Theoretical Research And Performance Analysis Of X-ray Grating Phase Contrast Imaging

Phase contrast imaging based on grating has many advantages,such as stable imaging system,large imaging field and common X-ray imaging.However,in the process of its further universal development,it faces two challenges: one is the difficulty of making large area and small period analysis grating;the other is that the traditional phase-stepping information separation and extraction algorithm requires high mechanical accuracy and low imaging efficiency of the system.In order to solve these problems,in recent years,the new grating phase-contrast imaging method based on dual energy X-ray and the inverse geometry Talbot-Lau grating phase-contrast imaging method have successfully realized the zero-stepping grating phase-contrast imaging technology,and the latter further omits the use of large area and small period analysis grating,so they have great research value.Based on the theory of interference and Fresnel diffraction,the imaging principle of grating phase-contrast imaging method based on dual energy X-ray is analyzed in detail in this paper.An algorithm of phase and absorption information separation and extraction suitable for the imaging system is proposed,and the algorithm is verified by simulation with Matlab software.Then,through specific experiments,the information extraction effect of this algorithm and the traditional phase-stepping information extraction algorithm is compared and analyzed.The results show that the information extraction algorithm proposed in this paper can extract sample information accurately.Through reasonable approximation and assumption,the mathematical model of the inverse geometry Talbot-Lau grating phase-contrast imaging system is constructed,and the simulation optical path of the system is designed based on the mathematical model.Then,through the Matlab software,the simulation of the optical path is carried out,and the correct diffraction intensity distribution law is observed successfully,and the magnified image of sample is obtained.Finally,the performance of the inverse geometry Talbot-Lau grating phase-contrast imaging system is analyzed in terms of diffraction efficiency,system noise,angle sensitivity and fringe contrast.The theoretical analysis and the algorithm of information separation and extraction provide a strong theoretical support for the optimization of system parameters and the development of this technology in the field of CT in the future.The establishment of imaging system simulation model and the analysis of system performance provide a reference for the system parameter design and imaging quality optimization of the inverse geometry Talbot-Lau grating phase-contrast imaging technology.