CN115068842A - Afterloading brachytherapy plan verification method - Google Patents
Afterloading brachytherapy plan verification method Download PDFInfo
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- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1001—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy
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- A61N5/1071—Monitoring, verifying, controlling systems and methods for verifying the dose delivered by the treatment plan
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- A61N5/1001—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy
- A61N5/1007—Arrangements or means for the introduction of sources into the body
- A61N2005/1008—Apparatus for temporary insertion of sources, e.g. afterloaders
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- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1048—Monitoring, verifying, controlling systems and methods
- A61N5/1075—Monitoring, verifying, controlling systems and methods for testing, calibrating, or quality assurance of the radiation treatment apparatus
- A61N2005/1076—Monitoring, verifying, controlling systems and methods for testing, calibrating, or quality assurance of the radiation treatment apparatus using a dummy object placed in the radiation field, e.g. phantom
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Abstract
The invention relates to the technical field of intracavitary radiotherapy, in particular to a verification method of a rear-loading brachytherapy plan, which comprises the steps of performing positioning scanning on a focus, creating a 3D model, printing a model by a 3D technology, positioning in a coordinate mode, marking a target area and an interested point, fixing a pyroelectric sheet, performing simulated radiotherapy, completing the radiotherapy plan according to a preset dwell point and dwell time, reading the radiation dose of the target area and comparing the preset dose, and judging whether parameters in the radiotherapy plan need to be adjusted.
Description
Technical Field
The invention relates to the technical field of intracavity radiation therapy, in particular to a back-loading brachytherapy plan verification method.
Background
The back-loading machine, namely the brachytherapy machine, is a new generation of tumor treatment equipment and can carry out back-loading radiotherapy. The post-loading radiotherapy is that a treatment container without a radioactive source is placed at a treatment part, the radioactive source is sent into the container by a computer remote control stepping motor to carry out radiotherapy, the radioactive source can be accurately and safely delivered to the part of a patient needing treatment by a source applicator to carry out radiotherapy, the dosage is preset by a computer remote control stepping sealed micro source according to a reference point, the residence time of the residence point is calculated by a treatment planning system to obtain optimized dose distribution, so that sufficient and accurate treatment dosage is given to a tumor area, the control rate of the tumor is improved, the radiation complications of normal tissues are reduced, and the radiation dosage of a post-loading therapy machine needs to be accurately controlled, so that the radiation treatment effect on the tumor can be achieved on the premise of reducing complications.
Chinese patent publication No.: CN215084351U discloses a device for space radiation dose verification in afterloading brachytherapy, which comprises a main body, a cover body and a radiation self-developing film, wherein the main body is detachably connected to the cover body, the cover body is provided with a plurality of through holes with different diameters, the bottom of the main body is provided with a plurality of fixing holes corresponding to the through holes, the bottom of the main body and the cover body are oppositely provided with annular grooves with the same diameter, the radiation self-developing film is rolled into a main body shape, and two ends of the radiation self-developing film are respectively arranged in the annular grooves on the main body and the cover body, so as to be used for radiation dose verification in afterloading radiotherapy, and the space accumulated radiation dose of a radioactive source under different paths can be measured, so as to ensure accurate control of radiation dose in clinical treatment. However, in the prior art, the position corresponding to the focus can not be simulated, the space resolution is insufficient, the cost is high, and the invasion condition can not be measured. However, through the radiation detection sensor radiation dose that the radiation source in the detection drum sent and show and the record through dose analysis display instrument, this kind of reading mode error is great, and the radiation self-development film is disposable consumptive material, and use cost is high, and this utility model discloses a scheme can't solve the spatial resolution problem moreover.
The afterloading brachytherapy has the characteristics of high local dose and rapid drop of peripheral dose, can well protect peripheral normal tissues, greatly improves the target area dose, and is an important means in cancer treatment, particularly cervical cancer treatment. Today, after 3D printing technology is gradually popularized, radiation therapy is increasingly precise, and a method for plan verification is urgently needed to ensure the accuracy and curative effect of dose. But also because of its rapid dose drop characteristics, its plan verification device requires high spatial resolution. The well-type ionization chamber can measure the maximum dose point dose at a certain distance from the central axis to calculate the source activity, but can not measure the doses of other points of interest; colloidal dosimeters have high spatial resolution, and the possibility of post-loading planning verification exists. However, the reading and comparison of the colloid dosimeter data are complex and difficult to realize. And the colloid dosimeter is a disposable measuring tool, so that the cost is high, and the popularization is not facilitated.
Disclosure of Invention
Therefore, the invention provides a verification method for a post-loading brachytherapy plan, which is used for overcoming the problems that in the prior art, the post-loading verification space resolution is insufficient, accurate positioning cannot be realized, the dose of each interest point cannot be accurately measured, the post-loading plan verification accuracy is poor, the cost is high, and popularization is not facilitated.
