热释光剂量仪测量体模植入125I粒子源的剂量学参数可行性

Experimental determination of dosimetry parameters for Sinko 125I seed source using thermoluminescent dosimeter

目的 探讨应用热释光剂量仪在体模中测量植入125I粒子源（型号Sinko BT-125-1）的剂量学参数可行性.方法 将测量体模进行改进使其可适用于剂量学测量.根据AAPM TG43建议测量的参数包括剂量率常数Λ、径向剂量函数gL（r）和各向异性函数F（r,θ）等,所测数据与文献中其他构造相似的125I粒子源数据进行比较.结果 125I粒子源的Λ为0.928 cGyh-1 U-1.所测得的gL（r）范围为径向距离在1.0～10.0cm内所对应的值.F（r,θ）范围为角度在0.～90.内所对应的值.与型号Amersham 6711 125I粒子源相比,二者gL（r）值的最大差异为9.6％.二者F（r=2 cm,θ=0）值的差异为10.2％.应用此体模进行测量总的不确定度＜6.0％.结论 测量结果具备较小的不确定性和良好自洽性,故应用热释光剂量仪体模测量永久植入粒子源的剂量学参数是可行的.

Objective To study the dosimetry parameters of 125I seed source （type Sinko BT-125- 1 ） with thermoluminescent dosimeter （TLD） in the phantom. Methods The new type of phantom was modified to suit to measurement of a common type of 125I seed source. The AAPM TG43 protocol recommended measurements of dose-rate constant （ A）, radial dose function （ gL （r） ）, and anisotropy function （F （r,O）） have been performed in the phantom with TLD. Results The A was 0. 928 cGyh-l U-1. The gL（r） was determined at different radial distances r ranging from 1.0 to 10. 0 cm with an interval of 1.0 cm;and F （r,O） at angles from 0° to 90° in 10° increments. The gL（r） of 125I seed source showed a difference of 9. 6% at the most in comparison to the corresponding values of 1~I seed source （type Amersham 6711 ）. The difference in F（2 cm,0） of 125I seed source and Amersham 6711 was up to 10. 2% near the source end. With the phantom the combined standard uncertainty in the whole measurement was less than 6. 0%. Conclusions The experimental results exhibit fairly small measurement uncertainties and good self-consistency. It＇s feasible to measure the dosimetry characters of permanent implant seeds in the modified phantom.