Dose distribution shifting part and beam shaping device for boron neutron capture therapy

Abstract

The utility model provides a dose distribution shifting member and a beam shaping device for boron neutron capture therapy, the dose distribution shifting member comprises one or more material layers along the neutron emission direction, and the material layers comprise an epithermal neutron moderation material layer and / or a thermal neutron absorption material layer; the shape of the dose distribution shifting part is matched with the shape of the neutron beam exit port. The dose distribution shifting part can be adjusted according to the specific position of a tumor in a human body, so that the maximum dose value caused by thermal neutrons is deposited in the center of the tumor, and the effects of the maximum killing effect on the tumor and the minimum damage to normal tissue are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of medical equipment, in particular to a dose distribution shifting component and a beam shaping device for boron neutron capture therapy. Background Art

[0002] Boron Neutron Capture Therapy (BNCT) is a new method for achieving precision cancer treatment with dual targeting characteristics. During BNCT treatment, a boron-containing ( 10 B) drugs, which have a strong affinity for tumors and can selectively accumulate in cancer cells, but are less distributed in normal tissues; then use epithermal neutrons (0.5e-6MeV) generated by reactors or accelerators and optimized by beam shaping assemblies (BSA) to <E epi <1e-2MeV) neutron beam irradiates the lesion site, in which the epithermal neutrons are slowed down when passing through human tissues and gradually become thermal neutrons (E th <0.5e-6MeV). Thermal neutrons interact with tumor-enriched 10 B has a high reaction cross section and the following reactions occur at the cellular scale: 10 B+n→α+ 7 Li+0.478MeV, the alpha particles produced and 7 Li particles have an extremely high linear energy transfer (LET), with average LETs of 164 keV / μm and 151 keV / μm, respectively, and a range of 4-10 μm, which is comparable to the scale of cells. Therefore, this method can kill cancer cells accurately and efficiently at the cellular scale.

[0003] BNCT mainly uses thermal neutrons to react with boron, nitrogen, hydrogen and other elements in the human body, causing secondary particles and depositing energy at the lesion site to achieve the purpose of treatment. To maximize the therapeutic effect of BNCT, it is necessary to make the neutrons at the beam outlet moderated by the human body to produce thermal neutrons, and the maximum value of the thermal neutron flux is exactly located at the center of the tumor. At this time, the dose caused by neutrons at the center of the tumor is the largest, the killing effect on the tumor is the strongest, and the damage to normal tissue is the smallest. In theory, this purpose can be achieved by changing the material and structure of the beam moderator BSA and adjusting the neutron energy spectrum at the beam outlet. However, since the beam moderator of the accelerator neutron source is usually large and it is difficult to install and disassemble frequently, the neutron energy spectrum at the BSA outlet is usually determined when the internal structure of the BSA is not changed.

[0004] However, different tumor types and the depths of the same type of tumor in different patients vary. Using a fixed neutron beam for treatment often fails to achieve the maximum deposition dose of thermal neutrons exactly at the center of the tumor, which easily causes damage to normal tissues. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a dose distribution shifting member and a beam shaping device for boron neutron capture therapy. By adding the dose distribution shifting member, the BNCT system can more flexibly adapt to different types of tumors or different depths of the same type of tumor, thereby solving the problems in the prior art.

[0006] To achieve the above object and other related objects, the present invention is realized by including the following technical solutions.

[0007] In the first aspect of the present invention, a dose distribution shifting member for boron neutron capture therapy is provided. Along the neutron exit direction, the dose distribution shifting member includes one or more material layers, and the material layer includes a thermal neutron moderation material layer and / or a thermal neutron absorption material layer; the outer shape of the dose distribution shifting member matches the shape of the neutron beam exit port.

[0008] In one embodiment, the outer shape of the dose distribution shifting member is in the shape of a round cake.

[0009] In one embodiment, a first positioning member for fixing is formed at the edge of the dose distribution shifting member.

[0010] In one embodiment, the thickness of any material layer of the dose distribution shifting member is 0.1 - 2.0 cm.

[0011] In a more specific embodiment, the thickness of any material layer of the dose distribution shifting member is 0.5 - 1.0 cm.

[0012] In one embodiment, any material layer is selected from a polyethylene material layer, a boron carbide material layer, a lithium fluoride layer, a paraffin layer, or an ink layer.

