Collimator and neutron capture treatment system

Abstract

The invention relates to a neutron capture therapy system. The neutron capture therapy system comprises a beam shaping body and a collimator, the beam shaping body comprises a target material, a beam inlet and a beam outlet which are arranged in the beam shaping body, the target material and a charged particle beam incident from the beam inlet are subjected to nuclear reaction to generate neutrons, the neutrons form neutron beams, the neutron beams are emitted from the beam outlet and define a neutron beam axis, and the collimator is arranged at the beam outlet; the collimator comprises a collimation body and a replacement part, the collimation body, the replacement part and the beam outlet are communicated, and at least part of the replacement part can be installed in the beam shaping body and can be detached from the collimation body. Compared with the beam shaping body and the collimating body, the replacement part of the collimator can be replaced, so that different beam shaping bodies can be adapted by selecting or replacing the replacement part meeting the requirement, the irradiation requirements of different treatment parts can be met, and the beam quality can be effectively ensured.

Description

Technical Field

[0001] The present application relates to the field of neutron therapy, and particularly to a collimator and a neutron capture therapy system. Background Art

[0002] The description in this part only provides background information related to the disclosure of the present application, and does not constitute prior art.

[0003] With the development of atomic science, neutron capture therapy (e.g., Boron Neutron Capture Therapy, BNCT) has become a new cancer treatment method with its precise targeting characteristics and high relative biological effectiveness. The treatment process is as follows: First, a boron-containing compound with specific adsorption ability to tumors is injected into the patient's body; then, after the 10 B atoms accumulate in the tumor, the tumor is irradiated with a beam of epithermal / thermal neutrons, and the neutrons are captured by the 10 B in the tumor and undergo a nuclear reaction. The α particles and 7 Li particles released by the reaction cause great damage to cells, and the total range is within one cell, so that tumor cells can be locally killed without damaging normal cells.

[0004] A neutron capture therapy system may include an accelerator and a beam shaping system. Among them, the beam shaping system may include a beam shaping body and a target material disposed in the beam shaping body. When the accelerator accelerates a charged particle beam to a sufficient extent to overcome the Coulomb repulsion of the atomic nucleus of the target material, the charged particle beam undergoes a nuclear reaction with the target material to generate neutrons, and after being adjusted by the energy spectrum of the beam shaping body (BSA), it is suitable for treatment.

[0005] Generally, a neutron capture therapy system may also include a collimator disposed downstream of the moderator along the direction of the beam movement, so as to collimate the neutron beam and reduce the exposure of neutrons and photons outside the treatment range. Currently, the collimators used in neutron capture therapy systems generally adopt two structures. The first type of collimator is a cylindrical structure with a hollow center in the shape of a frustum of a cone, which is not easy to disassemble and is mostly in a fixed configuration; the second type of collimator is based on the first type of collimator, and an externally extended fixed collimation structure is connected to meet the collimation requirements.

[0006] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solutions of the present application and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well-known to those skilled in the art just because these solutions are described in the background art part of the present application. Summary of the Invention

[0007] The present application creatively discovered that the collimator structure in the prior art is generally a fixed configuration. When the structure changes inside the beam shaper, the originally adapted collimator and beam shaper are no longer adapted. Especially for different treatment parts or different treatment populations, the treatment dose per unit time may change accordingly, and the structure of the beam shaper needs to be adjusted accordingly to meet different neutron beam intensity requirements.

[0008] For example, when the length of the moderator changes, the collimator that was originally attached to or adjacent to the moderator is no longer applicable. For example, when the length of the moderator increases, the moderator and the collimator cannot be installed. Therefore, a certain gap is usually reserved between the moderator and the collimator to avoid this situation. When the length of the moderator decreases, the gap between the moderator and the collimator will increase, or even increase further. Moreover, after many tests and studies, it has been shown that this gap between the moderator and the collimator is not conducive to the output neutron beam during actual use.

[0009] Therefore, for different beam shapers, especially for the needs of different treatment apertures corresponding to different treatment parts, how to make the collimator adapt to different beam shapers while ensuring the quality of the neutron beam is a technical problem that needs to be solved urgently.

[0010] In order to achieve the above-mentioned purpose, the present invention provides a neutron capture therapy system on one hand, which includes a beam shaper and a collimator; the beam shaper includes a target material, a beam inlet and a beam outlet arranged in the beam shaper, the target material undergoes a nuclear reaction with a charged particle beam incident from the beam inlet to produce neutrons, the neutrons form a neutron beam, the neutron beam is emitted from the beam outlet and defines a neutron beam axis, and the collimator is arranged at the beam outlet; the collimator includes a collimating body and a replacement part, the collimating body, the replacement part and the beam outlet are connected and arranged, and at least part of the replacement part can be installed in the beam shaper and can be separated from the collimating body and the beam shaper respectively.

[0011] Further, the replacement part has a first end and a second end opposite to each other along the axis direction of the neutron beam, the first end of the replacement part is adjacent to or in close contact with the collimating body, the second end of the replacement part is located inside the beam shaping body, and the interior of the beam shaping body has a wall surface adjacent to or in close contact with the second end of the replacement part.

[0012] Furthermore, the replacement part has a first end and a second end opposite to each other along the neutron beam axis direction, the first end of the replacement part can be separated from the collimation body, and the second end of the replacement part is fitted with the inside of the beam shaping body.

[0013] Further, at least part of the replacement part is made of any one or more of lead, molybdenum, bismuth, graphite, or Teflon.

[0014] Further, the inner surface of the replacement part is inclined from the beam inlet towards the collimating body to form a conical surface with a gradually decreasing diameter.

[0015] Further, the collimating body includes a reflection unit and a shielding unit wrapped outside the reflection unit, and the inner surface of the reflection unit is coplanar with the inner surface of the replacement part.

