Multi-shot Dual-Polarity GRAPPA for Nyquist Ghost and Fuzzy Ripple Artifact Correction of Echo-Planar Imaging

Motivation: Nyquist ghost artifacts and fuzzy ripple artifacts are more pronounced in high-resolution fMRI in 7-Tesla, which may introduce bias into fMRI signal. Goal(s): The target of this study is to develop a technique for multi-shot-EPI-based sub-millimeter fMRI, which can correct the artifacts without reducing temporal resolution. Approach: We developed multi-shot dual-polarity GRAPPA (msh-DPG) which is a combination of DPG and traditional GRAPPA. Results: Msh-DPG can effectively correct the Nyquist ghosts and reduce the fuzzy ripple artifacts. It outperforms the linear phase correction method. Impact: The proposed method can correct or reduce two common artifacts in sub-millimeter fMRI without reducing the temporal resolution. It may help to improve the image quality and stability of high-resolution fMRI, especially in ultra-high-field systems.