Radiation dose rate assessment method, device, storage medium and equipment in three-dimensional space

Abstract

The present application discloses a radiation dose rate assessment method, device, storage medium and equipment in three-dimensional space, which belongs to the field of radiation detection technology. The concentration data and physical parameter data of the radioactive nuclide at least one first position point in the three-dimensional space are obtained; the three-dimensional convolution of the photon flux rate of the second position point is determined, and its final kernel function is the kernel function composed of the interpolation basis functions of the first position point and the second position point obtained by approximating the original kernel function according to the FMM; the concentration data and the physical parameter data are convoluted using the three-dimensional convolution to obtain the target photon flux rate; the radiation dose rate in the three-dimensional space is assessed based on the physical parameter data and the target photon flux rate. The present application can quickly calculate the radiation dose rate of continuous and arbitrary discrete positions, reducing the computational complexity and computational cost; it can assess the radiation dose rate of complex building scenes based on the shielding matrix, and accelerate the dose calculation and improve the calculation accuracy through the nested grid FMM.

Description

Technical Field

[0001] The present application relates to the field of radiation detection technology, and in particular to a method, device, storage medium and equipment for evaluating radiation dose rate in three-dimensional space. Background Art

[0002] Rapid and accurate gamma dose rate assessment at any three-dimensional point is crucial for radiological environmental impact assessment and nuclear emergency planning zone (EPZ) optimization.

[0003] Because the mean free path of gamma rays in air is very high, the three-dimensional integration volume is significantly increased, resulting in very high computational costs. Consequently, numerous studies have been conducted both domestically and internationally to develop fast and efficient methods for dose rate calculation. For example, in 1968, Healy and Baker proposed the semi-infinite cloud method, which assumes a uniform distribution of radionuclides and relies on the concentration distribution for the calculation of the radiation dose rate. In 2004, Wang et al. proposed a new finite element method (5 / μ method). This method calculates the external exposure dose on a specially constructed three-dimensional cylindrical space, with the ground center being the receptor location and the ground radius and height being five times the mean free path of the gamma photons. The three-dimensional space is then divided into many grid cells for integration to calculate the external exposure dose (or dose rate). In 2010, Andronopoulos and Bartzis proposed the hypothetical Gaussian plume method, and in 1995, Han et al. proposed the spherical approximation method, both of which accelerate radiation dose rate calculations through dimensionality reduction. The hypothetical Gaussian plume method converts the three-dimensional integral into a one-dimensional integral by performing a coordinate transformation on each model puff and using a separation of variables technique. The resulting one-dimensional integral precomputes and stores a series of parameter values ​​covering the photon energy, puff size, and distance ranges encountered in atmospheric diffusion scenarios. During the computation, the model interpolates these stored values ​​to obtain the exact value. The spherical approximation method replaces the spatial composition of the radioactive material distribution with a sphere of equal volume instead of a regular hexahedron. In 2014, Pecha proposed a specific modification of the classical Gaussian plume model to approximate near-field diffusion problems. Specifically, the accidental radioactive release process is subdivided into consecutive one-hour Gaussian segments, each driven by the corresponding hourly short-term meteorological forecast. The determination of the photon flux rate irradiating the ambient cloud is coupled with the decomposition of the Gaussian plume shape into an equivalent virtual elliptical disk. This method simplifies the previously time-consuming three-dimensional integral calculation and facilitates computational acceleration at the local scale. Pecha also proposed a tabular factor method, which precomputes and stores key parameters to rapidly estimate the external radiation dose of radioactive clouds. Specifically, the method first precalculates parameters such as the linear attenuation coefficient, mass attenuation coefficient, and build factor for different photon energies and stores these parameters in a table. In practice, the required physical coefficients are interpolated from the pre-stored table based on the photon energy emitted by the nuclide. In 2018, Zhang et al. proposed a ground radiation calculation scheme based on the point kernel method, which takes into account both the spatial distribution of deposition and the characteristics of the air and soil layers. Two sets of "detector-centered" grids were proposed, and the deposition and radiation calculations were optimized to better simulate the results measured by the detector.In 2019, Li et al. proposed a convolution method based on fast Fourier transforms (FFTs), which can quickly and accurately calculate three-dimensional radiation dose rates while ensuring accuracy and versatility. This method redefines the three-dimensional integral in gamma dose rate calculations as a three-dimensional convolution problem and uses FFTs to reduce computational costs by several orders of magnitude. In 2020, Fang et al. proposed a method for accelerating the calculation of three-dimensional integrals based on non-uniform FFTs. This method divides the three-dimensional integral in gamma dose rate calculations into two parts: a correction term near the origin of a three-dimensional convolution kernel with a regularized smoothing function. The former uses non-uniform FFTs to accelerate the calculation, while the latter is calculated directly.

