HyperArc与VMAT技术脑转移瘤应用比较

Comparison between HyperArc and conventional VMAT approach for brain metastases

目的比较新型脑转移瘤治疗技术HyperArc与容积调强弧形治疗(VMAT)技术在剂量学参数及计划复杂性方面差异。方法选取26例脑转移瘤患者,处方为9 Gy 3次、6 Gy 5次,分别采用HyperArc(HA)、共面(Cop)及非共面(Non-cop)VMAT技术进行计划设计。比较3种计划靶区(PTV)RTOG适形指数(RTOG CI)、Paddick CI、均匀性指数(HI)、梯度指数(GI),脑干D_(max)以及Brain-PTV的V_(2Gy)-V_(26Gy)。此外,对机器跳数以及计划复杂性参数(包括MCSv和ALPO)进行比较。结果为了防止治疗时脱靶,所有计划RTOG CI都>1.1。对于Paddick CI,HA计划的高于Cop和Non-cop VMAT(0.89±0.019∶0.88±0.017,P=0.001和0.89±0.019∶0.87±0.036,P=0.003)。对于GI,HA计划的跌落最快(3.35±0.64),其次为Non-cop VMAT(3.70±0.80),最差为Cop VMAT(4.90±1.85)。对于脑干D_(max),HA计划低于Non-cop VMAT计划[(604.14±531.61)cGy∶(682.75±558.22)cGy,P<0.05]。对于V_(12Gy)和V_(24Gy),HA计划都低于VMAT计划(均P<0.05)。对于机器跳数,HA计划低于Non-cop VMAT、Cop VMAT计划(2872.60±566.93∶3771.28±1022.38、2872.60±566.93∶4494.08±1323.09,均P<0.05)。计划复杂性方面,Cop VMAT计划的MCSv最低,即复杂度最高(P<0.05);HA计划的ALPO较Non-cop更高,即HA计划复杂度较低(P<0.05)。结论对于脑转移瘤治疗,HyperArc较VMAT技术有更好的靶区适形性和剂量跌落,对脑干及正常脑组织保护更好,且计划复杂性也较低。

Objective To compare the dosimetric parameters and plan complexity between newly-delicated HyperArc(HA)and conventional volumetric-modulated arc therapy(VMAT)in the treatment of brain metastases.Methods For 26 patients with brain metastases,HA,conventional coplanar(Cop)and non-coplanar(Non-cop)VMAT plans with a prescription dose of 9 Gy 3fx or 6 Gy 5fx were generated.The dosimetric parameters for planning target volume(PTV),RTOG conformity index(RTOG CI),Paddick CI,homogeneity index(HI),gradient index(GI),maximum dose(D_(max))of brainstem and dose-volume parameters of brain-PTV(V_(2Gy)-V_(26Gy))were statisticaly compared among these three approaches.In addition,the monitor unit(MU)and the plan complexity parameters(including MCSv and AlPO)were statistically compared.Results To prevent missed targets during treatment,all plans were established with RTOG CI of greater than 1.1.For Paddick CI,HA provided significantly higher conformity(0.89±0.019)than Non-cop(0.87±0.036,P=0.001)and Cop(0.88±0.017,P=0.003)VMAT.For GI,the fastest dose fall-off was noted in HA(3.35±0.64),followed by conventional Non-cop VMAT of(3.70±0.80),and conventional Cop VMAT of(4.90±1.85)(all P<0.05).For the brainstem sparing,HA plan performed better than Non-cop plan[(604.14±531.61)cGy vs.(682.75±558.22)cGy,P<0.05].For normal brain tissue sparing,HA approach showed significant reduction than conventional Cop and Non-cop VMAT(both P<0.05).For MU,HA approach(2872.60±566.93)was significantly lower than those of Non-cop VMAT(3771.28±1022.38,P<0.05)and Cop VMAT(4494.08±1323.09,P<0.05).In terms of plan complexity,the MCSv of Cop plan was the lowest,indicating that the complexity was the highest(P<0.05).The AlPO of HA was significantly higher than that of Non-cop VMAT(P<0.05),suggesting that the complexity of HA plan was lower(P<0.05).Conclusion For the treatment of brain metastases,HA provides better conformity,more rapid dose fall-off,better sparing of brainstem and normal brain tissues and less plan complexity compared with conventional VMAT.