B0 navigator enables respiratory motion navigation in radial stack-of-stars liver T1 mapping

Motivation: The radial stack-of-stars trajectory allows to oversample k-space center in free-breathing liver imaging, but motion navigation may be challenging in acquisitions with varying contrast weightings. Goal(s): To develop a B0 self-navigation approach applicable for free-breathing acquisitions with varying contrasts and apply it in Look-Locker-based T1 mapping. Approach: A methodology is developed where the B0 self-navigator is estimated from oversampled k-space, water-fat separation is applied, and normalized breathing curve and amplitude of breathing-induced B0 variation are estimated through demodulating B0 drift and contrast variations. Results: The proposed method is successfully applied in simulations and in vivo, improving reconstructed T1 maps when used for navigation. Impact: B0 self-navigation allows to estimate respiratory motion in acquisitions with varying contrasts and quantifies the amplitude of B0 variations, enabling self-gated reconstruction without external motion sensors. This may be useful to develop patient-specific motion correction in future studies.