Research On Methods For Suppressing Artifacts Of MRI

Magnetic resonance imaging has been widely applied in clinics because of its important characteristics, such as high temperal and spatial resolution, non-invasive and no harmful radiation. However, in the processing of imaging, various artifacts would be produced due to defection of technology, limitation of device and patient movement. These artifacts degrade the quality of the image and make the detecting and locating of the functional active region more complicated. The objective of this work is to suppress these artifacts by after processing methods based on image.In this paper, we study EPI ghost and motion artifact, which are the most common artifacts in magnetic resonance imaging.Several methods, such as odd/even line reconstruction method, projection onto convex sets method, second moment method, have been studied to suppress EPI ghost artifact. And then a new method to supperess EPI ghost artifact based on image is promoted. As to motion artifact, we have studied some methods for suppressing rigid translational motion artifact, which is produced in the imaging plane. We promote an improved method based on the theory of POCS (projection onto convex sets) and the spectrum shift to remove translation motion artifact. The experiments show that this method is quite useful for suppressing artifacts caused by large movement. Furthermore, we implement a novel approach to suppress rigid translation motion based on Simulated Annealing (SA) algorithm combining with the theories of Snake and spectrum shift. This new method solves the convergent pursuit problem which hasn't been solved in classical convex sets method, and has the feature of auto-extracting the region of interest.The algorithms dissussed above have been proved to be effective for suppressing artifact and the quality of the image can be improved greatly by doing a lot of experiments.