WO2016177270A1 - 用于中子捕获治疗的射束整形体 - Google Patents

用于中子捕获治疗的射束整形体 Download PDF

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Publication number
WO2016177270A1
WO2016177270A1 PCT/CN2016/079568 CN2016079568W WO2016177270A1 WO 2016177270 A1 WO2016177270 A1 WO 2016177270A1 CN 2016079568 W CN2016079568 W CN 2016079568W WO 2016177270 A1 WO2016177270 A1 WO 2016177270A1
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Prior art keywords
neutron
powder
neutrons
sintering
beam shaping
Prior art date
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PCT/CN2016/079568
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English (en)
French (fr)
Inventor
刘渊豪
陈韦霖
李珮仪
张敏娟
徐文玉
Original Assignee
南京中硼联康医疗科技有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Priority claimed from CN201520281118.6U external-priority patent/CN204798657U/zh
Priority claimed from CN201510222234.5A external-priority patent/CN106310540A/zh
Priority claimed from CN201510579928.4A external-priority patent/CN106512233B/zh
Application filed by 南京中硼联康医疗科技有限公司 filed Critical 南京中硼联康医疗科技有限公司
Priority to EP19184558.5A priority Critical patent/EP3570294B1/en
Priority to CN201680022431.5A priority patent/CN107921273B/zh
Priority to EP16789264.5A priority patent/EP3254729B1/en
Priority to RU2017142120A priority patent/RU2682972C1/ru
Priority to JP2017557373A priority patent/JP6843766B2/ja
Publication of WO2016177270A1 publication Critical patent/WO2016177270A1/zh
Priority to US15/704,495 priority patent/US10328286B2/en
Priority to US16/401,328 priority patent/US10617893B2/en
Priority to US16/727,216 priority patent/US20200188695A1/en

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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
    • A61N5/1077—Beam delivery systems
    • 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
    • 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
    • A61N5/1042—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/553—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on fluorides
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64—Burning or sintering processes
    • C04B35/645—Pressure sintering
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64—Burning or sintering processes
    • C04B35/645—Pressure sintering
    • C04B35/6455—Hot isostatic pressing
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21G—CONVERSION OF CHEMICAL ELEMENTS; RADIOACTIVE SOURCES
    • G21G4/00—Radioactive sources
    • G21G4/02—Neutron sources
    • 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
    • G21K5/00—Irradiation devices
    • G21K5/04—Irradiation devices with beam-forming means
    • 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
    • A61N2005/1085—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy characterised by the type of particles applied to the patient
    • A61N2005/109—Neutrons
    • 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
    • A61N2005/1092—Details
    • A61N2005/1094—Shielding, protecting against radiation
    • 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
    • A61N2005/1092—Details
    • A61N2005/1095—Elements inserted into the radiation path within the system, e.g. filters or wedges

Definitions

  • the present invention relates to a beam shaping body, and more particularly to a beam shaping body for neutron capture therapy.
  • melanoma (melanoma) treatment often does not work well.
  • BNCT Boron Neutron Capture Therapy
  • Linear Energy Transfer (LET), short-range characteristics, linear energy transfer and range of ⁇ particles are 150 keV/ ⁇ ⁇ 8 ⁇ ⁇ , respectively, while 7 Li heavy particles are 175 keV/ ym, 5 ⁇ ⁇ , two particles
  • the total range is about the same as a cell size, so the radiation damage caused by the organism can be limited to the cell level.
  • the boron-containing drug is selectively aggregated in the tumor cells, with the appropriate neutron source, it can be abnormal. Under the premise that the tissue causes too much damage, the purpose of locally killing the tumor cells is achieved. Because the effectiveness of boron neutron capture therapy depends on the concentration of boron-containing drugs in the tumor cell position and the number of thermal neutrons, it is also called binary cancer therapy. It can be seen that in addition to the development of boron-containing drugs, The improvement of flux and quality of neutron source plays an important role in the study of boron neutron capture therapy. Summary of the invention
  • one aspect of the present invention provides a beam shaping body for neutron capture therapy, comprising a beam entrance, a target, a retarding body adjacent to the target, a reflector surrounded by a slow-moving body, and a slow speed a body-adjacent thermal neutron absorber, a radiation shield disposed within the beam shaping body, and a beam exit, the target reacts with a proton beam incident from the beam entrance to generate a neutron, and the neutron forms a neutron beam,
  • the sub-beam defines a main axis, and the retarding body decelerates the neutron generated from the target to the superheated neutron energy region, and the material of the retarding body is composed of PbF 4 , A1 2 0 3 , A1F 3 , 0 ⁇ 2 or 2 MgF one kind or more of a mixed material containing possession and PbF 4, A1 2 0 3, A1F 3, (3 ⁇ 4 MgF 2 or one or
  • the material containing the 6 Li element is mixed, wherein the material of the slow-speed body is changed from the powder or the powder compact to the block by the powder sintering process through the powder sintering process, and the reflector will deviate from the spindle neutron lead-back spindle to improve the superheat.
  • thermal neutron absorbers are used to absorb thermal neutrons to avoid excessive doses with shallow normal tissue during treatment.
  • Radiation shielding is used to shield leaking neutrons and photons to reduce normal tissue in non-irradiated areas. dose.
  • a beam shaping body for neutron capture therapy comprising a beam entrance, a target, a retarding body adjacent to the target, a reflector surrounded by the retarding body, and a gentle a thermal neutron absorber adjacent to the velocity body, a radiation shield disposed in the beam shaping body, and a beam exit, the target reacts with a proton beam incident from the beam entrance to generate a neutron, and the neutron forms a neutron beam.
  • the neutron beam defines a main shaft, and the retarding body decelerates the neutron generated from the target to the superheated neutron energy region.
  • the material of the retarding body is composed of LiF, Li 2 C0 3 , A1 2 0 3 , A1F 3 .
  • the thermal neutron absorber is used to absorb thermal neutrons to avoid excessive doses during treatment and shallow normal tissue. Radiation shielding is used to shield leaking neutrons and photons to reduce non- Normal tissue dose in the irradiated area.
  • the beam shaping body is further used for the accelerator boron neutron capture treatment, the accelerator boron neutron capture treatment accelerates the proton beam by the accelerator, the target is made of metal, and the proton beam is accelerated to an energy sufficient to overcome the coulomb repulsion of the target nucleus, and the target
  • the neutron energy region is between 0. 5eV and 40keV, and the neutron energy zone is in the range of 0. 5eV to 40keV.
  • the thermal neutron energy region is less than 0. 5 eV
  • the fast neutron energy region is greater than 40 keV
  • the reflector is made of a material having strong neutron reflection capability
  • the thermal neutron absorber is made of a material having a large cross section with thermal neutrons. .
  • the reflector is made of at least one of Pb or Ni
  • the thermal neutron absorber is made of 6 Li
  • an air passage is provided between the thermal neutron absorber and the beam outlet
  • the radiation shield includes Photon shielding made of Pb and neutron shielding made of PE.
  • the retarding body is disposed in a cone shape in which two opposite directions are adjacent to each other.
  • the cone shape includes a first diameter, a second diameter, and a third diameter, the first diameter is from 1 cm to 20 cm, the second diameter is from 30 cm to 100 cm, and the third diameter is from 1 cm to 50 cm.
  • the density of the material is between 80% and 100% of the theoretical density.
  • a retarder disposed between the reflector body and the gap channels to improve the epithermal neutron flux material, retarder MgF 2 powder by the body and occupied MgF 2 powder containing 0. 1-5 weight percent of 6% LiF powder is mixed and made.
  • the powder sintering apparatus is a hot press sintering apparatus or a discharge plasma sintering apparatus
  • the powder sintering process is a hot press sintering process or a discharge plasma sintering process.
  • the hot press sintering apparatus comprises a heating furnace, a pressurizing device placed in the heating furnace, a mold, and a powder loaded into the mold
  • the final or powder compact and the control device for controlling the normal operation of the hot press sintering apparatus, the hot press sintering process comprises the steps of: filling the mold with an appropriate amount of powder or powder compact; opening the hot press to preset pressure and temperature parameters; The moving pressurizing device pressurizes the powder or the powder compact in the mold; the control device controls the hot press sintering device under normal working conditions; and is energized to be sintered into a block.
  • the discharge plasma sintering apparatus includes a first electrode, a second electrode, a conductive mold disposed between the first electrode and the second electrode, a pulse current generator for supplying a pulse current to the mold, and a a pressing device for pressing the pressing member and a control device for controlling the pulse current transmitter and the pressing device, at least one of the first electrode and the second electrode being movable, at least one of the first electrode and the second electrode
  • the powder is connected to the pressurizing device to pressurize the powder placed in the mold;
  • the spark plasma sintering process comprises the steps of: filling a mold with an appropriate amount of powder; moving the second electrode to pressurize the powder in the mold; and opening a pulse current through the control device
  • the conductive mold is electrically conductive to generate a plasma, and the surface of the powder particles is activated and heated; sintered into a block.
  • the discharge plasma sintering apparatus further includes a displacement measuring system for measuring the displacement of the pressing device, an atmosphere control system for controlling the atmosphere in the mold, a water cooling system for cooling, and a temperature measurement for measuring the temperature in the discharge plasma sintering apparatus.
  • the apparatus, the discharge plasma sintering process further comprises the steps of: controlling the displacement measuring system to ensure that the displacement measuring system operates normally, and controlling the atmosphere control system to ensure that the atmosphere in the mold is in normal working condition, and the control device controls the water cooling system to ensure The water cooling system operates normally, and the control device controls the temperature measuring device to ensure that the temperature in the discharge plasma sintering apparatus is in normal operation.
  • the "cylinder” or “cylinder” as used in the embodiment of the present invention refers to a structure in which the overall tendency of the outer contour of the outer contour is substantially constant from one side to the other side in the illustrated direction, one of the contours of the outer contour
  • the line may be a line segment, such as a corresponding contour of a cylindrical shape, or an arc of a curved line close to a line segment, such as a spherical contour corresponding to a larger curvature, and the entire surface of the outer contour may be smooth Transitions can also be non-smooth transitions, such as a lot of protrusions and grooves on a spherical or curved spherical surface.
  • the "cone” or “tapered shape” as used in the embodiment of the present invention refers to a structure in which the overall tendency of the outer contour of the outer contour is gradually reduced from one side to the other side in the illustrated direction, and one contour of the outer contour
  • the line may be a line segment, such as a corresponding contour line of a cone shape, or may be an arc, such as a corresponding contour line of a spherical body.
  • the entire surface of the outer contour may be a smooth transition or a non-smooth transition, such as A lot of protrusions and grooves are made on the surface of the cone or spherical body.
  • Figure 1 is a schematic diagram of a boron neutron capture reaction.
  • Figure 2 is a (11, ⁇ ) 7 Li neutron capture nuclear reaction equation.
  • Fig. 3 is a plan view schematically showing a beam shaping body for neutron capture treatment in the first embodiment of the present invention, wherein a gap passage is provided between the retarding body and the reflector.
  • Figure 4 is a plan view schematically showing a beam shaping body for neutron capture treatment in a second embodiment of the present invention, wherein the retarding body is disposed as a double cone, and the gap passage position in the first embodiment is at a slow speed Body material is filled.
  • Figure 5 is a plan view schematically showing a beam shaping body for neutron capture treatment in a third embodiment of the present invention, wherein the retarding body is provided as a double cone, and the gap passage position in the first embodiment is a reflector Material filling.
  • Figure 6 is a neutron yield plot of neutron energy and neutron angle double differential.
  • Fig. 7 is a plan view schematically showing a beam shaping body for neutron capture treatment in a fourth embodiment of the present invention, wherein the retarding body is provided as a cylinder.
  • Fig. 8 is a plan view schematically showing a beam shaping body for neutron capture treatment in a fifth embodiment of the present invention, wherein the retarding body is provided as a cylinder + a cone.
  • Fig. 9 is a schematic view showing a preparation apparatus of a slow-moving body material in one embodiment of the present invention, wherein the preparation apparatus is a discharge plasma sintering apparatus.
  • Fig. 10 is a schematic view showing a device for preparing a slow-moving body material in one embodiment of the present invention, wherein the preparing device is a hot press sintering device.
  • Neutron capture therapy has been increasingly used as an effective treatment for cancer in recent years, with boron neutron capture therapy being the most common, and neutrons supplying boron neutron capture therapy can be supplied by nuclear reactors or accelerators.
  • Embodiments of the present invention take the accelerator boron neutron capture treatment as an example.
  • the basic components of the accelerator boron neutron capture treatment typically include an accelerator, target and heat removal for accelerating charged particles (eg, protons, helium cores, etc.).
  • System and beam shaping body wherein the accelerated charged particles interact with the metal target to generate neutrons, according to the required neutron yield and energy, the energy and current of the accelerated charged particles, and the physicochemical properties of the metal target.
  • the nuclear reactions that are often discussed are 7 Li (p,n) 3 ⁇ 4e and 3 ⁇ 46 , n) 9 B, both of which are endothermic.
  • the energy thresholds for the two nuclear reactions are 1. 881 MeV and 2. 055 MeV, respectively. Since the ideal neutron source for boron neutron capture therapy is the superheated neutron of the keV energy level, theoretically, if the energy used is only slightly higher than the threshold value Proton bombardment of lithium metal targets can produce relatively low-energy neutrons, which can be used clinically without too much slow processing. However, lithium metal (Li) and base metal (Be) targets and protons of threshold energy. The cross section of the action is not high.
