Afterloading brachytherapy plan verification method

Abstract

The present invention relates to the technical field of intracavitary radiotherapy, and in particular to a method for verifying a post-loading brachytherapy plan, comprising positioning and scanning a lesion, creating a 3D model, printing the model using 3D technology, positioning in a coordinate manner, marking a target area and points of interest, fixing a thermoluminescent sheet, performing simulated radiotherapy, completing a radiotherapy plan according to a preset dwell point and dwell time, reading a radiation dose of a target area and a preset dose for comparison, and determining whether it is necessary to adjust parameters in the radiotherapy plan. The present invention adopts 3D technology and a spatial coordinate positioning method to achieve precise positioning in plan verification for personalized design of patients. Meanwhile, a thermoluminescent dose detector can be annealed and can be repeatedly measured, thereby reducing the use cost and having higher feasibility and economy.

Description

Technical Field

[0001] The invention relates to the technical field of intracavitary radiotherapy, and in particular to a method for verifying a post-loading brachytherapy plan. Background Art

[0002] Afterloader, or brachytherapy machine, is a new generation of tumor treatment equipment that can perform afterloading radiotherapy. Afterloading radiotherapy refers to placing a treatment container without a radioactive source at the treatment site, and using a computer-controlled stepper motor to send the radioactive source into the container for radiotherapy. The radioactive source can be accurately and safely delivered to the site of the patient that needs treatment for radiotherapy through the source applicator. The computer-controlled remote-controlled stepper sealed micro-source presets the dose according to the reference point, and the residence time of the residence point is calculated by the treatment planning system to obtain the optimized dose distribution, thereby giving the tumor area sufficient and accurate treatment dose to improve the tumor control rate and reduce the radiation complications of normal tissues. The radiation dose of the afterloader needs to be precisely controlled to achieve the radiotherapy effect on the tumor while reducing complications.

[0003] Chinese Patent Publication No.: CN215084351U discloses a device for verifying the spatial radiation dose of post-loading brachytherapy, including a main body, a cover body and a radiation autoradiographic film, wherein the main body is detachably connected to the cover body, the cover body is provided with a plurality of perforations of different diameters, the bottom of the main body is provided with a plurality of fixing holes corresponding to the perforations, the bottom of the main body and the cover body are relatively provided with annular grooves of the same diameter, the radiation autoradiographic film is rolled into a main body shape, and the two ends are respectively arranged in the annular grooves on the main body and the cover body, and is used for verifying the radiation dose in post-loading radiotherapy, and can measure the spatial cumulative radiation dose of the radiation source under different paths to ensure accurate control of the radiation dose in clinical treatment. However, in the prior art, it is impossible to simulate the position corresponding to the lesion, the spatial resolution is insufficient, the cost is high, and the situation where there is an invasion cannot be measured. However, the radiation dose emitted by the radiation source in the cylinder is detected by a radiation detection sensor and displayed and recorded by a dose analysis display. This reading method has large errors. The radiation autoradiographic film is a disposable consumable and has a high cost. In addition, the solution disclosed in the utility model cannot solve the problem of spatial resolution.

[0004] Afterloading brachytherapy has the characteristics of high local dose and rapid drop of peripheral dose. It can well protect the surrounding normal tissues and greatly increase the dose of the target area. It is a very important means of cancer treatment, especially cervical cancer treatment. With the gradual popularization of 3D printing technology, afterloading radiotherapy is becoming more and more accurate, and a method of plan verification is urgently needed to ensure the accuracy and efficacy of the dose. However, due to the characteristics of its rapid dose drop, its plan verification equipment requires a high spatial resolution. The well-type ionization chamber can measure the dose of the maximum dose point at a certain distance from the central axis to calculate the source activity, but it cannot measure the dose of other points of interest; the colloid dosimeter has a high spatial resolution and there is a possibility of afterloading plan verification. However, the data reading and comparison of the colloid dosimeter are relatively complex and difficult, which is not conducive to implementation. Moreover, the colloid dosimeter is a one-time measurement tool, and its high cost is not conducive to popularization. Summary of the invention

[0005] To this end, the present invention provides a method for verifying a post-loading brachytherapy plan, so as to overcome the problems in the prior art of insufficient spatial resolution of post-loading verification, inability to accurately position, inability to accurately measure the dose of each point of interest, resulting in poor accuracy of post-loading plan verification and high cost that is not conducive to promotion.

[0006] To achieve the above object, the present invention provides a method for verifying a post-loading brachytherapy plan.

