阅读说明：本技术 放射治疗系统及其治疗计划生成方法 (Radiation therapy system and treatment plan generating method thereof ) 是由 陈江 陈韦霖 于 2020-06-11 设计创作，主要内容包括：一种放射治疗系统及其治疗计划生成方法,放射治疗系统包括射束照射装置、治疗计划模块和控制模块。射束照射装置产生治疗用射束并照射到被照射体形成被照射部位,治疗计划模块根据治疗用射束的参数和被照射部位的医学影像数据生成治疗计划,控制模块从治疗计划模块调取与被照射体对应的治疗计划,并控制射束照射装置按照治疗计划生成方法确定的至少两个照射角度和每个照射角度对应的照射时间依次对被照射体进行照射。本发明的放射治疗系统及其治疗计划生成方法,可以分散被照射部位浅部辐射量和增加病变组织深部的辐射量,以降低正常组织最大剂量和提升病变组织最小剂量,同时保证病变组织内的剂量的均匀分布。(A radiotherapy system includes a beam irradiation device, a treatment planning module, and a control module. The beam irradiation device generates a treatment beam and irradiates the irradiation object to form an irradiation target part, the treatment planning module generates a treatment plan according to parameters of the treatment beam and medical image data of the irradiation target part, and the control module calls the treatment plan corresponding to the irradiation target body from the treatment planning module and controls the beam irradiation device to sequentially irradiate the irradiation target body according to at least two irradiation angles determined by the treatment plan generating method and irradiation time corresponding to each irradiation angle. The radiotherapy system and the treatment plan generating method thereof can disperse the radiation quantity of the shallow part of the irradiated part and increase the radiation quantity of the deep part of the pathological change tissue so as to reduce the maximum dose of the normal tissue and promote the minimum dose of the pathological change tissue, and simultaneously ensure the uniform distribution of the dose in the pathological change tissue.)

1. A radiation therapy system, comprising:

a beam irradiation device that generates a treatment beam and irradiates the treatment object with the treatment beam to form an irradiation target site;

a treatment planning module, configured to generate a treatment plan according to the parameters of the treatment beam generated by the beam irradiation device and the medical image data of the irradiated portion, where the treatment plan determines at least two irradiation angles and an irradiation time corresponding to each irradiation angle, where the irradiation angles are defined as vector directions from an irradiation point of the treatment beam to a preset point of a lesion tissue of the irradiated portion;

and a control module that retrieves the treatment plan corresponding to the irradiation target from the treatment plan module, and controls the beam irradiation device to sequentially irradiate the irradiation target in accordance with at least two irradiation angles determined by the treatment plan and irradiation time corresponding to each of the irradiation angles.

2. The radiation therapy system of claim 1, wherein: the treatment planning module simulates the radiation dose distribution of the irradiated part when the treatment beam is irradiated and generates the treatment plan by combining a mathematical algorithm through a Monte Carlo simulation program.

3. The radiation therapy system of claim 2, wherein: the treatment planning module establishes an objective function of the region of interest according to the simulated radiation dose distribution, optimizes and solves the objective function, and calculates the at least two irradiation angles and the irradiation time corresponding to each irradiation angle.

4. The radiation therapy system of claim 3, wherein: the treatment planning module establishes a three-dimensional voxel false body tissue model according to the medical image data of the irradiated part, inputs the parameters of the treatment beam and the three-dimensional voxel false body tissue model into the Monte Carlo simulation program to simulate the sampling of different irradiation angles, and calculates the radiation dose D received by each voxel unit i in unit time under the sampled irradiation angle k_ki。

5. The radiation therapy system of claim 4, wherein: the objective function adopts a formula I:

wherein d is_iTotal dose for voxel i;a prescribed dose for voxel i;

for a certain integrin i, it is subjected to a total dose d_iThe calculation can be performed using equation two:

wherein, w_kFor the irradiation time at different irradiation angles, D_kiDose per unit time voxel i at illumination angle k, d_iTotal dose for voxel i;

prescription dose of voxel iThe calculation can be performed using equation three:

wherein d is^pNThe prescribed dose for the region of interest N, C_NThe number of voxels for the region of interest.

6. The radiation therapy system of claim 5, wherein: the treatment planning module adopts an optimization algorithm to optimize and solve the objective function through a formula IV:

min{F(d_i) } (four formula)

Defining a design variable of formula four as X, wherein the design variable X is expressed by formula five:

X＝{w₁,w₂…w_k} (formula five);

determining the at least two irradiation angles k and the irradiation time w corresponding to different irradiation angles k according to the optimal solution of the design variable X_k。

7. The radiation therapy system of claim 6, wherein: the treatment planning module establishes a constraint condition for the optimization solution of the objective function, wherein the constraint condition is that one or more normal organs or tissues M are selected, and the total dose d of all voxels i in each normal organ or tissue M_iAnd d_MThe formula six is satisfied:

g(d_M) < 0 (equation six).

