Relative biological effectiveness (RBE) is a key quantity for the description of radiobiological effects induced by charged-particle irradiation in the context of ion-beam cancer therapy. Since RBE is a complex function that depends on different physical, chemical, and biological parameters, a fundamental understanding of radiobiological effects becomes increasingly important for clinical applications. The phenomenon-based multiscale approach to the physics of radiation damage with ions (MSA) provides a tool for a molecular-level understanding of physical and chemical mechanisms of radiation biodamage and allows for quantification of macroscopic biological effects caused by ion irradiation. This study reports the first application of the MSA for the analysis of RBE of ion beams. As a case study, we quantify the response of human and rodent normal cells to carbon-ion irradiation at different values of linear energy transfer (LET). Clonogenic cell survival as a function of dose, RBE at a 10% survival level as well as other radiobiological parameters, such as the cross section of cell inactivation, are analyzed and compared with experimental data. The MSA is used also to evaluate RBE at high values of LET where RBE decreases due to the “overkill” effect. In this regime, the dose needed to achieve a given biological effect is deposited by only a few ions and the RBE becomes inversely proportional to LET. Good agreement with a large set of experimental data on clonogenic cell survival, inactivation cross section, and RBE emphasizes the predictive power of the MSA. In the high-LET regime, the fact that a given number of ions may produce more damage than needed for a given biological effect leads to a significant (up to 20%) variation in RBE. Consideration of this effect in the analysis of experimental data on irradiation with high-LET ions may lead to re-evaluation of RBE in this regime.

中文翻译：

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基于现象的多尺度方法评估离子束的相对生物有效性

相对生物学有效性（RBE）是描述离子束癌症治疗中带电粒子辐照引起的放射生物学效应的关键指标。由于RBE是一项复杂的功能，取决于不同的物理，化学和生物学参数，因此对放射生物学效应的基本了解对于临床应用变得越来越重要。基于现象的离子辐射损伤物理学的多尺度方法（MSA）提供了一种工具，可以从分子水平了解辐射生物损伤的物理和化学机理，并可以量化由离子辐射引起的宏观生物学效应。这项研究报告了MSA在离子束RBE分析中的首次应用。作为案例研究 我们在线性能量转移（LET）的不同值下量化人类和啮齿动物正常细胞对碳离子辐照的反应。分析了克隆细胞的存活率与剂量，存活率10％的RBE以及其他放射生物学参数（例如细胞灭活的横截面）的关系，并与实验数据进行了比较。MSA还用于评估LET高值时的RBE，其中LETE由于“过度杀伤”效应而降低。在这种情况下，实现给定生物学效果所需的剂量仅由几个离子沉积，并且RBE与LET成反比。与大量有关克隆细胞存活，灭活截面的实验数据吻合良好，RBE强调了MSA的预测能力。在高LET制下，给定数量的离子可能会产生比给定生物学效应所需的更多损害的事实，这导致RBE发生显着（高达20％）变化。在对高LET离子辐照的实验数据进行分析时考虑到这种效应，可能会导致在这种情况下重新评估RBE。