射野方向优化技术在胸中上段食管癌调强放疗中的应用

目的：比较射野方向优化设野和均匀布野的胸上段和胸中段食管癌调强放疗计划的剂量学差异,探讨射野方向优化技术在食管癌放疗计划设计中的作用。方法：使用Varian Eclipse 8.6治疗计划系统,对7例胸上段食管癌和7例胸中段食管癌患者分别制定7野均分（EGA）和射野方向优化（BAO）的调强计划。根据剂量体积直方图（DVH）比较靶区、脊髓、双肺、心脏和正常组织的剂量体积参数,靶区适形度指数（CI）、均匀度指数（HI）以及总治疗跳数（MU）,利用SPSS软件进行配对t检验。结果：BAO计划的射野方向分布明显不同于EGA计划,并且患者间的射野方向分布也存在一定的差异。对于胸上段食管癌,BAO计划PTVD2%（-1.12%）、CI（2.42%）、HI（-11.88%）劣于EGA计划（P〈0.05）,BAO计划双肺MLD（3.77%）、V5（6.48%）、V10（6.16%）,Body-PTV的V5（7.30%）明显优于EGA计划（P〈0.05）。对于胸中段食管癌,BAO计划PTV D2%（0.88%）、Dmean（0.34%）,脊髓D1%（5.65%）,双肺MLD（9.10%）、V5（11.93%）、V10（8.65%）、V15（8.60%）,Body-PTV的Dmean（3.63%）、V5（8.65%）以及MU（17.26%）均明显优于EGA计划（P〈0.05）。结论：在胸中上段食管癌放疗中,使用BAO技术能够产生个体化的治疗方案。对于胸上段食管癌,BGO计划对靶区剂量的覆盖没有改善,但降低了肺剂量,减少了放射性肺炎发生的可能性;对于胸中段食管癌,BGO计划在不降低靶区剂量覆盖和较少MU的情况下,可以显著减少肺、脊髓、正常组织的剂量。与胸上段食管癌相比,胸中段食管癌使用BAO技术能够更好的改进调强放疗计划的质量。

Application of Beam Angle Optimization in IMRT Planning for Esophageal Cancer in Upper and Middle Thorax

Objective：To compare the dosimetric results of IMRT plan with beam angle optimization（BAO） and equally-spaced gantry angles for esophageal cancer in upper and middle thorax,respectively and to investigate the effect of BAO technique on treatment planning improvement.Methods：Beam angle optimization plans and equally-spaced gantry angles（EGA） plans were generated for seven patients with esophageal cancer in upper thorax and seven patients with esophageal cancer in middle thorax respectively using the Varian Eclipse 8.6 treatment planning system.With dosimetric data extracted from dose-volume histogram（DVH）,dose coverage to PTV,CI,HI of PTV,sparing of spinal cord,lungs,heart and normal tissue,monitor units（MU）were compared using paired t-test method with SPSS software.Results：Gantryangle differences were observed between BAO and EGA plans.There were even significant gantry angle differences between patients in BAO plan.For the upper thorax case,BAO plans produced significantly worse D2%（-1.12%）,CI（2.42%）,HI（-11.88%） of PTV than EGA plans（P〈 0.05）,but better sparing of lungs （MLD（3.77%）,V5（6.48%）,V10（6.16%））,sparing of Body-PTV（V5（7.30%）） than EGA plans（P〈 0.05）.For the middle thorax case,BAO plans produced significantly better D2%（0.88%） and Dme an（0.34%） of PTV than EGA plans（P〈 0.05）,and also better D1%（5.65%） of cord,sparing of lungs（MLD（9.10%）,V5（11.93%）,V10（8.65%）and V15（8.60%））,sparing ofBody-PTV（Dmean（3.63%）,V5（8.65%）） and lower MU（17.26%） than EGA plans（P〈 0.05）.Conclusions：Individualized plan canbe produced using BAO technique.For the upper thorax case,dose coverage to PTV is not improved but better protection of lungs is achieved.For the middle thorax case,the dose delivered to spinal cord,lungs,surrounding normal tissue is decreased while improving the dose coverage to PTV with lower MU.IMRT plan with BAO provides more improvement on the plan quality in middle thorax esophage