WO2024078353A1 - 射束整形体及中子捕获治疗*** - Google Patents

射束整形体及中子捕获治疗*** Download PDF

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Publication number
WO2024078353A1
WO2024078353A1 PCT/CN2023/122407 CN2023122407W WO2024078353A1 WO 2024078353 A1 WO2024078353 A1 WO 2024078353A1 CN 2023122407 W CN2023122407 W CN 2023122407W WO 2024078353 A1 WO2024078353 A1 WO 2024078353A1
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Prior art keywords
neutron
epithermal
retarder
neutron flux
along
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PCT/CN2023/122407
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English (en)
French (fr)
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刘渊豪
卢威骅
舒迪昀
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中硼(厦门)医疗器械有限公司
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Publication of WO2024078353A1 publication Critical patent/WO2024078353A1/zh

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00—Radiation therapy
    • A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/06—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diffraction, refraction or reflection, e.g. monochromators

Definitions

  • the invention relates to the field of radiation irradiation, and in particular to a beam shaper and a neutron capture therapy system.
  • neutron capture therapy is a combination of the above two concepts, such as boron neutron capture therapy, which provides a better cancer treatment option than traditional radiation by specifically aggregating boron-containing drugs in tumor cells and coordinating precise neutron beam control.
  • BNCT Boron Neutron Capture Therapy
  • B-10 boron-containing
  • neutrons are captured by 10 B in tumor cells, fission occurs, producing alpha particles and 7 Li particles, releasing a highly lethal ray with a short range of only the length of a tumor cell, thereby accurately killing tumor cells while minimizing damage to surrounding normal cells.
  • BNCT Because the effectiveness of BNCT depends on the concentration of boron-containing drugs and the number of thermal neutrons at the tumor cell site, it is also called binary cancer therapy. It can be seen that 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 BNCT.
  • one aspect of the present invention provides a beam shaper for neutron capture therapy, the beam shaper comprising: a retarder, used to decelerate neutrons of a neutron beam into epithermal neutrons, the neutron beam defines a beam axis, the retarder extends along the beam axis by a first preset length and extends along the radial direction of the beam axis by a first preset width; a reflector, surrounding the retarder, used to reflect neutrons deviating from the neutron beam back to the neutron beam to increase the neutron beam intensity, at least a portion of the reflector extends along the beam axis by a second preset length and extends along the radial direction of the beam axis outside the retarder by a second preset width; and an epithermal neutron flux enhancer, used to increase the epithermal neutron flux in the neutron beam, disposed in the retarder and/or in the reflector and/or between the
  • the beam shaping body further comprises: a beam inlet for injecting a charged particle beam; a beam outlet for injecting a neutron beam; the beam inlet, the retarder and the beam outlet are arranged along the extending direction of the beam axis.
  • the beam shaper further includes a radiation shield surrounding the reflector, the radiation shield being used to shield leaked neutrons and photons to reduce normal tissue dose in non-irradiated areas, the radiation shield extending a fourth preset length along the beam axis and extending a fourth preset width outside the reflector in a radial direction of the beam axis.
  • the material of the reflector is Pb
  • the material of the retarder is at least one of D2O , AlF3 , CaF2 , Li2CO3 , MgF2 , Al2O3 and a mixed material of Al, AlF3 and LiF in a preset ratio.
  • the material of the epithermal neutron flux enhancement body is Ni.
  • the epithermal neutron flux enhancement body is constructed as a cylindrical structure, which includes a first side portion and a second side portion perpendicular to the beam axis and a first wall and a second wall circumferentially closed around the beam axis, the first side portion and the second side portion are sequentially arranged at two ends of the cylindrical structure along the neutron beam direction, the first side portion is provided with a first center hole, the first center hole is used to be combined with a beam inlet, and the second side portion is provided with a second center hole, the second center hole is used to be combined with a beam outlet.
  • the first side portion and/or the second side portion of the epithermal neutron flux enhancement body of the cylindrical structure is constructed as a conical structure that contracts toward the beam axis, the radial dimension of the outer contour of the first side portion gradually increases along the neutron beam direction, the size of the first central hole at least accommodates the beam entrance, the radial dimension of the outer contour of the second side portion gradually decreases along the neutron beam direction, and the size of the second central hole of the second side portion at least accommodates the beam exit.
  • the thickness of the epithermal neutron flux enhancement body is 1-8 cm; more preferably, the thickness of the epithermal neutron flux enhancement body is 3-5 cm.
  • the epithermal neutron flux enhancer is constructed as a conical structure, which includes a first end face and a second end face perpendicular to the beam axis and a third wall and a fourth wall circumferentially closed around the beam axis, the first end face and the second end face are arranged in sequence along the neutron beam direction, and the first end face and the second end face are both arranged to be open.
  • the radial dimension of the outer contour of the conical epithermal neutron flux enhancer gradually increases along the neutron beam direction, the first end face is adjacent to the end face of the retarder located upstream in the neutron beam direction, and the dimension of the first end face at least accommodates the beam entrance.
  • the radial dimension of the outer contour of the epithermal neutron flux enhancement body of the conical structure gradually decreases along the neutron beam direction
  • the second end face is adjacent to the end face of the beam shaping body located on the downstream side of the neutron beam direction, and the dimension of the second end face at least accommodates the beam exit.
  • the epithermal neutron flux enhancement body is arranged in a conical structure to reflect more epithermal neutrons back to the neutron beam, thereby enhancing the epithermal neutron beam flux.
  • the center line of the epithermal neutron flux enhancement body of the cylindrical or conical structure coincides with the beam axis.
  • a neutron capture therapy system comprising: a charged particle beam generating unit, for generating a charged particle beam; a neutron generating unit, for generating a neutron beam, comprising a target material and the above-mentioned beam shaper; and a beam transmission unit, for transmitting the charged particle beam to the neutron generating unit, wherein the charged particle beam interacts with the target material to generate a neutron beam, and the neutron beam is slowed down by the beam shaper to form an epithermal neutron beam required for neutron capture therapy.
  • the beam shaper comprises:
  • a retarder for decelerating neutrons of a neutron beam into epithermal neutrons, the neutron beam defining a beam axis, the retarder extending a first predetermined length along the beam axis and extending a first predetermined width in a radial direction of the beam axis;
  • a reflector surrounding the retarder and used to reflect neutrons deviated from the neutron beam back into the neutron beam to increase the neutron beam intensity, at least a portion of the reflector extending along the beam axis by a second preset length and extending along the radial direction of the beam axis outside the retarder by a second preset width;
  • An epithermal neutron flux enhancer used for increasing the epithermal neutron flux in the neutron beam, is disposed in the retarder and/or in the reflector and/or between the retarder and the reflector, the epithermal neutron flux enhancer extending a third preset length along the beam axis and a third preset width along the radial direction of the beam axis, wherein the third preset width is less than the sum of the first preset width and the second preset width.
  • FIG1 is a schematic diagram of a boron neutron capture reaction
  • FIG2 is the 10 B(n, ⁇ ) 7 Li neutron capture nuclear reaction equation.
  • FIG3 is a schematic diagram of the structure of a neutron capture therapy system according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of the structure of a beam shaping body in an embodiment of the present invention, wherein the epithermal neutron flux enhancement body is a cylindrical structure, at least part of which is disposed in the retarder.
  • FIG. 5 is a schematic diagram of the dimensions of a beam shaping body in an embodiment of the present invention, wherein the epithermal neutron flux enhancement body is a cylindrical structure, at least part of which is disposed in the retarder.
  • FIG. 6 is a schematic diagram of radial dimensions of a beam shaping body in an embodiment of the present invention, wherein the epithermal neutron flux enhancement body is a cylindrical structure, at least partly disposed in the retarder.
  • FIG. 7 is a schematic structural diagram of an epithermal neutron flux enhancement layer of a tubular structure in one embodiment of the present invention.
  • FIG8 is a cross-sectional view of an epithermal neutron flux enhancement layer of a cylindrical structure in one embodiment of the present invention.
  • FIG9 is a schematic diagram of the structure of a beam shaping body in an embodiment of the present invention, wherein the epithermal neutron flux enhancement body is a cylindrical structure and is disposed in a reflector.
  • FIG. 10 is a schematic diagram of radial dimensions of a beam shaping body in an embodiment of the present invention, wherein the epithermal neutron flux enhancement body is a cylindrical structure disposed in a reflector.
  • FIG. 11 is a schematic diagram of the structure of a beam shaping body in an embodiment of the present invention, wherein one side of the epithermal neutron flux enhancement body having a cylindrical structure is a conical structure.
  • FIG. 12 is a schematic diagram of the structure of a beam shaping body in an embodiment of the present invention, wherein the epithermal neutron flux enhancement body having a cylindrical structure has conical structures on both sides.
  • FIG. 13 is a schematic structural diagram of an epithermal neutron flux enhancement layer having a cylindrical structure with conical structures on both sides in one embodiment of the present invention.
  • FIG. 14 is a cross-sectional view of an epithermal neutron flux enhancement layer of a cylindrical structure with conical structures on both sides in one embodiment of the present invention.
  • FIG. 15( a ) shows the variation trend of ⁇ ep with the thickness of the epithermal neutron flux enhancement layer in one embodiment of the present invention
  • FIG. 15( b ) is a graph showing the variation trend of J ep / ⁇ ep with the thickness of the epithermal neutron flux enhancement layer in one embodiment of the present invention
  • FIG. 15( c ) is a graph showing the variation trend of D f / ⁇ ep with the thickness of the epithermal neutron flux enhancement layer in one embodiment of the present invention
  • FIG. 15( d ) shows the variation trend of D ⁇ / ⁇ ep with the thickness of the epithermal neutron flux enhancement layer in one embodiment of the present invention
  • FIG. 15( e ) shows the variation trend of ⁇ th / ⁇ ep with the thickness of the epithermal neutron flux enhancement layer in one embodiment of the present invention.
  • 16 is a schematic diagram of the structure of a beam shaper in an embodiment of the present invention, wherein the epithermal neutron flux enhancer is a cone-shaped structure and is located on the upstream side of the beam shaper along the neutron beam direction.
  • 17 is a schematic diagram of the dimensions of a beam shaper in an embodiment of the present invention, wherein the epithermal neutron flux enhancer is a cone-shaped structure and is located on the upstream side of the beam shaper along the neutron beam direction.
  • FIG. 18 is a schematic diagram of the radial dimensions of a beam shaper in an embodiment of the present invention, wherein the epithermal neutron flux enhancer is a conical structure and is located on the upstream side of the beam shaper along the neutron beam direction.
  • FIG. 19 is a schematic diagram of the structure of an epithermal neutron flux enhancement layer with a conical structure in one embodiment of the present invention.
  • FIG. 20 is a cross-sectional view of an epithermal neutron flux enhancement layer of a conical structure in one embodiment of the present invention.
  • 21 is a schematic diagram of the structure of a beam shaper in an embodiment of the present invention, wherein the epithermal neutron flux enhancer is a conical structure and is located on the downstream side of the beam shaper along the neutron beam direction.
  • FIG. 22 is a schematic diagram of the structure of a beam shaper in an embodiment of the present invention, wherein the epithermal neutron flux enhancer is a conical structure, which is located at the upstream and downstream sides of the beam shaper along the neutron beam direction.
  • first and second are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as “first” and “second” may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of “plurality” is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.
  • the terms “installed”, “connected”, “connected”, “fixed” and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.
