Maze-type neutron beam shaping device for neutron capture therapy

Abstract

The present invention relates to a maze-type neutron beam forming device for neutron capture therapy, which can maintain neutron flux while dramatically reducing gamma ray flux by varying the path of the beam forming device like a maze and providing reflecting surfaces at various angles from the front-to-rear axis.

Description

[Technical Field]

[0001] The present invention relates to a labyrinth-type neutron beam shaping device for medical boron neutron capture therapy. [Background technology]

[0002] Boron neutron capture therapy is a treatment method in which a boron-containing substance is injected into cancer cells to allow the boron to accumulate in the cells, and then neutrons are irradiated to cause nuclear fission within the cancer cells, releasing particles resulting from the fission and killing the cancer cells. Boron neutron capture therapy is known to be effective for treating brain tumors, head and neck cancer, and skin cancer, and is attracting attention as a next-generation cancer treatment method because it can minimize side effects caused by radiation exposure in normal cells compared to conventional radiation therapy methods.

[0003] Neutrons generated by boron neutron capture therapy devices are classified according to energy into fast neutrons with an energy of 10 keV or more, epithermal neutrons with an energy of 0.5 eV to 10 keV, and thermal neutrons with an energy of 0.5 eV or less. Of these, fast neutrons have high penetrating power and cause radioactive side effects in the tissue surrounding the tumor, while low-energy thermal neutrons cause radioactive side effects in the skin, making them unsuitable for therapeutic purposes.

[0004] US Patent No. US10124192 discloses a boron neutron capture therapy device. However, in this prior art, fast neutron filters, gamma ray filters, etc. are used in the beam direction to control unnecessary doses of radiation generated during neutron capture therapy. However, the use of such filters has the disadvantage of reducing the flux of epithermal neutrons required for treatment. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a beam shaping device that solves the problems of beam shaping devices used in conventional boron neutron capture therapy devices, minimizes the reduction in neutron flux, and minimizes dose contamination caused by gamma rays and fast neutrons. [Means for solving the problem]

[0006] As a means for solving the above problem, there is provided a labyrinth-type neutron beam forming device for neutron capture therapy, which includes a neutron beam forming module that is arranged along the direction of neutron movement and is configured to reduce gamma ray and fast neutron flux and minimize reduction in epithermal neutron flux, and a reflector that is arranged surrounding the neutron beam shaping module, wherein the neutron beam shaping module is arranged along an axis extending from the front to the rear and is arranged along a path at least part of which is different from the axis.

[0007] On the other hand, the neutron beam shaping module is configured to be able to shield fast neutrons and is configured to include a first shielding section arranged adjacent to the neutron generating target, a moderator provided at the rear end of the first shielding section and configured to be able to reduce the energy of neutrons, and a second shielding section provided at the rear end of the moderator and configured to be able to shield thermal neutrons and gamma rays.

[0008] Also, an inclined surface is formed at the boundary of at least one of the first shielding portion, the moderator, and the second shielding portion.

[0009] Furthermore, the reflecting surfaces provided on the left and right sides of the neutron beam shaping module are provided asymmetrically with respect to each other.

[0010] Meanwhile, the inclined surface is formed at the boundary surface between the moderator and the reflector, and is configured to have at least two different angles.

[0011] On the other hand, the two different inclined surfaces are arranged at a positive angle and a negative angle from a plane parallel to the direction of movement of the particle beam.

[0012] The interface between the moderator and the reflector includes a reflecting surface that is angled parallel to the direction of irradiation of the particle beam.

[0013] Meanwhile, the first and second shielding portions are provided parallel to each other.

[0014] Moreover, the centers of the first and second shielding parts are located on the irradiation path of the particle beam.

[0015] On the other hand, the centers of the first and second shielding parts are located at points different from the irradiation path of the particle beam.

[0016] The first and second shielding portions are provided at different angles.

