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 when conducting an examination with an imaging X-ray apparatus having an X-ray radiator for outputting an X-ray field for conducting the examination, wherein patient input dose information is determined for determining the radiation load information, wherein the pre-dose information is determined in the case of use of a matching filter arranged between the patient and the X-ray radiator, which causes a non-uniform dose distribution in a plane perpendicular to a central ray of the X-ray field, the pre-dose information describing a uniform distribution of the X-ray dose acting on the patient without the matching filter; dose distribution information is calculated using the pre-dose information by means of a filter model, which describes 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 matching filter; and the patient input dose information is determined using the dose distribution information.

Description

TECHNICAL FIELD

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

[0002] In imaging X-ray apparatuses, X-ray radiation is used for the purpose of fluoroscopy of an examination object, in particular a patient. Since X-ray radiation can act ionizingly, the radiation load of a patient is often determined, recorded and / or documented. It is known to determine the X-ray dose acting on the patient in order to determine radiation load information, for example in the case of the use of a patient phantom. Such radiation load information can comprise skin dose and / or organ dose, in particular determined in a spatially resolved manner. It is also known to determine local peaks of the radiation load.

[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 apparatus, which is usually arranged as a last component in the radiation path in front of the patient (in addition to the patient support means, if necessary). Here, a so-called DAP chamber is usually used downstream of the X-ray radiator, the beam shaping apparatus and the radiation filtering apparatus, if used, as a measuring apparatus for measuring the dose area product, DAP (English: dose area product). The dose area product is a radiation characteristic quantity which starts from a uniform distribution of the X-ray dose.

[0004] Since DAP chambers and other measuring apparatuses can trigger undesired scattered radiation, are relatively expensive and require structural space, it is also proposed, for example by the subsequently published European patent application 23197942.8, to provide a virtual measuring apparatus in such a way that a radiation characteristic quantity is determined in a calculated manner by means of an estimation model.

[0005] Many devices influencing the X-ray radiation of the X-ray field, such as beam shaping devices (e.g. collimators or other diaphragm devices) which predefine the geometry of the X-ray field and uniform attenuation, e.g. radiation filtering devices which influence the spectrum, maintain a uniform dose distribution perpendicular to the central ray (for which the specification of the radiation characteristic, e.g. the dose area product, is sufficient to describe the spatial distribution of the dose), radiation filtering devices are also known which result in a spatially non-uniform dose distribution in the plane perpendicular to the central ray of the X-ray field. Such radiation filtering devices are also referred to as matching filters hereinafter.

[0006] Matching filters can result in a non-uniform spatial distribution of the dose after its traversal by using different materials and / or different attenuation lengths. One well-known example of such a matching filter is the so-called wedge filter which has an increasing thickness towards one side and thus an attenuation length. In other words, the semi-transparent matching filter blocks the X-ray radiation with different intensity at different positions, which results in a non-uniform X-ray field.

[0007] Current methods for the determination of the radiation characteristic, e.g. DAP chambers and virtual measurement devices, do not take the non-uniformity into account. This can result in that the radiation load information is not correct for the patient, since the X-ray dose can be locally higher than assumed based on the radiation characteristic, e.g. the dose area product. SUMMARY

[0008] It is therefore an object of the present application to provide a possibility for a more precise determination of the radiation load information of a patient.

[0009] According to the application, in order to solve the above-mentioned technical problem, a computer-implemented method, an X-ray device, a computer program and an electronically readable data carrier according to the application are provided. Advantageous design embodiments are also given.

[0010] In the method of the type mentioned in the opening part, according to the application it is provided that, when a matching filter is used which is arranged between the patient and the X-ray radiator in the X-ray field, the matching filter causes a non-uniform dose distribution in the plane perpendicular to the central ray of the X-ray field,

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

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

[0013] - determining the patient input dose information using the dose distribution information.

[0014] Here, it is conceivable in the framework of the application that the pre-dose information suitably comprises a radiation characteristic quantity, which may, for example, comprise a dose area product and / or an air kerma and / or a quantity related to the dose area product and / or the air kerma. The patient input dose information can also be expressed by such a radiation characteristic quantity, then in particular spatially resolved.

