CN109925606B

CN109925606B - Neutron capture therapy system

Info

Publication number: CN109925606B
Application number: CN201711347618.5A
Authority: CN
Inventors: 刘渊豪; 卢威骅
Original assignee: Neuboron Medtech Ltd
Current assignee: Neuboron Medtech Ltd
Priority date: 2017-12-15
Filing date: 2017-12-15
Publication date: 2024-03-22
Anticipated expiration: 2037-12-15
Also published as: CN109925606A

Abstract

The utility model provides a neutron capture treatment system, it includes the beam shaping body, set up in the internal vacuum tube of beam shaping, the beam shaping body includes the beam entry, hold the holding chamber of vacuum tube, the retarder in holding chamber tip in the adjacency, surround the external reflector of retarder, set up the radiation shielding and the beam exit in the beam shaping body, the vacuum tube tip is equipped with the target, the target takes place nuclear reaction with the charged particle beam incident from the beam entry in order to produce the neutron, neutron beam forms neutron beam, neutron beam jets out and prescribes a limit to a neutron beam axis from the beam exit, the retarder will be from the neutron that the target produced to epithermal neutron energy region, the reflector will deviate the neutron guide back to the retarder, the radiation shielding is used for shielding the neutron and the photon of seepage, the retarder includes two cylinder-like retarders that the outside diameter is different at least, the retarder has the first tip that is close to the beam entry and the second tip that is close to the beam exit, the target is held between first tip and second tip.

Description

Neutron capture therapy system

Technical Field

The invention relates to a radioactive ray irradiation system, in particular to a neutron capture treatment system.

Background

With the development of atomic science, radiation therapy such as cobalt sixty, linac, electron beam, etc. has become one of the main means for cancer therapy. However, the traditional photon or electron treatment is limited by the physical condition of the radioactive rays, and a large amount of normal tissues on the beam path can be damaged while killing tumor cells; in addition, due to the different sensitivity of tumor cells to radiation, traditional radiotherapy often has poor therapeutic effects on malignant tumors with relatively high radiation resistance (such as glioblastoma multiforme (glioblastoma multiforme) and melanoma (melanoma)).

In order to reduce radiation damage to normal tissue surrounding a tumor, the concept of target treatment in chemotherapy (chemotherapy) has been applied to radiotherapy; for tumor cells with high radiation resistance, radiation sources with high relative biological effects (relative biological effectiveness, RBE) such as proton therapy, heavy particle therapy, neutron capture therapy, etc. are also actively developed. The neutron capture treatment combines the two concepts, such as boron neutron capture treatment, and provides better cancer treatment selection than the traditional radioactive rays by means of the specific aggregation of boron-containing medicaments in tumor cells and the accurate neutron beam regulation.

The success of boron neutron capture therapy is also known as binary radiation cancer therapy (binary cancer therapy) because it depends on the concentration of boron-containing drugs and the number of thermal neutrons at the tumor cell site; it is understood that improvement of neutron source flux and quality plays an important role in the study of boron neutron capture therapy in addition to the development of boron-containing drugs.

In addition, various radiations such as neutrons and photons with low energy to high energy are generated in the radiation treatment process, and the radiations may cause different degrees of damage to normal tissues of the human body. Therefore, in the field of radiotherapy, it is an extremely important task to reduce radiation pollution to the external environment, medical staff or normal tissues of a patient while achieving effective treatment.

Therefore, a new solution is needed to solve the above-mentioned problems.

Disclosure of Invention

To solve the above problems, one embodiment of the present application provides a neutron capture therapy system, including a beam shaping body, a vacuum tube disposed in the beam shaping body, the beam shaping body including a beam inlet, a receiving cavity for receiving the vacuum tube, a retarder adjacent to an end of the receiving cavity, a reflector surrounding the retarder, a radiation shield disposed in the beam shaping body, and a beam outlet, the end of the vacuum tube being provided with a target material, the target material being configured to react with a charged particle beam incident from the beam inlet to produce neutrons, the neutrons forming a neutron beam, the neutron beam being emitted from the beam outlet and defining a neutron beam axis, the retarder retarding body retarding neutrons produced from the target material to an epithermal neutron energy region, the reflector directing the deviated neutrons back to the retarder body to increase the epithermal neutron beam intensity, the radiation shield being configured to shield the leaking neutrons and photons to reduce normal tissue dose in the non-irradiated region, the retarder body including at least two cylindrical retarder bodies having different outer diameters, the retarder body having a first end portion adjacent to the beam inlet and a second end adjacent to the beam outlet, the target material being received between the first end and the second end.

Compared with the prior art, the technical scheme recorded in the embodiment has the following beneficial effects: the retarder comprises two cylindrical retarders with different outer diameters, and the target is accommodated in the retarder, so that the material cost can be reduced, the intensity of fast neutrons can be greatly reduced, and the quality of neutron beams can be improved.

Further, the retarder comprises a first retarder close to the beam inlet and a second retarder closely attached to the first retarder and close to the beam outlet, the first retarder at least comprises two cylindrical retarders with different outer diameters, the beam inlet, the retarder and the beam outlet extend along the neutron beam axis, and the distance from the target to the beam outlet is smaller than that from the first end to the beam outlet.

Preferably, the first retarder comprises three cylindrical retarders with different outer diameters, the first retarder comprises a first retarder close to the beam inlet, a second retarder closely attached to the first retarder and a third retarder closely attached to the second retarder, the first retarder, the second retarder and the third retarder are sequentially arranged along the axis direction of the neutron beam, the outer diameters of the first retarder, the second retarder, the third retarder and the second retarder are respectively a first outer diameter, a second outer diameter, a third outer diameter and a fourth outer diameter, the first outer diameter is smaller than the second outer diameter, the second outer diameter is smaller than the third outer diameter, and the third outer diameter is equal to the fourth outer diameter.

Further, the first retarding part is provided with a first front end face close to the beam inlet, a first rear end face close to the beam outlet and a first outer circumferential face; the second retarding part is provided with a second front end surface closely attached to the first rear end surface, a second rear end surface close to the beam outlet and a second outer circumferential surface; the third retarding part is provided with a third front end surface closely attached to the second rear end surface, a third rear end surface close to the beam outlet and a third outer circumferential surface; the second retarder is provided with a fourth front end face closely attached to the third rear end face, a fourth rear end face close to the beam outlet and a fourth outer circumferential face, the first, second, third and fourth front end faces, the first, second, third and fourth rear end faces are parallel to each other and are perpendicular to the neutron beam axis, a tangent plane passing through the neutron beam axis is perpendicular to the second front end face, and a tangent line passing through the neutron beam axis is perpendicular to the third front end face.

Further, in a tangential plane passing through the axis of the neutron beam, the first front end surface intersects with the first outer circumferential surface to obtain a first intersection point, the second front end surface intersects with the second outer circumferential surface to obtain a second intersection point, the third front end surface intersects with the third outer circumferential surface to obtain a third intersection point, and the first, second and third intersection points are located on the same straight line.

Preferably, a reflection compensation body is filled between the accommodating cavity and the vacuum tube, and the reflection compensation body is lead or Al or teflon or C.

Preferably, the first end protrudes from the target in a direction along the neutron beam axis towards the beam inlet and the second end protrudes from the target in a direction along the neutron beam axis towards the beam outlet.

