Multi-layer shielding bin for beam shaping assembly

Abstract

The invention provides a multi-layer shielding bin for a beam shaping assembly, and relates to the technical field of radiation medical treatment. A multilayer shielding bin for a beam shaping assembly comprises a first side cover plate and at least two second side cover plates, and the first side cover plate is provided with a beam outlet; the at least two second side cover plates and the first side cover plate jointly form an accommodating cavity, and the accommodating cavity is used for accommodating the beam shaping assembly; wherein the second side cover plate comprises a fast neutron moderation layer, an intermediate energy neutron moderation layer, a thermal neutron absorption layer and a gamma shielding layer which are sequentially stacked in the direction from the interior of the accommodating cavity to the exterior of the accommodating cavity; the fast neutron moderation layer is used for performing primary moderation on source neutrons to obtain intermediate energy neutrons; the intermediate energy neutron moderation layer is used for performing secondary moderation on the intermediate energy neutrons to obtain thermal neutrons; the thermal neutron absorption layer is used for absorbing the thermal neutrons; and the gamma shielding layer is used for shielding generated gamma rays.

Description

Technical Field

[0001] The present disclosure relates to the field of radiation medical technology, and more particularly, to a multi-layer shielding chamber for a beam shaping component. Background Art

[0002] Boron Neutron Capture Therapy (BNCT) is a new type of radiotherapy that uses the ability of boron to produce radioactive reactions under the action of neutrons to precisely kill cancer cells. This method is particularly suitable for treating brain tumors such as malignant meningioma, melanoma, and head and neck tumors.

[0003] The key components of the BNCT treatment device include the neutron source, beam shaping assembly (BSA) and shielding device.

[0004] Compared with traditional radiotherapy methods, BNCT has several characteristics: long single treatment time, high beam power, and strong neutron flux, which may cause transient radiation, as well as activation of structural components and air, generating radioactive substances, so they need to be effectively shielded.

[0005] Although the traditional shielding device can effectively slow down fast neutrons and reduce the neutron and gamma ray dose around the device, this method is too large and heavy, has low neutron slowing absorption efficiency, and does not consider the induced radioactivity generated by the treatment outlet. Summary of the invention

[0006] In view of this, the present disclosure provides a multi-layer shielding chamber for a beam shaping component, comprising: a first side cover plate and at least two second side cover plates, the first side cover plate being provided with a beam outlet; the at least two second side cover plates and the first side cover plate together form a accommodating cavity, the accommodating cavity being used to accommodate the beam shaping component; wherein, along the direction from the inside of the accommodating cavity to the outside of the cavity, the second side cover plate comprises a fast neutron moderation layer, a medium energy neutron moderation layer, a thermal neutron absorption layer and a γ shielding layer stacked in sequence; the fast neutron moderation layer is used to perform primary moderation on source neutrons to obtain medium energy neutrons; the medium energy neutron moderation layer is used to perform secondary moderation on medium energy neutrons to obtain thermal neutrons; the thermal neutron absorption layer is used to absorb thermal neutrons; and the γ shielding layer is used to shield the generated γ rays.

[0007] According to an embodiment of the present disclosure, along the direction from the inside of the accommodating cavity to the outside of the cavity, the first side cover plate includes a thermal neutron absorption layer for absorbing thermal neutrons and a γ shielding layer for shielding the generated γ rays.

[0008] According to an embodiment of the present disclosure, the thickness of the fast neutron moderator layer is 5-15 cm, the thickness of the medium energy neutron moderator layer is 10-30 cm, the thickness of the thermal neutron absorption layer is 10-20 cm, and the thickness of the gamma shielding layer is 5-10 cm.

[0009] According to an embodiment of the present disclosure, the material of the fast neutron moderator layer includes lead or tungsten.

[0010] According to an embodiment of the present disclosure, the material of the medium energy neutron moderator layer includes polyethylene, paraffin or aluminum.

[0011] According to an embodiment of the present disclosure, the material of the thermal neutron absorption layer includes boron-containing polyethylene; and the material of the gamma shielding layer includes lead.

[0012] According to an embodiment of the present disclosure, a lead curtain is further included, which is arranged on the first side cover plate and is used to cover the beam outlet.

[0013] According to an embodiment of the present disclosure, the lead curtain is arranged on a bracket, and the rise and fall of the lead curtain is regulated by controlling the reel through a transmission motor.

[0014] According to an embodiment of the present disclosure, it also includes: a lifting ring and a pulling rod, which are arranged on one of the second side cover plates and are used to replace the target body in the shielding chamber.

