利用背散射热中子监测硼中子俘获治疗期间的硼浓度：蒙特卡罗可行性研究
Using backscattered thermal neutrons to monitor boron concentration during BNCT: a Monte Carlo feasibility study
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中文总结 AI 辅助
研究BNCT中实时监测硼浓度的方法，用蒙特卡罗模拟评估背散射热中子作测量通道的可行性，通过薄LiF转换探测器捕获相关场，经差分成像和RDSR量化，得出其在体模中的相关特性及检测下限，为硼敏感测量概念奠定物理基础。
中文摘要 AI 辅助
硼中子俘获治疗（BNCT）需要了解患者特定的¹⁰B浓度以进行准确的剂量估计，但目前尚无成熟方法能在照射期间提供实时硼敏感信息。背散射热中子通过¹⁰B(n,α)⁷Li反应携带与¹⁰B相关的强度调制，虽在BNCT治疗室已记录三十年，但尚未发展为测量信号。本文用蒙特卡罗模拟评估背散射热中子作为¹⁰B浓度测量通道的可行性。在束流出口放置薄的天然LiF转换探测器捕获复合前向加背散射场，通过与无¹⁰B基线的差分成像分离出与¹⁰B相关的成分，用⁶Li俘获率的分数降低量（相对探测器信号降低，RDSR）量化。在均匀体模中，RDSR显示出线性浓度依赖性（R² = 0.997），实际深度极限约为6 cm。边缘响应分析得出在1 - 5 cm深度上扩散受限的半高宽为32 - 176 mm，浓度依赖性较弱。在包含12种硼配置的体素化患者体模中，⁶Li俘获截面提供了固有的热中子能量选择性，优先加权¹⁰B吸收集中的能带。感兴趣区域积分实现了低于10 ppm的计数统计灵敏度；系统检测下限（在±1%基线不确定性下约为22 - 28 ppm）表明基线参考精度是主要限制因素。模拟探测器产生的剂量扰动有限（治疗时间增加11.6%）。这些结果为BNCT中硼敏感的背散射中子测量概念奠定了物理基础。
英文摘要
Boron neutron capture therapy (BNCT) requires knowledge of patient-specific $^{10}$B concentration for accurate dose estimation, yet no established method provides real-time boron-sensitive information during irradiation. Backscattered thermal neutrons carry a $^{10}$B-dependent intensity modulation through the $^{10}$B(n,$α$)$^{7}$Li reaction, documented in BNCT treatment rooms for three decades but not yet developed as a measurement signal. This paper uses Monte Carlo simulation to assess the feasibility of backscattered thermal neutrons as a measurement channel for $^{10}$B concentration. A thin $^{nat}$LiF-converter detector placed at the beam exit captures the composite forward-plus-backscatter field; differential imaging against a $^{10}$B-free baseline isolates the $^{10}$B-dependent component, quantified by the fractional reduction in the $^{6}$Li capture rate, termed Relative Detector Signal Reduction (RDSR). In homogeneous phantoms, RDSR shows linear concentration dependence ($R^2 = 0.997$) with a practical depth limit of approximately 6 cm. Edge-response analysis yields a diffusion-limited FWHM of 32-176 mm over 1-5 cm depth, with weak concentration dependence. In a voxelized patient phantom across 12 boron configurations, the $^{6}$Li capture cross-section provides intrinsic thermal neutron energy selectivity that preferentially weights the band where $^{10}$B absorption is concentrated. Region-of-interest integration achieves counting-statistics sensitivity below 10 ppm; the systematic detection floor (~22-28 ppm at $\pm$1% baseline uncertainty) identifies baseline-reference precision as the dominant constraint. The modeled detector produces limited dose perturbation (+11.6% treatment-time increase). These results establish the physical basis for a boron-sensitive backscattered neutron measurement concept in BNCT.
