摘要目的 计算6711型125I种子源的剂量特性.方法 使用EGSnrc蒙特卡罗模拟程序对种子源的各向异性函数、径向剂量函数和剂量率常数进行计算,并给出了不同介质中的空间剂量率分布,将计算结果与美国医学物理师协会(AAPM)TG43-U1号报告中的推荐值和其他已发表的相关数据进行了比较.结果 各向异性函数与其他最新发表的数据符合较好;径向剂量函数与TG43-U1推荐值符合较好;剂量率常数为0.951 cGy·h-1·U-1,与TG43-U1推荐值在1.45%内吻合.结论 6711型125I种子源剂量场具有低剂量率,高梯度的特点;各向异性函数在近距离小角度处存在小突起的结构.

abstractsObjective To calculate the brachytherapy dosimetry parameters for Model 6711 125I seeds.Methods Brachytherapy dosimetry parameters are determined in accordance with the AAPM Task Group No.43 TG43-U1 dosimetry protocol.The anisotropy funetion,radial dose function,dose rate constant and dose distributions in different medium are calculated using EGSnrc code with the updated XCOM cross section libraries.Results The anisotropy function and the radial dose function are in good agreement with the data reported lately.The calculated dose rate constant is 0.951 cGy·h-1·U-1,in a 1.45% agreement with the consensus data recommended by AAPM TG43-U1 report.Conclusions The dose field around the seed source shows the characteristics of very low dose rate and very high dose gradient.A small structure iS found in the small polar angle range and the small distances of the anisotropy function.