In this study, we try to estimate the relative biological effectiveness (RBE) of low-energy electrons released during the gadolinium neutron capture reaction (¹⁵⁷GdNCR) using microdosimetric methods. It is assumed that the ¹⁵⁷Gd is uniformly distributed throughout the cells and can be bound to DNAs. The microdosimetric parameters of Gd electrons along with those of carbon ions and protons were calculated using the Geant4-DNA and ROOT software.

It was found that for a DNA target, the ${\text{y}}_{\text{D}}$-ratio of carbon ions relative to reference radiation is proportional to the relevant RBE, independent of the radiation quality. Comparing the microdosimetric parameters of Gd electrons with those of carbon ions obtained in a 10-nm target, we evaluated the RBE of Gd electrons. In the case where ¹⁵⁷Gd distributed inside of the DNA target, the RBE values of Gd electrons were obtained 2.36 and 2.21 using the modified microdosimetric kinetic model and biological weighting function with specific cell type and end-points, respectively. Although the amount of specific energy of Gd electrons in the DNA target is strongly dependent on the ¹⁵⁷Gd distribution relative to the target, the RBE variations to the ¹⁵⁷Gd distribution are low. The mean energy deposited of Gd electrons in the DNA target during one ¹⁵⁷GdNCR with a value of 220.41 eV (equivalent to 207.73 kGy) is large enough for the induction of double-strand break of DNA.

This microdosimetric estimation of the RBE of Gd electrons can be useful for assessing the biological dose of Gd electrons in neutron capture therapy. For other Gd compounds or Auger-electron emitters with heterogeneous distributions inside the cells, by comparing with the results obtained in this study, one can evaluate the RBE of their Auger electrons.

在这项研究中，我们尝试使用微剂量学方法估计钆中子俘获反应 ( ¹⁵⁷ GdNCR)期间释放的低能电子的相对生物有效性 (RBE) 。假设¹⁵⁷ Gd 均匀分布在整个细胞中并且可以与 DNA 结合。使用 Geant4-DNA 和 ROOT 软件计算 Gd 电子以及碳离子和质子的微剂量参数。

研究发现，对于 DNA 目标， ${\text{是}}_{\text{D}}$-碳离子相对于参考辐射的比率与相关的 RBE 成正比，与辐射质量无关。将 Gd 电子的微剂量参数与在 10 nm 靶中获得的碳离子的微剂量参数进行比较，我们评估了 Gd 电子的 RBE。在¹⁵⁷ Gd 分布在 DNA 靶标内部的情况下，使用改进的微剂量动力学模型和具有特定细胞类型和终点的生物加权函数，分别获得了 2.36 和 2.21 的 Gd 电子 RBE 值。尽管 DNA 靶标中 Gd 电子的比能量强烈依赖于¹⁵⁷ Gd 相对于靶标的分布，但 RBE 相对于¹⁵⁷Gd分布低。在一次¹⁵⁷ GdNCR期间，Gd 电子在 DNA 靶标中沉积的平均能量为 220.41 eV（相当于 207.73 kGy），足以诱导 DNA 的双链断裂。

这种 Gd 电子 RBE 的微剂量估计可用于评估中子俘获治疗中 Gd 电子的生物剂量。对于细胞内分布不均匀的其他Gd化合物或俄歇电子发射体，通过与本研究获得的结果进行比较，可以评估其俄歇电子的RBE。