Neutron generator

Abstract

To provide a neutron capture therapy apparatus capable of easily controlling an irradiation range.SOLUTION: A neutron capture therapy apparatus 1 comprises: a radiation shielding part 4 that surrounds the head including the lesion 3 of a patient 2 along the outer surface of the patient 2, and has an opening 7 at a position corresponding to the lesion 3; and a neutron reflecting part 6 that is made of a member that scatters neutron beams, and surrounds the radiation shielding part 4 via a space 5. The neutron reflecting part 6 has a neutron irradiation port 8 for introducing neutron beams into the space 5, and an opening 11 that allows the head of the patient 2 including the lesion 3 surrounded by the radiation shielding part 4 to pass therethrough and to be arranged in the space 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a neutron capture therapy apparatus that performs treatment by irradiating a lesion to be treated with neutron rays.

Background Art

[0002] Conventionally, a neutron capture therapy apparatus that performs treatment by irradiating a lesion to be treated with neutron rays has been known (see, for example, Patent Document 1). In such a neutron capture therapy apparatus, cancer cells and the like in the lesion are killed by a nuclear reaction between boron or the like taken up by the lesion and neutron rays, and a therapeutic effect is obtained.

[0003] The apparatus described in Patent Document 1 includes a target that generates neutron rays by being irradiated with a charged particle beam, a collimator that shapes the irradiation field of the neutron rays, and a reflector provided on the outlet side of the collimator and configured to be able to reflect neutron rays leaking from between the patient and the collimator toward the patient.

[0004] According to this, among the neutron rays emitted from the outlet of the collimator, the leakage neutron rays that are not directly irradiated to the patient are reflected toward the patient by the reflector, so that the irradiation dose to the tumor of the patient increases. The irradiation dose to the tumor is controlled by setting the shape of the reflector. Thereby, the treatment time can be shortened and the burden on the patient can be reduced to some extent.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, according to the apparatus of Patent Document 1 mentioned above, since the neutron beam reflected by the reflecting part is reflected by scattering in the reflecting part, it scatters in random directions with respect to the direction of the reflecting surface of the reflecting part. Therefore, the irradiation range of the reflected neutron beam cannot be controlled, so tissues with low tolerance dose cannot be protected. In addition, there may be a case where the neutron beam is intensively irradiated to unintended sites.

[0007] In addition, the neutron beam reflected by the reflecting surface far from the tumor contributes little to the tumor, while it causes unnecessary exposure to normal tissues close to the reflecting surface. Also, in order to significantly increase the irradiation dose, a considerable weight of a reflecting material, for example, a lead reflecting material with a thickness of 10 cm or more, is required. Therefore, it is difficult to optimize the amount of the reflecting material for each patient with different tumor positions and sizes.

[0008] An object of the present invention is to provide a neutron capture therapy apparatus capable of easily controlling the irradiation range in view of the problems of such prior art.

Means for Solving the Problems

[0009] The neutron capture therapy apparatus of the present invention includes a radiation shielding part that surrounds a part including a lesion to be treated along the outer surface of the treatment target and has an opening at a position corresponding to the lesion, and a member that scatters neutron beams, and includes a neutron reflecting part that surrounds the radiation shielding part through a space.

[0010] The neutron reflecting part has a neutron irradiation port for introducing neutron beams into the space and an opening part for passing through a part including the lesion surrounded by the radiation shielding part among the treatment targets and arranging it in the space.

[0011] According to the present invention, the neutron beam irradiated into the space from the neutron irradiation port travels toward the treatment target or is reflected in random directions by the neutron reflector. Therefore, by appropriately setting the number, position, size, and shape of the openings of the radiation shielding part, in addition to the neutron beam that travels directly from the neutron irradiation port toward the treatment target, the neutron beam scattered by the neutron reflector can also be utilized to easily control the irradiation range of the neutron beam so that the neutron beam appropriately irradiates the lesion of the treatment target.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-section of a neutron capture therapy device according to an embodiment of the present invention. As shown in FIG. 1, this neutron capture therapy device 1 includes a radiation shielding part 4 that surrounds the head including the lesion (treatment site) 3 of the patient 2 who is the treatment target along the outer surface of the patient 2, and a neutron reflector 6 that surrounds the radiation shielding part 4 via a space 5. The lesion 3 is tumor cells located deep in the brain.

[0014] The radiation shielding part 4 has an opening 7 at a position corresponding to the lesion 3 of the head that it surrounds. Further, the radiation shielding part 4 is configured such that the maximum dose applied to the normal tissue around the lesion is smaller than the tolerance dose. Specifically, it is configured to protect tissues with a low tolerance dose, sites where neutron beams are intensively irradiated, regions far from the affected area, and the like.

