Compensator intensity-modulated X-ray Flash radiotherapy planning system and method

Abstract

The invention provides an X-ray Flash radiotherapy system and method with intensity modulated by a compensator, and belongs to the technical field of radiotherapy equipment control. A patient data management module is used for acquiring basic information, patient image data and patient radiotherapy plan data of a patient; the region-of-interest determination module is used for determining a radiotherapy region-of-interest; and the Flash plan design module with the intensity modulated by the compensator can be used for calculating the Flash effective dose of a patient and obtaining an optimal X-ray Flash plan with the intensity modulated by the compensator according to clinical requirements. According to the method, the effective doses of different Flash effect models are calculated, and the X-ray Flash plan with the intensity modulated by the compensator is optimized in a step-by-step or synchronous mode; technical conditions are provided for realizing X-ray Flash intensity modulated radiation therapy and clinical application thereof; the blank of the X-ray Flash radiotherapy technology is filled, and the method has important significance for converting and applying the Flash radiotherapy technology.

Description

Technical Field

[0001] The present invention relates to the technical field of radiotherapy equipment control, and in particular to a compensator intensity-modulated X-ray Flash radiotherapy planning system and method. Background Art

[0002] Very high dose rate radiotherapy (FLASH radiotherapy) is an emerging radiotherapy technology, which is defined as irradiation with a dose rate of more than 40 Gy / s. The main feature of this technology is that compared with traditional radiotherapy, it can significantly reduce damage to normal tissues while maintaining the therapeutic effect on tumors. The protective effect of FLASH radiotherapy was first discovered in the 1950s and 1960s, but due to technical and cognitive limitations, research stagnated for about 40 years. In 2014, Favaudon et al. of the Curie Institute in France rediscovered this radiation protection effect and named it the FLASH effect. Since then, a number of animal model studies have verified the protective effect of ultra-high dose rate radiotherapy on normal tissues. The human trial FAST-01 conducted at Cincinnati Children's Hospital in the United States also showed that FLASH radiotherapy is comparable to traditional dose rates in terms of pain relief and is clinically feasible and safe. These studies have shown that FLASH radiotherapy, due to its extremely short radiation delivery time, has changed the biological effects of traditional radiotherapy on normal tissues, while solving the problem of tissue and organ movement management, and may bring economic benefits and improve patient treatment comfort and efficiency.

[0003] According to the different types of rays used, Flash radiotherapy technology can be divided into proton Flash, electron Flash and X-ray Flash. At present, X-rays are the most widely used in the field of radiotherapy, so X-ray Flash technology has received widespread attention. According to different implementation methods, X-ray Flash radiotherapy technology can be divided into open field irradiation technology, conformal irradiation technology and intensity modulated irradiation technology. Among them, open field X-ray Flash irradiation technology mainly uses tungsten gates to form irradiation fields of fixed shapes and different sizes. Since the shape of the radiation field formed by this technology is simple and cannot cope with the complex anatomical structure of patients, it is only used in clinical experiments. Conformal X-ray Flash irradiation technology can use multi-leaf collimator blocks to conform the radiation field according to the shape of the target area, or customize the block conformity. This technology can be used to treat some tumors with relatively simple geometric position relationships between the tumor target area and the organs at risk, but it cannot protect normal organs embedded in or surrounded by the tumor, nor can it achieve local dose increase of the tumor target area. Intensity modulated X-ray Flash irradiation can not only achieve conformal treatment of the tumor target, but also effectively protect normal organs embedded in or surrounded by the tumor, and can also achieve local dose increase in the tumor target. However, no researchers have yet proposed a feasible intensity modulated X-ray Flash radiotherapy method, mainly because Flash radiotherapy requires beam emission to be completed in a very short time (about tens of milliseconds), and the existing X-ray intensity modulated technology using multi-leaf collimators is difficult to complete the adjustment of leaf positions in such a short time.

[0004] Currently, X-ray Flash can only perform conformal radiotherapy, not intensity-modulated radiotherapy. This is mainly because the number of leaves and the speed of dose rate change required for X-ray Flash intensity-modulated radiotherapy using traditional multi-leaf collimators far exceed the engineering limit. This affects the quality of X-ray Flash radiotherapy plans and limits the protection effect of Flash.