To achieve the above object, the present invention provides an afterloading brachytherapy plan verification method,
step S1, the focus is positioned and scanned, the exact position and size of the tumor are displayed through the three-dimensional image to create a 3D model, the model is printed by using a 3D printing technology, if the tumor invades other tissues, the head of a reserved channel of the applicator is not sealed when the 3D model is printed, so that the applicator can penetrate through the 3D model to be inserted into the invading tissues;
step S2, determining the space coordinates of each point on the surface of the 3D model by using a space coordinate positioning method, simultaneously calibrating an interest point and acquiring the space coordinates of the interest point, wherein the interest point is used for simulating normal tissues around the tumor;
step S3, carrying out coding arrangement on the thermoluminescent dose detectors according to coordinates and fixing the thermoluminescent dose detectors around the 3D model and on the calibrated interest points in a spatial regular distribution manner;
step S4, performing simulated radiotherapy in the 3D model according to a radiotherapy plan preset by a computer system, reading the radiation dose received by the thermoluminescent dose detector after completing the simulated radiotherapy, and comparing the read data with preset data in the radiotherapy plan to judge whether the residence time corresponding to each residence point in the radiotherapy plan needs to be adjusted or not;
step S5, after the adjustment of the residence time corresponding to each residence point is completed, the simulated radiotherapy is carried out again, 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, and whether the number of the residence points in the radiotherapy plan needs to be adjusted or not is judged according to the three-dimensional dose model;
and step S6, performing simulated radiation therapy again after the adjustment of the number of the stagnation points is completed, reading data of a thermoluminescent dose detector of the point of interest after the simulated radiation therapy is completed, judging whether the radiation dose received by normal tissues exceeds a tolerance dose according to the read data, acquiring a three-dimensional dose contribution diagram of the point of interest when the radiation dose of the point of interest exceeds the tolerance dose so as to judge the stagnation points which have influences on the point of interest and the dose contribution proportion of each stagnation point, and adjusting the residence time of the corresponding stagnation point according to the dose contribution proportion.
Further, in the step S2, the specific method of the spatial coordinate positioning method is: and taking the geometric center of the front end of the 3D model as a coordinate origin, wherein the upper part and the lower part of the coordinate origin are positive and negative directions of an X axis, the front part and the rear part of the coordinate origin are positive and negative directions of a Z axis, and the right part and the left part of the coordinate origin are positive and negative directions of a Y axis.
Further, in step S3, the pyroelectric dose detectors are arranged according to coordinates and then regularly distributed and fixed in space, and at least one layer of pyroelectric dose detectors is fixed during fixing, so as to obtain a higher spatial resolution.
Further, in step S4, when performing simulated radiation therapy according to the radiation therapy plan pre-established by the computer system, performing simulated radiation therapy according to the positions of the residence points and the residence times of the residence points in the radiation therapy plan, after the simulated radiation therapy is completed, reading the radiation dose received by each thermoluminescent dose detector and comparing the read data with the preset data in the radiation therapy plan to determine whether the residence time corresponding to each residence point in the radiation therapy plan needs to be adjusted; regarding a single dwell point, the dwell point is taken as an original point, a region which extends a preset distance in the axial direction of the applicator in a bidirectional mode is taken as a dose judgment region, a thermoluminescent dose detector of the dose judgment region corresponding to the single dwell point is read, the average dose of each point in the space in the region is calculated to be taken as the actual received dose in the simulated radiation therapy, the computer system is provided with a standard dose difference value delta Db, the preset dose of the dwell point is recorded as D0, the actually received dose is recorded as D, the computer system calculates the difference value delta D between D and D0 and compares the delta D with the delta Db, and the delta D is set as | D0-D |,
if the delta D is less than or equal to the delta Db, the computer system judges that the radiation dose of the dwell point meets the standard;
if Δ D > Δ Db, the computer system determines that the dwell point radiation dose does not meet the criteria.
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 a corresponding value according to Δ D, and the computer system is provided with a preset dwell time t0, a first preset radiation dose difference Δ D1, a second preset radiation dose difference Δ D2, a first dwell time adjustment coefficient α 1, a second dwell time adjustment coefficient α 2, and a third dwell time adjustment coefficient α 3 of the dwell point, wherein Δ D1 < Δ D2, 1.3 < α 1 < α 2 < α 3 < 1.5,
if Δ D is less than or equal to Δ D1, the computer system adjusts the residence time of the residence point to a corresponding value using α 1;
if Δ D1 < Δ D ≦ Δ D2, the computer system adjusting the residence time of the residence point to a corresponding value using α 2;
if Δ D2 < Δ D, the computer system adjusts the residence time of the residence point to a corresponding value using α 3;
when the computer system uses alphan to adjust the residence time of the residence point to the corresponding value, setting n to be 1, 2, 3, recording the adjusted residence time of the residence point as t1,
if D < D0, set t1 ═ t0 × α n;
if D > D0, t1 is set to t0 × (2- α n).
Further, in step S5, after the computer system completes the adjustment of the residence time corresponding to the residence point, the simulated radiation therapy is performed again, after the simulated radiation therapy is completed, the 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 a three-dimensional dose model in a preset radiotherapy plan with a three-dimensional dose model obtained by simulating radiotherapy, calibrates regions with different radiation doses, positions the calibrated regions according to space coordinates to calculate the regions with different radiation doses, and determines and increases the number of the stay points according to the regions; the computer system is provided with a standard area S0, the area of the region with the difference of the radiation dose is marked as S, the computer system compares the S with the S0,
if S > S0, the computer calculates the difference value Delta S between S and S0, determines the number of the staying points needing to be increased according to Delta S, and sets Delta S to be S-S0;
and if S is less than or equal to S0, the computer system judges that a staying point needs to be added, takes the region with the difference of the radiation dose as a dose judgment region and determines the position of the staying point by dividing the dose judgment region.
