Computer-implemented method for determining spatially resolved radiation load information

Abstract

The invention relates to a computer-implemented method for determining spatially resolved radiation load information of a patient during an examination with an imaging X-ray device having an X-ray radiator for outputting an X-ray field for the examination, in which patient input dose information for determining the radiation load information is determined, wherein the pre-dose information is determined using a matched filter arranged between the patient and the X-ray radiator, the matched filter causing a non-uniform dose distribution in a plane perpendicular to the central radiation of the X-ray field, the pre-dose information describes a uniformly distributed X-ray dose acting on the patient without a matched filter; calculating dose distribution information using the pre-dose information by means of the filter model, said dose distribution information describing at least a dose distribution of an X-ray dose acting on the patient in the portion of the X-ray field covered by the matched filter; and determining patient input dose information using the dose distribution information.

Description

Technical Field

[0001] The invention relates to a computer-implemented method for determining spatially resolved radiation exposure information of a patient during an examination with an imaging X-ray device, the X-ray device having an X-ray radiator for outputting an X-ray field for the examination, wherein patient input dose information describing the X-ray dose acting on the patient is determined, and the radiation exposure information is determined from the patient input dose information. The invention also relates to an X-ray device, a computer program and an electronically readable data carrier. Background Art

[0002] In imaging X-ray devices, X-ray radiation is used to fluoroscopically examine an object, in particular a patient. Since X-ray radiation can act ionizingly, the radiation exposure of the patient is usually determined, recorded and / or documented. It is known to determine the X-ray dose acting on the patient in order to determine radiation exposure information, for example, using a patient model. Such radiation exposure information can include skin doses and / or organ doses, in particular skin doses and / or organ doses determined in a spatially resolved manner. It is also known to determine local peak values ​​of the radiation exposure.

[0003] In order to determine patient input dose information describing the X-ray dose acting on the patient, it is known to use a measuring device, which is usually arranged as the last component in the radiation path before the patient (in addition to the patient support if necessary). In this case, a so-called DAP chamber is usually used as a measuring device downstream of the X-ray radiator, the beam shaping device and the radiation filter device (if used) as a measuring device for measuring the dose area product, DAP (English: dose area product). The dose area product is a radiation characteristic variable based on a uniform distribution of the X-ray dose.

[0004] Since DAP chambers and other measuring devices can trigger unwanted scattered radiation, are relatively expensive and require installation space, it has also been proposed, for example through the later published European Patent Application 23197942.8, to provide a virtual measuring device by calculating the radiation characteristic variable using an estimation model.

[0005] Many devices that influence the X-ray radiation of the X-ray field (e.g., beam shaping devices that predetermine the geometry of the X-ray field (e.g., collimators or other aperture devices)) and radiation filtering devices that uniformly attenuate, for example, influence the spectrum, maintain a uniform dose distribution perpendicular to the central ray (for which the specification of radiation characteristic variables, such as the dose-area product, describes the spatial distribution of the dose with sufficient accuracy), radiation filtering devices are also known, which lead to a spatially inhomogeneous dose distribution in a plane perpendicular to the central ray of the X-ray field. Such radiation filtering devices are also referred to as matched filters in the following text.

[0006] Matched filters can lead to an inhomogeneous spatial distribution of the dose after it has traversed by using different materials and / or different attenuation lengths. A well-known example of such a matched filter is a so-called wedge filter, which has a thickness that increases toward one side and thus has an attenuation length. In other words, a semi-transparent matched filter blocks the X-ray radiation to different degrees at different locations, which leads to an inhomogeneous X-ray field.

[0007] Current methods for determining radiation characteristic variables, such as DAP rooms and virtual measuring devices, do not take inhomogeneities into account. This can result in incorrect radiation exposure information for the patient, since the X-ray dose may be locally higher than assumed based on radiation characteristic variables, such as the dose-area product. Summary of the invention

[0008] Therefore, the object of the present invention is to provide a possibility for more accurate determination of radiation exposure information of a patient.

[0009] According to the present invention, in order to solve the above technical problems, a computer-implemented method, an X-ray device, a computer program and an electronically readable data carrier according to the present invention are provided. The present invention also provides an advantageous design solution.

