CN113856069B - Method for fusing high-low energy beam with dose distribution - Google Patents
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- 238000009826 distribution Methods 0.000 title claims abstract description 74
- 238000000034 method Methods 0.000 title claims abstract description 43
- 238000010894 electron beam technology Methods 0.000 claims abstract description 95
- 238000004364 calculation method Methods 0.000 claims abstract description 22
- 238000000342 Monte Carlo simulation Methods 0.000 claims abstract description 9
- 210000001519 tissue Anatomy 0.000 claims description 44
- 230000009471 action Effects 0.000 claims description 41
- 230000005855 radiation Effects 0.000 claims description 31
- 238000004088 simulation Methods 0.000 claims description 20
- 230000004927 fusion Effects 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 210000004872 soft tissue Anatomy 0.000 claims description 11
- 210000004072 lung Anatomy 0.000 claims description 8
- 210000000988 bone and bone Anatomy 0.000 claims description 7
- 238000002722 intraoperative radiotherapy Methods 0.000 claims description 7
- 230000008021 deposition Effects 0.000 claims description 6
- 238000013334 tissue model Methods 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 5
- 230000001225 therapeutic effect Effects 0.000 claims description 3
- 230000007547 defect Effects 0.000 abstract description 6
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000000875 corresponding effect Effects 0.000 description 27
- 238000001959 radiotherapy Methods 0.000 description 4
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- 206010028980 Neoplasm Diseases 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 1
- 238000002939 conjugate gradient method Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- 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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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/103—Treatment planning systems
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1048—Monitoring, verifying, controlling systems and methods
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- 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
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- 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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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1092—Details
Abstract
A method for fusing dose distribution of high-low energy beams obtains optimal combination and irradiation dose in mixed irradiation through 5 steps. The method for fusing the high-energy beam and the low-energy beam into the dose distribution has the following beneficial effects: (1) The Monte Carlo method can accurately realize the calculation of the dose characteristics of high-energy electron beams and low-energy X rays; (2) The adopted iterative calculation method enables the calculation of the high-low energy irradiation dose to be more accurate; (3) The high-low energy mixed irradiation method eliminates the inherent defects of high-energy electron beams and low-energy X rays, and enables the object to receive more uniform dose irradiation.
Description
Technical Field
The invention relates to the technical field of radiophysics, in particular to a method for fusing high-low energy beams into dose distribution.
Background
Since the nineties of the last century, various types of mobile intraoperative radiotherapy devices have been developed successively, mainly divided into high-energy electron beam accelerators and low-energy X-ray devices.
Due to its radiation characteristics, a megavoltage high-energy electron beam often has a dose build-up zone after incidence on tissue, and the dose drops rapidly after reaching the maximum dose point depth of action. Taking the percentage depth dose curve of Mobetron in the water mold body as an example, the percentage doses of 4MeV, 6MeV, 9MeV and 12MeV energy electron beams on the surface of the water mold body are respectively 78+/-1.0%, 83+/-1.0%, 87+/-1.0% and 92+/-1.0%, and the action depths at 80% doses are respectively 1.0+/-0.2 cm, 2.0+/-0.2 cm, 3.0+/-0.2 cm and 4.0+/-0.2 cm. Because of the low surface dose caused by dose build-up areas, a specially shaped compensator is often placed on the object surface to counter-act the build-up area when the object is irradiated with mobatron et al.
Kilovolt low energy X-rays do not present a dose build-up area due to their low energy, and the dose drops rapidly after incidence on tissue. Taking the percentage depth dose curve of Intrabeam in the water phantom as an example, the depth of action of 50kV energy X-rays in the water phantom at 30% dose is 1.0+ -0.2 cm. Intrabeam is used primarily for superficial object treatment due to the shallower radiation depth of the low energy X-rays.
Therefore, in order to solve the deficiencies of the prior art, it is necessary to provide a method for fusing the dose distribution of the high-low energy beam.
Disclosure of Invention
One of the objects of the present invention is to avoid the disadvantages of the prior art and to provide a method for high and low energy beam fusion dose distribution. The method for fusing the high-energy beam and the low-energy beam into the dose distribution has the advantage of uniform dose irradiation.
