基于连续X射线谱的CT重建算法仿真

Simulation of Computed Tomography Reconstruction Algorithm Based on Consecutive X-ray Spectrum

关于提高CT图像精度的问题,传统的CT重建算法都是基于X射线源是单色源的假设,忽略了X射线的多色性。直接用多色投影数据进行图像重建易产生金属、硬化等伪影,降低图像质量,影响CT值标定,从而影响医学或工业诊断。考虑到X射线能谱的连续性,采用仿真手段实现连续X射线谱的统计重建。首先将连续X射线谱离散成若干单能谱,再根据待检工件的材质信息以及射线能量所对应的质量衰减系数,构建基于连续X射线谱的工件材质模型;最后利用多能统计重建算法对多能投影数据进行迭代重建。仿真结果表明,算法充分地利用了X射线的多能性,在一定程度上可以有效地降低图像伪影,提高CT重建图像质量。

Traditional reconstruction algorithms assume that the X-ray is monochromatic,while in fact,X-ray is polychromatic in actual CT.When the polychromatic projection data are used to reconstruct the images directly,metal artifacts and beam-hardening artifacts appear in the reconstructed images,which reduces image quality and affects medical or industrial diagnosis.This paper considers the consecution of X-ray spectrum,and simulats the statistical reconstruction algorithm based on consecutive X-ray spectrum.Firstly,consecutive spectrum was discretized as monochromatic spectrum.Secondly,according to the workpiece material information and mass attenuation coefficient corresponding to X-ray energy,the workpiece material model was formulated based on consecutive spectrum.Finally,using the polychromatic-energy statistics iterate algorithm,the reconstruction was caried out based on polychromatic projection data.Through the simulation experiment,the algorithm reduces the artifacts to a certain extent,and improves the image quality.