Dose estimation for the irradiation of an object

Abstract

Computer-implemented method for dose estimation for the irradiation of an object (5) with ionizing radiation, wherein a three-dimensional model with a total number (9) of spatial elements is provided on a storage element (4), wherein the model specifies a material composition of the object (5) for each spatial element, and by means of a computing unit (3) - for a connected neighborhood (10) of spatial elements of the total number (9) of spatial elements, depending on the respective material compositions of all spatial elements of the neighborhood of the model, a neighborhood material composition is determined by averaging or homogeneously approximating one or more material parameters of the respective material compositions; - a radiation dose for the neighborhood (10) with respect to ionizing radiation is determined by means of a simulation depending on the neighborhood material composition; and - a dose distribution for the object (5) with respect to ionizing radiation is determined based on the radiation dose for the neighborhood (10).

Description

[0001] The present invention relates to a computer-implemented method for dose estimation for the irradiation of an object with ionizing radiation, a method for parameter setting for the irradiation of an object, a method for imaging an object, an arrangement for dose estimation, an irradiation device and a computer program product.

[0002] In recent years, awareness of radiation dose has increased in the irradiation of objects with ionizing radiation and in imaging of objects based on ionizing radiation, partly due to legal regulations that require proof of consistent dose application. Therefore, the rapid and precise determination of an object-specific dose distribution is particularly relevant for predicting stochastic and deterministic risk factors and for dose monitoring.

[0003] Existing approaches to X-ray imaging, for example, use a Monte Carlo simulation of particle transport for computational dose estimation.

[0004] However, these methods exhibit a very high algorithmic complexity, so the computational effort required for reliable Monte Carlo simulations hinders widespread application.

[0005] From Schmidt, B.; Kalender, WA: A fast voxel-based Monte Carlo method for scanner- and patient-specific dose calculations in computed tomography, Physica Medica, Vol. 18, 2002, No. 2, pp. 43-53. (ISSN 1120-1797) a method for rapid dose calculation using Monte Carlo simulation is known. The method is based on a segmented image dataset. When calculating the dose for contiguous anatomical components, e.g., organs, the materials typical for these anatomical components are used. To accelerate the dose calculation, a reduced resolution is employed.

[0006] It is therefore an object of the present invention to provide an improved concept for dose estimation when an object is irradiated with ionizing radiation, which reduces the computational effort and, accordingly, the time required for dose estimation.

[0007] According to the invention, this problem is solved by the respective subject matter of the independent patent claims. Advantageous further developments and preferred embodiments are the subject matter of the dependent patent claims.

[0008] The improved concept is based on the idea of ​​determining an effective homogeneous material composition for a coherent neighborhood of numerous spatial elements, starting with a spatially discrete model of the object's material composition, and then performing a radiation dose simulation based on this. The dose distribution for the object can then be determined based on the radiation doses for individual neighborhoods thus calculated.

[0009] According to the improved concept, a computer-implemented method for dose estimation for the irradiation of an object with, in particular, predefined, ionizing radiation is described. This involves providing a, in particular, discrete, three-dimensional model with a total number of spatial elements on a storage element, wherein the model specifies a material composition of the object for each spatial element. The three-dimensional model can, for example, be based on a previous image of the same object, or it can be based on a statistical model, which may, in particular, have been adapted to the object in size and shape, or it can be based on a generic model. Using a processing unit, a neighborhood material composition is determined for a contiguous neighborhood of spatial elements from the total number of spatial elements, depending on the model.The processing unit determines the radiation dose for the surrounding area with respect to ionizing radiation based on a simulation that considers the composition of the surrounding materials. The processing unit then determines a dose distribution for the object with respect to ionizing radiation based on the radiation dose for the surrounding area.