[0016] Further, the neutron capture therapy system further includes a moderator. Along the direction of the neutron beam axis, the replacement part has a preset length adapted to the distance formed between the collimating body and the moderator.

[0017] Further, the replacement part is of an integral structure, or,

[0018] the replacement part includes at least two replacement units, and the at least two replacement units are separable from each other.

[0019] Further, along the direction of the neutron beam axis, the lengths of at least two of the replacement units are different.

[0020] On the other hand, the present invention provides a collimator, which includes a collimating body and a replacement part. The collimating body has opposite first and second ends. The first end of the collimating body has a collimation outlet. The replacement part can be separated from the second end of the collimating body, and the collimating body and the replacement part are communicatively arranged.

[0021] Further, the replacement part extends in a direction away from the collimation outlet.

[0022] Further, at least part of the replacement part is made of any one or more of lead, molybdenum, bismuth, graphite, or Teflon.

[0023] Further, the inner surface of the replacement part is inclined along the direction of the collimation outlet to form a conical surface with a gradually decreasing diameter.

[0024] Further, the collimating body includes a reflection unit and a shielding unit wrapped outside the reflection unit, and the inner surface of the reflection unit is coplanar with the inner surface of the replacement part.

[0025] Further, the replacement part is of an integral structure, or the replacement part includes at least two replacement units, and the at least two replacement units are separable from each other.

[0026] Further, along the direction of the collimation outlet, the lengths of at least two of the replacement units are different.

[0027] With the above technical solution, the replacement part of the collimator in the present application is replaceable compared with the beam shaper and the collimator body. Therefore, different beam shapers can be adapted by selecting or replacing the replacement part that meets the requirements, so that not only the irradiation requirements of different treatment parts can be satisfied, but also the beam quality can be effectively guaranteed.

[0028] Referring to the following description and drawings, specific embodiments of the present application are disclosed in detail, indicating the ways in which the principles of the present application can be employed. It should be understood that the embodiments of the present application are not limited in scope thereby. Within the spirit and terms of the appended claims, the embodiments of the present application include many variations, modifications, and equivalents.

[0029] Features described and / or illustrated for one embodiment can be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0030] It should be emphasized that the terms "comprising / including" when used herein refer to the presence of features, wholes, steps, or components, but do not exclude the presence or addition of one or more other features, wholes, steps, or components. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure of the present application in any way. Additionally, the shapes and proportional dimensions of the components in the drawings are only schematic and are used to assist in understanding the present application, rather than specifically limiting the shapes and proportional dimensions of the components of the present application. Those skilled in the art can, under the teaching of the present application, select various possible shapes and proportional dimensions according to specific circumstances to implement the present application. In the drawings:

[0032] Figure 1 is a schematic diagram of the overall structure of a neutron capture therapy system provided by an embodiment of the present invention.

[0033] Figure 2 is a schematic diagram of the structure of a neutron capture therapy system provided by an embodiment of the present invention.

[0034] Figure 3 is a schematic diagram of the structure of a collimator provided by an embodiment of the present invention.

[0035] Figure 4 is a partially enlarged schematic diagram of a neutron capture therapy system provided by one embodiment of the present invention.

[0036] Figure 5 is a partially enlarged schematic diagram of a neutron capture therapy system provided by another embodiment of the present invention.

[0037] Figure 6Schematic diagram of a structure of an optional replacement part of the present invention.

[0038] Figure 7 Schematic diagram of a structure of another optional replacement part of the present invention.

[0039] Figure 8 Schematic diagram of a structure of yet another optional replacement part of the present invention.

[0040] Figure 9 Schematic diagram of a neutron capture therapy system provided by another embodiment of the present invention.

[0041] Figure 10 Schematic diagram of a neutron capture therapy system provided by yet another embodiment of the present invention.

[0042] The reference numerals of the above-mentioned drawings are: 1, beam shaper; 11, target material; 12, beam inlet; 13, beam outlet; 14, moderator; 15, main body; 151, reflector; 1511, first channel; 1512, first conical surface; 1513, second conical surface; 152, shield; 1521, second channel; 16, thermal neutron absorber; 2, collimator; 21, collimator body; 211, reflection unit; 212, shielding unit; 2121, neutron shielding layer; 2122, photon shielding layer; 213, support structure; 215, collimator outlet; 22, replacement part; 221, through hole; 222, replacement unit; X, neutron beam axis. Detailed implementation manners

[0043] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the protection scope of this application.

[0044] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiments.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0046] Each embodiment in this specification is described in a progressive manner. For the same or similar parts between the embodiments, reference can be made to each other, and the key points of each embodiment are the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and for the relevant parts, reference can be made to the partial description of the method embodiment.

[0047] It should be noted that in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and to distinguish similar objects, and there is no sequence between them, nor can they be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise stated, the meaning of "plurality" includes two or more.

[0048] As an effective means of treating cancer, neutron capture therapy has been increasingly applied in recent years. Among them, boron neutron capture therapy is the most common. The neutrons for boron neutron capture therapy can be supplied by a nuclear reactor or an accelerator. The embodiments of this application take accelerator boron neutron capture therapy as an example. The basic components of accelerator boron neutron capture therapy usually include an accelerator for accelerating charged particles (such as protons, deuterons, etc.) and a neutron capture therapy system. Among them, the neutron capture therapy system includes a target and a beam shaper. Among them, the accelerated charged particles interact with the target to generate neutrons. Appropriate nuclear reactions are selected according to characteristics such as the required neutron yield and energy, the available energy and current magnitude of the accelerated charged particles, and the physical and chemical properties of the target. The nuclear reactions often discussed are 7 Li(p,n) 7 Be and 9 Be(p,n) 9 B. Both of these reactions are endothermic reactions.

