摘要
目的设计适用脑转移瘤术中放疗的施照器并评估其剂量学特征。方法施照器设计首先通过模拟计算电子束经过一系列不同厚度散射箔后的散射角和剂量率,确定散射箔厚度;其次,建立散射箔位于不同高度的位置评估模型,通过计算模型表面平均能量方差,确定散射箔位置;最后,建立调节层几何结构特征与施照器表面剂量之间的关系,确定调制器的内表面特征。使用蒙特卡罗(MC)EGSnrc/BEAMnrc和EGS4/DOSXYZ程序完成Mobetron加速器、位置评估模型、调节层、施照器建模和剂量学分析。结果半球囊状施照器的限光筒直径为2.5 cm、筒壁厚0.5 cm,材料为0.2 cm厚水等效材料加0.3 cm厚不锈钢;散射箔厚度0.14 cm,材料为金属钨,位置高度为0.5 cm;调制器为月牙形,材料为水等效材料。该施照器能够使Mobetron 12 MeV的电子束产生半球面剂量分布,剂量率为160 cGy/min,治疗深度为0.85 cm。结论采用MC模拟设计的适用于高能电子束的半球囊状施照器,能产生半球面剂量分布。
Objective To design a semi-spherical applicator for delivery of semi-spherical dose distributions and assess its dosemetric characteristics.Methods The applicator was designed in the following way.First,the scattering angle and dose rate of the electron beam having passed through a series of scattering foils of different thicknesses were calculated to determine the thickness of the scattering foil.And then,a series of location model was designed,and the variances of the mean electron energy on the surface of these models were calculated to determine the foil location.Finally,the relationship between the geometric characteristics of the layer and the surface dose on the applicator was established to design the modulator.Monte Carlo(MC)codes EGSnrc/BEAMnrc and EGS4/DOSXYZ were employed to model the head of the Mobetron,the location model,the layer,the semi-spherical applicator,and to calculate the dose distributions.Results A semi-spherical applicator was designed for electron beam of energy 12 MeV,which consisted of a 2.5 cm diametre cylindrical collimator with 0.5 cm thick wall made of 0.3 cm thick steel and 0.2 cm thick water equivalent material(WEM),a 0.14 cm-thick foil made of tansgen,and a 2.5 cm diametre hollow semi-sphere containing a crescent modulator made of WEM.The dose rate was about 160 cGy/min,and the depth of the 50%isodose curve was 0.85 cm.Conclutions We designed and performed a MC simulation of a semi-spherical applicator to deliver a semi-spherical dose distribution from a high energy electron beam.
作者
马攀
李永宝
李明辉
牛传猛
谢欣
马敏
刘博
周付根
戴建荣
Ma Pan;Li Yongbao;Li Minghui;Niu Chuanmeng;Xie Xin;Ma Min;Liu Bo;Zhou Fugen;Dai Jianrong(Department of Radiation Oncology,National Cancer Center,National Clinical Research Center for Cancer/Cancer Hospital,Chinese Academy of Medical Sciences and Peking Union Medical College,Beijing 100021,China;Department of Radiation Oncology,Sun Yat-Sen University Cancer Center,Guangzhou 510060,China;Image Processing Center,Beihang University,Beijing 100083,China)
出处
《中华放射医学与防护杂志》
CAS
CSCD
北大核心
2020年第11期868-872,共5页
Chinese Journal of Radiological Medicine and Protection
关键词
半球囊状施照器
电子束术中放疗
脑转移瘤
Semi-spherical applicator
Intraoperative electron beam radiotherapy
Intracranial metastatic tumor
