相移吸收二元性算法用于X射线混合衬度定量显微CT的可行性研究

本文采用相移吸收二元性(PAD)相位恢复算法来实现混合 衬度样品内部不同密度组分的定量成像, 采用数字模拟和实验研究验证该方法的可行性. 模拟结果表明, 对于三种不同材料其重构误差均小于1%, 且误差值随材料折射率的增大而减小. 利用上海光源X射线成像线站开展了实验研究, 结果表明用单距PAD相位恢复算法可获取样品的定量信息. 与模拟结果相比, 实验中的重构精度相对较低, 环状伪影可能是影响精度的主要原因. 模拟和实验研究过程中, 均只采用了一组单距投影数据. 可以认为, 相移吸收二元性算法可用于混合衬度样品的定量信息分析研究. 由于剂量相对较低, 应可适合于软组织和骨骼同时存在时生物医学样品的定量相衬CT研究.

Investigation on the application of phase-attenuation duality to X-ray mixed contrast quantitative micro-tomography

Weak absorption is the main condition of conventional phase retrieval of in-line X-ray phase-contrast CT. The absorption of most samples, however, cannot be neglected in practice, it is needed to find new algorithms of attaining quantitative information. The phase retrieval algorithm of phase-attenuation duality (PAD) is used to realize the quantitative imaging of different density parts in a mixed contrast sample, and the digital simulation and experimental investigation are carried out in order to prove its feasibility in this paper. The simulated results show that the reconstructive errors of three materials are less than 1%, and the values decrease with the increase of refractive index. The experiment was carried out in the X-ray imaging and biological application beam-line of Shanghai Synchrotron Facility, and the results show that the PAD method can attain the sample quantitative information and the reconstructive accuracy is relatively low compared with that of simulation. Through the analysis of experimental data, ring artifact is mostly the primary cause. One single projection data set is used only in simulation and experiment. So the PAD approach can be applied to the quantitative information research of mixed contrast objects. In addition, because of the relatively low radiation dose, it should be suited to investigate the quantitative phase-contrast CT of biomedical sample with soft tissue and bone together.