  • the ideal target should have high neutron yield, produce a neutron energy distribution close to the epithermal neutron energy zone (described in detail below), no excessively strong radiation generation, safe and cheap to operate, and high temperature resistance.
  • a target made of lithium metal is used in the embodiment of the present invention.
  • the material of the target can also be made of other metal materials than the metal materials discussed above.
  • the requirements for the heat removal system vary depending on the selected nuclear reaction, such as 7 Li (p,n) 3 ⁇ 4e due to metal target (lithium metal)
  • the difference in melting point and thermal conductivity is higher for the heat removal system than for 9 Be (p,n) 3 ⁇ 4.
  • a nuclear reaction of 7 Li (p, n) 3 ⁇ 4e is employed in the examples of the present invention.
  • the neutron source of boron neutron capture therapy comes from the nuclear reaction of the nuclear reactor or the charged particles of the accelerator and the target, and all produce a mixed radiation field, that is, the beam contains low-energy to high-energy neutrons and photons; for deep tumors in boron Sub-capture treatment, in addition to the super-thermal neutrons, the more the remaining radiation content, the greater the proportion of non-selective dose deposition in normal tissues, so these will cause unnecessary doses of radiation to be minimized.
  • the human head tissue prosthesis is used for dose calculation in the embodiment of the present invention, and the prosthetic beam quality factor is used as the neutron shot.
  • the design reference for the bundle will be described in detail below.
  • the International Atomic Energy Agency has given five air beam quality factor recommendations for clinical neutron sources for boron neutron capture therapy. These five recommendations can be used to compare the pros and cons of different neutron sources and provide The reference basis for selecting the neutron production route and designing the beam shaping body.
  • the five recommendations are as follows:
  • the superheated neutron energy region is between 0.5 eV and 40 keV, the thermal neutron energy region is less than 0.5 eV, and the fast neutron energy region is greater than 40 keV.
  • the neutron beam flux and the concentration of boron-containing drugs in the tumor determine the clinical treatment time. If the concentration of boron-containing drug in the tumor is high enough, the requirement for neutron beam flux can be reduced; conversely, if the concentration of boron-containing drug in the tumor is low, high-flux superheated neutrons are required to give the tumor a sufficient dose.
  • the IAEA's requirement for the epithermal neutron beam flux is that the number of epithermal neutrons per square centimeter per second is greater than 10 9 .
  • the neutron beam at this flux can roughly control the treatment of current boron-containing drugs. In less than one hour, short treatment time, in addition to the advantages of patient positioning and comfort, can also make more effective use of boron-containing drugs in the tumor for a limited residence time.
  • Photon pollution (gamma ray pollution): Gamma ray is a strong radiation that will non-selectively cause dose deposition of all tissues in the beam path. Therefore, reducing gamma ray content is also a necessary requirement for neutron beam design.
  • ⁇ ray pollution is defined as the unit of superheated neutron flux. the ⁇ radiation dose, IAEA recommendations ⁇ rays contamination is less than 2 ⁇ 10- 13 Gy-cm 2 / n.
  • thermal neutrons Due to the fast decay rate and poor penetrating ability of thermal neutrons, most of the energy deposited in the human body after deposition into the human body, in addition to melanoma and other epidermal tumors need to use thermal neutrons as a neutron source for boron neutron capture therapy, Deep tumors such as tumors should reduce the thermal neutron content.
  • the ratio of the thermal neutron to the superheated neutron flux is recommended to 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 neutron beam, and the high forward neutron beam can reduce the surrounding normal tissue dose caused by neutron divergence. It also increases the elasticity of the treatment depth and posture.
  • the ratio of the neutron current to flux ratio is recommended to be greater than 0.7.
  • the prosthesis is used to obtain the dose distribution in the tissue, and the prosthetic beam quality factor is derived based on the normal tissue and the dose-depth curve of the tumor.
  • the following three parameters can be used to compare the benefits of different neutron beam treatments.
  • the tumor dose is equal to the depth of the maximum dose of normal tissue. At this post-depth, the tumor cells receive a dose that is less than the maximum dose of normal tissue, ie, the advantage of boron neutron capture is lost. This parameter represents the penetrating ability of the neutron beam. The greater the effective treatment depth, the deeper the tumor depth that can be treated, in cm.
  • the effective dose rate of tumor treatment is also equal to the maximum dose rate of normal tissues. Because the total dose received by normal tissues is a factor that affects the total dose of tumor, the parameters affect the length of treatment. The greater the effective dose rate, the shorter the irradiation time required to give a tumor dose, the unit is cGy/mA. -min.
  • the effective therapeutic dose ratio received by the tumor and normal tissue is called the effective therapeutic dose ratio; the calculation of the average dose can be obtained by integrating the dose-depth curve.
  • the following embodiments are also used in the present invention to evaluate the neutron beam dose performance. Good and bad parameters:
  • the irradiation time is 30min (the proton current used by the accelerator is 10mA)
  • ORBE-Gy can treat depth 7cm 3, the maximum dose of tumor 60.
  • RBE Relative Biological Effectiveness
  • a beam shaping body 10 for neutron capture treatment in a first embodiment of the present invention includes a beam entrance 11, a target 12, a retarding body 13 adjacent to the target 12, and a surrounding a reflector 14 outside the retarding body 13, a thermal neutron absorber 15 adjacent to the retarding body 13, a radiation shield 16 and a beam outlet 17 provided in the beam shaping body 10, the target 12 and the self-beam
  • the proton beam incident at the inlet 11 undergoes a nuclear reaction to produce a neutron, the neutron forms a neutron beam, the neutron beam defines a major axis X, and the retarding body 13 decelerates the neutron generated from the target 12 to an epithermal neutron In the energy region, the reflector 14 guides the neutron away from the main axis X
  • the accelerator boron neutron capture treatment accelerates the proton beam by an accelerator.
  • the target 12 is made of lithium metal, and the proton beam is accelerated to an energy sufficient to overcome the coulomb repulsion of the target nucleus, which occurs with the target 12 7 Li (p,n) 7 Be nuclear reaction to produce neutrons.
  • the beam shaping body 10 can slow the neutron to the superheated neutron energy region and reduce the content of thermal neutrons and fast neutrons.
  • the retarding body 13 has a large cross section with fast neutron action and a small cross section of superheated neutron action.
  • the material is made, and as a preferred embodiment, the retarding body 13 is made of at least one of D 2 0, A1F 3 , FluentalTM, CaF 2 , Li 2 C0 3 , MgF 2 and A1 2 0 3 .
  • the reflector 14 is made of a material having a strong neutron reflection capability. As a preferred embodiment, the reflector 14 is made of at least one of Pb or Ni.
  • the thermal neutron absorber 15 is made of a material having a large cross section with thermal neutrons. As a preferred embodiment, the thermal neutron absorber 15 is made of 6 Li, the thermal neutron absorber 15 and the beam outlet 17 There is an air passage 19 between them.
  • the radiation shield 16 includes a photon shield 161 and a neutron shield 162. As a preferred embodiment, the radiation shield 16 includes a photon shield 161 made of lead (Pb) and a neutron shield 162 made of polyethylene (PE).
  • the retarding body 13 is disposed in a cone shape in which two opposite directions are adjacent to each other.
  • the left side of the retarding body 13 is a cone shape which gradually becomes smaller toward the left side
  • the right side is a cone shape that gradually becomes smaller toward the right side, and the two are adjacent to each other.
  • the left side of the retarding body 13 is disposed in a tapered shape that gradually becomes smaller toward the left side
  • the right side may be disposed in a shape similar to the tapered shape, such as a column shape or the like.
  • the reflector 14 is tightly enclosed in a slow speed Around the body 13, a gap passage 18 is provided between the retarding body 13 and the reflector 14, and the so-called gap passage 18 refers to an empty area which is not covered with a solid material and which easily passes the neutron beam, such as the gap passage. 18 can be set as an air passage or a vacuum passage.
  • the thermal neutron absorber 15 disposed adjacent to the retarding body 13 is made of a very thin layer of 6 Li material, and the photon shield 161 made of Pb in the radiation shield 16 may be integrally formed with the reflector 14 or may be provided.
  • the component body, and the neutron shield 162 made of PE in the radiation shield 16 may be disposed adjacent to the beam outlet 17.
  • An air passage 19 is provided between the thermal neutron absorber 15 and the beam outlet 17 where this region can continue to deviate from the neutron of the main axis X back to the main axis X to increase the intensity of the epithermal neutron beam.
  • the prosthesis B is placed about 1 cm from the beam exit 17.
  • the photon shield 161 can be made of other materials as long as it functions as a shield photon.
  • the neutron shield 162 can also be made of other materials or can be disposed elsewhere as long as it can satisfy the shielding. The conditions for leaking neutrons will do.
  • the beam shaping body 20 includes a beam entrance 21, a target 22, a retarding body 23 adjacent to the target 22, and a reflector 24 surrounding the retarding body 23, adjacent to the retarding body 23.
  • the sub-beam, the neutron beam defines a main axis XI
  • the retarding body 23 decelerates the neutron generated from the target 22 to the epithermal neutron energy region, and the reflector 24 will deviate from the neutron of the main axis XI to return to the main axis XI
  • the retarding body 23 is disposed in a cone shape in which two opposite directions are adjacent to each other, and the left side of the retarding body 23 is a cone shape which gradually becomes smaller toward the left side, and the retarding body 23 The right side is a cone shape that gradually becomes smaller toward the right side, and the two are adjacent to each other.
  • the thermal neutron absorber 25 is used to absorb thermal neutrons to avoid excessive doses with shallow normal tissues
  • the target 22, the retarding body 23, the reflector 24, the thermal neutron absorber 25, and the radiation shield 26 in the second embodiment may be the same as in the first embodiment, and the radiation shield therein 26 includes a photon shield 261 made of lead (Pb) and a neutron shield 262 made of polyethylene (PE), which may be disposed at the beam exit 27.
  • An air passage 28 is provided between the thermal neutron absorber 25 and the beam outlet 27.
  • the prosthesis B1 is placed about 1 cm from the beam exit 27.
  • the beam shaping body 30 includes a beam entrance 31, a target 32, a retarding body 33 adjacent to the target 32, and a reflector 34 surrounding the retarding body 33, adjacent to the retarding body 33.
  • the sub-beam, the neutron beam defines a main axis X2
  • the retarding body 33 decelerates the neutron generated from the target 32 to the superheated neutron energy region, and the reflector 34 will deviate from the neutron of the main axis X2 to return to the main axis X2.
  • the retarding body 33 is disposed in a cone shape in which two opposite directions are adjacent to each other, and the left side of the retarding body 33 is gradually reduced toward the left side.
  • the right side of the retarding body 33 is tapered toward the right side, and the two are adjacent to each other.
  • the thermal neutron absorber 35 is used to absorb thermal neutrons to avoid treatment with shallow normal tissues. Too much dose, radiation shield 36 is used to shield leaking neutrons and photons to reduce the normal tissue dose in the non-irradiated area.
  • the target 32, the retarding body 33, the reflector 34, the thermal neutron absorber 35, and the radiation shield 36 in the third embodiment may be the same as in the first embodiment, and the radiation shield therein 36 includes a photon shield 361 made of lead (Pb) and a neutron shield 362 made of polyethylene (PE), which may be disposed at the beam exit 37.
  • An air passage 38 is provided between the thermal neutron absorber 35 and the beam outlet 37.
  • the prosthesis B2 is placed about 1 cm from the beam exit 37.
  • the MCNP software (which is a Monte Carlo-based method for calculating neutrons, photons, charged particles, or coupled neutrons/photons in three-dimensional complex geometries) is developed by Los Alamos National Laboratory. /General software package for charged particle transport problems) Simulation calculations for these three examples:
  • Table 1 below shows the performance of the beam quality factor in the air in the three embodiments (the units of the nouns in the table are the same as above, and will not be described here, the same below):
  • Table 2 shows the performance of the dose performance in these three examples:
  • the average neutron energy of the neutron scattering angle between 0 ° -30 ° is about 478 keV, and the neutron scattering The average neutron energy between 30 ° and 180 ° is only about 290 keV. If the geometry of the beam shaping body is changed, the forward neutron and the retarding body will have more collisions, and the lateral middle When the beam reaches the beam exit with less collision, it is theoretically possible to achieve neutron retardation optimization and efficiently increase the superheat neutron flux.
  • the geometry of the beam shaping body is used to evaluate the effect of the geometry of the different beam shaping bodies on the hyperthermal neutron flux.
  • the beam shaping body 40 includes a beam inlet 41, a target 42, and a retarding body 43 adjacent to the target 42. a reflector 44 surrounding the retarding body 43, a thermal neutron absorber 45 adjacent to the retarding body 43, a radiation shield 46 disposed in the beam shaping body 40, and a beam outlet 47, the target 42 and
  • the proton beam incident at the beam entrance 41 undergoes a nuclear reaction to generate neutrons, and the retarding body 43 decelerates the neutrons generated from the target 42 to the superheated neutron energy region, and the reflector 44 conducts the deviated neutrons back to enhance the super
  • the thermal neutron beam intensity, the retarding body 43 is arranged in a cylindrical shape, preferably, in a cylindrical shape, and the thermal neutron absorber 45 is used to absorb thermal neutrons to avoid excessive formation with shallow normal tissues during treatment.
