Equivalent biological dose calculation and plan optimization method and system

Abstract

The invention discloses an equivalent biological dose calculation and plan optimization method and system, and the method comprises the steps: determining dose objective functions and constraint conditions of target regions and radiation-endangered organs, and setting parameters of loss functions of each target region and radiation-endangered organ; calculating the physical dose and irradiation time of each voxel by using a dose calculation method based on the parameters of the current radiotherapy machine; calculating the equivalent biological dose of each voxel according to the physical dose and the irradiation time of each voxel; and calculating a loss function according to the target function and the constraint condition based on the statistical distribution state of the equivalent biological dose, so as to optimize the parameters of the radiotherapy machine by using a preset optimization algorithm. According to the invention, the technical problem of how to utilize the FLASH effect to protect normal tissues and enhance tumor killing in a treatment plan can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of radiotherapy planning, and particularly to a method and system for equivalent biological dose calculation and plan optimization. Background Art

[0002] In 2014, the Curie Institute in France irradiated experimental animals with ultra-high dose rate rays and discovered the FLASH effect. Subsequently, the radiotherapy community has studied radiotherapy using the FLASH effect, which is called FLASH radiotherapy or ultra-high dose rate radiotherapy. The biggest feature of FLASH radiotherapy is to use the FLASH effect generated by ultra-high dose rays (generally considered > 40 Gy / s) to protect normal tissues while not affecting tumor killing. FLASH radiotherapy was first achieved using electron beams, and then using protons, carbon ions, etc. Research groups such as Tsinghua University have also achieved ultra-high dose rate X-ray accelerating tubes for FLASH radiotherapy.

[0003] How to utilize the FLASH effect in the treatment plan to protect normal tissues and enhance tumor killing is an unsolved problem. Existing studies have all optimized the dose rate distribution so that the dose weighted average dose rate or other dose rate indicators exceed a certain threshold. However, this optimization method only considers the influence of the dose rate and does not consider the influence of other factors such as dose. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent.

[0005] The present invention proposes a method for equivalent biological dose calculation and plan optimization, which helps to improve the safety and effectiveness of treatment, reduce the occurrence of side effects. Precise dose calculation is crucial for realizing personalized treatment plans and can ensure that each patient can obtain the best treatment effect.

[0006] Another object of the present invention is to propose a system for equivalent biological dose calculation and plan optimization.

[0007] To achieve the above object, on the one hand, the present invention proposes a method for equivalent biological dose calculation and plan optimization, including:

[0008] Determine the dose objective function and constraint conditions of the target area and radiation at-risk organs, and set the parameters of the loss function for each target area and radiation at-risk organ;

[0009] Based on the parameters of the current radiotherapy machine, and use the dose calculation method to calculate the physical dose and irradiation time of each voxel;

[0010] Calculate the equivalent biological dose of each voxel according to the physical dose and irradiation time of each voxel;

[0011] Based on the distribution state of the statistical equivalent biological dose, calculate the loss function according to the objective function and constraint conditions, so as to optimize the parameters of the radiotherapy machine by using a preset optimization algorithm.

[0012] The equivalent biological dose calculation and plan optimization method of the embodiments of the present invention may further have the following additional technical features:

[0013] In one embodiment of the present invention, calculating the equivalent biological dose of each voxel according to the physical dose and irradiation time of each voxel includes:

[0014] Obtain the physiological parameter distribution based on the medical imaging results; wherein, the physiological parameter distribution includes the distribution of oxygen concentration and antioxidant concentration in the patient's body;

[0015] Take the oxygen concentration and / or antioxidant concentration as physiological parameters, and take the dose and / or irradiation time during one FLASH beam output as physical parameters;

[0016] Input the physiological parameters and physical parameters into the dose correction factor formula for FLASH irradiation, and obtain the biological dose according to the calculated dose correction factor DMF and physical dose.

[0017] In one embodiment of the present invention, the method further includes:

[0018] Assume that the antioxidant concentration of a certain voxel obtained from the medical image is c, the second-order rate constant of the reaction between the antioxidant and the peroxyl radical is k, the physical dose of this voxel is D, and the irradiation time is T. The equivalent biological dose EBD is calculated by the following formula:

[0019] k 1 = k·c

[0020]

[0021] EBD = DMF·D

[0022] where k,g 2 ,k 2 ,f,T m are all constants independent of D, T, and c.

