Beam shaper and neutron capture therapy system

Abstract

One aspect of the present invention relates to a beam shaper (131) used in a neutron capture therapy system (100). The beam shaper (131) includes a moderator (1312), a reflector (1313), and an epithermal neutron flux increaser (1316), where the moderator (1312) moderates neutrons of a neutron beam (N) into epithermal neutrons, the reflector (1313) surrounds the moderator (1312) and reflects neutrons that deviate from the neutron beam (N) back into the neutron beam (N) to increase the intensity of the neutron beam (N), and the epithermal neutron flux increaser (1316) increases the epithermal neutron flux in the neutron beam (N) and is installed within the moderator (1312) and / or the reflector (1313) and / or between the moderator (1312) and the reflector (1313). Another aspect of the present invention relates to a neutron capture therapy system (100) including the beam shaper (131). By installing an epithermal neutron flux increaser (1316) within the beam shaper (131), the epithermal neutron flux in the neutron beam (N) is increased to improve the flux and quality of the neutron source.

Description

[Technical Field]

[0001] The present invention relates to the field of radiation delivery, and in particular to beam shapers and neutron capture therapy systems. [Background technology]

[0002] With the development of atomic science, radiation therapy using cobalt-60, linear accelerators, electron beams, etc. has become one of the main means of cancer treatment. However, conventional photon or electron therapy kills tumor cells due to the limitations of the physical conditions of the radiation itself, while damaging many normal tissues along the beam path. In addition, tumor cells have different degrees of sensitivity to radiation, so conventional radiation therapy has low therapeutic effectiveness against malignant tumors with high radiation resistance (e.g., glioblastoma multiforme, melanoma).

[0003] To reduce radiation damage to normal tissues surrounding tumors, the concept of targeted therapy in chemotherapy has been applied to radiotherapy. Furthermore, to target highly radiation-resistant tumor cells, radiation sources with high relative biological effectiveness (RBE) are currently being actively developed, such as proton therapy, heavy ion therapy, and neutron capture therapy. Among these, neutron capture therapy combines the two concepts mentioned above. For example, in boron neutron capture therapy, boron-containing drugs specifically concentrate in tumor cells, and, combined with precise neutron beam control, this offers a better cancer treatment option than conventional radiation.

[0004] In boron neutron capture therapy (BNCT), boron-containing drugs specifically collect in tumor cells, and when combined with the irradiation of a highly precise neutron beam, it offers a better cancer treatment option than conventional radiation therapy. In the boron neutron capture therapy process, a patient is first injected with a boron (B-10)-containing drug that has a high affinity for and selectively collects in tumor cells, and then a neutron beam is irradiated onto the patient's tumor site. The neutrons are then injected into the tumor cells. 10 When captured by B, it undergoes fission into α particles and 7 It generates Li particles and emits highly lethal radiation, which has a short range, equivalent to the length of just one tumor cell, precisely killing tumor cells while minimizing damage to surrounding normal cells.

[0005] Since the effectiveness of boron neutron capture therapy depends on the concentration of boron-containing drugs and the number of thermal neutrons at the location of tumor cells, it is also called two-dimensional radiation cancer therapy (binary cancer therapy). Therefore, in addition to the development of boron-containing drugs, the improvement of the flux and quality of neutron sources plays an important role in the research of boron neutron capture therapy. Summary of the Invention

[0006] In order to improve the flux and quality of a neutron source, a beam shaper used in neutron capture therapy according to one aspect of the present invention includes a moderator, a reflector, and an epithermal neutron flux increaser, wherein the moderator moderates neutrons of a neutron beam defining a beam axis into epithermal neutrons and extends a first predetermined length along the beam axis and a first predetermined width along a radial direction of the beam axis, and the reflector surrounds the moderator and reflects neutrons deviating from the neutron beam back into the neutron beam to improve the intensity of the neutron beam. At least a portion of the reflectors extend a second predetermined length along the beam axis and extend a second predetermined width radially of the beam axis outside the moderator, and the epithermal neutron flux augmenters increase the epithermal neutron flux in the neutron beam and are installed within the moderator and / or the reflector and / or between the moderator and the reflector, extending a third predetermined length along the beam axis and a third predetermined width radially of the beam axis, the third predetermined width being smaller than the sum of the first predetermined width and the second predetermined width. By installing the epithermal neutron flux augmenters within the beam shaper, the epithermal neutron flux in the neutron beam is increased to improve the flux and quality of the neutron source.

[0007] In one embodiment, the beam shaper further includes a beam entrance and a beam exit, the beam entrance being used for inputting the charged particle beam and the beam exit being used for outputting the neutron beam, and the beam entrance, the moderator and the beam exit being arranged along the extension direction of the beam axis.

[0008] In one embodiment, the beam shaper further includes a radiation shield surrounding the reflector, the radiation shield blocking leaked neutrons and photons to reduce the dose to normal tissue in the non-irradiated area, extending a fourth predetermined length along the beam axis and extending a fourth predetermined width radially of the beam axis outside the reflector.

[0009] In one embodiment, the reflector is made of Pb, and the moderator is made of at least one of D2O, AlF3, CaF2, Li2CO3, MgF2, Al2O3, and a material obtained by mixing Al, AlF3, and LiF in a predetermined ratio.

[0010] In one embodiment, the epithermal flux increaser is made of Ni material.

[0011] In one embodiment, the epithermal neutron flux augmenting body is configured as a cylindrical structure, which includes a first side portion and a second side portion perpendicular to the beam axis, and a first wall and a second wall closed circumferentially around the beam axis, the first side portion and the second side portion being arranged in order at both ends of the cylindrical structure along the neutron beam direction, the first side portion having a first central hole connected to the beam inlet, and the second side portion having a second central hole connected to the beam outlet.

[0012] In one embodiment, the first side and / or the second side of the epithermal neutron flux augmenter having a cylindrical structure is configured as a cone-shaped structure narrowing toward the beam axis, the first side has an outer contour whose radial dimension gradually increases along the neutron beam direction and the first central hole has a dimension that accommodates at least the beam inlet, and the second side has an outer contour whose radial dimension gradually decreases along the neutron beam direction and the second central hole of the second side has a dimension that accommodates at least the beam outlet.

[0013] In one embodiment, the epithermal neutron flux augmenting body has a thickness of 1-8 cm, more preferably, the epithermal neutron flux augmenting body has a thickness of 3-5 cm.

[0014] In one embodiment, the epithermal neutron flux augmenting body is configured as a cone-shaped structure, which includes first and second end faces perpendicular to the beam axis, and third and fourth walls circumferentially closed around the beam axis, and the first and second end faces are arranged in order along the neutron beam direction and are both arranged so as to be open.

[0015] In one embodiment, an epithermal neutron flux augmenting body having a cone-shaped structure has an outer contour whose radial dimension gradually increases along the neutron beam direction, and the first end face is adjacent to the end face of the moderator body located upstream in the neutron beam direction and has a dimension that accommodates at least the beam inlet.

