A fast neutron dosimetry method for boron neutron capture therapy

Abstract

The present application relates to neutron dosimetry method, specifically provide a kind of for boron neutron capture therapy fast neutron dosimetry method, by using the paired ionization chamber test system with different liquid environment, one kind of liquid environment has obvious absorption to thermal neutron, then the radiation source under the same power is measured, to obtain more accurate fast neutron dose and the rest two kinds of mixed radiation dose, to solve the problem of inaccurate neutron dose test of different kinds in the prior art in the application process of mixed radiation field, more accurate mixed radiation quantity value can be obtained, so that the different types of neutron dose in mixed radiation field are grasped, so as to improve the radiation effect in the application scene of mixed radiation field.

Description

Technical Field

[0001] This invention relates to the field of neutron dose measurement methods, and specifically provides a method for measuring different types of neutron doses in a mixed radiation field. Background Technology

[0002] In boron neutron capture therapy, when neutrons reach the tumor and exert their therapeutic effect, they inevitably react with various elemental components of both the tumor and normal tissues. Therefore, the tissue-absorbed dose in boron neutron capture therapy includes… 10 B(n, α) 7 The background dose generated by the Li reaction and other complex reactions includes fast neutron dose, thermal neutron dose, and gamma dose, forming a complex mixed radiation field. Similar mixed radiation fields are used in other fields, but there is no good classification and testing method for measuring different types of neutrons in mixed radiation fields.

[0003] Currently, the main methods for measuring mixed neutron and gamma radiation fields include paired thermoluminescence, paired ionization chamber, gel dosimeter, and film dosimeter methods. Among them, the paired ionization chamber method, recommended by the International Commission on Radiation Units (ICRU), is the standard measurement method for neutron and gamma dose determination. However, it is difficult to effectively distinguish and measure different types of neutron doses in mixed radiation fields.

[0004] Currently, in boron neutron capture therapy, besides those beneficial to the human body... 10 B-dose, the background dose includes thermal neutron dose, fast neutron dose, and gamma dose, such as Figure 1 As shown, the fast neutron dose is the highest, while the thermal neutron and gamma doses are relatively lower, especially at the surface (depth 0 cm), where the fast neutron dose is the highest. This means that when a patient's skin is irradiated, the first mixed radiation to be affected is fast neutron radiation. However, the existing paired ionization chamber method is affected by the thermal neutron dose when testing the fast neutron dose, resulting in inaccurate measurements. Even with simulation correction, the measurement results still have some errors. Dose verification experiments are very important when making patient treatment plans. This involves experimentally measuring the dose in a medium and comparing it with the theoretically calculated dose to verify the correctness of the patient's treatment plan. In addition, in many mixed radiation field applications, such as artificial breeding, it is also necessary to accurately grasp the actual values ​​of each dose in the mixed radiation field. Therefore, this is also an urgent problem to be solved in the application of mixed radiation fields.

[0005] Accordingly, a new measurement method is needed in this field to address the above problems. Summary of the Invention

[0006] This invention aims to solve the aforementioned technical problem, namely, the inaccuracy in the measurement of different types of neutron doses in existing technologies for applications in mixed radiation fields. To this end, this invention provides a method for measuring different types of neutron doses in mixed radiation fields. This method is applied to a paired ionization chamber testing system, which includes a first detection device, a second detection device, and a container filled with liquid. The first and second detection devices are arranged along the radiation direction within the container.

[0007] The measurement method includes the following steps:

[0008] S100: Place the test system in the test field, fill the container with the first liquid, and turn on the radiation source;

[0009] S200: Obtain the total mixed radiation dose D through the first detection device. 总 The gamma dose D is obtained through the second detection device. γ According to the total dose of mixed radiation D 总 and γ dose D γ Determine the total neutron dose D 中 ;

[0010] S300: Turn off the radiation source, replace the first liquid in the container with a second liquid that can absorb thermal neutrons, place the test system in the test field, and turn the radiation source back on at the same power.