8. The radiation therapy system of claim 3, wherein: the treatment planning module evaluates or prefers the results of the objective function optimization solution by dose review.

9. A treatment plan generation method, comprising:

establishing a three-dimensional voxel prosthesis tissue model according to medical image data;

defining beam parameters in a Monte Carlo simulation program, simulating by sampling different irradiation angles, and calculating the radiation dose D received by each voxel unit i in unit time under the irradiation angle k of the sample_kiA step (2);

and establishing an objective function of the region of interest, and calculating at least two irradiation angles and irradiation time corresponding to each irradiation angle by performing optimization solution on the objective function, wherein the irradiation angle is defined as the vector direction from the irradiation point of the beam to a preset point of lesion tissue of the three-dimensional voxel prosthesis tissue model.

10. The treatment plan generation method according to claim 9, characterized in that: the objective function adopts a formula I:

wherein d is_iIs the total dose of the voxel i,a prescribed dose for voxel i;

for a certain integrin i, it is subjected to a total dose d_iThe calculation can be performed using equation two:

wherein, w_kFor the irradiation time at different irradiation angles, D_kiDose per unit time voxel i at illumination angle k, d_iTotal dose for voxel i;

prescription dose of voxel iThe calculation can be performed using equation three:

wherein d is^pNThe prescribed dose for the region of interest N, C_NThe number of voxels for the region of interest.

11. The treatment plan generation method according to claim 10, characterized in that: and adopting an optimization algorithm to carry out optimization solution on the objective function through a formula four:

min{F(d_i) } (four formula)

Defining a design variable of formula four as X, wherein the design variable X is expressed by formula five:

X＝{w₁,w₂…w_k} (formula five);

determining the at least two irradiation angles k and the irradiation time w corresponding to different irradiation angles k according to the optimal solution of the design variable X_k。

12. The treatment plan generation method according to claim 11, characterized in that: the treatment plan generating method further comprises the step of establishing a constraint condition for the optimization solution of the objective function, wherein the constraint condition is that one or more normal organs or tissues M are selected, and the total dose d of all voxels i in each normal organ or tissue M is_iAnd d_MThe formula six is satisfied:

g(d_M) < 0 (equation six).

13. The treatment plan generation method according to claim 9, characterized in that: the treatment plan generation method further includes a dose review step by which the results of the objective function optimization solution are evaluated or optimized.

Technical Field

One aspect of the invention relates to a radiation therapy system; another aspect of the present invention relates to a treatment plan generating method, and more particularly, to a treatment plan generating method of a radiation treatment system.

Background

With the development of atomic science, radiation therapy such as cobalt sixty, linacs, electron beams, etc. has become one of the main means of cancer treatment. However, the traditional photon or electron therapy is limited by the physical conditions of the radiation, and can kill tumor cells and damage a large amount of normal tissues in the beam path; in addition, due to the difference in the sensitivity of tumor cells to radiation, conventional radiotherapy is often ineffective in treating malignant tumors with relatively high radiation resistance, such as multiple glioblastoma multiforme (glioblastoma multiforme) and melanoma (melanoma).

In order to reduce the radiation damage of normal tissues around tumor, the target therapy concept in chemotherapy (chemotherapy) is applied to radiotherapy; for tumor cells with high radiation resistance, radiation sources with high Relative Biological Effect (RBE) are also actively developed, such as proton therapy, heavy particle therapy, neutron capture therapy, etc. The Neutron Capture Therapy combines the two concepts, such as Boron Neutron Capture Therapy (BNCT), and provides a better cancer treatment option than conventional radiation by specific accumulation of Boron-containing drugs in tumor cells in combination with precise beam modulation.

Boron neutron capture therapy utilizing boron-containing (¹⁰B) The medicine has the characteristic of high capture cross section for thermal neutrons¹⁰B(n,α)⁷Li neutron capture and nuclear fission reaction generation⁴He and⁷the total range of the two heavily charged particles is about equal to one cell size, so that the radiation damage to organisms can be limited to the cell level, and when boron-containing drugs selectively gather in tumor cells and are matched with a proper neutron source, the aim of locally killing the tumor cells can be achieved on the premise of not causing too much damage to normal tissues.

