^60Co双投影辐射成像系统中的散射干扰模拟研究  

Simulation study on scattering interference in 60Co dual-projection radiation imaging system based on Monte Carlo method

作　　者：倪民子 王振涛[1,2] 丛鹏 李立涛[1,2] NI Minzi;WANG Zhentao;CONG Peng;LI Litao(Institute of Nuclear and New Energy Technology,Tsinghua University,Beijing 100084,China;Beijing Key Laboratory on Nuclear Detection&Measurement Technology,Beijing 100084,China)

机构地区：[1]清华大学核能与新能源技术研究院,北京100084 [2]核检测技术北京市重点实验室,北京100084

出　　处：《核技术》2020年第4期64-69,共6页Nuclear Techniques

基　　金："十三五"核能开发科研专项项目(No.20154602098)资助。

摘　　要：^60Co双投影辐射成像系统,采用两个射线源,分别底置和侧置,通过一次扫描即可获得仰视和侧视两个方向的投影图像。但由于散射的存在,两个投影平面的成像会相互干扰。为降低两投影平面间的散射影响,提高该系统辐射图像的质量,首先基于蒙特卡罗方法建立仿真模型,并对空载时散射分布的模拟值与实验值进行对比,验证了模型的可靠性,然后模拟分析了不同投影平面间距、探测器周围布置不同屏蔽材料(钨、铅、钢和铝)以及屏蔽层位置和厚度对散射的影响。结果表明:当投影平面间距为40 cm并且屏蔽层厚度相同时,使用铅并将其布置在支撑架和侧视电离室之间时,对散射的屏蔽效果最好;投影平面间距分别为40 cm和80 cm时,散射可以分别降低至间距为10 cm时的55%和40%以下,安装2.5 cm的铅片可以将散射进一步降低80%。此研究为双投影系统针对散射校正的硬件改良和升级提供参考与指导。[Background]In 60Co dual projection radiation imaging system,the radiation sources are arranged at the bottom and side while their corresponding ionization chamber detectors are set respectively in the gantry.With the synchronous movement of the sources and the gantry,the system can obtain both side-view and upward-view images of the objects simultaneously.However,due to the presence of scatter,the imaging of the two projection planes will interfere with each other.[Purpose]This study aims to reduce the effect of scattering between two projection planes and improve the imaging quality of the system by using Monte Carlo method.[Methods]Firstly,a simulation model based on Monte Carlo method was established,and its reliability was verified by comparing the simulation data with the experimental data of the scattering distribution at no-load.Secondly,the scattering effects of different projection plane spacings,different shielding materials(tungsten,lead,steel,and aluminum)around the detector with different installation positions,and thickness of the shielding layer on the scatter were calculated based on the model built.Finally,shielding correction effect of 2.5 cm thick lead layer was evaluated.[Results]Simulation results show that when the projection plane spacing is 40 cm and 80 cm,the scattering can be reduced to less than 55%and 40%of that of the 10 cm plane spacing respectively.When projection plane spacing is 40 cm,a lead shield placed between the gantry support and the side-view ionization chambers can achieve best shielding effect at the same thickness compared with steel and aluminum.When the thickness of the lead is 2.5 cm,scattering will be further reduced by 80%.[Conclusions]This study provides a reference and guidance for the hardware improvement and upgrade of the dual-projection system for scattering correction.

关 键 词：60Co双投影辐射成像系统 蒙特卡罗 散射分布 硬件校正 

分 类 号：TL99[核科学技术—核技术及应用]