The above object of the present invention is achieved by the following technical measures:
a method of high and low energy beam fusion dose distribution is provided, comprising the steps of:
step one, collecting images;
selecting an electron beam and an X-ray with corresponding energy from a database according to the tissue model body type corresponding to the image in the step one and the depth of the object in the image in the step one, and respectively selecting a light limiting cylinder and an illuminator with corresponding sizes of high-energy electron beam equipment and low-energy X-ray equipment according to the size of the object in the image in the step one, wherein the database comprises the corresponding relation between the electron beam energy and the depth and the corresponding relation between the X-ray energy and the depth under different tissue model body types;
step three, according to the electron beam, the X-ray, the light limiting cylinder and the illuminator selected in the step two, using Monte Carlo software to simulate the dose distribution of the electron beam and the X-ray in the object respectively, and carrying out dose correction;
step four, setting the center point of the objectA mixing dose value c of (2);
step five, according to the corrected dose obtained in the step three and the center point of the object in the step fourIteratively calculating the final dose of the electron beam and the X-ray.
Preferably, the method for establishing the database comprises the following steps:
firstly, using Monte Carlo software to simulate the complete structure of a megavoltage high-energy electron beam radiation source and the complete structure of a kilovoltage low-energy X-ray radiation source respectively to obtain a corresponding equipment simulation structure;
then, performing radiation dose simulation calculation and characteristic analysis of the electron beams with different energies in different tissue mold bodies respectively, and establishing a corresponding relation between the action depth and the electron beam energy; and simultaneously, performing radiation dose simulation calculation and characteristic analysis of X-rays with different energies in different tissue mold bodies respectively, and establishing a corresponding relation between the action depth and the X-ray energy.
Preferably, the radiation dose simulation calculation specifically uses monte carlo software and the equipment simulation structure to simulate the process of the electron rays with different energies and the X-rays with different energies in the incident tissue mold body respectively, so as to calculate the deposition dose distribution in various tissue mold bodies.
Preferably, the characteristic analysis specifically calculates a percentage depth dose curve and an effective action depth of the corresponding electron beam and the X-ray on the central axis according to the deposition dose distribution; wherein the effective depth of action of the electron beam is 90% of the dose depth, and the effective depth of action of the X-ray is 10% of the dose depth.
The dose correction in the third step is specifically that the Monte Carlo simulation correction coefficient of the electron beam is multiplied by the dose distribution of the electron beam to obtain electron beam dose distribution B under unit dose, and the electron beam percentage depth dose curve is calculatedThe method comprises the steps of carrying out a first treatment on the surface of the Multiplying the Monte Carlo simulation correction coefficient of the X-ray by the X-ray dose distribution to obtain X-ray dose distribution +.>。
Preferably, the fifth step specifically comprises:
step 5.1, setting an initial X-ray irradiation dose valueThere is->, wherein />For X-ray dose distribution->At the center point of the object->A dose value at;
step 5.2, order；
Step 5.3, object center Point according to step fourObtaining the electron beam irradiation dose through the formula (I) according to the mixing dose value c;
the formula (I),
step 5.4 obtaining a fused dose distribution by the formulae (II) and (III)And fusing the central axis percentage depth dose curve of the dose distribution +.>；
(II),
a step (III),
wherein ,is the central axisxAndycoordinates of->For each perpendicular to the central axisx-yCoordinates of the plane;
step 5.5, judging that the central axis percentage depth dose curve P of the fusion dose distribution is inA relation of a percentage dose at a maximum dose depth dmax to L2, and a relation of a percentage dose at an intermediate dose depth dmax/2 to L1, wherein L2 and L1 are both 90% or more and less than 100%,
when the percentage dose at dmax/2 is less than L1 and the percentage dose at dmax is greater than or equal to L2, go to step 5.6,
step 5.7 is entered when the percentage dose at dmax/2 is less than L1 and the percentage dose at dmax is less than L2,
when the percentage dose at dmax/2 is greater than or equal to L1 and the percentage dose at dmax is less than L2, go to step 5.8,
step 5.9 is entered when the percentage dose at dmax/2 is equal to or greater than L1 and the percentage dose at dmax is equal to or greater than L2;
step 5.6, order，/>Returning to the step 5.3 for constants greater than 0;
step 5.7, order，/>Returning to the step 5.3 for constants greater than 0;
step 5.8, order，/>Is largeReturning to the step 5.3 at a constant of 0;
step 5.9, the current X-ray irradiation doseAnd the current electron beam irradiation dose +.>Defined as final dose, current fusion dose distribution +.>Is the final dose distribution.
In the second step, a light limiting cylinder of the high-energy equipment and an illuminator of the low-energy equipment are selected according to the maximum transverse diameter of the object in the image of the first step, and the radiation field of the selected light limiting cylinder and the radiation field of the illuminator are larger than or equal to 1.18 times of the maximum transverse diameter of the object.
