摘要
双能液体安全检查系统采用CT成像方法,能够获得被扫描物体的原子序数和电子密度信息,具备物质识别能力,能准确排查出行李中所含液体的违禁品和危险品,相比于只提供衰减系数信息的传统成像方法有着突出的优势。然而,金属容器存在的情况下,重建出的原子序数图像中存在较大的误差,给物质识别造成了困难。该文提出了一种针对金属容器问题的校正方法:首先,进行初始重建,从重建图像中估计出容器的形状和位置参数;然后根据参数设置投影模型,采用计算机仿真技术,获得容器的光电系数积分和Compton系数积分的估计值;最后,分离出液体对应的光电系数积分和Compton系数积分,消除了金属容器的影响,重建出液体的原子序数和电子密度。实验证明,这一校正方法能有效地降低重建误差。以铁容器装水情况为例,进行了多组实验,经校正后,原子序数相对误差由高于14%降低为低于2%的水平。
Dual energy systems provide atomic number and electron density images of the scanned objects which are superior to traditional CT systems that measure only the attenuation coefficients to detect contraband and dangerous materials. However, metal containers cause errors in the reconstructed atomic images that hinder material recognition. This paper presents a correction method that first uses pre-reconstruction to obtain the container position and shape parameters. Then, a corrected model is created for a forward projection to estimate the photo electric coefficient integral and the Compton coefficient integral of the container via a computer simulation. Finally, the electric coefficient integral and Comptoncoefficient integral of the liquid are extracted to reconstruct the atomic number and electron density images for the interior liquid without the affection of the metallic container. Tests demonstrate the effectiveness of this method in reducing reconstruction errors. In experiments with iron containers filled with water, the relative error of the atomic number is lowered from more than 14% to less than 2% after correction using this method.
出处
《清华大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2012年第4期517-522,共6页
Journal of Tsinghua University(Science and Technology)
基金
国家自然科学基金资助项目(10905030)
关键词
液体安全检查系统
双能
原子序数
电子密度
liquid inspection system
dual energy
atomic number
electron density
