近距离治疗中^192Ir放射源的校准

叙述以参考空气比释动能率校准１９２Ｉｒ高剂量率放射源的刻度方法及对结果的分析。材料与方法使用ＮＥ０．６ｃｃ２５７１型石墨电离室和自行设计的测量支架。电离室及剂量仪经国家计量科学院校准，由于目前尚无１９２Ｉｒ刻度标准，一般对６０Ｃｏγ和２５０ＫＶＸ射线插值，以获得１９２Ｉｒ的校准因子。这一方法要求电离室具有较好的能响特性（１．０－２．０％），以及校准时有相同的室壁厚度。结果分别在１０ｃｍ和１５ｃｍ处刻度１９２Ｉｒ放射源，所得结果的差别小于１．０％。结论这一方法的系统误差，主要来自插值以获得１９２Ｉｒ的校准因子，由于使用的电离室能响较好及方法得当，插值的误差不会超过０．５％，而其他因子相对较小，对系统误差不会有较大影响，因此可以认为以参考空气比释动能率刻度１９２Ｉｒ剂量率的方法准确可行。

^Calibration of , Ir source for HDR brachytherapy

Purpose To describe a method of calibration 192 Ir source for HDR brachytherapy by using air Kerma rate . Materials and Methods NE 2570 electrometer with 0 . 6cc 2571 ionization chamber, which was calibrated at the National Institute of Metrology at the energies of 60 Co and 250KVp X rays ( HVL 2 . 5mm Cu ) . was used for the calibration Ir192 source . As there is no. national calibraton standard for Ir 192 source ,the calibration factor of EN 571 chamber for 192 Ir source was obtained by interpolating from the calibration factors at the energies of 60 Co rays and 250 KVp Xrays assuming that energy response of NE 2571 be withinand the exposure weighted average energy of Ir is KeV The chamber was fixed in aspecially designed calibration jig at the positions radially 10cm and 15 cm away from the source durinIrsource calibration Results The data obtained at 10 cm and 15 cm positions are very close with discrepancy of less that Conclusion It is estimated that the systematic uncertainty in the determination of Kr value ismainly caused by the uncertainty of obtaining Nx of Ir by interpolatin Nx of Co ray and 250 KVpXray the rays As NE 2570 with 2571 chamber has a good energy response at the range of Co th KVp Xray ,the estimated error for Nx of Ir radiation might be smaller than The uncertainties caused by other factors are expected to be relatively small and don't te significantly It is believable that our procedure could be acceptable fur the air Kerma rate calibration of Ir source .