[0015] It is proposed here that the inhomogeneous dose distribution perpendicular to the central ray is determined by applying a filter model into which the matched filter, in particular a wedge filter, enters, in particular at least the geometry and / or at least one material and the pre-dose information. Here, as is set out in more detail below, the dose distribution information already states the spatially resolved dose absolutely, however also only contains relative dose values as a pure distribution.

[0016] From the dose distribution information, the patient input dose information can be determined, if necessary in combination with the pre-dose information and / or in accordance with the implementation, further information being determined. The patient input dose information is likewise spatially resolved on the basis of the dose distribution information describing the dose distribution and describes the inhomogeneity produced by the matched filter.

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

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

[0019] A design scheme can be conceived where the wedge filter does not cover the entire X-ray field perpendicular to the central ray direction. It can then be specified that, to determine the patient input dose information in the portion of the X-ray field not covered by the matched filter, pre-dose information for that portion is used. In areas not covered by the matched filter, i.e., areas that have no effect on the X-ray field, the dose described by the pre-dose information (which addresses the case without the matched filter), such as a specific dose-area product, can be set in that region. The dose distribution information is then used for the remaining areas covered by the matched filter to determine the remaining patient input dose information.

[0020] In particular, different specific embodiments of the invention can be conceived depending on the presence or absence of a measuring device. It is worth considering a measuring device, such as a DAP chamber, that follows a matched filter in the ray direction, but starts from a uniform distribution of X-ray dose perpendicular to the central ray. However, within the scope of the invention, measurements using a measuring device can be advantageously employed.

[0021] Therefore, it can be stipulated that the X-ray device has a measuring device for total dose, particularly the dose-area product, located in the X-ray field after the matched filter in the direction towards the patient. This measuring device is used to determine the total dose information and is also used when determining the patient's input dose information. For example, a conventionally existing DAP chamber can be used as the measuring device. Additional useful information exists with the total dose information, which can further improve the quality of the determination of radiation load information. The total dose information can be used in various ways.

[0022] Therefore, it can be stipulated that filter dose information is determined from the total dose information, which describes the non-uniformly distributed total filter dose in the portion of the X-ray field covered by the matched filter. When the X-ray field is completely covered by the matched filter, the total dose information already corresponds to the filter dose information, because the total dose information is ultimately a uniformly redistributed dose from a non-uniform dose distribution. When the X-ray field is not completely covered by the matched filter, the filter dose information can be suitably determined by subtracting the patient input dose from the total dose described by the total dose information, which 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 quantity for the filter model, wherein the dose distribution information directly describes the absolute dose intensity, or a dose distribution is first determined which only illustrates the relative dose intensity and which is distributed by the filter model to the total filter dose of the filter dose information. In other words, the filter model can implicitly assume on the one hand the distribution of the dose remaining after the transmission of the matching filter. It is also conceivable, however, that a dose distribution is first determined which only illustrates the relative dose intensity, on the basis of which the filter model distributes the total filter dose of the filter dose information in order to determine the absolute dose intensity. Here, the relative dose intensity thus only describes the inhomogeneity triggered by the matching filter, thus the relative dose intensity. The total filter dose is then used for an exact normalization in order to obtain the absolute dose intensity in relation to the location. In both cases, if the part of the X-ray radiation field covered by the matching filter does not cover the entire X-ray radiation field, the absolute dose intensity in the part of the X-ray radiation field covered by the matching filter supplements the total dose set by the pre-dose information for the uncovered part of the X-ray field; when the X-ray field is completely covered by the matching filter, the patient input dose information is defined only by the dose distribution with the absolute dose intensity, i.e. the dose distribution information.

[0024] Alternatively, it is also conceivable in the scope of the method according to the application that the filter dose information is used for a plausibility check of the dose distribution information. Here, the dose distribution information is again determined, which contains the absolute dose intensity, from which the desired 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 in the case of plausibility. In the case of deviations, a correction and / or recalculation can be made.