[0004] Traditional radiation dose rate calculation methods mostly focus on the calculation of one-dimensional / two-dimensional ground dose rates. They improve computational efficiency by sacrificing accuracy and versatility, and these methods cannot accurately evaluate three-dimensional dose rate fields. Although the convolution method based on Fourier transform can accurately calculate three-dimensional radiation dose rates while ensuring accuracy and versatility, this method can only be applied to calculations on equidistant grids. The method of accelerating three-dimensional integral calculations using non-uniform Fourier transform can realize the calculation of three-dimensional dose rates on non-equidistant grids, but it requires more computing time. In addition, these two methods are not flexible in calculating dose rates at discrete locations and require interpolation at specific locations, which leads to low computational efficiency and very high computational cost during EPZ iterative optimization. Summary of the Invention

[0005] This application provides a method, apparatus, storage medium, and device for assessing radiation dose rate in three-dimensional space, which are used to address the problems of low computational efficiency and high computational cost when performing three-dimensional integration based on fast Fourier transform or non-uniform fast Fourier transform. The technical solution is as follows:

[0006] According to a first aspect of the present application, a method for evaluating radiation dose rate in three-dimensional space is provided, the method comprising:

[0007] Acquiring concentration data and physical parameter data of a radionuclide at at least one first location in a three-dimensional space;

[0008] Determine a three-dimensional convolution of a photon flux rate at a second location point, wherein the photon flux rate is the sum of photon flux rates of gamma rays passing through the second location point, the second location point is an arbitrary location point in the three-dimensional space, and a final kernel function in the three-dimensional convolution is a kernel function composed of interpolation basis functions of the first location point and interpolation basis functions of the second location point, obtained by approximating the original kernel function in the three-dimensional convolution according to a fast multipole algorithm (FMM);

[0009] Performing convolution calculation on the concentration data and the physical parameter data using the three-dimensional convolution to obtain a corresponding target photon flux rate;

[0010] A radiation dose rate in the three-dimensional space is estimated based on the physical parameter data and the target photon flux rate.

[0011] In one possible implementation, the three-dimensional convolution of the photon flux rate is ;

[0012] in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function, express The interpolation nodes used, express The corresponding interpolation basis function, Represents the concentration data of any radionuclide.

[0013] In a possible implementation, performing convolution calculation on the concentration data and the physical parameter data using the three-dimensional convolution to obtain a corresponding target photon flux rate includes:

[0014] If there is a building in the three-dimensional space, each face of the building is divided into non-coplanar triangles;

[0015] Calculating the intersection of the triangle and the gamma ray;

[0016] Calculating the length of the gamma ray passing through the concrete structure of the building according to the intersection condition;

[0017] Performing interpolation calculation based on the length to obtain a shielding matrix corresponding to the building, wherein the shielding matrix represents a combination of shielding factors of all first position points relative to second position points;

[0018] The concentration data, the physical parameter data and the shielding matrix are convoluted using the three-dimensional convolution to obtain a corresponding target photon flux rate.

[0019] In a possible implementation, the method further includes:

[0020] When there are multiple second location points in the three-dimensional space, dividing each second location point into different types of grids according to the distance between the second location point and the building;

[0021] For each grid, the shielding matrix corresponding to the center position point of the grid is determined as the shielding matrix corresponding to each second position point in the grid.

[0022] In one possible implementation, the three-dimensional convolution of the photon flux rate is ;

[0023] in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, represents the shielding matrix, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function, express The interpolation nodes used, express The corresponding interpolation basis function is, Represents the concentration data of any radionuclide.

[0024] In a possible implementation, the formula for calculating the length of the gamma ray passing through the concrete structure of the building is: , , ;

[0025] in, , , , , , , , , , , represents a triangle intersecting the first surface of the building when the gamma ray enters the first surface, represents the triangle that intersects the second surface of the building when the gamma ray is emitted from the second surface of the building, Indicates the first position point, The direction vector of the gamma ray.

[0026] In one possible implementation, the evaluation formula for the radiation dose rate in the three-dimensional space is: ;

[0027] in, represents the photon flux rate, Indicates the energy of gamma rays function, and , It represents the ratio of effective dose to absorbed dose in air, A represents the conversion coefficient, represents the linear energy absorption coefficient, represents the air density, Indicates the radionuclide n at a specific energy The branch ratio below.

[0028] According to a second aspect of the present application, a device for evaluating radiation dose rate in three-dimensional space is provided, the device comprising:

[0029] a data acquisition module, configured to acquire concentration data and physical parameter data of radioactive nuclides at at least one first position point in a three-dimensional space;

[0030] a convolution determination module, configured to determine a three-dimensional convolution of a photon flux rate at a second location point, wherein the photon flux rate is the sum of the photon flux rates of gamma rays passing through the second location point, the second location point is an arbitrary location point in the three-dimensional space, and a final kernel function in the three-dimensional convolution is a kernel function composed of an interpolation basis function of the first location point and an interpolation basis function of the second location point, obtained by approximating the original kernel function in the three-dimensional convolution according to a fast multipole algorithm (FMM);

[0031] an accelerated calculation module, configured to perform convolution calculation on the concentration data and the physical parameter data using the three-dimensional convolution to obtain a corresponding target photon flux rate;

[0032] A result evaluation module is used to evaluate the radiation dose rate in the three-dimensional space according to the physical parameter data and the target photon flux rate.