[0007] Step S1, performing a positioning scan on the lesion, displaying the exact location and size of the tumor through three-dimensional images to create a 3D model and printing the model using 3D printing technology. If the tumor invades other tissues, the head of the reserved applicator channel is not sealed when printing the 3D model, so that the applicator can pass through the 3D model to be inserted into the invaded tissue;

[0008] Step S2, using a spatial coordinate positioning method to determine the spatial coordinates of each point on the surface of the 3D model, and at the same time calibrating points of interest and obtaining the spatial coordinates of the points of interest, wherein the points of interest are used to simulate normal tissues around the tumor;

[0009] Step S3, arranging the thermoluminescent dose detectors according to the coordinates and distributing them according to a spatial regularity to be fixed around the 3D model and on the calibrated points of interest;

[0010] Step S4, performing simulated radiotherapy in the 3D model according to the radiotherapy plan pre-formulated by the computer system, reading the radiation dose received by the thermoluminescent dose detector after completing the simulated radiotherapy, and comparing the read data with the preset data in the radiotherapy plan to determine whether it is necessary to adjust the dwell time corresponding to each dwell point in the radiotherapy plan;

[0011] Step S5, after completing the adjustment of the dwell time corresponding to each dwell point, re-performing the simulated radiotherapy, after completing the simulated radiotherapy, drawing a three-dimensional dose model based on the 3D model according to the radiation dose received by the thermoluminescent dose detector, and determining whether it is necessary to adjust the number of dwell points in the radiotherapy plan according to the three-dimensional dose model;

[0012] Step S6, after completing the adjustment of the number of dwell points, re-performing simulated radiotherapy, after completing the simulated radiotherapy, reading the data of the thermoluminescent dose detector of the point of interest and determining whether the radiation dose received by the normal tissue exceeds the tolerance dose based on the read data, the computer system obtains a three-dimensional dose contribution diagram of the point of interest when the radiation dose of the point of interest exceeds the tolerance dose to determine the dwell points that affect the point of interest and the dose contribution ratio of each dwell point, and adjusts the dwell time of the corresponding dwell point based on the dose contribution ratio.

[0013] Furthermore, in step S2, the specific method of the spatial coordinate positioning method is: taking the geometric center of the front end of the 3D model as the coordinate origin, the above and below the coordinate origin are the positive and negative directions of the X-axis, the front and back of the coordinate origin are the positive and negative directions of the Z-axis, and the right and left of the coordinate origin are the positive and negative directions of the Y-axis.

[0014] Furthermore, in the step S3, the thermoluminescent dose detectors are arranged according to the coordinates and then regularly distributed and fixed in space. When fixed, at least one layer of thermoluminescent dose detectors is fixed to obtain a higher spatial resolution.

[0015] Further, in step S4, when simulated radiotherapy is performed according to the radiotherapy plan pre-formulated by the computer system, simulated radiotherapy is performed according to the position of the dwell point in the radiotherapy plan and the dwell time of each dwell point. After the simulated radiotherapy is completed, the radiation dose received by each thermoluminescent dose detector is read and the read data is compared with the preset data in the radiotherapy plan to determine whether it is necessary to adjust the dwell time corresponding to each dwell point in the radiotherapy plan; for a single dwell point, the dwell point is taken as the origin and the area extending in both directions along the axial direction of the applicator by a preset distance is used as the dose determination area, the thermoluminescent dose detector of the dose determination area corresponding to the single dwell point is read, and the average dose of each point in the space in the area is calculated as the actual received dose in the simulated radiotherapy, the computer system is provided with a standard dose difference ΔDb, and the preset dose of the dwell point is recorded as D0, and the actually received dose is recorded as D, the computer system calculates the difference ΔD between D and D0 and compares ΔD with ΔDb, and sets ΔD=|D0-D|,

[0016] If ΔD≤ΔDb, the computer system determines that the radiation dose at the dwell point meets the standard;

[0017] If ΔD>ΔDb, the computer system determines that the radiation dose at the dwell point does not meet the standard.

[0018] Further, when the computer system determines that the radiation dose of the dwell point does not meet the standard, the dwell time of the dwell point is adjusted to the corresponding value according to ΔD, and the computer system is provided with a preset dwell time t0 of the dwell point, a first preset radiation dose difference ΔD1, a second preset radiation dose difference ΔD2, a first dwell time adjustment coefficient α1, a second dwell time adjustment coefficient α2 and a third dwell time adjustment coefficient α3, wherein ΔD1<ΔD2, 1.3<α1<α2<α3<1.5,

[0019] If ΔD≤ΔD1, the computer system uses α1 to adjust the dwell time of the dwell point to a corresponding value;

[0020] If ΔD1<ΔD≤ΔD2, the computer system uses α2 to adjust the dwell time of the dwell point to a corresponding value;

[0021] If ΔD2<ΔD, the computer system uses α3 to adjust the dwell time of the dwell point to a corresponding value;

[0022] When the computer system uses αn to adjust the dwell time of the dwell point to a corresponding value, n=1, 2, 3 is set, and the computer system records the adjusted dwell time of the dwell point as t1.

[0023] If D<D0, then set t1=t0×αn;

[0024] If D>D0, then set t1=t0×(2-αn).

[0025] Further, in step S5, after the computer system completes the adjustment of the dwell time corresponding to the dwell point, the simulated radiotherapy is performed again, and after the simulated radiotherapy is completed, a three-dimensional dose model based on the 3D model is drawn according to the radiation dose received by the thermoluminescent dose detector.

[0026] The computer system compares the three-dimensional dose model in the pre-formulated radiotherapy plan with the three-dimensional dose model obtained by simulating radiotherapy, marks out the area where the radiation dose is different, and locates the marked area according to the spatial coordinates to calculate the area of ​​the area where the radiation dose is different. The computer system determines the number of additional dwelling points according to the area. The computer system is provided with a standard area S0, and the area of ​​the area where the radiation dose is different is recorded as S. The computer system compares S with S0.

