Motion‐induced phase‐corrected homodyne reconstruction for partial Fourier single‐shot diffusion‐weighted echo planar imaging of the liver

Abstract

AbstractPartial Fourier encoding is popular in single‐shot (ss) diffusion‐weighted (DW) echo planar imaging (EPI) because it enables a shorter echo time (TE) and, hence, improves the signal‐to‐noise‐ratio. Motion during diffusion encoding causes k‐space shifting and dispersion, which compromises the quality of the homodyne reconstruction. This work provides a comprehensive understanding of the artifacts in homodyne reconstruction of partial Fourier ss‐DW‐EPI data in the presence of motion‐induced phase and proposes the motion‐induced phase‐corrected homodyne (mpc‐hdyne) reconstruction method to ameliorate these artifacts. Simulations with different types of motion‐induced phase were performed to provide an understanding of the potential artifacts that occur in the homodyne reconstruction of partial Fourier ss‐DW‐EPI data. To correct for the artifacts, the mpc‐hdyne reconstruction is proposed. The algorithm recenters k‐space, updates the partial Fourier factor according to detected global k‐space shifts, and removes low‐resolution nonlinear phase before the conventional homodyne reconstruction. The mpc‐hdyne reconstruction is tested on both simulation and in vivo data. Motion‐induced phase can cause signal overestimation, worm artifacts, and signal loss in partial Fourier ss‐DW‐EPI data with the conventional homodyne reconstruction. Simulation and in vivo data showed that the proposed mpc‐hdyne reconstruction ameliorated artifacts, yielding higher quality DW images compared with conventional homodyne reconstruction. Based on the understanding of the artifacts in homodyne reconstruction of partial Fourier ss‐DW‐EPI data, the mpc‐hdyne reconstruction was proposed and showed superior performance compared with the conventional homodyne reconstruction on both simulation and in vivo data.