[0033] According to a third aspect of the present application, a computer-readable storage medium is provided, wherein the storage medium stores at least one instruction, and the at least one instruction is loaded and executed by a processor to implement the radiation dose rate assessment method in three-dimensional space as described above.

[0034] According to a fourth aspect of the present application, a computer device is provided, comprising the above-mentioned radiation dose rate evaluation device in three-dimensional space.

[0035] The beneficial effects of the technical solution provided by this application include at least:

[0036] By approximating the original kernel function in the three-dimensional convolution according to the FMM, the final kernel function consisting of the interpolation basis function of the first position point and the interpolation basis function of the second position point is obtained; then, the three-dimensional convolution is used to convolve the concentration data and the physical parameter data to obtain the corresponding target photon flux rate; finally, the radiation dose rate in the three-dimensional space is evaluated based on the physical parameter data and the target photon flux rate. It is possible to evaluate the radiation dose rate at continuous positions and arbitrary discrete positions, and the computational complexity is O(N), thereby improving computational efficiency and reducing computational cost.

[0037] By calculating the shielding matrix corresponding to the building and evaluating the radiation dose rate in three-dimensional space based on the shielding matrix, the radiation dose rate in the building scene can be quickly calculated and the calculation accuracy can be improved.

[0038] By dividing each second position point into different types of grids according to the distance between them and the building; for each grid, the shielding matrix corresponding to the central position point of the grid is determined as the shielding matrix corresponding to each second position point in the grid. In this way, multiple second position points in the same grid can share the same shielding matrix through nested grid FMM, which can speed up the calculation compared to calculating a shielding matrix for each second position point. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0040] Figure 1 This is a core process diagram of an FMM shown in this application;

[0041] Figure 2 This is a flow chart of a method for evaluating radiation dose rate in three-dimensional space provided by one embodiment of the present application;

[0042] Figure 3 This is a flow chart of a method for evaluating radiation dose rate in three-dimensional space provided by one embodiment of the present application;

[0043] Figure 4 This is a structural block diagram of a radiation dose rate assessment device in three-dimensional space provided by one embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0045] like Figure 1 As shown, the core process of the Fast Multipole Method (FMM) can be simply summarized into three parts: the aggregation, transfer, and divergence of particle forces in space. For different particle clusters in a remote region, the forces are first aggregated to multipole expansion points through multipole expansion, a process involving the Point to Multipole (P2M) theorem. For multipole expansion points at different levels, higher-level multipole expansion points are further aggregated toward lower-level multipole expansion points, a process involving the Multipole to Multipole (M2M) transfer theorem. The aggregated forces are then transferred to nearby points near the target point, a process involving the Multipole to Local (M2L) theorem. Finally, the nearby points distribute the forces to each target point, a process involving the Local to Point (L2P) transfer theorem.

[0046] In three-dimensional space, at the second position At , the evaluation formula for the gamma ray radiation dose rate contributed by all incident photons of different energies can be expressed as:

[0047] ; (1)

[0048] in, represents the photon flux rate, which takes into account the photons emitted from different positions, Indicates the energy of gamma rays The function of , its calculation formula can be expressed as:

[0049] (2)

[0050] in, It represents the ratio of effective dose to absorbed dose in air, A represents the conversion coefficient, represents the linear energy absorption coefficient, represents the air density, Indicates the radionuclide n at a specific energy Optional, A=1.6×10 -13 , =1.293.

[0051] In formula (1), the photon flux rate is the most time-consuming part of the radiation dose rate because it requires a three-dimensional integral operation for each second position point. The three-dimensional convolution of the monoenergetic photon flux rate is as follows:

[0052] (3)

[0053] in, represents the concentration data of any radionuclide, represents the accumulation factor of scattered photons, represents the linear attenuation coefficient of air, which is related to the energy of the photon; Indicates the second position point With the first position point The Euclidean distance between .

[0054] The accumulation factor is affected by three factors: photon energy, distance, and linear attenuation coefficient. In practical applications, there are many different forms of expression. This application mainly uses the linear form of the accumulation factor ,in, .

[0055] Given a specific photon energy , since the air density is constant, the linear attenuation is also a constant, and the right side of Equation (3) is essentially just and Therefore, formula (3) can be reformulated as:

[0056] (4)

[0057] Among them, the kernel function .

[0058] When the number of second locations and radionuclides is large, directly using Equation (4) is time-consuming. To improve computational efficiency, it is valuable to use a low-order approximation method using kernel functions. This concept forms the theoretical basis of FMM. This application uses the FMM algorithm and corresponding code to accelerate the computation.

