目的 针对2.7 MeV/30 mA质子加速器驱动的7Li(p,n)7Be中子源,分析其作为医用放射装置的辐射场特性,优化束流整形组件（BSA）及外围屏蔽结构,以降低泄漏辐射剂量并提升装置辐射安全性能。方法 采用MCNPX蒙特卡罗程序,分步优化慢化体、反射体、热中子吸收层及准直器,并对γ屏蔽层与外围含硼聚乙烯屏蔽体（质量分数为10%的B4C,厚度为10 cm）的中子和γ屏蔽效果进行评估。计算BSA出口及外围关注点的中子通量、能谱、剂量当量率等辐射场参数。对比单层MgF2、单层AlF3及双层（前MgF2后AlF3）慢化体方案对辐射场品质及泄漏辐射的影响。结果 优化后的双层复合慢化体BSA出口超热中子注量率Φepi达1.84×109 cm-2·s-1,热中子比例Φth/Φepi降至0.025,快中子剂量比Df/Φepi为1.80×10-13 Gy·cm2,γ剂量比Dγ/Φepi为1.52×10-13 Gy·cm2,方向性因子J/Φ为0.71,各项参数均优于IAEA限值。与单层AlF3方案（37 cm）相比,总厚度减少5 cm。外围含硼聚乙烯屏蔽层使装置侧向30 cm处中子剂量当量率降至2.3 μSv/h,γ剂量当量率降至0.8 μSv/h,满足GBZ 130—2020限值（≤2.5 μSv/h）。结论 本研究提出的双层复合慢化体不仅提升了治疗束品质,同时有效控制了装置泄漏辐射,为医用加速器中子源的辐射场优化及防护设计提供了理论依据。
Abstract
The work aims to analyze the radiation field characteristics and optimize the beam shaping assembly (BSA) and peripheral shielding structure for a medical radiological device driven by a 2.7 MeV/30 mA proton beam based on the 7Li(p,n)7Be reaction, so as to reduce stray radiation dose and enhance radiological safety performance. Monte Carlo simulations were conducted using the MCNPX code. A stepwise optimization was performed on the moderator, reflector, thermal neutron filter, and collimator, while the neutron and gamma shielding effectiveness of the gamma shield and an outer borated polyethylene layer (10 wt% B4C, 10 cm thick) was evaluated. Radiation field parameters, including neutron flux, energy spectra, and dose equivalent rates at the BSA exit and peripheral points of interest, were calculated. Three moderator configurations of single-layer MgF2, single-layer AlF3, and a double-layer structure (MgF2 in front, AlF3 at rear) were compared in terms of their effects on radiation field quality and stray radiation. The results showed that, for the optimized double-layer moderator, the epithermal neutron flux Φepi at the BSA exit reached 1.84×109 cm-2·s-1, the thermal-to-epithermal ratio Φth/Φepi was reduced to 0.025, the fast-neutron dose ratio Df/Φepi was 1.80×10-13 Gy·cm2, the gamma dose ratio Dγ/Φepi was 1.52×10-13 Gy·cm2, and the beam directionality J/Φ was 0.71, all superior to the IAEA recommended limits. Compared with the single-layer AlF3 scheme (37 cm), the total moderator thickness was reduced by 5 cm. The peripheral borated polyethylene shield reduced the neutron dose equivalent rate to 2.3 μSv/h and the gamma dose equivalent rate to 0.8 μSv/hat a lateral distance of 30 cm from the facility, meeting the national radiological protection standard GBZ 130-2020 (≤2.5 μSv/h). The proposed double-layer composite moderator not only improves the therapeutic beam quality but also effectively controls stray radiation from the facility, providing a theoretical basis for radiation field optimization and shielding design of medical accelerator-based neutron sources.
关键词
硼中子俘获治疗（BNCT） /
医用放射装置 /
辐射场特性 /
束流整形组件（BSA） /
屏蔽优化 /
蒙特卡罗模拟（MCNPX）
Key words
boron neutron capture therapy (BNCT) /
medical radiological device /
radiation field characteristic /
beam shaping assembly (BSA) /
shielding optimization /
Monte Carlo simulation (MCNPX)
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
参考文献
[1] LOCHER G L.Biological Effects and Therapeutic Possibilities of Neutrons[J]. American Journal of Roentgenology and Radium Therapy, 1936, 36: 1-13.
[2] BARTH R F, ZHANG Z Z, LIU T.A Realistic Appraisal of Boron Neutron Capture Therapy as a Cancer Treatment Modality[J]. Cancer Communications, 2018, 38(1): 36.