Radiotherapy is the treatment of tumor cells with high energy radiation to destroy and prevent their growth and division under the tolerance of normal tissue and organ to receive radiation or the slight side effect of restoring, so as to control or cure tumor. Meanwhile, the boron neutron capture treatment benefit depends on the distribution accumulation and the neutron aggregation quantity of boron drugs in the tumor. Boron-containing drugs are affected by tumor characteristics and the metabolic absorption capacity of patients, and patients suitable for boron neutron capture therapy are screened through Positron Emission Tomography (PET) scanning at present. The neutron flux decreases with the depth of the patient, and is inhibited by the action of boron in the medicine, so that the concentration of neutrons in the tumor deep along the neutron incidence direction is small.

The three-dimensional model is widely applied to the fields of scientific experimental analysis and scientific experimental simulation. For example, in the field of nuclear radiation and protection, in order to simulate the absorbed dose of a human body under a certain radiation condition to help a doctor to make a treatment plan, various processing needs to be performed on medical image data by using a computer technology to establish a lattice model required by accurate monte carlo software, and simulation calculation needs to be performed by combining the monte carlo software. In the existing neutron capture treatment planning system, an optimal angle is selected for a neutron beam to irradiate by evaluating the irradiation angle, on one hand, the radiation dose needs to be increased due to the small amount of the concentrated subset in the deep part of a tumor, and on the other hand, the radiation dose needs to be controlled due to the limitation of the acceptable radiation dose of normal tissues and organs, so that the treatment effect is greatly reduced.

Therefore, it is necessary to provide a radiation therapy system and a treatment plan generating method thereof.

Disclosure of Invention

To overcome the deficiencies of the prior art, one aspect of the present invention provides a radiation therapy system comprising a beam irradiation device, a treatment planning module, and a control module. The beam irradiation device generates a treatment beam and irradiates the irradiated body to form an irradiated site. The treatment planning module generates a treatment plan according to the parameters of the treatment beam generated by the beam irradiation device and the medical image data of the irradiated part, and the treatment plan determines at least two irradiation angles and irradiation time corresponding to each irradiation angle, wherein the irradiation angles are defined as the vector directions from the irradiation point of the treatment beam to a preset point of the lesion tissue of the irradiated part. The control module retrieves the treatment plan corresponding to the irradiation target from the treatment plan module, and controls the beam irradiation device to sequentially irradiate the irradiation target in accordance with at least two irradiation angles determined by the treatment plan and irradiation time corresponding to each of the irradiation angles. The radiation treatment is carried out by adopting a plurality of irradiation angles according to the distribution of the pathological tissues, the radiation quantity of the shallow part of the irradiated part is dispersed and reduced, the radiation dose received by normal tissues and the maximum dose of the normal tissues are reduced, and the probability of side effect of the normal tissues after the radiation treatment is further reduced; meanwhile, the total radiation dose can be properly increased so as to increase the dose of the pathological change tissue, particularly the radiation dose at the deep part of the pathological change tissue, and the minimum dose of the pathological change tissue is improved; multiple incidence directions may also make the dose more uniform within the diseased tissue.

Further, the treatment planning module simulates a radiation dose distribution of the irradiated part when the therapeutic beam is irradiated, and generates the treatment plan by combining a mathematical algorithm through a monte carlo simulation program. Furthermore, the treatment planning module establishes an objective function of the region of interest according to the simulated radiation dose distribution, performs optimization solution on the objective function, and calculates the at least two irradiation angles and the irradiation time corresponding to each irradiation angle.

Preferably, the treatment planning module establishes a three-dimensional voxel prosthetic tissue model according to the medical image data of the irradiated part, inputs the parameters of the treatment beam and the three-dimensional voxel prosthetic tissue model into the monte carlo simulation program to simulate the sampling at different irradiation angles, and calculates the radiation dose D received by each voxel unit i in unit time under the sampled irradiation angle k_ki。

Preferably, the three-dimensional voxel false body tissue model has information of tissue type and tissue density, the tissue type, element composition and density are provided more accurately, and the established geometric model is more matched with the real situation reflected by the medical image data. Furthermore, the radiotherapy system is a boron neutron capture treatment system, the three-dimensional voxel prosthesis tissue model also has tissue boron concentration information, the boron-containing medicine concentration in each tissue can be clearly known, and the actual situation can be reflected more truly when boron neutron capture treatment irradiation simulation is carried out.

Preferably, the sampled beam angles may be further filtered during or after sampling the different illumination angles.