[0015] That is, the number, position, size, or shape of the opening 7 in the radiation shielding part 4 can be optimized for each patient by calculating the dose distribution imparted to the lesion and normal tissues using Monte Carlo simulation. Further, the opening 7 is provided at a position corresponding to the neutron beam from the neutron irradiation port 8 described later and a position corresponding to the neutron beam from the neutron reflection part 6 according to the position of the lesion 3 of the patient 2.

[0016] Parts other than the opening 7 of the radiation shielding part 4 are formed to have a thickness of several cm using a material such as light water or polyethylene containing lithium fluoride in order to shield thermal and epithermal neutron beams (thermal neutron beams or epithermal neutron beams) 9 and fast neutron beams 10. Since this material has excellent workability, the arrangement (number, position, size, or shape) of the opening 7 can be easily optimized for each patient.

[0017] The radiation shielding part 4 often has a thickness of several cm and can sufficiently shield thermal and epithermal neutron beams 9 and fast neutron beams 10. However, as the thickness increases, the irradiation range of the neutron beam can be more strongly restricted by the opening 7.

[0018] The neutron reflection part 6 is composed of a member that scatters neutron beams. For example, the neutron reflection part 6 is composed of iron, lead, bismuth, etc., which efficiently scatter fast neutron beams 10 and thermal and epithermal neutron beams 9. The thickness of the neutron reflection part 6 is about 10 to 30 cm. However, as the thickness increases, the amount of neutron beam reflected toward the space 5 due to scattering increases, and the irradiation amount of the neutron beam to the lesion 3 can be increased.

[0019] The neutron reflection part 6 has a neutron irradiation port 8 for introducing neutron beams into the space 5 and an opening part 11 for passing through the head of the patient 2 surrounded by the neutron reflection part 6 and arranging it in the space 5. The neutron irradiation port 8 is composed of a collimator 12 for suppressing the diffusion of the introduced neutron beam.

[0020] The collimator 12 is formed of a material such as polyethylene containing lithium fluoride or lead in order to prevent fast neutrons and gamma rays from leaking out from outside the neutron irradiation port 8, and is formed as a plurality of blocks having different shapes and sizes. These blocks have a detachable structure with respect to the neutron reflector 6.

[0021] That is, these blocks are configured such that by selectively attaching and detaching them to and from the neutron reflector 6 as appropriate, the opening area of the neutron irradiation port 8 can be adjusted in several steps. By adjusting the opening area in several steps, not only the irradiation amount of neutron rays to the portion including the lesion 3, but also the ratio of the direct irradiation amount to the portion and the irradiation amount due to reflection from the neutron reflector 6 are adjusted.

[0022] The radiation shielding part 4 is configured such that its shape, the opening area of the neutron irradiation port 8, and the distance from the neutron irradiation port 8 to the lesion 3 to be treated can be independently adjusted. The adjustment of the shape of the radiation shielding part 4 is performed when molding the radiation shielding part 4. The adjustment of the opening area of the neutron irradiation port 8 and the distance to the lesion 3 is performed by selectively attaching and detaching the respective blocks constituting the collimator 12 described above.

[0023] A bed 13 is provided in the radiation shielding part 4 in order to position the head including the lesion 3 in the space 5 surrounded by it through the opening 11. The opening 7 has a size suitable for arranging the head surrounded by the neutron reflector 6 together with the bed 13 on which the patient 2 lies down through the opening 11 into the space 5.

[0024] The bed 13 is configured to be movable in three directions: the longitudinal direction, the vertical direction, and the left - right direction. Thereby, the position of the lesion 3 with respect to the neutron irradiation port 8 can be adjusted. Further, thereby, not only the irradiation amount of neutron rays to the lesion 3, but also the ratio of the irradiation amount of neutron rays directly irradiated from the neutron irradiation port 8 and the irradiation amount of neutron rays irradiated by reflection from the neutron reflector 6 can be adjusted.

[0025] Furthermore, the neutron capture therapy device 1 includes a neutron generator 14 that generates fast neutron beams 10, and a neutron moderator 15 that scatters the fast neutron beams 10 from the neutron generator 14 and efficiently moderates them into thermal and epithermal neutron beams 9. The neutron moderator 15 is composed of fluoride, aluminum, iron, lead, etc.

[0026] In some cases, thin lithium fluoride, lead, etc. may be added to the neutron moderator 15 as a removal filter for removing thermal neutron beams and gamma rays. The neutrons moderated by the neutron moderator 15 are supplied to the collimator 12.

[0027] In this configuration, when performing treatment with the neutron capture therapy device 1, the head including the lesion 3 surrounded by the radiation shielding part 4 of the patient 2 lying on the bed 13 is moved together with the bed 13 toward the inside of the space 5 through the opening 11 and is arranged inside the space 5.

