Radiotherapy planning method and system based on biological optimization

Abstract

The invention discloses a radiotherapy planning method and system based on biological optimization, and the method comprises the steps: carrying out the fusion of a positron emission computed tomography (PET) image and a computed tomography (CT) image, carrying out the sketching of a biological target region according to the threshold value of a developer standard uptake value (SUV), and meanwhile, carrying out the sketching of an endangered organ; setting physical constraints for the biological target region and the organ at risk, and performing primary optimization to obtain a primary dose result; setting biological constraints for the biological target region and the organ at risk based on the primary dose result; and constructing an objective function containing a biological constraint penalty term and a physical constraint penalty term, and obtaining a final radiotherapy plan through iterative optimization. According to the method, a biological target region is used for replacing a traditional target region, a tumor region is depicted finely, a plan optimization model combining biological constraint and physical constraint is used, the dose coverage of the target region can be ensured, meanwhile, the dose of a crisis organ is reduced, and finally a plan meeting clinical requirements is generated.

Description

Technical Field

[0001] The present invention relates to the technical field of intensity modulated radiotherapy optimization, and in particular to a radiotherapy planning method and system based on biological optimization. Background Art

[0002] Tumor radiotherapy is one of the three major methods of tumor treatment. Its basic goal is to maximize the therapeutic gain ratio, that is, to ensure that the target area receives a certain coverage rate of the prescribed dose while the surrounding normal tissue is protected from or less exposed to unnecessary radiation. The radiation dose is a very important parameter in radiotherapy, which determines the intensity and duration of radiation. Therefore, solving the dose prediction problem in radiotherapy has a great impact on the treatment effect and side effects.

[0003] In the radiotherapy industry, a radiotherapy plan is a document that controls the accelerator to project radiation. Just like the human brain controls human behavior, how the accelerator treats the patient is controlled by the radiotherapy plan. The radiation projection speed of modern accelerators has undergone a revolutionary development, and radiotherapy is also moving towards high precision and high individualization. The so-called individualization means taking into account the specific situation of each patient. Although the treatment methods for the same disease are roughly the same, the size, shape, specific location and surrounding conditions of each patient's tumor will be different. Modern radiotherapy technology needs to take into account the individual differences of patients and tailor a unique radiotherapy plan for the patient. The radiotherapy plan determines the patient's efficacy and the severity of the late side effects. During the entire treatment period, once the radiotherapy plan is designed and determined, it is rarely modified unless the patient's irradiation range needs to be modified midway, so the radiotherapy plan is very important.

[0004] In the existing patent technology, in order to improve the effect of radiotherapy, the application number is: 202310248954.3, and the name is a Chinese invention patent application for a method and device for optimizing radiotherapy plans based on equivalent uniform dose, which includes the following steps: pre-processing the case for optimization; generating individualized radiotherapy plan scoring rules based on the anatomical structure information of the case; selecting a suitable biological objective function based on the target area and normal tissue type, and setting constraint parameters for the selected biological objective function according to the individualized radiotherapy plan scoring rules; optimizing the flux map according to the above biological objective function, evaluating the optimization results, and obtaining the final dose distribution. The invention uses the EUD biological objective function to fully reflect the control probability of the target area or the complication probability of normal tissue when subjected to uneven dose distribution, while avoiding the situation where DVHs intersect with each other when dose-volume constraints occur and it is difficult to select a better plan. By extracting the individualized radiotherapy plan scoring rules to calculate the initial EUD value of the biological constraint, the plan quality problems caused by differences in physicist experience can be avoided.

[0005] The above-mentioned invention patent application solves the problem of radiotherapy plan optimization by implementing plan optimization using the equivalent uniform dose (EUD) biological objective function. However, this invention patent application method cannot directly reflect the actual biological response of tumors and normal tissues to radiotherapy because it does not directly model the dose-response relationship.

