Raju M R, Carpenter S G, Chmielewski J J, Schillaci M E, Wilder M E, Freyer J P, Johnson N F, Schor P L, Sebring R J, Goodhead D T
Radiat Res. 1987 Jun;110(3):396-412.
Ultrasoft X rays (approximately less than keV) provide a useful probe for the study of the physical parameters associated with the induction of biological lesions because the spatial scale of their energy depositions is of nanometer dimensions, comparable to that of critical structures within the cell. We report on cell-killing experiments using cultured hamster cells (V79) exposed to carbon K (0.28 keV), aluminum K (1.5 keV), copper K (8.0 keV), and 250 kVp X rays, under oxic and hypoxic conditions, and as a function of cell-cycle phase. Our principal results are: RBE increases with decreasing X-ray energy; OER decreases with decreasing X-ray energy; and cell-cycle response is similar for all X-ray energies. Our RBE results confirm earlier observations using ultrasoft X rays on mammalian cells. The shapes of fitted curves through the data for each energy are statistically indistinguishable from one another, implying that the enhanced effectiveness is purely dose modifying. The results reported herein generally support the view that single-track effects of radiation are predominantly due to very local energy depositions on the nanometer scale, which are principally responsible for observed radiobiological effects.
极软X射线（能量约低于keV）为研究与生物损伤诱导相关的物理参数提供了一种有用的探针，因为其能量沉积的空间尺度为纳米级，与细胞内关键结构的尺度相当。我们报告了在有氧和缺氧条件下，以及作为细胞周期阶段的函数，使用培养的仓鼠细胞（V79）暴露于碳K（0.28 keV）、铝K（1.5 keV）、铜K（8.0 keV）和250 kVp X射线下的细胞杀伤实验。我们的主要结果是：相对生物效应（RBE）随X射线能量降低而增加；氧增强比（OER）随X射线能量降低而降低；并且所有X射线能量下的细胞周期反应相似。我们的RBE结果证实了早期使用极软X射线对哺乳动物细胞的观察结果。通过每种能量数据的拟合曲线形状在统计学上彼此无法区分，这意味着增强的有效性纯粹是剂量修正。本文报道的结果总体上支持这样一种观点，即辐射的单轨迹效应主要是由于纳米尺度上非常局部的能量沉积，这主要是观察到的放射生物学效应的原因。
