鼻咽癌调强放疗等效均匀剂量优化方法对腮腺的保护作用

Intensity-modulated radiation therapy for nasopharyngeal carcinoma parotid sparing with euivalent uiform dose optimization

目的探索等效均匀剂量(EUD)优化方法在鼻咽癌调强放疗中对腮腺的保护作用。方法从已接受调强放疗的鼻咽癌患者中,随机抽取12例。这些患者的治疗计划均是采用物理约束条件优化设计的。以这些计划为基础,将腮腺的物理约束条件改为EUD约束,而保持其他危及器官和靶区的约束条件不变,为每位患者设计一个新的计划,并比较新旧治疗计划。结果在保证靶区和其他危及器官受照剂量不变情况下,EUD优化能够使腮腺的平均剂量和V_(30)显著降低,经T检验,P值都＜0．05。结论EUD优化能够降低腮腺的受照剂量,这对降低腮腺放疗并发症具有重要意义,也为靶区加量提供了空间。

Objective The aim of this study was to evaluate the role of an euivalent uiform dose （EUD） based optimization algorithm in sparing the parotids of patients with nasopharyngeal carcinoma （NPC） when they are treated with intensity-modulated radiation therapy（IMRT）. Methods 12 patients were randomly selected from the NPC patients who received IMRT treatments. For these patients, the treatment plans were designed with physical optimization constraints （close/dose-volume constraints）. Based on these plans, new plans were designed through replacing the physical constraints with maximum EUD for parotids, while keeping the physical objectives for targets and other organs at risk（OARs） unchanged. Comparison was then made between the new plan, which had EUD constraints to parotids, and the former for each individual patient. Results While maintaining the close to the targets and the other OARs unchanged, optimization with EUD constraints to parotids decreased the mean close and V30 of parotids significantly, simultaneously, the close of target volume and other organs at risk keep stable, the values of probability were less than 0.05 by T- test. Conclusions The doses to parotids can be reduced through optimization with EUD constraints. This finding is quite helpful to reduce the occurrence rate of parotid complications,and to provide spaces for escalating target dose.