[0010] In a method of the type mentioned at the outset, it is provided according to the invention that, when using a matched filter which is arranged in the x-ray field between the patient and the x-ray radiator, the matched filter causes an inhomogeneous dose distribution in a plane perpendicular to a central ray of the x-ray field.

[0011] - determining pre-dose information describing a uniformly distributed X-ray dose acting on the patient without a matched filter,

[0012] - calculating dose distribution information by means of a filter model using at least one filter parameter describing a matched filter and its arrangement in the X-ray field, the dose distribution information describing at least the dose distribution of the X-ray dose acting on the patient in the part of the X-ray field covered by the matched filter, using predose information, and

[0013] - Determine patient input dose information when dose distribution information is used.

[0014] In this context, it is conceivable within the scope of the present invention that the predose information expediently comprises a radiation characteristic variable, which may, for example, comprise a dose-area product and / or air kerma and / or a variable related to the dose-area product and / or air kerma. The patient input dose information may also be expressed by such a radiation characteristic variable, and then in particular in a spatially resolved manner.

[0015] It is proposed that an inhomogeneous dose distribution perpendicular to the central beam is determined by applying a filter model into which at least the geometry and / or at least one material of a matched filter, in particular a wedge filter, as well as predose information enters. In this case, as will be explained in more detail below, the dose distribution information already specifies the spatially resolved dose absolutely, but also contains only relative dose values ​​as a pure distribution.

[0016] From the dose distribution information, patient input dose information can be determined, possibly in combination with predose information and / or other information depending on the embodiment. The patient input dose information is also spatially resolved based on the dose distribution information describing the dose distribution and describes the inhomogeneities generated by the matched filter.

[0017] Thus, in this way, when estimating the radiation load information of the patient, the inhomogeneities caused by the matched filter can be appropriately taken into account. In particular, the local X-ray dose, such as the peak skin dose or the organ dose, is not underestimated. This leads to a significantly more accurate determination of the actual radiation load of the patient.

[0018] The matched filter can be, in particular, a wedge filter. The wedge filter can be made of metal, for example, aluminum.

[0019] Here, the following design is conceivable, in which the wedge filter does not cover the entire X-ray field perpendicular to the central beam direction. It can then be provided that in order to determine the patient input dose information in the part of the X-ray field that is not covered by the matched filter, the predose information for this part is used. Where the matched filter does not cover, that is, where it has no influence on the X-ray field, the dose described by the predose information (which relates to the case without the matched filter), for example a specific dose-area product, can therefore be set in this area. The dose distribution information is then used for the remaining area covered by the matched filter in order to determine the remaining patient input dose information.

[0020] In particular, depending on whether a measuring device is present, different embodiments of the invention are conceivable. It is to be taken into account that the measuring device, for example a DAP chamber, follows the matched filter in the beam direction, but assumes a uniform distribution of the X-ray dose perpendicular to the central beam. However, within the scope of the invention, measurements of the measuring device can be advantageously used.

[0021] Therefore, it can be provided that the X-ray device has a measuring device for the total dose, in particular the dose area product, which is located in the X-ray field after the matched filter in the direction toward the patient, wherein the total dose information is determined by means of the measuring device and is used when determining the patient input dose information. As a measuring device, for example, a DAP room which is usually present can be used. The total dose information contains additional useful information which can further improve the quality of the determination of the radiation exposure information. The total dose information can be used in different ways.

[0022] It can therefore be provided that filter dose information is determined from the total dose information, which describes the total filter dose which is distributed inhomogeneously in the portion of the X-ray field covered by the matched filter. In the case where the X-ray field is completely covered by the matched filter, the total dose information already corresponds to the filter dose information, since the total dose information is ultimately a uniformly redistributed dose of the inhomogeneous dose distribution. In the case where the X-ray field is not completely covered by the matched filter, the filter dose information can be determined expediently by subtracting the patient input dose from the total dose described by the total dose information, which patient input dose is determined as the patient input dose information for the portion not covered by the matched filter.