[0016] In one embodiment, the epithermal neutron flux augmenting body has a cone-shaped structure, the radial dimension of the outer contour of which gradually decreases along the neutron beam direction, and the second end face is adjacent to the end face of the beam shaper located downstream in the neutron beam direction and has a dimension to accommodate at least the beam exit. At the beam exit position, the epithermal neutron flux augmenting body is installed on the cone-shaped structure to reflect more epithermal neutrons into the neutron beam, thereby increasing the epithermal neutron beam flux.

[0017] In one embodiment, the epithermal neutron flux augmenter has a cylindrical or conical structure, and the centerline of the epithermal neutron flux augmenter overlaps with the beam axis.

[0018] A neutron capture therapy system according to another aspect of the present invention includes a charged particle beam generator, a neutron generator, and a beam transporter, wherein the charged particle beam generator generates a charged particle beam, the neutron generator generates a neutron beam, and includes a target and a beam shaper, and the beam transporter transports the charged particle beam to the neutron generator, where the charged particle beam interacts with the target to generate a neutron beam, and the neutron beam is slowed down by the beam shaper and then forms an epithermal neutron beam required for neutron capture therapy.

[0019] In one embodiment, the beam shaper includes a moderator, a reflector, and an epithermal neutron flux increaser, the moderator moderating neutrons of a neutron beam defining a beam axis into epithermal neutrons and extending a first predetermined length along the beam axis and a first predetermined width along a radial direction of the beam axis, the reflector surrounding the moderator and reflecting neutrons deviating from the neutron beam back into the neutron beam to improve the intensity of the neutron beam, and at least a portion of the reflector extending along the beam axis. the epithermal neutron flux augmenting body increases the epithermal neutron flux in the neutron beam, is installed within the moderator body and / or within the reflector and / or between the moderator body and the reflector, and extends by a third predetermined length along the beam axis and by a third predetermined width along the radial direction of the beam axis, the third predetermined width being smaller than the sum of the first predetermined width and the second predetermined width. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of a boron neutron capture reaction. [Figure 2] This is the nuclear reaction equation for neutron capture in 10B(n,α)7Li. [Figure 3] 1 is a schematic configuration diagram of a neutron capture therapy system according to one embodiment of the present invention. [Figure 4] 1 is a schematic diagram of a beam shaper in which an epithermal neutron flux augmenter has a cylindrical structure and at least a part of it is installed inside a moderator according to one embodiment of the present invention. FIG. [Figure 5] FIG. 2 is a schematic dimensional diagram of a beam shaper in which an epithermal neutron flux augmenter has a cylindrical structure and at least a portion of the beam shaper is installed within a moderator according to one embodiment of the present invention. [Figure 6] FIG. 1 is a schematic radial dimension diagram of a beam shaper in which an epithermal neutron flux augmenter has a cylindrical structure and at least a part of it is installed inside a moderator according to one embodiment of the present invention. [Figure 7] 1 is a schematic diagram of an epithermal neutron flux increasing layer having a cylindrical structure according to an embodiment of the present invention. FIG. [Figure 8] 1 is a cross-sectional view of an epithermal neutron flux enhancing layer having a cylindrical structure according to one embodiment of the present invention. [Figure 9] FIG. 2 is a schematic diagram of an epithermal neutron flux augmenting body having a cylindrical structure and a beam shaper installed inside a reflector according to one embodiment of the present invention. [Figure 10] FIG. 2 is a schematic radial dimension diagram of a beam shaper in an epithermal neutron flux augmenter having a cylindrical structure and installed in a reflector according to one embodiment of the present invention. [Figure 11] 1 is a schematic diagram of a beam shaper in which one side of an epithermal neutron flux increasing body having a cylindrical structure is a cone-shaped structure according to an embodiment of the present invention; FIG. [Figure 12] FIG. 1 is a schematic diagram illustrating the configuration of a beam shaper in which both sides of an epithermal neutron flux increasing body having a cylindrical structure are cone-shaped structures, according to one embodiment of the present invention. [Figure 13] 1 is a schematic diagram of an epithermal neutron flux increasing layer having a cylindrical structure with conical structures on both sides according to an embodiment of the present invention; FIG. [Figure 14] 1 is a cross-sectional view of an epithermal neutron flux augmentation layer having a cylindrical structure with conical structures on both sides according to one embodiment of the present invention. [Figure 15(a)] FIG. 10 is a graph showing the tendency of Φep ​​to change with the thickness of the epithermal neutron flux increasing layer according to an embodiment of the present invention. [Figure 15(b)] FIG. 10 is a graph showing the tendency of Jep / Φep to change with the thickness of the epithermal neutron flux increasing layer according to an embodiment of the present invention. [Figure 15(c)] FIG. 10 is a graph showing the tendency of Df / Φep to change with the thickness of the epithermal neutron flux increasing layer according to an embodiment of the present invention. [Figure 15(d)] Dγ / Φep tends to change with the thickness of the epithermal neutron flux increasing layer according to one embodiment of the present invention. [Figure 15(e)] FIG. 10 is a graph showing the tendency of Φth / Φep to change with the thickness of the epithermal neutron flux increasing layer according to an embodiment of the present invention. [Figure 16]FIG. 1 is a schematic diagram of a beam shaper in which an epithermal neutron flux augmenter has a cone-shaped structure and is located upstream along the neutron beam direction, according to one embodiment of the present invention. [Figure 17] FIG. 1 is a schematic dimensional diagram of an epithermal neutron flux augmenter having a cone-shaped structure and a beam shaper located upstream along the neutron beam direction, according to one embodiment of the present invention. [Figure 18] FIG. 1 is a schematic radial dimension diagram of a beam shaper in which the epithermal neutron flux augmenter has a cone-shaped structure and is located upstream along the neutron beam direction, according to one embodiment of the present invention. [Figure 19] 1 is a schematic diagram of an epithermal neutron flux increasing layer having a cone-shaped structure according to one embodiment of the present invention; FIG. [Figure 20] 1 is a cross-sectional view of an epithermal neutron flux enhancing layer having a cone-shaped structure according to one embodiment of the present invention. [Figure 21] FIG. 1 is a schematic diagram of a beam shaper in which an epithermal neutron flux augmenter has a cone-shaped structure and is located downstream along the neutron beam direction, according to one embodiment of the present invention. [Figure 22] 1 is a schematic diagram of an epithermal neutron flux augmenting body having a cone-shaped structure and beam shapers located upstream and downstream along the neutron beam direction, according to one embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to make the above-mentioned objects, features, and advantages of the present invention more clear, specific embodiments of the present invention will be described in detail below with reference to the drawings. In order to fully understand the present invention, many specific details will be set forth in the following description. However, the present invention can be embodied in many ways other than those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention, so the present invention is not limited to the specific examples disclosed below.

[0022] In the description of the present invention, the orientations or positional relationships indicated by terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are based on the orientations or positional relationships shown in the drawings, and are intended merely to facilitate and simplify the description of the present invention. They do not indicate or suggest that the devices or parts shown must have a specific orientation, be configured, or operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0023] Additionally, the terms "first" and "second" are for descriptive purposes only and should not be understood to indicate or suggest relative importance or to implicitly indicate the number of technical features depicted. Thus, a feature qualified by "first" or "second" may explicitly or implicitly include at least one of the feature. In describing the present invention, "plurality" means at least two, e.g., two, three, etc., unless otherwise clearly and specifically limited.