[0010] The object can be, for example, a human being or another living being, or a non-living object. Irradiation of the object can serve, for example, the purpose of examining, analyzing, modifying, or treating the object with ionizing radiation. Irradiation can, for example, be used for image-guided analysis or examination, or for imaging the object. For living beings, irradiation can also serve for medical treatment or therapy.

[0011] According to the model, the object or a part of the object is described as a discrete approximation by the total number of spatial elements. These spatial elements can also be referred to as voxels.

[0012] According to the model, each spatial element within the total number of spatial elements has a specific material composition. In particular, the model states that the material composition within each individual spatial element is homogeneous. However, different spatial elements, especially adjacent spatial elements or elements in the neighborhood, generally have different material compositions. In the case of living organisms, the different material compositions of different spatial elements can, for example, be attributed to different tissue types.

[0013] The neighborhood of spatial elements can be understood as a plurality of spatial elements out of the total number of spatial elements, where the plurality is smaller than the total number. The spatial elements of the neighborhood are connected such that any pair of spatial elements in the neighborhood is either directly adjacent to each other or indirectly connected via one or more other spatial elements in the neighborhood. In particular, the connected neighborhood can be a simply connected part of the discrete space given by the total number of spatial elements.

[0014] For example, all spatial elements located within a predefined three-dimensional geometric figure, such as a cuboid with defined edge lengths, can belong to the spatial elements of the neighborhood. However, other definitions of neighborhood are also possible.

[0015] The composition of materials in the neighborhood is homogeneous, especially within the neighborhood, meaning it is the same for all spatial elements in the neighborhood.

[0016] In other words, a fictitious or effective neighborhood material composition is constructed from the various material compositions of the individual spatial elements of the neighborhood, which approximately describes all spatial elements of the neighborhood equally with regard to their physical properties. In other words, determining the neighborhood material composition for the neighborhood in this way can be considered a reduction in the resolution of the model.

[0017] Determining the neighborhood material composition based on the model involves, in particular, determining the neighborhood material composition based on the respective material compositions of all spatial elements in the neighborhood. For this purpose, one or more material parameters of the individual material compositions can be averaged or otherwise homogeneously approximated, so that, in a sense, an effective or fictitious material is constructed for the entire neighborhood.

[0018] To determine the radiation dose for the surrounding area, it is assumed that the predefined ionizing radiation strikes the object or the surrounding area with the neighboring material composition determined as described. The radiation dose then corresponds, for example, to a constant value for the surrounding area.

[0019] The dose distribution for the object includes, in particular, a corresponding value for the radiation dose for each room element of the total number of room elements.

[0020] According to the procedure based on the improved concept, the corresponding value for the radiation dose for all room elements in the neighborhood is determined approximately depending on the radiation dose for the entire neighborhood.

[0021] The described steps can be carried out in particular for further neighborhoods of the total number of room elements, so that a radiation dose is determined for each neighborhood based on the corresponding neighborhood material composition and ultimately the dose distribution is determined based on all radiation doses determined for the different neighborhoods.

[0022] Ionizing radiation can include, for example, X-rays, alpha radiation, beta radiation, or neutron radiation. However, ionizing radiation can also include electromagnetic radiation, particularly with a wavelength of less than 200 nm, such as ultraviolet radiation or gamma radiation.

[0023] The fact that ionizing radiation is predefined can be understood, in particular, to mean that the type, energy, intensity, and / or wavelength of the radiation are predetermined. For example, the direction of the ionizing radiation relative to the object, especially relative to the spatial elements of the total number of spatial elements and thus also to the surrounding area and its spatial elements, can also be predetermined.

[0024] The improved concept enables a significant reduction in computational effort and time required to determine the dose distribution, particularly in high-resolution voxel models, through the effective reduction of resolution, without significant drawbacks in accuracy. The improved method can also be used for variance reduction.

