Neutron Capture Therapy System

Abstract

The neutron capture therapy system can prevent deformation and damage to the material of the beam shaper itself and improve the flux and quality of the neutron source. The neutron capture therapy system (100) according to the present invention includes a neutron generator (10) including an accelerator (11) and a target (T), and a beam shaper (20). The accelerator (11) accelerates and generates a charged particle beam (P), which interacts with the target (T) to generate neutrons. The neutrons form a neutron beam (N), which defines a single principal axis (X). The beam shaper (20) includes a moderator (231), a reflector (232), and a radiation shield (233), and further includes a frame (21) that houses the moderator (231).

Description

[Technical field]

[0001] The present invention relates to radiation delivery systems, and more particularly to 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, traditional photon or electron therapy kills tumor cells due to the limitations of the physical conditions of the radiation itself, and also damages many normal tissues along the beam path. In addition, tumor cells have different degrees of sensitivity to radiation, and traditional radiation therapy has poor therapeutic effects on malignant tumors with high radiation resistance (e.g., glioblastoma multiforme, melanoma).

[0003] To reduce radiation damage to normal tissues surrounding tumors, targeted therapy in chemotherapy is used in radiation therapy. In addition, radiation sources with high relative biological effectiveness (RBE) are now being actively developed for tumor cells with high radiation resistance (e.g., proton therapy, heavy ion therapy, neutron capture therapy, etc.). Among these, neutron capture therapy combines the above two concepts. For example, in boron neutron capture therapy, boron-containing drugs are specifically concentrated in tumor cells, and combined with the precise control of the neutron beam, it provides a better cancer treatment option compared to conventional radiation.

[0004] Boron Neutron Capture Therapy (BNCT) is a method to treat cancer by using 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 7The boron neutron capture reaction schematic and the boron neutron capture reaction schematic are shown in Figure 1 and Figure 2, respectively. 10 B(n,α) 7 The atomic nucleus reaction formula for Li neutron capture is shown below. The two types of heavy charged particles have an average energy of 2.33 MeV and are characterized by a high linear energy transfer (LET) and a short range. The linear energy transfer and range of the α particle are 150 keV / μm and 8 μm, respectively. 7 For Li heavy particles, the range is 175 keV / μm and 5μm, respectively. Since the combined range of the two particles is close to the size of a cell, the radiation damage to the living body can be limited to the cellular level. Therefore, by selectively concentrating boron-containing drugs in tumor cells and combining them with an appropriate neutron source, it is possible to partially kill tumor cells without causing much damage to normal tissues.

[0005] Since the effect of boron neutron capture therapy depends on the concentration of boron-containing drugs and the number of thermal neutrons at the site of tumor cells, it is also called two-dimensional radiation cancer therapy (binary cancer therapy). In view of this, in addition to the development of boron-containing drugs, the improvement of the radiation flux and quality of the neutron source is also very important for boron neutron capture therapy.

[0006] Therefore, it is necessary to provide a new technical means to solve the above problems. Summary of the Invention

[0007] In order to improve the flux and quality of a neutron source, a neutron capture therapy system according to one aspect of the present invention includes a neutron generating device including an accelerator and a target, and a beam shaper, the charged particle beam accelerated by the accelerator interacts with the target to generate neutrons, the neutrons form a neutron beam, and the neutron beam defines one main axis, the beam shaper includes a moderator, a reflector, and a radiation shield, the moderator moderates the neutrons generated by the target to an epithermal neutron energy region, the reflector surrounds the moderator and guides neutrons deviating from the main axis to the main axis to improve the epithermal neutron beam intensity, the radiation shield blocks escaping neutrons and photons to reduce the dose to normal tissue in a non-irradiated region, and the beam shaper further includes a frame that accommodates the moderator. The frame can position and support the moderator to improve the flux and quality of the neutron source.

[0008] Furthermore, the moderator is adjustable, and the frame includes a positioning member and a stopper member for fixing the moderator. Preferably, the half-life of the radioisotope generated after the material of the positioning member and the stopper member is activated by neutrons is less than 7 days. Preferably, the material of the positioning member and the stopper member is aluminum alloy, titanium alloy, lead-antimony alloy, cobalt-free steel, carbon fiber, PEEK or polymer. The positioning member can adjust the flux of the neutron beam by conveniently adjusting the size of the moderator, and after adjustment, the stopper member can quickly and conveniently realize the packaging of the moderator.

[0009] Furthermore, the decelerator includes a basic part and a complementary part, the basic part and the complementary part are made of different materials, the frame forms at least one accommodation unit, the accommodation unit includes a first accommodation unit and a second accommodation unit adjacent to each other, the basic part is accommodated in the first accommodation unit and is adjustable in multiple pieces, and when the number of the basic parts is reduced, the positioning member is installed in the first accommodation unit to complement it, and the stopper member fixes the basic part. The complementary part can reduce the manufacturing cost of the decelerator and does not significantly affect the beam quality, and the positioning member and the stopper member can conveniently adjust the basic part of the decelerator.

