Rapid quantitative susceptibility mapping using single-shot echo planar time-resolved imaging

<i>Objective.</i>Echo-planar imaging (EPI) can provide rapid quantitative susceptibility mapping (QSM) in single-shot acquisition but suffers from B₀inhomogeneity and susceptibility artifacts near air-tissue interfaces. To address these limitations, this work introduces single-shot echo planar time-resolved imaging (EPTI), which enables distortion-free and multi-contrast imaging for rapid QSM.<i>Approach.</i>A zig-zag<i>k_y-t</i>sampling trajectory was employed in two-dimensional single-shot EPTI and a locally low-rank subspace reconstruction with B₀updating was applied to generate distortion-free multi-echo images from highly undersampled data. The proposed EPTI-QSM method was systematically evaluated against the gold-standard three-dimensional (3D) gradient echo (GRE) and single-shot EPI with a uniform 4-step masking procedure. In addition, various echo selections from the EPTI images were investigated to assess their impact on QSM quality.<i>Main Results.</i>EPTI-QSM demonstrated better anatomical fidelity, reduced susceptibility artifacts, and a reliable brain coverage compared to single-shot EPI, particularly in regions affected by B₀inhomogeneity. Multi-echo EPTI data with echo times ranging from 10 to 30 ms further improved susceptibility quantification and mitigated signal dropouts near air-tissue interfaces. In addition, EPTI yielded distortion-free structural images compared to EPI, and improved image contrast compared to 3D GRE used for QSM, enabling clearer anatomical visualization.<i>Significance.</i>Single-shot EPTI enables distortion-free, multi-contrast images and rapid QSM reconstruction, offering a promising alternative to EPI-based QSM, particularly in applications requiring rapid and robust susceptibility quantification.