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Abstract #1081

Navigator-free multi-shot EPI with shift-invariant kernel extraction in subspace

Rui Tian1, Martin Uecker2, and Klaus Scheffler1,3
1High-Field MR center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, 2Institute of Biomedical Imaging, Graz University of Technology, Graz, Austria, 3Department for Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany

Synopsis

Keywords: Image Reconstruction, Image Reconstruction

Motivation: In functional and diffusion MRI, multi-shot EPI enhances spatial resolution and minimizes distortion compared to single-shot scans. However, its vulnerability to shot-to-shot phase variations presents a significant challenge, with various proposed methods having drawbacks.

Goal(s): We propose a robust, navigator-free, computational efficient multi-shot method without SNR penalty.

Approach: In readout-segmented multi-shot EPI, we exploit the k-space overlapped regions between adjacent segments to extract relative phase fluctuations. This method, inspired by ESPIRiT and nonlinear gradient calibration, efficiently extracts shot-dependent phase variations in subspace.

Results: Our ex-vivo and in-vivo scans, including diffusion-weighted imaging, successfully achieves a high in-plane resolution of about 0.6mm without ghost artifacts.

Impact: Our proposed multi-shot technique eliminates the needs for time-consuming navigators, provides robust high-resolution diffusion and potentially functional imaging, and could be easily adapted for interleaved Cartesian and spiral EPI allowing robust phase error estimation from merely small k-space regions.

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