[0059] According to FMM, the kernel function in formula (4) can be approximated as:

[0060] (5)

[0061] in, express The interpolation basis function, express The interpolation basis functions of .

[0062] Substituting formula (5) into formula (4) yields:

[0063] (6)

[0064] The above calculation framework can be summarized into the following two parts:

[0065] 1. Use basis functions Transform the first position:

[0066] (7)

[0067] 2. Use basis functions at each second position point calculate :

[0068] (8)

[0069] Among them, the computational complexity of formula (7) and (8) is O(nN), so the computational complexity of the above algorithm is O(2nN). When the condition is met When , the above algorithm can greatly reduce the computational complexity compared with the three-dimensional integration method.

[0070] The low-rank approximation of the matrix can be achieved by interpolation method. Specifically, for a continuous function defined on a closed interval , which can be expressed using a polynomial approximation containing n interpolation nodes:

[0071] (9)

[0072] in, express The interpolation nodes used, express The corresponding interpolation basis functions.

[0073] In FMM, by changing the parameters in the kernel function Fixed and treated as a variable function, and then use the matrix low rank approximation to optimize the calculation process:

[0074] (10)

[0075] Then, the interpolation calculation is applied to the variable , formula (10) can be expressed as:

[0076] (11)

[0077] Comparing formula (11) with formula (5), , .

[0078] Substituting formula (11) as the final kernel function into the three-dimensional convolution of the photon flux rate, we can obtain:

[0079] (12)

[0080] in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function is, express The interpolation nodes used, express The corresponding interpolation basis function is, Represents the concentration data of any radionuclide.

[0081] like Figure 2 FIG2 shows a flow chart of a method for evaluating radiation dose rate in three-dimensional space provided by an embodiment of the present application. The method for evaluating radiation dose rate in three-dimensional space can be applied to a computer device. The method for evaluating radiation dose rate in three-dimensional space can include:

[0082] Step 201: Acquire concentration data and physical parameter data of radioactive nuclides at at least one first position point in a three-dimensional space.

[0083] The first location point may also be referred to as a source point, which is a location point where radioactive nuclides are distributed in three-dimensional space.

[0084] The concentration data is obtained by simulating an atmospheric diffusion model, which may include but is not limited to any one or more of a Gaussian linear model, a Lagrangian particle model, and a Gaussian puff model.

[0085] The physical parameter data of radionuclides can be obtained by looking up tables, etc. according to the type of radionuclides. The physical parameter data may include but are not limited to: the ratio of effective dose to air absorption dose , conversion coefficient A, linear energy absorption coefficient , air density , the energy of gamma rays 、Radioactive nuclide n at a specific energy The branch ratio , linear attenuation coefficient of air Any one or more of the parameter data such as , distance, etc.

[0086] Step 202: determine the three-dimensional convolution of the photon flux rate at the second position point, where the photon flux rate is the sum of the photon flux rates of gamma rays passing through the second position point, the second position point is an arbitrary position point in the three-dimensional space, and the final kernel function in the three-dimensional convolution is a kernel function composed of the interpolation basis function of the first position point and the interpolation basis function of the second position point, obtained by approximating the original kernel function in the three-dimensional convolution according to FMM.

[0087] The second location point may also be referred to as a field point, which is a location point where the radiation dose rate is to be measured.

[0088] The three-dimensional convolution of the photon flux rate is shown in formula (12).

[0089] Step 203: Perform convolution calculation on the concentration data and the physical parameter data using three-dimensional convolution to obtain the corresponding target photon flux rate.

[0090] The target photon flux rate is the sum of the photon flux rates of the gamma rays passing through the second position, and the photon flux rate takes into account the contributions of radionuclides at different positions in the air.

[0091] Specifically, the concentration data and physical parameter data can be brought into formula (12) for calculation to obtain the corresponding target photon flux rate.

[0092] Step 204 : Evaluate the radiation dose rate in the three-dimensional space based on the physical parameter data and the target photon flux rate.

[0093] Specifically, the physical parameter data and the target photon flux rate can be substituted into formula (1) for calculation to obtain the radiation dose rate in three-dimensional space.

[0094] In summary, the radiation dose rate assessment method in three-dimensional space provided by the embodiment of the present application performs an approximate transformation of the original kernel function in the three-dimensional convolution according to the FMM to obtain a final kernel function composed of the interpolation basis function of the first position point and the interpolation basis function of the second position point; then, the three-dimensional convolution is used to perform convolution calculation on the concentration data and the physical parameter data to obtain the corresponding target photon flux rate; finally, the radiation dose rate in the three-dimensional space is evaluated based on the physical parameter data and the target photon flux rate, which can realize the evaluation of the radiation dose rate at continuous positions and arbitrary discrete positions, and the computational complexity is O(N), thereby improving computational efficiency and reducing computational cost.