[0027] If S>S0, the computer system calculates the difference ΔS between S and S0 and determines the number of dwell points to be increased according to ΔS, and sets ΔS=S-S0;

[0028] If S≤S0, the computer system determines that a dwell point needs to be added, and the area where the radiation dose is different is used as the dose determination area and the position of the dwell point is determined by dividing the dose determination area.

[0029] Further, when the area S>S0 of the region where the radiation dose calculated by the computer system is different, the computer system calculates the difference ΔS between S and S0 and determines the number of dwell points that need to be increased according to ΔS. The computer system is provided with a standard area difference ΔSb. The computer system compares ΔS with ΔSb.

[0030] If ΔS≤ΔSb, the computer system determines that two more dwelling points are needed, and the area where the radiation dose difference exists is used as the dose determination area, and the positions of the dwelling points are determined by dividing the dose determination area;

[0031] If ΔSb<ΔS≤2ΔSb, the computer system determines that three more dwelling points are needed, and the area where the radiation doses differ is used as the dose determination area and the positions of the dwelling points are determined by dividing the dose determination area.

[0032] Further, in step S6, the computer system re-performs simulated radiotherapy after completing the adjustment of the number of dwell points, reads data from the thermoluminescent dose detector of the point of interest after completing the simulated radiotherapy, and determines whether the radiation dose received by the normal tissue exceeds the tolerance dose based on the read data, the computer system records the tolerance dose of the normal tissue as U0, records the radiation dose received by the point of interest during the simulated radiotherapy as U, and compares U with U0,

[0033] If U>U0, the computer system determines that the radiation dose at the point of interest exceeds the tolerance dose;

[0034] If U≤U0, the computer system determines that the radiation dose of the point of interest meets the standard.

[0035] Further, when the computer system determines that the radiation dose of the point of interest exceeds the tolerance dose, the computer system calculates the difference ΔU between U and U0 and selects the corresponding adjustment coefficient according to ΔU to adjust the dwell time of the dwell point corresponding to the point of interest, and sets ΔU=U-U0. The computer system is provided with a first preset point of interest radiation dose excess difference ΔU1, a second preset point of interest radiation dose excess difference ΔU2, a first dwell time reduction adjustment coefficient β1, a second dwell time reduction adjustment coefficient β2, and a third dwell time reduction adjustment coefficient β3, wherein ΔU1<ΔU2, 0.8<β1<β2<β3<1,

[0036] If ΔU≤ΔU1, the computer system uses β3 to adjust the dwell time to a corresponding value;

[0037] If ΔU1<ΔU≤ΔU2, the computer system uses β2 to adjust the dwell time to a corresponding value;

[0038] If ΔU2<ΔU, the computer system uses β1 to adjust the dwell time to a corresponding value.

[0039] Furthermore, the method for obtaining the dwell point corresponding to the point of interest is as follows:

[0040] A three-dimensional dose contribution diagram of the point of interest is obtained to determine the dwell points that affect the point of interest and the dose contribution ratio of each dwell point. The computer system adjusts the dwell time of the corresponding dwell point according to the dose contribution ratio. The computer system records the contribution ratio of each corresponding dwell point as Bi, where i is a positive integer greater than 0, and the dwell time before adjustment is recorded as T0.

[0041] When the computer system uses βm to adjust the dwell time of the dwell point corresponding to the point of interest to the corresponding value, setting m=1, 2, 3, the computer system records the adjusted dwell time as T', and setting T'=T0×βm×Bi.

[0042] Compared with the prior art, the beneficial effect of the present invention lies in that the present invention uses 3D printing technology to print models to simulate treatment target areas. On the one hand, it can be designed on demand for patients in different situations. On the other hand, during plan verification, the real plan verification can be directly completed, thereby improving the accuracy of the method of the present invention in verifying the afterloading brachytherapy plan.

[0043] Furthermore, when there is a situation where the tumor invades other tissues, the present invention will leave the reserved applicator channel head unsealed when printing the 3D model, so that the applicator can be inserted outward into the invaded tissue, which can truly simulate the special treatment process and further improve the accuracy of the method of the present invention in verifying the after-loading brachytherapy plan.

[0044] Furthermore, the present invention obtains the spatial coordinates of the point of interest through the spatial coordinate positioning method to achieve precise positioning. The method is simple and easy to operate. Even for points outside the model, radiation dose measurement can be performed through spatial coordinate positioning, thereby realizing radiation dose measurement of points of interest outside the model, thereby improving the accuracy of the method of the present invention in verifying the afterloading brachytherapy plan and the practicality of the method of the present invention.

[0045] Furthermore, the present invention uses a thermoluminescent dose detector to measure the radiation dose. The thermoluminescent dose detector can be annealed and can be measured repeatedly, which reduces the cost of use and has higher feasibility and economy. The thermoluminescent dose detector has a good linear relationship between the radiation dose and the reading at 0-1000cGy and good repeatability. The effective atomic number of human soft tissue is 7.4, and the phosphor of the micro-thermoluminescent detector TLD is LiF containing activator impurities such as Mg, Cu, etc. Its effective atomic number is 8.2, which is close to soft tissue and suitable for after-sales plan verification. The size of the thermoluminescent dose detector itself can be 3mm long and 0.8mm thick, which is suitable for rapid drop dose measurement. By encoding the thermoluminescent dose detector and distributing it around the 3D model according to a certain spatial pattern, a higher spatial resolution can be obtained, and a higher measurement accuracy can be obtained.