[0024] In the present invention, unless otherwise clearly specified or limited, the terms "attached," "coupled," "connected," "fixed," etc. should be understood in a broad sense, and may refer to, for example, a fixed connection, a detachable connection, or an integral connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediate medium, an internal communication between two parts, or an interactive relationship between two parts. Those skilled in the art can understand the specific meanings of the above terms in the present invention according to specific circumstances.

[0025] In the present invention, unless otherwise clearly specified or limited, a first feature being "above" or "below" a second feature may include direct contact between the first and second features, or indirect contact between the first and second features via an intermediate medium. Furthermore, a first feature being "above," "above," or "on the upper surface" of a second feature may include the first feature being directly above or diagonally above the second feature, or may simply mean that the horizontal height of the first feature is higher than that of the second feature. A first feature being "below," "below," or "on the lower surface" of a second feature may include the first feature being directly below or diagonally below the second feature, or may simply mean that the horizontal height of the first feature is lower than that of the second feature.

[0026] It should be noted that when a component is described as being "fixed" or "mounted" to another component, the component may be directly located on the other component, or there may be intervening components. When a component is described as being "connected" to another component, the component may be directly connected to the other component, or there may be intervening components. As used herein, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions are for illustrative purposes only and do not represent the only embodiment.

[0027] Neutron capture therapy has been increasingly applied in recent years as an effective means of cancer treatment, and among them, boron neutron capture therapy has become the most common. Neutrons used in boron neutron capture therapy can be supplied by a nuclear reactor or an accelerator. In an embodiment of the present invention, accelerator boron neutron capture therapy is taken as an example. The basic components of accelerator boron neutron capture therapy usually include an accelerator that accelerates charged particles (protons, deuterons, etc.), a target, a heat removal system, and a beam shaper. The accelerated charged particles interact with a metal target to generate neutrons. An appropriate nuclear reaction is selected based on the required neutron yield and energy, the energy and current magnitude of the accelerated charged particles that can be provided, the physical and chemical properties of the metal target, etc., and well-studied nuclear reactions include: 7 Li(p,n) 7 Be and 9 Be(p,n)9 B, and these two reactions are both endothermic. The energy thresholds for these two nuclear reactions are 1.881 MeV and 2.055 MeV, respectively. Since the ideal neutron source for boron neutron capture therapy is epithermal neutrons at the keV energy level, theoretically, bombardment of a metallic lithium target with protons whose energy is slightly higher than the threshold can generate relatively low-energy neutrons, making clinical application possible without requiring significant moderation. However, because the cross section of interaction between the two targets, metallic lithium (Li) and metallic beryllium (Be), and protons with the threshold energy are not large, nuclear reactions are usually induced with protons with relatively high energies to generate a sufficient neutron flux.

[0028] In boron neutron capture therapy (BNCT), boron ( 10 B) Taking advantage of the property that the contained drug has a large capture cross section for thermal neutrons, 10 B(n,α) 7 Li neutron capture and fission reactions 4 He and 7 Figures 1 and 2 show a schematic diagram of the boron neutron capture reaction and the reaction time. 10 B(n,α) 7 The nuclear reaction formula for Li neutron capture is shown below. As shown in Figures 1 and 2, the two types of charged particles have an average energy of approximately 2.33 MeV and are characterized by high linear energy deposition and short range. The linear energy deposition and range of α particles are 150 keV / μm and 8 μm, respectively. 7 For Li heavy charged particles, the respective energy levels are 175 keV / μm and 5 μm. Because the combined range of the two types of particles is close to the size of a single cell, radiation damage to the living body can be limited to the cellular level. By selectively targeting boron-containing drugs to tumor cells and combining them with an appropriate neutron source, the goal of locally killing tumor cells can be achieved without causing significant damage to normal tissue.

[0029] Regardless of whether the neutron source for boron neutron capture therapy comes from a nuclear reactor or an accelerator, the neutrons produced by the nuclear reaction between charged particles and the target are both mixed radiation fields, i.e., the beam contains neutrons and photons ranging from low to high energy. For boron neutron capture therapy of deep-seated tumors, the higher the content of other radiation, excluding epithermal neutrons, the greater the proportion that causes non-selective dose deposition in normal tissues. Therefore, it is necessary to reduce these radiations that cause unnecessary doses as much as possible.

[0030] The International Atomic Energy Agency (IAEA) has proposed five proposals for beam quality factors in air for neutron sources used in clinical boron neutron capture therapy. These five proposals can be used to compare the advantages and disadvantages of different neutron sources, and can also be used as reference when selecting neutron generation paths and designing beam shapers. These five proposals are as follows:

[0031] Epithermal neutron flux>1×10 9 n / cm 2 s Fast neutron contamination<2×10 -13 Gy-cm 2 / n Photon contamination<2×10 -13 Gy-cm 2 / n Thermal to epithermal neutron flux ratio<0.05 Epithermal neutron current to flux ratio > 0.7. NOTE: The epithermal neutron energy region is 0.5 eV to 10 keV, the thermal neutron energy region is less than 0.5 eV, and the fast neutron energy region is greater than 10 keV.

[0032] Different fields may have different division standards for the epithermal neutron energy range, for example, the epithermal neutron energy range may be set to 0.5 eV to 40 keV, the thermal neutron energy range may be set to less than 0.5 eV, and the fast neutron energy range may be set to more than 40 keV.

[0033] 1. Epithermal neutron beam flux Φ ep : The neutron beam flux and the concentration of the boron-containing drug in the tumor jointly determine the duration of clinical treatment. If the concentration of the boron-containing drug in the tumor is sufficiently high, the requirement for neutron beam flux can be reduced; conversely, if the concentration of the boron-containing drug in the tumor is low, a high flux of epithermal neutrons is required to deliver a sufficient dose to the tumor. The IAEA recommends that for epithermal neutron beam flux, 10 epithermal neutrons per square centimeter per second is required. 9 For existing boron-containing drugs, neutron beams at this flux can control treatment times to approximately one hour. This short treatment time is not only advantageous for patient positioning and comfort, but also effectively utilizes the limited residence time of boron-containing drugs in tumors.

[0034] 2. Fast neutron contamination D f / Φ ep : Fast neutrons are considered to be contamination because they cause unnecessary doses to normal tissues, and since there is a positive correlation between this dose and neutron energy, it is necessary to reduce the content of fast neutrons as much as possible in the design of neutron beams. Fast neutron contamination is defined as the dose of fast neutrons associated with a unit epithermal neutron flux. The IAEA defines fast neutron contamination as 2 x 10 -13 Gy-cm 2 It is recommended to make it smaller than / n.

[0035] 3. Photon contamination (gamma ray contamination) D γ / Φ ep : Gamma rays belong to the category of radiation with strong penetrating power and cause dose deposition in all tissues in the beam path non-selectively, so reducing the gamma ray content is also a requirement for neutron beam design. Gamma contamination is defined as the gamma ray dose associated with a unit epithermal neutron flux. The IAEA defines gamma contamination as 2 x 10 -13 Gy-cm 2 It is recommended to make it smaller than / n.