[0010] Further, the frame includes a main frame and a subframe which are detachably connected, the first accommodation unit is formed by being surrounded by at least a part of the main frame, the second accommodation unit is formed by being surrounded by at least a part of the main frame and at least a part of the subframe, the complementary part is accommodated in the second accommodation unit, and the installation of the subframe facilitates the replacement of the complementary part of the moderator. Preferably, the material of the main frame is an aluminum alloy, which has excellent mechanical properties and the half-life of the radioisotope generated after being activated by neutrons is short, and preferably, the material of the subframe is a carbon fiber composite material, which has a short half-life and low radiation after being activated by neutrons. Preferably, the material of the basic part is D 2 O, Al, AlF 3 , MgF 2 , CaF 2 , LiF, Li 2 CO 3 Or Al 2 O 3The basic part contains at least one of Li-6, which has a large cross section with fast neutrons and a small cross section with epithermal neutrons, and has an excellent moderation effect, and the basic part contains Li-6 and also functions as a thermal neutron absorber. Preferably, the material of the complementary part contains at least one of Zn, Mg, Al, Pb, Ti, La, Zr, Bi, and C, and the complementary part is made of a material that is easily available, which can reduce the manufacturing cost of the moderator, has a certain neutron moderation effect, and does not significantly affect the beam quality.

[0011] Furthermore, the main frame includes a first wall and a second wall that are sequentially installed along the direction of the neutron beam and are closed in the circumferential direction around the main axis, and a first horizontal plate that connects the first wall and the second wall, the first horizontal plate extends perpendicular to the direction of the neutron beam, the first wall is for mounting a transport tube of the accelerator, and is surrounded by the second wall to form the first accommodation unit, and the radial distance from the first wall to the main axis is smaller than the radial distance from the second wall to the main axis. The basic part of the moderator surrounds the target, so that neutrons generated by the target are effectively moderated in all directions, and the neutron flux and beam quality can be further improved.

[0012] Further, the main frame includes a third wall circumferentially closed around the direction of the neutron beam, a radial distance from the second wall to the main axis being smaller than a radial distance from the third wall to the main axis, the frame further includes first and second side plates respectively installed on either side of the third wall along the direction of the neutron beam and connected to the third wall, and the subframe includes a second horizontal plate installed between the second wall and the second side plate along the direction of the neutron beam.

[0013] Preferably, the subframe further includes a fourth wall that is closed circumferentially around the direction of the neutron beam and extends between the second horizontal plate and the second side plate, and the neutron capture therapy system further includes a collimator, and the fourth wall forms a mounting portion and / or a beam outlet of the collimator, and a subframe made of carbon fiber is adopted in the beam outlet direction, which has a smaller activation degree and higher strength than aluminum alloy, and also has a certain deceleration effect, and the subframe also functions as a mounting portion of the collimator. The main frame further includes a radial partition plate installed between the first side plate and the second horizontal plate and extending from the first wall to the second wall or the third wall, the second accommodating unit being surrounded by the first wall, the second wall, the third wall, the first horizontal plate, the second horizontal plate and the first side plate, the radial partition plate dividing the second accommodating unit into a plurality of sub-regions in the circumferential direction, the third accommodating unit being surrounded by the third wall, the fourth wall, the second horizontal plate and the second side plate, at least a portion of the reflector / radiation shield body being further installed in the second accommodating unit, at least a portion of the radiation shield body being installed in the third accommodating unit, the material of the first and second side plates is a lead-antimony alloy, the lead can further act to block radiation, and the lead-antimony alloy has high strength.

[0014] More preferably, a first end face of the basic part facing the first side plate is provided with a central hole for accommodating the transport tube and target of the accelerator, and when the basic part is full, the first end face of the complementary part close to the second side plate is flush with the second end face of the basic part close to the second side plate. Furthermore, a shield plate is provided adjacent to the second end face of the basic part, the shield plate being a lead plate, the lead being capable of absorbing gamma rays emitted from the moderator, the thickness of the shield plate in the direction of the neutron beam being 5 cm or less, and the shield plate not reflecting neutrons passing through the moderator. When the number of the basic parts is reduced, a positioning member is provided adjacent to the shield plate. The stopper member is provided adjacent to the second side plate and is detachably connected to the main frame and / or subframe, facilitating adjustment and replacement of the basic part of the moderator.

[0015] According to another aspect of the present invention, a neutron capture therapy system includes a neutron generator and a beam shaper, wherein neutrons generated by the neutron generator form a neutron beam, and the neutron beam defines one main axis, and the beam shaper can adjust the beam quality of the neutron beam, and the beam shaper includes a moderator, a reflector, and a radiation shield, and the moderator moderates the neutrons generated by the neutron generator to an epithermal neutron energy region, and the reflector surrounds the moderator and guides neutrons that deviate from the main axis to the main axis to improve the epithermal neutron beam intensity, and the radiation shield blocks escaping neutrons and photons to reduce the dose to normal tissue in a non-irradiated region, and the beam shaper further includes a frame that houses the moderator, and the frame includes a main frame and a sub-frame that are detachably connected. The frame positions and supports the moderator to improve the flux and quality of the neutron source, and the main frame and subframe are removably connected to facilitate replacement of the moderator.

[0016] The neutron capture therapy system according to the present invention has a beam shaper frame that positions and supports the moderator, thereby improving the flux and quality of the neutron source. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of a boron neutron capture reaction. [Diagram 2] This is the nuclear reaction equation for neutron capture in 10B(n,α)7Li. [Diagram 3] 1 is a schematic diagram of a neutron capture therapy system in an embodiment of the present invention. [Figure 4] 1 is a schematic diagram of a beam shaper and collimator of a neutron capture therapy system in an embodiment of the present invention. [Diagram 5] FIG. 5 is a schematic diagram of the frame in FIG. [Figure 6] FIG. 6 is a schematic diagram of the main frame in FIG. 5 as viewed from the direction of the neutron beam N. [Figure 7] FIG. 6 is a schematic diagram of the main frame in FIG. 5, viewed from the opposite direction to the direction of the neutron beam N. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The embodiments of the present invention will be described in more detail below with reference to the drawings, so that those skilled in the art can practice the invention by referring to the specification.

