Rotating sweeping dynamic intensity modulation method and device considering double-layer grating side edge penumbra

Abstract

The application discloses a rotating scanning dynamic intensity modulation method and device considering double-layer grating side edge penumbra, and comprises the following steps: S1, obtaining the target flux intensity distribution of each field of view through a radiotherapy planning system; S2, performing grid subdivision processing on the optimized flux map to obtain the grid target flux intensity distribution; S3, dividing the field of view area into four quadrants; S4, determining the initial position of the leaf; S5, performing flux segmentation on the leaf of each quadrant, establishing a mathematical optimization model, obtaining the motion speed of the advancing leaf and the retreating leaf, and then obtaining the flux function of the leaf and the machine jump number of the four quadrants; and S6, repeating S3-S5, adjusting the boundary line of the quadrant by utilizing the relationship between the machine jump numbers of the four quadrants until the machine jump numbers of the four quadrants differ by a threshold value. The application considers the influence of the side edge penumbra on the double-layer grating rotating scanning dynamic intensity modulation method, makes the model closer to the real scene, and improves the segmentation accuracy by making the segmentation intensity closer to the optimized target flux.

Description

Technical Field

[0001] This invention belongs to the field of radiotherapy technology, specifically relating to a method and apparatus for dynamic intensity modulation by rotating sweeping considering the penumbra of a double-layer grating. Background Technology

[0002] Multi-leaf collimators (MLCs) have become an important tool in intensity-modulated radiotherapy (IMRT). During radiotherapy, MLCs can shape the projection of the tumor target area, protecting normal tissues and organs at risk while irradiating the tumor. Orthogonal double-layer collimators consist of two mutually perpendicular MLC layers. Because the two layers of leaves are independent, their movement is more flexible, allowing for better conformal treatment of complex target areas such as concave and annular shapes. The intensity is formed by the movement trajectory of the two orthogonal layers of leaves. At the target edge, the shape formed by the orthogonal double-layer collimator has a higher consistency with the target edge. Furthermore, the mutual shielding of the double-layer collimators greatly reduces interleaf leakage and intraleaf transmission, making radiotherapy more precise.

[0003] Among existing dynamic segmentation algorithms, orthogonal double-layer grating rotating sweep dynamic intensity-modulated segmentation (RS) has theoretically achieved a higher segmentation efficiency than the traditional sliding window (SW) algorithm by grating positioning, reaching a rate up to sqrt(2). Data from patent CN 112043974A, "A Dynamic Intensity-Modulated Segmentation Method and Device Based on Orthogonal Double-Layer Grating Rotating Sweep," shows that orthogonal double-layer grating rotating sweep dynamic intensity-modulated segmentation can reduce the number of monitor units (MUs) by approximately 20%, and can achieve better protection of low-dose areas through mutual occlusion of the upper and lower gratings, as well as simultaneous irradiation of multiple target tumors.

[0004] The orthogonal double-layer grating rotating sweep dynamic intensity-modulated segmentation algorithm can achieve segmentation of complex fluxes and has higher segmentation efficiency compared to the traditional blade sliding window scanning dynamic segmentation algorithm. The current algorithm uses flux segmentation instead of geometric segmentation for subfield motion trajectory optimization calculation, achieving some results and obtaining higher accuracy segmentation results in subfields that meet the convergence conditions. However, in actual flux segmentation, the effects of leaf-endpenumbra and lateral penumbra prevent it from achieving better planning results.

[0005] In summary, the existing technology has the following disadvantages:

[0006] 1. Existing dynamic segmentation algorithms are mainly sliding window algorithms for single-layer gratings. For dynamic segmentation of double-layer orthogonal gratings, sliding window algorithms are not applicable.

[0007] 2. Although the orthogonal double-layer grating rotating sweep dynamic intensity-modulated segmentation algorithm can achieve good conformal adaptation to complex target areas, in the actual throughput segmentation process, the presence of the lateral penumbra increases the dose to organs at risk and reduces the therapeutic effect.

