摘要目的:根据IAEA-483号报告对临床使用的各类半导体或电离室探头进行高能光子束小野输出因子(Scp)测量并修正，探讨其修正数据在小野Scp测量的准确性。方法:使用EGSnrc蒙特卡罗(MC)模拟软件模拟Varian Novalis Tx直线加速器参考测量剂量曲线(Profile)和百分深度剂量曲线，调整模拟参数。使用电离室A16、A14 sL、CC01、CC13和半导体探头PFD、EFD、Razor在不同射野下(0.5~10.0 cm方野)的剂量曲线测量值、半峰全宽等效方野Scp测量值分别与MC模拟结果对比分析。使用IAEA-483报告修正因子对测量Scp修正，比对和分析修正前后测量数据和MC模拟数据。结果:MC模拟对比PFD测量曲线偏差<2.0%。在<3.0 cm方野时MC模拟Profile曲线与半导体探头测量吻合。野外低剂量区Razor相对于MC和PFD偏高(2.3%)，随射野增加而增加，10.0 cm方野达3.0%。CC13在10.0 cm方野Profile曲线的20.0%~80.0%半影宽度最大偏差3.0 mm。随射野减小，7种探头修正前Scp测量均值相对MC模拟偏差增大，标准差在接近1.0 cm方野时迅速变大，由5.0~1.5 cm方野的0.009~0.014变化到1.0~0.5 cm方野的0.030~0.089，修正前全体均值0.030。修正后的6种探头测量的Scp标准差均值0.008，0.8 cm方野为0.013，0.6 cm方野为0.021。等效方野≥1.0 cm时修正后Scp与MC模拟偏差-3.6%~-0.5%，<1.0 cm偏差-6.9%~-1.3%。结论:经IAEA-483报告修正后各探头测量Scp标准差较小，与MC模拟结果吻合较好，可用于高能光子束小野的临床剂量学研究。

abstractsObjective:To evaluate the accuracy of measurement of the output factor of high-energy photon small field (Scp) using commercial semi-diodes and ionization chambers in small fields in accordance with the IAEA-483 report, which has been proposed that all kinds of detectors should be revised for small field Scp measurement in clinical practice.Methods:EGSnrc of Monte Carlo (MC) software was utilized to simulate the treatment head of Varian Novalis Tx linear accelerator, and the profile curve and relative dose value were generated by simulation in DOSXYZnrc based on derived phase space file. Measurement of PDD and Profiles was used to adjust and validate the simulation mode. Detectors including ionization chambers A16, A14 sL, CC01, CC13, PFD and EFD and semi-diodes PFD, EFD and Razor under different radiation field settings (0.5 cm to 10.0 cm) were employed to measure the profile curves and Scp of FWHM equivalent rectangular fields, which were compared with data of Monte-Carlo simulation. The measurement of Scp was revised by data given in the IAEA-483 report. The data with or without correction were compared with the data of MC simulation.Results:A curve deviation o F<2.0% between MC simulation and PFD measurement was accepted. MC simulated Profiles were consistent with PFD, EFD and Razor measurements, when the field was<3.0 cm. Razor response in the out-field region was 2.3% higher than those of MC and PFD, and it increased with the increment of field and was 3.0% at 10.0 cm. The maximum 20.0%-80.0% penumbra width was detected as 3.0 mm for CC13 at 10.0 cm rectangular field. With the decrease of the radiation field, the deviation relative to MC simulation was increased as for Scp mean values of 7 detectors before correction. The standard deviation (SD) of the measured value was increased rapidly when it was close to 1.0 cm, ranging from 0.009-0.014 for the field of 5.0 cm-1.5 cm to 0.030-0.089 for the field of 1.0 cm-0.5 cm. The mean value of SD for the whole measurement before correction was 0.030. The mean SD of Scp measured by the six probes was 0.008, 0.013 at 0.8 cm and 0.021 at 0.6 cm after correction. When the equivalent field was ≥1.0 cm, the corrected Scp and MC simulation deviation was ranged from -3.6% to -0.5%. The error was between -6.9% and -1.3% when the radiation field was<1.0 cm. Conclusion:The SD of Scp measured by different detectors after correction in accordance to the IAEA-483 report is small, which is in good agreement with the data of MC simulation, suggesting that it could be applied in clinical dosimetry.