碳离子放射治疗中细胞存活实验数据处理方式对生物剂量分布计算值的影响

Influence of Cell Survival Experiment Data Processing on the Calculated Values of Biological Dose Distribution in Carbon Ion Radiotherapy

探究了细胞克隆存活实验中不同数据处理方法对线性平方(LQ)模型参数拟合值的影响及其用于治疗计划中所得生物剂量分布计算值的影响。依据LQ模型拟合T98G细胞碳离子辐照细胞克隆存活实验的数据,分别按照是否考虑细胞存活率标准差和以两种不同方式考虑贴壁效率得到4组LET-α和LET-β数据,并选择其中3组构建了3套matRad治疗计划系统的基础数据用于治疗计划研究。在仅考虑0 Gy贴壁效率时,是否考虑细胞存活率标准差拟合,在LET较低时对α值影响较小,对β值影响较大;在LET较大时,对α值影响较大,对β值影响较小。在考虑细胞存活率标准差时,两种不同方式考虑贴壁效率拟合的结果偏差较小,除200 keV/μm外,两组α值的相对偏差不超过±10%。Planset2与Planset1相比,总是高估了D_(max),D_(min)和D_(95)。结果表明,是否考虑细胞存活率标准差与以两种不同方式考虑贴壁效率相比,前者对拟合得到的α,β系数影响更大。治疗计划系统中不同基础数据间生物剂量分布计算值的相对偏差范围,小于拟合实验数据获得的各组α,β值的相对偏差范围。

The influence of different data processing methods on the fitting values of linear square(LQ)model parameters and the calculated values of biological dose distribution used in treatment planning were investigated in the cell cloning survival experiment.Four sets of LET-α and LET-β data were obtained based on the LQ model fitted to the data from the clonogenic survival experiments of carbon ion irradiated cells from T98G cells,according to whether the standard deviation of the cell survival rate was taken into account,and the plating efficiency was taken into account in two different ways,respectively,and three of them were selected to build the basedata of three datasets of the matRad treatment planning system for the treatment planning study.When only the 0 Gy plating efficiency was considered,whether the fitting considered the standard deviation of survival rate had little influence on theαvalue when the LET was low,but had a greater influence on the β value;With the LET getting larger,it had a greater impact on theαvalue and a lesser impact on theβvalue.When considering the standard deviation of survival rate,the deviations of fitting results in 2 different ways to consider the plating efficiency were small.Except for 200 keV/μm,the relative deviation ofαvalues between the two groups did not exceed ±10%.Planset2 always overestimated D_(max),D_(min) and D_(95) compared to Planset1.The results illustrate that whether the standard deviation of survival rate were considered or not had a greater influence on the fitted α,β coefficients than considering the plating efficiency in 2 different ways.The relative deviation range of biological dose distribution’s calculation values among different datasets in the treatment planning system was smaller than the relative deviation range of α and β values of each group obtained by fitting the experimental data.