[0006] In view of this, the present invention patent is proposed. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a radiotherapy planning method and system based on biological optimization. Specifically, the following technical solutions are adopted:

[0008] A method for radiotherapy planning based on biological optimization, comprising:

[0009] The positron emission tomography (PET) and computed tomography (CT) images were fused, and the biological target area was delineated according to the threshold of the standard uptake value (SUV) of the imaging agent, and the organs at risk were delineated at the same time;

[0010] Set physical constraints for biological targets and organs at risk, perform primary optimization, and obtain primary dose results;

[0011] Based on the primary dose results, biological constraints are set for biological targets and organs at risk;

[0012] An objective function including biological constraint penalty terms and physical constraint penalty terms was constructed, and the final radiotherapy plan was obtained through iterative optimization.

[0013] As an optional embodiment of the present invention, in a radiotherapy planning method based on biological optimization of the present invention, the biological constraints set for biological targets and organs at risk based on primary dose results include: tumor control probability (TCP) constraints and normal tissue complication probability (NTCP) constraints.

[0014] As an optional embodiment of the present invention, in a radiotherapy planning method based on biological optimization of the present invention, the calculation formulas of the tumor control probability (TCP) constraint and the normal tissue complication probability (NTCP) constraint are:

[0015]

[0016] Where d is the single dose, D is the total dose, α and β are cell radiosensitivity parameters, t is the difference between the total treatment time and the proliferation lag time, T eff is the effective cell doubling time, D NTCP＝0.5 Indicates the dose when NTCP = 0.5 in the dose-effect curve, V effIt is called the effective volume of an organ or tissue, m describes the steepness of the dose-response curve, and n describes the relationship between the organ volume and the dose effect, with reference to the tumor control probability (TCP) constraint for setting the biological target volume (BTV).

[0017] As an optional embodiment of the present invention, in a radiotherapy planning method based on biological optimization of the present invention, the biological constraint limit value setting refers to the primary optimization result, including:

[0018] Select the type of biological restraint based on the current biological target area or organ at risk;

[0019] Combined with the primary dose result information obtained from the primary optimization, the corresponding tumor control probability (TCP) or normal tissue complication probability (NTCP) is calculated to obtain a reference for setting biological constraint limits, and then set biological constraints.

[0020] As an optional embodiment of the present invention, in a radiotherapy planning method based on biological optimization of the present invention, the physical constraints set for the biological target and the organ at risk include: the dose of the target or the organ at risk is greater than a certain limit value D min , the dose to the target area or the organ at risk is less than a certain limit value D max , and the average dose limit D for the target area or organs at risk mean .

[0021] As an optional embodiment of the present invention, in a radiotherapy planning method based on biological optimization of the present invention, the objective function including biological constraint penalty terms and physical constraint penalty terms is constructed, comprising:

[0022] Add prescription items to biological constraints,

[0023] cost(TCP)=W×(prescription*(TCP actual -TCPexpected))2

[0024] cost(NTCP)=W×(prescription*(NTCP actual -NTCPexpected))2

[0025] Add gEUD term to biological constraints,

[0026] cost(TCP)=W×(gEUD*(TCP actual -TCPexpected))2

[0027] cost(NTCP)=W×(gEUD*(NTCP actual -NTCPexpected))2

[0028] The objective function is

[0029]

[0030] Where W represents the weight, prescription represents the prescription dose, gEUD represents the generalized equivalent uniform dose, K represents the sum of physical constraints, H function is a 0-1 function, which is 0 when the constraint requirements are met and 1 when they are not met, and D actual is the actual value, D p is the limit value.

[0031] As an optional embodiment of the present invention, in a radiotherapy planning method based on biological optimization of the present invention, the primary dose result of the primary optimization can be a dose result obtained by a complete plan optimization, or an intermediate dose result obtained by a pause function in the plan optimization.

[0032] As an optional embodiment of the present invention, a radiotherapy planning method based on biological optimization of the present invention comprises: evaluating the planning quality of the final radiotherapy plan by various evaluation indicators, wherein the evaluation indicators include a target area dose volume indicator and an organ at risk dose volume indicator;

[0033] If the clinical requirements are met in terms of various evaluation indicators, the radiotherapy plan is formulated, otherwise the constraint settings are adjusted and optimization continues.