[0017] On the other hand, the first shielding agent is arranged so as not to be perpendicular to the irradiation direction of the particle beam. [Effects of the Invention]

[0018] The maze-type neutron beam forming device for neutron capture therapy according to the present invention has the effect of minimizing the dose contamination value (physical dose value / epithermal neutron value) in BNCT recommended by IAEA-TECDOC-1223. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a conceptual diagram of a neutron capture therapy device. [Figure 2] 1 is a conceptual diagram showing a beam shaping device and a target according to the present invention; [Figure 3] 10 shows the results of computer simulations of neutrons in a conventional beam shaping device and in a beam shaping device according to the present invention. [Figure 4a] The performance of the neutron shaping device is shown at the moderator angle of the beam shaping device. [Figure 4b] The performance of the neutron shaping device is shown at the moderator angle of the beam shaping device. [Figure 4c] The performance of the neutron shaping device is shown at the moderator angle of the beam shaping device. [Figure 4d] The performance of the neutron shaping device is shown at the moderator angle of the beam shaping device. [Figure 5] 1 is a cross-sectional view of a maze-type neutron beam forming device for neutron capture therapy, which is a first embodiment of the present invention. [Figure 6] FIG. 2 is a cross-sectional view of a maze-type neutron beam shaping device for neutron capture therapy, which is a second embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view of a labyrinth-type neutron beam shaping device for neutron capture therapy, which is a third embodiment of the present invention. [Figure 8] FIG. 10 is a cross-sectional view of a labyrinth-type neutron beam shaping device for neutron capture therapy, which is a fourth embodiment of the present invention. [Figure 9] FIG. 10 is a cross-sectional view of a maze-type neutron beam shaping device for neutron capture therapy according to a fifth embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view of a labyrinth-type neutron beam shaping device for neutron capture therapy according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a maze-type neutron beam shaping device for neutron capture therapy according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the embodiment, the names of the components may be referred to by other names in the art. However, if there is functional similarity or identity between the components, modified embodiments may be considered equivalent configurations. Furthermore, reference numerals are used for convenience of description. However, the illustrations in the drawings in which these reference numerals are used do not limit the scope of the components within the drawings. Similarly, if there is functional similarity or identity between the components in the drawings, modified embodiments may be considered equivalent configurations. Furthermore, if a component is deemed to be included in the embodiments based on the level of ordinary skill in the art, its description will be omitted.

[0021] Hereinafter, the terms "forward" and "rearward" will be used to describe directions. "Forward" refers to the direction in which the beam shaping device looks at the accelerator, and "rearward" refers to the direction in which the neutrons look at the patient, where the neutrons will ultimately arrive. According to these directions, neutrons are irradiated from the front side to the beam shaping device, pass through the beam shaping device, and exit rearward.

[0022] FIG. 1 is a conceptual diagram of a neutron capture therapy device.

[0023] As shown in the figure, in boron neutron capture therapy, a neutron generator that generates neutrons includes a particle accelerator 1 such as a cyclotron, linear accelerator, or electrostatic accelerator, an electrostatic accelerator 2 that accelerates the proton beam emitted at high speed from the particle accelerator 1, and a chamber 3 that is installed on the beam path of the proton beam and has a target that collides with the beam to emit neutrons from within it.

[0024] Neutrons generated in the target can be divided into fast neutrons with an energy of 10 keV or more, epithermal neutrons between 0.5 eV and 10 keV, and thermal neutrons with an energy of 0.5 eV or less, and the beam shaping device 100 is configured to convert fast neutrons into epithermal neutrons suitable for treatment.

[0025] The neutron beam that has passed through the beam shaping device 100 is configured to pass through a desired region by a collimator, and is finally irradiated onto the affected area of the patient 3, causing a nuclear reaction.

[0026] FIG. 2 is a conceptual diagram showing a beam shaping device and a target according to the present invention.

[0027] Referring to FIG. 2, during neutron capture therapy, a particle beam is irradiated onto a target 200, causing a nuclear reaction and generating gamma rays (γ). The generated neutrons and gamma rays are emitted backward at various angles.

[0028] As the neutrons pass through the ion beam, they are slowed down to an epithermal neutron region with appropriate energy, filtered, and then irradiated onto the patient.

[0029] Meanwhile, unlike conventional beam shaping devices 100 that are arranged linearly along the direction in which the particle beam is irradiated, i.e., the front-to-back direction, the beam shaping device 100 according to the present invention is configured to minimize the reduction in neutron flux and shield gamma rays by adjusting the angle of the beam shaping device 100 and the angle of the reflecting surface.

