Investigation On Dynamic X-ray Imaging Methods With High Efficiency And High Precision Simultaneously

Taking advantage of the characteristics of short wave length,high penetration of x-rays.X-ray imaging techniques can measuring the interior of objects with nondestructive and high precision.Especially in recent years,with the development of synchrotron radiation source technology,X-ray dynamic imaging technology with high signal-to-noise ratio and high spatial resolution has attracted much attention in studying the time evolution of the internal structure of matter under external or internal influence.However,there are a lot of problem to be solved on dynamic X-ray imaging with high efficiency and high precision simultaneously.In terms of X-ray speckle based imaging techniques,it has received increasing attention as they entail simple experimental setup,without optical element,efficient data acquisition and high phase sensitivity.However,due to the existence of the second-order phase effect of the sample,a large number of artifacts arise when extracting the phase,it is impossible to realize dynamic phase contrast imaging and maintain high precision phase reconstruction.Although speckle scanning method has been proposed and achieved accurate phase image,many scanning steps means large exposure time,high radiation dose and low data acquisition efficiency,which greatly hinders the popularization and application of this technology.Therefore,developed speckle based phase imaging method with fewer exposure even single exposure to achieve accurate phase reconstruction is the research focus.In other hand,traditional X-ray angiography technique has been widely used in diagnosis of vascular diseases and preclinical studies.This technology uses the contrast image injected with the contrast agent to subtract the background image to achieve high-definition imaging of blood vessels.However,due to the inevitable relative movement between different tissues in living tissues,motion artifacts are inevitable,especially in high-resolution microvascular imaging.Move contrast vascular angiography technique can eliminate motion artifacts and high frequency noise,but its long calculate time limits its real-time dynamic angiography.Therefore,fast image reconstruction while eliminating the interference of motion artifacts is a bottleneck problem for the further development of angiography.Based on the above background,this paper focuses on the Investigation on dynamic Xray imaging methods with high efficiency and high precision simultaneously.The main content is divided into two parts: in the aspect of speckle tracking X ray phase contrast imaging,high efficiency imaging with high precision phase reconstruction.In microvascular angiography,a high-precision real-time contrast imaging method for microvascular was developed.The following research results have been achieved in this paper:1.Aiming at the problem that the traditional X-ray speckle tracking micro-CT imaging method cannot accurately image complex structure samples,a doubleexposure X-ray speckle tracking micro-CT imaging method was proposed.The artifacts caused by edge-enhancement are eliminated by introduced one in-line phase image.Compared with speckle scanning micro-CT method,which improved data acquisition efficiency and reduce radiation dose greatly.The experiments result on model samples and biological sample show that the proposed method could reconstruct complex sample accurately.As a comparison,traditional speckle tracking method could not imaging correct the corresponding samples.On this basis,a speckle tracking X-ray phase contrast CT imaging platform based on Shanghai synchrotron radiation facility X-ray imaging and Application Beamline was established and opened to users,which provided a new research method for related subjects.2.On the basis of double exposure speckle tracking phase micro-CT method,a single exposure speckle tracking imaging method with deep learning was proposed and developed.And we for the first time realized speckle tracking X-ray dynamic imaging with precision phase reconstruction.This method utilizes deep learning to generate the inline image that needs a second single acquisition in the double exposure method.Thus,the accurate reconstruction of changing phase by speckle tracking method was achieved with single shot.Experiments with simple structure spheres and complex sponge structures verify that this method can eliminate phase distortion,and the 3D reconstruction results also show that this method can effectively remove radial artifacts compared with traditional methods.The multidensity phase reconstruction shows that the method can achieve accurate phase reconstruction of multi-density samples in a single exposure.Finally,Polyurethane foam experiment verifies the accurate phase reconstruction of the pure phase object with time evolution of the method.3.A real-time microvascular angiography method was developed,this method based on single pixel temporal domain moving averaging algorithm to remove motion artifacts efficiently.The experimental results of rat brain microvascular showed that the proposed method could quickly and efficiently remove the influence of motion artifacts during in vivo angiography,thus realizing high-resolution microvascular imaging.The reconstruction time of one hundred 2048*788 images was only 0.25 seconds,this can be considered quasi-real-time microvascular imaging.Furthermore,the photon flux is further reduced to 1/4 of that of the traditional method,and the developed method can also successfully eliminate the influence of motion artifacts and noise to achieve clear imaging of microvessels.Compared with the traditional method,the mean value of contrast to noise ratio is increased by 3 times.Finally,the X-ray tube experiment results show that this method has the prospect of clinical application...