Particle source model training method and dose distribution determination method for radiotherapy system

Abstract

The present application relates to a method for training a particle source model and a method for determining a dose distribution of a radiotherapy system. The method includes: based on the input energy and a preset source model, obtaining a percentage depth calculation curve and an off-axis ratio calculation curve corresponding to the particle source; obtaining a percentage depth measurement curve, an off-axis ratio measurement curve, and an output factor measurement value of the radiotherapy system under the action of the input energy; adjusting the correlation parameters that determine the distribution of the particle source in the preset source model according to the difference between the percentage depth calculation curve and the percentage depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, until the differences are all within a preset error range; determining a correction factor of the output factor based on the output factor measurement value and the adjusted preset source model; and correcting the adjusted preset source model based on the correction factor to obtain a particle source model. Based on the adjustment lag of the output factor, the influence of the percentage depth curve and the off-axis ratio curve is avoided, and the modeling speed and accuracy are improved.

Description

Technical Field

[0001] The present application relates to the technical field of radiotherapy, and particularly to a method for training a particle source model and a method for determining a dose distribution of a radiotherapy system. Background Art

[0002] Radiotherapy is one of the important means for treating malignant tumors. During the radiotherapy process, quickly and accurately determining the dose distribution in a patient's body is a very crucial issue.

[0003] Currently, the methods for determining the dose distribution are mainly divided into the analytical method and the Monte Carlo method. The analytical method has a relatively fast calculation speed, but the calculation accuracy is poor. The Monte Carlo method can accurately simulate the transport processes of electrons and photons in the treatment head and in the patient's body, and has a higher calculation accuracy.

[0004] However, the applicant found during the implementation process that in the current implementation solutions for simulating a radiotherapy system using the Monte Carlo algorithm, different methods or source models are mostly used to simulate the radiotherapy system under photon and electron irradiation modes, which increases the modeling difficulty and reduces the modeling speed. Summary of the Invention

[0005] Based on this, in view of the above technical problems, it is necessary to provide a method for training a particle source model and a method for determining a dose distribution of a radiotherapy system under a unified photon and electron irradiation mode, which are simple in modeling and fast in modeling speed.

[0006] In a first aspect, the present application provides a method for training a particle source model of a radiotherapy system, the method comprising:

[0007] Based on the input energy and a preset source model, obtaining a percentage depth dose calculation curve and an off-axis ratio calculation curve corresponding to the particle source;

[0008] Obtaining a percentage depth dose measurement curve, an off-axis ratio measurement curve, and an output factor measurement value of the radiotherapy system under the action of the input energy;

[0009] According to the difference between the percentage depth dose calculation curve and the percentage depth dose measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, adjusting the correlation parameters that determine the distribution of the particle source in the preset source model until the differences are all within a preset error range;

[0010] Based on the output factor measurement value and the adjusted preset source model, determining a correction factor for the output factor;

[0011] Based on the correction factor, correcting the adjusted preset source model to obtain a particle source model.

[0012] In one of the embodiments, the particle source includes a primary sub-source, a secondary sub-source, and a contamination sub-source.

[0013] In one embodiment, according to the differences between the percentage depth calculation curve and the percentage depth measurement curve, and between the off-axis ratio calculation curve and the off-axis ratio measurement curve, the correlation parameters determining the distribution of the particle source in the preset source model are adjusted, including:

[0014] Based on the difference between the percentage depth calculation curve and the percentage depth measurement curve, the weight of the percentage depth curve in the preset source model is adjusted so that the difference between the percentage depth calculation curve and the percentage depth measurement curve obtained based on the adjusted preset source model is within a first preset error range.

[0015] In one embodiment, the contamination sub-source includes a contamination photon source and / or a contamination electron source. According to the differences between the percentage depth calculation curve and the percentage depth measurement curve, and between the off-axis ratio calculation curve and the off-axis ratio measurement curve, the correlation parameters determining the distribution of the particle source in the preset source model are adjusted, including:

[0016] For the case where the radiotherapy system operates in the photon irradiation mode, based on the difference between the build-up region of the percentage depth calculation curve and the build-up region of the percentage depth measurement curve, the weight and size of the contamination electron source in the preset source model are adjusted so that the difference between the build-up region of the percentage depth calculation curve and the build-up region of the percentage depth measurement curve obtained based on the adjusted preset source model is within a first preset regional error range; and / or,

[0017] For the case where the radiotherapy system operates in the electron irradiation mode, based on the difference between the contamination photon tail of the percentage depth calculation curve and the contamination photon tail of the percentage depth measurement curve, the weight and size of the contamination photon source in the preset source model are adjusted so that the difference between the contamination photon tail of the percentage depth calculation curve and the contamination photon tail of the percentage depth measurement curve obtained based on the adjusted preset source model is within a second preset regional error range.

[0018] In one embodiment, according to the differences between the percentage depth calculation curve and the percentage depth measurement curve, and between the off-axis ratio calculation curve and the off-axis ratio measurement curve, the correlation parameters determining the distribution of the particle source in the preset source model are adjusted, including:

[0019] Based on the difference between the penumbra region of the off-axis ratio calculation curve and the penumbra region of the off-axis ratio measurement curve, the size of the primary sub-source in the preset source model is adjusted so that the error between the three-dimensional dose information of the penumbra region of the off-axis ratio calculation curve and the three-dimensional dose information of the penumbra region of the off-axis ratio measurement curve obtained based on the adjusted preset source model is within a preset dose error range.

[0020] In one embodiment, according to the difference between the percentage depth calculation curve and the percentage depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, adjust the correlation parameters that determine the distribution of the particle source in the preset source model, including:

[0021] Based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, adjust the model parameters in the preset source model that determine the probability density at different off-axis positions, so that the difference between the off-axis ratio calculation curve within the radiation field obtained based on the adjusted preset source model and the off-axis ratio measurement curve within the radiation field is within a second preset error range.

[0022] In one embodiment, based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, adjust the model parameters in the preset source model that determine the probability density at different off-axis positions, including:

[0023] Based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, adjust the correlation parameters of the probability density distribution function on the first sampling plane in the preset source model; the first sampling plane is a sampling plane that can reflect the distribution of the radiation projected by the radiotherapy system under the selected irradiation mode.

[0024] In one embodiment, when the probability density distribution function is a multi-segment linear distribution function, adjust the parameters of the probability density distribution function on the first sampling plane in the preset source model, including:

[0025] Adjust the parameters of the multi-segment linear distribution function on the first sampling plane in the preset source model.

