CN109513118B - Photon energy synthesis method and system of medical linear accelerator - Google Patents
Photon energy synthesis method and system of medical linear accelerator Download PDFInfo
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- 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
- A61N5/1042—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head
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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
- A61N5/1031—Treatment planning systems using a specific method of dose optimization
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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
- A61N5/1064—Monitoring, verifying, controlling systems and methods for adjusting radiation treatment in response to monitoring
- A61N5/1065—Beam adjustment
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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
- A61N5/1077—Beam delivery systems
- A61N5/1084—Beam delivery systems for delivering multiple intersecting beams at the same time, e.g. gamma knives
Abstract
The invention relates to a photon energy synthesis method and a system of a medical linear accelerator, wherein the photon energy synthesis method of the medical linear accelerator comprises the following steps: acquiring first energy photon beam dosimetry data, second energy photon beam dosimetry data and intermediate energy photon beam dosimetry data; performing mathematical fitting on the first energy photon beam dosimetry data and the second energy photon beam dosimetry data according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data; comparing and verifying the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data to obtain the fitting deviation of the dosimetry data; and comparing the fitting deviation of the dosimetry data with a preset threshold value to obtain a comparison result. According to the technical scheme, photon beams with high and low levels of energy can be utilized to synthesize photon beams with beam current characteristics similar to those of photon beams with any energy in two energy ranges.
Description
Technical Field
The invention relates to the technical field of radiotherapy, in particular to a photon energy synthesis method and a photon energy synthesis system of a medical linear accelerator.
Background
The medical linear accelerator is a radiotherapy device and is divided into an electron beam and a photon beam. The simplest medical linear accelerator at least comprises an accelerating tube, a high-power microwave source, a waveguide system, a control system, a ray leveling system, a protection system and the like. The medical linear accelerator is a product combining high, fine and sharp technologies in medical instruments, is one of the products with the highest technical content in the field of medical instruments, and can be produced in only a few developed countries in the world.
The traditional medical linear accelerator is divided into two types of traveling wave and standing wave according to the characteristics of microwave transmission, the basic structures of the traditional medical linear accelerator are similar, and the mechanism for generating high-energy electrons or photon beams is also the same. The high-energy electron beam with certain energy is interacted with the microwave electromagnetic field of the high-power microwave, so that the higher-energy electron beam is obtained. The electron beam is directly led out and can be used for electron beam therapy. The high energy electrons strike the heavy metal tungsten target, thereby generating bremsstrahlung, emitting high energy X-rays, the photons thus generated having a continuous energy spectrum, ranging from 0 to the initial electron beam energy. For example, a 6MV beam may produce a photon beam having an energy between 0 and 6MV, which is commonly referred to as a 6MV photon beam.
The penetration depth of different energy rays is different, the contribution to the tumor dose is different, and the photon beam with lower energy (less than or equal to 6MV) is often used for treating head and neck tumors or superficial tumors due to the depth percentage dose distribution in tissues; higher energy photon beams (>6MV) have a greater penetration into tissues and are more used to treat deep tumors. The high-energy photon ray (>6MV) has the characteristics of small skin damage, strong penetrability, high ray uniformity, good effect of ensuring normal tissues and the like, and is suitable for treating deep tumors. Therefore, for different tumors at different parts, radiation with different energies can be selected for radiotherapy when a treatment plan is made.
However, the accelerator design allows only a small amount of photon energy (typically 2 to 3 steps) to be available due to the process complexity of accelerator engineering and output dose rate requirements. As the number of selectable energy levels of the output photon beam of the medical linear accelerator increases, the technical complexity increases, so that the manufacturing cost increases sharply, which also translates into a higher purchase price. At present, the energy of the medical linear accelerator is mainly adjusted by a hardware control method, which comprises the following two methods: firstly, the output power of a magnetron or a klystron is changed by adjusting the high voltage of a modulator, so that multiple energy choices are realized, and the defect is that the energy adjusting range is small; and secondly, the energy switch method is used for selecting various energies, and the defects that the energy selectable by the accelerator is only two gears and cannot be continuously adjusted are overcome.