[0023] The filter dose information can be used as an input variable of the filter model, wherein the dose distribution information directly describes the absolute dose intensity, or first determines a dose distribution that only describes the relative dose intensity and is used to distribute the total filter dose of the filter dose information through the filter model. In other words, the filter model can implicitly assume the distribution of the remaining dose after the transmission matched filter. However, it is also conceivable that a dose distribution that only describes the relative dose intensity is first determined, and the filter model distributes the total filter dose of the filter dose information according to this, so as to determine the absolute dose intensity. Here, the relative dose intensity therefore only describes the inhomogeneity triggered by the matched filter, and is therefore a relative dose intensity. Then, the total filter dose is used for accurate normalization, so as to obtain the absolute dose intensity in a position-dependent manner. In both cases, if the portion of the X-ray radiation field covered by the matched filter does not cover the entire X-ray radiation field, the absolute dose intensity in the portion of the X-ray radiation field covered by the matched filter supplements the total dose set for the uncovered portion of the pre-dose information; when the X-ray field is completely covered by the matched filter, the patient input dose information is defined only by the dose distribution with absolute dose intensity, i.e., the dose distribution information.

[0024] Alternatively, it is also conceivable within the scope of the method according to the invention to use the filter dose information for a plausibility check of the dose distribution information. In this case, the dose distribution information is again determined, which contains the absolute dose intensity, from which the expected total filter dose can be determined accordingly, which can be compared with the total filter dose according to the filter dose information and should correspond to it if appropriate. In the case of deviations, a correction and / or a recalculation can be performed.

[0025] It should also be noted here that when the filter model outputs an absolute dose intensity in the dose distribution, it can be based in particular on an X-ray dose according to predose information as X-ray radiation incident on the matched filter. This X-ray dose is then attenuated accordingly in a position-dependent manner by the matched filter, as described by the filter model.

[0026] In summary, it can be said that the predose information is determined in such a way that it takes into account all devices in the radiation path that maintain a uniform dose distribution, which are also used during the examination. Such devices that maintain a uniform dose distribution can include, for example, other radiation filtering devices, for example for matching the X-ray spectrum, and / or beam shaping devices, such as collimators and / or other aperture devices.

[0027] In principle, it is conceivable, but less preferred due to the additional dose load, to measure the predose information, for example, before the matched filter is introduced into the radiation path, and a preferred development of the invention provides that the predose information is determined with the aid of an estimation model, which uses input data including at least one operating parameter of the X-ray radiator to determine output data including the predose information, and which is adapted to a uniformly distributed X-ray dose acting on the patient without a matched filter based on the measurement data. For measuring the measurement data, a measuring device as already described can be used, in particular a DAP chamber. In a development, the estimation model can also include a trained estimation function, i.e. an algorithm trained by machine learning.

[0028] In particular, the estimation model can be determined as in the already mentioned later published European patent application 23197942.8, where the estimation model is introduced there as a refined model (starting from a basic model). All disclosures of this application relating to the determination and use of the estimation model / refined model are hereby incorporated by reference into the present disclosure.

[0029] As already mentioned, the filter parameters can particularly advantageously describe the geometry and / or at least one material of the matched filter. The position and orientation can also be described by the filter parameters, which can also be used in advance to identify the parts covered by the matched filter and those not covered by the matched filter. In other words, it can be provided that at least one geometric parameter describing the geometry of the matched filter and / or at least one material parameter describing the material of the matched filter and / or at least one position parameter describing the position and / or orientation of the matched filter in the X-ray field are used as filter parameters. For example, a user can specify or automatically identify which matched filter is used in which position and orientation, wherein, for example, for different available matched filters, at least some of the filter parameters, in particular the filter parameters describing the geometry and the material, can be called up from a database by a computing device, in particular a control device of an X-ray device, which performs the method.