[0013] In a more specific embodiment, along the neutron exit direction, the dose distribution shifting member is a polyethylene material layer with a total thickness of 3 cm.

[0014] In a more specific embodiment, along the neutron exit direction, the dose distribution shifting member includes a polyethylene material layer with a total thickness of 2 cm and a boron carbide material layer with a total thickness of 1 cm.

[0015] In one embodiment, the number of the first positioning members is one or more.

[0016] In one embodiment, the first positioning member is formed at the edge of the dose distribution shifting member.

[0017] In one embodiment, the number of the first positioning members is at least two.

[0018] In one embodiment, a plurality of the first positioning members are evenly distributed along the circumferential direction of the dose distribution shifting member.

[0019] A beam shaping device for boron neutron capture therapy according to a second aspect of the present invention includes the dose distribution shifting member as described in any one of the above.

[0020] In one embodiment, the beam shaping device further includes a reflector, and the reflector is formed with a penetrating neutron beam channel; the dose distribution shifting member as described in any one of the above is provided at the outlet of the neutron beam channel.

[0021] In one embodiment, the dose distribution shifting member is detachably connected to the reflector.

[0022] In one embodiment, the beam shaping device further includes a moderator, and the moderator is disposed in the neutron beam channel.

[0023] In one embodiment, part or all of the dose distribution shifting member is embedded in the reflector.

[0024] In one embodiment, the dose distribution shifting member is hermetically connected to the reflector.

[0025] In one embodiment, a positioning mechanism for fixing is formed at the connection between the dose distribution shifting member and the reflector.

[0026] In one embodiment, the positioning mechanism includes a second positioning member provided on the reflector and a first positioning member formed on the dose distribution shifting member; one of the first positioning member and the second positioning member is a positioning protrusion, and the other is a positioning groove that is engaged or disengaged with the positioning protrusion.

[0027] As described above, a dose distribution shifting member and a beam shaping device for boron neutron capture therapy of the present invention have the following beneficial effects:

[0028] The dose distribution shifting member and the beam shaping device for boron neutron capture therapy proposed by the present invention can be adjusted according to the specific position of a tumor in the human body, so that the maximum value of the dose caused by thermal neutrons is deposited at the center position of the tumor, achieving the best effect of killing the tumor and minimizing the damage to normal tissues. Description of the Drawings

[0029] Figure 1 Shown is a schematic structural view of the dose distribution displacement member of the present utility model.

[0030] Figure 2 Shown is one of the schematic structural views of the beam shaping device of the present utility model.

[0031] Figure 3 Shown is another schematic structural view of the beam shaping device of the present utility model.

[0032] Figure 4 Shown is a schematic view of the normalized thermal neutron flux distribution when the DDS is not adopted and when the dose distribution displacement device is designed by the dose distribution displacement device design method described in the embodiments of the present application for BNCT.

[0033] Figures 1 to 3 The reference numerals in the figures are explained as follows:

[0034] 1 Reflector

[0035] 11 Neutron beam channel

[0036] 2 Dose distribution displacement member

[0037] 21 First positioning member

[0038] 3 Moderator Detailed implementation manners

[0039] The following specific embodiments illustrate the implementation manners of the present utility model. Those skilled in the art can easily understand other advantages and effects of the present utility model from the content disclosed in this specification.

[0040] Please refer to Figures 1 to 3 . It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in the art to understand and read, and are not used to limit the limiting conditions under which the present utility model can be implemented. Therefore, they do not have technical essence. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present utility model can produce and the purposes that can be achieved, should still fall within the scope that the technical content disclosed by the present utility model can cover. At the same time, the terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the convenience of description and are not used to limit the scope under which the present utility model can be implemented. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope under which the present utility model can be implemented.

[0041] As Figure 1 and Figure 2As shown in the figure, the present utility model provides a dose distribution shifter 2 for boron neutron capture therapy. Along the neutron emission direction, the dose distribution shifter includes one or more material layers, and the material layer includes a thermal neutron moderation material layer and / or a thermal neutron absorption material layer; the outer shape of the dose distribution shifter matches the shape of the neutron beam outlet.

[0042] The dose distribution shifter 2 for boron neutron capture therapy proposed by the present utility model can moderate or absorb thermal neutrons, thereby adjusting the neutron beam at the outlet of the neutron beam channel. Thus, by adjusting the thickness and material of the dose distribution shifter, it can be adjusted so that the maximum dose caused by thermal neutrons is deposited at the tumor center position, thereby achieving the best killing effect on tumors and the least damage to normal tissues.

