A lattice point optimization method for lattice space partitioning radiotherapy based on gravitational field model

Abstract

The present invention discloses a method for optimizing lattice points in lattice space segmentation radiotherapy based on a gravitational field model, which relates to the technical field of radiotherapy. The present invention more accurately identifies the key areas of the tumor, especially the hypoxic area (functional target area), by combining PET-CT functional imaging, and dynamically adjusts the position and spacing of the lattice points according to the biological characteristics of the tumor; by dynamically adjusting the arrangement of the lattice points through the gravitational field model, it can not only ensure that the high-dose area accurately covers the key areas of the tumor, but also minimize unnecessary side effects and reduce the risk of tumor recurrence. It can better adapt to the functional heterogeneity of the tumor, realize personalized treatment, and reduce the impact on normal tissues while improving the accuracy of treatment, providing a more reliable treatment plan for the treatment of complex tumors, and realizing accurate dose distribution for different biological characteristics of tumors.

Description

Technical Field

[0001] The present invention relates to the technical field of radiotherapy, and in particular to a method for optimizing lattice points of lattice space segmentation radiotherapy based on a gravitational field model. Background Art

[0002] Radiotherapy is the most common treatment modality for cancer. With the introduction of modern radiotherapy techniques such as intensity modulated radiotherapy (IMRT), stereotactic radiotherapy (SRS), and intensity modulated arc therapy (VMAT), the uniformity and accuracy of dose distribution in the tumor area have been significantly improved. However, although these technologies have greatly improved the accuracy of doses, radiotherapy still faces a high risk of toxicity, especially toxicity to organs at risk around the tumor. This high toxicity not only limits the further increase in radiotherapy doses, but also affects the treatment effect. For this reason, spatially fractionated radiotherapy (SFRT) has emerged as an innovative treatment strategy.

[0003] SFRT is suitable for the treatment of large metastatic and primary tumors. Compared with traditional uniform dose irradiation, SFRT can improve the treatment effect and reduce radiation damage to organs. However, the existing SFRT technology still faces the challenge of optimizing the design of lattice radiotherapy (LRT).

[0004] LRT has gradually become an important branch of SFRT. Its core role is to form different dose gradients in the tumor by designing lattice structures. However, in current research, the existing lattice design methods have not been able to effectively combine these biological information, resulting in deficiencies in the treatment of complex tumors. An optimization model that can combine tumor biological characteristics and traditional lattice design has not yet been systematically summarized. Most LRT designs still rely on empirical methods and have not explored in depth how to combine biological target information with lattice models. However, the biological heterogeneity of tumors is not considered. If the lattice design fails to fully cover these areas, it may lead to poor treatment effects and even cause local recurrence, especially in the treatment of complex tumors. Summary of the invention

[0005] The purpose of the present invention is to provide a lattice space segmentation radiotherapy lattice point optimization method based on a gravitational field model to improve the above technical problems.

[0006] In order to achieve the above-mentioned object of the invention, the embodiment of the present invention provides the following technical solutions:

[0007] A method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model includes:

[0008] S1. Obtain PET-CT functional images and CT anatomical images of the patient;

[0009] S2. Use rigid registration technology to register PET-CT functional images and CT anatomical images to determine the patient's tumor area;

[0010] S3, taking each functional target area and lattice target area as a sphere, and updating the tumor area through the HCP model;

[0011] S4. constructing a gravitational field model based on the updated tumor area; wherein the updated tumor area includes N functional target areas and M lattice target areas;

[0012] S5. Iteratively optimize the lattice points of the updated tumor area through the gravitational field model to complete the optimization of the lattice points of the lattice space segmentation radiotherapy; wherein the lattice points are the lattice target areas.

[0013] Furthermore, the S1 comprises the following steps:

[0014] S1-1. Set the PET scanning parameters and CT scanning parameters of the PET-CT scanning system; wherein the PET scanning parameters are: layer thickness of 4 mm, layer spacing of 4 mm, imaging range FOV of 57.6 cm×57.6 cm, matrix of 144×144, and scanning mode of 3D scanning; the CT scanning parameters are: layer thickness of 5 mm, layer spacing of 5 mm, imaging range FOV of 60 cm×60 cm, matrix of 512×512, and scanning mode of spiral scanning;

[0015] S1-2. Acquire the PET-CT functional image and the CT anatomical image respectively through the PET-CT scanning system.