[0049] An ideal target should have characteristics such as a high neutron yield, a neutron energy distribution close to the epithermal neutron energy region (which will be described in detail below), no too much strong penetrating radiation generated, being safe, cheap, easy to operate, and high-temperature resistant. However, in fact, no nuclear reaction that meets all requirements can be found. In the embodiments of this application, a target made of lithium metal is used. However, as is well known to those skilled in the art, the material of the target can also be made of other metal materials other than the above-mentioned metal materials.

[0050] Regardless of whether the neutron source for boron neutron capture therapy comes from a nuclear reactor or the nuclear reaction of charged particles in an accelerator with a target material, the resulting is a mixed radiation field, that is, the beam contains neutrons and photons with energies ranging from low to high. For the boron neutron capture therapy of deep tumors, except for epithermal neutrons, the greater the content of the remaining radiation, the greater the proportion of non-selective dose deposition in normal tissues. Therefore, the radiation that causes unnecessary dose should be minimized as much as possible.

[0051] The International Atomic Energy Agency (IAEA) has given five recommendations on the air beam quality factors for clinical boron neutron capture therapy neutron sources. These five recommendations can be used to compare the advantages and disadvantages of different neutron sources and serve as a reference basis for selecting the neutron generation path and designing the beam shaper. The five recommendations are as follows:

[0052] Epithermal neutron flux > 1 x 10 9 n / cm 2 s

[0053] Fast neutron contamination < 2 x 10 -13 Gy-cm 2 / n

[0054] Photon contamination < 2 x 10 -13 Gy-cm 2 / n

[0055] Thermal to epithermal neutron flux ratio < 0.05 Epithermal neutron current to flux ratio > 0.7

[0056] Note: The epithermal neutron energy range is between 0.5 eV and 10 keV, the thermal neutron energy range is less than 0.5 eV, and the fast neutron energy range is greater than 10 keV.

[0057] 1. Epithermal neutron flux:

[0058] The neutron beam flux and the concentration of boron-containing drugs in the tumor jointly determine the clinical treatment time. If the concentration of boron-containing drugs in the tumor is high enough, the requirement for the neutron beam flux can be reduced; conversely, if the concentration of boron-containing drugs in the tumor is low, high-flux epithermal neutrons are required to give the tumor sufficient dose. The IAEA's requirement for the epithermal neutron flux is that the number of epithermal neutrons per square centimeter per second is greater than 10 9, at this flux, the neutron beam can generally control the treatment time within one hour for current boron-containing drugs. In addition to the advantages for patient positioning and comfort, the short treatment time can also make more effective use of the limited residence time of boron-containing drugs in tumors.

[0059] 2. Fast neutron contamination:

[0060] Since fast neutrons can cause unnecessary normal tissue doses, they are regarded as contamination. The magnitude of this dose is positively correlated with neutron energy. Therefore, the content of fast neutrons should be minimized in the design of neutron beams. Fast neutron contamination is defined as the fast neutron dose accompanied by a unit epithermal neutron flux. The IAEA's recommendation for fast neutron contamination is less than 2x10 -13 Gy-cm 2 / n.

[0061] 3. Photon contamination (γ-ray contamination):

[0062] γ-rays belong to strong penetrating radiation and will non-selectively cause dose deposition in all tissues along the beam path. Therefore, reducing the content of γ-rays is also a necessary requirement for neutron beam design. γ-ray contamination is defined as the γ-ray dose accompanied by a unit epithermal neutron flux. The IAEA's recommendation for γ-ray contamination is less than 2x10 -13 Gy-cm 2 / n.

[0063] 4. Ratio of thermal neutron to epithermal neutron flux:

[0064] Since thermal neutrons have a fast attenuation rate and poor penetration ability, most of their energy is deposited in the skin tissue after entering the human body. Except for epidermal tumors such as melanoma that require thermal neutrons as the neutron source for boron neutron capture therapy, the content of thermal neutrons should be reduced for deep tumors such as brain tumors. The IAEA's recommendation for the ratio of thermal neutron to epithermal neutron flux is less than 0.05.

[0065] 5. Ratio of neutron current to flux:

[0066] The ratio of neutron current to flux represents the directivity of the beam. The larger the ratio, the better the forwardness of the neutron beam. A neutron beam with high forwardness can reduce the dose to surrounding normal tissues caused by neutron divergence. In addition, it also improves the treatable depth and the flexibility of the positioning posture. The IAEA's recommendation for the ratio of neutron current to flux is greater than 0.7.

[0067] 1. Effective treatment depth:

[0068] The depth at which the tumor dose is equal to the maximum dose of normal tissues. At positions beyond this depth, the dose received by tumor cells is less than the maximum dose of normal tissues, and thus the advantage of boron neutron capture is lost. This parameter represents the penetration ability of the neutron beam. The greater the effective treatment depth, the deeper the tumors that can be treated, and the unit is cm.

[0069] 2. Effective treatment depth dose rate:

[0070] That is, the tumor dose rate at the effective treatment depth, which is also equal to the maximum dose rate of normal tissue. Since the total dose received by normal tissue is a factor affecting the total dose that can be given to the tumor, this parameter affects the length of the treatment time. The larger the effective treatment depth dose rate, the shorter the irradiation time required to give a certain dose to the tumor, and the unit is cGy / mA-min.

[0071] 3. Effective treatment dose ratio:

[0072] The ratio of the average doses received by the tumor and normal tissue from the brain surface to the effective treatment depth is called the effective treatment dose ratio; the calculation of the average dose can be obtained by integrating the dose-depth curve. The larger the effective treatment dose ratio, the better the treatment benefit of the neutron beam.