[0005] In order to realize intensity-modulated X-ray Flash radiotherapy, a corresponding planning system is needed. This planning system should not only have the functions of a conventional X-ray radiotherapy planning system, but also have the function of compensator intensity-modulated X-ray Flash radiotherapy plan design. Specifically, it should include a biological dose calculation model that considers the Flash protection effect, an optimization algorithm for compensator intensity-modulated X-ray Flash radiotherapy plans, an interactive interface for inputting Flash radiotherapy plan optimization parameters, and a data interactive interface that can output compensator thickness step-by-step. Only by using this system can the clinical application of compensator intensity-modulated X-ray Flash radiotherapy be promoted. However, none of the existing planning systems have the function of intensity-modulated X-ray Flash radiotherapy plan design. Summary of the invention

[0006] The purpose of the present invention is to provide a compensator intensity-modulated X-ray Flash radiotherapy planning system and method to enhance the quality of X-ray Flash radiotherapy planning and improve the treatment effect, so as to solve at least one technical problem existing in the above-mentioned background technology.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a compensator intensity-modulated X-ray Flash radiotherapy planning system, comprising:

[0009] Patient data management module, used to obtain the patient's basic information, patient imaging data, and patient radiotherapy plan data;

[0010] A region of interest determination module is used to determine the region of interest for radiotherapy;

[0011] The compensator intensity-modulated Flash plan design module is used to calculate the Flash effective dose based on the plan parameters and the patient's plan CT, and calculate the Flash effective dose based on the set plan parameters to generate the optimal Flash plan parameters.

[0012] As a further limitation of the first aspect of the present invention, the Flash effective dose calculation is performed according to the planning parameters and the patient planning CT, including:

[0013] The instantaneous intensity distribution of the beam after passing through the compensator is:

[0014]

[0015] Among them, i represents the number of the radiation field, t represents the treatment time, and m i (t) represents the instantaneous machine dose rate varying with time, S i represents the field geometry parameters, and represents the thickness distribution and density information of the compensator; F is the function of calculating the intensity distribution using the dose engine of the conventional X-ray radiotherapy planning system, F S (t) is the time-varying instantaneous intensity distribution generated by the Flash accelerator head;

[0016] Then, the physical dose distribution in the patient's body that changes with time is:

[0017]

[0018] I ct represents the planned CT image, D is the function of calculating the physical dose distribution in the patient using the dose engine of the conventional X-ray radiotherapy planning system; G i It indicates the bed angle of the field; D phy(t) is converted into Flash effective dose D using the following formula FE (t):

[0019] D FE =∫M·dD phy .

[0020] As a further limitation of the first aspect of the present invention, in combination with the expected clinical goals of clinical target coverage and protection of organs at risk, the objective function of the planning optimization model is expressed as:

[0021]

[0022]

[0023] Among them, f is the total objective function to be optimized, Obj i With w T,i Respectively represent the dose objective function of the i-th tumor target area and the corresponding weight, N represents the total number of radiation fields, Res(P) function is the constraint function of the parameter to be optimized, P represents the parameter to be optimized, T represents the dose constraint to the organ at risk that must not be exceeded to ensure treatment safety. forced is the corresponding threshold.

[0024] As a further limitation of the first aspect of the present invention, a Flash effective dose calculation model that depends only on the dose rate is adopted, and the dose correction factor matrix is:

[0025]

[0026] Where d is a 3×1 vector representing the spatial coordinates of the voxel, R min The minimum dose rate that triggers the Flash protection effect, p is a constant less than 0 and greater than 1.

[0027] As a further limitation of the first aspect of the present invention, if a Flash effective dose calculation model that depends on dose and dose rate thresholds is adopted, the dose correction factor matrix is ​​expressed as:

[0028]

[0029] Among them, D min Indicates the minimum cumulative dose that triggers the Flash protection effect.

[0030] In a second aspect, the present invention provides a compensator intensity-modulated X-ray Flash radiotherapy planning method, comprising:

[0031] Obtain the patient's basic information, patient imaging data, and patient radiotherapy plan data;

[0032] Identify the region of interest for radiotherapy;

[0033] The Flash effective dose is calculated based on the planning parameters and the patient's planning CT, and the Flash effective dose is calculated based on the set planning parameters to generate the optimal Flash planning parameters.