Preferably, the kilovolt low-energy X-ray radiation source comprises a kilovolt X-ray therapeutic machine head, a low-energy X-ray intraoperative radiation therapy device and a cold cathode area array X-ray source, wherein the low-energy X-ray intraoperative radiation therapy device comprises Intrabeam and Xoft Axxent.
Preferably, the megavoltage high-energy electron beam radiation source comprises a conventional electron linear accelerator handpiece and a high-energy electron beam in-operation treatment equipment handpiece, wherein the high-energy electron beam in-operation treatment equipment comprises Mobetron, novac7 and Liac.
Preferably, the Monte Carlo software is EGSnrc, FLUKA, GEANT, ETRAN, ITS, MCNP or DPM.
Preferably, the image is a CT image or an ultrasound image.
Preferably, the tissue phantom is lung tissue, water tissue, soft tissue, and bone tissue.
Preferably, the different energies of the low energy X-rays are 40kV, 50kV and 60kV.
Preferably, the different energies of the high energy electron beam are 4MeV, 6MeV, 9MeV and 12MeV.
The method for fusing the dose distribution of the high-energy beam and the low-energy beam obtains the optimal combination and the irradiation dose in the mixed irradiation through 5 steps. The method for fusing the high-energy beam and the low-energy beam into the dose distribution has the following beneficial effects: (1) The Monte Carlo method can accurately realize the calculation of the dose characteristics of high-energy electron beams and low-energy X rays; (2) The adopted iterative calculation method enables the calculation of the high-low energy irradiation dose to be more accurate; (3) The high-low energy mixed irradiation method eliminates the inherent defects of high-energy electron beams and low-energy X rays, and enables the object to receive more uniform dose irradiation.
Drawings
The invention is further illustrated by the accompanying drawings, which are not to be construed as limiting the invention in any way.
Fig. 1 is a flow chart of a method of high and low energy beam fusion dose distribution.
Fig. 2 is a graph of the percent depth dose curve in lung tissue.
Fig. 3 is a graph of percent depth dose in water tissue.
Fig. 4 is a graph of the percent depth dose curve in soft tissue.
Fig. 5 is a graph of percent depth dose in bone tissue.
Fig. 6 is a graph of effective depth of action of megavoltage high energy electron beams and kilovoltage low energy X-rays of different energies in various tissues.
Fig. 7 is a schematic perspective view of a constructed reference object phantom.
FIG. 8 is a top view of a constructed reference object phantom.
FIG. 9 is a side view of a constructed reference object phantom.
Fig. 10 is a graph of the percent depth dose curve of high and low energy rays alone in an object phantom.
FIG. 11 is a graph of the percent depth dose curve of a high and low energy mixed illumination in a subject phantom.
Fig. 12 is a dose distribution of low energy X-rays alone in an object phantom.
Fig. 13 is a dose distribution of high-energy electron rays irradiated alone in the subject phantom.
Fig. 14 shows a dose distribution of the high-low energy mixed irradiation in the subject phantom.
Detailed Description
The technical scheme of the invention is further described with reference to the following examples.
Example 1.
A method of high and low energy beam fusion dose distribution, as shown in fig. 1, comprising the steps of:
step one, collecting images;
selecting an electron beam and an X-ray with corresponding energy from a database according to the tissue model body type corresponding to the image in the step one and the depth of the object in the image in the step one, and respectively selecting a light limiting cylinder and an illuminator with corresponding sizes of high-energy electron beam equipment and low-energy X-ray equipment according to the size of the object in the image in the step one, wherein the database comprises the corresponding relation between the electron beam energy and the depth and the corresponding relation between the X-ray energy and the depth under different tissue model body types;
step three, according to the electron beam, the X-ray, the light limiting cylinder and the illuminator selected in the step two, using Monte Carlo software to simulate the dose distribution of the electron beam and the X-ray in the object respectively, and carrying out dose correction;
step four, setting the center point of the objectA mixing dose value c of (2);
step five, according to the corrected dose obtained in the step three and the center point of the object in the step fourThe final dose of the electron beam and the X-ray is calculated.
The method for establishing the database comprises the following steps:
firstly, using Monte Carlo software to simulate the complete structure of a megavoltage high-energy electron beam radiation source and the complete structure of a kilovoltage low-energy X-ray radiation source respectively to obtain a corresponding equipment simulation structure;
then, performing radiation dose simulation calculation and characteristic analysis of the electron beams with different energies in different tissue mold bodies respectively, and establishing a corresponding relation between the action depth and the electron beam energy; and simultaneously, performing radiation dose simulation calculation and characteristic analysis of X-rays with different energies in different tissue mold bodies respectively, and establishing a corresponding relation between the action depth and the X-ray energy.
