Neutron capture therapy system and beam shaper for a neutron capture therapy system

Abstract

A neutron capture therapy system and a beam shaping body for the neutron capture therapy system can prevent deformation and damage of the beam shaping body material itself, and improve the flux and quality of a neutron source. The neutron capture therapy system includes a neutron generating device and a beam shaping body. The neutron generating device includes an accelerator and a target material. The accelerator accelerates generated charged particle beams and interacts with the target material to generate neutrons. The neutrons form a neutron beam. The neutron beam defines a main axis. The beam shaping body includes a moderator, a reflector and a radiation shielding body. The beam shaping body further includes a frame accommodating the moderator.

Description

TECHNICAL FIELD

[0001] One aspect of the present disclosure relates to a radiation irradiation system, in particular to a neutron capture therapy system. Another aspect of the present disclosure relates to a beam shaper for a radiation irradiation system, in particular to a beam shaper for a neutron capture therapy system. BACKGROUND

[0002] With the development of atomic science, radiotherapy such as cobalt-60, linear accelerator, electron beam, etc. has become one of the main means of cancer treatment. However, traditional photon or electron therapy is limited by the physical conditions of the radiation itself, which not only kills tumor cells but also causes damage to a large number of normal tissues along the beam path. In addition, due to the different sensitivities of tumor cells to radiation, the treatment effect of traditional radiotherapy on malignant tumors with high radiation resistance (such as glioblastoma multiforme and melanoma) is often poor.

[0003] In order to reduce the radiation damage to normal tissues around the tumor, the concept of targeted therapy in chemotherapy is applied to radiotherapy. For tumor cells with high radiation resistance, radiation sources with high relative biological effectiveness (RBE) are actively developed, such as proton therapy, heavy particle therapy, and neutron capture therapy. Among them, neutron capture therapy combines the above two concepts, such as boron neutron capture therapy, which provides a better choice for cancer treatment than traditional radiotherapy by using boron-containing drugs to specifically accumulate in tumor cells and precise neutron beam control.

[0004] Boron neutron capture therapy (BNCT) is a therapy that uses boron-containing drugs to have a high capture cross-section for thermal neutrons, and generates two heavy charged particles of He and Li by the B(n, α) Li neutron capture and nuclear fission reactions. Referring to FIGS. 1 and 2, which respectively show a schematic diagram of a boron neutron capture reaction and a B(n, α) Li neutron capture nuclear reaction equation, the average energy of the two charged particles is about 2.33 MeV, which has high linear energy transfer (LET) and short range characteristics. The linear energy transfer and range of α particles are 150 keV / μm and 8 μm, respectively, and the linear energy transfer and range of Li particles are 175 keV / μm and 5 μm, respectively. 10 10 7 4 7 Figure 1 Figure 2 10 7 ​​​​​​​​​7 The Li heavy particles are 175 keV / μm, 5 μm, and the total range of the two particles is about equivalent to a cell size, so the radiation damage to the organism can be limited to the cell level. When the boron-containing drug selectively accumulates in tumor cells, combined with a suitable neutron source, the purpose of locally killing tumor cells can be achieved without causing too much damage to normal tissues.

[0005] The effectiveness of boron neutron capture therapy depends on the concentration of boron-containing drugs in tumor cells and the number of thermal neutrons, so it is also called binary cancer therapy. Therefore, in addition to the development of boron-containing drugs, the improvement of neutron source flux and quality plays an important role in the research of boron neutron capture therapy.

[0006] Therefore, it is necessary to propose a new technical solution to solve the above problems. SUMMARY

[0007] In order to improve the flux and quality of the neutron source, one aspect of the present application provides a neutron capture therapy system, comprising a neutron generating device and a beam shaping body, the neutron generating device comprising an accelerator and a target material, the accelerator accelerating the generated charged particle beam to interact with the target material to generate neutrons, the neutrons forming a neutron beam, the neutron beam defining a main axis, the beam shaping body comprising a moderator, a reflector and a radiation shielding body, the moderator slowing down the neutrons generated from the target material to the epithermal neutron energy region, the reflector surrounding the moderator and guiding the neutrons deviating from the main axis back to the main axis to improve the intensity of the epithermal neutron beam, the radiation shielding body for shielding the leaked neutrons and photons to reduce the dose of normal tissues in the non-irradiated area, the beam shaping body further comprising a frame accommodating the moderator. The frame positions and supports the moderator, which can improve the flux and quality of the neutron source.

[0008] Further, the moderator is adjustable, the frame comprises a positioning member and a stop member for fixing the moderator, the material of the positioning member and the stop member has a half-life of less than 7 days after being activated by neutrons to generate a radioisotope, and the material of the positioning member and the stop member is aluminum alloy, titanium alloy, lead-antimony alloy, steel material without cobalt, carbon fiber, PEEK or high molecular polymer. The positioning member can conveniently adjust the size of the moderator, thereby adjusting the flux of the neutron beam, and the stop member can quickly and conveniently realize the packaging of the moderator after adjustment.

[0009] Further, the moderator comprises a basic part and a supplementary part, the basic part and the supplementary part are different in material, the frame forms at least one containing unit, the containing unit comprises a first containing unit and a second containing unit which are adjacent, the basic part is contained in the first containing unit and is adjustable in a piece-by-piece manner, and the positioning member is arranged in the first containing unit to supplement when the number of pieces of the basic part is reduced, and the stop member is used for fixing the basic part. The supplementary part can reduce the manufacturing cost of the moderator without greatly affecting the beam quality, and the positioning member and the stop member can conveniently adjust the basic part of the moderator.

