Department of Radiology, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8601, Japan.
J Radiat Res. 2013 Mar 1;54(2):367-73. doi: 10.1093/jrr/rrs089. Epub 2012 Oct 16.
We investigated the applicability of the repairable-conditionally repairable (RCR) model and the multi-target (MT) model to dose conversion in high-dose-per-fraction radiotherapy in comparison with the linear-quadratic (LQ) model. Cell survival data of V79 and EMT6 single cells receiving single doses of 2-12 Gy or 2 or 3 fractions of 4 or 5 Gy each, and that of V79 spheroids receiving single doses of 5-26 Gy or 2-5 fractions of 5-12 Gy, were analyzed. Single and fractionated doses to actually reduce cell survival to the same level were determined by a colony assay. Single doses used in the experiments and surviving fractions at the doses were substituted into equations of the RCR, MT and LQ models in the calculation software Mathematica, and each parameter coefficient was computed. Thereafter, using the coefficients and the three models, equivalent single doses for the hypofractionated doses were calculated. They were then compared with actually-determined equivalent single doses for the hypofractionated doses. The equivalent single doses calculated using the RCR, MT and LQ models tended to be lower than the actually determined equivalent single doses. The LQ model seemed to fit relatively well at doses of 5 Gy or less. At 6 Gy or higher doses, the RCR and MT models seemed to be more reliable than the LQ model. In hypofractionated stereotactic radiotherapy, the LQ model should not be used, and conversion models incorporating the concept of the RCR or MT models, such as the generalized linear-quadratic models, appear to be more suitable.
我们研究了可修复条件可修复（RCR）模型和多靶（MT）模型在与线性二次（LQ）模型比较时，在高剂量分数放射治疗中的剂量转换中的适用性。分析了 V79 和 EMT6 单细胞接受 2-12Gy 单次剂量或 4 或 5Gy 2 或 3 分次剂量，以及 V79 球体接受 5-26Gy 单次剂量或 5-12Gy 2-5 分次剂量的细胞存活数据。通过集落测定法确定实际上将细胞存活降低到相同水平的单次和分次剂量。在计算软件 Mathematica 中，将实验中使用的单次剂量和剂量下的存活分数代入 RCR、MT 和 LQ 模型的方程中，计算每个参数系数。然后，使用这些系数和三个模型，计算低分割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次剂量进行比较。使用 RCR、MT 和 LQ 模型计算的等效单次剂量往往低于实际确定的等效单次剂量。LQ 模型在 5Gy 或更低剂量时似乎拟合得相对较好。在 6Gy 或更高剂量时，RCR 和 MT 模型似乎比 LQ 模型更可靠。在低分割立体定向放射治疗中，不应使用 LQ 模型，而应使用包含 RCR 或 MT 模型概念的转换模型，例如广义线性二次模型，这些模型似乎更合适。
