Research On X-ray Differential Phase Contrast Imaging

Since the 1990 s,X-ray phase contrast imaging technology has been one of the hot research topics in the field of X-ray imaging.X-ray phase contrast imaging technology mainly includes crystal interferometer imaging,propagation-based imaging,diffraction enhanced imaging and grating-based phase contrast imaging.X-ray phase-contrast imaging is an imaging method that uses X-rays to change the phase after passing through an object.This phase change is converted into an intensity change that the detector can record through an optical element.Different from traditional X-ray attenuation-based imaging,they allow obtaining inner structure of an object by detecting the phase modulation derived from its internal structure,so the obtained phase contrast image has higher sensitivity.In X-ray phase contrast imaging technology,the intensity of the image recorded by the detector contains the three kinds of information of absorption,refraction,and scattering of the object.In order to quantitatively analyze the characteristics of the sample independently,a suitable information extraction method must be developed.This article introduces the imaging devices,imaging processes,and information extraction methods of the four phase contrast imaging technologies in detail.The main contributions of the thesis are summarized as follows:(1).Noise analysis for diffraction enhanced imagingX-ray diffraction enhanced imaging method is an effective means of characterizing the internal structure of materials based on synchrotron radiation light sources.In this work,Three-image algorithm of diffraction enhanced imaging is studied.First,based on the error propagation,the variance of the refraction and scattering noise is derived.The method to optimize the performance of the imaging system under the given system parameters of the sample and imaging device is derived.Secondly,the optimal analysis of the angular position of the three-image algorithm is theoretically derived,which provides a solid theoretical basis for the practical application of diffraction enhanced imaging technology.Finally,the matlab platform was used for numerical analysis to verify the theoretical prediction.(2).Transmission,refraction and dark-field retrieval in hard X-ray grating interferometryGrating phase contrast imaging technology can be imaged using conventional light sources and is the imaging technology most likely to be applied in clinical medicine.A three-image algorithm is proposed to retrieve the sample's transmission,refraction and dark-field information in hard X-ray grating interferometry.The analytical formula of the three-image algorithm is derived theoretically and verified experimentally in Shanghai synchrotron radiation source.The results confirm the feasibility of the proposed algorithm.Furthermore,this algorithm can also be adapted for samples with negligible refraction,reducing the number of required sample measurements to two.Furthermore,the noise properties of the retrieved images are investigated in terms of the standard deviations.Those results can serve as general guidelines to optimize the data acquisition scheme for specific applications and problems.