[0010] Further, the frame comprises a main frame and a secondary frame which are detachably connected, the first containing unit is formed by at least one part of the main frame, the second containing unit is formed by at least one part of the main frame and at least one part of the secondary frame, and the supplementary part is contained in the second containing unit. The arrangement of the secondary frame facilitates replacement of the supplementary part of the moderator. The material of the main frame is an aluminum alloy, which has good mechanical properties and produces a radioactive isotope with a short half-life after being activated by neutrons. The material of the secondary frame is a carbon fiber composite material, which produces a radioactive isotope with a short half-life after being activated by neutrons and causes low radiation. The material of the basic part comprises at least one of D2O, Al, AlF3, MgF2, CaF2, LiF, Li2CO3 or Al2O3, has a large fast neutron interaction cross section and a small epithermal neutron interaction cross section, and has good moderation effect. The basic part contains Li-6, and the basic part simultaneously serves as the thermal neutron absorber. The material of the supplementary part comprises at least one of Zn, Mg, Al, Pb, Ti, La, Zr, Bi and C, the supplementary part is selected from materials that are relatively easy to obtain, can reduce the manufacturing cost of the moderator, has certain neutron moderation effect, and does not greatly affect the beam quality.

[0011] Further, the main frame comprises a first wall, a second wall and a first transverse plate connecting the first wall and the second wall which are sequentially arranged along the direction of the neutron beam and circumferentially closed around the main shaft, the first transverse plate extends perpendicularly to the direction of the neutron beam, the first wall is used for mounting a transmission tube of the accelerator, the second wall forms the first containing unit, and the radial distance from the first wall to the main shaft is smaller than the radial distance from the second wall to the main shaft. The basic part of the moderator surrounds the target material, so that the neutrons generated by the target material can be effectively moderated in all directions, and the neutron flux and the beam quality can be further improved.

[0012] Furthermore, the main frame includes a third wall that is circumferentially closed around the neutron beam direction, the radial distance from the second wall to the main axis is less than the radial distance from the third wall to the main axis, the frame also includes first and second side plates respectively disposed on both sides of the third wall and connected to the third wall along the neutron beam direction, and the secondary frame includes a second transverse plate disposed between the second wall and the second side plate along the neutron beam direction.

[0013] As a preferred embodiment, the secondary frame further includes a fourth wall that is circumferentially closed around the neutron beam direction and extends between the second horizontal plate and the second side plate. The neutron capture therapy system also includes a collimator, and the fourth wall forms the mounting part of the collimator and / or the beam outlet. The secondary frame in the beam outlet direction is made of carbon fiber, which, compared to aluminum alloy, has a lower activation degree, higher strength, and a certain retardation effect. The secondary frame also serves as the mounting part of the collimator. The main frame further includes a radial partition disposed 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 first wall, the second wall, the third wall, the first horizontal plate, the second horizontal plate, and the first side plate surround to form the second receiving unit. The radial partition divides the second receiving unit circumferentially into several sub-regions. The third wall, the fourth wall, the second horizontal plate, and the second side plate surround to form a third receiving unit. At least a portion of the reflector / radiation shield is disposed within the second receiving unit, and at least a portion of the radiation shield is disposed within the third receiving unit. The first and second side plates are made of lead-antimony alloy, where lead can further shield radiation, and the lead-antimony alloy has high strength.

[0014] As another preferred embodiment, the basic part has a central hole on its first end face facing the first side plate. This central hole accommodates the accelerator's transmission tube and target material. When the basic part is fully loaded, the first end face of the supplementary unit near the second side plate is flush with the second end face of the basic part near the second side plate. A shielding plate, made of lead, is disposed adjacent to the second end face of the basic part. Lead absorbs gamma rays released from the retarder. The thickness of the shielding plate in the neutron beam direction is less than or equal to 5 cm, preventing reflection of neutrons passing through the retarder. When the number of pieces in the basic part is reduced, a positioning member is disposed adjacent to the shielding plate. The frame also includes a stop member for fixing the basic part. This stop member is disposed adjacent to the second horizontal plate and is detachably connected to the main frame and / or secondary frame, facilitating adjustment and replacement of the basic part of the retarder.

[0015] Another aspect of the present invention provides a neutron capture therapy system, including a neutron generating device and a beam shaper. The neutron generating device generates neutrons to form a neutron beam, which defines a main axis. The beam shaper is capable of adjusting the beam quality of the neutron beam. The beam shaper includes a decelerator, a reflector, and a radiation shield. The decelerator slows down the neutrons generated by the neutron generating device to the hyperthermal neutron energy region. The reflector surrounds the decelerator and guides neutrons deviating from the main axis back to the main axis to improve the hyperthermal neutron beam intensity. The radiation shield is used to shield leaked neutrons and photons to reduce the normal tissue dose in non-irradiated areas. The beam shaper also includes a frame housing the decelerator, which includes a detachably connected main frame and a secondary frame. The frame provides positioning and support for the decelerator, improving the neutron source flux and quality; the detachable connection between the main frame and the secondary frame facilitates replacement of the decelerator.

