分段弧和全弧旋转容积调强放疗治疗胸中段食管癌的剂量学比较

目的通过比较不同旋转容积调强放疗(全弧VMAT和分段弧VMAT)治疗胸中段食管癌的剂量学差异,分析应用分段弧VMAT治疗胸中段食管癌的可能性。方法选择11例胸中段食管癌患者,分别设计全弧VMAT、分段弧VMAT两种治疗计划,统计并比较靶区(PTV)、危及器官(肺、脊髓、心脏)、以及机器总跳数(MU)等参数的剂量学差异。应用SPSS17.0软件对两组数据进行配对t检验分析。结果全弧VMAT计划PTV D95(t=-7.699, P=0.000)、D98(t=-6.384, P=0.000)、均匀性指数(HI)(t=10.423, P=0.000)均优于分段弧VMAT,分段弧VMAT肺的平均剂量、V5(t=-4.048, P=0.002)要优于全弧VMAT。靶区的适形度指数(CI)、MU、双肺的V10、V20差异无统计学意义(P>0.05)。结论胸中段食管癌放疗时应用全弧VMAT、分段弧VMAT均可以满足靶区临床要求,但分段弧VMAT可以明显减少肺低剂量区域照射范围。

Dosimetry comparison of partial-arc and full-arc volumetric modulated arc therapy for middle esophageal cancer

Objective The study was performed to compare the dosimetric differences of different volumetric modulated arc therapy (VMAT) (full-arc VMAT and partial-arc VMAT) for middle esophageal cancer, and explore the feasibility of partial-arc VMAT in treatment.Methods Two plans were designed for 11 patients with middle esophageal cancer, including partial-arc VMAT and full-arc VMAT plan. The dosimetric differences of the parameter of the planning target volume (PTV), organs-at-risk (lung, spinal cord, and heart) and monitor units (MU) were compared. Paired t-test analysis was performed on the two groups of data using SPSS 17.0 software.Results The full-arc VMAT plan was superior to partial-arc VMAT plan in PTV D₉₅ (t = - 7.699, P = 0.000), D₉₈ (t = - 6.384, P = 0.000) and homogeneity index (HI)(t = 10.423, P = 0.000). The partial-arc VMAT plan was better than the full-arc VMAT in the V₅ of lungs (t = - 4.048, P = 0.002). There was no significant differences were found in the conformity index and homogeneity index of PTV, the V₁₀, V₂₀ of lungs (P > 0.05).Conclusion The partial-arc VMAT and full-arc VMAT plan met the clinical requirement for middle esophageal cancer, while the partial-arc VMAT can significantly reduce the dose to low dose area in lungs.