Study Of Image Distortion Correction For X-ray Micro-CT

As a nondestructive testing method with high resolution,Micro-CT system has widely applications in the fields of medicine,microelectronics,materials science,metrology and so on.The spatial resolution of Micro-CT has reached micrometer,and errors caused by imaging quality directly affect the spatial resolution of CT systems.Among these errors,image distortion is an important factor.The existence of the image distortion limits the spatial resolution of the Micro-CT system.Therefore,it is necessary to correct the image distortion to improve the image quality of the system.In this paper,we focus on the image distortion correction problems in Micro-CT systems.By analyzing the factors which cause image distortion,we propose an image distortion correction method for Micro-CT systems.And experimental verification and quantitative evaluation were carried out in our Micro-CT system.The main achievements of this research work are listed as follows:1.Reviewed the development history of CT and analyzed the characteristics of the Micro-CT and current research situation of image distortion correction.The research content of this paper is introduced.2.The working principle of the Micro-CT system is introduced in detail.Compared with existed image distortion correction methods,basing on standard grid plate,the correction model is proposed.3.The effect of distorted DR images on reconstruction CT images is analyzed by simulation.According to the principle of X-ray attenuation,a simulation CT system is constructed basing on MATLAB.And simulation images is reconstructed by FDK algorithm.MTF results show that the distortion of DR image reduces the spatial resolution of the 3D reconstruction image of the sample.4.Analyzed the effect of the radiation source and the optically coupled detector in the CT system on the imaging quality by theory.The simulation model of the optocoupler is established to simulate the influence of various errors on the imaging and the factors that cause the distortions.The theoretical analysis and simulation results show that both the characteristic of the lens and the installation errors of the detector can cause the distortion.5.The distortion correction model proposed in this paper is validated by experiments.The optically coupled detector system was visualized under visible light conditions and the type of distortion was analyzed qualitatively.The DR image of the standard grid distortion test target was obtained by X-ray micro-CT system,and the distortion coefficient of the polynomial model was obtained by using the DR image to complete the distortion correction of the DR image.The X-ray micro-CT system was used to complete the CT scan of the calibration sphere,and the three-dimensional structure of the calibration sphere was reconstructed by calculating the distortion coefficient to correct the CT images.The experimental results show that the spatial resolution of the system is improved from 8.5?m to 4.2?m,and the distortion correction improves the image quality of the system.