[0073] In order to have a basis for comparison in the design of the beam shaper, in addition to the five beam quality factors in air recommended by the IAEA and the above three parameters, the following parameters for evaluating the quality of the neutron beam dose performance are also used in the embodiments of the present application:

[0074] 1. Irradiation time ≤ 30 min (proton current used by the accelerator is 10 mA)

[0075] 2. The treatable depth of 30.0 RBE-Gy ≥ 7 cm

[0076] 3. The maximum tumor dose ≥ 60.0 RBE-Gy

[0077] 4. The maximum dose of normal brain tissue ≤ 12.5 RBE-Gy

[0078] 5. The maximum dose of skin ≤ 11.0 RBE-Gy

[0079] Note: RBE (Relative Biological Effectiveness) is the relative biological effect. Since the biological effects caused by photons and neutrons are different, the above dose terms are multiplied by the relative biological effects of different tissues to obtain the equivalent dose.

[0080] Refer to Figure 1 and Figure 2As shown, an embodiment of the present application discloses a neutron capture therapy system, which may include a beam shaper 1 and a collimator 2. Among them, the beam shaper 1 may include a main body 15, a target 11 and a moderator 14 arranged in the main body 15, a beam inlet 12 and a beam outlet 13. Among them, the main body 15 may include a reflector 151 wrapped outside the moderator 14 and a radiation shield 152 arranged in the beam shaper 1. The target 11 may be adjacent to the moderator 14. The target 11 undergoes a nuclear reaction with the proton beam incident from the beam inlet 12 to generate neutrons and form a neutron beam, and the neutron beam defines a main axis. The moderator 14 decelerates the neutrons generated from the target 11 to the epithermal neutron energy region, and the reflector 151 guides the neutrons deviating from the main axis back to the main axis to converge the epithermal neutrons. The radiation shield 152 is used to shield the leaked neutrons and photons to reduce the dose of normal tissues in the non-irradiated area. The neutron beam axis X can be understood as the overall or general movement direction of the proton beam from the target 11 to the moderator 14 to generate neutrons and then continue along the main axis towards the beam outlet 13.

[0081] The moderator 14 has a first side ( Figure 1 the right side in the figure) and a second side ( Figure 1 the left side in the figure) opposite to each other along the neutron beam axis X direction. Among them, the beam inlet 12 and the target 11 are arranged on the first side of the moderator 14. And the collimator 2 is arranged on the second side of the target 11. Combining Figure 2As shown, the collimator 2 includes a collimation body 21 and a replacement part 22. Among them, the collimation body 21 can be detachably connected to the beam shaper 1. For example, a detachable connection can be achieved through structures such as fasteners, quick-clamping structures, linkages, latches, concave-convex fasteners, etc. The replacement part 22 can be installed in the beam shaper 1 and can be separated from the beam shaper 1 and the collimation body 21 respectively. It can be understood that the fact that the replacement part 22 can be separated from the beam shaper 1 indicates that in an alternative embodiment, there may be a connection relationship between the replacement part 22 and the beam shaper 1. However, if necessary, the replacement part 22 and the beam shaper 1 can also be separated, disengaged, or moved away after disassembly; or, in another alternative embodiment, there is no direct connection relationship between the replacement part 22 and the beam shaper 1, but they are abutted between the beam shaper 1 and the collimation body 21 through the gap between the beam shaper 1 and the collimation body 21, and the replacement part 22 and the beam shaper 1 can be moved away, disengaged, or separated manually or by machine. The fact that the replacement part 22 can be separated from the collimation body 21 indicates that in an alternative embodiment, there may be a connection relationship between the replacement part 22 and the collimation body 21. However, if necessary, the replacement part 22 and the collimation body 21 can also be separated, disengaged, or moved away after disassembly, or, in another alternative embodiment, there is no direct connection relationship between the replacement part 22 and the collimation body 21, but they are abutted between the collimation body 21 and the beam shaper 1 through the gap between the collimation body 21 and the beam shaper 1, and the replacement part 22 and the collimation body 21 can be moved away, disengaged, or separated manually or by machine.

[0082] In other words, the replacement part 22 has at least two states. In the installed state, the replacement part 22 is installed inside the beam shaper 1. In the disassembled state, the replacement part 22 can be in a disassembled state with the beam shaper and the collimation body 21.

[0083] When the replacement part 22 is installed inside the beam shaper 1 and the collimation body 21 is installed on the beam shaper 1, the replacement part 22 is located between the moderator 14 and the collimation body 21 along the neutron beam axis X direction. In other words, the moderator 14, the replacement part 22, and the collimation body 21 are arranged along the neutron beam axis X direction ( Figure 1 the direction from right to left in the figure). The replacement part 22 also has a through hole 221. The through hole 221 penetrates the replacement part 22 along the neutron beam axis X direction, thereby connecting the beam outlet 13 and the collimation body 21, and further enabling the epithermal neutrons generated by the beam shaper 1 to be collimated by the collimation body 21 and then emitted outward.

[0084] Since the replacement part 22 is replaceable, it is possible to select or replace a replacement part 22 that meets the requirements according to the requirements of the beam energy range output by the beam shaper. That is, it is possible to select or replace a replacement part 22 that meets the requirements according to the actual parameters of the collimator body 21 and the beam shaper 1 (for example, the thickness of the moderator 14, whether a thermal neutron absorber 16 is installed (described in detail below), the thickness of the thermal neutron absorber 16, etc.). It can be understood that the length of the replacement part 22 that meets the requirements in the direction of the neutron beam axis X must be less than or equal to the distance between the moderator 14 and the collimator body 21 in the direction of the neutron beam axis X to avoid interference with the beam shaper 1 or the collimator body 21. Moreover, the replacement part 22 can utilize the gap space between the moderator 14 and the collimator body 21 in the direction of the neutron beam axis X, that is, reduce the distance between the moderator 14 and the collimator 2 in the direction of the neutron beam axis X, and can reflect neutrons deviating from the neutron beam back to the neutron beam to a certain extent, thereby increasing the intensity of the neutron beam current.