[0011] S400: Obtain the total mixed radiation dose M through the first detection device. 总 The gamma dose M is obtained through the second detection device. γ According to the total mixed radiation dose M 总 and γ dose M γ Determine the fast neutron dose M 快 ;

[0012] S500: Based on the total neutron dose D 中 and fast neutron dose M 快 Calculate the thermal neutron dose D in the test system filled with the first liquid. 热 .

[0013] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, step S500 specifically includes:

[0014] S510: Simulate the absorbed dose of fast neutrons by the first and second liquids, and determine the fast neutron dose M in the test system filled with the second liquid based on the simulated absorbed doses of the first and second liquids. 快 The fast neutron dose D equivalent to that in the test system filled with the first liquid.快 ;

[0015] The thermal neutron dose in the test system filled with the first liquid is calculated using the following formula: D 热 =D 中 -D 快 .

[0016] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, step S510 further includes:

[0017] According to the Monte Carlo procedure, the absorbed dose of fast neutrons in the first liquid was obtained by simulation as N1.

[0018] According to the Monte Carlo procedure, the absorption dose of fast neutrons in the second liquid was obtained by simulation as N2.

[0019] Calculate the fast neutron dose D of the first liquid test system 快 D is calculated using the following formula: 快 =N2 / N1×M 快 .

[0020] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, step S200 further includes:

[0021] Total neutron dose D 中 D is calculated using the following formula: 中 =D 总 -D γ .

[0022] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, step S400 further includes:

[0023] Fast neutron dose M 快 =M 总 -M γ .

[0024] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, the second liquid contains at least one of lithium-6, gadolinium-157, and boron-10.

[0025] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, the enrichment of lithium-6 in the second liquid ranges from 6% to 98%.

[0026] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, the enrichment of gadolinium-157 in the second liquid ranges from 15% to 98%.

[0027] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, the enrichment of boron-10 in the second liquid ranges from 19% to 98%.

[0028] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, the first liquid is water.

[0029] In the specific embodiment of the above-described method for measuring different types of neutron doses in a mixed radiation field, the first detection device is a TE-TE finger-type ionization chamber; and / or

[0030] The second detection device is a Mg-Ar finger-type ionization chamber; and / or

[0031] The first liquid is water.

[0032] By employing the above technical solution, this invention enables the classification and measurement of neutron doses of different types in mixed radiation field applications. For example, in the verification of treatment plans for patients undergoing boron neutron capture therapy, or in the field of radiation breeding, it classifies and measures the thermal neutron dose, fast neutron dose, and gamma dose in the mixed radiation dose. Based on this classification and measurement, further separate measurements of the thermal neutron dose and fast neutron dose yield accurate dose values. Considering that the fast neutron dose is highest at the radiation contact surface, this means that when a target in a mixed radiation field is irradiated, the first mixed radiation to be affected is fast neutron radiation. A more accurate grasp of fast neutron radiation allows for more effective utilization of the beneficial dose in the mixed radiation, reducing the negative impact of background dose. In the field of boron neutron capture therapy, it maximizes the output of beneficial doses, improving the accuracy of treatment plan verification based on more accurate fast neutron dose measurement. In the field of radiation breeding, it increases the success rate by accurately controlling the radiation dose. Attached Figure Description

[0033] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0034] Figure 1 This is a schematic diagram of the mixed radiation dose content relationship of the present invention, which shows that the neutron dose is divided into two parts and the neutron quantity at the surface;

[0035] Figure 2 This is a schematic diagram of the test system structure of the present invention;

[0036] Figure 3 This is a schematic diagram of the main measurement steps of the present invention;

[0037] Figure 4 M is the present invention 快 Equivalent to D 快 A step-by-step diagram;

[0038] In the diagram: 1. Neutron beam, 2. Treatment head, 3. Container, 4. Liquid, 5. First detection device, 6. Second detection device. Detailed Implementation

[0039] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings and in conjunction with boron neutron capture therapy. It should be understood by those skilled in the art that these embodiments are merely illustrative of the technical principles of the invention and are not intended to limit the scope of protection of the invention. Those skilled in the art can make adjustments as needed to adapt to specific applications. For example, although the specification describes the invention in conjunction with boron neutron capture therapy, this is not limiting, and those skilled in the art can apply the invention to any other mixed radiation field testing field as needed, as long as the mixed radiation field requires differentiation of different types of neutron doses.