[3] MALOUFF T D, SENEVIRATNE D S, EBNER D K, et al.Boron Neutron Capture Therapy: A Review of Clinical Applications[J]. Frontiers in Oncology, 2021, 11: 601820.
[4] SUZUKI M.Boron Neutron Capture Therapy (BNCT): A Unique Role in Radiotherapy with a View to Entering the Accelerator-Based BNCT Era[J]. International Journal of Clinical Oncology, 2020, 25(1): 43-50.
[5] YAMAMOTO T, TSUBOI K, NAKAI K, et al.Boron Neutron Capture Therapy for Brain Tumors[J]. Translational Cancer Research, 2013, 2: 80-86.
[6] KREINER A J, BERGUEIRO J, CARTELLI D, et al.Present Status of Accelerator-Based BNCT[J]. Reports of Practical Oncology & Radiotherapy, 2016, 21(2): 95-101.
[7] ZHU Y N, LIN Z K, YU H Y, et al.Study on the Optimal Incident Proton Energy of 7Li(P, n)7Be Neutron Source for Boron Neutron Capture Therapy[J]. Nuclear Science and Techniques, 2024, 35(3): 60.
[8] FANTIDIS J G.Beam Shaping Assembly Study for BNCT Facility Based on a 2.5MeV Proton Accelerator on Li Target[J]. Journal of Theoretical and Applied Physics, 2018, 12(4): 249-256.
[9] IAEA. Current Status of Neutron Capture Therapy[R]. Vienna: IAEA, 2001: IAEA-TECDOC-1223.
[10] 顾少娴, 崔凤洁, 王宁宇, 等. 基于2.5 MeV质子加速器BNCT装置的中子慢化材料性能模拟研究[J]. 原子核物理评论, 2022, 39(3): 367-372.
GU S X, CUI F J, WANG N Y, et al.Simulation of Neutron Moderating Materials Performance Based on BNCT of 2.5 MeV Proton Accelerator[J]. Nuclear Physics Review, 2022, 39(3): 367-372.
[11] 田永顺, 胡志良, 童剑飞, 等. 基于3.5 MeV射频四极质子加速器硼中子俘获治疗装置的束流整形体设计[J]. 物理学报, 2018, 67(14): 107-115.
TIAN Y S, HU Z L, TONG J F, et al.Design of Beam Shaping Assembly Based on 3.5 MeV Radio-Frequency Quadrupole Proton Accelerator for Boron Neutron Capture Therapy[J]. Acta Physica Sinica, 2018, 67(14): 107-115.
[12] 田永顺. 基于加速器的硼中子俘获治疗的束流整形体的设计与优化[D]. 湘潭: 湘潭大学, 2018: 45.
TIAN Y S.Design and Optimization of Beam Shaping Assembly for Accelerator-Based Boron Neutron Capture Therapy[D]. Xiangtan: Xiangtan University, 2018: 45.
[13] 朱益楠, 林作康, 卢林远, 等. 基于氘氚中子源硼中子俘获治疗的中子慢化整形研究[J]. 核技术, 2022, 45(1): 31-38.
ZHU Y N, LIN Z K, LU L Y, et al.Design of Beam Shaping Assembly for Boron Neutron Capture Therapy Based on D-T Neutron Source[J]. Nuclear Techniques, 2022, 45(1): 31-38.
[14] 朱益楠. 基于加速器中子源搭载可调式慢化体的BNCT人体仿真治疗模拟研究[D]. 北京: 中国科学院大学, 2024.
ZHU Y N.Simulation Study of BNCT Human Phantom Therapy Based on Accelerator Neutron Source with Adjustable Moderator[D]. Beijing: University of Chinese Academy of Sciences, 2024.
[15] ICRP. The 2007 Recommendations of the International Commission on Radiological Protection (ICRP Publication 103)[R]. Oxford: Pergamon Press, 2007.
[16] 国家卫生健康委员会. 放射治疗放射防护要求: GBZ 130—2020[S]. 北京: 中国标准出版社, 2020.
National Health Commission of the People's Republic of China. Requirements for Radiological Protection in Radiotherapy: GBZ 130-2020[S]. Beijing: China Standards Press, 2020.
[17] KOAY H W, FUKUDA M, TOKI H, et al.Feasibility Study of Compact Accelerator-Based Neutron Generator for Multi-Port BNCT System[J]. Nuclear Instruments and Methods in Physics Research Section A, 2018, 908: 1-10.
基金
中核集团领创项目（CNNC-LCKY-2024-043）;上海市探索者项目（25TS1402500）;国家自然科学基金（U24B2025）;松山湖材料试验室开放课题基金（2023SLABFN09）
PDF(1589 KB)
渝公网安备 50010702501716号 渝ICP备15012534号-2