[0046] Furthermore, after the thermoluminescent dose detector is fixed, the present invention performs simulated radiotherapy in the 3D model according to the radiotherapy plan preset by the computer system. After the simulated radiotherapy is completed, the radiation dose received by the thermoluminescent dose detector is read and the read data is compared with the preset data in the radiotherapy plan to determine whether it is necessary to adjust the dwell time corresponding to each dwell point in the radiotherapy plan, which further improves the accuracy of the method of the present invention in verifying the after-loading brachytherapy plan and the practicality of the method of the present invention.

[0047] Furthermore, the present invention re-performs simulated radiotherapy after completing the adjustment of the dwell time corresponding to each dwell point, draws a three-dimensional dose model based on the 3D model according to the radiation dose received by the thermoluminescent dose detector after completing the simulated radiotherapy, and determines whether the number of dwell points in the radiotherapy plan needs to be adjusted according to the three-dimensional dose model, which further improves the accuracy of the method of the present invention in verifying the afterloading brachytherapy plan and the practicality of the method of the present invention.

[0048] Furthermore, the present invention re-performs simulated radiotherapy after completing the adjustment of the number of dwell points, reads data from the thermoluminescent dose detector of the point of interest after completing the simulated radiotherapy, and determines whether the radiation dose received by the normal tissue exceeds the tolerance dose based on the read data. When the radiation dose of the point of interest exceeds the tolerance dose, the computer system obtains a three-dimensional dose contribution diagram of the point of interest to determine the dwell points that affect the point of interest and the dose contribution ratio of each dwell point, and adjusts the dwell time of the corresponding dwell point based on the dose contribution ratio, thereby further improving the accuracy of the method of the present invention in verifying the afterloading brachytherapy plan and the practicality of the method of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1A 3D model of a post-loading brachytherapy plan verification method according to an embodiment of the present invention and a perspective view of the position of a thermoluminescent dose detector;

[0050] Figure 2 A flowchart of the steps of a post-loading brachytherapy plan verification method according to an embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram of a spatial coordinate positioning method according to an embodiment of the present invention;

[0052] In the figure, 1. Thermoluminescent dose detector; 2. 3D model; 3. Applicator channel. DETAILED DESCRIPTION

[0053] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0055] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0056] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] See also Figure 1 As shown, it is a 3D model and a perspective view of the position of the thermoluminescent dose detector of the post-installed brachytherapy plan verification method according to an embodiment of the present invention, wherein the thermoluminescent dose detector 1 is arranged and coded according to coordinates and regularly distributed in space and fixed around the 3D model 2, so as to measure the radiation dose of the radiation source in the reserved applicator channel 3 during simulated radiotherapy.

[0058] See also Figure 2As shown, it is a flowchart of the steps of the afterloading brachytherapy plan verification method according to an embodiment of the present invention, including:

[0059] Step S1, perform a positioning scan on the lesion, display the exact position and size of the tumor through three-dimensional images to create a 3D model 2 and print the model using 3D printing technology. If the tumor invades other tissues, the head of the reserved applicator channel 3 is not sealed when printing the 3D model 2, so that the applicator can pass through the 3D model 2 and be inserted into the invaded tissue;

[0060] Preferably, CT is used to perform localization scanning of the lesion.

[0061] This embodiment uses 3D printing technology to print a model to simulate the treatment target area. On the one hand, it can be designed according to the needs of patients in different situations. On the other hand, during plan verification, the real plan verification can be completed directly, thereby improving the accuracy of the method of the present invention for afterloading brachytherapy plan verification.

[0062] By leaving the head of the reserved applicator channel 3 unsealed when printing the 3D model 2, the applicator can pass through the 3D model 2 through the reserved unsealed applicator channel 3 to be inserted into the invaded tissue externally, simulating the treatment of similar bladder invasion situations, thereby improving the accuracy of the method of the present invention in verifying the afterloading brachytherapy plan and the practicality of the method of the present invention.

[0063] Step S2, using a spatial coordinate positioning method to determine the spatial coordinates of each point on the surface of the 3D model 2, and at the same time, calibrating points of interest and obtaining the spatial coordinates of the points of interest, wherein the points of interest are used to simulate normal tissues around the tumor;

[0064] Step S3, the thermoluminescent dose detectors 1 are arranged according to the coordinates and fixed around the 3D model 2 and on the calibrated points of interest according to a certain spatial rule;

[0065] Step S4, performing simulated radiotherapy in the 3D model 2 according to the radiotherapy plan pre-formulated by the computer system, reading the radiation dose received by the thermoluminescent dose detector 1 after completing the simulated radiotherapy, and comparing the read data with the preset data in the radiotherapy plan to determine whether the dwell time corresponding to each dwell point in the radiotherapy plan needs to be adjusted;

[0066] Step S5, after completing the adjustment of the dwell time corresponding to each dwell point, re-performing the simulated radiotherapy, after completing the simulated radiotherapy, drawing a three-dimensional dose model based on the 3D model 2 according to the radiation dose received by the thermoluminescent dose detector 1, and determining whether it is necessary to adjust the number of dwell points in the radiotherapy plan according to the three-dimensional dose model;

[0067] Step S6, after completing the adjustment of the number of dwell points, re-perform simulated radiotherapy, after completing the simulated radiotherapy, read the data of the thermoluminescent dose detector 1 of the point of interest and determine whether the radiation dose received by the normal tissue exceeds the tolerance dose based on the read data, the computer system obtains a three-dimensional dose contribution diagram of the point of interest when the radiation dose of the point of interest exceeds the tolerance dose to determine the dwell points that affect the point of interest and the dose contribution ratio of each dwell point, and adjusts the dwell time of the corresponding dwell point according to the dose contribution ratio.