[0019] As shown in Fig. 3, the neutron capture therapy system in this embodiment is preferably a boron neutron capture therapy system 100, and includes a neutron generator 10, a beam shaper 20, a collimator 30, and a treatment table 40. The neutron generator 10 includes an accelerator 11 and a target T, the accelerator 11 accelerates charged particles (e.g., protons, deuterium nuclei, etc.) to generate a charged particle beam P such as a proton beam, the charged particle beam P irradiates the target T and interacts with the target T to generate neutrons, the neutrons form a neutron beam N, the neutron beam defines one principal axis X, and the target T is preferably a metal target. The direction of the neutron beam N shown in the figure and described below does not represent the actual neutron movement direction, but represents the direction of the overall movement tendency of the neutron beam N. Depending on the required neutron yield and energy, the energy and current of the accelerated charged particles that can be supplied, and the physical and chemical properties of the metal target, an appropriate nuclear reaction is selected. The nuclear reaction that is always discussed is 7 Li(p, n) 7 Be and 9 Be(p, n) 9B, both of which are endothermic reactions. The energy thresholds of these two nuclear reactions are 1.881 MeV and 2.055 MeV, respectively. The ideal neutron source for boron neutron capture therapy is epithermal neutrons at the keV energy level, so theoretically protons with energies slightly above the threshold can be used to bombard a metallic lithium target to generate neutrons of relatively low energy, which can be used clinically without too much moderation processing, but the cross section of action between the two targets, lithium metal (Li) and base metal (Be), and protons of the threshold energy is not high, so in order to generate a sufficiently large neutron flux, the nuclear reaction is generally initiated with protons of relatively high energy. The ideal target has a high neutron yield, the generated neutron energy distribution is close to the epithermal neutron energy region (described in detail below), does not generate too much strong radiation, is safe, inexpensive, easy to operate, and has high temperature resistance, etc., but in reality it is impossible to find a nuclear reaction that meets all the requirements. As known to those skilled in the art, the target T can be made of metallic materials other than Li and Be, such as Ta or W, and alloys thereof. The accelerator 11 can be a linear accelerator, a rotary accelerator, a synchronous accelerator, or a synchronous rotary accelerator.

[0020] The neutron source of boron neutron capture therapy generates a mixed radiation field, that is, the beam includes neutrons and photons from low energy to high energy. For boron neutron capture therapy of deep tumors, the higher the content of other radiations except epithermal neutrons, the higher the proportion of non-selective dose deposition in normal tissues, so it is necessary to reduce these unnecessary dose-causing radiations as much as possible. In order to further understand the dose distribution in the human body by neutrons, in addition to the beam quality factors in air, the embodiment of the present invention calculates the dose in the human head tissue of the prosthesis, and takes the beam quality factors in the prosthesis as a reference for neutron beam design. It will be described in detail later.

[0021] The International Atomic Energy Agency (IAEA) has put forward five proposals for air beam quality parameters for neutron sources used in clinical boron neutron capture therapy. These proposals can be used to compare the advantages and disadvantages of different neutron sources, and can also be used as a reference when selecting neutron generation pathways and designing beam shaping assemblies. The five proposals are as follows:

[0022] 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

[0023] NOTE: The epithermal neutron energy region is from 0.5 eV to 40 keV, the thermal neutron energy region is less than 0.5 eV, and the fast neutron energy region is greater than 40 keV.

[0024] 1. Epithermal neutron flux: The neutron flux and the concentration of the boron-containing drug in the tumor determine the duration of the clinical treatment. If the concentration of the boron-containing drug in the tumor is high enough, the requirement for neutron flux can be relaxed. On the other hand, 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 requires an epithermal neutron flux of more than 109 epithermal neutrons per second per square centimeter. For existing boron-containing drugs, a neutron beam with this flux can keep the treatment time to approximately 1 hour. The short treatment time contributes to improved positioning and comfort, and to the effective use of the limited residence time of the boron-containing drug in the tumor.

[0025] 2. Fast neutron contamination: Fast neutrons are considered contamination because they cause unnecessary doses to normal tissues. Since this dose is positively correlated with the neutron energy, it is necessary to reduce the fast neutron content as much as possible in the design of the neutron beam. Fast neutron contamination is defined as the fast neutron dose associated with unit epithermal neutron flux. The IAEA states that fast neutron contamination is 2×10 -13 Gy-cm 2 It is recommended to use less than / n.

[0026] 3. Photon contamination (gamma ray contamination): Since gamma rays belong to the strongly penetrating radiation and cause dose deposition in all tissues in the beam path non-selectively, reducing the gamma radiation content is also a prerequisite for neutron beam design. Gamma contamination is defined as the dose of gamma radiation associated with unit epithermal neutron flux. The IAEA has determined that gamma contamination is 2×10 -13 Gy-cm 2 It is recommended to use less than / n.