[0016] Further, the S2 comprises the following steps:

[0017] S2-1, drawing an initial tumor area based on the CT anatomical image;

[0018] S2-2, determining a corresponding initial functional target area based on the PET-CT functional image;

[0019] S2-3, registering the CT anatomical image and the PET-CT functional image by using the rigid registration technology to obtain a corresponding transformation matrix;

[0020] S2-4, mapping the initial functional target area to the initial tumor area based on the conversion matrix, and determining the positional relationship between the initial functional target area and the initial tumor area;

[0021] S2-5. Update the initial tumor area based on the positional relationship and draw the tumor area.

[0022] Furthermore, the specific process of S3 is as follows:

[0023] According to the arrangement rules, the spheres corresponding to each of the lattice target areas are arranged through the HCP model (hexagonal closest packing model), and the positions of the spheres corresponding to each of the lattice target areas are adjusted to obtain an updated tumor area; wherein the arrangement rules are as follows: the single-layer spheres are arranged symmetrically in a hexagonal shape, and the center of each sphere forms a regular hexagon with the centers of the six adjacent spheres; each layer of spheres is arranged in a staggered manner, so that the second layer of spheres is located in the gaps between the first layer of spheres, and the third layer of spheres is aligned with the first layer, forming a periodic stacking.

[0024] Furthermore, the single-layer arrangement of the lattice target area in the updated tumor area follows the planar hexagonal symmetry, that is:

[0025] ;

[0026] in, , , denote column index, row index and layer index respectively, , , Respectively represent the distances between the centers of two adjacent spheres in the x-axis, y-axis, and z-axis directions. Indicates Layer Column and The position vector of the center of the sphere of the row, represents a constant, Indicates absolute value;

[0027] The distribution volume of the lattice target area The corresponding formula is:

[0028] ;

[0029] in, represents the number of spheres corresponding to the lattice target area, that is, M, Represents the radius of the sphere.

[0030] Furthermore, the formula corresponding to the gravitational field model is:

[0031] ;

[0032] ;

[0033] ;

[0034] in, represents the total volume corresponding to N functional target areas, is the gravitational constant, Indicates The sphere corresponding to the functional target area, Indicates The sphere corresponding to the target area of ​​the lattice, Indicates Sphere corresponding to the functional target area and The sphere corresponding to the target area of ​​the lattice The gravitational field between represents the Euclidean distance, Indicates Sphere corresponding to the functional target area The gravitational force on the spheres corresponding to the adjacent lattice target areas, Indicates the total number of spheres corresponding to the functional target area, that is, N, Represents the total gravitational force of the sphere corresponding to all functional target areas, Represents a sum function.

[0035] Further, the S5 comprises the following steps:

[0036] S5-1. Obtaining the gravitational data between the spheres corresponding to each functional target area and the spheres corresponding to each lattice target area respectively through the gravitational field model; wherein the gravitational data includes the corresponding gravitational value and its gravitational direction;

[0037] S5-2, based on the gravity data, updating the position of the sphere corresponding to each of the lattice target areas;

[0038] S5-3, repeat S5-1 to S5-2 until the convergence condition is met, and the optimization of the lattice point position of the lattice space division radiotherapy is completed.

[0039] Furthermore, the specific process of S5-2 is as follows:

[0040] S5-2-1, calculating the collision adjustment amount of the sphere corresponding to each of the lattice target areas;

[0041] S5-2-2, calculating the displacement of the sphere corresponding to each of the lattice target areas based on the gravity value and the collision adjustment amount;

[0042] S5-2-3, based on the gravitational direction, determining the displacement direction of the spheres corresponding to each of the lattice target areas;

[0043] S5-2-4. Based on the displacement amount and the displacement direction, adjust the position of the sphere corresponding to each of the lattice target areas to complete the position update of the sphere corresponding to each of the lattice target areas.