[0030] In a specific design of the filter model, it can be provided that the filter model is an analytical physical model. This means in particular that the dose distribution information can be calculated based on physical laws, in particular described by at least one formula. In this case, it can also be assumed that, for example, there is no aging, the material is homogeneous, there is no scattered radiation, etc. Specifically, it can be provided, for example, that in an analytical model for partial radiation of the X-ray radiation field, the transmission length, in particular the thickness of the matching filter and / or the attenuation coefficient, in particular the attenuation coefficient based on the material of the matching filter, is used to calculate the corresponding attenuation. This means that, in principle, known physical relationships can be taken into account, which describe the attenuation characteristics of X-ray radiation when passing through matter. In this way, excellent results have been obtained on a physical basis, in particular depending on the specific assumptions made.

[0031] Additionally or alternatively, it can be provided that the filter model comprises a simulation model for performing a physical simulation. In this case, known physical simulation methods are used in principle in order to achieve a high-precision calculation of the interaction between the X-ray radiation and the filter material, in particular when physical effects are included, for which assumptions would be made in the case of purely analytical modeling. In particular, it can be provided that the simulation comprises or is a finite element simulation and / or a Monte Carlo simulation. In this case, a simulation that can be performed quickly, such as a fast Monte Carlo simulation, is particularly preferred.

[0032] Alternatively or additionally, it can also be provided that the filter model comprises a trained filter model function, thus a filter model algorithm trained by machine learning. The training function is usually characterized by a very short running time, so that the learned physical correlations can be used to determine the dose distribution information in a very time-efficient manner. In particular, it can be provided that the trained filter model function comprises a CNN (Convolutional Neural Network), preferably a two-dimensional U-Net.

[0033] The trained filter model function can be trained based on measurement data measured spatially resolved, in particular by means of X-ray film and / or X-ray detectors. Here, special measurement methods, in particular X-ray film and / or X-ray detectors, are used to spatially resolve the actual X-ray dose distribution after the previously uniformly distributed X-ray radiation has passed through the matched filter and use it as training data. However, it is also conceivable to use simulation results additionally or alternatively to train the filter model function. By selecting the input data in a correspondingly expanded manner, additional physical effects can be taken into account, which are covered by assumptions during the analysis and partially also in the physical simulation.

[0034] Typically, the training function maps cognitive functions that relate humans to other human brains. Through training based on training data (machine learning), the trained function is able to adapt to new environments and detect and extrapolate patterns.

[0035] In general, the parameters of the training function can be adjusted by training. In particular, supervised learning, semi-supervised learning, unsupervised learning, reinforcement learning and / or active learning can be used. In addition, representation learning (also called “feature learning”) can also be used. The parameters of the training function can be adjusted in particular iteratively via a plurality of training steps.

[0036] The training function may include, for example, a neural network, a support vector machine (SVM), a decision tree and / or a Bayesian network, and / or the training function may be based on k-means clustering, Q-learning, a genetic algorithm and / or an assignment rule. In particular, the neural network may be a deep neural network, a convolutional neural network (CNN) or a deep CNN. In addition, the neural network may be an adversarial network, a deep adversarial network and / or a generative adversarial network (GAN).

[0037] In order to determine the radiation load information, it can be provided in an improved solution of the present invention that the radiation load information is determined using a patient model virtually positioned in the X-ray field and / or including spatially resolved skin dose values ​​and / or at least one organ dose value and / or at least one scattered radiation information. Here, in principle, known methods can be used to determine the radiation load information based on the patient input dose information when the spatial distribution is known. Here, the dose distribution is finally projected forward onto the patient, in particular with the aid of the patient model. Of course, the weakening characteristics of the patient support device, such as the patient table and / or the mattress, can also be considered. The transition from air to skin and / or scattered radiation can also be considered when determining the radiation load information. Therefore, for example, the skin dose distribution, the organ dose distribution, the scattered radiation dose distribution, etc. can be determined in the end.

[0038] In addition to the method, the invention also relates to an imaging X-ray device having an X-ray radiator with an optionally used matched filter, which causes an inhomogeneous dose distribution in a plane perpendicular to the central ray of the X-ray field, an X-ray detector, and a control device, which is designed to carry out the method according to the invention. All embodiments of the method according to the invention can be transferred analogously to the X-ray device according to the invention and vice versa, so that the advantages mentioned can also be achieved with the X-ray device.