[0043] In a specific embodiment, the outer shape of the dose distribution shifter 2 is disc-shaped.

[0044] In a Figure 2 specific embodiment as shown in the figure, a first positioning member 21 for fixing is formed at the edge of the dose distribution shifter 2.

[0045] In a specific embodiment, the number of the first positioning members 21 is one or more. In a more specific embodiment, the number of the first positioning members 21 is at least 2. For example, it can be 2, 3, 4, or 5, etc. Specifically, as Figure 2 shown in the figure, the number of the first positioning members is 4.

[0046] In a specific embodiment, a plurality of the first positioning members 21 are evenly distributed along the circumferential direction of the dose distribution shifter 2.

[0047] In a specific embodiment, the thickness of any material layer of the dose distribution shifter 2 is 0.1 - 2.0 cm. For example, it can be 0.1 cm, 0.2 cm, 0.4 cm, 0.6 cm, 0.8 cm, 1.0 cm, 1.2 cm, 1.4 cm, 1.8 cm, 1.0 cm, or 2.0 cm.

[0048] In a more specific embodiment, the thickness of any material layer of the dose distribution shifter is 0.5 - 1.0 cm.

[0049] In a specific embodiment, any material layer is selected from a polyethylene (abbreviated as PE) material layer, a boron carbide (B 4 C) material layer, a lithium fluoride layer, a paraffin layer, or an ink layer.

[0050] In a more specific embodiment, along the neutron emission direction, the dose distribution shifter is a PE material layer with a total thickness of 3 cm.

[0051] In a more specific embodiment, along the neutron emission direction, the dose distribution shifting member includes a PE material layer with a total thickness of 2 cm and a B 4 C material layer with a total thickness of 1 cm.

[0052] The embodiment of the present utility model gives the relationship between the thermal neutron flux and the receptor depth when the dose distribution shifting device (DDS) is not adopted, and the relationship between the thermal neutron flux and the receptor depth corresponding to the dose distribution shifting devices respectively designed for three tumor center depths of 0 cm, 1.3 cm and 3.4 cm (taking the case where the number of material layers in the dose distribution shifting device is designed as 3 layers as an example), which is obtained by Monte Carlo software simulation. Specifically as Figure 4 shown, where Figure 4 the receptor depth corresponding to the abscissa is the depth from the receptor surface, and Figure 4 also gives the information of each layer of materials and material thicknesses corresponding to various DDSs. Referring to Figure 4 it can be seen that when the dose distribution shifting device (DDS) is not designed by using the dose distribution shifting device design method for BNCT in the embodiment of the present invention, the receptor depth at the maximum thermal neutron flux is 2.3 cm; if the position with the maximum thermal neutron flux is to be transferred to 1.3 cm from the skin surface and exactly at the skin surface (0 cm) in the superficial direction of the receptor, 1 cm of PE and 3 cm of PE are required respectively (in both cases, the three layers of materials in the dose distribution shifting device are PE materials, and the above centimeters are the total thickness of the DDS); and when the maximum position of the thermal neutron flux distribution is to be moved to a deeper position of 3.4 cm, a combination of 2 cm PE + 1 cm B 4 C is required (the dose distribution shifting device for this case can be composed of 2 layers of PE materials and 1 layer of B 4 C materials, or composed of 1 layer of PE material and 2 layers of B 4 C materials, and the above centimeters are the total thickness of the corresponding materials). Therefore, it is proved that the dose distribution shifting device designed by using the dose distribution shifting device design method for BNCT in the embodiment of the present utility model can realize the modulation of the thermal neutron flux dose distribution in the human body and has the effect of optimizing the treatment effect of tumors at different depths.

