Chen F, Hendry J H, Chu G, Greene D, Bianchi M
Br J Radiol. 1983 Aug;56(668):551-8. doi: 10.1259/0007-1285-56-668-551.
The RBE of the leakage radiation from the Hiletron 14.7 MeV neutron therapy unit has been measured using three sensitive biological systems in mice, which differ markedly in their radiobiological characteristics. These systems comprise type A spermatogonia and bone marrow stem cells, which are affected insignificantly by dose rate, and pigment abnormalities in hair follicles which are affected markedly by dose rate. For mice irradiated at 10 cm depth in a water phantom, the leakage radiation up to 40 cm from the beam axis was virtually as effective as the primary beam for the latter two biological systems, and for spermatogonia in mice when irradiated in air. At this distance, the total dose rate was about 0.2 cGy (rad) per minute (3% of that in the primary beam), and the gamma-ray component was about 70%. This equal effectiveness of the total dose for all three systems was considered fortuitous, and it implied high RBE values for equal effect with the small neutron component at far distances. Considering published data on RBE versus neutron energy, the evidence suggested either a positive interaction of neutron and gamma-ray components in killing bone marrow stem cells when the neutron component was less than 40% of the total dose, or an increased efficiency of neutrons when delivered at very low dose rates. However the components were additive in killing spermatogonia.
利用小鼠体内三种敏感的生物系统，对希莱tron 14.7 MeV中子治疗装置泄漏辐射的相对生物效应（RBE）进行了测量，这三种生物系统的放射生物学特性有显著差异。这些系统包括A型精原细胞和骨髓干细胞，它们受剂量率的影响不明显，以及毛囊中的色素异常，其受剂量率的影响显著。对于在水模体中10 cm深度处受照射的小鼠，对于后两种生物系统以及在空气中受照射的小鼠精原细胞而言，距束轴40 cm范围内的泄漏辐射实际上与原射线一样有效。在此距离处，总剂量率约为每分钟0.2 cGy（拉德）（为原射线剂量率的3%），γ射线成分约为70%。所有三种系统总剂量的这种同等有效性被认为是偶然的，这意味着在远距离处，对于同等效应而言，小剂量中子成分具有较高的RBE值。考虑到已发表的关于RBE与中子能量关系的数据，证据表明，当中子成分小于总剂量的40%时，中子和γ射线成分在杀死骨髓干细胞方面存在正相互作用，或者在极低剂量率下传递中子时其效率增加。然而，在杀死精原细胞方面，这些成分是相加的。
