Beam shaper for neutron capture therapy

Abstract

The application discloses a beam shaping body for neutron capture therapy, which comprises a proton beam flow hole, a target body, a slowing-down body, a reflecting body surrounding the slowing-down body and the proton beam flow hole, a thermal neutron absorption layer adjacent to the slowing-down body, a gamma shielding layer adjacent to the thermal neutron absorption layer, and a collimating body arranged in the beam shaping body; the target body is arranged in the slowing-down body and at the end of the proton beam flow hole. The target body is arranged in the inside of the slowing-down body, and the target body is arranged to a depth of not less than 50 mm in the slowing-down body, so that the recoil neutrons are fully slowed down, and the super-thermal neutron flux of the exit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of BNCT boron neutron capture therapy, and in particular to a beam shaping body for treating deep tumors. Background Art

[0002] Currently, photon or charged particle therapy is limited by the properties of radiation. While killing tumor cells, it can also cause significant damage to normal tissue in the radiation's path. Furthermore, traditional radiotherapy is often ineffective for highly radioresistant tumor cells, such as glioblastoma multiforme and melanoma. Neutron capture therapy, which minimizes radiation damage to surrounding normal tissue and exhibits a high relative biological effect in the target area, offers a superior cancer treatment option compared to traditional radiation therapy by combining boron-containing drugs with the specific accumulation of tumor cells and a precisely controlled neutron beam.

[0003] Boron Neutron Capture Therapy (BNCT) utilizes boron ( 10 The thermal neutron capture cross section of B is very large. Boron (10B) is enriched in the tumor area. After thermal neutrons / epitaxmal neutrons pass through a certain thickness of biological tissue, they are 10 B(n,α) 7 Li reaction produces 4 He and 7 The two charged particles of Li have average energies of 0.84 MeV and 1.47 MeV respectively, with high LET and short range. The LET and range of α particles are 150 keV / μm and 4-5 μm, while 7 Li has a range of 175keV / μm and a wavelength of 8-9μm, both of which are within the cellular range, equivalent to the size of a single cell. Therefore, radiation damage to organisms is limited to the cellular level. When boron-loaded drugs selectively accumulate in tumor cells and are paired with an appropriate neutron radiation source, they can achieve localized tumor cell destruction without causing significant damage to normal tissue.

[0004] The efficacy of boron neutron capture therapy depends on the boron content in tumor cells ( 10 B) concentration and the number of thermal neutrons reaching the region. Therefore, in addition to the development of high-performance boron-containing drugs, the improvement of neutron source beam quality also plays an important role in boron neutron capture therapy.

[0005] Chinese patent application publication CN104548388B discloses a beam shaping body for neutron capture therapy, which provides a beam shaping body for neutron capture therapy, wherein the beam shaping body comprises a beam inlet, a target material, a moderator body adjacent to the target material, a reflector body surrounding the moderator body, a thermal neutron absorption body adjacent to the moderator body, a radiation shield arranged in the beam shaping body, and a beam outlet. The target material has a nuclear reaction with a proton beam incident from the beam inlet to generate neutrons, and the neutrons form a neutron beam defining a main axis. The moderator body slows down the neutrons generated from the target material to a super-thermal neutron energy region, and is arranged in a shape comprising at least one cone. The reflector body reflects the neutrons deviating from the main axis to the main axis to increase the intensity of the super-thermal neutron beam. The thermal neutron absorption body is used to absorb thermal neutrons to avoid excessive dose to the shallow tissue during treatment. The radiation shield is used to shield the leaked neutrons and photons to reduce the dose to the normal tissue in the non-irradiated area. The patent has the following defects:

[0006] (1) The moderator body is a one-piece conical moderator body, which is not conducive to processing and manufacturing, and the neutron flux after moderation cannot meet the effect of treating deep tumors.

[0007] (2) The proton incident channel is a hollow cylindrical channel, which is easy to cause more neutrons to leak from the area, has low utilization rate, and also harms the accelerator end. SUMMARY

[0008] The present application proposes a beam shaping body for neutron capture therapy to solve the technical problems in the background art.