Further, the reflector is protruding the retarder in the both sides of neutron beam axis, holds the chamber and holds the chamber including the reflector that forms by the reflector and hold the chamber and extend the retarder that forms by the retarder enclosure from the reflector, and the vacuum tube is including holding the extension section and holding the embedding section in the retarder holding the intracavity from the extension section extension in the reflector holding the intracavity, and the tip of embedding section is located to the target.

Further, the neutron capture therapy system further comprises at least one cooling device, at least one containing pipeline for containing the cooling device is arranged in the beam shaping body, and lead alloy or aluminum alloy is filled between the cooling device and the inner wall of the containing pipeline.

Further, the neutron capture therapy system further comprises a shielding body arranged at the beam inlet and closely attached to the beam shaping body.

The "cone" or "cone" in this embodiment of the present application refers to a structure in which the overall trend of the outer contour gradually decreases from one side to the other side along the direction of illustration, and the entire surface of the outer contour may be smoothly transitioned or may be non-smoothly transitioned, such as a conical surface with a plurality of protrusions and grooves.

Drawings

FIG. 1 is a schematic diagram of a neutron capture therapy system in accordance with a first embodiment of the present application, wherein the second and third cooling sections of the cooling device are parallel to the neutron beam axis;

FIG. 2 is a schematic diagram of a neutron capture treatment system with an unfilled reflection compensator and reflection compensator in accordance with a first embodiment of the present application;

FIG. 3 is a cross-sectional view of the neutron capture therapy system of FIG. 1 taken perpendicular to the axis of the neutron beam and through the second moderator in accordance with one embodiment of the present application;

FIG. 4 is a schematic diagram of a neutron capture therapy system in a second embodiment of the application, wherein the moderators are configured as biconic moderators;

FIG. 5 is an enlarged partial schematic view of a cooling device of a neutron capture therapy system according to the first and second embodiments of the present application;

FIG. 6 is a schematic diagram of a neutron capture therapy system in a third embodiment of the application, wherein the second and third cooling sections of the cooling device are perpendicular to the neutron beam axis;

FIG. 7 is a schematic view of a target structure in a neutron capture therapy system in an embodiment of the application;

FIG. 8 is a schematic diagram of a neutron capture therapy system with a cooling device removed and the target not extending into the retarder in a fourth embodiment of the present application;

FIG. 9 is a schematic diagram of a neutron capture therapy system with a cooling device removed and a first retarder being a stepless retarder in a fifth embodiment of the present application;

FIG. 10 is a schematic diagram of a neutron capture therapy system with a cooling device removed and the first retarder being a 2-stage retarder in a sixth embodiment of the present application;

FIG. 11 is a schematic diagram of a neutron capture therapy system with a cooling device removed and the first retarder being a 4-stage retarder in embodiment seven of the present application;

FIG. 12 is a schematic diagram of a neutron capture therapy system with a cooling device removed and the first retarder being a 10-order retarder in embodiment eight of the application;

Detailed Description

Neutron capture therapy has been an effective treatment for cancer in recent yearsApplications are increasing, where neutrons for which boron neutron capture therapy is supplied may be supplied by nuclear reactors or accelerators, most commonly with boron neutron capture therapy. Taking accelerator boron neutron capture therapy as an example, the basic components of accelerator boron neutron capture therapy generally include an accelerator for accelerating charged particles (e.g., protons, deuterons, etc.), a neutron production and heat removal system, and a beam shaping body. The accelerating charged particles and the metal neutron generating part act to generate neutrons, and proper nuclear reactions are selected according to the required neutron yield and energy, available accelerating charged particle energy and current, physicochemical properties of the metal neutron generating part and the like. The nuclear reactions in question are ⁷ Li(p,n) ⁷ Be and Be ⁹ Be(p,n) ⁹ And B, the two reactions are endothermic reactions, and the energy threshold values of the two nuclear reactions are 1.881MeV and 2.055MeV respectively. Because the ideal neutron source for boron neutron capture treatment is epithermal neutrons with a keV energy level, theoretically, if protons with energy only slightly higher than a threshold are used to bombard a metallic lithium neutron generating part, relatively low-energy neutrons can Be generated, and the neutron capturing treatment can Be used clinically without too much retarding treatment, however, the proton action cross section of the two neutron generating parts of lithium metal (Li) and beryllium metal (Be) and the threshold energy is not high, and in order to generate enough neutron flux, protons with higher energy are generally selected to initiate nuclear reaction.

The ideal target should have high neutron yield, a neutron energy distribution close to that of the epithermal neutron energy region (described in detail below), no too much intense penetrating radiation, safety, low cost, easy operation, and high temperature resistance, but practically no nuclear reaction meeting all the requirements can be found. In the embodiment of the application, a target made of lithium metal is adopted. However, it is well known to those skilled in the art that the material of the target may be made of other metallic materials than those mentioned above.

The requirements for the heat removal system will vary depending on the chosen nuclear reaction, e.g ⁷ Li(p,n) ⁷ Be has lower requirements for heat removal systems due to the lower melting point and thermal conductivity of the metal target (lithium metal) ⁹ Be(p,n) ⁹ B is high. In the examples of the present application use is made of ⁷ Li(p,n) ⁷ Nuclear reaction of Be. Therefore, the temperature of the target irradiated by the high-energy-level accelerated charged particle beam is inevitably greatly increased, and the service life of the target is affected.

Regardless of whether the neutron source of the boron neutron capture treatment is from the nuclear reaction of charged particles of a nuclear reactor or an accelerator with a target, a mixed radiation field is generated, i.e. the beam contains neutrons and photons with low energy to high energy. For boron neutron capture treatment of deep tumors, the more radiation content, except for epithermal neutrons, the greater the proportion of non-selective dose deposition of normal tissue, and therefore the less radiation that will cause unnecessary doses. In addition to the air beam quality factor, in order to better understand the dose distribution of neutrons in the human body, the embodiments of the present application use a human head tissue prosthesis for dose calculation, and use the prosthesis beam quality factor as a design reference for neutron beams, as will be described in detail below.

The international atomic energy organization (IAEA) gives five air beam quality factor suggestions for neutron sources for clinical boron neutron capture treatment, and the five suggestions can be used for comparing the advantages and disadvantages of different neutron sources and serve as reference bases for selecting neutron production paths and designing beam shaping bodies. These five suggestions are as follows:

Epithermal neutron beam flux Epithermal neutron flux>1x 10 ⁹ n/cm ² s

Fast neutron contamination Fast neutron contamination<2x 10 ^-13 Gy-cm ² /n

Photon pollution Photon contamination<2x 10 ^-13 Gy-cm ² /n

The ratio thermal to epithermal neutron flux ratio of thermal neutron to epithermal neutron flux is less than 0.05

Neutron flux ratio epithermal neutron current to flux ratio >0.7

Note that: the epithermal neutron energy region is between 0.5eV and 40keV, the thermal neutron energy region is less than 0.5eV, and the fast neutron energy region is more than 40keV.

1. Epithermal neutron beam flux:

the neutron beam flux and the boron-containing drug concentration in the tumor together determine the clinical treatment time. If the concentration of the boron-containing medicament in the tumor is high enough, the requirement on the neutron beam flux can be reduced; conversely, if the boron-containing drug concentration in the tumor is low, a high flux epithermal neutron is required to administer a sufficient dose to the tumor. IAEA requires a epithermal neutron beam flux of greater than 10 epithermal neutrons per square centimeter per second ⁹ The neutron beam at this flux can generally control the treatment time to within one hour for current boron-containing drugs, and short treatment times can more effectively utilize the limited residence time of boron-containing drugs within tumors in addition to advantages for patient positioning and comfort.