[0025] Before the simulation is performed, the effective resolution is reduced by determining the neighborhood material composition, and the simulation is then carried out based on the neighborhood. This reduces the number of units to be simulated while still achieving a stable solution with low uncertainty. Tests have shown, in particular, that with 16 spatial elements per neighborhood, the accuracy reduction compared to a full Monte Carlo simulation is only about 10%.

[0026] According to at least one embodiment of the computer-implemented method based on the improved concept, the computing unit determines the material composition of each neighborhood for a plurality (i.e., two or more) of additional, interconnected neighborhoods of spatial elements, depending on the model. For each of these additional neighborhoods, the computing unit determines a further radiation dose with respect to ionizing radiation based on a simulation, depending on the neighborhood material composition of the respective additional neighborhood. The computing unit then determines the dose distribution for the object based on the further radiation doses for these additional neighborhoods, and in particular based on all further radiation doses of all additional neighborhoods and based on the radiation dose of the neighborhood itself.

[0027] This allows the entire object or an entire area of ​​interest of the object to be taken into account, so that a meaningful distribution of the radiation doses is obtained in the form of the dose distribution.

[0028] According to at least one embodiment, the processing unit determines a fluence for the surrounding area with respect to ionizing radiation, depending on the radiation dose. The dose distribution for the object is then determined by the processing unit based on this fluence.

[0029] Fluence can be understood as the number of photons or other particles of ionizing radiation incident on a surface per unit area. Fluence is therefore closely related to irradiance, which indicates the incident radiation energy per unit area.

[0030] The fluence can be approximated as being proportional to the radiation dose. This is a particularly good approximation when, as in the case of large homogeneous spatial elements, a charged particle equilibrium (CPE) can be assumed. In this approximation, the radiation dose can be approximately equated to the corresponding collision kerma. In other words, the radiation kerma can be neglected.

[0031] The collision kerma is directly proportional to the fluence, with the proportionality factor being given in particular by the corresponding mass attenuation coefficient. The mass attenuation coefficient is equal to the quotient of the absorption coefficient and the density of the material in question. In summary, the fluence can therefore be determined according to the following relationship: ψ_N≈D_N / (μ / ρ)_N,

[0032] Where ψ_N denotes the fluence of the neighborhood N, D_N the radiation dose of the neighborhood N and (µ / ρ)_N the mass attenuation coefficient of the neighborhood N.

[0033] According to at least one embodiment, the processing unit determines a corresponding fluence for the respective neighboring area with respect to ionizing radiation, depending on each of the further radiation doses. The dose distribution for the object is then determined by the processing unit based on the fluence and the further fluences.

[0034] According to at least one embodiment, a smoothing filter algorithm is executed by means of the computing unit, depending on the radiation dose for the neighborhood and depending on the further radiation doses for the further neighborhoods, in order to determine the dose distribution for the object.

[0035] The smoothing filter algorithm is, in particular, an edge-preserving smoothing filter algorithm.

[0036] The smoothing filter algorithm can reduce jumps in the dose distribution between different spatial elements or neighborhoods resulting from the effective resolution reduction.

[0037] The smoothing filter algorithm is determined in particular depending on the fluence and the other influences.

[0038] One result of the smoothing filter algorithm can therefore be understood as a fluence distribution over spatial elements. This fluence distribution is then, in turn, approximately proportional to the dose distribution for the object.

[0039] In particular, the dose distribution can be determined according to the relationships D≈(μ / ρ)*ψ,with ψ=F({ψ_N}) can be determined approximately. Here, D and ψ denote the dose distribution and the fluence distribution for the object respectively, F the smoothing filter algorithm, and {ψ_N} the entirety of all fluences for all considered neighborhoods of spatial elements.

[0040] According to at least one embodiment, the smoothing filter algorithm includes a guided filter algorithm, a Perona-Malik filter algorithm, a Savitzky-Golay filter algorithm, or a bilateral filter algorithm. The Perona-Malik filter algorithm may also be referred to as the Perona-Malik diffusion algorithm or the anisotropic diffusion algorithm. The bilateral filter algorithm may also be referred to as a joint bilateral filter.