[0095] like Figure 3 FIG2 shows a flow chart of a method for evaluating radiation dose rate in three-dimensional space provided by an embodiment of the present application. The method for evaluating radiation dose rate in three-dimensional space can be applied to computer equipment. The method for evaluating radiation dose rate in three-dimensional space can include:

[0096] Step 301: Acquire concentration data and physical parameter data of radioactive nuclides at at least one first position point in a three-dimensional space.

[0097] The first location point may also be referred to as a source point, which is a location point where radioactive nuclides are distributed in three-dimensional space.

[0098] The concentration data is obtained by simulating an atmospheric diffusion model, which may include but is not limited to any one or more of a Gaussian linear model, a Lagrangian particle model, and a Gaussian puff model.

[0099] The physical parameter data of radionuclides can be obtained by looking up tables, etc. according to the type of radionuclides. The physical parameter data may include but are not limited to: the ratio of effective dose to air absorption dose , conversion coefficient A, linear energy absorption coefficient , air density , the energy of gamma rays 、Radioactive nuclide n at a specific energy The branch ratio , linear attenuation coefficient of air Any one or more of the parameter data such as , distance, etc.

[0100] Step 302: determine the three-dimensional convolution of the photon flux rate at the second position point, where the photon flux rate is the sum of the photon flux rates of gamma rays passing through the second position point, the second position point is an arbitrary position point in the three-dimensional space, and the final kernel function in the three-dimensional convolution is a kernel function composed of the interpolation basis function of the first position point and the interpolation basis function of the second position point, obtained by approximating the original kernel function in the three-dimensional convolution according to FMM.

[0101] The second location point may also be referred to as a field point, which is a location point where the radiation dose rate is to be measured.

[0102] The three-dimensional convolution of the photon flux rate is shown in formula (12).

[0103] Step 303: Perform convolution calculation on the concentration data and the physical parameter data using three-dimensional convolution to obtain the corresponding target photon flux rate.

[0104] If there are no buildings in the three-dimensional space, the three-dimensional convolution of the photon flux rate is ;

[0105] in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function, express The interpolation nodes used, express The corresponding interpolation basis function, Represents the concentration data of any radionuclide.

[0106] Specifically, the concentration data and physical parameter data can be brought into the above formula for calculation to obtain the corresponding target photon flux rate.

[0107] If there are buildings in the three-dimensional space, the shielding effect of the buildings on gamma rays also needs to be considered, and steps 304 to 307 are executed to calculate the target photon flux rate.

[0108] Step 304: If there is a building in the three-dimensional space, each face of the building is divided into non-coplanar triangles.

[0109] We can introduce the shielding matrix into Equation (4) , then the three-dimensional convolution of the photon flux rate can be expressed as:

[0110] (13)

[0111] in, Represents the shielding matrix, representing all first position points Relative to the second position Shielding factor Therefore, formula (13) can also be expressed as:

[0112] (14)

[0113] According to the references, the shielding factor is calculated by Length through the building's concrete structure To achieve this, each face of the building is first divided into non-coplanar triangles; then, the triangles are interpolated with the gamma ray Calculate the length by the intersection of , the detailed process is as follows:

[0114] ray It can be expressed as:

[0115] (15)

[0116] in, Indicates the first position point, Represents the direction vector of the gamma ray, the point inside the triangle It can be expressed as:

[0117] (16)

[0118] in, 、 、 are the coordinates of the three vertices of the triangle, 、 is the coordinate of the center of the triangle, and satisfies , , .

[0119] Step 305 , calculating the intersection between the triangle and the gamma ray, and calculating the length of the gamma ray passing through the concrete structure of the building based on the intersection.

[0120] If the gamma ray intersects the triangle, then according to formulas (15) and (16) we can obtain:

[0121] (17)

[0122] Convert the above formula into matrix form:

[0123] (18)

[0124] make , , , and using Kramer's theorem for formula (18), formula (18) can be expressed as:

[0125] (19)

[0126] make , , formula (19) can be expressed as:

[0127] (20)

[0128] For a gamma ray passing through a building, it will intersect with two triangles corresponding to different surfaces in the building. Suppose these two triangles are and , for passing through The gamma ray, the t value is:

[0129] (twenty one)

[0130] in, , , , , .

[0131] For passing through The gamma ray, the t value is:

[0132] (twenty two)

[0133] in, , , , , .

[0134] Combining formula (21) and formula (22), we can get The length is:

[0135] (twenty three)

[0136] In calculating length When , it is assumed that the building is hollow and The maximum length is 50 cm, which is the thickness of two layers of concrete exterior walls.

[0137] Step 306 : Perform interpolation calculation based on the length to obtain a shielding matrix corresponding to the building. The shielding matrix represents a combination of shielding factors of all first position points relative to the second position points.

[0138] When faced with scenes with multiple buildings, a separate shielding matrix needs to be calculated for each second position point, which leads to computational inefficiency. To address this issue, we introduce a hierarchical network to implement nested grid FMM.