2. Fast neutron contamination:

since fast neutrons cause unnecessary normal tissue doses, which are positively correlated with neutron energy, as a matter of pollution, the fast neutron content should be minimized in the neutron beam design. Fast neutron contamination is defined as the fast neutron dose accompanied by a unit epithermal neutron flux, with IAEA recommended for fast neutron contamination as less than 2x 10 ^-13 Gy-cm ² /n。

3. Photon pollution (gamma ray pollution):

gamma rays belonging to the intense penetrating radiation can cause non-selective dose deposition of all tissues on the beam path, so reducing the gamma ray content is also an essential requirement for neutron beam design, gamma ray pollution is defined as the gamma ray dose accompanied by the unit epithermal neutron flux, and the proposal of IAEA on gamma ray pollution is less than 2x 10 ^-13 Gy-cm ² /n。

4. Ratio of thermal neutron to epithermal neutron flux:

because of high thermal neutron attenuation speed and poor penetrating capacity, most of energy is deposited on skin tissues after entering a human body, and thermal neutrons are required to be used as neutron sources for boron neutron capture treatment for superficial tumors such as melanoma and the like, so that the thermal neutron content is required to be reduced for deep tumors such as brain tumors and the like. The IAEA to thermal neutron to epithermal neutron flux ratio is recommended to be less than 0.05.

5. Neutron current to flux ratio:

The ratio of neutron current to flux represents the directionality of the beam, the larger the ratio is, the better the frontage of the neutron beam is, the high frontage neutron beam can reduce the surrounding normal tissue dose caused by neutron divergence, and the treatable depth and the posture setting elasticity are improved. IAEA is recommended to have a neutron current to flux ratio greater than 0.7.

In order to reduce the manufacturing cost of the beam shaping body of the neutron capture therapy system and obtain better neutron beam quality, referring to fig. 1, a neutron capture therapy system 1 is provided in a first embodiment of the present application, and the neutron capture therapy system 1 includes a beam shaping body 10, a cooling device 20 disposed in the beam shaping body 10, a vacuum tube 30, and a shielding body 40 disposed outside the beam shaping body 10 and closely attached to the beam shaping body 10.

As shown in fig. 1 and 2, the beam shaper 10 comprises a beam inlet 11, a receiving chamber 12 for receiving a vacuum tube 30, a receiving duct 13 for receiving a cooling device 20, a retarder 14 adjacent to an end of the receiving chamber 12, a reflector 15 surrounding the retarder 14, a thermal neutron absorber 16 adjacent to the retarder 14, a radiation shield 17 arranged within the beam shaper 10, and a beam outlet 18. The end of the evacuated tube 30 is provided with a target 31, the target 31 undergoing nuclear reaction with a charged particle beam incident from the beam inlet 11 and passing through the evacuated tube 30 to produce neutrons, the neutrons forming a neutron beam, the neutron beam exiting from the beam outlet 18 and defining a neutron beam axis X1 coincident with the central axis of the evacuated tube 30. The retarder 14 retards neutrons generated from the target 31 to the epithermal neutron energy region, and the reflector 15 directs neutrons offset from the neutron beam axis X1 back to the retarder 14 to increase epithermal neutron beam intensity. The reflector 15 projects beyond the retarder 14 on both sides of the neutron beam axis X1. The thermal neutron absorber 16 is used to absorb thermal neutrons to avoid overdosing with shallow normal tissue during treatment. The radiation shield 17 serves to shield the leaking neutrons and photons to reduce the normal tissue dose in the non-irradiated region.

Accelerator neutron capture therapy system the charged particle beam is accelerated by an accelerator, as a preferred embodiment, the target 31 is made of lithium metal, in particular, of ⁷ Li content is 98%, ⁶ Li content of2% of lithium metal, the charged particle beam is accelerated to an energy sufficient to overcome the coulomb repulsion of the nuclei of the target, and is generated with the target 31 ⁷ Li(p,n) ⁷ Be nuclear reactions to produce neutrons, the beam shaping body 10 can retard neutrons to the epithermal neutron energy region and reduce thermal and fast neutron content. The retarder 14 is made of a material having a large fast neutron action cross section and a small epithermal neutron action cross section, the reflector 15 is made of a material having a strong neutron reflection capability, and the thermal neutron absorber 16 is made of a material having a large thermal neutron action cross section. As a preferred embodiment, the retarder 14 is made of MgF ₂ Sum to MgF ₂ Is made of 4.6% by weight of LiF, the reflector 15 is made of Pb, and the thermal neutron absorber 16 is made of Pb ⁶ Li. The radiation shield 17 includes a photon shield 171 and a neutron shield 172, and as a preferred embodiment, the radiation shield 17 includes a photon shield 171 made of lead (Pb) and a neutron shield 172 made of Polyethylene (PE). As shown in fig. 7, the target 31 includes a lithium target layer 311 and an oxidation-resistant layer 312 located at one side of the lithium target layer 311 for preventing oxidation of the lithium target layer 311. The antioxidation layer 312 of the target 31 is made of Al or stainless steel.