[0008] 3. Existing segmentation algorithms mainly reduce the penumbra width through the shape design of MLC or some physical means (such as penumbra trimmer, compensator, etc.), and rarely consider the influence of the penumbra in the optimization model. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention proposes a method and apparatus for dynamic intensity modulation by rotational sweeping that considers the penumbra of the side of a double-layer grating.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows:

[0011] On one hand, this invention discloses a method for dynamic intensity modulation by rotational sweep considering the penumbra of the side edges of a double-layer grating, comprising the following steps:

[0012] S1: Through the radiotherapy planning system, flux map optimization is performed to obtain the target flux intensity distribution for each radiation field;

[0013] S2: The optimized flux map is further subdivided into grids, and the overlapping area formed by each pair of orthogonal blades is divided equally to obtain a target flux intensity distribution with a finer grid.

[0014] S3: Divide the shooting field area into four quadrants. Each quadrant corresponds to two sets of mutually orthogonal blades. One set of blades is the forward blade and the other set of blades is the backward blade. The forward blade is defined to move towards the center of the shooting field, and the backward blade moves away from the center of the shooting field.

[0015] S4: Determine the initial position of the blades. The initial position of the forward blades is at the edge of the target area, and the initial position of the backward blades is at the intersection of the quadrants.

[0016] S5: Perform flux segmentation on the blades in each quadrant. Take any two orthogonal blades to form a local region P(x,y). This local region is formed by the overlap of the advancing blade n and the retreating blade m. Simultaneously consider the influence of the penumbra of the four blades adjacent to the two orthogonal blades on the flux of this region. The flux intensity of this region... The calculation method is as follows:

[0017]

[0018] in,(*) + This is a ReLU function, specifically max{0,*};

[0019] For the forward blade u i The flux trajectory function formed in the i-th column of the local region from the right;

[0020] For the retracting blade v j The flux trajectory function formed by the j-th sub-region starting from the local region;

[0021] For the forward blade u i The penumbra coefficient for occlusion of region P(x,y);

[0022] For the retracting blade v j The penumbra coefficient for occlusion of region P(x,y);

[0023] Specifically, and Obtained by the following formula;

[0024]

[0025] in, The initial flux value of the advancing blade entering this local region is a known quantity.

[0026] R dose Dose rate;

[0027] The velocity of the forward blade in the a-th column from the right in the local region;

[0028] Δx a This represents the distance to the sub-region in the rightmost column a of the local region.

[0029] The initial flux value of the retracting blade entering this local region is a known quantity. The velocity of the retracting blade in the b-th sub-region of the local area;

[0030] Δy b This represents the distance to the b-th sub-region starting from the local region.

[0031] Furthermore, with and the gridded target flux intensity I of this local region oUsing the square of the L2 norm of the (x,y) deviation as the objective function, and considering that the blade's movement speed is constrained by the upper speed limit, the following mathematical optimization model is established to obtain the movement speeds of the forward and backward blades, and then to obtain the blade's flux function and the number of machine hops in the four quadrants.

[0032]

[0033]

[0034]

[0035] in, The maximum speed of the forward blade u;

[0036] The maximum speed of the retracting blade is v;

[0037] The aforementioned local region P(x,y) is divided into p*q subregions;

[0038] S6: Repeat S3-S5, using the relationship between the number of machine hops in the four quadrants to adjust the boundary lines of the quadrants until the difference in the number of machine hops in the four quadrants meets the threshold.

[0039] This invention incorporates the influence of the penumbra of adjacent leaves on the flux intensity of local areas during dynamic leaf segmentation. It establishes a segmentation optimization model using orthogonal double-layer grating rotation sweeping, ensuring that the segmented flux matches the optimized flux as closely as possible, thus improving segmentation accuracy. Simultaneously, by considering the penumbra's influence, this invention enhances the model's accuracy, making the optimized model more realistic and facilitating more accurate treatment planning.

[0040] Based on the above technical solution, the following improvements can be made:

[0041] As a preferred option, S2 also includes the following: interpolating each gridded flux map by referring to the optimized flux map.

[0042] As a preferred option, in S3, the flux in each quadrant is independent of each other.

[0043] As a preferred embodiment, in S3, the forward or backward blades in adjacent quadrants are not adjacent to each other.

