Friedland W, Kundrát P, Schmitt E
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany.
Radiat Prot Dosimetry. 2015 Sep;166(1-4):34-7. doi: 10.1093/rpd/ncv146. Epub 2015 Apr 16.
Microbeam experiments approximating high-LET tracks by bunches of lower-LET particles focussed to submicrometre scales (Schmid et al. 2012, Phys. Med. Biol. 57, 5889) provide an unprecedented benchmark for models of biological effects of radiation. PARTRAC track structure-based Monte Carlo simulations have verified that focussed 20 MeV proton bunches resemble the radial dose distributions of single 55 MeV carbon ions as used in the experiments. However, the predicted yields of double-strand break and short (<1 kbp) DNA fragments by focussed protons correspond to homogeneous proton irradiation and are much smaller than for carbon tracks. The calculated yields of dicentrics overestimate the effect of focussing but reproduce the fourfold difference between carbon ions and homogeneously distributed protons. The extent to which focussed low-LET particles approximate high-LET radiation is limited by the achievable focussing: submicrometre focussing of proton bunches cannot reproduce local nanometre clustering, i.e. DNA damage complexity characteristic of high-LET radiation.
通过聚焦到亚微米尺度的低传能线密度粒子束来近似高传能线密度径迹的微束实验（施密德等人，2012年，《物理医学与生物学》57卷，5889页）为辐射生物效应模型提供了前所未有的基准。基于PARTRAC径迹结构的蒙特卡罗模拟已经证实，聚焦的20兆电子伏特质子束类似于实验中使用的单个55兆电子伏特碳离子的径向剂量分布。然而，聚焦质子产生的双链断裂和短（<1千碱基对）DNA片段的预测产额与均匀质子照射相对应，并且远小于碳径迹的产额。计算得到的双着丝粒体产额高估了聚焦效应，但再现了碳离子与均匀分布质子之间的四倍差异。聚焦的低传能线密度粒子近似高传能线密度辐射的程度受到可实现聚焦的限制：质子束的亚微米聚焦无法再现局部纳米级聚集，即高传能线密度辐射特有的DNA损伤复杂性。