[0016] The neutron capture therapy system and its beam shaping body described in this invention, with the frame providing positioning and support for the slowing body, can improve the flux and quality of the neutron source. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the boron neutron capture reaction;

[0018] Figure 2 for 10 B(n,α) 7 Li neutron-capturing nuclear reaction equation;

[0019] Figure 3 This is a schematic diagram of a neutron capture therapy system according to an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of the beam shaper and collimator of the neutron capture therapy system according to an embodiment of the present invention;

[0021] Figure 5 for Figure 4 A schematic diagram of the framework within;

[0022] Figure 6 for Figure 5 A schematic diagram of the main frame as seen from the N direction of the neutron beam;

[0023] Figure 7 for Figure 5 A schematic diagram of the main frame as viewed from the direction opposite to the N-direction of the neutron beam. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0025] likeFigure 3 The neutron capture therapy system in the embodiment is preferably a boron neutron capture therapy system 100, which comprises a neutron generating device 10, a beam shaper 20, a collimator 30, and a treatment table 40. The neutron generating device 10 comprises an accelerator 11 and a target material T. The accelerator 11 accelerates charged particles (such as protons, deuterons, etc.) to generate a charged particle beam P (such as a proton beam), and the charged particle beam P irradiates the target material T to generate neutrons. The neutrons form a neutron beam N, which has a main axis X. The target material T is preferably a metal target material. The direction of the neutron beam N shown in the figure and described below does not represent the actual direction of the motion of the neutrons, but represents the direction of the overall motion trend of the neutron beam N. Suitable nuclear reactions are selected according to the required neutron yield and energy, the available energy and current of the accelerated charged particles, the physicochemical properties of the metal target material, and the like. The commonly discussed nuclear reactions are 7 Li(p,n) 7 Be and 9 Be(p,n) 9 B. Both of the reactions are endothermic reactions. The energy threshold of the two nuclear reactions is 1.881 MeV and 2.055 MeV, respectively. Since the ideal neutron source for boron neutron capture therapy is superthermal neutrons at the keV energy level, theoretically, if protons with energy slightly higher than the threshold energy are used to bombard a lithium metal target, relatively low-energy neutrons can be generated, which do not need too much slowing down and can be used in clinical practice. However, the interaction cross section of lithium metal (Li) and beryllium metal (Be) with protons at the threshold energy is not high. In order to generate a large enough neutron flux, protons with higher energy are usually selected to initiate the nuclear reaction. The ideal target material should have high neutron yield, neutron energy distribution close to the superthermal neutron energy range (which will be described in detail below), low production of strong penetrating radiation, safety, convenience, easy operation, and high temperature resistance, etc. However, in practice, it is difficult to find a nuclear reaction that meets all the requirements. As known by those skilled in the art, the target material T can also be made of metal materials other than Li and Be, such as Ta or W and their alloys, etc. The accelerator 11 can be a linear accelerator, a cyclotron, a synchrotron, or a synchrocyclotron.

[0026] The neutron source for boron neutron capture therapy generates a mixed radiation field, i.e., the beam contains neutrons and photons with low to high energy. For boron neutron capture therapy of deep tumors, the more the content of the remaining radiation lines other than superthermal neutrons, the greater the proportion of non-selective dose deposition in normal tissues, so these unnecessary dose radiations should be reduced as much as possible. In addition to the air beam quality factor, in order to better understand the dose distribution caused by neutrons in the human body, the dose calculation is performed using a human head tissue phantom in the embodiment of the present application, and the phantom beam quality factor is used as a design reference for the neutron beam, which will be described in detail below.

[0027] The International Atomic Energy Agency (IAEA) has given five recommendations for air kerma quality factors for clinical boron neutron capture therapy (BNCT) neutron sources. These five recommendations can be used to compare different neutron sources and as a guide for choosing a neutron production route and designing beam shapers. The five recommendations are as follows:

[0028] Epithermal neutron flux > 1 x 10 9 n / cm 2 s

[0029] Fast neutron contamination < 2 x 10 -13 Gy-cm 2 / n

[0030] Photon contamination < 2 x 10 -13 Gy-cm 2 / n

[0031] Thermal to epithermal neutron flux ratio < 0.05

[0032] Epithermal neutron current to flux ratio > 0.7

[0033] Note: The epithermal neutron energy range is between 0.5 eV and 40 keV, the thermal neutron energy range is less than 0.5 eV, and the fast neutron energy range is greater than 40 keV.

[0034] 1. Epithermal neutron flux:

[0035] The neutron flux and the boron concentration in the tumor together determine the treatment time. If the boron concentration in the tumor is high, the neutron flux requirement can be reduced. Conversely, if the boron concentration in the tumor is low, a high flux of epithermal neutrons is required to give the tumor a sufficient dose. The IAEA requirement for the epithermal neutron flux is greater than 1 x 10 9 n / cm2 / s. A neutron flux of this magnitude can control the treatment time to be approximately one hour for current boron-containing drugs. Short treatment times have the advantage of patient positioning and comfort, and can also effectively utilize the limited residence time of the boron-containing drug in the tumor.

[0036] 2. Fast neutron contamination:

[0037] Since fast neutrons cause unnecessary normal tissue dose, they are considered as contamination, the magnitude of this dose and the neutron energy are positively correlated, so the content of fast neutrons should be reduced as much as possible in the design of neutron beam. Fast neutron contamination is defined as the fast neutron dose per unit epithermal neutron flux, IAEA recommends that the fast neutron contamination should be less than 2x10 -13 Gy-cm 2 / n.

[0038] 3、Photon contamination (γ-ray contamination):

[0039] γ-rays are strong penetrating radiation, which will cause dose deposition in all tissues along the beam path non-selectively, so reducing the content of γ-rays is also necessary for the design of neutron beam. Photon contamination is defined as the γ-ray dose per unit epithermal neutron flux, IAEA recommends that the photon contamination should be less than 2x10 -13 Gy-cm 2 / n.