[0034] As a further limitation of the second aspect of the present invention, the Flash effective dose calculation is performed according to the planning parameters and the patient's planning CT, including:

[0035] The instantaneous intensity distribution of the beam after passing through the compensator is:

[0036]

[0037] Among them, i represents the number of the radiation field, t represents the treatment time, and m i (t) represents the instantaneous machine dose rate varying with time, S i represents the field geometry parameters, and represents the thickness distribution and density information of the compensator; F is the function of calculating the intensity distribution using the dose engine of the conventional X-ray radiotherapy planning system, F S (t) is the time-varying instantaneous intensity distribution generated by the Flash accelerator head;

[0038] Then, the physical dose distribution in the patient's body that changes with time is:

[0039]

[0040] I ct represents the planned CT image, D is the function of calculating the physical dose distribution in the patient using the dose engine of the conventional X-ray radiotherapy planning system; G i It indicates the bed angle of the field; D phy (t) is converted into Flash effective dose D using the following formula FE (t):

[0041] D FE =∫M·dD phy .

[0042] As a further limitation of the second aspect of the present invention, in combination with the expected clinical goals of clinical target coverage and protection of organs at risk, the objective function of the planning optimization model is expressed as:

[0043]

[0044] Among them, f is the total objective function to be optimized, Obj i With w T,iRespectively represent the dose objective function of the i-th tumor target area and the corresponding weight, N represents the total number of radiation fields, Res(P) function is the constraint function of the parameter to be optimized, P represents the parameter to be optimized, T represents the dose constraint to the organ at risk that must not be exceeded to ensure treatment safety. forced is the corresponding threshold.

[0045] As a further limitation of the second aspect of the present invention, a Flash effective dose calculation model that only depends on the dose rate is adopted, and the dose correction factor matrix is:

[0046]

[0047] Where d is a 3×1 vector representing the spatial coordinates of the voxel, R min The minimum dose rate that triggers the Flash protection effect, p is a constant less than 0 and greater than 1.

[0048] As a further limitation of the second aspect of the present invention, if a Flash effective dose calculation model that depends on dose and dose rate thresholds is adopted, the dose correction factor matrix is ​​expressed as:

[0049]

[0050] Among them, D min Indicates the minimum cumulative dose that triggers the Flash protection effect.

[0051] Beneficial effects of the invention: The invention proposes a compensator-modulated X-ray Flash radiotherapy method and system, realizes the calculation of the effective dose of different Flash effect models, and optimizes the compensator-modulated X-ray Flash plan in a step-by-step or synchronous manner; provides technical conditions for realizing X-ray Flash intensity-modulated radiotherapy and its clinical application; fills the gap in X-ray Flash radiotherapy technology, which is of great significance for the transformation and application of Flash radiotherapy technology and improving the level of cancer treatment.

[0052] Additional advantages of the present invention will be more clearly given in the following description or learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0054] Figure 1This is a functional principle framework diagram of the compensator intensity-modulated X-ray Flash radiotherapy planning system described in an embodiment of the present invention.

[0055] Figure 2 This is a schematic diagram of the compensator intensity-modulated X-ray Flash radiotherapy principle described in an embodiment of the present invention.

[0056] Figure 3 Schematic diagram of the relationship between the effective dose of Flash and the physical dose depending on the dose rate threshold according to an embodiment of the present invention.

[0057] Figure 4 It is a schematic diagram of the relationship between the physical dose and the Flash effective dose in the X-ray Flash plan including three fields according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below by the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0059] It should be understood by those skilled in the art that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.

[0060] It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning consistent with that in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless as defined herein.

[0061] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or groups thereof.

[0062] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. Different embodiments or examples described in this specification and features of different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

[0063] To facilitate understanding of the present invention, the present invention is further explained below with reference to specific embodiments in conjunction with the accompanying drawings, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0064] Those skilled in the art should understand that the drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily necessary for implementing the present invention.