[0015] According to an embodiment of the present disclosure, the pull rod passes through the second side cover plate, and a base is provided inside the second side cover plate for fixing the pull rod. A lifting ring is fixed on the pull rod outside the second side cover plate, and the lifting ring is controlled by a robotic arm to move the second side cover plate.

[0016] According to the embodiments of the present disclosure, a technical means is adopted to prepare the second side plate by sequentially stacking a fast neutron moderating layer, a medium energy neutron moderating layer, a thermal neutron absorption layer and a gamma shielding layer, which effectively improves the neutron moderation absorption efficiency and reduces the volume and weight of the shielding device.

[0017] According to the embodiments of the present disclosure, a lead curtain is used to cover the beam outlet after the treatment, which can effectively shield the generated induced radioactivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0019] Figure 1 A schematic diagram of a shielding chamber according to an embodiment of the present disclosure is schematically shown;

[0020] Figure 2 Schematically shows a front view according to an embodiment of the present disclosure;

[0021] Figure 3Schematically shows a rear view according to an embodiment of the present disclosure;

[0022] Figure 4 A cross-sectional view at position AA in a front view according to an embodiment of the present disclosure is schematically shown;

[0023] Figure 5 A cross-sectional view at position BB in a front view according to an embodiment of the present disclosure is schematically shown;

[0024] Figure 6 A cross-sectional view at the CC position in the front view according to an embodiment of the present disclosure is schematically shown;

[0025] Figure 7 Schematically shows a flow chart of using the lead curtain according to an embodiment of the present disclosure;

[0026] Figure 8 The Monte Carlo simulation calculation of the ambient dose equivalent rate of the BSA unshielded device is schematically shown;

[0027] Fig. 9 The Monte Carlo simulation calculation of the ambient dose equivalent rate after the shielding chamber of the present disclosure is used to shield the BSA is schematically shown;

[0028] Fig.10 The Monte Carlo simulation calculation of the induced dose rate 5 minutes after the beam irradiation ends according to an embodiment of the present disclosure is schematically shown;

[0029] Fig.11 The Monte Carlo simulation calculation of the induced dose rate of the traditional shielding lead-free curtain 5 minutes after the beam irradiation ends is shown schematically;

[0030] Description of reference numerals:

[0031] 11. Bracket; 12. Reel; 13. Drive motor; 14. Lead curtain; 21. Side cover of fast neutron moderator; 22. Rear cover of fast neutron moderator; 31. Side cover of medium energy neutron moderator; 32. Rear cover of medium energy neutron moderator; 41. Side cover of thermal neutron absorption layer; 42. Rear cover of thermal neutron absorption layer; 51. Side cover of gamma shielding layer; 52. Rear cover of gamma shielding layer; 61. Front cover of thermal neutron absorption layer; 62. Front cover of gamma shielding layer; 71. Lifting ring; 72. Pull rod. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0033] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0034] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0035] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0036] Boron neutron capture therapy (BNCT) is a new type of radiotherapy that can precisely kill cancer cells. However, unlike conventional radiotherapy, BNCT has a long single treatment time.

[0037] The beam shaping assembly (BSA) is a key component in the BNCT device, which is used to adjust the shape and intensity of the neutron beam. During the BNCT treatment process, due to the characteristics of the neutron beam, namely the high beam power and strong neutron flow, the traditional shielding material composed of boron-containing polyethylene and lead can effectively slow down fast neutrons, but it is large in size and weight, and the slowing-down efficiency is not high; and the induced radioactivity generated at the treatment exit is not considered to harm the device and medical staff.

[0038] Based on this, the present disclosure provides a multi-layer shielding chamber for a beam shaping component, wherein a first side cover plate and a second side cover plate are designed to form a receiving cavity, wherein the second side cover plate includes a fast neutron moderation layer, a medium energy neutron moderation layer, a thermal neutron absorption layer and a γ shielding layer stacked in sequence, and the scattered source neutrons are initially moderated by the added fast neutron moderation layer, and the medium energy neutron moderation layer is used for secondary moderation, which effectively reduces the instantaneous radiation of neutrons and improves the neutron moderation absorption efficiency, wherein the fast neutrons are mainly decelerated by inelastic collision with the nuclei of matter, and the energy is reduced to 1MeV-2MeV, and as the neutron energy is reduced to below 1MeV, elastic scattering will dominate the neutron moderation, and when the neutron energy is reduced to the thermal neutron energy zone, a radiation capture reaction will occur. At the same time, a lead curtain is designed at the treatment outlet, which effectively realizes the shielding of the induced radioactivity of BSA after the radiation is completed, reducing the damage to medical personnel and equipment.