[0036] 4. Ratio of thermal neutron flux to epithermal neutron flux Φ th / Φ ep : Thermal neutrons have a fast decay rate and poor penetration, and most of their energy is deposited in skin tissue after entering the human body. Therefore, except when using thermal neutrons as a neutron source for boron neutron capture therapy for skin tumors such as melanoma, the content of thermal neutrons must be reduced for deep tumors such as brain tumors. The IAEA recommends that the ratio of thermal neutron flux to epithermal neutron flux be less than 0.05.

[0037] 5. Ratio of neutron current to neutron flux J ep / Φ ep : The ratio of neutron current to neutron flux indicates the beam directionality, and the larger this ratio, the better the forward directionality of the neutron beam. A neutron beam with high forward directionality can reduce the dose to surrounding normal tissue due to neutron scattering, and also improve the treatable depth and flexibility of setup posture. The IAEA recommends that the ratio of neutron current to neutron flux be greater than 0.7.

[0038] Hereinafter, the quality of the neutron beam in air in an embodiment of the present invention will be calculated using MCNP software (a general-purpose software package developed by Los Alamos National Laboratory in the United States that calculates neutron, photon, charged particle, or combined neutron / photon / charged particle transport problems in three-dimensional complex geometric structures based on the Monte Carlo method).

[0039] Fig. 3 shows a schematic diagram of a neutron capture therapy system according to one embodiment of the present invention. As shown in Fig. 3, the neutron capture therapy system according to this embodiment is preferably a boron neutron capture therapy system 100. A neutron beam N generated by a neutron generator is irradiated onto an affected area M of an irradiated subject 200 positioned on a treatment table 20. The neutron beam N causes the aforementioned boron neutron capture reaction with a boron (B-10)-containing drug in the affected area M, thereby eliminating tumor cells or other substances in the affected area M and achieving a therapeutic effect.

[0040] The boron neutron capture therapy system 100 includes a charged particle beam generator 11, a beam transporter 12, and a neutron beam generator 13. The charged particle beam generator 11 generates a charged particle beam P such as a proton beam, and the beam transporter 12 transports the charged particle beam P to the neutron beam generator 13. The neutron beam generator 13 generates a therapeutic neutron beam N, which is then irradiated onto an object 200 on a treatment table 20. The charged particle beam generator 11 includes an ion source 111 and an accelerator 112. The ion source 111 generates H - The ion source 111 generates charged particles such as protons, deuterons, etc., and the accelerator 112 accelerates the charged particles generated by the ion source 111 to obtain a charged particle beam P such as a proton beam of a required energy. The accelerator 112 may be a linear accelerator, a cyclotron, a synchrotron, or a synchrocyclotron. The neutron beam generator 13 includes a beam shaper 131, a collimator 132, and a target 133. The charged particle beam P generated by the accelerator 112 reaches the neutron beam generator 13 via the beam transport unit 12, interacts with the target 133 to generate neutrons, and the beam quality is adjusted by the beam shaper 131 and the collimator 132 to form a therapeutic neutron beam N, which is then irradiated onto the irradiated object 200 on the treatment table 20.

[0041] The beam shaper 131 can adjust the quality of the neutron beam N. The collimator 132 collects the neutron beam N so that the neutron beam N has high targetability during treatment. The beam shaper 131 further includes a beam entrance 1311, a moderator 1312, a reflector 1313 surrounding the moderator 1312, and a beam exit 1314.

[0042] In the boron neutron capture therapy system 100, the accelerator 112 accelerates the charged particle beam P generated in the ion source 111, and the charged particle beam P passes through a beam inlet 1311 and enters the beam shaper 131. A portion of the beam inlet 1311 is housed in a decelerator 1312, and another portion is housed in a reflector 1313.

[0043] An ideal target 133 has properties such as a high neutron yield, an energy distribution of the generated neutrons close to the epithermal neutron energy region, not much radiation with strong penetrating power, safety, low cost, easy operation, and high temperature resistance. However, in reality, no nuclear reaction that satisfies all of the requirements has been found. In this embodiment, a material that satisfies the above requirements as much as possible, such as Li or Be, is selected for the target 133. As is well known to those skilled in the art, the target 133 may be made of a metal material other than Li or Be, such as Ta or W and their alloys. In a preferred embodiment, the target 133 is made of metallic lithium and is housed in a moderator 1312. The charged particle beam P is accelerated to an energy sufficient to overcome the Coulomb repulsion of the nuclei of the target 133 and is then coupled to the target 133. 7 Li(p,n) 7 Neutrons are generated by a Be nuclear reaction, and the neutrons form a neutron beam N that defines a beam axis X. Because the neutrons generated by the charged particle beam P interacting with the target 133 have a wide energy spectrum, it is necessary to minimize the content of other types of neutrons and photons other than epithermal neutrons that meet the treatment needs in order to avoid damage to the operator or the irradiated object. Therefore, the neutrons emitted from the target 133 must be adjusted to the epithermal neutron energy range (0.5 eV to 10 keV) through a moderator 1312, thereby reducing the content of thermal neutrons (<0.5 eV) as much as possible.

[0044] 5, the moderator 1312 extends a first predetermined length L1 along the beam axis X and a first predetermined width D1 radially of the beam axis X. The moderator 1312 is made of a material having a large cross section for interacting with fast neutrons and a small cross section for interacting with epithermal neutrons. In this embodiment, the moderator 1312 is made of at least one of DO, AlF, CaF, LiCO, MgF, AlO, and a material obtained by mixing Al, AlF, and LiF in a predetermined ratio. The material obtained by mixing Al, AlF, and LiF in a predetermined ratio is preferably a Fluental material.

[0045] The reflector 1313 surrounds the moderator 1312 and reflects neutrons that have passed through the moderator 1312 and diffused to the surroundings back into the neutron beam N to improve the intensity of the neutron beam N, and at least a portion of the reflector 1313 extends by a second predetermined length L2 along the beam axis X and extends by a second predetermined width D2 outside the moderator 1312 in the radial direction of the beam axis X. The reflector 1313 is made of a material with high neutron reflection ability, and in this embodiment, the reflector 1313 is made of Pb.

[0046] In this embodiment, the beam shaper 131 further includes a beam outlet 1314 and a radiation shielding body 1315 surrounding the reflector 1313. The radiation shielding body 1315 blocks leaking neutrons and photons to reduce the dose to normal tissue in non-irradiated areas, extends a fourth predetermined length L4 along the beam axis X, and extends a fourth predetermined width D4 outside the reflector 1313 in the radial direction of the beam axis X, and is flush with the reflector 1313 at the beam outlet 1314. It should be noted that in other embodiments described below, other members extend a third predetermined length L3 along the beam axis X and a third predetermined width D3 in the radial direction of the beam axis X, and therefore the expressions fourth predetermined length L4 and fourth predetermined width D4 are used for the radiation shielding body herein. The material of the radiation shielding body 1315 includes at least one of a photon-shielding material and a neutron-shielding material, and may be a rigid solid cut to an appropriate size, such as a lead-antimony alloy, Teflon (registered trademark), graphite, paraffin, PE, PE containing boron carbide, lithium carbonate, or lithium fluoride, PMMA (acrylic), PMMA containing boron carbide, lithium carbonate, or lithium fluoride, or boron-containing barite concrete; a powder cut to an appropriate size and filled in a rigid or flexible container, such as boron carbide, lithium carbonate, or lithium fluoride powder; a liquid cut to an appropriate size and filled in a rigid or flexible container, such as water in which boron carbide, lithium carbonate, or lithium fluoride powder is dissolved, heavy water, or boric acid; or a flexible solid, such as rubber or silica gel. In this embodiment, the radiation shielding body 1315 is preferably made of a material different from that of the reflector, such as boron-containing barite concrete.