[0040] It should be noted that in the description of this invention, terms such as "upper," "lower," "left," "right," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the relevant devices or elements must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, ordinal numbers such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Furthermore, in order to more clearly demonstrate the core technical solution of the present invention, the description of the boron neutron capture therapy treatment head and the known structure of the paired ionization chamber test system is omitted in the following description. However, this omission is only for the convenience of description and does not mean that the above device can be without these structures.

[0043] like Figure 1The figure shows the dose and relationship of various radiations in boron neutron capture therapy. From the figure, we can see that the absorbed dose (physical dose) of human tissues in boron neutron capture therapy can be roughly divided into four parts: 10 B dose (by 10 B(n, a) 7 This is due to the Li neutron capture reaction, which is the main dose with tumor therapeutic effect in the tumor target area during boron neutron capture therapy, and the thermal neutron dose (mainly caused by...). 14 N(n, p) 14 (caused by C thermal neutron capture reaction), fast neutron dose (mainly due to C thermal neutron capture reaction), and fast neutron dose (mainly caused by C thermal neutron capture reaction). 1 H(n, n') 1 The dose is caused by the reaction-moderated neutrons such as H, whose energy is higher than that of thermal neutrons; the gamma dose (mainly caused by the dose of gamma rays associated with neutron sources and gamma rays produced by neutron irradiation of the human body), among which 10 B-dose is beneficial to the human body; the rest are mixed radiation. Within the background dose, fast neutron dose is the highest, while thermal neutron and gamma doses are relatively lower. Especially at the surface (0 cm depth), the fast neutron dose is the highest. This means that when a patient's skin is irradiated, the primary source of mixed radiation is fast neutron radiation. Current measurement methods can only obtain the sum of fast and thermal neutron doses and the gamma dose, without further subdivision of the neutron dose. During treatment plan verification, the influence of the thermal neutron dose leads to a decrease in the accuracy of fast neutron dose measurement, affecting the accuracy of the verification.

[0044] like Figure 2 , 3 As shown, this invention proposes a method for measuring the dose of different types of neutrons in a mixed radiation field. The method is applied to a paired ionization chamber testing system, which includes a first detection device 5, a second detection device 6, and a container 3 containing liquid. The first detection device 5 and the second detection device 6 are arranged along the radiation direction within the container 3.

[0045] The measurement method includes the following steps:

[0046] S100: Place the test system in the test field, fill the container 3 with the first liquid, and turn on the radiation source;

[0047] S200: Obtain the total mixed radiation dose D through the first detection device 5. 总 The γ dose D is obtained through the second detection device 6. γ According to the total dose of mixed radiation D 总 and γ dose D γ Determine the total neutron dose D 中 ;

[0048] S300: Turn off the radiation source, replace the first liquid in the container 3 with a second liquid that can absorb thermal neutrons, place the test system in the test field, and turn the radiation source back on at the same power.

[0049] S400: Obtain the total mixed radiation dose M through the first detection device 5. 总 The γ dose M is obtained through the second detection device 6. γ According to the total mixed radiation dose M 总 and γ dose M γ Determine the fast neutron dose M 快 ;

[0050] S500: Based on the total neutron dose D 中 and fast neutron dose M 快 Calculate the thermal neutron dose D in the test system filled with the first liquid. 热 .

[0051] In this embodiment, the fast neutron dose is obtained by measuring the radiation source using a paired ionization chamber testing system. At the same time, the thermal neutron dose and gamma dose can also be obtained, thereby enabling more accurate verification of the feasibility of the treatment plan. Specifically, the measurement method of the present invention is applied to a paired ionization chamber testing system. Its specific structure is that the container 33 can contain liquid. In this embodiment, the container 33 can be a water tank, but it is not limited to this. Those skilled in the art can use other containers that can contain liquid and install two detection devices inside them. In this embodiment, the first detection device 55 is the first ionization chamber and the second detection device 66 is the second ionization chamber. During measurement, the radiation port in the middle of the treatment head 22 emits a neutron beam 11. The neutron beam 11 passes through the liquid in the container 33 and then passes through the first detection device 55 and the second detection device 66 in its radiation direction, thereby testing the radiation dose in sequence.