[0065] The invention provides an X-ray Flash radiotherapy technology using compensator intensity modulation, designs an optimization model applied to X-ray Flash radiotherapy plan design; and designs a complete set of compensator intensity modulation Flash radiotherapy plan system.

[0066] The compensator in the present invention is made of high-density materials (such as copper or lead), which can effectively attenuate the intensity of the X-ray beam, thereby reducing the dose of the X-ray passing through the area. Figure 1 As shown in the figure, since the dose reduction degree of different regions is different, the compensator will be processed into uneven thickness. During radiotherapy, when the X-ray Flash beam passes through different parts of the compensator, it will be attenuated to different degrees due to the different thickness of the compensator, and the beam intensity distribution will change accordingly, thereby realizing the intensity adjustment of the X-ray Flash beam. In addition, the dose rate of the beam will decrease after the compensator is modulated, and the generation of the Flash protection effect generally requires a dose rate ≥40Gy / s. Therefore, unlike conventional dose radiotherapy, the thickness of the compensator for X-ray Flash radiotherapy cannot be too thick, so that the dose rate of the beam after intensity modulation can meet the requirements of Flash technology as much as possible.

[0067] A compensator intensity-modulated X-ray Flash radiotherapy plan design method is proposed, which is an inverse optimization design method. In terms of the objective function, since the Flash protection effect is related to the uninterrupted cumulative dose and dose rate, the present invention will first calculate the physical dose distribution and dose rate distribution in the patient's body. Afterwards, the physical dose in the traditional optimization algorithm is converted into the Flash effective dose according to the Flash effect model. Finally, the objective functions of the tumor target area and each organ at risk are calculated according to the Flash effective dose distribution, so as to maximize the Flash protection effect.

[0068] A compensator intensity-modulated X-ray flash radiotherapy planning system is proposed. Based on the existing conventional dose rate X-ray radiotherapy planning system, the planning system adds the function of X-ray flash radiotherapy planning design. In addition, the system supports two types of X-ray flash plan designs, namely, X-ray flash plans using multi-leaf grating collimators and X-ray flash plans with compensator intensity modulation. Finally, in addition to outputting standard Dicom RT plan data, the planning system can also output the thickness distribution information of the compensator to make the compensator required for the intensity-modulated flash plan.

[0069] The following is a further comparison and explanation of the limitations of the existing Flash radiotherapy method and the innovation of the present invention by retrieving the literature (currently there is no patent for X-ray Flash with compensator intensity modulation):

[0070] First, in terms of proton flash radiotherapy, the existing technologies mainly include shot & through proton irradiation (Shoot & Through) and conformal proton irradiation (Conformal Flash). Shoot & Through irradiation technology uses a large amount of energy to make the proton beam penetrate the patient's body, and completely relies on the flash effect to protect the endangered organs. This technology does not need to consider the uncertainty of the Bragg Peak position, but correspondingly, it cannot give full play to the advantage of the rapid drop in proton dose. Conformal irradiation uses ridge filters to modulate the proton beam intensity, which can achieve conformal intensity-modulated proton flash radiotherapy. However, both of the above methods require large and expensive proton radiotherapy systems, and the equipment cost is relatively high. Electronic Flash can use multi-leaf grating collimators for conformal radiotherapy, but the quality of the plan needs to be improved. In addition, electronic Flash can also use compensators to achieve intensity-modulated radiotherapy, but the compensator will cause the maximum range of the electronic treatment beam to decrease rapidly, making it difficult to apply to tumor targets with deeper locations. Compared with the above technologies, the compensator-modulated X-ray Flash radiotherapy technology constructed by the present invention does not require the high equipment cost of proton Flash; in addition, due to the strong penetrability of X-rays, there is no problem like electron Flash that cannot treat deeper target areas; finally, compared with conformal X-ray Flash radiotherapy, the present invention can obtain better plan quality.

[0071] The present invention provides a method and system for compensator intensity-modulated X-ray Flash radiotherapy, which provides perfect technical support for effectively carrying out X-ray Flash radiotherapy and promotes its clinical application.