[0023] In one embodiment of the present invention, the loss function is Loss(*):

[0024]

[0025] where, w OAR is the weight of the radiation critical organ, D i is the dose of the voxel in the critical organ region, wt arget is the weight of the target area, Dj is the dose of the voxel in the target area, D target is the expected target area dose.

[0026] In one embodiment of the present invention, the method further includes: calculating Loss(EBD) based on the equivalent biological dose EBD and the loss function Loss(*), and updating the parameters of the radiotherapy machine using the L-BFGS optimizer.

[0027] To achieve the above object, on the other hand, the present invention provides an equivalent biological dose calculation and plan optimization system, including:

[0028] An initial parameter setting module, configured to determine the objective function and constraints of the doses of the target area and the radiation critical organs, and set the parameters of the loss functions of each target area and radiation critical organ;

[0029] A physical dose calculation module, configured to calculate the physical dose and irradiation time of each voxel based on the parameters of the current radiotherapy machine and using a dose calculation method;

[0030] An equivalent biological dose calculation module, configured to calculate the equivalent biological dose of each voxel according to the physical dose and irradiation time of each voxel;

[0031] A loss calculation parameter optimization module, configured to calculate a loss function based on the distribution state of the statistically equivalent biological dose, and optimize the parameters of the radiotherapy machine using a preset optimization algorithm according to the objective function and constraints.

[0032] The equivalent biological dose calculation and plan optimization method and system according to the embodiments of the present invention achieve one-stop processing from imaging to dose and then to optimizing radiotherapy parameters by integrating physical dose calculation, biological effect modeling, and mathematical optimization. It improves the quality of radiotherapy, improves the treatment results of patients, reduces the risk of potential side effects, simplifies the workflow of doctors and physicists, and improves work efficiency.

[0033] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0035] Figure 1 is a flowchart of an equivalent biological dose calculation and plan optimization method according to an embodiment of the present invention;

[0036] Figure 2It is a structural diagram of an equivalent biological dose calculation and plan optimization system according to an embodiment of the present invention. Detailed implementation manners

[0037] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0038] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] The equivalent biological dose calculation and plan optimization method and system according to an embodiment of the present invention will be described below with reference to the drawings.

[0040] Figure 1 It is a flowchart of an equivalent biological dose calculation and plan optimization method according to an embodiment of the present invention. As Figure 1 shown, the method includes:

[0041] S1. Determine the dose objective function and constraint conditions of the target area and radiation critical organs, and set the parameters of the loss function for each target area and radiation critical organ;

[0042] S2. Based on the parameters of the current radiotherapy machine, calculate the physical dose and irradiation time of each voxel using a dose calculation method;

[0043] S3. Calculate the equivalent biological dose of each voxel according to the physical dose and irradiation time of each voxel;

[0044] S4. Based on the statistical distribution state of the equivalent biological dose, calculate the loss function according to the objective function and constraint conditions, so as to optimize the parameters of the radiotherapy machine using a preset optimization algorithm.

[0045] Specifically, the present invention uses the equivalent biological dose as a basis for plan optimization, which specifically includes the following steps:

[0046] (1) The radiotherapy doctor and physicist determine the dose objective function and constraint conditions of the target area and radiation critical organs;

[0047] (2) Set the loss function parameters such as the weights of each target area and radiation critical organ;

[0048] (3) Using the current radiotherapy machine parameters, calculate the physical dose and irradiation time for each voxel using a dose calculation algorithm / module;

[0049] (4) Calculate the equivalent biological dose for each voxel based on the physical dose and irradiation time of each voxel;

[0050] (5) Statistically analyze the distribution of the equivalent biological dose, and calculate the loss function / cost function according to the objective function and constraint conditions;

[0051] (6) Optimize the radiotherapy machine parameters using an optimization algorithm (including but not limited to L-BFGS, IPOPT, genetic algorithm, etc.);

[0052] (7) Repeat steps (2)-(6) until the distribution and statistical characteristics of the equivalent biological dose meet the requirements. At this time, the machine parameters are the optimized radiotherapy plan.