[0041] These algorithms are particularly suitable due to their edge-preserving property.

[0042] The guided filter algorithm is particularly advantageous, as it allows, for example, the mass attenuation coefficient to be used as a reference variable, so that ψ=GF((μ / ρ),I({ψ_N}),r), where GF denotes the guided filter algorithm, r the filter radius, and (µ / ρ) serves as the reference variable. I denotes a function, for example an interpolation function or the result of an interpolation algorithm.

[0043] According to at least one embodiment, an interpolation algorithm is executed by the processing unit, depending on the radiation dose and subsequent radiation doses. The smoothing filter algorithm is then performed based on a result of the interpolation algorithm.

[0044] The interpolation algorithm can be understood as follows: for each neighborhood or subsequent neighborhood, the result of the interpolation algorithm assigns a corresponding value for fluence or radiation dose to each spatial element within the respective neighborhood. In other words, a fluence or radiation dose is first determined for the entire neighborhood, and based on this determined fluence or radiation dose, an individual fluence or radiation dose is determined for each spatial element within the neighborhood. In the simplest case, the individual fluence or radiation dose can be the same for all spatial elements within the neighborhood. Thus, the interpolation formally increases the resolution of the voxel model back to its original resolution.

[0045] According to at least one embodiment, the simulation for determining the radiation dose and / or the simulations for determining the further radiation doses includes a Monte Carlo simulation or a finite difference simulation.

[0046] In particular, the corresponding Boltzmann equations can be solved numerically approximately using Monte Carlo simulation or finite difference simulation. These simulation methods have proven to be particularly robust and precise.

[0047] According to the improved concept, a procedure for setting parameters for irradiating an object is also specified. For this purpose, a predefined first set of parameters for ionizing radiation is defined. Based on this first set of parameters, a dose estimation procedure, according to the improved concept, is performed to determine a corresponding dose distribution. Depending on the dose distribution determined by the dose estimation procedure based on the first set of parameters, a second set of parameters for ionizing radiation is determined, specifically automatically, for example, by the processing unit.

[0048] A parameter set for ionizing radiation can include one or more parameters for the radiation itself or for its application during irradiation. These parameter sets can, for example, include corresponding values ​​or time-dependent value profiles for the energy, wavelength, and / or intensity of the radiation. The parameter sets can also include irradiation durations.

[0049] According to at least one embodiment of the parameter setting method, the dose distribution determined based on the first parameter set is compared by the processing unit with a target distribution for the dose distribution, a maximum value, or another target value for the dose distribution. The second parameter set is then determined depending on the result of the comparison.

[0050] According to at least one embodiment, a radiation source for generating the ionizing radiation for irradiating the object is set depending on the second set of parameters, for example automatically.

[0051] According to the improved concept, a method for imaging an object is described. This involves a procedure for setting the parameters for irradiating the object according to the improved concept. The object is irradiated with ionizing radiation according to the second set of parameters in order to image the object.

[0052] The method for imaging the object is, in particular, a non-therapeutic method.

[0053] According to the improved concept, a device for dose estimation for the irradiation of an object with ionizing radiation is also described. The device includes a storage element that stores a three-dimensional model, particularly a discrete one, with a total number of spatial elements, where the model specifies the material composition of the object for each spatial element. The device also includes a processing unit configured to determine the neighborhood material composition for a contiguous area of ​​spatial elements within the total number of spatial elements, depending on the model.The computing unit is designed to determine a radiation dose for the neighborhood with respect to ionizing radiation based on a simulation depending on the neighborhood material composition and to determine a dose distribution for the object with respect to ionizing radiation based on the radiation dose for the neighborhood.

[0054] Further embodiments of the dose estimation arrangement according to the improved concept arise directly from the various configurations of the computer-implemented dose estimation method according to the improved concept, and vice versa. In particular, an arrangement according to the improved concept can be configured or programmed to perform a computer-implemented dose estimation method according to the improved concept, or the arrangement can perform such a method.