[0028] In this state, when the neutron generator 14 generates fast neutron beams 10, the neutron beams pass through the neutron moderator 15 and the neutron irradiation port 8 formed by the collimator 12, and fill the space 5 surrounded by the neutron reflector 6. During this time, the fast neutron beams 10 change into thermal and epithermal neutron beams 9 suitable for boron neutron capture therapy (BNCT) by repeatedly scattering in the neutron moderator 15 and the neutron reflector 6.

[0029] At this time, a part of the neutron beams from the collimator 12 that are not directly irradiated to the lesion 3 is returned toward the lesion 3 by the neutron reflector 6. Thereby, a sufficient irradiation dose to the lesion 3 is ensured. That is, the thermal and epithermal neutron beams 9 are irradiated to the lesion 3 of the head of the patient 2 arranged in the space 5 from a plurality of directions corresponding to the opening 7 of the radiation shielding part 4 through the opening 7.

[0030] At this time, the irradiation range is limited by the opening 7 of the radiation shielding part 4. That is, not only the neutron rays directly arriving from the neutron irradiation port 8 but also the irradiation range of the neutron rays arriving after being reflected by the neutron reflection part 6 is limited. Thereby, the maximum dose imparted to the normal tissue around the lesion 3 of the patient 2 is made equal to or less than the tolerance dose, and while protecting the normal tissue with a low tolerance dose, the thermal / epithermal neutron rays 9 are intensively irradiated to the lesion 3.

[0031] The thermal / epithermal neutron rays 9 irradiated to the lesion 3 collide with the boron agent accumulated in the tumor cells in the lesion 3 of the patient 2 by injection in advance, and generate alpha particles and lithium nuclei by a nuclear reaction. By this radiation, the tumor cells are selectively pinpointed and destroyed, killed, and a therapeutic effect on the lesion 3 is obtained.

[0032] As described above, according to the present embodiment, since the above-described radiation shielding part 4 and the neutron reflection part 6 are provided, according to the position, size, and shape of the lesion 3 of the patient 2, the number, position, size, and shape of the openings 7 of the radiation shielding part 4 are selected, and the irradiation range of the neutron rays can be appropriately controlled through the openings 7, and the neutron rays can be irradiated to the lesion 3.

[0033] In addition, since the maximum value of the dose imparted to the normal tissue per unit time can be reduced by the radiation shielding part 4, the total dose of the dose that can be imparted to the lesion 3 can be increased. Therefore, tumors showing high radiation resistance that were not targets conventionally can also be newly targeted for treatment.

[0034] In addition, as the material of the radiation shielding part 4, a material that is easy to process and lightweight can be selected, so that the radiation shielding part 4 optimized for each patient 2 can be easily molded, and the irradiation range can be controlled with higher accuracy.

[0035] In addition, since the shape of the radiation shielding part 4, the opening area of the neutron irradiation port 8, and the distance from the neutron irradiation port 8 to the lesion 3 can be independently adjusted, the irradiation range can be controlled with even higher accuracy.

[0036] In addition, the opening 7 of the radiation shielding part 4 is provided at a position corresponding to the direct neutron beam from the neutron irradiation port 8 and a position corresponding to the indirect neutron beam from the neutron reflection part according to the position of the lesion 3 in the patient 2. Therefore, the irradiation dose to the lesion 3 can effectively utilize both the direct and indirect neutron beams while adjusting the ratio of the direct and indirect neutron beams.

[0037] In addition, the number, position, size, or shape of the opening 7 in the radiation shielding part 4 is optimized for each patient 2 by calculating the dose distribution imparted to the lesion 3 and normal tissues of the patient 2 using Monte Carlo simulation. Therefore, the irradiation range can be controlled with high accuracy for each patient 2.

[0038] FIG. 2 shows a modified example of the radiation shielding part 4. As shown in FIG. 2, the radiation shielding part 4 may be configured by laminating shielding layers 16, 17, and 18 each composed of a plurality of different shielding materials. That is, in addition to the shielding layer 16 for thermal out neutrons and fast neutrons 10, the radiation shielding part 4 can be provided with a shielding layer 17 for thermal neutrons and a shielding layer 18 for gamma rays, and these can be stacked to form a layer structure.

[0039] In this case, the shielding layers 16 and 17 each have openings 7a and 7b. However, since the parts that need to be shielded by the shielding layers 16 and 17 are different depending on the position of the lesion 3 and the like, the positions of the openings 7a and 7b of the shielding layers 16 and 17 do not necessarily coincide. For example, the shielding layer 17 exists at the opening 7a of the shielding layer 16, and the shielding layer 16 exists at the opening 7b of the shielding layer 17.

