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【目的】通过对局部晚期鼻咽癌调强适形放射治疗（IM RT ）分阶段两次设计治疗计划的剂量学比较，探讨两次IM RT计划的必要性及可行性。【方法】选取本院50例局部晚期鼻咽癌患者为研究对象，随机分成两组，试验组和对照组，每组各25例。两组患者均先行诱导化疗2～4个疗程后行IM RT放疗，试验组采用两次IM RT计划设计，对照组则采用一次性IM RT 计划设计。观察比较两组患者的靶区及周围敏感器官剂量变化。【结果】对照组患者的双侧腮腺的平均剂量（Dmean）和超出限量体积占腮腺总体积的30％比例（V30）均明显高于试验组，且两组相比较差异有显著性（ P ＜0．05）；对照组患者的脑干和脊髓的Dmax及脑干总体积50％比例（V50）和脊髓总体积40％比例（V40）均明显高于试验组，且两组相比较差异有显著性（ P＜0．05）。【结论】采用两次IM RT计划治疗局部晚期鼻咽癌对于确保靶区的剂量和保证正常组织剂量、更有效地保护腮腺功能及脑干和脊髓等重要器官具有一定的优势。“,”To explore the necessity and feasibility of twice intensity modulated radiation thera-py(IMRT ) plans for locally advanced nasopharyngeal carcinoma through the dosiology comparison of IMRT therapy plan by stages for twice .[Methods]A total of 50 patients with locally advanced nasopharyngeal carci-noma were chosen as the research objects and randomly divided into experimental group and control group with 25 patients in each group .The patients in two groups were treated by chemotherapy for 2~4 periods ,and then IMRT radiotherapy .The experimental group was given twice IMRT plan design ,while the control group was given once IMRT plan design .The dose changes of target area and the surrounding sensitive organs in two groups were observed and compared .[Results] Mean dose(Dmean) and V30 of bilateral parotid in control group were obviously higher than those in experimental group ,and there was significant difference between two groups( P <0 .05) .Dmax and V50 of brain stem and spinal cord in control group were obviously higher than those in experimental group ,and there was significant difference between two groups ( P<0 .05) .[Con-clusion]The twice IMRT plans for the treatment of locally advanced nasopharyngeal carcinoma have a certain advantage for ensuring radiation dose of target area and normal tissue dose and protecting parotid function and important organs such as brain stem and spinal cord effectively .