在管激发X射线荧光CT(XFCT)成像研究中,探测角度与系统背景噪声、探测灵敏度、信噪比等参数密切相关。鉴于此,基于Geant4设计一套多针孔准直管激发XFCT成像系统,并对探测角度与成像系统信噪比、重建图像质量之间的关系进行研究。通过改变管电压、金纳米溶液质量分数、感兴趣区域直径三个参数,模拟60°、90°、120°和150°等不同探测角度下的X射线荧光投影数据和散射噪声的探测过程,并计算其信噪比。仿真结果表明:探测角度的增大能够提升信噪比和重建图像质量,多数情况下,探测角度为120°时的信噪比最佳。

Detection angle is closely related to background noise, detection sensitivity, signal-to-noise ratio, and other parameters in the study of tube-excited X-ray fluorescence computed tomography (XFCT) imaging. Accordingly, we simulate a polychromatic tube-excited XFCT imaging system with multi-pinhole collimator using Geant4 to investigate the effect of detection angle on the signal-to-noise ratio and the reconstructed image quality. By changing the tube voltage, mass fraction of gold nanometer solution, and diameter of the region of interest, the signal-to-noise ratio is calculated by simulating the detection processes of the X-ray fluorescence projection data and scattering noise at four angles: 60°, 90°, 120°, and 150°. The simulation results reveal that the signal-to-noise ratio and reconstructed image quality could be effectively improved by increasing the detection angle. For most circumstances, the highest signal-to-noise ratio could be obtained when the detection angle is set to 120°.