[0044] As a preferred option, in S5, the penumbra coefficient α is tested using a water tank. u (x,y) and the penumbra coefficient β v Extract (x,y).

[0045] As a preferred approach, the gradient optimization algorithm is used to solve the mathematical optimization model in S5 to obtain the motion speeds of the forward and backward blades.

[0046] Furthermore, on the other hand, the present invention also discloses a rotating sweep dynamic intensity modulation device that takes into account the penumbra of the side of a double-layer grating, comprising:

[0047] One or more processors;

[0048] Memory;

[0049] And one or more programs, wherein the one or more programs are stored in memory and configured to be executed by one or more processors, and the one or more programs include instructions for implementing any of the above-described rotating sweep dynamic intensity modulation methods.

[0050] In summary, the present invention discloses a method and apparatus for dynamic intensity modulation by rotational sweeping considering the penumbra of the side of a double-layer grating, which has the following beneficial effects:

[0051] First, this invention improves the efficiency of dynamic intensity modulation and shortens the irradiation treatment time. It divides the target area by quadrants, reducing the distance each leaf moves. Compared with the sliding window segmentation method, it can theoretically achieve a speed up to sqrt(2).

[0052] Second, it improves the conformity of the target area and protects the organs at risk as much as possible. The orthogonal double-layer grating conforms the target area from two mutually perpendicular directions, reducing the leakage and penetration of radiation, and better protecting the tissues and organs around the target area.

[0053] Third, the influence of the side penumbra is considered when segmenting the blades, making the model closer to the real scene and the segmentation intensity closer to the optimized target flux, thus improving the segmentation accuracy. Attached Figure Description

[0054] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 The diagram shows the position distribution of the orthogonal double-layer grating in the field coordinate system according to an embodiment of the present invention.

[0056] Figure 2 This is a diagram of the overlapping area formed by a pair of orthogonal double-layer grating blades provided in an embodiment of the present invention.

[0057] Figure 3 This is a diagram showing the quadrants and blade configuration of the orthogonal double-layer grating blades provided in an embodiment of the present invention.

[0058] Figure 4 This diagram illustrates the initial position division of the four quadrant orthogonal double-layer grating blades provided in an embodiment of the present invention.

[0059] Figure 5 This diagram illustrates the impact of the motion trajectories of the six grating blades in the upper and lower layers on the overlapping area, as provided in an embodiment of the present invention.

[0060] Figure 6 The diagram illustrates the influence of three adjacent blades of a single-layer grating on the regional flux, as provided in an embodiment of the present invention.

[0061] Figure 7 This diagram illustrates the effect of a double-layer grating on regional flux, as provided in an embodiment of the present invention.

[0062] Figure 8 A three-dimensional view of the radiation flux intensity of a nasopharyngeal carcinoma target area provided in an embodiment of the present invention.

[0063] Figure 9 The diagram shows the positional relationship of the six upper and lower grating blades provided in an embodiment of the present invention. Detailed Implementation

[0064] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] Using ordinal numbers such as “first,” “second,” “third,” etc. to describe ordinary objects merely indicates different instances of similar objects and is not intended to imply that the objects being described must have a given order in time, space, sequence, or any other way.

[0067] Furthermore, the expression "includes" is an "open-ended" expression, which only means that the corresponding component exists and should not be interpreted as excluding additional components.

[0068] To achieve the objectives of this invention, in some embodiments of a rotating sweep dynamic intensity modulation method and apparatus considering the penumbra of a double-layer grating, the invention is based on... Figure 1The movement is performed on an orthogonal double-layer grating, where both the upper and lower layers of blades consist of a pair of opposing blades. The directions of movement of the upper and lower layers of blades are perpendicular to each other, and the positions of the double-layer blades are as follows: Figure 1 A pair of orthogonal blades pass through the same position at different times. Within the time difference, the radiation forms a corresponding flux intensity. The method proposed in this invention is to solve the position of the blades at different times so as to ensure that the radiation flux distribution is consistent with the target flux intensity distribution.

[0069] The rotating sweep dynamic intensity modulation method includes the following steps:

[0070] S1: Through the radiotherapy planning system, flux map optimization is performed to obtain the target flux intensity distribution for each radiation field.