[0085] The replacement part 22 has a first end ( Figure 1 the right end in the figure) and a second end ( Figure 1 the left end in the figure) in the direction of the neutron beam axis X. In the installed state, in order to minimize the distance between the moderator 14 and the collimator 2 in the direction of the neutron beam axis X, a replacement part 22 with a more appropriate length and shape can be selected, so that the first end of the replacement part 22 can be as close to or fit against the second side of the moderator 14 as possible. Moreover, in order to minimize the distance between the second end of the replacement part 22 and the collimator body 21, a replacement part 22 with a more appropriate length and shape can be selected, so that the second end of the replacement part 22 can be as close to or fit against the collimator body 21 as possible.

[0086] For example, originally the length of the moderator 14 in the direction of the neutron beam axis X is 30 cm. At this time, the distance between the moderator 14 and the collimator body 21 in the direction of the neutron beam axis X is 8 cm. At this time, a replacement part 22 with a length of 8 cm can be selected. When the length of the moderator 14 in the direction of the neutron beam axis X is adjusted to 28 cm, and at this time the distance between the moderator 14 and the collimator body 21 in the direction of the neutron beam axis X is adjusted to 10 cm, a replacement part 22 with a length of 10 cm can be selected at this time. When the length of the moderator 14 in the direction of the neutron beam axis X is adjusted to 32 cm, and at this time the distance between the moderator 14 and the collimator body 21 in the direction of the neutron beam axis X is adjusted to 6 cm, a replacement part 22 with a length of 6 cm can be selected at this time. In summary, this neutron capture therapy system, especially the collimator 2 part, is easy to install and highly replaceable, and can meet the requirements of different beam shapers 1 (especially the moderator 14) while ensuring the intensity of the neutron beam current.

[0087] Ideally, the first end and the second end of the replacement part 22 are respectively in contact with the moderator 14 and the collimator body 21. However, considering the assembly accuracy or the actual situation, the first end and the second end of the replacement part 22 can be respectively as close as possible to the moderator 14 and the collimator body 21 (that is, there is a certain distance between the first end of the replacement part 22 and the moderator 14, and / or there is a certain distance between the second end of the replacement part 22 and the collimator body 21), or, in order to satisfy that the first end and the second end of the replacement part 22 are respectively adjacent to the moderator 14 or the collimator body 21, a corresponding assembly structure is adopted.

[0088] In order to further improve the collimation effect of the collimator 2, the replacement part 22 can be made of any one or more of materials with better reflection effects such as lead, molybdenum, bismuth, graphite or Teflon.

[0089] In order to further illustrate the influence of the replacement part 22 on the neutron beam, in this embodiment, the neutron beam parameters are also compared at different lengths along the X direction of the neutron beam axis and without the replacement part 22. Among them, the neutron source is the neutron beam moderated by the beam shaper 1, located on the upstream side of the replacement part 22, and the neutron direction is cosine distribution. The results are shown in Table 1. The epithermal neutron flux Φ ep_有 with the replacement part 22 installed and the epithermal neutron flux Φ ep_无 without the replacement part 22 installed has a ratio greater than 1, and the ratio increases as the length of the replacement part 22 increases. Therefore, by installing the replacement part 22, the intensity of the neutron beam can be increased, and the benefit increases as the length of the replacement part 22 increases.

[0090] Table 1 Comparison of neutron beam parameters without and with the replacement part 22 installed at different lengths

[0091]

[0092] In an alternative embodiment, the replacement part 22 can be detachably connected to the collimation body 21. After the replacement part 22 is installed on the collimation body 21, the replacement part 22 and the collimation body 21 are simultaneously installed on the beam shaper 1. Continuing with the previous embodiment, in order to match the length of the moderator 14 along the neutron beam axis X direction of 30 cm and the distance between the moderator 14 and the collimation body 21 along the neutron beam axis X direction of 8 cm, a replacement part 22 with a length of 8 cm can be selected first, and then the replacement part 22 with a length of 8 cm is detachably connected to the collimation body 21 through structures such as fasteners, quick-clamping structures, linkages, latches, concave-convex buttons, etc. Then, the collimation body 21 installed with the replacement part 22 is detachably connected to the beam shaper 1 through structures such as fasteners, quick-clamping structures, linkages, latches, concave-convex buttons, etc. During the process of installing the collimation body 21 installed with the replacement part 22 onto the beam shaper 1, the replacement part 22 extends into the interior of the beam shaper 1 until it abuts or is adjacent to the second side of the moderator 14.

[0093] In an alternative embodiment, the replacement part 22 can be detachably connected to the beam shaper 1. Before the collimation body 21 is installed on the beam shaper 1, the replacement part 22 is first installed on the beam shaper 1. Continuing with the previous embodiment, in order to match the length of the moderator 14 along the neutron beam axis X direction of 32 cm and the distance between the moderator 14 and the collimation body 21 along the neutron beam axis X direction of 6 cm, a replacement part 22 with a length of 6 cm can be selected first, and then the replacement part 22 with a length of 6 cm is detachably connected to the beam shaper 1 through structures such as fasteners, quick-clamping structures, linkages, latches, concave-convex buttons, etc. Then, the collimation body 21 is detachably connected to the beam shaper 1 through structures such as fasteners, quick-clamping structures, linkages, latches, concave-convex buttons, etc. During the process of installing the replacement part 22 onto the beam shaper 1, the replacement part 22 extends into the interior of the beam shaper 1 until it abuts or is adjacent to the second side of the moderator 14. After the collimation body 21 is installed on the beam shaper 1, the collimation body 21 abuts or is adjacent to the second end of the replacement part 22.