  • the dose, radiation shield 46 is used to shield leaking neutrons and photons to reduce the normal
  • the beam shaping body 50 includes a beam entrance 51, a target 52, and a retarding body 53 adjacent to the target 52. , the reflector 54 surrounding the retarding body 53, and the slow speed
  • the sub-beam forms a neutron beam
  • the neutron beam defines a major axis X3
  • the retarding body 53 decelerates the neutrons generated from the target 52 to the epithermal neutron energy region, and the reflector 54 will deviate from the neutron guide of the main axis X3.
  • the retarding body 53 is disposed in a cone shape in which two opposite directions are adjacent to each other, and the left side of the retarding body 53 is in the shape of a cylinder, and the right side of the retarding body 53 is The cone shape gradually decreases toward the right side, and the two are adjacent to each other.
  • the thermal neutron absorber 25 is used to absorb the thermal neutrons to avoid excessive doses to the normal tissues in the shallow layer during the treatment, and the radiation shield 26 is used to shield the leakage. Neutrons and photons to reduce the normal tissue dose in the non-irradiated area.
  • the target 52, the retarding body 53, the reflector 54, the thermal neutron absorber 55, and the radiation shield 56 in the fifth embodiment may be the same as in the first embodiment, and the radiation shield therein 56 includes a photon shield 561 made of lead (Pb) and a neutron shield 562 made of polyethylene (PE), which may be disposed at the beam exit 57.
  • An air passage 58 is provided between the thermal neutron absorber 55 and the beam outlet 57.
  • Prosthesis B3 is placed about 1 cm from the beam exit 57.
  • Table 4 shows the performance of the beam quality factor in air in these three embodiments:
  • Table 5 shows the performance of the dose performance in these three examples:
  • Effective treatment depth 11. 8 10. 9 10. 9 Effective treatment of deep dose rate 2. 95 4. 28 4. 47 Effective therapeutic dose ratio 5. 52 5. 66 5. 66
  • Table 6 shows the simulated values of the parameters for evaluating the neutron beam dose performance in these three examples: Table 6: Parameters for evaluating the pros and cons of the neutron beam dose
  • the retarding body is set to at least one cone shape, wherein the sub-beam has better therapeutic benefit.
  • the "cylinder” or “cylinder” as used in the embodiment of the present invention refers to a structure in which the overall tendency of the outer contour of the outer contour is substantially constant from one side to the other side in the illustrated direction, one of the contours of the outer contour
  • the line may be a line segment, such as a corresponding contour of a cylindrical shape, or an arc of a curved line close to a line segment, such as a spherical contour corresponding to a larger curvature, and the entire surface of the outer contour may be smooth Transitions can also be non-smooth transitions, such as a lot of protrusions and grooves on a spherical or curved spherical surface.
  • the "cone” or “tapered shape” as used in the embodiment of the present invention refers to a structure in which the overall tendency of the outer contour of the outer contour is gradually reduced from one side to the other side in the illustrated direction, and one contour of the outer contour
  • the line may be a line segment, such as a corresponding contour line of a cone shape, or may be an arc, such as a corresponding contour line of a spherical body.
  • the entire surface of the outer contour may be a smooth transition or a non-smooth transition, such as A lot of protrusions and grooves are made on the surface of the cone or spherical body.
  • the slowing body 13 will be further described below by taking the first embodiment and Fig. 3 as examples.
  • the retarding body 13 exhibits a double-cone structure in which the two cone directions are completely opposite, and the material of the retarding body 13 is made of at least one material containing 41 or CaF 2 or MgF 2 , and the retarding body 13 has the first The diameter D1, the second diameter D2, and the third diameter D3. An opening is provided at the first diameter D1 to accommodate the target 12, and the second diameter D2 is set at the largest dimension of the double-cone structure.
  • the first diameter D1 has a length of 1 cm to 20 cm
  • the second diameter D2 has a length of 30 cm to 100 cm
  • the third diameter D3 has a length of 1 cm to 50 cm, as a preferred
  • a diameter D1 is 10cm in length
  • the second diameter D2 has a length of 70 cm
  • the third diameter D3 has a length of 30 cm.
  • MgF 2 as an example, please refer to the patent application publication No. CN102925963A, which is incorporated herein by reference in its entirety.
  • a seed crystal and a powder containing MgF 2 are usually placed in a crucible to grow a MgF 2 single crystal in a certain manner.
  • single crystal refers to a single crystal formed by a single growth, and is not a single crystal grain (that is, there is only one crystal form and only one crystal grain, the intragranular molecules, the yard They are all arranged regularly.) It is better understood that such a single grain corresponds to a plurality of grains (i.e., each grain is different in size and shape, and the orientation is also messy, has no obvious shape, and does not exhibit anisotropy).
  • single crystal refers to a single crystal formed by a single growth, and is not a single crystal grain (that is, there is only one crystal form and only one crystal grain, the intragranular molecules, the yard They are all arranged regularly.) It is better understood that such a single grain corresponds to a plurality of grains (i.e., each grain is different in size and shape, and the orientation is also messy, has no obvious shape, and does not exhibit anisotropy).
  • the definition of "single crystal” below is the same as here.
  • PbF 4 , A1F 3 , CaF n Al 2 0 3 can also be prepared in a similar manner.
  • the powder or powder compact of ⁇ or 1 or CaF 2 is further combined, and the powder particles undergo physical and chemical processes such as mutual flow, diffusion, dissolution, recrystallization, etc. during the sintering process to further densify the powder and eliminate some of them or All pores.
  • sintering methods such as solid phase sintering, that is, the sintering temperature is below the melting point of each component in the powder; liquid phase sintering, that is, if there are more than two components in the powder compact, sintering may be some kind The melting point of the component is above the melting point, so that a small amount of liquid phase appears in the powder compact during sintering; hot pressing sintering, that is, when sintering, pressure is applied to the powder to promote the densification process, and hot pressing is the formation of the powder and Sintering combines to directly obtain the process of the product; discharge plasma sintering, that is, by adding ON-OFF DC pulse voltage generated by a special power control device to the powder sample, in addition to utilizing the sintering promotion effect caused by the usual electric discharge machining (Discharge shock pressure and Joule heating)
  • discharge plasma sintering that is, by adding ON-OFF DC pulse voltage generated by a special power control device to the powder sample, in addition to utilizing the
  • an example of powder sintering is carried out by adding 1 to 5% of a mixed powder of 6 LiF in a weight percentage of MgF 2 powder, or MgF 2 , preferably, MgF 2 is added as MgF 2 powder.
  • a percentage by weight of 0.1 to 5% of a 6 LiF mixed powder is used as an example for powder sintering.
  • the slow-moving body plays an extremely important role in the beam shaping body, and it is responsible for the slow response of the neutron. It is possible to suppress the fast neutron intensity and not to slow the neutron excessively into thermal neutrons. On the other hand, it is also necessary to suppress the gamma rays derived during the deceleration. Studies have shown that evenly adding a small amount of 6 Li-containing material to the slow-moving body can effectively suppress the intensity of the gamma ray. Although the neutron intensity is slightly reduced, the original beam quality is preserved. After further study, the MgF 2 powder doped MgF 2 powder accounts for 0.
  • the MgF 2 powder is doped in an amount of 0.1 to 5% by weight of the MgF 2 powder.
  • the material containing 6 Li is mixed as a retarding material. As is well known to those skilled in the art, the material containing 6 Li may be any Any material form that is easily doped with the MgF 2 powder, such as the 6 Li-containing material, may be a liquid or a powder.
  • the 6 Li-containing material may be any compound that is easily doped with the MgF 2 powder, and the 6 Li-containing material may be 6 LiF or 6 Li 2 C0 3 .
  • the MgF 2 powder is further combined with 0.1 to 5% of the 6 LiF powder or powder compact according to the weight percentage of the MgF 2 powder, and the powder particles are mutually flowed and diffused during the sintering process. Physical and chemical processes such as dissolution and recrystallization make the powder denser and eliminate some or all of the pores.
  • sintering methods such as solid phase sintering, that is, the sintering temperature is below the melting point of each component in the powder; liquid phase sintering, that is, if there are more than two components in the powder compact, sintering may be some kind The melting point of the component is above the melting point, so that a small amount of liquid phase appears in the powder compact during sintering; hot pressing sintering, that is, when sintering, pressure is applied to the powder to promote the densification process, and hot pressing is the formation of the powder and Sintering combines to directly obtain the process of the product; discharge plasma sintering, that is, by adding ON-OFF DC pulse voltage generated by a special power supply control device to the powder sample, in addition to utilizing the sintering promotion effect caused by the usual electric discharge machining (Discharge shock pressure and Joule heating)
  • discharge plasma sintering that is, by adding ON-OFF DC pulse voltage generated by a special power supply control device to the powder sample, in addition to utilizing
  • sintering means can also be used to prepare a material of at least one or a mixture of 1 or 41 or & or PbF 4 and a powder of 6 LiF as a retarding material.
  • hot press sintering and spark plasma sintering are exemplified below as powder sintering.
  • Discharge plasma sintering melt plasma activation, hot pressing, resistance heating as one, rapid heating rate, short sintering time, low sintering temperature, uniform grain, favorable control of the fine structure of the sintered body, high density of materials obtained, and operation Simple, reproducible, safe, reliable, space saving, energy saving and low cost.
  • Discharge plasma sintering Because a strong pulse current is applied between the powder particles, there is an electric field-induced positive and negative electrode between the powder particles. Under the pulse current, a discharge occurs between the particles, and the plasma is excited, and the high-energy particles generated by the discharge strike the contact between the particles.
  • the substance is caused to evaporate to purify and activate, and the electrical energy is stored in the dielectric layer of the particle group, and the dielectric layer undergoes intermittent rapid discharge.
  • the pulse current Due to the pulse current between the powder or the powder compact, the pulse current is instantaneous, intermittent, and high frequency, the heat of discharge generated at the non-contact portion of the powder particles, and the Joule heat generated at the contact portion of the powder particles are greatly promoted.
  • Powder granule The diffusion of atoms, the diffusion coefficient is much larger than that under normal hot pressing conditions, so as to achieve rapid powder sintering.
  • the discharge portion and the Joule heating portion in the powder are rapidly moved, so that the sintering of the powder or the powder compact can be uniformized.
  • the grain is heated by the pulse current and the vertical unidirectional pressure, the bulk diffusion and the grain boundary diffusion are all strengthened, and the sintering densification process is accelerated, so that a high-quality sintered body can be obtained with a lower temperature and a shorter time.
  • the spark plasma sintering process can be seen as a result of the combined action of particle discharge, conductive heating and pressurization.
  • the discharge plasma sintering apparatus 100 includes a first electrode 101, a second electrode 102, a conductive mold 103 interposed between the first electrode 101 and the second electrode 102, and a pulse current generator 104 that supplies a pulse current to the mold 103, with Pressurizing device 105 of pressurized pressurizing members 1051, 1052 and control device 106 for controlling pulse current generator 104 and pressurizing device 105, at least one of first electrode 101 and second electrode 102 can be moved, plus At least one of the pressing members 1051, 1052 is movable, and preferably, the first electrode 101 and the pressing member 1051 are fixed, and the second electrode 102 and the pressing member 1052 are movable so as to be pressurizable into the mold 103.
  • the discharge plasma sintering apparatus 100 further includes a displacement measuring system 108 for measuring the displacement of the pressing device 105, an atmosphere control system 109 for controlling the atmosphere in the mold 103, and a water cooling system 111 for controlling the water-cooling vacuum chamber 110 to be cooled.
  • a temperature measuring device 112 for measuring the temperature within the discharge plasma sintering apparatus 100.
  • the mold 103 and the powder or powder compact 107 are subjected to a pulse current, in addition to providing discharge shock pressure and Joule heat for sintering, and further utilizing a spark discharge phenomenon (instantaneously generating a high-temperature plasma) generated between the powders at the initial stage of the pulse discharge.
  • the sintering promotion effect is rapid sintering by the instantaneous high temperature field, so that the powder or powder compact 107 is changed from a powder state to a block shape, and the so-called block shape is integrally formed, and does not need to be polished by a single crystal, such as a crystal growth method.
  • the polishing and other processes are spliced into a size suitable for the slow speed body.
  • the discharge plasma sintering apparatus 100 directly conducts sintering and pressurization using a direct current pulse current, and the temperature rise rate and the sintering temperature are controlled by the control unit 106 by adjusting the magnitude of the pulsed direct current.
  • the entire sintering process can be carried out under vacuum or in a protective atmosphere such as oxygen or hydrogen.
  • Sintering temperature is one of the key parameters in the rapid plasma sintering process. Sintering temperature is determined by considering the sintered body The phase transition of the sample at high temperatures, the growth rate of the grains, the quality requirements of the samples, and the density requirements of the samples. Under normal circumstances, as the sintering temperature increases, the density of the sample increases as a whole, which indicates that the sintering temperature has a significant effect on the density of the sample. The higher the sintering temperature, the faster the material transfer speed during the sintering process. The easier it is to be dense.
  • the higher the temperature the faster the growth rate of the grains and the worse the mechanical properties.
  • the temperature is too low, the density of the sample is very low, and the quality is not up to the requirement.
  • the contradiction between temperature and grain size requires a suitable parameter in the choice of temperature.
  • Prolonging the holding time at the sintering temperature generally promotes the sintering to a different extent and improves the microstructure of the sample. This is more obvious for the viscous flow mechanism, but less for the bulk diffusion and surface diffusion mechanism.
  • the density of the sample reaches 96.5% of the theoretical density.