[0068] Preferably, in step S1, the density of the model is the same as the density of human tissue.

[0069] See also Figure 3 As shown, it is a schematic diagram of the spatial coordinate positioning method of an embodiment of the present invention. In the step S2, the specific method of the spatial coordinate positioning method is: the geometric center of the front end of the 3D model 2 is used as the coordinate origin, the upper and lower parts of the coordinate origin are the positive and negative directions of the X-axis, the front and rear parts of the coordinate origin are the positive and negative directions of the Z-axis, and the right and left parts of the coordinate origin are the positive and negative directions of the Y-axis.

[0070] The present invention obtains the spatial coordinates of the point of interest through a spatial coordinate positioning method to achieve precise positioning. The method is simple and easy to operate. Even for points outside the model, radiation dose measurement can be performed by obtaining and positioning through spatial coordinates, thereby realizing radiation dose measurement of points of interest outside the model, and improving the accuracy of the method of the present invention in verifying the afterloading brachytherapy plan and the practicality of the method of the present invention.

[0071] In step S3, the thermoluminescent dose detectors 1 are arranged according to the coordinates and then regularly distributed and fixed in space. When fixed, at least one layer of thermoluminescent dose detectors 1 is fixed to obtain a higher spatial resolution. The thermoluminescent dose detector 1 can also be fixed only at the point of interest to measure the dose of the point of interest, reducing costs. The size of the thermoluminescent dose detector 1 itself can be 3 mm long and 0.8 mm thick. It can be fixed in multiple layers as needed to meet the dose measurement of rapid drops and obtain a higher spatial resolution.

[0072] The method for fixing the thermoluminescent dose detector 1 adopted in the present invention is to use a material with an effective atomic number of about 7.2 to make an elastic strip, and reserve slots around the elastic strip for placing the thermoluminescent dose detector 1. When in use, take a length that is suitable for the circumference of the 3D model 2 and surround the 3D model 2 to quickly fix the thermoluminescent dose detector 1. Other methods can also be used for fixing. The present invention does not limit the fixing method of the thermoluminescent dose detector 1.

[0073] Specifically, in step S4, when simulating radiotherapy according to the radiotherapy plan pre-formulated by the computer system, the simulated radiotherapy is performed according to the position of the dwelling point in the radiotherapy plan and the dwelling time of each dwelling point. After the simulated radiotherapy is completed, the radiation dose received by each thermoluminescent dose detector 1 is read and the read data is compared with the preset data in the radiotherapy plan to determine whether it is necessary to adjust the dwelling time corresponding to each dwelling point in the radiotherapy plan; for a single dwelling point, the area with the dwelling point as the origin and the preset distance extending in both directions along the axial direction of the applicator is used as the dose determination area, and the dose corresponding to each dwelling point is determined by comparing the read data ... The determination areas do not overlap and the sum of the areas after division is equal to the surface area of ​​the 3D model 2. The distance of the bidirectional extension distance along the axial direction of the applicator is proportional to the residence time of each residence point. The thermoluminescent dose detector 1 of the dose determination area corresponding to a single residence point is read, and the average dose of each point in the space within the area is calculated as the actual received dose in the simulated radiotherapy. The computer system is provided with a standard dose difference ΔDb. At the same time, the preset dose of the residence point is recorded as D0 and the actual received dose is recorded as D. The computer system calculates the difference ΔD between D and D0 and compares ΔD with ΔDb, and sets ΔD=|D0-D|.

[0074] If ΔD≤ΔDb, the computer system determines that the radiation dose at the dwell point meets the standard;

[0075] If ΔD>ΔDb, the computer system determines that the radiation dose at the dwell point does not meet the standard.

[0076] Preferably, in this embodiment, the value of ΔDb is set to ±5% D0.

[0077] Specifically, when the computer system determines that the radiation dose of the dwell point does not meet the standard, the dwell time of the dwell point is adjusted to the corresponding value according to ΔD. The computer system is provided with a preset dwell time t0 of the dwell point, a first preset radiation dose difference ΔD1, a second preset radiation dose difference ΔD2, a first dwell time adjustment coefficient α1, a second dwell time adjustment coefficient α2 and a third dwell time adjustment coefficient α3, wherein ΔD1<ΔD2, 1.3<α1<α2<α3<1.5,

[0078] If ΔD≤ΔD1, the computer system uses α1 to adjust the dwell time of the dwell point to a corresponding value;

[0079] If ΔD1<ΔD≤ΔD2, the computer system uses α2 to adjust the dwell time of the dwell point to a corresponding value;

[0080] If ΔD2<ΔD, the computer system uses α3 to adjust the dwell time of the dwell point to a corresponding value;

[0081] When the computer system uses αn to adjust the dwell time of the dwell point to a corresponding value, n=1, 2, 3 is set, and the computer system records the adjusted dwell time of the dwell point as t1.

