Simultaneous Quantitation of T1 and T2 Using a Novel 2D Magnetization-Prepared Multi-Slice Pulse Sequence

Introduction In recent years numerous approaches for the efficient, accurate and simultaneous quantitation of T1, T2, and M0 have been proposed – Ref 1 and 2 among them. Indeed, growing interest in generating synthetic MR images [2] and in “quantitative” tissue characterization continues to drive technical developments in MR relaxometry. Here we propose a novel 2D multi-slice pulse sequence that uses a magnetization preparation (mag prep) scheme to impart varying degrees of T1and T2weighting in a single scan – enabling simultaneous quantitation of T1, T2, and M0. A mag prep approach enables the use of non-selective composite pulses and MLEV phase cycling to reduce the sequence’s sensitivity to B0 and B1 inhomogeneities. Background In Ref 3, Wright et. al. formulated an approach to maintain, during a subsequent 2D multi-slice acquisition, the contrast generated by a non-selective mag prep. To eliminate contrast contamination caused by T1 re-growth, two acquisitions with identical mag prep and slice acquisition order are acquired – one with its magnetization inverted immediately after mag prep (Fig 1a, inversion pulse in red) and the other without signal inversion (Fig 1b). The resulting data can then be combined to yield Eq 1 and Eq 2 (Fig 1c). By pairing acquisitions as in Fig 1, combining their acquired data per Eq 1, and then acquiring additional such pairings – each with a different mag-prep contrast weighting, a multi-shot spiral pulse sequence can be modified for quantitative T2 [4] and T1ρ [5] imaging. In the case of quantitative T2, different mag-prep contrast weightings (i.e. different effective TE’s) are generated by changing for a fixed refocusing interval the number of refocusing pulses in the T2 Prep module [6] that precedes image acquisition.