[0009] The beam shaping body for neutron capture therapy comprises a proton beam flow channel, a target body, a moderator body, a reflector body surrounding the moderator body and the proton beam flow channel, a thermal neutron absorption layer adjacent to the moderator body, a gamma shield layer adjacent to the thermal neutron absorption layer, and a collimator arranged in the beam shaping body. The moderator body is provided with the target body, and the target body is arranged at the end of the proton beam flow channel.

[0010] In a specific embodiment, the moderator body is a cylindrical stepped shaft, and the number of stepped shaft segments is 2-10.

[0011] In a specific embodiment, the outer diameter of the stepped shaft end surface near the target body part is the largest, and the outer diameter of the stepped shaft end surface near the thermal neutron absorption layer part is the smallest.

[0012] In a specific embodiment, the stepped shaft segment with the largest outer diameter surrounds the end of the proton beam flow channel.

[0013] The target body is arranged in the stepped shaft section with the largest outer diameter and at the end of the proton beam flow channel.

[0014] In a specific embodiment, a gap is present between the stepped shaft section with the smallest outer diameter and the reflector, and the gap ranges from 1 to 20 mm.

[0015] The thermal neutron absorption layer is adjacent to the stepped shaft section with the smallest outer diameter.

[0016] In a specific embodiment, the proton beam flow channel is cylindrical, and a ring-shaped blocking block is arranged in the proton beam flow channel.

[0017] In a specific embodiment, the outer diameter of the thermal neutron absorption layer is greater than the outer diameter of the moderator.

[0018] In a specific embodiment, the thickness of each stepped shaft section ranges from 50 to 100 mm.

[0019] In a specific embodiment, the outer diameter of the adjacent two stepped shaft sections differs by 0 to 50 mm.

[0020] In a specific embodiment, the distance between the blocking block in the proton beam flow channel and the target body ranges from 50 to 500 mm.

[0021] The beam shaping body for neutron capture therapy provided by the present application has the following beneficial effects:

[0022] 1. The moderator of the present application is designed in a cylindrical stepped shaft shape, which is easier to process, maintain or replace, and is also convenient to assemble and disassemble. The cylindrical stepped shaft-shaped moderator can effectively avoid straight-through beams.

[0023] 2. The target body of the present application is arranged inside the moderator, and the depth of the target body into the moderator is not less than 50 mm, which is beneficial to the full moderation of the recoil neutrons and also improves the flux of epithermal neutrons at the exit.

[0024] 3. In the present application, a gap is present between the stepped shaft section with the smallest outer diameter of the moderator and the reflector, which can increase the leakage of epithermal neutrons at the exit and improve the flux of epithermal neutrons.

[0025] 4. In the present application, a ring-shaped blocking block is arranged in the proton beam flow channel, which not only reduces the leakage of recoil neutrons to the accelerator end and reduces the irradiation dose to the accelerator end, but also improves the flux of epithermal neutrons at the exit and reduces the loss of epithermal neutron beam. BRIEF DESCRIPTION OF DRAWINGS

[0026] For better understanding of the present application, embodiments of the present application will be described with reference to the following drawings:

[0027] Figure 1 is a schematic diagram of the cross-sectional structure of Example One;

[0028] Figure 2 is a schematic diagram of the cross-sectional structure of Example Two;

[0029] Figure 3 is a schematic diagram of the cross-sectional structure of Example Three;

[0030] Figure 4 is a schematic diagram of the cross-sectional structure of Example Four;

[0031] Figure 5 is a schematic diagram of the cross-sectional structure of Example Five;

[0032] Figure 6 is a schematic diagram of the cross-sectional structure of Modification Example One;

[0033] Figure 7 is a graph of the relationship between the exit port neutron energy spectrum of Modification Example One (A) and Example One (B);

[0034] Figure 8 is a graph of the relationship between the exit port neutron energy spectrum of Example One (B) and Example Two (C);

[0035] Figure 9 is a graph of the relationship between the exit port neutron energy spectrum of Example Two (C) and Example Three (D);

[0036] Figure 10 is a graph of the relationship between the exit port neutron energy spectrum of Example Three (D) and Example Four (E);

[0037] In the drawings, reference numerals:

[0038] 1 - beam shaping body, 11 - proton beam channel, 12 - target body, 13 - moderator body, 131 - front end body, 132 - middle end body, 133 - rear end body, 14 - reflection body, 15 - thermal neutron absorption layer, 16 - radiation shielding layer, 17 - collimating body, 18 - exit port, 19 - gap, 20 - blocking block. DETAILED DESCRIPTION

[0039] The specific embodiments of the present application will be described in detail below, it should be noted that the embodiments described herein are only used for illustration and do not limit the present application. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application does not necessarily have to be implemented with these specific details. In other examples, in order to avoid confusion of the present application, well-known circuits, materials or methods are not specifically described.

[0040] Throughout this specification, reference can be made to "one embodiment", "an embodiment", "one example", or "an example" meaning that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the application. The appearance of the phrases "in one embodiment", "in an embodiment", "one example", or "an example" in various places in the specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics can be combined in any suitable

[0041] Embodiment One

[0042] The existing moderator for slowing down the neutron beam is generally a one-piece conical moderator, which is not conducive to processing and manufacturing, and the neutron flux after moderation cannot meet the effect of treating deep tumors.

[0043] As shown in Figure 1 The embodiment of the present application comprises a proton beam hole and a target body. The direction of proton incidence is positive. One end of the proton beam hole is connected with an accelerator, and the other end is connected with the target body. The exit is the rear end (i.e. the end of the super-thermal neutron beam). Therefore, the target body is arranged at the end of the proton beam hole.

[0044] The beam shaping body further comprises a moderator, a reflecting body surrounding the moderator and the proton beam hole, a thermal neutron absorbing layer adjacent to the moderator, a gamma shielding layer adjacent to the thermal neutron absorbing layer, and a collimating body arranged in the beam shaping body. In addition, the target body is arranged in the moderator, i.e. the target body is wrapped in the moderator. The outer diameter of the thermal neutron absorbing layer is larger than the outer diameter of the moderator.

[0045] Embodiment Two

[0046] As shown in Figure 2As shown, the embodiment is based on the optimization of the first embodiment, specifically, the moderator in the embodiment is in the shape of a cylindrical stepped shaft, the number of stepped shaft segments is 2-10, preferably 3-8, and most preferably 5. Those skilled in the art can also understand that, with the proton incidence as the front end, the moderator can sequentially include a front end body, a plurality of middle end bodies, and a rear end body, the front end body, the middle end body, and the rear end body form the moderator in the shape of a cylindrical stepped shaft, the number of stepped shaft segments of the middle end body is 0-8, preferably 0-6, and most preferably 3; and with the direction of proton incidence as the positive direction, the stepped shaft segments gradually decrease in distribution according to the different outer diameters (those skilled in the art can easily understand that, with the direction of proton incidence as the positive direction, the front end body, the middle end body, and the rear end body gradually decrease in distribution according to the different outer diameters, and the stepped shaft segments of the middle end body gradually decrease in distribution according to the different outer diameters), at this time, the stepped shaft end face of the stepped shaft segment close to the target body part has the largest outer diameter (those skilled in the art can easily understand that the stepped shaft segment with the largest outer diameter is the front end body), and the stepped shaft end face of the stepped shaft segment close to the thermal neutron absorption layer part has the smallest outer diameter (those skilled in the art can easily understand that the stepped shaft segment with the smallest outer diameter is the rear end body). In addition to the direction of proton incidence as the positive direction, those skilled in the art can also understand that, with the direction of the stepped shaft close to the thermal neutron absorption layer part, the outer diameter of the stepped shaft segment gradually decreases. The thickness of each stepped shaft segment ranges from 50 to 100 mm, preferably 50 mm, and the outer diameter of the adjacent two stepped shaft segments differs by 0-50 mm, preferably 20 mm. Such a moderator structure is easier to process, maintain, or replace, and is also convenient to assemble and disassemble. The moderator in the shape of a cylindrical stepped shaft can effectively avoid the straight-through beam, and greatly improve the flux of the super-thermal neutron beam and the economy of the beam shaping body without increasing the proton hitting power.