[0071] Specifically, based on information such as the prescription and location of the target area and organs at risk, the angle and number of firing fields are determined, and the target flux intensity distribution of each firing field is calculated through the treatment planning system.

[0072] Within the isocentric plane field, the flux map is discretized into many beamlets, each beamlet having a corresponding position (x, y) and a corresponding intensity value I(x, y).

[0073] S2: The optimized flux map is further subdivided into smaller grids, and the overlapping area formed by each pair of orthogonal blades is divided equally to obtain a target flux intensity distribution with a finer grid.

[0074] Specifically, because the width of the grating blades may not match the size of the unit grid in the flux map, to make the segmentation more precise, the overlapping area formed by each pair of orthogonal grating blades is divided equally in two directions, such as... Figure 2 As shown, the overlapping area between a certain upper blade and a certain lower blade is divided into p*q grids. Furthermore, the entire optimized flux map is divided into an even finer grid.

[0075] Furthermore, by comparing the optimized flux map with the flux distribution of each grid cell, the flux intensity of each grid cell is interpolated to obtain a target flux intensity distribution with a finer grid, denoted as I. o (x,y).

[0076] S3: Divide the shooting field into four quadrants. Each quadrant corresponds to two sets of mutually orthogonal blades. One set of blades is the forward blade, and the other set is the backward blade. The forward blade is defined to move towards the center of the shooting field, and the backward blade moves away from the center of the shooting field.

[0077] Specifically, to improve the efficiency of segmentation, the firing field is divided into four quadrants, each corresponding to two sets of mutually perpendicular blades. Thus, the four quadrants within the firing field are formed by four sets of blades arranged in the front, back, left, and right directions. Each quadrant corresponds to a portion of the firing field's flux intensity distribution, and corresponds to two sets of orthogonal blades, such as... Figure 3 As shown, the flux intensity distribution in each quadrant is divided by two sets of orthogonal blades, one set of which is defined as the forward blade and the other as the backward blade.

[0078] The flux intensity distribution in each quadrant is formed by the motion flux trajectories of two sets of orthogonal blades, and the flux in each quadrant is independent of each other.

[0079] The forward or backward blades in adjacent quadrants are not adjacent to each other.

[0080] S4: Determine the initial position of the blades. The initial position of the forward blades is at the edge of the target area, and the initial position of the backward blades is at the intersection of the quadrants. Figure 4 As shown.

[0081] S5: Perform flux segmentation on the blades in each quadrant. Take any two orthogonal blades to form a local region P(x,y). This local region is formed by the overlap of the advancing blade n and the retreating blade m. Simultaneously consider the influence of the penumbra of the four blades adjacent to the two orthogonal blades on the flux of this region. The flux intensity of this region... The calculation method is as follows:

[0082]

[0083] in,(*) + This is a ReLU function, specifically max{0,*};

[0084] For the forward blade u i The flux trajectory function formed in the i-th column of the local region from the right;

[0085] For the retracting blade v j The flux trajectory function formed by the j-th sub-region starting from the local region;

[0086] For the forward blade u i The penumbra coefficient for occlusion of region P(x,y);

[0087] For the retracting blade v j The penumbra coefficient for occlusion of region P(x,y);

[0088] The penumbra coefficient was determined through water tank testing. And the penumbra coefficient Extract;

[0089] Specifically, and Obtained by the following formula;

[0090]

[0091] in, The initial flux value of the advancing blade entering this local region is a known quantity.

[0092] R dose Dose rate;

[0093] The velocity of the forward blade in the a-th column from the right in the local region;

[0094] Δx a This represents the distance to the sub-region in the rightmost column a of the local region.

[0095] The initial flux value of the retracting blade entering this local region is a known quantity.

[0096] The velocity of the retracting blade in the b-th sub-region of the local area;

[0097] Δy b This represents the distance to the b-th sub-region starting from the local region.

[0098] Furthermore, with and the gridded target flux intensity I of this local region o Using the square of the L2 norm of the (x,y) deviation as the objective function, and considering that the blade's movement speed is constrained by the upper limit of speed, the following mathematical optimization model is established. The gradient optimization algorithm is used to solve for the movement speed of the forward and backward blades, and then the flux function of the blades and the number of machine hops in the four quadrants are obtained.