  • installed can be a fixed connection, a detachable connection, or an integral connection
  • it can be a mechanical connection or an electrical connection
  • it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.
  • the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
  • a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium.
  • a first feature being “above”, “above” or “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature.
  • a first feature being “below”, “below” or “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.
  • Neutron capture therapy is an effective means of treating cancer. Its application has gradually increased in recent years. Among them, boron neutron capture therapy is the most common.
  • the neutrons supplied for boron neutron capture therapy can be supplied by nuclear reactors or accelerators.
  • the embodiment of the present invention takes accelerator boron neutron capture therapy as an example.
  • the basic components of accelerator boron neutron capture therapy usually include an accelerator for accelerating charged particles (such as protons, deuterons, etc.), a target material and a heat removal system and a beam shaper. The accelerated charged particles interact with the metal target material to produce neutrons.
  • the appropriate nuclear reaction is selected based on the required neutron yield and energy, the energy and current of the accelerated charged particles that can be provided, the physical and chemical properties of the metal target material, and other characteristics.
  • the nuclear reactions that are often discussed are 7 Li(p,n) 7 Be and 9 Be(p,n) 9 B, both of which are endothermic reactions.
  • the energy thresholds of the two nuclear reactions are 1.881 MeV and 2.055 MeV, respectively. Since the ideal neutron source for BNCT is epithermal neutrons at the keV energy level, theoretically, if protons with energy only slightly higher than the threshold are used to bombard lithium metal targets, relatively low-energy neutrons can be produced, which can be used clinically without much slowing down. However, the cross-sections of lithium metal (Li) and beryllium metal (Be) targets with protons of threshold energy are not high. In order to produce a sufficiently large neutron flux, protons with higher energy are usually used to initiate nuclear reactions.
  • BNCT Boron Neutron Capture Therapy
  • 10B boron
  • 10B boron
  • Figures 1 and 2 which respectively show a schematic diagram of the boron neutron capture reaction and the 10B (n, ⁇ ) 7Li neutron capture nuclear reaction equation
  • the average energy of the two charged particles is about 2.33MeV, with high linear transfer and short range characteristics.
  • the linear energy transfer and range of ⁇ particles are 150keV/ ⁇ m and 8 ⁇ m, respectively, while those of 7Li heavy-charged particles are 175keV/ ⁇ m and 5 ⁇ m.
  • the total range of the two particles is approximately equivalent to the size of a cell. Therefore, the radiation damage caused to the organism can be limited to the cellular level.
  • the boron-containing drugs selectively accumulate in tumor cells and are combined with an appropriate neutron source, the purpose of locally killing tumor cells can be achieved without causing too much damage to normal tissues.
  • the nuclear reaction between charged particles and the target material produces a mixed radiation field, that is, the beam contains neutrons and photons ranging from low energy to high energy.
  • the beam contains neutrons and photons ranging from low energy to high energy.
  • the International Atomic Energy Agency has given five recommendations for air beam quality factors for neutron sources used in clinical boron neutron capture therapy. These five recommendations can be used to compare the advantages and disadvantages of different neutron sources and serve as a reference for selecting neutron production methods and designing beam shapers. The five recommendations are as follows:
  • the epithermal neutron energy range is between 0.5eV and 10keV, the thermal neutron energy range is less than 0.5eV, and the fast neutron energy range is greater than 10keV.
  • the epithermal neutron energy region may be set between 0.5eV-40keV, the thermal neutron energy region may be less than 0.5eV, and the fast neutron energy region may be greater than 40keV.
  • the neutron beam flux and the concentration of boron-containing drugs in the tumor jointly determine the clinical treatment time. If the concentration of boron-containing drugs in the tumor is high enough, the requirement for neutron beam flux can be reduced; conversely, if the concentration of boron-containing drugs in the tumor is low, a high flux of epithermal neutrons is required to give the tumor a sufficient dose.
  • the IAEA's requirement for epithermal neutron beam flux is that the number of epithermal neutrons per square centimeter per second is greater than 10 9. Neutron beams at this flux can roughly control the treatment time for current boron-containing drugs within one hour. In addition to the advantages of patient positioning and comfort, short treatment time can also more effectively utilize the limited residence time of boron-containing drugs in the tumor.
  • fast neutrons can cause unnecessary normal tissue doses, they are considered contamination.
  • the dose is positively correlated with the neutron energy, so the content of fast neutrons should be minimized in neutron beam design.
  • Fast neutron contamination is defined as the fast neutron dose associated with a unit epithermal neutron flux.
  • the IAEA recommends that fast neutron contamination be less than 2 ⁇ 10 -13 Gy-cm 2 /n.
  • Gamma rays are highly penetrating radiation that non-selectively causes dose deposition in all tissues along the beam path. Therefore, reducing the gamma ray content is also a necessary requirement for neutron beam design.
  • Gamma ray contamination is defined as the gamma ray dose associated with a unit epithermal neutron flux.
  • the IAEA recommends gamma ray contamination to be less than 2 ⁇ 10 -13 Gy-cm 2 /n.
  • thermal neutrons decay quickly and have poor penetration, most of their energy is deposited in the skin tissue after entering the human body.
  • epidermal tumors such as melanocytoma
  • thermal neutrons as a neutron source for boron neutron capture therapy
  • the thermal neutron content should be reduced for deep tumors such as brain tumors.
  • the IAEA recommends that the ratio of thermal neutrons to epithermal neutrons be less than 0.05.
  • the ratio of neutron current to flux represents the directionality of the beam. The larger the ratio, the better the forward direction of the neutron beam.
  • a highly forward-directed neutron beam can reduce the dose to surrounding normal tissues caused by neutron divergence, and also increase the treatment depth and positioning flexibility.
  • the IAEA recommends that the ratio of neutron current to flux be greater than 0.7.
  • the MCNP software (a general software package based on the Monte Carlo method developed by Los Alamos National Laboratory in the United States for calculating neutron, photon, charged particle or coupled neutron/photon/charged particle transport problems in three-dimensional complex geometric structures) is used to calculate the quality of the neutron beam in the air in the embodiment of the present invention.
  • FIG. 3 shows a schematic diagram of the structure of a neutron capture therapy system in an embodiment of the present invention.
  • the neutron capture therapy system is preferably a boron neutron capture therapy system 100.
  • the neutron beam N generated by the neutron generation unit irradiates the affected part M of the irradiated body 200 located on the treatment table 20.
  • the neutron beam N and the boron (B-10)-containing drug in the affected part M undergo a boron neutron capture reaction as described above, thereby eliminating tumor cells or other substances in the affected part M to achieve a therapeutic effect.
  • the boron neutron capture therapy system 100 includes a charged particle beam generating unit 11, a beam transmission unit 12, and a neutron beam generating unit 13.
  • the charged particle beam generating unit 11 generates a charged particle beam P such as a proton beam; the beam transmission unit 12 transmits the charged particle beam P to the neutron beam generating unit 13; the neutron beam generating unit 13 generates a therapeutic neutron beam N and irradiates the irradiated body 200 on the treatment table 20.
  • the charged particle beam generating unit 11 includes an ion source 111 and an accelerator 112.
  • the ion source 111 is used to generate charged particles such as H- , protons, deuterons, etc.; the accelerator 112 accelerates the charged particles generated by the ion source 111 to obtain a charged particle beam P of required energy, such as a proton beam.
  • the accelerator 112 can be a linear accelerator, a cyclotron, a synchrotron, or a synchrocyclotron.
  • the neutron beam generating unit 13 includes a beam shaper 131, a collimator 132 and a target material 133.
  • the charged particle beam P generated by the accelerator 112 reaches the neutron beam generating unit 13 via the beam transmission unit 12, reacts with the target material 133 to generate neutrons, and the beam quality is adjusted by the beam shaper 131 and the collimator 132 to form a therapeutic neutron beam N and irradiate the irradiated object 200 on the treatment table 20.
  • the beam shaper 131 can adjust the beam quality of the neutron beam N.
  • the collimator 132 is used to converge the neutron beam N so that the neutron beam N has a higher targeting during the treatment process.
  • the beam shaper 131 further includes a beam inlet 1311, a retarder 1312, a reflector 1313 surrounded by the retarder 1312, and a beam outlet 1314.
  • the boron neutron capture therapy system 100 accelerates the charged particle beam P generated by the ion source 111 through the accelerator 112, and the charged particle beam P enters the beam shaping body 131 through the beam entrance 1311.
  • a part of the beam entrance 1311 is accommodated in the retarder 1312, and another part is accommodated in the reflector 1313.
  • the ideal target material 133 should have the characteristics of high neutron yield, neutron energy distribution close to the epithermal neutron energy zone, no too much strong penetrating radiation, safe, cheap, easy to operate and high temperature resistance, but in fact it is impossible to find a nuclear reaction that meets all the requirements.
  • the target material 133 in this embodiment is selected from materials that meet the above requirements as much as possible, such as Li or Be. It is well known to those skilled in the art that the target material 133 can also be made of metal materials other than Li and Be, such as Ta or W and their alloys. As a preferred embodiment, the target material 133 is made of lithium metal and contained in the retarder 1312.
  • the charged particle beam P is accelerated to an energy sufficient to overcome the Coulomb repulsion of the nuclei of the target material 133, and a 7 Li(p,n) 7 Be nuclear reaction occurs with the target material 133 to produce neutrons.
  • the neutrons form a neutron beam N, and the neutron beam N defines the beam axis X. Since the neutrons generated by the charged particle beam P and the target material 133 have a wide energy spectrum, in addition to epithermal neutrons that meet the treatment needs, it is necessary to reduce other types of neutrons and light as much as possible.
  • the neutrons coming out of the target 133 need to pass through the retarder 1312 to adjust the fast neutron energy (>10keV) to the epithermal neutron energy region (0.5eV-10keV) and reduce the thermal neutrons ( ⁇ 0.5eV) as much as possible.
  • the retarder 1312 extends a first preset length L1 along the beam axis X and extends a first preset width D1 along the radial direction of the beam axis X.
  • the retarder 1312 is made of a material having a large cross section for interaction with fast neutrons and a small cross section for interaction with epithermal neutrons.
  • the retarder 1312 is made of at least one of D 2 O, AlF 3 , CaF 2 , Li 2 CO 3 , MgF 2 , Al 2 O 3 and a mixed material of Al, AlF 3 and LiF in a preset ratio, wherein the mixed material of Al, AlF 3 and LiF in a preset ratio is preferably a Fluental material.
  • the reflector 1313 surrounds the retarder 1312 and reflects the neutrons diffused around through the retarder 1312 back to the neutron beam N to increase the intensity of the neutron beam N. At least part of the reflector 1313 extends along the beam axis X by a second preset length L2 and extends outside the retarder 1312 by a second preset width D2 in the radial direction of the beam axis X.
  • the reflector 1313 is made of a material with strong neutron reflection capability. In this embodiment, the reflector 1313 is made of Pb.
  • the beam shaping body 131 further includes a beam outlet 1314 and a radiation shield 1315 surrounding the reflector 1313.
  • the radiation shield 1315 is used to shield leaked neutrons and photons to reduce the normal tissue dose in the non-irradiated area.
  • the radiation shield 1315 extends a fourth preset length L4 along the beam axis X and extends a fourth preset width D4 outside the reflector 1313 in the radial direction of the beam axis X, and the radiation shield 1315 is flush with the reflector 1313 at the beam outlet 1314.