To ensure that the dose is accurately and reliably prescribed, each energy photon beam must be separately calibrated and tested, and each energy photon beam must be separately modeled and tested in the treatment planning system. During the adjustment test, a three-dimensional water tank is used, and the dosimetry parameters under various geometric conditions, such as a percent Depth Dose curve (PDD), an Off-axis Dose distribution curve (OAR) and an Output Factor (OF), are measured in water and introduced into a treatment planning system to generate a proper Dose calculation model. The physicist selects one of the available energy photons from the treatment planning system to plan at the time of planning. Therefore, the cost of commissioning and maintenance is generally proportional to the amount of photon energy that can be used by the medical linear accelerator. As the amount of photon energy available increases, the operating costs of the medical linear accelerator will increase substantially.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art or the related art.
Therefore, an object of the present invention is to provide a method for synthesizing photon energy of a medical linear accelerator, which can synthesize a photon beam having a beam characteristic similar to any energy in two energy ranges by using the photon beam characteristics such as a percentage depth dose curve and an off-axis dose distribution curve of two photons having known energies.
Another object of the present invention is to provide a system for synthesizing photon energy of a medical linear accelerator, which can implement the steps of synthesizing photon energy of the medical linear accelerator according to the above method.
In order to achieve the above object, a technical solution of a first aspect of the present invention provides a method for synthesizing photon energy of a medical linear accelerator, including the following steps: acquiring first energy photon beam dosimetry data, second energy photon beam dosimetry data and intermediate energy photon beam dosimetry data corresponding to the first energy photon beam dosimetry data and the second energy photon beam dosimetry data; performing mathematical fitting on the first energy photon beam dosimetry data and the second energy photon beam dosimetry data according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data; comparing and verifying the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data to obtain the fitting deviation of the dosimetry data; comparing the fitting deviation of the dosimetry data with a preset threshold value to obtain a comparison result; synthesizing energy photon beam dosimetry data into final dosimetry data when the comparison result is that the fitting deviation of the dosimetry data is smaller than or equal to a preset threshold; and when the comparison result is that the fitting deviation of the dosimetry data is larger than a preset threshold value, performing iterative optimization adjustment on the fitting coefficient according to the fitting deviation of the dosimetry data.
In the technical scheme, rays with high and low energy levels output from the conventional medical linear accelerator are mixed according to the fitting coefficient determined above, and rays with similar beam characteristics of any energy in the two energy ranges are simulated, so that the radiation treatment scheme of the known photon beam can be realized on the same or another medical linear accelerator with different photon energy to achieve nearly the same dose distribution; meanwhile, more than two photon energies do not need to be equipped on the medical linear accelerator, so that the development expense and the later maintenance expense of equipment can be saved; and can be used to provide any continuously tunable photon energy, providing the user with the greatest degree of freedom, which is not currently available in hardware.
In the above technical solution, preferably, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data measured on the same medical linear accelerator.
In the above technical solution, preferably, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data measured on different medical linear accelerators.
In any of the above embodiments, preferably the dosimetry data comprises a percent depth dose profile and an off-axis dose distribution profile.
In any of the above technical solutions, preferably, the first energy photon beam dosimetry data and the second energy photon beam dosimetry data are mathematically fitted according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data, and the specific formula is as follows:
PDDsyn＝α·PDDlow+β·PDDhigh；
OARsyn＝α·OARlow+β·OARhigh；
wherein syn represents the energy E corresponding to the dosimetry data of the synthesized energy photon beamsynAnd low represents the energy E corresponding to the dosimetry data of the first energy photon beamlowAnd high represents the energy E corresponding to the dosimetry data of the second energy photon beamhighAnd α and β represent fitting coefficients.