[0044] Furthermore, the convergence condition includes a displacement convergence condition and an iteration number convergence condition;

[0045] The displacement convergence condition is: when the displacement of the spheres corresponding to all lattice target areas satisfies:

[0046] ;

[0047] When , it is determined that the convergence condition is met, and the optimization of the lattice point position of the lattice space segmentation radiotherapy is completed; among them, represents the threshold value, Indicates The displacement of the spheres corresponding to all lattice target areas in the iteration, Indicates The displacement of the spheres corresponding to all lattice target areas in the iteration, is the universal quantifier symbol, meaning "for all", It means for all lattice target areas;

[0048] The convergence condition of the number of iterations is: the number of iterations is equal to the iteration threshold T; wherein the initial value of the number of iterations is 0, and after completing the processing corresponding to S5-3, the number of iterations is increased by 1.

[0049] The beneficial effects of the present invention are:

[0050] The present invention combines PET-CT functional imaging to more accurately identify key areas of the tumor, especially the hypoxic area (functional target area), and dynamically adjusts the position and spacing of the lattice points according to the biological characteristics of the tumor; by dynamically adjusting the arrangement of the lattice points through the gravitational field model, it can not only ensure that the high-dose area accurately covers the key areas of the tumor, but also minimize unnecessary side effects and reduce the risk of tumor recurrence. It can better adapt to the functional heterogeneity of the tumor and realize personalized treatment. It can also reduce the impact on normal tissues while improving the accuracy of treatment, provide a more reliable treatment plan for the treatment of complex tumors, and achieve precise dose distribution for different biological characteristics of tumors. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0052] Figure 1 2D plane schematic diagram of the LRT lattice in an embodiment of the present invention;

[0053] Figure 2 A flow chart of a method in an embodiment of the present invention;

[0054] Figure 3 This is an updated tumor area structure diagram in an embodiment of the present invention;

[0055] Figure 4 This is a structural diagram of the optimized tumor area in an embodiment of the present invention;

[0056] FIG5 (a) is a schematic diagram of a GTV drawn by PET-CT functional imaging in another embodiment of the present invention;

[0057] FIG5( b ) is a lattice point arrangement diagram generated by the HCP model in another embodiment of the present invention;

[0058] Figure 6 is an optimized lattice point arrangement diagram in another embodiment of the present invention;

[0059] FIG. 7 ( a ) is an initial dose distribution diagram corresponding to the lattice point arrangement generated by the HCP model in another embodiment of the present invention;

[0060] FIG. 7( b ) is an initial dose distribution diagram corresponding to the optimized lattice point arrangement in another embodiment of the present invention;

[0061] FIG7( c ) is a diagram showing the final dose distribution corresponding to the lattice point arrangement generated by the HCP model in another embodiment of the present invention;

[0062] FIG. 7( d ) is a diagram showing the final dose distribution corresponding to the optimized lattice point arrangement in another embodiment of the present invention. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0064] like Figure 1As shown in the figure, the lattice arrangement commonly used in LRT currently adopts the form of the densest packing. Currently, the low ADC value of the DWI sequence of nuclear magnetic resonance imaging can be used to accurately identify the proliferation area with high tumor cell density, which is used to guide the position optimization, arrangement and delineation of the high-dose lattice points of LRT. However, the hypoxic area (functional target area) inside the tumor identified by PET-CT is still ignored in LRT treatment, resulting in the traditional densest packing model failing to fully consider the biological heterogeneity inside the tumor. Since the hypoxic area inside the tumor is less sensitive to radiotherapy, if high doses fail to cover these areas, it may lead to early recurrence of the tumor. Secondly, the existing lattice target area layout usually relies on fixed spacing and arrangement patterns, and fails to dynamically adjust according to the actual functional characteristics of the tumor. This approach not only affects the peak-to-valley dose ratio, but may also cause the dose distribution to not fully match the actual target area of ​​the tumor, thereby reducing the treatment effect. In addition, most of the current treatment methods rely on experience and lack a dynamic optimization method based on tumor biological information, which makes the treatment process impossible to achieve personalized customization and easily causes unnecessary high-dose exposure to normal tissues. Figure 1 In the figure, the red area is the most densely packed lattice points, the blue area is the high tumor cell density proliferation area identified by DWI (nuclear magnetic resonance imaging), and the green area is the hypoxic area (functional target area) inside the tumor identified by PET-CT.

