铱-192新源剂量学参数测量方法研究

Experimental measurements of dosimetric parameters of Ir-192 new source

目的 通过192Ir新源径向剂量函数gL（r）和各向异性函数F（r,θ）的测量值与计算值的比较建立剂量学参数评价方法 .方法 用聚苯树脂材料制成实验体模,其上包括放射源出入孔和各测量位置上用于盛放热释光剂量计（TLD）管的孔.用体模在192Ir辐射场中测量参考方向上1～14 cm半径的剂量,用以计算gL（r）;测量1、3、5 cm半径圆周上各向（0°～165°,间隔15°）剂量,用以计算F（r,θ）.上述测量值与蒙特卡罗（MC）模拟计算值进行配对t检验比较差异.结果 gL（r）在1～14cm半径计算值为1.007～0.681,测量值为1.007～0.598（t=0.00～2.89,P值均〉0.05）.F（r,θ）在1、3、5 cm半径圆周上0°～165°的计算值分别为0.631～1、0.660～1、0.696～1,测量值分别为0.701～1、0.668～1、0.629～1（t=0.40～1.63、0.02～2.10、0.08～2.03,P值均〉0.05）.结论 TLD测量的192Ir源gL（r）和F（r,θ）值与MC计算结果 一致,其数据均可用于治疗计划系统.

Objective To perform thermoluminescent measurements of radial dose function and anisotropy function of a newly designed 192Ir microSelectron-HDR source, and establish evaluation methods for HDR dosimetry.Methods A polystyrene phantom with sylindrical holes in different measure positions was designed to accommodate thermo luminescent dosimeter （TLD） rods and radiation source.TLD rods with similar sensitivity were placed on a semicircle around the source center which had been precisely localized by either radiographic means or dose measurement.Dose-rates were measured at θ = 90° and r = 1-14 cm to calculate radial dose function （gL （r））, while measured along polar angles θ = 0° -165°（interval 15°） at radial distances r = 1 cm, 3 cm and 5 cm to calculate anisotropy function （F（r,θ））.All data were compared with those calculated by Monte Carlo （MC） method.The t-test was used for the statistics.Results The values of gL （r） were 1.007 -0.681 by calculation and 1.007 -0.598 by measurement with r = 1 - 14 cm（t = 0.00 - 2.89, all P 〉 0.05）.The values of F （r,θ） were 0.631 - 1,0.660 - 1 and 0.696 - 1 by calculation, while 0.701 - 1, 0.668 - 1 and 0.629 - 1 by measurement at 1 cm, 3 cm and 5 cm with θ=0° -165°（t=0.40 -1.63, 0.02 -2.10, 0.08 -2.03, all P〉0.05）.Conclusions The results of radial dose function and anisotropy function measured by TLD measurement are in consistent with those calculated by MC calculations, which can be applied in treatment planning system as original input.