The radiation dose simulation calculation specifically comprises simulating the process of the electron rays with different energies and the X-rays with different energies in the incident tissue die body by utilizing Monte Carlo software and the equipment simulation structure, and calculating the deposition dose distribution in various tissue die bodies.
The characteristic analysis specifically comprises the steps of respectively calculating a percentage depth dose curve and an effective action depth of corresponding electron rays and X-rays on a central axis according to the deposition dose distribution; wherein the effective depth of action of the electron beam is 90% of the dose depth, and the effective depth of action of the X-ray is 10% of the dose depth.
The dose correction in the third step is specifically that the Monte Carlo simulation correction coefficient of the electron beam is multiplied by the dose distribution of the electron beam to obtain the dose distribution of the electron beam under unit doseAnd calculate the electron line percentage depth dose curve +.>The method comprises the steps of carrying out a first treatment on the surface of the Multiplying the Monte Carlo simulation correction coefficient of the X-ray by the X-ray dose distribution to obtain X-ray dose distribution +.>。
The invention comprises the following steps:
step 5.1, setting an initial X-ray irradiation dose valueThere is->, wherein />For objectsX-ray dose distribution at the centre point +.>；；
Step 5.2, order；
Step 5.3, object center Point according to step fourObtaining the electron beam irradiation dose through the formula (I) according to the mixing dose value c;
the formula (I),
step 5.4 obtaining a fused dose distribution by the formulae (II) and (III)And fusing the central axis percentage depth dose curve of the dose distribution +.>；
(II),
a step (III),
wherein ,is the central axisxAndycoordinates of->For each perpendicular to the central axisx-yCoordinates of the plane;
step 5.5, judging the central axis percentage depth dose curve of the fusion dose distributionAt->A relation of a percentage dose at a maximum dose depth dmax to L2, and a relation of a percentage dose at an intermediate dose depth dmax/2 to L1, wherein L2 and L1 are both 90% or more and less than 100%,
when the percentage dose at dmax/2 is less than L1 and the percentage dose at dmax is greater than or equal to L2, go to step 5.6,
step 5.7 is entered when the percentage dose at dmax/2 is less than L1 and the percentage dose at dmax is less than L2,
when the percentage dose at dmax/2 is greater than or equal to L1 and the percentage dose at dmax is less than L2, go to step 5.8,
step 5.9 is entered when the percentage dose at dmax/2 is equal to or greater than L1 and the percentage dose at dmax is equal to or greater than L2;
step 5.6, order，/>Returning to the step 5.3 for constants greater than 0;
step 5.7, order，/>Returning to the step 5.3 for constants greater than 0;
step 5.8, order，/>Returning to the step 5.3 for constants greater than 0;
step 5.9, the current X-ray irradiation doseAnd the current electron beam irradiation dose +.>Defined as final dose, current fusion dose distribution +.>Is the final dose distribution.
It should be noted that, in addition to the calculation using steps 5.1 to 5.9, the iterative optimization algorithm of the present invention may also use the gradient descent method, newton method, quasi-newton method, or conjugate gradient method in the prior art to obtain the optimal irradiation dose of the electron beam and the X-ray. Compared with the iterative optimization algorithm in the prior art, the iterative optimization method has the advantages that the iterative conditions are simpler from step 5.1 to step 5.9. In the step 5.5 of the invention, only the depth dose values at the maximum dose depth and the intermediate dose depth are considered, and multiple experiments prove that when the maximum dose depth and the intermediate dose depth are higher than 90%, the dose value from the surface of the object to the maximum dose depth is higher than 90%. The L2 and L1 of the invention can also be set according to the target uniformity requirement in the fused dose distribution.
In the second step, a light limiting cylinder of the high-energy equipment and an illuminator of the low-energy equipment are selected according to the maximum transverse diameter of the object in the image of the first step, and the radiation field of the selected light limiting cylinder and the radiation field of the illuminator are larger than or equal to 1.18 times of the maximum transverse diameter of the object.
The kilovolt low-energy X-ray radiation source comprises a kilovolt X-ray therapeutic machine head, a low-energy X-ray intraoperative radiation therapy device and a cold cathode area array X-ray source, wherein the low-energy X-ray intraoperative radiation therapy device comprises Intrabeam and Xoft Axxent.
The megavoltage high-energy electron beam radiation source comprises a conventional electron linear accelerator machine head and a high-energy electron beam in-operation treatment equipment machine head, wherein the high-energy electron beam in-operation treatment equipment comprises Mobetron, novac7 and Liac.