[0139] Specifically, when there are multiple second position points in the three-dimensional space, each second position point is divided into different types of grids according to the distance between the second position point and the building; for each grid, the shielding matrix corresponding to the center position point of the grid is determined as the shielding matrix corresponding to each second position point in the grid.

[0140] We can divide the calculation area into grids of different resolutions. The grid division method can be set according to actual needs and is not limited here.

[0141] In one example, we can divide the computational domain into three grids of different resolutions: fine, medium, and coarse.

[0142] 1) The fine grid is the area immediately adjacent to buildings where accurate calculation of shielding effects is crucial.

[0143] 2) Medium grids are areas close to buildings but not directly adjacent.

[0144] 3) The coarse grid is the area away from buildings, where the shielding effect is not so significant.

[0145] For each grid, the shielding matrix corresponding to the center position point of the grid can be calculated, and the shielding matrix can be determined as the shielding matrix corresponding to each second position point in the grid. The nested grid FMM can be used to make multiple second position points in the same grid share the same shielding matrix, which can speed up the calculation compared to calculating a shielding matrix for each second position point.

[0146] Step 307 : Perform convolution calculation on the concentration data, the physical parameter data, and the shielding matrix using three-dimensional convolution to obtain the corresponding target photon flux.

[0147] In this embodiment, the three-dimensional convolution of the photon flux rate is ;

[0148] in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, represents the shielding matrix, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function, express The interpolation nodes used, express The corresponding interpolation basis function, Represents the concentration data of any radionuclide.

[0149] Specifically, the concentration data, physical parameter data, and shielding matrix can be brought into the above formula for calculation to obtain the corresponding target photon flux rate.

[0150] Step 308 : Calculate the radiation dose rate in the three-dimensional space according to the physical parameter data and the target photon flux rate.

[0151] In this embodiment, the evaluation formula for the radiation dose rate in three-dimensional space is: ;

[0152] in, represents the photon flux rate, Indicates the energy of gamma rays function, and , It represents the ratio of effective dose to absorbed dose in air, A represents the conversion coefficient, represents the linear energy absorption coefficient, represents the air density, Indicates the radionuclide n at a specific energy The branch ratio below.

[0153] Specifically, the physical parameter data and the target photon flux rate can be brought into the above formula for calculation to obtain the radiation dose rate in three-dimensional space.

[0154] In summary, the radiation dose rate assessment method in three-dimensional space provided by the embodiment of the present application performs an approximate transformation of the original kernel function in the three-dimensional convolution according to the FMM to obtain a final kernel function composed of the interpolation basis function of the first position point and the interpolation basis function of the second position point; then, the three-dimensional convolution is used to perform convolution calculation on the concentration data and the physical parameter data to obtain the corresponding target photon flux rate; finally, the radiation dose rate in the three-dimensional space is evaluated based on the physical parameter data and the target photon flux rate, which can realize the evaluation of the radiation dose rate at continuous positions and arbitrary discrete positions, and the computational complexity is O(N), thereby improving computational efficiency and reducing computational cost.

[0155] By calculating the shielding matrix corresponding to the building and evaluating the radiation dose rate in three-dimensional space based on the shielding matrix, the radiation dose rate in the building scene can be quickly calculated and the calculation accuracy can be improved.

[0156] By dividing each second position point into different types of grids according to the distance between them and the building; for each grid, the shielding matrix corresponding to the central position point of the grid is determined as the shielding matrix corresponding to each second position point in the grid. In this way, multiple second position points in the same grid can share the same shielding matrix through nested grid FMM, which can speed up the calculation compared to calculating a shielding matrix for each second position point.

[0157] like Figure 4 FIG. 1 shows a structural block diagram of a radiation dose rate assessment device in a three-dimensional space provided by an embodiment of the present application. The radiation dose rate assessment device in a three-dimensional space can be applied to a computer device. The radiation dose rate assessment device in a three-dimensional space includes:

[0158] The data acquisition module 410 is used to acquire concentration data and physical parameter data of radioactive nuclides at at least one first position point in the three-dimensional space;

[0159] a convolution determination module 420 configured to determine a three-dimensional convolution of a photon flux rate at a second location, wherein the photon flux rate is the sum of the photon flux rates of gamma rays passing through the second location, the second location is any location in three-dimensional space, and a final kernel function in the three-dimensional convolution is a kernel function composed of an interpolation basis function of the first location and an interpolation basis function of the second location, obtained by approximating the original kernel function in the three-dimensional convolution according to the FMM;

[0160] An accelerated calculation module 430 is used to perform convolution calculation on the concentration data and the physical parameter data using three-dimensional convolution to obtain a corresponding target photon flux rate;

[0161] The result evaluation module 440 is configured to evaluate the radiation dose rate in the three-dimensional space according to the physical parameter data and the target photon flux rate.