[0027] 4. Ratio of thermal neutron flux to epithermal neutron flux: Thermal neutrons have a fast decay rate and poor penetration, and most of their energy is deposited in the skin tissue after entering the human body, so in addition to using thermal neutrons as the neutron source for boron neutron capture therapy for skin tumors such as melanoma, the content of thermal neutrons needs to 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.

[0028] 5. Ratio of neutron flow to flux: The ratio of neutron flow to flux indicates the beam directionality. The larger the ratio, the more forward-directed the beam is. A neutron beam with strong forward directionality can reduce the dose to surrounding normal tissue due to neutron scattering, and can improve the treatment depth and positioning flexibility. The IAEA recommends a neutron flow to flux ratio greater than 0.7.

[0029] By obtaining the dose distribution in the tissues at the prosthesis and by the dose-depth curves of the normal tissues and the tumor, the beam quality factors at the prosthesis are derived. The following three parameters can be used to compare the therapeutic effects of different neutron beam therapies:

[0030] 1. Effective treatment depth: The tumor dose is the depth equal to the maximum normal tissue dose. After this depth, the dose received by the tumor cells is less than the maximum normal tissue dose, so there is no advantage in boron neutron capture. This parameter indicates the penetration of the neutron beam, the greater the effective treatment depth, the deeper the tumor depth that can be treated, and its unit is cm.

[0031] 2. Effective treatment depth dose rate: That is, the tumor dose rate at the effective treatment depth, which is equal to the maximum normal tissue dose rate. This parameter determines the treatment time, since the total dose received by normal tissue is a factor that affects the total tumor dose that can be delivered. The greater the dose rate at the effective treatment depth, the shorter the irradiation time required to deliver a given dose to the tumor, and its unit is cGy / mA-min.

[0032] 3. Effective therapeutic dose ratio: The ratio of the average dose received by the tumor and normal tissue from the brain surface to the effective treatment depth is called the effective treatment dose ratio. The average dose can be calculated by integrating the dose-depth curve. The larger the effective treatment dose ratio, the better the therapeutic effect of the neutron beam.

[0033] In addition to the IAEA's five proposed air beam quality factors and the three parameters mentioned above as a basis for comparison in the design of the beam shaping assembly, embodiments of the present invention utilize the following parameters to evaluate the neutron beam dosimetry performance:

[0034] 1. Irradiation time ≦30min (proton current used in accelerator is 10mA) 2. 30.0RBE-Gy treatable depth ≥ 7cm 3. Maximum tumor dose ≥ 60.0 RBE-Gy 4. Maximum normal brain tissue dose ≦12.5RBE-Gy 5. Maximum skin dose ≦11.0 RBE-Gy

[0035] Note: RBE (Relative Biological Effectiveness) is the relative biological effectiveness. Since the biological effects of photons and neutrons are different, the above doses are multiplied by the relative biological effectiveness of different tissues to calculate the equivalent dose.

[0036] The neutron beam N generated by the neutron generator 10 passes through a beam shaper 20 and a collimator 30 in sequence, and is irradiated to a patient 200 on a treatment couch 40. The beam shaper 20 can adjust the beam quality of the neutron beam N generated by the neutron generator 10, and the collimator 30 collects the neutron beam N and provides the neutron beam N with high targetability during the treatment process. The beam shaper 20 further includes a frame 21 and a main body 23, and at least a part of the main body 23 is accommodated in the frame 21, and the frame 21 supports the main body 23 and prevents deformation and damage of the material itself from affecting target replacement and beam quality. The main body 23 includes a moderator 231, a reflector 232, and a radiation shield 233. Since the neutrons generated by the neutron generator 10 have a wide energy spectrum, the content of other types of neutrons and photons other than epithermal neutrons that meet the needs of treatment should be reduced as much as possible to avoid causing injury to the operator or patient. Therefore, the neutrons emitted from the neutron generator 10 need to pass through the moderator 22 to adjust the fast neutron energy to the epithermal neutron energy range. The moderator 231 is made of a material that has a large cross section with fast neutrons and a small cross section with epithermal neutrons, such as D 2 O, Al, AlF 3 , MgF 2 , CaF 2 , LiF, Li 2 CO 3 Or Al 2 O 3The reflector 232 surrounds the moderator 231 and reflects the neutrons that pass through the moderator 231 and diffuse to the periphery into the neutron beam N to improve the utilization rate of the neutrons, and is made of a material with high neutron reflectivity, for example, at least one of Pb or Ni, and the radiation shield 233 blocks the seeping neutrons and photons to reduce the dose to the normal tissue in the non-irradiated area, and the material of the radiation shield 233 includes at least one of a photon shield material and a neutron shield material, for example, lead (Pb) as a photon shield material and polyethylene (PE) as a neutron shield material. As can be understood, the main body may have other structures as long as it can obtain the epithermal neutron beam required for treatment. The target T is installed between the accelerator 11 and the beam shaper 20, and the accelerator 11 has a transport tube 111 for transporting the charged particle beam P. In this embodiment, the transport tube 111 extends into the beam shaper 20 along the direction of the charged particle beam P and passes through the moderator 231 and the reflector 232 in sequence. The target T is installed in the moderator 231 and located at the end of the transport tube 111, thereby obtaining high neutron beam quality. In this embodiment, first and second cooling tubes D1 and D2 are installed between the transport tube 111 and the moderator 231 and the reflector 232, and one end of the first and second cooling tubes D1 and D2 is connected to the cooling inlet (not shown) and cooling outlet (not shown) of the target T, respectively, and the other end is connected to an external cooling source (not shown). As can be understood, the first and second cooling tubes may be installed in the beam shaper in other forms, and may even be omitted when the target is disposed outside the beam shaper.