  • the radiation shield here is expressed as a fourth preset length L4 and a fourth preset width D4.
  • the material of the radiation shielding body 1315 includes at least one of a photon shielding material and a neutron shielding material, and can be a rigid solid cut into a suitable size, such as lead-antimony alloy, Teflon, graphite, paraffin, PE, PE containing boron carbide or lithium carbonate or lithium fluoride, PMMA (acrylic), PMMA containing boron carbide or lithium carbonate or lithium fluoride, or boron-containing barite concrete; it can also be a powder filled in a rigid container or a flexible container cut into a suitable size, such as boron carbide or lithium carbonate or lithium fluoride powder; it can also be a liquid filled in a rigid container or a flexible container cut into a suitable size, such as water, heavy water, boric acid that dissolves boron carbide or lithium carbonate or lithium fluoride powder; it can also be a flexible solid, such as rubber or silica gel.
  • the radiation shielding body 1315 is preferably made of a material
  • the beam shaping body 131 may also have other components and structures, such as a thermal neutron absorber that absorbs thermal neutrons, a beam inlet that is not contained in a retarder, etc., as long as the epithermal neutron beam required for treatment can be obtained.
  • the collimator 132 is disposed behind the beam outlet 1314 or inside the beam shaping body 131, and the epithermal neutron beam from the collimator 132 irradiates the irradiated object 200. It is understood that the collimator 132 may also be eliminated or replaced by other structures, and the neutron beam from the beam outlet 1314 directly irradiates the irradiated object 200.
  • the beam shaping body 131 further includes an epithermal neutron flux enhancer 1316, which is disposed in the retarder 1312 and/or in the reflector 1313 and/or between the retarder 1312 and the reflector 1313.
  • an epithermal neutron flux enhancer 1316 which is disposed in the retarder 1312 and/or in the reflector 1313 and/or between the retarder 1312 and the reflector 1313.
  • the epithermal neutron flux enhancer 1316 extends a third preset length L3 along the beam axis X and extends a third preset width D3 in the radial direction of the beam axis X, wherein the third preset width D3 is less than the sum of the first preset width D1 and the second preset width D2.
  • the third preset width D3 is less than the first preset width D1.
  • the epithermal neutron flux enhancer 1316 extends a third preset width D3 in the radial direction of the beam axis X, including the thickness of the epithermal neutron flux enhancer.
  • the epithermal neutron flux enhancer 1316 is made of a material with strong neutron reflection ability.
  • the epithermal neutron flux enhancer 1316 is made of Ni, including natural nickel or purified nickel.
  • the epithermal neutron flux enhancement body 1316 is constructed as a cylindrical structure, which includes a first side portion 1316a and a second side portion 1316b perpendicular to the beam axis X, and a first wall 1316c and a second wall 1316d circumferentially closed around the beam axis X.
  • the first side portion 1316a and the second side portion 1316b are sequentially arranged along the direction of the neutron beam N, and the first side portion 1316a is farther away from the beam outlet 1314 than the second side portion 1316b.
  • the first side portion 1316a is arranged between the retarder 1312 and the reflector 1313 along the direction of the beam axis X, and is adjacent to the end surface of the retarder 1312 located on the upstream side of the neutron beam N.
  • the first side portion 1316a is configured as a circular ring structure and is provided with a first central hole, and the first central hole is used to allow the beam entrance 1311 to pass through, so that the beam entrance 1311 can be accommodated in the retarder 1312.
  • the second side portion 1316b is provided with a second central hole, adjacent to the end surface of the beam shaping body 131 located on the downstream side of the neutron beam N, and is used to be combined with the beam outlet 1314.
  • the second side portion 1316b When the radial dimension of the second central hole is equal to the outer diameter of the first wall 1316c, the second side portion 1316b is in an open state without a closed structure, and the first wall 1316c and the second wall 1316d are arranged along the radial direction of the beam axis X, perpendicular to the first side portion 1316a and the second side portion 1316b.
  • the first wall 1316c and the second wall 1316d are connected to the first side portion 1316a and extend to the second side portion 1316b along the beam axis X.
  • the center line of the epithermal neutron flux enhancer 1316 of the tubular structure coincides with the axis of the neutron beam N
  • the third preset width D3 is smaller than the first preset width D1
  • at least a portion of the first wall 1316c and the second wall 1316d are accommodated in the retarder 1312, that is, the epithermal neutron flux enhancer 1316 of the tubular structure is
  • the strong body 1316 is at least partially disposed in the slow body 1312. It can be understood that the upstream side of the neutron beam N is the side close to the beam entrance 1311 and the target 133, and the downstream side of the neutron beam N is the side close to the beam exit 1314.
  • FIGS. 9 and 10 show schematic diagrams of the structure of the beam shaper in one embodiment of the present invention from different perspectives, wherein the epithermal neutron flux enhancer 1316 is a cylindrical structure.
  • the difference from the embodiment disclosed in FIGS. 4 to 8 is that the first wall and the second wall of the epithermal neutron flux enhancer 1316 are at least partially disposed in the reflector 1313.
  • the third preset width D3 of the epithermal neutron flux enhancer 1316 of the tubular structure extending along the radial direction of the beam axis X is greater than the first preset width D1 of the retarder 1312 extending along the radial direction of the beam axis X, and is smaller than the sum of the first preset width D1 of the retarder 1312 extending along the radial direction of the beam axis X and the second preset width D2 of the partial reflector 1313 extending along the radial direction of the beam axis X outside the retarder 1312, and the first wall 1316c and the second wall 1316d are both adjacent to the reflector 1313, that is, the epithermal neutron flux enhancer 1316 of the tubular structure is arranged in the reflector 1313.
  • Table 1 shows the performance of the beam quality factor in the air when the epithermal neutron flux enhancement body is not provided and the epithermal neutron flux enhancement body of the cylindrical structure is provided at different positions (the units of the terms in the table are the same as those described above, and will not be repeated here, the same below):
  • Table 1 Beam quality of the epithermal neutron flux enhancer with a cylindrical structure at different locations
  • the first side portion 1316a and/or the second side portion 1316b of the epithermal neutron flux enhancer 1316 of the cylindrical structure are configured as a conical structure that contracts toward the beam axis X.
  • the radial dimension of the outer contour of the first side portion 1316a gradually increases along the direction of the neutron beam N, and the radial dimension of the outer contour of the second side portion 1316b gradually decreases along the direction of the neutron beam N.
  • the radial dimension of the outer contour of the first side portion 1316a is at least greater than the radial dimension of the central hole, and the radial dimension of the outer contour of the second side portion 1316b at least accommodates the beam outlet 1314.
  • FIG. 11 shows a schematic diagram of the structure of a beam shaping body in an embodiment of the present invention, wherein one side of the epithermal neutron flux enhancement body 1316 of the cylindrical structure is a conical structure.
  • the same reference numerals as those described in the above embodiments are not shown in FIG. 11, such as the first preset width D1, the third preset width D3, the first side portion 1316a, the second side portion 1316b, the first wall 1316c and the second wall 1316d, etc., which can be specifically referred to in the above embodiments.
  • reference numerals that appear but do not appear in the corresponding drawings can be referred to here.
  • the third preset width D3 of the epithermal neutron flux enhancement body 1316 of the cylindrical structure extending along the radial direction of the beam axis X is smaller than the first preset width D1 of the retarder 1312 extending along the radial direction of the beam axis X, and the first wall 1316c and the second wall 1316d are at least partially accommodated in the retarder 1312, that is, the epithermal neutron flux enhancement body 1316 is at least partially disposed in the retarder 1312.
  • the first side portion 1316a is adjacent to the end face of the retarder 1312 located on the upstream side of the neutron beam N
  • the second side portion 1316b is adjacent to the end face of the retarder 1312 located on the downstream side of the neutron beam N.
  • the radial dimension of the outer contour of the second side portion 1316b gradually decreases along the direction of the neutron beam N, and the radial dimension of the outer contour gradually decreases from the third preset width D3 to the size of the beam outlet 1314, that is, the second side portion 1316b shrinks toward the beam outlet 1314, and one side of the tubular structure of the epithermal neutron flux enhancer 1316 is a conical structure.
  • FIG. 12 shows a schematic diagram of the structure of a beam shaping body in an embodiment of the present invention, wherein both sides of the epithermal neutron flux enhancement body 1316 of the cylindrical structure are conical structures.
  • the third preset width D3 of the tubular epithermal neutron flux enhancer 1316 extending in the radial direction of the beam axis X is smaller than the first preset width D1 of the retarder 1312 extending in the radial direction of the beam axis X
  • the first wall 1316c and the second wall 1316d are at least partially accommodated in the retarder 1312, that is, the epithermal neutron flux enhancer 1316 is at least partially disposed in the retarder 1312
  • the first side portion 1316a is adjacent to the end surface of the retarder 1312 located on the upstream side of the neutron beam N
  • the radial dimension of the outer contour of the first side portion 1316a gradually increases along the direction of the neutron beam N
  • the second side portion 1316b is adjacent to the end face of the retarder 1312 located on the downstream side of the neutron beam N, and the radial dimension of the outer contour of the second side portion 1316b gradually decreases along the direction of the neutron beam N.
  • the radial dimension of the outer contour of the second side portion 1316b gradually decreases from the third preset width D3 to the size of the beam outlet 1314, that is, the second side portion 1316b shrinks toward the beam outlet 1314, and both sides of the tubular structure of the epithermal neutron flux enhancer 1316 are conical structures.
  • Table 2 shows the performance of the beam quality factor in air when no epithermal neutron flux enhancer is provided, a cylindrical (without a conical structure) epithermal neutron flux enhancer is provided, and a cylindrical epithermal neutron flux enhancer with a conical structure on one or both sides:
  • Table 2 Beam quality of the epithermal neutron flux enhancer with a cylindrical structure when one or both sides are conical
  • the epithermal neutron flux enhancer is provided in the beam shaper and one or both sides of the epithermal neutron flux enhancer with a cylindrical structure is provided with a conical structure, which can increase the epithermal neutron flux in the neutron beam and improve the neutron beam quality.
  • the third preset width D3 of the epithermal neutron flux enhancement body 1316 of the cylindrical structure extending in the radial direction of the beam axis X is smaller than the first preset width D1 of the retarder 1312 extending in the radial direction of the beam axis X, and the first wall 1316c and the second wall 1316d are at least partially accommodated in the retarder 1312, that is, the epithermal neutron flux enhancement body 1316 is at least partially disposed in the retarder 1312.
  • the first side portion 1316a is adjacent to the end surface of the retarder 1312 located on the upstream side of the neutron beam N, and the radial dimension of the outer contour of the first side portion 1316a gradually increases along the neutron beam N direction, and the radial dimension of the outer contour of the first side portion 1316a gradually increases from the radial dimension of the central hole to the third preset width D3, that is, the first side portion 1316a shrinks toward the beam entrance 1311.
  • the second side portion 1316b is adjacent to the end face of the retarder 1312 located on the downstream side of the neutron beam N, the radial dimension of the outer contour of the second side portion 1316b gradually decreases along the direction of the neutron beam N, and the radial dimension of the outer contour of the second side portion 1316b gradually decreases from the third preset width D3 to the size of the beam outlet 1314, that is, the second side portion 1316b shrinks toward the beam outlet 1314, and both sides of the epithermal neutron flux enhancement body 1316 of the tubular structure are conical structures.