Further, when the area S of the region with the difference of the radiation dose calculated by the computer system is more than S0, the computer system calculates the difference Delta S between S and S0 and determines that the number of the staying points needs to be increased according to the Delta S, the computer system is provided with a standard area difference Delta Sb, the computer system compares the Delta S with the Delta Sb,
if the delta S is less than or equal to the delta Sb, the computer system judges that two staying points need to be added, takes the area with the difference of radiation doses as a dose judging area and determines the positions of the staying points in a mode of dividing the dose judging area;
if the delta Sb is larger than the delta S and smaller than or equal to 2 delta Sb, the computer system judges that three staying points need to be added, the region with the difference of the radiation dose is used as a dose judging region, and the positions of the staying points are determined in a mode of dividing the dose judging region.
Further, in the step S6, the computer system performs simulated radiation therapy again after adjusting the number of the stagnation points, performs data reading on the thermoluminescent dose detector of the point of interest after completing the simulated radiation therapy and determines whether the radiation dose received by the normal tissue exceeds the tolerance dose according to 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 radiation therapy as U and compares U with U0,
if U > U0, the computer system determining that the point of interest radiation dose exceeds a tolerated dose;
if U is less than or equal to U0, the computer system determines that the radiation dose at the point of interest meets the criteria.
Further, when the computer system determines that the radiation dose at the point of interest exceeds the tolerance dose, the computer system calculates a difference Δ U between U and U0 and selects a corresponding adjustment coefficient according to Δ U to adjust the residence time of the residence point corresponding to the point of interest, and sets Δ U to be U-U0, the computer system is provided with a first preset point of interest radiation dose overdose difference Δ U1, a second preset point of interest radiation dose overdose difference Δ U2, a first residence time reduction adjustment coefficient β 1, a second residence time reduction adjustment coefficient β 2, and a third residence time reduction adjustment coefficient β 3, wherein Δ U1 < Δ U2, 0.8 < β 1 < β 2 < β 3 < 1,
if Δ U is less than or equal to Δ U1, the computer system adjusts the residence time to a corresponding value using β 3;
if Δ U1 < Δ U ≦ Δ U2, the computer system adjusts the residence time to a corresponding value using β 2;
if Δ U2 < Δ U, the computer system adjusts the residence time to a corresponding value using β 1.
Further, the method for acquiring the residence point corresponding to the interest point is as follows:
acquiring a three-dimensional dose contribution graph of an interest point to judge dwell points which have influences on the interest point and dose contribution proportion of each dwell point, adjusting the dwell time of the corresponding dwell points according to the dose contribution proportion by the computer system, recording the contribution proportion of each corresponding dwell point as Bi by the computer system, wherein i is a positive integer larger than 0, recording the dwell time before adjustment as T0,
when the computer system adjusts the residence time of the residence point corresponding to the interest point to a corresponding value by using β m, setting m to 1, 2, 3, and setting T' to T0 × β m × Bi.
Compared with the prior art, the method has the advantages that the model is printed through the 3D printing technology to simulate the treatment target area, on one hand, the method can be designed according to needs of patients under different conditions, on the other hand, real plan verification can be directly completed during plan verification, and the accuracy of the method for verifying the afterloading brachytherapy plan is improved.
Further, when the tumor invades other tissues, the head of the reserved channel of the applicator is not sealed when the 3D model is printed, so that the applicator can be inserted into the invaded tissues, a special treatment process can be simulated really, and the accuracy of the method for verifying the afterloading brachytherapy plan is further improved.
Furthermore, the spatial coordinates of the interest point are obtained through a spatial coordinate positioning method to achieve accurate positioning, the method is simple and easy to operate, even if the interest point is a point position outside the model, radiation dose measurement can be performed through the spatial coordinate obtaining positioning, the radiation dose measurement of the interest point outside the model is achieved, and the accuracy of verification of the afterloading brachytherapy plan and the practicability of the method are improved.
Furthermore, the invention adopts the thermoluminescent dose detector to measure the radiation dose, and the thermoluminescent dose detector can be annealed and can be repeatedly measured, thereby reducing the use cost and having higher feasibility and economy. The thermoluminescent dose detector has good linear relation between the radiation dose of 0-1000cGy and the reading, and good repeatability. The effective atomic number of the human soft tissue is 7.4, the phosphor of the micro thermoluminescent detector TLD is LiF impurity containing activator, such as Mg, Cu, etc., the effective atomic number of the phosphor is 8.2, the phosphor is close to the soft tissue, and the phosphor is suitable for post-loading plan verification. The size of the thermoluminescent dose detector can be 3mm long and 0.8mm thick, and the thermoluminescent dose detector is suitable for dose measurement of quick falling. The pyroelectric dose detector is coded and distributed around the 3D model according to a certain spatial rule, so that higher spatial resolution can be obtained, and higher measurement accuracy can be obtained.
