摘要目的 探究通过容积调强弧形治疗(VMAT)共面电弧调节放疗的强度,头部倾斜的位置是否对放疗剂量的分布产生影响.方法 2015-2017年间500例头部肿瘤患者接受头部放疗并保持头部倾斜位置,通过旋转原始CT图像获得模拟的非倾斜CT图像资料.计划靶区剂量30 Gy,海马区最大剂量限制为16 Gy,视神经、视交叉与眼球的剂量＜37.5Gy.采用配对t检验对相关剂量学参数进行比较.结果 平均头部倾斜角度为(11.12°±0.68°);均匀性指数与适形指数倾斜与非倾斜相比分别降低(8.3±9.6)％(P=0.033)与(5.2±4.1)％(P=0.009);头部倾斜位置海马区剂量较非倾斜位置平均降低(13.6±6.2)％(P=0.004);晶状体剂量平均降低(15.5±11.1)％(P=0.008);视神经与眼球的剂量亦分别降低(6.8±5.6)％(P=0.013)与(8.6±6.5)％(P=0.016).结论 VMAT全脑放疗时通过将头部倾斜适当角度可明显改善靶体积的辐射剂量分布,同时降低海马区与视觉系统的辐射剂量,从而保证治疗的同时减少对患者认知与记忆功能的相关影响.

abstractsObjective To explore the intensity of coplanar arc-adjusted radiotherapy with volume-modulated arc therapy (VMAT) and whether the position of the head tilt influences the distribution of radiotherapy dose.Methods From 2015 to 2017,500 patients underwent radiotherapy of the head and kept their head tilted.The simulated non-inclined CT images were obtained by rotating the original CT images.The protocol of the coplanar VMAT whole brain irradiation was 30 Gy and the maximum dose of planning target volume in the hippocampus was limited to 16 Gy.The doses of the optic nerve,optic chiasm and eyeball were lower than 37.5 Gy.The dosimetric parameters of two different protocols were statistically compared by paired t-test.Results The average head tilt angle was (11.12°±0.68°).The homogeneity and the conformal index in the tilted and non-tilted positions were decreased by (8.3±9.6) ％(P=0.033) and (5.2±4.1)％(P=0.009).The dose of hippocampus in the tilted position of the head was decreased by (13.6±6.2) ％ on average compared with that in the non-inclined position (P=0.004).The dose of the lenses was decreased by (15.5±11.1)％(P=0.008) on average.The doses of optic nerve and eyeball were declined by (6.8±5.6) ％(P=0.013) and (8.6±6.5) ％(P=0.016).Conclusions By tilting the head at an appropriate angle during VMAT whole-brain radiotherapy,the radiation dose distribution of the target volume can be significantly improved and the radiation dose in the hippocampus and visual system can be reduced simultaneously to maintain the therapeutic effect and minimize the effect upon the cognitive and memory function of patients.