Further, the objective function adopts formula one:

wherein d is_iIs the total dose of the voxel i,a prescribed dose for voxel i;

for a certain integrin i, it is subjected to a total dose d_iThe calculation can be performed using equation two:

wherein, w_kFor the irradiation time at different irradiation angles, D_kiDose per unit time voxel i at illumination angle k, d_iTotal dose for voxel i;

prescription dose of voxel iThe calculation can be performed using equation three:

wherein d is^pNThe prescribed dose for the region of interest N, C_NThe number of voxels for the region of interest.

Further, the treatment planning module adopts an optimization algorithm to optimize and solve the objective function through a formula four:

min{F(d_i) } (four formula)

Defining a design variable of formula four as X, wherein the design variable X is expressed by formula five:

X＝{w₁,w₂…w_k} (formula five);

determining the at least two irradiation angles k and the corresponding irradiation at different irradiation angles k according to the optimal solution of the design variable XTime of flight w_k. Preferably, the optimization algorithm is a support vector machine, a response surface method or least squares vector regression.

Further, the treatment planning module establishes constraints on the optimization solution of the objective function. Further, the constraint is to select one or more normal organs or tissues M, and the total dose d of all voxels i in each normal organ or tissue M_iAnd d_MThe formula six is satisfied:

g(d_M) < 0 (equation six).

Preferably, the unit of the dose, the total dose, and the prescribed dose in the above formulae one to six is eq-Gy, and the unit of the irradiation time is s.

As another preference, the treatment planning module evaluates or prefers the results of the objective function optimization solution by dose inspection.

Another aspect of the invention provides a radiation therapy system including a beam irradiation device, a treatment planning module, and a control module. The beam irradiation device generates a treatment beam and irradiates the irradiated body to form an irradiated site. The treatment planning module generates a treatment plan according to the parameters of the treatment beam generated by the beam irradiation device and the medical image data of the irradiated part, and the treatment plan determines a plurality of irradiation angles and a planned irradiation dose corresponding to each irradiation angle, wherein the irradiation angles are defined as the vector directions from the irradiation point of the treatment beam to a preset point of the lesion tissue of the irradiated part. The control module retrieves the treatment plan corresponding to the irradiation target from the treatment plan module, and controls the beam irradiation device to sequentially irradiate the irradiation target at the plurality of irradiation angles and the planned irradiation dose corresponding to each of the irradiation angles in one irradiation treatment process of the irradiation target according to the treatment plan. The radiation treatment is carried out by adopting a plurality of irradiation angles according to the distribution of the pathological tissues, the radiation quantity of the shallow part of the irradiated part is dispersed and reduced, the radiation dose received by normal tissues and the maximum dose of the normal tissues are reduced, and the probability of side effect of the normal tissues after the radiation treatment is further reduced; meanwhile, the total radiation dose can be properly increased so as to increase the dose of the pathological change tissue, particularly the radiation dose at the deep part of the pathological change tissue, and the minimum dose of the pathological change tissue is improved; multiple incidence directions may also make the dose more uniform within the diseased tissue.

Yet another aspect of the present invention provides a treatment plan generating method, including: establishing a three-dimensional voxel prosthesis tissue model according to medical image data; defining beam parameters in a Monte Carlo simulation program, simulating by sampling different irradiation angles, and calculating the radiation dose D received by each voxel unit i in unit time under the irradiation angle k of the sample_kiA step (2); and establishing an objective function of the region of interest, and calculating at least two irradiation angles and irradiation time corresponding to each irradiation angle by performing optimization solution on the objective function, wherein the irradiation angle is defined as the vector direction from the irradiation point of the beam to a preset point of lesion tissue of the three-dimensional voxel prosthesis tissue model. The radiation treatment is carried out by adopting a plurality of irradiation angles, so that the radiation quantity of the shallow part of the irradiated part is dispersed and reduced, the radiation dose received by normal tissues and the maximum dose of the normal tissues are reduced, and the probability of side effect of the normal tissues after the radiation treatment is further reduced; meanwhile, the total radiation dose can be properly increased so as to increase the dose of the pathological change tissue, particularly the radiation dose at the deep part of the pathological change tissue, and the minimum dose of the pathological change tissue is improved; multiple incidence directions may also make the dose more uniform within the diseased tissue.

Preferably, the objective function adopts formula one:

wherein d is_iIs the total dose of the voxel i,a prescribed dose for voxel i;

for a certain integrin i, it is subjected to a total dose d_iCan adoptCalculating by using a formula two:

wherein, w_kFor the irradiation time at different irradiation angles, D_kiDose per unit time voxel i at illumination angle k, d_iTotal dose for voxel i;

prescription dose of voxel iThe calculation can be performed using equation three:

wherein d is^pNThe prescribed dose for the region of interest N, C_NThe number of voxels for the region of interest.

