Freyer J P, Schillaci M E, Raju M R
Life Sciences Division, Los Alamos National Laboratory, NM 87545.
Int J Radiat Biol. 1989 Dec;56(6):885-92. doi: 10.1080/09553008914552361.
Although there are several theoretical predictions of the dependence of the G-value on X-ray energy, measurements have not been made below approximately equal to 7 keV. Using a ferrous sulfate solution modified by the addition of benzoic acid, we have measured the relative G-values for Alk characteristic X-rays (1.5 keV), 238Pu alpha-particles (3.7 MeV), 60Co (1.17 MeV) and 137Cs (0.66 MeV) gamma-rays. This modified ferrous sulfate solution gave a 4-fold increase in sensitivity relative to the conventional solution, making measurements with the Alk X-rays feasible. The relative ferrous-to-ferric conversions as a function of dose were similar for the two gamma-ray energies, yielding G-values of 1.62 and 1.59 mumol J-1 for the 60Co and 137Cs radiations, respectively. The alpha-particle G-value was 0.52 mumol J-1, or 31 per cent of that for the 60Co gamma-rays, in good agreement with previous measurements. The Alk X-rays had a G-value of 0.92 mumol J-1 or 57 per cent of that of the 60Co radiation. This G-value for the 1.5 keV X-rays is within 20 per cent of the values predicted by current theories, and theoretical values are within the error range of our measurement. The consistency between the experimental value reported here and theoretical G-values for ultrasoft X-rays should be valuable for models of radiation action on biological systems.
尽管对于G值与X射线能量的依赖关系有若干理论预测，但在大约等于或低于7keV的能量下尚未进行测量。我们使用添加了苯甲酸进行改性的硫酸亚铁溶液，测量了Alk特征X射线（1.5keV）、238Puα粒子（3.7MeV）、60Co（1.17MeV）和137Cs（0.66MeV）γ射线的相对G值。这种改性硫酸亚铁溶液的灵敏度相对于传统溶液提高了4倍，使得用Alk X射线进行测量成为可能。对于两种γ射线能量，亚铁到铁的相对转化率与剂量的函数关系相似，60Co和137Cs辐射的G值分别为1.62和1.59μmol J-1。α粒子的G值为0.52μmol J-1，是60Coγ射线G值的31%，与先前的测量结果高度一致。Alk X射线的G值为0.92μmol J-1，是60Co辐射G值的57%。1.5keV X射线的这个G值在当前理论预测值的20%以内，并且理论值在我们测量的误差范围内。此处报道的实验值与超软X射线理论G值之间的一致性对于生物系统辐射作用模型应该是有价值的。
