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Abstract #3783

Nonlinear Phase Correction of Multi-Shot Diffusion Weighted EPI Using Parallel Imaging Estimated Phase Cycled Reconstruction (PIPCR) Method

Wentao Liu1, Xin Tang1, Yajun Ma1, Jia-Hong Gao1, 2

1MRI Research Center and Beijing City Key Lab for Medical Physics and Engineering, Peking University, Beijing, China; 2Brain Research Imaging Center and Department of Radiology, The University of Chicago, Chicago, IL, United States

Multi-shot echo-planar imaging (msEPI) has advantages of high spatial resolution and less distortion when comparing to single-shot EPI (ssEPI). However, in the application of diffusion imaging, msEPI often suffers ghosting artifacts due to phase shifts from shot to shot. A recently proposed phase cycled reconstruction (PCR) method can correct 2D linear phase errors in msEPI efficiently using a search algorithm, but phase shifts caused by the pulsing of cerebrospinal fluid (CSF) are nonlinear and hard to be compensated by PCR method directly. In this study, an efficient parallel imaging estimated phase cycled reconstruction (PIPCR) method is introduced. The inter-shot phase maps are estimated from the parallel imaging (PI) reconstruction of the subset k-space of msEPI data. After a smoothing process, these phase maps are utilized as nonlinear phase compensation for PCR msEPI reconstruction. The proposed PIPCR is a fast and robust method to correct arbitrary inter-shot phase errors of diffusion weighted msEPI and the reconstruction result is demonstrated in the report.