[0034] The present invention also provides a system for implementing the radiotherapy planning method based on biological optimization, comprising:

[0035] The biological target delineation module fuses positron emission tomography (PET) images and computed tomography (CT) images, delineates the biological target area according to the threshold of the standard uptake value (SUV) of the imaging agent, and delineates the organs at risk at the same time;

[0036] The primary optimization module sets physical constraints for biological targets and organs at risk, performs primary optimization, and obtains primary dose results;

[0037] The constraint setting module sets biological constraints for biological targets and organs at risk based on the primary dose results;

[0038] The re-optimization module constructs an objective function that includes biological constraint penalty terms and physical constraint penalty terms, and obtains the final radiotherapy plan through iterative optimization.

[0039] As an optional embodiment of the present invention, a radiotherapy planning system based on biological optimization of the present invention includes a planning evaluation module:

[0040] Evaluating the planning quality of the final radiotherapy plan by various evaluation indicators, wherein the evaluation indicators include target area dose volume indicators and organ at risk dose volume indicators;

[0041] If the clinical requirements are met in terms of various evaluation indicators, the radiotherapy plan is formulated, otherwise the constraint settings are adjusted and optimization continues.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention provides a radiotherapy planning method and system based on biological optimization, which uses biological target areas to replace traditional target areas, accurately depicts the tumor area, and uses a planning optimization model that combines biological constraints with physical constraints. This can ensure target area dose coverage while reducing the dose to critical organs, and ultimately generate a plan that meets clinical requirements, thereby achieving accurate and reasonable plan optimization.

[0044] Therefore, the radiotherapy planning method and system based on biological optimization of the present invention have important practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A flow chart of a radiotherapy planning method based on biological optimization according to an embodiment of the present invention;

[0046] Figure 2 A radiotherapy planning method based on biological optimization in an embodiment of the present invention includes a plan optimization result table taking cervical cancer as an example;

[0047] Figure 3 A schematic diagram comparing the planning optimization results of a radiotherapy planning method based on biological optimization in an embodiment of the present invention with the planning optimization results of a radiotherapy planning method without biological constraints, taking cervical cancer as an example;

[0048] Figure 4 A modular block diagram of a radiotherapy planning system based on biological optimization in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0050] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents some embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0051] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features and technical solutions in the embodiments may be combined with each other.

[0052] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0053] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed when in use, or the orientation or positional relationship commonly understood by those skilled in the art. Such terms are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0054] See also Figure 1 As shown, a radiotherapy planning method based on biological optimization in this embodiment includes:

[0055] The positron emission tomography (PET) and computed tomography (CT) images were fused, and the biological target area was delineated according to the threshold of the standard uptake value (SUV) of the imaging agent, and the organs at risk were delineated at the same time;

[0056] Set physical constraints for biological targets and organs at risk, perform primary optimization, and obtain primary dose results;

[0057] Based on the primary dose results, biological constraints are set for biological targets and organs at risk;

[0058] An objective function including biological constraint penalty terms and physical constraint penalty terms was constructed, and the final radiotherapy plan was obtained through iterative optimization.

[0059] The radiotherapy planning method based on biological optimization in this embodiment uses biological target areas to replace traditional target areas, finely depicts the tumor area, and uses a planning optimization model that combines biological constraints with physical constraints. It can ensure target area dose coverage while reducing the dose to critical organs, and ultimately generate a plan that meets clinical requirements, achieving accurate and reasonable plan optimization. Therefore, the radiotherapy planning method based on biological optimization in this embodiment has important practical value.

[0060] Furthermore, in a radiotherapy planning method based on biological optimization of this embodiment, the biological constraints set for biological targets and organs at risk based on primary dose results include: tumor control probability (TCP) constraints and normal tissue complication probability (NTCP) constraints.