Furthermore, after the thermoluminescent dose detector is fixed, simulated radiotherapy is carried out in the 3D model according to a radiotherapy plan preset by the computer system, the radiation dose received by the thermoluminescent dose detector is read after the simulated radiotherapy is finished, and the read data is compared with preset data in the radiotherapy plan to judge whether the residence time corresponding to each residence point in the radiotherapy plan needs to be adjusted or not, so that the accuracy of verification of the afterloading brachytherapy plan by the method and the practicability of the method are further improved.
Further, the method is carried out. According to the method, the simulated radiotherapy is performed again after the adjustment of the residence time corresponding to each residence point is completed, the three-dimensional dose model based on the 3D model is drawn according to the radiation dose received by the thermoluminescent dose detector after the simulated radiotherapy is completed, and whether the number of the residence points in the radiotherapy plan needs to be adjusted or not is judged according to the three-dimensional dose model, so that the accuracy of the verification of the afterloading brachytherapy plan and the practicability of the method are further improved.
Furthermore, the simulated radiotherapy is carried out again after the adjustment of the number of the stagnation points is finished, data reading is carried out on the thermoluminescent dose detector of the interest point after the simulated radiotherapy is finished, whether the radiation dose received by normal tissues exceeds the tolerance dose is judged according to the read data, the computer system obtains the three-dimensional dose contribution diagram of the interest point when the radiation dose of the interest point exceeds the tolerance dose so as to judge the stagnation points which have influences on the interest point and the dose contribution proportion of each stagnation point, and the residence time of the corresponding stagnation point is adjusted according to the dose contribution proportion, so that the accuracy of the method for verification of the after-loading brachytherapy plan and the practicability of the method are further improved.
Drawings
FIG. 1 is a perspective view of a 3D model and a pyroelectric dose detector position of a back-loading brachytherapy plan validation method of an embodiment of the present invention;
FIG. 2 is a flowchart illustrating steps of a method for afterloading a brachytherapy plan validation process in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram of a spatial coordinate positioning method according to an embodiment of the present invention;
in the figure, 1, a thermoluminescent dose detector; 2. a 3D model; 3. an applicator channel.
Detailed Description
In order that the objects and advantages of the invention will be more clearly understood, the invention is further described below with reference to examples; it should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
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 for explaining the technical principle of the present invention, and do not limit the scope of the present invention.
It should be noted that in the description of the present invention, the terms of direction or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, which are only for convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
Furthermore, it should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Fig. 1 is a perspective view showing positions of a 3D model and a thermoluminescent dose detector of a back-loading brachytherapy plan verification method according to an embodiment of the present invention, wherein the thermoluminescent dose detectors 1 are arranged by encoding according to coordinates and fixed around the 3D model 2 in a regular distribution in space, so as to measure the radiation dose of the radioactive source in the reserved applicator channel 3 during simulated radiotherapy.
Referring to FIG. 2, a flowchart illustrating steps of a method for validating a brachytherapy plan in accordance with an embodiment of the present invention is shown, including:
step S1, the focus is positioned and scanned, the exact position and size of the tumor are displayed through a three-dimensional image to create a 3D model 2, the 3D printing technology is used for printing the model, if the tumor invades other tissues, the head of a reserved applicator channel 3 is not sealed when the 3D model 2 is printed, so that the applicator can pass through the 3D model 2 to externally insert the invading tissues in the past;
preferably, the focus is scanned locally by CT.
In the embodiment, the treatment target area is simulated by printing the model through the 3D printing technology, on one hand, the treatment target area can be designed according to needs of patients under different conditions, on the other hand, real plan verification can be directly completed during plan verification, and the accuracy of the method disclosed by the invention on verification of a post-loading brachytherapy plan is improved.
By unsealing the head of the reserved applicator channel 3 when the 3D model 2 is printed, the applicator can pass through the 3D model 2 through the unsealed applicator channel 3 to externally insert invasion tissues in the past, and the treatment similar to the bladder invasion condition is simulated, so that the accuracy of the method for verifying the afterloading brachytherapy plan and the practicability of the method are improved.
Step S2, determining the space coordinates of each point on the surface of the 3D model 2 by using a space coordinate positioning method, and simultaneously calibrating an interest point and acquiring the space coordinates of the interest point, wherein the interest point is used for simulating normal tissues around the tumor;
step S3, carrying out coding arrangement on the thermoluminescent dose detector 1 according to coordinates and fixing the thermoluminescent dose detector 1 around the 3D model 2 and on a calibrated interest point according to a certain spatial rule;
step S4, performing simulated radiotherapy in the 3D model 2 according to a radiotherapy plan preset by a computer system, reading the radiation dose received by the thermoluminescent dose detector 1 after completing the simulated radiotherapy, and comparing the read data with preset data in the radiotherapy plan to judge whether the residence time corresponding to each residence point in the radiotherapy plan needs to be adjusted or not;
step S5, after the adjustment of the residence time corresponding to each residence point is completed, the simulated radiotherapy is carried out again, 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, and whether the number of the residence points in the radiotherapy plan needs to be adjusted or not is judged according to the three-dimensional dose model;
and step S6, performing simulated radiation therapy again after the adjustment of the number of the stagnation points is completed, reading data of the thermoluminescent dose detector 1 of the point of interest after the simulated radiation therapy is completed, judging whether the radiation dose received by normal tissues exceeds the tolerance dose according to the read data, acquiring a three-dimensional dose contribution diagram of the point of interest when the radiation dose of the point of interest exceeds the tolerance dose so as to judge the stagnation points which have influence on the point of interest and the dose contribution proportion of each stagnation point, and adjusting the residence time of the corresponding stagnation point according to the dose contribution proportion.