[0025] It should also be noted here that when the filter model outputs the absolute dose intensity in the dose distribution, the X-ray dose according to the pre-dose information can be started from, in particular, as the X-ray radiation incident on the matching filter. This X-ray dose is then correspondingly attenuated by the matching filter in relation to the location, as described by the filter model.

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

[0027] It is conceivable in principle, but less preferred due to the additional dose load, to measure the pre-dose information, for example, before the introduction of the matching filter into the radiation path, whereas a preferred refinement of the application provides that the pre-dose information is determined by means of an estimation model which uses input data comprising at least one operating parameter of the X-ray radiator to determine output data comprising the pre-dose information, and which is based on measurement data matched to a uniformly distributed X-ray dose acting on the patient without a matching filter. For measuring the measurement data, it is possible here to use a measuring device as already described, in particular a DAP chamber. In a refinement, the estimation model can also comprise 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, wherein the estimation model is introduced there as a refined model (starting from a basic model). All the disclosures of the present application relating to the determination and application of the evaluation model / refined model are hereby incorporated into the present disclosure by reference.

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

[0030] In a specific design of the filter model, it can be provided that the filter model is an analytical physical model. This in particular means that the dose distribution information can be calculated on the basis of physical laws which are described in particular by at least one formula. In this case, it can also be assumed, for example, that there is no aging, the material is homogeneous, there is no scattered radiation, etc. In particular, it can be provided, for example, that in an analytical model for the partial radiation of the X-ray radiation field the respective attenuation is calculated using the transmission length, in particular the thickness and / or the attenuation coefficient of the matching filter, in particular the attenuation coefficient based on the material of the matching filter. This means that in principle a known physical relationship describing the attenuation behavior of X-ray radiation when passing through a substance can be taken into account. In this way, excellent results have already been achieved 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, in principle known physical simulation methods are used in order to achieve a high-precision calculation of the interaction between the X-ray radiation and the filter material, in particular taking into account physical effects for which assumptions would be made in the case of pure analytical modeling. It can in particular be provided that the simulation comprises or is a finite element simulation and / or a Monte Carlo simulation. Particularly preferred here are simulations which can be performed quickly, for example a fast Monte Carlo simulation.

[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 means of machine learning. The trained function is generally characterized by a very short runtime, so that the learned physical correlations can be used extremely time-efficiently for determining the dose distribution information. It can in particular 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 on the basis of measurement data which are measured spatially resolved in particular by means of an X-ray film and / or an X-ray detector. Here, special measurement methods, in particular X-ray films and / or X-ray detectors, are used in order to spatially resolve the actual X-ray dose distribution after the previously uniformly distributed X-ray radiation has passed through the matching filter and to use it as training data. However, it is also conceivable that in addition or alternatively simulation results are used to train the filter model function. By correspondingly extended selection of the input data, additional physical effects can be taken into account which are covered by assumptions when analytically observing and also partly in the physical simulation.

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

[0035] Generally, 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. Furthermore, representation learning (also referred to as "feature learning") can also be used. The parameters of the training function can be adjusted, inter alia, iteratively by a plurality of training steps.

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

[0037] For determining the radiation load information, it can be provided in an embodiment of the application 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 scatter radiation information. Here, in principle known methods can be used in order to determine the radiation load information from the patient input dose information with a known spatial distribution. Here, finally the dose distribution is forward projected onto the patient, in particular with the aid of the patient model. Of course, also the weakening properties of patient support means, such as a patient table and / or a bed mat, can be taken into account. The transition from air to skin and / or the scatter radiation can also be taken into account when determining the radiation load information. Thus, finally, for example, a skin dose distribution, an organ dose distribution, a scatter radiation dose distribution, etc. can be determined.

[0038] In addition to the method, the application also relates to an imaging X-ray apparatus having an X-ray radiator with a selectively usable matching filter which causes a non-uniform dose distribution in a plane perpendicular to a central ray of the X-ray field, an X-ray detector and a control device designed to carry out the method according to the application. All the embodiments with respect to the method according to the application can be similarly transferred to the X-ray apparatus according to the application and vice versa, so that the advantages already mentioned can also be achieved with the X-ray apparatus.