[0047] It should be further pointed out that, in addition to the shape of a cylindrical stepped shaft, the moderator in the process of the embodiment can also be in the shape of a circular stepped shaft, or other structures that can form a stepped shaft.

[0048] Meanwhile, the front end body (the stepped shaft segment with the largest outer diameter) surrounds the end of the proton beam hole, is used for slowing down the recoil neutrons, improves the flux of the super-thermal neutrons at the exit, and the target body is arranged in the front end body (the stepped shaft segment with the largest outer diameter) and at the end of the proton beam hole, and the depth of the target body into the moderator is not less than 50 mm, which is beneficial to the sufficient slowing down of the recoil neutrons.

[0049] In addition, the outer diameter of the thermal neutron absorption layer is greater than that of the front end body (the stepped shaft segment with the largest outer diameter), which is used for absorbing thermal neutrons, preventing the escape of thermal neutrons, and avoiding excessive dose to the superficial tissue during treatment; and the gamma shielding layer adjacent to the thermal neutron absorption layer is used for shielding the leaked neutrons and photons, so as to reduce the dose of normal tissue in the non-irradiated area.

[0050] Example 3

[0051] like Figure 3 As shown, this embodiment is further optimized on the basis of the aforementioned embodiment 2. Specifically, there is a gap between the rear end body (the stepped shaft section with the smallest outer diameter) and the reflector of this embodiment. The designed gap cannot be too large, as a too large gap will significantly increase the fast neutron component at the outlet. The gap cannot be too small, as a too small gap will result in a limited increase in the epithermal neutron component at the outlet. Therefore, the gap range is 1 to 20 mm, preferably 10 mm, which can increase the leakage of epithermal neutrons at the outlet and improve the epithermal neutron flux. In addition, the rear end body (the stepped shaft section with the smallest outer diameter) is adjacent to the thermal neutron absorption layer, which has better economic efficiency.

[0052] Example 4

[0053] like Figure 4 As shown, this embodiment is further optimized on the basis of the aforementioned embodiment three. Specifically, the proton beam channel of this embodiment is hollow cylindrical, and a circular blocking block is provided in the proton beam channel, and the blocking block is arranged at a position 50 to 500 mm away from the target. In this embodiment, the blocking block is preferably arranged at a position 50 mm away from the target. Such a structural design is compact and smart, which not only reduces the leakage of recoil neutrons to the accelerator end and reduces the irradiation dose to the accelerator end, but also increases the epithermal neutron flux at the outlet and reduces the loss of the epithermal neutron beam.

[0054] Example 5

[0055] like Figure 5 As shown, the difference between this embodiment and the fourth embodiment is that the blocking block is set at a position 500 mm away from the target body, which can also reduce the leakage of recoil neutrons generated by proton target shooting along the proton beam channel. At the same time, after these neutrons are slowed down, they can also increase the epithermal neutron flux at the outlet.

[0056] Modification 1

[0057] like Figure 6 As shown, the difference between this modification and the first embodiment is that the target in this modification is not arranged inside the moderator, but is arranged on the front surface of the moderator and at the end of the proton beam channel.

[0058] Comparative Example 1

[0059] Through experimental comparison, the neutron flux rate (n / cm2) of the outlet of the modification example 1 and the embodiment 1 is obtained. 2 The comparison data table of / p) is as follows:

[0060]

[0061] likeFigure 7 The relationship diagram of the neutron energy spectrum at the outlet between Modification Example 1 (A) and Example 1 (B) is shown. It can be seen that in Example 1, the target body is wrapped by the moderator material. It can be seen that the total neutron fluence rate of Modification Example 1 and Example 1 is equivalent, but the epithermal neutron fluence rate of Example 1 is higher, and the proportion of epithermal neutrons is significantly improved.

[0062] Comparative Example 2

[0063] Through experimental comparison, the neutron flux rate (n / cm2) of the outlet of Example 1 and Example 2 was obtained. 2 The comparison data table of / p) is as follows:

[0064]

[0065] like Figure 8 The relationship diagram of the neutron energy spectrum at the outlet between Example 1 (B) and Example 2 (C) is shown. It can be seen that when the moderator in Example 2 adopts a cylindrical stepped shaft shape, the total neutron fluence rate of Example 1 and Example 2 is equivalent, but the epithermal neutron fluence rate of Example 2 is higher, and the proportion of epithermal neutrons is also significantly improved.

