论文部分内容阅读
目的 用电离室测量外挂式多叶准直器 (MLC)对准直器散射因子 (Sc)的影响 ,并用双源模型对结果进行分析。方法 测量MLC形成的 2个不规则射野序列 ,并与等效方野的测量值进行了比较 ,应用双源模型得出MLC对Sc产生影响时叶片所处的位置公式。结果 当MLC叶片位置离中心足够近时 ,叶片将对准直器散射因子产生影响 ;产生影响时叶片位置计算值与测量结果相符。结论 基于双源模型的MLC位置公式较好地描述了当外挂式准直器 (MLC或铅块 )形成的射野小于公式给出值时 ,准直器散射因子将受其影响。
Objective To measure the influence of the MLC on the scattering factor (Sc) of the collimator with an ionization chamber and analyze the results with a dual source model. Methods The two random field sequences formed by MLC were measured and compared with the measured values of equivalent square fields. The dual-source model was used to derive the position formula of the blade when MLC affected Sc. Results When the MLC leaf position is close enough to the center, the leaf will have an influence on the scattering factor of the collimator. When the influence is made, the calculated value of the leaf position is consistent with the measurement result. Conclusions The MLC position formula based on the dual source model better describes the collimator scatter factor that will be affected when the field formed by the plug-in collimator (MLC or lead block) is less than the value given by the equation.