[0026] In one embodiment, according to the difference between the percentage depth calculation curve and the percentage depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, adjust the correlation parameters that determine the distribution of the particle source in the preset source model until the differences are all within the preset error range, including:

[0027] Based on the difference between the off-axis ratio calculation curve outside the radiation field and the off-axis ratio measurement curve outside the radiation field, adjust the size of the secondary sub-source in the preset source model, so that the difference between the off-axis ratio calculation curve outside the radiation field obtained based on the adjusted preset source model and the off-axis ratio measurement curve outside the radiation field is within a third preset error range.

[0028] In a second aspect, a method for determining the dose distribution of a radiotherapy system is provided, and the method includes:

[0029] Obtain the energy to be input to the radiotherapy system;

[0030] Based on the energy to be input and the particle source model of the radiotherapy system, determine the percentage depth calculation curve, the off-axis ratio calculation curve, and the output factor calculated value of the radiotherapy system;

[0031] Among them, the particle source model is generated by performing the steps of the particle source model training method of the above radiotherapy system.

[0032] The particle source model training method and dose distribution determination method of the above radiotherapy system have at least the following beneficial effects:

[0033] Based on the differences between the percentage depth dose calculation curve and off-axis ratio calculation curve obtained from the preset source model at each input energy and the actual measurement results of the radiotherapy system at the same input energy. Such differences can be understood as being caused by the distribution of each particle source not reaching the expected value. By adjusting the correlation parameters in the preset source model that determine the distribution of each particle source until the differences between the calculation curves (percentage depth dose calculation curve and off-axis ratio calculation curve) and the measurement curve are within the preset error range. At this time, the correction factor can be further determined based on the difference between the measured value of the output factor and the calculated value determined based on the adjusted preset source model. Based on this correction factor, the preset source model adjusted previously is corrected and optimized to obtain the particle source model of the radiotherapy system.

[0034] By only defining the particle source to characterize the energy distribution inside the radiotherapy system and using the differences between the calculated values and actual measured values of the percentage depth dose calculation curve and off-axis ratio calculation curve, the correlation parameters in the preset source model that determine the particle source distribution can be quickly adjusted, reducing the modeling difficulty and improving the modeling speed. Considering that the adjustment of the output factor will affect the percentage depth dose calculation curve and off-axis ratio calculation curve, therefore, the preset source model is first adjusted based on the differences between the calculated values and measured values of the percentage depth dose calculation curve and off-axis ratio calculation curve, and finally, the adjusted preset source model is further adjusted based on the correction factor of the output factor, improving the modeling speed and the accuracy of the source model of the radiotherapy system.

[0035] In addition, the probability density distribution function on the second sampling plane in the preset source model adopts a multi-segment linear distribution function, which can effectively reduce the modeling difficulty of the radiotherapy system and improve the modeling accuracy. In addition, the number of segments of the probability density can be arbitrarily given to adapt to the off-axis ratio calculation curve characteristics of accelerators from different manufacturers. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is an application environment diagram of the particle source model training method and dose distribution determination method of the radiotherapy system in an embodiment;

[0037] Figure 2 It is a schematic flowchart of the particle source model training method of the radiotherapy system in an embodiment;

[0038] Figure 3is a schematic diagram of the structure of an accelerator treatment head in one embodiment;

[0039] Figure 4 A schematic diagram of the field of view and penumbra in one embodiment;

[0040] Figure 5 is a structural block diagram of a particle source model training device for a radiotherapy system in one embodiment;

[0041] Figure 6 is a structural block diagram of a device for determining a dose distribution of a radiotherapy system in one embodiment;

[0042] Figure 7 FIG. 4 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0044] The source model training method of the radiotherapy system provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown. Among them, the radiotherapy system 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be integrated on the server 104, or it can be placed on the cloud or other network servers. The server obtains the measured data of the radiotherapy system under different input energies, including but not limited to the percentage depth measurement curve, the off-axis ratio measurement curve and the output factor measurement value. In addition, the server 104 can determine the percentage depth calculation curve and the off-axis ratio calculation curve corresponding to the particle source, the difference between the percentage depth calculation curve and the percentage depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve according to the input energy and the preset source model, and adjust the associated parameters that determine the distribution of the particle source in the preset source model until the differences are all within the preset error range, and then further correct the adjusted preset source model based on the correction factor to obtain the particle source model for subsequent dose distribution determination. When the radiotherapy system 102 is working, the energy to be input can be sent to the server 104. The server 104 can determine the dose distribution calculation curve and output factor calculation value of the radiotherapy system according to the energy to be input and the particle source model. The staff can know the parameters such as the energy, position, speed, and direction of the emitted particles in advance, providing data basis for precise radiotherapy. Among them, the radiotherapy system 102 can include equipment such as an accelerator treatment head. The server 104 can be implemented as an independent server or a server cluster composed of multiple servers.

[0045] In one embodiment, as Figure 2 shown, a method for training a particle source model of a radiotherapy system is provided. Taking the application of this method to the Figure 1 server in as an example, the method includes the following steps:

[0046] S202, based on the input energy and a preset source model, obtain the percentage depth calculation curve and the off-axis ratio calculation curve corresponding to the particle source; the particle source is used to simulate the energy change of the input energy in the radiotherapy system. The percentage depth curve, also known as the PDD (percentage depth dose) curve, refers to the percentage of the dose at any depth along the central axis of the beam to the dose at the reference depth, and is a physical quantity describing the relative dose distribution at different depths along the central axis of the ray. The off-axis ratio curve, also known as the Profile, is used to characterize the relationship between the position deviating from the central axis and the dose, and is used to describe the energy deposition characteristics in the longitudinal direction of the beam, and can reflect the flatness and symmetry of the dose distribution. The PDD reflects the longitudinal dose distribution characteristics, and the Profile reflects the lateral dose distribution characteristics. The percentage depth calculation curve and the off-axis ratio calculation curve are the theoretical results of the percentage depth curve and the off-axis ratio curve at the input energy obtained by taking this input energy as the input of the preset source model, that is, the output of the preset source model. If the output meets the constraint conditions of the preset error range with the measured percentage depth measurement curve and the off-axis ratio measurement curve, it means that the preset source model meets the expectations and can be used as the model for determining the dose distribution to determine the dose distribution of the input energy during the use of the radiotherapy system. If not, the model needs to be trained to obtain a particle source model in which the difference between the calculation result and the measured result meets the constraint of the preset error range.

