Wilson J W, Thibeault S A, Cucinotta F A, Shinn J L, Kim M, Kiefer R, Badavi F F
NASA Langley Research Center, Hampton, VA 23681-0001, USA.
Radiat Environ Biophys. 1995 Nov;34(4):217-22. doi: 10.1007/BF01209745.
Radiation risks to astronauts depend on the microscopic fluctuations of energy absorption events in specific tissues. These fluctuations depend not only on the space environment but also on the modifications of that environment by the shielding provided by structures surrounding the astronauts and the attenuation characteristics of the astronaut's body. The effects of attenuation within the shield and body depends on the tissue biological response to these microscopic fluctuations. In the absence of an accepted method for estimating astronaut risk, we examined the attenuation characteristics using conventional linear energy transfer (LET)-dependent quality factors (as one means of representing relative biological effectiveness, RBE) and a track-structure repair model to fit cell transformation (and inactivation) data in the C3H10 T1/2 mouse cell system obtained for various ion beams. Although the usual aluminum spacecraft shield is effective in reducing dose equivalent with increasing shield thickness, cell transformation rates are increased for thin aluminum shields. Clearly, the exact nature of the biological response to LET and track width is critical to evaluation of biological protection factors provided by a shield design. A significant fraction of biological injury results from the LET region above 100 keV/mu m. Uncertainty in nuclear cross-sections results in a factor of 2-3 in the transmitted LET spectrum beyond depths of 15 g/cm2, but even greater uncertainty is due to the combined effects of uncertainty in biological response and nuclear parameters. Clearly, these uncertainties must be reduced before the shield design can be finalised.
宇航员所面临的辐射风险取决于特定组织中能量吸收事件的微观波动。这些波动不仅取决于太空环境，还取决于宇航员周围结构所提供的屏蔽对该环境的改变以及宇航员身体的衰减特性。屏蔽层和身体内部的衰减效应取决于组织对这些微观波动的生物学反应。在缺乏公认的估计宇航员风险方法的情况下，我们使用传统的与线能量转移（LET）相关的品质因数（作为表示相对生物效应，即RBE的一种方式）和一个径迹结构修复模型来研究衰减特性，以拟合在C3H10 T1/2小鼠细胞系统中针对各种离子束获得的细胞转化（和失活）数据。尽管通常的铝制航天器屏蔽层能随着屏蔽层厚度增加有效降低剂量当量，但薄铝屏蔽层会使细胞转化率增加。显然，对LET和径迹宽度的生物学反应的确切性质对于评估屏蔽设计所提供的生物防护因子至关重要。相当一部分生物损伤是由LET高于100 keV/μm的区域造成的。核截面的不确定性导致在深度超过15 g/cm2时，透射LET谱有2至3倍的差异，但更大的不确定性是由于生物反应和核参数不确定性的综合影响。显然，在最终确定屏蔽设计之前，必须减少这些不确定性。