  • the holding time increases, the density of the sample increases, but the variation range is not very large, indicating the holding time to the sample.
  • the density of the film has a certain influence, the effect is not very obvious.
  • the acceleration of the time heating rate allows the sample to reach the required temperature in a short period of time, and the growth time of the crystal grains is greatly reduced, which is not only beneficial for suppressing the growth of crystal grains, but also obtaining fine-grain ceramics of uniform size. Save time, save energy and increase the utilization of sintering equipment.
  • the rapid heating rate can have a devastating effect on the device. Therefore, the heating rate is accelerated as much as possible within the allowable range. However, it is reflected in the measured experimental data. Different from the sintering temperature and holding time, the effect of heating rate on the density of the sample shows the opposite result. That is, as the heating rate increases, the densification of the sample shows a tendency to gradually decrease.
  • the temperature rising process is generally divided into three stages, from room temperature to 600 ° C, 600 ° C to 900 ° C, 900 to sintering temperature: the first stage is the preparation stage, the heating rate Relatively slow; the second stage is a controlled rapid temperature rise phase, the heating rate is generally controlled at 100 ⁇ 500 (°C/min) ; the third stage is the buffering stage of temperature rise, the temperature slowly rises to the sintering temperature, the holding time It is usually 1 ⁇ 7 minutes, and it is cooled with the furnace after heat preservation, and the cooling rate can reach 300 °C/min.
  • the powder is subjected to press forming and sintering immediately after being sufficiently discharged.
  • the sintered material undergoes severe plastic deformation under the joint action of the resistance Joule heat and pressure.
  • the application of the forming pressure is beneficial to enhance the contact between the powder particles, increase the sintering area, discharge the residual gas between the sintered powders, and improve the strength and density of the workpiece. Surface finish.
  • the forming pressure is generally determined by the compressibility of the sintered powder and the requirements for the properties such as the density and strength of the sintered material, and is generally in the range of 15 to 30 MPa, and sometimes as high as 50 MPa or even higher. Generally, the greater the forming pressure, the higher the density of the sintered material.
  • the duration of pressurization also has a large effect on the density of the sintered material.
  • the appropriate pressurization time varies depending on the type of sintered material, the particle size of the sintered material and the geometrical size of the material to be sintered, and needs to be determined experimentally. Experiments have shown that the duration of pressurization is equal to or slightly greater than the discharge time, which is a necessary condition for obtaining the highest density sintered material. It is easy to understand from the mechanism of sintering and solid phase reaction. The higher the pressure, the tighter the particle packing in the sample, and the mutual contact point and contact area increase the sintering speed. This allows the sample to have a better density and effectively inhibits grain growth and lowers the sintering temperature.
  • the pressure chosen is generally 30 ⁇ 50Mpa.
  • the density of the sample is not much different, which indicates that the phenomenon of density increase with pressure is only obvious within a certain range.
  • Spark plasma sintering has the following advantages over conventional sintering techniques: Fast sintering speed; improved material microstructure and improved material properties.
  • the mold can be made of other electrically conductive materials, and the discharge plasma sintering apparatus can be arranged such that both electrodes are stationary and only at least one of the pressing members can be moved.
  • the main process flow of spark plasma sintering is divided into four stages.
  • First stage Applying an initial pressure to the powder sample to allow sufficient contact between the powder particles to subsequently produce a uniform and sufficient discharge plasma in the powder sample;
  • Stage 2 Applying a pulsed current, under the action of a pulsed current, powder The particle contact point generates a discharge plasma, and the surface of the particle generates a micro-discharge phenomenon due to activation;
  • the third stage the pulse power supply is turned off, and the sample is subjected to resistance heating until the predetermined sintering temperature is reached and the sample shrinks completely;
  • the fourth stage pressure relief.
  • Reasonable control of the initial process pressure, sintering time, forming pressure, pressurization duration, sintering temperature, heating rate and other major process parameters can obtain a good overall performance of the material.
  • the surface of the particle is maximally activated to accelerate the sintering densification process, which requires sintering.
  • the powder is applied with an appropriate initial pressure to bring the powder particles into full contact.
  • the initial pressure can vary depending on the type of sintered powder, the size of the sintered part, and the properties. When the initial pressure is too small, the discharge phenomenon is limited to a part of the powder, causing the powder to partially melt; if the pressure is too large, the discharge will be suppressed, thereby delaying the sintering diffusion process. According to the prior literature, in order to continue the discharge sufficiently, the initial pressure is generally not more than 10 MPa.
  • the sintering time is extremely short or even instantaneous, but the length of the sintering should be based on the powder quality, variety and performance. The difference is usually a few seconds to a few minutes; when sintering large, refractory metal powder materials, it can be as long as several tens of minutes.
  • the sintering time has a great influence on the density of the part. In order to make the densification process sufficiently, it is necessary to ensure a certain sintering time.
  • the spark plasma sintering process comprises the steps of: filling the mold 103 with an appropriate amount of powder or powder compact 107; moving the pressurizing device 105 to pressurize the powder or powder compact 107 in the mold 103; through the control device 106
  • the pulse current generator 104 is turned on to conduct the mold 103 to generate plasma, the surface of the powder particles is activated and heated; and sintered into a block.
  • the spark plasma sintering process further includes the steps of: the control device 106 controls the displacement measuring system 108 to ensure that the displacement measuring system 108 is functioning properly, and the control device 106 controls the atmosphere control system 109 to ensure that the atmosphere within the mold 103 is in normal operation, the control device 106 controls the water cooling system 111 to ensure that it is in normal operation, and the control device 106 controls the temperature measuring device 112 to ensure that the temperature within the spark plasma sintering apparatus 100 is in normal operation.
  • the so-called normal work refers to an alarm signal such as visual, tactile or auditory that does not occur to humans in the discharge plasma sintering apparatus, such as an alarm indicator light, an alarm indicator sound, an alarm indication vibration, and the like.
  • Hot-pressing sintering is to fill the dry powder into the mold, and then pressurize it from the uniaxial direction while pressurizing, so that molding and sintering are simultaneously performed. A sintering method that is completed.
  • the hot pressing sintering technology is very rich in production process, and there is no uniform specification and standard for classification. According to the status quo, it can be divided into vacuum hot pressing, atmospheric hot pressing, vibration hot pressing, equilibrium hot pressing, hot isostatic pressing, reactive hot pressing and ultra high pressure sintering.
  • the hot pressing sintering is carried out simultaneously by heating and pressing, and the powder is in a thermoplastic state, which contributes to the contact diffusion of the particles and the flow mass transfer process, so that the molding pressure is only 1/10 of the cold pressure; the sintering temperature can also be lowered and shortened.
  • the sintering time, thereby resisting grain growth, results in a product having fine crystal grains, high density, and good mechanical and electrical properties.
  • the hot press sintering apparatus 200 mainly includes a heating furnace 201, a pressurizing device 202 placed in the heating furnace 201, a mold 203, and a powder loaded into the mold 203. Or powder compact 204 and control device 205.
  • the heating furnace 201 usually uses electricity as a heat source, and the heating element is made of SiC, MoSi or nickel filament, white gold wire, molybdenum wire or the like.
  • the pressurizing device 202 requires a gentle speed, a constant pressure holding, and a flexible pressure adjustment, and is generally of a lever type and a hydraulic type.
  • the pressure atmosphere may be air or a reducing atmosphere or an inert atmosphere depending on the material properties.
  • the mold 203 is required to have high strength, high temperature resistance, oxidation resistance and no adhesion to the hot pressing material, and the thermal expansion coefficient of the mold 203 should be identical or similar to that of the hot pressing material.
  • a graphite mold is used in the embodiment.
  • the control device 205 causes the hot press sintering apparatus 200 to operate under normal conditions.
  • the so-called normal work refers to the visual, tactile or auditory alarm signals that the human plasma sensing device does not have human perception, such as the alarm indicator lights up, the alarm indicator lights, the alarm indicates vibration, and the like.
  • the production process generally includes the following steps: MgF 2 raw material preparation raw material grinding, sieving treatment, transfer to mold high temperature sintering, high temperature hot pressing sintering, cooling hot isostatic pressing High-temperature sintering cools out the furnace for grinding, polishing, and bonding of finished products.
  • the hot press sintering process comprises the steps of: filling the mold 203 with an appropriate amount of powder or powder compact 204; opening the hot press 201 to preset pressure and temperature parameters; moving the pressurizing device 202 to the powder or powder compact 204 in the mold 203 Pressurization; control device 205 controls hot press sintering apparatus 200 in the case of normal operation; energization to sinter into a block.
  • the step in the hot press sintering process “the moving pressurizing device 202 pressurizes the powder or the powder compact 204 in the mold 203" may be pre-pressurized, or may be performed in synchronization with the energization, that is, the step "moving"
  • the pressurizing device 202 energizes the powder or powder compact 204 in the mold 203 to "press and energize” to form a block "two in one.”
  • Sintered A1F 3 is more than 500,000 in January depending on the actual size.
  • CaF 2 needs about 500,000 or so in January.
  • MgF 2 needs about 1 million in about 2 months. It is easier to vacuum hot-pressed A1F 3 according to the actual size. It takes about 1 million or so in February.
  • CaF 2 needs about 1 million or so in February.
  • MgF 2 needs 2-2 according to the actual size. May 500,000 is more easily hot isostatic pressing AIF3 according to the actual size needs 2-2. About 500,000 is easy
  • CaF 2 is required to be 2-2 according to the actual size. It is easier to note about 500,000 in May.
  • the above table is used as the main material of the powder, and the 0.1% to 5% of the 6LiF powder is omitted. Although only the MgF is listed in the above table.
  • the two slow-acting materials of 2 + LiF, AlF 3 + LiF and CaF 2 + LiF are compared using the parameters of the above process, but other slow-moving materials such as Al 2 0 3 + LiF can be very well known to those skilled in the art. Easy to make comparisons.
  • the density of the slow-body material prepared by the growth of the crystal growth can reach a theoretical density, such as 99.99% of the theoretical density, since the single crystal size is small, it is necessary to achieve the target large size.
  • the slow-moving material needs to be spliced by a large number of single crystals, and other processes such as mirror polishing may be required in the process, which is not only time consuming, but also costly and technically difficult.
  • the density of the slow-acting material prepared by powder sintering can also reach 80%-100% of the theoretical density. 01% ⁇
  • the density of the slow-moving body material reaches a theoretical density of 99.99%. While the theoretical density is substantially indistinguishable from the theoretical density of the slow-moving bulk material obtained by the long-crystal method, it has advantages in terms of size, time, cost, and process difficulty.
  • the actual size of the retarding material prepared by spark plasma sintering is obtained as needed.
  • One way can be customized to suit the required mold, and the other way is to use a common mold, such as a mold with a diameter of 70 cm* and a thickness of 2 cm, and then several pieces. It can be completed by splicing. Under the premise that the cost and process difficulty are comparable to vacuum hot pressing sintering and hot isostatic pressing, the manufacturing time only takes about one month.
  • the beam shaping body for neutron capture treatment disclosed in the present invention is not limited to the contents described in the above embodiments and the structures shown in the drawings. Obvious modifications, substitutions, or alterations of the materials, shapes, and positions of the components in the present invention are within the scope of the invention as claimed. Therefore, the scope of the invention should be determined by the scope of the claims.