As shown in fig. 1-2, the retarder 14 comprises a first retarder 140 close to the beam inlet 11 and a second retarder 144 closely fitting the first retarder 140 and close to the beam outlet 18, the retarder 14 having a first end 146 close to the beam inlet 11, a second end 148 close to the beam outlet 18 and a third end 147 between the first end 146 and the second end 148, the third end 147 being located between the first retarder 140 and the second retarder 144. The beam inlet 11, the moderator 14 and the beam outlet 18 all extend along a neutron beam axis X1, and the distance from the target 31 to the beam outlet 18 is smaller than the distance from the first end 146 to the beam outlet 18, in other words, the first end 146 protrudes from the target 31 along the neutron beam axis X towards the beam inlet 11, and the second end 148 protrudes from the target 31 along the neutron beam axis X1 towards the beam outlet 18. The first speed bump 140 is composed of at least 2 hollow cylindrical speed bumps having different outer diameters and the same inner diameter. Referring to fig. 1-2, 6 and 8, in the first, third and fourth embodiments, the first retarder 140 is composed of 3 hollow cylindrical retarders with different outer diameters and the same inner diameter, and the first retarder 140 and the second retarder 144 are formed by stacking and splicing a plurality of retarders molded from a mold with a corresponding size after being processed by polishing, grinding and other processes. Specifically, the first retarder 140 includes a first retarder 141 near the beam inlet 11, a second retarder 142 located on the right side of the first retarder 141 and closely attached to the first retarder 141, and a third retarder 143 located on the right side of the second retarder 142 and closely attached to the second retarder 142, that is, the first, second, and third retarders 141, 142, 143 are sequentially aligned along the direction of the neutron beam axis X1. The outer diameters of the first, second and third retarding parts 141, 142, 143 and the second retarding body 144 are respectively a first, second, third and fourth outer diameter, the first outer diameter is smaller than the second outer diameter, the second outer diameter is smaller than the third outer diameter, the third outer diameter is equal to the fourth outer diameter, and the inner diameters of the first, second and third retarding parts 141, 142, 143 are equal. The central axes of the first, second and third retarders 141, 142, 143 coincide with the central axis of the second retarder 144, and the central axis also coincides with the neutron beam axis X1. The first retarding portion 141 has a first front end surface 1411 on the left side, a first rear end surface 1412 on the right side, a first outer circumferential surface 1413, and a first inner circumferential surface 1414; the second retarding portion 142 has a second front end surface 1421 on the left side, a second rear end surface 1422 on the right side, a second outer circumferential surface 1423, and a second inner circumferential surface 1424; the third retarding portion 143 has a third front end face 1431 on the left side, a third rear end face 1432 on the right side, a third outer circumferential face 1433, and a third inner circumferential face 1434; the second speed bump 144 has a fourth front end surface 1441 on the left side, a fourth rear end surface 1442 on the right side, and a fourth outer circumferential surface 1443. The first, second, third, and fourth front end surfaces 1411, 1421, 1431, 1441 and the first, second, third, and fourth rear end surfaces 1412, 1422, 1432, 1442 are parallel to each other and perpendicular to the neutron beam axis X1, the first rear end surface 1412 of the first retarder 141 is tightly bonded to the second front end surface 1421 of the second retarder 142, the second rear end surface 1422 of the second retarder 142 is tightly bonded to the third front end surface 1431 of the third retarder 143, and the third rear end surface 1432 of the third retarder 143 is tightly bonded to the fourth front end surface 1441 of the second retarder 144. The intersection line passing through the neutron beam axis X1 and the first outer circumferential surface 1413 is perpendicular to the second front end surface 1421, the intersection line passing through the neutron beam axis X1 and the second outer circumferential surface 1423 is perpendicular to the third front end surface 1431, and a smooth transition is formed between the third outer circumferential surface 1433 of the third retarder and the fourth outer circumferential surface 1443 of the second retarder 144. As shown in fig. 2, in a tangential plane passing through the neutron beam axis X1, the first front end surface 1411 of the first retarder 141 intersects the first outer circumferential surface 1413 to obtain a first intersection point 1410, the second front end surface 1421 of the second retarder 142 intersects the second outer circumferential surface 1423 to obtain a second intersection point 1420, the third front end surface 1431 of the third retarder 143 intersects the third outer circumferential surface 1433 to obtain a third intersection point 1430, the first, second and third intersection points 1410, 1420, 1430 are located on the same straight line X2, and an included angle between the straight line X2 and the neutron beam axis X1 is smaller than 90 degrees. The reflector 15 has an inner surface 150 surrounding the retarder 14, which inner surface 150 is in close contact with the first front end surface 1411, the first outer circumferential surface 1413, the second front end surface 1421, the second outer circumferential surface 1423, the third front end surface 1431, the third outer circumferential surface 1433, the fourth rear end surface 1442 and the fourth outer circumferential surface 1443 of the retarder 14.

As shown in fig. 1 to 2, 6 and 8, in the first, third and fourth embodiments, the first retarder 140 is composed of 3 concentric hollow cylindrical retarders having different outer diameters and the same inner diameter, and outer contours of the first, second and third retarders 141, 142 and 143 are combined to be stepped as viewed from a direction perpendicular to the neutron beam axis X1, whereby the first retarder 140 is named as a 3-stage retarder. As shown in fig. 10-12, in the sixth to eighth embodiments, the first retarder 140 is composed of 2, 4, 10 hollow cylindrical retarders with different outer diameters and the same inner diameter, i.e. the first retarder 140 may be a 2-step, 4-step, 10-step retarder, and in other embodiments, the first retarder 140 may be composed of other hollow cylindrical retarders with different outer diameters and the same inner diameter, for example, 12, 15, etc. In other embodiments, the second retarder 144 may be configured as a stepped retarder; the polygonal prism can be used for replacing a cylinder to form a retarder; in addition, the first, second, and third intersection points 1410, 1420, 1430 may not be on the same straight line, and may be located on an arc; in addition, according to actual needs, the retarder forming the first retarder 140 may be provided as a partially non-hollow structure; the central axis of each of the retarders of the first retarder 140 and the central axis of the second retarder 14 may not coincide with each other.

In general, the retarder is formed by stacking and splicing a plurality of retarder pieces formed from a mold with corresponding dimensions after being processed by polishing, grinding and the like, the retarder formed from the grinding tool is disc-shaped, and when the retarder is designed into a whole cylinder shape or cone shape, the volume of consumed retarder material is the product of the size of the retarder in the direction of the neutron beam axis X1 and the bottom area of the disc, and it is required to explain that the cone-shaped retarder is formed by grinding a cylindrical retarder, that is, the volume of materials required by designing the retarder into the cylinder shape or cone shape is the same. In this application, the first retarder 140 is designed into a stepped retarder, and under the premise that the size of the retarder in the direction of the neutron beam axis X1 and the maximum diameter of the retarder are unchanged, the bottom area of the disk-shaped retarder forming each step of retarder is gradually increased, so that the retarder material required for designing the retarder into the stepped retarder is smaller than the material required for designing the retarder into a whole cylindrical or cone-shaped retarder. Therefore, the stepped retarder can greatly reduce the material for manufacturing the retarder, so that the manufacturing cost is reduced.

Referring to fig. 2, the accommodating chamber 12 is a cylindrical chamber surrounded by the reflector 15 and the first retarder 140 of the retarder 14. The accommodating cavity 12 comprises a reflector accommodating cavity 121 surrounded by the reflector 15 and a retarder accommodating cavity 122 extending from the reflector accommodating cavity 121 and surrounded by the first retarder 140 of the retarder 14, i.e. the retarder accommodating cavity 122 is surrounded by the first, second and third inner circumferential surfaces 1414, 1424, 1434 of the first, second and third retarders 141, 142, 143. The vacuum tube 30 comprises an extension 32 surrounded by the reflector 15 and an embedded section 34 extending from the extension 32 into the retarder 14, the extension 32 being accommodated in the reflector accommodating chamber 121 and the embedded section 34 being accommodated in the retarder accommodating chamber 122. The target 31 is arranged at the end of the embedded section 34 of the vacuum tube 30, which end is flush with the third rear end face 1432 of the first speed bump 140. In the first to third embodiments and the fifth to eighth embodiments, the vacuum tube 30 is partially embedded in the retarder 14, i.e. the target 31 is disposed in the retarder 14. The depth of the target 31 extending into the retarder 14 is marked as X, the value of X being equal to the size of the retarder receiving chamber 122 in the direction of the neutron beam axis X1, i.e. the size of the first retarder 140 in the direction of the neutron beam axis X1.

In other embodiments, the depth X of the target 31 extending into the buffer body 14 may be smaller or larger than the dimension of the first buffer body 140 in the direction of the neutron beam axis X1, i.e. the target 31 may be arranged to extend in the direction of the neutron beam axis X1 not beyond the first buffer body 140 or to extend beyond the first buffer body 140 into the second buffer body 144, and correspondingly, when the target 31 is arranged to extend in the direction of the neutron beam axis X1 not beyond the first buffer body 140, the first buffer body 140 is arranged to be in a partially non-hollow configuration, and when the target 31 is arranged to extend in the direction of the neutron beam axis X1 beyond the first buffer body 140 into the second buffer body 144, the first buffer body 140 is in a hollow configuration, and the second buffer body 144 is in a partially hollow configuration.

As shown in fig. 1, 2 and 3, a gap exists between the accommodating chamber 12 and the vacuum tube 30, and a reflection compensating body 50 is filled in the gap, and the reflection compensating body 50 is Pb or Al or Teflon (Teflon) or C capable of absorbing or reflecting neutrons. The reflection compensating body 50 can reflect neutrons reflected or scattered into the gap into the retarder 14 or the reflector 15, thereby increasing the intensity of epithermal neutrons and reducing the time required for the irradiated body to be irradiated. On the other hand, the leakage of neutrons to the outside of the beam shaping body 10 is avoided, the adverse effect is caused on the instrument of the neutron capture treatment system, and the radiation safety is improved.

