探测角度对笔束X射线荧光CT成像质量的影响

Influence of Detection Angle on the Quality of Pencil-Beam X-Ray Fluorescence CT

常规X射线荧光计算机断层扫描(XFCT)成像中,探测角度与荧光收集效率密切相关。基于MCNP5设计了多探测角度下笔束XFCT成像系统,对质量浓度为1%的金纳米溶液柱形模体进行成像仿真,并采用滤波反投影(FBP)算法、联合代数重建(SART)算法和最大似然模型期望最大化(ML-EM)算法重建元素分布。通过对比度噪声比定量分析不同角度下不同算法重建图像的效果,研究探测角度对成像质量的影响。结果表明,FBP算法在背向散射角度下有较好的成像质量,SART算法和ML-EM算法在垂直角度和背向散射角度均有较好的成像质量。

The detection angle within X-ray fluorescence computed tomography(XFCT)is closely related to fluorescence collecting efficiency.We design a multi-detection angle pencil-beam XFCT imaging system base on MCNP5 to simulate the imaging of a gold nano-solution columnar phantom with a mass concentration of 1%,and use filtered back projection(FBP)algorithm and joint simultaneous algebraic reconstruction technology(SART)and maximum likelihood expectation maximization(ML-EM)algorithm to reconstruct the element distribution.The contrast-to-noise ratio is calculated to quantitatively analyze reconstruction image quality with different algorithms at different angles.The results show that the FBP algorithm has better imaging quality at the backscatter angle.The SART algorithm and the ML-EM algorithm have better imaging quality at the vertical angle and the backscatter angle.