[0072] In this embodiment, Figure 2 As shown, a compensator intensity-modulated X-ray Flash radiotherapy planning system is first provided. It can be seen that, similar to the conventional dose rate planning system, the planning system includes a patient data management module to manage basic patient information, patient imaging data, patient planning data, etc.; the region of interest delineation module allows doctors or physicists to manually or automatically delineate the target area, organs at risk, and other contours. Afterwards, the patient's planned CT, delineated region of interest, and other information can be used for planning design.

[0073] According to clinical needs, the planning system described in this embodiment can design three types of plans: 1) The conventional dose rate plan design module includes three submodules: conventional dose rate plan parameter input, physical dose calculation, and conventional dose rate plan reverse optimization. This module can realize the design of traditional conventional dose IMRT or VMAT radiotherapy plans; 2) The MLC conformal Flash plan design module includes two submodules: parameter input and Flash effective dose calculation. The parameter input submodule mainly provides users with an interactive interface for inputting conformal Flash parameters such as gantry angle, dose rate range, and conformal boundary magnification. The Flash effective dose calculation submodule calculates the Flash effective dose based on the plan parameters and the patient plan CT. Since the conformal Flash plan generally adopts forward optimization, there is no reverse optimization function; 3) The compensator intensity modulated Flash plan design module includes three submodules: parameter input, Flash effective dose calculation, and compensator intensity modulated Flash plan reverse optimization. Among them, the parameter input submodule is mainly used to input parameters such as gantry angle, compensator material, and compensator initial thickness. The Flash effective dose calculation submodule calculates the Flash effective dose based on the plan parameters and the patient plan CT. The reverse optimization function of the compensator intensity-modulated Flash plan calculates the Flash effective dose based on the set plan parameters and automatically generates the optimal Flash plan parameters.

[0074] For the three plans obtained, this planning system can transmit them to other systems in standard DicomRT format through the planning parameter output module. In addition, since the flash plan of compensator intensity modulation requires the preparation of the compensator, this planning system includes a compensator parameter output module that can output the thickness distribution information of the compensator.

[0075] This system can be used to design X-ray flash radiotherapy plans with compensator intensity modulation. At the same time, you can also freely choose X-ray conventional dose rate plans or MLC conformal X-ray flash plans to meet various clinical needs.

[0076] In this embodiment, for the X-ray Flash effective dose distribution calculation model with compensator intensity modulation, the dose distribution calculation model of the existing X-ray radiotherapy plan design system does not take the Flash protection effect into consideration. Therefore, in this embodiment, it is necessary to combine the traditional dose distribution calculation model with the Flash effect model to construct a Flash effective dose distribution calculation model.

[0077] The instantaneous intensity distribution of the beam after passing through the compensator can be calculated using the following formula:

[0078]

[0079] Where i represents the number of the radiation field, and t represents the treatment time. i (t) represents the instantaneous machine dose rate (in beats / minute) varying with time, S i Indicates the field geometry parameters, such as shape, size, etc. and represents the thickness distribution and density information of the compensator. F is the function of intensity distribution calculated by the dose engine of the conventional X-ray radiotherapy planning system, F S (t) is the instantaneous intensity distribution generated by the flash accelerator head that varies with time. According to (1), the physical dose distribution in the patient's body that varies with time can be obtained:

[0080]

[0081] Here I ct G represents the planned CT image, and D is the function of calculating the physical dose distribution in the patient using the dose engine of the conventional X-ray radiotherapy planning system. i It represents the bed angle of the field. According to the work of MacKay et al. (MacKay, 2021), D phy (t) can be converted into the effective dose of Flash D using the following formula FE (t):

[0082] D FE =∫M·dD phy (3)

[0083] For the X-ray Flash plan optimization model with compensator intensity modulation, since the Flash effect is mainly reflected in the protection of organs at risk, the dose target of the tumor target area is still calculated using the physical dose to reduce the amount of calculation; while for the dose constraint conditions of organs at risk, the calculated D FE Perform calculations.