[0039] Figure 1 Schematic diagram of a shielding chamber according to an embodiment of the present disclosure

[0040] Figure 2 Schematically shows a front view according to an embodiment of the present disclosure;

[0041] Figure 3 Schematically shows a rear view according to an embodiment of the present disclosure;

[0042] Figure 4 A cross-sectional view at position AA in a front view according to an embodiment of the present disclosure is schematically shown;

[0043] Figure 5 A cross-sectional view at position BB in a front view according to an embodiment of the present disclosure is schematically shown;

[0044] Figure 6 A cross-sectional view at position CC in a front view according to an embodiment of the present disclosure is schematically shown.

[0045] like Figure 1-6 As shown, the present disclosure provides a multi-layer shielding chamber for a beam shaping component, comprising: a first side cover plate and at least two second side cover plates, the first side cover plate is provided with a beam outlet; the at least two second side cover plates and the first side cover plate together form a accommodating cavity, the accommodating cavity is used to accommodate the beam shaping component; wherein, along the cavity inside the accommodating cavity pointing to the outside of the cavity, the second side cover plate comprises a fast neutron moderation layer, a medium energy neutron moderation layer, a thermal neutron absorption layer and a γ shielding layer stacked in sequence; the fast neutron moderation layer is used to perform primary moderation on source neutrons to obtain medium energy neutrons; the medium energy neutron moderation layer is used to perform secondary moderation on medium energy neutrons to obtain thermal neutrons; the thermal neutron absorption layer is used to absorb thermal neutrons; and the γ shielding layer is used to shield the generated γ rays.

[0046] In the embodiments of the present disclosure, a first side cover plate and at least two second side cover plates are used to form a accommodating cavity, and the size can be adjusted according to the structure of the beam shaping component. At the same time, in combination with the action cross-section of neutrons and different materials, a fast neutron moderator layer is used for initial moderation, a medium energy neutron moderator layer is used for secondary moderation, a thermal neutron absorption layer is used for capture absorption, and a second side cover plate formed by a γ shielding layer can effectively improve the neutron moderation and absorption efficiency, reduce neutron radiation, and reduce the weight of the shielding chamber.

[0047] According to an embodiment of the present disclosure, when assembling the shielding compartment, aluminum or stainless steel materials may be used for assembly.

[0048] According to an embodiment of the present disclosure, along the direction from the inside of the accommodating cavity to the outside of the cavity, the first side cover plate includes a thermal neutron absorption layer for absorbing thermal neutrons and a γ shielding layer for shielding the generated γ rays.

[0049] In the embodiments of the present disclosure, Figure 4 As shown, the first side cover plate includes a thermal neutron absorption layer front cover plate 61 and a γ shielding layer front cover plate 62, which can be connected to the shielding layer of the beam shaping assembly, and form a receiving cavity with the second side cover plate for receiving the beam shaping assembly, and the size can be adjusted according to the structure of the beam shaping assembly.

[0050] According to an embodiment of the present disclosure, the thickness of the fast neutron moderator layer is 5-15 cm, the thickness of the medium energy neutron moderator layer is 10-30 cm, the thickness of the thermal neutron absorption layer is 10-20 cm, and the thickness of the gamma shielding layer is 5-10 cm.

[0051] In the embodiments of the present disclosure, by adopting a second side cover formed by a fast neutron moderator layer, a medium energy neutron moderator layer, a thermal neutron absorption layer and a γ shielding layer, the volume and weight of the prepared shielding chamber are reduced while meeting the radiation shielding requirements.

[0052] According to an embodiment of the present disclosure, the material of the fast neutron moderator layer includes lead or tungsten.

[0053] In the embodiments of the present disclosure, by using heavy metals with a large cross-section for interaction with scattered source neutrons for preliminary moderation, the moderation efficiency can be effectively improved and the volume can be reduced compared to the traditional direct interaction with low-density hydrogen-rich shielding materials such as paraffin, polyethylene, water and boron-containing polyethylene. This is mainly because when the low-density hydrogen-rich shielding material interacts with fast neutrons, the interaction cross-section is not large and the fast neutrons cannot be quickly slowed down. A larger size is required to reduce the radiation dose to a safe level.

[0054] According to an embodiment of the present disclosure, the material of the medium energy neutron moderator layer includes polyethylene, paraffin or aluminum.

[0055] According to an embodiment of the present disclosure, the material of the thermal neutron absorption layer includes boron-containing polyethylene; and the material of the gamma shielding layer includes lead.

[0056] Figure 7 Schematically shows the use flow chart of the lead curtain according to the embodiment of the present disclosure

[0057] like Figure 2 As shown, according to an embodiment of the present disclosure, a lead curtain 14 is further included, which is arranged on the first side cover plate and is used to cover the beam outlet.