[0047] S204. Obtain the percentage depth dose curve, off-axis ratio curve, and output factor measurement values of the radiotherapy system under the action of the input energy. A three-dimensional water tank system can be used to measure the central axis percentage depth dose curve of the radiotherapy system under the action of the input energy. The detector can be placed at a certain depth in the three-dimensional water tank, and then moved from one side of the water tank to the other side for dose measurement. The measured point dose is divided by the central axis dose to obtain the off-axis ratio curve at this depth. The implementation methods of the measurement are not enumerated here. The output factor, also known as the field output factor, refers to the ratio of the output dose rate of the radiation field in the phantom to the output dose rate of the reference radiation field in the phantom. The output factor measurement value can be determined according to the measurement of the output dose. For example, in one example, the source skin distance (SSD, the distance from the center of the radiation source to the center of the skin irradiation field on the body surface) is 100 cm. At a depth of 10 cm underwater, dose data of different field sizes are collected. The reference field is a 10 cm x 10 cm field. The output factors of different fields can be determined according to the dose data of different fields and the dose data of the reference field.

[0048] S206. Adjust the correlation parameters that determine the distribution of the particle source in the preset source model according to the differences between the percentage depth calculation curve and the percentage depth measurement curve, and the differences between the off-axis ratio calculation curve and the off-axis ratio measurement curve, until the differences are all within the preset error range. The difference between the upper limit value and the lower limit value of the preset error range can be set based on the accuracy requirements of the user. In one embodiment, the upper limit value and the lower limit value of the preset error range can be equal. In this case, it should be understood that the end condition of this training process is that the differences between the percentage depth calculation curve and the percentage depth measurement curve, and the differences between the off-axis ratio calculation curve and the off-axis ratio measurement curve are equal to the upper limit value (or lower limit value) of the preset error range. In one embodiment, the upper limit value and the lower limit value of the preset error range can both be 0. In this case, the calculation results and the measurement results of the percentage depth curve and the off-axis ratio curve are consistent, which is an ideal state. Of course, the user can set the preset error range according to the accuracy requirements for the determination of the dose distribution. It should be noted that the differences between the percentage depth calculation curve and the percentage depth measurement curve, and the differences between the off-axis ratio calculation curve and the off-axis ratio measurement curve being within the preset error range can mean that the difference between the percentage depth calculation curve and the percentage depth measurement curve is within the first preset error range, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve is within the second preset error range. The first preset error range and the second preset error range can be the same or different.

[0049] S208. Determine the correction factor of the output factor based on the measured value of the output factor and the adjusted preset source model. Considering that the calculation result of the correction factor will be affected when determining the correlation parameters of the percentage depth dose curve and the off-axis ratio curve in the model, the correlation parameters of the curves are first determined, and then the correction factor is calculated. The correction factor of the output factor is determined by using the measured value of the output factor and the adjusted preset source model, which is used to guide the further correction of the source model.

[0050] In one embodiment, step S208 of determining the correction factor of the output factor based on the measured value of the output factor and the adjusted preset source model includes:

[0051] Obtain the calculated value of the output factor of the radiotherapy system based on the particle source and the adjusted preset source model; at this time, the calculated value of the output factor obtained based on the adjusted preset source model can be obtained.

[0052] Determine the correction factor of the output factor based on the measured value of the output factor and the calculated value of the output factor. In one embodiment, the correction factor at a given position = measured value of the output factor / calculated value of the output factor. For example, the given position is the position at a depth of 5 cm.

[0053] S210. Correct the adjusted preset source model based on the correction factor to obtain a particle source model. Steps S202 to S208 can make the shapes of the calculated curve and the measured curve determined based on the adjusted preset source model relatively consistent. Further, by correcting the adjusted preset model with the correction factor, the absolute magnitudes between the measured value and the calculated value determined based on the obtained particle source model after correction can be made consistent.

[0054] Specifically, the energy distribution inside the radiotherapy system is characterized by only defining the particle source, and the differences between the calculated values and the actual measured values of the percentage depth dose calculation curve and the off-axis ratio calculation curve are used to quickly adjust the correlation parameters that determine the particle source distribution in the preset source model, reducing the modeling difficulty and improving the modeling speed. And the calculation result of the correction factor will be affected when determining the correlation parameters of the percentage depth dose curve and the off-axis ratio curve in the model. Therefore, first adjust the preset source model based on the differences between the calculated values and the measured values of the percentage depth dose calculation curve and the off-axis ratio calculation curve, and finally further adjust the adjusted preset source model based on the correction factor of the output factor to improve the modeling speed and the accuracy of the source model of the radiotherapy system.

[0055] In one embodiment, the particle source includes a primary sub-source, a secondary sub-source, and a contamination sub-source. By dividing the particle source into virtual primary, secondary, and contamination sub-sources, it is possible to simulate the particle source distribution of most radiotherapy systems while simplifying the model, improving the modeling speed and efficiency. For example, when the radiotherapy system operates in the electron irradiation mode, using the particle source model training method proposed in this application, compared with the traditional method that uses four to five virtual sources or even more virtual sources, the number of sub-sources can be greatly reduced without reducing the algorithm accuracy, the modeling difficulty is reduced, and the water tank curves required for modeling are reduced. At the same time, it is not necessary to read the scattering kernel data calculated for different types of collimators in advance like the electron beam algorithms in other radiotherapy systems. Therefore, the execution speed of modeling is further improved, the storage space is saved, and it is not restricted by the accelerator and collimator models of different manufacturers, expanding the scope of application.

[0056] It should be noted that the particle source model training method provided in the embodiments of this application is applicable to all radiotherapy systems with photon source and / or electron source emission functions. For example, the accelerator treatment head (as Figure 3 shown). The three sub-sources here (primary sub-source, secondary sub-source, and contamination sub-source) mean that in the source model, all accelerator treatment heads with electron source and / or photon source emission functions are approximately considered to only include three parts: primary sub-source, secondary sub-source, and contamination sub-source. For the treatment head that emits electrons, the three sub-sources include a primary electron source, a secondary electron source, and a contamination photon source; for the treatment head that emits photons, the three sub-sources include a primary photon source, a secondary photon source, and a contamination electron source.

