后装^(192)Ir放射源空气比释动能强度的测量及不确定度分析

Measurement and Uncertainty Analysis of Air Kerma Strength for Afterloading Radioactive Source ^(192)Ir

目的分析验证后装^(192)Ir放射源的空气比释动能强度,探讨井型电离室法测量过程中各项不确定度的来源并评定其扩展不确定度。方法首先按照井型电离室法测量^(192)Ir源的空气比释动能强度,在验证完成的基础上建立对应的数学模型,再综合运用A类或B类不确定度评定计算得出测量结果的扩展不确定度。结果在34次的测量计算中,我院3颗^(192)Ir源的测量值与计划系统计算值相对误差均符合美国医学物理学家学会临床应用小于±3%的标准,且二者无统计学差异(P>0.05),测量结果的扩展不确定度为4.1%(k=2)。结论井型电离室法能够精准测量^(192)Ir源的空气比释动能强度,该方法扩展不确定度的最大影响因素为井型电离室的参考空气比释动能率校准因子。

Objective To analyze and verify the air kerma strength of after loading radioactive source ^(192)Ir,explore the various sources of uncertainties in the measurement process of the well-type ionization chamber method,and evaluate the expanded uncertainties.Methods Firstly,the air kerma strength of the ^(192)Ir source according to the guidance of the well-type ionization chamber method were measured.Based on the completion of the verification,the corresponding mathematical model was established.Then the extended uncertainty of the measurement results was calculated by comprehensive application of class A or class B uncertainty evaluation.Results Among the 34 measurement calculation,the relative errors between the measured data and the planning system calculated data of the three ^(192)Ir source in our hospital were all met the standard of AAPM clinical application of less than±3%.There was no statistically difference between them(P>0.05),and the expanded uncertainty of the measurement result was 4.1%(k=2).Conclusion The well-type ionization chamber method can accurately measure the air kerma strength of the ^(192)Ir source.The largest influencing factor of the expanded uncertainty of this method is the calibration factor of the reference air kerma rate of the well-type ionization chamber.