The Monte Carlo software of the present invention is EGSnrc, FLUKA, GEANT, ETRAN, ITS, MCNP or DPM. The image is a CT image or an ultrasound image. The tissue mold body is lung tissue, water tissue, soft tissue and bone tissue. The different energies of the low energy X-rays are 40kV, 50kV and 60kV. The different energies of the high energy electron beams were 4MeV, 6MeV, 9MeV and 12MeV.
It should be noted that, the invention establishes the corresponding relation between the action depth and the electron beam energy according to the effective action depth of the corresponding electron beam in different tissue mold bodies, and establishes the rule between the electron beam energy and the tissue mold body type and action depth.
The invention is illustrated by taking a water tissue die body as an example, the effective action depth of the 4MeV, 6MeV, 9MeV and 12MeV electron lines in water is respectively 11mm, 18mm, 28mm and 37mm, and the effective action depth (90% dose depth) of the electron lines is based on the principle that the trailing edge of an object is included, and the corresponding action depths of the 4MeV, 6MeV, 9MeV and 12MeV electron lines in the object are respectively 0-11 mm, 12-18 mm, 19-28 mm and 29-37 mm.
It should be noted that, the corresponding relation between the action depth and the X-ray energy is established according to the effective action depth of the corresponding X-ray energy in different tissue mold bodies, and the rule between the X-ray energy and the tissue mold body types and action depths is established.
The invention is illustrated by taking a water tissue die body as an example, and the effective action depths of the X-rays of 40kV, 50kV and 60kV in water are respectively 14mm, 25mm and 41mm, and the corresponding action depths of the X-rays of 40kV, 50kV and 60kV in an object are respectively 0-14 mm, 15-25 mm and 26-41 mm.
The working principle of the invention is that the two rays are combined with different irradiation doses by utilizing the dose characteristics of different action depths of megavoltage high-energy electron rays and kilovolt low-energy X-rays to obtain uniform dose distribution at a plurality of action depths, thereby eliminating the defects that the high-energy electron rays need to use compensators to offset a built-up area and the irradiation depth of the low-energy X-rays is shallow.
The method for fusing the high-energy beam and the low-energy beam into the dose distribution has the following beneficial effects: (1) The Monte Carlo method can accurately realize the calculation of the dose characteristics of high-energy electron beams and low-energy X rays; (2) The adopted iterative calculation method enables the calculation of the high-low energy irradiation dose to be more accurate; (3) The high-low energy mixed irradiation method eliminates the inherent defects of high-energy electron beams and low-energy X rays, and enables the object to receive more uniform dose irradiation.
Example 2.
In the method for fusing the dose distribution of high-energy and low-energy beams, for example, mobetaron which is an intraoperative radiotherapy device for generating high-energy electron beams and Intrabeam which is an intraoperative radiotherapy device for generating low-energy X rays, monte Carlo software is used for respectively simulating the dose characteristics of the two devices under different energies, wherein the most commonly used 4MeV, 6MeV, 9MeV and 12MeV electron beams are simulated for Mobetaron, and 40kV and 50kV X rays are simulated for Intrabeam. The invention establishes a reference object model to verify the effectiveness of the high-low energy beam fusion method.
The method for establishing the database comprises the following steps: firstly, using Monte Carlo software to simulate the complete structure of Mobetron and the complete structure of Intrabeam respectively to obtain a corresponding equipment simulation structure.
The Monte Carlo software adopted in the embodiment takes EGSnrc as an example, uses a software package BEAMnrc in EGSnrc to simulate the basic structure of the intraoperative radiotherapy equipment, and uses an internal software package DOSXYZnrc to simulate the dosage calculation of the equipment in various mold bodies. Firstly, simulating the basic structure of a Mobelron machine head, and sequentially simulating the structures of a target, a primary scattering foil, a secondary scattering foil, a primary collimator, an ionization chamber, a secondary collimator, a light limiting cylinder and the like according to the composition of the Mobelron machine head mechanism; and secondly, simulating the basic structure of an Intrabeam treatment head, and sequentially simulating the structures such as a gold target, a beryllium window and the like. Both simulations used 10×10 cm 2 The field can be modified according to the size of the light limiting cylinder and the illuminator. And then compiling the simulated Mobelron and Intrabeam structures into dynamic libraries respectively, and directly calling dynamic library files to calculate when DOSXYZnrc is used for dose simulation, so that a phase space file is not required to be generated, and the time and the hard disk space are saved.
