胸中段食管癌VMAT与IMRT的心脏及其亚结构剂量学比较

摘要

目的:比较胸中段食管癌VMAT与IMRT的心脏及心脏亚结构的剂量学差异,寻找对心脏保护更佳的放疗技术.方法:对15例病理确诊的胸中段食管癌患者在相同标准下进行靶区及危及器官勾画,同时分别行7野IMRT计划和单弧全弧VMAT计划,并对两计划的心脏及心脏亚结构剂量进行比较.结果:在满足靶区相似覆盖的情况下,心脏及心脏亚结构高剂量区:全心V20~V40、心包V20和V25、左心房V40、右心房V25和V30、右心室V20~V30、右冠脉计划危险体积的V20~V30等比较上VMAT更低,差异具有统计学意义(P<0.05).相比IMRT,VMAT在全心、左心室、右心室、右冠脉计划危险体积等Dmean上也更低(P<0.05).而低剂量区比较上右心室V5则VMAT更高,但是在左冠脉前降支计划危险体积的V5、V10上却相反(P<0.05).其余参数比较则不具有统计学意义(P>0.05).结论:VMAT与IMRT均能满足胸中段食管癌患者的放疗要求,但VMAT较IMRT能提供更好的心脏保护,从剂量学方面降低了放疗导致的心脏损伤.%Objective To compare the differences in the doses of heart and substructures in volumetric modulated arc therapy (VMRT) and intensity-modulated radiotherapy (IMRT) of middle thoracic esophageal cancer, and investigate a better radiotherapy technology for heart protection. Methods Fifteen patients with middle thoracic esophageal cancer confirmed by pathology were enrolled in this study. The target areas and organs-at-risk were delineated with the same criterion, and meanwhile 7-fields IMRT and 1-arc VMAT plan were designed for each patient. The dose of heart and substructures were compared between the two plans. Results Under the same target coverage, compared with IMRT plan, VMAT plan had significant reductions in the high-dose regions of heart and substructures, particularly in V20-V40of the whole heart, V20and V25of pericardium, V40of left atrium, V25 and V30of right atrium, V20-V30of right ventricle, V20-V30of planning risk volume-right coronary artery (PRV-RCA) (all P<0.05). Moreover, the mean dose of the whole heart, left ventricle, right ventricle and PRV-RCA in VMAT plan were much lower than those in IMRT plan (P<0.05). The comparison in low-dose regions revealed that the V5of right ventricle was higher and the V5 and V10of PRV-LAD were lower in VMAT plan as compared with IMRT plan (P<0.05). No statistical differences were found in other parameters (P>0.05). Conclusion Both VMAT and IMRT can meet the radiotherapy needs of middle thoracic esophageal cancer patients, but VMAT can further decrease the doses of heart and substructures and reduce the heart injuries caused by radiotherapy.