[0040] 4、Thermal to epithermal flux ratio:

[0041] Since thermal neutrons have fast decay rate and poor penetration ability, most of their energy is deposited in the skin tissue after entering the human body. Except for epidermal tumors such as melanoma, which need thermal neutrons as the source of boron neutron capture therapy, the content of thermal neutrons should be reduced for deep tumors such as brain tumors. IAEA recommends that the thermal to epithermal flux ratio should be less than 0.05.

[0042] 5、Neutron current to flux ratio:

[0043] The neutron current to flux ratio represents the directionality of the beam, the larger the ratio, the better the forward directionality of the neutron beam. High forward directionality of the neutron beam can reduce the dose to the surrounding normal tissue caused by neutron divergence, and also improves the treatable depth and flexibility of the positioning posture. IAEA recommends that the neutron current to flux ratio should be greater than 0.7.

[0044] The dose distribution in the tissue is obtained by using the phantom, and the beam quality factor of the phantom is obtained according to the dose-depth curve of the normal tissue and the tumor. The following three parameters can be used to compare the treatment benefits of different neutron beams.

[0045] 1、Effective treatment depth:

[0046] The depth at which the tumor dose is equal to the maximum dose of normal tissue, at this depth, the dose received by the tumor cells is less than the maximum dose of normal tissue, i.e. the advantage of boron neutron capture is lost. This parameter represents the penetration ability of the neutron beam, the larger the effective treatment depth, the deeper the treatable tumor depth, and the unit is cm.

[0047] 2、Effective treatment depth dose rate:

[0048] The effective treatment depth dose rate, which is equal to the maximum dose rate of normal tissue. The total dose received by normal tissue is a factor affecting the total dose that can be given to the tumor, so the parameters affect the length of the treatment time. The greater the effective treatment depth dose rate means the shorter the irradiation time required to give the tumor a certain dose, in units of cGy / mA-min.

[0049] 3. Effective treatment dose ratio:

[0050] The average dose ratio of tumor and normal tissue from the surface of the brain 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 greater the effective treatment dose ratio, the better the treatment benefit of the neutron beam.

[0051] In order to have a basis for the design of the beam shaping body, in addition to the five IAEA recommended air beam quality factors and the three parameters described above, the following parameters for evaluating the advantages and disadvantages of the neutron beam dose are also used in the embodiments of the present application:

[0052] 1. Irradiation time ≤ 30 min (proton current of 10 mA for accelerator)

[0053] 2. 30.0 RBE-Gy treatable depth ≥ 7 cm

[0054] 3. Maximum tumor dose ≥ 60.0 RBE-Gy

[0055] 4. Maximum normal brain tissue dose ≤ 12.5 RBE-Gy

[0056] 5. Maximum skin dose ≤ 11.0 RBE-Gy

[0057] Note: RBE (Relative Biological Effectiveness) is the relative biological effect. Since photons and neutrons will cause different biological effects, the above dose items are respectively multiplied by the relative biological effects of different tissues to obtain the equivalent dose.

[0058]

[0059] ​The neutron beam N generated by the neutron generating device 10 irradiates the patient 200 on the treatment table 40 through the beam shaper 20 and the collimator 30 in turn. The beam shaper 20 can adjust the beam quality of the neutron beam N generated by the neutron generating device 10, and the collimator 30 is used to converge the neutron beam N so that the neutron beam N has higher targeting during treatment. The beam shaper 20 further includes a frame 21 and a main body 23, at least part of the main body 23 is contained in the frame 21, the frame 21 supports the main body 23 to prevent the material itself from being deformed and damaged, affecting the target replacement and beam quality. The main body 23 includes a moderator 231, a reflector 232 and a radiation shielding body 233. Since the neutron generated by the neutron generating device 10 has a very wide energy spectrum, in addition to the epithermal neutrons meeting the treatment needs, it is necessary to reduce the content of other types of neutrons and photons as much as possible to avoid harm to the operator or the patient. Therefore, the neutrons coming out of the neutron generating device 10 need to pass through the moderator 231 to adjust the energy of the fast neutrons in it to the epithermal neutron energy region. The moderator 231 is made of a material with a large fast neutron interaction cross section and a small epithermal neutron interaction cross section, such as at least one of D2O, Al, AlF3, MgF2, CaF2, LiF, Li2CO3 or Al2O3. The reflector 232 surrounds the moderator 231 and reflects the neutrons diffused to the four around the moderator 232 back to the neutron beam N to improve the utilization rate of neutrons. The reflector 232 is made of a material with strong neutron reflection ability, such as at least one of Pb or Ni. The radiation shielding body 234 is used to shield the leaked neutrons and photons to reduce the normal tissue dose in the non-irradiated area. The material of the radiation shielding body 234 includes at least one of a photon shielding material and a neutron shielding material, such as the photon shielding material lead (Pb) and the neutron shielding material polyethylene (PE). It can be understood that the main body can also have other configurations as long as the required epithermal neutron beam for treatment can be obtained. The target material T is arranged between the accelerator 11 and the beam shaper 20. The accelerator 11 has a transmission tube 111 for transmitting the charged particle line P. In this embodiment, the transmission tube 111 extends into the beam shaper 20 along the direction of the charged particle line P and passes through the moderator 231 and the reflector 232 in turn. The target material T is arranged in the moderator 231 and located at the end of the transmission tube 111 to obtain better neutron beam quality. In this embodiment, first and second cooling pipes D1 and D2 are arranged between the transmission tube 111 and the moderator 231 and the reflector 232. One end of the first and second cooling pipes D1 and D2 is connected to the cooling inlet (not shown) and the cooling outlet (not shown) of the target material T respectively, and the other end is connected to an external cooling source (not shown). It can be understood that the first and second cooling pipes can also be arranged in other ways in the beam shaper, and when the target material is arranged outside the beam shaper, the first and second cooling pipes can also be removed.