[0057] In one embodiment, according to the differences between the percentage depth calculation curve and the percentage depth measurement curve, and the differences between the off-axis ratio calculation curve and the off-axis ratio measurement curve, the correlation parameters that determine the distribution of the particle source in the preset source model are adjusted, including:

[0058] Based on the difference between the percentage depth calculation curve and the percentage depth measurement curve, the weight of the percentage depth curve in the preset source model is adjusted so that the difference between the percentage depth calculation curve obtained based on the adjusted preset source model and the percentage depth measurement curve is within the first preset error range.

[0059] Among them, the percentage depth curve corresponding to one input energy includes multiple monoenergetic percentage depth dose curves corresponding to single energies. Adjusting the weight of the percentage depth curve in the preset source model means adjusting the weight of each single energy curve, and the adjustment of the weight can be achieved through algorithms such as the ant colony algorithm and simulated annealing. For example, the above preset source model is a neural network model, and the simulated annealing algorithm is used to update the network weights of each neuron in the network to determine the weight of the percentage depth curve.

[0060] The first preset error range can be pre-configured according to the requirements for determining the accuracy of the dose distribution. That the difference between the percentage depth calculation curve and the percentage depth measurement curve is within the first preset error range can be understood as that the differences corresponding to each point on the curve all fall within this first preset error range. At this time, it can be considered that the shapes of the percentage depth calculation curve and the percentage depth measurement curve are consistent.

[0061] In one embodiment, the contaminated sub-source includes a contaminated photon source and / or a contaminated electron source. According to the difference between the percentage depth calculation curve and the percentage depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, the correlation parameters determining the distribution of the particle source in the preset source model are adjusted, including:

[0062] For the case where the radiotherapy system operates in the photon irradiation mode, based on the difference between the build-up region of the percentage depth calculation curve and the build-up region of the percentage depth measurement curve, the weight and size of the contaminated electron source in the preset source model are adjusted so that the difference between the build-up region of the percentage depth calculation curve obtained based on the adjusted preset source model and the build-up region of the percentage depth measurement curve is within the first preset regional error range.

[0063] Among them, the build-up region refers to the region from a depth of zero to the maximum dose depth. A depth of zero can be understood as the body surface position. The build-up region is related to the secondary electron source. When X-rays irradiate the body surface, the X-rays will ionize the secondary electron source. The secondary electron source carries a certain amount of energy and will continue to move forward until all the energy is consumed, so it reaches a certain depth under the body surface. Therefore, the build-up region can characterize the energy deposition of the beam (particle source). The higher the energy of the X-rays, the lower the dose at the body surface and the deeper the depth of the maximum dose point. Therefore, by adjusting the weight and size of the contaminated sub-source in the model according to the difference between the calculated result and the measured result of the build-up region, the adjusted preset source model can accurately predict the build-up region and provide a data basis for determining the dose distribution. Similar to the explanation of the first preset error range in the above embodiment, the first preset regional error range can also be pre-configured, and the user can set this first preset regional error range according to the required dose determination accuracy. That the difference in the build-up region is within the first preset regional error range can be understood as that the shapes of the percentage depth calculation curve and the percentage depth measurement curve in the build-up region are consistent.

[0064] For the case where the radiotherapy system operates in the electron irradiation mode, based on the difference between the contaminated photon tail of the percentage depth calculation curve and the contaminated photon tail of the percentage depth measurement curve, the weight and size of the contaminated photon source in the preset source model are adjusted so that the difference between the contaminated photon tail of the percentage depth calculation curve obtained based on the adjusted preset source model and the contaminated photon tail of the percentage depth measurement curve is within the second preset regional error range.

[0065] Among them, the contaminated photon tail refers to a long low-dose bremsstrahlung "tail" (contaminated area) formed after the high-dose plateau region and the dose fall-off region on the PDD. The error range of the second preset region can also be configured in advance according to needs.

[0066] It should be noted that in the case where the radiotherapy system only supports the photon irradiation mode, the contaminated source includes the contaminated electron source. During the above model training process, only the step of adjusting the weight and size of the contaminated electron source can be executed based on the condition that the difference between the calculated result and the measured result of the PDD build-up region is within the error range of the first preset region.

[0067] For the case where the radiotherapy system only supports the electron irradiation mode, the contaminated source includes the contaminated photon source. At this time, only the step of adjusting the weight and size of the contaminated photon source can be executed based on the condition that the difference between the calculated result and the measured result of the PDD contaminated photon tail is within the error range of the second preset region.

[0068] For the case where the radiotherapy system supports both the photon irradiation mode and the electron irradiation mode, the contaminated source includes the contaminated photon source and the contaminated electron source. At this time, for the training process of the particle source model, it includes the step of adjusting the weight and size of the contaminated electron source, and also includes the step of adjusting the weight and size of the contaminated photon source. Based on this, the trained particle source model can be used to determine the dose distribution in the actual use process of the radiotherapy system in the photon irradiation mode or the electron irradiation mode.

[0069] In one embodiment, according to the difference between the percentage depth calculation curve and the percentage depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, the correlation parameters that determine the distribution of the particle source in the preset source model are adjusted, including:

[0070] Based on the difference between the penumbra region of the off-axis ratio calculation curve and the penumbra region of the off-axis ratio measurement curve, the size of the primary source in the preset source model is adjusted so that the error between the three-dimensional dose information of the penumbra region of the off-axis ratio calculation curve obtained based on the adjusted preset source model and the three-dimensional dose information of the penumbra region of the off-axis ratio measurement curve is within the preset dose error range.

[0071] The penumbra region can be understood as shown in Figure 4 If the difference between the calculated result and the measured result of the penumbra region is too large, it means that the current preset source model cannot be accurately used to determine the off-axis ratio measurement curve. At this time, by adjusting the size of the primary source in the source model, the difference between the calculated result and the measured result of the penumbra region is constrained within the preset dose error range.

[0072] In one embodiment, according to the differences between the percentage depth calculation curve and the percentage depth measurement curve, and between the off-axis ratio calculation curve and the off-axis ratio measurement curve, the correlation parameters that determine the distribution of the particle source in the preset source model are adjusted, including:

[0073] Based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, the model parameters that determine the probability density at different off-axis positions in the preset source model are adjusted, so that the difference between the off-axis ratio calculation curve within the radiation field obtained based on the adjusted preset source model and the off-axis ratio measurement curve within the radiation field is within a second preset error range.