Preferably, in the step S1, the density of the model is the same as the density of human tissue.
Referring to fig. 3, which is a schematic diagram of a spatial coordinate positioning method according to an embodiment of the present invention, in the step S2, the specific method of the spatial coordinate positioning method includes: and taking the geometric center of the front end of the 3D model 2 as a coordinate origin, wherein the upper part and the lower part of the coordinate origin are positive and negative directions of an X axis, the front part and the rear part of the coordinate origin are positive and negative directions of a Z axis, and the right part and the left part of the coordinate origin are positive and negative directions of a Y axis.
The method obtains the space coordinates of the interest points through the space coordinate positioning method to achieve accurate positioning, is simple and easy to operate, can measure the radiation dose even for the points outside the model through the space coordinate positioning method, achieves the radiation dose measurement of the interest points outside the model, and improves the accuracy of the method for verifying the afterloading brachytherapy plan and the practicability of the method.
In step S3, the pyroelectric dose detectors 1 are arranged by coordinates and then regularly distributed and fixed in space, and at least one layer of pyroelectric dose detectors 1 is fixed during fixing, so as to obtain a higher spatial resolution. The pyroelectric dose detector 1 can be fixed only at the interested point so as to measure the dose of the interested point, the cost is reduced, the size of the pyroelectric dose detector 1 can be 3mm long and 0.8mm thick, multiple layers of pyroelectric dose detectors can be fixed as required, the fast falling dose measurement can be met, and higher spatial resolution is obtained.
The fixing method of the thermoluminescent dose detector 1 adopted by the invention is that the material with the effective atomic number of about 7.2 is used for manufacturing the elastic strip, the clamping groove is reserved around the elastic strip for placing the thermoluminescent dose detector 1, when the fixing method is used, the elastic strip is taken to surround the 3D model 2 with the length which is matched with the circumference of the 3D model 2, the thermoluminescent dose detector 1 can be quickly fixed, and other modes can be adopted for fixing, and the fixing method of the thermoluminescent dose detector 1 is not limited.
Specifically, in step S4, when performing simulated radiotherapy according to a radiotherapy plan pre-established by a computer system, performing simulated radiotherapy according to the positions of the dwell points and the dwell times of the dwell points in the radiotherapy plan, after the simulated radiotherapy is completed, reading the radiation dose received by each thermoluminescent dose detector 1 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; regarding a single dwell point, taking the dwell point as an origin, taking a region which extends in the axial direction of the applicator in two directions for a preset distance as a dose determination region, taking the dose determination region corresponding to each dwell point as a non-coincident region, and taking the sum of the divided regions as the surface area of the 3D model 2, taking the distance of the distance extending in the axial direction of the applicator in two directions as a direct ratio to the dwell time of each dwell point, reading the thermoluminescent dose detector 1 of the dose determination region corresponding to the single dwell point, calculating the average dose of each point in the region as the actual received dose in the simulated radiotherapy, setting a standard dose difference value delta Db by the computer system, simultaneously recording the preset dose of the dwell point as D0, recording the actually received dose as D, calculating the difference value delta D between D and D0 by the computer system, comparing the delta D with the delta Db, and setting the delta D as | D0-D |,
if the delta D is less than or equal to the delta Db, the computer system judges that the radiation dose of the dwell point meets the standard;
if Δ D > Δ Db, the computer system determines that the dwell point radiation dose does not meet the criteria.
Preferably, the present embodiment sets the value of Δ Db to ± 5% D0.
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 a corresponding value according to Δ D, and the computer system is provided with a preset dwell time t0, a first preset radiation dose difference Δ D1, a second preset radiation dose difference Δ D2, a first dwell time adjustment coefficient α 1, a second dwell time adjustment coefficient α 2, and a third dwell time adjustment coefficient α 3 of the dwell point, wherein Δ D1 < Δ D2, 1.3 < α 1 < α 2 < α 3 < 1.5,
if Δ D is less than or equal to Δ D1, the computer system adjusts the residence time of the residence point to a corresponding value using α 1;
if Δ D1 < Δ D ≦ Δ D2, the computer system adjusting the residence time of the residence point to a corresponding value using α 2;
if Δ D2 < Δ D, the computer system adjusts the residence time of the residence point to a corresponding value using α 3;
when the computer system uses alphan to adjust the residence time of the residence point to the corresponding value, setting n to be 1, 2, 3, recording the adjusted residence time of the residence point as t1,
if D < D0, set t1 ═ t0 × α n;
if D > D0, t1 is set to t0 × (2- α n).