In any of the above technical solutions, preferably, the dosimetry data of the synthetic energy photon beam and the dosimetry data of the intermediate energy photon beam are compared and verified to obtain a fitting deviation of the dosimetry data, and a specific formula is as follows:
where mid represents the energy E corresponding to intermediate energy photon beam dosimetry datamid，RjFitting deviation, W, of the resultant energy photon beam dosimetry data of step j with the intermediate energy photon beam dosimetry dataPDDAnd WOARRepresenting user adjustable weight coefficients.
In any of the above technical solutions, preferably, the comparison result is that the fitting deviation of the dosimetry data is less than or equal to a preset threshold, specifically: rj≤δ；
The comparison result is that the fitting deviation of the dosimetry data is greater than a preset threshold, and specifically comprises the following steps: rj＞δ。
The technical solution of the second aspect of the present invention provides a system for synthesizing photon energy of a medical linear accelerator, including: an acquisition module for acquiring first energy photon beam dosimetry data, second energy photon beam dosimetry data, and intermediate energy photon beam dosimetry data corresponding to the first energy photon beam dosimetry data and the second energy photon beam dosimetry data; the mathematical fitting module is used for performing mathematical fitting on the first energy photon beam dosimetry data and the second energy photon beam dosimetry data according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data; the verification module is used for comparing and verifying the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data to obtain the fitting deviation of the dosimetry data; the comparison module is used for comparing the fitting deviation of the dosimetry data with a preset threshold value to obtain a comparison result; when the comparison result is that the fitting deviation of the dosimetry data is smaller than or equal to a preset threshold value, synthesizing the energy photon beam dosimetry data as final dosimetry data; and when the comparison result is that the fitting deviation of the dosimetry data is larger than a preset threshold value, performing iterative optimization adjustment on the fitting coefficient according to the fitting deviation of the dosimetry data.
In the above technical solution, preferably, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data of the same medical linear accelerator.
In the above technical solution, preferably, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data of different medical linear accelerators.
In any of the above embodiments, preferably the dosimetry data comprises a percent depth dose profile and an off-axis dose distribution profile.
In any of the above technical solutions, preferably, the dosimetry data of the first energy photon beam dosimetry data and the dosimetry data of the second energy photon beam dosimetry data are mathematically fitted according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data, and the specific formula is as follows:
PDDsyn＝α·PDDlow+β·PDDhigh；
OARsyn＝α·OARlow+β·OARhigh；
wherein syn represents the energy E corresponding to the dosimetry data of the synthesized energy photon beamsynAnd low represents the energy E corresponding to the dosimetry data of the first energy photon beamlowAnd high represents the energy E corresponding to the dosimetry data of the second energy photon beamhighAnd alpha and beta represent preset fitting coefficients;
comparing and verifying the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data to obtain the fitting deviation of the dosimetry data, wherein the specific formula is as follows:
where mid represents the energy E corresponding to intermediate energy photon beam dosimetry datamid，RjFitting deviation, W, of the resultant energy photon beam dosimetry data of step j with the intermediate energy photon beam dosimetry dataPDDAnd WOARRepresenting user adjustable weight coefficients;
the comparison result is that the fitting deviation of the dosimetry data is less than or equal to a preset threshold, and specifically comprises the following steps: rj≤δ；
The comparison result is that the fitting deviation of the dosimetry data is greater than a preset threshold, and specifically comprises the following steps: rj＞δ。
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 illustrates a block flow diagram of a method for photon energy synthesis for a medical linear accelerator in accordance with some embodiments of the invention;
FIG. 2 illustrates a block diagram of a photon energy synthesis system for a medical linear accelerator in accordance with certain embodiments of the present invention;
FIG. 3 is a graph of PDD of a beam of energy photons from a medical linear accelerator 6, 10, 15MV in accordance with an embodiment of the present invention;
FIG. 4 is a graph of fitting coefficient α, β values in an embodiment of the present invention;
FIG. 5 is a graph comparing the PDD curve of the synthetic and intermediate dosimetry data in an example of the invention;
FIG. 6 is a graph comparing OAR curves for synthetic and intermediate dosimetry data in an embodiment of the invention;
FIG. 7 is a dose plan comparison of synthetic and intermediate dosimetry data in an embodiment of the invention;
FIG. 8 is a graph comparing dose volume histograms of synthetic and intermediate dosimetry data in an example of the invention.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited to the specific embodiments disclosed below.