[0047] As can be appreciated, the beam shaper 131 may have other components and structures as long as it provides the epithermal neutron beam required for treatment, for example, it may include a thermal neutron absorber that absorbs thermal neutrons, and the beam entrance may not be housed within a moderator.

[0048] The collimator 132 is installed behind the beam outlet 1314 or inside the beam shaper 131, and the epithermal neutron beam emerging from the collimator 132 is irradiated onto the irradiated object 200. As can be understood, the collimator 132 may be omitted or replaced with another structure, and the neutron beam emerges from the beam outlet 1314 and is directly irradiated onto the irradiated object 200.

[0049] 4 to 21, in order to further improve the flux and quality of the neutron source, the beam shaper 131 further includes an epithermal neutron flux augmenter 1316, which is installed in the moderator 1312 and / or in the reflector 1313 and / or between the moderator 1312 and the reflector 1313. For ease of comparison and representation, the same components are denoted by the same reference numerals in the embodiments described in the present invention.

[0050] First, as shown in FIGS. 4 to 6 , the epithermal neutron flux augmenting body 1316 extends a third predetermined length L3 along the beam axis X and a third predetermined width D3 radially about the beam axis X, where the third predetermined width D3 is smaller than the sum of the first predetermined width D1 and the second predetermined width D2. Preferably, in the embodiment shown in FIGS. 4 to 6 , the third predetermined width D3 is smaller than the first predetermined width D1. In one embodiment of the present invention, the epithermal neutron flux augmenting body 1316 extends a third predetermined width D3 radially about the beam axis X, including the thickness of the epithermal neutron flux augmenting body. The epithermal neutron flux augmenting body 1316 is made of a material with high neutron reflectivity, and preferably, the epithermal neutron flux augmenting body 1316 is made of Ni, including natural nickel or refined nickel.

[0051] 7 and 8, and in combination with FIGS. 4 and 6, the epithermal neutron flux augmenting body 1316 is configured as a cylindrical structure including a first side portion 1316a and a second side portion 1316b perpendicular to the beam axis X, and a first wall 1316c and a second wall 1316d circumferentially closed around the beam axis X, where the first side portion 1316a and the second side portion 1316b are arranged in order along the direction of the neutron beam N, and the first side portion 1316a is farther from the beam exit 1314 than the second side portion 1316b. In these embodiments, the first side portion 1316a is arranged between the moderator 1312 and the reflector 1313 along the direction of the beam axis X, and is adjacent to the end face of the moderator 1312 located upstream of the neutron beam N. The first side portion 1316a is configured as a ring structure and has a first central hole formed therein. The first central hole penetrates the beam inlet 1311 so that the beam inlet 1311 can be accommodated within the moderator 1312. The second side portion 1316b has a second central hole formed therein. The second side portion 1316b is adjacent to an end face of the beam shaper 131 located downstream of the neutron beam N. The second central hole is connected to the beam outlet 1314. When the radial dimension of the second central hole is equal to the outer diameter of the first wall 1316c, the second side portion 1316b is in an open state without a closed structure, and the first wall 1316c and the second wall 1316d are configured along the radial direction of the beam axis X and perpendicular to the first side portion 1316a and the second side portion 1316b. The first wall 1316c and the second wall 1316d are connected to the first side 1316a and extend to the second side 1316b along the beam axis X. In these embodiments, the epithermal neutron flux augmenting body 1316 having a cylindrical structure has a centerline overlapping with the axis of the neutron beam N, the third predetermined width D3 is smaller than the first predetermined width D1, and at least a portion of the first wall 1316c and the second wall 1316d is housed within the moderator body 1312, i.e., at least a portion of the epithermal neutron flux augmenting body 1316 having a cylindrical structure is disposed within the moderator body 1312. As can be understood, the upstream side of the neutron beam N is the side proximate to the beam entrance 1311 and the target 133, and the downstream side of the neutron beam N is the side proximate to the beam exit 1314.

[0052] 9 and 10 are schematic diagrams of a beam shaper having a cylindrical epithermal neutron flux increasing body 1316 according to an embodiment of the present invention, viewed from different angles. As shown in FIGS. 9 and 10, the difference from the embodiment disclosed in FIGS. 4 to 8 is that at least a part of the first wall and the second wall of the epithermal neutron flux increasing body 1316 is installed inside the reflector 1313. In this embodiment, the third predetermined width D3 of the cylindrical epithermal neutron flux augmenting body 1316 extending radially along the beam axis X is larger than the first predetermined width D1 of the moderator 1312 extending radially along the beam axis X, and is smaller than the sum of the first predetermined width D1 of the moderator 1312 extending radially along the beam axis X and the second predetermined width D2 of the part of the reflector 1313 extending radially along the beam axis X outside the moderator 1312. Both the first wall 1316c and the second wall 1316d are adjacent to the reflector 1313, i.e., the cylindrical epithermal neutron flux augmenting body 1316 is installed inside the reflector 1313.

[0053] The beam quality expressed in air by the embodiments disclosed in Figures 3, 4 to 8, and 9 to 10 will be described below. Table 1 shows the expression of beam quality elements in air when no epithermal neutron flux augmenting body is installed and when an epithermal neutron flux augmenting body having a cylindrical structure is installed at a different position (the units of each noun in the table are the same as above, and explanations will be omitted here, and the same applies below).

[0054] [Table 1]

[0055] As can be seen from the above table, the quality of the neutron beam can be improved by installing an epithermal neutron flux increaser with a cylindrical structure in the beam shaper, and the epithermal neutron flux can be significantly increased when the epithermal neutron flux increaser is installed in the moderator.

[0056] 11 to 14 , in one embodiment of the present invention, a first side portion 1316a and / or a second side portion 1316b of an epithermal neutron flux auger 1316 having a cylindrical structure is configured as a cone-like structure narrowing toward the beam axis X, and the radial dimension of the outer contour of the first side portion 1316a gradually increases along the neutron beam N direction, while the radial dimension of the outer contour of the second side portion 1316b gradually decreases along the neutron beam N direction. The radial dimension of the outer contour of the first side portion 1316a is at least equal to or greater than the radial dimension of the central hole, and the radial dimension of the outer contour of the second side portion 1316b is large enough to accommodate at least the beam exit 1314.

