G4射波刀治疗头的蒙特卡罗模拟  

Monte Carlo simulation for treatment head of G4 Cyberknife

作　　者：戴春艳[1] 刘永明[2] 于春山[2] 曹洋森[2] 张明涛[2] 涂彧[1] 

机构地区：[1]苏州大学医学部放射医学与防护学院,江苏苏州215123 [2]第二军医大学长海医院放疗科,上海200433

出　　处：《中国医学物理学杂志》2016年第5期525-529,共5页Chinese Journal of Medical Physics

摘　　要：用BEAMnrc程序代码构建G4射波刀治疗头,用DOSXYZnrc程序代码计算6种不同准直器射野的百分深度剂量及离轴比。通过与测量数据对比,分别微调次级准直器大小,从而确保模型的合理构建,并借助BEAMDP程序代码分析射波刀射束中光子谱分布及平均能量、粒子能谱分布及角分布等特点。结果显示各射野的百分深度剂量误差均在2%以内;在辐射野范围内,对于>20 mm的射野,蒙特卡罗方法计算的离轴比与测量值间的误差在3%以内,而对于<20 mm的射野,误差最大不超过5%;光子谱峰值能量为0.380 MeV,光子平均能量为1.570 MeV;出射光子强度比电子强度高出3个数量级;光子角分布集中在与中心轴成5°的范围内,而电子角分布范围较大。这些信息对临床与辐射防护有一定意义,该模型也为射波刀剂量学特点的后续研究提供了基础。The BEAMnrc code was used to model the treatment head of G4 Cyberknife, and the DOSXYZnrc code was used to calculate the percentage depth dose（PDD） and off-axis ration（OAR） of the field of six collimators. The calculated data were compared with the measured data and the sizes of secondary collimators were fine-tuned respectively to ensure the model was built correctly. The photon spectrum distribution and mean energy, particle energy spectrum distribution and angular distributions of Cyberknife were analyzed by using the BEAMDP code. The results showed the PDD error of each field was within 2%. In the range of radiation field, the OAR errors between calculated data and measured data were within3% for the fields larger than 20 mm, and the maximum error was less than 5% for the fields smaller than 20 mm. The peak energy of photon spectra was 0.380 MeV, and the average energy of photon was 1.570 MeV; emerging photon intensity was three orders of magnitude higher than electron intensity; the angular distribution of photon was mainly concentrated within the range of 5° off the central axis, while that of electron was in a relatively larger range. All the information is significant for the clinic and radiation protection, and the constructed model also provides basis for the further research on the dosimetric characteristics of Cyberknife.

关 键 词：蒙特卡罗 G4射波刀 光子谱 能谱 角分布 

分 类 号：R730.55[医药卫生—肿瘤] R144.1[医药卫生—临床医学]