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目的：寻找限光筒、挡块开孔、电子线能量对电子线百分深度剂量的影响，明确它们的变化趋势和幅度，针对性地用于临床。方法：采用三维水箱系统测量Ｐｒｉｍｕｓ直线加速器各种条件下的中心轴百分深度剂量。结果：（１）电子线的百分深度剂量与射野大小（即挡块开孔）有很大的关系，特别是照射野较小及能量较高时，小野的时候，随着照射野的减小，最大剂量点深度移向表面，治疗深度变浅，剂量跌落变缓，能量升高，这种效应更明显；当射野尺寸大于射程时，已看不出这种效应。（２）百分深度剂量曲线与限光筒的关系不大，能量较高时，限光筒的影响变大，但差异不会超过４％。（３）电子线矩形射野的百分深度量可根据平方根的算法计算。结论：应分别实测限光筒和射野的百分深度量。选择能量时要同时考虑照射野的大小，防止由于深度剂量不足而引起复发，小射野时更要小心。
OBJECTIVE: To find out the effects of limiting light tube, stop hole and the energy of electron beam on the percentage depth of electron beam, to clarify their changing tendency and amplitude, and to use it in clinic. Methods: The three-dimensional water tank system was used to measure the central axis percent depth dose under various conditions of the Primus linear accelerator. Results: (1) The percentage depth of electron beam dose has a great relationship with the field size (ie, the opening of the stopper). Especially when the radiation field is small and the energy is high, Decrease, the maximum dose point depth to the surface, the treatment depth becomes shallow, the dose falls slowly, the energy increases, the effect is more obvious; when the field size is greater than the range, this effect can not be seen. (2) The percentage depth dose curve has little to do with the light-limiting tube. When the energy is higher, the influence of the light-limiting tube becomes larger, but the difference will not exceed 4%. (3) The percentage of the rectangular depth of field of electronic wire can be calculated according to the algorithm of square root. CONCLUSIONS: The percent depth of light-limiting cylinder and field should be separately measured. Select the energy to consider the size of the radiation field at the same time, to prevent recurrence due to insufficient doses of depth, but also be careful when a small radio field.