  • the thickness of the epithermal neutron flux enhancement body 1316 is less than the sum of the first preset width D1 and the second preset width D2, preferably 1-5 cm, and more preferably 3-5 cm.
  • Table 3 shows the performance of the beam quality factor in the air when no epithermal neutron flux enhancer is set and the thickness of the epithermal neutron flux enhancer is different:
  • the epithermal neutron flux enhancer is provided in the beam shaper and the thickness of the epithermal neutron flux enhancer is appropriately increased, which can increase the epithermal neutron flux in the neutron beam and improve the neutron beam quality.
  • the thickness of the epithermal neutron flux enhancer is preferably 1-8 cm, more preferably 3-5 cm, so as to obtain an epithermal neutron beam with good beam quality that meets the requirements of neutron capture therapy.
  • the epithermal neutron flux enhancer 1316 is constructed as a conical structure, which includes a first end face 1316e and a second end face 1316f perpendicular to the beam axis X and a third wall 1316g and a fourth wall 1316h circumferentially closed around the beam axis X.
  • the first end face 1316e and the second end face 1316f are arranged in sequence along the direction of the neutron beam N
  • the third wall 1316g and the fourth wall 1316h are arranged along the radial direction of the beam axis X
  • the first end face 1316e and the second end face 1316f are both arranged to be openings.
  • FIGS 16 to 20 show schematic diagrams of the structure of the beam shaping body in an embodiment of the present invention, wherein the epithermal neutron flux enhancement body 1316 is a conical structure, and is located on the upstream side of the beam shaping body 131 along the direction of the neutron beam N.
  • the radial dimension of the outer contour of the conical epithermal neutron flux enhancement body 1316 gradually increases along the direction of the neutron beam N, and the first end face 1316e is adjacent to the end face of the retarder 1312 located on the upstream side of the neutron beam N, and the size of the first end face 1316e at least accommodates the beam entrance 1311, that is, the conical epithermal neutron flux enhancement body 1316 is arranged on the upstream side of the neutron beam N, and the radial inner diameter of the first end face 1316e is greater than the radial outer diameter of the beam entrance 1311.
  • a third preset width D3 of the epithermal neutron flux enhancer 1316 extending in the radial direction of the beam axis is smaller than a first preset width D1 of the retarder 1312 extending in the radial direction of the beam axis, and the third wall 1316g and the fourth wall 1316h are accommodated in the retarder 1312, that is, the epithermal neutron flux enhancer 1316 of the conical structure is arranged in the retarder 1312, close to the beam entrance 1311, the center line of the epithermal neutron flux enhancer 1316 of the conical structure coincides with the beam axis X, and the radial dimension of the outer contour of the epithermal neutron flux enhancer 1316 of the conical structure gradually increases from the dimension of the beam entrance 1311 to the third preset width D3 along the neutron beam N direction.
  • FIG. 21 shows a schematic diagram of the structure of a beam shaping body in an embodiment of the present invention, wherein the epithermal neutron flux enhancement body 1316 is a conical structure, and is located at the downstream side of the beam shaping body 131 along the direction of the neutron beam N.
  • the radial dimension of the outer contour of the conical epithermal neutron flux enhancement body 1316 gradually decreases along the direction of the neutron beam N, the second end face 1316f is adjacent to the end face of the beam shaping body 100 located at the downstream side of the neutron beam, and the dimension of the second end face 1316f at least accommodates the beam outlet 1314, that is, the conical epithermal neutron flux enhancement body 1316 is disposed at the downstream side of the neutron beam N, and the radial inner diameter of the second end face 1316f is greater than the radial outer diameter of the beam outlet 1314.
  • the third preset width D3 of the epithermal neutron flux enhancer 1316 extending in the radial direction of the beam axis X is smaller than the first preset width D1 of the retarder 1312 extending in the radial direction of the beam axis X, the third wall 1316g is adjacent to the reflector 1313, and the fourth wall 1316h is adjacent to the beam outlet 1314.
  • the center line of the epithermal neutron flux enhancer 1316 of the conical structure coincides with the beam axis X, and the radial dimension of the outer contour of the epithermal neutron flux enhancer 1316 of the conical structure gradually decreases from the third preset width D3 to the dimension of the beam outlet 1314 along the neutron beam N direction.
  • FIG. 22 shows a schematic diagram of the structure of a beam shaper in an embodiment of the present invention, wherein the epithermal neutron flux enhancer 1316 is a combination of two conical structures, which are respectively located at the upstream side and the downstream side of the beam shaper 131 along the neutron beam N direction.
  • the radial dimension of the outer contour of the conical structure of the epithermal neutron flux enhancer 1316 on the upstream side gradually increases along the neutron beam N direction, and the first end face 1316e is adjacent to the end face of the retarder 1312 on the upstream side of the neutron beam N, and the size of the first end face 1316e at least accommodates the beam inlet 1311.
