Paterson Laura C, Ali Fawaz, Naseri Mohsen, Perez Loureiro David, Festarini Amy, Stuart Marilyne, Boyer Chad, Rogge Ronald, Costello Christie, Ybarra Norma, Kildea John, Richardson Richard B
Radiobiology and Health Branch, Canadian Nuclear Laboratories, 286 Plant Rd, Chalk River, ON K0J 1J0, Canada.
Medical Physics Unit, McGill University, Montreal, QC H4A 3J1, Canada.
Radiat Prot Dosimetry. 2025 Mar 21;201(4):297-313. doi: 10.1093/rpd/ncae231.
The reported relative biological effectiveness (RBE) for thermal neutrons has a large range (5-51, for cytogenetic endpoints), which can confound radiation protection decision-making. To determine whether thermal neutron spectra can influence RBE, the RBE of reactor-derived thermal neutrons of average energy 31 meV was evaluated in human peripheral blood lymphocytes using two classical DNA double-strand break endpoints: the dicentric chromosome assay (DCA) and the cytokinesis-block micronucleus assay. Dose-response curves for 41 to 408 mGy revealed a preference for linear regression. Maximum RBE (RBEM) values of 6.7 ± 0.9 and 4.4 ± 0.7 were calculated for the DCA and the micronucleus assay, respectively. These 31 meV RBEM values were significantly lower than our prior results for 64 meV thermal neutrons, which yielded a DCA RBEM of 11.3 ± 1.6 and a micronucleus RBEM of 9.0 ± 1.1. Dose-specific RBE values decreased with increasing dose for both assays. Microdosimetry simulations demonstrated similar quality factor values for both thermal neutron spectra. Dose deposition differences on the cellular scale, the difference in dose rate between irradiation configurations, or a not-yet understood phenomenon may be responsible for the RBE difference between the 31 and 64 meV thermal spectra. These findings indicate that the currently accepted radiation weighting factor wR value of 2.5 for thermal neutrons may underestimate the radiation detriment to small or shallow tissue targets including the lens of the eye.
据报道，热中子的相对生物效应（RBE）范围很大（细胞遗传学终点的RBE为5 - 51），这可能会混淆辐射防护决策。为了确定热中子能谱是否会影响RBE，使用两种经典的DNA双链断裂终点：双着丝粒染色体分析（DCA）和胞质分裂阻滞微核分析，对平均能量为31 meV的反应堆衍生热中子在人外周血淋巴细胞中的RBE进行了评估。41至408 mGy的剂量反应曲线显示出线性回归的趋势。DCA和微核分析的最大RBE（RBEM）值分别计算为6.7±0.9和4.4±0.7。这些31 meV的RBEM值显著低于我们之前对64 meV热中子的结果，后者得出的DCA RBEM为11.3±1.6，微核RBEM为9.0±1.1。两种分析中，特定剂量的RBE值均随剂量增加而降低。微剂量学模拟表明，两种热中子能谱的品质因数相似。细胞尺度上的剂量沉积差异、照射配置之间的剂量率差异或尚未理解的现象可能是31和64 meV热中子能谱之间RBE差异的原因。这些发现表明，目前公认的热中子辐射权重因子wR值2.5可能低估了对包括眼球晶状体在内的小或浅组织靶标的辐射危害。
