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[目的]探讨电子直线加速器的注入电流改变对剂量学参数照射野对称性产生的影响。[方法]手动模拟加速器注入电流的改变,在照射野对称性良好的注入电流工作点附近设置正负模拟值,以胶片法测量和分析对应的照射野对称性改变。[结果]注入电流的数值在加速器的左右方向不会影响照射野对称性的质量,在枪靶方向的对称性偏差值受注入电流数值的影响近似为线性关系,当注入电流偏离中值200mA时,相应的对称性误差接近3%。[结论]检测加速器注入电流的改变可以提示照射野对称性的误差,经常性监视照射野剂量特性和注入电流应纳入每周的质控检验内容。
[Objective] To investigate the influence of the change of injection current of electron linear accelerator on the field symmetry of dosimeter parameters. [Method] The injection current of manual accelerator was changed manually. Positive and negative analog values were set near the operating point of injection current with good symmetry of irradiation field. The corresponding changes of irradiation field were measured and analyzed by film method. [Result] The results show that the injection current has no influence on the symmetry quality in the left and right of the accelerator. The symmetry deviation in the gun target direction is approximately linear with the injection current. When the injection current deviates from the median value of 200 mA , The corresponding symmetry error is close to 3%. [Conclusion] Detecting the change of injector ’s injection current can indicate the error of irradiation field symmetry. The dose characteristics of injection field and injection current should be included in the weekly quality control test.