Abstract

一种用于中子捕获治疗的射束整形体，包括射束入口、靶材、邻接于靶材的缓速体、包围在缓速体外的反射体、与缓速体邻接的热中子吸收体、设置在射束整形体内的辐射屏蔽和射束出口，靶材与自射束入口入射的质子束发生核反应以产生中子，中子形成限定一根主轴的中子射束，缓速体将自靶材产生的中子减速至超热中子能区，缓速体的材料由MgF2制成或含有MgF2和占有MgF2的重量百分比为0.1-5％的含有6LiF混合制成，其经粉末烧结设备通过粉末烧结工艺由粉末或粉末压坯变成块，反射体将偏离主轴的中子导回主轴以提高超热中子射束强度，热中子吸收体用于吸收热中子以避免治疗时与浅层正常组织造成过多剂量，辐射屏蔽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。

Description

用于中子捕获治疗的射束整形体 技术领域
本发明涉及一种射束整形体， 尤其涉及一种用于中子捕获治疗的射束整形体。
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
( gl ioblastoma multiforme ), 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) 是利用含硼 （WB) 药物对热 中子具有高捕获截面的特性， 借由 a ) 7Li中子捕获及核分裂反应产生 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 (!!， a ) 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（Linear Energy Transfer, LET) , 短射程特征， α粒子的线性能量转移与射程分别为 150 keV/ μ πκ 8 μ πι, 而 7Li重荷粒 子则为 175 keV/ y m、 5 μ πι, 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。 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
为了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， 其包括射束入口、 靶材、 邻接于靶材的缓速体、 包围在缓速体外的反射体、 与缓速 体邻接的热中子吸收体、 设置在射束整形体内的辐射屏蔽和射束出口， 靶材与自射束入口入 射的质子束发生核反应以产生中子， 中子形成中子射束， 中子射束限定一根主轴， 缓速体将 自靶材产生的中子减速至超热中子能区，缓速体的材料由含有 PbF4、 A1203、 A1F3、 0^2或 MgF2 中的一种或多种混合材料和占有含有 PbF4、 A1203、 A1F3、 （¾ 或 MgF2中的一种或多种混合材 料的重量百分比为 0. 1-5%的含有 6Li元素的材料混合制成， 其中缓速体的材料经粉末烧结设 备通过粉末烧结工艺由粉末或粉末压坯变成块， 反射体将偏离主轴的中子导回主轴以提高超 热中子射束强度，热中子吸收体用于吸收热中子以避免治疗时与浅层正常组织造成过多剂量， 辐射屏蔽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。
本发明的另一方面提供一种用于中子捕获治疗的射束整形体， 其包括射束入口、 靶材、 邻接于靶材的缓速体、 包围在缓速体外的反射体、 与缓速体邻接的热中子吸收体、 设置在射 束整形体内的辐射屏蔽和射束出口，靶材与自射束入口入射的质子束发生核反应以产生中子， 中子形成中子射束， 中子射束限定一根主轴， 缓速体将自靶材产生的中子减速至超热中子能 区， 缓速体的材料由含有 LiF、 Li2C03、 A1203、 A1F3、 CaF2或 MgF2中的至少一种材料制成， 其 中缓速体的材料经粉末烧结设备通过粉末烧结工艺由粉末或粉末压坯变成块， 反射体将偏离 主轴的中子导回主轴以提高超热中子射束强度， 热中子吸收体用于吸收热中子以避免治疗时 与浅层正常组织造成过多剂量， 辐射屏蔽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。
射束整形体进一步用于加速器硼中子捕获治疗， 加速器硼中子捕获治疗通过加速器将质 子束加速， 靶材由金属制成， 质子束加速至足以克服靶材原子核库伦斥力的能量， 与靶材发 生核反应以产生中子， 射束整形体能将中子缓速至超热中子能区， 并降低热中子及快中子含 量， 超热中子能区在 0. 5eV到 40keV之间， 热中子能区小于 0. 5eV， 快中子能区大于 40keV， 反射体由具有中子反射能力强的材料制成，热中子吸收体由与热中子作用截面大的材料制成。
作为一种优选地， 反射体由 Pb或 Ni中的至少一种制成， 热中子吸收体由 6Li制成， 热 中子吸收体和射束出口之间设有空气通道， 辐射屏蔽包括由 Pb制成的光子屏蔽和由 PE制成 的中子屏蔽。
为了有效的对中子射束进行减速， 一方面， 作为一种优选地， 缓速体设置成两个相反方 向相互邻接的锥体状。
进一步地， 锥体状包括第一直径、 第二直径和第三直径， 第一直径长度为 lcm-20cm， 第 二直径长度为 30cm-100cm， 第三直径长度为 lcm-50cm， 缓速体的材料的密度为理论密度的 80%- 100%。
再进一步地， 缓速体和反射体之间设置间隙通道以提高超热中子通量， 缓速体的材料由 含有 MgF2粉末和占有 MgF2粉末重量百分比为 0. 1-5%的 6LiF粉末混合制成。
另一方面， 粉末烧结设备为热压烧结设备或放电等离子烧结设备， 粉末烧结工艺为热压 烧结工艺或放电等离子烧结工艺。
优选地， 热压烧结设备包括加热炉、 置于加热炉内的加压装置、 模具、 装入模具内的粉 末或粉末压坯和用于控制热压烧结设备正常工作的控制装置， 热压烧结工艺包括如下步骤： 用适量的粉末或粉末压坯填充模具； 开启热压炉以预设压力和温度参数； 移动加压装置对模 具内的粉末或粉末压坯加压； 控制装置控制热压烧结设备在正常工作的情形下； 通电以烧结 成块。
作为另一种优选地， 放电等离子烧结设备包括第一电极、 第二电极、 置于第一电极和第 二电极之间的导电模具、 给模具提供脉冲电流的脉冲电流发生器、 带有用于加压的加压件的 加压装置和用于控制脉冲电流发送器和加压装置的控制装置， 第一电极和第二电极中的至少 一个能够移动， 第一电极和第二电极中的至少一个与加压装置相连从而能够加压置于模具内 的粉末； 放电等离子烧结工艺包括如下步骤： 将适量的粉末填充模具； 移动第二电极对模具 内的粉末加压； 通过控制装置打开脉冲电流发生器以将导电模具导电从而产生等离子体， 粉 末颗粒表面被活化和发热； 烧结成块。
放电等离子烧结设备进一步包括用于测量加压装置的位移的位移测量系统， 用于控制模 具内气氛的气氛控制系统， 用于冷却的水冷系统， 用于测量放电等离子烧结设备内的温度的 温度测量装置， 放电等离子烧结工艺进一步包括如下步骤： 控制装置控制位移测量系统以确 保位移测量系统正常工作， 控制装置控制气氛控制系统以确保模具内气氛在正常工作的情形 下， 控制装置控制水冷系统以确保水冷系统正常工作， 控制装置控制温度测量装置以确保放 电等离子烧结设备内的温度在正常工作的情形下。
本发明实施例中所述的 "柱体"或 "柱体状"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 "锥体"或 "锥体状"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。
附图说明
为了更清楚地说明本发明实施例的技术方案， 下面将对本发明实施例中所需要使用的附 图作简单地介绍， 显而易见地， 下面描述中的附图仅仅是本发明的一些实施例， 对于本领域 普通技术人员来讲， 在不付出创造性劳动的前提下， 还可以根据这些附图获得其他的附图。
图 1是硼中子捕获反应示意图。
图 2是 (11， α ) 7Li中子捕获核反应方程式。 图 3是本发明第一实施例中的用于中子捕获治疗的射束整形体的平面示意图， 其中， 在 缓速体和反射体之间设置有间隙通道。
图 4是本发明第二实施例中的用于中子捕获治疗的射束整形体的平面示意图， 其中， 缓 速体设置成双锥体， 且第一实施例中的间隙通道位置以缓速体材料填充。
图 5是本发明第三实施例中的用于中子捕获治疗的射束整形体的平面示意图， 其中， 缓 速体设置成双锥体， 且第一实施例中的间隙通道位置以反射体材料填充。
图 6是中子能量与中子角度双微分的中子产率图。
图 7是本发明第四实施例中的用于中子捕获治疗的射束整形体的平面示意图， 其中， 缓 速体设置成柱体。
图 8是本发明第五实施例中的用于中子捕获治疗的射束整形体的平面示意图， 其中， 缓 速体设置成柱体 +锥体。
图 9是本发明其中一个实施例中的缓速体材料的制备装置示意图， 其中， 该制备装置为 放电等离子烧结设备。
图 10是本发明其中一个实施例中的缓速体材料的制备装置示意图， 其中， 该制备装置为 热压烧结设备。
具体实施方式
中子捕获治疗作为一种有效的治疗癌症的手段近年来的应用逐渐增加， 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、 靶材与热移除系统和射束整形体， 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) ¾e 及¾6 ， 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。 理想的靶材应具备高中子产率、 产生的中子能量分布接近超热中子能区 （将在下文详细 描述)、 无太多强穿辐射产生、 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，本发明的实施例中采用锂金属制成的靶材。但是本领域技术人员熟知的， 靶材的材料也可以由其他除了上述谈论到的金属材料之外的金属材料制成。
针对热移除系统的要求则根据选择的核反应而异， 如 7Li (p，n) ¾e因金属靶材 （锂金属） 的熔点及热导系数差， 对热移除系统的要求便较 9Be (p，n) ¾ 高。 本发明的实施例中采用 7Li (p, n) ¾e的核反应。
无论硼中子捕获治疗的中子源来自核反应堆或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。 除了空气射束品质因素， 为更了解中子在人体 中造成的剂量分布， 本发明的实施例中使用人体头部组织假体进行剂量计算， 并以假体射束 品质因素来作为中子射束的设计参考， 将在下文详细描述。
国际原子能机构 （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 x 109 n/ cm2s
快中子污染] ¾st neutron contamination < 2 x 10— 13 Gy-cm2/n
光子污染 Photon contamination < 2 x 10— 13 Gy-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 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：
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， 则需高 通量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：
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 X 10— 13 Gy-cm2/n o
3、 光子污染 （ γ射线污染）： γ射线属于强穿辐射， 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 χ 10— 13 Gy-cm2/n。
4、 热中子与超热中子通量比值：
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：
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及 摆位姿势弹性。 IAEA对中子电流与通量比值建议为大于 0. 7。
利用假体得到组织内的剂量分布， 根据正常组织及肿瘤的剂量 -深度曲线， 推得假体射束 品质因素。 如下三个参数可用于进行不同中子射束治疗效益的比较。
1、 有效治疗深度：
肿瘤剂量等于正常组织最大剂量的深度， 在此深度之后的位置， 肿瘤细胞得到的剂量 小于正常组织最大剂量，即失去了硼中子捕获的优势。此参数代表中子射束的穿透能力， 有效治疗深度越大表示可治疗的肿瘤深度越深， 单位为 cm。
2、 有效治疗深度剂量率：
即有效治疗深度的肿瘤剂量率， 亦等于正常组织的最大剂量率。 因正常组织接收总剂 量为影响可给予肿瘤总剂量大小的因素， 因此参数影响治疗时间的长短， 有效治疗深度 剂量率越大表示给予肿瘤一定剂量所需的照射时间越短， 单位为 cGy/mA-min。
3、 有效治疗剂量比：
从大脑表面到有效治疗深度， 肿瘤和正常组织接收的平均剂量比值， 称之为有效治疗 剂量比； 平均剂量的计算， 可由剂量-深度曲线积分得到。 有效治疗剂量比值越大， 代表 该中子射束的治疗效益越好。
为了使射束整形体在设计上有比较依据，除了五项 IAEA建议的空气中射束品质因素和上 述的三个参数， 本发明实施例中也利用如下的用于评估中子射束剂量表现优劣的参数：
1、 照射时间 30min (加速器使用的质子电流为 10mA)
2、 30. ORBE-Gy可治疗深度 7cm 3、 肿瘤最大剂量 60. ORBE-Gy
4、 正常脑组织最大剂量 12. 5RBE-Gy