[0082] If D<D0, then set t1=t0×αn;

[0083] If D>D0, then set t1=t0×(2-αn).

[0084] Specifically, in step S5, after the computer system completes the adjustment of the dwell time corresponding to the dwell point, the simulated radiotherapy is performed again, and after the simulated radiotherapy is completed, a three-dimensional dose model based on the 3D model 2 is drawn according to the radiation dose received by the thermoluminescent dose detector 1.

[0085] The computer system compares the three-dimensional dose model in the pre-formulated radiotherapy plan with the three-dimensional dose model obtained by simulating radiotherapy, marks out the area where the radiation dose is different, and locates the marked area according to the spatial coordinates to calculate the area of ​​the area where the radiation dose is different. The computer system determines the number of additional dwelling points according to the area. The computer system is provided with a standard area S0, and the area of ​​the area where the radiation dose is different is recorded as S. The computer system compares S with S0.

[0086] If S>S0, the computer system calculates the difference ΔS between S and S0 and determines the number of dwell points to be increased according to ΔS, and sets ΔS=S-S0;

[0087] If S≤S0, the computer system determines that a dwell point needs to be added, and the area where there is a difference in radiation dose is used as the dose determination area and the position of the dwell point is determined by dividing the dose determination area. At the same time, the computer system calculates the dwell time of the dwell point according to the preset radiation dose of the area where there is a difference in radiation dose in the radiotherapy plan.

[0088] Specifically, when the area S>S0 of the region where the radiation dose calculated by the computer system is different, the computer system calculates the difference ΔS between S and S0 and determines the number of dwell points that need to be increased according to ΔS. The computer system is provided with a standard area difference ΔSb. The computer system compares ΔS with ΔSb.

[0089] If ΔS≤ΔSb, the computer system determines that two dwelling points need to be added, and the area where the radiation dose is different is used as the dose determination area, and the positions of the dwelling points are determined by dividing the dose determination area, and the computer system calculates the dwell time of each dwelling point according to the preset radiation dose of the area where the radiation dose is different in the radiotherapy plan;

[0090] If ΔSb<ΔS≤2ΔSb, the computer system determines that three more dwelling points are needed, and the area where there is a difference in radiation dose is used as the dose determination area and the positions of the dwelling points are determined by dividing the dose determination area. At the same time, the computer system calculates the dwell time of each dwelling point according to the preset radiation dose of the area where there is a difference in radiation dose in the radiotherapy plan.

[0091] Specifically, in step S6, the computer system re-performs simulated radiotherapy after completing the adjustment of the number of dwell points, reads data from the thermoluminescent dose detector 1 of the point of interest after completing the simulated radiotherapy, and determines whether the radiation dose received by the normal tissue exceeds the tolerance dose based on the read data. The computer system records the tolerance dose of the normal tissue as U0, records the radiation dose received by the point of interest during the simulated radiotherapy as U, and compares U with U0.

[0092] If U>U0, the computer system determines that the radiation dose at the point of interest exceeds the tolerance dose;

[0093] If U≤U0, the computer system determines that the radiation dose of the point of interest meets the standard.

[0094] Specifically, when the computer system determines that the radiation dose of the point of interest exceeds the tolerance dose, the computer system calculates the difference ΔU between U and U0 and selects the corresponding adjustment coefficient according to ΔU to adjust the dwell time of the dwell point corresponding to the point of interest, and sets ΔU=U-U0. The computer system is provided with a first preset point of interest radiation dose excess difference ΔU1, a second preset point of interest radiation dose excess difference ΔU2, a first dwell time reduction adjustment coefficient β1, a second dwell time reduction adjustment coefficient β2, and a third dwell time reduction adjustment coefficient β3, wherein ΔU1<ΔU2, 0.8<β1<β2<β3<1,

[0095] If ΔU≤ΔU1, the computer system uses β3 to adjust the dwell time to a corresponding value;

[0096] If ΔU1<ΔU≤ΔU2, the computer system uses β2 to adjust the dwell time to a corresponding value;

[0097] If ΔU2<ΔU, the computer system uses β1 to adjust the dwell time to a corresponding value.

[0098] Specifically, since the radiation dose received by the point of interest is a superimposed radiation dose, the dwelling point where the radiation source that affects the radiation dose of the point of interest is located is called the dwelling point corresponding to the point of interest. When the computer system determines that the radiation dose of the point of interest exceeds the tolerance dose and adjusts the dwell time of the dwelling point corresponding to the point of interest, the method for obtaining the dwelling point corresponding to the point of interest is as follows:

[0099] A three-dimensional dose contribution diagram of the point of interest is obtained to determine the dwell points that affect the point of interest and the dose contribution ratio of each dwell point. The computer system adjusts the dwell time of the corresponding dwell point according to the dose contribution ratio. The computer system records the contribution ratio of each corresponding dwell point as Bi, where i is a positive integer greater than 0, and the dwell time before adjustment is recorded as T0.

