ESTIMATION OF ERRORS ASSOCIATED WITH USE OF LINEAR-QUADRATIC FORMALISM FOR EVALUATION OF BIOLOGIC EQUIVALENCE BETWEEN SINGLE AND HYPOFRACTIONATED RADIATION DOSES: AN IN VITRO STUDY
ESTIMATION OF ERRORS ASSOCIATED WITH USE OF LINEAR-QUADRATIC FORMALISM FOR EVALUATION OF BIOLOGIC EQUIVALENCE BETWEEN SINGLE AND HYPOFRACTIONATED RADIATION DOSES: AN IN VITRO STUDY
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DOI：
10.1016/j.ijrobp.2008.12.093
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发表时间：
2009-10-01
影响因子：
7
通讯作者：
Ito, Masato
中科院分区：
文献类型：
--
作者：
Iwata, Hiromitsu;Shibamoto, Yuta;Ito, Masato
目的：研究线性二次方程（LQ）在评估单次、高剂量和低分割辐射剂量间生物等效性时的可靠性和误差大小。方法和材料：V79和EM76单细胞接受2-12 Gy单次剂量或4或5 Gy 2或3次剂量，间隔4 h。通过菌落试验确定了单剂量和分剂量将细胞存活率降低到相同水平的效果。α / β比值由细胞存活曲线得到。利用α / β比和LQ公式，计算了减分剂量的等效单次剂量。然后将它们与实际确定的低分割剂量的等效单剂量进行比较。V79球体接受5-26 Gy的单次剂量或5-12 Gy的2至5次剂量，间隔2或4小时，然后测定细胞存活率。接下来，像对单个细胞所做的那样，确定低分割剂量的等效单剂量。结果：V79单细胞α / β比值为5.1 Gy， EMT6单细胞α / β比值为0.36 Gy。在V79中，使用LQ公式计算的减分剂量的等效单次剂量比实际测量的生物等效单次剂量低12-19%。在EMT6细胞中，也可以看到这种趋势，但差异不显著。在V79球体中，计算剂量比测量剂量低18-30%。结论：用LQ公式将低分割辐射剂量换算成单剂量时，可能低估了低分割辐射的影响
Purpose: To investigate the reliability of the linear-quadratic (LQ) formalism and the magnitude of errors associated with its use in assessing biologic equivalence between single, high radiation doses and hypofractionated radiation doses.Methods and Materials: V79 and EM76 single cells received single doses of 2-12 Gy or two or three fractions of 4 or 5 Gy, each at 4-h intervals. Single and fractionated doses to actually reduce the cell survival to the same level were determined by a colony assay. The alpha/beta ratio was obtained from the cell survival curves. Using the alpha/beta ratio and the LQ formalism, equivalent single doses for the hypofractionated doses were calculated. They were then compared with the actually determined equivalent single doses for the hypofractionated doses. The V79 spheroids received single doses of 5-26 Gy or two to five fractions of 5-12 Gy at 2 or 4-h interval, and then were assayed for cell survival. Next, equivalent single doses for the hypofractionated doses were determined, as were done for the single cells.Results: The alpha/beta ratio was 5.1 Gy for the V79 single cells and 0.36 Gy for EMT6. In V79, the equivalent single doses for the hypofractionated doses calculated using the LQ formalism were 12-19% lower than the actually measured biologically equivalent single doses. In the EMT6 cells, this trend was also seen, but the differences were not significant. In the V79 spheroids, the calculated doses were 18-30% lower than the measured doses.Conclusion: Conversion of hypofractionated radiation doses to single doses using the LQ formalism could underestimate the effect of hypofractionated radiation by