Further, an optimization algorithm is adopted to optimize and solve the objective function through a formula four:

min{F(d_i) } (four formula)

Defining a design variable of formula four as X, wherein the design variable X is expressed by formula five:

X＝{w₁,w₂…w_k} (formula five);

determining the at least two irradiation angles k and the irradiation time w corresponding to different irradiation angles k according to the optimal solution of the design variable X_k. Further, the optimization algorithm is a support vector machine, a response surface method or least squares vector regression.

Further, the treatment plan generating method further includes a step of establishing a constraint condition for the optimization solution of the objective function. Further, the constraint is to select one or more normal organs or tissues M, and the total dose d of all voxels i in each normal organ or tissue M_iAnd d_MThe formula six is satisfied:

g(d_M) < 0 (equation six).

Preferably, the unit of the dose, the total dose, and the prescribed dose in the above formulae one to six is eq-Gy, and the unit of the irradiation time is s.

Preferably, the treatment plan generating method further comprises a step of dose inspection, by which the result of the objective function optimization solution is evaluated or preferred.

Preferably, the step of building a three-dimensional voxel prosthetic tissue model from the medical image data further comprises: reading medical image data; establishing a three-dimensional medical image voxel model; a step of defining or reading the boundary of the region of interest; a step of defining a tissue type (element composition) and a tissue density of each voxel unit; and establishing a three-dimensional voxel false body tissue model. The three-dimensional voxel false body tissue model is established according to the conversion relation between the medical image data and the tissue type and the tissue density, the tissue type (element composition) and the tissue density are more accurately provided, and the established geometric model is more matched with the real situation reflected by the medical image data. Furthermore, the treatment plan generating method is applied to boron neutron capture treatment, the step of establishing the three-dimensional voxel prosthesis tissue model according to the medical image data further comprises the step of defining the tissue boron concentration of each voxel unit, the boron-containing medicine concentration in each tissue can be clearly known, and the actual situation can be reflected more truly when boron neutron capture treatment irradiation simulation is carried out.

Preferably, the sampled beam angles may be further filtered during or after sampling the different illumination angles.

The radiotherapy system and the treatment plan generating method thereof can disperse the radiation quantity of the shallow part of the irradiated part and increase the radiation quantity of the deep part of the pathological change tissue so as to reduce the maximum dose of the normal tissue and promote the minimum dose of the pathological change tissue, and simultaneously ensure the uniform distribution of the dose in the pathological change tissue.

Drawings

FIG. 1 is a schematic diagram of a boron neutron capture reaction.

FIG. 2 is¹⁰B(n,α)⁷Li neutron capture nuclear reaction equation.

FIG. 3 is a block diagram of a neutron capture therapy system of an embodiment of the invention.

FIG. 4 is a flow chart of a method of a treatment planning module generating a treatment plan in an embodiment of the invention.

Fig. 5 is a flow chart of a method of creating a three-dimensional voxel prosthetic tissue model in an embodiment of the invention.

Fig. 6 is a flowchart of a method of establishing an objective function of a region of interest and solving a calculation through optimization in an embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings so that those skilled in the art can implement the embodiments with reference to the description.

As a preferred embodiment of the present invention, a neutron capture treatment system and a treatment plan generating method thereof are used. The following will briefly describe neutron capture therapy, particularly boron neutron capture therapy.

Neutron capture therapy has been increasingly used in recent years as an effective means of treating cancer, with boron neutron capture therapy being the most common, the neutrons that supply boron neutron capture therapy being supplied by nuclear reactors or accelerators. The embodiments of the present invention are exemplified by an accelerator boron neutron capture therapy, the basic components of which generally include an accelerator for accelerating charged particles (e.g., protons, deuterons, etc.), a target and heat removal system, and a beam shaper, wherein the accelerated charged particles interact with a metal target to generate neutrons, and the appropriate nuclear reactions are selected according to the desired neutron yield and energy, the available energy and current of the accelerated charged particles, the physical properties of the metal target, and the like, and the nuclear reactions in question are generally characterized by⁷Li(p,n)⁷Be and⁹Be(p,n)⁹b, both reactions are endothermic. The energy threshold of the two nuclear reactions is 1.881MeV and 2.055MeV respectively, and the ideal neutron source for boron neutron capture treatment is the ultra-high of keV energy levelThermal neutrons, theoretically if a metallic lithium target is bombarded by protons with energy only slightly higher than a threshold value, can produce neutrons with relatively low energy, and can Be used clinically without too much slowing treatment, however, the interaction cross section of the metallic lithium (Li) target and the metallic beryllium (Be) target with protons with threshold energy is not high, and in order to produce a sufficiently large neutron flux, the protons with higher energy are usually selected to initiate nuclear reactions.

