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目的:对调强放射治疗(IMRT)中靶区与器官不同分次剂量的生物效应进行计划优化设计,评价和探索以生物等效剂量条件改善中晚期鼻咽癌IMRT计划质量的可行性。方法:选择IMRT计划20例鼻咽癌患者,按治疗分次和线性二次模型设定危及器官的等效剂量限制条件并重新进行治疗计划的优化计算。分析和比较生物等效剂量优化计划(BEPlan)与原物理剂量优化计划(PHPlan)的结果,包括靶区适形性指数(CI)、剂量均匀性指数(HI)、危及器官平均剂量和最大剂量等参数。结果:与PHPlan比较,BEPlan处方剂量包绕的靶区体积(TV95%)无明显差别,CI和HI分别改善了8.03%和8.33%,较靠近靶区的危及器官剂量略有上升但生物等效剂量远小于各器官的剂量限制值。结论:采用等效剂量优化方法有助于提高治疗计划的靶区剂量适形性和均匀性。
OBJECTIVE: To plan and optimize the biological effects of different doses of targets and organs in IMRT and evaluate the feasibility of using bioequivalent doses to improve the quality of IMRT plans in patients with advanced nasopharyngeal carcinoma. METHODS: Twenty patients with nasopharyngeal carcinoma were enrolled in the IMRT plan. The dose-limiting conditions of organs at risk were set according to the treatment and linear quadratic models, and the optimal treatment plan was re-calculated. Analyze and compare the results of BEPlan and PHPlan, including the target conformability index (CI), dose uniformity index (HI), mean organ dose at risk and maximum dose Other parameters. RESULTS: Compared with PHPlan, there was no significant difference in volume of target area (TV95%) surrounded by BEPlan prescription dose, CI and HI were improved by 8.03% and 8.33%, respectively, but organ dose was slightly higher than that of target area The dose is much smaller than the dose limit for each organ. Conclusion: The equivalent dose optimization method can help to improve the target dose conformability and uniformity of the treatment plan.