[0039] The X-ray apparatus can also comprise further radiation filtering means and / or beam shaping means, such as a matching filter in the radiation path downstream of the X-ray radiator. Furthermore, a measurement device, in particular a DAP chamber, can be provided. The X-ray apparatus can for example be an X-ray apparatus with a C-arm, on which the X-ray radiator and the X-ray detector are arranged opposite to each other. The patient can for example be supported on a patient table.

[0040] The control device, which can have at least one processor and / or at least one storage device, can have functional units constituted by hardware and / or software for carrying out parts of the method according to the application. In addition to a recording unit, which can control the recording operation of the X-ray apparatus, the control device can for example comprise:

[0041] - a first determination unit for determining, when a matching filter arranged between the patient and the X-ray radiator in the X-ray field is used, pre-dose information, which describes a uniformly distributed X-ray dose acting on the patient without the matching filter,

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

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

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

[0045] Of course, further functional units can also be provided in order to realize further, in particular optional, steps.

[0046] The computer program according to the application can be directly loadable into the memory of a computing device, in particular of a control device of an X-ray device, and has a program device which, when the computer program is executed on a computing device, causes the computing device to carry out the steps of the method according to the application. The computer program can be stored on an electronically readable data carrier, which therefore comprises control information stored thereon, which control information comprises at least one computer program according to the application and which control information is designed such that, when the data carrier is used in a computing device, in particular in a control device of a magnetic resonance device, the computing device is designed for carrying out the method according to the application. The data carrier can in particular be a non-transitory data carrier, for example a CD-ROM. BRIEF DESCRIPTION OF DRAWINGS

[0047] Further advantages and details of the application result from the embodiments described below and from the figures. Therein, in the figures:

[0048] Figure 1 a diagram is shown for explaining the formation of a non-uniform distribution of the X-ray dose,

[0049] Figure 2 a flow chart of a first embodiment of the method according to the application is shown,

[0050] Figure 3 a diagram of a portion of an X-ray field is shown,

[0051] Figure 4 a diagram for determining radiation load information is shown,

[0052] Figure 5 a flow chart of a second embodiment of the method according to the application is shown,

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

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

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

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

[0057] However, if now a wedge filter 5 is used as an example of a matched filter 6, which position-dependently attenuates the X-ray radiation, the current attenuation of the X-ray radiation by means of a wedge shape, then an inhomogeneous distribution of the X-ray dose is caused in a plane perpendicular to the direction of the rays (direction of the central ray), as is shown by the schematically shown X-rays 2' which have a greater spacing with respect to the greater thickness of the wedge filter 7.

[0058] If now a DAP chamber is connected downstream of the device shown in Figure 1 the DAP chamber will however output the only measured value for the dose area product or other radiation characteristic quantity, 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 which is derived therefrom. In particular, the local X-ray dose can be underestimated.

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

[0060] Figure 2 A flowchart of a first embodiment of the method according to the application is shown. Here, in step S1, pre-dose information is first determined in a computed manner by means of an estimation model. The pre-dose information can for example (assuming a uniform distribution of the X-ray dose) be determined as the only radiation characteristic quantity, in particular the dose area product. When no matched filter 6 is used, the pre-dose information describes the uniformly distributed X-ray dose which would act on the patient. However, the pre-dose information takes into account all other possibly used devices, in particular the beam shaping device 3 and the radiation filter device 5.

[0061] In step S2, total dose information is then determined by means of the measuring device, in particular the DAP chamber, which describes the total dose before the action on the patient under the assumption of a uniform distribution of the X-ray dose. The total dose information can also be determined as a radiation characteristic variable, in particular as a dose area product in the case of the DAP chamber. The total dose information thus merely states how much total dose is present, without taking into account the action of the matching filter 6.

[0062] In step S3, it is determined on the basis of the position and orientation of the matching filter 6 in the X-ray field 4 whether the matching 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 matching filter 6, it is already possible to determine a portion of the patient input dose information, namely the X-ray dose described by the pre-dose information in the portion not covered, since no homogenization takes place there. It is thus possible, in particular, to set the dose area product determined as the pre-dose information for the portion not covered.