[0053] Exemplarily, the radiotherapy machine parameters include but are not limited to energy level, field size, MLC (multi-leaf collimator) configuration, etc.

[0054] Exemplarily, select a suitable dose calculation algorithm, such as Monte Carlo simulation, analytical algorithm, or convolution / superconvolution algorithm. Using the selected algorithm, combined with the parameters of the radiotherapy machine and the patient's anatomical information, calculate the physical dose received by each voxel.

[0055] Exemplarily, each voxel refers to the smallest volume unit that constitutes the patient's three-dimensional anatomical image. Each voxel has its specific spatial coordinates ((x, y, z)), and during the dose calculation process, the physical dose and irradiation time are calculated separately for each such voxel. This is done to ensure a highly accurate dose distribution and thus optimize the treatment effect.

[0056] In one embodiment of the present invention, the equivalent biological dose of each voxel is calculated using the X-ray FLASH radiotherapy equivalent biological effect calculation method. It may include the following steps:

[0057] Obtain the physiological parameter distribution based on the medical imaging results; wherein, the physiological parameter distribution includes the distribution of oxygen concentration and antioxidant concentration in the patient's body. It can be obtained by using medical imaging (including but not limited to magnetic resonance, SPECT, PET, fluorescence imaging, etc.) to obtain the distribution of oxygen concentration and antioxidant (including but not limited to glutathione, vitamin C, etc.) concentration in the patient's body;

[0058] Use the oxygen concentration and antioxidant concentration as inputs of physiological parameters (both are input or only one of them is input), and use the dose and irradiation time (or replace with dose rate) during one FLASH beam output as inputs of physical parameters (both are input or only one of them is input);

[0059] Input physiological parameters and physical parameters into the dose correction factor formula for FLASH irradiation, and then multiply the calculated dose correction factor DMF by the physical dose to obtain the biological dose.

[0060] It can be understood that if the physiological parameter distribution of the patient cannot be obtained through medical imaging as the input of physiological parameters, the results of the population can be used to replace the results of the individual patient.

[0061] Furthermore, assuming that the antioxidant concentration of a certain voxel obtained from a medical image is c, the second-order rate constant of the reaction between the antioxidant and the peroxyl radical is k, the physical dose of this voxel is D, and the irradiation time is T, then the equivalent biological dose EBD can be calculated by the following formula.

[0062] k 1 = k·c

[0063]

[0064] EBD = DMF·D

[0065] where k,g 2 ,k 2 ,f,T m are all constants independent of D, T, and c, and can be determined through prior calculations or experiments.

[0066] Furthermore, M represents the machine parameters. The dose D(M) and irradiation time T(M) of the voxel at position r can be calculated. Also, the physiological parameters of this voxel are obtained based on medical images or estimated results. At this time, the DMF and equivalent biological dose EBD of this voxel can be calculated.

[0067] It can be understood that in radiotherapy planning, the position r usually refers to a specific position in three-dimensional space, usually represented by coordinates (r = (x, y, z)). This position corresponds to the specific location of a certain voxel (i.e., the smallest volume unit) in the patient's body. A voxel is the basic unit that makes up a 3D medical image (such as a CT or MRI scan image). Each voxel represents a small piece of tissue and has specific spatial coordinates.

[0068] The loss function given by the doctor and the physicist is Loss(*), for example:

[0069]

[0070] where w OAR is the weight of the radiation critical organ, D i is the dose of the voxel within the critical organ region, wt arget is the weight of the target area, D j is the dose of the voxel in the target area, Dtarget is the expected target dose

[0071] Then, the distribution of EBD can be substituted to calculate Loss(EBD), and then the machine parameters M can be updated using the L-BFGS optimizer.

[0072] Until the EBD distribution and statistical analysis results meet the requirements of doctors and physicists, and at this time, M is used as the machine parameters for subsequent processes.