[0066] Comparative Example 3

[0067] Through experimental comparison, the neutron flux rate (n / cm2) of the outlet of Example 2 and Example 3 was obtained. 2 The comparison data table of / p) is as follows:

[0068]

[0069] like Figure 9 The relationship diagram of the neutron energy spectrum at the outlet between Example 2 (C) and Example 3 (D) is shown. It can be seen that when a gap is designed between the rear end body (the stepped shaft section with the smallest outer diameter) and the reflector in Example 3, the total neutron fluence rate of Example 3 is higher and the epithermal neutron fluence rate is also improved.

[0070] Comparative Example 4

[0071] Through experimental comparison, the neutron flux rate (n / cm2) of the outlet of Example 3, Example 4 and Example 5 is obtained. 2 The comparison data table of / p) is as follows:

[0072]

[0073] like Figure 10The neutron energy spectrum relationship diagram of the outlet of the third embodiment (D) and the fourth embodiment (E) is shown, from which it can be seen that the fourth embodiment and the fifth embodiment use blocking blocks, although the positions of the blocking blocks are different, but compared with the third embodiment, the total neutron flux of the outlet of the fourth embodiment and the fifth embodiment is obviously improved, and the super-thermal neutron flux and the super-thermal neutron ratio are also obviously improved, at the same time, the leakage of the backscattering neutron in the proton beam hole is significantly reduced.

[0074] In addition, it needs to be explained that in the process of all embodiments, variants and comparative examples of the present application, the fast neutrons mentioned in the present application are higher than 10 keV, the super-thermal neutrons mentioned in the present application are between 0.5 eV and 10 keV, and the thermal neutrons mentioned in the present application are lower than 0.5 eV.

[0075] The above embodiments are only specific embodiments of the present application, which are described in detail, but cannot be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of variants and improvements can be made, and these obvious replacement forms belong to the protection scope of the present application.

Claims

1. A beam shaper for neutron capture therapy, characterized in that: The invention comprises a proton beam channel, a target, a moderator, a reflector surrounding the moderator and the proton beam channel, a thermal neutron absorption layer adjacent to the moderator, a gamma shielding layer adjacent to the thermal neutron absorption layer, and a collimator arranged in the beam line shaping body. The moderator is provided with a target, the target is arranged at the end of the proton beam channel, and the depth of the target penetrating into the moderator is not less than 50 mm. The moderator is in the shape of a cylindrical stepped shaft, and the number of stepped shaft sections of the cylindrical stepped shaft is 2 to 10. The outer diameter of the stepped shaft end face of the moderator close to the target body is the largest, and the outer diameter of the stepped shaft end face close to the thermal neutron absorption layer is the smallest. A blocking block is provided in the proton beam channel, and the distance between the blocking block and the target body is 50 to 500 mm.

2. The beam shaping body for neutron capture therapy according to claim 1, characterized in that: The stepped shaft section with the largest outer diameter is surrounded by the end of the proton beam channel; the target body is arranged in the stepped shaft section with the largest outer diameter and at the end of the proton beam channel.

3. The beam shaping body for neutron capture therapy according to claim 1, characterized in that: There is a gap between the stepped shaft section with the smallest outer diameter and the reflector, and the gap ranges from 1 to 20 mm; the thermal neutron absorption layer is adjacent to the stepped shaft section with the smallest outer diameter.

4. The beam shaping body for neutron capture therapy according to claim 1, characterized in that: The proton beam channel is cylindrical, and the blocking block is annular.

5. The beam shaping body for neutron capture therapy according to claim 1, characterized in that: The outer diameter of the thermal neutron absorption layer is larger than the outer diameter of the moderator.

6. The beam shaping body for neutron capture therapy according to claim 1, characterized in that: The thickness of each stepped shaft segment ranges from 50 to 100 mm.

7. The beam shaping body for neutron capture therapy according to claim 1, characterized in that: The outer diameters of two adjacent stepped shaft segments differ by 0 to 50 mm.

Images