Author Description

This dissertation, "Echo Planar Imaging Artifact Correction With Parallel Imaging" by Bin, Xie,, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Echo planar imaging (EPI) is a fast imaging technique that has been widely used in various MRI applications, such diffusion, perfusion and functional magnetic resonance imaging (fMRI). However, the EPI image quality is intrinsically hindered by three major artifacts, i.e., Nyquist ghost, geometric distortion and fat residue. The main objective of this dissertation is to investigate and develop novel methods to correct different EPI artifacts using parallel imaging. Firstly, a new Nyquist ghost and geometric distortion correction method using parallel imaging was proposed in EPI. This method calibrates the parallel imaging from two frames of EPI acquired with different phase labels. Then Nyquist ghost is subsequently removed by reconstructing images from only positive or negative echoes. Meanwhile, this phase labeling strategy shifts the TE of the second frame and allows the B0 field map generation from positive and negative images for distortion correction. The phantom results at 7T and 3T demonstrated that our method could greatly reduce Nyquist ghost even under oblique imaging and poor eddy current conditions, yielding significant improvements over the existing reference scan and image entropy minimization methods, and eliminate the geometric distortion simultaneously. The phantom results indicated that the SNR efficiency was largely preserved while the fMRI results showed no apparent degradation of temporal resolution. Secondly, in order to further imp