[0057] 11 is a schematic diagram of a beam shaper in which one side of a cylindrical epithermal neutron flux augmenting body 1316 has a conical structure, according to one embodiment of the present invention. As shown in FIG. 11, in order to simplify the drawing, some reference symbols similar to those in the above embodiment, such as the first predetermined width D1, the third predetermined width D3, the first side 1316a, the second side 1316b, the first wall 1316c, and the second wall 1316d, are not shown in FIG. 11, and reference may be made to the above embodiment. In other embodiments described below, if reference symbols are not shown in the corresponding drawings, reference may be made to the corresponding drawings. In one embodiment of the present invention, the third predetermined width D3 of the cylindrical epithermal neutron flux augmenting body 1316 extending along the radial direction of the beam axis X is smaller than the first predetermined width D1 of the moderator body 1312 extending along the radial direction of the beam axis X, and both the first wall 1316c and the second wall 1316d are at least partially housed within the moderator body 1312, i.e., at least a portion of the epithermal neutron flux augmenting body 1316 is installed within the moderator body 1312. The first side 1316a is adjacent to the end face of the moderator 1312 located upstream of the neutron beam N, and the second side 1316b is adjacent to the end face of the moderator 1312 located downstream of the neutron beam N. The radial dimension of the outer contour of the second side 1316b gradually decreases along the direction of the neutron beam N, and gradually decreases from the third predetermined width D3 to the dimension of the beam exit 1314. That is, the second side 1316b contracts toward the beam exit 1314. One side of the cylindrical epithermal neutron flux augmenting body 1316 has a cone-shaped structure.

[0058] FIG. 12 is a schematic diagram of a beam shaper in which both sides of an epithermal neutron flux increasing body 1316 having a cylindrical structure are cone-shaped structures, according to one embodiment of the present invention. As shown in FIG. 12 , in one embodiment of the present invention, the third predetermined width D3 of the cylindrical epithermal neutron flux augmenting body 1316 extending along the radial direction of the beam axis X is smaller than the first predetermined width D1 of the moderator body 1312 extending along the radial direction of the beam axis X. The first wall 1316 c and the second wall 1316 d are both at least partially housed within the moderator body 1312, i.e., at least a part of the epithermal neutron flux augmenting body 1316 is installed within the moderator body 1312. The first side portion 1316 a is adjacent to the end face of the moderator body 1312 located upstream of the neutron beam N. The radial dimension of the outer contour of the first side portion 1316 a gradually increases along the neutron beam N direction, and gradually increases from the radial dimension of the central hole to the third predetermined width D3. That is, the first side portion 1316 a narrows toward the beam entrance 1311. The second side portion 1316b is adjacent to the end face of the moderator 1312 located downstream of the neutron beam N, and the radial dimension of the outer contour of the second side portion 1316b gradually decreases along the direction of the neutron beam N, and gradually decreases from the third predetermined width D3 to the dimension of the beam exit 1314, that is, the second side portion 1316b contracts toward the beam exit 1314, and both sides of the epithermal neutron flux increaser 1316 having a cylindrical structure are conical structures.

[0059] The beam quality expressed in air by the embodiments disclosed in Figures 3, 4, 11, and 12 will be described below. Table 2 shows the expression of beam quality factors in air when no epithermal neutron flux augmenting body is installed, when a cylindrical epithermal neutron flux augmenting body (without a cone-shaped structure) is installed, and when one or both sides of an epithermal neutron flux augmenting body with a cylindrical structure are provided with a cone-shaped structure.

[0060] [Table 2]

[0061] As can be seen from the above table, by installing an epithermal neutron flux augmenter on the beam shaper and installing a cone-shaped structure on one or both sides of the cylindrical epithermal neutron flux augmenter, the epithermal neutron flux in the neutron beam can be increased and the quality of the neutron beam can be improved.

[0062] 12 , and combining FIGS. 13 and 14 , in one embodiment of the present invention, the third predetermined width D3 of the cylindrical epithermal neutron flux augmenting body 1316 extending radially along the beam axis X is smaller than the first predetermined width D1 of the moderator body 1312 extending radially along the beam axis X, and the first wall 1316 c and the second wall 1316 d are both at least partially housed within the moderator body 1312, i.e., at least a part of the epithermal neutron flux augmenting body 1316 is installed within the moderator body 1312. The first side portion 1316 a is adjacent to an end face of the moderator body 1312 located upstream of the neutron beam N, and the radial dimension of the outer contour of the first side portion 1316 a gradually increases along the neutron beam N direction, and gradually increases from the radial dimension of the central hole to the third predetermined width D3, i.e., the first side portion 1316 a narrows toward the beam entrance 1311. The second side portion 1316b is adjacent to the end face of the moderator 1312 located downstream of the neutron beam N, and the radial dimension of the outer contour of the second side portion 1316b gradually decreases along the direction of the neutron beam N, gradually decreasing from the third predetermined width D3 to the dimension of the beam exit 1314, i.e., the second side portion 1316b contracts toward the beam exit 1314, and both sides of the cylindrical epithermal neutron flux augmenting body 1316 have a cone-shaped structure. In this embodiment, the thickness of the epithermal neutron flux augmenting body 1316 is smaller than the sum of the first predetermined width D1 and the second predetermined width D2, and is preferably 1 to 5 cm, more preferably 3 to 5 cm.

[0063] 3 and 12 when epithermal neutron flux augmenters 1316 of different thicknesses are installed will be described below. Table 3 shows the expression of beam quality factors in air when no epithermal neutron flux augmenters are installed and when the thicknesses of the epithermal neutron flux augmenters are different.

[0064] [Table 3] [Table 4]

[0065] As can be seen from the above table, by installing an epithermal neutron flux multiplier on the beam shaper and appropriately increasing the thickness of the epithermal neutron flux multiplier, the epithermal neutron flux in the neutron beam can be increased and the quality of the neutron beam can be improved. Referring to Figures 15(a) to 15(e), it can be seen that when the thickness of the epithermal neutron flux multiplier is 0-5cm, the epithermal neutron flux also increases with increasing thickness, and fast neutron contamination tends to decrease and then increase. When the thickness of the epithermal neutron flux multiplier is 0-1cm, the neutron flux tends to increase significantly, and the fast neutron contamination and the ratio of thermal neutron flux to epithermal neutron flux all tend to decrease significantly. When the thickness of the epithermal neutron flux multiplier is 1cm, When the thickness of the epithermal neutron flux multiplier reaches 5 cm, the epithermal neutron flux reaches its maximum value. When the thickness of the epithermal neutron flux multiplier is 3 cm or 4 cm, fast neutron contamination is minimal. If the thickness of the epithermal neutron flux multiplier continues to increase, the epithermal neutron flux decreases and fast neutron contamination increases, resulting in unnecessary dose to normal tissue and a decrease in neutron beam quality. Therefore, in order to obtain an epithermal neutron beam that satisfies the beam quality required for neutron capture therapy, the thickness of the epithermal neutron flux multiplier is preferably 1 to 8 cm, more preferably 3 to 5 cm.