Then, performing radiation dose simulation calculation and characteristic analysis of the electron beams with different energies on different tissue mold bodies respectively, and establishing a corresponding relation between the action depth and the electron beam energy; simultaneously performing X-rays with different energiesAnd (3) carrying out radiation dose simulation calculation and characteristic analysis on the wires in different tissue mold bodies, and establishing a corresponding relation between the action depth and the X-rays. This example constructed 20×20×10× 10 cm using DOSXYZnrc 3 Uniform mode body of size, voxel size of 0.2x0.2x0.1 cm 3 The mold body materials are lung tissue, water tissue, soft tissue and bone tissue respectively. And secondly, respectively calling dynamic library files simulated by the Mobelron and the Intrabeam, and respectively calculating simulated doses in four die bodies when two types of equipment have different energies. Then, a dose file output by DOSXYZnrc is read by using functions such as 'fopen' in MATLAB, a three-dimensional dose matrix is calculated, a percentage depth dose curve on a central axis is extracted, and depth dose characteristics of two intraoperative radiotherapy devices in different tissue mold bodies are analyzed.
FIGS. 2 to 5 are graphs of the percentage depth dose of high energy electron beams and low energy X-rays of different energies in a lung tissue phantom, a water tissue phantom, a soft tissue phantom and a bone tissue phantom, respectively, wherein the irradiation depth of the two low energy X-rays is shallow, the dose is rapidly reduced after the four models are incident, and a dose build-up area is not present; the 9MeV and 12MeV electron beams in the four high-energy electron beams have no dose built-in area in the lung tissue mould body, and have dose built-in areas in other tissue mould bodies, and the dose drops rapidly after the maximum dose is reached.
Fig. 6 is a graph showing the effective depth of action of high energy electron beams and low energy X-rays of different energies in four tissue phantom. The high-energy electron beams and X-rays of all energies have deeper action depth in the lung tissue mould body and shallower action depth in the bone tissue mould body; effective depth of action (R) of 4MeV, 6MeV, 9MeV and 12MeV electron beam in soft tissue phantom 90 ) 11mm, 18mm, 28mm and 37mm respectively; depth of action (R) of X-rays of 40kV and 50kV in soft tissue phantom 10 ) 14mm, 25mm.
Finally, an object reference die body is constructed, and the die body is taken as an example to select a high-energy electron beam and low-energy X-ray combination mode. Taking a flat tumor bed as an example, 20×20×10× 10 cm was constructed using DOSXYZnrc 3 Reference motif of size, voxel size 0.2x0.2x0.1 cm 3 Designing object tissue mould body in mould bodyThe upper surface of the object is positioned on the upper surface of the die body, and the upper surface of the object is a cylinder with the diameter of 40mm and the thickness of 18 mm. The subject part material is soft tissue (icrptissu 700 ICRU) and the surrounding phantom material is water (H2O 700 ICRU).
Fig. 7 to 9 are block diagrams of constructed object motifs. Since the depth of the object is 18mm, the effective action depth of the 6MeV electron beam in the soft tissue die body is 18mm and the effective action depth of the 50kV X-ray in the soft tissue die body is 25mm according to the action depth of the high-energy electron beam in the database in different die bodies, and therefore the combination of the 6MeV electron beam and the 50kV X-ray is selected for reference die body irradiation. Since the object size is a cylinder with a diameter of 40mm, the mobatron selects a light-limiting cylinder with a diameter of 50mm, and the Intrabeam selects a flat-panel illuminator with a diameter of 50 mm.
Then simulating the dose distribution of the 6MeV electron beam and a light limiting cylinder with the diameter of 50mm in the object die body by using Monte Carlo software DOSXYZnrc, and carrying out dose correction; dose distribution of 50kV X-rays and a flat plate illuminator with a diameter of 50mm in a subject mold body was simulated using Monte Carlo software DOSXYZnrc, and dose correction was performed. Based on dose distribution and subject center point with dose correctionThe final dose of the electron beam and the X-ray is calculated. The experiment aims at the uniformity of the dose in the object to calculate the two energy irradiation doses, and meanwhile, the dose at the dose reference point is ensured to reach the reference total dose of the set center of the object.