[0100] When the computer system uses βm to adjust the dwell time of the dwell point corresponding to the point of interest to the corresponding value, setting m=1, 2, 3, the computer system records the adjusted dwell time as T', and setting T'=T0×βm×Bi.

[0101] The present invention uses a thermoluminescent dose detector 1 to measure the radiation dose. The thermoluminescent dose detector 1 can be annealed and can be measured repeatedly, which reduces the cost of use and has higher feasibility and economy. The thermoluminescent dose detector 1 has a good linear relationship between the radiation dose and the reading at 0-1000cGy and good repeatability. The effective atomic number of human soft tissue is 7.4. The phosphor of the micro-thermoluminescent detector TLD is LiF containing activator impurities such as Mg, Cu, etc. Its effective atomic number is 8.2, which is close to soft tissue and suitable for after-installation plan verification. The size of the thermoluminescent dose detector 1 itself can be 3mm long and 0.8mm thick, which is suitable for rapid drop dose measurement. By encoding the thermoluminescent dose detector 1 and distributing it around the 3D model 2 according to a certain spatial law, a higher spatial resolution can be obtained, and a higher measurement accuracy can be obtained.

[0102] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for verifying afterloading brachytherapy plan, characterized in that: include: Step S1, performing a positioning scan on the lesion, displaying the exact location and size of the tumor through three-dimensional images to create a 3D model and printing the model using 3D printing technology. If the tumor invades other tissues, the head of the reserved applicator channel is not sealed when printing the 3D model, so that the applicator can pass through the 3D model to be inserted into the invaded tissue; Step S2, using a spatial coordinate positioning method to determine the spatial coordinates of each point on the surface of the 3D model, and at the same time calibrating points of interest and obtaining the spatial coordinates of the points of interest, wherein the points of interest are used to simulate normal tissues around the tumor; Step S3, arranging the thermoluminescent dose detectors according to the coordinates and distributing them according to a spatial regularity to be fixed around the 3D model and on the calibrated points of interest; Step S4, performing simulated radiotherapy in the 3D model according to the radiotherapy plan pre-formulated by the computer system, reading the radiation dose received by the thermoluminescent dose detector after completing the simulated radiotherapy, and comparing the read data with the preset data in the radiotherapy plan to determine whether it is necessary to adjust the dwell time corresponding to each dwell point in the radiotherapy plan; Step S5, after completing the adjustment of the dwell time corresponding to each dwell point, re-performing the simulated radiotherapy, after completing the simulated radiotherapy, drawing a three-dimensional dose model based on the 3D model according to the radiation dose received by the thermoluminescent dose detector, and determining whether it is necessary to adjust the number of dwell points in the radiotherapy plan according to the three-dimensional dose model; Step S6, after completing the adjustment of the number of dwell points, re-performing the simulated radiotherapy, after completing the simulated radiotherapy, reading the data of the thermoluminescent dose detector of the point of interest and determining whether the radiation dose received by the normal tissue exceeds the tolerance dose according to the read data, the computer system acquires a three-dimensional dose contribution diagram of the point of interest when the radiation dose of the point of interest exceeds the tolerance dose to determine the dwell points that affect the point of interest and the dose contribution ratio of each dwell point, and adjusts the dwell time of the corresponding dwell point according to the dose contribution ratio; In step S4, when simulating radiotherapy according to the radiotherapy plan pre-formulated by the computer system, the simulated radiotherapy is performed according to the position of the dwell point in the radiotherapy plan and the dwell time of each dwell point. After the simulated radiotherapy is completed, the radiation dose received by each thermoluminescent dose detector is read and the read data is compared with the preset data in the radiotherapy plan to determine whether the dwell time corresponding to each dwell point in the radiotherapy plan needs to be adjusted; For a single dwelling point, the dwelling point is taken as the origin, and an area extending in both directions along the axial direction of the applicator by a preset distance is taken as a dose determination area. The thermoluminescent dose detector of the dose determination area corresponding to the single dwelling point is read, and the average dose of each point in the space within the area is calculated as the actual received dose in the simulated radiotherapy. The computer system is provided with a standard dose difference ΔDb, and the preset dose of the dwelling point is recorded as D0, and the actual received dose is recorded as D. The computer system calculates the difference ΔD between D and D0 and compares ΔD with ΔDb, and sets ΔD=|D0-D|. If ΔD≤ΔDb, the computer system determines that the radiation dose at the dwell point meets the standard; If ΔD>ΔDb, the computer system determines that the radiation dose at the dwell point does not meet the standard; When the computer system determines that the radiation dose of the dwell point does not meet the standard, the dwell time of the dwell point is adjusted to the corresponding value according to ΔD. The computer system is provided with a preset dwell time t0 of the dwell point, a first preset radiation dose difference ΔD1, a second preset radiation dose difference ΔD2, a first dwell time adjustment coefficient α1, a second dwell time adjustment coefficient α2 and a third dwell time adjustment coefficient α3, wherein ΔD1<ΔD2, 1.3<α1<α2<α3<1.5, If ΔD≤ΔD1, the computer system uses α1 to adjust the dwell time of the dwell point to a corresponding value; If ΔD1<ΔD≤ΔD2, the computer system uses α2 to adjust the dwell time of the dwell point to