[0065] See also Figure 2 The present embodiment provides a method for optimizing lattice points of lattice space segmentation radiotherapy based on a gravitational field model, including:

[0066] S1. Obtain PET-CT functional images and CT anatomical images of the patient;

[0067] The S1 comprises the following steps:

[0068] S1-1. Set the PET scanning parameters and CT scanning parameters of the PET-CT scanning system; the PET scanning parameters are: layer thickness of 4 mm, layer spacing of 4 mm, imaging range FOV of 57.6 cm×57.6 cm, matrix of 144×144, and scanning mode of 3D scanning; the CT scanning parameters are: layer thickness of 5 mm, layer spacing of 5 mm, imaging range FOV of 60 cm×60 cm, matrix of 512×512, and scanning mode of spiral scanning;

[0069] Before the patient undergoes a PET-CT scan, the examination conditions must be met. The examination conditions are: (1) fasting for at least 6 hours; (2) undergoing the examination; insulin testing is prohibited before the examination, and when the patient's blood sugar is less than 11mmol / L. During the scan, the patient needs to be intravenously injected with 4.4MBq / kg of 18F-FDG, and the PET-CT scan will be performed 1 hour later. The scanning range of the PET-CT scan is from the top of the skull to the upper part of the femur on both sides.

[0070] S1-2. Acquire the PET-CT functional image and the CT anatomical image respectively through the PET-CT scanning system.

[0071] S2. Use rigid registration technology to register PET-CT functional images and CT anatomical images to determine the patient's tumor area;

[0072] The S2 comprises the following steps:

[0073] S2-1, based on the CT anatomical image, drawing the initial tumor area, that is, the clinical oncologist outlines the tumor volume (GTV) on the CT anatomical image;

[0074] S2-2, determining a corresponding initial functional target area based on the PET-CT functional image;

[0075] S2-3, register the CT anatomical image and the PET-CT functional image through the rigid registration technology, align the CT anatomical image and the PET-CT functional image, and obtain the corresponding transformation matrix, which is a key step to further ensure that the subsequent functional target area is consistent with the actual tumor anatomical structure and the spatial position of the lattice target area. The formula corresponding to the transformation matrix is:

[0076] ;

[0077] in, Represents the spatial coordinates after registration of PET-CT functional images and CT anatomical images, i.e., the transformation matrix; The translation matrix represents the rigid registration, which is used to adjust the position of the functional image; Represents the translation matrix of the rigid registration, which is used to adjust the position of the functional image.

[0078] S2-4, based on the conversion matrix, mapping the initial functional target area to the initial tumor area, determining the positional relationship between the initial functional target area and the initial tumor area, ensuring that the high dose can be accurately concentrated to the functional target area of ​​the tumor, and providing a basis for the layout of the lattice target area;

[0079] S2-5. The initial tumor region is updated based on the positional relationship, and the tumor region is obtained by drawing. That is, a clinical oncologist manually outlines a biological target region or a functional target region (GTV-H) on a CT anatomical image with reference to the positional relationship.

[0080] The present invention determines the functional target area through PET-CT functional imaging, which helps to accurately set the lattice target area, realizes the precise docking of the spatial position of PET-CT functional imaging and CT anatomical imaging through the registration technology, realizes the unification of images of different modalities, and provides a basis for constructing a gravitational field model and optimizing lattice points through the gravitational field.

[0081] S3. Treat each functional target area and lattice target area as a sphere, and update the tumor area through the HCP model; the lattice target area is automatically generated inside the tumor area.

[0082] like Figure 3 As shown, the specific process of S3 is:

[0083] According to the arrangement rules, the spheres corresponding to each of the lattice target areas are arranged by the HCP model (hexagonal closest packing model), and the positions of the spheres corresponding to each of the lattice target areas are adjusted to obtain an updated tumor area; wherein the arrangement rules are as follows: the single-layer spheres are arranged in hexagonal symmetry, and the center of each sphere forms a regular hexagon with the centers of the six adjacent spheres; each layer of spheres is arranged in a staggered manner, so that the second layer of spheres is located in the gaps between the first layer of spheres, and the third layer of spheres is aligned with the first layer, forming a periodic stacking. Figure 3 In the figure, the red spheres are lattice targets and the blue spheres are functional targets.