[0052] It should be noted that the testing procedures in this invention are based on the different absorption amounts of different types of neutrons in different liquid environments, thereby achieving the classification and measurement of different neutron doses. Therefore, in practical applications, steps S200, S300, and S400 in this invention should not restrict the application and testing order of the first and second liquids. Those skilled in the art can adjust the selection of the first and second liquids in the testing order according to actual operation. Therefore, even if the application of the first and second liquids in the testing order is adjusted, it should be understood that it falls within the protection scope of this invention. Thus, the application order of the first and second liquids will not affect the protection scope of this invention.

[0053] The specific testing procedure involves first adding a first liquid to container 33, then placing the entire system in the test field. In this embodiment, water is used as the first liquid, but it can be selected as needed for other tests without affecting the scope of protection of this invention. The focus is on describing the principle and inventive concept. The treatment head 22 is turned on, and the radiation source radiates the neutron beam 11 towards the test equipment. Water is used as the first liquid, which has very little absorption effect on thermal neutrons, fast neutrons, and gamma doses. Therefore, the first detection device 55 can detect the total background dose, which is the sum of the above three, D. 总 The second detection device 66 tests the dose D of gamma rays. γ By subtracting the two, we can obtain the sum of the doses D of thermal neutrons and fast neutrons. 中 At this point, the treatment head 22 needs to be turned off, the radiation source needs to stop radiating, and the liquid in container 33 needs to be replaced with a second liquid. The second liquid is a new type of solution containing lithium-6, gadolinium-157, or boron-10. Any one of these three solutions can be used alone, or a mixture of two or all three can be used in any ratio. Standard solutions are preferred. Commercially available lithium single-element standard solutions, gadolinium single-element standard solutions, and boron single-element standard solutions have a concentration range of 0.1% to 99%. The lithium element standard solution... The enrichment range of lithium-6 in the liquid is 6%–98%, the enrichment range of gadolinium-157 in the gadolinium standard solution is 15%–98%, and the enrichment range of boron-10 in the boron standard solution is 19%–98%. These enrichment rates refer to the percentage of lithium-6, gadolinium-157, or boron-10 contained in the novel solution. The purpose of the second liquid is to reduce the influence of thermal neutrons on the first detection device 55. The second liquid has a relatively significant absorption effect on thermal neutrons. After the container 33 is filled, another measurement is performed to obtain the background total dose M. 总 γ dose M γ Subtracting the two yields the fast neutron dose M. 快 At this point, due to the change of solution, the influence of thermal neutrons is reduced with almost no change in the magnitude and distribution of fast neutron dose. Therefore, through D 中 Subtract M 快 By obtaining the thermal neutron dose, and simultaneously measuring the doses of other components in the background, it becomes possible to validate the treatment plan.

[0054] Based on the above embodiments, see [link / reference] Figure 4The core concept of this invention addresses the requirement that the fast neutron dose measured in the second liquid needs to be equivalent to the fast neutron dose in the first liquid. This involves using simulation to obtain the theoretical values ​​of the fast neutron absorption doses in both the first and second liquids, and then proportionally obtaining the fast neutron dose in the first liquid. It should be noted that there are various methods to simulate the fast neutron absorption amounts in the first and second liquids. This invention focuses on protecting the inventive concept, specifically using a Monte Carlo program. However, this does not affect the scope of protection of this application. The fast neutron absorption dose in the first liquid, i.e., water, can be simulated, denoted as N1; the fast neutron absorption dose in ordinary aqueous solutions can be simulated using a Monte Carlo program, denoted as N2; and the absorption dose can be obtained through formula D. 快 =N2 / N1×M 快 Obtain the equivalent value D 快 The ratio N2 / N1 is almost equal to 1, meaning that the second liquid, compared to the first liquid, reduces the thermal neutron background without significantly altering the magnitude and distribution of the fast neutron dose. This results in a smaller error in the fast neutron experimental measurement value D2. Furthermore, through equivalence conversion, the measurement results are more accurate and can be verified and compared with the simulation results of the treatment plan.