[0055] According to the improved concept, an irradiation device for irradiating an object is also specified, wherein the irradiation device includes a dose estimation arrangement according to the improved concept. The irradiation device also includes a control unit configured to determine a parameter set for ionizing radiation for irradiating the object, depending on the dose distribution for the object.

[0056] According to at least one embodiment of the irradiation device, the irradiation device has a radiation source and the control unit is configured to control the radiation source to emit the ionizing radiation according to the specified set of parameters.

[0057] According to at least one embodiment, the radiation source is designed as an X-ray radiation source.

[0058] Further embodiments of the irradiation device according to the improved concept arise directly from the various configurations of the computer-implemented method for dose estimation according to the improved concept, the method for parameter setting according to the improved concept, and the method for imaging the object according to the improved concept, and vice versa. In particular, the irradiation device according to the improved concept can be configured or programmed to perform a method according to the improved concept, or it can perform such a method.

[0059] According to the improved concept, a first computer program containing first instructions is also specified. When the first instructions are executed by a computer system, in particular by a dose estimation arrangement according to the improved concept, for example by the arithmetic unit of the arrangement, the first instructions cause the computer system to perform a computer-implemented dose estimation procedure according to the improved concept or a parameter setting procedure according to the improved concept.

[0060] According to the improved concept, a second computer program with second instructions is also specified. When the second instructions are executed by an irradiation device according to the improved concept, in particular by the processing unit of the irradiation device, the second instructions cause the irradiation device to perform a computer-implemented method for dose estimation according to the improved concept, or a method for parameter setting according to the improved concept, or a method for imaging an object according to the improved concept.

[0061] According to the improved concept, a computer-readable storage medium is also specified. This computer-readable storage medium stores a first and / or a second computer program according to the improved concept.

[0062] The computer programs and the computer-readable storage medium according to the improved concept can each be understood as computer program products containing the first and second instructions, respectively.

[0063] The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the figure description and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations without departing from the scope of the invention. Embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim and / or that go beyond or deviate from the combinations of features set out in the cross-references of the claims are also to be considered disclosed.

[0064] The figures show Fig. 1 a schematic block diagram of an exemplary embodiment of an irradiation device according to the improved concept; and Fig. 2 a flowchart of an exemplary embodiment of a computer-implemented method for dose estimation according to the improved concept.

[0065] In Fig. Figure 1 shows a block representation of an exemplary embodiment of an irradiation device 1 for irradiating an object 5.

[0066] The irradiation device 1 comprises an exemplary embodiment of an arrangement 2 for dose estimation for the irradiation of the object 5 with ionizing radiation. The arrangement 2 for dose estimation includes a computing unit 3 and a storage element 4, which is coupled to or encompassed by the computing unit 3.

[0067] The irradiation device 1 also includes a control unit 6 and a radiation source 7, for example, an X-ray source. Furthermore, the irradiation device 1 may include a detector 8 for detecting ionizing radiation generated by the radiation source 7 and at least partially passing through the object 5. The irradiation device 1 is shown here, purely by way of example and without limitation, in Fig. Figure 1 is shown as a C-arm device. Depending on the specific design of the irradiation device 1 and the type of radiation used, the construction of the irradiation device 1 may also differ.

[0068] The control unit 6 is coupled to the radiation source 7 to control it. The control unit 6 is also coupled to the processing unit 3. The detector 8 can be coupled to the processing unit 3 and / or the control unit 6.

[0069] Storage element 4 contains a discrete three-dimensional model, for example a voxel model, which approximately describes object 5 or a part of object 5. The three-dimensional model may be based, for example, on a previous recording of the same object, or it may be based on a statistical model that may have been adjusted to the object in terms of size and shape, or it may be based on a generic model.