[0066] As shown in FIGS. 16 to 22 , in some embodiments of the present invention, the epithermal neutron flux augmenting body 1316 is configured as a cone-shaped structure, which includes a first end face 1316 e and a second end face 1316 f perpendicular to the beam axis X, and a third wall 1316 g and a fourth wall 1316 h circumferentially closed around the beam axis X, where the first end face 1316 e and the second end face 1316 f are arranged in order along the direction of the neutron beam N, the third wall 1316 g and the fourth wall 1316 h are arranged radially of the beam axis X, and both the first end face 1316 e and the second end face 1316 f are arranged to be open.

[0067] 16 to 20, which are schematic diagrams of a beam shaper 131 according to an embodiment of the present invention, in which an epithermal neutron flux augmenting body 1316 has a cone-shaped structure and is located upstream along the direction of the neutron beam N. In this embodiment, the epithermal neutron flux augmenting body 1316 having a cone-shaped structure has an outer contour whose radial dimension gradually increases along the direction of the neutron beam N, and the first end face 1316e is adjacent to the end face of the moderator body 1312 located upstream along the neutron beam N and has a dimension sufficient to accommodate at least the beam inlet 1311. That is, the epithermal neutron flux augmenting body 1316 having a cone-shaped structure is located upstream along the neutron beam N, and the first end face 1316e has a radial inner diameter greater than the radial outer diameter of the beam inlet 1311. In this embodiment, the third predetermined width D3 of the epithermal neutron flux augmenting body 1316 extending radially along the beam axis is smaller than the first predetermined width D1 of the moderator 1312 extending radially along the beam axis. The third wall 1316g and the fourth wall 1316h are accommodated within the moderator 1312. That is, the epithermal neutron flux augmenting body 1316 having a cone-shaped structure is installed within the moderator 1312 and is close to the beam entrance 1311. The center line of the epithermal neutron flux augmenting body 1316 having a cone-shaped structure overlaps with the beam axis X, and the radial dimension of the outer contour gradually increases from the dimension of the beam entrance 1311 to the third predetermined width D3 along the neutron beam N direction.

[0068] 21 is a schematic diagram of a beam shaper 131 having an epithermal neutron flux augmenting body 1316 with a cone-shaped structure, the epithermal neutron flux augmenting body 1316 being located downstream along the direction of the neutron beam N, according to an embodiment of the present invention. As shown in FIG. 21 , in the embodiment of the present invention, the epithermal neutron flux augmenting body 1316 with a cone-shaped structure has an outer contour whose radial dimension gradually decreases along the direction of the neutron beam N, and the second end face 1316f is adjacent to the end face of the beam shaper 100 located downstream along the neutron beam, and has a dimension sufficient to accommodate at least the beam outlet 1314. That is, the epithermal neutron flux augmenting body 1316 with a cone-shaped structure is located downstream along the neutron beam N, and the second end face 1316f has a radial inner diameter larger than the radial outer diameter of the beam outlet 1314. In this embodiment, the epithermal neutron flux augmenting body 1316 extends in a radial direction of the beam axis X with a third predetermined width D3 that is smaller than the first predetermined width D1 that the moderator 1312 extends in a radial direction of the beam axis X, and the third wall 1316g is adjacent to the reflector 1313, and the fourth wall 1316h is adjacent to the beam outlet 1314. The epithermal neutron flux augmenting body 1316 has a cone-shaped structure, and its center line overlaps with the beam axis X. The radial dimension of the outer contour of the epithermal neutron flux augmenting body 1316 gradually decreases from the third predetermined width D3 to the dimension of the beam outlet 1314 along the neutron beam N direction.

[0069] 22 is a schematic diagram of a beam shaper 131 according to an embodiment of the present invention, in which the epithermal neutron flux augmenting body 1316 is a combination of two cone-shaped structures, and the two cone-shaped structures are located on the upstream and downstream sides, respectively, along the neutron beam N direction. As shown in FIG. 22 , the upstream epithermal neutron flux augmenting body 1316 having the cone-shaped structure has an outer contour whose radial dimension gradually increases along the neutron beam N direction, and a first end face 1316e is adjacent to the end face of the moderator 1312 located upstream of the neutron beam N and has a dimension sufficient to accommodate at least the beam inlet 1311. The downstream epithermal neutron flux augmenting body 1316 having the cone-shaped structure has an outer contour whose radial dimension gradually decreases along the neutron beam N direction, and a second end face 1316f is adjacent to the end face of the beam shaper 131 located downstream of the neutron beam and has a dimension sufficient to accommodate at least the beam outlet 1314. In this embodiment, the epithermal neutron flux augmenting body 1316 extends radially along the beam axis X with a third predetermined width D3 that is smaller than the first predetermined width D1 that the moderator body 1312 extends radially along the beam axis X, and the centerline of the epithermal neutron flux augmenting body 1316 overlaps with the beam axis X. The upstream epithermal neutron flux augmenting body 1316 with a cone-shaped structure has an outer contour whose radial dimension gradually increases from the dimension of the beam entrance 1311 to the third predetermined width D3 along the neutron beam N direction, while the downstream epithermal neutron flux augmenting body 1316 with a cone-shaped structure has an outer contour whose radial dimension gradually decreases from the third predetermined width D3 to the dimension of the beam exit 1314 along the neutron beam N direction.

[0070] The beam quality expressed in air by the embodiments of Figure 3 and Figures 16 to 22 when epithermal neutron flux augmenters 1316 with different shapes are installed will be described below. Table 4 shows the expression of beam quality factors in air when no epithermal neutron flux augmenters are installed and when epithermal neutron flux augmenters with cone-shaped structures are installed at different positions.

[0071] [Table 5]

[0072] As can be seen from the above table, by installing an epithermal neutron flux increaser with a cone-shaped structure at the downstream end of the beam shaper along the neutron beam N direction, the epithermal neutron flux can be significantly increased, which is more advantageous in improving the quality of the neutron beam.

[0073] In these embodiments of the present invention, the epithermal neutron flux augmenter 1316 has an overall cylindrical structure, a conical structure, or a structure combining a cylindrical shape and a conical shape. The epithermal neutron flux augmenter 1316 may be integrally molded or may be obtained by combining multiple pieces. The epithermal neutron flux augmenter 1316 may be assembled together with the moderator 1312 and the reflector 1313 to realize the placement of the epithermal neutron flux augmenter 1316 within the beam shaper 131. Alternatively, a containment chamber may be provided within the moderator 1312 or the reflector 1313, and the epithermal neutron flux augmenter 1316 may be placed within the containment chamber to realize the placement of the epithermal neutron flux augmenter 1316 within the beam shaper 131.

[0074] The term "cylindrical" used in the embodiments of the present invention refers to a structure in which the entire outer contour tends to remain essentially unchanged from one side to the other in the illustrated direction, and one contour line of the outer contour may be a line segment, for example, a corresponding contour line of a cylinder, or may be an arc with a large curvature that is close to a line segment, for example, a corresponding contour line of a sphere with a large curvature, and the entire surface of the outer contour may or may not transition smoothly, for example, a large number of protrusions and grooves are formed on the surface of a cylinder or a sphere with a large curvature.