5、 皮肤最大剂量 11. 0RBE-Gy
注： RBE (Relative Biological Effectiveness ) 为相对生物效应， 由于光子、 中子会 造成的生物效应不同， 所以如上的剂量项均分别乘上不同组织的相对生物效应以求得等 效剂量。
为了改善中子射源的通量与品质， 本发明的实施例是针对用于中子捕获治疗的射束整形 体提出的改进， 作为一种优选地， 是针对用于加速器硼中子捕获治疗的射束整形体的改进。 如图 3所示，本发明第一实施例中的用于中子捕获治疗的射束整形体 10，其包括射束入口 11、 靶材 12、 邻接于靶材 12的缓速体 13、 包围在缓速体 13外的反射体 14、 与缓速体 13邻接的 热中子吸收体 15、 设置在射束整形体 10内的辐射屏蔽 16和射束出口 17， 靶材 12与自射束 入口 11入射的质子束发生核反应以产生中子，中子形成中子射束，中子射束限定一根主轴 X， 缓速体 13将自靶材 12产生的中子减速至超热中子能区，反射体 14将偏离主轴 X的中子导回 主轴 X以提高超热中子射束强度，缓速体 13和反射体 14之间设置间隙通道 18以提高超热中 子通量， 热中子吸收体 15用于吸收热中子以避免治疗时与浅层正常组织造成过多剂量， 辐射 屏蔽 16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。
加速器硼中子捕获治疗通过加速器将质子束加速， 作为一种优选实施例， 靶材 12由锂金 属制成， 质子束加速至足以克服靶材原子核库伦斥力的能量， 与靶材 12发生 7Li (p，n) 7Be核 反应以产生中子。射束整形体 10能将中子缓速至超热中子能区，并降低热中子及快中子含量， 缓速体 13由具有快中子作用截面大、超热中子作用截面小的材料制成，作为一种优选实施例， 缓速体 13由 D20、 A1F3、 Fluental™, CaF2、 Li2C03 、 MgF2和 A1203中的至少一种制成。 反射体 14由具有中子反射能力强的材料制成， 作为一种优选实施例， 反射体 14由 Pb或 Ni中的至 少一种制成。 热中子吸收体 15由与热中子作用截面大的材料制成， 作为一种优选实施例， 热 中子吸收体 15由 6Li制成， 热中子吸收体 15和射束出口 17之间设有空气通道 19。辐射屏蔽 16包括光子屏蔽 161和中子屏蔽 162， 作为一种优选实施例， 辐射屏蔽 16包括由铅（Pb)制 成的光子屏蔽 161和由聚乙烯 （PE) 制成的中子屏蔽 162。
其中， 缓速体 13设置成两个相反方向相互邻接的锥体状， 如图 3所示的方向， 缓速体 13 的左侧为向着左侧逐渐变小的锥体状， 缓速体 13 的右侧为向着右侧逐渐变小的锥体状， 两者相互邻接。 作为一种优选地， 缓速体 13的左侧设置为向着左侧逐渐变小的锥体状， 而右 侧也可以设置成其他形体状与该锥体状相互邻接， 如柱体状等。反射体 14紧密的包围在缓速 体 13周围， 在缓速体 13和反射体 14之间设置有间隙通道 18， 所谓的间隙通道 18指的是未 用实体材料覆盖的空的容易让中子束通过的区域，如该间隙通道 18可以设置为空气通道或者 真空通道。 紧邻缓速体 13设置的热中子吸收体 15由很薄的一层 6Li 材质制成， 辐射屏蔽 16 中的由 Pb制成的光子屏蔽 161可以与反射体 14设置为一体， 也可以设置成分体， 而辐射屏 蔽 16中由 PE制成的中子屏蔽 162可以设置在邻近射束出口 17的位置。 在热中子吸收体 15 和射束出口 17之间设置有空气通道 19， 于此区域可持续将偏离主轴 X的中子导回主轴 X以 提高超热中子射束强度。 假体 B设置在距离射束出口 17约 lcm处。 本领域技术人员熟知的， 光子屏蔽 161可以由其他材料制成， 只要起到屏蔽光子的作用就行， 中子屏蔽 162也可以由 其他材料制成， 也可以设置在其它地方， 只要能够满足屏蔽渗漏中子的条件就行。
为了比较设置有间隙通道的射束整形体与未设置间隙通道的射束整形体的差异， 如图 4 和图 5所示， 其分别示出了将间隙通道采用缓速体填充的第二实施例和将间隙通道采用反射 体填充的第三实施例。 首先参照图 4， 该射束整形体 20包括射束入口 21、 靶材 22、 邻接于 靶材 22的缓速体 23、包围在缓速体 23外的反射体 24、与缓速体 23邻接的热中子吸收体 25、 设置在射束整形体 20内的辐射屏蔽 26和射束出口 27， 靶材 22与自射束入口 21入射的质子 束发生核反应以产生中子， 中子形成中子射束， 中子射束限定一根主轴 XI， 缓速体 23将自 靶材 22产生的中子减速至超热中子能区， 反射体 24将偏离主轴 XI的中子导回主轴 XI以提 高超热中子射束强度， 缓速体 23设置成两个相反方向相互邻接的锥体状， 缓速体 23的左侧 为向着左侧逐渐变小的锥体状， 缓速体 23的右侧为向着右侧逐渐变小的锥体状， 两者相互邻 接， 热中子吸收体 25用于吸收热中子以避免治疗时与浅层正常组织造成过多剂量， 辐射屏蔽 26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。
作为一种优选地， 第二实施例中的靶材 22、 缓速体 23、 反射体 24、 热中子吸收体 25和 辐射屏蔽 26可以与第一实施例中的相同， 而其中的辐射屏蔽 26包括由铅 （Pb ) 制成的光子 屏蔽 261和由聚乙烯（PE)制成的中子屏蔽 262，该中子屏蔽 262可以设置在射束出口 27处。 在热中子吸收体 25和射束出口 27之间设置有空气通道 28。 假体 B1设置在距离射束出口 27 约 lcm处。
请参照图 5， 该射束整形体 30包括射束入口 31、 靶材 32、 邻接于靶材 32的缓速体 33、 包围在缓速体 33外的反射体 34、 与缓速体 33邻接的热中子吸收体 35、 设置在射束整形体 30内的辐射屏蔽 36和射束出口 37， 靶材 32与自射束入口 31入射的质子束发生核反应以产 生中子， 中子形成中子射束， 中子射束限定一根主轴 X2， 缓速体 33将自靶材 32产生的中子 减速至超热中子能区，反射体 34将偏离主轴 X2的中子导回主轴 X2以提高超热中子射束强度， 缓速体 33设置成两个相反方向相互邻接的锥体状， 缓速体 33的左侧为向着左侧逐渐变小的 锥体状， 缓速体 33 的右侧为向着右侧逐渐变小的锥体状， 两者相互邻接， 热中子吸收体 35 用于吸收热中子以避免治疗时与浅层正常组织造成过多剂量，辐射屏蔽 36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。
作为一种优选地， 第三实施例中的靶材 32、 缓速体 33、 反射体 34、 热中子吸收体 35和 辐射屏蔽 36可以与第一实施例中的相同， 而其中的辐射屏蔽 36包括由铅 （Pb ) 制成的光子 屏蔽 361和由聚乙烯（PE)制成的中子屏蔽 362，该中子屏蔽 362可以设置在射束出口 37处。 在热中子吸收体 35和射束出口 37之间设置有空气通道 38。 假体 B2设置在距离射束出口 37 约 1cm处。
下面采用 MCNP 软件 （是由美国洛斯阿拉莫斯国家实验室（LosAlamos 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） 对这三种实施例的模拟计算：
其中， 如下表一示出了空气中射束品质因素在这三种实施例中的表现 （表格中各名词的 单位同上所述， 在此不再赘述， 下同）：
表一： 空气中射束品质因素
Figure imgf000011_0001
其中， 如下表二示出了剂量表现在这三种实施例中的表现:
表二： 剂量表现
剂量表现 缓速体填充间隙通道 反射体填充间隙通道 间隙通道 有效治疗深度 10. 9 10. 9 11. 0 有效治疗深度剂量率 4. 47 4. 60 4. 78
有效治疗剂量比 5. 66 5. 69 5. 68 其中，如下表三示出了评估中子射束剂量表现优劣的参数在这三种实施例中的模拟数值： 表三： 评估中子射束剂量表现优劣的参数
Figure imgf000012_0001
注：从上述的三个表中可以得知：在缓速体和反射体之间设置有间隙通道的射束整形体， 其中子射束的治疗效益最好。
由于自锂靶材产生的中子具有前向平均能量较高的特性， 如图 6所示， 中子散射角度在 0 ° -30 ° 之间的平均中子能量约为 478keV，而中子散射角度在 30 ° -180 ° 之间的平均中子能 量约只有 290keV， 若能借由改变射束整形体的几何形状， 使前向中子与缓速体产生较多的碰 撞， 而侧向中子经较少碰撞便可到达射束出口， 则理论上应可达到中子缓速最佳化， 有效率 的提高超热中子通量。 下面从射束整形体的几何形状着手， 来评价不同射束整形体的几何形 状对于超热中子通量的影响。
如图 7所示， 其示出了第四实施例中的射束整形体的几何形状， 该射束整形体 40包括射 束入口 41、 靶材 42、 邻接于靶材 42的缓速体 43、 包围在缓速体 43外的反射体 44、 与缓速 体 43邻接的热中子吸收体 45、 设置在射束整形体 40内的辐射屏蔽 46和射束出口 47， 靶材 42与自射束入口 41入射的质子束发生核反应以产生中子， 缓速体 43将自靶材 42产生的中 子减速至超热中子能区， 反射体 44将偏离的中子导回以提高超热中子射束强度， 缓速体 43 设置成柱体状， 优选地， 设置成圆柱体状， 热中子吸收体 45用于吸收热中子以避免治疗时与 浅层正常组织造成过多剂量，辐射屏蔽 46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， 在热中子吸收体 45和射束出口 47之间设置有空气通道 48。
如图 8所示， 其示出了第五实施例中的射束整形体的几何形状， 该射束整形体 50包括射 束入口 51、 靶材 52、 邻接于靶材 52的缓速体 53、 包围在缓速体 53外的反射体 54、 与缓速 体 53邻接的热中子吸收体 55、 设置在射束整形体 50内的辐射屏蔽 56和射束出口 57， 靶材 52与自射束入口 51入射的质子束发生核反应以产生中子， 中子形成中子射束， 中子射束限 定一根主轴 X3， 缓速体 53将自靶材 52产生的中子减速至超热中子能区， 反射体 54将偏离 主轴 X3的中子导回主轴 X3以提高超热中子射束强度，缓速体 53设置成两个相反方向相互邻 接的锥体状， 缓速体 53的左侧为柱体状， 缓速体 53的右侧为向着右侧逐渐变小的锥体状， 两者相互邻接，热中子吸收体 25用于吸收热中子以避免治疗时与浅层正常组织造成过多剂量， 辐射屏蔽 26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。
作为一种优选地， 第五实施例中的靶材 52、 缓速体 53、 反射体 54、 热中子吸收体 55和 辐射屏蔽 56可以与第一实施例中的相同， 而其中的辐射屏蔽 56包括由铅 （Pb ) 制成的光子 屏蔽 561和由聚乙烯（PE )制成的中子屏蔽 562，该中子屏蔽 562可以设置在射束出口 57处。 在热中子吸收体 55和射束出口 57之间设置有空气通道 58。 假体 B3设置在距离射束出口 57 约 1cm处。
下面采用 MCNP软件对第二实施例中双锥体的缓速体、第四实施例中的柱体的缓速体及第 五实施例中的柱体 +锥体的模拟计算：
其中， 如下表四示出了空气中射束品质因素在这三种实施例中的表现：
表四： 空气中射束品质因素
Figure imgf000013_0001
其中， 如下表五示出了剂量表现在这三种实施例中的表现:
表五： 剂量表现
剂量表现 柱体 柱体 +锥体 双锥体
有效治疗深度 11. 8 10. 9 10. 9 有效治疗深度剂量率 2. 95 4. 28 4. 47 有效治疗剂量比 5. 52 5. 66 5. 66
其中，如下表六示出了评估中子射束剂量表现优劣的参数在这三种实施例中的模拟数值： 表六： 评估中子射束剂量表现优劣的参数
Figure imgf000014_0001
注： 从上述的三个表中可以得知： 将缓速体设置成至少一个锥体状， 其中子射束的治疗 效益较好。
本发明实施例中所述的 "柱体"或 "柱体状"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 "锥体"或 "锥体状"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。
在一个重要的改善射源通量方面， 有必要讨论缓速体的材料制成， 下文以第一实施例及 附图 3为例， 对缓速体 13做进一步详述。
缓速体 13呈现出两个锥体方向完全相反的双锥状结构， 缓速体 13的材料由含有 41 或 CaF2或 MgF2中的至少一种材料制成，缓速体 13具有第一直径 D1、第二直径 D2和第三直径 D3。 第一直径 D1处设置有开口以便容纳靶材 12， 第二直径 D2设置为双锥状结构的最大尺寸处。 对于 BNCT而言， 为了达到足够的缓速效果， 第一直径 D1长度为 lcm-20cm， 第二直径 D2长 度为 30cm-100cm，第三直径 D3长度为 lcm-50cm，作为一种优选地，第一直径 D1长度为 10cm， 第二直径 D2长度为 70cm， 第三直径 D3长度为 30cm。 为了得到如此大尺寸的缓速体 13， 且 其材料的密度为理论密度的 80%-100%， 提供如下三种缓速体材料的制备。
1· 长晶
首先以 MgF2为例， 请进一步参照发明专利申请公开号为 CN102925963A, 在此全文引入作 为长晶制备的参考。 作为长晶的方式， 通常将种晶和含有 MgF2的粉末放入坩埚内， 通过一定 的方式生长 MgF2单晶。