As shown in fig. 1 and 2, the accommodating duct 13 includes second and third accommodating ducts 132 and 133 extending in the direction of the neutron beam axis X1 and located on both sides of the accommodating chamber 12 at 180 ° intervals, and a first accommodating duct 131 located in a plane perpendicular to the neutron beam axis X1 and located between the target 31 and the retarder 14. The second and third accommodation ducts 132, 133 extend beyond the accommodation chamber 12 in the direction of the neutron beam axis X1 and communicate with the first accommodation duct 131, respectively. That is, the first accommodating duct 131 is located at the end of the accommodating chamber 12 and between the target 31 and the retarder 14, and the second accommodating duct 132 and the third accommodating duct 133 are located at both sides of the accommodating chamber 12 and are respectively communicated with the first accommodating duct 131, so that the entire accommodating duct 30 is arranged in a '' type structure. As shown in connection with fig. 2, the second and third receiving ducts 132, 133 comprise second and third reflector receiving ducts 1321, 1331 located outside the reflector receiving cavity 121, respectively, and second and third retarder receiving ducts 1322, 1332 extending from the second and third reflector receiving ducts 1321, 1331, respectively, located outside the retarder receiving cavity 122. In the present embodiment, the second and third accommodating ducts 132, 133 extend along the direction of the neutron beam axis X1 and are parallel to the neutron beam axis X1, i.e., the angle between the second and third accommodating ducts 132, 133 and the neutron beam axis X1 is 0 °.

In the first and second embodiments, the second and third accommodation ducts 132, 133 are not in communication with the accommodation chamber 12, i.e. the second and third accommodation ducts 132, 133 are separated from the accommodation chamber 12 by the reflector 15 and the retarder 14. In other embodiments, the second and third receiving ducts 132, 133 may communicate with the receiving chamber 12, i.e., the outer surface portions of the vacuum tube 30 received in the receiving chamber 12 are exposed inside the second and third receiving ducts 132, 133, and in summary, the second and third receiving ducts 132, 133 are located outside the inner wall of the receiving chamber 12. In the present embodiment, the second and third receiving pipes 132 and 133 are provided as circular arc-shaped pipes extending in the axial direction of the vacuum pipe 30, and in other embodiments, square, triangular or other polygonal pipes may be used instead. In the present embodiment, the second and third accommodation ducts 132, 133 are two accommodation ducts that are spaced apart from each other in the circumferential direction of the accommodation chamber 12, and in other embodiments, the second and third accommodation ducts 132, 133 communicate in the circumferential direction of the accommodation chamber 12, that is, are replaced by one accommodation duct that surrounds the accommodation chamber 12.

As shown in fig. 5, the cooling device 20 includes a first cooling portion 21 arranged in a vertical direction and located in front of the target 31 for cooling the target 31, a second cooling portion 22 and a third cooling portion 23 extending in a direction of the neutron beam axis X1 and located on both sides of the vacuum tube 30 and parallel to the neutron beam axis X1, the first cooling portion 21 being connected between the second and third cooling portions 22, 23. The first cooling portion 21 is accommodated in a first accommodation duct 131 arranged in a direction perpendicular to the neutron beam axis X1, and the second and third cooling portions 22, 23 are accommodated in second and third accommodation ducts 132, 133 arranged in a direction of the neutron beam axis X1, respectively. The second cooling unit 22 inputs the cooling medium to the first cooling unit 21, and the third cooling unit 23 outputs the cooling medium in the first cooling unit 21. The first cooling part 21 is located between the target 31 and the retarder 14, one side of the first cooling part 21 is in direct contact with the target 31 and the other side is in contact with the retarder 14. The second cooling part 22 and the third cooling part 23 comprise a first and a second cooling section 221, 231 located outside the reflector housing cavity 121 and a third and a fourth cooling section 222, 232 extending from the first and the second cooling section 221, 231 and located outside the retarder housing cavity 122, respectively. The third and fourth cooling sections 222 and 232 communicate with the first cooling portion 21, respectively. That is, the first cooling part 21 is located at the end of the insertion section 121 of the vacuum tube 30 at one side of the target 31 and is in direct contact with the target 31, and the second and third cooling parts 22 and 23 are respectively located at the upper and lower sides of the vacuum tube 30 accommodated in the accommodating chamber 12 and are respectively communicated with the first cooling part 21, so that the entire cooling device 20 is provided in a '' type structure. In this embodiment, the first cooling portion 21 is in planar contact with the target 31, the second cooling portion 22 and the third cooling portion 23 are both tubular structures made of copper, and the second cooling portion 22 and the third cooling portion 23 extend in the direction of the neutron beam axis X1 and are parallel to the neutron beam axis X1, that is, an angle between the second cooling portion 22 and the third cooling portion 23 and the neutron beam axis X1 is 0 °.

The first cooling portion 21 includes a first contact portion 211, a second contact portion 212, and a cooling groove 213 between the first contact portion 211 and the second contact portion 212 through which a cooling medium passes. The first contact portion 211 is in direct contact with the target 31, and the second contact portion 212 may be in direct contact with the retarder 14 or may be in indirect contact with the retarder through air. The cooling tank 213 has an input tank 214 communicating with the second cooling portion 22 and an output tank 215 communicating with the third cooling portion 23. The first contact portion 211 is made of a heat conductive material. The upper edge of the input groove 214 is located above the upper edge of the second cooling part 22, and the lower edge of the output groove 215 is located below the lower edge of the third cooling part 23. The advantage of this arrangement is that the cooling device 20 can more smoothly input cooling water into the cooling tank 213 and cool the target 31 in time, and the heated cooling water can be smoothly output from the cooling tank 213, and at the same time, the water pressure of the cooling water in the cooling tank 213 can be reduced to a certain extent.

The first contact portion 211 is made of a heat conductive material (such as a material having good heat conductive properties such as Cu, fe, al, etc.) or a material capable of both heat conduction and foaming inhibition, and the second contact portion 212 is made of a material capable of foaming inhibition, either of Fe, ta, or V. The target 31 is heated by the accelerated irradiation temperature rise of the high energy level, and the first contact portion 211 extracts heat and brings the heat out by the cooling medium flowing through the cooling tank 213, thereby cooling the target 31. In the present embodiment, the cooling medium is water.

Referring to fig. 2, the shield 40 covers and closely contacts the left end surface of the beam shaping body 10, and prevents neutron beams and gamma rays formed at the target 31 from overflowing the left end surface of the beam shaping body 10. The shield 40 is composed of Pb and PE, and specifically, the shield 40 is composed of at least two layers Pb and at least one layer PE. In the present embodiment, the shield 40 includes a first Pb layer 41 closely attached to the left end surface of the beam shaping body 10, a PE layer 42 closely attached to the first Pb layer 41, and a second Pb layer 43 covering the PE layer 42 and closely attached to the PE layer 42. Pb is capable of absorbing gamma rays escaping from the beam shaper 10 and reflecting neutrons escaping from the beam shaper 10 back to the retarder 14 to increase the epithermal neutron beam intensity.