[0058] According to an embodiment of the present disclosure, the lead curtain 14 is disposed on the bracket 11 , and the reel 12 is controlled by the transmission motor 13 to regulate the rise and fall of the lead curtain 14 .

[0059] In the embodiment of the present disclosure, in the outer structure of the shielding chamber facing the treatment room, a bracket and a reel are set at a suitable height, and the lead curtain is raised and lowered through the interlocking system connected to the transmission motor. Figure 7 As shown, when the transmission motor receives a patient treatment signal, the lead curtain is rolled up to expose the beam outlet. After the treatment is completed, the transmission motor receives a signal and controls the lead curtain to descend to block the neutron beam outlet, thereby achieving the purpose of reducing the induced radioactivity level.

[0060] like Figure 3 and Figure 6 As shown, according to an embodiment of the present disclosure, it also includes: a lifting ring 71 and a pulling rod 72, which are arranged on one of the second side cover plates and are used to replace the target body in the shielding chamber.

[0061] According to an embodiment of the present disclosure, the pull rod 72 passes through the second side cover plate, and a base is provided inside the second side cover plate to fix the pull rod. The lifting ring 71 is fixed on the pull rod outside the second side cover plate, and the lifting ring is controlled by a robotic arm to move the second side cover plate.

[0062] In the embodiment of the present disclosure, the need for regular target replacement of the beam shaping assembly is taken into consideration, and a lifting ring and a pull rod are provided on the second cover plate on one side of the shielding chamber. The lifting ring is controlled by a robotic arm to move the second side cover plate, thereby achieving the purpose of remote target replacement.

[0063] Figure 8 Schematic diagram showing the Monte Carlo simulation calculation of the ambient dose equivalent rate of the BSA unshielded device.

[0064] Fig. 9 The Monte Carlo simulation calculation of the ambient dose equivalent rate after the shielding chamber of the present disclosure is used to shield the BSA is schematically shown.

[0065] Fig.10 The Monte Carlo simulation calculation of the induced dose rate 5 minutes after the beam irradiation ends according to an embodiment of the present disclosure is schematically shown.

[0066] Fig.11 The Monte Carlo simulation calculation of the induced dose rate of the traditional shielding lead-free curtain 5 minutes after the beam irradiation ends is shown schematically.

[0067] In one embodiment of the present disclosure, a multilayer shielding chamber for a beam shaping assembly is a rectangular parallelepiped, and is composed of a first side cover plate and three second side cover plates, wherein a beam outlet is provided on the first side cover plate; the three second side cover plates and the first side cover plate together form a receiving cavity for receiving the beam shaping assembly; the second side cover plate includes a fast neutron moderation layer, a medium energy neutron moderation layer, a thermal neutron absorption layer, and a gamma shielding layer stacked in sequence along the cavity inside the receiving cavity and pointing to the outside of the cavity;

[0068] The three second side cover plates include two side cover plates and a rear cover plate, such as Figure 3 As shown, the rear cover is provided with holes for the beam transport pipeline. Figure 4 As shown, specifically, the side cover plate includes a fast neutron moderator layer side cover plate 21, a medium energy neutron moderator layer side cover plate 31, a thermal neutron absorption layer side cover plate 41, and a γ shielding layer side cover plate 51 stacked in sequence. The rear cover plate includes a fast neutron moderator layer rear cover plate 22, a medium energy neutron moderator layer rear cover plate 32, a thermal neutron absorption layer rear cover plate 42, and a γ shielding layer rear cover plate 52 stacked in sequence.

[0069] Along the direction from the inside of the accommodating cavity to the outside of the cavity, the first side cover plate includes a thermal neutron absorption layer and a gamma shielding layer, which are sequentially provided, specifically, a thermal neutron absorption layer front cover plate 61 and a gamma shielding layer front cover plate 62 .

[0070] Among them, the thickness of the fast neutron moderation layer is 5 cm, the thickness of the medium energy neutron moderation layer is 10 cm, the thickness of the thermal neutron absorption layer is 10 cm, and the thickness of the gamma shielding layer is 5 cm.

[0071] The material of the fast neutron moderator layer is tungsten, the material of the medium energy neutron moderator layer is polyethylene, the material of the thermal neutron absorption layer is boron-containing polyethylene, and the material of the gamma shielding layer is lead.