[0162] In an optional embodiment, the three-dimensional convolution of the photon flux rate is ;

[0163] in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function is, express The interpolation nodes used, express The corresponding interpolation basis function is, Represents the concentration data of any radionuclide.

[0164] In an optional embodiment, the accelerated calculation module 430 is further configured to:

[0165] If there is a building in the three-dimensional space, each face of the building is divided into non-coplanar triangles;

[0166] Calculate the intersection of the triangle and the gamma ray;

[0167] Calculate the length of the gamma ray passing through the building's concrete structure based on the intersection;

[0168] Perform interpolation calculation based on the length to obtain the shielding matrix corresponding to the building, where the shielding matrix represents the combination of shielding factors of all first position points relative to the second position points;

[0169] The concentration data, physical parameter data and shielding matrix are convolved using three-dimensional convolution to obtain the corresponding target photon flux.

[0170] In an optional embodiment, the accelerated calculation module 430 is further configured to:

[0171] When there are multiple second location points in the three-dimensional space, each second location point is divided into different types of grids according to the distance between the second location point and the building;

[0172] For each grid, the shielding matrix corresponding to the center position point of the grid is determined as the shielding matrix corresponding to each second position point in the grid.

[0173] In an optional embodiment, the three-dimensional convolution of the photon flux rate is ;

[0174] in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, represents the shielding matrix, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function is, express The interpolation nodes used, express The corresponding interpolation basis function is, Represents the concentration data of any radionuclide.

[0175] In an optional embodiment, the formula for calculating the length of the gamma ray passing through the concrete structure of the building is: , , ;

[0176] in, , , , , , , , , , , represents the triangle that intersects the first surface when the gamma ray hits the first surface of the building. represents the triangle that intersects the second surface when the gamma ray exits from the second surface of the building. Indicates the first position point, The direction vector of the gamma ray.

[0177] In an optional embodiment, the evaluation formula for the radiation dose rate in three-dimensional space is: ;

[0178] in, represents the photon flux rate, Indicates the energy of gamma rays function, and , It represents the ratio of effective dose to absorbed dose in air, A represents the conversion coefficient, represents the linear energy absorption coefficient, represents the air density, Indicates the radionuclide n at a specific energy The branch ratio below.

[0179] In summary, the radiation dose rate assessment device in three-dimensional space provided by the embodiment of the present application obtains a final kernel function composed of the interpolation basis function of the first position point and the interpolation basis function of the second position point by approximately transforming the original kernel function in the three-dimensional convolution according to the FMM; then, the three-dimensional convolution is used to perform convolution calculation on the concentration data and the physical parameter data to obtain the corresponding target photon flux rate; finally, the radiation dose rate in the three-dimensional space is evaluated based on the physical parameter data and the target photon flux rate, which can realize the evaluation of the radiation dose rate at continuous positions and arbitrary discrete positions, and the computational complexity is O(N), thereby improving computational efficiency and reducing computational cost.

[0180] By calculating the shielding matrix corresponding to the building and evaluating the radiation dose rate in three-dimensional space based on the shielding matrix, the radiation dose rate in the building scene can be quickly calculated and the calculation accuracy can be improved.

[0181] By dividing each second position point into different types of grids according to the distance between them and the building; for each grid, the shielding matrix corresponding to the central position point of the grid is determined as the shielding matrix corresponding to each second position point in the grid. In this way, multiple second position points in the same grid can share the same shielding matrix through nested grid FMM, which can speed up the calculation compared to calculating a shielding matrix for each second position point.

[0182] One embodiment of the present application provides a computer-readable storage medium, wherein the storage medium stores at least one instruction, and the at least one instruction is loaded and executed by a processor to implement the radiation dose rate assessment method in three-dimensional space as described above.

[0183] One embodiment of the present application provides a computer device, which includes the above-mentioned radiation dose rate evaluation device in any three-dimensional space.

[0184] It should be noted that the above-described embodiment of the device for assessing radiation dose rate in three-dimensional space, when performing radiation dose rate assessment in three-dimensional space, uses only the division of the above-described functional modules as an example. In actual applications, the above-described functions can be assigned to different functional modules as needed, that is, the internal structure of the device for assessing radiation dose rate in three-dimensional space can be divided into different functional modules to complete all or part of the functions described above. In addition, the device for assessing radiation dose rate in three-dimensional space provided in the above-described embodiment and the embodiment of the method for assessing radiation dose rate in three-dimensional space are based on the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0185] Those skilled in the art will understand that all or part of the steps to implement the above embodiments may be accomplished by hardware, or by a program to instruct the relevant hardware, and the program may be stored in a computer-readable storage medium, which may be a read-only memory, a disk, or an optical disk, etc.

[0186] The above description is not intended to limit the embodiments of the present application. Any adjustments, equivalent replacements, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of the embodiments of the present application.

