Free‐Breathing Fat Quantification Using a Phase Error‐Corrected Cartesian Acquisition With Spiral Profile Ordering

Purpose To develop a phase‐corrected time‐interleaved multi‐echo gradient echo Cartesian acquisition with spiral profile ordering (TIMGRECASPR) for abdominal large‐FOV proton density fat fraction (PDFF) mapping at 3 T , demonstrating its sampling flexibility and inherent self‐gating capabilities at high isotropic resolutions. Methods A methodological framework was developed to correct eddy current‐ and concomitant gradient‐related phase errors in a TIMGRECASPR acquisition. Sequence parameters were optimized with an XCAT simulation. Validation was conducted in phantoms and in vivo thigh and abdominal imaging. In five healthy volunteers, liver PDFF and T2 *, alongside pancreatic PDFF, were compared to a clinical Cartesian breath‐hold vendor technique. Liver PDFF homogeneity was evaluated visually and across five different axial subvolumes. Mean absolute PDFF bias and within‐subject standard deviation (wSD) across repeated scans were quantified. Pancreatic delineation was quantified by line profiles across the tissue boundary. Results Short shot lengths were required for a sufficient temporal resolution of the respiratory motion self‐navigation. Without phase corrections, data showed severe peripheral PDFF bias, especially at higher spatial resolutions. In a water phantom, PDFF bias ranged from −5% to 5% over 400 mm in readout direction, successfully mitigated by the proposed phase corrections. Liver PDFF maps exhibited improved homogeneity and accurate quantification results, verified by the breath‐hold reference scan (0.6% PDFF bias, wSD = 0.11%). Pancreatic boundaries were clearly visualized and provided accurate pancreatic PDFF maps (1.1% PDFF bias, wSD = 0.37%). Conclusion This work demonstrates the feasibility of a free‐breathing monopolar time‐interleaved gradient echo sequence based on a Cartesian spiral acquisition at 3 T when accounting for phase errors.