a corresponding value; If ΔD2<ΔD, the computer system uses α3 to adjust the dwell time of the dwell point to a corresponding value; When the computer system uses αn to adjust the dwell time of the dwell point to a corresponding value, n=1, 2, 3 is set, and the computer system records the adjusted dwell time of the dwell point as t1. If D<D0, then set t1=t0×αn; If D>D0, then set t1=t0×(2-αn); In step S5, after the computer system completes the adjustment of the dwell time corresponding to the dwell point, the simulated radiotherapy is performed again, and after the simulated radiotherapy is completed, a three-dimensional dose model based on the 3D model is drawn according to the radiation dose received by the thermoluminescent dose detector. The computer system compares the three-dimensional dose model in the pre-formulated radiotherapy plan with the three-dimensional dose model obtained by simulating radiotherapy, marks out the area where the radiation dose is different, and locates the marked area according to the spatial coordinates to calculate the area of ​​the area where the radiation dose is different. The computer system determines the number of additional dwelling points according to the area. The computer system is provided with a standard area S0, and the area of ​​the area where the radiation dose is different is recorded as S. The computer system compares S with S0. If S>S0, the computer system calculates the difference ΔS between S and S0 and determines the number of dwell points that need to be increased according to ΔS, setting ΔS=S-S0; If S≤S0, the computer system determines that a dwell point needs to be added, and the area where the radiation dose difference exists is used as the dose determination area and the position of the dwell point is determined by dividing the dose determination area; When the area S>S0 of the region where the radiation dose calculated by the computer system is different, the computer system calculates the difference ΔS between S and S0 and determines the number of dwell points that need to be increased according to ΔS. The computer system is provided with a standard area difference ΔSb. The computer system compares ΔS with ΔSb. If ΔS≤ΔSb, the computer system determines that two more dwelling points are needed, and the area where the radiation dose difference exists is used as the dose determination area, and the positions of the dwelling points are determined by dividing the dose determination area; If ΔSb<ΔS≤2ΔSb, the computer system determines that three more dwelling points are needed, and the area where the radiation dose is different is used as the dose determination area, and the positions of the dwelling points are determined by dividing the dose determination area; In step S6, the computer system re-performs simulated radiotherapy after completing the adjustment of the number of dwell points, reads data from the thermoluminescent dose detector of the point of interest after completing the simulated radiotherapy, and determines whether the radiation dose received by the normal tissue exceeds the tolerance dose based on the read data. The computer system records the tolerance dose of the normal tissue as U0, records the radiation dose received by the point of interest during the simulated radiotherapy as U, and compares U with U0. If U>U0, the computer system determines that the radiation dose at the point of interest exceeds the tolerance dose; If U≤U0, the computer system determines that the radiation dose of the point of interest meets the standard; When the computer system determines that the radiation dose of the point of interest exceeds the tolerance dose, the computer system calculates the difference ΔU between U and U0 and selects the corresponding adjustment coefficient according to ΔU to adjust the dwell time of the dwell point corresponding to the point of interest, and sets ΔU=U-U0. The computer system is provided with a first preset point of interest radiation dose excess difference ΔU1, a second preset point of interest radiation dose excess difference ΔU2, a first dwell time reduction adjustment coefficient β1, a second dwell time reduction adjustment coefficient β2, and a third dwell time reduction adjustment coefficient β3, wherein ΔU1<ΔU2, 0.8<β1<β2<β3<1, If ΔU≤ΔU1, the computer system uses β3 to adjust the dwell time to a corresponding value; If ΔU1<ΔU≤ΔU2, the computer system uses β2 to adjust the dwell time to a corresponding value; If ΔU2<ΔU, the computer system uses β1 to adjust the dwell time to a corresponding value; The method for obtaining the dwelling point corresponding to the point of interest is as follows: A three-dimensional dose contribution diagram of the point of interest is obtained to determine the dwell points that affect the point of interest and the dose contribution ratio of each dwell point. The computer system adjusts the dwell time of the corresponding dwell point according to the dose contribution ratio. The computer system records the contribution ratio of each corresponding dwell point as Bi, where i is a positive integer greater than 0, and the dwell time before adjustment is recorded as T0. When the computer system uses βm to adjust the dwell time of the dwell point corresponding to the point of interest to the corresponding value, setting m=1, 2, 3, the computer system records the adjusted dwell time as T', and setting T'=T0×βm×Bi.

2. The afterloading brachytherapy plan verification method according to claim 1, characterized in that: In step S2, the specific method of the spatial coordinate positioning method is: taking the geometric center of the front end of the 3D model as the coordinate origin, the above and below the coordinate origin are the positive and negative directions of the X-axis, the front and back of the coordinate origin are the positive and negative directions of the Z-axis, and the right and left of the coordinate origin are the positive and negative directions of the Y-axis.

3. The afterloading brachytherapy plan verification method according to claim 1, characterized in that: In the step S3, the thermoluminescent dose detectors are arranged and coded according to coordinates and then regularly distributed and fixed in space. When fixed, at least one layer of thermoluminescent dose detectors is fixed to obtain a higher spatial resolution.

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