The incorporation of the concept of minimum RBE (RBEmin) into the linear-quadratic model and the potential for improved radiobiological analysis of high-LET treatments
The incorporation of the concept of minimum RBE (RBEmin) into the linear-quadratic model and the potential for improved radiobiological analysis of high-LET treatments
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DOI：
10.1080/09553000601087176
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发表时间：
2007-01-01
影响因子：
2.6
通讯作者：
Jones, Bleddyn
中科院分区：
文献类型：
--
作者：
Carabe-Fernandez, Alejandro;Dale, Roger G.;Jones, Bleddyn
目的：重新探讨高线性能量传递（高LET）放射治疗的相对生物学效应（RBE）公式。现在通过RBEmin概念考虑不同LET下亚致死损伤产生变化的影响，其中RBEmin代表每分次高剂量时RBE趋向的下限。
材料与方法：对用于计算高LET辐射随分次剂量的RBE变化的现有线性 - 二次方公式进行修改，以纳入RBEmax（代表有效每分次剂量为0 Gy时的RBE值）和RBEmin这两个概念。
结果：模型对数据的拟合显示RBEmin值在0.1 - 2.27范围内。在所有情况下，原始数据对包含RBEmin的模型具有更好的统计拟合性，尽管在一种情况下这种差异才具有非常高的显著性。以小鼠食管为例，结果表明，如果认为β放射敏感性系数随LET的变化微不足道，那么在2 Gy/分次的X射线剂量下，如果不考虑RBEmin，预计RBE会被低估>5%。为确保结果不受用于获取与该分析相关的参数值的统计方法（即使用分次大小效应或Fe图）的影响，使用了一种替代方法，该方法与数据具有非常相似的相关性。
结论：如果认为亚致死损伤的产生与LET无关，那么在每分次低剂量（临床相关区域）时，未校正的RBE评估将存在高估或低估RBE的风险。
Purpose: The formulation of relative biological effectiveness (RBE) for high linear energy transfer (high-LET) radiation treatments is revisited. The effects of changed production of sub-lethal damage with varying LET is now considered via the RBEmin concept, where RBEmin represents the lower limit to which RBE tends at high doses per fraction.Materials and methods: An existing linear-quadratic formulation for calculating RBE variations with fractional dose for high-LET radiations is modified to incorporate the twin concepts of RBEmax (which represents the value of RBE at an effective close-per-fraction of 0 Gy) and RBEmin.Results: Fits of the model to data showed RBEmin values in the range of 0.1 - 2.27. In all cases the raw data was a better statistical fit to the model which included RBEmin, although this was only very highly significant in one case. In the case of the mouse oesophagus it is shown that, if change in the beta-radiosensitivity coefficient with LET is considered as trivial, an underestimation > 5% in RBE can be expected at X-ray doses of 2 Gy/fraction if RBEmm is not considered. To ensure that the results were not biased by the statistical method used to obtain the parameter values relevant to this analysis (i.e., using fraction-size effect or Fe-plots), an alternative method was used which provided very similar correlation with the data.Conclusions: If the production of sublethal damage is considered independent of LET, there will be a risk that non-corrected evaluation of RBE will lead to an over- or under-estimate of RBE at low doses per fractions (the clinically relevant region).