Claims

1. A method for evaluating radiation dose rate in three-dimensional space, characterized in that: The method comprises: Acquiring concentration data and physical parameter data of a radionuclide at at least one first location in a three-dimensional space; Determine a three-dimensional convolution of a photon flux rate at a second location point, wherein the photon flux rate is the sum of photon flux rates of gamma rays passing through the second location point, the second location point is an arbitrary location point in the three-dimensional space, and a final kernel function in the three-dimensional convolution is a kernel function composed of interpolation basis functions of the first location point and interpolation basis functions of the second location point, obtained by approximating the original kernel function in the three-dimensional convolution according to a fast multipole algorithm (FMM); Performing convolution calculation on the concentration data and the physical parameter data using the three-dimensional convolution to obtain a corresponding target photon flux rate; A radiation dose rate in the three-dimensional space is estimated based on the physical parameter data and the target photon flux rate.

2. The method for evaluating radiation dose rate in three-dimensional space according to claim 1, wherein: The three-dimensional convolution of the photon flux rate is ; in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function, express The interpolation nodes used, express The corresponding interpolation basis function, Represents the concentration data of any radionuclide.

3. The method for evaluating radiation dose rate in three-dimensional space according to claim 1, wherein: The convolution calculation of the concentration data and the physical parameter data using the three-dimensional convolution to obtain a corresponding target photon flux rate includes: If there is a building in the three-dimensional space, each face of the building is divided into non-coplanar triangles; Calculating the intersection of the triangle and the gamma ray; Calculating the length of the gamma ray passing through the concrete structure of the building according to the intersection condition; Performing interpolation calculation based on the length to obtain a shielding matrix corresponding to the building, wherein the shielding matrix represents a combination of shielding factors of all first position points relative to second position points; The concentration data, the physical parameter data and the shielding matrix are convoluted using the three-dimensional convolution to obtain a corresponding target photon flux rate.

4. The method for evaluating radiation dose rate in three-dimensional space according to claim 3, wherein: The method further comprises: When there are multiple second location points in the three-dimensional space, dividing each second location point into different types of grids according to the distance between the second location point and the building; For each grid, the shielding matrix corresponding to the center position point of the grid is determined as the shielding matrix corresponding to each second position point in the grid.

5. The method for evaluating radiation dose rate in three-dimensional space according to claim 3, wherein: The three-dimensional convolution of the photon flux rate is ; in, represents the energy of the gamma ray, Indicates the second position point, represents the photon flux rate of monoenergetic gamma rays at the second position, represents the shielding matrix, Indicates the first position point, express The interpolation nodes used, express The corresponding interpolation basis function is, express The interpolation nodes used, express The corresponding interpolation basis function is, Represents the concentration data of any radionuclide.

6. The method for evaluating radiation dose rate in three-dimensional space according to claim 3, wherein: The calculation formula for the length of the gamma ray passing through the concrete structure of the building is: , , ; in, , , , , , , , , , , 、 and represents the three vertices of a triangle intersecting the first surface of the building when the gamma ray enters the first surface, 、 and represents the three vertices of a triangle intersecting the second surface of the building when the gamma ray is emitted from the second surface of the building, Indicates the first position point, The direction vector of the gamma ray.

7. The method for evaluating radiation dose rate in three-dimensional space according to any one of claims 1 to 6, characterized in that: The evaluation formula for the radiation dose rate in the three-dimensional space is: ; in, represents the photon flux rate, Indicates the energy of gamma rays function, and , It represents the ratio of effective dose to absorbed dose in air, A represents the conversion coefficient, represents the linear energy absorption coefficient, represents the air density, Indicates the radionuclide n at a specific energy The branch ratio below.

8. A radiation dose rate assessment device in three-dimensional space, characterized in that: The device comprises: a data acquisition module, configured to acquire concentration data and physical parameter data of radioactive nuclides at at least one first position point in a three-dimensional space; a convolution determination module, configured to determine a three-dimensional convolution of a photon flux rate at a second location point, wherein the photon flux rate is the sum of the photon flux rates of gamma rays passing through the second location point, the second location point is an arbitrary location point in the three-dimensional space, and a final kernel function in the three-dimensional convolution is a kernel function composed of an interpolation basis function of the first location point and an interpolation basis function of the second location point, obtained by approximating the original kernel function in the three-dimensional convolution according to a fast multipole algorithm (FMM); an accelerated calculation module, configured to perform convolution calculation on the concentration data and the physical parameter data using the three-dimensional convolution to obtain a corresponding target photon flux rate; A result evaluation module is used to evaluate the radiation dose rate in the three-dimensional space according to the physical parameter data and the target photon flux rate.

9. A computer-readable storage medium, characterized in that The storage medium stores at least one instruction, and the at least one instruction is loaded and executed by the processor to implement the radiation dose rate assessment method in three-dimensional space according to any one of claims 1 to 7.

10. A computer device, characterized in that: The computer device includes the radiation dose rate evaluation device in three-dimensional space according to claim 8.

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