[0060] Referring to Figure 4 and Figure 5The frame 21 comprises a first wall 211 closed in the circumferential direction around the main axis X, and a first and a second side plate 221, 222 disposed on both sides of the first wall 211 in the direction of the neutron beam N and connected to the first wall 211, a hole 2211 is provided on the first side plate 221 through which the transmission tube 111 passes, a hole 2221 is provided on the second side plate 222 to form a beam exit, and a containing portion C of the moderator is formed between the first wall 211 and the first and second side plates 221, 222. At least a part of the reflector and / or the radiation shielding body is also disposed in the containing portion C. The containing portion C comprises at least one containing unit C1-C3 (described in detail below), each containing unit C1-C3 contains at least one of the moderator 231, the reflector 232 and the radiation shielding body 233, at least one containing unit simultaneously contains at least two of the moderator, the reflector and the radiation shielding body or simultaneously contains at least two different materials, the moderator 231 comprises a basic part and a supplementary part, and the basic part and the supplementary part are contained in different containing units respectively. It can be understood that the first and second side plates can also not be provided, and the containing portion can be formed by the first wall.

[0061] The frame 21 further comprises a first cross plate 223 disposed between the first and second side plates 221, 222 in the direction of the neutron beam N, a second wall 212 closed in the circumferential direction around the main axis X and extending between the first cross plate 223 and the first side plate 221, and a third wall 213 closed in the circumferential direction around the main axis X and extending from the first cross plate 223 to the second side plate 222. The second wall 212 is closer to the main axis X in the radial direction than the third wall 213, the third wall 213 is located radially between the first wall 211 and the second wall 212, and the first cross plate 223 extends between the second wall 212 and the third wall 213. The inner surface of the second wall 212 is on the same surface as the side wall of the hole 2211 on the first side plate 221, and the second wall 212 forms a mounting portion for the transmission tube 111, the first and second cooling tubes D1, D2, etc. It can be understood that the first cross plate can extend to the first wall.

[0062] The frame 21 further comprises a second transverse plate 224 arranged between the third wall 213 and the second side plate 222 in the direction of the neutron beam N, a fourth wall 214 circumferentially closed around the main axis X and extending between the second transverse plate 224 and the second side plate 222, and a third transverse plate 225 arranged adjacent to the second transverse plate 224 between the second transverse plate 224 and the second side plate 222. The second transverse plate 224 extends from the first wall 211 to the inner side of the third wall 213, the fourth wall 214 is radially located between the first wall 211 and the third wall 213, the inner surface of the fourth wall 214 is on the same surface as 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 jointly form a beam exit, the third transverse plate 225 forms a hole 2251 through which the neutron beam N passes, the third wall 213 is radially located between the inner wall of the fourth wall 214 and the hole 2251 on the third transverse plate 225, and the outer wall of the third transverse plate 225 is located between the inner surface of the fourth wall 214 and the inner surface of the third wall 213.

[0063] In the embodiment, the first, second, third and fourth walls are all circular rings around the main axis X and extend parallel to the main axis X in the cross section perpendicular to the main axis X, and the side plates and the transverse plates are all flat plates extending perpendicular to the main axis X. It can be understood that other arrangements can also be provided, such as an extension direction inclined to the main axis. The frame can further comprise a plurality of walls circumferentially closed around the main axis X and a plurality of transverse plates arranged between the walls, and can also be used to accommodate or support other parts of the beam shaping body.

[0064] The region from the first transverse plate 223 to the third transverse plate 225 in the direction of the neutron beam N and surrounded by the third wall 213 forms a first accommodating unit C1 in the shape of a cylinder, the second accommodating unit C2 is formed between the first wall 211, the second wall 212, the third wall 213, the first side plate 221, the first transverse plate 223 and the second transverse plate 224, and the second accommodating unit C3 is formed between the first wall 211, the fourth wall 214, the second transverse plate 224 and the second side plate 222.

[0065] The first receiving unit C1 contains a magnesium fluoride block 241 as the basic part of the retarder 232. The magnesium fluoride block 241 contains Li-6 and can also serve as a thermal neutron absorber. The magnesium fluoride block 241 is cylindrical in shape, and its end face facing the first side plate 221 has a central hole 2411. The central hole 2411 is used to accommodate the transmission tube 111, the first and second cooling tubes D1 and D2, and the target material T. The central hole 2411 is a cylindrical hole. The side wall 2411a of the central hole is on the same surface as the inner surface of the second wall 212. The radial distance L1 from the second wall 212 to the main axis X is less than the radial distance L2 from the third wall 213 to the main axis X. Thus, the basic part of the retarder 231 surrounds the target material T, so that the neutrons generated by the target material T can be effectively slowed down in all directions, which can further improve the neutron flux and beam quality. A lead plate 242 is placed between the magnesium fluoride block 241 and the third horizontal plate 225. The lead plate 242 acts as a photon shield. Lead can absorb the gamma rays released in the slowing body. At the same time, the thickness of the lead plate 242 in the N direction of the neutron beam is less than or equal to 5 cm, so it will not reflect neutrons passing through the slowing body. This is understandable, but other arrangements are also possible. For example, the magnesium fluoride block 241 does not contain Li-6. Instead, a separate thermal neutron absorber composed of Li-6 is placed between the magnesium fluoride block 241 and the third horizontal plate 225. The lead plate can also be omitted.