[0084] In this embodiment, the objective function of the planning optimization model can be expressed as follows, combining the expected clinical goals of clinical target coverage and protection of organs at risk:

[0085] f=∑ i w T, i i (D phy )+∑ j w o,j Con j (D FE )+N (4)

[0086]

[0087] Where f is the overall objective function to be optimized.i With w T,i Respectively represent the dose objective function of the i-th tumor target area and the corresponding weight. N represents the total number of fields. This item is mainly due to the fact that when a certain field finishes beam emission, the Flash effect will be interrupted. If a new field produces a Flash effect again, the cumulative dose needs to be recalculated and made to exceed the threshold. Therefore, the more fields there are, the weaker the Flash protection effect will be. The Res(P) function is a constraint function of the parameters to be optimized, and P represents the parameters to be optimized. In this embodiment, P can be multiple parameters such as the instantaneous intensity distribution after compensation and the thickness of the compensator. T represents the dose constraint to the organ at risk that must not be exceeded to ensure treatment safety. forced is the corresponding threshold.

[0088] In a specific embodiment, if a Flash effective dose calculation model that only depends on the dose rate is used, the dose correction factor matrix can be expressed as follows:

[0089]

[0090] Where d is a 3×1 vector representing the spatial coordinates of the voxel. min is the minimum dose rate that triggers the Flash protection effect. p is a constant less than 0 and greater than 1. It should be noted that the dose correction factor matrix is ​​a four-dimensional matrix. This is mainly because the dose of voxel points at different positions in the patient's body will continue to change over time, which means that the dose rate of voxel points at different positions and times may be different. Therefore, the corresponding dose correction factor matrix needs to contain three spatial dimensions and one time dimension to achieve accurate calculation of the effective Flash dose in the patient's body.

[0091] Figure 3 The relationship between the effective dose and physical dose of Flash that depends on the dose rate threshold is shown. It can be seen that the effective dose and physical dose of traditional X-ray radiotherapy are in a 1:1 relationship. However, for X-ray Flash radiotherapy, as the accumulated physical dose increases, the growth rate of the effective dose is less than 1. This means that X-ray Flash radiotherapy can provide better protection of normal tissues and organs.

[0092] In another specific embodiment, if a Flash effective dose calculation model that depends on dose and dose rate thresholds is used, the dose correction factor matrix can be expressed as follows:

[0093]

[0094] Among them, d and R min The definition of is consistent with that in (4). minrepresents the minimum cumulative dose that triggers the Flash protection effect. p is a constant less than 0 and greater than 1. It can be seen that, unlike (4), in (5), the generation of the Flash protection effect requires that the dose rate is greater than R min And the cumulative dose is greater than D min If one of the two conditions is not met, the Flash protection effect will be small.

[0095] Figure 4 The relationship between physical dose and effective dose in an X-ray Flash plan with three fields is shown. It can be seen that for the first field in X-ray Flash radiotherapy, when the cumulative dose is less than the threshold, the effective dose is equal to the physical dose, which is consistent with traditional X-ray radiotherapy. However, when the cumulative dose exceeds the threshold, the Flash protection effect occurs, and the growth rate of the effective dose is significantly reduced. After the first field ends and switches to the second field, the cumulative dose needs to be recalculated, so the growth rate of the effective dose relative to the physical dose returns to 1 again. When the cumulative physical dose exceeds the threshold, the growth rate of the effective dose decreases again. Therefore, we can see that when the number of fields increases, the relationship between the physical dose and the effective dose becomes more complicated. It is necessary to clarify the relationship between the changes in the patient's body dose distribution and each field in order to obtain an accurate effective dose distribution.

[0096] In another specific embodiment, a traditional X-ray intensity modulation plan optimization framework can be used, that is, firstly optimizing the intensity distribution, and then solving the executable plan parameters according to the obtained intensity distribution. In this way, the optimization objective function can be expressed as:

[0097] f=Σ i w T,i Obj i (D phy (F c (t),G i ))+Σ j w o,j Con j (D FE (F c (t),G i ))+N (7)

[0098]

[0099] It can be seen that f is expressed as the corrected field intensity matrix F c (t) is a function of the number of fields N. c The nth column of (t) corresponds to the vectorization F_d min Indicates the minimum instantaneous field intensity that can produce the Flash protection effect.max It is the maximum instantaneous field intensity after compensation that can be achieved by the accelerator. It should be noted that the number of fields is added to the optimization objective function mainly because for the calculation of Flash effective dose that depends on the dose and dose rate threshold, the more fields there are, the closer the Flash effective dose and physical dose are, and the weaker the Flash protection effect is.