A photon energy synthesis method and system for a medical linear accelerator according to an embodiment of the present invention will be described with reference to fig. 1 to 8.
As shown in fig. 1, a photon energy synthesis method of a medical linear accelerator according to some embodiments of the present invention includes the following steps:
s100, acquiring first energy photon beam dosimetry data (a percent depth dose curve, an off-axis dose distribution curve, and the like) corresponding to a low energy photon beam, second energy photon beam dosimetry data corresponding to a high energy photon beam having energy higher than that of the first energy photon beam, and intermediate energy photon beam dosimetry data corresponding to intermediate energy photon beams of the low energy photon beam and the high energy photon beam;
s200, performing mathematical fitting on the dosimetry data of the first energy photon beam dosimetry data and the dosimetry data of the second energy photon beam dosimetry data according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data corresponding to synthesized energy photon beams;
s300, comparing and verifying the dosimetry data of the synthetic energy photon beam and the dosimetry data of the intermediate energy photon beam to obtain fitting deviation of the dosimetry data;
s400, comparing the fitting deviation of the dosimetry data with a preset threshold value to obtain a comparison result;
s500, when the fitting deviation of the dosimetry data is smaller than or equal to a preset threshold value as a comparison result, the synthesized energy photon beam dosimetry data in the step S200 is used as final dosimetry data;
and when the comparison result shows that the fitting deviation of the dosimetry data is larger than the preset threshold, performing iterative optimization adjustment on a fitting coefficient according to the fitting deviation of the dosimetry data, performing mathematical fitting on the first energy photon beam and the second energy photon beam according to the adjusted fitting coefficient to obtain a new synthesized energy photon beam with beam characteristics similar to those of the intermediate energy photon beam, and repeating the steps S200-S400 until the fitting deviation of the dosimetry data corresponding to the new synthesized energy photon beam is smaller than or equal to the preset threshold.
In the embodiment, the rays with high and low energy levels output from the existing medical linear accelerator are mixed according to the fitting coefficient determined above, and rays with similar beam characteristics of any energy in the two energy ranges are simulated and realized, so that the radiation treatment scheme of the known photon beam can be realized on the same or another medical linear accelerator with different photon energy levels to achieve nearly the same dose distribution; meanwhile, more than two photon energies do not need to be equipped on the medical linear accelerator, so that the development expense and the later maintenance expense of equipment can be saved; and can be used to provide any continuously tunable photon energy, providing the user with the greatest degree of freedom, which is not currently available in hardware.
In this embodiment, the first energy photon beam dosimetry data and the second energy photon beam dosimetry data are photon beams with different energies of the medical linear accelerator, and if the first energy photon beam dosimetry data is medicalOne or more low energies E of a linear acceleratorlowThe dose data corresponding to the photon beam and the dose data of the second energy photon beam are one or more high energy EhighDosimetry data corresponding to the photon beam; the intermediate-energy photon beam dosimetry data may be dosimetry data corresponding to one or more intermediate-energy photon beams of the medical linear accelerator, and the energy value E of the intermediate-energy photon beammidAt an energy value E of the low-energy photon beamlowAnd the energy value E of the high-energy photon beamhighIn the meantime.
The photon energy synthesis method is irrelevant to a planning treatment system, and directly acts on the data measured by the water tank, is the foreground of the planning system, and can be applied to all treatment planning systems.
In one embodiment of the present invention, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data measured on the same medical linear accelerator.
In another embodiment of the present invention, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data measured on different medical linear accelerators.
In this embodiment, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data may be one or more dosimetry data measured on a medical linear accelerator; or the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data may be dosimetry data measured on different medical linear accelerators; or the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data may be dosimetry data measured on the same medical linear accelerator; or at least two of the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data may be dosimetry data measured on the same medical linear accelerator.
