5种铅门X轴固定技术在鼻咽癌容积旋转调强放疗中的剂量学比较

目的:比较鼻咽癌容积旋转调强（VMAT）计划设计中X轴方向不同铅门大小的剂量学差异，探讨鼻咽癌VMAT设计中最优的铅门固定大小。方法:在Eclipse 11.0计划系统中采用5种铅门固定方法分别对10例鼻咽癌患者设计放疗计划，比较5种计划得到的靶区和危及器官的剂量学参数以及机器跳数。采用SPSS 23.0软件对数据进行配对t检验分析。结果:5种固定铅门技术得到的靶区D95、Dmean和HI等剂量学参数均无明显差异（P>0.05），铅门在X2方向全关（FJ1）计划组的CI好于其他计划组（t=-2.97~-1.06, P<0.05）；FJ1计划组得到的脊髓Dmax、左右侧腮腺、喉以及口咽的V30和Dmean等剂量学参数均优于其他计划组（t=-5.83~1.14, P<0.05），而对于脑干、耳蜗和颞叶等器官，5种固定铅门技术无明显差异（t=-0.99~2.99, P>0.05）；FJ1计划组的机器跳数高于其他计划组（t=8.15~8.86, P<0.05）。结论:5种铅门固定技术均能满足临床要求，而FJ1计划组能够更好地降低危及器官照射剂量，但同时增加了机器跳数，增加了照射时间；而铅门在X2方向从半开到全关（FJ2）计划组相比于FJ1计划组对于器官的保护较差，但提高了治疗效率。

Dosimetric study of 5 fixed-jaw techniques in volumetric modulated arc therapy for nasopharyngeal carcinoma

Objective To compare dosimetric differences of X-axis directional fixed-jaw techniques in volumetric modulated arc therapy(VMAT)for nasopharyngeal carcinoma(NPC)for investigating the optimal fixed-jaw scheme.Methods In Eclipse 11.0 treatment planning system,5 fixed-jaw techniques were used to design radiotherapy plans for 10 NPC patients.The differences in dosimetric parameters of target areas and organs-at-risk as well as monitor units were compared among 5 plans,and SPSS 23.0 software was used to perform paired sample t-test on the obtained data.Results There was no significant difference among 5 plans in the Dmean,D95 and homogeneity index of target areas(P>0.05),but the conformity index in FJ1 plan in which the jaw was fully closed in X2 direction was better than that in other fixed-jaw techniques(t=-2.97--1.06,P<0.05).The Dmaxof spinal cord,the V30 and Dmeanof parotid glands,larynx and oral cavity in FJ1 plan were lower than those in the others,with statistical significances(t=-5.83-1.14,P<0.05).No statistical significance was found in brainstem,cochlea and temporal lobes(t=-0.99-2.99,P>0.05).Moreover,FJ1 plan had the highest monitor units(t=8.15-8.86,P<0.05).Conclusion All the 5 fixed-jaw techniques can meet the clinical requirements,while FJ1 techniques can reduce organs-at-risk doses,but increase monitor units and delivery time.Compared with FJ1 techniques,FJ2 technique in which the jaw is changed from half-open to fully-closed in X2 direction has inferior organsat-risk sparing,but improves treatment efficiency.