[0040] In this case, the opening 7a of the shielding layer 16 may be provided at a position corresponding to the direct neutron beam from the neutron irradiation port 8 and a position corresponding to the indirect neutron beam from the neutron reflection part 6 according to the position of the lesion 3.

[0041] According to this, even when tissues with a low tolerance dose are included in the irradiation field, they can be newly targeted for treatment. For example, even in cases such as tumors deep in the brain close to the lens or oral mucosa, tumors that have spread extensively with invasiveness or dissemination, or cases where the whole body, like a small pet animal, enters the irradiation field, depending on the position, size, etc. of the tumor, by setting the thickness of the shielding layers 16, 17, 18 and the position, size, shape, etc. of the openings 7a, 7b, it can be targeted for treatment.

[0042] FIG. 3 shows a modified example of the neutron generator 14, the neutron moderator 15, and the collimator 12. As shown in FIG. 3, the periphery of the neutron generator 14 and the neutron moderator 15 may be surrounded by a neutron reflector 19 such as lead. According to this, the neutron beam from the neutron generator 14 can be efficiently guided to the neutron irradiation port 8.

[0043] Furthermore, the periphery of the collimator 12 and the neutron moderator 15 may be surrounded by a radiation shielding material 20 such as polyethylene or lead. According to this, exposure due to leakage of neutron rays and gamma rays can be prevented.

[0044] Note that the present invention is not limited to the above-described embodiments and can be implemented with appropriate modifications. For example, the treatment target is not limited to the patient 2 and may be an animal. Also, the neutron irradiation port 8 may be provided at two or more locations of the neutron reflection part 6.

Explanation of reference numerals

[0045] 1... Neutron capture therapy device, 2... Patient, 3... Lesion, 4... Radiation shielding part, 5... Space, 6... Neutron reflection part, 7, 7a, 7b... Opening, 8... Neutron irradiation port, 9... Thermal and epithermal neutron rays, 10... Fast neutron rays, 11... Open part, 12... Collimator, 13... Bed, 14... Neutron generator, 15... Neutron moderator, 16, 17, 18... Shielding layer, 19... Neutron reflector, 20... Radiation shielding material.

Claims

1. A radiation shielding part that surrounds a part including a lesion to be treated along the outer surface of the treatment target and has an opening at a position corresponding to the lesion, A neutron reflector that is composed of a member for scattering neutron rays and surrounds the radiation shielding part through a space. The neutron reflector has a neutron irradiation port for introducing neutron rays into the space and an opening part for passing through a part including the lesion surrounded by the radiation shielding part in the treatment target and arranging it in the space. A neutron capture therapy apparatus characterized by this.

2. The neutron capture therapy apparatus according to claim 1, wherein the shape of the radiation shielding part, the opening area of the neutron irradiation port, and the distance from the neutron irradiation port to the lesion can be independently adjusted.

3. The radiation shielding part is configured by laminating a plurality of shielding layers each formed of a different plurality of shielding materials, the opening of the radiation shielding part is provided for each shielding layer, and the positions of the openings do not necessarily coincide between the shielding layers. A neutron capture therapy apparatus according to claim 1, characterized by this.

4. The radiation shielding part includes, as the plurality of shielding layers, a first shielding layer that shields thermal external neutron rays and fast neutron rays, a second shielding layer that shields thermal neutron rays, and a third shielding layer that shields gamma rays. A neutron capture therapy apparatus according to claim 3, characterized by this.

5. The opening is provided in the first shielding layer and the second shielding layer, the second shielding layer exists in the opening of the first shielding layer, the first shielding layer exists in the opening of the second shielding layer, and the opening of the first shielding layer is provided at a position corresponding to a direct neutron ray from the neutron irradiation port and a position corresponding to an indirect neutron ray from the neutron reflector according to the position of the lesion in the treatment target. A neutron capture therapy apparatus according to claim 4, characterized by this.

6. The neutron irradiation port is provided at two or more positions on the neutron reflector. A neutron capture therapy apparatus according to claim 1, characterized by this.

7. The opening of the radiation shielding part is provided at a position corresponding to a direct neutron ray from the neutron irradiation port and a position corresponding to an indirect neutron ray from the neutron reflector according to the position of the lesion in the treatment target. A neutron capture therapy apparatus according to claim 1, characterized by this.

8. The opening in the radiation shielding portion is optimized for each treatment target by calculating the dose distribution imparted to the lesion and normal tissue of the treatment target using Monte Carlo simulation, in terms of its number, position, size, or shape. The neutron capture therapy apparatus according to claim 1, characterized in that.

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