In any of the above embodiments, preferably, the dosimetry data comprises a percent depth dose curve (PDD), an off-axis dose distribution curve (OAR).
In this embodiment, a percent depth dose Profile (PDD) is defined as the absorbed dose rate D at a certain depth D on the ray center axis in the body membranedAnd a reference depth d0At the absorption dose rate D0The percentage of the ratio is a physical quantity describing the relative dose distribution at different depths of the ray center axis.
In any of the above embodiments, preferably, the first energy photon beam dosimetry data and the second energy photon beam dosimetry data are mathematically fitted according to a preset fitting coefficient to obtain the synthesized energy photon beam dosimetry data, and the specific formula is as follows:
PDDsyn＝α·PDDlow+β·PDDhigh；
OARsyn＝α·OARlow+β·OARhigh；
wherein syn represents the energy E corresponding to the dosimetry data of the synthesized energy photon beamsynAnd low represents the energy E corresponding to the dosimetry data of the first energy photon beamlowAnd high represents the energy E corresponding to the dosimetry data of the second energy photon beamhighα and β represent preset fitting coefficients, and the initial values of the preset fitting coefficients may be set to (0.5 ).
In any of the above embodiments, preferably, the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are compared and verified to obtain a fitting deviation of the dosimetry data, where the specific formula is as follows:
wherein mid represents the energy corresponding to the intermediate energy photon beam dosimetry dataQuantity Emid，RjFitting deviation, W, of the resultant energy photon beam dosimetry data of step j with the intermediate energy photon beam dosimetry dataPDDAnd WOARRepresenting user adjustable weight coefficients.
In any of the above embodiments, preferably, the comparison result is that the fitting deviation of the dosimetry data is less than or equal to a preset threshold, specifically: rj≤δ；
The comparison result is that the fitting deviation of the dosimetry data is greater than a preset threshold, and specifically comprises the following steps: rj＞δ。
As shown in fig. 2, a system 1000 for photon energy synthesis for a medical linear accelerator according to some embodiments of the present invention includes: an obtaining module 100, configured to obtain first energy photon beam dosimetry data corresponding to a low-energy photon beam, second energy photon beam dosimetry data corresponding to a high-energy photon beam having energy higher than that of the low-energy photon beam, and intermediate energy photon beam dosimetry data corresponding to an intermediate energy photon beam corresponding to the low-energy photon beam and the high-energy photon beam; a mathematical fitting module 200, configured to perform mathematical fitting on the first energy photon beam dosimetry data and the second energy photon beam dosimetry data according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data corresponding to a synthesized energy photon beam; the verification module 300 is configured to compare and verify the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data to obtain a fitting deviation of the dosimetry data; the comparison module 400 is configured to compare the fitting deviation of the dosimetry data with a preset threshold to obtain a comparison result; when the fitting deviation of the dosimetry data is smaller than or equal to a preset threshold value, synthesizing the energy photon beam dosimetry data as final dosimetry data; and when the comparison result shows that the fitting deviation of the dosimetry data is greater than the preset threshold, performing iterative optimization adjustment on a fitting coefficient according to the fitting deviation of the dosimetry data, performing mathematical fitting on the first energy photon beam and the second energy photon beam according to the adjusted fitting coefficient, obtaining a new synthesized energy photon beam with beam characteristics similar to those of the intermediate energy photon beam, and until the fitting deviation of the dosimetry data corresponding to the new synthesized energy photon beam is less than or equal to the preset threshold.
In this embodiment, the system can implement the steps of the photon energy synthesis method of the medical linear accelerator according to any one of the above embodiments.
In the above embodiment, preferably, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data measured on the same medical linear accelerator.
In the above embodiment, preferably, the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data measured on different medical linear accelerators.
In any of the above embodiments, preferably, the dosimetry data comprises a percent depth dose profile and an off-axis dose distribution profile.