[0099]

[0100]

[0101]

[0102] in, The maximum speed of the forward blade u;

[0103] The maximum speed of the retracting blade is v;

[0104] The aforementioned local region P(x,y) is divided into p*q subregions;

[0105] S6: Repeat S3-S5, using the relationship between the number of machine hops in the four quadrants to adjust the boundary lines of the quadrants until the difference in the number of machine hops in the four quadrants meets the threshold.

[0106] This invention incorporates the influence of the penumbra of adjacent leaves on the flux intensity of local areas during dynamic leaf segmentation. It establishes a segmentation optimization model using orthogonal double-layer grating rotation sweeping, ensuring that the segmented flux matches the optimized flux as closely as possible, thus improving segmentation accuracy. Simultaneously, by considering the penumbra's influence, this invention enhances the model's accuracy, making the optimized model more realistic and facilitating more accurate treatment planning.

[0107] For S5, the following section describes the detailed reasoning process for solving the blade trajectory considering the side penumbra.

[0108] Consider any local region P(x,y), formed by the overlap of the advancing blade n and the retracting blade m. Also consider the influence of the penumbra of the four blades adjacent to the orthogonal blade on the flux in this region. The flux value of this region is determined by the flux trajectories of the six blades in the upper and lower layers. Figure 5 As shown.

[0109] As shown in S3, the overlapping region is divided into p*q sub-regions. Assuming the initial trajectory values ​​of the advancing and retracting blades entering this region are known, i.e. Figure 5 The position of the solid circular trajectory point determines the planned operating speed of each forward and backward blade. Figure 5 The trajectory point positions (hollow circles represent advancing blades, and crosses represent retreating blades) are used to calculate the flux distribution function I of each sub-region and the target flux distribution function. o If (x,y) are consistent, then it is the optimization problem to be solved. The modeling process is as follows.

[0110] 1) Establish an optimization model for the local region

[0111] To ensure that the split flux and the optimized flux are as consistent as possible, the objective function is set as follows:

[0112] min||I d -I o || 2

[0113] That is

[0114]

[0115] Constraints

[0116]

[0117]

[0118] Among them, I d The flux intensity formed by the motion trajectory of the orthogonal double-layer blades;

[0119] I o The target flux derived from the radiotherapy planning system;

[0120] and These are the maximum speeds of the forward blade u and the retracting blade v, respectively.

[0121] Let be the optimized flux of the sub-region from the i-th column from the right to the j-th row from the bottom of the local region, which is a known quantity;

[0122] The actual flux of the sub-region starting from the i-th column from the right and the j-th row from the bottom of the local region is calculated as follows.

[0123] The following three scenarios will be discussed:

[0124] Scenario 1: Ignoring the influence of the side penumbra

[0125] Without considering the penumbra between the leaves The calculation method is as follows:

[0126]

[0127] in, To avoid obstruction by the retracting blades, the forward blades u i The flux function, Indicates the retracting blade v j The occlusion flux function.

[0128] Scenario 2: Considering the influence of the penumbra on the side of a single-layer blade

[0129] When considering the penumbra of a single-layer blade, the flux in a local region P(x,y) is simultaneously affected by the penumbra of multiple blades. Here, we only consider the penumbra formed by three adjacent blades; the influence of the penumbra of other blades on this region is negligible. Figure 6 As shown.

[0130] The flux functions of blades n-1, n, and n+1 are g, respectively. n-1 (x,y),g n (x,y),g n+1 (x,y), with occlusion coefficients α and α, respectively. n-1 ,α n ,α n+1 .

[0131] Sort the values ​​of any flux function by g n-1(x,y)≤g n (x,y)≤g n+1 For the entire time series T, the regional flux F(x,y) is calculated as follows.

[0132]

[0133] Scenario 3: Considering the influence of the penumbra on the sides of the double-layered orthogonal blades

[0134] According to the flux model of a single-layer blade, the flux in a certain local region (x,y) is generated by the superposition of three blades. Considering the penumbra of the side of the double-layer orthogonal blade, the flux in a certain region is affected by the six blades in the upper and lower layers.