[0070] The operation of an irradiation device 1, as described in Fig. As shown in 1, the following will be discussed with reference to Fig. 2 explained in more detail using exemplary embodiments of methods according to the improved concept.

[0071] In Fig. Figure 2 shows a flowchart of an exemplary embodiment of a computer-implemented method for dose estimation according to the improved concept.

[0072] In step S1, the model for object 5 is provided on storage element 4. The model approximates object 5, or a part of object 5, using a total of 9 spatial elements or voxels, where storage element 4 stores a material composition of object 5 for each of the 9 spatial elements. The material composition is homogeneous within each spatial element.

[0073] In step S2, for a connected neighborhood 10 of room elements, a neighborhood material composition is determined based on the model, in particular based on the material compositions of the individual room elements, which is the same for all room elements of the neighborhood 10.

[0074] In other words, the neighborhood 10 is treated like an artificially enlarged spatial element 10' with a homogeneous effective material composition, namely the neighborhood material composition.

[0075] In step S3, a radiation dose value for ionizing radiation is simulated for neighborhood 10. This simulation can be based, for example, on a Monte Carlo simulation or a finite element simulation.

[0076] Based on the simulated radiation dose for neighborhood 10 and, if applicable, based on correspondingly simulated radiation doses for further neighborhoods of the total number 9 of room elements, a dose distribution is determined for object 5 or for the total number 9 of room elements.

[0077] In particular, as described in steps S2 and S3, all room elements of the total number 9 room elements can be assigned to corresponding neighborhoods and corresponding radiation doses can be simulated.

[0078] In step S3, for example, a fluence is determined for neighborhood 10 and for all other neighborhoods based on the respective simulated radiation dose. For this purpose, it is assumed, for example, that an equilibrium of charged particles exists and that the radiation dose for neighborhood 10 is therefore directly proportional to the fluence.

[0079] In step S4, for example, an interpolation, such as a nearest-neighbor interpolation, is performed for each of the neighborhoods 10 to formally restore the original resolution. Specifically, each spatial element of a neighborhood 10 is assigned a corresponding fluence depending on the fluence determined for the entire neighborhood 10. For example, every spatial element within a neighborhood 10 can be assigned the same fluence.

[0080] In step S5, a smoothing filter algorithm is applied to all spatial elements or the influences assigned by interpolation. In particular, an edge-preserving smoothing filter algorithm, such as a guided filter algorithm, is used.

[0081] The smoothing filter algorithm now yields a fluence distribution across all nine room elements. Based on the approximately direct proportional relationship between fluence and radiation dose mentioned above, the dose distribution for all nine room elements can therefore be directly determined from the fluence distribution.

[0082] The dose distribution thus determined can, for example, be compared with a target distribution or a maximum value for the dose, and corresponding parameters for the ionizing radiation can be adjusted, for example automatically by the control unit 6 or the computing unit 3, in order to meet the target specifications.

[0083] Then the control unit 6 can control the radiation source 7 to direct the ionizing radiation accordingly towards the object 5 in order to irradiate it.

[0084] As described in particular with regard to the figures, the improved concept makes it possible to determine a reliable estimate of the radiation dose distribution when an object is irradiated with ionizing radiation with reduced computational effort and reduced variances.

