胸段食管癌VMAT计划的剂量学验证研究

Study on dosimetric verification of VMAT treatment planning for chest esophageal carcinoma

目的 探讨VMAT计划在胸段食管癌放疗中的适应性.方法 应用0.6 cm3指形电离室和COMPASS三维剂量验证系统分别对10例胸上段、10例胸中段食管癌的VMAT计划进行绝对剂量和相对剂量的验证.应用DVH比较靶区、肺、心脏和脊髓受照剂量和体积差异,并分析GTV、CTV、PTV和OAR的γ通过率.结果 胸上、中段食管癌的等中心处绝对剂量精确度均≥99％,GTV、PTV和OAR的γ通过率均≥97％.胸上段食管癌GTV、CTV、PTV的D95％、Dmean的验证差异均≤3％,脊髓D1％差异为2.21％,左肺和右肺的V5～ V30、Dmean的差异≤2％.胸中段食管癌的GTV、CTV、PTV和OAR的D95％、Dmean的验证差异≤2％,脊髓D1％差异为2.04％.左肺和右肺的V5～ V30以V10为界差异呈逐渐增大的趋势,处于1.5％以内.心脏Dmean的差异为2.68％.结论 VMAT技术在胸段食管癌放疗中是适用的.

Objective To study the dosimetry characteristics of VMAT plan in the esophageal carcinoma radiotherapy.Methods Application of 0.6 cm3 ionization chamber and COMPASS threedimensional dose verification system,20 cases of upper and middle chest esophageal carcinoma on the VMAT plans for absolute dose and relative dose verification.Dose volume histogram （DVH） comparison treatment target,lungs,heart,and differences in the spinal cord irradiation dose and volume,and analyses γpass rate of GTV,CTV,PTV and organs at risks.Results The center dose of upper and middle chest esophageal carcinoma accurate rates were above 99%.Thoracic segment esophageal：GTV,PTV and organs at risks of γ pass rate above 97%.D95% and Dmean of GTV,CTV and PTV were relatively undervalued within 3%.D1% of spinal cord is 2.21% overvalued.Left and right pulmonary V5 were slightly overvalued by about 0.5%,V10-D30,Dmean undervalued within 2%.In period of middle chest esophageal carcinoma：the gamma passed rate of GTV,CTV,PTV and organs at risks of above 97%,GTV,CTV,PTV D95%,Dmean were relatively undervalued within 2%.Spinal cord D1% is 2.04% overvalued.Left and right pulmonary V5-D30 to V10 as a trend of gradually to be underestimated,at 1.5%.Heart Dmean was undervalued by 2.68%.Conclusion VMAT technology is applicable in the chest esophageal carcinoma radiotherapy.