[0039] The X-ray device may also include further radiation filtering devices and / or radiation shaping devices, such as a matched filter in the radiation path downstream of the X-ray radiator. In addition, a measuring device, in particular a DAP chamber, may be provided. The X-ray device may be, for example, an X-ray device with a C-arm, on which the X-ray radiator and the X-ray detector are arranged opposite each other. The patient may be supported, for example, on a patient table.

[0040] The control device, which may have at least one processor and / or at least one storage device, may have functional units, which are formed by hardware and / or software, for executing parts of the method according to the invention. In addition to a recording unit, which may control the recording operation of the X-ray device, the control device may, for example, include:

[0041] - a first determination unit for determining predose information when using a matched filter arranged between the patient and the X-ray radiator in the X-ray field, the predose information describing a uniformly distributed X-ray dose acting on the patient without the matched filter,

[0042] a calculation unit for calculating dose distribution information by means of a filter model using at least one filter parameter describing a matched filter and its arrangement in the X-ray field, the dose distribution information describing at least the dose distribution of the X-ray dose acting on the patient in the part of the X-ray field covered by the matched filter, using predose information,

[0043] - a second determination unit for determining patient input dose information using the dose distribution information, the patient input dose information describing the X-ray dose acting on the patient,

[0044] - A third determination unit, for determining radiation load information of the patient from the patient input dose information.

[0045] Of course, other functional units may also be provided to implement other, in particular optional, steps.

[0046] The computer program according to the invention can be directly loaded into a storage device of a computing device, in particular a control device of an X-ray device, and has program means which, when the computer program is executed on the computing device, cause the computing device to perform the steps of the method according to the invention. The computer program can be stored on an electronically readable data carrier, 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 computing device, in particular a control device of a magnetic resonance device, the computing device is designed to perform the method according to the invention. The data carrier can in particular be a non-transitory data carrier, for example a CD-ROM. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Further advantages and details of the invention are apparent from the exemplary embodiments described below and from the accompanying drawings, in which:

[0048] Figure 1 A simplified diagram for explaining the formation of an uneven distribution of X-ray dose is shown,

[0049] Figure 2 shows a flow chart of a first embodiment of the method according to the present invention,

[0050] Figure 3 A simplified diagram showing a portion of an X-ray field,

[0051] Figure 4 shows a simplified diagram for determining radiation load information,

[0052] Figure 5 shows a flow chart of a second embodiment of the method according to the present invention,

[0053] Figure 6 An X-ray device according to the invention is shown, and

[0054] Figure 7 The functional structure of the control device of the X-ray device is shown. DETAILED DESCRIPTION

[0055] Figure 1 The diagram is a schematic diagram for generating an X-ray field with an X-ray dose (patient input dose) which is emitted to a patient by an X-ray device for an imaging examination in order to determine an X-ray image by fluoroscopy. For better illustration, a parallel beam geometry is shown here instead of a conical beam geometry (as is often used); of course, the described embodiment can be transferred to a conical beam geometry accordingly.

[0056] The X-ray radiation is generated by an X-ray radiator 1, for example an X-ray tube. Perpendicularly to the emission direction, the X-ray dose is distributed uniformly, thus uniformly, as shown by the schematically equally spaced X-rays 2. This does not change even when a beam shaping device 3, for example a collimator, is used, which defines the extension of the X-ray field 4 to be ultimately used for the imaging examination. Optionally, a radiation filtering device 5 can also be used which does not affect the uniform distribution of the X-ray dose, for example for adjusting the spectrum of the X-ray radiation. After traversing the radiation filtering device 5, the distribution of the X-ray dose is also uniform, as schematically shown by the equally spaced X-rays 2.

[0057] However, if a wedge filter 5 is now used as an example of a matched filter 6, which attenuates the X-ray radiation in a position-dependent manner, in the present case by means of the wedge shape, then an inhomogeneous distribution of the X-ray dose results in a plane perpendicular to the beam direction (direction of the central beam), as is shown by the schematically illustrated X-ray 2 ′ which has a greater spacing relative to the greater thickness of the wedge filter 7.