[0053] Theoretical analysis: The neutrons at the BSA exit are mainly epithermal neutrons. After entering the patient's body, the epithermal neutrons are gradually moderated to produce thermal neutrons; the thermal neutrons react with elements such as boron, nitrogen, and hydrogen in the human body and are gradually consumed. Therefore, when the neutron beam just enters the patient's body, the production rate of thermal neutrons is greater than the consumption rate, and the thermal neutron flux increases. As the penetration depth of the neutron beam in the patient's body increases, the number of epithermal neutrons decreases, the production rate of thermal neutrons decreases, the consumption rate of thermal neutrons is greater than the production rate, and the thermal neutron flux decreases. Therefore, when treating superficial tumors, the maximum value of the thermal neutron flux should be shifted towards the surface, and it is necessary to reduce the proportion of epithermal neutrons in the neutron beam at the BSA exit. The DDS can use some thermal neutron moderating materials, such as polyethylene (PE), paraffin, water, graphite, etc.; when treating deep tumors, the thermal neutrons with relatively high energy in the neutron beam should be dominant, that is, it is necessary to reduce the proportion of thermal neutrons in the neutron beam at the BSA exit. The DDS can use some thermal neutron absorbing materials, such as boron carbide (B 4 C), lithium fluoride, etc. The realization of this effect is at the cost of the loss of thermal neutrons.

[0054] As Figure 2 and Figure 3 shown, in the embodiment of the present utility model, a beam shaping device for boron neutron capture therapy is further provided, and the dose distribution shifting member 2 as described in any one of the above embodiments is adopted.

[0055] In a specific embodiment as Figure 2 shown, the beam shaping device includes a reflector 1, and the reflector 1 is formed with a penetrating neutron beam channel 11; at the exit of the neutron beam channel 11, the dose distribution shifting member 2 as described in any one of the above embodiments is provided.

[0056] In a specific embodiment as Figure 2 shown, the dose distribution shifting member 2 is detachably connected to the reflector 1.

[0057] In an embodiment as Figure 3 shown, the dose distribution shifting member 2 is hermetically connected to the reflector 1.

[0058] In an embodiment as Figure 3 shown, part or all of the dose distribution shifting member 2 is embedded in the reflector 1.

[0059] In an embodiment as Figure 2 shown, a positioning mechanism for fixing is formed at the connection between the dose distribution shifting member 2 and the reflector 1.

[0060] In one embodiment, the positioning mechanism includes a second positioning member disposed on the reflector 1 and a first positioning member 21 formed on the dose distribution shifting member 2; one of the first positioning member 21 and the second positioning member is a positioning protrusion, and the other is a positioning groove that mates with and engages or disengages from the positioning protrusion. Specifically, as Figure 2 shown, the first positioning member 21 on the dose distribution shifting member 2 is a positioning protrusion, and the second positioning member on the reflector 1 is a positioning groove.

[0061] In a more specific embodiment, the beam shaping device further includes a moderator 3, and the moderator 3 is disposed in the neutron beam channel 11.

[0062] In a more specific embodiment, the dose distribution shifting member 2 includes a disc-shaped body, and the second positioning member is formed at the edge of the disc-shaped body.

[0063] Through simulation by Monte Carlo software, the following results are obtained:

[0064] 1) When the DDS is not installed, the thermal neutron flux distribution of the neutron beam at the outlet of the neutron beam channel of the beam shaping device in the water phantom is obtained, and the depth corresponding to the maximum thermal neutron flux is obtained;

[0065] 2) At the BSA outlet, a certain thickness of PE or B 4 C is installed, and the thermal neutron flux distribution of the neutron beam at the BSA outlet in the water phantom is calculated. After installing DDSs of different materials and different thicknesses, the maximum thermal neutron flux and its corresponding depth are obtained.

[0066] The results are shown in Tables 1 and 2.

[0067] When the DDS is not installed, the maximum thermal neutron flux is 2.129×10 9 , and the maximum depth is 2.2 cm.

[0068] As can be seen from Table 1, when the DDS material is PE, the depth of the maximum thermal neutron flux moves towards the superficial layer. When the PE thickness is 0.5, 1.0, 1.5, 2.0 cm, the depths of the maximum thermal neutron flux are 1.7, 1.2, 0.8, 0.4 respectively. When the PE thickness reaches 2.5 cm, the maximum thermal neutron flux appears on the skin surface. Moreover, when compared with the control group (without installing DDS), when installing a DDS with a certain thickness of PE as the material, the maximum thermal neutron flux increases by about 3% to 7.5%. It can be seen that installing a DDS with PE as the material has a significant effect in the treatment of superficial tumors. It not only realizes the deposition of the maximum dose caused by thermal neutrons at the tumor center position, but also increases the maximum value of the deposited dose, further improving the treatment effect, shortening the treatment time, and better protecting normal tissues.