[0030] The beam shaping device 100 according to the present invention can be configured to include a beam shaping module 110 that determines a region through which neutrons pass, and a reflector that is provided surrounding the side of the beam shaping module 110.

[0031] In one embodiment according to the present invention, the beam shaping modules 110 may be arranged along an axis extending from the front to the rear, with at least a portion of the beam shaping modules 110 arranged along a path different from the axis.

[0032] The beam shaping module 110 may include a first shielding portion 111, a moderator 112, and a second shielding portion 113. The first shielding portion 111, the moderator 112, and the second shielding portion 113 may be arranged in order from the front to the rear.

[0033] The first shielding portion 111 is configured to be able to shield fast neutrons. The first shielding portion 111 may be configured to include, for example, iron or aluminum.

[0034] The moderator 112 is configured to be able to slow down the neutrons that have passed through the first shielding portion 111 to the epithermal neutron region. The moderator 112 may be configured to contain fluorine, and may be configured to contain materials such as MgF2, CaF2, PbF2, AlF3, PTFE [(CF2)n], and Fludental (AlF3: 69%, Al: 30%, LiF: 1%).

[0035] The second shielding section 113 is configured to block thermal neutrons and also block gamma rays, and may include a thermal neutron filter and a gamma filter.

[0036] The thermal neutron filter can be configured to prevent thermal neutrons from passing through. For example, the thermal neutron filter can be configured to include cadmium (Cd) or boron, and has a density of 8.65 g / cm. 3The gamma filter may be configured to have a density of 9.75 g / cm. Meanwhile, the gamma filter may be configured to prevent gamma rays generated during filtering or deceleration of neutrons from leaking to the collimator side. For example, the gamma filter may be configured to contain bismuth, and have a density of 9.75 g / cm. 3 The density of the granular material can be configured to be 0.05 to 0.15.

[0037] The reflector 120 is configured to shield and prevent gamma rays and neutrons from being emitted to unintended areas. The reflector is configured to surround the upper and lower surfaces and both side surfaces of the beam shaping module 110. The reflector 120 may be made of, for example, lead or nickel.

[0038] FIG. 3 shows the results of a computer simulation of neutrons in a conventional beam shaping device and in a beam shaping device according to the present invention.

[0039] Referring to Figure 3, which shows the neutron iso-flux distribution, a simulation result using Monte Carlo N-Particle code (MCNP, v6.2), it can be seen that when an inclined neutron shaping device is used, the neutron direction can be guided to the outlet side, i.e., the neutron flux can be maintained.

[0040] 4a, 4b, 4c, and 4d show the performance of the neutron beam shaper as a function of the moderator angle of the beam shaper.

[0041] Figure 4a shows the fluence of neutrons by energy at the exit of the neutron shaping device depending on the moderator angle. The fluence of epithermal neutrons was highest when the angle between the beam shaping module and the longitudinal axis (moderator angle) was around 10 degrees, and it can be seen that the epithermal neutron fluence decreased at angles above that.

[0042] Referring to FIG. 4b, it can be seen that the epithermal ratio at the exit of the neutron beam shaping device according to the present invention is maximized.

[0043] Figure 4c shows the physical dose (Gy) of fast neutrons and gamma rays depending on the tilt angle of the neutron beam shaping device. It can be seen that the physical dose (Gy) of gamma rays decreases as the tilt angle of the neutron beam shaping module from the front-to-back axis increases.

[0044] Figure 4d shows dose contamination as defined by the IAEA. Dose contamination is the physical dose (Gy) from fast neutrons and gamma rays divided by the epithermal neutron flux at the outlet. When the angle (moderator angle) between the beam shaping module and the longitudinal axis was between 0 and 40 degrees, the dose contamination maintained a constant level, but it tended to increase after 40 degrees. This is because, as shown in Figure 4c, as the angle (moderator angle) of the beam shaping module from the longitudinal axis increased, the physical dose (Gy) decreased, but the epithermal neutron flux also decreased, resulting in an increase in dose contamination.

[0045] As a result, the epithermal neutron ratio can be maintained at an appropriate level when the angle (moderator angle) between the beam shaping module and the front-to-back axis is within 0 to 40 degrees, and at this time, gamma ray shielding is also performed appropriately, allowing for the maintenance of low dose contamination.

