T2 shuffling: Sharp, multicontrast, volumetric fast spin‐echo imaging

Purpose A new acquisition and reconstruction method called T 2 Shuffling is presented for volumetric fast spin‐echo (three‐dimensional 3D FSE) imaging. T 2 Shuffling reduces blurring and recovers many images at multiple T 2 contrasts from a single acquisition at clinically feasible scan times (6–7 min). Theory and Methods The parallel imaging forward model is modified to account for temporal signal relaxation during the echo train. Scan efficiency is improved by acquiring data during the transient signal decay and by increasing echo train lengths without loss in signal‐to‐noise ratio (SNR). By (1) randomly shuffling the phase encode view ordering, (2) constraining the temporal signal evolution to a low‐dimensional subspace, and (3) promoting spatio‐temporal correlations through locally low rank regularization, a time series of virtual echo time images is recovered from a single scan. A convex formulation is presented that is robust to partial voluming and radiofrequency field inhomogeneity. Results Retrospective undersampling and in vivo scans confirm the increase in sharpness afforded by T 2 Shuffling. Multiple image contrasts are recovered and used to highlight pathology in pediatric patients. A proof‐of‐principle method is integrated into a clinical musculoskeletal imaging workflow. Conclusion The proposed T 2 Shuffling method improves the diagnostic utility of 3D FSE by reducing blurring and producing multiple image contrasts from a single scan. Magn Reson Med 77:180–195, 2017. © 2016 Wiley Periodicals, Inc.