[0084] The single-layer arrangement of the lattice target area in the updated tumor area follows the planar hexagonal symmetry, that is:

[0085] ;

[0086] in, , , denote column index, row index and layer index respectively, , , Respectively represent the distances between the centers of two adjacent spheres in the x-axis, y-axis, and z-axis directions. Indicates Layer Column and The position vector of the center of the sphere of the row, represents a constant, Indicates absolute value;

[0087] The distribution volume of the lattice target area The corresponding formula is:

[0088] ;

[0089] in, represents the number of spheres corresponding to the lattice target area, that is, M, Represents the radius of the sphere.

[0090] S4. constructing a gravitational field model based on the updated tumor region; wherein the updated tumor region includes N functional target regions (GTV-H) and M lattice target regions (GTV-L);

[0091] The sphere corresponding to each functional target area generates a gravitational field, the strength of which is related to its volume and position. The role of the gravitational field is to attract the spheres corresponding to the lattice target area to the high priority area of ​​the functional target area, thereby achieving dynamic optimization of the lattice points.

[0092] Therefore, the formula corresponding to the gravitational field model is:

[0093] ;

[0094] ;

[0095] ;

[0096] in, represents the total volume corresponding to N functional target areas, is the gravitational constant, Indicates The sphere corresponding to the functional target area, Indicates The sphere corresponding to the target area of ​​the lattice, Indicates Sphere corresponding to the functional target area and The sphere corresponding to the target area of ​​the lattice The gravitational field between represents the Euclidean distance, Indicates Sphere corresponding to the functional target area The gravitational force on the spheres corresponding to the adjacent lattice target areas, Indicates the total number of spheres corresponding to the functional target area, that is, N, Represents the total gravitational force of the sphere corresponding to all functional target areas, Represents a sum function.

[0097] S5. Iteratively optimize the lattice points of the updated tumor area through the gravitational field model to complete the optimization of the lattice points of the lattice space segmentation radiotherapy; wherein the lattice points are the lattice target areas.

[0098] The S5 comprises the following steps:

[0099] S5-1. Obtaining the gravitational data between the spheres corresponding to each functional target area and the spheres corresponding to each lattice target area respectively through the gravitational field model; wherein the gravitational data includes the corresponding gravitational value and its gravitational direction;

[0100] S5-2, based on the gravity data, updating the position of the sphere corresponding to each of the lattice target areas, such as Figure 4 shown in Figure 4 In the figure, the red sphere is the lattice target area, the blue sphere is the functional target area, and the green arrow is the displacement direction of the red sphere.

[0101] In the process of updating the position of the sphere corresponding to the lattice target area, the transformation matrix , which can ensure that GTV-H is accurately mapped in the space of CT anatomical images and generate the corresponding gravitational field, so that GTV-L can move to the correct position during the dynamic adjustment process, ensuring that the dynamic adjustment of the lattice points is consistent with the spatial position of GTV-H.

[0102] Since the strength of the gravitational field changes nonlinearly with the distance and volume ratio, the gravitational field model has the following characteristics: (1) Local enhancement: the force on the red sphere near the blue sphere is significantly enhanced, pushing it to gather towards the blue sphere. (2) Global equilibrium: the gravitational force on the blue sphere gradually weakens when it moves away from the red sphere, avoiding excessive interference with the overall layout. (3) Volume dependence: when , the strength of the gravitational field increases, and the blue sphere’s guiding effect on the lattice points becomes more significant. From the formula corresponding to the gravitational field model, it can be seen that the volume of the blue sphere The strength of gravity This means that the larger the volume of the blue sphere, the stronger the gravitational field it generates, and the more significant the attraction to the red sphere, thereby accelerating its approach to the functional target area and optimizing the lattice point distribution, that is:

[0103] when , then the corresponding gravitational value increases, that is ; It means that it is proportional to and There is a positive proportional relationship between the changes;

[0104] when , then the corresponding total gravitational force value approaches equilibrium.

[0105] The practical significance of the volume dependence effect of the gravitational field model: the increase in the volume of the blue sphere has a significant impact on the nonlinear effect of the gravitational field of the red sphere. This volume dependence effect plays an important role in the following aspects.

