Robust Nyquist ghost correction for high-resolution EPI using multishot dual-polarity GRAPPA reconstruction

Motivation: Multishot EPI acquisition improves image fidelity and reduces distortion but is prone to Nyquist ghosts. Dual-polarity GRAPPA (DPG) effectively addresses ghosts in single-shot EPI but has not been extended to multishot acquisitions. Goal(s): To develop a robust Nyquist ghost correction method for multishot EPI by tailoring DPG. Approach: We introduce multishot DPG (msDPG), which uses DPG kernels to synthesize polarity-free data and permits incorporation with advanced regularized reconstruction to further address physiologic shot-to-shot phase variations. Results: On scanners with ultra-high field (Terra.X) or high-performance gradients (Connectome 2.0), msDPG can effectively reduce ghost levels on multishot EPI data, enabling high-fidelity, submillimeter diffusion imaging. Impact: The proposed msDPG method provides robust Nyquist ghost correction for multishot EPI, effectively suppressing ghosts on modern scanners and facilitating seamless integration with other advanced reconstruction techniques.