In any of the above embodiments, preferably, the dosimetry data of the first energy photon beam dosimetry data and the dosimetry data of the second energy photon beam dosimetry data are mathematically fitted according to a preset fitting coefficient to obtain the synthesized energy photon beam dosimetry data, where the specific formula is as follows:
PDDsyn＝α·PDDlow+β·PDDhigh；
OARsyn＝α·OARlow+β·OARhigh；
αj+1＝αj+τ；
βj+1＝βj+τ；
wherein syn represents the energy E corresponding to the dosimetry data of the synthesized energy photon beamsynAnd low represents the energy E corresponding to the dosimetry data of the first energy photon beamlowAnd high represents the energy E corresponding to the dosimetry data of the second energy photon beamhighα and β represent preset fitting coefficients, the initial values of the preset fitting coefficients can be set to (0.5 ), and the iteration step τ can be set to 0.05;
comparing and verifying the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data to obtain the fitting deviation of the dosimetry data, wherein the specific formula is as follows:
where mid represents the energy E corresponding to intermediate energy photon beam dosimetry datamid，RjFitting deviation, W, of the resultant energy photon beam dosimetry data of step j with the intermediate energy photon beam dosimetry dataPDDAnd WOARRepresenting user adjustable weight coefficients;
the comparison result is that the fitting deviation of the dosimetry data is less than or equal to a preset threshold, and specifically comprises the following steps: rj≤δ；
The comparison result is that the fitting deviation of the dosimetry data is greater than a preset threshold, and specifically comprises the following steps: rj＞δ。
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The photon beam of the medical linear accelerator can be selected from one to three gears of 4-18 MV, such as 6MV, 10MV and 15 MV. After the third gear energy is debugged and accepted, the dosimetry data of each gear energy under various geometric conditions are measured, and a 10MV energy photon beam is synthesized by 6MV and 15MV, and the specific implementation process is as follows:
1. acquiring first energy photon beam dosimetry data, second energy photon beam dosimetry data and intermediate energy photon beam dosimetry data corresponding to the first energy photon beam dosimetry data and the second energy photon beam dosimetry data; the low-energy photon beam corresponding to the first-energy photon beam dosimetry data and the high-energy photon beam corresponding to the second-energy photon beam dosimetry data are 6MV photon beams and 15MV photon beams respectively, and the intermediate-energy photon beam corresponding to the intermediate dosimetry data is a 10MV photon beam;
2. the PDD curves corresponding to the low energy (6MV) photon beam, the intermediate energy (10MV) photon beam and the high energy (15MV) photon beam are shown in fig. 3. Setting the initial values of α and β to (0.5 ), the iteration step τ can be set to 0.05 and the dosimetry data corresponding to the synthesized energy photon beam calculated is shown in fig. 4.
3. The PDD and OAR data of the synthesized 10_ syn energy photon beam obtained by each mathematical fitting optimization and the PDD and OAR data of the known 10MV energy measured by the medical linear accelerator are subjected to fitting verification, as shown in fig. 5 and 6.
4. As shown in fig. 7 and 8, in the planning system, we fit 10MV energy rays using 6MV and 15MV for planning design and compare the planning results with the actual 10MV energy ray plan. We found that the dose distributions of both sets of plans and the dose volume histogram results for each organ were substantially consistent.