[0037] As shown in Figures 4 and 5, the frame 21 includes a first wall 211 closed in the circumferential direction around the main axis X, and first and second side plates 221, 222 respectively installed on either side of the first wall 211 along the direction of the neutron beam N and connected to the first wall 211, the first side plate 221 has a hole 2211 through which the transport tube 111 passes, the second side plate 222 has a hole 2221 forming a beam outlet, a storage section C for the moderator is formed between the first wall 211 and the first and second side plates 221, 222, and at least a portion of the reflector and / or radiation shield body is also installed in the storage section C. The accommodation section C includes at least one accommodation unit C1-C3 (described in detail below), each accommodation unit C1-C3 accommodates at least one of the moderator 231, the reflector 232 and the radiation shield body 233, at least one accommodation unit accommodates at least two of the moderator, the reflector and the radiation shield body simultaneously or accommodates at least two different materials simultaneously, the moderator 231 includes a base part and a complementary part, and the base part and the complementary part are respectively accommodated in different accommodation units. As can be understood, the first and second side panels do not need to be provided, and the accommodation section is formed by being surrounded by the first wall.

[0038] The frame 21 further includes a first horizontal plate 223 installed between the first and second side plates 221, 222 along the direction of the neutron beam N, a second wall 212 that is closed in the circumferential direction around the main axis X and extends between the first horizontal plate 223 and the first side plate 221, and a third wall 213 that is closed in the circumferential direction around the main axis X and extends from the first horizontal plate 223 to the second side plate 222. The second wall 212 is closer to the main axis X than the third wall 213 in the radial direction, and the third wall 213 is located between the first wall 211 and the second wall 212 in the radial direction, and the first horizontal plate 223 extends between the second wall 212 and the third wall 213. The inner surface of the second wall 212 is flush with the side wall of the hole 2211 on the first side plate 221, and the second wall 212 forms a mounting for the transport tube 111, the first and second cooling tubes D1, D2, etc. As can be appreciated, the first side plate can extend up to the first wall.

[0039] The frame 21 further includes a second cross plate 224 installed between the third wall 213 and the second side plate 222 along the direction of the neutron beam N, a fourth wall 214 that closes circumferentially around the main axis X and extends between the second cross plate 224 and the second side plate 222, and a third cross plate 225 installed adjacent to the second cross plate 224 and between the second cross plate 224 and the second side plate 222. The second horizontal plate 224 extends from the first wall 211 to the inside of the third wall 213, the fourth wall 214 is located radially between the first wall 211 and the third wall 213, the inner surface of the fourth wall 214 is flush with the side wall of the hole 2221 on the second side plate 222, the fourth wall 214 and the hole 2221 on the second side plate 222 together form a beam outlet, the third horizontal plate 225 has a hole 2251 through which the neutron beam N passes, the third wall 213 is located radially between the fourth wall 214 and the inner wall of the hole 2251 on the third horizontal plate 225, and the outer wall of the third horizontal plate 225 is located between the inner surface of the fourth wall 214 and the inner surface of the third wall 213.

[0040] In this embodiment, the cross sections of the first, second, third and fourth walls in a direction perpendicular to the main axis X are all rings surrounding the main axis X and extending parallel to the main axis X, and the side plates and cross plates are all flat plates extending perpendicular to the main axis X. As can be understood, other installation forms are also possible, for example, the extension direction is inclined with respect to the main axis, and the frame can further include a number of walls closed in the circumferential direction around the main axis X and a number of cross plates installed between the walls, and can further accommodate or support other parts of the beam shaper.

[0041] The area surrounded by the third wall 213 from the first horizontal plate 223 to the third horizontal plate 225 in the direction of the neutron beam N forms a cylindrical first storage unit C1, and a second storage unit C2 is formed between the first wall 211, the second wall 212, the third wall 213, the first side plate 221, the first horizontal plate 223 and the second horizontal plate 224, and a second storage unit C3 is formed between the first wall 211, the fourth wall 214, the second horizontal plate 224 and the second side plate 222.

[0042] A magnesium fluoride block 241 that functions as a basic part of the moderator 231 is installed in the first containing unit C1. The magnesium fluoride block 241 contains Li-6 and can also function as a thermal neutron absorber. The entire block is columnar, and a central hole 2411 is installed on its end face facing the first side plate 221. The central hole 2411 is a cylindrical hole that accommodates the transport tube 111, the first and second cooling tubes D1 and D2, the target T, etc., and the side wall 2411a of the central hole is flush with the inner surface of the second wall 212. The radial distance L1 from the second wall 212 to the main axis X is smaller than the radial distance L2 from the third wall 213 to the main axis X. As a result, the basic part of the moderator 231 surrounds the target T, and the neutrons generated by the target T are effectively moderated in all directions, which can further improve the neutron flux and beam quality. A lead plate 242 is installed between the magnesium fluoride block 241 and the third cross plate 225, and the lead plate 242 functions as a photon shield, and the lead can absorb gamma rays emitted from the moderator, and the thickness of the lead plate 242 in the direction of the neutron beam N is 5 cm or less and does not reflect neutrons passing through the moderator. As can be understood, other installation forms are also possible, for example, the magnesium fluoride block 241 does not contain Li-6, and a separate thermal neutron absorber composed of Li-6 is installed between the magnesium fluoride block 241 and the third cross plate 225, and the lead plate may also be omitted.