[0061] Specifically, in a radiotherapy planning method based on biological optimization in this embodiment, the calculation formulas of the tumor control probability (TCP) constraint and the normal tissue complication probability (NTCP) constraint are:

[0062]

[0063] Where d is the single dose, D is the total dose, α and β are cell radiosensitivity parameters, t is the difference between the total treatment time and the proliferation lag time, T eff is the effective cell doubling time, D NTCP=0.5 Indicates the dose when NTCP = 0.5 in the dose-effect curve, V eff It is called the effective volume of an organ or tissue, m describes the steepness of the dose-response curve, and n describes the relationship between the organ volume and the dose effect, with reference to the tumor control probability (TCP) constraint for setting the biological target volume (BTV).

[0064] In a radiotherapy planning method based on biological optimization of this embodiment, the biological constraint limit value setting refers to the primary optimization result, including:

[0065] Select the type of biological restraint based on the current biological target area or organ at risk;

[0066] Combined with the primary dose result information obtained from the primary optimization, the corresponding tumor control probability (TCP) or normal tissue complication probability (NTCP) is calculated to obtain a reference for setting biological constraint limits, and then set biological constraints.

[0067] Furthermore, in a radiotherapy planning method based on biological optimization of this embodiment, the physical constraints set for the biological target and the organ at risk include: the dose of the target or the organ at risk is greater than a certain limit value D min , the dose to the target area or the organ at risk is less than a certain limit value D max , and the average dose limit D for the target area or organs at risk mean .

[0068] In a radiotherapy planning method based on biological optimization of this embodiment, constructing an objective function including biological constraint penalty terms and physical constraint penalty terms includes:

[0069] Add prescription items to biological constraints,

[0070] cost(TCP)=W×(prescription*(TCP actual -TCPexpected))2

[0071] cost(NTCP)=W×(prescription*(NTCP actual -NTCPexpected))2

[0072] Add gEUD term to biological constraints,

[0073] cost(TCP)=W×(gEUD*(TCP actual -TCPexpected))2

[0074] cost(NTCP)=W×(gEUD*(NTCP actual -NTCPexpected))2

[0075] The objective function is

[0076]

[0077]

[0078] Where W represents the weight, prescription represents the prescription dose, gEUD represents the generalized equivalent uniform dose, K represents the sum of physical constraints, H function is a 0-1 function, which is 0 when the constraint requirements are met and 1 when they are not met, and D actual is the actual value, D p is the limit value.

[0079] In a radiotherapy planning method based on biological optimization of this embodiment, the primary dose result of the primary optimization may be a dose result obtained by a complete plan optimization, or may be an intermediate dose result obtained by a pause function in the plan optimization.

[0080] A radiotherapy planning method based on biological optimization in this embodiment includes: evaluating the planning quality of the final radiotherapy plan through various evaluation indicators, wherein the evaluation indicators include target area dose volume indicators, such as D 95 , D5, etc., and dose-volume indicators for organs at risk, such as V 30 、V 40 wait;

[0081] If the clinical requirements are met in terms of various evaluation indicators, the radiotherapy plan is formulated, otherwise the constraint settings are adjusted and optimization continues.

[0082] Taking cervical cancer as an example, the specific implementation mode of the present invention is described below:

[0083] A radiotherapy planning method based on biological optimization, the specific implementation steps are as follows:

[0084] 1) Use 18F-FDG PET-CT to locate the cervix and delineate the biological target volume (BTV) based on the PET image standard SUV ≥ 2.0 threshold, and also delineate other organs at risk.

[0085] 2) Set routine physical constraints on biological target areas and key organs at risk, including the bladder, rectum, small intestine, and left and right femoral heads, and complete a plan optimization.