Specifically, in step S5, after the computer system completes the adjustment of the dwell time corresponding to the dwell point, the simulated radiation therapy is performed again, and after the simulated radiation therapy is completed, the three-dimensional dose model based on the 3D model 2 is drawn according to the radiation dose received by the thermoluminescent dose detector 1,
the computer system compares a three-dimensional dose model in a preset radiotherapy plan with a three-dimensional dose model obtained by simulating radiotherapy, calibrates regions with different radiation doses, positions the calibrated regions according to space coordinates to calculate the regions with different radiation doses, and determines and increases the number of the stay points according to the regions; the computer system is provided with a standard area S0, the area of the region with the difference of the radiation dose is marked as S, the computer system compares the S with the S0,
if S > S0, the computer calculates the difference value Delta S between S and S0 and determines that the number of the resident points needs to be increased according to the Delta S, and sets the Delta S to be S-S0;
and if S is less than or equal to S0, the computer system judges that a staying point needs to be added, the region with the difference of the radiation dose is used as a dose judgment region, the position of the staying point is determined in a mode of dividing the dose judgment region, and meanwhile, the computer system calculates the staying time of the staying point according to the preset radiation dose of the region with the difference of the radiation dose in the radiation treatment plan.
Specifically, when the computer calculates the area S > S0 where the difference of the radiation dose is larger, the computer calculates the difference Δ S between S and S0 and determines the number of the staying points to be increased according to Δ S, the computer system sets the standard area difference Δ Sb, the computer system compares Δ S with Δ Sb,
if the delta S is less than or equal to the delta Sb, the computer system judges that two residence points need to be added, the areas with the difference of the radiation doses are used as dose judgment areas, the positions of the residence points are determined in a mode of dividing the dose judgment areas, and meanwhile, the residence time of each residence point is calculated through computer statistics according to the preset radiation doses of the areas with the difference of the radiation doses in the radiation treatment plan;
if the delta Sb is larger than the delta S and smaller than or equal to 2 delta Sb, the computer system judges that three residence points need to be added, the areas with the difference in radiation dose are used as dose judging areas, the positions of the residence points are determined in a mode of dividing the dose judging areas, and meanwhile, the residence time of each residence point is calculated through computer statistics according to the preset radiation dose of the areas with the difference in radiation dose in the radiation treatment plan.
Specifically, in the step S6, the computer system performs the simulated radiation therapy again after the adjustment of the number of the stagnation points is completed, reads data of the thermoluminescent dose detector 1 at the point of interest after the completion of the simulated radiation therapy and determines whether the radiation dose received by the normal tissue exceeds the tolerance dose according to the read data, records the normal tissue tolerance dose as U0, records the radiation dose received by the point of interest during the simulated radiation therapy as U and compares U with U0,
if U > U0, the computer system determining that the point of interest radiation dose exceeds a tolerated dose;
if U is less than or equal to U0, the computer system determines that the radiation dose at the point of interest meets the criteria.
Specifically, when the computer system judges that the radiation dose at the point of interest exceeds the tolerance dose, the computer system calculates a difference value delta U between U and U0, selects a corresponding adjusting coefficient according to the delta U, and adjusts the residence time of the residence point corresponding to the point of interest, and sets the delta U as U-U0, wherein the computer system is provided with a first preset point of interest radiation dose oversize difference value delta U1, a second preset point of interest radiation dose oversize difference value delta U2, a first residence time reduction adjusting coefficient beta 1, a second residence time reduction adjusting coefficient beta 2 and a third residence time reduction adjusting coefficient beta 3, wherein the delta U1 is less than delta U2, the beta 1 is more than 0.8 and less than beta 2 and less than beta 3 and less than 1,
if Δ U is less than or equal to Δ U1, the computer system adjusts the residence time to a corresponding value using β 3;
if Δ U1 < Δ U ≦ Δ U2, the computer system adjusts the residence time to a corresponding value using β 2;
if Δ U2 < Δ U, the computer system adjusts the residence time to a corresponding value using β 1.
Specifically, since the radiation dose received by the point of interest is the superimposed radiation dose, the dwell point at which the radiation source having an influence on the radiation dose of the point of interest is located is referred to as the dwell point corresponding to the point of interest, and when the computer system determines that the radiation dose of the point of interest exceeds the tolerated dose and adjusts the dwell time of the dwell point corresponding to the point of interest, the dwell point corresponding to the point of interest is acquired in the following manner:
acquiring a three-dimensional dose contribution graph of an interest point to judge dwell points which have influences on the interest point and dose contribution proportion of each dwell point, adjusting the dwell time of the corresponding dwell points according to the dose contribution proportion by the computer system, recording the contribution proportion of each corresponding dwell point as Bi by the computer system, wherein i is a positive integer larger than 0, recording the dwell time before adjustment as T0,
when the computer system adjusts the residence time of the residence point corresponding to the interest point to a corresponding value by using β m, setting m to 1, 2, 3, and setting T' to T0 × β m × Bi.