[0046] Referring to Figures 3 and 4, when the path of the beam shaping module is changed as in the embodiment of the present invention, it is possible to guide the neutrons required for treatment to the exit of the neutron shaping device while minimizing the dose contamination value due to epithermal neutron flux, gamma rays, and fast neutrons, which change depending on the angle.

[0047] Hereinafter, modified examples of the beam shaping device according to the present invention will be described in detail with reference to Figures 5 to 10. For convenience of explanation, Figures 5 to 10 conceptually illustrate the state in which the target and the beam shaping device are cut along a plane parallel to the horizontal.

[0048] FIG. 5 is a cross-sectional view of a labyrinth-type neutron beam forming device for neutron capture therapy, which is a first embodiment of the present invention.

[0049] 5, in the maze-type neutron beam shaping device for neutron capture therapy according to the first embodiment of the present invention, the first shielding unit 111 and the second shielding unit 113 can be arranged parallel to each other or can be arranged offset from each other. Meanwhile, the moderator 112 is formed by extending at a certain angle from the front-rear axis (x1, the same as the irradiation path of the particle beam). In this case, the second shielding unit 113 can be positioned so that the front-rear axis (x1) does not protrude to the outside.

[0050] FIG. 6 is a cross-sectional view of a labyrinth-type neutron beam forming device for neutron capture therapy, which is a second embodiment of the present invention.

[0051] Referring to FIG. 6, unlike the first embodiment, the moderator 112 may be divided into a first region, a second region, and a third region. The first and third regions may be arranged parallel to the longitudinal axis (x1). Meanwhile, the second region may be arranged at a predetermined angle from the longitudinal axis (x1). In this case, the reflective surface formed at the boundary between the reflector 120 and the beam shaping module 110 may be arranged at two angles. That is, it may include a reflective surface parallel to the longitudinal axis and a reflective surface at a predetermined angle to the longitudinal axis. In this embodiment, the second shielding portion 113 may also be provided at a position through which the longitudinal axis can pass.

[0052] FIG. 7 is a cross-sectional view of a labyrinth-type neutron beam forming device for neutron capture therapy, which is a third embodiment of the present invention.

[0053] Referring to FIG. 7, unlike the second embodiment, the first shielding portion 111 and the second shielding portion 113 are arranged along the longitudinal axis (x1), and the interior of the moderator 112 can be configured to extend along three axes.

[0054] The moderator 112 may be composed of a first region extending along an axis (x2) that slopes from a point connected to the first shielding part 111, a second region extending along an axis (x3) parallel to the longitudinal axis (x1), and a third region extending along an axis (x4) that extends back toward the longitudinal axis. In this case, the reflecting surface of the reflector 120 may have an inclined surface inclined at a positive angle and an inclined surface inclined at a negative angle based on a plane parallel to the longitudinal direction.

[0055] FIG. 8 is a cross-sectional view of a labyrinth-type neutron beam forming device for neutron capture therapy, which is a fourth embodiment of the present invention.

[0056] 8, in the fourth embodiment, the beam shaping device is configured in a diamond shape, and the first shielding part 111 may be provided at a predetermined angle to the longitudinal axis (x1) rather than perpendicular thereto. In this case, the second shielding part 113 may be provided at a position where the longitudinal axis (x1) passes. Meanwhile, the first shielding part 111, the moderator 112, and the second shielding part 113 of the beam shaping module 110 may be linearly arranged along an axis (x2) that is formed at a predetermined angle to the longitudinal axis (x1). In this case, an inclined surface may be formed at the boundary between the first shielding part 111, the moderator 112, and the second shielding part 113.

[0057] FIG. 9 is a cross-sectional view of a labyrinth-type neutron beam forming device for neutron capture therapy, which is a fifth embodiment of the present invention.

[0058] 9, the fifth embodiment may be divided into three regions (S1, S2, S3) similar to the configuration of the moderator 112 in FIG. 2. Meanwhile, the first and second shielding portions 111 and 113 may be parallel to each other and not perpendicular to the longitudinal axis (x1). In this case, the beam shaping module 110 may be arranged with its path adjusted along five axes (x2, x3, x4, x5, x6). In this case, an inclined surface may be formed at the boundary of the second region (S2) of the first and second shielding portions 111, 113, and moderator 112.