Referring to fig. 1-2, 6, 8 and 10-12, in the first, third, fourth and sixth-eighth embodiments, the retarder 14 is partially composed of a multi-stage retarder, in the fifth embodiment, as shown in fig. 9, the retarder 14 is composed of a whole cylindrical retarder, and in other embodiments, the retarder 14 may be composed of one cone-shaped retarder and one cylindrical retarder, or may be composed of two cone-shaped retarders in the second embodiment as shown in fig. 4. In the second embodiment, the speed bump 14 'consists of two opposite conical bodies, in this application the speed bump 14' in the second embodiment is called a double conical speed bump. Referring to fig. 4, the retarder 14 'has a first end 141', a second end 142 'and a third end 143' located between the first end 141 'and the second end 142'. The first, second and third ends 141', 142', 143 'are circular in cross-section and the diameters of the first and second ends 141', 14'2 are smaller than the diameter of the third end 143'. A first taper 146 'is formed between first end 141' and third end 143', and a second taper 148' is formed between third end 143 'and second end 142'. The target 31 is accommodated in the first cone 142'.

In the second embodiment, the angles between the second and third accommodation pipes 132, 133 and the second and third cooling portions 22, 23 and the neutron beam axis X1 are 0 °. In other embodiments, the angles between the second and third accommodating ducts 132, 133 and the second and third cooling portions 22, 23 and the neutron beam axis X1 may be any other angle greater than 0 ° and less than or equal to 180 °, for example, as shown in fig. 6, the angles between the second and third accommodating ducts 132', 133' and the second and third cooling portions 22', 23' and the neutron beam axis X1 are 90 °.

As shown in fig. 6, it discloses a neutron capture treatment system 1 "in a third embodiment of the present application, wherein the second cooling portion 22 'and the third cooling portion 23' of the cooling device 20 'are perpendicular to the neutron beam axis X1, i.e. the cooling device 20' is arranged in an" I "type structure to cool the target 31 in the embedded vacuum tube 30. The first cooling portion 21 'of the "I" type cooling device 20' is identical to the first cooling portion 21 of the type cooling device 20 in arrangement, except that the second cooling portion 22 'and the third cooling portion 23' of the "I" type cooling device 20 'are located in the same plane perpendicular to the neutron beam axis X1' as the first cooling portion 21', and the second cooling portion 22' and the third cooling portion 23 'penetrate out of the retarder 14' respectively along the direction perpendicular to the neutron beam axis X1, i.e. the included angle between the second cooling portion 22 'and the third cooling portion 23' and the neutron beam axis X1 is 90 °, so that the entire cooling device is rectangular in arrangement, i.e. the "I" type structure. With continued reference to fig. 6, the accommodating duct 30 'is also configured in an "I" shape, and the first accommodating duct 131' of the "I" shape accommodating duct 30 'is configured identically to the first accommodating duct 131 of the type cooling duct 30, except that the second accommodating duct 132' and the third accommodating duct 133 'of the "I" shape accommodating duct 30' are located in the same plane perpendicular to the neutron beam axis X1 as the first accommodating duct 131', and the second accommodating duct 132' and the third accommodating duct 133 'are respectively penetrated out of the retarder 14' in a direction perpendicular to the neutron beam axis X1, i.e., an included angle between the second and third accommodating ducts 132', 133' and the neutron beam axis X1 is 90 °, such that the entire accommodating duct is configured in a rectangular shape, i.e., the "I" shape structure described above. It is easily understood that in the structure shown in fig. 4 and 9, the cooling device 20 and the accommodating duct 30 may be provided in an "I" type structure.

Fig. 8 is a schematic view of the neutron capture therapy system 1, 1 'of fig. 1 or fig. 6 with the cooling device 20, 20' removed and the target 31 not extending into the retarder 14. In contrast to the neutron capture therapy system 1, 1″ of fig. 1 or fig. 6, the neutron capture therapy system 1 disclosed in fig. 8 is only configured with the target 31 outside the retarder 14, i.e. the receiving chamber 12 receiving the vacuum tube 30 does not extend into the retarder 14 but is surrounded by the reflector 15. The structures of the retarder 14, the reflector 15, the shielding 40, the cooling device 20, 20', the thermal neutron absorber 16, the radiation shielding 17, etc. are the same as those disclosed in fig. 1 or fig. 6, and the description of the related structures is referred to above, and is not repeated here.

Fig. 9 is a schematic diagram of a neutron capture treatment system 1 with cooling devices 20 and 20' removed and the first retarder being a stepless retarder, and the neutron capture treatment system 1 disclosed in fig. 9 is compared with the neutron capture treatment systems 1 and 1″ disclosed in fig. 1 or fig. 6, only the first retarder 140 is replaced by a 3-step retarder, i.e. the first retarder 140 is composed of a hollow cylindrical second retarder with an outer diameter equal to that of the cylindrical retarder 144. The structures of the reflector 15, the shielding body 40, the cooling devices 20, 20', the thermal neutron absorber 16, the radiation shield 17, etc. are the same as those disclosed in fig. 1 or fig. 6, and the description of the related structures is referred to above, and will not be repeated here.

Fig. 10 is a schematic diagram of a neutron capture treatment system 1 with cooling devices 20 and 20 'removed and the first retarder being a stepless retarder according to the present application, and in comparison with the neutron capture treatment system 1 and 1″ disclosed in fig. 1 or 6, the neutron capture treatment system 1 disclosed in fig. 10 is only to replace the first retarder 140 with a 2-step retarder from a 3-step retarder, and the structures of the reflector 15, the shielding body 40, the cooling devices 20 and 20', the thermal neutron absorber 16, the radiation shield 17, etc. are the same as those disclosed in fig. 1 or 6, and the description of the related structures is referred to above, and is not repeated herein.

Fig. 11 is a schematic diagram of a neutron capture treatment system 1 with cooling devices 20 and 20 'removed and the first retarder being a stepless retarder, and in comparison with the neutron capture treatment system 1 and 1″ disclosed in fig. 1 or fig. 6, the neutron capture treatment system 1 disclosed in fig. 11 is only to replace the first retarder 140 with a 4-step retarder from a 3-step retarder, and the structures of the reflector 15, the shielding body 40, the cooling devices 20 and 20', the thermal neutron absorber 16, the radiation shielding 17, etc. are the same as those disclosed in fig. 1 or fig. 6, and the description of the related structures is referred to above, and is not repeated herein.

Fig. 12 is a schematic diagram of a neutron capture treatment system 1 with cooling devices 20 and 20 'removed and the first retarder being a stepless retarder, and in comparison with the neutron capture treatment system 1 and 1″ disclosed in fig. 1 or 6, the neutron capture treatment system 1 disclosed in fig. 12 is only to replace the first retarder 140 with a 10-step retarder from a 3-step retarder, and the structures of the reflector 15, the shielding body 40, the cooling devices 20 and 20', the thermal neutron absorber 16, the radiation shield 17, etc. are the same as those disclosed in fig. 1 or 6, and the description of the related structures is referred to above, and is not repeated herein.

Referring to fig. 1, 2, 4 and 6, the second and third cooling units 22 and 23;22', 23' and the second and third containment ducts 132, 133, respectively; 132', 133' are filled with a reflective compensator 80;80', a reflective compensator 80;80' are substances such as lead alloy or aluminum alloy capable of absorbing or reflecting neutrons. A reflection compensator 80;80' are capable of reflecting neutrons reflected or scattered into the gap into the retarder 14 or reflector 15, thereby increasing the yield of epithermal neutrons and thus reducing the time that the irradiated body needs to be irradiated. On the other hand, the leakage of neutrons to the outside of the beam shaping body 10 is avoided, the adverse effect is caused on the instrument of the neutron capture treatment system, and the radiation safety is improved. In the embodiment of the application, the content of lead in the lead alloy is more than or equal to 85%, and the content of aluminum in the aluminum alloy is more than or equal to 85%.