[0106] (1) Accurate coverage of functional target areas: When the dose is high, the red sphere quickly moves toward the blue sphere, ensuring that the high-dose area covers the hypoxic area or the high-metabolism area.

[0107] (2) Control the overall layout: When the gravitational field is balanced, the overall layout gradually stabilizes, avoiding disturbances caused by excessive adjustments.

[0108] (3) Dynamic adjustment capability: By adjusting the volume of the blue sphere, the intensity and range of the gravitational field can be flexibly changed, thereby dynamically optimizing the distribution of the red sphere.

[0109] The specific process of S5-2 is as follows:

[0110] S5-2-1. Calculate the collision adjustment amount of the sphere corresponding to each of the lattice target areas through the collision detection mechanism. The corresponding formula is:

[0111] ;

[0112] in, represents the collision adjustment amount, Indicates the adjustment strength.

[0113] The present invention can optimize the dose distribution for different patients through the gravitational field model and collision detection mechanism, significantly improve the peak-to-valley dose ratio, and concentrate the lattice points in the hypoxic area and the high proliferation area so that the dose peak is formed in these key parts. At the same time, a natural low-dose valley is formed in the uncovered area to avoid the waste of ineffective dose. The higher the peak-to-valley dose ratio, the more effective it is in reducing the radiation damage to the surrounding normal tissues. In addition, the hypoxic area is a high-risk area for tumor recurrence. This method can accurately cover these areas, greatly reducing the risk of local recurrence, thereby significantly improving the long-term treatment control rate of patients.

[0114] S5-2-2, based on the gravity value and the collision adjustment amount, calculate the displacement of the sphere corresponding to each of the lattice target areas, and the corresponding formula is:

[0115] ;

[0116] in, Indicates The displacement of the spheres corresponding to all lattice target areas in the iteration, Indicates The displacement of the spheres corresponding to all lattice target areas in the iteration, represents the step size coefficient, Indicates the collision adjustment amount.

[0117] S5-2-3, based on the gravitational direction, determining the displacement direction of the spheres corresponding to each of the lattice target areas;

[0118] S5-2-4. Based on the displacement amount and the displacement direction, adjust the position of the sphere corresponding to each of the lattice target areas to complete the position update of the sphere corresponding to each of the lattice target areas.

[0119] S5-3, repeat S5-1 to S5-2 until the convergence condition is met, and the optimization of the lattice point position of the lattice space division radiotherapy is completed.

[0120] The convergence conditions include a displacement convergence condition and an iteration number convergence condition;

[0121] The displacement convergence condition is: when the displacement of the spheres corresponding to all lattice target areas satisfies:

[0122] ;

[0123] When , it is determined that the convergence condition is met, and the optimization of the lattice point position of the lattice space segmentation radiotherapy is completed; among them, represents the threshold value, is the universal quantifier symbol, meaning "for all", It means for all lattice target areas;

[0124] The convergence condition of the number of iterations is: the number of iterations is equal to the iteration threshold T; wherein the initial value of the number of iterations is 0, and after completing the processing corresponding to S5-3, the number of iterations is increased by 1.

[0125] The present invention calculates the displacement and direction of the spheres corresponding to the lattice target area through the gravitational force between the spheres corresponding to each functional target area and the spheres corresponding to each lattice target area, and dynamically adjusts the positions of the spheres corresponding to the lattice target area through the gravitational field model, thereby changing the limitations of the traditional fixed lattice layout method, solving the problem that the existing method adopts a fixed spacing and symmetrical layout method, lacks the adaptability to the tumor size, shape and functional characteristics (such as hypoxic zone distribution) of different patients, resulting in poor generalization effect of dose distribution, and can maximize the coverage of key parts of the functional target area while avoiding excessive impact on normal tissues, and provide patients with personalized treatment plans to reduce unnecessary high-dose exposure to normal tissues.

[0126] In one embodiment, as shown in FIG5(a), the tumor region is scanned by PET-CT, and the GTV is obtained by drawing on the CT anatomical image by a clinical oncologist. In FIG5(a), the pink region is the tumor volume (GTV), and the green dot is the lattice target volume (GTV-L).

