Simulation And Experimental Research Of In-line Phase Contrast Imaging Based On Degradation Model

Traditional X-ray imaging technology generally form an image by exploiting the different levels of radiation attenuation of the each component within the measured object.However,when the sample is a weakly absorbing material,this technology is difficult to distinguish the internal structure and show clear imaging results.Based on phase information,X-ray phase contrast imaging(XPCi)is a novel method which transforms the phase shift introduced by the object into image intensity,widely used in early clinical diagnosis,industrial materials detection,art connoisseurship research field and so on.Various XPCi methods have been proposed,the in-line phase contrast imaging is regarded as one of the most promising clinical methods owing to no additional optical devices.This work is focused on in-line phase contrast imaging,aiming to guide the actual imaging by the numerical simulation model,improving the image visibility and optimizing the image quality.This paper mainly includes the following four parts.Firstly,based on the Fresnel-Kirchhoff diffraction theory,the numerical models of in-line and coded aperture phase contrast imaging are established,and reasonable and reliable phantom experiments are carried out to prove the validity of the model.On this basis,we explore the effects of system geometric parameters,source and detector characteristics and material materials on the imaging results.Contrast and modulation transfer function(MTF)are used as quality evaluation parameters of the simulation system.Then,we calibrate the system transfer function of the laboratory actual PiXarray-100 phase contrast imaging system and apply the calibration results to the numerical simulation.In order to suppress the deterioration impact of the non-ideal imaging system on the imaging results,this paper finally researches the image restoration method based on Wiener filter and wavelet Wiener filtering and then verifies the method by simulation experiments and actual imaging.The conclusion is that wavelet Wiener filtering can overcome the phase deterioration effect,and improve the visibility of the image.