[0094] In an alternative embodiment, the replacement part 22 can be in transitional fit with the beam shaper 1 by means of embedding or the like. Before the collimation body 21 is installed on the beam shaper 1, the replacement part 22 is first placed (i.e., installed) inside the beam shaper 1. Continuing with the previous embodiment, in order to match the length of the moderator 14 along the neutron beam axis X being 28 and the distance between the moderator 14 and the collimation body 21 along the neutron beam axis X being 10 cm, a replacement part 22 with a length of 10 cm can be selected first, and then the replacement part 22 with a length of 10 cm is placed inside the beam shaper 1 by means of embedding or the like. Then, the collimation body 21 is detachably connected to the beam shaper 1 through structures such as fasteners, quick-clamping structures, linkages, latches, concave-convex fasteners, etc. During the process of placing the replacement part 22 inside the beam shaper 1, the replacement part 22 extends into the interior of the beam shaper 1 until it fits or is adjacent to the second side of the moderator 14. After the collimation body 21 is installed on the beam shaper 1, the collimation body 21 fits or is adjacent to the second end of the replacement part 22.

[0095] In summary, the neutron capture therapy system in this application can be assembled and replaced with matching replacement parts according to treatment requirements, so it has strong replaceability.

[0096] The following takes Figure 1 and 2 as examples to specifically illustrate an embodiment of this application. Referring to Figure 1 and 2 shown, the neutron capture therapy system includes a beam shaper 1 and a collimator 2. The neutron capture therapy system includes a main body 15, a moderator 14, a target 11, and a beam inlet 12. The main body 15 includes a reflector 151 and a shield 152 arranged in sequence along the neutron beam axis X. That is, the shield 152 is located on the downstream side of the reflector 151 along the neutron beam axis X ( Figure 2 the left side in

[0097] The moderator 14 has an upstream side ( Figure 2 the right side in Figure 2On the upper left side. The beam entrance 12 and the target 11 are both provided on the upstream side of the moderator 14. When the replacement part 22 is installed in the beam shaper 1 (reflector 151), the replacement part 22 is located on the downstream side of the moderator 14. Moreover, the upstream end of the replacement part 22 is adjacent to or in contact with the downstream side of the moderator 14.

[0098] Combined Figure 2 and Figure 3 As shown, for the convenience of installing the collimation body 21, generally, the second channel 1521 of the shielding body 152 is larger than the first channel 1511 of the reflector 151, so as to expose a part of the downstream end face of the reflector 151. The collimation body 21 can be connected to the downstream end face of the exposed part of the reflector 151 through fasteners such as fastening bolts. In this embodiment, the collimation body 21 can include a reflection unit 211 and a shielding unit 212 wrapped outside the reflection unit 211. The inner surface of the reflection unit 211 is inclined to form a conical surface with a gradually decreasing diameter along the neutron beam axis X direction ( Figure 1 from right to left in the figure). The reflection unit 211 is used to reflect the neutrons deviating from the neutron beam back to the neutron beam to improve the neutron beam intensity and play a collimation role, and a material with a relatively large neutron elastic scattering cross-section can be used. For example, the reflection unit 211 can be made of any one or more of lead, molybdenum, bismuth, graphite or Teflon. The shielding unit 212 can include a neutron shielding layer 2121 and a photon shielding layer 2122 wrapped outside the neutron shielding layer 2121. A neutron absorption material is added to the shielding material in the neutron shielding layer 2121 to prevent neutron leakage, and the shielding material also has a reflection effect and can improve the neutron beam intensity. Among them, the material of the neutron shielding layer 2121 includes but is not limited to polyethylene (PE). The photon shielding layer 2122 is used to shield the photons in the beam current and reduce photon contamination. Among them, the material of the photon shielding layer 2122 includes but is not limited to lead (Pb).

[0099] The collimation body 21 can further include a support structure 213, and this support structure 213 is used to fix the remaining components of the collimation body 21 and facilitate disassembly. Specifically, this support structure 213 is wrapped outside the shielding unit 212, and is fixed to the reflection unit 211 and the shielding unit 212 through a pressing block. Generally, the support structure 213 can also include a first support part and a second support part. Among them, the first support part is adapted to the inner side wall of the shielding body 152 for forming the second channel 1521, and the second support part is in contact with the downstream side wall of the shielding body 152.

[0100] To verify the performance superiority of multi-layer materials compared with single-layer or double-layer materials, in this embodiment, the comparison is respectively made between Figure 2 or Figure 3The collimator 2 of the multi-layer material shown (including the reflection unit 211, the neutron shielding layer 2121, and the photon shielding layer 2122), the collimator of the double-layer material (including the neutron shielding layer 2121 made of boron-containing polyethylene (PE) material or boron-containing polyethylene material or lithium-containing polyethylene material, and the photon shielding layer 2122 made of lead), and the collimator of the single-layer material (including the neutron shielding layer 2121 made of boron-containing polyethylene (PE) material). The neutron beam performance in these three cases. The neutron source is the neutron beam moderated by the beam shaper 1, located at the entrance of the collimator 2, and the neutron direction is cosine-distributed. The evaluation parameters are the epithermal neutron flux Φ ep (n·cm -2 ·s -1 ), the neutron flux at the beam exit of the collimator 2 with an energy between 0.5 eV - 10 keV; the fast neutron contamination D f / Φ ep (Gy·cm 2 ), the fast neutron dose accompanying per unit epithermal neutron flux at the beam exit of the collimator 2; the photon contamination D γ / Φ ep (Gy·cm 2 ), the γ-ray dose accompanying per unit epithermal neutron flux at the beam exit of the collimator 2. All calculation results are normalized with Φ ep of the multi-layer material as the benchmark.

[0101] The comparison of the neutron beam parameters of the collimator 2 composed of the above three different materials is shown in Table 2. For the epithermal neutron flux, the multi-layer material has a significantly higher epithermal neutron flux compared to the combination of the double-layer material (boron-containing PE and lead) and the single-layer material (boron-containing PE). The performance of the double-layer material (boron-containing PE and lead) and the single-layer material (boron-containing PE) is comparable; for the fast neutron contamination, the performance of the three is comparable; for the photon contamination, the multi-layer material combination is significantly lower than the other two, and the difference is nearly 8 - 10 times. Therefore, the multi-layer material combination can improve the epithermal neutron flux and reduce the beam radiation contamination, and is more suitable for actual needs.

