Institute of Radiation Medicine, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Ingolstädter Landstr. 1, 85764 Neuherberg, Germany.
Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS, Portugal.
Phys Med. 2020 Jan;69:147-163. doi: 10.1016/j.ejmp.2019.12.011. Epub 2020 Jan 6.
Targeted radiation therapy has seen an increased interest in the past decade. In vitro and in vivo experiments showed enhanced radiation doses due to gold nanoparticles (GNPs) to tumors in mice and demonstrated a high potential for clinical application. However, finding a functionalized molecular formulation for actively targeting GNPs in tumor cells is challenging. Furthermore, the enhanced energy deposition by secondary electrons around GNPs, particularly by short-ranged Auger electrons is difficult to measure. Computational models, such as Monte Carlo (MC) radiation transport codes, have been used to estimate the physical quantities and effects of GNPs. However, as these codes differ from one to another, the reliability of physical and dosimetric quantities needs to be established at cellular and molecular levels, so that the subsequent biological effects can be assessed quantitatively.
In this work, irradiation of single GNPs of 50 nm and 100 nm diameter by X-ray spectra generated by 50 and 100 peak kilovoltages was simulated for a defined geometry setup, by applying multiple MC codes in the EURADOS framework.
The mean dose enhancement ratio of the first 10 nm-thick water shell around a 100 nm GNP ranges from 400 for 100 kVp X-rays to 600 for 50 kVp X-rays with large uncertainty factors up to 2.3.
It is concluded that the absolute dose enhancement effects have large uncertainties and need an inter-code intercomparison for a high quality assurance; relative properties may be a better measure until more experimental data is available to constrain the models.
在过去十年中，靶向放射治疗越来越受到关注。体外和体内实验表明，由于金纳米粒子（GNPs）在小鼠肿瘤中导致辐射剂量增加，并展示了临床应用的巨大潜力。然而，找到一种功能性分子配方来主动靶向肿瘤细胞中的 GNPs 是具有挑战性的。此外，由于 GNPs 周围的次级电子，特别是短程俄歇电子，增强了能量沉积，因此很难测量。计算模型，如蒙特卡罗（MC）辐射输运代码，已被用于估计 GNPs 的物理量和效应。然而，由于这些代码彼此不同，因此需要在细胞和分子水平上建立物理和剂量学量的可靠性，以便可以定量评估随后的生物学效应。
在这项工作中，通过在 EURADOS 框架中应用多个 MC 代码，模拟了由 50 和 100 峰值千伏的 X 射线光谱对直径为 50nm 和 100nm 的单个 GNPs 的照射，对于定义的几何结构设置。
100nm GNP 周围第一个 10nm 厚水壳的平均剂量增强比范围从 100kVp X 射线的 400 到 50kVp X 射线的 600，不确定性因素高达 2.3。
得出的结论是，绝对剂量增强效应具有很大的不确定性，需要进行代码间比较以确保高质量；相对特性可能是更好的衡量标准，直到有更多的实验数据来约束模型。