The invention adopts the thermoluminescent dose detector 1 to measure the radiation dose, and the thermoluminescent dose detector 1 can be annealed and can be repeatedly measured, thereby reducing the use cost and having higher feasibility and economy. The linear relation between the radiation dose of the thermoluminescent dose detector 1 and the reading is good at 0-1000cGy, and the repeatability is good. The effective atomic number of the human soft tissue is 7.4, the phosphor of the micro thermoluminescent detector TLD is LiF impurity containing activator, such as Mg, Cu, etc., the effective atomic number of the phosphor is 8.2, the phosphor is close to the soft tissue, and the phosphor is suitable for post-loading plan verification. The size of the thermoluminescent dose detector 1 can be 3mm long and 0.8mm thick, and the thermoluminescent dose detector is suitable for dose measurement of quick falling. The thermoluminescent dose detector 1 is coded and distributed around the 3D model 2 according to a certain spatial rule, so that higher spatial resolution can be obtained, and higher measurement accuracy can be obtained.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention; various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method of afterloading brachytherapy plan validation, comprising:
step S1, the focus is positioned and scanned, the exact position and size of the tumor are displayed through the three-dimensional image to create a 3D model, the model is printed by using a 3D printing technology, if the tumor invades other tissues, the head of a reserved channel of the applicator is not sealed when the 3D model is printed, so that the applicator can penetrate through the 3D model to be inserted into the invading tissues;
step S2, determining the space coordinates of each point on the surface of the 3D model by using a space coordinate positioning method, simultaneously calibrating an interest point and acquiring the space coordinates of the interest point, wherein the interest point is used for simulating normal tissues around the tumor;
step S3, carrying out coding arrangement on the thermoluminescent dose detector according to coordinates and fixing the thermoluminescent dose detector around the 3D model and on a calibrated interest point according to spatial regular distribution;
step S4, performing simulated radiotherapy in the 3D model according to a radiotherapy plan preset by a computer system, reading the radiation dose received by the thermoluminescent dose detector after completing the simulated radiotherapy, and comparing the read data with preset data in the radiotherapy plan to judge whether the residence time corresponding to each residence point in the radiotherapy plan needs to be adjusted or not;
step S5, after the adjustment of the residence time corresponding to each residence point is completed, the simulated radiotherapy is carried out again, 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, and whether the number of the residence points in the radiotherapy plan needs to be adjusted or not is judged according to the three-dimensional dose model;
and step S6, performing simulated radiation therapy again after the adjustment of the number of the stagnation points is completed, reading data of a thermoluminescent dose detector of the point of interest after the simulated radiation therapy is completed, judging whether the radiation dose received by normal tissues exceeds a tolerance dose according to the read data, acquiring a three-dimensional dose contribution diagram of the point of interest when the radiation dose of the point of interest exceeds the tolerance dose so as to judge the stagnation points which have influences on the point of interest and the dose contribution proportion of each stagnation point, and adjusting the residence time of the corresponding stagnation point according to the dose contribution proportion.
2. The afterloading brachytherapy plan verification method of claim 1, wherein in step S2, the spatial coordinate positioning method is specifically: and taking the geometric center of the front end of the 3D model as a coordinate origin, wherein the upper part and the lower part of the coordinate origin are positive and negative directions of an X axis, the front part and the rear part of the coordinate origin are positive and negative directions of a Z axis, and the right part and the left part of the coordinate origin are positive and negative directions of a Y axis.
3. The afterloading brachytherapy plan verification method of claim 1, wherein in step S3, after the pyroelectric dose detectors are arranged by coordinates in a coding manner, the pyroelectric dose detectors are regularly distributed and fixed in space, and at least one layer of pyroelectric dose detectors is fixed during fixing, so as to obtain higher spatial resolution.
4. The afterloading brachytherapy plan verification method of claim 1, wherein in step S4, when performing simulated radiotherapy according to a radiotherapy plan pre-established by the computer system, performing simulated radiotherapy according to the positions of dwell points and dwell times of the dwell points in the radiotherapy plan, after completion of the simulated radiotherapy, reading the radiation dose received by each thermoluminescent dose detector and comparing the read data with preset data in the radiotherapy plan to determine whether adjustment of the dwell time corresponding to each dwell point in the radiotherapy plan is required; regarding a single dwell point, the dwell point is taken as an original point, a region which extends a preset distance in the axial direction of the applicator in a bidirectional mode is taken as a dose judgment region, a thermoluminescent dose detector of the dose judgment region corresponding to the single dwell point is read, the average dose of each point in the space in the region is calculated to be taken as the actual received dose in the simulated radiation therapy, the computer system is provided with a standard dose difference value delta Db, the preset dose of the dwell point is recorded as D0, the actually received dose is recorded as D, the computer system calculates the difference value delta D between D and D0 and compares the delta D with the delta Db, and the delta D is set as | D0-D |,
if the delta D is less than or equal to the delta Db, the computer system judges that the radiation dose of the residence point meets the standard;
if Δ D > Δ Db, the computer system determines that the dwell point radiation dose does not meet the criteria.