[0063] Figure 3 It is graphically explained in Figure 1 the case already shown in Fig. 1, in which only a first portion 8 of the X-ray field 4 is covered by the matching filter 6 in the plane perpendicular to the direction of the central ray, i.e. there is the wedge filter 7. The remaining second portion 9 is thus not covered by the matching filter 6. The distribution of the dose remains particularly uniform here.

[0064] In step S4, it is also determined in the case in which the X-ray field 4 is not completely covered by the matching filter 6 which portion of the X-ray dose described by the pre-dose information falls on or is influenced by the matching filter 6. The filter dose information is thus determined, which describes the total filter dose, which is homogenized in its distribution by the matching filter 6. The total filter dose is currently determined by subtracting the X-ray dose for the portion 9 of the X-ray field 4 not covered by the matching filter 6 from the total dose of the total dose information.

[0065] In step S5, a filter model is used in order to determine dose distribution information which describes which inhomogeneous distribution of the dose results from the matched filter 6. Here, the filter model uses as input quantities in any case at least one filter parameter, the current plurality of filter parameters, which describe the geometry of the matched filter 6 in the X-ray field 4 (geometric parameters), at least one material (material parameters) and the position and orientation (position parameters). The filter model can comprise 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, this can comprise a two-dimensional U-Net and / or be trained on the basis of simulated training data or training data derived from measurement data. In the case of a simulation model which performs a physical simulation, the physical simulation is preferably a fast Monte Carlo simulation.

[0066] The total filter dose determined in step S4 can here already be entered into the filter model as the X-ray dose which should be inhomogeneously distributed. However, it is additionally or alternatively conceivable that the filter model works on the basis of pre-dose information which does indeed describe how much X-ray dose has impinged on the matched filter 6 and is here inhomogeneously attenuated spatially. If the pre-dose information which describes the dose impinging on the matched filter 6 is not used directly, it is possible first to determine a dose distribution with a relative dose intensity and then the filter model 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 expediently already contains the absolute dose intensity in the dose distribution.

[0067] Here, it is noted here that this is not shown more precisely in the flowchart 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 on the basis of the pre-dose information alone, the total filter dose which remains overall 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, an untrustworthiness is given and a recalculation, correction, etc. can be carried out.

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

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

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

[0071] Figure 5 A flow chart of a second embodiment of the method according to the application is shown, wherein the measuring device is dispensed with. This means in particular that now only the pre-dose information determined in step S1 is utilized. In step S3 it is also invariable checked whether there is a portion 8 of the X-ray field 4 not covered by the matching filter 6, for which the pre-dose information can again be applied directly.

[0072] In step S5' the filter model is used without taking into account the filter dose information on the basis of the filter parameters and the pre-dose information in order to determine the dose distribution information and thus in step S6 to consolidate the patient input dose information analogously to the first embodiment. Step S7 is also carried out analogously to the first embodiment.

[0073] Figure 6 A schematic diagram of an embodiment of an X-ray device 13 according to the application is shown, which here exemplarily has a C-arm 14 on which the X-ray emitter 1 and the X-ray detector 15 are arranged opposite one another. The C-arm 14 is movable, in particular swingable, about different rotational axes about a patient table 16 on which a patient can be supported.

[0074] Other embodiments of the X-ray device 13 are also conceivable, for example as a computed tomography device, a radiographic device, etc.

[0075] As part of an emitter device also comprising the X-ray emitter 1, in Figure 6 The beam shaping device 3, the radiation filtering device 5 and the matching filter 6 are shown in

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

[0077] The control device 18 thus comprises a storage device 19 in which different information processed by the method and the recorded X-ray data or X-ray images can be stored. For controlling the recording run, the control device 18 furthermore has a recording unit 20 as is known in principle.

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

[0079] In a distribution unit 23, it can be checked according to step S3 whether the matching filter 6 covers the entire X-ray field 4 in its respective position and orientation or whether there are uncovered portions 9. Furthermore, the pre-dose information can be applied accordingly in this portion 9.