The X-ray and electron beam exposure dose was calculated as follows:
step 5.1, setting an initial X-ray irradiation dose value∈10 of the present embodiment>=10Gy；
Step 5.2, order；
Step 5.3, object center Point according to step fourThe mixed dose value c=20gy, and the electron beam irradiation dose is obtained by the formula (i);
the formula (I),
step 5.4 obtaining a fused dose distribution by the formulae (II) and (III)And fusing the central axis percentage depth dose curve of the dose distribution +.>；
(II),
a step (III),
wherein ,for the x and y coordinates where the central axis is located, < >>Layer coordinates perpendicular to the central axis;
step 5.5, judging the central axis percentage depth dose curve of the fusion dose distributionAt->The relation of the percentage dose at the maximum dose depth dmax to L2 and the relation of the percentage dose at the intermediate dose depth dmax/2 to L1Wherein, dmax at the maximum dose depth is 14mm and dmax/2 at the intermediate dose depth is 7mm, L2 of the embodiment is 95%, L1 is 98%,
when P 7mm <95%，P 14mm If the percentage is more than or equal to 98 percent, the step 5.6 is carried out,
when P 7mm <95% and P 14mm <98 percent, the process proceeds to step 5.7,
when P 7mm More than or equal to 95 percent and P 14mm <98 percent, the process proceeds to step 5.8,
when P 7mm More than or equal to 95 percent and P 14mm If the ratio is more than or equal to 98%, entering a step 5.9;
step 5.6, let a=a+0.4, return to step 5.3;
step 5.7, let a=a-0.4, return to step 5.3;
step 5.8, let a=a-0.2, return to step 5.3;
step 5.9, the current X-ray irradiation doseAnd the current electron beam irradiation dose +.>Defined as final dose, current fusion dose distribution +.>Is the final dose distribution.
When 100 iterations are performed, a=5.80 is finally calculated, and according to the center point of the objectThe mixed dose value of (2) was 20Gy, and b=19.23, i.e., the irradiation dose of the low-energy X-ray was 5.80Gy and the irradiation dose of the high-energy electron beam was 19.23Gy was calculated. And combining the dose rates of the Mobelron device and the Intrabeam device, and respectively calculating the irradiation time under definite energy of the databases of the two devices.
Fig. 10 and 11 are respectively the percent depth dose curves (PDD) of high and low energy rays irradiated alone and mixed in the subject. In the PDD of the high-low energy mixed irradiation in the figure, the dosage value from the upper surface of the die body to the maximum dosage action depth is higher than 95% of the maximum dosage, so that the defect of lower surface dosage when the high-energy electron beam irradiates alone is overcome.
Fig. 12 to 14 are dose distributions of low-energy X-ray single irradiation, high-energy electron beam single irradiation, and high-low beam fusion in the subject phantom, respectively, and the broken lines in fig. 12 to 14 are 90% isodose lines. The graph shows that the high-energy and low-energy mixed irradiation is uniform in dose in the object, the total dose 90% isodose line completely comprises the object, the phenomenon of low surface dose and high central dose can occur when the high-energy electron beam is singly irradiated, and the irradiation dose 90% isodose line cannot completely cover the object. The high-low energy mixed irradiation intra-operative treatment method can form uniform dose irradiation, and overcomes the defect of single intra-operative treatment equipment.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.
Claims (10)
1. A method of high and low energy beam fusion dose distribution comprising the steps of:
step one, collecting images;
selecting an electron beam and an X-ray with corresponding energy from a database according to the tissue model body type corresponding to the image in the step one and the depth of the object in the image in the step one, and respectively selecting a light limiting cylinder and an illuminator with corresponding sizes of high-energy electron beam equipment and low-energy X-ray equipment according to the size of the object in the image in the step one, wherein the database comprises the corresponding relation between the electron beam energy and the depth and the corresponding relation between the X-ray energy and the depth under different tissue model body types;
step three, according to the electron beam, the X-ray, the light limiting cylinder and the illuminator selected in the step two, using Monte Carlo software to simulate the dose distribution of the electron beam and the X-ray in the object respectively, and carrying out dose correction;
step four, setting the center point of the objectA mixing dose value c of (2);
step five, according to the corrected dose obtained in the step three and the center point of the object in the step fourIteratively calculating the final dose of the electron beam and the X-ray.
2. The method of claim 1, wherein the database is established by:
firstly, using Monte Carlo software to simulate the complete structure of a megavoltage high-energy electron beam radiation source and the complete structure of a kilovoltage low-energy X-ray radiation source respectively to obtain a corresponding equipment simulation structure;
then, performing radiation dose simulation calculation and characteristic analysis of the electron beams with different energies in different tissue mold bodies respectively, and establishing a corresponding relation between the action depth and the electron beam energy; and simultaneously, performing radiation dose simulation calculation and characteristic analysis of X-rays with different energies in different tissue mold bodies respectively, and establishing a corresponding relation between the action depth and the X-ray energy.