[0135] Here, we consider the relationship between the superimposed flux of a single forward blade n in the upper layer and the three retracting blades m-1, m, m+1 in the lower layer, such as... Figure 7 As shown, the flux is calculated as follows.

[0136] For the retracting blade m-1, its blocking flux function is h. m-1 The penumbra coefficient for occlusion of a region P(x,y) is β. m-1 , and the flux function g of the upper advancing blade n n The flux generated by the combined action of (x,y) for:

[0137]

[0138] For the retracting blade m, its blocking flux function is h. m The penumbra coefficient for occlusion of a region P(x,y) is β. m , and the flux function g of the upper advancing blade n n The flux generated by the combined action of (x,y) for:

[0139]

[0140] For the retracting blade m+1, its blocking flux function is h. m+1 The penumbra coefficient for occlusion of a region P(x,y) is β. m+1 , and the flux function g of the upper advancing blade n n The flux generated by the combined action of (x,y) for:

[0141]

[0142] The derivation process is similar to the calculation of the penumbra on the side of a single-layer grating.

[0143] In summary, considering the combined effect of six adjacent blades in the upper and lower layers, the flux for a certain region P(x,y) is calculated as follows:

[0144]

[0145] Where, (x) + This is a ReLU function, specifically max{0,*};

[0146] For the forward blade u i The flux trajectory function formed in the i-th column of the local region from the right;

[0147] For the retracting blade v j The flux trajectory function formed by the j-th sub-region starting from the local region;

[0148] For the forward blade u i The penumbra coefficient for occlusion of region P(x,y);

[0149] For the retracting blade v j The penumbra coefficient for occlusion of region P(x,y);

[0150] The penumbra coefficient reflects the relationship between the area P(x,y) through which the blade passes and the total intensity of the penumbra after passing versus the intensity without considering the penumbra. This coefficient can be obtained through water tank testing.

[0151] The calculation method is as follows:

[0152]

[0153] in, The initial flux value of the advancing blade u as it enters the overlapping region is a known quantity.

[0154] R dose Dose rate;

[0155] The velocity of the forward blade in the a-th column from the right in the local region;

[0156] Δx a This represents the distance to the sub-region in the rightmost column a of the local region.

[0157] The calculation method is as follows:

[0158]

[0159] in, The initial flux value of the retracting blade v as it enters the overlapping region is a known quantity.

[0160] The velocity of the retracting blade in the b-th sub-region of the local area;

[0161] Δy b This represents the distance to the b-th sub-region starting from the local region.

[0162] In summary, solving this optimization problem is transformed into solving the discrete velocity of the blades. and The solution is then used to obtain the flux trajectories of the orthogonal double-layer forward and backward blades.

[0163] Furthermore, embodiments of the present invention also disclose a rotating sweep dynamic intensity modulation device that considers the penumbra of the side of a double-layer grating, comprising:

[0164] One or more processors;

[0165] Memory;

[0166] And one or more programs, wherein the one or more programs are stored in memory and configured to be executed by one or more processors, and the one or more programs include instructions for implementing the rotating sweep dynamic intensity modulation method disclosed in any of the above embodiments.

[0167] To clearly illustrate the specific implementation process of this invention, a nasopharyngeal carcinoma case is used as an example to introduce the specific implementation details. The method for dynamic intensity modulation of the side penumbra of a double-layer grating includes the following steps:

[0168] S1: In the radiotherapy planning system, import nasopharyngeal carcinoma cases, optimize the flux map, and obtain the target flux intensity distribution for each radiation field. Within the radiation field range on the isocentric plane, the flux intensity can be represented as I(x,y), and its three-dimensional view is as follows: Figure 8 As shown.

[0169] S2: Process the optimized flux map by equally dividing the overlapping region formed by each pair of orthogonal grating blades into p*q small grids, such as... Figure 2 As shown, the entire flux map is divided into flux maps with a finer grid, denoted as I. o Compare the optimized flux map I(x,y) with each refined intensity map I. o Grid interpolation of (x,y).

