Philippo H, Huiskamp R, Winter A M, Gharbaran B, van der Kogel A J
Division of Radiation & Environment, NRG, Petten, The Netherlands.
Radiat Res. 2000 Jul;154(1):44-53. doi: 10.1667/0033-7587(2000)154[0044:adotro]2.0.co;2.
O-2A progenitor cells are the stem cells of the myelin-forming oligodendrocytes in the central nervous system. In the epithermal reactor beams used for boron neutron capture therapy (BNCT) for treatment of brain tumors, fission neutrons are a contaminating component. To estimate the radiosensitivity of the O-2A progenitors for fission neutrons, an in vivo-in vitro clonogenic assay was used. Radiosensitivity of progenitors obtained from the spinal cord of 1- or 5-day-old rats or the optic nerve of 2- or 12-week-old rats for 1 MeV fission neutrons was compared to that for 300 kVp X rays. Dose-survival curves were fitted according to the linear-quadratic model. The resulting beta component was very small to negligible. Progenitor cells obtained from rats of different ages show differences in radiosensitivity, characterized by different alpha values. RBE values for fission neutrons were 3.5 for 1-day-old spinal cord, 3.2 for 5-day-old spinal cord, 3.0 for 2-week-old optic nerve, and 4.3 for 12-week-old optic nerve. These high RBE values indicate the importance of minimizing the fast-neutron component in the epithermal neutron beams used for BNCT.
O-2A祖细胞是中枢神经系统中形成髓鞘的少突胶质细胞的干细胞。在用于脑肿瘤硼中子俘获疗法（BNCT）的超热反应堆束中，裂变中子是一种污染成分。为了评估O-2A祖细胞对裂变中子的放射敏感性，采用了体内-体外克隆形成试验。将从1日龄或5日龄大鼠脊髓或2周龄或12周龄大鼠视神经中获得的祖细胞对1兆电子伏裂变中子的放射敏感性与对300千伏峰值X射线的放射敏感性进行了比较。根据线性二次模型拟合剂量-存活曲线。所得的β成分非常小，可以忽略不计。从不同年龄大鼠获得的祖细胞在放射敏感性上存在差异，其特征在于α值不同。1日龄脊髓的裂变中子相对生物效应（RBE）值为3.5，5日龄脊髓为3.2，2周龄视神经为3.0，12周龄视神经为4.3。这些高RBE值表明在用于BNCT的超热中子束中尽量减少快中子成分的重要性。