[0100] Using (6), the model can generate the compensated instantaneous intensity distribution matrix and the number of fields:

[0101]

[0102] After obtaining the target intensity distribution, we can solve the compensator thickness distribution according to the classical X-ray attenuation equation. The objective function is as follows:

[0103]

[0104] in, Represents the target intensity distribution of the nth field. open Represents the intensity distribution of the accelerator open field. represents the compensator thickness distribution of the nth field. |.|2 represents the operator for calculating the second norm. μ0 is the linear attenuation coefficient corresponding to the compensator material. c1, c2, c3 are hyperparameters, and their specific values ​​will be updated during the iterative optimization process. r represents the off-axis distance of the beam, and S represents the size of the open field of the accelerator head. Here c2·r and c3.S are used to correct the influence of beam hardening effect, beam divergence effect and X-ray scattering on intensity distribution, respectively.

[0105] Using (10), we can obtain the thickness distribution of the compensator, the number of machine jumps, and the size of the open field:

[0106]

[0107] In this embodiment, the compensator parameters can also be directly output. At this time, the objective function of the optimization model can be expressed as:

[0108] f=∑ j u i Obj i (D phy (C,Ma(t)))+∑ j v j Con j (D FE (C,Ma(t)))+N (11)

[0109]

[0110] It can be seen that f is expressed as a function of the compensator parameter matrix C, the accelerator parameters Ma(t), and the number of fields N. Ma(t) consists of the instantaneous machine dose rate m(t) and the field size S(t). C consists of the compensator thickness distribution matrix of all field vectorizations. min With m max They represent the minimum machine dose rate required to produce the Flash effect and the maximum machine dose rate that the accelerator can achieve. min With S max Represents the minimum and maximum field sizes respectively. max Indicates the maximum compensator thickness allowed to produce the Flash protection effect. By solving the minimum value of f, the optimal compensator and accelerator parameters can be obtained:

[0111]

[0112] In summary, the present invention proposes a compensator-modulated X-ray Flash radiotherapy method and system, providing technical conditions for realizing X-ray Flash intensity modulated radiotherapy and its clinical application. Compensator-modulated X-ray Flash radiotherapy not only includes current research hotspots (Flash radiotherapy), but also includes areas that have never been explored in Flash radiotherapy. The technical conditions provided not only provide a comprehensive and flexible X-ray Flash intensity modulated radiotherapy technical framework and basic methods, but also describe the specific implementation details, such as calculating the effective dose of different Flash effect models, and optimizing the compensator-modulated X-ray Flash plan in a step-by-step or synchronous manner. The method and system provided by the present invention can fill the gap in X-ray Flash radiotherapy technology, which is of great significance to the transformation and application of Flash radiotherapy technology and improving the level of cancer treatment.

[0113] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0114] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0115] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing device, and a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0117] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. A compensator intensity-modulated X-ray Flash radiotherapy planning system, characterized in that: include: Patient data management module, used to obtain the patient's basic information, patient imaging data, and patient radiotherapy plan data; A region of interest determination module is used to determine the region of interest for radiotherapy; The compensator intensity-modulated Flash plan design module is used to calculate the Flash effective dose based on the plan parameters and the patient's plan CT, and calculate the Flash effective dose based on the set plan parameters to generate the optimal Flash plan parameters.

2. The compensator intensity-modulated X-ray Flash radiotherapy planning system according to claim 1, characterized in that: Flash effective dose calculation is performed based on planning parameters and patient planning CT, including: The instantaneous intensity distribution of the beam after passing through the compensator is: Among them, i represents the number of the radiation field, t represents the treatment time, and m i (t) represents the instantaneous machine dose rate varying with time, S i represents the field geometry parameters, and represents the thickness distribution and density information of the compensator; F is the function of intensity distribution calculated by the dose engine of the conventional X-ray radiotherapy planning system, F S (t) is the time-varying instantaneous intensity distribution generated by the Flash accelerator head; Then, the physical dose distribution in the patient's body that changes with time is: I ct represents the planned CT image, D is the function of calculating the physical dose distribution in the patient using the dose engine of the conventional X-ray radiotherapy planning system; G i It indicates the bed angle of the field; D phy (t) is converted into Flash effective dose D using the following formula FE (t): D FE =∫M·dD phy 。 3. The compensator intensity-modulated X-ray Flash radiotherapy planning system according to claim 2, characterized in that: Combining the expected clinical goals of clinical target coverage and protection of organs at risk, the objective function of the planning optimization model is expressed as: Among them, f is the total objective function to be optimized, Obj i With w T,i Respectively represent the dose objective function of the i-th tumor target area and the corresponding weight, N represents the total number of radiation fields, Res(P) function is the constraint function of the parameter to be optimized, P represents the parameter to be optimized, T represents the dose constraint to the organ at risk that must not be exceeded to ensure treatment safety. forced is the corresponding threshold.

