基于蒙特卡罗模拟的CyberKnife病人治疗计划剂量验证  

Dose verification of CyberKnife treatment plan based on Monte Carlo simulation

作　　者：陈上河 王石[1] 吴朝霞[1] 徐寿平[1,2] 李永宝[1] 

机构地区：[1]清华大学工程物理系,北京100084 [2]解放军总医院放疗科,北京100853

出　　处：《中国医学物理学杂志》2015年第4期451-457,共7页Chinese Journal of Medical Physics

基　　金：国家自然科学基金(11275105)

摘　　要：目的:为保证CyberKnife的精确治疗,本研究利用蒙卡方法建立一套适用于CyberKnife的蒙卡剂量验证系统,并与实际计划的放射治疗计划系统(Treatment Planning System,TPS)优化结果相比较,验证TPS所得的优化剂量。方法:采用BEAMnrc和DOSXYZnrc模拟代码,模拟Accuray第4代CyberKnife治疗系统。研究中对直径分别为25 mm、30 mm、40 mm、50 mm、60 mm的5个准直器进行模拟得到组织体模比(Tissue Phantom Ratio,TPR)数据和剂量离轴比(Off Axis Ratio,OAR)数据,并与测量数据比较,以确保系统的精确性。结果:在TPR和OAR数据的比较中,模拟系统所得数据和实际测量所得数据吻合的很好。在深度为5 cm时,准直器视野范围内OAR数据的全局相对误差均小于1%;自动化质量验证模体40%等剂量线内伽玛因子通过率为99.88%(3 mm,3%),1例肝部病人计划模拟中,对应的伽玛因子通过率为88.56%(3 mm,3%)。结论:建立的蒙卡系统能够正确地模拟CyberKnife出束情况,实施治疗前病人计划的剂量验证工作,适用于作为基于蒙卡的第三方剂量检验软件。Objective To ensure the accuracy of CyberKnife treatment by establishing a Monte Carlo （MC） dose verification system for CyberKnife based on MC simulation, and to verify the optimized doses of treatment planning system （TPS） by comparing doses from established system with the doses optimized by the TPS. Methods Based on BEAMnrc and DOSXYZnrc, the MC dose verification system simulated the fourth generation of CyberKnife treatment system of Accuray. The data of tissue phantom ratio （TPR） and off-axis ratio （OAR） of five collimators, respectively with 25 mm, 30 mm, 40 mm, 50 mm, 60 mm diameter, were compared with the measured data to ensure the accuracy of system. Results The comparison between TPR date and OAR date showed that the data from simulated system perfectly matched with the measured data. With 5 cm depth of beams, the global relative errors of OAR data in the scope of collimators were less than 1%. For the automatic quality assurance phantom, the passing rate of Gamma factor was 99.88% （3 mm, 3%）. In the simulation of one patient with liver disease, the passing rate of Gamrna factor was 88.56% （3 mm, 3%）. Conclusion The established MC simulation system is suitable to be applied as the third-party dose verification system, because it can correctly simulate the beams of CyberKnife to achieve the dose verification of plan before the treatment.

关 键 词：CYBERKNIFE 剂量验证 蒙特卡罗模拟 组织体模比 剂量离轴比 伽玛因子通过率 

分 类 号：R730.55[医药卫生—肿瘤] R815.2[医药卫生—临床医学]