[0127] As shown in Figure 5(b), S2 is used to process the GTV shown in Figure 5(a) to obtain the relative position distribution of GTV-L and GTV-H. In Figure 5(b), the pink area is the GTV, the green dots are the lattice target area (GTV-L), and the yellow area is the hypoxic area, that is, the functional target area (GTV-H).

[0128] like Figure 6As shown, S5 is used to process the GTV shown in Figure 5 (b), and the position of each lattice target area is adjusted according to the displacement and displacement direction obtained by the gravitational field model to obtain the optimized lattice point. Figure 6 In the figure, the pink area is GTV, the green dots are the lattice target area (GTV-L), the yellow area is the hypoxic area, i.e. the functional target area (GTV-H), the blue dots are the optimized lattice points, and the blue arrows are the moving direction of the lattice target area.

[0129] Based on the lattice points in Figure 5 (a), the dose distribution is performed on the corresponding tumor area, and the corresponding results are shown in Figures 7 (a) and 7 (c). Figure 6 The optimized lattice points are used to distribute the dose to the corresponding tumor area, and the corresponding results are shown in Figure 7 (b) and Figure 7 (d). It can be seen that after the position and spacing of the lattice points are optimized by the present invention, a higher peak dose (10~25Gy) can be directly applied to the hypoxic area (GTV-H, i.e., the area that is anti-radiation and has a high tumor cell density), resulting in a higher ablation ratio in the hypoxic area without pursuing the peak-to-valley ratio; the peak-to-valley ratio is pursued in the tumor area outside the hypoxic area. Compared with Figure 7 (a) and Figure 7 (c), the present invention can not only ensure the peak-to-valley ratio of spatial segmentation treatment, but also better control the risk of local recurrence in the tumor area with low ADC, thereby improving the treatment effect of LRT.

[0130] In summary, the present invention combines PET-CT functional imaging to more accurately identify key areas of the tumor, especially the hypoxic area (functional target area), and dynamically adjusts the position and spacing of the lattice points according to the biological characteristics of the tumor; by dynamically adjusting the arrangement of the lattice points through the gravitational field model, it can not only ensure that the high-dose area accurately covers the key areas of the tumor, but also minimize unnecessary side effects and reduce the risk of tumor recurrence. It can better adapt to the functional heterogeneity of the tumor and realize personalized treatment. It can also reduce the impact on normal tissues while improving the accuracy of treatment, provide a more reliable treatment plan for the treatment of complex tumors, and realize accurate dose distribution for different biological characteristics of tumors.

[0131] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model, characterized in that: include: S1. Obtain PET-CT functional images and CT anatomical images of the patient; S2. Use rigid registration technology to register PET-CT functional images and CT anatomical images to determine the patient's tumor area; S3, taking each functional target area and lattice target area as a sphere, and updating the tumor area through the HCP model; S4. constructing a gravitational field model based on the updated tumor area; wherein the updated tumor area includes N functional target areas and M lattice target areas; S5, iteratively optimizing the lattice points of the updated tumor area through the gravitational field model to complete the optimization of the lattice points of the lattice space segmentation radiotherapy; wherein the lattice points are the lattice target areas; The formula corresponding to the gravitational field model is: ； ； ； in, represents the total volume corresponding to N functional target areas, is the gravitational constant, Indicates The sphere corresponding to the functional target area, Indicates The sphere corresponding to the target area of ​​the lattice, Indicates Sphere corresponding to the functional target area and The sphere corresponding to the target area of ​​the lattice The gravitational field between represents the Euclidean distance, Indicates Sphere corresponding to the functional target area The gravitational force on the spheres corresponding to the adjacent lattice target areas, Indicates the total number of spheres corresponding to the functional target area, that is, N, Represents the total gravitational force of the sphere corresponding to all functional target areas, Represents a sum function.

2. The method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model according to claim 1, characterized in that: The S1 comprises the following steps: S1-1. Set the PET scanning parameters and CT scanning parameters of the PET-CT scanning system; wherein the PET scanning parameters are: layer thickness of 4 mm, layer spacing of 4 mm, imaging range FOV of 57.6 cm×57.6 cm, matrix of 144×144, and scanning mode of 3D scanning; the CT scanning parameters are: layer thickness of 5 mm, layer spacing of 5 mm, imaging range FOV of 60 cm×60 cm, matrix of 512×512, and scanning mode of spiral scanning; S1-2. Acquire the PET-CT functional image and the CT anatomical image respectively through the PET-CT scanning system.

