有无均整器调强与容积旋转调强在甲状腺功能亢进突眼放射治疗中的剂量学研究

A dosimetric study of intensity modulated radiotherapy, volumetric modulated arctherapy for hyperthyroidism exophthalmus patients using flattening filter free orflattening filter modes

目的探讨非均整模式调强放射治疗(flattening filter free intensity modulated radiotherapy,3FIMRT)、非均整模式容积旋转调强放射治疗(flattening filter free volumetric modulated arc therapy,3FVMAT)、均整模式调强放射治疗(flattening filter intensity modulated radiotherapy,IMRT)和均整模式容积旋转调强放射治疗(flattening filter volumetric modulated arc therapy,VMAT)4种计划应用于甲状腺功能亢进(甲亢)突眼放射治疗(放疗)的剂量学差异。方法选取2016年9月—2017年9月已行放疗的29例甲亢突眼患者的CT图像作为研究对象。对29例患者以相同处方剂量和目标条件分别重新设计IMRT、VMAT、3FIMRT、3FVMAT 4套放疗计划。评估4种计划靶区剂量分布、正常组织受照射剂量、机器跳数和治疗时间。结果 4种治疗计划均能满足临床治疗的要求,在靶区最大剂量、平均剂量、均匀指数方面差异无统计学意义(P>0.05)。在靶区最小剂量、50%处方剂量包裹体积、适形指数、梯度指数方面4套计划差异均有统计学意义(F=10.920、35.860、11.320、17.790,P<0.05)。IMRT和3FIMRT在适形指数方面优于VMAT和3FVMAT,但IMRT和3FIMRT二者之间无明显差异。在眼晶状体平均剂量和脑组织平均剂量方面4套计划差异具有统计学意义(F=5.054、83.780,P<0.05)。和其他3种计划相比较,3FVMAT可以更好地保护眼晶状体和脑组织。3FVMAT和VMAT之间机器跳数和治疗时间无明显差异。3FVMAT相比IMRT、3FIMRT的机器跳数分别减少65.07%、70.22%,治疗时间分别减少48.1%、35.24%。结论 3FVMAT与IMRT、3FIMRT、VMAT相比能为甲亢突眼放疗带来更多的剂量学优势。

Objective To compare the dosimetric differences among flattening filter free intensity modulated radiotherapy(3 FIMRT), flattening filter free volumetric modulated arc therapy(3 FVMAT), filter free intensity modulated radiotherapy(IMRT), and filter free volumetric modulated arc therapy(VMAT) for hyperthyroidism exophthalmus patients. Methods Computed tomography(CT) scans of 29 patients, who were diagnosed with hyperthyroidism exophthalmus and treated with radiation therapy between September 2016 and September 2017, were selected for study.Four treatment plans with the same dose prescription and objective constrains were designed for each patient based on their images, consisting of IMRT, VMAT, 3 FIMRT, and 3 FVMAT. The target dosimetric distribution, normal tissue radiation dose, monitor units, and treatment time of each plan were evaluated. Results Four types of plans were all able to satisfy the clinical treatment requirements, and there were no significant differences in maximum dose, mean dose(Dmean), homogeneity index of the targets(P>0.05). For the parameters minimum dose, V50%, conformity index(CI),gradient index of the targets, statistically significant differences were observed among the four kinds of technologies(F=10.920, 35.860, 11.320, 17.790;P<0.05). The CI of IMRT and 3 FIMRT were superior to those of VMAT and 3 FVMAT,but there was no significant difference between IMRT and 3 FIMRT. In terms of Lens Dmean and Brain Dmean, statistically significant differences were observed among the four kinds of technologies(F=5.054, 83.780;P<0.05). For Lens Dmean and Brain Dmean, 3 FVMAT achieved better sparing effects when compared with the other three plans. The total monitor units and treatment time did not significantly differ between 3 FVMAT and VMAT. The mean monitor units of 3 FVMAT were65.07% and 70.22% less than that of IMRT and 3 FIMRT respectively. The mean treatment time of 3 FVMAT were 48.1%and 35.24% less than that of IMRT and 3 FIMRT respectively. Conclusion 3 FVMAT can bring more dosimetric advantages for hyperthyroidism exophthalmus radiation therapy when compared with IMRT, 3 FIMRT, and VMAT.