中晚期鼻咽癌调强放疗生物等效剂量优化的可行性探讨

Feasibility study of biologically effective dose optimization of IMRT for locally advanced nasopharyngeal carcinoma

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 account the biological effect of fraction dose difference in target and OARs when planning IMRT treatment, and evaluate the feasibility of improving plan quality using biological equivalent dose. METHODS： Twenty NPC IMRT plans were selected and re-optimized with biological equivalent dose constraint according to fraction dose and L-Q model. Dose distribution of biological re-optimized plans （BEPlan）, including target CI and HI, mean dose and maximum dose of OARs, etc. , were compared with the original physical optimized plans （PHPlan）. RESULTS： BE-Plan and PHPlan had similar score on target TV95;, but improved CI and HI by 8.03; and 8.33% respectively. Mean dose increased slightly for OARs closing to target volume but lower than limitation. CONCLUSION： Using BED optimization can improve target conformity and homogeneity.