3. The method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model according to claim 1, characterized in that: The S2 comprises the following steps: S2-1, drawing an initial tumor area based on the CT anatomical image; S2-2, determining a corresponding initial functional target area based on the PET-CT functional image; S2-3, registering the CT anatomical image and the PET-CT functional image by using the rigid registration technology to obtain a corresponding transformation matrix; S2-4, mapping the initial functional target area to the initial tumor area based on the conversion matrix, and determining the positional relationship between the initial functional target area and the initial tumor area; S2-5. Update the initial tumor area based on the positional relationship and draw the tumor area.

4. The method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model according to claim 1, characterized in that: The specific process of S3 is as follows: According to the arrangement rules, the spheres corresponding to each of the lattice target areas are arranged through the HCP model, and the positions of the spheres corresponding to each of the lattice target areas are adjusted to obtain an updated tumor area; wherein the arrangement rules are as follows: the single-layer spheres are arranged symmetrically in a hexagon, and the center of each sphere forms a regular hexagon with the centers of the six adjacent spheres; each layer of spheres is arranged in a staggered manner, so that the second layer of spheres is located in the gaps between the first layer of spheres, and the third layer of spheres is aligned with the first layer of spheres, forming a periodic stacking.

5. The method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model according to claim 4, characterized in that: The single-layer arrangement of the lattice target area in the updated tumor area follows the planar hexagonal symmetry, that is: ； in, , , denote column index, row index and layer index respectively, , , Respectively represent the distances between the centers of two adjacent spheres in the x-axis, y-axis, and z-axis directions. Indicates Layer Column and The position vector of the center of the sphere of the row, represents a constant, Indicates absolute value; The distribution volume of the lattice target area The corresponding formula is: ； in, represents the number of spheres corresponding to the lattice target area, that is, M, Represents the radius of the sphere.

6. The method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model according to claim 1, characterized in that: The S5 comprises the following steps: S5-1. Obtaining the gravitational data between the spheres corresponding to the functional target areas and the spheres corresponding to the lattice target areas respectively through the gravitational field model; wherein the gravitational data includes the corresponding gravitational value and its gravitational direction; S5-2, based on the gravity data, updating the position of the sphere corresponding to each of the lattice target areas; S5-3, repeat S5-1 to S5-2 until the convergence condition is met, and the optimization of the lattice point position of the lattice space division radiotherapy is completed.

7. The method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model according to claim 6, characterized in that: The specific process of S5-2 is as follows: S5-2-1, calculating the collision adjustment amount of the sphere corresponding to each of the lattice target areas; S5-2-2, calculating the displacement of the sphere corresponding to each of the lattice target areas based on the gravity value and the collision adjustment amount; S5-2-3, based on the gravitational direction, determining the displacement direction of the spheres corresponding to each of the lattice target areas; S5-2-3. Based on the displacement amount and the displacement direction, adjust the position of the sphere corresponding to each of the lattice target areas to complete the position update of the sphere corresponding to each of the lattice target areas.

8. The method for optimizing lattice points for lattice space segmentation radiotherapy based on a gravitational field model according to claim 7, characterized in that: The convergence conditions include a displacement convergence condition and an iteration number convergence condition; The displacement convergence condition is: when the displacement of the spheres corresponding to all lattice target areas satisfies: ； When , it is determined that the convergence condition is met, and the optimization of the lattice point position of the lattice space segmentation radiotherapy is completed; among them, represents the threshold value, Indicates The displacement of the spheres corresponding to all lattice target areas in the iteration, Indicates The displacement of the spheres corresponding to all lattice target areas in the iteration, is the universal quantifier symbol, meaning "for all", It means for all lattice target areas; The convergence condition of the number of iterations is: the number of iterations is equal to the iteration threshold T; wherein the initial value of the number of iterations is 0, and after completing the processing corresponding to S5-3, the number of iterations is increased by 1.

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