In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more unless expressly limited otherwise. The terms "mounted," "connected," "fixed," and the like are to be construed broadly, and for example, "connected" may be a fixed connection, a removable connection, or an integral connection; "coupled" may be direct or indirect through an intermediary. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "left", "right", "front", "rear", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the referred device or unit must have a specific direction, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
In the description herein, the terms "one embodiment," "some embodiments," "specific embodiments," and the like, describe or imply that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by 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 (3)
1. A photon energy synthesis method of a medical linear accelerator is characterized by comprising the following steps:
acquiring first energy photon beam dosimetry data, second energy photon beam dosimetry data, and intermediate energy photon beam dosimetry data corresponding to the first energy photon beam dosimetry data and the second energy photon beam dosimetry data;
performing mathematical fitting on the first energy photon beam dosimetry data and the second energy photon beam dosimetry data according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data, wherein the specific formula is as follows:
PDDsyn＝α·PDDlow+β·PDDhigh；
OARsyn＝α·OARlow+β·OARhigh；
wherein syn represents the energy E corresponding to the dosimetry data of the synthetic energy photon beamsynAnd low represents the energy E corresponding to the dosimetry data of the first energy photon beamlowAnd high represents the energy E corresponding to the second energy photon beam dosimetry datahighAnd α and β represent the fitting coefficients;
comparing and verifying the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data to obtain the fitting deviation of the dosimetry data, wherein the specific formula is as follows:
wherein mid represents the energy corresponding to the intermediate-energy photon beam dosimetry dataQuantity Emid，RjFitting deviation, W, of the resultant energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data of step jPDDAnd WOARRepresenting user adjustable weight coefficients;
comparing the fitting deviation of the dosimetry data with a preset threshold value to obtain a comparison result;
when the comparison result is that the fitting deviation of the dosimetry data is smaller than or equal to the preset threshold, the synthesized energy photon beam dosimetry data is final dosimetry data;
when the comparison result is that the fitting deviation of the dosimetry data is larger than the preset threshold value, performing iterative optimization to adjust the fitting coefficient according to the fitting deviation of the dosimetry data;
the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data measured on the same or different medical linear accelerators, and the dosimetry data comprise a percent depth dose curve and an off-axis dose distribution curve.
2. The method for synthesizing photon energy of a medical linear accelerator according to claim 1, wherein: the comparison result is that the fitting deviation of the dosimetry data is less than or equal to the preset threshold, and specifically comprises the following steps: rj≤δ；
The comparison result indicates that the fitting deviation of the dosimetry data is greater than the preset threshold, and specifically includes: rj＞δ。
3. A system for synthesizing photon energy for a medical linear accelerator, comprising:
an acquisition module for acquiring first energy photon beam dosimetry data, second energy photon beam dosimetry data, and intermediate energy photon beam dosimetry data corresponding to the first energy photon beam dosimetry data and the second energy photon beam dosimetry data;
a mathematical fitting module, configured to perform mathematical fitting on the first energy photon beam dosimetry data and the second energy photon beam dosimetry data according to a preset fitting coefficient to obtain synthesized energy photon beam dosimetry data, where the specific formula is as follows:
PDDsyn＝α·PDDlow+β·PDDhigh；
OARsyn＝α·OARlow+β·OARhigh；
wherein syn represents the energy E corresponding to the dosimetry data of the synthetic energy photon beamsynAnd low represents the energy E corresponding to the dosimetry data of the first energy photon beamlowAnd high represents the energy E corresponding to the second energy photon beam dosimetry datahighAnd α and β represent the fitting coefficients;
a verification module, configured to compare and verify the synthetic energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data to obtain a fitting deviation of the dosimetry data, where the specific formula is as follows:
wherein mid represents the energy E corresponding to the intermediate-energy photon beam dosimetry datamid，RjFitting deviation, W, of the resultant energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data of step jPDDAnd WOARRepresenting user adjustable weight coefficients;
the comparison module is used for comparing the fitting deviation of the dosimetry data with a preset threshold value to obtain a comparison result;
wherein, when the comparison result is that the fitting deviation of the dosimetry data is less than or equal to the preset threshold, the method specifically comprises the following steps: rjDelta is less than or equal to delta, and the dosimetry data of the synthesized energy photon beam is final dosimetry data;
when the comparison result is that the fitting deviation of the dosimetry data is greater than the preset threshold, specifically: rjδ, iterating according to the dosimetry data fitting deviationAdjusting the fitting coefficient by means of optimization;
the first energy photon beam dosimetry data, the second energy photon beam dosimetry data and the intermediate energy photon beam dosimetry data are dosimetry data measured on the same or different medical linear accelerators, and the dosimetry data comprise a percent depth dose curve and an off-axis dose distribution curve.
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