of the preceding claims, wherein the sensor arrangement (20) encloses the detector device (16) in a frame-like manner. [10] Object radiography device (10) according to one of claims 1 to 8, wherein at least a part of the sensor arrangement (20) is located laterally of a radiography region of the object radiography device (10), in which objects can be placed for radiography and within which the invasive radiation propagates from the radiation source (12) to the detector device (16). [11] Method for determining a state of an object radiography device (10), comprising the steps: - emitting electromagnetic radiation by means of a radiation source (12) of the object irradiation device (10), so that the radiation is directed at an object to be irradiated and radiation passing through the object falls at least partially on a detector device (16) of the object irradiation device (10); - capturing a radiographic image of the object by means of the detector device (16); - determining a radiation characteristic associated with the radiation source (12), wherein the radiation characteristic is a radiation power or a radiation flux density or a radiation dose, - Determining a quality parameter of the acquired radiographic image, - Evaluation of the radiation parameter taking into account the quality parameter and - Determining a state of the detector device (16) from a result of the evaluation, wherein, if the quality parameter satisfies a predetermined degradation criterion, it is checked whether the radiation characteristic lies in a predetermined range which indicates a desired functioning of the radiation source (12), wherein, if the degradation criterion is fulfilled and if the radiation characteristic is present in the predetermined range, a degradation of the detector device (16) is determined.

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