  • the radial dimension of the outer contour of the conical structure of the epithermal neutron flux enhancer 1316 on the downstream side gradually decreases along the neutron beam N direction, and the second end face 1316f is adjacent to the end face of the beam shaper 131 on the downstream side of the neutron beam, and the size of the second end face 1316f at least accommodates the beam outlet 1314.
  • the third preset width D3 of the epithermal neutron flux enhancer 1316 extending in the radial direction of the beam axis X is smaller than the first preset width D1 of the retarder 1312 extending in the radial direction of the beam axis X, and the center line of the epithermal neutron flux enhancer 1316 coincides with the beam axis X.
  • the radial dimension of the outer contour of the epithermal neutron flux enhancer 1316 of the cone-shaped structure on the upstream side gradually increases from the dimension of the beam entrance 1311 to the third preset width D3 along the direction of the neutron beam N
  • the radial dimension of the outer contour of the epithermal neutron flux enhancer 1316 of the cone-shaped structure on the downstream side gradually increases from the dimension of the beam entrance 1311 to the third preset width D3.
  • the radial dimension of the outer contour of the conical epithermal neutron flux enhancer 1316 gradually decreases along the neutron beam N direction from the third preset width D3 to the dimension of the beam exit 1314 .
  • Table 4 shows the performance of the beam quality factor in the air when no epithermal neutron flux enhancer is set and the epithermal neutron flux enhancer of the cone structure is set at different positions:
  • Table 4 Beam quality of the epithermal neutron flux enhancer with a cone-shaped structure at different positions
  • the epithermal neutron flux enhancer 1316 is a cylindrical structure or a conical structure or a cylindrical plus conical structure as a whole.
  • the epithermal neutron flux enhancer 1316 can be integrally formed as a whole, or it can be obtained by combining a plurality of components in blocks.
  • the epithermal neutron flux enhancer 1316 can be assembled and formed together with the retarder 1312 and the reflector 1313, so that the epithermal neutron flux enhancer 1316 is arranged in the beam shaping body 131; or a receiving cavity can be arranged in the retarder 1312 or the reflector 1313, and then the epithermal neutron flux enhancer 1316 is placed in the receiving cavity, so that the epithermal neutron flux enhancer 1316 is arranged in the beam shaping body 131.
  • the "cylindrical” described in the embodiment of the present invention refers to a structure in which the overall trend of the outer contour remains basically unchanged from one side to the other side along the direction shown in the figure.
  • One of the contour lines of the outer contour can be a line segment, such as the corresponding contour line of a cylinder, or it can be an arc with a large curvature close to a line segment, such as the corresponding contour line of a spherical body with a large curvature.
  • the entire surface of the outer contour can be a smooth transition or a non-smooth transition, such as making many protrusions and grooves on the surface of a cylinder or a spherical body with a large curvature.
  • the "cone” in the embodiment of the present invention refers to a structure in which the overall trend of the outer contour gradually decreases from one side to the other side along the direction shown in the figure.
  • One of the contour lines of the outer contour can be a line segment, such as the corresponding contour line of a cone, or It is an arc, such as the corresponding contour line of a spherical body.
  • the entire surface of the outer contour can be smoothly transitioned or non-smoothly transitioned, such as making many protrusions and grooves on the surface of a cone or spherical body.

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Abstract

一种用于中子捕获治疗***(100)的射束整形体(131)，包括：缓速体(1312)，用于将中子射束(N)的中子减速至超热中子；包围缓速体(1312)的反射体(1313)，用于将偏离中子射束(N)的中子反射回中子射束(N)以提高中子射束(N)强度；及超热中子通量增强体(1316)，用于提高中子射束(N)中的超热中子通量，设置于缓速体(1312)中和/或反射体(1313)中和/或缓速体(1312)与反射体(1313)之间。一种包含上述射束整形体(131)的中子捕获治疗***(100)，通过在射束整形体(131)中设置超热中子通量增强体(1316)，增加中子射束(N)中的超热中子通量，改善中子射源的通量与品质。

Description

射束整形体及中子捕获治疗*** 技术领域
本发明涉及辐射线照射领域，特别是涉及一种射束整形体及中子捕获治疗***。
背景技术
随着原子科学的发展，例如钴六十、直线加速器、电子射束等放射线治疗已成为癌症治疗的主要手段之一。然而传统光子或电子治疗受到放射线本身物理条件的限制，在杀死肿瘤细胞的同时，也会对射束途径上大量的正常组织造成伤害；另外由于肿瘤细胞对放射线敏感程度的不同，传统放射治疗对于较具抗辐射性的恶性肿瘤(如：多行性胶质母细胞瘤(glioblastomamultiforme)、黑色素细胞瘤(melanoma))的治疗成效往往不佳。
为了减少肿瘤周边正常组织的辐射伤害，化学治疗(chemotherapy)中的标靶治疗概念便被应用于放射线治疗中；而针对高抗辐射性的肿瘤细胞，目前也积极发展具有高相对生物效应(relative biological effectiveness,RBE)的辐射源，如质子治疗、重粒子治疗、中子捕获治疗等。其中，中子捕获治疗便是结合上述两种概念，如硼中子捕获治疗，借由含硼药物在肿瘤细胞的特异性集聚，配合精准的中子射束调控，提供比传统放射线更好的癌症治疗选择。
硼中子捕获治疗(Boron Neutron Capture Therapy,BNCT)借由含硼药物在人体肿瘤细胞的特异性集聚，配合精准可控的中子束照射，提供比传统放射治疗更好的癌症治疗选择。在硼中子捕获治疗过程中，首先，为患者注射含硼(B-10)药物，该药物和肿瘤细胞有很强的亲和力，会选择性地聚集在肿瘤细胞内，然后对患者的肿瘤部位进行中子束照射。当中子被肿瘤细胞中的10B捕获时会发生裂变，产生α粒子和7Li粒子，释放出一种杀伤力极强的射线，该射线射程很短，只有一个肿瘤细胞的长度，从而在尽可能不损伤周围正常细胞的情况下精准地杀死肿瘤细胞。
因硼中子捕获治疗的成效取决于肿瘤细胞位置含硼药物浓度和热中子数量，故又被称为二元放射线癌症治疗(binary cancer therapy)；由此可知，除了含硼药物的开发，中子射源通量与品质的改善在硼中子捕获治疗的研究中占有重要角色。
发明内容
为改善中子射源的通量与品质，本发明的一个方面提供一种用于中子捕获治疗的射束整形体，该射束整形体包括：缓速体，用于将中子射束的中子减速至超热中子，中子射束限定射束轴线，缓速体沿着射束轴线延伸第一预设长度并且沿着射束轴线的径向方向延伸第一预设宽度；反射体，包围缓速体，用于将偏离中子射束的中子反射回中子射束以提高中子射束强度，至少部分反射体沿着射束轴线延伸第二预设长度并且在缓速体之外沿着射束轴线的径向方向延伸第二预设宽度；及超热中子通量增强体，用于提高中子射束中的超热中子通量，设置于缓速体中和/或反射体中和/或缓速体与反射体之间，超热中子通量增强体沿着射束轴线延伸第三预设长度并且沿着射束轴线的径向方向延伸第三预设宽度，其中，第三预设宽度小于第一预设宽度与第二预设宽度之和。通过在射束整形体中设置超热中子通量增强体，中子射束中的超热中子通量提高，从而改善中子射源的通量与品质。
在其中一个实施例中，射束整形体还包括：射束入口，用于带电粒子束的射入；射束出口，用于中子射束的射出；射束入口、缓速体和射束出口沿着射束轴线延伸方向设置。
在其中一个实施例中，射束整形体还包括包围反射体的辐射屏蔽体，辐射屏蔽体用于屏蔽渗漏的中子和光子以减少非照射区的正常组织剂量，辐射屏蔽体沿着射束轴线延伸第四预设长度并且在反射体之外沿着射束轴线的径向方向延伸第四预设宽度。
在其中一个实施例中，反射体的材料为Pb，缓速体的材料为D2O，AlF3，CaF2，Li2CO3，MgF2，Al2O3和Al、AlF3和LiF的预设比例的混合材料中的至少一种。
在其中一个实施例中，超热中子通量增强体的材料为Ni。
在其中一个实施例中，超热中子通量增强体被构造为筒状结构，该筒状结构包括与射束轴线垂直的第一侧部和第二侧部和围绕射束轴线周向封闭的第一壁和第二壁，第一侧部和第二侧部沿中子射束方向依次设置在筒状结构的两端，第一侧部设置第一中心孔，第一中心孔用于与射束入口结合，第二侧部设置第二中心孔，第二中心孔用于与射束出口结合。