[0073] According to the equivalent biological dose calculation and plan optimization method of the embodiments of the present invention, by determining the dose objective function and constraint conditions of the target area and radiation critical organs, and setting loss function parameters for each target area and OAR, it ensures effective irradiation of tumor tissues while minimizing damage to surrounding healthy tissues. Precise dose calculation is crucial for implementing personalized treatment plans, ensuring that each patient can obtain the best treatment effect. The introduction of EBD improves the accuracy of dose calculation. The optimized parameter settings not only ensure high-precision irradiation of the tumor area but also effectively reduce the impact on surrounding healthy tissues, improving the overall treatment effect. It can solve the technical problem of how to utilize the FLASH effect in the treatment plan to protect normal tissues and enhance tumor killing.

[0074] To implement the above embodiments, as Figure 2 shown, the equivalent biological dose calculation and plan optimization system 10 is further provided in this embodiment, including:

[0075] An initial parameter setting module 100, configured to determine the dose objective function and constraint conditions of the target area and radiation critical organs, and set the parameters of the loss function for each target area and radiation critical organ;

[0076] A physical dose calculation module 200, configured to calculate the physical dose and irradiation time of each voxel based on the parameters of the current radiotherapy machine and using a dose calculation method;

[0077] An equivalent biological dose calculation module 300, configured to calculate the equivalent biological dose of each voxel according to the physical dose and irradiation time of each voxel;

[0078] A loss calculation parameter optimization module 400, configured to calculate a loss function based on the distribution state of the statistically equivalent biological dose and according to the objective function and constraint conditions, so as to optimize the parameters of the radiotherapy machine using a preset optimization algorithm.

[0079] Furthermore, the equivalent biological dose calculation module 200 is further configured to:

[0080] Obtain the physiological parameter distribution based on the medical imaging results; wherein, the physiological parameter distribution includes the distribution of the oxygen concentration and antioxidant concentration in the patient's body;

[0081] Take the oxygen concentration and / or antioxidant concentration as physiological parameters, and take the dose and / or irradiation time during a single FLASH beam delivery as physical parameters;

[0082] Input the physiological parameters and physical parameters into the dose correction factor formula for FLASH irradiation, and obtain the biological dose based on the calculated dose correction factor DMF and physical dose.

[0083] Furthermore, the system is also used for:

[0084] Assume that the antioxidant concentration of a certain voxel obtained from a medical image is c, the second-order rate constant for the reaction of the antioxidant with peroxyl radicals is k, the physical dose of this voxel is D, and the irradiation time is T. Calculate the equivalent biological dose EBD by the following formula:

[0085] k 1 = k·c

[0086]

[0087] EBD = DMF·D

[0088] where k,g 2 ,k 2 ,f,T m are all constants independent of D, T, and c.

[0089] Furthermore, the loss function is Loss(*):

[0090]

[0091] where w OAR is the weight of the radiation critical organ, D i is the dose of the voxel within the critical organ region, wt arget is the weight of the target area, D j is the dose of the voxel in the target area, D target is the expected dose of the target area.

[0092] Furthermore, the system is also used for: calculating Loss(EBD) based on the equivalent biological dose EBD and the loss function Loss(*), and updating the parameters of the radiotherapy machine using the L-BFGS optimizer.

[0093] An equivalent biological dose calculation and treatment planning optimization system according to an embodiment of the present invention determines the dose objective functions and constraints for the target region and radiation critical organs, and sets loss function parameters for each target region and OAR, ensuring effective irradiation of tumor tissues while minimizing damage to surrounding healthy tissues. Precise dose calculation is crucial for implementing personalized treatment plans and can ensure that each patient achieves the best treatment effect. The introduction of EBD improves the accuracy of dose calculation. The optimized parameter settings not only ensure high-precision irradiation of the tumor region but also effectively reduce the impact on surrounding healthy tissues, improving the overall treatment effect. It can solve the technical problem of how to utilize the FLASH effect in treatment planning to protect normal tissues and enhance tumor killing.