需要特别留意的是， 这里所谓的 "单晶"是指单次生长成型的单颗晶体， 而并不是单个 晶粒（即只有一种晶形且只含有一个晶粒， 该晶粒内分子、 院子都是有规则地排列）。 更好理 解的是这种单个晶粒与多个晶粒 （即每个晶粒的大小和形状不同， 而且取向也是凌乱的， 没 有明显的外形， 也不表现各向异性） 相对应。 下文关于 "单晶" 的定义与此处相同。
经过调研， PbF4、 A1F3、 CaF n Al203也可以通过类似的方式制备。
2. 粉末烧结
将 ^^ 或 1 或 CaF2的粉末或粉末压坯进一步结合起来，在烧结过程中粉末颗粒要发生 相互流动、 扩散、 溶解、 再结晶等物理化学过程， 使粉末进一步致密， 消除其中的部分或全 部孔隙。 烧结方式可以有很多种， 如固相烧结， 即烧结温度在粉末体中各组元的熔点以下； 液相烧结， 即粉末压坯中如果有两种以上的组元， 烧结有可能在某种组元的熔点以上进行， 因而烧结时粉末压坯中出现少量的液相； 热压烧结， 即在烧结时， 对粉末体施加压力， 以促 进其致密化过程， 热压是把粉末的成形和烧结结合起来， 直接得到制品的工艺过程； 放电等 离子烧结， 即通过将特殊电源控制装置发生的 ON-OFF直流脉冲电压加到粉体试料上， 除了 能利用通常放电加工所引起的烧结促进作用 （放电冲击压力和焦耳加热） 外， 还有效利用脉 冲放电初期粉体间产生的火花放电现象 （瞬间产生高温等离子体） 所引起的烧结促进作用通 过瞬时高温场实现致密化的快速烧结技术。 缓速体的材料经粉末烧结设备通过粉末烧结工艺 由粉末或粉末压坯变成块。
本领域技术人员熟知的，其他的烧结方式也可实现 1^ 或 41 或 CaF2中的至少一种或几 种混合物作为缓速体的材料的制备。 作为一种优选地， 下文以热压烧结和放电等离子烧结作 为粉末烧结的实施例。
再以 1^ 粉末或者 MgF2添加占 MgF2粉末重量百分比的 0. 1-5%的 6LiF的混合粉末为例， 来进行粉末烧结的介绍， 优选地， 下面以 MgF2添加占 MgF2粉末重量百分比的 0. 1-5%的 6LiF 的混合粉末为例来进行粉末烧结的介绍。
缓速体在射束整形体中扮演着极为重要的角色， 其担负着中子缓速的重责大任， 需要尽 可能地抑低快中子强度， 又不能将中子过度缓速为热中子， 另一方面， 也必须抑低减速过程 中所衍生出的 γ射线。 经研究表明， 在缓速体中均匀地添入少量的含有 6Li的材料， 可以有 效地抑低 γ射线的强度， 虽将使中子强度略减， 但仍保有原有射束的品质。 经进一步研究， 将 MgF2粉末掺杂占 MgF2粉末重量百分比的 0. 1-5%的 6LiF的粉末混合， 相比于单独的未添加 6LiF粉末的 MgF2粉末， 该混合粉末能够更加有效地吸收热中子并且有效地抑制 γ射线。 将 MgF2粉末掺杂占 MgF2粉末重量百分比的 0. 1-5%的含有 6Li的材料混合作为一种缓速体 材料， 本领域技术人员熟知的， 该含有 6Li的材料可以是任何易于与 MgF2粉末掺杂在一起的 任何物质形态， 如该含有 6Li的材料可以是液体、 也可以是粉末。 该含有 6Li的材料可以是任 何易于与 MgF2粉末掺杂在一起的任何化合物， 该含有 6Li的材料可以是 6LiF或 6Li2C03。 作为 一种优选地， 将 MgF2粉末与占 MgF2粉末重量百分比的 0. 1-5%的 6LiF的粉末或粉末压坯进一 步结合起来，在烧结过程中粉末颗粒要发生相互流动、扩散、溶解、再结晶等物理化学过程， 使粉末进一步致密， 消除其中的部分或全部孔隙。 烧结方式可以有很多种， 如固相烧结， 即 烧结温度在粉末体中各组元的熔点以下； 液相烧结， 即粉末压坯中如果有两种以上的组元， 烧结有可能在某种组元的熔点以上进行，因而烧结时粉末压坯中出现少量的液相；热压烧结， 即在烧结时， 对粉末体施加压力， 以促进其致密化过程， 热压是把粉末的成形和烧结结合起 来，直接得到制品的工艺过程；放电等离子烧结， 即通过将特殊电源控制装置发生的 ON-OFF 直流脉冲电压加到粉体试料上， 除了能利用通常放电加工所引起的烧结促进作用 （放电冲击 压力和焦耳加热） 外， 还有效利用脉冲放电初期粉体间产生的火花放电现象 （瞬间产生高温 等离子体） 所引起的烧结促进作用通过瞬时高温场实现致密化的快速烧结技术。 缓速体的材 料经粉末烧结设备通过粉末烧结工艺由粉末或粉末压坯变成块。
本领域技术人员熟知的， 其他的烧结方式也可实现 1^ 或 41 或 & 或 PbF4中的至少 一种或几种混合物再添加 6LiF的粉末作为缓速体的材料的制备。 作为一种优选地， 下文以热 压烧结和放电等离子烧结作为粉末烧结的实施例。
2. 1 放电等离子烧结
放电等离子烧结融等离子活化、 热压、 电阻加热为一体， 升温速度快、 烧结时间短、 烧 结温度低、 晶粒均匀、 有利于控制烧结体的细微结构、 获得材料的致密度高， 并且有着操作 简单、 再现性高、 安全可靠、 节省空间、 节省能源及成本低等优点。 放电等离子烧结由于强 脉冲电流加在粉末颗粒间， 在粉末颗粒间存在电场诱导的正负极， 在脉冲电流作用下颗粒间 发生放电， 激发等离子体， 由放电产生的高能粒子撞击颗粒间的接触部分， 使物质产生蒸发 作用而起到净化和活化作用， 电能贮存在颗粒团的介电层中， 介电层发生间歇式快速放电。 由于粉末或粉末压坯之间存在脉冲电流， 而脉冲电流是瞬间、 断续、 高频率发生， 在粉末颗 粒未接触部位产生的放电热， 以及粉末颗粒接触部位产生的焦耳热， 都大大促进了粉末颗粒 原子的扩散，其扩散系数比通常热压条件下的要大得多，从而达到粉末烧结的快速化。再者， 由于脉冲电流的加入， 使粉末内的放电部位及焦耳发热部位都会快速移动， 使粉末或粉末压 坯的烧结能够均匀化。 放电等离子烧结过程中， 颗粒之间放电时， 会瞬时产生高达几千度至 1 万度的局部高温， 在颗粒表面引起蒸发和熔化， 在颗粒接触点形成颈部， 由于热量立即从 发热中心传递到颗粒表面和向四周扩散， 颈部快速冷却而使蒸汽压低于其他部位。 气相物质 凝聚在颈部形成高于普通烧结方法的蒸发-凝固传递是放电等离子烧结过程的另一个重要特 点。 晶粒受脉冲电流加热和垂直单向压力的作用， 体扩散、 晶界扩散都得到加强， 加速了烧 结致密化过程， 因此用较低的温度和比较短的时间可得到高质量的烧结体。 放电等离子烧结 过程可以看作是颗粒放电、 导电加热和加压综合作用的结果。
请参照图 9， 其揭示了一种放电等离子烧结设备的示意图。 放电等离子烧结设备 100包 括第一电极 101、 第二电极 102、 置于第一电极 101和第二电极 102之间的导电模具 103、 给 模具 103提供脉冲电流的脉冲电流发生器 104、 带有用于加压的加压件 1051、 1052的加压装 置 105和用于控制脉冲电流发生器 104和加压装置 105的控制装置 106， 第一电极 101和第 二电极 102中的至少一个能够移动， 加压件 1051、 1052中的至少一个能够移动， 作为一种优 选地， 第一电极 101和加压件 1051固定， 第二电极 102和加压件 1052能够移动， 从而能够 加压置于模具 103内的粉末或粉末压坯 107。 作为一种优选地， 导电模具 103设置为铅或石 墨。放电等离子烧结设备 100进一步包括用于测量加压装置 105的位移的位移测量系统 108， 用于控制所述模具 103内气氛的气氛控制系统 109， 用于控制水冷真空室 110来冷却的水冷 系统 111， 用于测量放电等离子烧结设备 100内的温度的温度测量装置 112。模具 103和粉末 或粉末压坯 107通上脉冲电流， 除了提供放电冲击压力和焦耳热进行烧结之外， 进一步利用 脉冲放电初期粉体间产生的火花放电现象 （瞬间产生高温等离子体） 所引起的烧结促进作用 通过瞬时高温场实现快速烧结， 从而使得粉末或粉末压坯 107从粉末状态变成块状， 所谓的 块状为一体成型， 而不需要如长晶的方式， 由单晶通过打磨或抛光等工序拼接成适合缓速体 尺寸大小。
该放电等离子烧结设备 100利用直流脉冲电流直接通电烧结和加压， 经控制装置 106通 过调节脉冲直流电流的大小控制升温速率和烧结温度。 整个烧结过程可在真空环境下进行， 也可在保护气氛中进行， 如氧气或氢气。
在氧气气氛下， 由于氧被烧结物表面吸附或发生化学反应作用， 使晶体表面形成正离子 缺位型的非化学计量化合物， 正离子空位增加， 同时使闭口气孔中的氧可直接进入晶格， 并 和氧离子空位一样沿表面进行扩散， 扩散和烧结加速。 当烧结由正离子扩散控制时， 氧化气 氛或氧分压较高并有利于正离子空位形成， 促进烧结； 由负离子扩散控制时， 还原气氛或较 低的氧分压将导致氧离子空位产生并促进烧结。
在氢气气氛下烧结样品时， 由于氢原子半径很小， 易于扩散并有利于闭口气孔的消除， 氧化铝等类型的材料于氢气气氛下烧结可得到接近于理论密度的烧结体样品。
烧结温度是等离子快速烧结过程中一个关键的参数之一。 烧结温度的确定要考虑烧结体 样品在高温下的相转变、 晶粒的生长速率、 样品的质量要求以及样品的密度要求。 一般情况 下， 随着烧结温度的升高， 试样致密度整体呈上升趋势， 这说明烧结温度对样品致密度程度 有明显的影响， 烧结温度越高， 烧结过程中物质传输速度越快， 样品越容易密实。
但是， 温度越高， 晶粒的生长速率就越快， 其力学性能就越差。 而温度太低， 样品的致 密度就很低， 质量达不到要求。 温度与晶粒大小之间的矛盾在温度的选择上要求一个合适的 参数。
延长烧结温度下的保温时间，一般都会不同程度地促进烧结完成，完善样品的显微结构， 这对粘性流动机理的烧结较为明显， 而对体积扩散和表面扩散机理的烧结影响较小。 在烧结 过程中， 一般保温仅 1分钟时， 样品的密度就达到理论密度的 96.5%以上， 随着保温时间的 延长， 样品的致密度增大， 但是变化范围不是很大， 说明保温时间对样品的致密度虽然有一 定的影响， 但是作用效果不是很明显。 但不合理地延长烧结温度下的保温时间， 晶粒在此时 间内急剧长大， 加剧二次重结晶作用， 不利于样品的性能要求， 而时间太短会引起样品的致 密化下降， 因此需要选择合适的保温时间。
时间升温速率的加快， 使得样品在很短的时间内达到所要求的温度， 晶粒的生长时间会 大大减少， 这不仅有利于抑制晶粒的长大， 得到大小均匀的细晶粒陶瓷， 还能节约时间、 节 约能源以及提高烧结设备的利用率。 但是， 由于设备本身的限制， 升温速率过快对设备会造 成破坏性影响。 因此在可允许的范围内尽可能的的加快升温速率。 但是， 在实测的实验数据 中反映到。 与烧结温度和保温时间不同， 升温速率对样品致密度的影响显示出相反的结果， 即随着升温速率的增大， 样品致密度表现粗化逐渐下降的趋势， 有学者提出这是因为在烧结 温度附近升温速率的提高相当于缩短了保温时间， 因而样品致密度会有所下降。 在实际的高 温烧结过程中， 升温过程一般分为三个阶段， 分别为从室温至 600°C左右、 600°C至 900°C左 右、 900 至烧结温度： 第一阶段是准备阶段， 升温速率相对比较缓慢； 第二阶段是可控的快 速升温阶段， 升温速率一般控制在 100~500(°C/min); 第三阶段是升温的缓冲阶段， 该阶段温 度缓慢升至烧结温度，保温时间一般是 1~7分钟，保温后随炉冷却，冷却速率可达 300°C/min。
粉末经充分放电处理后立即进行压制成形与烧结。 烧结材料在电阻焦耳热和压力的共同 作用下发生严重的塑性变形， 施加成形压力有利于增强粉末颗粒间的接触、 增加烧结面积、 排出烧结粉末间的残余气体、 提高制件强度、 密度及其表面光洁度。 成形压力的大小一般根 据烧结粉末的压缩性和对烧结材料密度、 强度等性能的要求决定， 一般在 15〜30 MPa 范围 内， 有时可能高达 50 MPa， 甚至更高。 通常， 成形压力越大， 烧结材料的密度越高。 加压持 续时间对烧结材料密度也有很大的影响， 合适的加压时间视烧结材料的种类、 粉末粒度和所 烧结材料的几何尺寸而不同， 需要通过实验确定。 实验证明， 加压持续时间等于或稍大于放 电时间， 这是获取最高密度烧结材料的必要条件。 从烧结和固相反应机理容易理解， 压力越 大， 样品中颗粒堆积就越紧密， 相互的接触点和接触面积增大烧结被加速。 这样能使样品得 到更好的致密度， 并能有效的抑制晶粒长大和降低烧结温度。 因此选择的压力一般为 30~50Mpa。 不过有研究表明， 当烧结时外压力为 30Mpa和 50Mpa时， 样品的致密度相差并 不大， 这说明致密度随压力增大的现象仅在一定范围内较为明显。 放电等离子烧结相比于常规烧结技术有以下优点： 烧结速度快； 改进材料显微结构和提 高材料的性能。
本领域技术人员熟知的， 模具可以使用其他的导电材料制成， 放电等离子烧结设备也可 以设置成两个电极均固定不动， 而只有至少一个加压件能够移动。
放电等离子烧结的主要工艺流程共分四个阶段。 第一阶段： 向粉末样品施加初始压力， 使粉末颗粒之间充分接触， 以便随后能够在粉末样品内产生均匀且充分的放电等离子； 第二 阶段： 施加脉冲电流， 在脉冲电流的作用下， 粉末颗粒接触点产生放电等离子， 颗粒表面由 于活化产生微放热现象； 第三阶段： 关闭脉冲电源， 对样品进行电阻加热， 直至达到预定的烧 结温度并且样品收缩完全为止； 第四阶段： 卸压。合理控制初始压力、烧结时间、成形压力、 加压持续时间、 烧结温度、 升温速率等主要工艺参数可获得综合性能良好的材料。
由于粉末颗粒之间的拱桥效应， 它们一般不能充分接触， 因此， 为了使电火花烧结时在 样品内产生均匀并且充分放电的等离子， 最大程度地活化颗粒表面以加速烧结致密化过程， 需要向烧结粉末施加适当的初始压力， 使粉末颗粒充分接触。 初始压力的大小可随烧结粉末 品种、 烧结件大小和性能而不同。 初压过小， 放电现象只局限于部分粉末中， 导致粉末局部 熔化； 压力过大， 将会抑制放电， 进而延缓烧结扩散过程。 根据现有文献， 为使放电持续而 充分地进行， 此初始压力一般不宜超过 10MPa。
