Research On The Theory And Method Of X-ray Grating Phase Contrast Imaging

Since the 1990s,X ray phase contrast imaging technology has been becoming one of current research focus in the field of X-ray imaging,phase contrast imaging uses X-ray phase shift information to detect the internal composition of the imaging object,revealing the internal structure of the object.In comparison with X-ray absorption imaging,X-ray phase contrast imaging,which is a technique that utilizes X-ray phase shift for the detection of weakly absorbing materials,can provide much better contrast-enhanced images.Therefore,X-ray phase contrast imaging has significant scientific value and wide application potential value in medicine,biology,materials science and non-destructive testing.Within all the various X-ray phase contrast imaging techniques,the method using an X-ray Talbot-Lau interferometer with a conventional X-ray tube is regarded as most popular and most widely used strategy at present.However,the method of extracting phase information need to move the grating,so the requirement for accuracy of the step position is very high,and challenges in the production of high aspect ratio gratings limit the construction of a compact setup for high x-ray energies.Based on the above mentioned problems,this thesis is carried out in the hope of overcoming some weaknesses and also in the hope of trying to improve this technique in the following way.Firstly,this thesis proposes a dual energy multi-line X-ray source and a dual energy analysis grating.By the use of dual energy multi-line X-ray source and dual energy analysis grating in grating-based X-ray differential phase contrast imaging system,A dual energy grating-based X-ray phase contrast imaging system has been proposed in this thesis;Secondly,this thesis demonstrates the imaging principle of the imaging system in detail,and proposes a phase information extraction method which is suitable for the system.The imaging system can get high and low energy X-ray imaging without moving grating.Thus creates a simpler imaging system and the problem of image quality degradation causes by stepping error was avoided.In this system,the new phase information extraction method,which needs only two X-ray images of sample,improves imaging efficiency.By the use of dual energy multi-line X-ray source and dual energy analysis grating,high energy X-ray can be used in X-ray phase contrast imaging.The simulation and experimental results shows that the imaging system can realize normal imaging,and the first-order derivative distribution of the sphere phase extracted by the dual energy X ray method is consistent with the experimental results.In order to meet the requirements of the system for imaging X-ray center energy,an X-ray filter is designed,and the spectrum is simulated.