3. The method of high and low energy beam fusion dose distribution according to claim 2, characterized in that: the radiation dose simulation calculation specifically comprises the step of simulating the process of incidence of electron rays with different energies and X-rays with different energies on a tissue die body by utilizing Monte Carlo software and the equipment simulation structure, and calculating the deposition dose distribution in various tissue die bodies.
4. A method of high and low energy beam fusion dose distribution according to claim 3, characterized in that: the characteristic analysis specifically comprises the steps of respectively calculating a percentage depth dose curve and an effective action depth of corresponding electron rays and X-rays on a central axis according to the deposition dose distribution; wherein the effective depth of action of the electron beam is 90% of the dose depth, and the effective depth of action of the X-ray is 10% of the dose depth.
5. The method of claim 4, wherein the high and low energy beams fuse the dose distribution: the dose correction in the third step is specifically that the Monte Carlo simulation correction coefficient of the electron beam is multiplied by the dose distribution of the electron beam to obtain the dose distribution of the electron beam under unit doseAnd calculate the electron line percentage depth dose curve +.>The method comprises the steps of carrying out a first treatment on the surface of the Multiplying the Monte Carlo simulation correction coefficient of the X-ray by the X-ray dose distribution to obtain X-ray dose distribution +.>。
6. The method of claim 4, wherein the step five is specifically:
step 5.1, setting an initial X-ray irradiation dose valueThere is->, wherein />For X-ray dose distribution->At the center point of the object->A dose value at;
step 5.2, order；
Step 5.3, object center Point according to step fourThe electron beam irradiation dose is calculated by the formula (I) for the mixing dose value c>；
The formula (I),
step 5.4, calculating the fusion dose distribution by the formulae (II) and (III)And fusing the central axis percentage depth dose curve of the dose distribution +.>；
(II),
a step (III),
wherein ,is the central axisxAndycoordinates of->For each perpendicular to the central axisx-yCoordinates of the plane;
step 5.5, judging that the central axis percentage depth dose curve P of the fusion dose distribution is inA relation of a percentage dose at a maximum dose depth dmax to L2, and a relation of a percentage dose at an intermediate dose depth dmax/2 to L1, wherein L2 and L1 are both 90% or more and less than 100%,
when the percentage dose at dmax/2 is less than L1 and the percentage dose at dmax is greater than or equal to L2, go to step 5.6,
step 5.7 is entered when the percentage dose at dmax/2 is less than L1 and the percentage dose at dmax is less than L2,
when the percentage dose at dmax/2 is greater than or equal to L1 and the percentage dose at dmax is less than L2, go to step 5.8,
step 5.9 is entered when the percentage dose at dmax/2 is equal to or greater than L1 and the percentage dose at dmax is equal to or greater than L2;
step 5.6, order，/>Returning to the step 5.3 for constants greater than 0;
step 5.7, order，/>Returning to the step 5.3 for constants greater than 0;
step 5.8, order，/>Returning to the step 5.3 for constants greater than 0;
step 5.9, the current X-ray irradiation doseAnd the current electron beam irradiation dose +.>Defined as final dose, current fusion dose distribution +.>Is the final dose distribution.
7. The method of claim 6, wherein the high and low energy beams fuse the dose distribution: in the second step, a light limiting cylinder of the high-energy equipment and an illuminator of the low-energy equipment are selected according to the maximum transverse diameter of the object in the image of the first step, and the radiation field of the selected light limiting cylinder and the radiation field of the illuminator are larger than or equal to 1.18 times of the maximum transverse diameter of the object.
8. The method of claim 7, wherein the high and low energy beams fuse the dose distribution: the kilovolt low-energy X-ray radiation source comprises a kilovolt X-ray therapeutic machine head, a low-energy X-ray intraoperative radiotherapy device ray source and a cold cathode area array X-ray source, wherein the low-energy X-ray intraoperative radiotherapy device comprises Intrabeam and Xoft Axxent;
the megavoltage high-energy electron beam radiation source comprises a conventional electron linear accelerator machine head and a high-energy electron beam in-operation treatment equipment machine head, wherein the high-energy electron beam in-operation treatment equipment comprises Mobetron, novac and Liac.
9. The method of claim 8, wherein the high and low energy beams fuse the dose distribution: the Monte Carlo software is EGSnrc, FLUKA, GEANT, ETRAN, ITS, MCNP or DPM;
the image is a CT image or an ultrasonic image.
10. The method of high and low energy beam fusion dose distribution according to claim 9, wherein: the tissue mold body is lung tissue, water tissue, soft tissue and bone tissue;
the different energies of the low-energy X-rays are 40kV, 50kV and 60kV;
the different energies of the high energy electron lines were 4MeV, 6MeV, 9MeV and 12MeV.
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