[0072] like Figure 8 , 9 As shown in Table 1, a Monte Carlo simulation result comparison of the dose rate at three detection points of the non-shielding body, the traditional shielding body and the shielding body of the disclosed embodiment is shown, wherein three detection points A, B, and C at a distance of 30 cm from the device in the forward, lateral, and rear directions are selected to calculate the dose rate. The structure of the traditional shielding body is that a thermal neutron absorption layer and a γ shielding layer are sequentially arranged along the direction from the inside of the accommodating cavity to the outside of the cavity.

[0073] Table 1 Dose rate simulation results at each detection point (μSv / h)

[0074]

[0075] As can be seen from Table 1, the shielding body of the embodiment of the present disclosure is similar to the traditional structure in the forward direction except for the forward detection position A that needs to be used for output beam treatment, so there is no difference in the dose rate in terms of magnitude. For the lateral B and rear C, the dose rate at the lateral B position is reduced by 3 orders of magnitude compared to the unshielded structure, and the dose rate at the rear C position is reduced by 1 order of magnitude compared to the traditional one.

[0076] like Fig.10 , 11 As shown, the instantaneous induced dose rate distribution at the end of 30 minutes of irradiation, compared with the traditional shielding structure without lead curtain, the shielding chamber of the embodiment of the present disclosure reduces the induced radioactivity in the forward and lateral directions of the beam to a very low level, and reduces the activation of the air by neutrons. At the same time, the shielding chamber limits the neutrons generated by the BSA to activate the walls and structural components. After the treatment is completed, the lead curtain is controlled to descend to block the neutron beam outlet, which effectively reduces the level of induced radioactivity and alleviates the induced radioactivity of medical staff.

[0077] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A multi-layer shielding chamber for a beam shaping assembly, characterized in that: include: A first side cover plate and at least two second side cover plates, wherein the first side cover plate is provided with a beam outlet; at least two second side cover plates and the first side cover plate together form a receiving cavity, wherein the receiving cavity is used to receive the beam shaping assembly; Wherein, along the direction from the inside of the accommodating cavity to the outside of the cavity, the second side cover plate includes a fast neutron moderation layer, a medium energy neutron moderation layer, a thermal neutron absorption layer and a gamma shielding layer stacked in sequence; The fast neutron moderation layer is used to initially moderate the source neutrons to obtain medium energy neutrons; The medium energy neutron moderator is used to perform secondary moderation on the medium energy neutrons to obtain thermal neutrons; The thermal neutron absorption layer is used to absorb the thermal neutrons; and The gamma shielding layer is used for shielding the generated gamma rays.

2. The multi-layer shielding chamber for a beam shaping assembly according to claim 1, characterized in that: Along the direction from the inside of the accommodating cavity to the outside of the cavity, the first side cover plate includes a thermal neutron absorption layer arranged in sequence for absorbing the thermal neutrons; and a γ shielding layer for shielding the generated γ rays.

3. The multi-layer shielding chamber for a beam shaping assembly according to claim 1 or 2, characterized in that: The thickness of the fast neutron moderation layer is 5-15 cm, the thickness of the medium energy neutron moderation layer is 10-30 cm, the thickness of the thermal neutron absorption layer is 10-20 cm, and the thickness of the gamma shielding layer is 5-10 cm.

4. The multi-layer shielding chamber for a beam shaping assembly according to claim 3, characterized in that: The material of the fast neutron moderator layer includes lead or tungsten.

5. The multi-layer shielding chamber for a beam shaping assembly according to claim 3, characterized in that: The material of the medium energy neutron moderator layer includes polyethylene, paraffin or aluminum.

6. The multi-layer shielding chamber for a beam shaping assembly according to claim 3, characterized in that: The material of the thermal neutron absorption layer includes boron-containing polyethylene; the material of the gamma shielding layer includes lead.

7. The multi-layer shielding chamber for a beam shaping assembly according to claim 1, characterized in that: It also includes a lead curtain, which is arranged on the first side cover plate and is used to cover the beam outlet.

8. The multi-layer shielding chamber for a beam shaping assembly according to claim 7, characterized in that: The lead curtain is arranged on a bracket, and the raising and lowering of the lead curtain is regulated by controlling a reel through a transmission motor.

9. The multi-layer shielding chamber for a beam shaping assembly according to claim 8, characterized in that: Also includes: A lifting ring and a pulling rod are arranged on one of the second side cover plates and are used for replacing the target body in the shielding chamber.

10. The multi-layer shielding chamber for a beam shaping assembly according to claim 9, characterized in that: The pull rod passes through the second side cover plate, and a bottom bracket is arranged inside the second side cover plate for fixing the pull rod. The lifting ring is fixed on the pull rod outside the second side cover plate, and the lifting ring is controlled by a mechanical arm to move the second side cover plate.

Images