[0170] S3: Divide the system into quadrants. Based on the principle of minimizing the difference in MU within each quadrant, initially divide the system into quadrants and determine the boundaries Qx1, Qx2, and Qy for each quadrant. This yields the flux distribution across the four quadrants, as shown below. Figure 3 As shown.

[0171] The flux of each quadrant is independent of each other. Each quadrant corresponds to two sets of mutually orthogonal blades. One set of blades is the forward blade and the other set is the backward blade. The forward blade is defined to move towards the center of the field of fire, and the backward blade moves away from the center of the field of fire.

[0172] By determining the motion trajectory of the aforementioned blades, the desired flux distribution can be obtained.

[0173] S4: Determine the initial position of the blades. The initial position of the forward blades is near the edge of the target area, and the initial position of the retracting blades is at the boundary of the quadrants. Figure 4 As shown.

[0174] S5: Perform flux segmentation on the blades in each quadrant. Take any two orthogonal blades forming a local region P(x,y). The forward blade u moves along the coordinate axis towards the center of the field at a certain speed, while the backward blade v moves away from the center of the field along the coordinate axis at a certain speed. Figure 9 As shown, the flux in this region is affected by the combined effects of the penumbra of the four adjacent blades, and the flux intensity in this region is... The calculation method is as follows:

[0175]

[0176] in,(*) + This is a ReLU function, specifically max{0,*};

[0177] For the forward blade u i The flux trajectory function formed in the i-th column of the local region from the right;

[0178] For the retracting blade v j The flux trajectory function formed by the j-th sub-region starting from the local region;

[0179] For the forward blade u i The penumbra coefficient of region P(x,y) is extracted by water tank testing;

[0180] For the retracting blade v j The penumbra coefficient of region P(x,y) is extracted by water tank testing;

[0181] Specifically, and Obtained by the following formula;

[0182]

[0183] in, The initial flux value of the advancing blade entering this local region is a known quantity.

[0184] R dose Dose rate;

[0185] The velocity of the forward blade in the a-th column from the right in the local region;

[0186] Δx a This represents the distance to the sub-region in the rightmost column a of the local region.

[0187] The initial flux value of the retracting blade entering this local region is a known quantity. The velocity of the retracting blade in the b-th sub-region of the local area;

[0188] Δy b This represents the distance to the b-th sub-region starting from the local region.

[0189] Furthermore, with and the gridded target flux intensity I of this local region o Using the square of the L2 norm of the (x,y) deviation as the objective function, and considering that the blade's motion speed is constrained by a speed upper limit, the following mathematical optimization model is established.

[0190]

[0191]

[0192]

[0193] in, The maximum speed of the forward blade u;

[0194] The maximum speed of the retracting blade is v;

[0195] The aforementioned local region P(x,y) is divided into p*q subregions;

[0196] The above mathematical model is a convex problem. The motion speeds of the forward and backward blades can be solved using gradient-based optimization algorithms, thereby obtaining the blade flux function and the number of machine hops in the four quadrants.

[0197] S6: Repeat S3-S5, using the machine hop counts of the four quadrants to adjust the quadrant boundaries until the difference in machine hop counts of the four quadrants meets the threshold.

[0198] In summary, the present invention discloses a method and apparatus for dynamic intensity modulation by rotational sweeping considering the penumbra of the side of a double-layer grating, which has the following beneficial effects:

[0199] First, this invention improves the efficiency of dynamic intensity modulation and shortens the irradiation treatment time. It divides the target area by quadrants, reducing the distance each leaf moves. Compared with the sliding window segmentation method, it can theoretically achieve a speed up to sqrt(2).

[0200] Second, it improves the conformity of the target area and protects the organs at risk as much as possible. The orthogonal double-layer grating conforms the target area from two mutually perpendicular directions, reducing the leakage and penetration of radiation, and better protecting the tissues and organs around the target area.

[0201] Third, the influence of the side penumbra is considered when segmenting the blades, making the model closer to the real scene and the segmentation intensity closer to the optimized target flux, thus improving the segmentation accuracy.