[0059] FIG. 10 is a cross-sectional view of a labyrinth-type neutron beam forming device for neutron capture therapy, which is a sixth embodiment of the present invention.

[0060] In the sixth embodiment, unlike the previous embodiments, the first and second shielding portions 111 and 113 may be arranged not parallel to each other, and the beam shaping device may be formed in a trapezoidal shape overall.

[0061] In this embodiment, the first shielding portion 111 is disposed along an axis (x2) inclined relative to the longitudinal axis (x1), and the moderator 112 may be extended in sections along three axes. In this case, the moderator 112 may be configured similarly to the third embodiment, in which the moderator 112 is divided into three regions (S1, S2, S3). Also, unlike the third embodiment, the first shielding portion 111 may be disposed at an angle adjusted clockwise from the longitudinal axis (x1) in FIG. 10, and the second shielding portion 113 may be disposed at an angle adjusted counterclockwise from the longitudinal axis (x1).

[0062] As described above, the maze-type neutron beam shaping device for neutron capture therapy according to the present invention has a path that varies like a maze and the angle of the reflecting surface is set at various angles from the front-to-back axis, thereby maintaining the neutron flux while dramatically reducing the gamma ray flux. [Explanation of symbols]

[0063] 1 particle accelerator 2. Electrostatic Accelerator 3 patients 100 Beam shaping device 110 Beamforming Module 111 First shielding part 112 Moderator 113 Second shielding section 120 Reflector 200 targets

Claims

1. a neutron beam shaping module arranged along the direction of neutron movement and configured to reduce the gamma ray and fast neutron flux and minimize the reduction of epithermal neutron flux; and a reflector disposed around the neutron beam shaping module; the neutron beam shaping module is arranged along an axis extending from the front to the rear, and at least a portion of the neutron beam shaping module is arranged along a path different from the axis; The neutron beam shaping module includes: a first shielding portion configured to be able to shield the fast neutrons and disposed adjacent to the neutron generating target; a moderator provided at the rear end of the first shielding portion and configured to reduce the energy of neutrons; and a second shielding portion provided at the rear end of the moderator and configured to be able to block thermal neutrons and gamma rays; an inclined surface is formed at a boundary between at least one of the first shielding portion, the moderator, and the second shielding portion; A labyrinth-type neutron beam forming device for neutron capture therapy, wherein the reflecting surfaces provided on the left and right sides of the neutron beam forming module are provided asymmetrically with respect to the axis.

2. The inclined surface is formed on the interface between the moderator and the reflector, 2. The labyrinth-type neutron beam shaping device for neutron capture therapy according to claim 1, having at least two mutually different angles with respect to said axis.

3. 3. The labyrinth-type neutron beam shaping device for neutron capture therapy according to claim 2, wherein the at least two inclined surfaces having different angles from each other are arranged at positive and negative angles from a plane parallel to the moving direction of the particle beam.

4. 4. The labyrinth-type neutron beam shaping device for neutron capture therapy according to claim 3, wherein an interface between the moderator and the reflector includes a reflecting surface provided at an angle parallel to an irradiation direction of the particle beam.

5. 2. The labyrinth-type neutron beam shaping device for neutron capture therapy according to claim 1, wherein the first shielding portion and the second shielding portion are provided in parallel to each other.

6. 6. The labyrinth-type neutron beam shaping device for neutron capture therapy according to claim 5, wherein centers of the first shielding portion and the second shielding portion are located on an irradiation path of a particle beam.

7. 6. The labyrinth-type neutron beam shaping device for neutron capture therapy according to claim 5, wherein centers of the first shielding portion and the second shielding portion are located at points different from an irradiation path of the particle beam.

8. The labyrinth-type neutron beam shaping device for neutron capture therapy according to claim 1 , wherein the first shielding portion and the second shielding portion are provided along different angles relative to the axis.

9. 2. The labyrinth-type neutron beam shaping device for neutron capture therapy according to claim 1, wherein the first shielding portion is arranged so as not to be perpendicular to the irradiation direction of the particle beam.

Images