[0075] The term "cone-shaped" used in the embodiments of the present invention refers to a structure in which the entire outer contour tends to become gradually smaller from one side to the other in the illustrated direction, and one contour line of the outer contour may be a line segment, for example, a corresponding contour line of a cone, or an arc, for example, a corresponding contour line of a sphere, and the entire surface of the outer contour may or may not have a smooth transition, for example, a number of protrusions and grooves are formed on the surface of a cone or sphere.

[0076] The technical features of the above-described embodiments can be combined in any manner, and for the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, any combination should be considered to be within the scope of the present specification.

[0077] The above examples illustrate some embodiments of the present invention, and although the descriptions are specific and detailed, they should not be understood as limiting the scope of the present invention. Those skilled in the art may make further modifications and improvements without departing from the concept of the present invention, and all of these fall within the scope of the present invention. Therefore, the scope of the present invention should be determined based on the scope of the appended claims. [Explanation of symbols]

[0078] 100 Neutron Beam Capture Therapy System 11 Charged particle generator 111 Ion Source 112 Accelerator 12 Beam Transport Section 13 Neutron beam generator 131 Beam Shaper 1311 Beam entrance 1312 Reducer 1313 Reflector 1314 Beam Exit 1315 Radiation shield 1316 Epithermal neutron flux increaser 1316a First side 1316b Second side 1316c First Wall 1316d 2nd wall 1316e 1st end face 1316f 2nd end face 1316g 3rd wall 1316h 4th wall 132 Collimator 133 Target 200 Irradiated object 20 treatment table M Affected area L1 First specified length L2 Second specified length L3 Third specified length L4 Fourth specified length D1 1st predetermined width D2 Second predetermined width D3 Third specified width D4 4th predetermined width X-beam axis

Claims

1. A beam shaper for use in a neutron capture therapy system, comprising: the beam shaper includes a moderator, a reflector, and an epithermal neutron flux increaser; the moderator moderates neutrons of a neutron beam defining a beam axis into epithermal neutrons, extends a first predetermined length along the beam axis, and extends a first predetermined width along a radial direction of the beam axis; the reflector surrounds the moderator and reflects neutrons deviating from the neutron beam back into the neutron beam to increase the intensity of the neutron beam, and at least a portion of the reflector extends a second predetermined length along the beam axis and extends a second predetermined width outside the moderator along the radial direction of the beam axis; the epithermal neutron flux augmenter increases epithermal neutron flux in the neutron beam, and is installed within the moderator and / or the reflector and / or between the moderator and the reflector, the epithermal neutron flux augmenter extending a third predetermined length along the beam axis and a third predetermined width along a radial direction of the beam axis, the third predetermined width being smaller than the sum of the first predetermined width and the second predetermined width; the beam shaper further includes a beam inlet and a beam outlet, the beam inlet being used for inputting a charged particle beam and the beam outlet being used for outputting the neutron beam, and the beam inlet, the moderator and the beam outlet being installed along an extension direction of the beam axis.

2. 2. The beam shaper of claim 1, further comprising a radiation shield surrounding the reflector, the radiation shield blocking leaked neutrons and photons to reduce a dose to normal tissue in a non-irradiated area, extending a fourth predetermined length along the beam axis, and extending a fourth predetermined width outside the reflector along a radial direction of the beam axis.

3. 2. The beam shaper according to claim 1, wherein the epithermal neutron flux increasing body is made of Ni.

4. The decelerator is made of a material D ２ O, AlF ３ , CaF ２ , Li ２ CO ３ , MgF ２ , Al ２ O ３ , and Al, AlF ３ 2. The beam shaping body according to claim 1, wherein the beam shaping body is at least one of materials obtained by mixing LiF and LiF in a predetermined ratio.

5. The beam shaper of claim 1 , wherein the reflector is made of lead.

6. 2. The beam shaper of claim 1, wherein the epithermal neutron flux multiplier has a cylindrical structure and includes first and second side portions perpendicular to the beam axis and first and second walls closed in a circumferential direction around the beam axis, the first and second side portions being disposed in order at both ends of the cylindrical structure along the neutron beam direction, a first central hole connected to a beam inlet being disposed in the first side portion, and a second central hole connected to a beam outlet being disposed in the second side portion.

7. 7. The beam shaper of claim 6, wherein the first side and / or the second side of the epithermal neutron flux augmenting body is configured as a cone-shaped structure narrowing toward the beam axis, the first side having a radial dimension of an outer contour that gradually increases along the neutron beam direction and the first central hole having a dimension that accommodates at least a beam inlet, and the second side having a radial dimension of an outer contour that gradually decreases along the neutron beam direction and the second central hole having a dimension that accommodates at least a beam outlet.

8. 8. The beam shaper according to claim 7, wherein the epithermal neutron flux increasing body has a thickness of 1 to 8 cm.

9. 9. The beam shaper according to claim 8, wherein the epithermal neutron flux increasing body has a thickness of 3 to 5 cm.

10. 2. The beam shaper of claim 1, wherein the epithermal neutron flux multiplier has a cone-shaped structure, the cone-shaped structure including first and second end faces perpendicular to the beam axis, and third and fourth walls closed in a circumferential direction around the beam axis, the first and second end faces being arranged in order along the neutron beam direction and both being open.

11. 11. The beam shaper according to claim 10, wherein the epithermal neutron flux augmenting body has an outer contour whose radial dimension gradually increases along the neutron beam direction, and the first end surface is adjacent to an end surface of the moderator body located upstream of the neutron beam and has a dimension that accommodates at least a beam inlet.

12. 11. The beam shaper according to claim 10, wherein the epithermal neutron flux augmenting body has an outer contour whose radial dimension gradually decreases along the neutron beam direction, and the second end surface is adjacent to an end surface of the beam shaper located downstream of the neutron beam and has a dimension that accommodates at least a beam outlet.

13. The beam shaper according to claim 6 or 10, wherein a center line of the cylindrical structure or the conical structure overlaps with a beam axis.

14. It includes a charged particle beam generator, a neutron beam generator, and a beam transport unit, the charged particle beam generating unit generates a charged particle beam, the neutron beam generating unit generates a neutron beam and includes a target and a beam shaper; a beam transport unit that transports the charged particle beam to the neutron beam generation unit, the charged particle beam interacting with the target to generate a neutron beam, and the neutron beam being decelerated by the beam shaper to form an epithermal neutron beam required for neutron capture therapy.

15. the beam shaper includes a moderator, a reflector, and an epithermal neutron flux increaser; the moderator moderates neutrons of a neutron beam defining a beam axis into epithermal neutrons, extends a first predetermined length along the beam axis, and extends a first predetermined width along a radial direction of the beam axis; the reflector surrounds the moderator and reflects neutrons deviating from the neutron beam back into the neutron beam to increase the intensity of the neutron beam, and at least a portion of the reflector extends a second predetermined length along the beam axis and extends a second predetermined width outside the moderator along the radial direction of the beam axis; 15. The neutron capture therapy system of claim 14, wherein the epithermal neutron flux increaser increases epithermal neutron flux in the neutron beam, is installed within the moderator and / or the reflector and / or between the moderator and the reflector, extends along the beam axis by a third predetermined length and extends along a radial direction of the beam axis by a third predetermined width, and the third predetermined width is smaller than the sum of the first predetermined width and the second predetermined width.

Images