[0058] If we now connect the DAP chamber as a measuring device Figure 1 , the DAP room would however output a single measured value for the dose-area product or other radiation characteristic variable, thus not taking into account the inhomogeneous distribution of the X-ray dose, which also applies to the spatially resolved radiation load information for the patient derived therefrom. In particular, the local X-ray dose could be underestimated.

[0059] In order to achieve an improved determination of radiation load information taking into account an inhomogeneous dose distribution, in the now presented embodiment of the method according to the invention, patient input dose information describing the X-ray dose (patient input dose) acting on the patient is determined (taking into account the inhomogeneity of the distribution), i.e. ultimately as a dose distribution with absolute dose intensities.

[0060] Figure 2 The flowchart of the first embodiment of the method according to the invention is shown. In this case, in step S1, predose information is first determined by calculation with the aid of an estimation model. The predose information can be determined, for example (assuming a uniform distribution of the X-ray dose) as a single radiation characteristic variable, in particular a dose-area product. When no matched filter 6 is used, the predose information describes a uniformly distributed X-ray dose that would act on the patient. However, the predose information takes into account all other possible devices, in particular the radiation shaping device 3 and the radiation filtering device 5.

[0061] In step S2, total dose information is then determined with the aid of a measuring device, in particular a DAP room, which describes the total dose before it acts on the patient assuming a uniform distribution of the X-ray dose. The total dose information can also be determined as a radiation characteristic variable, in particular in the case of a DAP room as a dose-area product. The total dose information therefore only indicates how much total dose is present, without taking into account the effect of the matched filter 6.

[0062] In step S3, it is determined based on the position and orientation of the matched filter 6 in the X-ray field 4 whether the matched filter 6 covers the entire X-ray field 4 perpendicularly to the direction of the central ray or whether a portion is not covered. If a portion of the X-ray field 4 is not covered by the matched filter 6, a portion of the patient input dose information can already be determined, i.e., as the X-ray dose described by the predose information in the uncovered portion, since no inhomogenization occurs here. Therefore, in particular, a dose surface product determined as predose information can be set for the uncovered portion.

[0063] Figure 3 The diagram explains Figure 1 , in which only the first part 8 of the X-ray field 4 is covered by the matched filter 6 (that is, the wedge filter 7 there) in a plane perpendicular to the central beam direction. Therefore, the remaining second part 9 is not covered by the matched filter 6. In this case, the distribution of the dose remains particularly uniform.

[0064] In step S4, also in the case that the X-ray field 4 is not completely covered by the matched filter 6, it is determined which part of the X-ray dose described by the predose information falls on the matched filter 6 or is influenced by the matched filter 6. Thus, filter dose information is determined which describes the total filter dose which is inhomogenized in its distribution by the matched filter 6. In the present case, the total filter dose is determined by subtracting the X-ray dose for the part 9 of the X-ray field 4 which is not covered by the matched filter 6 from the total dose of the total dose information.

[0065] In step S5, a filter model is used to determine dose distribution information, which describes what kind of inhomogeneous distribution of the dose is caused by the matched filter 6. Here, the filter model uses at least one filter parameter, currently a plurality of filter parameters as input parameters in any case, and the filter parameters describe the geometry (geometric parameters), at least one material (material parameters) and the position and orientation (position parameters) of the matched filter 6 in the X-ray field 4. The filter model may include an analytical physical model and / or a physical simulation model and / or a trained filter model function. In the case of a trained filter model function, the trained filter model function may include a two-dimensional U-Net and / or training data based on simulated training data or training data derived from measured data. In the case of a simulation model that performs physical simulation, the physical simulation is preferably a fast Monte Carlo simulation.

[0066] The total filter dose determined in step S4 can already be entered into the filter model as an X-ray dose that is to be distributed inhomogeneously. However, it is also conceivable that the filter model works on the basis of predose information, which actually describes how much X-ray dose is incident on the matched filter 6 and is spatially inhomogeneously attenuated here. If the predose information describing the dose incident on the matched filter 6 is not used directly, a dose distribution with relative dose intensities can first be determined, and the filter model then applies this dose distribution to the total filter dose to be distributed in order to determine the absolute dose intensity. In all cases, the dose distribution information preferably already contains the absolute dose intensity in the dose distribution.