The epithermal neutron flux, the fast neutron flux, the epithermal neutron forward direction reference value and the gamma ray intensity in the related structures of the application are counted and analyzed through simulation experiments, in all the simulation experiments of the application, the charged particle source energy is 2.5MeV and 10mA, the epithermal neutron flux and fast neutron flux counting surface is positioned at the beam outlet 18 of the beam integer 10, the diameter of the beam outlet 18 is 14CM, and the counting surface of the gamma ray intensity is the left end surface of the beam integer 10.

Referring to fig. 1 and 2, the target 31 in the first embodiment is accommodated in the speed body 14, and referring to fig. 8, the target 31 in the fourth embodiment is disposed outside the speed body 14, and in order to compare the influence of the disposition position of the target 31 in the first embodiment and the fourth embodiment on the epithermal neutron flux, the fast neutron flux and the neutron forward direction, the data in the first embodiment are obtained through a simulation experiment for comparison and analysis. In the present application, the thickness of the retarder 14 refers to the size of the retarder 14 in the direction of the neutron beam axis X1.

Table one: the target is contained in the retarder and is arranged outside the retarder, and the epithermal neutron flux, the fast neutron flux and the epithermal neutron forward reference value are obtained

As can be seen from the first table, compared with the case where the target 31 is contained in the retarder 14 and the target 31 is disposed outside the retarder 14, the forward direction of neutrons is not significantly changed, the intensity of fast neutrons is reduced by 12.52%, and the intensity of epithermal neutron beams is reduced by only 1.83%, so that the manner of containing the target 31 in the retarder 14 is better than the manner of disposing the target 31 outside the retarder 14. The epithermal neutron forward direction is better as the epithermal neutron forward direction reference value is closer to 1.

Referring to fig. 1 and 2, in the first embodiment, the first retarder 140 is a 3-order retarder, and referring to fig. 9 to 12, in the fifth embodiment to the eighth embodiment, the first retarder 140 is respectively set to be an order-free retarder, an order-2 retarder, an order-3 retarder, an order-4 retarder, and an order-10 retarder, and in order to compare the influence of the first retarders 140 with different orders on epithermal neutron flux, fast neutron flux, and neutron forward direction, the first retarder 140 is respectively set to be an order-free retarder, an order-2 retarder, an order-3 retarder, an order-4 retarder, and an order-10 retarder on the premise that an included angle θ and a depth X of the target 31 extending into the retarder 14 are kept unchanged, and data of the second table are obtained through simulation experiments for comparison and analysis.

And (II) table: the first retarder is respectively a epithermal neutron flux, a fast neutron flux and an epithermal neutron forward reference value without steps, 1 order, 2 order, 3 order, 4 order and 10 order retarder

As can be seen from the table two data, the first retarder 140 has no step (cylindrical retarder) or a multi-step retarder has little influence on epithermal neutrons, fast neutron intensity and neutron front property, but less retarder material is required for manufacturing the multi-step retarder compared with the non-step retarder, and the material cost and the manufacturing process cost are comprehensively considered, preferably, the first retarder 140 is set as a 3-step retarder or a 4-step retarder.

Referring to fig. 1-4, 8 and 10-12, a gap exists between the receiving chamber 12 and the vacuum tube 30, and a reflection compensating body 50 is filled in the gap. In order to compare the effect of filling the gap with the reflection compensator 50 or not filling the gap with the reflection compensator 50 on epithermal neutrons, fast neutron intensity and epithermal neutron forward direction, table three is listed for detailed comparison and analysis.

Table three: epithermal neutron flux, fast neutron flux and epithermal neutron forward reference value with and without filled reflection compensator

As can be seen from table 3, the gap between the receiving chamber 12 and the vacuum tube 30 fills the reflection compensating body 50 by 7.33% to 7.46% compared to the case where the reflection compensating body 50 is not filled. Neutron front has no significant change.

In this application, only data obtained by performing a simulation experiment on the retarder 140 set as a multi-step retarder are listed, but it is obtained by research that the intensity of epithermal neutrons can be increased to different degrees by setting the retarder 14 as an entire cylindrical retarder shown in fig. 9 or as a biconical retarder shown in fig. 4 or a retarder composed of a conical retarder and a cylindrical retarder or a retarder composed of a multi-step retarder and a conical retarder, and the gap between the accommodating cavity 12 and the vacuum tube 30 is filled with the reflection compensation body 50 without obvious influence on the forward direction of neutrons.

Referring to fig. 1-2 and 8-12, a shield 40 is provided at the left end of the beam shaping body 10 of the present application, i.e., at the charged particle beam entrance end, to prevent the neutron beam and gamma rays formed at the target 31 from escaping from the left end face of the beam shaping body 10. The first retarder 140 is a non-step, 2-step, 3-step, 4-step, and 10-step retarder, and the shield 40 and/or the reflection compensator 50 are/is set or the shield 40 and/or the reflection compensator 50 are/is not set, respectively, to analyze the neutron and gamma ray intensities of the shield 40 and the reflection compensator 50 on the left end of the beam shaper 10 and the data of the epithermal neutron, fast neutron intensity, and epithermal neutron forward direction reference value at the beam outlet 18 of the beam shaper 10 The effect of epithermal neutrons, fast neutrons, and epithermal neutron fronts at the beam exit 18. Wherein the units of neutrons, gamma rays, epithermal neutrons and fast neutrons are as follows: n/cm ² /sec。

Table four: neutron and gamma ray intensities at the left end of the beam shaping body, epithermal neutron and fast neutron intensities at the beam outlet of the beam shaping body and epithermal neutron forward reference values

As can be seen from table four, the addition of the shielding body 40 can significantly reduce the intensity of gamma rays and neutron beams behind the beam shaping body 10, the shielding body 40 has no significant effect on the epithermal neutron and fast neutron intensity at the beam outlet 18, and the addition of the reflection compensation body 50 can significantly improve the epithermal neutron intensity at the beam outlet 18.

The data obtained by performing a simulation experiment on the retarder 140 is only listed in the application, but it is obtained by research that when the retarder 14 is set to be a biconical retarder shown in fig. 4 or a retarder composed of a cone-shaped retarder and a cylindrical retarder or a retarder composed of a multilevel retarder and a cone-shaped retarder, the gap between the accommodating cavity 12 and the vacuum tube 30 is filled with the reflection compensation body 50, and the shielding body 40 is set at the left end of the beam shaping body 10, the intensity of epithermal neutrons can be increased to different degrees, the intensity of gamma rays and neutron beams behind the beam shaping body 10 can be reduced, and no obvious influence is exerted on the forward direction of neutrons.

On the premise of keeping the angle theta unchanged through experimental simulation data analysis, the depth X of the target 31 extending into the retarder 14 is changed, namely the dimension of the first retarder 140 along the direction of the neutron beam axis X1 is changed, and the influence on epithermal neutron flux, fast neutron flux and neutron forward direction is changed.