当用电火花烧结导电性能较好的粉末试样时， 由于电阻加热从样品的外部和内部同时进 行， 因此烧结时间极短，甚至是瞬间的，但烧结时间长短应视粉末质量、 品种和性能而不同， 一般为几秒钟到几分钟； 当烧结大型、 难熔金属粉末材料时， 甚至长达几十分钟。 烧结时间 对制件密度影响较大， 为使致密化过程得以充分进行， 需要确保一定的烧结时间。
一般认为， 放电等离子烧结过程中快速升温对粉末的烧结是很有利的， 因为它抑制了材 料的非致密化机制而激活了材料的致密化机制， 因此， 提高升温速率， 能使样品的致密化程 度得到提高。
作为一种优选地， 放电等离子烧结工艺包括如下步骤： 用适量的粉末或粉末压坯 107填 充模具 103; 移动加压装置 105对模具 103内的粉末或粉末压坯 107加压； 通过控制装置 106 打开脉冲电流发生器 104以将模具 103导电从而产生等离子体，粉末颗粒表面被活化和发热； 烧结成块。 放电等离子烧结工艺进一步包括如下步骤： 控制装置 106控制位移测量系统 108 以确保位移测量系统 108正常工作， 控制装置 106控制气氛控制系统 109以确保模具 103内 的气氛在正常工作的情形下，控制装置 106控制水冷系统 111以确保其在正常工作的情形下， 控制装置 106控制温度测量装置 112以确保放电等离子烧结设备 100内的温度在正常工作的 情形下。 所谓的正常工作指的是放电等离子烧结设备未发生人类感知的视觉、 触觉或听觉等 报警信号， 如报警指示灯亮起， 报警指示灯响起， 报警指示振动等等诸如此类。
2. 2热压烧结
热压烧结是将干燥粉料充填入模型内， 再从单轴方向边加压边加热， 使成型和烧结同时 完成的一种烧结方法。 热压烧结技术生产工艺十分丰富， 分类目前无统一规范和标准。 依据 现状可以分为真空热压、 气氛热压、 震动热压、 均衡热压、 热等静压、 反应热压和超高压烧 结。 热压烧结由于加热加压同时进行， 粉料处于热塑性状态， 有助于颗粒的接触扩散、 流动 传质过程的进行， 因而成型压力仅为冷压的 1/10 ; 还能降低烧结温度， 缩短烧结时间， 从而 抵制晶粒长大， 得到晶粒细小、 致密度高和机械、 电学性能良好的产品。
为了采用热压烧结工艺制备缓速体材料， 请参照图 10， 热压烧结设备 200主要包括加热炉 201、 置于加热炉 201内的加压装置 202、 模具 203、 装入模具 203内的粉末或粉末压坯 204和控 制装置 205。加热炉 201通常以电作为热源，加热元件由 SiC、 MoSi或镍络丝、 白金丝、钼丝等。 加压装置 202要求速度平缓、 保压恒定、 压力灵活调节， 一般有杠杆式和液压式。 根据材料性 质的要求，压力气氛可以是空气也可以是还原气氛或惰性气氛。模具 203要求高强度、耐高温、 抗氧化且不与热压材料黏结，模具 203热膨胀系数应与热压材料一致或近似，作为一种优选地， 本实施例中采用石墨模具。 控制装置 205使得热压烧结设备 200在正常工作的情形下。 所谓的 正常工作指的是放电等离子烧结设备未发生人类感知的视觉、 触觉或听觉等报警信号， 如报 警指示灯亮起， 报警指示灯响起， 报警指示振动等等诸如此类。
以 MgF2采用热压烧结工艺制备目标缓速体为例， 其生产工艺流程大致包括如下步骤， MgF2 原料制备 原料研磨、 筛分处理 转入模具 高温烧结 高温热压烧结 冷却出 炉 热等静压高温烧结 冷却出炉 磨削、 抛光加工、 粘接 成品。
作为一种优选地， 在此省略前序的粉末处理步骤和后序的烧结完成的处理步骤。 热压烧 结工艺包括如下步骤： 用适量的粉末或粉末压坯 204填充模具 203 ; 开启热压炉 201以预设压力 和温度参数； 移动加压装置 202对模具 203内的粉末或粉末压坯 204加压； 控制装置 205控制热 压烧结设备 200在正常工作的情形下； 通电以烧结成块。
需要进一步说明的是， 热压烧结工艺中的步骤 "移动加压装置 202对模具 203内的粉末或 粉末压坯 204加压"可以作为预加压， 也可以与通电同步进行， 即将步骤 "移动加压装置 202 对模具 203内的粉末或粉末压坯 204加压"和步骤 "通电以烧结成块"合二为一。
下表中列出了长晶、 放电等离子烧结和热压烧结的一些参数比较， 作为一种更便于本发 明中揭示的中子捕获治疗的射束整形体中的缓速体应用的材料， 尤其是需要制造第二直径 D2 最大达 100cm的尺寸的前提条件下， 这里建议使用粉末烧结制成的缓速体材料， 具体详述请见 下文。
表七： 长晶及粉末烧结工艺的比较
工艺 材料 尺寸 时间 成本 工艺难度
MgF2 单晶 10- 20cm (最大直径) 半年左右 500万元左右 较难 曰
曰曰 A1F3 单晶 10- 20cm (最大直径) 半年左右 500万元左右 较难
CaF2 单晶 10- 20cm (最大直径) 半年左右 500万元左右 较难 放电等离子 MgF2 按实际尺寸需要 1月左右 50万左右 较易 烧结 A1F3 按实际尺寸需要 1月左右 50万左右 较易
CaF2 按实际尺寸需要 1月左右 50万左右 较易
MgF2 按实际尺寸需要 2月左右 100万左右 较易 真空热压烧结 A1F3 按实际尺寸需要 2月左右 100万左右 较易
CaF2 按实际尺寸需要 2月左右 100万左右 较易
MgF2 按实际尺寸需要 2-2. 5月 50万左右 较易 热等静压烧结 AIF3 按实际尺寸需要 2-2. 5月 50万左右 较易
CaF2 按实际尺寸需要 2-2. 5月 50万左右 较易 注： 上表作为粉末主要材料而省略了各自添加的 0. 1-5%的 6LiF粉末， 上表中虽仅列出了 MgF2+LiF、 AlF3+LiF和 CaF2+LiF这三种缓速体材料采用如上工艺的参数比较， 但本领域技术人 员熟知的， 其他缓速体材料如 Al203+LiF也可以很容易的做出对比。
从上表可以得知， 虽然采用长晶的方式制备缓速体材料的密度能够达到接近理论密度， 如达到理论密度的 99. 99%， 但是由于单晶尺寸较小， 要想达到目标大尺寸的缓速体材料需要 通过很多个单晶进行拼接，过程中还可能需要对其进行镜面抛光等其他工序，不仅耗时很长， 而且成本和工艺难度都很大。
采用粉末烧结的方式制备缓速体材料的密度也能够达到理论密度的 80%-100%。 作为一种 优选地， 缓速体材料的密度达到理论密度的 99. 99%。 在理论密度与长晶方式获得的缓速体材 料的理论密度相比基本无差别的同时， 其在获得的尺寸、 时间、 成本和工艺难度方面均优势 明显。 采用放电等离子烧结制备得到的缓速体材料其实际尺寸按照需要获得， 一种方式可以 定制出适合需要的模具， 另一种方式采用普通模具， 如直径 70cm*厚度 2cm的模具， 然后通过 几片进行拼接就能完成， 在成本和工艺难度均与真空热压烧结及热等静压烧结不相上下的前 提下， 其制造时间上只需要 1个月左右的时间即可。
以上所述， 仅为本发明的具体实施方式， 本发明揭示的用于中子捕获治疗的射束整形体 并不局限于以上实施例所述的内容以及附图所表示的结构。 任何熟悉本技术领域的技术人员 在本发明的基础上对其中构件的材料、 形状及位置所做的显而易见地改变、 替代或者修改， 都在本发明要求保护的范围之内。 因此， 本发明的保护范围应以权利要求的保护范围为准。

Claims

权 利 要 求 书 、 一种用于中子捕获治疗的射束整形体，其特征在于：所述射束整形体包括射束入口、靶材、 邻接于所述靶材的缓速体、包围在所述缓速体外的反射体、与所述缓速体邻接的热中子吸 收体、设置在所述射束整形体内的辐射屏蔽和射束出口， 所述靶材与自所述射束入口入射 的质子束发生核反应以产生中子， 所述中子形成中子射束， 所述中子射束限定一根主轴， 所述缓速体将自所述靶材产生的中子减速至超热中子能区，所述缓速体的材料由含有 PbF4、 A1203、 A1F3、 & 或 MgF2中的一种或多种混合材料和占有所述含有 PbF4、 A1203、 A1F3、 CaF2 或 MgF2中的一种或多种混合材料的重量百分比为 0. 1-5%的含有 6Li元素的材料混合制成， 其中所述缓速体的材料经粉末烧结设备通过粉末烧结工艺由粉末或粉末压坯变成块，所述 反射体将偏离所述主轴的中子导回所述主轴以提高超热中子射束强度，所述热中子吸收体 用于吸收热中子以避免治疗时与浅层正常组织造成过多剂量，所述辐射屏蔽用于屏蔽渗漏 的中子和光子以减少非照射区的正常组织剂量。 、 一种用于中子捕获治疗的射束整形体，其特征在于：所述射束整形体包括射束入口、靶材、 邻接于所述靶材的缓速体、包围在所述缓速体外的反射体、与所述缓速体邻接的热中子吸 收体、设置在所述射束整形体内的辐射屏蔽和射束出口， 所述靶材与自所述射束入口入射 的质子束发生核反应以产生中子， 所述中子形成中子射束， 所述中子射束限定一根主轴， 所述缓速体将自所述靶材产生的中子减速至超热中子能区，所述缓速体的材料由含有 LiF、 Li2C03、 A1203、 A1F3、 （¾ 或^^ 中的至少一种材料制成， 其中所述缓速体的材料经粉末 烧结设备通过粉末烧结工艺由粉末或粉末压坯变成块，所述反射体将偏离所述主轴的中子 导回所述主轴以提高超热中子射束强度，所述热中子吸收体用于吸收热中子以避免治疗时 与浅层正常组织造成过多剂量，所述辐射屏蔽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。 、 根据权利要求 1或 2所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述射束整形 体进一步用于加速器硼中子捕获治疗， 加速器硼中子捕获治疗通过加速器将质子束加速， 所述靶材由金属制成， 所述质子束加速至足以克服靶材原子核库伦斥力的能量， 与所述靶 材发生核反应以产生中子， 所述射束整形体能将中子缓速至超热中子能区， 并降低热中子 及快中子含量， 所述超热中子能区在 0. 5eV到 40keV之间， 所述热中子能区小于 0. 5eV， 所述快中子能区大于 40keV， 所述反射体由具有中子反射能力强的材料制成， 所述热中子 吸收体由与热中子作用截面大的材料制成。 、 根据权利要求 3所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述反射体由 Pb 或 Ni 中的至少一种制成， 所述热中子吸收体由 6Li制成， 所述热中子吸收体和所述射束 出口之间设有空气通道，所述辐射屏蔽包括由 Pb制成的光子屏蔽和由 PE制成的中子屏蔽。 、 根据权利要求 1或 2所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述缓速体设 置成两个相反方向相互邻接的锥体状。 、 根据权利要求 5所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述锥体状包括第 一直径、 第二直径和第三直径， 所述第一直径长度为 lcm-20cm， 所述第二直径长度为 30cm-100cm, 所述第三直径长度为 lcm-50cm， 所述缓速体的材料的密度为理论密度的 80%- 100%。 、 根据权利要求 1或 2所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述缓速体和 所述反射体之间设置间隙通道以提高超热中子通量。 、 根据权利要求 1或 2所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述粉末烧结 设备为热压烧结设备或放电等离子烧结设备，所述粉末烧结工艺为热压烧结工艺或放电等 离子烧结工艺。 、 根据权利要求 8所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述热压烧结设备 包括加热炉、 置于所述加热炉内的加压装置、 模具、 装入所述模具内的粉末或粉末压坯和 用于控制所述热压烧结设备正常工作的控制装置， 所述热压烧结工艺包括如下步骤： 用适 量的粉末或粉末压坯填充所述模具； 开启所述热压炉以预设压力和温度参数； 移动所述加 压装置对所述模具内的粉末或粉末压坯加压；所述控制装置控制所述热压烧结设备在正常 工作的情形下； 通电以烧结成块。0、 根据权利要求 8所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述放电等离 子烧结设备包括第一电极、第二电极、置于所述第一电极和所述第二电极之间的导电模具、 给所述模具提供脉冲电流的脉冲电流发生器、带有用于加压的加压件的加压装置和用于控 制所述脉冲电流发送器和所述加压装置的控制装置，所述第一电极和第二电极中的至少一 个能够移动，所述第一电极和第二电极中的至少一个与所述加压装置相连从而能够加压置 于所述模具内的粉末； 所述放电等离子烧结工艺包括如下步骤： 将适量的粉末填充所述模 具； 移动所述第二电极对所述模具内的粉末加压； 通过控制装置打开脉冲电流发生器以将 导电模具导电从而产生等离子体， 粉末颗粒表面被活化和发热； 烧结成块。
1、 根据权利要求 10所述的用于中子捕获治疗的射束整形体， 其特征在于： 所述放电等 离子烧结设备进一步包括用于测量加压装置的位移的位移测量系统，用于控制所述模具内 气氛的气氛控制系统， 用于冷却的水冷系统， 用于测量所述放电等离子烧结设备内的温度 的温度测量装置， 所述放电等离子烧结工艺进一步包括如下步骤： 所述控制装置控制所述 位移测量系统以确保所述位移测量系统正常工作，所述控制装置控制所述气氛控制系统以 确保所述模具内气氛在正常工作的情形下，所述控制装置控制所述水冷系统以确保所述水 冷系统正常工作，所述控制装置控制所述温度测量装置以确保所述放电等离子烧结设备内 的温度在正常工作的情形下。
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US20200188695A1 (en) 2020-06-18
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