Claims

[1] Computer-implemented method for dose estimation for the irradiation of an object (5) with ionizing radiation, wherein a three-dimensional model with a total number (9) of spatial elements is provided on a storage element (4), wherein the model specifies a material composition of the object (5) for each spatial element, and by means of a computing unit (3) - for a connected neighborhood (10) of spatial elements of the total number (9) of spatial elements, depending on the respective material compositions of all spatial elements of the neighborhood of the model, a neighborhood material composition is determined by averaging or homogeneously approximating one or more material parameters of the respective material compositions; - a radiation dose for the neighborhood (10) with respect to ionizing radiation is determined by means of a simulation depending on the neighborhood material composition; and - a dose distribution for the object (5) with respect to ionizing radiation is determined based on the radiation dose for the neighborhood (10). [2] Computer-implemented method according to claim 1, wherein by means of the computing unit (3) - depending on the radiation dose, a fluence for the neighborhood (10) with respect to ionizing radiation is determined; and - the dose distribution for the object (5) is determined depending on the fluence. [3] Computer-implemented method according to any of the preceding claims, wherein the computing unit (3) - for a large number of further interconnected neighborhoods (10) of spatial elements of the total number (9) of spatial elements, a neighborhood material composition is determined depending on the model; - for each of the further neighborhoods (10), a further radiation dose with respect to ionizing radiation is determined by means of a simulation depending on the neighborhood material composition of the respective further neighborhood (10); and - the dose distribution for the object (5) is determined based on the further radiation doses for the further neighborhoods (10). [4] Computer-implemented method according to claim 3, wherein a smoothing filter algorithm is executed by means of the computing unit (3) depending on the radiation dose and the further radiation doses in order to determine the dose distribution for the object (5). [5] Computer-implemented method according to claim 4, wherein the smoothing filter algorithm comprises a guided filter algorithm or a Perona-Malik filter algorithm or a Savitzky-Golay filter algorithm or a bilateral filter algorithm. [6] Computer-implemented method according to one of claims 4 or 5, wherein an interpolation algorithm is performed by means of the computing unit (3) depending on the radiation dose and the further radiation doses and the smoothing filter algorithm is carried out based on a result of the interpolation algorithm. [7] Computer-implemented method according to one of the preceding claims, wherein the simulation for determining the radiation dose includes a Monte Carlo simulation or a finite difference simulation. [8] Method for setting parameters for irradiating an object (5), wherein - a predefined first parameter set for ionizing radiation is specified, - based on the first set of parameters, a method for dose estimation according to one of the preceding claims is carried out; and - to determine a second set of parameters for ionizing radiation, depending on the dose distribution determined based on the first set of parameters using the dose estimation method. [9] Method for mapping an object (5) wherein - a method according to claim 8 is carried out; and - the object (5) is irradiated with ionizing radiation according to the second set of parameters in order to image the object (5). [10] A device for estimating the dose of an object (5) being irradiated with ionizing radiation, the device (2) comprising a storage element (4) which stores a three-dimensional model with a total number (9) of spatial elements, wherein the model specifies for each spatial element a material composition of the object (5), wherein the device (2) comprises a computing unit (3) which is configured to - to determine a neighborhood material composition for a connected neighborhood (10) of spatial elements of the total number (9) of spatial elements depending on the respective material compositions of all spatial elements of the neighborhood of the model by averaging or homogeneously approximating one or more material parameters of the respective material compositions; - to determine a radiation dose for the neighborhood (10) with respect to ionizing radiation by means of a simulation depending on the neighborhood material composition; and - to determine a dose distribution for the object (5) with respect to ionizing radiation based on the radiation dose for the neighborhood (10). [11] Irradiation device for irradiating an object (5), wherein the irradiation device (1) - an arrangement (2) according to claim 10; and - contains a control unit (6) which is configured to determine a parameter set for ionizing radiation for irradiating the object (5) depending on the dose distribution for the object (5). [12] Irradiation device according to claim 11, comprising a radiation source (7) and the control unit (6) being configured to control the radiation source (7) to emit the ionizing radiation according to the specified set of parameters. [13] Irradiation device according to claim 12, wherein the radiation source (7) is designed as an X-ray source. [14] Computer program product comprising instructions which, when executed by a computer system, cause the computer system to perform a method according to any one of claims 1 to 9 [15] computer program product comprising instructions which, when executed by an irradiation device (1) according to any one of claims 11 to 13, cause the irradiation device (1) to carry out a method according to any one of claims 1 to 9.

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