[0086] 3) In addition to conventional physical constraints, biological constraints are set according to the above optimization results. The tumor control probability (TCP) and normal tissue complication probability (NTCP) are calculated using the following formulas:

[0087]

[0088] Where d is a single dose, D is the total dose, α and β are cell radiosensitivity parameters, t is the difference between the total treatment time and the proliferation lag time, T_eff is the effective cell doubling time, D NTCP =0.5 represents the dose when NTCP=0.5 in the dose-effect curve, V_eff is called the effective volume of the organ or tissue, m describes the steepness of the dose-response curve, and n describes the relationship between the organ volume and the dose-effect. Refer to the TCP constraints for setting the biological target volume (BTV). The specific parameters are: limit requirement 55%, α=0.2, β=0.01, T eff = 23, set the NTCP constraint of the bladder, the specific parameters are: limit requirement 1%, m = 0.1, n = 0.5, D NTCP =0.5=6500, the value of a in EUD is set to 1.

[0089] 4) Use the following formula to construct biological constraints, combined with physical constraints, to construct the overall objective function:

[0090] cost(TCP)=W×(prescription*(TCP actual -TCP expected )) 2

[0091] cost(NTCP)=W×(prescription*(NTCP actual -NTCP expected )) 2

[0092] Through iterative optimization, the final plan is obtained.

[0093] 5) If Figure 2 As shown in the table, the key indicators all meet the clinical limit requirements, such as Figure 3 As shown, the dose to the bladder is reduced compared to the plan without biological constraints (Note: circles indicate no biological constraints, squares indicate inclusion of biological constraints).

[0094] See also Figure 4 As shown, this embodiment also provides a system for implementing the radiotherapy planning method based on biological optimization, including:

[0095] The biological target delineation module fuses positron emission tomography (PET) images and computed tomography (CT) images, delineates the biological target area according to the threshold of the standard uptake value (SUV) of the imaging agent, and delineates the organs at risk at the same time;

[0096] The primary optimization module sets physical constraints for biological targets and organs at risk, performs primary optimization, and obtains primary dose results;

[0097] The constraint setting module sets biological constraints for biological targets and organs at risk based on the primary dose results;

[0098] The re-optimization module constructs an objective function that includes biological constraint penalty terms and physical constraint penalty terms, and obtains the final radiotherapy plan through iterative optimization.

[0099] The radiotherapy planning system based on biological optimization in this embodiment uses biological target areas to replace traditional target areas, finely depicts the tumor area, and uses a planning optimization model that combines biological constraints with physical constraints. It can ensure target area dose coverage while reducing the dose to critical organs, and ultimately generate a plan that meets clinical requirements, achieving accurate and reasonable plan optimization. Therefore, the radiotherapy planning system based on biological optimization in this embodiment has important practical value.

[0100] Furthermore, a radiotherapy planning system based on biological optimization in this embodiment includes a planning evaluation module:

[0101] The quality of the final radiotherapy plan is evaluated by various evaluation indicators, including target dose volume indicators, such as D 95 , D5, etc., and dose-volume indicators for organs at risk, such as V 30 、V 40 wait;

[0102] If the clinical requirements are met in terms of various evaluation indicators, the radiotherapy plan is formulated, otherwise the constraint settings are adjusted and optimization continues.

[0103] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the above specific implementation methods. Therefore, any modification or equivalent replacement of the present invention; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the invention are included in the scope of the claims of the present invention.

Claims

1. A radiotherapy planning method based on biological optimization, characterized in that: include: The positron emission tomography (PET) and computed tomography (CT) images were fused, and the biological target area was delineated according to the threshold of the standard uptake value (SUV) of the imaging agent, and the organs at risk were delineated at the same time; Set physical constraints for biological targets and organs at risk, perform primary optimization, and obtain primary dose results; Based on the primary dose results, biological constraints are set for biological targets and organs at risk; An objective function including biological constraint penalty terms and physical constraint penalty terms was constructed, and the final radiotherapy plan was obtained through iterative optimization.

2. A radiotherapy planning method based on biological optimization according to claim 1, characterized in that: The biological constraints set for the biological target and organs at risk based on the primary dose results include: tumor control probability (TCP) constraints and normal tissue complication probability (NTCP) constraints.