在其中一个实施例中，筒状结构的超热中子通量增强体的第一侧部和/或第二侧部被构造为朝向射束轴线收缩的锥状结构，第一侧部的外轮廓的径向尺寸沿中子射束方向逐渐增大，第一中心孔的尺寸至少容纳射束入口，第二侧部的外轮廓的径向尺寸沿中子射束方向逐渐减小，第二侧部的第二中心孔的尺寸至少容纳射束出口。
在其中一个实施例中，超热中子通量增强体的厚度为1-8cm；更优选地，超热中子通量增强体的厚度为3-5cm。
在其中一个实施例中，超热中子通量增强体被构造为锥状结构，该锥状结构包括与射束轴线垂直的第一端面和第二端面和围绕射束轴线周向封闭的第三壁和第四壁，第一端面和第二端面沿中子射束方向依次设置，第一端面与第二端面均设置为开口。
在其中一个实施例中，锥状结构的超热中子通量增强体的外轮廓的径向尺寸沿中子射束方向逐渐增大，第一端面邻接于缓速***于中子射束方向上游侧的端面，第一端面的尺寸至少容纳射束入口。
在其中一个实施例中，锥状结构的超热中子通量增强体的外轮廓的径向尺寸沿中子射束方向逐渐减小，第二端面邻接于射束整形***于中子射束方向下游侧的端面，第二端面的尺寸至少容纳射束出口。在射束出口的位置，超热中子通量增强体设置成锥形结构，将更多的超热中子反射回中子束，从而增强超热中子束通量。
在其中一个实施例中，筒状结构或锥状结构的超热中子通量增强体的中心线与射束轴线重合。
本发明的另一个方面提供了一种中子捕获治疗***，包括：带电粒子束生成部，用于产生带电粒子束；中子生成部，用于产生中子束，包括靶材和上述射束整形体；及射束传输部，将带电粒子束传输至中子生成部，所述带电粒子束与所述靶材作用产生中子束，所述中子束经所述射束整形体慢化后形成中子捕获治疗所需的超热中子束。
在其中一个实施例中，所述射束整形体包括：
缓速体，用于将中子射束的中子减速至超热中子，所述中子射束限定射束轴线，所述缓速体沿着所述射束轴线延伸第一预设长度并且沿着所述射束轴线的径向方向延伸第一预设宽度；
反射体，包围所述缓速体，用于将偏离中子射束的中子反射回中子射束以提高中子射束强度，至少部分反射体沿着所述射束轴线延伸第二预设长度并且在所述缓速体之外沿着所述射束轴线的径向方向延伸第二预设宽度；及
超热中子通量增强体，用于提高中子射束中的超热中子通量，设置于所述缓速体中和/或所述反射体中和/或所述缓速体与所述反射体之间，所述超热中子通量增强体沿着所述射束轴线延伸第三预设长度并且沿着所述射束轴线的径向方向延伸第三预设宽度，其中，所述第三预设宽度小于所述第一预设宽度与所述第二预设宽度之和。
附图说明
图1为硼中子捕获反应示意图；
图2为10B(n,α)7Li中子捕获核反应方程式。
图3为本发明一实施例中中子捕获治疗***的结构示意图。
图4为本发明一实施例中射束整形体的结构示意图，其中超热中子通量增强体为筒状结构，至少部分设置于缓速体中。
图5为本发明一实施例中射束整形体的尺寸示意图，其中超热中子通量增强体为筒状结构，至少部分设置于缓速体中。
图6为本发明一实施例中射束整形体的径向尺寸示意图，其中超热中子通量增强体为筒状结构，至少部分设置于缓速体中。
图7为本发明一实施例中筒状结构的超热中子通量增强层的结构示意图。
图8为本发明一实施例中筒状结构的超热中子通量增强层的剖面图。
图9为本发明一实施例中射束整形体的结构示意图，其中超热中子通量增强体为筒状结构，设置于反射体中。
图10为本发明一实施例中射束整形体的径向尺寸示意图，其中超热中子通量增强体为筒状结构，设置于反射体中。
图11为本发明一实施例中射束整形体的结构示意图，其中筒状结构的超热中子通量增强体一侧为锥状结构。
图12为本发明一实施例中射束整形体的结构示意图，其中筒状结构的超热中子通量增强体两侧为锥状结构。
图13为本发明一实施例中两侧为锥状结构的筒状结构的超热中子通量增强层的结构示意图。
图14为本发明一实施例中两侧为锥状结构的筒状结构的超热中子通量增强层的剖面图。
图15(a)为本发明一实施例中Φep随超热中子通量增强层厚度变化趋势；
图15(b)为本发明一实施例中Jep/Φep随超热中子通量增强层厚度变化趋势；
图15(c)为本发明一实施例中Df/Φep随超热中子通量增强层厚度变化趋势；
图15(d)为本发明一实施例中Dγ/Φep随超热中子通量增强层厚度变化趋势；
图15(e)为本发明一实施例中Φth/Φep随超热中子通量增强层厚度变化趋势。
图16为本发明一实施例中射束整形体的结构示意图，其中超热中子通量增强体为锥状结构，沿中子射束方向位于射束整形体的上游侧。
图17为本发明一实施例中射束整形体的尺寸示意图，其中超热中子通量增强体为锥状结构，沿中子射束方向位于射束整形体的上游侧。
图18为本发明一实施例中射束整形体的径向尺寸示意图，其中超热中子通量增强体为锥状结构，沿中子射束方向位于射束整形体的上游侧。
图19为本发明一实施例中锥状结构的超热中子通量增强层的结构示意图。
图20为本发明一实施例中锥状结构的超热中子通量增强层的剖面图。
图21为本发明一实施例中射束整形体的结构示意图，其中超热中子通量增强体为锥状结构，沿中子射束方向位于射束整形体的下游侧。
图22为本发明一实施例中射束整形体的结构示意图，其中超热中子通量增强体为锥状结构，沿中子射束方向分别位于射束整形体的上游侧和下游侧。
附图标记说明：
100、中子束捕获治疗***；11、带电粒子生成部；111、离子源；112、加速器；12、
射束传输部；13、中子束生成部；131、射束整形体；1311、射束入口；1312、缓速体；1313、反射体；1314、射束出口；1315、辐射屏蔽体；1316、超热中子通量增强体；1316a、第一侧部；1316b、第二侧部；1316c、第一壁；1316d、第二壁；1316e、第一端面；1316f、第二端面；1316g、第三壁；1316h、第四壁；132、准直器；133、靶材；200、被照射体；20、治疗台；M、患处部位；L1、第一预设长度；L2、第二预设长度；L3、第三预设长度；L4、第四预设长度；D1、第一预设宽度；D2、第二预设宽度；D3、第三预设宽度；D4、第四预设宽度；X、射束轴线。
具体实施方式
为使本发明的上述目的、特征和优点能够更加明显易懂，下面结合附图对本发明的具体实施方式做详细的说明。在下面的描述中阐述了很多具体细节以便于充分理解本发明。但是本发明能够以很多不同于在此描述的其它方式来实施，本领域技术人员可以在不违背本发明内涵的情况下做类似改进，因此本发明不受下面公开的具体实施例的限制。
在本发明的描述中，需要理解的是，术语“中心”、“纵向”、“横向”、“长度”、“宽度”、“厚 度”、“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底”、“内”、“外”、“顺时针”、“逆时针”、“轴向”、“径向”、“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括至少一个该特征。在本发明的描述中，“多个”的含义是至少两个，例如两个，三个等，除非另有明确具体的限定。
在本发明中，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系，除非另有明确的限定。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本发明中的具体含义。
在本发明中，除非另有明确的规定和限定，第一特征在第二特征“上”或“下”可以是第一和第二特征直接接触，或第一和第二特征通过中间媒介间接接触。而且，第一特征在第二特征“之上”、“上方”和“上面”可是第一特征在第二特征正上方或斜上方，或仅仅表示第一特征水平高度高于第二特征。第一特征在第二特征“之下”、“下方”和“下面”可以是第一特征在第二特征正下方或斜下方，或仅仅表示第一特征水平高度小于第二特征。
需要说明的是，当元件被称为“固定于”或“设置于”另一个元件，它可以直接在另一个元件上或者也可以存在居中的元件。当一个元件被认为是“连接”另一个元件，它可以是直接连接到另一个元件或者可能同时存在居中元件。本文所使用的术语“垂直的”、“水平的”、“上”、“下”、“左”、“右”以及类似的表述只是为了说明的目的，并不表示是唯一的实施方式。
中子捕获治疗作为一种有效的治疗癌症的手段，近年来其应用逐渐增加，其中以硼中子捕获治疗最为常见，供应硼中子捕获治疗的中子可以由核反应堆或加速器供应。本发明的实施例以加速器硼中子捕获治疗为例，加速器硼中子捕获治疗的基本组件通常包括用于对带电粒子(如质子、氘核等)进行加速的加速器、靶材与热移除***和射束整形体，其中加速带电粒子与金属靶材作用产生中子，依据所需的中子产率与能量、可提供的加速带电粒子能量与电流大小、金属靶材的物化性等特性来挑选合适的核反应，常被讨论的核反应有7Li(p,n)7Be 及9Be(p,n)9B，这两种反应皆为吸热反应。两种核反应的能量阀值分别为1.881MeV和2.055MeV，由于硼中子捕获治疗的理想中子源为keV能量等级的超热中子，理论上若使用能量仅稍高于阀值的质子轰击金属锂靶材，可产生相对低能的中子，不须太多的缓速处理便可用于临床，然而锂金属(Li)和铍金属(Be)两种靶材与阀值能量的质子作用截面不高，为产生足够大的中子通量，通常选用较高能量的质子来引发核反应。
硼中子捕获治疗(Boron Neutron Capture Therapy,BNCT)是利用含硼(10B)药物对热中子具有高捕获截面的特性，借由10B(n,α)7Li中子捕获及核***反应产生4He和7Li两个重荷电粒子。参照图1和图2，其分别示出了硼中子捕获反应的示意图和10B(n,α)7Li中子捕获核反应方程式，两荷电粒子的平均能量约为2.33MeV，具有高线性转移、短射程特征，α粒子的线性能量转移与射程分别为150keV/μm、8μm，而7Li重荷粒子则为175keV/μm、5μm，两粒子的总射程约相当于一个细胞大小，因此对于生物体造成的辐射伤害能局限在细胞层级，当含硼药物选择性地聚集在肿瘤细胞中，搭配适当的中子射源，便能在不对正常组织造成太大伤害的前提下，达到局部杀死肿瘤细胞的目的。
无论硼中子捕获治疗的中子源来自核反应堆还是来自加速器,带电粒子与靶材的核反应产生的皆为混合辐射场，即射束包含了低能至高能的中子、光子；对于深部肿瘤的硼中子捕获治疗，除了超热中子外，其余的辐射线含量越多，造成正常组织非选择性剂量沉积的比例越大，因此这些会造成不必要剂量的辐射应尽量降低。
国际***(IAEA)针对临床硼中子捕获治疗用的中子源，给定了五项空气射束品质因素建议，此五项建议可用于比较不同中子源的优劣，并供以作为挑选中子产生途径、设计射束整形体时的参考依据。这五项建议分别如下：
超热中子射束通量Epithermal neutron flux>1×109n/cm2s
快中子污染Fast neutron contamination<2×10-13Gy-cm2/n
光子污染Photon contamination<2×10-13Gy-cm2/n
热中子与超热中子通量比值thermal to epithermal neutron flux ratio<0.05
中子电流与通量比值epithermal neutron current to flux ratio>0.7
注：超热中子能区在0.5eV到10keV之间，热中子能区小于0.5eV，快中子能区大于10keV。
不同的领域对于超热中子能区可以有不同的划分标准，比如还可以设定超热中子能区在0.5eV-40keV之间，热中子能区小于0.5eV，快中子能区大于40keV。
1、超热中子射束通量Φep：
中子射束通量和肿瘤中含硼药物浓度共同决定了临床治疗时间。若肿瘤含硼药物浓度够高，对于中子射束通量的要求便可降低；反之，若肿瘤中含硼药物浓度低，则需要高通量的超热中子来给予肿瘤足够的剂量。IAEA对于超热中子射束通量的要求为每秒每平方厘米的超热中子个数大于109，此通量下的中子射束对于目前的含硼药物而言可大致控制治疗时间在一小时内，短的治疗时间除了对病人定位和舒适度有优势外，也可较有效利用含硼药物在肿瘤内有限的滞留时间。
2、快中子污染Df/Φep：
由于快中子会造成不必要的正常组织剂量，因此视之为污染，此剂量大小和中子能量呈正相关，因此在中子射束设计上应尽量减少快中子的含量。快中子污染定义为单位超热中子通量伴随的快中子剂量，IAEA对快中子污染的建议为小于2×10-13Gy-cm2/n。
3、光子污染(γ射线污染)Dγ/Φep：
γ射线属于强贯穿辐射，会非选择性地造成射束路径上所有组织的剂量沉积，因此降低γ射线含量也是中子束设计的必要要求，γ射线污染定义为单位超热中子通量伴随的γ射线剂量，IAEA对γ射线污染的建议为小于2×10-13Gy-cm2/n。
4、热中子与超热中子通量比值Φth/Φep：
由于热中子衰减速度快、穿透能力差，进入人体后大部分能量沉积在皮肤组织，除黑色素细胞瘤等表皮肿瘤需用热中子作为硼中子捕获治疗的中子源外，针对脑瘤等深层肿瘤应降低热中子含量。IAEA对热中子与超热中子通量比值建议为小于0.05。
5、中子电流与通量比值Jep/Φep：
中子电流与通量比值代表了射束的方向性，比值越大表示中子射束前向性佳，高前向性的中子束可减少因中子发散造成的周围正常组织剂量，另外也提高了可治疗深度和摆位姿势弹性。IAEA对中子电流与通量比值建议为大于0.7。
采用MCNP软件(是由美国洛斯阿拉莫斯国家实验室(Los Alamos National Laboratory)开发的基于蒙特卡罗方法的用于计算三维复杂几何结构中的中子、光子、带电粒子或者耦合中子/光子/带电粒子输运问题的通用软件包)对本发明实施例中的空气中中子射束品质进行计算。