[0067] It should be noted here, which is not shown more precisely in the flow chart, that the filter dose information can also be used for a plausibility check of the result of the filter model, i.e. the dose distribution information. If the dose distribution information is determined only on the basis of the predose information, then the total filter dose remaining after the matched filter 6 must still correspond to the total filter dose according to the filter dose information. If this is not the case, implausibility is indicated and a recalculation, correction, etc. can be performed.

[0068] The patient input dose information is then summarized in step S6, either as dose distribution information when the matched filter 6 completely covers the X-ray field 4, otherwise as dose distribution information in the covered part 8 and the X-ray dose in part 9 according to the predose information, see step S3.

[0069] Finally, in step S7, the now spatially resolved patient input dose information, more precisely the patient input dose described thereby, is used in its spatial distribution in order to thereby determine radiation exposure information for the patient. For this purpose, the patient input dose is forward projected onto a patient model virtually placed in the X-ray field 4, wherein, of course, if necessary, the properties of the patient support, the air-skin transition and / or scattered radiation effects can be taken into account, as is known in principle in the prior art. The radiation exposure information can, for example, contain skin dose, organ dose and / or scattered radiation information.

[0070] Figure 4 It is explained by way of example how the patient input dose 10 is projected forward onto the virtual patient model 11 and which areas 12 of the patient are particularly affected.

[0071] Figure 5 The flow chart of a second exemplary embodiment of the method according to the invention is shown, in which the measuring device is omitted. This means in particular that only the predose information determined in step S1 is now used. In step S3, it is also checked whether there is a part 8 of the X-ray field 4 that is not covered by the matched filter 6, for which the predose information can again be used directly.

[0072] In step S5', the filter model is used based on the filter parameters and the pre-dose information without taking into account the filter dose information to determine the dose distribution information and thus in step S6 the patient input dose information is summarized similarly to the first embodiment. Step S7 is also performed similarly to the first embodiment.

[0073] Figure 6 The schematic diagram shows an exemplary embodiment of an X-ray device 13 according to the invention, which has, by way of example, a C-arm 14 on which an X-ray emitter 1 and an X-ray detector 15 are arranged opposite each other. The C-arm 14 can be moved around a patient table 16 on which a patient can be supported, in particular can be pivoted around different rotation axes.

[0074] Other exemplary embodiments of the X-ray device 13 are also conceivable, for example as a computed tomography device, a radiography device or the like.

[0075] As part of a radiator arrangement which also comprises an X-ray radiator 1, Figure 6 3, the radiation filtering device 5 and the matched filter 6 are shown. The optional measuring device 17 is indicated only by dashed lines.

[0076] The operation of the X-ray device 13 is controlled by a control device 18, which is also designed to carry out the method described herein and whose functional structure will be described in detail below. Figure 7 Explain in more detail.

[0077] The control device 18 therefore firstly comprises a memory device 19 in which various information processed by the method and recorded x-ray data or x-ray images can be stored. To control the recording operation, the control device 18 also has a recording unit 20, as is known in principle.

[0078] In the first determination unit 21 , as described above, pre-dose information may be determined according to step S1 . The optional measuring and processing unit 22 , if present, controls the measuring device 17 for determining total dose information (step S2 ) and may also determine filter dose information according to step S4 .

[0079] In the allocation unit 23, according to step S3, it can be checked whether the matched filter 6 in its corresponding position and orientation covers the entire X-ray field 4 or whether there is an uncovered section 9. Furthermore, predose information can be used accordingly in this section 9.

[0080] In the calculation unit 24, the filter model is applied according to step S5, wherein the patient input dose information is then combined according to step S6 in the second determination unit 25. The patient input dose information is used by the third determination unit 26 to determine the radiation exposure information according to step S7.

[0081] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art may derive other variations therefrom without departing from the scope of protection of the present invention.

[0082] Regardless of the grammatical gender of a particular term, people with either male or female identities are included.

