不同束流模式对肺癌中等分割容积旋转调强放射治疗剂量学的影响OACSTPCD

Objective:To study the effect of different beam modes on planned dosimetry of volumetric modulated arc therapy(VMAT)in medium-dose fractionated radiotherapy for lung cancer.Methods:Twelve patients with lung cancer were selected,and three partial arc treatment plans were designed flattening filter(FF)model and flattening filter free(FFF)model using VMAT technology.The dosimetric parameters of target and organs at risk,monitor unit,minimum gantry rotation speed and optimization time obtained with the two plans were compared.Results:There were no significant differences in the dosimetry parameters of D98%of ITVs[internal target volume(ITV)+lymph node metastasis],Dmean,CI,D98%of HI and PTV between the two groups(P>0.05).The difference in dosimetric parameters of D2%of ITVs and D2%of PTV,Dmean and CI were statistically significant(P<0.05).The Dmean and D2%of FFF mode were lower than FF mode,while the CI of PTV mode was better than FF mode.The differences in the dosimetric parameters of the two lungs V5 and the healthy lung V5 and Dmean,the heart V40 and V30,the esophagus D1cc,V30 and the trachea D1cc,V30 and Dmean,and the spinal cord Dmax were not statistically significant(P>0.05).In FFF mode,V30,V20,Dmean of both lungs,V30,V20,V5,Dmean of the affected lung,and Dmean of the heart were significantly lower than those in FF mode and the difference(P<0.05),while Dmean of the esophagus was significantly higher than that in FF mode(P<0.05).Besides,the monitor unit,minimum rotation speed and optimization time in FFF mode were significantly higher than those in FF mode(P<0.05).Conclusion:Both models can meet the clinical requirements.FFF model has better protection for lungs,especially the affected lung.Although the monitor unit of FFF model is higher than that of FF model,the minimum rotation speed of the gantry is higher in FFF model,which guaranteed a higher execution efficiency for FFF model.The FFF model may be preferred for the medium-dose fractiation treatment plan for lung cancer.