参阅图3，图3示出了本发明一实施例中的中子捕获治疗***的结构示意图，本实施例 中的中子捕获治疗***优选为硼中子捕获治疗***100。中子生成部产生的中子射束N照射位于治疗台20上的被照射体200的患处部位M。中子射束N与患处部位M的含硼(B-10)药物发生如前述的硼中子捕获反应，从而消灭患处部位M的肿瘤细胞或者其他物质，达到治疗的效果。
硼中子捕获治疗***100包括带电粒子束生成部11、射束传输部12和中子束生成部13。带电粒子束生成部11产生如质子束的带电粒子束P；射束传输部12，将带电粒子束P传输至中子束生成部13；中子束生成部13产生治疗用中子射束N并照射向治疗台20上的被照射体200。带电粒子束生成部11包括离子源111和加速器112，离子源111用于产生带电粒子，如H-、质子、氘核等；加速器112对离子源111产生的带电粒子加速以获得所需能量的带电粒子束P，如质子束。加速器112可以是直线加速器、回旋加速器、同步加速器或同步回旋加速器。中子束生成部13包括射束整形体131、准直器132和靶材133，加速器112产生的带电粒子束P经射束传输部12到达中子束生成部13，与靶材133作用产生中子，经射束整形体131和准直器132调整射束品质，形成治疗用中子射束N并照射向治疗台20上的被照射体200。
射束整形体131能够调整中子射束N的射束品质。准直器132用以汇聚中子射束N，使中子射束N在治疗过程中具有较高的靶向性。射束整形体131进一步地包括射束入口1311、缓速体1312、包围在缓速体1312外的反射体1313和射束出口1314。
硼中子捕获治疗***100通过加速器112将由离子源111生成的带电粒子束P加速，带电粒子束P经射束入口1311进入射束整形体131中。射束入口1311一部分容纳于缓速体1312中，另一部分容纳于反射体1313中。
理想的靶材133应具备高中子产率、产生的中子能量分布接近超热中子能区、无太多强贯穿辐射产生、安全便宜易于操作且耐高温等特性，但实际上并无法找到符合所有要求的核反应。本实施例中的靶材133选用尽可能满足上述要求的材料，如Li或Be，本领域技术人员熟知的，靶材133也可以由Li、Be之外的金属材料制成，例如由Ta或W及其合金等形成。作为一种优选实施例，靶材133由锂金属制成，容纳于缓速体1312中，带电粒子束P加速至足以克服靶材133原子核库伦斥力的能量，与靶材133发生7Li(p,n)7Be核反应以产生中子，中子形成中子射束N，中子射束N限定射束轴线X。带电粒子束P与靶材133作用生成的中子由于能谱很广，除了超热中子满足治疗需要以外，需要尽可能的减少其他种类的中子及光 子含量以避免对操作人员或被照射体造成伤害，因此从靶材133出来的中子需要经过缓速体1312将其中的快中子能量(＞10keV)调整到超热中子能区(0.5eV-10keV)并尽可能减少热中子(＜0.5eV)。
参阅图5，缓速体1312沿着射束轴线X延伸第一预设长度L1并且沿着射束轴线X的径向方向延伸第一预设宽度D1。缓速体1312由与快中子作用截面大、超热中子作用截面小的材料制成，本实施例中，缓速体1312由D2O，AlF3，CaF2，Li2CO3，MgF2，Al2O3和Al、AlF3和LiF的预设比例的混合材料中的至少一种制成，其中，Al、AlF3和LiF的预设比例的混合材料优选为Fluental材料。
反射体1313包围缓速体1312，并将穿过缓速体1312向四周扩散的中子反射回中子射束N以提高中子射束N强度，至少部分反射体1313沿着射束轴线X延伸第二预设长度L2并且在缓速体1312之外沿着射束轴线X的径向方向延伸第二预设宽度D2。反射体1313由中子反射能力强的材料制成，本实施例中，反射体1313由Pb制成。
本实施例中，射束整形体131还包括射束出口1314和包围反射体1313的辐射屏蔽体1315。辐射屏蔽体1315用于屏蔽渗漏的中子和光子以减少非照射区的正常组织剂量，辐射屏蔽体1315沿着射束轴线X延伸第四预设长度L4并且在反射体1313之外沿着射束轴线X的径向方向延伸第四预设宽度D4，并且辐射屏蔽体1315在射束出口1314处与反射体1313齐平。需要注意的是，在下文描述的其他实施例中，其他构件沿着射束轴线X延伸第三预设长度L3和沿着射束轴线X的径向方向延伸第三预设宽度D3，因此，此处的辐射屏蔽体采用第四预设长度L4和第四预设宽度D4的表述。辐射屏蔽体1315的材料包括光子屏蔽材料和中子屏蔽材料中的至少一种，可以是裁切成合适尺寸的刚性固体，如铅锑合金、铁氟龙、石墨、石蜡、PE、含碳化硼或碳酸锂或氟化锂的PE、PMMA(亚克力)、含碳化硼或碳酸锂或氟化锂的PMMA或含硼重晶石混凝土；也可以是填充在裁切成合适尺寸的刚性容器或柔性容器内的粉末，如碳化硼或碳酸锂或氟化锂的粉末；也可以是填充在裁切成合适尺寸的刚性容器或柔性容器内的液体，如溶解碳化硼或碳酸锂或氟化锂粉末的水、重水、硼酸；还可以是柔性固体，如橡胶或硅胶。本实施例中，辐射屏蔽体1315优选由不同于反射体的材料制成，如含硼重晶石混凝土。
可以理解，射束整形体131还可以有其他的构件和构造，如包括吸收热中子的热中子吸收体、射束入口不容纳在缓速体内等，只要能够获得治疗所需超热中子射束即可。
准直器132设置于射束出口1314后部或射束整形体131内部，从准直器132出来的超热中子射束向被照射体200照射。可以理解，准直器132也可以取消或由其他结构代替，中子射束从射束出口1314出来直接向被照射体200照射。
参阅图4-图21，为了进一步改善中子射源的通量与品质，射束整形体131还包括超热中子通量增强体1316，超热中子通量增强体1316设置于缓速体1312中和/或反射体1313中和/或缓速体1312与反射体1313之间。为了便于对比和表述，相同构件在本发明所述实施例中均采用相同的附图标记来表示。
请先参阅图4-图6，超热中子通量增强体1316沿着射束轴线X延伸第三预设长度L3并且沿着射束轴线X的径向方向延伸第三预设宽度D3，其中，第三预设宽度D3小于第一预设宽度D1和第二预设宽度D2之和。优选地，在图4-图6揭示的实施例中，第三预设宽度D3小于第一预设宽度D1。本发明一实施例中，超热中子通量增强体1316沿着射束轴线X的径向方向延伸第三预设宽度D3包括超热中子通量增强体的厚度。超热中子通量增强体1316由中子反射能力强的材料制成，优选地，超热中子通量增强体1316由Ni制成，包括天然镍或提纯镍。
参阅图7-图8，并结合图4-6所示，超热中子通量增强体1316被构造为筒状结构，该筒状结构包括与射束轴线X垂直的第一侧部1316a和第二侧部1316b以及围绕射束轴线X周向封闭的第一壁1316c和第二壁1316d，第一侧部1316a和第二侧部1316b沿中子射束N方向依次设置，且第一侧部1316a比第二侧部1316b更远离射束出口1314。在这些实施例中，第一侧部1316a沿射束轴线X的方向设置于缓速体1312和反射体1313之间，邻接于缓速体1312位于中子射束N上游侧的端面。第一侧部1316a设置为圆环结构，并且设置有第一中心孔，第一中心孔用于让射束入口1311贯穿通过，使得射束入口1311可容纳于缓速体1312中。第二侧部1316b设置第二中心孔，邻接于射束整形体131位于中子射束N下游侧的端面，用于与射束出口1314结合，第二中心孔的径向尺寸与第一壁1316c的外径相等时，第二侧部1316b为未设置封闭结构的敞开状态，第一壁1316c和第二壁1316d沿射束轴线X的径向方向设置，垂直于第一侧部1316a和第二侧部1316b。第一壁1316c和第二壁1316d与第一侧部1316a连接并沿射束轴线X延伸至第二侧部1316b，在这些实施例中，筒状结构的超热中子通量增强体1316的中心线与中子射束N的轴线重合，第三预设宽度D3小于第一预设宽度D1，第一壁1316c和第二壁1316d至少一部分容纳在缓速体1312内，即筒状结构的超热中子通量增 强体1316至少部分设置于缓速体1312中。可以理解，中子射束N上游侧为靠近射束入口1311及靶材133的一侧，中子射束N下游侧为靠近射束出口1314的一侧。
参阅图9和图10，图9和图10示出了本发明一实施例中的射束整形体的不同视角的结构示意图，其中超热中子通量增强体1316为筒状结构。与图4-图8揭示的实施例不同之处在于，超热中子通量增强体1316的第一壁和第二壁至少部分设置于反射体1313中。本实施例中，筒状结构的超热中子通量增强体1316沿着射束轴线X的径向方向延伸的第三预设宽度D3大于缓速体1312沿着射束轴线X的径向方向延伸的第一预设宽度D1，小于缓速体1312沿着射束轴线X的径向方向延伸的第一预设宽度D1和部分反射体1313在缓速体1312之外沿着射束轴线X的径向方向延伸的第二预设宽度D2之和，第一壁1316c和第二壁1316d均邻接于反射体1313，即筒状结构的超热中子通量增强体1316设置于反射体1313中。
下面描述图3、图4-8及图9-10揭示的实施例在空气中表现的射束品质。表一示出了未设置超热中子通量增强体及筒状结构的超热中子通量增强体设置于不同位置时空气中射束品质因素的表现(表格中各名词的单位同上所述，在此不再赘述，下同)：
表一：筒状结构的超热中子通量增强体设置于不同位置时的射束品质
从上述表中可以得知：在射束整形体中设置筒状结构的超热中子通量增强体，可以改善中子射束品质；超热中子通量增强体设置于缓速体中时，对于超热中子通量的增加更加显著。
参阅图11-图14，本发明一些实施例中，筒状结构的超热中子通量增强体1316的第一侧部1316a或/和第二侧部1316b被构造为朝着射束轴线X收缩的锥状结构，第一侧部1316a的外轮廓的径向尺寸沿中子射束N方向逐渐增大，第二侧部1316b的外轮廓的径向尺寸沿中子射束N方向逐渐减小。第一侧部1316a的外轮廓的径向尺寸至少在中心孔的径向尺寸以上，第二侧部1316b的外轮廓的径向尺寸至少容纳射束出口1314。
再次参阅图11，图11示出了本发明一实施例中的射束整形体的结构示意图，其中筒状结构的超热中子通量增强体1316一侧为锥状结构。需要注意的是，为了让附图更加简洁，部 分与上述实施例相同描述的附图标记，在图11中并未体现，如第一预设宽度D1、第三预设宽度D3、第一侧部1316a、第二侧部1316b、第一壁1316c和第二壁1316d等，具体可参照上述实施例。下文描述其他实施例中，出现的附图标记但并未出现在相应附图中的，可以参照此处的情况。本发明一实施例中，筒状结构的超热中子通量增强体1316沿着射束轴线X的径向方向延伸的第三预设宽度D3小于缓速体1312沿着射束轴线X的径向方向延伸的第一预设宽度D1，第一壁1316c和第二壁1316d均至少部分容纳于缓速体1312，即超热中子通量增强体1316至少部分设置于缓速体1312中。第一侧部1316a邻接于缓速体1312位于中子射束N上游侧的端面，第二侧部1316b邻接于缓速体1312位于中子射束N下游侧的端面，第二侧部1316b的外轮廓的径向尺寸沿中子射束N方向逐渐减小，并且外轮廓径向尺寸由第三预设宽度D3逐渐减小至射束出口1314的尺寸，即第二侧部1316b朝向射束出口1314收缩，筒状结构的超热中子通量增强体1316一侧为锥状结构。
再次参阅图12，图12示出了本发明一实施例中的射束整形体的结构示意图，其中筒状结构的超热中子通量增强体1316两侧为锥状结构。本发明一实施例中，筒状结构的超热中子通量增强体1316沿着射束轴线X的径向方向延伸的第三预设宽度D3小于缓速体1312沿着射束轴线X的径向方向延伸的第一预设宽度D1，第一壁1316c和第二壁1316d均至少部分容纳于缓速体1312，即超热中子通量增强体1316至少部分设置于缓速体1312中，第一侧部1316a邻接于缓速体1312位于中子射束N上游侧的端面，第一侧部1316a的外轮廓的径向尺寸沿中子射束N方向逐渐增大，第一侧部1316a的外轮廓的径向尺寸由中心孔的径向尺寸逐渐增大至第三预设宽度D3，即第一侧部1316a朝向射束入口1311收缩。第二侧部1316b邻接于缓速体1312位于中子射束N下游侧的端面，第二侧部1316b的外轮廓的径向尺寸沿中子射束N方向逐渐减小，第二侧部1316b的外轮廓的径向尺寸由第三预设宽度D3逐渐减小至射束出口1314的尺寸，即第二侧部1316b朝向射束出口1314收缩，筒状结构的超热中子通量增强体1316两侧均为锥状结构。
下面描述图3、图4、图11及图12揭示的实施例在空气中表现的射束品质。表二示出了未设置超热中子通量增强体、设置筒状(无锥状结构)超热中子通量增强体及筒状结构的超热中子通量增强体一侧或两侧为锥状结构时空气中射束品质因素的表现：
表二：筒状结构的超热中子通量增强体一侧或两侧为锥状结构时的射束品质

从上述表中可以得知：在射束整形体中设置超热中子通量增强体并且将筒状结构的超热中子通量增强体的一侧或者两侧设置为锥状结构，可以提高中子射束中的超热中子通量，改善中子射束品质。
再次参阅图12，并结合图13和图14，本发明一实施例中，筒状结构的超热中子通量增强体1316沿着射束轴线X的径向方向延伸的第三预设宽度D3小于缓速体1312沿着射束轴线X的径向方向延伸的第一预设宽度D1，第一壁1316c和第二壁1316d均至少部分容纳于缓速体1312，即超热中子通量增强体1316至少部分设置于缓速体1312中。第一侧部1316a邻接于缓速体1312位于中子射束N上游侧的端面，第一侧部1316a的外轮廓的径向尺寸沿中子射束N方向逐渐增大，第一侧部1316a的外轮廓的径向尺寸由中心孔的径向尺寸逐渐增大至第三预设宽度D3，即第一侧部1316a朝向射束入口1311收缩。第二侧部1316b邻接于缓速体1312位于中子射束N下游侧的端面，第二侧部1316b的外轮廓的径向尺寸沿中子射束N方向逐渐减小，第二侧部1316b的外轮廓的径向尺寸由第三预设宽度D3逐渐减小至射束出口1314的尺寸，即第二侧部1316b朝向射束出口1314收缩，筒状结构的超热中子通量增强体1316两侧均为锥状结构。本实施例中，超热中子通量增强体1316的厚度小于第一预设宽度D1和第二预设宽度D2之和，优选为1-5cm，进一步优选为3-5cm。