[0069] As can be seen from Table 2, when the DDS material is B 4 C, the depth of the maximum thermal neutron flux is shifted towards the deep layer. When the thickness of B 4 C is 0.2, 0.4, and 1.0 cm, the depths of the maximum thermal neutron flux are 2.4, 2.6, and 2.8 cm respectively. Compared with the control group, when the installation material is B 4 C with a certain thickness for the DDS, the maximum thermal neutron flux is lost by about 27% to 51%. It can be seen that for the DDS with the installation material of B 4 C, the maximum deposition dose of thermal neutrons shows a shift towards the deep layer, but at the same time, a relatively large amount of thermal neutron flux is lost, and its actual effect during treatment remains to be demonstrated.

[0070] Table 1 Thermal neutron flux distribution when the DDS material is PE

[0071]

[0072]

[0073] Table 2 Thermal neutron flux distribution when the DDS material is B 4 C

[0074]

[0075] The beam shaping device for boron neutron capture therapy proposed by the present utility model has remarkable effects in treating superficial tumors. It not only realizes the deposition of the maximum dose caused by thermal neutrons at the tumor center position, but also increases the maximum deposition dose, further improving the treatment effect, shortening the treatment time, and protecting normal tissues.

[0076] The beam shaping device provided by the present utility model can flexibly expand the indications of BNCT and achieve precise treatment of tumors with different depths and types only by using a dose distribution shifting member without changing the entire system. Thus, it has low cost, strong operability and flexibility.

[0077] The above embodiments are only illustrative of the principles and effects of the present utility model, and are not used to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A dose distribution shifter for boron neutron capture therapy, characterized in that: Along the neutron emission direction, the dose distribution shifter includes one or more material layers, and the material layers include thermal neutron moderation material layers and / or thermal neutron absorption material layers; the shape of the dose distribution shifter matches the shape of the neutron beam exit port.

2. The dose distribution shifting element according to claim 1, characterized in that: The dose distribution shifter has a round pancake shape; and / or a first positioning piece for fixing is formed on the edge of the dose distribution shifter; and / or the thickness of any material layer of the dose distribution shifter is 0.1 to 2.0 cm; and / or the thickness of any material layer of the dose distribution shifter is 0.5 to 1.0 cm.

3. The dose distribution shifting element according to claim 1, characterized in that: Any material layer is selected from a polyethylene material layer, a boron carbide material layer, a lithium fluoride layer, a paraffin layer or an ink layer.

4. The dose distribution shifting element according to claim 2, characterized in that: The number of the first positioning members is one or more; and / or the first positioning members are formed at the edge of the dose distribution shifter; and / or, along the neutron emission direction, the dose distribution shifter is a polyethylene material layer with a total thickness of 3 cm; and / or, along the neutron emission direction, the dose distribution shifter includes a polyethylene material layer with a total thickness of 2 cm and a boron carbide material layer with a total thickness of 1 cm.

5. The dose distribution shifting element according to claim 4, characterized in that: The plurality of first positioning members are evenly distributed along the circumference of the dose distribution shifting member.

6. A beam shaping device for boron neutron capture therapy, characterized in that: The beam shaping device comprises the dose distribution shifting element according to any one of claims 1 to 5.

7. The beam shaping device according to claim 6, characterized in that: The beam shaping device further comprises a reflector, wherein the reflector forms a penetrating neutron beam channel; and a dose distribution shifting member as claimed in any one of claims 1 to 5 is arranged at an outlet of the neutron beam channel.

8. The beam shaping device according to claim 7, characterized in that: The dose distribution shifting member is detachably connected to the reflector; and / or, the beam shaping device further comprises a moderator, and the moderator is arranged in the neutron beam channel; And / or, part or all of the dose distribution shifting element is embedded in the reflector; and / or, the dose distribution shifting element and the reflector are sealedly connected.

9. The beam shaping device according to claim 7, characterized in that: A positioning mechanism for fixing is formed at the connection between the dose distribution shifting member and the reflector.

10. The beam shaping device according to claim 9, characterized in that: The positioning mechanism includes a second positioning member arranged on the reflector and a first positioning member formed on the dose distribution shifting member; one of the first positioning member and the second positioning member is a positioning protrusion, and the other is a positioning groove that matches or is engaged with or disengaged from the positioning protrusion.

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