基于蒙特卡洛方法对小野数据测量比较研究

摘要

目的 采用临床上常见的探测器对小野的相对剂量曲线进行测量并和蒙特卡洛方法模拟计算结果进行比较,得出比较准确的测量方法,并对误差较大的探测器进行修正.方法 采用探测器CC13、PFD、SFD联合蓝水箱的使用,对美国瓦立安公司的Trilogy直线加速器的6 MV X射线下的2 cm×2 cm,3 cm×3 cm,4 cm×4 cm的百分深度剂量曲线和平坦度对称性曲线进行数据采集,测量结果与当前的金标准即蒙特卡洛方法模拟计算的结果进行比较,得出适合小野相对剂量数据测量的方法,并给出误差较大的探测器的修正因子,为临床上提供参考数据.结果 SFD探测器与蒙卡模拟计算的结果最接近.CC13、PFD测量误差较大.CC13、PFD的测量结果中半影区内的修正因子最大可达到1.499,小的可以达到0.664.结论 SFD较CC13、PFD更适合小野相对数据的测量,CC13、PFD可以通过相应的修正为临床提供参考数据.%Objective To compare the relative dose of small fields measured by clinically common detectors and those obtained from Monte Carlo simulation in order to obtain the accurate measurement method, and to modify the inappropriate detectors.Methods The percentage depth-dose distribution curve and profile (flatness and symmetry) curves were collected at 2 cm×2 cm, 3 cm×3 cm, and 4 cm×4 cm under 6-MV X-ray of Trilogy linear accelerator by CC13, PFD, SFD, and blue phantom.The results were compared with the stimulation results from Monte Carlo method (the current gold standard).The correction factors for the detectors with large error were calculated to provide reference data for clinical practice.Results The results measured by SFD detector were most close to the results from Monte Carlo simulation.The measurement errors of CC13 and PFD detectors were large.The correction factor in the penumbra for CC13 and PFD detector was 0.664-1.499.Conclusions SFD detector is better than CC13 and PFD detector in the measurement of small fields, but CC13 and PFD detector can provide reference data for clinical practice after the corresponding correction.