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目的:探讨Monaco计划系统控制点统计不确定度的选择对鼻咽癌剂量分布的影响，给出蒙特卡罗计算中满足临床的单个控制点统计不确定度。方法:设置9个等机架角度间隔的10 cm×10 cm方野并随机抽取5例9个野调强放疗(IMRT)和5例容积调强弧形治疗(VMAT)鼻咽癌计划，以各自计划CT作为质量保证模体创建验证计划，计算时格点步长选择3 mm，单个控制点的统计不确定度分别选择1%、2%、3%、4%和5%，分析选择不同统计不确定度的计算结果与选择统计不确定度为1%时的差异。结果:对于单一方野和单一调强野，当控制点统计不确定度选取为4%时中心点剂量偏差高达7%；对于9个野IMRT和单弧VMAT不同控制点统计不确定度选取时中心点剂量偏差均≤1.5%，计划靶区体积平均剂量偏差均≤0.3%；对于9个野IMRT当控制点统计不确定度≤3%和单弧VMAT当控制点统计不确定度≤4%时中心冠状平面剂量中偏差99%。结论:基于蒙特卡罗计算的Monaco计划系统，控制点统计不确定度在1%～5%变化对于单一射野影响较大；在临床计算中，建议9个野IMRT的控制点统计不确定度选取应≤3%，VMAT的控制点统计不确定度选取应≤4%。“,”Objective:To explore the influence of the selection of statistical uncertainty of control points in Monaco planning system on the dose distribution of nasopharyngeal carcinoma (NPC), aiming to provide the statistical uncertainty of single control point in Monte Carlo calculation which satisfies clinical needs.Methods:First, nine 10 cm×10 cm square fields with an equal interval of gantry angle were designed and five cases of 9-field intensity-modulated radiotherapy (IMRT) and five cases of single-arc volumetric-modulated arc therapy (VMAT) plans were randomly selected, Then, quality assurance (QA) verification plan using patient CT as QA phantom was created. Second, the grid spacing was selected as 3 mm during the calculation of dose distribution of QA plan. The statistical uncertainties of single control point were selected as 1%, 2%, 3%, 4% and 5%, respectively. Last, the deviation of dose distribution between different statistical uncertainties and 1% statistical uncertainty was analyzed.Results:For a square field and single IMRT field, the dose deviation of center point was almost 7% while the statistical uncertainty was selected 4%. For 9-field IMRT and single-arc VMAT, the dose deviation of center point was ≤ 1.5% and the average dose deviation of PTV was ≤ 0.3% when the statistical uncertainty of control points was changed from 1% to 5%. The percentage of the point dose deviation of the coronary plane of ≤ 1% was greater than 99% when the statistical uncertainty was ≤ 3% for 9-filed IMRT and 4% for single-arc VMAT.Conclusions:For the Monaco treatment planning system based on Monte Carlo calculation, the changes in the statistical uncertainty of control point from 1% to 5% exert significant effect upon the single field. In clinical application, the statistical uncertainty of control point should be ≤ 3% for 9-field IMRT and ≤ 4% for single-arc VMAT.