RapidArc与HybridArc技术在大体积脑转移瘤立体定向放射外科中的剂量学比较

Stereotactic radiosurgery for large brain metastases: a dosimetric comparison of volumetric modulated arc therapy generated with RapidArc versus HybridArc

目的:探讨RapidArc与HybridArc技术对大体积脑转移瘤的立体定向放射外科计划剂量学参数和机器跳数的影响。方法:选择10例颅内大体积脑转移瘤患者作为研究对象。分别采用RapidArc和HybridArc技术设计计划,比较两组计划的靶区适形度指数(CI)、梯度跌落指数(GI)、均匀性指数(HI),危及器官剂量分布,靶区周边正常组织受量体积以及机器跳数。结果:与RapidArc计划相比,HybridArc计划的靶区HI差异无统计学意义(t=-1.400,P=0.161),CI不接近1,而GI更接近于1,差异具有统计学意义(CI:t=-2.521,P=0.012;GI:t=-2.240,P=0.025)。与RapidArc计划相比,HybridArc计划的周边正常组织2 Gy剂量受照体积更少,差异有统计学意义(P=0.012),4、6、8和12 Gy剂量受照体积比较,差异无统计学意义(P=0.575、0.050、0.069、0.068),16和20 Gy剂量受照体积更高,差异有统计学意义(P=0.012、0.017)。与RapidArc计划相比,HybridArc计划的脑干、右眼、左侧视神经和右侧视神经最大受照剂量更低,差异具有统计学意义(P=0.012、0.017、0.017、0.017),左侧晶体、右侧晶体、左眼、视交叉最大受照剂量相似(P≥0.05)。与RapidArc计划相比,HybridArc计划的机器跳数平均减少908 MU。结论:在大体积脑转移瘤立体定向放射外科中,采用HybridArc技术设计计划,靶区适形度更好,剂量梯度跌落更陡,且可明显减少机器跳数,但正常组织高剂量区受量更高,部分危及器官最大受照剂量更低。

Objective To explore the effects of HybridArc and Rapidarc on the dosimetric parameters and machine units of stereotactic radiosurgery plans for large brain metastases.Methods Ten patients with large brain metastases were enrolled in this study.Different techniques,namely RapidArc and HybridArc,were used to design two kinds of treatment plans for each patient.The conformity index(CI),gradient index(GI),homogeneity index(HI)of target areas,the dose distributions of organs-at-risk,the doses to normal tissues and machine units between RapidArc plan and HybridArc plan were compared.Results The HI of target areas was similar in RapidArc plan and HybridArc plan,without statistical difference(t=-1.400,P=0.161);the CI of target areas in RapidArc plan was closer to 1,while the GI of target areas in HybridArc plan was closer to 1,with statistical differences(CI:t=-2.521,P=0.012;GI:t=-2.240,P=0.025).Compared with RapidArc plan,HybridArc plan had reduced 2 Gy isodose volume,with statistical difference(P=0.012)and increased 16 and 20 Gy isodose volumes,with statistical difference(P=0.012,0.017).No significant difference was found between RapidArc plan and HybridArc plan in 4,6,8 and 12 Gy isodose volumes(P=0.575,0.050,0.069,0.068).The maximum dose of brainstem,right eye,left optic nerve and right optic nerve in HybridArc plan were lower than those in RapidArc plan,with statistical differences(P=0.012,0.017,0.017,0.017),but the maximum dose of bilateral lens,left eye and chiasm were similar in the two kinds of plans(P≥0.05).Compared with that of RapidArc plan,the machine units of HybridArc plan was reduced by 908 MU.Conclusion Using HybridArc to design stereotactic radiosurgery for large brain metastases provided better target conformity and GI,less machine monitor units,higher dose in high-dose area of normal tissues and lower maximum dose of some organs-at-risk.