中文摘要：

目的：评价逆向静态调强和容积弧形调强两种不同技术用于全脑放疗（Whole Body Radiotherapy,WBRT）及单个到多个脑转移瘤同期加量（Simultaneous Integrated Boost,SIB）治疗的可行性，比较靶区和危及器官的剂量学差异，探讨物理剂量对肿瘤局部控制及器官毒副反应的影响。方法：随机选取10例在本院确诊的脑转移瘤患者，采用瑞典RayStationv4.5计划系统分别为每例病人设计两种同期加量计划：五野静态调强（SIB-IMRT）和双弧容积弧形调强（SIB-VMAT）。全脑计划靶区（Planning Target Volume，PTV）、脑转移瘤计划靶区（Planning Gross Target Volume，PGTV）处方剂量分别为40 Gy，46 Gy,均为20次。在靶区达到处方剂量要求下，利用剂量体积直方图（Dose-Volume Histogram，DVH）比较靶区剂量的均匀性及适形性，晶体、眼球、视神经、视交叉、外耳道等器官的最大或平均剂量。且比较两种治疗技术的机器跳数（MU）和治疗时间差异。结果：两种计划在满足靶区剂量的同时都可以较好地保护危及器官。但VMAT计划的靶区适形度和剂量均匀性指数都明显优于IMRT计划（P〈0.05），且在转移瘤个数越多时，优势越加明显。对于脑干、晶体、视神经、中内耳的最大剂量，两者之间并无明显差异。相比于IMRT, VMAT能够显著降低眼球的最大及平均剂量，外耳道的最大剂量及V25、V30。同时平均MU降低了35.9%（P=0.023），减少了治疗所需时间，结论：VMAT在应用于全脑放疗及脑转移瘤同期加量时,相比于IMRT技术能够给予肿瘤靶区更加均匀适形的物理剂量，同时也能降低重要正常器官的受量，在转移瘤数目愈多、分布较散的情况下更应优先考虑VMAT计划。

英文摘要：

Objective To assess the feasibility of inverse static intensity modulated radiotherapy （IMRT） and volumetric modulated arc therapy （VMAT） used for whole brain radiotherapy （WBRT） and simultaneous integrated boost （SIB） for single or multiplebrain metastases; to compare the dosimetry difference of target volumes and organs at risk （OARs）; to discuss on the effects of physical dose on the local tumor control and toxic side effects of organs. Methods Ten patients diagnosed of brain metastases were randomly selected. Swedish RayStation v4.5 planning system was applied to design five- field SIB-IMRT and two-arc SIB-VMAT for each patient. Doses of 40 Gy/20 fractions and 46 Gy/20 fractions were respectively prescribed to the planning target volume of whole brain and the planning gross target volume of brain metastases. Based on the target volume meeting the requirement of the prescribed dose, dose-volume histogram （DVH） was applied to compare the homogeneity and conformation of target doses, and the maximum or mean doses of lens, eyeball, optic nerve, optic chiasma, external auditory canal and so on. The monitor units （MU） and treatment time were also compared between the two treatment techniques. Results Both SIB-VMAT and SIB-IMRT planssatisfied the target dose andpreferably protected OARs. Compared with SIB-IMRT plan, SIB-VMAT plan achieved better conformal number （CN） and homogeneity index （HI） of target volumes （P〈0.05）. If the number of metastases was larger, the advantages were more obvious. No significant differences were found in the maximum dose of brainstem, lens, optic nerve, optic chiasm and middle-innercochlea.Compared with SIB-IMRT, SIB-VMAT significantly reduced maximum and mean doses of eyeball, maximum and the volume doses （V25, V30） of external auditory canal. Meanwhile the mean MU of SIB VMAT reduced by 35.9% （P=0.023）, reducing the treatment time. Conclusion Compared with IMRT, VMAT applied for WBRT and SIB for brain metastases achieves physical dose