[0102] Table 2 Comparison of neutron beam parameters of collimator 2 with different component materials

[0103] Beam evaluation parameters This embodiment (multi-layer material) Double-layer material Single-layer material <![CDATA[Normalize Φ ep > 1 0.767 0.769 <![CDATA[Normalized D f / Φ ep > 1 1.008 0.974 <![CDATA[Normalized D γ / Φ ep > 1 7.868 9.997

[0104] In this embodiment, the replacement part 22 can also be detachably connected to the collimation body 21 by means of fasteners, adhesives, etc. In order to further improve the neutron converging effect of the replacement part 22, the inner surface of the replacement part 22 slopes from the beam inlet 12 towards the collimation body 21 to form a conical surface with a gradually decreasing diameter. Of course, in other alternative embodiments, the inner surface of the replacement part 22 can also be set to be circular, stepped, arc-shaped, etc. according to needs. Generally, the outer surface of the replacement part 22 is adapted to the inner side wall of the reflector 151 for forming the first channel 1511, that is, a circular surface. Of course, in other alternative embodiments, the outer surface of the replacement part 22 can also be square, oval, etc., as long as part or all of the replacement part 22 can be placed inside the reflector 151.

[0105] In this embodiment, the upstream side of the reflection unit 211 has a first wall surface located in the first channel 1511 of the reflector 151. The replacement part 22 can be detachably connected to the first wall surface of the reflection unit 211 by means of fasteners, adhesives, etc. Preferably, the inner surface of the reflection unit 211 and the inner surface of the replacement part 22 are coplanar. The material of the replacement part 22 is the same as that of the reflection unit 211. Thereby, the collimation effect of the collimator 2 on thermal neutrons / super-thermal neutrons can be made more stable.

[0106] Refer to Figure 4 As shown, the inner surface of the reflection unit 211 and the inner surface of the replacement part 22 can also form an angle other than 0° or 180°. Refer to Figure 5 As shown, the inner surface of the reflection unit 211 can also be stepped. Of course, in other alternative embodiments, the inner surface of the reflection unit 211 can also be set to other shapes according to needs.

[0107] In this embodiment, the replacement part 22 can be of an integral structure. Of course, in other alternative embodiments, refer to Figure 6As shown, the replacement part 22 may also include at least two replacement units 222 as needed. The at least two replacement units 222 are detachably connected by means such as fasteners or adhesives. Preferably, the at least two replacement units 222 are arranged along the neutron beam axis X direction. Among them, the length of each replacement unit 222 can be the same. For example, the length of each replacement unit 222 can be 1 cm. When a replacement part 22 with a length of 6 cm is needed, 6 replacement units 222 are required. When a replacement part 22 with a length of 8 cm is needed, 8 replacement units 222 are required. Alternatively, the lengths of the replacement units 222 can be designed to be different lengths so as to meet the stacking requirements. For example, the lengths of the respective replacement units 222 can be set to 1 cm, 2 cm, 5 cm, etc. When a replacement part 22 with a length of 6 cm is needed, two replacement units 222 with lengths of 1 cm and 5 cm can be selected. When a replacement part 22 with a length of 8 cm is needed, three replacement units 222 with lengths of 1 cm, 2 cm, and 5 cm can be selected.

[0108] Referring to Figure 6 As shown, the inner surfaces of the replacement units 222 can be coplanar. Referring to Figure 7 As shown, an angle other than 0° or 180° can be formed between the inner surfaces of the respective replacement units 222. Referring to Figure 8 As shown, the inner surfaces of the respective replacement units 222 can also be non-coplanar and in a stepped shape. Of course, in other alternative embodiments, the inner surfaces of the respective replacement units 222 can also be set to other shapes as needed.

[0109] Referring to Figure 9As shown, in another alternative embodiment, the first channel 1511 of the reflector 151 includes a first conical surface 1512 and a second conical surface 1513 arranged along the neutron beam axis X direction. The first conical surface 1512 is inclined along the neutron beam axis X direction to form a conical surface with a gradually increasing diameter. The second conical surface 1513 is inclined along the neutron beam axis X direction to form a conical surface with a gradually decreasing diameter. Correspondingly, the moderator 14 has a first end and a second end corresponding to the neutron beam axis X direction. The outer wall surface of the first end of the moderator 14 is inclined along the neutron beam axis X direction to form a conical surface with a gradually increasing diameter, and the outer wall surface of the first end of the moderator 14 is adapted to the first conical surface 1512. The outer wall surface of the second end of the moderator 14 is inclined along the neutron beam axis X direction to form a conical surface with a gradually decreasing diameter. The outer wall surface of the second end of the moderator 14 is adapted to the second conical surface 1513. In this embodiment, the outer wall surface of the replacement part 22 is inclined along the neutron beam axis X direction to form a conical surface with a gradually decreasing diameter. Moreover, the outer wall surface of the replacement part 22 cooperates with the second conical surface 1513 of the reflector 151, so that the replacement part 22 can be embedded in the reflector 151. As described above, before the collimation body 21 is installed on the beam shaper 1, the replacement part 22 is first embedded in the beam shaper 1.