[0055] The first detection device 55 and the second detection device 66 respectively employ a TE-TE finger-type ionization chamber and a Mg-Ar finger-type ionization chamber, but this does not limit the scope of protection of the present invention. The TE-TE finger-type ionization chamber can detect neutron dose and gamma dose, while the Mg-Ar finger-type ionization chamber can only detect gamma dose.

[0056] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A fast neutron dosimetry method for boron neutron capture therapy, the dosimetry method being applied to a paired ionization chamber test system, the test system comprising a first detecting device, a second detecting device, and a container provided with a liquid, the first detecting device and the second detecting device being disposed in the container along a radiation direction, characterized in that, The measurement method includes the following steps: S100: Place the test system in the test field, fill the container with the first liquid, and turn on the radiation source; S200: Obtain the total mixed radiation dose D through the first detection device. 总 The gamma dose D is obtained through the second detection device. γ According to the total dose of mixed radiation D 总 and γ dose D γ Determine the total neutron dose D 中 ; S300: Turn off the radiation source, replace the first liquid in the container with a second liquid that can absorb thermal neutrons, place the test system in the test field, and turn the radiation source back on at the same power. S400: obtaining a mixed radiation total dose M by the first detecting device 总 , obtaining a gamma dose M by the second detecting device γ , determining a fast neutron dose M 总 based on the mixed radiation total dose M γ and the gamma dose M 快 ; S500: Calculate the thermal neutron dose D 中 and the fast neutron dose M 快 in the test system filled with the first liquid from the total neutron dose D 热 ; Step S500 specifically includes: S510: simulate the absorption dose of fast neutrons of the first liquid and the second liquid, and determine the fast neutron dose M in the test system filled with the second liquid according to the absorption dose of fast neutrons of the first liquid and the second liquid obtained by simulation 快 equivalent to the fast neutron dose D in the test system filled with the first liquid 快 ; S520: Calculate the thermal neutron dose in the test system filled with the first liquid by the following equation: D 热 = D 中 - D 快 .

2. The fast neutron dosimetry method for boron neutron capture therapy according to claim 1, characterized in that, Step S510 further includes: According to the Monte Carlo procedure, the absorbed dose of fast neutrons in the first liquid was obtained by simulation as N1. According to the Monte Carlo procedure, the absorption dose of fast neutrons in the second liquid was obtained by simulation as N2. The fast neutron dose in the test system filled with the first liquid is calculated by the following equation: D 快 = N2 / N1 x M 快 .

3. The fast neutron dosimetry method for boron neutron capture therapy according to claim 1 or 2, characterized in that, Step S200 further includes: Neutron total dose D 中 D = D 中 = D 总 -D γ .

4. The fast neutron dosimetry method for boron neutron capture therapy according to claim 1 or 2, characterized by, Step S400 further includes: Fast neutron dose M 快 = M 总 - M γ .

5. The fast neutron dosimetry method for boron neutron capture therapy according to claim 1 or 2, characterized by, The second liquid contains at least one of lithium-6, gadolinium-157, and boron-10.

6. The fast neutron dosimetry method for boron neutron capture therapy according to claim 5, characterized in that, The enrichment of lithium-6 in the second liquid ranges from 6% to 98%.

7. The fast neutron dosimetry method for boron neutron capture therapy according to claim 5, wherein, The enrichment of gadolinium-157 in the second liquid ranges from 15% to 98%.

8. The fast neutron dosimetry method for boron neutron capture therapy according to claim 5, wherein, The enrichment of boron-10 in the second liquid ranges from 19% to 98%.

9. The fast neutron dosimetry method for boron neutron capture therapy according to claim 1 or 2, characterized by, The first detection device is a TE-TE finger-type ionization chamber; and / or The second detection device is a Mg-Ar finger-type ionization chamber; and / or the first liquid is water.

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