[0074] If the difference between the calculation result and the measurement result of the off-axis ratio curve is not within the second preset error range, it indicates that the current preset source model cannot accurately reflect the distribution of particles. Based on this, the model parameters that determine the probability density at different off-axis positions in the preset source model are adjusted according to this difference. For example, the coefficients of the probability density distribution function, etc. Until the difference between the off-axis ratio calculation curve and the measurement curve determined based on the adjusted preset source model is constrained within the second preset error range.

[0075] The radiotherapy system operates in the photon or electron irradiation mode. The particle source model proposed in this application includes two sampling planes:

[0076] For the photon irradiation mode, the positions of the first sampling planes of the primary photon source, the secondary photon source, and the contaminating electron source are all located on the lower surface of the beam limiting device (multi-leaf collimator or secondary collimator) as shown in Figure 3 The second sampling plane of the primary photon source is located at the target as shown in Figure 3 The second sampling planes of the secondary photon source and the contaminating electron source are both located at the flattening filter.

[0077] For the electron irradiation mode, the first sampling planes of the primary electron source, the secondary electron source, and the contaminating photon source are located on the lower surface of the electron cone. If there is no electron cone, they are located on the lower surface of the beam limiting device. The second sampling plane of the primary electron source is located at the primary scattering foil, and the second sampling planes of the secondary electron source and the contaminating electron source are located at the secondary scattering foil.

[0078] In one embodiment, based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, the model parameters that determine the probability density at different off-axis positions in the preset source model are adjusted, including:

[0079] Based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, the correlation parameters of the probability density distribution function on the first sampling plane in the preset source model are adjusted; the first sampling plane is the sampling plane that can reflect the distribution of the radiation projected by the radiotherapy system in the selected irradiation mode.

[0080] Among them, the first sampling plane has considered radiotherapy systems such as accelerator treatment heads with different structures. Taking the accelerator treatment head as an example, the main structural differences of the accelerator treatment heads on the market currently lie in the beam limiting device, that is, the positional relationship between the secondary collimator and the multi-leaf collimator as shown in Figure 3 . At this time, the position of the first sampling plane is on the lower surface of the multi-leaf collimator. For another treatment head with the multi-leaf collimator above the secondary collimator, at this time, the lower surface position of the secondary collimator is taken as the first sampling plane. In summary, the first sampling plane can be defined as the lower surface of the beam limiting device. The first sampling plane is mainly selected according to the structure of the accelerator treatment head and the actual physical position.

[0081] If any two planes are randomly selected as the sampling planes, it may lead to inconsistent results between the model calculation and the actual measurement. Then, the positions of these two sampling planes need to be adjusted as separate parameters, increasing the complexity of modeling. The particle source model training method provided by the embodiments of the present application defines the first sampling plane as a sampling plane that can reflect the distribution of the radiation projected by the radiotherapy system. For example, the lower surface of the beam limiting device of the accelerator treatment head can directly determine the projection direction, speed and other characteristics of the emitted particles. Only the parameters of the probability density distribution function on the first sampling plane need to be adjusted, reducing unnecessary parameter adjustment and lowering the modeling difficulty.

[0082] In one embodiment, the probability density distribution function is a multi-segment linear distribution function. Adjusting the parameters of the probability density distribution function on the first sampling plane in the preset source model includes:

[0083] Adjusting the parameters of the multi-segment linear distribution function on the first sampling plane in the preset source model.

[0084] In one embodiment, adjusting the parameters of the multi-segment linear distribution function on the first sampling plane in the preset source model may include:

[0085] Adjusting at least one of the slope parameter or the intercept parameter in the following expression:

[0086]

[0087] where y(x) represents the probability density at the off-axis distance x on the first sampling plane, x represents the off-axis distance, a n represents the slope parameter of the linear distribution of the probability density when the off-axis distance is between x n-1 and x n , b n is the intercept parameter of the linear distribution of the probability density when the off-axis distance is between x n-1 and x nThe intercept parameter of the linear distribution of the probability density between them. By adjusting the probability density values at different off-axis positions in the model, the off-axis ratio calculation curve and the off-axis ratio measurement curve are made to be within the second preset error range.

[0088] At the first sampling plane and the second sampling plane, the positions (i.e., the distribution) of the particles at the first sampling plane and the second sampling plane are obtained by random sampling respectively. Then, according to the connection line of the positions of a single particle at these two planes, the direction of the particle movement is determined, and the energy of the particle is obtained by random sampling of the energy spectrum.

[0089] The probability density distribution of photons and electrons at the first sampling plane proposed in this application adopts a multi-segment linear probability density distribution form, which can reduce the modeling difficulty and improve the modeling accuracy. In addition, by adopting the multi-segment linear probability density distribution form at the first sampling plane, the number of segments of the probability density can be arbitrarily given, which can adapt to the off-axis ratio curve (Profile) characteristics of accelerators from different manufacturers and expand the applicable range.

[0090] In one embodiment, according to the differences between the percentage depth calculation curve and the percentage depth measurement curve, and the differences between the off-axis ratio calculation curve and the off-axis ratio measurement curve, the correlation parameters that determine the distribution of the particle source in the preset source model are adjusted until the differences are all within the preset error range, including:

[0091] Based on the differences between the off-axis ratio calculation curve outside the radiation field and the off-axis ratio measurement curve outside the radiation field, the size of the secondary sub-source in the preset source model is adjusted so that the differences between the off-axis ratio calculation curve outside the radiation field and the off-axis ratio measurement curve outside the radiation field obtained based on the adjusted preset source model are within the third preset error range.

[0092] After adjusting the probability density distribution, the differences between the off-axis ratio calculation curve outside the radiation field and the off-axis ratio measurement curve outside the radiation field can be further adjusted by adjusting the size of the secondary sub-source in the preset source model to make the differences within the third preset error range, thus completing the adjustment of the curve correlation parameters in the model.

[0093] To better illustrate the implementation of the particle source model training method for the radiotherapy system provided in this application embodiment, here, taking the determination process of the particle source model of a linear accelerator in the radiotherapy system as an example for illustration. When the energy file is selected as the 6MV photon irradiation mode:

[0094] (1) The radiation field size can be set to 10cm * 10cm. Based on the preset source model, the percentage depth calculation curves of different mono-energetic photons are calculated. By adjusting the weights of these mono-energetic photon percentage depth calculation curves, the percentage depth calculation curve and the percentage depth measurement curve are made to be consistent within a given difference range (the first preset error range) to obtain the energy spectra of the primary photon source and the secondary photon source.