Boron Neutron Capture Therapy (BNCT) utilizes Boron-containing (B: (B-N-C-B-N-C-N-C¹⁰B) The medicine has the characteristic of high capture cross section for thermal neutrons¹⁰B(n,α)⁷Li neutron capture and nuclear fission reaction generation⁴He and⁷li two heavily charged particles. Referring to FIGS. 1 and 2, schematic and graphical illustrations of boron neutron capture reactions are shown, respectively¹⁰B(n,α)⁷The Li neutron capture nuclear reaction equation has the average Energy of two charged particles of about 2.33MeV, has high Linear Energy Transfer (LET) and short-range characteristics, and the Linear Energy Transfer and range of alpha particles are 150 keV/mum and 8μm respectively⁷The Li heavily-charged particles are 175 keV/mum and 5μm, the total range of the two particles is about equal to the size of a cell, so the radiation damage to organisms can be limited at the cell level, when boron-containing drugs selectively gather in tumor cells, and a proper neutron source is matched, the aim of locally killing the tumor cells can be achieved on the premise of not causing too much damage to normal tissues.

Referring to fig. 3, the radiation therapy system of the present embodiment is preferably a neutron capture therapy system 100, which includes a neutron beam irradiation device 10, a therapy planning module 20, and a control module 30. The neutron beam irradiation device 10 includes a neutron generation device 11 and a treatment table 12, and the neutron generation device 12 generates a treatment neutron beam N and irradiates the treatment neutron beam N onto a patient on the treatment table 12 to form an irradiation target portion. In neutron capture therapy, in order to simulate the absorption dose of an organism under a certain radiation condition to help a doctor to make a treatment plan, various processes are often carried out on medical images by utilizing computer technology to establish a lattice model required by accurate Monte Carlo software, and simulation calculation is carried out by combining the Monte Carlo software. The treatment planning module 20 simulates radiation dose distribution of the patient during irradiation treatment by a monte carlo simulation program according to the parameters of the neutron beam N generated by the neutron generator 11 and the medical image data of the irradiated part of the patient, and generates a treatment plan by combining a mathematical algorithm. In one embodiment, the treatment planning module 20 establishes an objective function of the region of interest according to the simulated radiation dose distribution, and performs an optimization solution on the objective function to calculate at least two irradiation angles and an irradiation time corresponding to each irradiation angle. It is understood that the at least two illumination angles and the illumination time corresponding to each illumination angle may also be calculated by other methods. The control module 30 retrieves a treatment plan corresponding to the current patient from the treatment planning module 20, and controls the irradiation of the neutron beam irradiation device 10 according to the treatment plan, such as controlling the neutron generation device 11 to generate the neutron beam N and sequentially irradiating the patient on the treatment table 12 according to at least two irradiation angles determined by the treatment plan and the irradiation time corresponding to each irradiation angle. It is understood that the irradiation time corresponding to each irradiation angle may also be a planned irradiation dose corresponding to each irradiation angle, and may be transformed through analog calculation.

Referring to fig. 4, the method for generating a treatment plan by the treatment plan module 20 of the present embodiment specifically includes the following steps:

s410: establishing a three-dimensional voxel prosthesis tissue model according to the medical image data;

s420: defining beam parameters in a Monte Carlo simulation program (such as MCNP, Monte Carlo N Particle Transport Code), simulating by sampling different irradiation angles k, and calculating the dose distribution D of the voxel i of the three-dimensional voxel false body tissue model at different irradiation angles k in unit time_ki；

S430: and establishing an objective function of the region of interest, and calculating at least two irradiation angles and irradiation time corresponding to each irradiation angle through optimization solution. The so-called region of interest may be a critical organ, such as an eye, a liver, etc.; but also important tissues such as bone tissue, brain tissue, etc.; or may be a tumor cell.

S440: and dose inspection, namely evaluating or optimizing the result of the optimization solution of the objective function.