[0094] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0095] In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

Claims

1. A method for calculating and optimizing equivalent biological dose, characterized in that: include: Determine the dose objective function and constraint conditions of the target area and radiation-endangered organs, and set the parameters of the loss function of each target area and radiation-endangered organ; Based on the parameters of the current radiotherapy machine, the physical dose and irradiation time of each voxel are calculated using the dose calculation method; The equivalent biological dose of each voxel is calculated based on the physical dose and irradiation time of each voxel; Based on the statistical distribution of the equivalent biological dose, the loss function is calculated according to the objective function and the constraint conditions to optimize the parameters of the radiotherapy machine using a preset optimization algorithm.

2. The method according to claim 1, characterized in that: The equivalent biological dose of each voxel is calculated based on the physical dose and irradiation time of each voxel, including: Acquiring physiological parameter distribution based on medical imaging results; wherein the physiological parameter distribution includes the distribution of oxygen concentration and antioxidant concentration in the patient; The oxygen concentration and / or antioxidant concentration are used as physiological parameters, and the dose and / or irradiation time during one FLASH beam is used as physical parameters; The physiological parameters and physical parameters are input into the dose correction factor formula of FLASH irradiation, and the biological dose is obtained based on the calculated dose correction factor DMF and physical dose.

3. The method according to claim 2, characterized in that The method further comprises: Assuming that the antioxidant concentration of a certain voxel obtained from the medical image is c, the second-order rate constant of the reaction between the antioxidant and the peroxide free radical is k, the physical dose of this voxel is D, and the irradiation time is T, the equivalent biological dose EBD is calculated by the following formula: k1=k·c EBD=DMF·D where k,g2,k2,f,T m They are all constants independent of D, T, and c.

4. The method according to claim 1, characterized in that: The loss function is Loss(*): Among them, w OAR is the weight of the radiation-endangered organ, D i is the dose to the voxels in the organ at risk region, wt arget is the weight of the target area, D j is the voxel dose in the target area, D target is the expected target dose.

5. The method according to claim 4, characterized in that The method further includes: calculating Loss(EBD) based on the equivalent biological dose EBD and the loss function Loss(*), and updating the parameters of the radiotherapy machine using the L-BFGS optimizer.

6. An equivalent biological dose calculation and planning optimization system, characterized in that: include: The initial parameter setting module is used to determine the objective function and constraint conditions of the dose of the target area and the radiation-endangered organ, and to set the parameters of the loss function of each target area and radiation-endangered organ; A physical dose calculation module, used to calculate the physical dose and irradiation time of each voxel based on the parameters of the current radiotherapy machine and using a dose calculation method; An equivalent biological dose calculation module is used to calculate the equivalent biological dose of each voxel according to the physical dose and irradiation time of each voxel; The loss calculation parameter optimization module is used to calculate the loss function based on the statistical distribution state of the equivalent biological dose and the objective function and constraint conditions to optimize the parameters of the radiotherapy machine using a preset optimization algorithm.

7. The system according to claim 6, characterized in that The equivalent biological dose calculation module is also used for: Acquiring physiological parameter distribution based on medical imaging results; wherein the physiological parameter distribution includes the distribution of oxygen concentration and antioxidant concentration in the patient; The oxygen concentration and / or antioxidant concentration are used as physiological parameters, and the dose and / or irradiation time during one FLASH beam is used as physical parameters; The physiological parameters and physical parameters are input into the dose correction factor formula of FLASH irradiation, and the biological dose is obtained based on the calculated dose correction factor DMF and physical dose.

8. The system according to claim 7, characterized in that The system is also used for: Assuming that the antioxidant concentration of a certain voxel obtained from the medical image is c, the second-order rate constant of the reaction between the antioxidant and the peroxide free radical is k, the physical dose of this voxel is D, and the irradiation time is T, the equivalent biological dose EBD is calculated by the following formula: k1=k·c EBD=DMF·D where k,g2,k2,f,T m They are all constants independent of D, T, and c.

9. The system according to claim 6, characterized in that The loss function is Loss(*): Among them, w OAR is the weight of the radiation-endangered organ, D i is the dose to the voxels in the organ at risk region, wt arget is the weight of the target area, D j is the voxel dose in the target area, D target is the expected target dose.

10. The system according to claim 9, characterized in that The system is also used to calculate Loss(EBD) based on equivalent biological dose EBD and loss function Loss(*), and update the parameters of the radiotherapy machine using the L-BFGS optimizer.

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