[0095] Then, adjust the weight and source size of the contaminated electron source so that the build-up region of the percentage depth calculation curve is consistent with that of the percentage depth measurement curve within a given range (the error range of the first preset region) to determine the energy spectrum of the contaminated electron source.

[0096] (2) Adjust parameters such as the primary photon source size and the position of the first sampling plane (such as Figure 3 the position where the target is located as shown), compare the penumbra regions of the off-axis ratio calculation curve and the off-axis ratio measurement curve. When there is a difference between the two, adjust the radius of the primary photon source. The larger the radius, the larger the penumbra. Conversely, the smaller the radius, the smaller the penumbra. After adjusting the radius of the primary photon source in the preset source model, recalculate the three-dimensional dose based on the adjusted preset source model until the difference between the calculated value and the measured value of the three-dimensional dose in the penumbra region is within the preset dose error range.

[0097] (3) Adjust the probability density value of the off-axis ratio curve of the large field (for example, adjust it to 30 cm * 30 cm) so that the off-axis ratio calculation curve is consistent with the measured value of the off-axis ratio measurement curve within a given error threshold range (the second preset error range) within the radiation field.

[0098] (4) Adjust the size of the secondary sub-source so that the off-axis ratio calculation curve can be consistent with the off-axis ratio measurement curve within a given error threshold range (the second preset error range) outside the radiation field (which can be understood in combination with Figure 4 the outside of the radiation field). The size of the secondary source refers to the radius of the secondary source, which is a parameter related to the size of the secondary source in the particle source model. For the understanding of the outside of the radiation field, taking a 10 cm * 10 cm radiation field as an example, define its size on the isocenter plane (usually SSD = 100 cm) as X = 10 cm, Y = 10 cm, and the part exceeding 10 cm is the outside of the radiation field. For a non-isocenter plane, such as SSD = 110 cm, at this time, the size of the 10 cm * 10 cm radiation field should be 10 cm * 110 cm / 100 cm, that is, 11 cm, and the part exceeding 11 cm is the outside of the radiation field.

[0099] (5) Finally, calculate the correction factor of the output factor according to the output factors measured for different radiation fields. Further correct the preset source model adjusted in steps (1)-(4) based on the correction factor to obtain the particle source model.

[0100] The steps for establishing the particle source model of the electron source are similar to those of photons. For example, select the 12 MeV electron irradiation mode for the energy range:

[0101] (1) The size of the collimator is selected as 10 cm * 10 cm. Based on the preset source model, the PDDs of different monoenergetic electrons are calculated. By adjusting the weights of these monoenergetic electron PDDs, the percentage depth dose calculation curve is made to be consistent with the percentage depth dose measurement curve within a given difference range (the first preset error range) to obtain the energy spectra of the primary electron source and the secondary electron source. The weight and size of the contaminant photon source are adjusted so that the contaminant photon tails of the percentage depth dose calculation curve and the percentage depth dose measurement curve are consistent within a given range (the second preset regional error range) to ensure that the adjusted preset source model can be used to accurately determine the energy spectrum of the contaminant photon source.

[0102] (2) Parameters such as the size and position of the primary electron source are adjusted, and the penumbra regions of the calculated and measured Profiles are compared so that the error between the Profile calculated based on the adjusted preset source model and the Profile measured by the accelerator in the penumbra region is within the preset dose error range.

[0103] (3) The probability density value of the off-axis ratio curve of the large field (for example, a collimator with a size of 25 cm * 25 cm) in the preset source model is adjusted so that the calculated Profile is consistent with the measured Profile within a given threshold range (the preset dose error range) within the radiation field.

[0104] (4) The size of the secondary source (radius of the secondary source) in the preset source model is adjusted so that the calculated electron Profile outside the radiation field is consistent with the measured Profile within a given error threshold range (the preset dose error range).

[0105] (5) Finally, according to the output factors measured with collimators of different sizes, the correction factors of the output factors are calculated. Based on the correction factors, the preset source model adjusted in steps (1)-(4) is further corrected to obtain the particle source model.

[0106] It can be seen that the particle source model training method provided in the embodiments of the present application is applicable to both photon sources and electron sources. By using an identical particle source model to simulate the radiotherapy system (accelerator treatment head) under photon and electron irradiation modes. Using the particle source training method proposed in the present application can not only reduce the modeling difficulty of the photon-electron source model, improve the modeling speed, but also enhance the algorithm accuracy and expand the applicable range of the algorithm.

[0107] It should be noted that the order between steps (1)-(4) can be interchanged, not limited to the order given here, but step (5) must be after steps (1)-(4). The reason can be seen in the above embodiments. During the adjustment process of the correlation parameters of PDD and Profile in the model, the calculation result of the correction factor will be affected.

[0108] The embodiment of the present application further provides a method for determining the dose distribution of a radiotherapy system, and the method includes:

[0109] Obtain the energy to be input into the radiotherapy system;

[0110] Based on the energy to be input and the particle source model of the radiotherapy system, determine the percentage depth calculation curve, off-axis ratio calculation curve, and output factor calculation value of the radiotherapy system;

[0111] Wherein, the particle source model is generated by performing the steps of the above-mentioned particle source model training method of the radiotherapy system.

[0112] During the use of the radiotherapy system, the percentage depth calculation curve, off-axis ratio calculation curve, and output factor calculation value of the energy to be input can be determined based on the trained particle source model to understand whether the distribution of the particle source meets the expectations. If not, the percentage depth calculation curve, off-axis ratio calculation curve, and output factor calculation value can be adjusted by increasing or decreasing the energy to be input so that these dose distribution parameters meet the expectations.

[0113] It should be understood that although the steps in the flowcharts involved in the above-mentioned embodiments are sequentially shown according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same moment, but can be executed at different moments. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least a part of other steps or steps or stages in other steps.

[0114] Based on the same inventive concept, the embodiment of the present application further provides a particle source model training device for a radiotherapy system for implementing the above-mentioned particle source model training method of the radiotherapy system. The solution provided by this device to solve the problem is similar to the solution described in the above method. Therefore, the specific limitations in one or more embodiments of the following particle source model training device for a radiotherapy system can refer to the limitations on the particle source model training method of the radiotherapy system in the above text, and will not be repeated here.