Referring to fig. 5, in an embodiment, the step S310 of building a three-dimensional voxel prosthesis tissue model according to the medical image data may further include:

s510: reading medical image data;

s520: establishing a three-dimensional medical image voxel model;

s530: defining or reading the boundary of the region of interest;

s540: defining the tissue type (element composition) and tissue density of each voxel unit, which can be automatically defined according to the conversion relationship between the CT image data and the tissue type and tissue density; it may also be manually user defined, such as by giving a specific tissue type and tissue density to the voxel cells within the boundary of each region of interest.

S550: and establishing a three-dimensional voxel false body tissue model.

The three-dimensional voxel false body tissue model is established according to the conversion relation between the medical image data and the tissue type and the tissue density, the tissue type (element composition) and the tissue density are more accurately provided, and the established geometric model is more matched with the real situation reflected by the medical image data. When the radiotherapy system is a boron neutron capture therapy system, the step S410 of establishing a three-dimensional voxel prosthesis tissue model according to the medical image data may further include, after S540, S560: the tissue boron concentration per voxel unit is defined. It is understood that S560 may also precede S540. The boron concentration information of the tissues is marked on the geometric model, so that the boron-containing medicine concentration in each tissue can be clearly known, and then the practical situation can be more truly reflected when neutron irradiation simulation is carried out.

A detailed process for establishing a three-dimensional voxel prosthesis tissue model according to medical image data can refer to patent application with publication number CN106474634A and invented name "geometric model establishing method based on medical image data" published in 2017, 03, 08, which is incorporated herein in its entirety.

The Monte Carlo method is a tool which can accurately simulate the collision track and energy distribution of nuclear particles in three-dimensional space in an irradiation target at present, and a human body model is combined with MonteAnd the carlo simulation program can be used for carrying out accurate calculation and evaluation on the absorbed dose of the human body in the radiation environment. Step S420, defining beam parameters (such as beam energy, intensity, radius, etc.) in the monte carlo simulation program, and simulating and calculating the dose distribution of the three-dimensional voxel prosthetic tissue model at different irradiation angles by sampling different irradiation angles, i.e. respectively simulating and calculating the radiation dose D received by each voxel unit i at a unit time under the defined beam irradiation at the irradiation angle k of the sampling_ki。

The initial position and the beam angle of the beam are determined and calculated during sampling, the determination of the initial position and the angle in the calculation can be a forward algorithm or a reverse algorithm, the initial position is determined at the position outside the body in the forward algorithm, the sampling calculation can be carried out according to the fixed angle or the distance interval in sequence, and the sampling can also be carried out in a random sampling mode; the beam angle part can be set as the vector direction from the irradiation point to the center of mass of the tumor or the deepest part of the tumor, and the specific tumor end point position can be adjusted according to the requirements of users; in the inverse algorithm, the starting position is determined within the tumor range, the starting position can be the center of mass, the deepest part of the tumor, or a random point within the tumor range, and the beam angle can be sampled randomly or at specified intervals.

The beam angle can be screened during sampling, for example, the beam angle is evaluated, and the beam angle for subsequent calculation is selected according to the evaluation result; or the beam angle is screened after the sampling calculation, such as screening according to the result of the radiation dose distribution or the result of the beam angle evaluation. The evaluation method of the beam angle is not described in detail herein, and reference may be made to patent application publication No. CN106853272A entitled "evaluation method of irradiation angle of beam" published on 16/06/2017, which is incorporated herein in its entirety.

Referring to fig. 6, the step S430 of establishing an objective function of the region of interest, and calculating at least two illumination angles and an illumination time corresponding to each illumination angle by an optimization solution is further described in detail below, in an embodiment, the step includes:

s610: for a certain region of interest N, in this example tumor cells, an objective function of this region of interest N is established. In one embodiment, in order to evenly distribute the dose to all voxels within the region of interest N, the objective function is the square of the difference between the desired dose (the prescribed dose) and the calculated dose, it being understood that other objective functions may be used. The objective function in this embodiment adopts formula one:

wherein d is_iIs the total dose of the voxel i,is the prescribed dose for voxel i.

For a certain integrin i, it is subjected to a total dose d_iThe calculation can be performed using equation two:

wherein, w_kFor the irradiation time at different irradiation angles, D_kiDose per unit time voxel i at illumination angle k, d_iIs the total dose of voxel i.

Prescription dose of voxel iThe calculation can be performed using equation three:

wherein d is^pNThe prescribed dose for the region of interest N, C_NThe number of voxels for the region of interest. Wherein the prescribed dose d of the region of interest N^pNUsually, the judgment is given by the doctor according to the patient condition.

S620: solving and calculating the objective function by adopting an optimization algorithm through a formula IV, so that the distribution difference between the expected dose and the calculated dose is reduced as much as possible:

min{F(d_i) } (four formula)

Defining a design variable of formula four as X, wherein the design variable X is expressed by formula five:

X＝{w₁,w₂…w_kand (formula five).