[0080] In a calculation unit 24, the filter model is applied according to step S5, wherein the patient input dose information is then summarized in a second determination unit 25 according to step S6. This patient input dose information is used by a third determination unit 26 for determining the radiation load information according to step S7.

[0081] Although the application is illustrated and described in detail by preferred embodiments in terms of details, the application is not restricted to the disclosed examples and other variants can be derived therefrom by those skilled in the art without departing from the scope of the application.

[0082] Regardless of the grammatical gender of specific terms, both men and women with a male or female identity are included.

Claims

1. A computer-implemented method for determining spatially resolved radiation load information of a patient when being examined with an imaging X-ray apparatus (13) having an X-ray radiator (1) for outputting an X-ray field (4) for the examination, wherein patient input dose information is determined, which describes the X-ray dose acting on the patient, from which the radiation load information is determined, characterized in that - in the use of a matching filter (6) arranged between the patient and the X-ray radiator (1) in the X-ray field (4), which causes a non-uniform dose distribution in a plane perpendicular to the central ray of the X-ray field (4), - determining pre-dose information, which describes a uniformly distributed X-ray dose acting on the patient without the matching filter (6), - calculating dose distribution information using the pre-dose information by means of a filter model, which uses at least one filter parameter describing the matching filter and the arrangement of the matching filter in the X-ray field (4), which describes 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 matching filter (6), and - determining the patient input dose information using the dose distribution information.

2. The method of claim 1, wherein, For determining the patient input dose information in the part (9) of the X-ray field (4) not covered by the matching filter (6), the pre-dose information is applied for this part (9).

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

4. The method of claim 3, wherein, From the total dose information, a filter dose information is determined, which describes the total filter dose distributed non-uniformly in the part (8) of the X-ray field (4) covered by the matching filter (6), in particular in the case that the X-ray field (4) is not completely covered by the matching filter (6), by subtracting the patient input dose determined for the part (9) not covered by the matching filter (6) from the total dose described by the total dose information.

5. The method of claim 4, wherein, The filter dose information is used as an input quantity for the filter model, wherein the dose distribution information either directly describes the absolute dose intensity or a dose distribution is first determined which only illustrates the relative dose intensity and is used by the filter model for distributing the total filter dose of the filter dose information.

6. The method of claim 4, wherein, The filter dose information is used for plausibility checking of the dose distribution information.

7. The method according to claim 1 or 2, characterized in that, The pre-dose information is determined by means of an estimation model which uses input data comprising at least one operating parameter of the X-ray radiator (1) to determine output data comprising the pre-dose information and which is based on measured data matching a uniformly distributed X-ray dose acting on a patient in the absence of the matching filter (6).

8. The method of claim 1 or 2, wherein, At least one geometry parameter describing a geometry of the matching filter (6) and / or at least one material parameter describing a material of the matching filter (6) and / or at least one position parameter describing a position and / or orientation of the matching filter (6) in the X-ray field (4) are used as filter parameters.

9. The method of claim 1 or 2, wherein, The filter model is or comprises an analytical physical model and / or a simulation model for performing a physical simulation.

10. The method of claim 1 or 2, wherein, The filter model comprises a trained filter model function.

11. The method of claim 10, wherein, The trained filter model function comprises a CNN, in particular a two-dimensional U-Net, and / or is trained based on measured data measured spatially resolved, in particular by means of an X-ray film and / or an X-ray detector.

12. The method of claim 1 or 2, wherein, The radiation load information is determined using a patient model (11) positioned in the X-ray field (4) and / or comprising spatially resolved skin dose values and / or at least one organ dose value and / or at least one scatter radiation information.

13. An X-ray apparatus (13) having an X-ray radiator (1) with a selectively usable matching filter (6) which causes a non-uniform dose distribution in a plane perpendicular to a central ray of an X-ray field (4) emitted by the X-ray radiator (1), an X-ray detector (15) and a control device (18) which is set up to carry out the method according to any one of the preceding claims.

14. An electronically readable data carrier on which a computer program is stored which, when executed on a computing device, causes the computing device to carry out the steps of the method according to any one of claims 1 to 12.

Images