[0115] In one embodiment, as Figure 5 shown, a particle source model training device for a radiotherapy system is provided. The device includes: a distribution curve calculation module 502, a measurement parameter acquisition module 504, a first adjustment module 506, a correction factor determination module 508, and a particle source model determination module 510. Wherein:

[0116] A distribution curve calculation module 502, configured to obtain a percentage depth calculation curve and an off-axis ratio calculation curve corresponding to a particle source based on input energy and a preset source model;

[0117] A measurement parameter acquisition module 504, configured to acquire a percentage depth measurement curve, an off-axis ratio measurement curve, and an output factor measurement value of a radiotherapy system under the action of input energy;

[0118] A first adjustment module 506, configured to adjust correlation parameters that determine the distribution of the particle source in the preset source model according to the difference between the percentage depth calculation curve and the percentage depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, until the differences are all within a preset error range;

[0119] A correction factor determination module 508, configured to determine a correction factor of the output factor based on the output factor measurement value and the adjusted preset source model;

[0120] A particle source model determination module 510, configured to correct the adjusted preset source model based on the correction factor to obtain a particle source model.

[0121] In one embodiment, the particle source includes a primary sub-source, a secondary sub-source, and a contaminant sub-source.

[0122] In one embodiment, the first adjustment module 506 includes:

[0123] A percentage depth dose weight adjustment unit, configured to adjust the weight of the percentage depth curve in the preset source model according to the difference between the percentage depth calculation curve and the percentage depth measurement curve, so that the difference between the percentage depth calculation curve obtained based on the adjusted preset source model and the percentage depth measurement curve is within a first preset error range.

[0124] In one embodiment, the contaminant sub-source includes a contaminant photon source and / or a contaminant electron source, and the first adjustment module 506 includes:

[0125] A contaminant electron source adjustment unit, configured to, for the case where the radiotherapy system operates in a photon irradiation mode, adjust the weight and size of the contaminant electron source in the preset source model according to the difference between the build-up region of the percentage depth calculation curve and the build-up region of the percentage depth measurement curve, so that the difference between the build-up region of the percentage depth calculation curve obtained based on the adjusted preset source model and the build-up region of the percentage depth measurement curve is within a first preset regional error range; and / or,

[0126] The contaminated photon source adjustment unit is used, when the radiotherapy system operates in the electron irradiation mode, to adjust the weight and size of the contaminated photon source in the preset source model based on the difference between the contaminated photon tail of the percentage depth calculation curve and the contaminated photon tail of the percentage depth measurement curve, so that the difference between the contaminated photon tail of the percentage depth calculation curve obtained based on the adjusted preset source model and the contaminated photon tail of the percentage depth measurement curve is within the second preset regional error range.

[0127] In one embodiment, the first adjustment module 506 includes:

[0128] The primary sub-source adjustment unit is used to adjust the size of the primary sub-source in the preset source model based on the difference between the penumbra region of the off-axis ratio calculation curve and the penumbra region of the off-axis ratio measurement curve, so that the error between the three-dimensional dose information of the penumbra region of the off-axis ratio calculation curve obtained based on the adjusted preset source model and the three-dimensional dose information of the penumbra region of the off-axis ratio measurement curve is within the preset dose error range.

[0129] In one embodiment, the first adjustment module 506 includes:

[0130] The probability density adjustment unit is used to adjust the model parameters in the preset source model that determine the probability density at different off-axis positions based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, so that the difference between the off-axis ratio calculation curve within the radiation field obtained based on the adjusted preset source model and the off-axis ratio measurement curve within the radiation field is within the second preset error range.

[0131] In one embodiment, the probability density adjustment unit includes:

[0132] The correlation parameter adjustment unit is used to adjust the correlation parameters of the probability density distribution function on the first sampling plane in the preset source model based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field; the first sampling plane is the sampling plane that can reflect the distribution of the radiation projected by the radiotherapy system under the selected irradiation mode.

[0133] In one embodiment, the probability density distribution function is a multi-segment linear distribution function, and the correlation parameter adjustment unit includes:

[0134] The linear parameter adjustment unit is used to adjust the parameters of the multi-segment linear distribution function on the first sampling plane in the preset source model.

[0135] In one embodiment, the first adjustment module 506 includes:

[0136] The secondary sub-source adjustment unit is configured to adjust the size of the secondary sub-sources in the preset source model based on the difference between the off-axis ratio calculation curve outside the radiation field and the off-axis ratio measurement curve outside the radiation field, so that the difference between the off-axis ratio calculation curve outside the radiation field obtained based on the adjusted preset source model and the off-axis ratio measurement curve outside the radiation field is within a third preset error range.

[0137] In one embodiment, the linear parameter adjustment unit includes:

[0138] The slope-intercept adjustment unit is configured to adjust at least one of the slope parameter or the intercept parameter in the following expression:

[0139]

[0140] where y(x) represents the probability density at the off-axis distance x on the first sampling plane, x represents the off-axis distance, a n represents the slope parameter of the linear distribution of the probability density when the off-axis distance is between x n-1 and x n , and b n is the intercept parameter of the linear distribution of the probability density when the off-axis distance is between x n-1 and x n . By adjusting the probability density values at different off-axis positions in the model, the off-axis ratio calculation curve and the off-axis ratio measurement curve are within a second preset error range.

[0141] Based on the same inventive concept, an embodiment of the present application further provides a dose distribution determination device for a radiotherapy system for implementing the dose distribution determination method of the radiotherapy system involved above. The solution provided by this device to solve the problem is similar to the solution described in the above method. Therefore, the specific limitations in one or more of the following embodiments of the dose distribution determination method device for a radiotherapy system can refer to the limitations on the dose distribution determination method for a radiotherapy system in the above text, and will not be repeated here.

[0142] In one embodiment, as Figure 6 shown, a dose distribution determination device for a radiotherapy system is provided. The device includes: a to-be-input energy acquisition module 602 and a dose distribution determination module 604. Wherein:

[0143] The to-be-input energy acquisition module 602 is configured to acquire the to-be-input energy of the radiotherapy system;

[0144] The dose distribution determination module 604 is configured to determine the dose distribution calculation curve and the output factor calculation value of the radiotherapy system based on the to-be-input energy and the particle source model of the radiotherapy system;

[0145] Among them, the particle source model is generated by performing the steps of the particle source model training method of the above radiotherapy system.

[0146] Each module in the above device can be implemented in whole or in part by software, hardware, and their combination. Each of the above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to each of the above modules.