下面描述图3和图12实施例在设置不同厚度的超热中子通量增强体1316时在空气中表现的射束品质。表三示出了未设置超热中子通量增强体及超热中子通量增强体厚度不同时空气中射束品质因素的表现：
表三：超热中子通量增强体厚度不同时的射束品质
表三(续)：超热中子通量增强体厚度不同时的射束品质
从上述表中可以得知：在射束整形体中设置超热中子通量增强体并且适当增加超热中子通量增强体的厚度可以提高中子射束中的超热中子通量，改善中子射束品质。结合图15(a)-图15(e)分析可知，超热中子通量增强体的厚度在0-5cm时，随着其厚度的增加，超热中子通量也随之增大，快中子污染则有先减小后增大的趋势；其中，当超热中子通量增强体的厚度在0-1cm时，中子通量增加趋势明显，且快中子污染、热中子与超热中子的通量比值均有明显的降低趋势，超热中子通量增强体的厚度达到1cm时，与无超热中子通量增强体的射束整形体相比，射束品质得到提高显著；当超热中子通量增强体的厚度达到5cm时，超热中子通量达到最大值，超热中子通量增强体的厚度为3cm、4cm时，快中子污染最小；若继续增大超热中子通量增强体厚度，超热中子通量反而减小，同时快中子污染增加，会造成不必要的正常组织剂量，中子射束的品质下降。因此，优选超热中子通量增强体的厚度为1-8cm，更优选3-5cm，可以获得符合中子捕获治疗所需的射束品质较好的超热中子束。
请参阅图16-图22，本发明一些实施例中，超热中子通量增强体1316被构造为锥状结构，该锥状结构包括与射束轴线X垂直的第一端面1316e和第二端面1316f和围绕射束轴线X周向封闭的第三壁1316g和第四壁1316h，第一端面1316e和第二端面1316f沿中子射束N方向依次设置，第三壁1316g和第四壁1316h沿射束轴线X的径向方向设置，第一端面1316e与第二端面1316f均设置为开口。
参阅图16-图20，图16-图20示出了本发明一实施例中的射束整形体的结构示意图，其中超热中子通量增强体1316为锥状结构，沿中子射束N方向位于射束整形体131的上游侧。本发明一实施例中，锥状结构的超热中子通量增强体1316的外轮廓的径向尺寸沿中子射束N方向逐渐增大，第一端面1316e邻接于缓速体1312位于中子射束N上游侧的端面，第一端面1316e的尺寸至少容纳射束入口1311，即锥状结构的超热中子通量增强体1316设置于中子射束N的上游侧，且第一端面1316e的径向内径大于射束入口1311的径向外径。本实施例 中，超热中子通量增强体1316沿着射束轴线的径向方向延伸的第三预设宽度D3小于缓速体1312沿着射束轴线的径向方向延伸的第一预设宽度D1，第三壁1316g和第四壁1316h容纳于缓速体1312，即锥状结构的超热中子通量增强体1316设置于缓速体1312中，靠近射束入口1311，锥状结构的超热中子通量增强体1316的中心线与射束轴线X重合，并且锥状结构的超热中子通量增强体1316的外轮廓的径向尺寸沿中子射束N方向由射束入口1311的尺寸逐渐增大到第三预设宽度D3。
再次参阅图21，图21示出了本发明一实施例中的射束整形体的结构示意图，其中超热中子通量增强体1316为锥状结构，沿中子射束N方向位于射束整形体131的下游侧。本发明一实施例中，锥状结构的超热中子通量增强体1316的外轮廓的径向尺寸沿中子射束N方向逐渐减小，第二端面1316f邻接于射束整形体100位于中子射束下游侧的端面，第二端面1316f的尺寸至少容纳射束出口1314，即锥状结构的超热中子通量增强体1316设置于中子射束N的下游侧，且第二端面1316f的径向内径大于射束出口1314的径向外径。本实施例中，超热中子通量增强体1316沿着射束轴线X的径向方向延伸的第三预设宽度D3小于缓速体1312沿着射束轴线X的径向方向延伸的第一预设宽度D1，第三壁1316g邻接于反射体1313，第四壁1316h邻接于射束出口1314。锥状结构的超热中子通量增强体1316的中心线与射束轴线X重合，并且锥状结构的超热中子通量增强体1316的外轮廓的径向尺寸沿中子射束N方向由第三预设宽度D3逐渐减小到射束出口1314的尺寸。
再次参阅图22，图22示出了本发明一实施例中的射束整形体的结构示意图，其中超热中子通量增强体1316为两个锥状结构的组合，沿中子射束N方向分别位于射束整形体131的上游侧和下游侧。1316上游侧的锥状结构的超热中子通量增强体1316的外轮廓的径向尺寸沿中子射束N方向逐渐增大，第一端面1316e邻接于缓速体1312位于中子射束N上游侧的端面，第一端面1316e的尺寸至少容纳射束入口1311。下游侧的锥状结构的超热中子通量增强体1316的外轮廓的径向尺寸沿中子射束N方向逐渐减小，第二端面1316f邻接于射束整形体131位于中子射束下游侧的端面，第二端面1316f的尺寸至少容纳射束出口1314。本实施例中，超热中子通量增强体1316沿着射束轴线X的径向方向延伸的第三预设宽度D3小于缓速体1312沿着射束轴线X的径向方向延伸的第一预设宽度D1，并且超热中子通量增强体1316的中心线与射束轴线X重合。上游侧锥状结构的超热中子通量增强体1316的外轮廓的径向尺寸沿中子射束N方向由射束入口1311的尺寸逐渐增大到第三预设宽度D3，下游侧的 锥状结构的超热中子通量增强体1316的外轮廓的径向尺寸沿中子射束N方向由第三预设宽度D3逐渐减小到射束出口1314的尺寸。
下面描述图3和图16-22实施例在设置不同形状的超热中子通量增强体1316在空气中表现的射束品质。表四示出了未设置超热中子通量增强体及锥状结构的超热中子通量增强体设置于不同位置时空气中射束品质因素的表现：
表四：锥状结构的超热中子通量增强体设置于不同位置时的射束品质
从上述表中可以得知：在射束整形体沿中子射束N方向的下游端设置锥状结构的超热中子通量增强体，对于提高超热中子通量的效果更显著，更有利于改善中子射束品质。
本发明这些实施例中，超热中子通量增强体1316整体上为筒状结构或锥状结构或筒状加锥状的结构。超热中子通量增强体1316整体可以一体成型，也可以由多个部件分块组合，经组合后得到。超热中子通量增强体1316可以与缓速体1312及反射体1313一起组装成型，实现超热中子通量增强体1316设置于射束整形体131中；也可以在缓速体1312或反射体1313中设置容纳腔，再将超热中子通量增强体1316放置到容纳腔中，从而实现超热中子通量增强体1316设置于射束整形体131中。
本发明实施例中所述的“筒状”是指沿着图示方向的一侧到另一侧其外轮廓的整体趋势基本不变的结构，外轮廓的其中一条轮廓线可以是线段，如圆柱体状的对应的轮廓线，也可以是曲率较大的接近线段的圆弧，如曲率较大的球面体状的对应的轮廓线，外轮廓的整个表面可以是圆滑过渡的，也可以是非圆滑过渡的，如在圆柱体状或曲率较大的球面体状的表面做了很多凸起和凹槽。
本发明实施例中所述的“锥状”是指沿着图示方向的一侧到另一侧其外轮廓的整体趋势逐渐变小的结构，外轮廓的其中一条轮廓线可以是线段，如圆锥体状的对应的轮廓线，也可以 是圆弧，如球面体状的对应的轮廓线，外轮廓的整个表面可以是圆滑过渡的，也可以是非圆滑过渡的，如在圆锥体状或球面体状的表面做了很多凸起和凹槽。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本发明的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变形和改进，这些都属于本发明的保护范围。因此，本发明专利的保护范围应以所附权利要求为准。

Claims (15)

  1. 一种射束整形体，用于中子捕获治疗***，其特征在于，所述射束整形体包括：
    缓速体，用于将中子射束的中子减速至超热中子，所述中子射束限定射束轴线，所述缓速体沿着所述射束轴线延伸第一预设长度并且沿着所述射束轴线的径向方向延伸第一预设宽度；
    反射体，包围所述缓速体，用于将偏离中子射束的中子反射回中子射束以提高中子射束强度，至少部分反射体沿着所述射束轴线延伸第二预设长度并且在所述缓速体之外沿着所述射束轴线的径向方向延伸第二预设宽度；及
    超热中子通量增强体，用于提高中子射束中的超热中子通量，设置于所述缓速体中和/或所述反射体中和/或所述缓速体与所述反射体之间，所述超热中子通量增强体沿着所述射束轴线延伸第三预设长度并且沿着所述射束轴线的径向方向延伸第三预设宽度，其中，所述第三预设宽度小于所述第一预设宽度与所述第二预设宽度之和；
    所述射束整形体还包括：射束入口，用于带电粒子束的射入；射束出口，用于所述中子射束的射出；所述射束入口、所述缓速体和所述射束出口沿着所述射束轴线延伸方向设置。
  2. 根据权利要求1所述的射束整形体，其特征在于，所述射束整形体还包括包围所述反射体的辐射屏蔽体，所述辐射屏蔽体用于屏蔽渗漏的中子和光子以减少非照射区的正常组织剂量，所述辐射屏蔽体沿着所述射束轴线延伸第四预设长度并且在所述反射体之外沿着所述射束轴线的径向方向延伸第四预设宽度。
  3. 根据权利要求1所述的射束整形体，其特征在于，所述超热中子通量增强体的材料为Ni。
  4. 根据权利要求1所述的射束整形体，其特征在于，所述缓速体的材料为D2O，AlF3，CaF2，Li2CO3，MgF2，Al2O3和Al、AlF3和LiF的预设比例的混合材料中的至少一种。
  5. 根据权利要求1所述的射束整形体，其特征在于，所述反射体的材料为铅。
  6. 根据权利要求1所述的射束整形体，其特征在于，所述超热中子通量增强体为筒状结构，所述超热中子通量增强体包括与所述射束轴线垂直的第一侧部和第二侧部以及围绕所述射束轴线周向封闭的第一壁和第二壁，所述第一侧部和第二侧部沿中子射束方向依次设置在所述筒状结构的两端，所述第一侧部设置第一中心孔，所述第一中心孔用于与射束入口结合，所述第二侧部设置第二中心孔，所述第二中心孔用于与射束出口结合。
  7. 根据权利要求6所述的射束整形体，其特征在于，所述超热中子通量增强体的第一侧 部和/或第二侧部被构造为朝向所述射束轴线收缩的锥状结构，所述第一侧部的外轮廓的径向尺寸沿所述中子射束方向逐渐增大，所述第一中心孔的尺寸至少容纳射束入口，所述第二侧部的外轮廓的径向尺寸沿所述中子射束方向逐渐减小，所述第二中心孔的尺寸至少容纳射束出口。
  8. 根据权利要求7所述的射束整形体，其特征在于，所述超热中子通量增强体的厚度为1-8cm。
  9. 根据权利要求8所述的射束整形体，其特征在于，所述超热中子通量增强体的厚度为3-5cm。
  10. 根据权利要求1所述的射束整形体，其特征在于，所述超热中子通量增强体为锥状结构，所述锥状结构包括与所述射束轴线垂直的第一端面和第二端面和围绕所述射束轴线周向封闭的第三壁和第四壁，所述第一端面和第二端面沿中子射束方向依次设置，所述第一端面与第二端面均设置为开口。
  11. 根据权利要求10所述的射束整形体，其特征在于，所述超热中子通量增强体的外轮廓的径向尺寸沿所述中子射束方向逐渐增大，所述第一端面邻接于所述缓速***于所述中子射束上游侧的端面，所述第一端面的尺寸至少容纳射束入口。
  12. 根据权利要求10所述的射束整形体，其特征在于，所述超热中子通量增强体的外轮廓的径向尺寸沿所述中子射束方向逐渐减小，所述第二端面邻接于所述射束整形***于所述中子射束下游侧的端面，所述第二端面的尺寸至少容纳射束出口。
  13. 根据权利要求6或10所述的射束整形体，其特征在于，所述筒状结构或锥状结构的的中心线与射束轴线重合。
  14. 一种中子捕获治疗***，其特征在于，包括：
    带电粒子束生成部，用于产生带电粒子束；
    中子束生成部，用于产生中子束，包括靶材和射束整形体；及
    射束传输部，将所述带电粒子束传输至所述中子束生成部，所述带电粒子束与所述靶材作用产生中子束，所述中子束经所述射束整形体慢化后形成中子捕获治疗所需的超热中子束。
  15. 根据权利要求14的中子捕获治疗***，其特征在于，所述射束整形体包括：
    缓速体，用于将中子射束的中子减速至超热中子，所述中子射束限定射束轴线，所述缓速体沿着所述射束轴线延伸第一预设长度并且沿着所述射束轴线的径向方向延伸第一预设宽 度；
    反射体，包围所述缓速体，用于将偏离中子射束的中子反射回中子射束以提高中子射束强度，至少部分反射体沿着所述射束轴线延伸第二预设长度并且在所述缓速体之外沿着所述射束轴线的径向方向延伸第二预设宽度；及
    超热中子通量增强体，用于提高中子射束中的超热中子通量，设置于所述缓速体中和/或所述反射体中和/或所述缓速体与所述反射体之间，所述超热中子通量增强体沿着所述射束轴线延伸第三预设长度并且沿着所述射束轴线的径向方向延伸第三预设宽度，其中，所述第三预设宽度小于所述第一预设宽度与所述第二预设宽度之和。
PCT/CN2023/122407 2022-10-10 2023-09-28 射束整形体及中子捕获治疗*** WO2024078353A1 (zh)

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JP2018161449A (ja) * 2017-03-27 2018-10-18 株式会社八神製作所 中性子減速照射装置及び延長コリメータ
CN107799195A (zh) * 2017-11-24 2018-03-13 北京新核医疗科技有限公司 水平中子束照射方法、微型堆中子治疗装置及医疗***
CN114904154A (zh) * 2021-02-09 2022-08-16 中硼(厦门)医疗器械有限公司 中子捕获治疗***

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