保乳术后全乳照射 VMAT 与 IMRT 的计量学比较

摘要

目的：比较保乳术后全乳照射 VMAT 与静态 IMRT 的剂量学差异，探索 VMAT 的可行性。方法：2014年－2015年入组乳腺癌患者10例，左侧、右侧乳腺癌各5例。用 Varian Eclipse 计划系统分别设计双弧VMAT 和5野 IMRT 计划，PTV 处方剂量50Gy 分25次，用 Delta 4进行剂量验证。配对 t 检验比较两组计划PTV、OAR 受量、机器跳数及有效治疗时间。结果：两组计划均能满足临床剂量学要求。 VMAT 与 IMRT相比CI 值分别为（1．01±0．1）和（1．36±0．2）（P ＜0．05）；HI 值分别为（0．124±0．01）和（0．173±0．02）（P ＜0．05）；心脏 V20、V30、Dmean增高（P ＝0．041、0．012、0．002）；肺 V20－V30无明显统计学差异，但是增加了患侧肺的 V5（58．2±3．5）％ vs （51．4±4．2）％（P ＜0．05）；机器跳数分别为（452±98）和（786±32）（P ＜0．05）；有效治疗时间（2．5±0．89）min 和（15±1．78）min（P ＜0．05）。结论：在靶区覆盖率相似前提下，VMAT 可降低部分 OAR 受量，并能改善 CI 值、减少机器跳数、缩短有效治疗时间。Synergy 平台上的 VMAT 计划剂量稳定可靠。%Objective:To compare the dosimetric difference in VMAT and IMRT planning for breast cancer.Methods:Varian Eclipse,ten patients received radiotherapy alone after breast-conserving surgery were randomly selected.For each patient,two plans(VMAT and IMRT)were designed.In each plan,the volume of planning target volume (PTV)received prescription dose was not less than 95%.The dosimetric parameters were assessed with dosevolume histogram (DVH)and mean dose in PTV and organ at risk(OAR).Results:The irradition volume and meandose of heart and V5 of the lung can be increased by VMAT.Better conformal index(CI)and homogeneity index (HI)of PTV can be achieved.The MU and the therapy time can be reduced by the VMAT.Conclusion:The design ofVMAT plan for breast cancer should combined with clinic.VMAT can be considered for patients with good order incardio-pulmonary function.