Claims

1. A computer-implemented method for determining spatially resolved radiation exposure information of a patient during an examination using an imaging X-ray device (13), the X-ray device (13) having an X-ray radiator (1) for outputting an X-ray field (4) for the examination, wherein patient input dose information is determined, the patient input dose information describing the X-ray dose acting on the patient, and the radiation exposure information is determined based on the patient input dose information. It is characterized in that When using a matched filter (6) arranged between the patient and the x-ray radiator (1) in the x-ray field (4), the matched filter (6) causes an inhomogeneous dose distribution in a plane perpendicular to a central ray of the x-ray field (4), - determining predose information describing a uniformly distributed X-ray dose acting on the patient in the absence of the matched filter (6), - calculating dose distribution information by means of a filter model using the predose information, the filter model using at least one filter parameter describing the matched filter and the arrangement of the matched filter in the X-ray field (4), the dose distribution information describing at least the dose distribution of the X-ray dose acting on the patient in the part (8) of the X-ray field (4) covered by the matched filter (6), and - determining the patient input dose information using the dose distribution information.

2. The method according to claim 1, characterized in that In order to determine the patient input dose information in the portion (9) of the X-ray field (4) not covered by the matched filter (6), the predose information is used for this portion (9).

3. The method according to claim 1 or 2, characterized in that: The X-ray device (13) has a measuring device (17) for a total dose, in particular a dose-area product, which is located in the X-ray field (4) downstream of the matched filter (6) in the direction toward the patient, wherein total dose information is determined using the measuring device (17) and is used when determining the patient input dose information.

4. The method according to claim 3, characterized in that Filter dose information is determined based on the total dose information, the filter dose information describing a total filter dose that is unevenly distributed in a portion (8) of the X-ray field (4) covered by the matched filter (6), in particular, when the X-ray field (4) is not completely covered by the matched filter (6), the filter dose information is determined by subtracting a patient input dose determined for the portion (9) not covered by the matched filter (6) from the total dose described by the total dose information.

5. The method according to claim 4, characterized in that The filter dose information is used as an input variable for the filter model, wherein the dose distribution information directly describes the absolute dose intensity or a dose distribution is first determined which only describes the relative dose intensity and is used by the filter model to distribute the total filter dose of the filter dose information.

6. The method according to claim 4, characterized in that The filter dose information is used for a plausibility check of the dose distribution information.

7. The method according to any one of the preceding claims, characterized in that The predose information is determined with the aid of an estimation model which uses input data including at least one operating parameter of the X-ray radiator (1) to determine output data including the predose information and which is matched based on measurement data to a uniformly distributed X-ray dose acting on the patient without the matched filter (6).

8. The method according to any one of the preceding claims, characterized in that At least one geometry parameter describing the geometry of the matched filter (6) and / or at least one material parameter describing the material of the matched filter (6) and / or at least one position parameter describing the position and / or orientation of the matched filter (6) in the x-ray field (4) is used as filter parameter.

9. The method according to any one of the preceding claims, characterized in that The filter model is or includes an analytical physical model and / or a simulation model for performing a physical simulation.

10. The method according to any one of the preceding claims, characterized in that The filter model includes a trained filter model function.

11. The method according to claim 10, characterized in that The trained filter model function comprises a CNN, in particular a two-dimensional U-Net, and / or is trained on the basis of measurement data, in particular measured with spatial resolution using x-ray film and / or an x-ray detector.

12. The method according to any one of the preceding claims, characterized in that The radiation exposure information is determined using a patient model (11) positioned in the X-ray field (4) and / or including spatially resolved skin dose values ​​and / or at least one organ dose value and / or at least one scattered radiation information.

13. An X-ray device (13) comprising an X-ray radiator (1), an X-ray detector (15), and a control device (18), wherein the X-ray radiator (1) has an optionally usable matched filter (6) which causes an inhomogeneous dose distribution in a plane perpendicular to a central ray of an X-ray field (4) emitted by the X-ray radiator (1), the control device (18) being configured to carry out the method according to any of the preceding claims.

14. A computer program which, when executed on a computing device, causes the computing device to perform the steps of the method according to any one of claims 1 to 12.

15. An electronically readable data carrier on which a computer program according to claim 14 is stored.

Images