Research On X-ray Grating Phase Contrast CT Based On Dual-energy Analysis Grating

Since the 1990s,a variety of X-ray phase contrast imaging(referred to as phase contrast imaging)methods have been proposed,unlike traditional absorption-based X-ray imaging,which uses the phase-shift information of X-ray passing through the object to obtain the detailed information of the object.In the hard X-ray band,the change of the X-ray phase of the light element material is 1000-100,000 times of the X-ray absorption amplitude,so phase contrast imaging can obtain higher image quality than absorption imaging.The grating-based phase contrast imaging method can be imaged using a common X-ray source,and is the most likely phase contrast imaging method for clinical medicine.However,the grating-based phase contrast imaging method usually requires a step grating in phase information extraction,which increases the requirement of imaging stability for the system.At the same time,since the analysis grating cannot completely absorb high-energy X-rays,it is limited that high-energy X-rays cannot be used for imaging.In view of the problems existing in current grating-based phase contrast imaging,the research group proposed an improved grating-based phase contrast imaging system.The system realizes the application of high-energy X-rays in grating-based phase contrast imaging,and does not require step gratings for imaging.This dissertation has carried out researh and analysis on the system.The main work is as follows:(1)The principle of X-ray grating-based phase contrast imaging is analyzed in detail.The intormation extraction method in grating-based phase contrast imaging is deeply studied,and the advantages and disadvantages of various methods are pointed out.(2)Based on the above theory,the imaging principle of the system is deeply studied.By normalizing the light intensity obtained by the detectors with high and low energy X-rays,a phase information extraction method suitable for the system is proposed and given the exact analytical formula,the refraction angle extracted by this method is compared with the theoretical refraction angle by simulation experiments.and the correctness of the method is proved.(3)The principle of phase contrast CT algorithm is analyzed.Then the system is combined with phase contrast CT.The phase contrast CT imaging of the system is completed by simulation experiments.The simulation results prove the correctness of the system for phase contrast CT.