An optimal solution of the design variable X can be obtained by adopting a proper optimization algorithm, such as a support vector machine, a response surface method, least square vector regression and the like, and the irradiation time w corresponding to a plurality of irradiation angles k and different irradiation angles k can be determined based on the obtained optimal solution_k. It will be appreciated that the optimal solution of the objective function may take other forms.

S630: and (4) establishing a constraint condition to enable the optimization solution of the objective function to meet the treatment requirement. In this embodiment, one or more normal organs or tissues M are selected under the constraint of a dose limit of the normal organs or tissues M, and the total dose d of all voxels i in each normal organ or tissue M_iAnd d_MThe formula six is satisfied:

g(d_M) < 0 (equation six).

It is understood that no constraint condition may be established, or different constraint conditions may be established to find different optimal solutions, so as to form different treatment plan schemes for selection by an operator such as a physician.

After the objective function optimization solution, the result of the objective function optimization solution is evaluated or preferred through the step S440 of dose inspection. Multiple illumination angles k and illumination times w corresponding to different illumination angles k, as determined by optimal solution of Dose Volume Histogram (DVH) to design variable X_kEvaluating the superposed dose distribution obtained by simulating the three-dimensional voxel prosthesis tissue model; evaluation can also be performed by performing the above-described irradiation angle evaluation. Different optimal solutions obtained by different constraint conditions can be simultaneously evaluated so as to provide doctors and other operators to select a more satisfactory treatment plan scheme. It is understood that dose review may not be performed.

The radiation therapy is carried out by adopting a plurality of irradiation angles according to the tumor distribution, so that the neutron quantity in the shallow part of the irradiated part of a patient is dispersed and reduced, the radiation dose received by normal tissues and the maximum dose of the normal tissues are reduced, and the probability of side effect of the normal tissues after the radiation therapy is received is further reduced; meanwhile, the total radiation dose can be properly increased to increase the tumor dose, particularly the neutron dose in the deep part of the tumor, so that the minimum tumor dose is improved; multiple incidence directions can also make the dose within the tumor more uniform.

The unit of the dose, the total dose and the prescription dose in the formulas I to VI is eq-Gy, and the unit of the irradiation time is s, so that it can be understood that some simple transformations in the formulas I to VI, and simple conversion of the dose and the time unit still fall within the protection scope of the invention; the total number of the irradiation angles k is at least two, the specific number can be manually set or automatically obtained through an algorithm or continuously regulated by an arc, and the sampling of the irradiation angles k can be performed on the same side or the opposite side of the patient.

After the treatment planning module 20 determines the treatment planning scheme through calculation and manual selection by the operator, the control module 30 retrieves the treatment plan according to the instruction, and controls the neutron beam irradiation device 10 to sequentially irradiate the patient according to a plurality of irradiation angles and corresponding irradiation times determined by the treatment plan. It should be understood that the first irradiation angle and the corresponding irradiation time for irradiating the patient may be the irradiation capable of giving the maximum dose to the tumor, and then the irradiation with other supplementary dose irradiation angles is performed, and after the irradiation with the current irradiation angle is completed, the adjustment is performed according to the next irradiation angle. The adjustment of the irradiation angle can be achieved by the control module 30 by controlling the direction of the beam outlet of the neutron beam generating device 11 (e.g. a rotatable gantry); this may also be accomplished by controlling the patient's positioning, which may be the movement of the treatment table 12 as directly controlled by the control module 30 according to the treatment plan; or the operator such as a doctor performs the patient positioning in the simulated positioning room (not shown) according to the treatment plan, and then the patient positioning determined by the simulated positioning is transferred to the irradiation room (not shown) to manually or automatically adjust the positions of the treatment table 12 and the patient.

It is understood that the present invention can also be applied to other radiation therapy fields that can be simulated by monte carlo software, such as proton, heavy ion, X-ray or gamma ray therapy, etc., and the neutron beam irradiation device is other radiation beam irradiation devices; can also be applied to other diseases which can be treated by radiation irradiation, such as Alzheimer disease and rheumatoid arthritis, and tumor cells are other pathological tissues; the patient may also be other irradiated objects.

Although illustrative embodiments of the invention have been described above to facilitate the understanding of the invention by those skilled in the art, it should be understood that the invention is not limited to the scope of the embodiments, and that various changes will become apparent to those skilled in the art within the spirit and scope of the invention as defined and defined in the appended claims.