[0043] An aluminum alloy block 243 and a lead block 244 are installed in the second accommodation unit C2, and the aluminum alloy block 243 has a surface in contact with the second wall 212, the third wall 213 and the first horizontal plate 223, thereby surrounding the basic part of the moderator 231 installed in the first accommodation unit C1 as a complementary part of the moderator 231. As a complementary part of the moderator 231, the aluminum alloy block 243 can reduce the manufacturing cost of the moderator and does not significantly affect the beam quality. A PE block 245 of a corresponding shape is installed in the third accommodation unit C3. In this embodiment, the radiation shielding body 233 includes a neutron shielding body and a photon shielding body, and the PE block 245 functions as a neutron shielding body, and the lead block 244 simultaneously functions as a reflector 232 and a photon shielding body. As can be understood, the PE block may be installed as a neutron shielding body in the second accommodation unit C2.

[0044] The magnesium fluoride block 241 is manufactured in multiple pieces, allowing the quality to be easily controlled and the beam intensity to be adjusted by increasing or decreasing the number of pieces. In the embodiment shown in Figure 4, when the magnesium fluoride block 241 is full, it is flush with the end face of the aluminum alloy block 243 near the second side plate 222, and the lead plate 242 is installed adjacent to the end face of the magnesium fluoride block 241 near the second side plate 222 and contacts the third cross plate 225. When the number of magnesium fluoride blocks 241 is reduced, a positioning ring 226 (shown in FIG. 5) is installed between the lead plate 242 and the third cross plate 225 to make a corresponding complement, as can be understood, the positioning ring 226 can be installed between the magnesium fluoride block 241 and the lead plate 242, the third cross plate 225 functions as a stopper ring, and the positioning ring 226 further has a hole 2261, which is the same as the hole diameter of the stopper ring, for the neutron beam N to pass through. The positioning ring 226 with different thickness can be pre-installed to play the role of positioning the magnesium fluoride block 241, and the material of the positioning ring 226 and the stopper ring (third cross plate 225) is carbon fiber, which has a short half-life of the radioisotope generated after being activated by neutrons. As can be understood, the positioning ring and the stopper ring can also be replaced with other types of positioning members and stopper members. The positioning member can conveniently adjust the dimension of the moderator to adjust the flux of the neutron beam, and after the adjustment, the stopper member can quickly and conveniently realize the packaging of the moderator.

[0045] As can be understood, the PE as the neutron shielding body in this embodiment may be replaced by other neutron shielding materials, the lead as the photon shielding body may be replaced by other photon shielding materials, the lead as the reflector may be replaced by other materials with high neutron reflecting ability, the magnesium fluoride as the basic part of the moderator may be replaced by other materials with a large cross section with fast neutrons and a small cross section with epithermal neutrons, the Li-6 as the thermal neutron absorber may be replaced by other materials with a large cross section with thermal neutrons, the aluminum alloy as the complementary part of the moderator may be replaced by a material containing at least one of Zn, Mg, Al, Pb, Ti, La, Zr, Bi, and C, and the complementary part may select an easily available material, which can reduce the manufacturing cost of the moderator and has a certain neutron moderation effect without significantly affecting the beam quality.

[0046] 6 and 7, the frame 21 is further provided with a radial partition plate 210, the plane on which the radial partition plate 210 is located extends through the main axis X, and divides the second receiving unit C2 into at least two sub-regions in the circumferential direction, so as to uniformly divide the lead block, aluminum alloy block provided in the second receiving unit C2 into at least two sub-modules in the circumferential direction. In this embodiment, the radial partition plate 210 is provided between the first side plate 221 and the second cross plate 224, extends from the first wall 211 to the second wall 212 or the third wall 213, and is four flat plates uniformly distributed along the circumferential direction, as can be understood, it may be provided in other quantities or in other distribution forms, and the radial partition plate may not be provided.