Table five: the target material stretches into the retarder to have the depths X of 5 CM, 10 CM, 15 CM and 20CM respectively, and the epithermal neutron flux, the fast neutron flux and the neutron forward reference value

As can be seen from table five, as the depth of the target 3 extending into the retarder 14 increases, the epithermal neutron beam intensity slightly decreases (about 2%), the fast neutron intensity decreases by about 6%, the epithermal neutron forward direction has no obvious change, and the epithermal neutron to fast neutron flux ratio is improved.

In this application, only data obtained by performing a simulation experiment on the retarder 140 set to be a non-step or multi-step retarder are listed, but it is obtained by research that when the retarder 14 is set to be a biconical retarder as shown in fig. 4, or a retarder composed of a conical retarder and a cylindrical retarder, or a retarder composed of a multi-step retarder and a conical retarder, as the depth of the target 3 extending into the retarder 14 increases, the epithermal neutron beam intensity slightly decreases, the fast neutron intensity decreases, the epithermal neutron front has no obvious change, and the epithermal neutron to fast neutron flux ratio is improved.

In order to compare the effect of the reflective compensator 80, which is a lead alloy or an aluminum alloy, respectively, and the absence of the reflective compensator 80 (i.e. filled with air) in the gap between the cooling device 20, 20 'and the receiving pipe 13, 13', on the yield of epithermal neutrons, the amount of fast neutron contamination and the irradiation time, a detailed comparison is made from table six to table eight.

Wherein Table six shows the yields (n/cm) of epithermal neutrons when air, aluminum alloy, lead alloy are filled respectively at different bore diameters of the accommodation chambers ² mA)：

Table six: yield of epithermal neutrons (n/cm) ² mA)

Table seven shows the fast neutron pollution (Gy-cm 2/n) when air, aluminum alloy, lead alloy are filled separately under the aperture of different accommodation chambers:

table seven: fast neutron contamination (Gy-cm) ² /n)

Table eight shows the irradiation time (minutes) required for the irradiated body when the air, the aluminum alloy, and the lead alloy are filled respectively at the apertures of the different accommodating chambers:

table eight (Min) time required for irradiation of the object to be irradiated

From tables six to eight, it can be seen that when the aperture of the accommodation cavity is the same, the productivity of epithermal neutrons is higher and the amount of fast neutron contamination and the required irradiation time are less when filling the lead alloy or aluminum alloy than when filling air.

The neutron capture therapy systems disclosed herein are not limited to the structures described in the above embodiments and shown in the drawings. For example, the retarder may be provided as a conical or polygonal prism, the cooling means may be provided in several numbers, the receiving conduit in correspondence with several numbers, etc. Obvious changes, substitutions, or modifications to the materials, shapes, and locations of the components therein are within the scope of the present application.

Claims

1. A neutron capture therapy system, characterized by: the neutron capture treatment system comprises a beam shaping body, a vacuum tube arranged in the beam shaping body, wherein the beam shaping body comprises a beam inlet, a containing cavity for containing the vacuum tube, a retarder adjacent to the end part of the containing cavity, a reflector surrounding the retarder, a radiation shield and a beam outlet, wherein the radiation shield and the beam outlet are arranged in the beam shaping body, the end part of the vacuum tube is provided with a target material, the target material reacts with a charged particle beam entering from the beam inlet to generate neutrons, the neutrons form a neutron beam, the neutron beam is emitted from the beam outlet and defines a neutron beam axis, the retarder decelerates neutrons generated from the target material to an epithermal neutron energy region, the reflector guides deviated neutrons back to the retarder to improve the epithermal neutron beam intensity, the radiation shield is used for shielding leaked neutrons and photons to reduce normal tissue dose of a non-irradiation region, and the retarder comprises at least two cylindrical bodies with different outer diameters, and the retarder comprises a first end part close to the beam inlet and a second end part close to the beam outlet, and the retarder is accommodated between the first end part and the second end part; the retarder comprises a first retarder close to the beam inlet and a second retarder closely attached to the first retarder and close to the beam outlet, the first retarder at least comprises two cylindrical retarders with different outer diameters, the beam inlet, the retarder and the beam outlet all extend along the neutron beam axis, and the distance from the target to the beam outlet is smaller than the distance from the first end to the beam outlet; the accommodating cavity is a cylindrical cavity formed by enclosing the reflector and part of the retarder.

2. The neutron capture therapy system of claim 1, wherein: the first retarder comprises three cylindrical retarders with different outer diameters, the first retarder comprises a first retarder close to the beam inlet, a second retarder closely attached to the first retarder and a third retarder closely attached to the second retarder, the first retarder, the second retarder and the third retarder are sequentially arranged along the axis direction of the neutron beam, the outer diameters of the first retarder, the second retarder, the third retarder and the second retarder are respectively the first outer diameter, the second outer diameter, the third outer diameter and the fourth outer diameter, the first outer diameter is smaller than the second outer diameter, the second outer diameter is smaller than the third outer diameter, and the third outer diameter is equal to the fourth outer diameter.

3. The neutron capture therapy system of claim 2, wherein: the first retarding part is provided with a first front end face close to the beam inlet, a first rear end face close to the beam outlet and a first outer circumferential surface; the second retarding part is provided with a second front end surface closely attached to the first rear end surface, a second rear end surface close to the beam outlet and a second outer circumferential surface; the third retarding part is provided with a third front end surface closely attached to the second rear end surface, a third rear end surface close to the beam outlet and a third outer circumferential surface; the second retarder is provided with a fourth front end face closely attached to the third rear end face, a fourth rear end face close to the beam outlet and a fourth outer circumferential face, the first, second, third and fourth front end faces, the first, second, third and fourth rear end faces are parallel to each other and are perpendicular to the neutron beam axis, a tangent plane passing through the neutron beam axis is perpendicular to the second front end face, and a tangent line passing through the neutron beam axis is perpendicular to the third front end face.

4. The neutron capture therapy system of claim 3, wherein: in a section passing through the axis of the neutron beam, the first front end surface intersects with the first outer circumferential surface to obtain a first intersection point, the second front end surface intersects with the second outer circumferential surface to obtain a second intersection point, the third front end surface intersects with the third outer circumferential surface to obtain a third intersection point, and the first intersection point, the second intersection point and the third intersection point are located on the same straight line.

5. The neutron capture therapy system of claim 1, wherein: and a reflection compensation body is filled between the accommodating cavity and the vacuum tube, and the reflection compensation body is lead or Al or Teflon or C.

6. The neutron capture therapy system of claim 1, wherein: the first end protrudes from the target along the neutron beam axis toward the beam inlet, and the second end protrudes from the target along the neutron beam axis toward the beam outlet.

7. The neutron capture therapy system of claim 1, wherein: the reflector is in the equal protrusion retarder of both sides of neutron beam axis, hold the chamber and hold the chamber including the reflector that forms by the reflector and hold the chamber and extend the retarder that forms by the retarder enclosure from the reflector, the vacuum tube is including holding the extension section and the embedding section that extends and hold in the retarder holding the intracavity from the extension section that holds in the reflector holding the intracavity, the target is located the tip of embedding section.

8. The neutron capture therapy system of claim 1, wherein: the neutron capture treatment system further comprises at least one cooling device, at least one containing pipeline for containing the cooling device is arranged in the beam shaping body, and lead alloy or aluminum alloy is filled between the cooling device and the inner wall of the containing pipeline.

9. The neutron capture therapy system of claim 1, wherein: the neutron capture treatment system further comprises a shielding body arranged at the beam inlet and closely attached to the beam shaping body.