The Design And Evaluating Of Diffraction Enhanced Imaging Setup Based On Microfocus X-ray Tube

DEI is one of the most advanced technologies that differ from traditional radiography.Compared to conventional absorbing imaging,it can greatly improve the detail,contrast and sensitivity with much lower radiation dose.Not only can it to obtain the absorption image,but also to obtain higher quality refraction image and ultra-small angle scattering image.Traditional X-ray absorption imaging by recording the intensity changes of X-ray through the object,due to the low absorption coefficient of bio-soft tissue composed of light elements,the traditional X-ray absorption imaging of soft tissue is less than ideal,such as liver,breast and tumor.The experiment Breast imaging,tumor sample imaging,articular cartilage imaging,and small animal imaging based on the DEI system have all demonstrated that it can achieve better results than traditional X-ray absorption imaging,more detailed information of the internal structure of the sample can be observed.The analyzer crystal convert refraction angle into intensity changing when X-ray pass through sample.The analyzer crystal Si(111)is able to distinguish sub-micron-radian angle changing,it makes image quality better fundamentally.In this paper,the physical design and performance evaluation of DEI setup and other related work have been done,the main contents are as follows:First,the physical design of DEI set-up was analyzed systematically.In the overall physical design,the results show that the compactness of the system should be maintained to improve the luminous flux;to reduce the geometric penumbral and chromatic dispersion artifacts,the CCD camera and the sample stage should be as close as possible to the analyzer crystal.The monochromatic crystal Si(111)be asymmetric cut to shorten the Exposure time multiply.The set-up eliminate double-shadow by limiting the size of the crystal.Then,the thermal deformation of Si(111)crystal is calculated,which shows that the deformation hardly affects the crystal performance and is not necessary to install the cooling device.Secondly,the key components were selected to set up the DEI experimental platform.Silicon crystal was machined by Professional institutes according to requirements.After researching market and analyzing experimental requirements,both X-ray tube and CCD camera were applied with mature technology,economy cost,and supervisor performance.Other components,such as the stage and the driver,as much as possible to choose the same manufacturer's related products(except for the ceramic motor),so that there are some advantages in system integration,protocol communication and manufacturer support,it's necessary to reserve some redundancy for upgrading.Thirdly,in order to evaluate the performance of DEI set-up,the theory model of spatial resolution of DEI system is established by calculating the Modulate transfer function.The theory model takes into account the inherent influence of the geometric factors by Geometry Optic Approximation,CCD pixel size and scintillator's fluorescence dispersion effect.Finally,the artifacts caused by asymmetric design of monochromatic crystals are analyzed and discussed,including anisotropic amplification,penumbra and dispersion artifact.Improving the luminous flux by cutting monochromatic crystal asymmetrical is at the cost of the image quality,so how to choose the asymmetric factor b is the key of asymmetric diffraction.