[0110] In the structure of some beam shapers 1, due to structural limitations, the upstream end of the replacement part 22 can only be in contact with or close to the inner wall surface of the beam shaper 1 without interference, so as to be as close as possible to the moderator 14. Refer to Figure 10 As shown, for example, in an alternative embodiment, a thermal neutron absorber 16 adjacent to the moderator 14 can also be provided on the downstream side ( Figure 10 the left side in Figure 10 ) of the moderator 14. The thermal neutron absorber 16 is used to absorb thermal neutrons to avoid excessive dose to the superficial normal tissues during treatment. When the replacement part 22 is installed in the beam shaper 1, the upstream end of the replacement part 22 can be adjacent to or in contact with the thermal neutron absorber 16, so as to be as close as possible to the moderator 14 to adapt to the lengths of different moderators 14 required for different beam output energy requirements. Also, for example, in an alternative embodiment, a part of the reflector 151 not only wraps around the circumferential side of the moderator 14, but also a part of the reflector 151 also wraps around the downstream side (

[0111] the left side in Figure 3As shown, the present application further includes a collimator 2, which includes a collimator body 21 and a replacement part 22. The first end of the collimator body 21 has a collimation outlet 215. The replacement part 22 can be disassembled from the second end of the collimator body 21.

[0112] In an alternative embodiment, there may be a connection relationship between the replacement part 22 and the second end of the collimator body 21. However, if necessary, the replacement part 22 and the second end of the collimator body 21 can also be separated, disengaged or moved away after disassembly.

[0113] In another alternative embodiment, the replacement part 22 and the collimator body 21 have no direct connection relationship. However, the replacement part 22 and the collimator body 21 can be moved away, disengaged or separated by manual or machine means. The collimator body 21 and the replacement part 22 are communicatively arranged.

[0114] In other words, the replacement part 22 has at least two states. In the disassembled state, the replacement part 22 can be detached, separated or moved away from the collimator body 21, so that the replacement part 22 can be selected and / or replaced as needed. After the replacement part 22 is selected, the replacement part 22 can be installed, so that the replacement part 22 is switched to the installed state. In the installed state, the replacement part 22 is adjacent to or abuts against the second end of the collimator body 21. The through hole 221 of the replacement part 22 communicates with the collimation outlet 215. The replacement part 22 and the collimator body 21 can be in a state of being about to be installed together on the beam shaper 1 or having been installed together on the beam shaper 1, or they can also be in a state of having been separately installed on the beam shaper 1. At this time, thermal neutrons / epithermal neutrons can leave through the collimation outlet 215 via the through hole 221 of the replacement part 22 after passing through the collimation action of the replacement part 22 and the collimator body 21. When the replacement part 22 needs to be replaced, the replacement part 22 can be removed from the collimator body 21 and / or the beam shaper 1, so that the replacement part 22 to be replaced is switched to the disassembled state, so as to facilitate the replacement with a new replacement part 22.

[0115] It should be understood that the above description is for illustrative purposes and not for limitation. By reading the above description, many embodiments and many applications other than the provided examples will be obvious to those skilled in the art. Therefore, the scope of this teaching should not be determined by reference to the above description, but should be determined by reference to the full scope of the foregoing claims and the equivalents of these claims. For the sake of completeness, all articles and references, including patent applications and published announcements, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to abandon such subject matter, nor should it be considered that the applicant has not considered such subject matter as part of the disclosed subject matter of the application.

Claims

1. A neutron capture therapy system, characterized in that, The neutron capture therapy system includes a beam shaper and a collimator; the beam shaper includes a target, a beam inlet, and a beam outlet disposed within the beam shaper. The target undergoes a nuclear reaction with the charged particle beam incident from the beam inlet to generate neutrons. The neutrons form a neutron beam, which exits from the beam outlet and defines a neutron beam axis. The collimator is disposed at the beam outlet; The collimator includes a collimator body and a replacement part. The collimator body, the replacement part, and the beam outlet are communicatively disposed. At least a part of the replacement part can be installed inside the beam shaper and can be disassembled from the collimator body and the beam shaper respectively.

2. The neutron capture therapy system according to claim 1, characterized in that, The replacement part has a first end and a second end opposite to each other along the neutron beam axis direction. The first end of the replacement part is adjacent to or in contact with the collimator body, and the second end of the replacement part is located inside the beam shaper. The inside of the beam shaper has a wall surface adjacent to or in contact with the second end of the replacement part.

3. The neutron capture therapy system according to claim 1, wherein, The replacement part has a first end and a second end opposite to each other along the neutron beam axis direction. The first end of the replacement part can be disassembled from the collimator body, and the second end of the replacement part is in contact with the inside of the beam shaper.

4. The neutron capture therapy system according to claim 1, characterized in that At least a part of the replacement part is made of any one or more of lead, molybdenum, bismuth, graphite, or Teflon.

5. The neutron capture therapy system according to claim 1, characterized in that, The inner surface of the replacement part is inclined from the beam inlet towards the collimator body to form a conical surface with a gradually decreasing diameter.

6. The neutron capture therapy system according to claim 5, wherein The collimator body includes a reflection unit and a shielding unit wrapped outside the reflection unit. The inner surface of the reflection unit is coplanar with the inner surface of the replacement part.

7. The neutron capture therapy system according to claim 1, characterized in that, The neutron capture therapy system further includes a moderator. Along the neutron beam axis direction, the replacement part has a preset length adapted to the distance formed between the collimator body and the moderator.

8. The neutron capture therapy system according to claim 1, wherein The replacement part is of an integral structure, or, The replacement part includes at least two replacement units, and the at least two replacement units are separable from each other.

9. The neutron capture therapy system according to claim 8, wherein, Along the neutron beam axis direction, the lengths of the at least two replacement units are different.

10. A collimator, characterized in that, It includes a collimator body and a replacement part. The collimator body has a first end and a second end opposite to each other. The first end of the collimator body has a collimation outlet. The replacement part can be disassembled from the second end of the collimator body, and the collimator body and the replacement part are communicatively disposed.

11. The collimator according to claim 10, characterized in that, The replacement part is of an integral structure, or, The replacement part includes at least two replacement units, and the at least two replacement units are separable from each other.

12. The collimator according to claim 11, wherein, Along the collimation outlet direction, the lengths of the at least two replacement units are different.

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