3. A radiotherapy planning method based on biological optimization according to claim 2, characterized in that: The calculation formulas for the tumor control probability (TCP) constraint and the normal tissue complication probability (NTCP) constraint are: Where d is the single dose, D is the total dose, α and β are the cell radiosensitivity parameters, t is the difference between the total treatment time and the proliferation lag time, T eff is the effective cell doubling time, D NTCP=0.5 Indicates the dose when NTCP = 0.5 in the dose-effect curve, V eff It is called the effective volume of an organ or tissue, m describes the steepness of the dose-response curve, and n describes the relationship between the organ volume and the dose effect, with reference to the tumor control probability (TCP) constraint for setting the biological target volume (BTV).

4. A radiotherapy planning method based on biological optimization according to claim 2, characterized in that: The biological constraint limit setting refers to the primary optimization results, including: Select the type of biological restraint based on the current biological target area or organ at risk; Combined with the primary dose result information obtained from the primary optimization, the corresponding tumor control probability (TCP) or normal tissue complication probability (NTCP) is calculated to obtain a reference for setting biological constraint limits, and then set biological constraints.

5. The method for radiotherapy planning based on biological optimization according to claim 2, characterized in that: The physical constraints set for the biological target and the organ at risk include: the dose of the target or the organ at risk is greater than a certain limit value D min , the dose to the target area or the organ at risk is less than a certain limit value D max , and the average dose limit D for the target area or organs at risk mean .

6. A radiotherapy planning method based on biological optimization according to claim 5, characterized in that: The objective function constructed including biological constraint penalty term and physical constraint penalty term includes: Add prescription items to biological constraints, cost(TCP)=W×(prescription*(TCP actual -TCP expected )) 2 c0st(NTCP)=W×(prescription*(NTCP actual -NTCP expected )) 2 Add gEUD term to biological constraints, cost(TCP)=W×(gEUD*(TCP actual -TCP expected )) 2 cost(NTCP)=W×(gEUD*(NTCP actual -NTCP expected )) 2 The objective function is Where W represents the weight, prescription represents the prescription dose, gEUD represents the generalized equivalent uniform dose, K represents the sum of physical constraints, H function is a 0-1 function, which is 0 when the constraint requirements are met and 1 when they are not met, D actual is the actual value, D p is the limit value.

7. A radiotherapy planning method based on biological optimization according to claim 1, characterized in that: The primary dose result of the primary optimization may be a dose result obtained by a complete plan optimization, or may be an intermediate dose result obtained by a pause function in the plan optimization.

8. The method for radiotherapy planning based on biological optimization according to claim 1, characterized in that: include: Evaluating the planning quality of the final radiotherapy plan by various evaluation indicators, wherein the evaluation indicators include target area dose volume indicators and organ at risk dose volume indicators; If the clinical requirements are met in terms of various evaluation indicators, the radiotherapy plan is formulated, otherwise the constraint settings are adjusted and optimization continues.

9. A system for implementing the radiotherapy planning method based on biological optimization as claimed in any one of claims 1 to 8, characterized in that: include: The biological target delineation module fuses positron emission tomography (PET) images and computed tomography (CT) images, delineates the biological target area according to the threshold of the standard uptake value (SUV) of the imaging agent, and delineates the organs at risk at the same time; The primary optimization module sets physical constraints for biological targets and organs at risk, performs primary optimization, and obtains primary dose results; The constraint setting module sets biological constraints for biological targets and organs at risk based on the primary dose results; The re-optimization module constructs an objective function that includes biological constraint penalty terms and physical constraint penalty terms, and obtains the final radiotherapy plan through iterative optimization.

10. A radiotherapy planning system based on biological optimization according to claim 9, characterized in that: Includes program evaluation modules: Evaluating the planning quality of the final radiotherapy plan by various evaluation indicators, wherein the evaluation indicators include target area dose volume indicators and organ at risk dose volume indicators; If the clinical requirements are met in terms of various evaluation indicators, the radiotherapy plan is formulated, otherwise the constraint settings are adjusted and optimization continues.

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