[0047] In this embodiment, the radial partition plate 210, the first horizontal plate 223, and the first, second, and third walls 211-213 are integral and function as the main frame 21a, the material is aluminum alloy, which has excellent mechanical properties, and the half-life of the radioisotope generated after activation by neutrons is short. A casting process can be adopted, the support and the formwork are integrally molded, the formwork can select a wooden form or an aluminum form, the sand core can select red sand or resin sand, and the specific process selects the method commonly used in the industry. Since a draft angle is applied to casting, it is necessary to remove it all in machining according to the requirements of design and beam quality. Due to the structural form and casting process, the frame structure has the advantages of high integrity, high rigidity, and high load-bearing capacity. Considering the limitations of the cutting tool for machining and the stress concentration of the right-angled sides, all corners are rounded and chamfered. The plate material may be rolled and welded, or the aluminum alloy cylinder may be forged first, and then the cylinder may be machined to form it. The second horizontal plate 224 and the fourth wall 214 are integral and function as the sub-frame 21b. Carbon fiber composite material is used, and the specific process is selected from the common method in the industry. The radioisotopes generated after the aluminum alloy and carbon fiber composite material are activated by neutrons have a short half-life and low radiation. Carbon fiber is used in the beam exit direction, which is less activated than the aluminum alloy, has high strength, and has a certain deceleration effect. The main frame 21a and the sub-frame 21b are connected by bolts, and the end surface of the third wall 213 facing the second side plate 222 is machined uniformly with a first screw hole, and the position corresponding to the first screw hole of the second horizontal plate 224 is machined uniformly with a first through hole, and the bolt passes through the first through hole and is connected to the first screw hole.Taking into consideration the installation of the stopper ring (third cross plate 225), second screw holes are uniformly pre-installed on the end face of the third wall 213 facing the second side plate 222, the positions of the second screw holes and the first screw holes are different, a second through hole is pre-installed at a position corresponding to the second screw hole of the second cross plate 224, a third through hole is machined in the stopper ring (third cross plate 225), the position of the third through hole corresponds to the second through hole, a bolt is passed through the third through hole and the second through hole in sequence and connected to the second screw hole, and the stopper ring (third cross plate 225) is fixed to the main frame 21a by the bolt, and as can be understood, the stopper ring may also be fixed to the subframe. Also, a fourth through hole is machined in the stopper ring (third horizontal plate 225), the position of the fourth through hole corresponds to the first through hole, and the hole diameter is slightly larger than the maximum radial dimension of the head of the bolt connecting the main frame 21a and the subframe 21b, and the fourth through hole may be a blind hole to accommodate the head of the bolt. In consideration of the assembly of the bolt, the hole diameter of the first through hole is slightly larger than the hole diameter of the first screw hole, the hole diameters of the second and third through holes are slightly larger than the hole diameter of the second screw hole, and the number of the first screw hole, the first through hole, the second screw hole, the second through hole, and the third through hole may satisfy the connection strength. As can be understood, the subframe, the positioning ring, and the stopper ring do not need to be installed.

[0048] The first and second side plates 221, 222 are made of lead-antimony alloy material, the lead can play a role in further blocking radiation, and the lead-antimony alloy has high strength. The first and second side plates 221, 222 and the main frame are all connected by bolts, and the end faces of the inner walls of the main frame 21a facing the first and second side plates are machined uniformly with third screw holes, respectively, and the positions corresponding to the third screw holes of the first and second side plates 221, 222 are machined uniformly with fourth through holes, and considering the assembly of the bolts, the diameter of the fourth through holes is slightly larger than the diameter of the third screw holes, and the number of the third screw holes and the fourth through holes only needs to satisfy the connection strength.

[0049] It can be understood that the materials of the main frame, subframe, side plate, positioning ring, and stopper ring in this embodiment only need to have a certain strength, and the half-life of the radioisotope generated after activation by neutrons is short (for example, less than 7 days), and the material performance of the main frame can meet the support for the beam shaper, for example, aluminum alloy, titanium alloy, lead-antimony alloy, cobalt-free steel, carbon fiber, PEEK, high molecular weight polymer, etc. can be adopted, as long as it ensures the detachable connection between the stopper ring and the frame and facilitates the adjustment and replacement of the basic parts of the moderator, and other connection methods can also be adopted. Removable or non-removable connections can be adopted between the subframe, side plate, and main frame, and when a detachable connection is adopted, each part of the main body can be easily replaced. The frame and main body of the beam shaper in this embodiment may also have other structural forms.

[0050] The collimator 30 is installed at the rear of the beam outlet, and the epithermal neutron beam emitted from the collimator 30 irradiates the patient 200, and after passing through the superficial layer of normal tissue, is decelerated to thermal neutrons and reaches the tumor cells M. As shown in FIG. 4, in this embodiment, the collimator 30 and the subframe 21b are fixed by a screw connection, and the fourth wall 214 of the subframe 21b forms the mounting part of the collimator 30, and the end of the collimator 30 close to the beam shaping body 20 has a flange 31 surrounding the main axis X, and the outer wall of the flange 31 has a male thread (not shown), and the inner wall of the fourth wall 214 has a female thread (not shown) that screws with the male thread. As can be understood, the collimator 30 may be fixed by other connection forms, and the collimator 30 may be omitted or replaced with other structures, and the neutron beam comes out of the beam outlet and directly irradiates the patient 200. In this embodiment, a radiation shielding device 50 is also provided between the patient 200 and the beam exit, and it should be understood that the beam exiting the beam exit blocks radiation to normal tissue of the patient, and therefore the radiation shielding device 50 does not need to be installed.

[0051] The "cylinder" or "columnar" described in the embodiments of the present invention is a structure whose overall flow of the outer contour is almost the same from one side to the other along the direction shown in the drawing. A contour line of the outer contour may be a line segment. For example, the corresponding contour line of a cylinder. Or it may be an arc close to a line segment with a large curvature. For example, the corresponding contour line of a sphere with a large curvature. The entire surface of the outer contour may be smooth or not smooth. For example, the surface of a cylinder or a sphere with a large curvature has bumps.

[0052] The above describes exemplary specific embodiments of the present invention to facilitate understanding of the present invention for those skilled in the art. However, it is obvious that the present invention is not limited to the scope of the specific embodiments. Various changes are obvious to those skilled in the art, so long as they are within the spirit and scope of the present invention, which is defined and determined by the appended claims. Therefore, all of these changes are within the scope of the claims of the present invention.