5. The afterloader brachytherapy plan verification method of claim 4, wherein the dwell time of the dwell point is adjusted to a corresponding value according to Δ D when the computer system determines that the dwell point radiation dose does not meet the criteria, the computer system being provided with a preset dwell time t0, a first preset radiation dose difference Δ D1, a second preset radiation dose difference Δ D2, a first dwell time adjustment factor α 1, a second dwell time adjustment factor α 2, and a third dwell time adjustment factor α 3 for the dwell point, wherein Δ D1 < Δ D2, 1.3 < α 1 < α 2 < α 3 < 1.5,
if Δ D is less than or equal to Δ D1, the computer system adjusts the residence time of the residence point to a corresponding value using α 1;
if Δ D1 < Δ D ≦ Δ D2, the computer system adjusting the residence time of the residence point to a corresponding value using α 2;
if Δ D2 < Δ D, the computer system adjusts the residence time of the residence point to a corresponding value using α 3;
when the computer system uses alphan to adjust the residence time of the residence point to the corresponding value, setting n to be 1, 2, 3, recording the adjusted residence time of the residence point as t1,
if D < D0, set t1 ═ t0 × α n;
if D > D0, t1 is set to t0 × (2- α n).
6. The afterloading brachytherapy plan verification method of claim 5, wherein in step S5, after the computer system completes the adjustment of the dwell time corresponding to the dwell point, the simulated radiotherapy is re-performed, a 3D model-based three-dimensional dose model is drawn according to the radiation dose received by the thermoluminescent dose detector after the simulated radiotherapy is completed,
the computer system compares a three-dimensional dose model in a preset radiotherapy plan with a three-dimensional dose model obtained by simulating radiotherapy, calibrates regions with different radiation doses, positions the calibrated regions according to space coordinates to calculate the regions with different radiation doses, and determines and increases the number of the stay points according to the regions; the computer system is provided with a standard area S0, the area of the region with the difference of the radiation dose is marked as S, the computer system compares the S with the S0,
if S > S0, the computer calculates the difference value Delta S between S and S0, determines the number of the staying points needing to be increased according to Delta S, and sets Delta S to be S-S0;
and if S is less than or equal to S0, the computer system judges that a staying point needs to be added, takes the region with the difference of the radiation dose as a dose judgment region and determines the position of the staying point by dividing the dose judgment region.
7. The afterloader brachytherapy plan verification method of claim 6, wherein when the computer system calculates a difference Δ S between S and S0 and determines from Δ S that the number of dwelling points needs to be increased when the computer system calculates a difference area S > S0 in the radiation doses calculated by the computer system, the computer system sets a standard area difference Δ Sb, the computer system compares Δ S with Δ Sb,
if the delta S is less than or equal to the delta Sb, the computer system judges that two staying points need to be added, takes the area with the difference of radiation doses as a dose judging area and determines the positions of the staying points in a mode of dividing the dose judging area;
if the delta Sb is larger than the delta S and smaller than or equal to 2 delta Sb, the computer system judges that three staying points need to be added, the region with the difference of the radiation dose is used as a dose judging region, and the positions of the staying points are determined in a mode of dividing the dose judging region.
8. The afterloading brachytherapy plan verification method of claim 7, wherein in the step S6, the computer system performs simulated radiotherapy again after completing the adjustment of the number of the stagnation points, performs data reading on a thermoluminescent dose detector of a point of interest after completing the simulated radiotherapy and determines whether the radiation dose received by the normal tissue exceeds a tolerated dose according to the read data, the computer system records the normal tissue tolerated dose 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 determining that the radiation dose at the point of interest exceeds the tolerance dose;
if U is less than or equal to U0, the computer system determines that the radiation dose at the point of interest meets the criteria.
9. The aftermarket brachytherapy plan verification method of claim 8, wherein when the computer system determines that the point-of-interest radiation dose exceeds the tolerated dose, the computer system calculates Δ U, which is a difference between U and U0, and selects a corresponding adjustment factor according to Δ U to adjust the dwell time of the dwell point corresponding to the point-of-interest, and sets Δ U-U0, the computer system has a first preset point-of-interest radiation dose overdose difference Δ U1, a second preset point-of-interest radiation dose overdose difference Δ U2, a first dwell time reduction adjustment factor β 1, a second dwell time reduction adjustment factor β 2, and a third dwell time reduction adjustment factor β 3, wherein Δ U1 < Δ U2, 0.8 < β 1 < β 2 < β 3 < 1,
if Δ U is less than or equal to Δ U1, the computer system adjusts the residence time to a corresponding value using β 3;
if Δ U1 < Δ U ≦ Δ U2, the computer system adjusts the residence time to a corresponding value using β 2;
if Δ U2 < Δ U, the computer system adjusts the residence time to a corresponding value using β 1.
10. The afterloader brachytherapy plan verification method of claim 9, wherein the dwell points corresponding to the points of interest are obtained by:
acquiring a three-dimensional dose contribution graph of an interest point to judge dwell points which have influences on the interest point and dose contribution proportion of each dwell point, adjusting the dwell time of the corresponding dwell points according to the dose contribution proportion by the computer system, recording the contribution proportion of each corresponding dwell point as Bi by the computer system, wherein i is a positive integer larger than 0, recording the dwell time before adjustment as T0,
when the computer system adjusts the residence time of the residence point corresponding to the interest point to a corresponding value by using β m, setting m to 1, 2, 3, and setting T' to T0 × β m × Bi.
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