[0202] It should be understood that the various techniques described herein can be implemented in combination with hardware or software, or a combination thereof. Thus, the methods and apparatus of the present invention, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embedded in a tangible medium, such as a floppy disk, CD-ROM, hard disk, or any other machine-readable storage medium, wherein when the program is loaded into and executed by a machine such as a computer, that machine becomes an apparatus for practicing the present invention.

[0203] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A dynamic intensity modulation method for rotating and sweeping the penumbra of a double-layer grating includes the following steps: S1: Through the radiotherapy planning system, flux map optimization is performed to obtain the target flux intensity distribution for each radiation field; S2: The optimized flux map is further subdivided into grids, and the overlapping area formed by each pair of orthogonal blades is divided equally to obtain a target flux intensity distribution with a finer grid. S3: Divide the shooting field area into four quadrants. Each quadrant corresponds to two sets of mutually orthogonal blades. One set of blades is the forward blade and the other set of blades is the backward blade. The forward blade is defined to move towards the center of the shooting field, and the backward blade moves away from the center of the shooting field. S4: Determine the initial position of the blades. The initial position of the forward blades is at the edge of the target area, and the initial position of the backward blades is at the intersection of the quadrants. S5: Perform flux segmentation on the blades in each quadrant. Take any two orthogonal blades forming a local region P(x, y), where this region is formed by the overlap of the advancing blade n and the retreating blade m. Simultaneously consider the influence of the penumbra of the four blades adjacent to the two orthogonal blades on the flux of this region. Determine the flux intensity of this region. The calculation method is as follows: in,(*) + This is a ReLU function, specifically max{0, *}; For the forward blade u i The flux trajectory function formed in the i-th column of the local region from the right; For the retracting blade v j The flux trajectory function formed by the j-th sub-region starting from the local region; For the forward blade u i The penumbra coefficient for occlusion of region P(x,y); For the retracting blade v j The penumbra coefficient for occlusion of region P(x,y); Specifically, and Obtained by the following formula; in, The initial flux value of the advancing blade entering this local region is a known quantity. R dose Dose rate; The velocity of the forward blade in the a-th column from the right in the local region; This represents the distance to the sub-region in the rightmost column a of the local region. The initial flux value of the retracting blade entering this local region is a known quantity. The velocity of the retracting blade in the b-th sub-region of the local area; This represents the distance to the b-th sub-region starting from the local region. Furthermore, with and the gridded target flux intensity I of this local region o Using the square of the L2 norm of the (x, y) deviation as the objective function, and considering that the blade's movement speed is constrained by the upper speed limit, the following mathematical optimization model is established to obtain the movement speeds of the forward and backward blades, and then to obtain the blade's flux function and the number of machine hops in the four quadrants. in, The maximum speed of the forward blade u; The maximum speed of the retracting blade is v; The aforementioned local region P(x, y) is divided into p*q subregions; S6: Repeat S3-S5, using the relationship between the number of machine hops in the four quadrants to adjust the boundary lines of the quadrants until the difference in the number of machine hops in the four quadrants meets the threshold.

2. The rotating sweep dynamic intensity modulation method according to claim 1, characterized in that, S2 also includes the following: interpolating each gridded flux map against the optimized flux map.

3. The rotating sweep dynamic intensity modulation method according to claim 1, characterized in that, In S3, the flux in each quadrant is independent of each other.

4. The rotating sweep dynamic intensity modulation method according to claim 1, characterized in that, In S3, the forward or backward blades in adjacent quadrants are not adjacent to each other.

5. The rotating sweep dynamic intensity modulation method according to claim 1, characterized in that, In S5, the penumbra coefficient α was tested using a water tank. u (x,y) and the penumbra coefficient β v Extract (x,y).

6. The rotating sweep dynamic intensity modulation method according to claim 1, characterized in that, The mathematical optimization model in S5 is solved using the gradient optimization algorithm to obtain the motion speeds of the forward and backward blades.

7. A dynamic intensity modulation device considering the rotational sweep of the penumbra on the sides of a double-layer grating, characterized in that, include: One or more processors; Memory; And one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by one or more processors, and the one or more programs include instructions for implementing the rotating sweep dynamic intensity modulation method according to any one of claims 1-6.

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