Claims

1. A neutron capture therapy system including a neutron generator including an accelerator and a target, and a beam shaper, wherein a charged particle beam accelerated by the accelerator interacts with the target to generate neutrons, the neutrons form a neutron beam, and the neutron beam defines one principal axis, The beam shaper includes a moderator, a reflector, and a radiation shield, the moderator moderating neutrons generated by the target to an epithermal neutron energy region, the reflector surrounding the moderator and directing neutrons deviating from the main axis to the main axis to improve the epithermal neutron beam intensity, the radiation shield blocking escaping neutrons and photons to reduce the dose to normal tissue in non-irradiated regions, the beam shaper further including a frame housing the moderator, the moderator being adjustable, and the frame fixing the moderator. A neutron capture therapy system comprising a positioning member and a stopper member, the positioning member being used to adjust a dimension of the moderator, the stopper member being used to package the moderator after adjustment, the stopper member and a portion of the frame other than the stopper member being detachably attached to each other, the moderator comprising a basic portion and a complementary portion, the basic portion and the complementary portion being made of different materials, the basic portion being arranged along the main axis, and the complementary portion being arranged to surround the basic portion.

2. The neutron capture therapy system according to claim 1 , wherein the half-life of the radioisotope generated after the materials of the positioning member and the stopper member are activated by neutrons is less than 7 days.

3. The neutron capture therapy system according to claim 1, characterized in that the material of the positioning member and the stopper member is an aluminum alloy, a titanium alloy, a lead-antimony alloy, a cobalt-free steel, a carbon fiber, PEEK or a polymer.

4. A neutron capture therapy system as described in claim 1, characterized in that the frame forms at least one accommodating unit, the accommodating unit includes adjacent first and second accommodating units, the basic part is accommodated within the first accommodating unit and is adjustable in multiple pieces, and when the number of basic parts is reduced, the positioning member is installed within the first accommodating unit to complement it, and the stopper member fixes the basic part.

5. 5. The neutron capture therapy system of claim 4, wherein the frame includes a main frame and a subframe that are detachably connected, the first accommodation unit being formed by being surrounded by at least a portion of the main frame, the second accommodation unit being formed by being surrounded by at least a portion of the main frame and at least a portion of the subframe, and the complementary portion being accommodated within the second accommodation unit.

6. The neutron capture therapy system according to claim 5, wherein the main frame is made of an aluminum alloy, and the subframe is made of a carbon fiber composite material.

7. The material of the base part is D ２ O, Al, AlF ３ , MgF ２ , CaF ２ , LiF, Li ２ CO ３ Or Al ２ O ３ The neutron capture therapy system according to claim 4, wherein the base portion includes Li-6 and also functions as a thermal neutron absorber.

8. 5. The neutron capture therapy system of claim 4, wherein the material of the complementary portion includes at least one of Zn, Mg, Al, Pb, Ti, La, Zr, Bi, and C.

9. 6. The neutron capture therapy system according to claim 5, wherein the main frame includes a first wall, a second wall, and a first horizontal plate that are arranged in order along the direction of the neutron beam and are closed circumferentially around the main axis, the first wall and the second wall being connected to each other, the first horizontal plate extending perpendicular to the direction of the neutron beam, the first wall being for mounting a transport tube of the accelerator, and the first housing unit being formed by being surrounded by the second wall, and a radial distance from the first wall to the main axis being smaller than a radial distance from the second wall to the main axis.

10. 10. The neutron capture therapy system of claim 9, wherein the main frame includes a third wall circumferentially closed around the direction of the neutron beam, a radial distance from the second wall to the main axis being smaller than a radial distance from the third wall to the main axis, the frame further includes first and second side plates respectively installed on either side of the third wall along the direction of the neutron beam and connected to the third wall, and the subframe includes a second horizontal plate installed between the second wall and the second side plate along the direction of the neutron beam.

11. The subframe is closed in a circumferential direction around the direction of the neutron beam and further includes a fourth wall extending between the second horizontal plate and the second side plate, the neutron capture therapy system further includes a collimator, the fourth wall forms a mounting portion of the collimator and / or a beam outlet, the main frame further includes a radial partition plate installed between the first side plate and the second horizontal plate and extending from the first wall to the second wall or the third wall, and is surrounded by the first wall, the second wall, the third wall, the first horizontal plate, the second horizontal plate and the first side plate.

11. The neutron capture therapy system according to claim 10, wherein the second containment unit is formed, the radial partition plate divides the second containment unit into a plurality of sub-regions in the circumferential direction, and a third containment unit is formed by being surrounded by the third wall, the fourth wall, the second horizontal plate and the second side plate, at least a portion of the reflector / radiation shield body is further installed within the second containment unit, at least a portion of the radiation shield body is installed within the third containment unit, and the material of the first and second side plates is a lead-antimony alloy.

12. 11. The neutron capture therapy system of claim 10, wherein a first end face of the basic part facing the first side plate has a central hole for accommodating a transport tube and a target of the accelerator, and when the basic part is full, a first end face of the complementary part close to the second side plate becomes flush with a second end face of the basic part close to the second side plate.

13. The neutron capture therapy system of claim 12, characterized in that a shield plate is installed adjacent to the second end face of the basic part, the shield plate being a lead plate, the thickness of the shield plate in the direction of the neutron beam being 5 cm or less, and when the number of the basic parts is reduced, the positioning member is installed adjacent to the shield plate, and the stopper member is installed adjacent to the second horizontal plate and is removably connected to the main frame and / or subframe.

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