[0066] An aluminum alloy block 243 and a lead block 244 are disposed within the second receiving unit C2. The aluminum alloy block 243 has a surface that contacts the second wall 212, the third wall 213, and the first horizontal plate 243. Thus, the aluminum alloy block 243 serves as a supplementary part of the deceleration body 231, surrounding the basic part 2311 of the deceleration body 231 disposed within the first receiving unit C1. The aluminum alloy block 243, as a supplementary part of the deceleration body 232, can reduce the manufacturing cost of the deceleration body without significantly affecting the beam quality. A PE block 245 of a corresponding shape is disposed within the third receiving unit C3. In this embodiment, the radiation shield 233 includes a neutron shield and a photon shield. The PE block 245 serves as the neutron shield, and the lead block 244 serves simultaneously as the reflector 232 and the photon shield. It can be understood that a PE block can also be disposed within the second receiving unit C2 as a neutron shield.

[0067] Magnesium fluoride block 241 is manufactured in sections, which facilitates quality control and allows for adjustment of beam intensity by adding or removing sections. Figure 4 In the illustrated embodiment, when the magnesium fluoride block 241 is fully loaded, the end faces of the magnesium fluoride block 241 and the aluminum alloy block 243 near the second side plate 242 are flush. The lead plate 242 is adjacent to the end face of the magnesium fluoride block 241 near the second side plate 242 and contacts the third horizontal plate 225. When the number of magnesium fluoride blocks 241 is reduced, a positioning ring 226 is provided between the lead plate 242 and the third horizontal plate 225 (e.g., Figure 5) corresponding supplement, it is understood that the positioning ring 226 can also be arranged between the magnesium fluoride block 241 and the lead plate 242, and the third transverse plate 225 serves as a stop ring, and the positioning ring 226 also has a hole 2261 with the same aperture as the stop ring for the neutron beam N to pass through. The positioning ring 226 with different thicknesses can be pre-set to position the magnesium fluoride block 241, and the materials of the positioning ring 226 and the stop ring (the third transverse plate 225) are carbon fibers, which are activated by neutrons to generate radioactive isotopes with a short half-life. It is understood that the positioning ring and the stop ring can also be replaced by other forms of positioning and stopping components. The positioning component can conveniently adjust the size of the moderator, thereby adjusting the neutron beam flux, and the stopping component can quickly and conveniently realize the packaging of the moderator after adjustment.

[0068] It is understood that the PE as the neutron shielding body in the embodiment can be replaced by other neutron shielding materials; the lead as the photon shielding body can be replaced by other photon shielding materials; the lead as the reflector can be replaced by other materials with strong neutron reflection ability; the magnesium fluoride as the basic part of the moderator can be replaced by other materials with large fast neutron interaction cross section and small epithermal neutron interaction cross section; Li-6 as the thermal neutron absorber can be replaced by other materials with large thermal neutron interaction cross section; the aluminum alloy as the supplementary part of the moderator can be replaced by a material including at least one of Zn, Mg, Al, Pb, Ti, La, Zr, Bi, Si, and C, and the supplementary part is selected from a material that is relatively easy to obtain, which can reduce the manufacturing cost of the moderator and has a certain neutron slowing effect without greatly affecting the beam quality.

[0069] Referring to Figure 6 and Figure 7 The frame 21 is also provided with a radial partition plate 210, and the plane where the radial partition plate 210 is located extends through the main shaft X, so as to divide the containing unit C2 into at least two sub-regions in the circumferential direction, so that the lead blocks and aluminum alloy blocks arranged in the containing unit C2 are divided into at least two sub-modules in the circumferential direction. In the embodiment, the radial partition plate 210 is arranged between the first side plate 221 and the second transverse plate 224, and extends from the first wall 211 to the second wall 212 or the third wall 213, and the radial partition plate 210 is four plates evenly distributed in the circumferential direction; it is understood that the number of radial partition plates can be other numbers or have other arrangements, or no radial partition plate is arranged.