[0147] In one embodiment, a computer device is provided. The computer device can be a server, and its internal structure diagram can be as Figure 7 shown. The computer device includes a processor, a memory, and a network interface connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store data such as the trained particle source model. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, it implements a particle source model training method and a dose distribution determination method of a radiotherapy system.

[0148] Those skilled in the art can understand that Figure 7 the structure shown in

[0149] merely represents a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computer device to which the solution of this application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0150] In one embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, it implements the steps in any of the above method embodiments.

[0151] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by the processor, it implements the steps in any of the method embodiments.

[0152] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0153] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memories. Non-volatile memories can include read-only memory (ROM), magnetic tapes, floppy disks, flash memories, optical memories, high-density embedded non-volatile memories, resistive random access memories (ReRAM), magnetoresistive random access memories (MRAM), ferroelectric random access memories (FRAM), phase change memories (PCM), graphene memories, etc. Volatile memories can include random access memory (RAM) or external cache memories, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in this application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in this application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logics, data processing logics based on quantum computing, etc., without limitation.

[0154] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0155] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A method for training a particle source model of a radiotherapy system, characterized in that, The method includes: Based on the input energy and a preset source model, obtaining the percentage depth dose calculation curve and the off-axis ratio calculation curve corresponding to the particle source; Obtaining the percentage depth dose measurement curve, the off-axis ratio measurement curve, and the output factor measurement value of the radiotherapy system under the action of the input energy; According to the difference between the percentage depth dose calculation curve and the percentage depth dose measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, adjusting the correlation parameters in the preset source model that determine the distribution of the particle source until the differences are all within a preset error range; Based on the output factor measurement value and the adjusted preset source model, determining the correction factor of the output factor; Based on the correction factor, correcting the adjusted preset source model to obtain the particle source model; The particle source includes a contaminant sub-source, and the contaminant sub-source includes a contaminant photon source and / or a contaminant electron source. The adjusting the correlation parameters in the preset source model that determine the distribution of the particle source according to the difference between the percentage depth dose calculation curve and the percentage depth dose measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve includes: For the case where the radiotherapy system operates in the photon irradiation mode, based on the difference between the build-up region of the percentage depth dose calculation curve and the build-up region of the percentage depth dose measurement curve, adjusting the weight and the size of the contaminant electron source in the preset source model so that the difference between the build-up region of the percentage depth dose calculation curve obtained based on the adjusted preset source model and the build-up region of the percentage depth dose measurement curve is within the first preset regional error range; and / or, For the case where the radiotherapy system operates in the electron irradiation mode, based on the difference between the contaminant photon tail of the percentage depth dose calculation curve and the contaminant photon tail of the percentage depth dose measurement curve, adjusting the weight and the size of the contaminant photon source in the preset source model so that the difference between the contaminant photon tail of the percentage depth dose calculation curve obtained based on the adjusted preset source model and the contaminant photon tail of the percentage depth dose measurement curve is within the second preset regional error range.

2. The method according to claim 1, wherein The particle source further includes a primary sub-source and a secondary sub-source.

3. The method according to claim 1, wherein The adjusting the correlation parameters in the preset source model that determine the distribution of the particle source according to the difference between the percentage depth dose calculation curve and the percentage depth dose measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve includes: Based on the difference between the percentage depth dose calculation curve and the percentage depth dose measurement curve, adjusting the weight of the percentage depth dose curve in the preset source model so that the difference between the percentage depth dose calculation curve obtained based on the adjusted preset source model and the percentage depth dose measurement curve is within the first preset error range.

4. The method according to claim 2, wherein The adjusting the correlation parameters in the preset source model that determine the distribution of the particle source according to the difference between the percentage depth dose calculation curve and the percentage depth dose measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve includes: Based on the difference between the penumbra region of the off-axis ratio calculation curve and the penumbra region of the off-axis ratio measurement curve, adjust the size of the primary sub-source in the preset source model so that the error between the three-dimensional dose information of the penumbra region of the off-axis ratio calculation curve obtained based on the adjusted preset source model and the three-dimensional dose information of the penumbra region of the off-axis ratio measurement curve is within a preset dose error range.

5. The method according to claim 1, wherein Adjust the correlation parameters that determine the distribution of the particle source in the preset source model according to the difference between the percent depth calculation curve and the percent depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve, including: Based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, adjust the model parameters in the preset source model that determine the probability density at different off-axis positions so that the difference between the off-axis ratio calculation curve within the radiation field obtained based on the adjusted preset source model and the off-axis ratio measurement curve within the radiation field is within a second preset error range.

6. The method according to claim 5, characterized in that, The adjusting the model parameters in the preset source model that determine the probability density at different off-axis positions based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field includes: Based on the difference between the off-axis ratio calculation curve within the radiation field and the off-axis ratio measurement curve within the radiation field, adjust the correlation parameters of the probability density distribution function on the first sampling plane in the preset source model; the first sampling plane is a sampling plane that can reflect the distribution of the radiation projected by the radiotherapy system under the selected irradiation mode.

7. The method according to claim 6, wherein The probability density distribution function is a multi-segment linear distribution function, and the adjusting the parameters of the probability density distribution function on the first sampling plane in the preset source model includes: Adjust the parameters of the multi-segment linear distribution function on the first sampling plane in the preset source model.

8. The method according to claim 2, wherein The adjusting the correlation parameters that determine the distribution of the particle source in the preset source model according to the difference between the percent depth calculation curve and the percent depth measurement curve, and the difference between the off-axis ratio calculation curve and the off-axis ratio measurement curve until the differences are all within the preset error range includes: Based on the difference between the off-axis ratio calculation curve outside the radiation field and the off-axis ratio measurement curve outside the radiation field, adjust the size of the secondary sub-source in the preset source model so that the difference between the off-axis ratio calculation curve outside the radiation field obtained based on the adjusted preset source model and the off-axis ratio measurement curve outside the radiation field is within a third preset error range.

9. A method for determining the dose distribution of a radiotherapy system, characterized in that, The method includes: Obtain the energy to be input of the radiotherapy system; Based on the energy to be input and the particle source model of the radiotherapy system, determine the percent depth calculation curve, the off-axis ratio calculation curve and the output factor calculated value of the radiotherapy system; Wherein, the particle source model is generated by performing the steps of the particle source model training method of the radiotherapy system according to any one of claims 1-8.

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