4. The compensator intensity-modulated X-ray Flash radiotherapy planning system according to claim 2, characterized in that: Using the Flash effective dose calculation model that only depends on the dose rate, the dose correction factor matrix is: Where d is a 3×1 vector representing the spatial coordinates of the voxel, R min The minimum dose rate that triggers the Flash protection effect, p is a constant less than 0 and greater than 1.

5. The compensator intensity-modulated X-ray Flash radiotherapy planning system according to claim 2, characterized in that: If the Flash effective dose calculation model that depends on the dose and dose rate threshold is used, the dose correction factor matrix is ​​expressed as: Among them, D min Indicates the minimum cumulative dose that triggers the Flash protection effect.

6. A compensator intensity-modulated X-ray Flash radiotherapy planning method, characterized in that: include: Obtain the patient's basic information, patient imaging data, and patient radiotherapy plan data; Identify the region of interest for radiotherapy; The Flash effective dose is calculated based on the planning parameters and the patient's planning CT, and the Flash effective dose is calculated based on the set planning parameters to generate the optimal Flash planning parameters.

7. The compensator intensity-modulated X-ray Flash radiotherapy planning method according to claim 6, characterized in that: Flash effective dose calculation is performed based on planning parameters and patient planning CT, including: The instantaneous intensity distribution of the beam after passing through the compensator is: Among them, i represents the number of the radiation field, t represents the treatment time, and m i (t) represents the instantaneous machine dose rate varying with time, S i represents the field geometry parameters, and represents the thickness distribution and density information of the compensator; F is the function of intensity distribution calculated by the dose engine of the conventional X-ray radiotherapy planning system, F S (t) is the time-varying instantaneous intensity distribution generated by the Flash accelerator head; Then, the physical dose distribution in the patient's body that changes with time is: I ct represents the planned CT image, D is the function of calculating the physical dose distribution in the patient using the dose engine of the conventional X-ray radiotherapy planning system; G i It indicates the bed angle of the field; D phy (t) is converted into Flash effective dose D using the following formula FE (t): D FE =∫M·dD phy 。 8. The compensator intensity-modulated X-ray Flash radiotherapy planning method according to claim 7, characterized in that: Combining the expected clinical goals of clinical target coverage and protection of organs at risk, the objective function of the planning optimization model is expressed as: Among them, f is the total objective function to be optimized, Obj i With w T,i Respectively represent the dose objective function of the i-th tumor target area and the corresponding weight, N represents the total number of radiation fields, Res(P) function is the constraint function of the parameter to be optimized, P represents the parameter to be optimized, T represents the dose constraint to the organ at risk that must not be exceeded to ensure treatment safety. forced is the corresponding threshold.

9. The compensator intensity-modulated X-ray Flash radiotherapy planning method according to claim 7, characterized in that: Using the Flash effective dose calculation model that only depends on the dose rate, the dose correction factor matrix is: Where d is a 3×1 vector representing the spatial coordinates of the voxel, R min The minimum dose rate that triggers the Flash protection effect, p is a constant less than 0 and greater than 1.

10. The compensator intensity-modulated X-ray Flash radiotherapy planning method according to claim 7, characterized in that: If the Flash effective dose calculation model that depends on the dose and dose rate threshold is used, the dose correction factor matrix is ​​expressed as: Among them, D min Indicates the minimum cumulative dose that triggers the Flash protection effect.

Images