[0070] In this embodiment, the radial partition plate 210, the first horizontal plate 223, and the first, second, and third walls 211-213 are integrated as the main frame 21a, made of aluminum alloy, have good mechanical properties, and produce radioactive isotopes with short half-lives after being activated by neutrons. Casting process can be used for integrated forming of the support form, in which the form plate is selected from wood form or aluminum form, and the sand core can be selected from red sand or resin sand, and the specific process is selected from the commonly used manner in the industry. Due to the demolding slope caused by casting, according to the design and beam quality requirements, machining is required to remove all of them. This structure and casting process make the frame structure have the advantages of good integrity, large stiffness, and high carrying capacity. Considering the limitations of machining tools and stress concentration of right-angle edges, all corners are rounded. It can also be a plate rolling and welding or first forging an aluminum alloy cylinder, and then machining the cylinder into a shape. The second horizontal plate 224 and the fourth wall 217 are integrated as the secondary frame 21b, made of carbon fiber composite material, and the specific process is selected from the commonly used manner in the industry. Aluminum alloy and carbon fiber composite material produce radioactive isotopes with short half-lives after being activated by neutrons, resulting in low radiation. Carbon fiber is used in the direction of the beam outlet, which has smaller activation degree and higher strength than aluminum alloy, and also has a certain speed reduction effect. The main frame 21a and the secondary frame 21b are connected by bolts, first threaded holes are uniformly machined on the end face of the third wall 213 towards the second side plate 222, first through holes are uniformly machined on the second horizontal plate 224 corresponding to the first threaded holes, and the bolts are connected through the first through holes and the first threaded holes. Considering the installation of the stop ring (third horizontal plate 225), second threaded holes are uniformly reserved on the end face of the third wall 213 towards the second side plate 222, the positions of the second threaded holes are different from those of the first threaded holes, second through holes are reserved on the second horizontal plate 224 corresponding to the second threaded holes, third through holes are machined on the stop ring (third horizontal plate 225), the positions of the third through holes correspond to those of the second through holes, and the bolts are sequentially connected through the third through holes, the second through holes, and the second threaded holes, so that the stop ring (third horizontal plate 225) is fixed to the main frame 21a by the bolts. It can be understood that the stop ring can also be fixed to the secondary frame. Meanwhile, fourth through holes are machined on the stop ring (third horizontal plate 225), the positions of the fourth through holes correspond to those of the first through holes, and the diameters of the fourth through holes are slightly larger than the maximum radial dimension of the head of the bolt connecting the main frame 21a and the secondary frame 21b, so as to accommodate the bolt head. It can be understood that the fourth through holes can also be blind holes. Considering the assembly of the bolts, the diameter of the first through hole is slightly larger than that of the first threaded hole, and the diameters of the second and third through holes are slightly larger than that of the second threaded hole. The number of the first threaded holes, the first through holes, the second threaded holes, the second through holes, and the third through holes meets the connection strength. It can be understood that the secondary frame, the positioning ring, and the stop ring can not be provided.

[0071] The first and second side plates 221 and 222 are made of lead-antimony alloy material, and the lead can further shield radiation, and the lead-antimony alloy has high strength. The first and second side plates 221 and 222 are connected to the main frame by bolts. Third threaded holes are uniformly machined on the end faces of the inner wall of the main frame 21a towards the first and second side plates. Fourth through holes are uniformly machined on the first and second side plates 221 and 222 at positions corresponding to the third threaded holes. Considering the assembly of the bolts, the diameter of the fourth through holes is slightly larger than that of the third threaded holes, and the number of the third threaded holes and the fourth through holes can meet the connection strength.

[0072] It can be understood that, in the embodiment, the materials of the main frame, the secondary frame, the side plates, the positioning ring and the stop ring only need to have certain strength and produce radioactive isotopes with short half-life (e.g., less than 7 days) after being activated by neutrons. The material performance of the main frame can meet the requirements of supporting the beam shaping body, such as aluminum alloy, titanium alloy, lead-antimony alloy, steel material without cobalt, carbon fiber, PEEK, high molecular polymer, etc. Other connection methods can also be used, as long as the stop ring and the frame can be detachably connected to facilitate adjustment and replacement of the basic part of the moderator. The secondary frame and the side plates are detachably connected or non-detachably connected to the main frame. When detachable connection is used, each part of the main body can be replaced. In the embodiment, the frame and the main body of the beam shaping body can also have other structures.

[0073] The collimator 30 is arranged at the rear of the beam exit. The super-thermal neutron beam from the collimator 30 irradiates the patient 200, and is slowed down to thermal neutrons after passing through the normal tissue of the shallow layer to reach the tumor cells M. In combination with Figure 4 In the embodiment, the collimator 30 is fixed by threaded connection with the secondary frame 21b, and the fourth wall 214 of the secondary frame 21b forms a mounting part of the collimator 30. The collimator 30 has a flange 31 around the main shaft X at the end close to the beam shaping body 20. The outer wall of the flange 31 has external threads (not shown in the figure), and the inner wall of the fourth wall 214 is provided with internal threads (not shown in the figure) matched with the external threads. It can be understood that the collimator 30 can also be fixed by other connection methods, and the collimator 30 can be cancelled or replaced by other structures, and the neutron beam directly irradiates the patient 200 from the beam exit. In the embodiment, the radiation shielding device 50 is arranged between the patient 200 and the beam exit to shield the radiation of the beam from the beam exit to the normal tissue of the patient. It can be understood that the radiation shielding device 50 can also not be arranged.

[0074] The "cylinder" or "cylinder-like" in the embodiments of the present application refers to a structure whose overall trend of the outer contour is basically unchanged from one side to the other side along the direction of the illustration. One of the contour lines of the outer contour can be a line segment, such as the corresponding contour line of a cylindrical shape. Alternatively, the contour line can be a circular arc with relatively large curvature close to a line segment, such as the corresponding contour line of a spherical body with relatively large curvature. The entire surface of the outer contour can be smoothly transitioned, or can be non-smoothly transitioned, such as a cylindrical or spherical body surface with many protrusions and grooves.

[0075] Although the above describes the illustrative specific embodiments of the present application in order to facilitate the understanding of the present application by those skilled in the art, it should be clear that the present application is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present application defined and determined by the appended claims, these changes are obvious and within the scope of the present application.

