A single‐shot T₂ mapping protocol based on echo‐split gradient‐spin‐echo acquisition and parametric multiplexed sensitivity encoding based on projection onto convex sets reconstruction

Purpose To develop a high‐speed T 2 mapping protocol that is capable of accurately measuring T 2 relaxation time constants from a single‐shot acquisition. Theory A new echo‐split single‐shot gradient‐spin‐echo (GRASE) pulse sequence is developed to acquire multicontrast data while suppressing signals from most nonprimary echo pathways in Carr‐Purcell‐Meiboom‐Gill (CPMG) echoes. Residual nonprimary pathway signals are taken into consideration when performing T 2 mapping using a parametric multiplexed sensitivity encoding based on projection onto convex sets (parametric‐POCSMUSE) reconstruction method that incorporates extended phase graph modeling of GRASE signals. Methods The single‐shot echo‐split GRASE‐based T 2 mapping procedure was evaluated in human studies at 3 Tesla. The acquired data were compared with reference data obtained with a more time‐consuming interleaved spin‐echo echo planar imaging protocol. T 2 maps derived from conventional single‐shot GRASE scans, in which nonprimary echo pathways were not appropriately addressed, were also evaluated. Results Using the developed single‐shot T 2 mapping protocol, quantitatively accurate T 2 maps can be obtained with a short scan time (<0.2 seconds per slice). Conclusion Accurate T 2 mapping with minimal signal contamination from CPMG high‐order echo pathways can be achieved by the developed method that integrates single‐shot echo‐split GRASE acquisition and parametric‐POCSMUSE reconstruction. Magn Reson Med 79:383–393, 2018.