Claims

1. A neutron capture therapy system comprising a neutron generating device and a beam shaping body, the neutron generating device comprising an accelerator and a target material, the accelerator accelerating a generated charged particle beam to interact with the target material to generate neutrons, the neutrons forming a neutron beam, the neutron beam defining a main axis, characterized in that, The beam shaping body comprises a moderator for slowing down neutrons generated from the target material to the epithermal neutron energy region, a reflector surrounding the moderator and guiding the neutrons deviated from the main axis back to the main axis to increase the intensity of the epithermal neutron beam, and a radiation shielding body for shielding the leaked neutrons and photons to reduce the normal tissue dose of the non-irradiated region, and further comprises a frame containing the moderator; the moderator is adjustable, the frame comprises a positioning member and a stop member for fixing the moderator, the moderator comprises a basic part and a supplementary part, the basic part and the supplementary part are made of different materials, the frame forms at least one containing unit, the containing unit comprises adjacent first and second containing units, the basic part is contained in the first containing unit and is adjustable in a segmented manner, the positioning member is arranged in the first containing unit to supplement when the number of segments of the basic part is reduced, and the stop member is used for fixing the basic part.

2. The neutron capture therapy system of claim 1, wherein, The material of the positioning member and the stop member has a radioactive isotope half-life of less than 7 days after being activated by neutrons, and the material of the positioning member and the stop member is an aluminum alloy, a titanium alloy, a lead-antimony alloy, a steel material without cobalt, carbon fiber or a high polymer.

3. The neutron capture therapy system of claim 1, wherein, The frame comprises a main frame and a secondary frame connected detachably, the first containing unit is formed by surrounding at least a part of the main frame, the second containing unit is formed by surrounding at least a part of the main frame and at least a part of the secondary frame, the supplementary part is contained in the second containing unit, the material of the main frame is an aluminum alloy, the material of the secondary frame is a carbon fiber composite material, the material of the basic part comprises at least one of D2O, Al, AlF3, MgF2, CaF2, LiF, Li2CO3 or Al2O3, the basic part contains Li-6, the basic part simultaneously serves as a thermal neutron absorber, and the material of the supplementary part comprises at least one of Zn, Mg, Al, Pb, Ti, La, Zr, Bi and C.

4. The neutron capture therapy system of claim 3, wherein, The main frame comprises a first wall, a second wall and a first transverse plate connecting the first wall and the second wall, which are arranged in sequence along the direction of the neutron beam and circumferentially closed around the main axis, the first transverse plate extends perpendicularly to the direction of the neutron beam, the first wall is used for mounting a transmission tube of the accelerator, and the second wall forms the first containing 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.

5. The neutron capture therapy system of claim 4, wherein, The main frame comprises a third wall circumferentially closed around the direction of the neutron beam, the radial distance from the second wall to the main axis is smaller than the radial distance from the third wall to the main axis, and the frame further comprises first and second side plates arranged on both sides of the third wall along the direction of the neutron beam and connected with the third wall, and the secondary frame comprises a second transverse plate arranged between the second wall and the second side plate along the direction of the neutron beam.

6. The neutron capture therapy system of claim 5, wherein, The sub-frame further comprises a fourth wall which is circumferentially closed around the neutron beam direction and extends between the second transverse plate and the second side plate, the neutron capture therapy system further comprises a collimator, the fourth wall forms a mounting portion and / or a beam exit of the collimator, the main frame further comprises a radial partition plate which is arranged between the first side plate and the second transverse plate and extends from the first wall to the second wall or the third wall, the first wall, the second wall, the third wall, the first transverse plate, the second transverse plate and the first side plate enclose to form the second containing unit, the radial partition plate divides the second containing unit into a plurality of sub-regions in the circumferential direction, the third wall, the fourth wall, the second transverse plate and the second side plate enclose to form a third containing unit, at least a part of the reflector / radiation shield is further arranged in the second containing unit, at least a part of the radiation shield is arranged in the third containing unit, the first and second side plates are made of lead-antimony alloy.

7. The neutron capture therapy system of claim 5, wherein, The basic part is provided with a central hole at the first end face facing the first side plate, the central hole is used for accommodating the transmission tube and target material of the accelerator, when the basic part is full, the supplementary part is flush with the basic part at the first end face close to the second side plate and the second end face close to the second side plate.

8. The neutron capture therapy system of claim 7, wherein, A shielding plate is arranged adjacent to the second end face of the basic part, the shielding plate is a lead plate, the thickness of the shielding plate in the neutron beam direction is less than or equal to 5 cm, when the number of the basic part is reduced, the positioning member is arranged adjacent to the shielding plate, the stop member is arranged adjacent to the second transverse plate, and the stop member is detachably connected to the main frame and / or the sub-frame.

9. A neutron capture therapy system comprising a neutron generating device and a beam shaping body, the neutron generating device generating neutrons forming a neutron beam, the neutron beam defining a main axis, the beam shaping body being capable of adjusting the beam quality of the neutron beam, characterized in that, The beam shaping body comprises a moderator, a reflector and a radiation shield, the moderator is used for slowing down the neutrons generated from the neutron generating device to the epithermal neutron energy region, the reflector encloses the moderator and guides the neutrons deviated from the main axis back to the main axis to improve the intensity of the epithermal neutron beam, and the radiation shield is used for shielding the leaked neutrons and photons to reduce the normal tissue dose of the non-irradiated area, the beam shaping body further comprises a frame for containing the moderator, the frame comprises a main frame and a sub-frame which are detachably connected, the moderator is adjustable, the frame comprises a positioning member and a stop member for fixing the moderator, the moderator comprises a basic part and a supplementary part, the materials of the basic part and the supplementary part are different, the frame forms at least one containing unit, the containing unit comprises adjacent first and second containing units, the basic part is contained in the first containing unit and is adjustable in a segmented manner, when the number of the basic part is reduced, the positioning member is arranged in the first containing unit for supplement, and the stop member is used for fixing the basic part.

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